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Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods
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Cite this: ACS Omega 2024, 9, 2, 2060–2079
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https://doi.org/10.1021/acsomega.3c04425
Published January 4, 2024

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Abstract

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Gasification is an advanced thermochemical process that converts carbonaceous feedstock into syngas, a mixture of hydrogen, carbon monoxide, and other gases. However, the presence of tar in syngas, which is composed of higher molecular weight aromatic hydrocarbons, poses significant challenges for the downstream utilization of syngas. This Review offers a comprehensive overview of tar from gasification, encompassing gasifier chemistry and configuration that notably impact tar formation during gasification. It explores the concentration and composition of tar in the syngas and the purity of syngas required for the applications. Various tar removal methods are discussed, including mechanical, chemical/catalytic, and plasma technologies. The Review provides insights into the strengths, limitations, and challenges associated with each tar removal method. It also highlights the importance of integrating multiple techniques to enhance the tar removal efficiency and syngas quality. The selection of an appropriate tar removal strategy depends on factors such as tar composition, gasifier operating and design factors, economic considerations, and the extent of purity required at the downstream application. Future research should focus on developing cleaning strategies that consume less energy and cause a smaller environmental impact.

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1. Introduction

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Gasification technology offers clean technological intervention to offset fossil energy. (1,2) It effectively transforms any carbon/hydrogen-based solid matter (3,4) into a combustible gaseous fuel that contains CO, H2, and CH4 as the primary combustibles, providing a fundamental advantage of product and feed stock flexibility. The feedstock includes coal, biomass, waste materials such as municipal solid waste (MSW), sewage sludge, and other waste. (3−13) It should be noted that due to the anticipated 70% rapid increase in the global waste generation between the year 2016 and 2050, gasification of waste materials is becoming a key technology interest. (10) Apart from thermal applications, the product gas known as “syngas” from gasification can be utilized in various applications, such as fuelling an internal combustion (IC) engine, (14,15) gas turbine, (16) and integrated gasification combined cycle (17−19) for power generation; as a feed for Fischer–Tropsch/Alcohol synthesis reactors, synthetic natural gas, and hydrogen; and in advanced technologies like solid oxide fuel cells. (15,19−26) Several reactor configurations are available for gasification, including fixed bed, fluidized bed, entrained bed, and others, each with specific preferences for process conditions. By selecting the appropriate reactor configuration, the required syngas composition and conversion rates can be achieved to meet the specific needs of a particular application. Although syngas can be used in various applications, such as those mentioned earlier, one of the most significant challenges associated with its production is the presence of byproducts known as “tar”. These are condensable higher-hydrocarbon compounds that are produced during the gasification process. Compounds designated as tar can degrade the downstream equipment and applications (27) by methods as simple as clogging the flow paths (as in IC engines and turbines) to as critical as poisoning catalytic layers (as in fuel cells and alcohol synthesis processes). As such, syngas must be cleaned to the extent demanded by specific applications to meet the tar permissible limits. (28) It should also be noted that, based on the nature of feedstock chemical composition, there are other undesirable vapor-phase products such as halides, ammonia, cyanide, etc. (19) that can also affect the performance of downstream applications as well as the syngas cleaning and tar removal. A more comprehensive review on impurities other than tar can be found in the literature, (29,30) while this Review focuses mainly on tar compounds formed in the gasification process.
It is important to note that tar formation forms a part of the fundamental thermochemistry of gasification, and as such the presence of tar in syngas is inevitable. The amount of tar in the syngas is affected by both the gasifier configuration and the operating conditions. Therefore, reducing tar in raw gas is a key area of research and development in the gasification process. (31) Irrespective of the attempts to reduce the tar content within the gasifier itself by in situ methods, the literature reports the tar content in the raw syngas to be well above the permissible limits posed by the applications. (32−35) Hence, ex situ tar destruction or conversion, i.e., treating the gas after coming out of the gasifier, becomes critical. (36) Literature reports on the adoption of several methods of ex situ tar destruction, such as the separation of tar compounds by filters, electrostatic precipitators, and cooling the product stream using scrubbers and spray towers. (37) In recent times, raw syngas cleaning has been attempted using plasma technology, particularly by using nonthermal plasma or low-temperature plasma, which is known for allowing thermodynamically unfavorable chemical reactions even at ambient conditions and thereby seems promising for energy-efficient chemical conversion. (38) (39−41) Nonthermal plasma is a soup of reactive species, including electrons, ions, radicals, metastable, excited neutrals, ground-state neutrals, and radiation. These species can dissociate and further reform the stable compounds like “tar” generated in gasification.
This Review provides a holistic review of gasification tar and existing methods available to ensure that the product gas contains tar in permissible limits so that the gas can be used in applications without any issues. The Review is divided into four sections. A brief introduction is presented in this section, followed by a summary of gasification technology in section 2. Section 3 provides a detailed discussion of the formation, evolution, and nature of tar. Section 4 discusses the cleaning technologies to remove or reduce tar in product gas.

2. Gasification Technology

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Gasification is a substochiometric thermochemical conversion process carried out in a reactor termed as “gasifier” wherein solid carbonaceous matter (CM) like biomass (∼C1.0H1.4O0.6), coal (∼C11.0H1.0O1.4), municipal solid waste (MSW) (∼C100H250O80N), refuse-derived fuel (RDF) (∼CH1.569O0.541) etc., is converted predominantly to a gaseous mixture of combustible compounds (H2, CO, and CH4), incombustible compounds (CO2 and N2), a trace quantity of condensable higher hydrocarbons known as “tar”, and compounds like NH3, HCN, H2S, etc. Char and ash are the solid-phase byproducts, and the exact composition of the gas phase is process-specific with a dependence on the gasifying media, i.e., air, oxygen, and/or oxygen–steam. Figure 1 shows the routes of formation of these combustible products and byproducts. It can be seen from Figure 1 that these compounds or products are formed from the moisture, volatile matter, and fixed carbon contents of CM, which go through various stages of thermochemical conversion. Before the reactor/gasifier configurations are discussed, the chemistry of gasification, which is facilitated in different gasifier types, is discussed first.

Figure 1

Figure 1. Route map of biomass and wastewater conversion into products through gasification.

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2.1. Gasification Chemistry

For the sake of explaining the gasification chemistry, consider a reactor/downdraft gasifier, i.e., a vertical cylinder where the flow direction of both product gas and carbonaceous matter (CM) is downward, as can be seen in Figure 2a. The CM is fed into the reactor from the top, which forms a bed in the reactor. The feed rate and the bed height are governed by the gasifier geometry. The gasifying media (42−45) (air, steam, and oxygen) are supplied at various heights of the reactor far from the top, where the solid feed is initially ignited. Typically, air is used as the gasifying medium. Concurrently, research is also being reported on the use of a mixture of steam and oxygen (oxygen–steam gasification), (46−48) and oxygen-enriched air (49−52) as gasifying media. Chemical looping gasification is another novel approach that replaces the gasifying gas medium with oxygen-carrying solids acting as intermediary materials in chemical reactions by releasing or capture the lattice oxygen. (53−56) The supply of gasifying media to the gasifier creates a combustion zone locally. With the local availability of a continuous supply of oxidizing media, this zone facilitates the combustion of CM. The flame sets up a temperature gradient across the bed height, marking different zones without any distinct separation as (1) drying, (2) pyrolysis, (3) oxidation, and (4) reduction.

Figure 2

Figure 2. Gasifier configurations: (a) downdraft, (b) updraft, and (c) fluidized bed gasifier. (d) Picture of condensed tar stuck to the downstream component of a gasifier at Indian Institute of Science.

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The temperature profile along the height of a gasifier plays a crucial role in determining the nature of the chemical reactions or processes that occur in each zone. Different temperature zones within the gasifier are required to achieve specific reactions, and the temperature profile must be carefully controlled to optimize the gasification process. (1) In the drying zone, which is typically seen near the CM feed ports, the temperature can go up to about 473 K, and the feed material mostly loses moisture in this zone. (57) (2) Once the temperature of CM reaches 623–673 K, the release of volatiles begins, and simultaneously, over a certain residence time, CM becomes transformed into char. (3) The released volatiles undergo subsequent reactions downstream, controlled by the local bed temperature and availability of gasifying medium, and form primary oxygenates and gases like CO, CO2, and H2O wherever combustion is favored. (4) These products further react with the hot char to generate noncondensable gases, and simultaneously the gases react among themselves through reforming and shift reactions, generating CO, CO2, H2, CH4, and complex polymerized compounds. The reactions favored in the presence of hot char “C” are gasification reactions, which are represented as reactions R1–R3. The Reactions R1 and R2 are considered principal gasification reactions, which are endothermic.
C+CO2↔2CO⁣ΔHr0=172.82⁡kJ/mol
(R1)
C+H2O↔CO+H2⁣ΔHr0=175.3⁡kJ/mol
(R2)
C+2H2↔CH4⁣ΔHr0=−74.8⁡kJ/mol
(R3)
It is important to note that the endothermic reactions in a gasifier are supported by heat generated in the combustion zone. The heat generated in the combustion zone provides the energy necessary to drive the gasification reactions and sustain the gasification process. Hence, gasification is fundamentally an autothermal process. It should be noted that the tar formation is a persistent byproduct of gasification, which evolves during the pyrolysis stage as primary oxygenates and matures into aromatic hydrocarbons that react with other gases and moisture as described earlier. Reaction R4 shows the water gas shift reaction, and reaction R5 shows the global gasification reaction.
CO+H2O↔CO2+H2⁣ΔHr0=−41.2⁡kJ/mol
(R4)
Carbonaceous matter+O2+H2O+N2→CO+H2+CO2+CH4+H2O+other hydrocarbons+tar+ash+char+inorganics⁡(NH3,HCl,COS,H2S)+other gases
(R5)

2.2. Gasifier Configurations

Configuration of gasifiers can be broadly classified into three types, namely, fixed bed, fluidized bed, and entrained flow. In fixed bed gasifiers like the one mentioned in section 2.1, the feed CM is fed at the top, creating a bed of CM that is supported on a grate/screw system placed at the bottom of the gasifier. The feed CM moves with the plug profile during the gasification process, facilitated by the moving grate/screw system. Updraft and downdraft fixed bed systems are the most commonly seen, as shown in Figure 2a and b, respectively. In downdraft systems, the feed and gas move cocurrently, and the product gas leaves from the bottom of the reactor, passing through the zone near the grate of fire. In updraft systems, the movement of feed is countercurrent to the gas, with product gas leaving from the top. It should be noted that because of the exit of product gas at the top, the combustion and reduction zones are swapped, with the bottom-most zone being the combustion zone in the updraft, unlike the reduction zone in the downdraft gasifier. Figure 2c shows fluidized bed gasifiers, wherein the feed particles are suspended in the gasifying medium, resulting in the bed acting like a fluid. Thorough mixing between the gasifying medium and feed results in a uniform temperature profile and facilitates the gasification chemistry. Hot inert solids, such as sand, limestone, dolomite, etc., are suspended in contact with the CM feed to support drying and pyrolysis. In entrained flow gasifiers, the gas and the feed (mostly coal) are fed together (cocurrent) at a very high velocity into the reactor from the side or top. Sometimes, entrained flow gasifiers can be viewed as plug flow reactors having CM and a gasifying medium as inputs at one end and the product gas at the other end. Oxygen is the most used gasifying medium, and the combustion can happen right at the entry point on one end; the typical composition of the product gas and its energy value expected from these gasifier configurations in the presence of various gasifying media are consolidated and reported in Table 1. The influence of the factors shown in Table 1, such as feed stock, gasifying medium, and temperature, is discussed in detail in section 3.2.
Table 1. Product Gas Composition in Different Oxidizing Media
    gas composition (vol %)  
feedoxidizing/gasifying mediumERSBRH2COCO2CH4N2C2H4LHV (MJ/Nm3)ref
fixed bed gasifiers 
biomass pellet woodair  9–1012–1514–172–456–59 3–6 (58)
dry casuarina woodoxygen + steam0.18145–5113–2515–281–40 7–10 (31,57)
pellet woodoxygen + steam0.32.552133230 8.3 (47)
rice strawair  61063143 5.62 (59)
palm oil wastessteam 0.5–235–6012–3314–263–12 29–14 (60)
olive kernelair0.14 20–3015–2040–5510–12  9–10.4 (61)
RDFair  7.1719.7114.451.76  3.9 (62)
sewage sludge + woody biomassair  4.515171.5 1–25.5 (63)
sewage sludge + residue from hydrolysisair0.2–0.3 11.616.717.65.94  6.42 (64)
fluidized bed gasifiers 
pellet woodsteam/air 0.89–3815–3216–174–140–53 3.5–14.4 (65,66)
empty fruit bunchair0.2–0.4 10.27–3822–36.410–656–15  8–16 (67)
pine sawdustoxygen + steam/steam0.21.6–2.721–3915–4315–255–7  7.4–9 (68,69)
silica sandair0.4 7–8.224–3159–634–5  1.6–1.9 (70)
empty fruit bunchair0.15 18.4–27.432–4517–3610–12  12.4–15.4 (67)
bambooair0.4 3.2–9.121.4–32    60–80 (70)
sewage sludge + coalair  7–279–1112–151–446.19 2–6 (71,72)
pine chips + coalair/steam  13.0516.818.391.6359.13 4.29 (73)
MSW + pine dustair0.5–0.2 9–1117–1915–194–6  5.3 (74)
MSW + switchgrassair  1014.115–182–4  6.7 (75)
beechwood + polyethylenesteam  37.123.6    8.7 (76)
entrained flow gasifiers 
pellet woodair0.28 7.626103.3521.16 (77)

3. Tar from Gasification

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As mentioned earlier, tar from gasification is a persistent byproduct that is neither in large amounts for beneficial use nor small enough amounts to be ignored. (42) The tar consists of a mixture of compounds that are largely aromatic, having molecular weights heavier than that of benzene. (78) Tar compounds form fine droplets of size <1 μm like a mist and can agglomerate into large droplets that can condense over a wide range of temperatures, much higher than the ambient temperature. They also are known to coat the solid particles (78) and stick to the surfaces, causing fouling, corrosion, and blockage in downstream passages and equipment. Figure 2d shows a picture of condensed tar sticking to the flange surface, having a typical appearance, i.e., thick, viscous liquid-brownish to deep black color; (78) tar is also known to have a pungent smell. (78) Regardless of the amount and composition of the tar formed, handling it is a universal challenge of gasification systems. (79) The concentration and composition of tar formed are strongly dependent on various factors such as (1) temperature, (2) gasifier design (downdraft/updraft/fluidized bed), (3) gasification medium, (4) feed stock, (5) residence time, and (6) pressure. (33) Hence, the effect of these factors on tar formation has been studied by various researchers over many decades. (80−93) While few researchers have focused on developing new approaches to quantify tar formation, others have attempted to compare available methods to identify and quantifying the tar formed from gasification, (94−100) which itself is very complex and tricky.

3.1. Classification of Tar

Researchers have classified or grouped tar compounds in many ways. (58) One way is to classify the tar compounds into primary, secondary, and tertiary classes (58) based on the functional group(s) that make up the tar. Figure 3 shows the functional groups of the tar compounds that represent one of these three classes. As can be seen in Figure 3, the classification is based on the temperature gradient in the gasifier bed (presence of thermal or partial-oxidation regimes in the gasifier (58)), due to which the released oxygenates go through various reactions such as chemolysis, depolymerization, oxidation, polymerization, and cycloaddition, (31) evolving into polynuclear aromatic hydrocarbons (PAHs). (58) Based on the residence time available in distinct temperature zones/regimes, the proportion/presence of these three classes of tar will vary, spanning over a range of temperatures. (101) The tar maturation is well connected to the gasifier zones presented in section 2.2.

Figure 3

Figure 3. Maturation and temperature ranges of tar classes.

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In another way, tar is classified into five classes distinguishing different properties of tar compounds such as molecular weight, condensation behavior and water solubility/polarity, (31) as shown in Table 2. (31,102) Figure 4 shows that the dew point of tar compounds belongs to either of these five classes. It is interesting to note that, excluding class 1, the dew point of the tar compounds of classes 2–5 varies with the concentration of the individual class of tar compounds, as shown in Figure 4. The importance of the dew point at a given concentration of these tar class compounds will be emphasized in the discussion presented in section 3.3.
Table 2. Tar Compound Classification Is Based on Solubility, Condensability, And Chemical Composition
tar classclass namepropertyrepresentative compounds
1gas chromatography (GC)-undetectablevery heavy tars cannot be detected by GCsubtracting GC-detectable tar from total gravimetric tar
2heterocyclic aromaticsheteroatoms, highly water-soluble compoundspyridine, phenol, cresols, quinoline
3light aromatic (1 ring)usually, a light HC with a single ring does not pose a problem regarding condensability and solubilitytoluene, ethylbenzene, xylenes, styrene
4light PAH (2–3 rings)two- and three-ring compounds condense at low temperatures, even at very low concentrationsindene, naphthalene, biphenyl, fluorene, anthracene
5heavy PAH (4–7 rings)larger than three-ring, these components condense at high temperatures at low concentrationsfluoranthene, pyrene, chrysene, perylene, coronene

Figure 4

Figure 4. Tar concentration of different classes as a function of dew point temperatures: class 2 (□), class 3 (▲), class 4 (●), and class 5 (◆).

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3.2. Concentration and Composition of Tar

Tar concentration is generally expressed in terms of the total mass of tar compounds present in a unit volume of the product stream, i.e., g/Nm3 or mg/Nm3. Sometimes it is also expressed as a mass fraction of the dry CM feed or as ppm, as mentioned earlier; the amount/concentration/yield of tar depends on several factors, out of which the choice of gasifier type inherently decides the tar yield. Factors/operating conditions such as feed, gasification temperature, gasification agent, residence time, equivalence ratio, steam-to-biomass ratio, and pressure can also affect tar yield and composition. It is to be noted that there is no single factor independently affecting the evolution of tar, but all of these factors are highly coupled with one another. The composition and yield of tar are based on the combination of the operating conditions of these factors. Table S1 of the Supporting Information shows typical tar levels reported in the literature for various operating conditions.

3.2.1. Gasifier Type

Figure 5 shows a box plot of tar concentrations reported in the literature for various gasifier types, and Table 3 compares the minima/maxima reported in Figure 5 with the typical tar levels reported in literature. (31) As can be observed from Figure 5 and Table 3, the downdraft gasifier gives a low tar yield, as the product gas stream exits the gasifier through a temperature zone favoring tar cracking. Although typical residence time is not reported as such in the literature, an increase in residence time reduces the primary and secondary tar content, with a slight increase in the amount of PAHs (>3 rings). However, a down-draft gasifier is appropriate for smaller units limited to a thermal input of 10 MWth. This is equivalent to 2.4 tonnes/h of feed having a lower calorific value (LCV) of 15 MJ/kg. Thus, for larger feed operations, using a fluidized bed is necessary to achieve uniform temperature distribution over the bed; handling large amounts of tar becomes necessary.

Figure 5

Figure 5. Box plot of tar concentrations for the various gasifier types.

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Table 3. Tar Formation Expected in a Range from Various Gasifier Types
 tar yield (g/m3)  
reffixed bed, updraftfixed bed, downdraftfluidized bed
(31)10–1500.01–0.55–40
Table S11–132.40.04–32.30.01–180

3.2.2. Gasification Temperature

Gasification temperature is another important factor that is inversely related to the tar yield. That is, higher gasification temperatures yield low tar. However, at high gasification temperatures, i.e., above 1123 K, the formation of class 4 and class 5 tar compounds is known to dominate, as shown in Table 2. (103) The literature suggests that, for a fluidized bed gasifier, increasing the gasification temperature from 1023 to 1053 K reduces the tar yield from 180 to 40 g/Nm3 in the presence of steam as the gasifying medium. (104) However, to achieve considerable carbon conversion in the process, at least 1023 K is required irrespective of the values of the other operating parameters. It should also be noted that, as can be seen in Figure 2a and b, the product gas exits by passing the combustion zone, while in an updraft system the gas passes through the drying zone. Because of this, the tar cracking reactions occur in the product gas before the exit in the downdraft system, which reduces the tar content. In general, assuming other operating conditions are the same, the tar yield will be less in the downdraft system than in the updraft system. Typically, the gasifier temperature varies in the range of 500–1150 K in the literature data summarized in Table S1.

3.2.3. Feed Type

Figure 6 shows the effect of wood, waste (RDF/MSW), and agroresidue on the tar concentration for air as a gasifying medium. As can be seen, the median tar concentration is high for waste compared to that of wood or agroresidue within the gasifier type and is higher for a fluidized bed than for downdraft gasification of waste. Figure 7 shows the effect of the feed CM, gasification temperature, and other parameters, including the tar content. In the case of agrofuels and RDF, gasification temperatures are restricted to the lower range (below 1173 K) to avoid sintering issues. This optimal gasification temperature range, as shown in Figure 7, is also reported in various literature works. (103,105) Even though higher gasification temperature reduces tar content, allowing longer residence time for cracking reactions will compromise the gas heating value and risk a rapid increase in the formation of three- or four-ring PAHs. (103) Typically, the cellulose and hemicellulose contents of the biomass are associated with the gas yield, and lignin is associated with the tar yield. High amounts of lignin lead to high tar yield. (106) Based on Table 1 and from the literature, (106) there is no trend observed for the effect of biomass type on the tar content, which is reported to be more affected by other factors such as reactor type and operating conditions, including gasification temperature, gasifying medium, etc., then the biomass type. (106) Experimental conditions should be fixed to confirm this observation further, and only the biomass type should be varied.

Figure 6

Figure 6. Box plot showing the effect of wood, waste (RDF/MSW), and agroresidue on the tar concentration for air as a gasifying medium.

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Figure 7

Figure 7. Typical gasification temperature for various feedstocks and its influence on a few parameters.

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3.2.4. Gasifying Medium

Typically, a low equivalence ratio is maintained in the gasification zone to avoid lowering the gas heating value. However, the availability of oxygen for volatiles can stop the maturation of primary tars over time, thereby reducing the tar content (the equivalence ratio (φ, ER) is a parameter used in combustion engineering to describe the ratio of the actual fuel/air ratio to the stoichiometric fuel/air ratio required for complete combustion of a fuel). At higher ER, formation of PAHs (four- or five-ring) is known to increase. (33) This effect of the equivalence ratio becomes significant at a very high gasification temperature. The effect of oxygen on reducing the tar content can also be realized by using steam as a gasifying medium. However, careful selection of the steam to biomass ratio is important to avoid compromising on gas quality. (33) The addition of oxygen to steam (oxygen–steam) further reduces the tar yield to the lowest value. For a biomass–RDF mix, Catarina et al. (107) observed very little effect of the ER on tar composition at a gasification temperature of 800 °C, an expected behavior since the main tar components are already PAHs; this observation is opposite that of Mastellone et al. (108) It should be noted that the presence of these PAHs makes the tar more toxic due to its hydrophobic, persistent, and genotoxic nature.
The typical (expected) compositions of tar compounds from the gasification process are shown in Table 4. (33) It is evident from the data that 85% of tar composition by weight consists of class 2, 3, and 4 tar compounds, and 66% of total tar composition is made up of specific compounds, namely, benzene, phenol, toluene, and naphthalene, out of which nearly 40% is benzene. It should be noted that though benzene is not classified as a tar compound, it is detected, quantified, and reported in the literature. (109−117)
Table 4. Typical Tar Composition from Gasificationa
tar compoundtypical composition by weight (%)tar class
benzene37.93
toluene14.33
other one-ring aromatic HC13.93
naphthalene9.64
other two-ring aromatic HC7.84
three-ring aromatic HC3.64
four-ring aromatic HC0.85
phenolic4.62
heterocyclic6.52
others1 
a

Note: benzene is not usually classified as a tar compound, and only compounds having a molecular weight greater than that of benzene are considered as tar. Statistical information was not found, and only typical values were available in the literature.

3.3. Permissible Tar Limits in Syngas for Various Applications

It can be seen from Figure 4 that the dew point at which the tar compounds of a particular class condense varies with the concentration. This means that a tar compound of class 2, as defined in Table 2, condenses at ≈323 K if it is concentration is about 1 mg/Nm3; however, if the same class compound is present in a large concentration, which is about 10000 mg/Nm3, it will start to condense even at temperatures >373 K. Hence, understanding the dew points of different tar classes at different concentration is important to decide the amount of cleaning required to achieve the desired gas quality. This means that by reducing the concentration of tar in the product gas, the temperature at which they condense, i.e., the dew point of the tar compound, is lowered. If the dew point is lowered below the operating temperature of the application or preferably much below the ambient temperature, the condensation of tar leading to clogging can be avoided.
It can be inferred from Figure 4 that the class 5 tar compounds such as pyrene, i.e., heavy PAHs, are very critical in cleaning, as they can condense at a very high temperature, i.e., > 423 K, even if they are present in small concentrations of about 0.1 mg/Nm3. It is also to be noted that these heavy PAHs are the precursors of soot. (58) On the other hand, class 3 compounds, which are light aromatics such as benzene and toluene, seem to not condense at ambient temperatures and higher, even if their concentration is as high as about 10000 mg/Nm3. However, removing these compounds is necessary, (102) since BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are classified as priority pollutants and are considered as inhibitory compounds in FT synthesis. (78) Based on Table 4 and Figure 4, compounds that represent 33% of the tar formed can condense between 323 and 573 K if their concentration exceeds 1 mg/Nm3.
Figure 8 shows the tolerance level of tar concentration for several applications, (19) which implies that a higher gas purity level is required moving from applications such as IC engines (tar permissible limit of 100 mg/Nm3) to FT/methanol synthesis (tar permissible limit of 0.1 mg/Nm3).

Figure 8

Figure 8. Tar tolerance limits for downstream applications of a gasifier.

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4. Tar Destruction/Removal: Existing Technologies

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Measures for abatement or mitigation of tar can be broadly classified into primary (within the gasifier, in situ) and secondary (outside the gasifier, ex-situ). (27,36) Even though primary measures are the ideal approach for tar mitigation, it may not always be possible to completely achieve the desired tar levels for applications, as shown in Figure 8, without negatively impacting the quality of the gas, leading to a decrease in cold gas efficiency. In some cases, this may also result in complex gasifier construction, and achieving low tar levels might require a trade-off between gas quality and cold gas efficiency. Hence, a combination of in situ and ex situ measures is very effective to meet the gas purity standards. The following section will discuss the secondary measures for gas cleaning, which can be further classified into (1) physical or mechanical methods, (2) chemical methods, and (3) nonthermal plasma methods.
1.

Physical or mechanical methods involve the separation of tar compounds from the product gas and are used either directly on raw gas coming at a temperature >673 K (hot gas cleaning) or after cooling the raw gas to a temperature between 293 and 333 K (wet gas cleaning). (36) Hot gas cleaning prevents loss of heating value of the gas with minimal byproduct formation, whereas cold gas cleaning systems are much cheaper and effective with the loss of sensible heat. (31)

2.

Chemical methods involve the reformation or cracking of the tar compounds into useful gaseous compounds using a catalyst, heat, and/or steam. (118)

3.

Nonthermal plasma methods involve technology approaches like thermal/catalytic cracking, where instead of physical separation of unwanted compounds from the gas stream, cracking or reforming of condensable vapors to noncondensable gases is carried out. (119−128)

4.1. Mechanical or Physical Gas Cleaning Systems

Table 5 shows various hot and wet gas cleaning equipment whose working principles and other details are available in the literature. (36,78,102,129−133) Though physical cleaning systems are designed primarily to capture particulate matter from the product gas, they are also efficient for tar removal. This is possible because tars, while condensing at temperatures below 723.15 K, form aerosols heavier than vapors and can be removed by physical forces similar to removing particulate matter. (103) Table 6 shows the typical separation efficiencies reported in the literature for some of these systems. (133) As can be observed from Table 6, the separation efficiencies of these systems are not 100%; hence, depending on the type of removal system, multistage cleaning might be required, which adds to the cost of operation and maintenance. Though hot gas cleaning prevents the loss of energy value of the product gas, wet/dry gas cooling/scrubbing is the highly recommended method, since cooling gas is very effective to bring down the tar’s dew point. Typically, chiller water is used in gas cooling, which also scrubs the gas of particulate matter and tar compounds. Instead of water, organic scrubbing liquids are also used in a technology named OLGA technology. (134) Figure 9 shows a performance comparison of OLGA with other conventional technologies such as wet scrubber and wet ESP. (134,135) OLGA shows promising results, achieving removal efficiencies of >99% for all the classes of tar, whereas the ESP and wet scrubbers show selective performance of tar removal based on their classes, achieving efficiency mostly in the range of 50–75%.
Table 5. Mechanical/Physical Gas Cleaning Systems
methodequipment
hot or dry gas cleaningcyclone, rotating particle separators (RPS), electrostatic precipitators (ESP), filters (bag/baffle/ceramic/fabric/tube/sand bed), absorbers, etc.
cold or wet gas cleaningspray towers, packed column scrubbers (wash tower), scrubbers (impingement/venturi), wet ESP, OLGA, wet cyclones, etc.
Table 6. Tar Reduction Efficiency and Operating Temperature in Various Gas Cleaning Systems
 temperature (K)tar reduction (%)
sand bed filter283–29350–97
wash tower323–33310–25
venturi scrubber 50–90
wet ESP313–3230–60
fabric filter4030–50
RPS40330–70

Figure 9

Figure 9. Comparison of the tar removal performance of scrubber, ESP, and OLGA: heavy tar (black bar), light tar (red bar), heterocyclic (orange), and dew point (●).

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Although the physical separation process (like scrubbers) plays a significant role in tar removal from product gas, as predicted by Milne et al. (58) in 1998, the carcinogenic/hazardous tar is transferred into the scrubbing phase (water, oil, etc.) during the tar removal process, and the contaminated phase should be treated before disposal, keeping environmental concerns as a high priority. The recycling and reuse of these waste streams are reported to be complex, involving the separation of tar and contaminants from water.
The utilization of mechanical methods for the removal of tar from gasification processes faces certain limitations. These methods, such as filtration, condensation, and cyclones, encounter challenges when it comes to effectively removing fine tar particles and maintaining the overall efficiency of the system. Mechanical equipment used for tar removal, such as filters or scrubbers, can be prone to fouling and clogging. Tar deposits can accumulate on surfaces, reducing the efficiency of the equipment and necessitating frequent maintenance or cleaning. This can result in downtime and increased operational costs. Gasification processes often involve high temperatures, corrosive environments, and high-pressure conditions. These conditions can pose challenges for mechanical equipment and materials, as they may lead to corrosion, erosion, and mechanical failure. Specialized materials and designs may be required to handle these conditions effectively. These methods often require energy input to operate pumps, fans, or other equipment involved in tar removal. This energy consumption adds to the overall energy demands of the gasification process and can impact the efficiency and economics of the system. A concurrent summary of typical gas cleaning systems employed in an industrial scale gasifier, their tar removal efficiencies (in %), and concentration of tar left over is presented in section 4.2.3.

4.2. Chemical Methods of Gas Cleaning

4.2.1. Thermal and Steam Cracking

In thermal cracking, tar is converted into lighter gases with the help of oxidizing species at high temperatures, giving them enough residence time. The residence time is inversely related to the cracking temperature. For example, 80% of naphthalene is destructed/cracked in a residence time of 1 s when the cracking temperature is 1423 K, whereas when the temperature is reduced from 1423 to 1273 K the residence time for the same conversion level needs to be increased beyond 12 s; (103,13) at same time, by increasing the cracking temperature from 1273 to 1523 K, only 0.5 s of residence time was needed. (19,31) Hence, even though thermal cracking is simple conceptually, high process temperatures demand more sophisticated equipment and materials, which increase the cost. Also, very high cracking temperatures in the range of 1373–1573 K are necessary to minimize the reactor’s space. Thermal cracking is known to be economical only when it is used for large-capacity gasifiers.
Thermal cracking is also known for soot formation due to its high operating temperatures, though removing soot by spending additional energy is an option. (132) Soot formation can also be minimized through partial oxidation of product gas by adding oxygen or air or sometimes even steam─steam cracking/reforming. This might result in a decreased heating value, as the product gases also get partially oxidized. (103) For steam cracking of tar, higher steam-to-carbon molar ratios are required compared to that of industrial hydrocarbon steam reformation. (136) It is also reported that steam has a poor influence on the conversion of aromatics (58) and yields more phenolic tars, which are easy to reform catalytically. (58,137) According to Brandt et al., (138) employing steam cracking followed by charcoal catalysis can achieve a tar yield of as low as 15 mg/Nm3, which is still not enough to meet the purity levels expected by applications such as fuel cells, the FT process, or methanol synthesis, as shown in Figure 8.
Thermal cracking as a method for tar removal from gasification processes also has its limitations. While it can effectively break down tar into simpler compounds through high-temperature reactions, it may face challenges in completely converting complex tar molecules. Additionally, the process requires careful control of the temperature and residence time to avoid potential issues such as coke formation and reactor fouling. Proper design and optimization are crucial to achieving efficient and reliable tar removal using thermal cracking techniques.

4.2.2. Catalytic Cracking

Tar reduction using a catalyst is another promising technique, which can be implemented in two ways: (139) one way is integrating the catalyst with the input biomass to eliminate the tar within the gasifier itself (in situ approach), leading to what’s known as catalytic gasification or pyrolysis, and the second way is where tar is removed outside the gasifier in a secondary reactor packed with the catalyst. (58,139) Catalysts are effective in cracking tar compounds through reforming, cracking, hydrogenation, and selective oxidation, and many researchers have widely studied their performance over time. (27,68,70,115,140−151) Catalytic tar cracking is considered to be promising, as it can be performed at temperatures close to that of gasifier outlet. (151) The expectations of a catalyst material for tar cracking are summarized as follows: (152)
1.

Good activity and efficiency in removing tar present in a gas mixture (producer gas)

2.

Good stability to deactivation and poisoning

3.

Easy regeneration

4.

Good abrasive strength

5.

Inexpensive and ready availability

6.

Less harm to the environment

Although it is also mentioned in the literature that the catalyst should be capable of reforming methane, keeping hydrogen or syngas as the desired product, it should be noted that the volumetric composition of methane is significantly lower than those other species, such as H2, CO, and CO2, in the gasifier product gas. (153,154) Typically, the performance of catalytic tar cracking is dependent on the type of catalyst and its composition. A catalyst is composed of a metal (catalytic phase), a promoter (increase the activity or stability of the catalyst), and a support (for dispersion of the active phase). Typically, in the literature, (143,146,150,155−157) catalysts for tar reduction are broadly classified, as shown in Figure 10. The compositions of various catalysts with operating conditions that are used for tar reduction are shown in Table 7.

Figure 10

Figure 10. Catalyst materials for tar cracking.

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Table 7. Performance of Catalytic Tar Cracking
catalystsupportoperating conditions (°C)tar cracking (%)ref
Niquartz wool500–90043.2–100 (115,146−148,158−160)
RhSiO2550–700100 (143−145,161,162)
PtCeO280020–50 (149)
Ru(PPh3)3Cl260011.8–80 (163,164)
FeO 900100 (142)
Co and Nioxidized Shengli lignite char (OXAWSL)450–50076.3 (165)
Cawaste peat char (activated by CO2 (CPC) and KOH (APC))90094.4 (166)
Ru and Niα-Al2O3400–80097.8 (167)
Ni-xSiO2 @Cwood carbon (WC)500–65097 (168)
Ni-dopedbiochar (BC)60060 (169)
Ni–PtCe1-xZrxO2300–60090.4 (170)
Fe–NiAl2O3500–70063.8–100 (171,172)
CaNiRu MnNiRuα-Al2O3300–900100 (173)
Fe–Ni Cu–Niactivated carbon20099.1 (174)
Ni, Fe, and Mgzeolite80086 (175)
CaO-Ca12Al14O33Al2O3600–80073 (176)
Ni/Ru–Mnα-Al2O3600–1100100 (177)
PtCexZr1-X O2/Al2O370082 (178)
Ni/ACactivated carbon500–70099 (179)
biomass porous charK/Fe80094.9 (180,181)
activated char loaded with nickelactivated char600–80080 (182)
biochar 600–90082–100 (183−188)
Nickel is the most widely used catalyst among group VIII for steam/dry reformation, and it is also used for tar cracking. (153,154) Two types of Ni-tar cracking studies are reported in the literature: one is the oxidation of tar with O2, and another is the steam reformation of tar. The Ni is oxidized to NiO in the presence of oxygen, which catalyzes the combustion reaction, and Ni prefers a reformation reaction in the absence of O2. It is reported that partial oxidation is better in terms of removal (specifically in fluidized beds) and tar conversion than steam reforming. (153) Ni catalysts are reported to be more active for heavier hydrocarbons, which is key to avoid agglomeration of soot, and improves the H2 to CO ratio and the gas quality. It should be noted that the gasifier product gas also contains inorganic contaminants or impurities, as seen in Figure 1. Based on the nature of impurities, such as halides, siloxanes, etc., sintering, deactivation, and blocking of active sites of catalysts can occur. Although Ni is preferred due to its low cost and wide availability, (151) Ni catalysts (prereduced) are known for being poisoned by sulfides, metal chlorides, and alkali oxides, with reports of rapid deactivation from sulfur and high tar contents due to chemisorption. This could necessitate pretreatment of feed gas, which is not fulfilling the objective of catalytic tar cracking. Mohamed et al. (151) investigated influence of the prereduction stage on the tar reforming activity or cleaning of syngas in the presence of impurities such as HCl and H2S. The study showed that the prereduction stage, particularly the higher temperature in the prereduction stage, is important for stable and high activity of the Ni catalyst for tar reduction in the presence of impurities. Mohamed et al. (150) has discussed in detail advanced Ni tar-reforming catalysts that can resist syngas impurities, the current knowledge, research gaps, and future prospects; they emphasized that long-term studies on sintering due to impurities is important and mentioned the requirement of computations studies to understand the mechanism of deactivation.
Other transition metal catalysts, such as Rh, Ru, Pd, Pt, etc., were also developed and used for tar reduction. These catalysts are reported to have a high catalytic activity resisting impurities such as sulfides. (153) However, these transition metal catalysts are more expensive than the conventional Ni-based catalysts, making them difficult to use in large-scale systems despite the complete abatement of tar in the following order of performance Rh > Pt > Pd > Ni = Ru. Other metal catalysts such as Co, Fe, Zn, and Cu have been investigated for tar reduction, and some of them are more promising than Ni. (153)
Though alkaline catalysts are used in several studies showing improvement in gas quality and tar reduction, they have disadvantages due to their evaporation, formation of silicates as sticky deposits, and agglomeration at high temperatures. However, the alkaline species contained in the biomass can always play a catalytic role in situ and ex situ if released and mixed in the product gas, although they can be affected by sintering. The same is true for using ash as a catalyst, but it is known for particle agglomeration, which is a disadvantage.
Natural minerals such as dolomite and olivine are directly used as catalysts and show activity toward tar reforming. Their activity can be further increased by pretreating them using calcination. Calcined dolomite becomes very fragile, whereas calcined olivine maintains good mechanical strength. Both are cheaper and deactivated due to coke formation and carbon deposition, since the deposition reduces the surface area of the catalyst. Olivine has higher attrition resistance compared to dolomite, and its mechanical strength is comparable to that of sand, even at high temperatures. However, it is reported that the catalytic activity for tar reformation is slightly lower for olivine than for dolomite by 1.4×. Aluminosilicate earth metal minerals, such as zeolite, are known as molecular sieves. Zeolite diversity is extremely large; from both structure and chemistry points of view, each zeolite type has a three-letter nomenclature code assigned by the IUPAC commission. Among the zeolite types, Y, ZY, Zβ, ZSM5, and F-9 were studied for tar removal. These catalysts were also supported by a metal catalyst such as Ni, Fe, or Rh, and the Rh support showed the best effective tar removal at the lower loading concentration. Zeolites provide good thermal and hydrothermal stability in addition to high catalytic activity. More importantly, they are highly resistant to sulfides in the product gas of the gasifier and easily regenerated. Yet, deactivation due to coke formation/deposition is a major challenge, as for other catalytic materials, and the effect is dependent on the topology and associated acidic properties of the zeolite type. From this aspect, it is reported that carbon-supported catalysts having neutral or weak base properties have higher resistance to coke deposition and heavy metals than solid acid catalysts. Activated carbon is one such catalyst being explored for tar removal. Its mesopores effectively convert heavy hydrocarbon compounds to lighter catalysts, which will prevent coke/soot formation. In addition to the benefits of activated carbon’s macro- and mesopores improving the dispersion of metal ions, they also provide transport of reactant molecules into internal catalyst surfaces. Similarly, char (biochar/mineral char) is also widely used as a catalyst for tar cracking due to its highly porous structure. Feng et al. (189) proposed a mechanism and attributed tar-reforming reactions in the presence of biochar to the H/O/OH radicals. The tar compound adsorbed onto the active sites through the biochar layer suffers electron pair shift and breaks down at high temperatures, catalytically cracking to form the corresponding free radicals. Acid-washed char is reported to have better tar reformation activity than raw char, although the latter has higher catalytic activity. A detailed review on the performance of catalysts in tar removal is reported in literature. (36,150,153,156,157)

4.2.3. Performances of Some Tar Handling Methods in an Industrial Scale

In summary, Table 8 shows the performances of most of the above-discussed tar handling methods reported, which are operated on an industrial scale. (133,190−193) By observing Table 8, it is understood that OLGA manages to achieve removal efficiencies of 80–92% even when employed as hot gas cleaning (673 K), since oil-based scrubbers can be effective without cooling. Other than OLGA, which is used at high temperatures, only the venturi scrubbers and bed filters, which are used at low temperatures, show removal efficiencies >90%. Hence, multistage cleaning systems are always preferred, which is evident by observing Table 8. A combination of OLGA, a cyclone separator, and a wet scrubber is used in one system, (19) whereas a sand bed filter, wash tower, venturi scrubber, wet ESP, and fabric filter combination is used in another system. (133)
Table 8. Tar Removal Efficiencies Reported in the Literature during Operation on an Industrial Scale
methodtar compoundscaletreatment temperature (K)tar at inlet (g/Nm3)Tar at outlet (g/Nm3)removal efficiency in %ref
mechanical or physical removal methods 
OLGAreal tarindustrial673.158.6–3.20.7–0.680–92 (190)
cyclone separatortolueneindustrial 7.5–6.62.6–1.866–72 (191)
wet scrubbertolueneindustrial 2.6–1.81.0–0.759–63 (191)
sand bed filterreal tarindustrial283–293  50–97 (133)
wash towerreal tarindustrial323–333  10–25 (133)
venturi scrubberreal tarindustrial   50–90 (133)
wet electrostatic precipitatorreal tarindustrial313–323  0–60 (133)
fabric filterreal tarindustrial∼473.15  0–50 (133)
cracking methods
catalytic (dolomite, olivine)real tarindustrial973–11738.60.057>95 (192)
thermal (secondary air, partial oxidation)real tarindustrial>1373.1550.5212.974 (193)

4.3. Plasma Technology for Tar Reduction

As mentioned earlier in the introduction, plasma is a soup of reactive species, including electrons, ions, radicals, metastable compounds, excited neutrals, ground-state neutrals, and radiation. These species can dissociate and further reform the stable compounds like “tar” generated in gasification. For this reason, plasma technology has recently been explored for generating relatively clean raw gas from gasifiers and also for cleaning the raw impure gas, i.e., tar destruction. (124,125,194−198)
1.

Thermal plasma (TP) is used as a source of heat to provide a very high-temperature environment (>2273 K) inside the gasifier, enabling in situ tar cracking─plasma gasification.

2.

Nonthermal plasma (NTP) is used as a source of chemically active species by ionizing the compounds present in the gas to be cleaned, thereby enabling compounds of tar to be reformed; this reformation is possible at lower temperatures than that for the catalytic/thermal cracking.

Recent advancements in gasification technologies have honed in on in situ thermal plasma gasification as a progressive and efficient method for converting carbonaceous materials. In this process the feedstock, whether it is coal, biomass, or waste materials, undergoes high-temperature plasma treatment right at its original location. This approach offers notable benefits, including operational flexibility and reduced transportation costs. In situ, thermal plasma gasification enables the direct conversion of various feedstocks into high-quality syngas, CO, and H2 at elevated temperatures. This technology marks a significant leap toward sustainable waste management and clean energy production, providing a more compact and integrated solution for decentralized applications. Ongoing research aims to optimize the parameters, enhance the energy efficiency, and improve the economic feasibility of this innovative gasification approach. Kim et al. (199) applied nontransferred DC steam plasma to liquid hazardous waste (PCBs, chlorinated solvents, and pesticides) at atmospheric pressure (1200–1400 °C). Treating a PCB/CCl4 mixture (27–73%) with superheated steam as a plasma gas, heat carrier, and reactive gas resulted in approximately 30% combustible gas in the syngas (29% CO, 1% CH4). The study concluded steam plasma is more effective in waste-to-energy and hazardous waste treatment than air plasma. (199) Vecten et al. (200) conducted pioneering experiments on the steam gasification of biomass, specifically wood pellets. These experiments were carried out in a lab-scale atmospheric pressure moving bed microwave-induced plasma reactor utilizing pure steam as the plasma gas. Notably, this study marked the initial application of microwave (MW) technology for biomass gasification in the presence of pure steam. (200) The advantages of employing pure steam plasma are emphasized through the production of hydrogen-rich syngas featuring a high calorific value within the range of 10.5–12 MJ/Nm3. The suggested method holds promise as an efficient avenue for the sustainable generation of fuels, chemicals, and energy from biomass. Vecten et al. (200) provide insights into the composition of syngas, reporting the following volume percentages: H2 (45–65%), CO (15–30%), CO2 (10–20%), CH4 (5–10%), and LHV (10.5–12 MJ/m3). A more comprehensive review on thermal plasma gasification can be found in the literature. (201−213)
Nonthermal plasma (NTP) technology offers several advantages for tar removal from gasification processes. (116,124,125,127,194,195,214−221) Some of the key advantages of using nonthermal plasma for tar removal include the following: (1) high reaction rates (222−226) due to the presence of energetic electrons and other species; (2) nonselective reactivity (223−225,227) due to the possibility to simultaneously break down a wide range of tar compounds in the mix unlike catalysts, a suitable feature for scenarios such as gasifier tar containing mixture of tar compounds; (3) wide operating temperature ranges; (114,228−232) (4) scalability, allowing gas cleaning in different scales of gasification operations from lab and pilot scales to industrial scale; and (5) environmental benefits (225,228,233) due to converting the tar compound rather than separating the tar compounds from the gas, which pollutes the environment upon disposal.
In recent times, plasma combined with catalysts (plasma catalysis) has also been explored for tar reduction to get a synergetic effect. The integration of nonthermal plasma and catalysts can enhance the overall efficiency and effectiveness of tar removal. (36,94,95,117,216,224,229,234−238) On one hand, plasma can aid the regeneration of catalysts, increasing the life span of the catalysts. (239) On the other hand, the catalyst can provide selective tar decomposition, since plasma is nonselective in treating the tar compounds because it can collide and react with any chemical species. (117,229,234) Plasma catalysis can support lowering the operating temperatures, leading to energy savings, and reduced operational costs. (197,240) Further research and development efforts are needed to optimize the combination of these technologies, including catalyst selection, plasma reactor design, and operating conditions, to maximize the synergistic benefits and enhance the overall efficiency of removal of tar from gasification-derived syngas. Typical plasma sources attempted for tar destruction include corona, dielectric barrier discharge, gliding arc, and spark/glow discharge, including microwave and radio frequency discharge systems, which are considered as nonthermal plasmas. (225,227,233,241) Tar resulting from gasification consists of a blend of aromatic compounds. When subjecting such a complex mixture to a plasma environment, the comprehension of the chemistry between tar and plasma during the initial stages of research becomes challenging. Therefore, most of the available studies on tar destruction using plasmas focus on investigating the destruction of simulated individual tar compounds, except for the study conducted by Eliott et al., (242) which examined pine tar. Naphthalene and toluene are commonly chosen as representative tar compounds for analysis, as they are known to be the predominant constituents of gasification tar. (123−125,194,195,216,219,221,243−246) On the other hand, benzene, pyrene, anthracene, fluorine, and acenaphthene are rarely studied. Nair et al. (247) also reported that the efficiency of tar removal using plasma is influenced by the structure of the compounds. For instance, naphthalene is highly stable and difficult to decompose, while one-ring aromatic compounds can be easily dissociated but may require more energy for decomposition due to the high likelihood of recombination among their dissociated fragments.
Figure 11 shows the specific energy input (SEI) for tar destruction. Mostly toluene and naphthalene were chosen as tar compounds to be cleaned by various plasma sources (123−125,194,195,216,219,221,243−247) considering mostly they are representative tar compounds. Typically, an electricity consumption of 5–15% of the total electricity produced is considered reasonable to spend for cleaning the gasification product, which is 100–300 J/L or 0.03–0.08 kWh/m3 that can be kept as target SEI to achieve. (227) From Figure 11, it is evident that dielectric barrier discharge (DBD) exhibits the highest average SEI compared with other plasma sources. The average SEI values for the catalytic DBD and DBD are 6.1 and 12.9 kWh/m3, respectively. Corona (227) demonstrates the lowest average SEI of 0.2 kWh/m3, followed by gliding arc, catalytic gilding arc, and rotating gliding arc in the range of 0.5–0.8 kWh/m3. However, it is important to note that the graphical representation in Figure 11 obscures the influence of other operating conditions. Gliding arc reactors seem promising in achieving low SEIs and have been the recent focus of research. However, it is true that energy spending using this approach can still be relatively high, and ongoing research is focused on addressing this challenge.

Figure 11

Figure 11. Specific energy inputs for various plasma sources used for tar destruction.

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4.3.1. Modeling in Gasification

As mentioned, the gasification process has many key operating factors, such as feed stock, gasifying agent, pressure, and temperature, whose changes can influence the product composition and thereby the gasification performance heavily. This might result in time-consuming and costly experiments to design a reactor. Under such circumstances, a computational route can be effective to design and optimize the gasifier in less cost and time. The fundamental approach in the computational route is to have a mathematical model that can represent the physical and chemical phenomena involved in the gasification process, both in situ and ex situ processes. Based on the objective of the modeling, suitable assumptions can be made to simplify the model’s complexity, and one should be careful with the understandings derived from the modeling. However, qualitative information derived from the modeling on the influence of the operating factors is considered useful. In 2022, Kushwah et al. (248) published a detailed review in the modeling approaches for biomass gasifiers. Similarly, Sikarwar et al. (19) also provided a brief discussion on modeling. The modeling approaches are typically classified into thermodynamic, reaction kinetic, computational fluid dynamics (CFD), and data-driven.
Thermodynamic modeling is based on minimization of the Gibbs free energy, predicting the stable composition of the product and the probable species to be present in the product when the gasifier is in chemical equilibrium. (249−253) The predicted composition is considered the benchmark and is compared to the performance of the gasifier in the real scenario. Thermodynamic modeling is further classified into stoichiometric and nonstoichiometric modeling. Thermodynamic modeling has its own advantages, since it can be used easily for a wide range of systems due to low computational requirements and can be used to see if gasifier has achieved equilibrium that will give stable yield. However, this model does not consider reaction time and reactor geometry.
Kinetic modeling considers factors that are not accounted for in the thermodynamic modeling that will help to represent the chemistry inside the gasifier, which varies in space and time. Kinetic model includes many operating variables representing the property of fuel, the hydrodynamics of the reactor, the design of the reactor, and so on in addition to temperature and pressure considered in the thermodynamic modeling. Kinetic modeling helps to predict the temporal gas composition and can be used to understand the reaction mechanisms. However, the model relies heavily on reaction rate estimation, and complete reaction mechanics are partially understood and computationally more expensive than those in thermodynamic modeling. (254−260)
With the kinetic modeling accounting for the effect of operational parameters on the chemistry, CFD modeling invokes the kinetic modeling and the resulting fluxes (in/out) of mass, momentum and energy on a suitable control domain constrained by boundary conditions. With the CFD model, a scenario close to real gasifier operation can be simulated, predicting the heterogeneous chemistry in the gasifier taking into the account the changes in energy, mass, and momentum spatially. (261−263) An inappropriate solution is also possible if the flow models involving turbulence and multiphase are wrongly chosen.
Because the CFD model most accurately mimics the gasifier, it is also computationally expensive. This motivates the use of data-driven modeling, wherein correlations between the variables are used to gain helpful findings without getting an analytical answer. To balance the lack of physics in the pure data-drive model, a stoichiometric equilibrium model was coupled with regression of data driven models such as artificial neural network (ANN). (264,265) Although data-driven modeling is reported to accurately reflect nonlinearity, it requires large data sets from experiments, and the performance will be poor with new inputs (change in input features considered in the model).
There is still significant scope for improving the modeling approaches to understand the physics/chemistry of gasification to support the design and optimization of the gasifier. Relevant to the context of this review work, the modeling of tar is likely to be one of the most active research topics to understand how to regulate tar formation. Tar modeling is reported to be difficult even in CFD modeling, which accounts for most of the operational factors that influence the tar formation and yield.

Conclusion

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Syngas cleaning for tar removal is a critical step for the syngas to be used further in the applications. A thorough understanding of gasifier chemistry, gasifier configuration, tar formation during gasification, tar classification based on composition, required extent of tar removal from syngas, and working science of tar removal technology is important. It is very evident that only through multistage cleaning (addition to in situ mitigation of tar formation) can the desired syngas purity be achieved using the existing secondary tar removal technologies. Catalytic tar removal techniques have shown great potential in tar removal with high thermal stability, without the necessity to use syngas cooling, which is required in most other technologies, thereby preventing a loss in cold gas efficiency. However, catalyst deactivation due to other syngas impurities and coke, fouling, and sintering needs to be addressed for successful implementation.
Nonthermal plasma technologies offer an alternative approach to tar removal by utilizing energetic electrons and reactive species to break down tars through oxidation and cracking reactions. Plasma-assisted tar removal exhibits high reaction rates and can handle a wide range of tar compositions. However, careful control of operating parameters, reactor design, and effective energy management is crucial for achieving cost-effectiveness and scalability.
Overall, a combination of mechanical, catalytic, and nonthermal plasma methods holds significant promise for efficient tar removal from gasification processes. Integrating multiple techniques can synergistically enhance the tar conversion efficiency and syngas quality. Future research should focus on developing hybrid systems that capitalize on the strengths of each method and optimizing operating conditions to minimize energy consumption and environmental impact. Both experimental and simulation techniques should be used to optimize the syngas cleaning. The successful implementation of tar removal strategies will contribute to the wider adoption of gasification technology for clean energy production and various downstream applications. Advancements in tar removal techniques will not only improve the overall efficiency of gasification processes but also reduce the environmental footprint associated with syngas utilization. Continued research and development efforts in this field are essential for achieving sustainable and economically viable gasification systems in the future.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.3c04425.

  • Typical tar levels reported in literature for various operating conditions (PDF)

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Author Information

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  • Corresponding Author
  • Authors
    • Ananthanarasimhan Jayanarasimhan - Centre for Sustainable Technologies, Indian Institute of Science, Bengaluru, Karnataka 560012, India;  Orcidhttps://orcid.org/0000-0001-7490-9354
    • Ram Mohan Pathak - Centre for Sustainable Technologies, Indian Institute of Science, Bengaluru, Karnataka 560012, India;  Orcidhttps://orcid.org/0000-0002-4444-0185
    • Anand M. Shivapuji - Centre for Sustainable Technologies, Indian Institute of Science, Bengaluru, Karnataka 560012, India
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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No external funding agency was involved in this work. Authors would like to acknowledge and thank Indian Institute of Science, Bangalore, India, for the support.

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    Climate change and fossil fuel depletion are the main reasons leading to hydrogen technol. There are many processes for hydrogen prodn. from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen prodn. methods is carried out. The process descriptions along with the tech. and economic aspects of 14 different prodn. methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochem. pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 prodn. with costs in the range of 1.34-2.27 $/kg. Biol. methods appear to be a promising pathway but further research studies are needed to improve their prodn. rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources.
  3. 3
    Angelis-Dimakis, A.; Biberacher, M.; Dominguez, J.; Fiorese, G.; Gadocha, S.; Gnansounou, E.; Guariso, G.; Kartalidis, A.; Panichelli, L.; Pinedo, I.; Robba, M. Methods and Tools to Evaluate the Availability of Renewable Energy Sources. Renewable and Sustainable Energy Reviews 2011, 15 (2), 1182– 1200,  DOI: 10.1016/j.rser.2010.09.049
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    Tripathi, P.; Rao, L. Single Particle and Packed Bed Combustion Characteristics of High Ash and High Plastic Content Refuse Derived Fuel. Fuel 2022, 308, 121983  DOI: 10.1016/j.fuel.2021.121983
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    Single particle and packed bed combustion characteristics of high ash and high plastic content refuse derived fuel
    Tripathi, Priyanka; Rao, Lakshminarayana
    Fuel (2022), 308 (), 121983CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    This work reports fundamental combustion characteristics of high ash (≈ 18%), high plastic (30-35%) content refuse derived fuel (RDF) pellets produced currently in India. Single particle and packed bed studies of RDF were carried out to quantify RDF combustion times and RDF ash fusion behavior, resp. Single particle studies concluded that RDF has glowing time to flaming time ratio of ∼ 3.5, which was similar to that of biomass and four times lower than that of coal. It was also obsd. that unlike biomass, upon heating, RDF particle showed a unique 5.6 to 10.3% swelling behavior due to the melting of plastic. Packed bed expts. at different air mass flux on RDF pellets concluded that apart from air mass flux, ash content plays a decisive role on rate of flame propagation. The high plastic content of fuel increased ash fusion tendency inside the packed bed. Packed bed studies suggested max. superficial velocity of ≤ 0.03 m s-1 to avoid clinker formation. Sieve anal. of RDF ash collected from packed bed studies reported soft ash at a lower air mass flux and bigger lumps of fused ash at higher air mass flux. Clinkers obtained at different air mass flux 0.02, 0.07, 0.13 kg m-2 s-1 were 1%, 8% and 11% of the feed, resp.
  5. 5
    Choi, Y. K.; Ko, J. H.; Kim, J. S. Gasification of Dried Sewage Sludge Using an Innovative Three-Stage Gasifier: Clean and H2-Rich Gas Production Using Condensers as the Only Secondary Tar Removal Apparatus. Fuel 2018, 216, 810– 817,  DOI: 10.1016/j.fuel.2017.12.068
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    Gasification of dried sewage sludge using an innovative three-stage gasifier: Clean and H2-rich gas production using condensers as the only secondary tar removal apparatus
    Choi, Young-Kon; Ko, Ji-Ho; Kim, Joo-Sik
    Fuel (2018), 216 (), 810-817CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Air gasification of dried sewage sludge was performed in a new-type three-stage gasifier consisting of an auger, a fluidized bed, and a tar-cracking reactors. The study aimed to evaluate the possibility of gasification using only condensers for the secondary tar removal method. The effects of Ni- and Fe-impregnated active carbons on the quality of producer gas were also investigated. Finally, to investigate the deactivation behavior of active carbon, a spent active carbon obtained after about 4.3 h of gasification, was used again for approx. 3.7 h of gasification. The active carbons used effectively reduced the contents of condensed and gaseous tars. Ni-impregnated active carbon produced a gas with a high H2 content (26 vol%) and a low NH3 content (198 ppmv), while Fe-impregnated active carbon produced a gas with a low H2S content (96 ppmv). The compns. of the producer gases obtained solely using condensers were similar to those obtained using electrostatic precipitator. During the total ∼8 h of gasification, active carbon could efficiently remove tar; however, its surface area and total pore vol. slowly decreased with time.
  6. 6
    Munir, M. T.; Mardon, I.; Al-Zuhair, S.; Shawabkeh, A.; Saqib, N. U. Plasma Gasification of Municipal Solid Waste for Waste-to-Value Processing. Renewable Sustainable Energy Rev. 2019, 116, 109461,  DOI: 10.1016/j.rser.2019.109461
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    Plasma gasification of municipal solid waste for waste-to-value processing
    Munir, M. T.; Mardon, I.; Al-Zuhair, S.; Shawabkeh, A.; Saqib, N. U.
    Renewable & Sustainable Energy Reviews (2019), 116 (), 109461CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Plasma gasification can be a viable technol. for converting municipal solid waste (MSW) into value for the circular economy. However, in its current state, plasma gasification is mostly limited to lab or pilot scales as there are various challenges assocd. with it; there exist knowledge gaps which need attention and research for its successful future commercialization. The present study critically reviewed the current status of plasma gasification for waste-to-value processing. Various traditional techniques for MSW disposal and processing available in the literature were discussed and were compared with plasma gasification in terms of cost, service life, energy comparison, and environmental impact comparison. After the review, knowledge gaps were identified, challenges assocd. with the plasma gasification technol. were discussed, and a possible roadmap for the successful future commercialization of plasma gasification for waste-to-value processing was suggested. Furthermore, various strategies to cope with challenges assocd. with plasma gasification were discussed. The successful commercialization of plasma gasification can be achieved by reducing its costs by generating revenue or value in the form of synthesis gas or fuels from MSW, energy can be saved or reused using insulation, process integration, and process intensification, the technol. and community readiness levels can be improved with better communication between relevant stakeholders and adding extra layers of safety, and process understanding can be improved by conducting extensive fundamental studies, as well as plasma gasification technol. being standardized by establishing stds. and stds. organizations.
  7. 7
    Ciuta, S.; Tsiamis, D.; Castaldi, M. J. Gasification of Waste Materials: Technologies for Generating Energy, Gas, and Chemicals from Municipal Solid Waste, Biomass, Nonrecycled Plastics, Sludges, and Wet Solid Wastes; Academic Press, 2018.
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    Quan, L. M.; Kamyab, H.; Yuzir, A.; Ashokkumar, V.; Hosseini, S. E.; Balasubramanian, B.; Kirpichnikova, I. Review of the Application of Gasification and Combustion Technology and Waste-to-Energy Technologies in Sewage Sludge Treatment. Fuel 2022, 316, 123199,  DOI: 10.1016/j.fuel.2022.123199
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    Application of gasification and combustion technology and waste-to-energy technologies in sewage sludge treatment
    Quan, Le Minh; Kamyab, Hesam; Yuzir, Ali; Ashokkumar, Veeramuthu; Hosseini, Seyed Ehsan; Balasubramanian, Balamuralikrishnan; Kirpichnikova, Irina
    Fuel (2022), 316 (), 123199CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    A review. Gasification and combustion processing is deemed reliable and feasible methods in response to concerns about landfilling - a traditional treatment due to rapid growth in disposal capacity and pollution. In gasification and combustion processing, various processes are integrated with different configurations to carry out energy conversion of the thermal treatment process and improve the energy recovery efficiency. This study aimed to propose an effective soln. to waste treatment by considering the sustainability and economic perspectives. This paper provided the observation on the tech. perspectives of the gasification and combustion processes: the properties of sludge, reactor, combustion or gasification media and operating conditions applied to sewage sludge treatment. In addn., the application of the thermodn. cycle with various heat recovery strategies for electricity generation was summarized in this paper. According to the research data, sewage sludge combustion efficiency reached up to 99% at the combustion temp. of 800-850°C. The max. hydrogen gas (H2) content was recorded at 40 mol% under steam/oxygen gasifying agent, and the low heating value of syngas was 6-7 MJ/Nm3 for sewage sludge gasification. The integration between air gasification, external fired gas turbines (EFGT) without carbon capture process showed the highest exergy efficiency at 37.1%, which was higher than 35.7% resulted from waste combustion technol.
  9. 9
    Migliaccio, R.; Brachi, P.; Montagnaro, F.; Papa, S.; Tavano, A.; Montesarchio, P.; Ruoppolo, G.; Urciuolo, M. Sewage Sludge Gasification in a Fluidized Bed: Experimental Investigation and Modeling. Ind. Eng. Chem. Res. 2021, 60 (13), 5034– 5047,  DOI: 10.1021/acs.iecr.1c00084
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    Sewage sludge gasification in a fluidized bed: Experimental investigation and modeling
    Migliaccio, Renata; Brachi, Paola; Montagnaro, Fabio; Papa, Salvatore; Tavano, Alberto; Montesarchio, Pietro; Ruoppolo, Giovanna; Urciuolo, Massimo
    Industrial & Engineering Chemistry Research (2021), 60 (13), 5034-5047CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Fluidized bed gasification is a promising process technol. to manage the growing amt. of sewage sludge (SS) requiring disposal. Two samples of SS, produced in different seasons of the year by a municipal wastewater treatment plant, were subjected to gasification at 850°C in a bench-scale fluidized bed reactor using, as a gasification agent, a nitrogen/air mixt. at different values of oxygen/fuel equivalence ratio (ER = 0.1-0.2). The starting materials and the output streams (syngas, tar, and solid residues) were thoroughly characterized. The fate of specific SS constituents and the characteristics of bottom ashes were addressed, so contributing to the problem of a proper SS management approach in the context of the circular economy. Computer-aided simulations were also performed, which allowed us to predict the compn. of the syngas from SS gasification under operating conditions different from those exptl. investigated (i.e., reactor temp. and ER).
  10. 10
    Chanthakett, A.; Arif, M. T.; Khan, M. M. K.; Oo, A. M. T. Performance Assessment of Gasification Reactors for Sustainable Management of Municipal Solid Waste. J. Environ. Management 2021, 291, 112661,  DOI: 10.1016/j.jenvman.2021.112661
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    Performance assessment of gasification reactors for sustainable management of municipal solid waste
    Chanthakett Apinya; Arif M T; Oo Aman M T; Khan M M K
    Journal of environmental management (2021), 291 (), 112661 ISSN:.
    The issue of waste management has received considerable critical attention due to the increase of waste generation worldwide. One of the solutions for waste disposal that has been widely implemented is through the use of the landfill due to its economic benefits. Landfill, however, results in many adverse impacts on the environment and human health. Recycling can extract some useful materials from waste, however not every waste can be recycled and a significant volume of waste, particularly the municipal solid waste (MSW) goes to landfill even though it has extractable energy potentials. Extraction of energy from MSW has been a key focus of research due to the scope of energy recovery, environmental and economic benefits. The principal concept of waste to energy is to convert waste into energy through thermal and/or biological processes. In addition, thermochemical processes such as gasification have been found as a promising technology offering several benefits. This paper presents a critical assessment of waste to energy gasification technology for MSW on processing, energy recovery, environmental performance and economic perspectives. These aspects have been analyzed for the landfill as well. The review also explored and identified suitable simulation tools for optimizing gasification. Subsequently, an assessment and comparison of different gasification reactors were carried out which indicate that the plasma gasification can be a feasible technology for MSW management due to higher energy efficiency (816 kWh/tonne) with minimum emission and lowest residue. Although plasma gasification is an energy intensive application which has relatively higher investment cost, it can be built as a large system (up to several 1000 MW system), which can make it economically competitive too. Other technologies such as; fluidized bed gasifier, fixed bed gasifier also have good energy efficiency (547-571 kWh/tonne) however, they contribute to higher CO2 emission. Considering overall waste management, it was found that gasification technology is beneficial to economy, environment and energy extraction compared to the landfill option. A number of tools and their relevant properties have been identified to develop appropriate gasifier model. It is expected that this study will advance further research and innovation that will be helpful to manage waste efficiently as well as to improve the environment.
  11. 11
    Wang, B.; Gupta, R.; Bei, L.; Wan, Q.; Sun, L. A Review on Gasification of Municipal Solid Waste (MSW): Syngas Production, Tar Formation, Mineral Transformation and Industrial Challenges. Int. J. Hydrogen Energy 2023, 48, 26676– 26706,  DOI: 10.1016/j.ijhydene.2023.03.086
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    11
    A review on gasification of municipal solid waste (MSW): Syngas production, tar formation, mineral transformation and industrial challenges
    Wang, Ben; Gupta, Rajender; Bei, Lei; Wan, Qianmin; Sun, Lushi
    International Journal of Hydrogen Energy (2023), 48 (69), 26676-26706CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    This review provides an overview of the research progress related to syngas quality, tar formation, and minerals transformation. In addn., this paper gives a detailed description of the current technol. under construction and com. applications. On this basis, the challenges and prospects for the com. operation are outlined. In general, different gasification agents have crit. temps. and attention should be paid to the temp. window of 700-850°C, between which free energy of Boudouard reaction is lower than that of water-gas reaction. Above the crit. temp., the reverse water-gas shift reaction will be promoted to inhibit H2 release. Oxidant/municipal solid waste (MSW) ratio has an optimal value, which is esp. obvious for air atm. The optimal equivalence ratio is usually in the range of 0.1-0.4, and the LHV of the synthetic gas is in 4-10 MJ/m3. Steam to MSW ratio usually varies in a wide range and excess steam may have little impact on syngas quality. Simulation evaluation of parameter wt. shows steam to MSW ratio in steam atm. is the most important influencing factor, while temp. in air atm. plays a decisive role in the conversion of syngas. High temp. in the air atm. and low temp. in the steam atm. are the best choice for MSW gasification. The existence form of tar in different atmospheres is also quite different, such as PAHs in CO2 atmosphere and chain hydrocarbons in steam atm. The development of efficient catalyst gradually becomes a tech. bottleneck. Non-volatile minerals usually retain in bottom slag during MSW gasification. Elements with high b.ps. are existed in the form of metal, while heavy metals with low b.ps. are captured in the fly ash. The steam atm. can promote the volatilization of heavy metals. Most of the toxic heavy metals enter into the fly ash, so the leaching ability of the bottom slag is significantly weakened. Apart from tech. bottlenecks such as unstable syngas quality, catalyst deactivation, fouling and slagging, and MSW treatment capacity, great effort should be given to lower its investment cost and operation costs such as syngas purifn. and reforming. At the same time, energy price regulatory and policy barriers that affect the market should be addressed.
  12. 12
    Erdiwansyah; Gani, A.; Zaki, M.; Mamat, R.; Nizar, M.; Rosdi, S. M.; Yana, S.; Sarjono, R. E. Analysis of Technological Developments and Potential of Biomass Gasification as a Viable Industrial Process: A Review. Case Stud. Chem. Environ. Eng. 2023, 8, 100439,  DOI: 10.1016/j.cscee.2023.100439
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    12
    Analysis of technological developments and potential of biomass gasification as a viable industrial process: A review
    Erdiwansyah; Gani, Asri; Zaki, M.; Mamat, Rizalman; Nizar, Muhammad; Rosdi, S. M.; Yana, Syaifuddin; Sarjono, R. E.
    Case Studies in Chemical and Environmental Engineering (2023), 8 (), 100439CODEN: CSCED5; ISSN:2666-0164. (Elsevier Ltd.)
    - They use technologies for the thermochem. conversion of substances for biomass, like pyrolysis, torrefaction, gasification, and hydrothermal process. In recent years, the generation of synthetic gas has significantly developed. This is esp. true when assocd. with the biomass gasification processes, primarily related to syngas prodn. The review focuses on technologies for cleaning syngas, gasification processes, and simulation methods on procedure parameters. In conclusion, prospect growths and opportunities are investigated, and discussions culminate with the presentation of a novel hydrogen fabrication strategy predicated on utilizing a modified combustion process that operates with such an air deficit.
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    Mishra, S.; Upadhyay, R. K. Review on Biomass Gasification: Gasifiers, Gasifying Mediums, and Operational Parameters. Mater. Sci. Energy Technol. 2021, 4, 329– 340,  DOI: 10.1016/j.mset.2021.08.009
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    Review on biomass gasification: Gasifiers, gasifying mediums, and operational parameters
    Mishra, Somya; Upadhyay, Rajesh Kumar
    Materials Science for Energy Technologies (2021), 4 (), 329-340CODEN: MSETBW; ISSN:2589-2991. (Elsevier B.V.)
    A review. The burning of fossil fuels causes the av. global surface temp. to rise every year by 0.6 to 0.9 K between 1906 and 2005 causing massive ecol. imbalance and an increase in global warming as reported by Intergovernmental Panel on Climate Change (IPCC). Biomass gasification is an enhanced and mature technol. that has the capability of replacing fossil fuels. Despite the presence of vast literature, biomass technol. still needs improvement. This paper discusses the crit. overview of biomass gasification, the technologies embedded, and the deciding parameters for producing valuable products such as syngas, bio-fuels, bio-char, power, heat, and fertilizer, which can be further utilized in power generation units, and fuel-cell technologies. The paper assimilates the information available in past studies of biomass gasification and presents a comprehensive of various gasifiers and gasifying mediums employed, followed by introducing supercrit. water (SCW) gasification. Future directions for readers are also discussed.
  14. 14
    Shivapuji, A. M.; Dasappa, S. Influence of Fuel Hydrogen Fraction on Syngas Fueled SI Engine: Fuel Thermo-Physical Property Analysis and in-Cylinder Experimental Investigations. Int. J. Hydrogen Energy 2015, 40 (32), 10308– 10328,  DOI: 10.1016/j.ijhydene.2015.06.062
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    14
    Influence of fuel hydrogen fraction on syngas fueled SI engine: Fuel thermo-physical property analysis and in-cylinder experimental investigations
    Shivapuji, Anand M.; Dasappa, S.
    International Journal of Hydrogen Energy (2015), 40 (32), 10308-10328CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Hydrogen, either in pure form or as a gaseous fuel mixt. specie enhances the fuel conversion efficiency and reduce emissions in an internal combustion engine. This is due to the redn. in combustion duration attributed to higher laminar flame speeds. Hydrogen is also expected to increase the engine convective heat flux, attributed (directly or indirectly) to parameters like higher adiabatic flame temp., laminar flame speed, thermal cond. and diffusivity and lower flame quenching distance. These factors (adversely) affect the thermo-kinematic response and offset some of the benefits. The current work addresses the influence of mixt. hydrogen fraction in syngas on the engine energy balance and the thermo-kinematic response for close to stoichiometric operating conditions. Four different bio-derived syngas compns. with fuel calorific value varying from 3.14 MJ/kg to 7.55 MJ/kg and air fuel mixt. hydrogen fraction varying from 7.1% to 14.2% by vol. are used. The anal. comprises of (a) use of chem. kinetics simulation package CHEMKIN for quantifying the thermo-phys. properties (b) 0-D model for engine in-cylinder anal. and (c) in-cylinder investigations on a two-cylinder engine in open loop cooling mode for quantifying the thermo-kinematic response and engine energy balance.With lower adiabatic flame temp. for Syngas, the in-cylinder heat transfer anal. suggests that temp. has little effect in terms of increasing the heat flux. For typical engine like conditions (700 K and 25 bar at CR of 10), the laminar flame speed for syngas exceeds that of methane (55.5 cm/s) beyond mixt. hydrogen fraction of 11% and is attributed to the increase in H based radicals. This leads to a redn. in the effective Lewis no. and laminar flame thickness, potentially inducing flame instability and cellularity.Use of a thermodn. model to assess the isolated influence of thermal cond. and diffusivity on heat flux suggests an increase in the peak heat flux between 2% and 15% for the lowest (0.420 MW/m2) and highest (0.480 MW/m2) hydrogen contg. syngas over methane (0.415 MW/m2) fueled operation. Exptl. investigations indicate the engine cooling load for syngas fueled engine is higher by about 7% and 12% as compared to methane fueled operation; the losses are seen to increase with increasing mixt. hydrogen fraction. Increase in the gas to electricity efficiency is obsd. from 18% to 24% as the mixt. hydrogen fraction increases from 7.1% to 9.5%. Further increase in mixt. hydrogen fraction to 14.2% results in the redn. of efficiency to 23%; argued due to the changes in the initial and terminal stages of combustion. On doubling of mixt. hydrogen fraction, the flame kernel development and fast burn phase duration decrease by about 7% and 10% resp. and the terminal combustion duration, corresponding to 90%-98% mass burn, increases by about 23%. This increase in combustion duration arises from the cooling of the near wall mixt. in the boundary layer attributed to the presence of hydrogen. The enhancement in engine cooling load and subsequent redn. in the brake thermal efficiency with increasing hydrogen fraction is evident from the engine energy balance along with the cumulative heat release profiles.
  15. 15
    Moriconi, N.; Laranci, P.; D’Amico, M.; Bartocci, P.; D’Alessandro, B.; Cinti, G.; Baldinelli, A.; Discepoli, G.; Bidini, G.; Desideri, U.; Cotana, F.; Fantozzi, F. Design and Preliminary Operation of a Gasification Plant for Micro-CHP with Internal Combustion Engine and SOFC. Energy Procedia 2015, 81, 298– 308,  DOI: 10.1016/j.egypro.2015.12.100
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    Design and Preliminary Operation of a Gasification Plant for Micro-CHP with Internal Combustion Engine and SOFC
    Moriconi, N.; Laranci, P.; D'Amico, M.; Bartocci, P.; D'Alessandro, B.; Cinti, G.; Baldinelli, A.; Discepoli, G.; Bidini, G.; Desideri, U.; Cotana, F.; Fantozzi, F.
    Energy Procedia (2015), 81 (), 298-308CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
    A gasification plant was designed and built to test syngas prodn. from biomass for electricity generation on microscale. The plant is mainly composed by a downdraft reactor, a gas cleaning section with a cyclone and a wet scrubber, a blower for syngas extn. and an ICE (Internal Combustion Engine, Lombardini LGA 340), equipped with an alternator. A small quantity of producer was also eventually sent to a button cell SOFC (Solid Oxide Fuel Cell) for preliminary characterization. The plant was tested in a preliminary exptl. campaign to evaluate mass and energy balances and process efficiency. Woody biomass was used and the producer gas firstly passed through impingers bottles, to condense and measure tar concn. (according to CEN/TS 15439), and then the remaining uncondensed gas was analyzed with a micro-GC (Gas Chromatograph). The paper presents and discusses the results of the preliminary tests carried out.
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    Sridhar, H. V.; Sridhar, G.; Dasappa, S.; Paul, P. J.; Mukunda, H. S. On the Operation of a High Pressure Biomass Gasifier with Gas Turbine; In Proceedings of the 15th European Biomass Conference Paper and Exhibition, Berlin, Germany, May 7–11, 2007; ETA-Florence Renewable Energies: Florence, Italy, 2007.
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    Proceedings of the 10th Asian Mining Congress 2023: Roadmap for Best Mining Practices Vis-À-VIS Global Transformation; Sinha, A., Sarkar, B. C., Mandal, P. K., Eds.; Springer Proceedings in Earth and Environmental Sciences; Springer, 2023.
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    Handbook of Climate Change Mitigation; Chen, W. Y., Seiner, J., Suzuki, T., Lackner, M., Eds.; Springer, 2012.  DOI: 10.1007/978-1-4419-7991-9 .
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    Sikarwar, V. S.; Zhao, M.; Clough, P.; Yao, J.; Zhong, X.; Memon, M. Z.; Shah, N.; Anthony, E. J.; Fennell, P. S. An Overview of Advances in Biomass Gasification. Energy Environ. Sci. 2016, 9, 2939,  DOI: 10.1039/C6EE00935B
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    An overview of advances in biomass gasification
    Sikarwar, Vineet Singh; Zhao, Ming; Clough, Peter; Yao, Joseph; Zhong, Xia; Memon, Mohammad Zaki; Shah, Nilay; Anthony, Edward J.; Fennell, Paul S.
    Energy & Environmental Science (2016), 9 (10), 2939-2977CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
    Biomass gasification is a widely used thermochem. process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technol. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modeling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technol. into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technol. advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technol.
  20. 20
    Sharma, M.; N, R.; Dasappa, S. Solid Oxide Fuel Cell Operating with Biomass Derived Producer Gas: Status and Challenges. Renewable Sustainable Energy Rev. 2016, 60, 450– 463,  DOI: 10.1016/j.rser.2016.01.075
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    Solid oxide fuel cell operating with biomass derived producer gas: Status and challenges
    Sharma, Monikankana; N, Rakesh; Dasappa, S.
    Renewable & Sustainable Energy Reviews (2016), 60 (), 450-463CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    Solid oxide fuel cell as a conversion device is finding importance in the energy sector due to its high efficiency, low emissions and fuel flexibility. The use of producer gas as a fuel is gaining importance due to certain advantages over the conventional fuels while challenges lie in its usage due to the inherent contaminants present. This paper consolidates the efforts carried out using fossil fuels and highlights the challenges, and further, the progress made in the use of producer gas is critically examd. The effects of contaminants such as tar, particulate matter, H2S etc. on anode materials are highlighted, and the published results are consolidated to examine whether the max. tolerance limits of the contaminants be identified. However, it is obsd. that due to many inexorable factors viz., differences in the electrode material, microstructure, diverse operating conditions, the conclusions obtained are diverse and it is difficult to predict the general behavior of a particular contaminant. The need for a comprehensive study having both exptl. and theor. components focusing on the role of contaminants under the same operating conditions and using the same materials is highlighted as a major conclusion of this study.
  21. 21
    Hofmann, P.; Panopoulos, K. D.; Aravind, P. V.; Siedlecki, M.; Schweiger, A.; Karl, J.; Ouweltjes, J. P.; Kakaras, E. Operation of Solid Oxide Fuel Cell on Biomass Product Gas with Tar Levels > 10 g Nm −3. Int. J. Hydrogen Energy 2009, 34 (22), 9203– 9212,  DOI: 10.1016/j.ijhydene.2009.07.040
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    Operation of solid oxide fuel cell on biomass product gas with tar levels >10 g Nm-3
    Hofmann, Ph.; Panopoulos, K. D.; Aravind, P. V.; Siedlecki, M.; Schweiger, A.; Karl, J.; Ouweltjes, J. P.; Kakaras, E.
    International Journal of Hydrogen Energy (2009), 34 (22), 9203-9212CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    This work assesses exptl. the feasibility of feeding a high tar load product gas from biomass gasification to a planar solid oxide fuel cell (SOFC) for renewable electricity generation. The SOFC had a nickel gadolinium-doped ceria anode (Ni-GDC) and the gasifier was a pilot scale circulating fluidized bed, employing hot gas-cleaning to remove particulates, HCl and H2S. The SOFC operated for several hours on either pre-reformed gas (reduced tar levels < 0.5 g Nm-3) as well as on high tar-laden wood gas (tar levels > 10 g Nm-3) i.e. with no pre-reforming of tars. The tests were carried out at low fuel utilization Uf of around 20% at a c.d. j = 130 mA cm-2. In all cases stable continuous SOFC performance was established. Post exptl. examn. of the SOFC showed that the anode was not affected by carbon deposition or other impurity accumulation.
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    Costa, P.; Pinto, F.; André, R. N.; Marques, P. Integration of Gasification and Solid Oxide Fuel Cells (SOFCs) for Combined Heat and Power (CHP). Processes 2021, 9, 254,  DOI: 10.3390/pr9020254
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    Integration of gasification and solid oxide fuel cells (SOFCs) for combined heat and power (CHP)
    Costa, Paula; Pinto, Filomena; Andre, Rui Neto; Marques, Paula
    Processes (2021), 9 (2), 254CODEN: PROCCO; ISSN:2227-9717. (MDPI AG)
    This paper reviews the most recent information about the main operations to produce energy from carbonaceous materials, namely biomass and wastes through the integration of gasification, syngas cleaning and solid oxide fuel cells (SOFCs), which have shown to be a good option for combined heat and power (CHP) prodn., due to high efficiency and low environmental impact. However, some challenges still need to be overcome, mainly when mixed feedstocks with high contents of hazardous contaminants are used, thus syngas cleaning and conditioning is of major importance. Another drawback is SOFC operation, hence new materials esp. for the anode has been proposed and tested. An overall process to produce CHP by gasification integration with SOFC is proposed.
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    Recalde, M.; Woudstra, T.; Aravind, P. V. Gasifier, Solid Oxide Fuel Cell Integrated Systems for Energy Production From Wet Biomass. Front Energy Res. 2019, 7, 129,  DOI: 10.3389/fenrg.2019.00129
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    Karl, J.; Frank, N.; Karellas, S.; Saule, M.; Hohenwarter, U. Hohenwarter Ulrich. Conversion of Syngas From Biomass in Solid Oxide Fuel Cells. J. Fuel Cell Sci. Technol. 2009, 6, 021005,  DOI: 10.1115/1.2971172
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    Conversion of syngas from biomass in solid oxide fuel cells
    Karl, Jurgen; Frank, Nadine; Karellas, Sotirios; Saule, Mathilde; Hohenwarter, Ulrich
    Journal of Fuel Cell Science and Technology (2009), 6 (2), 021005/1-021005/6CODEN: JFCSAU; ISSN:1550-624X. (American Society of Mechanical Engineers)
    Conversion of biomass in syngas by means of indirect gasification offers the option to improve the economic situation of any fuel cell system due to lower costs for feedstock and higher power revenues in many European countries. The coupling of an indirect gasification of biomass and residues with highly efficient solid oxide fuel cell (SOFC) systems is therefore a promising technol. for reaching economic feasibility of small decentralized combined heat and power prodn. (CHP). The predicted efficiency of common high temp. fuel cell systems with integrated gasification of solid feedstock is usually significantly lower than the efficiency of fuel cells operated with hydrogen or methane. Addnl. system components like the gasifier as well as the gas cleaning reduce this efficiency. Hence common fuel cell systems with integrated gasification of biomass will hardly reach elec. efficiencies above 30%. An extraordinary efficient combination is achieved in case that the fuel cells waste heat is used in an indirect gasification system. A simple combination of a SOFC and an allothermal gasifier enables then elec. efficiencies above 50%. However, this system requires an innovative cooling concept for the fuel cell stack. Another significant question is the influence of impurities on the fuel cell degrdn. The European Research Project "BioCellus" focuses on both questions-the influence of the biogenous syngas on the fuel cells and an innovative cooling concept based on liq. metal heat pipes. First expts. showed that, in particular, higher hydrocarbons-the so-called tars-do not have any significant influence on the performance of SOFC membranes. The innovative concept of the TopCycle comprises to heat an indirect gasifier with the exhaust heat of the fuel cell by means of liq. metal heat-pipes. Internal cooling of the stack and the recirculation of waste heat increases the system efficiency significantly. This concept promises elec. efficiencies of above 50% even for small-scale systems without any combined processes.
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    Song, H.; Yang, G.; Xue, P.; Li, Y.; Zou, J.; Wang, S.; Yang, H.; Chen, H. Recent Development of Biomass Gasification for H2 Rich Gas Production. Appl. Energy Combustion Sci. 2022, 10, 100059,  DOI: 10.1016/j.jaecs.2022.100059
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    Alptekin, F. M.; Celiktas, M. S. Review on Catalytic Biomass Gasification for Hydrogen Production as a Sustainable Energy Form and Social, Technological, Economic, Environmental, and Political Analysis of Catalysts. ACS Omega. 2022, 7, 24918– 24941,  DOI: 10.1021/acsomega.2c01538
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    Review on Catalytic Biomass Gasification for Hydrogen Production as a Sustainable Energy Form and Social, Technological, Economic, Environmental, and Political Analysis of Catalysts
    Alptekin, Fikret Muge; Celiktas, Melih Soner
    ACS Omega (2022), 7 (29), 24918-24941CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
    A review. Sustainable energy prodn. is a worldwide concern due to the adverse effects and limited availability of fossil fuels, requiring the development of suitable environmentally friendly alternatives. Hydrogen is considered a sustainable future energy source owing to its unique properties as a clean and nontoxic fuel with high energy yield and abundance. Hydrogen can be produced through renewable and nonrenewable sources where the prodn. method and feedstock used are indicators of whether they are carbon-neutral or not. Biomass is one of the renewable hydrogen sources that is also available in large quantities and can be used in different conversion methods to produce fuel, heat, chems., etc. Biomass gasification is a promising technol. to generate carbon-neutral hydrogen. However, tar prodn. during this process is the biggest obstacle limiting hydrogen prodn. and commercialization of biomass gasification technol. This review focuses on hydrogen prodn. through catalytic biomass gasification. The effect of different catalysts to enhance hydrogen prodn. is reviewed, and social, technol., economic, environmental, and political (STEEP) anal. of catalysts is carried out to demonstrate challenges in the field and the development of catalysts.
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    Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G. A Review of the Primary Measures for Tar Elimination in Biomass Gasification Processes. Biomass Bioenergy 2003, 24 (2), 125– 140,  DOI: 10.1016/S0961-9534(02)00102-2
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    A review of the primary measures for tar elimination in biomass gasification processes
    Devi, Lopamudra; Ptasinski, Krzysztof J.; Janssen, Frans J. J. G.
    Biomass and Bioenergy (2003), 24 (2), 125-140CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
    A review. Tar formation is one of the major problems to deal with during biomass gasification. Tar condenses at reduced temp., thus blocking and fouling process equipments such as engines and turbines. Considerable efforts have been directed on tar removal from fuel gas. Tar removal technologies can broadly be divided into two approaches; hot gas cleaning after the gasifier (secondary methods), and treatments inside the gasifier (primary methods). Although secondary methods are proven to be effective, treatments inside the gasifier are gaining much attention as these may eliminate the need for downstream cleanup. In primary treatment, the gasifier is optimized to produce a fuel gas with min. tar concn. The different approaches of primary treatment are (a) proper selection of operating parameters, (b) use of bed additive/catalyst, and (c) gasifier modifications. The operating parameters such as temp., gasifying agent, equivalence ratio, residence time, etc. play an important role in formation and decompn. of tar. There is a potential of using some active bed additives such as dolomite, olivine, char, etc. inside the gasifier. Ni-based catalyst are reported to be very effective not only for tar redn., but also for decreasing the amt. of nitrogenous compds. such as ammonia. Also, reactor modification can improve the quality of the product gas. The concepts of two-stage gasification and secondary air injection in the gasifier are of prime importance. Some aspects of primary methods and the research and development in this area are reviewed and cited in the present paper.
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    Asadullah, M. Barriers of Commercial Power Generation Using Biomass Gasification Gas: A Review. Renewable and Sustainable Energy Reviews 2014, 29, 201– 215,  DOI: 10.1016/j.rser.2013.08.074
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    Barriers of commercial power generation using biomass gasification gas: A review
    Asadullah, Mohammad
    Renewable & Sustainable Energy Reviews (2014), 29 (), 201-215CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Gasification is one of the promising technologies to convert biomass to gaseous fuels for distributed power generation. However, the com. exploitation of biomass energy suffers from a no. of logistics and technol. challenges. In this review, the barriers in each of the steps from the collection of biomass to electricity generation are highlighted. The effects of parameters in supply chain management, pretreatment and conversion of biomass to gas, and cleaning and utilization of gas for power generation are discussed. Based on the studies, until recently, the gasification of biomass and gas cleaning are the most challenging part. For electricity generation, either using engine or gas turbine requires a stringent specification of gas compn. and tar concn. in the product gas. Different types of updraft and downdraft gasifiers have been developed for gasification and a no. of phys. and catalytic tar sepn. methods have been investigated. However, the most efficient and popular one is yet to be developed for com. purpose. In fact, the efficient gasification and gas cleaning methods can produce highly burnable gas with less tar content, so as to reduce the total consumption of biomass for a desired quantity of electricity generation. According to the recent report, an advanced gasification method with efficient tar cleaning can significantly reduce the biomass consumption, and thus the logistics and biomass pretreatment problems can be ultimately reduced.
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    Meng, X. Biomass Gasification: The Understanding of Sulfur, Tar, and Char Reaction in Fluidized Bed Gasifiers. Doctoral Thesis, Tianjin University, Tianjin, China, 2012.
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    Abdoulmoumine, N.; Adhikari, S.; Kulkarni, A.; Chattanathan, S. A Review on Biomass Gasification Syngas Cleanup. Appl. Energy 2015, 155, 294– 307,  DOI: 10.1016/j.apenergy.2015.05.095
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    A review on biomass gasification syngas cleanup
    Abdoulmoumine, Nourredine; Adhikari, Sushil; Kulkarni, Avanti; Chattanathan, Shyamsundar
    Applied Energy (2015), 155 (), 294-307CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
    Energy, fuel and chem. prodn. from biomass is increasingly attracting interest in the world. Gasification of biomass can produce raw syngas which contains CO, CO2, H2 and CH4. In addn., raw syngas contains minor but significant quantities of undesirable impurities - collectively known as syngas contaminants. Syngas contaminants are composed of tars, nitrogen based compds. (NH3, HCN, etc.), sulfur based compds. (H2S, COS, etc.), hydrogen halides (HCl, HF, etc.) and trace metals (Na, K, etc.). Raw syngas cleanup is an essential step prior to syngas utilization in downstream applications. In recent years, significant research attention has been devoted to syngas cleanup to reduce contaminants below tolerable limits. The present paper is a comprehensive review of cold gas and hot gas syngas cleanup for major contaminants in syngas (tar, NH3, H2S, HCl and trace metals). This review organizes and discusses investigations on syngas for all major contaminants, critically reviews important challenges in syngas cleanup and discusses recent advancements in hot and cold gas cleanup.
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    Rakesh N; Dasappa, S. A Critical Assessment of Tar Generated during Biomass Gasification - Formation, Evaluation, Issues and Mitigation Strategies. Renewable Sustainable Energy Rev. 2018, 91, 1045– 1064,  DOI: 10.1016/j.rser.2018.04.017
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    A critical assessment of tar generated during biomass gasification - Formation, evaluation, issues and mitigation strategies
    Rakesh N; Dasappa, S.
    Renewable & Sustainable Energy Reviews (2018), 91 (), 1045-1064CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    Biomass gasification receives attention as a promising method to utilize biomass, a fuel which is carbon neutral. The producer gas/syngas which is an energy carrier obtained through this method finds use in engines, fuel cells, Fischer-Tropsch reactors, methanol synthesis and as an input for chem. industries, after the required quality levels for the above applications are achieved. To use the producer gas/syngas for power generation on a com. scale, the required gas quality has to be established. Producer gas obtained from biomass gasification has several contaminants like particulate matter, tar and gaseous species like H2S, NH3. The contaminants present in the producer gas, depending upon their nature and the amt., pose issues to power generation systems. Tar, which is a mixt. of varying mol. wt. hydrocarbon mols., generated from the thermo-chem. conversion processes of org. materials, could condense at low temps., and lead to clogging or blockage in end-use application devices, filters, and fuel lines. So, it is essential to reduce or transform the tar present in the producer gas to utilize the biomass gasification systems for power generation. This paper attempts to provide a crit. assessment of tar generated during biomass gasification, covering the sundry aspects of formation, evaluation, issues and mitigation strategies. The paper gives an introduction to biomass gasification systems, followed by a detailed description of tar, including the definition and the chem. of formation and destruction. An explanation of the various aspects of tar sampling, characterization and anal., is presented next. The suitability of different tar anal. approaches is compared from an end-use device perspective. Then the multifarious issues posed by the presence of tar in the syngas on the end-use devices is discussed. The last part of the paper describes several tar mitigation strategies used by researchers.
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    Balas, M.; Lisy, M.; Kubicek, J.; Pospisil, J. Syngas Cleaning by Wet Scrubber. WSEAS Trans. Heat Mass Transfer 2014, 9, 195– 204
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    Basu, P. Biomass Gasification and Pyrolysis: Practical Design and Theory; Academic Press, 2010.  DOI: 10.1016/C2009-0-20099-7 .
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    Kinoshita, C. M.; Wang, Y.; Zhou, J. Tar Formation under Different Biomass Gasification Conditions. J. Anal Appl. Pyrolysis 1994, 29, 169– 181,  DOI: 10.1016/0165-2370(94)00796-9
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    Tar formation under different biomass gasification conditions
    Kinoshita, C. M.; Wang, Y.; Zhou, J.
    Journal of Analytical and Applied Pyrolysis (1994), 29 (2), 169-81CODEN: JAAPDD; ISSN:0165-2370.
    Parametric tests on tar formation, varying temp., equivalence ratio, and residence time, were performed on a bench-scale, indirectly-heated fluidized bed gasifier. Prepd. tar samples were analyzed in a gas chromatograph (GC) with a flame ionization detector, using a capillary column. Std. test mixts. contg. the dominant tar species were prepd. for GC calibration. The identified peaks included single-ring hydrocarbons, such as benzene, to five-ring hydrocarbons, such as perylene; these compds. represent about 70-90% (mass basis) of the tar constituents. The influences of the above-mentioned gasification parameters on tar formation were analyzed.
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    Lv, P.; Yuan, Z.; Wu, C.; Ma, L.; Chen, Y.; Tsubaki, N. Bio-Syngas Production from Biomass Catalytic Gasification. Energy Convers Manag 2007, 48 (4), 1132– 1139,  DOI: 10.1016/j.enconman.2006.10.014
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    Bio-syngas production from biomass catalytic gasification
    Lv, Pengmei; Yuan, Zhenhong; Wu, Chuangzhi; Ma, Longlong; Chen, Yong; Tsubaki, Noritatsu
    Energy Conversion and Management (2007), 48 (4), 1132-1139CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    A promising application for biomass is liq. fuel synthesis, such as methanol or di-Me ether (DME). Previous studies have studied syngas prodn. from biomass-derived char, oil and gas. This study intends to explore the technol. of syngas prodn. from direct biomass gasification, which may be more economically viable. The ratio of H/CO is an important factor that affects the performance of this process. In this study, the characteristics of biomass gasification gas, such as H/CO and tar yield, as well as its potential for liq. fuel synthesis is explored. A fluidized bed gasifier and a downstream fixed bed are employed as the reactors. Two kinds of catalysts: dolomite and Ni based catalyst are applied, and they are used in the fluidized bed and fixed bed, resp. The gasifying agent used is an air-steam mixt. The main variables studied are temp. and wt. hourly space velocity in the fixed bed reactor. Over the ranges of operating conditions examd., the max. H content reaches 52.47 vol.%, while the ratio of H/CO varies between 1.87 and 4.45. The results indicate that an appropriate temp. (750° for this study) and more catalyst are favorable for getting a higher H/CO ratio. Using a simple 1st order kinetic model for the overall tar removal reaction, the apparent activation energies and pre-exponential factors are obtained for nickel based catalysts. The results indicate that biomass gasification gas has great potential for liq. fuel synthesis after further processing.
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    Anis, S.; Zainal, Z. A. Tar Reduction in Biomass Producer Gas via Mechanical, Catalytic and Thermal Methods: A Review. Renewable and Sustainable Energy Reviews 2011, 15 (5), 2355– 2377,  DOI: 10.1016/j.rser.2011.02.018
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    Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review
    Anis, Samsudin; Zainal, Z. A.
    Renewable & Sustainable Energy Reviews (2011), 15 (5), 2355-2377CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compns., which is assocd. with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar redn. are discussed.
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    Zhang, W.; Liu, H.; Ul Hai, I.; Neubauer, Y.; Schröder, P.; Oldenburg, H.; Seilkopf, A.; Kolling, A. Gas Cleaning Strategies for Biomass Gasification Product Gas. International Journal of Low-Carbon Technologies 2012, 7 (2), 69– 74,  DOI: 10.1093/ijlct/ctr046
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    Gas cleaning strategies for biomass gasification product gas
    Zhang, Wenbin; Liu, Hao; Ul Hai, Irfan; Neubauer, York; Schroeder, Philipp; Oldenburg, Holger; Seilkopf, Alexander; Koelling, Axel
    International Journal of Low-Carbon Technologies (2012), 7 (2), 69-74CODEN: IJLTAR; ISSN:1748-1317. (Oxford University Press)
    A review. In general, the raw product gas of biomass gasification contains a range of minor species and contaminants, including particles, tar, alkali metals, chlorine, nitrogen compds. and sulfur compds. This study reviews the recent developments in product gas cleaning technologies for these species and summarizes the findings of the research project Mop fan and electrofilter: an innovative approach for cleaning product gases from biomass gasification' which was recently carried out by the authors. The results of the project showed that combination of mop fan and electrofilter (ESP) has great potential in removing fine particles, tars and chem. contaminants in the product gas.
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    Adamovich, I.; Baalrud, S. D.; Bogaerts, A.; Bruggeman, P. J.; Cappelli, M.; Colombo, V.; Czarnetzki, U.; Ebert, U.; Eden, J. G.; Favia, P.; Graves, D. B.; Hamaguchi, S.; Hieftje, G.; Hori, M.; Kaganovich, I. D.; Kortshagen, U.; Kushner, M. J.; Mason, N. J.; Mazouffre, S.; Thagard, S. M.; Metelmann, H. R.; Mizuno, A.; Moreau, E.; Murphy, A. B.; Niemira, B. A.; Oehrlein, G. S.; Petrovic, Z. L.; Pitchford, L. C.; Pu, Y. K.; Rauf, S.; Sakai, O.; Samukawa, S.; Starikovskaia, S.; Tennyson, J.; Terashima, K.; Turner, M. M.; Van De Sanden, M. C. M.; Vardelle, A. The 2017 Plasma Roadmap: Low Temperature Plasma Science and Technology. J. Phys. D Appl. Phys. 2017, 50 (32), 323001,  DOI: 10.1088/1361-6463/aa76f5
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    The 2017 Plasma Roadmap: Low temperature plasma science and technology
    Adamovich, I.; Baalrud, S. D.; Bogaerts, A.; Bruggeman, P. J.; Cappelli, M.; Colombo, V.; Czarnetzki, U.; Ebert, U.; Eden, J. G.; Favia, P.; Graves, D. B.; Hamaguchi, S.; Hieftje, G.; Hori, M.; Kaganovich, I. D.; Kortshagen, U.; Kushner, M. J.; Mason, N. J.; Mazouffre, S.; Thagard, S. Mededovic; Metelmann, H.-R.; Mizuno, A.; Moreau, E.; Murphy, A. B.; Niemira, B. A.; Oehrlein, G. S.; Petrovic, Z. Lj.; Pitchford, L. C.; Pu, Y.-K.; Rauf, S.; Sakai, O.; Samukawa, S.; Starikovskaia, S.; Tennyson, J.; Terashima, K.; Turner, M. M.; van de Sanden, M. C. M.; Vardelle, A.
    Journal of Physics D: Applied Physics (2017), 50 (32), 323001/1-323001/46CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)
    Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temp. plasma science and technol. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temp. plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temp. plasma field in the development of plasmas as an enabling technol. for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technol. challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.
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    Bogaerts, A.; Neyts, E. C. Plasma Technology: An Emerging Technology for Energy Storage. ACS Energy Lett. 2018, 3 (4), 1013– 1027,  DOI: 10.1021/acsenergylett.8b00184
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    Plasma Technology: An Emerging Technology for Energy Storage
    Bogaerts, Annemie; Neyts, Erik C.
    ACS Energy Letters (2018), 3 (4), 1013-1027CODEN: AELCCP; ISSN:2380-8195. (American Chemical Society)
    Plasma technol. is gaining increasing interest for gas conversion applications, such as CO2 conversion into value-added chems. or renewable fuels, and N2 fixation from the air, to be used for the prodn. of small building blocks for, e.g., mineral fertilizers. Plasma is generated by elec. power and can easily be switched on/off, making it, in principle, suitable for using intermittent renewable electricity. In this Perspective article, we explain why plasma might be promising for this application. We briefly present the most common types of plasma reactors with their characteristic features, illustrating why some plasma types exhibit better energy efficiency than others. We also highlight current research in the fields of CO2 conversion (including the combined conversion of CO2 with CH4, H2O, or H2) as well as N2 fixation (for NH3 or NOx synthesis). Finally, we discuss the major limitations and steps to be taken for further improvement.
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    Gimžauskaitė, D.; Aikas, M.; Tamošiu̅nas, A. Recent Progress in Thermal Plasma Gasification of Liquid and Solid Wastes. Recent Adv. Renewable Energy Technol. 2022, 2, 155– 196,  DOI: 10.1016/B978-0-12-823532-4.00007-0
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    Sanjaya, E.; Abbas, A. Plasma Gasification as an Alternative Energy-from-Waste (EFW) Technology for the Circular Economy: An Environmental Review. Resour., Conserv. Recycl. 2023, 189, 106730,  DOI: 10.1016/j.resconrec.2022.106730
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    Dasappa, S.; Paul, P. J.; Mukunda, H. S.; Rajan, N. K. S.; Sridhar, G.; Sridhar, H. V. Biomass Gasification Technology-a Route to Meet Energy Needs. Curr. Sci. 2004, 87 (7), 908– 916
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    Biomass gasification technology - a route to meet energy needs
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    Current Science (2004), 87 (7), 908-916CODEN: CUSCAM; ISSN:0011-3891. (Current Science Association)
    A review. The paper addresses a distributed power generation system that has evolved at the Indian Institute of Science, Bangalore. The technol. and field-related experience pertaining to open top re-burn down draft biomass gasification system coupled with the internal combustion engine or thermal device are brought out. The gasifier reactor design uses dual air entry - air nozzles and open top to help in establishing a thick high temp. zone to remove the contaminants in the product gas; a gas clean-up system to further refine the gas to ultra-pure quality. These elements are integrated with other sub-systems, namely feedstock prepn., ash handling, water treatment, process automation and other accessories to form an Independent Power Producer. Based on this technol. there are over 30 units operating in-India and abroad, with an accumulated capacity of over 20 MW. Over 80,000 h of operation of these systems have resulted in a saving of about 350 tons of fossil fuel, implying a saving of about 1120 tons of CO2 - a promising candidate for Clean Development Mechanisms (CDMs), other than redn. in toxic gases like NOx and SOx.
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    Ravindranath, N. H.; Somashekar, H. I.; Dasappa, S.; Reddy, C. N. J. Sustainable Biomass Power for Rural India: Case Study of Biomass Gasifier for Village Electrification. Curr. Sci. 2004, 87 (7), 932– 941
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    Sandeep, K.; Dasappa, S. First and Second Law Thermodynamic Analysis of Air and Oxy-Steam Biomass Gasification. Int. J. Hydrogen Energy 2014, 39 (34), 19474– 19484,  DOI: 10.1016/j.ijhydene.2014.09.134
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    First and second law thermodynamic analysis of air and oxy-steam biomass gasification
    Sandeep, K.; Dasappa, S.
    International Journal of Hydrogen Energy (2014), 39 (34), 19474-19484CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Gasification is an energy transformation process in which solid fuel undergoes thermochem. conversion to produce gaseous fuel, and the two most important criteria involved in such process to evaluate the performance, economics, and sustainability of the technol. are: the total available energy (exergy) and the energy conserved (energy efficiency). Current study focuses on the energy and exergy anal. of the oxy-steam gasification and comparing with air gasification to optimize the H2 yield, efficiency and syngas energy d. Casuarina wood is used as a fuel, and mixt. of oxygen and steam in different proportion and amt. are used as a gasifying media. The results are analyzed with respect to varying equivalence ratio and steam to biomass ratio (SBR). Elemental mass balance technique is employed to ensure the validity of results. First and second law thermodn. anal. is used towards time evaluation of energy and exergy anal. Different component of energy input and output has been studied carefully to understand the effect of varying SBR on the availability of energy and irreversibility in the system to minimize the losses with change in input parameters for optimum performance. The energy and exergy losses (irreversibility) for oxy-steam gasification system are compared with the results of air gasification, and losses are found to be lower in oxy-steam thermal conversion; which has been argued and reasoned due to the presence of N2 in the air-gasification. The max. exergy efficiency of 85% with energy efficiency of 82% is achieved at SBR of 0.75 on the molar basis. It has been obsd. that increase in SBR results in lower exergy and energy efficiency, and it is argued to be due to the high energy input in steam generation and subsequent losses in the form of phys. exergy of steam in the product gas, which alone accounts for over 18% in exergy input and 8.5% in exergy of product gas at SBR of 2.7. Carbon boundary point (CBP), is identified at the SBR of 1.5, and water gas shift (WGS) reaction plays a crucial role in H2 enrichment after carbon boundary point (CBP) is reached. Effects of SBR and CBP on the H2/CO ratio is analyzed and discussed from the perspective of energy as well as the reaction chem. Energy d. of syngas and energy efficiency is favored at lower SBR but higher SBR favors H2 rich gas at the expense of efficiency.
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    Sandeep, K.; Dasappa, S. Oxy–Steam Gasification of Biomass for Hydrogen Rich Syngas Production Using Downdraft Reactor Configuration. Int. J. Energy Res. 2014, 38 (2), 174– 188,  DOI: 10.1002/er.3019
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    Oxy-steam gasification of biomass for hydrogen rich syngas production using downdraft reactor configuration
    Sandeep, K.; Dasappa, S.
    International Journal of Energy Research (2014), 38 (2), 174-188CODEN: IJERDN; ISSN:0363-907X. (John Wiley & Sons Ltd.)
    SUMMARY : The paper focuses on the use of oxygen and steam as the gasification agents in the thermochem. conversion of biomass to produce hydrogen rich syngas, using a downdraft reactor configuration. Performance of the reactor is evaluated for different equivalence ratios (ER), steam to biomass ratios (SBR) and moisture content in the fuel. The results are compared and evaluated with chem. equil. anal. and reaction kinetics along with the results available in the literature. Parametric study suggests that, with increase in SBR, hydrogen fraction in the syngas increases but necessitates an increase in the ER to maintain reactor temp. toward stable operating conditions. SBR is varied from 0.75 to 2.7 and ER from 0.18 to 0.3. The peak hydrogen yield is found to be 104 g/kg of biomass at SBR of 2.7. Further, significant enhancement in H2 yield and H2 to CO ratio is obsd. at higher SBR (SBR = 1.5-2.7) compared with lower range SBR (SBR = 0.75-1.5). Expts. were conducted using wet wood chips to induce moisture into the reacting system and compare the performance with dry wood with steam. The results clearly indicate the both hydrogen generation and the gasification efficiency (ηg) are better in the latter case. With the increase in SBR, gasification efficiency (ηg) and lower heating value (LHV) tend to reduce. Gasification efficiency of 85.8% is reported with LHV of 8.9 MJ Nm-3 at SBR of 0.75 compared with 69.5% efficiency at SBR of 2.5 and lower LHV of 7.4 at MJ Nm-3 at SBR of 2.7. These are argued on the basis of the energy required for steam generation and the extent of steam consumption during the reaction, which translates subsequently in the LHV of syngas. From the anal. of the results, it is evident that reaction kinetics plays a crucial role in the conversion process. The study also presents the importance of reaction kinetics, which controls the overall performance related to efficiency, H2 yield, H2 to CO fraction and LHV of syngas, and their dependence on the process parameters SBR and ER. Copyright © 2013 John Wiley & Sons, Ltd.
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    Sharma, S. K.; Shivapuji, A. M.; Dasappa, S. Char Reactivity Assessment with Steam in Packed Bed and Pilot Scale under Oxy-Steam Environment. Fuel 2023, 344, 128086  DOI: 10.1016/j.fuel.2023.128086
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    Char reactivity assessment with steam in packed bed and pilot scale under oxy-steam environment
    Sharma, Shirish Kumar; Shivapuji, Anand M.; Dasappa, S.
    Fuel (2023), 344 (), 128086CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    This paper focuses on char gasification in steam towards generating syngas as a part of two-stage gasification technol. developed inhouse to handle high-ash coal. Controlled expts. in a small-scale packed bed reactor are used to arrive at the dependence of char reactivity using parametric studies like the evolution of temp., gas compn., flow rate, and carbon conversion rate with time and are compared for different particle sizes. The vol. percentages of CO, CO2, CH4, and H2 were 7, 26, 1, and 66, resp., in steam char expts., over a particle size range from 1 mm to 4 mm. If the CO2 is sepd., the H2 vol. percentage reaches 90%. In small-scale expts., the gas compn. for all the particle sizes was invariable; however, the reactivity of small particles is higher than the bigger particles, i.e., 0.5 g/g-hr as against 0.38 g/g-hr for bigger particles due to the transition from diffusion to the kinetic regime, which establishes the suitability of small particles for pilot-scale operations. Finally, the expts. were carried out on pilot-scale char gasification in an oxy-steam environment, and the results were compared with simulated expts. for small-size particles. The consequences of adding oxygen with steam to keep the system auto-thermal are discussed. In the pilot scale under oxy-steam conditions, the volumetric concns. of CO, CO2, CH4, and H2 were 10.8, 39.9, 4.7, and 44.6%, resp. In contrast, the reactivity increased from 0.46 to 0.90 g/g-hr with a decrease in the calorific value of gas from 9.7 to 8.6 MJ/Nm3.
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    Park, S. W.; Lee, S. Y.; Jeong, Y. O.; Han, G. H.; Seo, Y. C. Effects of Oxygen Enrichment in Air Oxidants on Biomass Gasification Efficiency and the Reduction of Tar Emissions. Energies (Basel) 2018, 11 (10), 2664,  DOI: 10.3390/en11102664
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    Effects of oxygen enrichment in air oxidants on biomass gasification efficiency and the reduction of tar emissions
    Park, Se-Won; Lee, Sang-Yeop; Jeong, Yean-Ouk; Han, Gun-Ho; Seo, Yong-Chil
    Energies (Basel, Switzerland) (2018), 11 (10), 2664/1-2664/13CODEN: ENERGA; ISSN:1996-1073. (MDPI AG)
    This study applied oxygen-enrichment conditions to remove tar (the main problem in biomass gasification) and increase gasification efficiency. Expts. on oxygen-enrichment conditions were conducted at oxygen concns. of 21%, 25%, 30%, and 35% in oxidants. This was expected to increase the partial oxidn. reaction in gasification reactions, thus leading to thermal decompn. of tar in producer gas. The decompd. tar was expected to be converted into syngas or combustible gases in the producer gas. The results were as follows: Tar-redn. efficiency was 72.46% at 30% oxygen enrichment compared to the std. 21% enrichment condition. In addn., the concns. of syngas and combustible gases in the producer gas tended to increase. Therefore, the 30% oxygen-enrichment condition was optimal, resulting in 78.00% for cold gas efficiency and 80.24% for carbon conversion efficiency. The application of oxygen enrichment into the lab-scale gasification system clearly reduced the concn. of tar and tended to increase some indexes of gasification efficiency, thus suggesting the usefulness of this technique in large-scale biomass gasification operations.
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    Cao, Y.; Wang, Q.; Du, J.; Chen, J. Oxygen-Enriched Air Gasification of Biomass Materials for High-Quality Syngas Production. Energy Convers. Manag. 2019, 199, 111628,  DOI: 10.1016/j.enconman.2019.05.054
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    Oxygen-enriched air gasification of biomass materials for high-quality syngas production
    Cao, Y.; Wang, Q.; Du, J.; Chen, J.
    Energy Conversion and Management (2019), 199 (), 111628CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    The oxygen-enriched gasification of five biomasses (pine sawdust, rice husk, corn core, legume straw and wood chips) for high-quality gas prodn. was studied using Aspen Plus software. At first, in order to ensure the model accuracy, the simulation results performed at different temps. were compared with the exptl. data, and a good agreement was obtained. The performance of the process was evaluated based on the yield of producer gas, lower heating value of the fuel gas (LHVFG) and the tar yield. The simulation results indicated that temp. was the most important parameter in the process; higher temp. contributed to higher gas prodn. and lower tar yield. The gas yield also increased with the increase of equivalence ratio (ER), while the LHVFG and tar yield significantly reduced. Results also showed that the use of oxygen-enriched air was more favorable for gas quality and tar cracking; however, it lowered the gas yield. As ER increased from 0.19 to 0.27, the tar yields decreased markedly which is attributed to the thermal conversion of volatiles with the rise of oxidant. As a result, gasification of all the biomasses was feasible; however, gasification of pine sawdust showed the highest gas yield and gas heating value. The lowest tar yield was obtained from gasification of rice husk.
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    Liu, W.; Tian, Y.; Yan, H.; Zhou, X.; Tan, Y.; Yang, Y.; Li, Z.; Yuan, L. Gasification of Biomass Using Oxygen-Enriched Air as Gasification Agent: A Simulation Study. Biomass Convers. Biorefin. 2023, 13, 15993,  DOI: 10.1007/s13399-021-02035-2
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    Gasification of biomass using oxygen-enriched air as gasification agent: a simulation study
    Liu, Wentao; Tian, Ye; Yan, Hui; Zhou, Xiong; Tan, Yu; Yang, Yu; Li, Zheng; Yuan, Liang
    Biomass Conversion and Biorefinery (2023), 13 (17), 15993-16000CODEN: BCBIBN; ISSN:2190-6823. (Springer)
    A steady-state Aspen Plus model was established to numerically study biomass (ramie residues) gasification using air as gasification agent. This study proposed a comprehensive model which used the thermodn. equil. and chem. kinetics to accurately simulate the char combustion and char/volatiles gasification, resp., to search for optimal gasifier operating conditions. The proposed model correctly predicted the products yield, gasifier performance and the compn. of the produced syngas, and therefore the higher heating value (HHV). The effects of air temp. and oxygen content in gasification agent on the gasification characteristics were discussed. The gas yield slightly increased with the increase of air temp., while char conversion efficiency (CCE) firstly increased and then declined attributing to the slight increase of tar cracking with the increase of air temp. The results also indicate that higher oxygen ratio (OR) leads to higher H2 prodn. and lower tar yield. Compared to the max. H2 content (11.17 vol%) and the syngas HHV (6.22 MJ/Nm3) at OR = 31.4%, they are resp. reduced to about 35.45% and 21.7% when OR drops to 21%. The present model opens the possibility of predicting the gasification characteristics using different gasification agents and feedstocks based on their chem. compns.
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    Banerjee, S.; Tiarks, J. A.; Kong, S. C. Modeling Biomass Gasification System Using Multistep Kinetics under Various Oxygen-Steam Conditions. Environ. Prog. Sustain Energy 2015, 34 (4), 1148– 1155,  DOI: 10.1002/ep.12109
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    Di Giuliano, A.; Capone, S.; Anatone, M.; Gallucci, K. Chemical Looping Combustion and Gasification: A Review and a Focus on European Research Projects. Ind. Eng. Chem. Res. 2022, 61 (39), 14403– 14432,  DOI: 10.1021/acs.iecr.2c02677
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    Chemical looping combustion and gasification, and review and focus on European research projects
    Di Giuliano, Andrea; Capone, Serena; Anatone, Michele; Gallucci, Katia
    Industrial & Engineering Chemistry Research (2022), 61 (39), 14403-14432CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    A review. Climate change has driven attention toward promoting sustainable policies and processes to contain global warming below +1.5°C. Neg. emission technologies (NET)-bioenergy with carbon capture and storage in particular (BECCS)-are expected to contribute to the achievement of that target. Recent research and development concerning NET focused on chem. looping combustion (CLC) and chem. looping gasification (CLG), as they should limit cost- and energy-penalties assocd. with carbon capture and storage thanks to solid materials known as oxygen carriers (OCs). This review aims to provide an introductory tool about CLC and CLG and their possible role as NET if fed with biomasses to obtain BECCS. A crit. overlook is proposed concerning chem. looping reactions, fuels, types of OCs, and reactor systems developed at different scales, focusing on recent and current European research projects and remarks on the subsequent developments.
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    Coppola, A.; Scala, F. Chemical Looping for Combustion of Solid Biomass: A Review. Energy and Fuels. 2021, 35, 19248– 19265,  DOI: 10.1021/acs.energyfuels.1c02600
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    Chemical Looping for Combustion of Solid Biomass: A Review
    Coppola, Antonio; Scala, Fabrizio
    Energy & Fuels (2021), 35 (23), 19248-19265CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    A review. Chem. looping combustion of solid biomass has the unique potential to generate energy with neg. carbon emissions, while entailing an energy penalty compared to traditional combustion that is lower than that of the competing carbon capture technologies. In spite of these attractive features, research is still needed to bring the technol. to a fully com. level. The reason relies on a no. of technol. challenges mostly related to the oxygen carrier performance, its possible detrimental interaction with the biomass ash components, and the efficiency of the gas-solid contact with the biomass volatiles. This review is focused on these specific challenges which are particularly relevant when firing biomass rather than coal in a solid-based chem. looping combustion process. Special attention will be given to the most recent findings published on these aspects. Related performance evaluation by modeling, system integration, and techno-economic anal. will also be briefly reviewed.
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    Woolcock, P. J.; Brown, R. C. A Review of Cleaning Technologies for Biomass-Derived Syngas. Biomass and Bioenergy. 2013, 52, 54– 84,  DOI: 10.1016/j.biombioe.2013.02.036
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    A review of cleaning technologies for biomass-derived syngas
    Woolcock, Patrick J.; Brown, Robert C.
    Biomass and Bioenergy (2013), 52 (), 54-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    A review. Syngas from gasification of carbonaceous feedstocks is used for power prodn. and synthesis of fuels and commodity chems. Impurities in gasification feedstocks, esp. sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temp. exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the tech. difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
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    Lyngfelt, A. Chemical Looping Combustion: Status and Development Challenges. Energy and Fuels. 2020, 34, 9077– 9093,  DOI: 10.1021/acs.energyfuels.0c01454
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    Chemical Looping Combustion: Status and Development Challenges
    Lyngfelt, Anders
    Energy & Fuels (2020), 34 (8), 9077-9093CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    A review. Because the CO2 capture is inherent in chem. looping combustion (CLC), thus ideally avoiding costly gas sepn., this process has potential for uniquely low costs of CO2 capture. The review reports on operational experiences with different oxygen carriers in CLC pilot operation. Further, the application to solid fuels is discussed in terms of technol. challenges, routes for upscaling to com. size, downstream gas treatment, options for achieving adequate circulation, and the use of biofuels in CLC to reach neg. emissions. It is concluded that the necessary elements for a scale-up are at hand. Oxygen carrier materials of low cost have been tested in extended operation and found to have reasonable performance with respect to reactivity and lifetime. Designs for large-scale units have been performed, indicating that the process is tech. realistic and should have a low cost of CO2 capture. A scale-up strategy to minimize risk and costs has been suggested.
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    Prando, D.; Shivananda Ail, S.; Chiaramonti, D.; Baratieri, M.; Dasappa, S. Characterisation of the Producer Gas from an Open Top Gasifier: Assessment of Different Tar Analysis Approaches. Fuel 2016, 181, 566– 572,  DOI: 10.1016/j.fuel.2016.04.104
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    Characterisation of the producer gas from an open top gasifier: Assessment of different tar analysis approaches
    Prando, D.; Shivananda Ail, S.; Chiaramonti, D.; Baratieri, M.; Dasappa, S.
    Fuel (2016), 181 (), 566-572CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    The paper addresses a comprehensive screening procedure of the tar present in the raw producer gas generated by an open top downdraft gasifier developed at the Indian Institute of Science (IISc), Bangalore. The main objectives of this research are the comparison of different approaches for the sampling and anal. of tar (i.e. GC-MS and gravimetric methods), and the assessment of the capability of this gasifier to produce low-tar producer gas. The results of the GC-MS anal. of the collected samples showed that tar is mainly composed of light arom. compds., where benzene and toluene account for about 70% of the total detected tar. Contrastingly, the gravimetric tar is roughly one order of magnitude lower than the total tar that was detd. by GC-MS anal. on the collected samples. The light and heavy polycyclic arom. hydrocarbons (PAH) compds. that have a mol. wt. higher than 150 g mol-1 account for the gravimetric tars, but the main fraction is GC-undetectable. The two approaches for the anal. of tar have different capabilities and the choice of either the approaches would strongly depend on the selected gasification technol. The detailed exptl. anal. evidenced that the IISc open-top reactor design results in a low tar content in the producer gas. The gravimetric tar in the raw gas were measured at 50-80 mg N m-3, with min. dependence on the choice of the feedstock used (i.e. Casuarina wood chip or coconut shell).
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    Milne, T. A.; Evans, R. J.; Abatzoglou, N. Biomass Gasifier “Tars”: Their Nature, Formation, and Conversion; NREL/TP-570-25357; National Renewable Energy Laboratory: Golden, CO, 1998.
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    Calvo, L. F.; Gil, M. V; Otero, M.; Morán, A.; García, A. I. Gasification of Rice Straw in a Fluidized-Bed Gasifier for Syngas Application in Close-Coupled Boiler-Gasifier Systems. Bioresource Technol. 2012, 109, 206– 214,  DOI: 10.1016/j.biortech.2012.01.027
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    Gasification of rice straw in a fluidized-bed gasifier for syngas application in close-coupled boiler-gasifier systems
    Calvo, L. F.; Gil, M. V.; Otero, M.; Moran, A.; Garcia, A. I.
    Bioresource Technology (2012), 109 (), 206-214CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
    The feasibility and operation performance of the gasification of rice straw in an atm. fluidized-bed gasifier was studied. The gasification was carried out between 700 and 850 °C. The stoichiometric air-fuel ratio (A/F) for rice straw was 4.28 and air supplied was 7-25% of that necessary for stoichiometric combustion. Mass and power balances, tar concn., produced gas compn., gas phase ammonia, chloride and potassium concns., agglomeration tendencies and gas efficiencies were assessed. Agglomeration was avoided by replacing the normal alumina-silicate bed by a mixt. of alumina-silicate sand and MgO. It was shown that it is possible to produce high quality syngas from the gasification of rice straw. Under the exptl. conditions used, the higher heating value (HHV) of the produced gas reached 5.1 MJ Nm-3, the hot gas efficiency 61% and the cold gas efficiency 52%. The obtained results prove that rice straw may be used as fuel for close-coupled boiler-gasifier systems.
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    Li, J.; Yin, Y.; Zhang, X.; Liu, J.; Yan, R. Hydrogen-Rich Gas Production by Steam Gasification of Palm Oil Wastes over Supported Tri-Metallic Catalyst. Int. J. Hydrogen Energy 2009, 34, 9108– 9115,  DOI: 10.1016/j.ijhydene.2009.09.030
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    Hydrogen-rich gas production by steam gasification of palm oil wastes over supported tri-metallic catalyst
    Li, Jianfen; Yin, Yanfang; Zhang, Xuanming; Liu, Jianjun; Yan, Rong
    International Journal of Hydrogen Energy (2009), 34 (22), 9108-9115CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    The catalytic steam gasification of palm oil wastes for hydrogen-rich gas prodn. was exptl. investigated in a combined fixed bed reactor using the newly developed tri-metallic catalyst. The results indicated that the supported tri-metallic catalyst had greater activity for the cracking of hydrocarbons and tar in vapor phase and higher hydrogen yield than the calcined dolomite in catalytic steam gasification of palm oil wastes. A series of expts. have been performed to explore the effects of temp., steam to biomass ratio (S/B) and biomass particle size on gas compn., gas yield, low heating value (LHV) and hydrogen yield. The expts. demonstrated that temp. was the most important factor in this process; higher temp. contributed to higher hydrogen prodn. and gas yield, however, it lowered gas heating value. Comparing with biomass catalytic gasification, the introduction of steam improved gas quality and yield, the optimal value of S/B was found to be 1.33 under the present operating condition. It was also shown that a smaller particle size was more favorable for gas quality and yield. However, the LHV of fuel gas decreased with the increasing S/B ratio and the decreasing biomass particle size.
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    Skoulou, V.; Zabaniotou, A.; Stavropoulos, G.; Sakelaropoulos, G. Syngas Production from Olive Tree Cuttings and Olive Kernels in a Downdraft Fixed-Bed Gasifier. Int. J. Hydrogen Energy 2008, 33 (4), 1185– 1194,  DOI: 10.1016/j.ijhydene.2007.12.051
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    Syngas production from olive tree cuttings and olive kernels in a downdraft fixed-bed gasifier
    Skoulou, V.; Zabaniotou, A.; Stavropoulos, G.; Sakelaropoulos, G.
    International Journal of Hydrogen Energy (2008), 33 (4), 1185-1194CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Fixed-bed gasification of olive kernels and olive tree cuttings was studied on lab. scale. Gasification took place with air at 750-950°, for various air equivalence ratios (0.14-0.42) and under atm. pressure. In each run, the main components of the gas phase were CO, CO2, H2 and CH4. Gasification with air at 950° favored gas yields. Syngas prodn. increased with reactor temp., while CO2, CH4, light hydrocarbons and tar followed an opposite trend. An increase of the air equivalence ratio decreased syngas prodn. and lowered the product gas heating value, but favoring tar destruction. Gas from olive tree cuttings at 950° and with an air equivalence ratio of 0.42 had a higher LHV (9.41 MJ/Nm3) in comparison to olive kernels (8.60 MJ/Nm3). Olive kernels produced more char with a higher content of fixed C (16.39 wt./wt.%) than olive tree cuttings; thus, they might be considered an attractive source for carbonaceous material prodn.
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    Fazil, A.; Kumar, S.; Mahajani, S. M. Gasification and Co-Gasification of Paper-Rich, High-Ash Refuse-Derived Fuel in Downdraft Gasifier. Energy 2023, 263, 125659,  DOI: 10.1016/j.energy.2022.125659
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    Gasification and Co-gasification of paper-rich, high-ash refuse-derived fuel in downdraft gasifier
    Fazil, A.; Kumar, Sandeep; Mahajani, Sanjay M.
    Energy (Oxford, United Kingdom) (2023), 263 (Part_A), 125659CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    Among the various waste-to-energy conversion methods, gasification is a tech. feasible option for municipal solid waste valorization, meeting current emission limits and reducing landfill disposal burden. This work investigates the potential of paper rich ( 76% wt.) com. refuse-derived fuel (RDF) having high ash content (/// 17% wt.) for gasification and co-gasification in downdraft gasifier. The ash formed from RDF, with higher proportion of alk. earth metals (Ca and Mg) and lower proportion of alkali metals (Na and K), can effectively av.
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    Seggiani, M.; Puccini, M.; Raggio, G.; Vitolo, S. Effect of Sewage Sludge Content on Gas Quality and Solid Residues Produced by Cogasification in an Updraft Gasifier. Waste Management 2012, 32 (10), 1826– 1834,  DOI: 10.1016/j.wasman.2012.04.018
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    Effect of sewage sludge content on gas quality and solid residues produced by cogasification in an updraft gasifier
    Seggiani, Maurizia; Puccini, Monica; Raggio, Giovanni; Vitolo, Sandra
    Waste Management (Oxford, United Kingdom) (2012), 32 (10), 1826-1834CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
    In the present work, the gasification with air of dehydrated sewage sludge (SS) with 20 wt.% moisture mixed with conventional woody biomass was investigated using a pilot fixed-bed updraft gasifier. Attention was focused on the effect of the SS content on the gasification performance and on the environmental impact of the process. The results showed that it is possible to co-gasify SS with wood pellets (WPs) in updraft fixed-bed gasification installations. However, at high content of sewage sludge the gasification process can become instable because of the very high ash content and low ash fusion temps. of SS. At an equiv. ratio of 0.25, compared with wood pellets gasification, the addn. of sewage sludge led to a redn. of gas yield in favor of an increase of condensate prodn. with consequent cold gas efficiency decrease. Low concns. of dioxins/furans and PAHs were measured in the gas produced by SS gasification, well below the limiting values for the exhaust gaseous emissions. NH3, HCl and HF contents were very low because most of these compds. were retained in the wet scrubber systems. On the other hand, high H2S levels were measured due to high sulfur content of SS. Heavy metals supplied with the feedstocks were mostly retained in gasification solid residues. The leachability tests performed according to European regulations showed that metals leachability was within the limits for landfilling inert residues. On the other hand, sulfate and chloride releases were found to comply with the limits for non-hazardous residues.
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    Chen, G.; Liu, F.; Guo, X.; Zhang, Y.; Yan, B.; Cheng, Z.; Xiao, L.; Ma, W.; Hou, L. Co-Gasification of Acid Hydrolysis Residues and Sewage Sludge in a Downdraft Fixed Gasifier with CaO as an In-Bed Additive. Energy Fuels 2018, 32 (5), 5893– 5900,  DOI: 10.1021/acs.energyfuels.7b03960
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    Co-gasification of Acid Hydrolysis Residues and Sewage Sludge in a Downdraft Fixed Gasifier with CaO as an In-Bed Additive
    Chen, Guanyi; Liu, Fang; Guo, Xiang; Zhang, Yanru; Yan, Beibei; Cheng, Zhanjun; Xiao, Lin; Ma, Wenchao; Hou, Li-an
    Energy & Fuels (2018), 32 (5), 5893-5900CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Co-gasification expts. of acid hydrolysis residues (AHR) and sewage sludge (SS) both derived from a lignocellulosic ethanol plant were preliminarily investigated in a downdraft fixed gasifier at atm. pressure. Attention was focused on the effects of the gasifier bed temp. (600-800 °C), SS content (0-100 wt %), and equivalence ratio (ER, 0.15-0.30) on the gas quality and cold gas efficiency (CGE). The results showed that the optimal low heating value (LHV) of fuel gas of 6.83 MJ/Nm3, CGE of 70.68%, and low tar content of 5.84 g/Nm3 were obtained at 800 °C, SS content of 50 wt %, CaO/C (molar ratio) of 1.0, and ER of 0.22. A high temp. was favorable for high-quality gas prodn., and the optimum temp. was 800 °C, at which CaO mainly played the catalyst role but not the CO2 sorbent. Synergetic effects occurred in the co-gasification, and gas quality could be improved in an appropriate proportion by blending 50 wt % SS with AHR. ER ranging from 0.20 to 0.22 improved gas quality and CGE; however, a higher ER favored the decrease of the tar content, and the optimal tar content of 4.00 g/Nm3 was obtained with ER = 0.30. The results indicated the potential technol. for air co-gasification of AHR and SS as an option for energy recovery and waste disposal as well as for light industry with agricultural feedstock.
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    Pfeifer, C.; Koppatz, S.; Hofbauer, H. Steam Gasification of Various Feedstocks at a Dual Fluidised Bed Gasifier: Impacts of Operation Conditions and Bed Materials. Biomass Convers Biorefin 2011, 1 (1), 39– 53,  DOI: 10.1007/s13399-011-0007-1
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    Steam gasification of various feedstocks at a dual fluidised bed gasifier: Impacts of operation conditions and bed materials
    Pfeifer, Christoph; Koppatz, Stefan; Hofbauer, Hermann
    Biomass Conversion and Biorefinery (2011), 1 (1), 39-53CODEN: BCBIBN; ISSN:2190-6823. (Springer)
    Gasification of biomass is an attractive technol. for combined heat and power prodn. as well as for synthesis processes such as prodn. of liq. and gaseous biofuels. Dual fluidized bed (DFB) technol. offers the advantage of a nearly nitrogen-free product gas mainly consisting of H2, CO, CO2 and CH4. The DFB steam gasification process has been developed at Vienna University of Technol. over the last 15 years using cold flow models, lab. units, math. modeling and simulation. The main findings of the exptl. work at a 100-kW pilot scale unit are presented. Different fuels (wood pellets, wood chips, lignite, coal, etc.) and different bed materials (natural minerals such as olivine, limestones, calcites, etc. as well as modified olivines) have been tested and the influence on tar content as well as gas compn. was measured and compared among the different components. Moreover, the influence of operating parameters such as fuel moisture content, steam/fuel ratio and gasification temp. on the product gas has been investigated. DFB steam gasification of solid biomass coupled with CO2 capture, the so-called absorption enhanced reforming (AER) process, is highlighted. The expts. in pilot scale led to com. realization of this technol. in demonstration scale. Summarising, the DFB system offers excellent fuel flexibility to be used in advanced power cycles as well as in polygeneration applications.
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    Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G.; Van Paasen, S. V. B.; Bergman, P. C. A.; Kiel, J. H. A. Catalytic Decomposition of Biomass Tars: Use of Dolomite and Untreated Olivine. Renew Energy 2005, 30 (4), 565– 587,  DOI: 10.1016/j.renene.2004.07.014
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    Catalytic decomposition of biomass tars: use of dolomite and untreated olivine
    Devi, Lopamudra; Ptasinski, Krzysztof J.; Janssen, Frans J. J. G.; van Paasen, Sander V. B.; Bergman, Patrick C. A.; Kiel, Jacob H. A.
    Renewable Energy (2005), 30 (4), 565-587CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Although biomass is getting increased attention as a renewable energy source, one of the remaining problems still to be solved is the redn. of the high level of tar present in the product gas from gasification of biomass. The purpose of the present work is to study the activity of olivine and dolomite for tar destruction. Some researchers investigated olivine as bed material for biomass gasification. But it is not yet known how tars behave in the presence of olivine and whether olivine has some activity towards tar destruction. A slipstream from a lab-scale atm. bubbling-fluidized-bed gasifier (located at ECN) is passed through a secondary fixed-bed reactor where the additives are placed. For easy understanding, the results are represented in terms of the following tar classes; GC-undetectable tars (class 1), heterocyclic compds. (class 2), arom. compds. (class 3), light polyarom. compds. (class 4), heavy polyarom. compds. (class 5). The general observation is that the conversion of all tar classes increases as the temp. was raised from 800 to 900°C for both additives. The water-sol. heterocyclic compds. can be easily converted by thermal treatment. At the temp. of 900°C, the water-sol. heterocyclic compds. are completely converted. A 48% decrease in heavy PAHs is obsd. with pure sand. Addn. of 17 wt% olivine to the sand leads to a 71% decrease of PAHs at 900°C, whereas addn. of 17 wt% (pre-calcined) dolomite converted 90%. Also improvement in conversion of other tar classes is obsd. when olivine and dolomite are added during hot gas cleaning. A total tar amt. of 4.0 g m0-3 could be reduced to 1.5 and 2.2 g m0-3 using dolomite and olivine, resp., at a temp. of 900°C. Inspite of this redn. in total tar concn., a limited impact on the tar dew point is obsd.
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    Mohammed, M.; Salmiaton, A.; Wan Azlina, W.; Mohammad Amran, M.; Fakhru'l-Razi, A. Air Gasification of Empty Fruit Bunch for Hydrogen-Rich Gas Production in a Fluidized-Bed Reactor. Energy Convers. Manage. 2011, 52, 1555– 1561,  DOI: 10.1016/j.enconman.2010.10.023
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    Luo, S.; Xiao, B.; Guo, X.; Hu, Z.; Liu, S.; He, M. Hydrogen-Rich Gas from Catalytic Steam Gasification of Biomass in a Fixed Bed Reactor: Influence of Particle Size on Gasification Performance. Int. J. Hydrogen Energy 2009, 34 (3), 1260– 1264,  DOI: 10.1016/j.ijhydene.2008.10.088
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    Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of particle size on gasification performance
    Luo, Siyi; Xiao, Bo; Guo, Xianjun; Hu, Zhiquan; Liu, Shiming; He, Maoyun
    International Journal of Hydrogen Energy (2009), 34 (3), 1260-1264CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    The catalytic steam gasification of biomass was carried out in a lab-scale fixed bed reactor in order to evaluate the effects of particle size at different bed temps. on the gasification performance. The bed temp. was varied from 600 to 900 °C and the biomass was sepd. into five different size fractions (below 0.075 mm, 0.075-0.15 mm, 0.15-0.3 mm, 0.3-0.6 mm and 0.6-1.2 mm). The results show that with decreasing particle size, the dry gas yield, carbon conversion efficiency and H2 yield increased, and the content of char and tar decreased. And the differences due to particle sizes in gasification performance practically disappear as the higher temp. bound is approached. Hydrogen and carbon monoxide contents in the produced gas increase with decreasing particle size at 900 °C, reaching to 51.2% and 22.4%, resp.
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    Lv, P. M.; Xiong, Z. H.; Chang, J.; Wu, C. Z.; Chen, Y.; Zhu, J. X. An Experimental Study on Biomass Air-Steam Gasification in a Fluidized Bed. Bioresource Technol. 2004, 95, 95– 101,  DOI: 10.1016/j.biortech.2004.02.003
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    An experimental study on biomass air-steam gasification in a fluidized bed
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    The characteristics of biomass air-steam gasification in a fluidized bed are studied in this paper. A series of experiments have been performed to investigate the effects of reactor temperature, steam to biomass ratio (S/B), equivalence ratio (ER) and biomass particle size on gas composition, gas yield, steam decomposition, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the fuel gas yield varied between 1.43 and 2.57 Nm3/kg biomass and the LHV of the fuel gas was between 6741 and 9143 kJ/Nm3. The results showed that higher temperature contributed to more hydrogen production, but too high a temperature lowered gas heating value. The LHV of fuel gas decreased with ER. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality. It was also shown that a smaller particle was more favorable for higher gas LHV and yield.
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    Wongsiriamnuay, T.; Kannang, N.; Tippayawong, N. Effect of Operating Conditions on Catalytic Gasification of Bamboo in a Fluidized Bed. Int. J. Chem. Eng. 2013, 2013, 1,  DOI: 10.1155/2013/297941
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    Jeong, Y. S.; Choi, Y. K.; Park, K. B.; Kim, J. S. Air Co-Gasification of Coal and Dried Sewage Sludge in a Two-Stage Gasifier: Effect of Blending Ratio on the Producer Gas Composition and Tar Removal. Energy 2019, 185, 708– 716,  DOI: 10.1016/j.energy.2019.07.093
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    Air co-gasification of coal and dried sewage sludge in a two-stage gasifier: Effect of blending ratio on the producer gas composition and tar removal
    Jeong, Yong-Seong; Choi, Young-Kon; Park, Ki-Bum; Kim, Joo-Sik
    Energy (Oxford, United Kingdom) (2019), 185 (), 708-716CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    The co-gasification of coal and dried sewage sludge (DSS) was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor. In this study, the effect of the blending ratio of coal and DSS was investigated. Producer gases that were obtained from the tar-cracking reactor filled with active carbon contained high levels of hydrogen (max. H2: 27.7 vol%) and low tar contents (min. tar: 0 mg/Nm3). Upon gasification of the coal/DSS blends, the hydrogen content decreased and tar content increased with increasing DSS. Blends with coal/DSS ratios of 70/30 and 50/50 showed a synergetic effect on tar redn., which could be attributed to the high ash content of the DSS. The gasification of the 70% DSS blend increased the condensed tar yield by only 0.1 wt%, compared to coal gasification. Lastly, a hot filter filled with Fe-impregnated active carbon was applied to completely remove tar from producer gas, which led to the prodn. of a tar-free and hydrogen-rich gas (30 vol%). Furthermore, the Fe-impregnated active carbon reduced the H2S content to 229 ppmv. In summary, it was possible to produce a clean gas from coal and DSS blends in the UOS gasification process.
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    García, G.; Campos, E.; Fonts, I.; Sánchez, J. L.; Herguido, J. Gas Catalytic Upgrading in a Two-Zone Fluidized Bed Reactor Coupled to a Cogasification Plant. Energy Fuels 2013, 27 (5), 2835– 2845,  DOI: 10.1021/ef400227z
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    Gas catalytic upgrading in a two-zone fluidized bed reactor coupled to a cogasification plant
    Garcia, G.; Campos, E.; Fonts, I.; Sanchez, J. L.; Herguido, J.
    Energy & Fuels (2013), 27 (5), 2835-2845CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    An integrated system has been designed and started up for sewage sludge and coal cogasification + desulfurization + gas reforming in a two-zone fluidized bed reactor (TZFBR). The system is capable of reforming tar compds. to nondetectable levels and improving gasification gas quality in terms of higher H2 and CO concns. The use of a TZFBR enables both the catalytic upgrading of the gasification gas and the regeneration of the catalyst deactivated by coke deposition in a single vessel. Both an increase of 37% of gas LHV and a redn. of tar compds. to nondetectable levels are achieved in the best conditions used, with a 2 vol % of oxygen in the regeneration flow. Dolomite was used in the desulfurization unit at 800 °C, allowing the redn. of the H2S content in the produced gas from 1100 ppm to less than 300 ppm, and a tar redn. from 15 g/m3(STP) to 0.2 g/m3(STP). With this novel integrated system, the catalytic cracking and reforming of a real gasification gas stream produced in the cogasification of sewage sludge and coal has been achieved, operating in a stable mode.
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    Pan, Y. G.; Velo, E.; Roca, X.; Manyà, J. J.; Puigjaner, L. Fluidized-Bed Co-Gasification of Residual Biomass/Poor Coal Blends for Fuel Gas Production. Fuel 2000, 79, 1317– 1326,  DOI: 10.1016/S0016-2361(99)00258-6
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    Fluidized-bed co-gasification of residual biomass/poor coal blends for fuel gas production
    Pan, Y. G.; Velo, E.; Roca, X.; Manya, J. J.; Puigjaner, L.
    Fuel (2000), 79 (11), 1317-1326CODEN: FUELAC; ISSN:0016-2361. (Elsevier Science Ltd.)
    Expts. involving the co-gasification of residual biomass/poor coal blends and gasification of individual feedstocks used in the blends were performed in a bench scale, continuous fluidized-bed working at atm. pressure. Two types of blends were prepd., mixing pine chips (from Valcabadillo, Spain) with black coal, a low-grade coal from Escatron, Spain, and Sabero coal, a refuse coal from Sabero, Spain, in the ratio range of 0/100-100/0. Exptl. tests were carried out by using as a gasification agent mixts. of air and steam with dew points of 74-85°C at gasification temps. of 840-910°C and superficial fluidized gas velocities of 0.7-1.4 m/s. Feasibility studies were very pos., showing that blending effectively improved the performance of fluidized-bed co-gasification of the low-grade coal, and the possibility of converting the refuse coal to a low-Btu fuel gas. This study indicates that a blend ratio with no less than 20% pine chips for the low-grade coal and 40% pine chips for the refuse coal are the most appropriate. The dry product gas low heating value augments with increasing blend ratio from 3700 to 4560 kJ/N m3 for pine chips/low-grade coal, and from 4000 to 4750 kJ/N m3 for pine chips/refuse coal. Dry product gas yield rises with the increase of the blend ratio from 1.80 to 3.20 N m3/kg (pine chips/low-grade coal), and from 0.75 to 1.75 N m3/kg (pine chips/refuse coal), resp. About 50% co-gasification process overall thermal efficiency can be achieved for the two types of blend.
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    Cao, Y.; Fu, L.; Mofrad, A. Combined-Gasification of Biomass and Municipal Solid Waste in a Fluidized Bed Gasifier. Journal of the Energy Institute 2019, 92 (6), 1683– 1688,  DOI: 10.1016/j.joei.2019.01.006
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    Combined-gasification of biomass and municipal solid waste in a fluidized bed gasifier
    Cao, Yan; Fu, Leijie; Mofrad, Amir
    Journal of the Energy Institute (2019), 92 (6), 1683-1688CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
    Due to the environmental problems assocd. with burning of fossil fuels and population growth, more attention has been paid to develop renewable energies in recent years. Among all options for renewable energy utilization, biomass gasification is more popular because of environmental benefits and economic issues. In the present study, a series of expts. were carried out to study the influence of blending ratio, reaction temp., equivalence ratio (ER) on co-gasification characteristics of pine sawdust (SD) and municipal solid waste (MSW). By increasing the blending ratio from 100% SD to 100% MSW, CO and CH4 resp. increased from 16.7 to 18.8 vol% and from 4.1 to 5.1 vol%, while an opposite trend was found for H2 and CO2. Over the ranges of the exptl. conditions used, the tar content and gas yield varied from 5.4 to 10.1 g/Nm3 and 1.34 to 1.15 Nm3/kg, resp.
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    Bhoi, P. R.; Huhnke, R. L.; Kumar, A.; Indrawan, N.; Thapa, S. Co-Gasification of Municipal Solid Waste and Biomass in a Commercial Scale Downdraft Gasifier. Energy 2018, 163, 513– 518,  DOI: 10.1016/j.energy.2018.08.151
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    Co-gasification of municipal solid waste and biomass in a commercial scale downdraft gasifier
    Bhoi, Prakashbhai R.; Huhnke, Raymond L.; Kumar, Ajay; Indrawan, Natarianto; Thapa, Sunil
    Energy (Oxford, United Kingdom) (2018), 163 (), 513-518CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    In this study, municipal solid waste was gasified with switchgrass, i.e., co-gasification, using a com.-scale downdraft gasifier to produce power. The expts. were performed using a com.-scale 100 kg/h downdraft gasifier at co-gasification ratios of 0, 20 and 40%. The hot and cold gas efficiencies, syngas compns., heating value and yield, gasifier temps. and tar content were measured and analyzed. The results indicate that co-gasification of up to 40% MSW performed satisfactorily. The heating values of syngas were 6.2, 6.5 and 6.7 MJ/Nm3 for co-gasification ratios of 0, 20 and 40%, resp. The cold and hot gas efficiencies were 60.1, 51.1 and 60.0% and 65.0, 55.2 and 64.4% for co-gasification ratios of 0, 20 and 40%, resp.
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    Zhu, H. L.; Zhang, Y. S.; Materazzi, M.; Aranda, G.; Brett, D. J. L.; Shearing, P. R.; Manos, G. Co-Gasification of Beech-Wood and Polyethylene in a Fluidized-Bed Reactor. Fuel Process. Technol. 2019, 190, 29– 37,  DOI: 10.1016/j.fuproc.2019.03.010
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    Co-gasification of beech-wood and polyethylene in a fluidized-bed reactor
    Zhu, Hua Lun; Zhang, Ye Shui; Materazzi, Massimiliano; Aranda, Guadalupe; Brett, Dan J. L.; Shearing, Paul R.; Manos, George
    Fuel Processing Technology (2019), 190 (), 29-37CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidized-bed reactor in the presence of four different types of bed materials (silica sand, olivine, Na-Y zeolite and ZSM-5 zeolite). ZSM-5 zeolite is very effective as a catalytic bed material in fluidized-bed reactor for wood-only gasification and co-gasification in terms of high hydrogen prodn.and CGE. Na-Y zeolite is more effective compared with ZSM-5 zeolite in co-gasification of the beech-wood and polyethylene process. The catalytic activity in co-gasification of beech-wood and polyethylene can be ranked accordingly: Na-Y zeolite > ZSM-5 zeolite > olivine. In general, higher amts.of steam injected in the fluidized-bed reactor and more polyethylene would lead to higher hydrogen prodn.in the co-gasification process.
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    Zhao, Y.; Sun, S.; Zhou, H.; Sun, R.; Tian, H.; Luan, J.; Qian, J. Experimental Study on Sawdust Air Gasification in an Entrained-Flow Reactor. Fuel Process. Technol. 2010, 91, 910– 914,  DOI: 10.1016/j.fuproc.2010.01.012
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    Experimental study on sawdust air gasification in an entrained-flow reactor
    Zhao, Yi-Jun; Sun, Shao-Zeng; Zhou, Hao; Sun, Rui; Tian, Hong-Ming; Luan, Ji-Yi; Qian, Juan
    Fuel Processing Technology (2010), 91 (8), 910-914CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Expts. were performed in an entrained-flow reactor to better understand the processes involved in biomass air gasification. Effects of the reaction temps. (700°, 800°, 900°, and 1000°), residence time and the equivalence ratio in the range of 0.22-0.34 on the gasification process were investigated. The behavior of biomass gasification was discussed in terms of compn. of produced gas. Four parameters, i.e. the low heating value, fuel gas prodn., carbon conversion and cold gas efficiency were used to evaluate the gasification. The results show that CO, CO2, and H2 are the main gasification products, while hydrocarbons (CH4 and C2H4) are the minor ones. With the increase of the reaction temp., the concn. of CO decreases, while the concns. of CO2 and H2 increase. The concns. of CH4 and C2H4 reach their max. value when the reaction temp. is 800°. The optimal reaction temp. is considered to be 800° and the optimal equivalence ratio is 0.28 in that the low heating value of the produced gas, carbon conversion and cold gas efficiency achieve their max. values. The kinetic parameters of sawdust air gasification are calcd. basing on the Arrhenius correlation.
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    Reed, T. B.; Das, A. Handbook of Biomass Downdraft Gasifier Engine Systems; Solar Energy Research Institute: Golden, CO, 1988.
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    Van De Kamp, W.; De Wild, P.; Zielke, U.; Suomalainen, M.; Knoef, H.; Good, J.; Liliedahl, T.; Unger, C.; Whitehouse, M.; Neeft, J.; Van De Hoek, H.; Kiel, J. Tar Measurement Standard for Sampling and Analysis of Tars and Particles in Biomass Gasification Product Gas. In Proceedings of the 14th European Biomass Conference and Exhibition, Paris, France, October 17–21, 2005; Energy Research Centre of the Netherlands: Petten, Netherlands, 2005.
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    Eghtedaei, R.; Mirhosseini, S. A.; Esfahani, M. J.; Foroughi, A.; Akbari, H. Co-Gasification of Biomass and Municipal Solid Waste for Hydrogen-Rich Gas Production. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects 2017, 39 (14), 1491– 1496,  DOI: 10.1080/15567036.2017.1315757
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    Co-gasification of biomass and municipal solid waste for hydrogen-rich gas production
    Eghtedaei, R.; Mirhosseini, S. A.; Esfahani, M. J.; Foroughi, A.; Akbari, H.
    Energy Sources, Part A: Recovery, Utilization, and Environmental Effects (2017), 39 (14), 1491-1496CODEN: ESPACB; ISSN:1556-7036. (Taylor & Francis, Inc.)
    Gasification is a high-temp. thermochem. process to generate a clean syngas which can be used as an alternative method for fuel conversion. In this article, a kinetic model of co-gasification of biomass and municipal solid waste (MSW) was developed to study the influence of several crit. parameters such as biomass/MSW ratio, reactor temp., and steam/fuel ratio on gas compn., hydrogen yield, and tar content. Results showed that the H2 concn. significantly varies in the produced syngas with changing the MSW/biomass ratio may be due to limited water gas shift and tar cracking reactions. Also, it was found that the tar content does not change significantly with av. values of steam/fuel ratio probably due to the slow kinetics of the hydrocarbon steam reforming reactions at a const. temp.
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    Qin, Y. H.; Campen, A.; Wiltowski, T.; Feng, J.; Li, W. The Influence of Different Chemical Compositions in Biomass on Gasification Tar Formation. Biomass Bioenergy 2015, 83, 77– 84,  DOI: 10.1016/j.biombioe.2015.09.001
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    The influence of different chemical compositions in biomass on gasification tar formation
    Qin, Yu Hong; Campen, Adam; Wiltowski, Tomasz; Feng, Jie; Li, Wenying
    Biomass and Bioenergy (2015), 83 (), 77-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    To elucidate the relationship between biomass compn. and tar formation, forest residue sawdust, rich in lignin, and agriculture waste cornstalks, rich in cellulose, were gasified in a spout-fluidized bed reactor from 700 °C to 900 °C. Gel permeation chromatog. (GPC) coupled with a photodiode array detector (PDA) and gas chromatog. - mass spectrometry (GC-MS) were used to analyze the tar character. The GPC results showed that the mol. mass distribution of the gasified tars were unchanged, only the amt. of each component changed when the temp. increased during gasification. The amt. of heaviest mol. mass components decreased, while the lighter components increased with temp. Sawdust tar and cornstalks tar both showed arom. character, while cornstalks tar contained more aliph. compds. than sawdust tar. The tar formation mechanism has been proposed from the exptl. data anal.
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    Guangul, F. M.; Sulaiman, S. A.; Raghavan, V. R. Gasification and Effect of Gasifying Temperature on Syngas Quality and Tar Generation: A Short Review. AIP Conf. Proc. 2012, 1440, 491– 498,  DOI: 10.1063/1.4704254
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    Gasification and effect of gasifying temperature on syngas quality and tar generation: A short review
    Guangul, Fiseha Mekonnen; Sulaiman, Shaharin Anwar; Raghavan, Vijay R.
    AIP Conference Proceedings (2012), 1440 (Pt. 1, 4th International Meeting of Advances in Thermofluids, 2011), 491-498CODEN: APCPCS; ISSN:0094-243X. (American Institute of Physics)
    A review. Corrosion, erosion and plugging of the downstream equipments by tar and ash particle and, low energy content of syngas are the main problems of biomass gasification process. This paper attempts to review the findings of literature on the effect of temp. on syngas quality, and in alleviating the tar and ash problems in the gasification process. The review of literature indicates that as the gasification temp. increases, concn. of the resulting H2 and carbon conversion efficiency increase, the amt. of tar in the syngas decreases. For the same condition, CH4 and CO concn. do not show consistent trend when the feedstock and gasification process varies. These necessitate the need for conducting an expt. for a particular gasification process and feedstock to understand fully the benefits of controlling the gasification temp. This paper also tries to propose a method to improve the syngas quality and to reduce the tar amt. by using preheated air and superheated steam as a gasifying media for oil palm fronds (OPF) gasification. (c) 2012 American Institute of Physics.
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    Chen, Y.; Luo, Y. H.; Wu, W. G.; Su, Y. Experimental Investigation on Tar Formation and Destruction in a Lab-Scale Two-Stage Reactor. Energy Fuels 2009, 23 (9), 4659– 4667,  DOI: 10.1021/ef900623n
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    Experimental Investigation on Tar Formation and Destruction in a Lab-Scale Two-Stage Reactor
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    Energy & Fuels (2009), 23 (9), 4659-4667CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    A lab-scale two-stage reactor has been constructed for studying the release and destruction of tars in the two-stage gasifier. First, the pyrolysis characteristics of three fuel samples are investigated only using the single stage reactor. The results show that the max. value of tar yield is: rice straw 25%, corn straw 22%, and fir sawdust 31% of the initial fuel. Then, the exptl. program is extended to investigate the effect of operating conditions in the second stage of the reactor on tar removal. The effects of temp., residence time, char particle size, char type, fuel type, and dild. air feeding to throat on tar emission has been studied. The results show that the tar decreased with increasing temp. and residence time and with decreasing char particle size. The char type has little effect on tar redn. Tar emission with limited dild. air feeding is obviously less than that with empty second stage due to the more reactive radicals produced in oxidative conditions. The straw tars appear to have a different suite of compds. than the other two samples of derived material and presumably have different cracking pathways. The tars collected from first stage and second stage have been characterized by gas chromatog./mass spectrometry (GC/MS) and gel permeation chromatog. The results indicate that tar after pyrolysis contains a large amt. of oxygenated constituents. With the increasing of reaction severity (from the empty heated second stage to heated second stage with char bed), the tar compds. reacted further (polymd.) to form larger mol. mass material. It is clear that the material characterized by GC/MS represents a very small part of the total tar. The results have shown that the tar emission from two-stage gasifier can be reduced to low levels using optimized operating conditions, but complete tar removal is difficult to realize due to manipulation of operating parameters and fuel type.
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    Knight, R. A. Experience with Raw Gas Analysis from Pressurized Gasification of Biomass. Biomass Bioenergy 2000, 18 (1), 67– 77,  DOI: 10.1016/S0961-9534(99)00070-7
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    Waste material in the form of wood waste, municipal solid waste and rice husks was pyrolyzed in a gas-purged static batch reactor and a fluidized bed reactor. The condensed pyrolytic oils were analyzed for their content of polycyclic arom. hydrocarbons (PAH). The oils were fractionated into chem. classes using mini-column liq. chromatog. followed by anal. using GC/FID and GC/MS for identification and quantitation of PAH. The waste derived oils were found to contain substantial concns. of PAH, which were formed via secondary Diels-Alder and deoxygenation reactions. The concns. of PAH were influenced by reactor temp. and residence time. The PAH consisted mainly of naphthalene, fluorene and phenanthrene and their alkylated homologues, but also included some PAH which were of known carcinogenic or mutagenic activity.
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    Nemanova, V.; Engvall, K. Tar Variability in the Producer Gas in a Bubbling Fluidized Bed Gasification System. Energy Fuels 2014, 28 (12), 7494– 7500,  DOI: 10.1021/ef5015617
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    Tar Variability in the Producer Gas in a Bubbling Fluidized Bed Gasification System
    Nemanova, Vera; Engvall, Klas
    Energy & Fuels (2014), 28 (12), 7494-7500CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Previous studies in an atm. bubbling fluidized bed (BFB) gasification system indicated significant tar variability along the system. In this paper, the exptl. procedure has been improved for reliable results and understanding of tar variability in the producer gas. By introducing a new sample point for tar anal. to the system, expts. indicated tar redn. in the gasifier, probably due to continuous accumulation of char and ash in the bed, as well as in the ceramic filter because of thermo- and catalytic effects. Thermogravimetric anal. of the filter sample indicated 14% of volatile inorg. compds., and addnl. anal. of inorg. parts showed alkali and alk. earth metal content, well-known as tar breakdown catalysts.
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    Dabai, F.; Paterson, N.; Millan, M.; Fennell, P.; Kandiyoti, R. Tar Formation and Destruction in a Fixed-Bed Reactor Simulating Downdraft Gasification: Equipment Development and Characterization of Tar-Cracking Products. Energy Fuels 2010, 24, 4560– 4570,  DOI: 10.1021/ef100681u
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    Tar Formation and Destruction in a Fixed-Bed Reactor Simulating Downdraft Gasification: Equipment Development and Characterization of Tar-Cracking Products
    Dabai, Fadimatu; Paterson, Nigel; Millan, Marcos; Fennell, Paul; Kandiyoti, Rafael
    Energy & Fuels (2010), 24 (8), 4560-4570CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    The aim of the present study is to examine operating parameters that would reduce the residual tar content in the fuel gas in downdraft gasifiers and eventually eliminate it altogether. A two-stage fixed-bed reactor was employed to simulate elements of tar cracking in a downdraft gasifier. In this reactor, tar is generated by pyrolysis in the first stage and cracking and gasification take place in the second stage. Modifications to a previous configuration of this reactor are described, which have enabled the use of smaller char particle sizes in the second stage and the generation of a more complete inventory of the reaction products. In this work, the effect of the temp. and the presence of char on product distributions are reported. Increasing the temp. from 700 to 1000°C resulted in a decrease in the quantity of tar recovered and an increase in the total amt. of CO released. The amt. of CH4 released increased between 700 and 800°C before remaining steady up to 1000°C. The CO2 content of the gas was relatively const. between 700 and 800°C and increased as the temp. increased from 800 to 1000°C. The amt. of water and light hydrocarbons (C2-C5 alkanes and alkenes) sharply decreased at 1000°C. The presence of char in the second stage had significant effects on tar cracking and product distributions. These effects were more obvious on the concns. of CO, CO2, and H2O, which may be a result of redn. reactions taking place with the carbon in the packed char bed. These reactions appear to be more significant at temps. between 900 and 1000°C, where the rates of gasification are expected to increase.
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    Atnaw, S. M.; Kueh, S. C.; Sulaiman, S. A. Study on Tar Generated from Downdraft Gasification of Oil Palm Fronds. Sci. World J. 2014, 2014, 497830,  DOI: 10.1155/2014/497830
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    Mahapatra, S.; Dasappa, S. Influence of Surface Area to Volume Ratio of Fuel Particles on Gasification Process in a Fixed Bed. Energy for Sustainable Development 2014, 19 (1), 122– 129,  DOI: 10.1016/j.esd.2013.12.013
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    Influence of surface area to volume ratio of fuel particles on gasification process in a fixed bed
    Mahapatra, Sadhan; Dasappa, S.
    Energy for Sustainable Development (2014), 19 (), 122-129CODEN: ESDEFY; ISSN:0973-0826. (Elsevier B.V.)
    The paper addresses the effect of particle size on tar generation in a fixed bed gasification system. Pyrolysis, a diffusion limited process, depends on the heating rate and the surface area of the particle influencing the release of the volatile fraction leaving behind residual char. The flaming time has been estd. for different biomass samples. It is found that the flaming time for wood flakes is almost one fourth than that of coconut shells for same equiv. diam. fuel samples. The particle d. of the coconut shell is more than twice that of wood spheres, and almost four times compared with wood flakes; having a significant influence on the flaming time. The ratio of the particle surface area to that of an equiv. diam. is nearly two times higher for flakes compared with wood pieces. Accounting for the d. effect, on normalizing with d. of the particle, the flaming rate is double in the case of wood flakes or coconut shells compared with the wood sphere for an equiv. diam. This is due to increased surface area per unit vol. of the particle. Expts. are conducted on estn. of tar content in the raw gas for wood flakes and std. wood pieces. It is obsd. that the tar level in the raw gas is about 80% higher in the case of wood flakes compared with wood pieces. The anal. suggests that the time for pyrolysis is lower with a higher surface area particle and is subjected to fast pyrolysis process resulting in higher tar fraction with low char yield. Increased residence time with staged air flow has a better control on residence time and lower tar in the raw gas.
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    Surjosatyo, A.; Vidian, F.; Nugroho, Y. S. Experimental Gasification of Biomass in an Updraft Gasifier with External Recirculation of Pyrolysis Gases. J. Combustion 2014, 2014, 832989,  DOI: 10.1155/2014/832989
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    Font Palma, C. Model for Biomass Gasification Including Tar Formation and Evolution. Energy Fuels 2013, 27, 2693– 2702,  DOI: 10.1021/ef4004297
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    Model for Biomass Gasification Including Tar Formation and Evolution
    Font Palma, Carolina
    Energy & Fuels (2013), 27 (5), 2693-2702CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Since tar elimination from the product gas is necessary to make gasification an attractive option, the presence of tar was included in a kinetic model. Lignin was assumed as the main precursor of tars due to its arom. nature; therefore, the lignin content of biomass was considered as part of the fuel characterization. This work shows the results from the simulation of the fluidized bed gasifier that incorporates the proposed mechanism for tar formation and evolution into the kinetic model. Model results were compared with exptl. data from wood gasification. The comparison showed that the model was consistent with what was expected during the evolution of primary tars according to exptl. work from previous reports. However, the model overestimated tars of class 2 and the total tar concn.
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    Qian, K.; Kumar, A.; Patil, K.; Bellmer, D.; Wang, D.; Yuan, W.; Huhnke, R. L. Effects of Biomass Feedstocks and Gasification Conditions on the Physiochemical Properties of Char. Energies 2013, 6 (8), 3972– 3986,  DOI: 10.3390/en6083972
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    Effects of biomass feedstocks and gasification conditions on the physiochemical properties of char
    Qian, Kezhen; Kumar, Ajay; Patil, Krushna; Bellmer, Danielle; Wang, Donghai; Yuan, Wenqiao; Huhnke, Raymond L.
    Energies (Basel, Switzerland) (2013), 6 (), 3972-3986CODEN: ENERGA; ISSN:1996-1073. (MDPI AG)
    Char is a low-value byproduct of biomass gasification and pyrolysis with many potential applications, such as soil amendment and the synthesis of activated carbon and carbon-based catalysts. Considering these high-value applications, char could provide economic benefits to a biorefinery utilizing gasification or pyrolysis technologies. However, the properties of char depend heavily on biomass feedstock, gasifier design and operating conditions. This paper reports the effects of biomass type (switchgrass, sorghum straw and red cedar) and equivalence ratio (0.20, 0.25 and 0.28), i.e., the ratio of air supply relative to the air that is required for stoichiometric combustion of biomass, on the physiochem. properties of char derived from gasification. Results show that the Brunauer-Emmett-Teller (BET) surface areas of most of the char were 1-10 m2/g and increased as the equivalence ratio increased. Char moisture and fixed carbon contents decreased while ash content increased as equivalence ratio increased. The corresponding Fourier Transform IR spectra showed that the surface functional groups of char differed between biomass types but remained similar with change in equivalence ratio.
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    Hwang, I. H.; Kobayashi, J.; Kawamoto, K. Characterization of Products Obtained from Pyrolysis and Steam Gasification of Wood Waste, RDF, and RPF. Waste Management 2014, 34 (2), 402– 410,  DOI: 10.1016/j.wasman.2013.10.009
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    93
    Characterization of products obtained from pyrolysis and steam gasification of wood waste, RDF, and RPF
    Hwang, In-Hee; Kobayashi, Jun; Kawamoto, Katsuya
    Waste Management (Oxford, United Kingdom) (2014), 34 (2), 402-410CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
    Pyrolysis and steam gasification of woody biomass chip (WBC) obtained from construction and demolition wastes, refuse-derived fuel (RDF), and refuse paper and plastic fuel (RPF) were performed at various temps. using a lab-scale instrument. The gas, liq., and solid products were examd. to det. their generation amts., properties, and the carbon balance between raw material and products.The amt. of product gas and its hydrogen concn. showed a considerable difference depending on pyrolysis and steam gasification at higher temp. The reaction of steam and solid product, char, contributed to an increase in gas amt. and hydrogen concn. The amt. of liq. products generated greatly depended on temp. rather than pyrolysis or steam gasification. The compns. of liq. product varied relying on raw materials used at 500 °C but the polycyclic arom. hydrocarbons became the major compds. at 900 °C irresp. of the raw materials used. Almost fixed carbon (FC) of raw materials remained as solid products under pyrolysis condition whereas FC started to decomp. at 700 °C under steam gasification condition.For WBC, both char utilization by pyrolysis at low temp. (500 °C) and syngas recovery by steam gasification at higher temp. (900 °C) might be practical options. From the results of carbon balance of RDF and RPF, it was confirmed that the carbon conversion to liq. products conspicuously increased as the amt. of plastic increased in the raw material. To recover feedstock from RPF, pyrolysis for oil recovery at low temp. (500 °C) might be one of viable options. Steam gasification at 900 °C could be an option but the method of tar reforming (e.g. catalyst utilization) should be considered.
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    Norisada, K.; Murakami, T.; Yasuda, H. New Approach to Analysis of Tar Components in Syngas Generated by Steam Gasification of Lignite in Fluidized Bed Gasifier. Energy Fuels 2017, 31 (1), 249– 254,  DOI: 10.1021/acs.energyfuels.6b02210
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    New Approach to Analysis of Tar Components in Syngas Generated by Steam Gasification of Lignite in Fluidized Bed Gasifier
    Norisada, Kazushi; Murakami, Takahiro; Yasuda, Hajime
    Energy & Fuels (2017), 31 (1), 249-254CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Lignite is a low-rank coal that is not used as a fuel in Japan. However, the effective use of this resource could be enabled by prodn. of syngas (hydrogen, carbon monoxide, etc.) from lignite through gasification. Tar in the syngas generated using the fluidized bed gasifier must be removed, and the tar compn. should be considered for the design of effective tar removal equipment. A new anal. and anal. methods of the tar were developed herein. Gas chromatograph mass spectrometry (GC/MS) and field desorption mass spectrometry (FD-MS) were used in combination to analyze the tar obtained during steam gasification of lignite at 1123 K using a lab.-scale fluidized bed gasifier. The low-boiling-point components were previously identified by GC/MS. However, the combined use of GC/MS and FD-MS in the new approach presented herein enabled elucidation of the overall compn. of tar, including the high-boiling-point components.
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    Rakesh, N.; Dasappa, S. Analysis of Tar Obtained from Hydrogen-Rich Syngas Generated from a Fixed Bed Downdraft Biomass Gasification System. Energy Convers Manag 2018, 167, 134– 146,  DOI: 10.1016/j.enconman.2018.04.092
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    Analysis of tar obtained from hydrogen-rich syngas generated from a fixed bed downdraft biomass gasification system
    Rakesh, N.; Dasappa, S.
    Energy Conversion and Management (2018), 167 (), 134-146CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    This paper focuses on the development of a test protocol for the anal. of tar collected from an oxy-steam gasification system with a downdraft reactor configuration using biomass. A 10 kg·h-1 oxy-steam gasification system developed at the Indian Institute of Science, Bangalore was used for the studies. The present work involves qual. and quant. analyses to est. the amt. and nature of the tar present in the gas produced. The major focus of the work has been towards establishing protocols to est. the content and concn. of various species present in the raw and clean gas. The method uses internal std. alongside external stds. while analyzing compds. using GC-MS and GC-FID. The study clearly establishes the need for using different ref. compds. like naphthalene and phenol for the quantification process depending upon the nature of compds. manifesting as tar mols. Further, it has been established that the conventionally used gravimetric anal. has limitations towards estg. the total amt. of tar. GC-MS is used for the identification of the compds. The results from the study indicate that the av. values obtained for clean gas and raw gas are 2.7 mg·Nm-3 and 168 mg·Nm-3 with gravimetric anal. and 37.6mg·Nm-3 and 267 mg·Nm-3 with GC-MS/FID method. The lower hydrocarbons, having the no. of carbon atoms in the range of 1-5, which are not considered as tar compds., are absent in the clean gas and are quantified to be 10.6mg·Nm-3 in the raw gas. Finally, the study also captures a technique of anal. and quantification which is of general nature, used generally in org. compd. estn., and therefore can be applied as a generic procedure. The results indicate that the level of tar in the clean gas is low, making the gas suitable for a variety of applications, and the effluent treatment process simpler. The anal. presents an est. of the tar level obtained with the GC-FID technique using both internal and external calibration curves. These results are compared with results from a similar approach using GC-MS for quantification and from the external calibration curves using GC-FID and GC-MS. These studies confirm that the approach presented here is suitable for the present research activity.
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    Meng, X.; Mitsakis, P.; Mayerhofer, M.; de Jong, W.; Gaderer, M.; Verkooijen, A. H.M.; Spliethoff, H. Spliethoff Hartmut. Tar Formation in a Steam-O 2 Blown CFB Gasifier and a Steam Blown PBFB Gasifier (BabyHPR): Comparison between Different on-Line Measurement Techniques and the off-Line SPA Sampling and Analysis Method. Fuel Process. Technol. 2012, 100, 16– 29,  DOI: 10.1016/j.fuproc.2012.03.002
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    Tar formation in a steam-O2 blown CFB gasifier and a steam blown PBFB gasifier (BabyHPR): Comparison between different on-line measurement techniques and the off-line SPA sampling and analysis method
    Meng, Xiangmei; Mitsakis, Panagiotis; Mayerhofer, Matthias; de Jong, Wiebren; Gaderer, Matthias; Verkooijen, Adrian H. M.; Spliethoff, Hartmut
    Fuel Processing Technology (2012), 100 (), 16-29CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Two online tar measurement campaigns were carried out using an atm. pressure 100 ""kWth steam-O2 blown circulating fluidized bed (CFB) gasifier at the Delft University of Technol. (TUD) and a 30-40kWth steam blown pressurized bubbling fluidized bed (PBFB) gasifier BabyHPR (Heatpipe Reformer) at the Tech. University Munich (TUM). Agrol, willow and Dry Distiller's Grains with Solubles (DDGS) were used. An FID based online tar analyzer (OTA), an induced fluorescence spectroscopy (LIFS) based online laser instrument, and off-line solid phase adsorption (SPA) were used to quantify tar content. In general, there was a fairly good agreement between the measured results of the 10 corresponding individual tar compds. obtained from Agrol and willow CFB and PBFB atm. pressure tests using the SPA and LIFS methods. The measured tar concn. difference between these two methods was less than 10%. However, a higher difference (up to 30%) was obsd. for fluoranthene and pyrene obtained from DDGS CFB test as well as those obtained from willow PBFB under pressure test. The total tar concn. measured by the LIFS, SPA and OTA methods varied in a comparable way with changing process parameters. Both the LIFS and OTA methods can be used as indicators to observe gasifier's performance change in real time, but a regular calibration of the OTA analyzer is required to achieve good and reliable results.
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    Sun, R.; Zobel, N.; Neubauer, Y.; Cardenas Chavez, C.; Behrendt, F. Analysis of Gas-Phase Polycyclic Aromatic Hydrocarbon Mixtures by Laser-Induced Fluorescence. Opt. Lasers Eng. 2010, 48, 1231– 1237,  DOI: 10.1016/j.optlaseng.2010.06.009
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    Li, C.; Suzuki, K. Tar Property, Analysis, Reforming Mechanism and Model for Biomass Gasification-An Overview. Renewable Sustainable Energy Rev. 2009, 594– 604,  DOI: 10.1016/j.rser.2008.01.009
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    Tar property, analysis, reforming mechanism and model for biomass gasification-An overview
    Li, Chunshan; Suzuki, Kenzi
    Renewable & Sustainable Energy Reviews (2009), 13 (3), 594-604CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review, with 41 refs. Biomass becomes an important primary energy source as well as renewable energy source. As the most promising biomass use method, biomass gasification is gaining attention as a route for biomass energy prodn., but producer gas from this process usually contains unacceptable levels of tar. The tar control and convert is a key issue for a successful application of biomass-derived producer gas. A detail overview on tar chem. and phys. properties, reforming mechanism and reaction kinetic model are summarized.
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    Carpenter, D. L.; Deutch, S. P.; French, R. J. Quantitative Measurement of Biomass Gasifier Tars Using a Molecular-Beam Mass Spectrometer: Comparison with Traditional Impinger Sampling. Energy Fuels 2007, 21 (5), 3036– 3043,  DOI: 10.1021/ef070193c
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    Quantitative Measurement of Biomass Gasifier Tars Using a Molecular-Beam Mass Spectrometer: Comparison with Traditional Impinger Sampling
    Carpenter, Daniel L.; Deutch, Steve P.; French, Richard J.
    Energy & Fuels (2007), 21 (5), 3036-3043CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Removal of tars produced during biomass gasification continues to be a tech. barrier confronted by developers of com. thermochem. conversion systems. Quant. measurement of tar in the synthesis gas (syngas) stream is important to assess the effectiveness of cleanup and conditioning processes and verify the suitability of the cleaned syngas for its intended downstream use (e.g., catalytic conversion to liq. fuels, hydrogen recovery, or electricity prodn.). In an effort to advance the art of gasifier tar measurement and address some limitations of traditional impinger sampling, the use of a mol.-beam mass spectrometer (MBMS) sampling system was investigated as an alternative method for quantifying real-time tar concns. in biomass gasifier-derived syngas. The 0.5 ton/day pilot-scale biomass gasification system of the National Renewable Energy Lab. (NREL) was used to make direct comparisons between MBMS sampling and replicate impinger sampling during continuous operations. Some systematic differences between the methods were obsd., although they do appear correlated. Using a synthetic tar mixt., as well as actual corn-stover-derived syngas, expts. were carried out to compare the accuracy of the two methods. Both methods demonstrated good reproducibility, but the MBMS measurements appear to be more accurate. Tar concns. detd. from impinger sampling averaged 11-21% lower than expected, depending upon the compd. Av. MBMS measurements were within 6% of the known values, demonstrating that the MBMS can be used to improve quant., continuous, real-time monitoring of gasifier tar.
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    Brage, C.; Yu, Q.; Chen, G.; Sjöström, K. Use of Amino Phase Adsorbent for Biomass Tar Sampling and Separation. Fuel 1997, 76 (2), 137– 142,  DOI: 10.1016/S0016-2361(96)00199-8
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    Use of amino phase adsorbent for biomass tar sampling and separation
    Brage, Claes; Yu, Qizhuang; Chen, Guanxing; Sjoestroem, Krister
    Fuel (1997), 76 (2), 137-142CODEN: FUELAC; ISSN:0016-2361. (Elsevier)
    To reduce sampling and sample sepn. time, a highly efficient gas chromatog. method was designed based on solid-phase adsorption (SPA) on an aminopropylsilane-silica gel column. The method was suitable for intermittent trapping of tar compds., ranging from benzene to coronene, prevailing in product gases from thermal decompn. of biomass at 700-1000°. Using eluotropic elution, adsorbates were selectively desorbed into arom. and phenolic fractions and then detd. by gas chromatog. with flame-ionization detection. Use of this sampling step resulted in collection of one to three samples per min, compared with one or two samples per h using conventional cold trapping techniques. Thus, the progress of pyrolysis and gasification processes in terms of mol. distribution is easily followed. Furthermore, the method can be readily applied to establish cold-trap and filter performance and for industrial emission control. The method also compared favorably with a novel solid-phase micro extn. technique with respect to analyte discrimination and speed.
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    Morf, P.; Hasler, P.; Nussbaumer, T. Mechanisms and Kinetics of Homogeneous Secondary Reactions of Tar from Continuous Pyrolysis of Wood Chips. Fuel 2002, 81 (7), 843– 853,  DOI: 10.1016/S0016-2361(01)00216-2
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    Mechanisms and kinetics of homogeneous secondary reactions of tar from continuous pyrolysis of wood chips
    Morf, Philipp; Hasler, Philipp; Nussbaumer, Thomas
    Fuel (2002), 81 (7), 843-853CODEN: FUELAC; ISSN:0016-2361. (Elsevier Science Ltd.)
    The change of mass and compn. of biomass tar due to homogeneous secondary reactions was exptl. studied by a lab reactor system that allows the spatially sepd. prodn. and conversion of biomass tar. A tarry pyrolysis gas was continuously produced by pyrolysis of wood chips (fir and spruce, 10-40 mm diam.) under fixed-bed biomass gasification conditions. Homogeneous secondary tar reactions without the external supply of oxidizing agents were studied in a tubular flow reactor operated at 500-1000° and with space times <0.2 s. Extensive chem. anal. of wet chem. tar samples provided quant. data about the mass and compn. of biomass tar during homogeneous conversion. These data were used to study the kinetics of the conversion of gravimetric tar and the formation of PAH compds., like naphthalene. Under the reactions conditions chosen for the expts., homogeneous secondary tar reactions become important at temps. >650, which is indicated by the increasing concns. of the gases CO, CH, and H in the pyrolysis gas. The gravimetric tar yield decreases with increasing reactor temps. during homogeneous tar conversion. The highest conversion reached in the expts. was 88% at a ref. temp. of 990° and isothermal space time of 0.12 s. Hydrogen is a good indicator for reactions that convert the primary tar into aroms., esp. PAH. Soot appears to be a major product from homogeneous secondary tar reactions.
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    Valderrama Rios, M. L.; González, A. M.; Lora, E. E. S.; Almazán del Olmo, O. A. Reduction of Tar Generated during Biomass Gasification: A Review. Biomass Bioenergy 2018, 108, 345– 370,  DOI: 10.1016/j.biombioe.2017.12.002
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    Reduction of tar generated during biomass gasification: A review
    Valderrama Rios, Martha Lucia; Gonzalez, Aldemar Martinez; Lora, Electo Eduardo Silva; Almazan del Olmo, Oscar Agustin
    Biomass and Bioenergy (2018), 108 (), 345-370CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    A review. One of the main problems that happen during biomass gasification is tar formation, which could make this technol. unsuccessfully from a com. point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, lab. and industrial methods and technologies for its redn.-removal, as well as research and development in this area are reviewed and evaluated in this paper.
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    Bosmans, A.; Wasan, S.; Helsen, L. Waste-to-Clean Syngas: Avoiding Tar Problems. In Proceedings of the 2nd International Academic Symposium on Enhanced Landfill Mining, Houthalen-Helchteren, Belgium, October 14–16, 2013; .EURELCO: Leuven, Belgium, 2013.
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    Delgado, J.; Aznar, M. P.; Corella, J. Biomass Gasification with Steam in Fluidized Bed: Effectiveness of CaO, MgO, and CaO-MgO for Hot Raw Gas Cleaning. Ind. Eng. Chem. Res. 1997, 36, 1535– 1543,  DOI: 10.1021/ie960273w
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    Biomass Gasification with Steam in Fluidized Bed: Effectiveness of CaO, MgO, and CaO-MgO for Hot Raw Gas Cleaning
    Delgado, Jesus; Aznar, Maria P.; Corella, Jose
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    The upgrading of the raw hot gas from a bubbling fluidized bed biomass gasifier is studied using cheap calcined minerals or rocks downstream from the gasifier. Biomass gasification is made with steam (not air) at 750-780° and about 0.5-1.0 kg of biomass/h. Calcined solids used are dolomite (MgO-CaO), pure calcite (CaO), and pure magnesite (MgO). Variables studied have been temp. of the secondary bed (780-910°), time of contact or space-time of the gas (0.08-0.32 kg·h/m3n), and particle diam. (1-4 mm) and type of mineral. Their effects on tar conversion, tar amt. in the exit gas, product distribution, and gas compn. are presented. Using a macro-kinetic model for the tar disappearance network, the activities of the stones are expressed by their apparent kinetic const. Apparent energies of activation for tar elimination (42-47 kJ/mol) and preexponential and effectiveness factors are given for all tested solids of which the most active is the calcined dolomite.
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    Van Paasen, S. V. B.; Neeft, J. P. A.; Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G.; Meijer, R.; Berends, R. H.; Temmink, H. M. G.; Brem, G.; Padban, N.; Bramer, E A. Primary Measures to Reduce Tar Formation in Fluidised-Bed Biomass Gasifiers; Final Report SDE project P1999-012; Kiel, J. H. A., Ed.; Energy Research Centre of the Netherlands: Petten, Netherlands, 2004.
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    Cortazar, M.; Santamaria, L.; Lopez, G.; Alvarez, J.; Zhang, L.; Wang, R.; Bi, X.; Olazar, M. A Comprehensive Review of Primary Strategies for Tar Removal in Biomass Gasification. Energy Convers Manag 2023, 276, 116496  DOI: 10.1016/j.enconman.2022.116496
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    A comprehensive review of primary strategies for tar removal in biomass gasification
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    Energy Conversion and Management (2023), 276 (), 116496CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    A review. In the current energy scenario, the prodn. of heat, power and biofuels from biomass have become of major interest. Amongst diverse thermochem. routes, gasification has stood out as a key technol. for the large-scale application of biomass. However, the development of biomass gasification is subjected to the efficient conversion of biochar and the mitigation of troublesome byproducts, such as tar. Syngas with high tar content can cause pipeline fouling, downstream corrosion, catalyst deactivation, as well as adverse impact on health and environment, which obstruct the commercialization of biomass gasification technologies. Since the redn. of tar formation is a key challenge in biomass gasification, a comprehensive overview is provided on the following aspects, which particularly include the definition and complementary classifications of tar, as well as possible tar formation and transformation mechanisms. Moreover, the adverse effects of tar on downstream applications, human health or environment, and tar analyzing techniques (online and off-line) are discussed. Finally, the primary tar removal strategies are summarized. In this respect, the effect of key operation parameters (temp., ER and S/B), catalysts utilization (natural and supported metal catalysts) and the improvement of reactor design on tar formation and elimination was thoroughly analyzed.
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    Nobre, C.; Longo, A.; Vilarinho, C.; Goncalves, M. Gasification of Pellets Produced from Blends of Biomass Wastes and Refuse Derived Fuel Chars. Renew Energy 2020, 154, 1294– 1303,  DOI: 10.1016/j.renene.2020.03.077
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    Gasification of pellets produced from blends of biomass wastes and refuse derived fuel chars
    Nobre, Catarina; Longo, Andrei; Vilarinho, Candida; Goncalves, Margarida
    Renewable Energy (2020), 154 (), 1294-1303CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Refuse derived fuel (RDF) was carbonized at 300°C for 30 min and the resulting RDF char was used as additive for biomass pellets. Pine waste pellets with 0, 5 and 10% incorporation of RDF char were prepd. and characterized. RDF char incorporation caused an increase in fixed carbon and ash contents of the pellets. The pellets were subjected to gasification in a 1 kg/h bubbling-fluidized-bed gasifier at different temps. (800 and 850°C) and equivalence ratios (0.25 and 0.30). The producer gas yield varied from 1.5 to 2.5 m3/kg and was higher for an ER of 0.25. Carbon conversion and cold gas efficiency presented values between 60.4% - 96.1% and 42.3%-73.7%, resp. Concns. of CO, CO2, H2 and CH4 reached values between 13.3-17.4 vol% dry for CO, 13.1-14.7 vol% dry for CO2, 4.9-11.1 vol% dry for H2 and 3.5-4.4 vol% dry for CH4. Tars produced during gasification contained mainly arom. hydrocarbons and phenols, showing an increase in heavy PAHs concn. with higher RDF char incorporation. The RDF char can be used as a gasification additive at moderate incorporation ratios.
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    Mastellone, M. L.; Zaccariello, L.; Arena, U. Co-Gasification of Coal, Plastic Waste and Wood in a Bubbling Fluidized Bed Reactor. Fuel 2010, 89, 2991– 3000,  DOI: 10.1016/j.fuel.2010.05.019
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    Co-gasification of coal, plastic waste and wood in a bubbling fluidized bed reactor
    Mastellone, Maria Laura; Zaccariello, Lucio; Arena, Umberto
    Fuel (2010), 89 (10), 2991-3000CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Seven mixts. of coals, plastics and wood have been pelletized and fed into a pre-pilot scale fluidized bed gasifier in order to investigate the main aspects of the co-gasification of these materials. The main components of the obtained syngas (CO, H2, CO2, N2, CH4, CnHm) were measured by means of online analyzers and a gas cromatograph. The performance of the gasifier was evaluated on the basis of syngas compn., carbon conversion efficiency, energy content of syngas, cold gas efficiency and yield of undesired byproducts (tar and soot-like particulate). The results of a first series of exptl. tests showed the effect of gas fluidizing velocity and that of equivalence ratio on the main performance parameters for a specific coal-plastics mixt. A second series of tests has been carried out by changing the mixt. compn. keeping fixed the gas velocity and equivalence ratio. The presence of wood and coal in the mixt. with plastics contributed to reduce the tar prodn. even though it is accompanied by a lower syngas specific energy.
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    Kostyniuk, A.; Grilc, M.; Likozar, B. Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds to Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures. Ind. Eng. Chem. Res. 2019, 58 (19), 7690– 7705,  DOI: 10.1021/acs.iecr.9b01219
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    Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds To Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures
    Kostyniuk, Andrii; Grilc, Miha; Likozar, Blaz
    Industrial & Engineering Chemistry Research (2019), 58 (19), 7690-7705CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    A review. The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chem. substances, and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodol. unsuccessfully due to the blockage of sepg. particle filters, fuel line flow, and substantial transfer losses. Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, it is still highly desirable to enhance the catalysts' activity kinetics, selectivity, stability, resistance to (ir)reversible coke deposition, and regeneration solns. The purpose of this review is to provide a comparative systematic evaluation of the various natural, synthetic, and hybrid ways to convert the model mol. compds. into benzene, toluene, xylene, (poly)aroms., syngas, and others. The recent scientific progress, including calcite, dolomite, lime, magnesite, olivine, char, nonmetallic activated carbons, supported alkali, noble, and transition metals, and (metal-promoted) zeolites, is presented. A special concd. attention is paid to effectiveness, related to hydrogenation, peculiar pore structure, and formulations' suitable acidity. The role of catalysis is described, recommendations for prospective catalyzed mechanisms are provided, and future tech. feasibility is discussed as well.
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    Zhen, H.; Wang, Y.; Fang, S.; Lin, Y.; Song, D.; Zhao, K.; Zhang, Y.; Xia, H.; Zhao, Z.; Huang, H. Chemical Looping Gasification of Benzene as a Biomass Tar Model Compound Using Hematite Modified by Ni as an Oxygen Carrier. Appl. Energy Combust. Sci. 2023, 15, 100172,  DOI: 10.1016/j.jaecs.2023.100172
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    Simell, P. A.; Hirvensalo, E. K.; Smolander, V. T.; Krause, A. O. I. Steam Reforming of Gasification Gas Tar over Dolomite with Benzene as a Model Compound. Ind. Eng. Chem. Res. 1999, 38, 1250– 1257,  DOI: 10.1021/ie980646o
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    Steam Reforming of Gasification Gas Tar over Dolomite with Benzene as a Model Compound
    Simell, Pekka A.; Hirvensalo, Elisa K.; Smolander, Visa T.; Krause, A. Outi I.
    Industrial & Engineering Chemistry Research (1999), 38 (4), 1250-1257CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Tar decompn. over a dolomite catalyst in gasification conditions was modeled using benzene as a tar model compd. The reactions of the gas main components were included in the models studied. Kinetic studies were carried out at 750-925 °C and under ambient pressure in a plug flow reactor using a mixt. of simulated gasification gas. Operation conditions without external or internal mass-transfer limitations were applied. Mechanistic models of the Langmuir-Hinshelwood type describing benzene decompn. were developed and tested. Exptl. results could be best described by a kinetic rate equation based on the assumption that single-site adsorption of benzene was the rate-detg. step and that adsorption of hydrogen inhibited benzene decompn.
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    Colby, J. L.; Wang, T.; Schmidt, L. D. Steam Reforming of Benzene as a Model for Biomass-Derived Syngas Tars over Rh-Based Catalysts. Energy Fuels 2010, 24 (2), 1341– 1346,  DOI: 10.1021/ef901033d
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    Steam Reforming of Benzene As a Model for Biomass-Derived Syngas Tars over Rh-Based Catalysts
    Colby, Joshua L.; Wang, Tao; Schmidt, Lanny D.
    Energy & Fuels (2010), 24 (2), 1341-1346CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    The ability of Rh based catalysts to remove undesired tars from biomass-derived syngas was examd. under realistic operating conditions. Expts. were performed in a fixed bed reactor at temps. of 650-850°C and atm. pressure using C6H6 as a model tar compd. Benzene conversion exhibited a strong dependence on temp. and H2O concn. in the feed. Significantly better catalyst performance was obsd. upon addn. of Ce to the catalyst, which increased Rh dispersion and stability. The concn. of C6H6 in the feed had little effect on catalyst performance. CO2, H2, and CO cofeeds had pos., neutral, and neg. effects, resp., on C6H6 conversion. A representative biomass-derived syngas mixt. of N2, H2, CO, CO2, H2O, and C6H6 was tested on the Rh-Ce catalyst at 850°C and 2 SLPM total flow rate, resulting in almost complete C6H6 conversion to a near equil. product stream.
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    Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Removal Characteristics of Tar Benzene Using the Externally Oscillated Plasma Reformer. Chemical Engineering and Processing: Process Intensification 2012, 57–58, 65– 74,  DOI: 10.1016/j.cep.2012.03.007
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    Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Decomposition of Benzene as a Surrogate Tar in a Gliding Arc Plasma. Environ. Prog. Sustain Energy 2013, 32 (3), 837– 845,  DOI: 10.1002/ep.11663
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    Park, H. J.; Park, S. H.; Sohn, J. M.; Park, J.; Jeon, J.-K.; Kim, S.-S.; Park, Y.-K. Steam Reforming of Biomass Gasification Tar Using Benzene as a Model Compound over Various Ni Supported Metal Oxide Catalysts. Bioresour. Technol. 2010, 101, S101– S103,  DOI: 10.1016/j.biortech.2009.03.036
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    Saleem, F.; Khoja, A. H.; Umer, J.; Ahmad, F.; Abbas, S. Z.; Zhang, K.; Harvey, A. Removal of Benzene as a Tar Model Compound from a Gas Mixture Using Non-Thermal Plasma Dielectric Barrier Discharge Reactor. J. Energy Institute 2021, 96, 97– 105,  DOI: 10.1016/j.joei.2021.02.008
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    116
    Removal of benzene as a tar model compound from a gas mixture using non-thermal plasma dielectric barrier discharge reactor
    Saleem, Faisal; Khoja, Asif Hussain; Umer, Jamal; Ahmad, Farhan; Abbas, Syed Zaheer; Zhang, Kui; Harvey, Adam
    Journal of the Energy Institute (2021), 96 (), 97-105CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
    In the present work, the decompn. of benzene as a tar model compd. was studied in a gas mixt. (CO2, H2, CO, and CH4) using a dielec. barrier discharge (DBD) non-thermal plasma reactor. The combined effect of temp. and power was studied to investigate the performance of the DBD reactor. The decompn. of tar compd. increased from 49.9 to 96% with increasing specific input energy (SIE) from 2.05 to 16.4 kWh/m3. The major products were lower hydrocarbons (C2-C5) and solid residues. The higher temp. (400°C) in the presence of plasma (40 W), decreased the conversion of tar compd. from 96 to 78%. However, the selectivity of lower hydrocarbons increases substantially to 52%, and the formation of solid residues is significantly reduced. Hence, the problematic solid residues formation can be controlled at a higher temp. during the treatment of gasifier product gas using non-thermal plasma.
  117. 117
    Pan, W.; Meng, J.; Gu, T.; Zhang, Q.; Zhang, J.; Wang, X.; Bu, C.; Liu, C.; Xie, H.; Piao, G. Plasma Catalytic Steam Reforming of Benzene as a Tar Model Compound over Ni-HAP and Ni-GammaAl2O3 Catalysts: Insights into the Importance of Steam and Catalyst Support. Fuel 2023, 339, 127327,  DOI: 10.1016/j.fuel.2022.127327
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    Plasma-catalytic steam reforming of benzene as a tar model compound over Ni-HAP and Ni-γAl2O3 catalysts: Insights into the importance of steam and catalyst support
    Pan, Wei; Meng, Junguang; Gu, Tingting; Zhang, Qian; Zhang, Jubing; Wang, Xinye; Bu, Changsheng; Liu, Changqi; Xie, Hao; Piao, Guilin
    Fuel (2023), 339 (), 127327CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Non-thermal plasma (NTP) coupled Ni-based catalysts are a promising method for tar steam reforming to syngas. In this work, Ni-based catalysts supported on hydroxyapatite (Ni-HAP) and γAl2O3 (Ni-γAl2O3) coupled with a coaxial dielec. barrier discharge (DBD) plasma were used to degrade biomass tar, and benzene was selected as a typical unbranched benzene ring structured tar model compd. In the NTP alone system, an increase in discharge power leads to benzene deep cracking to carbon deposition. In the NTP-catalytic system, the reaction temp. is a crit. factor for catalysis, and the catalyst leads to a significant increase in benzene conversion and total gas yield, prompting the conversion of more cracking intermediates to gaseous products. Steam in the system has both pos. and neg. effects: a certain amt. of steam can increase the amt. of H. and .OH, promoting benzene decompn. and carbon deposit elimination; excessive steam will compete for energetic electrons or oxidize the active metal in the catalyst, inhibiting benzene conversion. The Ni3-HAP catalyst exhibits the max. benzene conversion (92.13%) and energy efficiency (8.49 g/kWh), thanks to the formed Ni2+[I] and Ni2+[II] in the lattice due to the flexible ion exchange properties of the HAP support. The main reason for the catalyst activity degrdn. is carbon deposition rather than catalyst sintering. A good match among tar conversion rate, degree of decompn., steam content and steam decompn. rate is crit. for efficient and stable operation of the NTP-catalytic system.
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    Han, J.; Kim, H. The Reduction and Control Technology of Tar during Biomass Gasification/Pyrolysis: An Overview. Renewable and Sustainable Energy Reviews 2008, 12 (2), 397– 416,  DOI: 10.1016/j.rser.2006.07.015
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    The reduction and control technology of tar during biomass gasification/pyrolysis: An overview
    Han, Jun; Kim, Heejoon
    Renewable & Sustainable Energy Reviews (2007), 12 (2), 397-416CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review, with 127 refs. Biomass is an important primary energy source as well as renewable energy source. As the most promising biomass use method, gasification/pyrolysis produces not only useful fuel gases, char and chems., but also some byproducts like fly ash, NOx, SO2 and tar. Tar in the product gases will condense at low temp., and lead to clogged or blockage in fuel lines, filters and engines. Also, too much tar in product gases will reduce the use efficiency of biomass. Therefore, the redn. or decompn. of tar in biomass derived fuel gases is one of the biggest obstacles in its use for power generation. The authors review the literatures pertaining to tar redn. or destruction methods during biomass gasification/pyrolysis. From their characteristics, the current tar redn. or destruction methods can be broadly divided into 5 main groups: mechanism methods, self-modification, thermal cracking, catalyst cracking and plasma methods.
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    Gong, X.; Lin, Y.; Li, X.; Wu, A.; Zhang, H.; Yan, J.; Du, C. Decomposition of Volatile Organic Compounds Using Gliding Arc Discharge Plasma. J. Air Waste Manage. Assoc. 2020, 70, 138– 157,  DOI: 10.1080/10962247.2019.1698476
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    Decomposition of volatile organic compounds using gliding arc discharge plasma
    Gong, Xiangjie; Lin, Yanchun; Li, Xiaodong; Wu, Angjian; Zhang, Hao; Yan, Jianhua; Du, Changming
    Journal of the Air & Waste Management Association (2020), 70 (2), 138-157CODEN: JAWAFC; ISSN:1096-2247. (Taylor & Francis Ltd.)
    A review. This work provides a systematic review on the decompn. of volatile org. pollutants in flue gas through the gliding arc (GA) plasma technol. To begin with, the basic mechanisms of GA plasma generation are summarized and three characteristic stages existed during the GA plasma generation process are revealed: gas breakdown stage, equil. stage, and non-equil. stage. Then, the types of GA reactors are comparatively illustrated. Possible destruction mechanisms of volatile org. compds. (VOCs) by GA plasma are discussed by taking chloroform, benzene, and methanol as examples. Furthermore, the effects of many operating parameters on the VOCs destruction efficiency are comprehensively analyzed. Simultaneously, the product distribution, energy cost, tech. and economic during the whole decompn. process are considered. Finally, the advantages and disadvantages of GA plasma and its further development trend are concluded from the academic and industrial application of GA plasma in VOCs decompn. Implications: This paper comprehensively describes the principle, characteristics, research progress and engineering application examples of the degrdn. of volatile orgs. by gliding arc discharge plasma, so that readers can fully understand the degrdn. of volatile orgs. by gliding arc discharge plasma and provide theor. basis for the industrial application of the degrdn. of volatile orgs. by gliding arc discharge plasma.
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    Shao, S.; Ye, Z.; Sun, J.; Liu, C.; Yan, J.; Liu, T.; Li, X.; Zhang, H.; Xiao, R. A Review on the Application of Non-Thermal Plasma (NTP) in the Conversion of Biomass: Catalyst Preparation, Thermal Utilization and Catalyst Regeneration. Fuel 2022, 330, 125420,  DOI: 10.1016/j.fuel.2022.125420
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    A review on the application of non-thermal plasma (NTP) in the conversion of biomass: Catalyst preparation, thermal utilization and catalyst regeneration
    Shao, Shanshan; Ye, Zian; Sun, Jiayuan; Liu, Chengyue; Yan, Jinlong; Liu, Tieyi; Li, Xiaohua; Zhang, Huiyan; Xiao, Rui
    Fuel (2022), 330 (), 125420CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    A review. A brief review of non-thermal plasma (NTP) technol. as a new technol. for the thermal conversion of biomass is presented in this paper. Three aspects of the entire process are generally considered from the viewpoint of (i) biomass pretreatment, catalyst prepn. assisted by NTP prior to the thermochem. conversion; (ii) thermochem. conversion of biomass or its derivates assisted by NTP; and (iii) regeneration of deactivated catalyst after thermochem. conversion. A stable catalyst is a requisite for any industrial application of catalysis to make it com. viable. However, there is still a challenge to achieving a controlled morphol., which majorly affects the catalytic performance in the thermochem. conversion of biomass or its derivates, and template removal and metal loading by NTP are focused. At the same time, the reforming of tar, catalytic pyrolysis of biomass, gasification of biomass, and upgrading of bio-oil assisted by NTP are given great attention, including the reaction mechanism, product distribution, etc. In the thermochem. conversion of biomass, the deactivation of catalysts easily occurs in the process due to sintering, coke accumulation, and other reasons. The deposited coke is oxidized to generate gaseous products by introducing oxidizing gas, which is generally used in the regeneration of catalysts. Generally, this article reviews the plasma-assisted prepn. of catalysts used in the thermochem. conversion of biomass, the application of plasma technol. in the thermal conversion of biomass, and the regeneration of deactivated catalysts in plasma-assisted thermochem. conversion of biomass.
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    Kawi, S.; Ashok, J.; Dewangan, N.; Pati, S.; Junmei, C. Recent Advances in Catalyst Technology for Biomass Tar Model Reforming: Thermal, Plasma and Membrane Reactors. Waste Biomass Valor. 2022, 13, 1– 30,  DOI: 10.1007/s12649-021-01446-6
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    Yu, X.; Dang, X.; Li, S.; Zhang, J.; Zhang, Q.; Cao, L. A Comparison of In- and Post-Plasma Catalysis for Toluene Abatement through Continuous and Sequential Processes in Dielectric Barrier Discharge Reactors. J. Clean Prod 2020, 276, 124251  DOI: 10.1016/j.jclepro.2020.124251
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    Trushkin, A. N.; Kochetov, I. V. Simulation of Toluene Decomposition in a Pulse-Periodic Discharge Operating in a Mixture of Molecular Nitrogen and Oxygen. Plasma Physics Reports 2012, 38 (5), 407– 431,  DOI: 10.1134/S1063780X12040083
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    Simulation of toluene decomposition in a pulse-periodic discharge operating in a mixture of molecular nitrogen and oxygen
    Trushkin, A. N.; Kochetov, I. V.
    Plasma Physics Reports (2012), 38 (5), 407-431CODEN: PPHREM; ISSN:1063-780X. (MAIK Nauka/Interperiodica)
    The kinetic model of toluene decompn. in nonequil. low-temp. plasma generated by a pulse-periodic discharge operating in a mixt. of nitrogen and oxygen is developed. The results of numerical simulation of plasma-chem. conversion of toluene are presented; the main processes responsible for C6H5CH3 decompn. are identified; the contribution of each process to total removal of toluene is detd.; and the intermediate and final products of C6H5CH3 decompn. are identified. It was shown that toluene in pure nitrogen is mostly decompd. in its reactions with metastable N2(A3Σu+) and N2(a'1Σu+) mols. In the presence of oxygen, in the N2:O2 gas mixt., the largest contribution to C6H5CH3 removal is made by the hydroxyl radical OH which is generated in this mixt. exclusively due to plasma-chem. reactions between toluene and oxygen decompn. products. Numerical simulation showed the existence of an optimum oxygen concn. in the mixt., at which toluene removal is max. at a fixed energy deposition.
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    Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Y. S. Decomposition of Toluene in a Steady-State Atmospheric-Pressure Glow Discharge. Plasma Physics Reports 2013, 39 (2), 167– 182,  DOI: 10.1134/S1063780X13020025
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    Decomposition of toluene in a steady-state atmospheric-pressure glow discharge
    Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.
    Plasma Physics Reports (2013), 39 (2), 167-182CODEN: PPHREM; ISSN:1063-780X. (MAIK Nauka/Interperiodica)
    Results are presented from exptl. studies of decompn. of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atm. pressure glow discharge at different water vapor contents in the working gas. The exptl. results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chem. decompn. of toluene in the N2: O2: H2O gas mixt. A substantial influence of the gas flow humidity on toluene decompn. in the atm. pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decompn. are detd. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chem. decompn. of C6H5CH3 is established. Based on the results of computer simulations, the compn. of the products of plasma chem. reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.
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    Wang, Y.; Yang, H.; Tu, X. Plasma Reforming of Naphthalene as a Tar Model Compound of Biomass Gasification. Energy Convers. Manag. 2019, 187, 593– 604,  DOI: 10.1016/j.enconman.2019.02.075
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    Plasma reforming of naphthalene as a tar model compound of biomass gasification
    Wang, Yaoling; Yang, Haiping; Tu, Xin
    Energy Conversion and Management (2019), 187 (), 593-604CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    The contamination of producer gas with tars from biomass gasification remains a significant challenge in the bioenergy industry and a crit. barrier, limiting the com. applications of biomass gasification. Non-thermal and non-equil. plasma offers an unconventional and emerging technol. for the effective redn. of problematic tars from gasification. In this study, we investigated plasma reforming of naphthalene as a two-ring tar model compd. using a gliding arc discharge (GAD) reactor with/without steam. The influence on the plasma conversion of naphthalene based on the inlet naphthalene concn., discharge power and steam-to-carbon ratio was examd. to understand the effects of these operating parameters on the destruction of tar, gas selectivity/yield and energy efficiency. Adding H2O in the plasma process generates oxidative OH radicals, creating addnl. reaction routes for the step-wised oxidn. of naphthalene and its fragments towards the CO, CO2 and water. The optimum ratio (2.0) of steam-to-carbon was identified to achieve the highest naphthalene conversion (84.8%), C2H2 yield (33.0%), total gas yield (72.2%) and energy efficiency (5.7 g/kWh). The effect of the amt. of steam on the plasma redn. of tars was dependent on the balance between two opposite effects due to the presence of steam: pos. effect of OH radicals and the neg. effect of electron attachment on water mols. Introducing an appropriate amt. of steam to the plasma redn. of naphthalene also substantially minimized the formation of byproducts and enhanced the carbon balance. Plausible reaction mechanisms for the plasma decompn. of naphthalene were proposed through a comprehensive anal. of gaseous and condensable products combined with plasma spectroscopic diagnostics.
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    Liu, S.; Zhou, J.; Liu, W.; Zhang, T. Removal of Toluene in Air by a Non-Thermal Plasma-Catalytic Reactor Using MnOx/ZSM-5. Catal. Lett. 2022, 152 (1), 239– 253,  DOI: 10.1007/s10562-021-03629-1
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    Removal of Toluene in Air by a Non-thermal Plasma-Catalytic Reactor Using MnOx/ZSM-5
    Liu, Su; Zhou, Jiabin; Liu, Wenbo; Zhang, Tianlei
    Catalysis Letters (2022), 152 (1), 239-253CODEN: CALEER; ISSN:1011-372X. (Springer)
    Dielec. barrier discharge (DBD) reactor at non-thermal plasma (NTP) in combination with catalysts was used to remove toluene in air. Several manganese oxides catalysts with ZSM-5 zeolite as the carrier were prepd. for plasma-catalytic degrdn. of toluene. The prepd. catalysts were characterized utilizing the SEM, transmission electron microscope (TEM), H2 temp.-programmed redn. (H2-TPR), x-ray diffraction (x-ray diffraction), and N2 adsorption-desorption. And the residence time, plasma power, toluene concn. and specific input energy, which are crit. operating factors in this process, were investigated. The expt. proved that the catalysts significantly improved the degrdn. effect of NTP, the conversion increased from 58 to 91.5% after loading MnOx/ZSM-5-300 at 750 ppm, and the improving trend became more obvious with the increase of concn. The degrdn. of toluene can reach 92.4% at the optimal process parameters of residence time 5.8 s, initial concn. 1000 ppm, input power 30 W, SIE 6000 J/L. The results of the evaluation indicate that it is effective to use MnOx/ZSM-5 catalyst combined with DBD-plasma for synergistic degrdn. of toluene at room temp. and a relatively low energy consumption.
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    Wang, C.; Zhu, L.; Zhao, F.; Xu, D. The Chemistry of Gaseous Benzene Degradation Using Non-Thermal Plasma. Environmental Science and Pollution Research 2021, 28, 1565– 1573,  DOI: 10.1007/s11356-020-10506-8
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    The chemistry of gaseous benzene degradation using non-thermal plasma
    Wang, Chunyu; Zhu, Ling; Zhao, Fei; Xu, Danyun
    Environmental Science and Pollution Research (2021), 28 (2), 1565-1573CODEN: ESPLEC; ISSN:0944-1344. (Springer)
    In this study, the abatement of benzene in a dielec. barrier discharge (DBD) reactor was studied. The efficiency was investigated in terms of benzene conversion and product formation. The compn. of gas-liq.-solid three-phase product produced during degrdn. was obsd. by GC-MS. Under the optimal SED, the solid-phase product was analyzed by FT-IR, SEM, and EDS. The results suggested that the product were mainly benzonitriles, benzenedicarbonitrile, phenols, esters, and amides. The wt% of C in product decreased as SED increased, demonstrating that the high discharge voltage facilitated the conversion of VOCs to gaseous intermediate product and CO2. Possible degrdn. mechanism and pathways of benzene destruction in the DBD reactor were proposed.
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    Zhu, F.; Li, X.; Zhang, H.; Wu, A.; Yan, J.; Ni, M.; Zhang, H.; Buekens, A. Destruction of Toluene by Rotating Gliding Arc Discharge. Fuel 2016, 176, 78– 85,  DOI: 10.1016/j.fuel.2016.02.065
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    Destruction of toluene by rotating gliding arc discharge
    Zhu, Fengsen; Li, Xiaodong; Zhang, Hao; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Zhang, Hanwei; Buekens, Alfons
    Fuel (2016), 176 (), 78-85CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Non-thermal plasma is considered as an alternative treatment of tar present in the effluent from gasification processes. In this study, a novel rotating gliding arc (RGA) discharge reactor was developed for tar destruction. Toluene in nitrogen flow was used as a tar surrogate. The phys. features of RGA discharge and its application to toluene destruction are investigated at different input concns. and total gas flow rates. As a result, the highest destruction efficiency could exceed 95%, with a toluene concn. of 10 g/N m3 and a total flow rate of 0.24 N m3/h. The two major gaseous products are H2 and C2H2, with max. selectivity of 39.35% and 27.0%, resp. A higher input concn. slightly reduces this destruction efficiency but the energy efficiency further expanded, with a highest value of 16.61 g of toluene eliminated/kW h. In addn., the liq. and solid byproducts are collected downstream of the RGA reactor and detd. qual. and semi-quant. The amt. and structure of these byproducts is instructive for reaching a better comprehension of the chem. consequences of plasma treatment to the model compd. and to the carrier gas nitrogen.
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    Shen, Y.; Wang, J.; Ge, X.; Chen, M. By-Products Recycling for Syngas Cleanup in Biomass Pyrolysis – An Overview. Renewable and Sustainable Energy Reviews 2016, 59, 1246– 1268,  DOI: 10.1016/j.rser.2016.01.077
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    By-products recycling for syngas cleanup in biomass pyrolysis - An overview
    Shen, Yafei; Wang, Junfeng; Ge, Xinlei; Chen, Mindong
    Renewable & Sustainable Energy Reviews (2016), 59 (), 1246-1268CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    Bio-char and bio-oil have a potential to be used for gas cleaning in biomass pyrolysis/gasification. On one hand, tar in producer gas could be removed by phys. treatment, such as oil absorption and char adsorption; on the other hand, tar could be eliminated by chem. treatment, such as catalytic conversion over char-supported catalysts. This paper reviewed the recent progress in gas cleaning esp. for tar removal during biomass pyrolysis/gasification by using the byproducts (i.e. bio-char, bio-oil, low-viscosity tar). In general, bio-char could effectively adsorb the light tar compds. such as volatile org. compds. (VOCs), while bio-oil is normally benefit for the absorption of heavy tars. Addnl., catalytic reforming is considered as one of the promising alternatives for the removal of tars, because it converts the tars into the addnl. gas products. Bio-char could be used as a carbon catalyst or support with fair performance in tar removal. It is noteworthy that the char-supported catalysts could be gasified to recover energy of char without the need of frequent regeneration after deactivation. Furthermore, the carbon-based catalysts derived from bio-chars could be urgently developed for the removal of contaminants including NH3, H2S and tar simultaneously in the producer gas from the real biomass gasification processes.
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    Liu, M.; Aravind, P. V. The Fate of Tars under Solid Oxide Fuel Cell Conditions: A Review. Appl. Therm Eng. 2014, 70 (1), 687– 693,  DOI: 10.1016/j.applthermaleng.2014.05.068
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    The fate of tars under solid oxide fuel cell conditions: A review
    Liu, Ming; Aravind, P. V.
    Applied Thermal Engineering (2014), 70 (1), 687-693CODEN: ATENFT; ISSN:1359-4311. (Elsevier Ltd.)
    A review. Biomass is a renewable and low-carbon energy source. Its use via gasification is an attractive way for solid oxide fuel cells (SOFCs). However, tars are the major bottleneck as tars produced from biomass gasification may have detrimental effects on the SOFC. This work comprehensively reviews the fate of tars under SOFC conditions. Specifically, it summarizes tar evolution during biomass gasification, discusses currently available studies on the interaction between tars and SOFC anodes or anode materials. In addn., readily available gas cleaning technologies for reducing tar content are discussed. Future research perspectives are also addressed.
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    Singh, R. N.; Singh, S. P.; Belwanshi, J. B. Tar Removal from Producer Gas: A Review. Res. J. Eng. Sci. 2014, 3 (10), 16– 22
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    Tar removal from producer gas: a review
    Singh, R. N.; Singh, S. P.; Balwanshi, J. B.
    Research Journal of Engineering Sciences (2014), 3 (10), 16-22CODEN: RJESCM; ISSN:2278-9472. (International Science Congress Association)
    A review. Gasification is the most appropriate technol. for conversion of solid fuel (biomass) into a gaseous fuel, known as producer gas. Producer gas is a mixt. of gases which consists of hydrogen, carbon monoxide, methane, carbon dioxide, water vapor, nitrogen, tar and suspended particulate matter. For motive applications such as internal combustion engines, the tar present in producer gas may create problem, if the tar content in the producer gas is above 50-100 mg/Nm3. A tar-free gaseous fuel can be obtained in a suitably designed producer gas conditioning unit whose sole purpose is to provide clean producer gas. Gas cleaning and conditioning systems to control tar levels are being continuously modified for better efficiency and cost effectiveness. Major techniques used in tar cleaning are thermal cracking, catalytic cracking and phys. removal of tar. Many a times, combination of these techniques are used for better cleaning of producer gas. The following paper critically reviews the different techniques used for collection, identification and quantification of tars in producer gas obtained from biomass.
  132. 132
    Woolcock, P. J.; Brown, R. C. A Review of Cleaning Technologies for Biomass-Derived Syngas. Biomass Bioenergy 2013, 52, 54– 84,  DOI: 10.1016/j.biombioe.2013.02.036
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    A review of cleaning technologies for biomass-derived syngas
    Woolcock, Patrick J.; Brown, Robert C.
    Biomass and Bioenergy (2013), 52 (), 54-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    A review. Syngas from gasification of carbonaceous feedstocks is used for power prodn. and synthesis of fuels and commodity chems. Impurities in gasification feedstocks, esp. sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temp. exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the tech. difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
  133. 133
    Hasler, P.; Nussbaumer, T. Gas Cleaning for IC Engine Applications from Fixed Bed Biomass Gasification. Biomass Bioenergy 1999, 16 (6), 385– 395,  DOI: 10.1016/S0961-9534(99)00018-5
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    Gas cleaning for IC engine applications from fixed bed biomass gasification
    Hasler, P.; Nussbaumer, Th.
    Biomass and Bioenergy (1999), 16 (6), 385-395CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
    Gas cleaning for tar and particle removal is necessary for internal combustion (IC) engine applications of producer gas from fixed bed biomass gasifiers which are usually in the capacity range from 100 kW up to 5000 kW. In the present investigation, tar and particle collection efficiencies have been detd. in a sand bed filter, a wash tower, two different fabric filters, and a rotational particle separator in different test runs with fixed bed gasifiers. Tar adsorption on coke has been investigated in a fixed bed batch reactor. Furthermore data from literature for catalytic tar crackers, venturi scrubbers, a rotational atomizer, and a wet electrostatic precipitator (ESP) are given. Based on the presented gas cleaning efficiencies and the investment cost, an assessment of gas cleaning systems is made for IC engine applications from cocurrent gasifiers. The postulated gas quality requirements for IC engines cannot be safely achieved with state-of-the-art gas cleaning techniques and that 90% particle removal is easier to achieve than 90% tar removal. Except for the catalytic tar crackers which are considered as an option for applications above several MW and for gases with a high tar level, none of the investigated gas cleaning systems can securely meet a tar redn. exceeding 90%. Therefore one of the key issues for a successful application of biomass derived producer gas from small scale gasifiers is the tar removal, where further development is needed.
  134. 134
    Boerrigter, H.; Van Paasen, S. V. B.; Bergman, P. C. A.; Könemann, J. W.; Emmen, R.; Wijnands, A. OLGA Tar Removal Technology. Proof-of-Concept (PoC) for Application in Integrated Biomass Gasification Combined Heat and Power (CHP) Systems; ECN-RX-05-009; Energy Research Centre of the Netherlands: Petten, Netherlands, 2005.
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    Fjellerup, J.; Ahrenfeldt, J.; Henriksen, U.; Go̷bel, B. Formation, Decomposition and Cracking of Biomass Tars in Gasification; Technical University of Denmark: Lyngby, Denmark, 2005.
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    Coll, R.; Salvadó, J.; Farriol, X.; Montané, D. Steam Reforming Model Compounds of Biomass Gasification Tars: Conversion at Different Operating Conditions and Tendency towards Coke Formation. Fuel Process. Technol. 2001, 74 (1), 19– 31,  DOI: 10.1016/S0378-3820(01)00214-4
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    Steam reforming model compounds of biomass gasification tars: conversion at different operating conditions and tendency towards coke formation
    Coll, Roberto; Salvado, Joan; Farriol, Xavier; Montane, Daniel
    Fuel Processing Technology (2001), 74 (1), 19-31CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Science B.V.)
    The purifn. of biomass-derived syngas via tar abatement by catalytic steam reforming has been investigated using benzene, toluene, naphthalene, anthracene and pyrene as surrogated mols. The effects of temp. and steam-to-carbon (S/C) ratio on conversion, and the tendency towards coke formation were explored for each model compd. Two com. nickel-based catalysts, the UCI G90-C and the ICI 46-1, were evaluated. The five tar model compds. had very different reaction rates. Naphthalene was the most difficult compd. to steam reform, with conversions from 0.008 gorg_conv/gcat min (790 °C) to 0.022 gorg_conv/gcat min (890 °C) at an S/C ratio of 4.2. The most reactive compd. was benzene, with a conversion of 1.1 gorg_conv/gcat min at 780 °C and an S/C ratio of 4.3. The tendency towards coke formation grew as the mol. wt. of the arom. increased. The min. S/C ratio for toluene was 2.5 at a catalyst temp. of 725 °C, and for pyrene at 790 °C, it was 8.4. In general, catalyst temps. and S/C ratios need to be higher than for naphtha in order to prevent the formation of coke on the catalyst.
  137. 137
    Developments in Thermochemical Biomass Conversion; Bridgwater, A. V., Boocock, D. G. B., Eds.; Springer, 1997.
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    Brandt, P.; Larsen, E.; Henriksen, U. High Tar Reduction in a Two-Stage Gasifier. Energy Fuels 2000, 14 (4), 816– 819,  DOI: 10.1021/ef990182m
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    High Tar Reduction in a Two-Stage Gasifier
    Brandt, Peder; Larsen, Elfinn; Henriksen, Ulrik
    Energy & Fuels (2000), 14 (4), 816-819CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    The work with a 100-kWth two-stage gasifier at the Tech. University of Denmark (DTU) has resulted in a gas with a very low tar content. The redn. in tar has come about by combining the partial oxidn. of the pyrolysis gas with the reactions that follow on a charcoal bed in the char gasification unit. Tar is defined as org. contaminants which have retention times equal to or greater than those of phenol on a nonpolar GC column. Two test series were made with wood chips as feedstock, before and after the gasifier was optimized. The effect on tar redn. of a charcoal bed has been investigated by measuring the tar content and compn. of the gas after the partial oxidn. (above the charcoal bed) and after the passage of the gas through the charcoal. By introducing the correct supply of air, the tar content in the gas after its partial oxidn. was about 3000 mg/kg dry wood chips. Furthermore, a conclusive high tar redn. of the arom. hydrocarbons including PAH was obtained by avoiding bypasses of the charcoal bed. A gas was produced with a tar content as low as 10-40 mg/kg dry wood.
  139. 139
    Shen, Y.; Yoshikawa, K. Recent Progresses in Catalytic Tar Elimination during Biomass Gasification or Pyrolysis - A Review. Renewable and Sustainable Energy Reviews. 2013, 21, 371– 392,  DOI: 10.1016/j.rser.2012.12.062
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    Recent progresses in catalytic tar elimination during biomass gasification or pyrolysis-A review
    Shen, Yafei; Yoshikawa, Kunio
    Renewable & Sustainable Energy Reviews (2013), 21 (), 371-392CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Biomass gasification is an interesting technol. in the future development of a worldwide sustainable energy system, which can help to decrease our current dependence on fossil fuels. Biomass gasification is a thermal process where solid fuel is converted into a useful gas using several gasifying agents such as air, and steam. The producer gas has a great no. of applications. The most important is being combustion for power and heat generation as well as raw gas for prodn. of fuels or chems. This review mainly presents the recent progresses on tar elimination during the biomass gasification. Then, novel non-catalytic absorption and adsorption methods of tar removal under ambient temp. conducted by our lab. members were also explained. In our opinion, the tar removal can be conducted by combination of catalytic reforming in the gasifier and oil materials adsorption in the scrubber. Furthermore, the tar catalytic reforming is a most significant step during biomass gasification or pyrolysis. Thus, the development of reasonable catalysts for tar elimination has been faced with a significant challenge in current society.
  140. 140
    Huang, Q.; Lu, P.; Hu, B.; Chi, Y.; Yan, J. Cracking of Model Tar Species from the Gasification of Municipal Solid Waste Using Commercial and Waste-Derived Catalysts. Energy Fuels 2016, 30 (7), 5740– 5748,  DOI: 10.1021/acs.energyfuels.6b00711
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    140
    Cracking of Model Tar Species from the Gasification of Municipal Solid Waste Using Commercial and Waste-Derived Catalysts
    Huang, Qunxing; Lu, Peng; Hu, Binhang; Chi, Yong; Yan, Jianhua
    Energy & Fuels (2016), 30 (7), 5740-5748CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    The cracking of model tar species from municipal solid waste gasification using dried sewage sludge char (DSS char) and bottom ash catalyst (BAC) was investigated, and the catalytic performance was compared to that of well-studied calcined dolomite, NiO/γ-Al2O3, and non-catalytic thermal cracking. The effects of the temp., internal structure, chem. compn., and functional groups on the performance of tar cracking were characterized. , When toluene was selected as the model tar species, conversion ratios for all catalysts were over 94% at 950°. The cracking efficiency was ordered as NiO/γ-Al2O3 > calcined dolomite > DSS char > BAC > thermal cracking. When the temp. increased from 750 to 850°, the conversion ratios for DSS char and BAC increased from 68.8 and 40.1% to 81.5 and 63.2%, resp. H2 and coke were the major products of toluene cracking, and catalysts promoted the yield of hydrogen. The lower heating value of the product gas followed the same rules of the conversion ratio. Coke deposition from toluene cracking will decrease the Brunauer-Emmett-Teller surface area of the catalysts, inevitably leading to the deactivation.
  141. 141
    Min, Z.; Yimsiri, P.; Zhang, S.; Wang, Y.; Asadullah, M.; Li, C. Z. Catalytic Reforming of Tar during Gasification. Part III. Effects of Feedstock on Tar Reforming Using Ilmenite as a Catalyst. Fuel 2013, 103, 950– 955,  DOI: 10.1016/j.fuel.2012.09.019
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    141
    Catalytic reforming of tar during gasification. Part III. Effects of feedstock on tar reforming using ilmenite as a catalyst
    Min, Zhenhua; Yimsiri, Piyachat; Zhang, Shu; Wang, Yi; Asadullah, Mohammad; Li, Chun-Zhu
    Fuel (2013), 103 (), 950-955CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Australia mallee wood, bark and leaf samples (Eucalyptus loxophleba, subspecies lissophloia) were pyrolyzed to produce volatiles for in situ catalytic steam reforming with ilmenite as a catalyst. The results demonstrated that the properties of biomass feedstock (wood, bark and leaves) significantly influenced their product yields and properties. Bark produced the highest amts. of solid products, whereas leaf generated the highest amts. of tar during pyrolysis. The differences in the chem. compn. and the tar yields among wood, bark and leaf decreased with increasing temp. Ilmenite showed good activity for the reforming of all tars from different parts of mallee trees. However, its activity for reforming tar from bark and leaf decreased with prolonging feeding time due to their high gradual coke deposits. Compared with sintering, the accumulated coke deposited on ilmenite is a dominant factor to its deactivation during the steam reforming process. Burning coke is an effective method to regenerate the catalyst activity of ilmenite.
  142. 142
    Nordgreen, T.; Liliedahl, T.; Sjöström, K. Metallic Iron as a Tar Breakdown Catalyst Related to Atmospheric, Fluidised Bed Gasification of Biomass. Fuel 2006, 85 (5–6), 689– 694,  DOI: 10.1016/j.fuel.2005.08.026
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    Metallic iron as a tar breakdown catalyst related to atmospheric, fluidised bed gasification of biomass
    Nordgreen, Thomas; Liliedahl, Truls; Sjoestroem, Krister
    Fuel (2006), 85 (5-6), 689-694CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Tar formation is a major drawback when biomass is converted in a gasifier to obtain gas aimed for utilization in power prodn. plants or for prodn. of chems. Catalytic cracking is an efficient method to diminish the tar content in the gas mixt. In this study, the capability of metallic iron and iron oxides to catalytically crack tars has been exptl. examd. To obtain metallic iron, small grains of hematite (Fe2O3) were placed in a secondary reactor downstream the gasifier and reduced in situ prior to catalytic operation. The fuel used in the atm. fluidized bed gasifier was Swedish birch with a moisture content of approx. 7 wt%. The influence of temp. in the range 700-900 °C and λ values (i.e. equivalence ratio, ER) between 0 and 0.20 have been investigated. In essence, the results show that raising the temp. in the catalytic bed to approx. 900 °C yields almost 100% tar breakdown. Moreover, increasing the λ value also improves the overall tar cracking activity. The iron oxides did not demonstrate any catalytic activity.
  143. 143
    Miyazawa, T.; Kimura, T.; Nishikawa, J.; Kunimori, K.; Tomishige, K. Catalytic Properties of Rh/CeO2/SiO2 for Synthesis Gas Production from Biomass by Catalytic Partial Oxidation of Tar. Sci. Technol. Adv. Mater. 2005, 6 (6), 604– 614,  DOI: 10.1016/j.stam.2005.05.019
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    143
    Catalytic properties of Rh/CeO2/SiO2 for synthesis gas production from biomass by catalytic partial oxidation of tar
    Miyazawa, Tomohisa; Kimura, Takeo; Nishikawa, Jin; Kunimori, Kimio; Tomishige, Keiichi
    Science and Technology of Advanced Materials (2005), 6 (6), 604-614CODEN: STAMCV; ISSN:1468-6996. (Elsevier Ltd.)
    Performance of Rh/CeO2/SiO2 in the partial oxidn. of tar from the pyrolysis of wood biomass (architectural salvage) was investigated and compared with various materials such as steam reforming Ni catalyst, active clay, USY zeolite, MS-13X, dolomite, alumina, silica sand, fluorite and non-catalyst. Rh/CeO2/SiO2 and the steam reforming Ni catalyst exhibited much higher performance than any other materials in terms of hydrogen prodn. and the amt. of tar. Therefore, the performance of Rh/CeO2/SiO2 and steam reforming Ni catalyst was particularly compared. From the result on the dependence of reaction temp., equivalence ratio, and biomass feeding rate, Rh/CeO2/SiO2 exhibited higher performance than the Ni catalyst, esp. in terms of tar and coke amt. Furthermore, Rh/CeO2/SiO2 was also more stable than the Ni catalyst. The catalyst deactivation can be related to the amt. of coke deposition. The results indicate that Rh/CeO2/SiO2 has high resistance to coke formation, and this is related to higher combustion activity of Rh/CeO2/SiO2 than the Ni catalyst. Furthermore, from the TPR profiles, Rh/CeO2/SiO2 had higher reducibility than the Ni catalyst. The combination of high combustion activity with high reducibility and reforming activity can be related to high performance of tar conversion in the fluidized bed reactor.
  144. 144
    Asadullah, M.; Miyazawa, T.; Ito, S. I.; Kunimori, K.; Yamada, M.; Tomishige, K. Catalyst Development for the Gasification of Biomass in the Dual-Bed Gasifier. Appl. Catal. A Gen 2003, 255 (2), 169– 180,  DOI: 10.1016/S0926-860X(03)00539-8
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    Catalyst development for the gasification of biomass in the dual-bed gasifier
    Asadullah, Mohammad; Miyazawa, Tomohisa; Ito, Shin-ichi; Kunimori, Kimio; Yamada, Muneyoshi; Tomishige, Keiichi
    Applied Catalysis, A: General (2003), 255 (2), 169-180CODEN: ACAGE4; ISSN:0926-860X. (Elsevier Science B.V.)
    A dual-bed gasifier system combined with catalysts was evaluated in the catalytic gasification of cedar wood at low temps. (823-973 °K). The dual-bed gasifier consisted of a primary-bed section for pyrolysis of biomass and sepn. of pyrolyzed gas and tar from solid products and a secondary-catalytic tar reformer. Catalyst development was carried out from Rh/CeO2/SiO2, which was developed for the higher conversion of carbon to gas and higher yield of CO + H2 + CH4. The authors have also carried out the optimization of reaction conditions. Esp., the tar derived from max. of 250 mg biomass/min can be totally converted to the gas product by 3 g catalyst in this system using ER = 0.25 of total carbon present in the biomass. This performance was much higher than that over com. steam reforming catalyst. The amt. of coke deposited on Rh/CeO2/SiO2 was much smaller. In the dual-bed system combined with excellent catalysts, almost all the tar can be converted to syngas at lower temp. than that needed by the conventional method with high energy efficiency.
  145. 145
    Asadullah, M.; Miyazawa, T.; Ito, S. I.; Kunimori, K.; Koyama, S.; Tomishige, K. A Comparison of Rh/CeO2/SiO2 Catalysts with Steam Reforming Catalysts, Dolomite and Inert Materials as Bed Materials in Low Throughput Fluidized Bed Gasification Systems. Biomass Bioenergy 2004, 26 (3), 269– 279,  DOI: 10.1016/S0961-9534(03)00105-3
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    A comparison of Rh/CeO2/SiO2 catalysts with steam reforming catalysts, dolomite and inert materials as bed materials in low throughput fluidized bed gasification systems
    Asadullah, Mohammad; Miyazawa, Tomohisa; Ito, Shin-ichi; Kunimori, Kimio; Koyama, Shuntarou; Tomishige, Keiichi
    Biomass and Bioenergy (2004), 26 (3), 269-279CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
    The gasification of cedar wood in the presence of Rh/CeO2/SiO2 has been conducted in the lab. scale fluidized bed reactor using air as a gasifying agent at low temps. (823-973 K) in order to produce high-quality fuel gas for gas turbine for power generation. The performance of the Rh/CeO2/SiO2 catalyst has been compared with conventional catalysts such as com. steam reforming catalyst G-91, dolomite and noncatalyst systems by measurements of the cold gas efficiency, tar concn., carbon conversion to gas and gas compn. The tar concn. was completely negligible in the Rh/CeO2/SiO2-catalyzed product gas whereas it was about 30, 113, and 139 g/m3 in G-91, dolomite and noncatalyzed product gas, resp. Since the carbon conversion to useful gas such as CO, H2, and CH4 are much higher on Rh/CeO2/SiO2 catalyst than others at 873 K, the cold gas efficiency is much higher (71%) in this case than others. The hydrogen content in the product gas is much higher (>24 vol%) than the specified level (>10 vol%) for efficient combustion in the gas turbine engine. The char and coke formation is also very low on Rh/CeO2/SiO2 catalyst than on the conventional catalysts. Although the catalyst surface area was slightly decreased after using the same catalyst in at least 20 expts., the deactivation problem was not severe.
  146. 146
    Zhao, Z.; Lakshminarayanan, N.; Kuhn, J. N.; Senefeld-Naber, A.; Felix, L. G.; Slimane, R. B.; Choi, C. W.; Ozkan, U. S. Optimization of Thermally Impregnated Ni-Olivine Catalysts for Tar Removal. Appl. Catal. A 2009, 363, 64– 72,  DOI: 10.1016/j.apcata.2009.04.042
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    Optimization of thermally impregnated Ni-olivine catalysts for tar removal
    Zhao, Zhongkui; Lakshminarayanan, Nandita; Kuhn, John N.; Senefeld-Naber, Allyson; Felix, Larry G.; Slimane, Rachid B.; Choi, Chun W.; Ozkan, Umit S.
    Applied Catalysis, A: General (2009), 363 (1-2), 64-72CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Thermally impregnated Ni-olivines are potential catalysts for hot cleanup of tars generated in fluidized bed biomass gasifiers. The present study examd. the influence of synthesis parameters, namely Ni precursor, prepn. temp., and olivine support upon the physicochem. and catalytic properties of Ni-olivine catalysts prepd. by thermal impregnation. Catalytic activity and stability was monitored by reforming naphthalene, a model tar compd. in simulated biomass-derived syngas and by reforming methane. Physicochem. properties, which include both structural (x-ray diffraction, temp. programmed redn., and Raman spectroscopy) and surface measurements (BET surface area and XPS), were evaluated for both fresh and spent catalysts. Choice of Ni precursor (NiO or Ni) demonstrated minimal influence upon physicochem. properties and catalytic activity and stability for naphthalene and methane steam reforming. The synthesis temp. (1100 and 1400°) and olivine support, however, did have an impact. Large structural changes and deactivation were obsd. when lower synthesis temps. were used, which indicated that this formulation was not desirable. The use of the Washington olivine as the support demonstrated improved catalytic performance and stability compared to two other olivine supports and further characterization showed that treatments are important in detg. the final structural features.
  147. 147
    Wang, T.; Chang, J.; Lv, P.; Zhu, J. Novel Catalyst for Cracking of Biomass Tar. Energy Fuels 2005, 19 (1), 22– 27,  DOI: 10.1021/ef030116r
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    Novel Catalyst for Cracking of Biomass Tar
    Wang, Tiejun; Chang, Jie; Lu, Pengmei; Zhu, Jingxu
    Energy & Fuels (2005), 19 (1), 22-27CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Cracking of biomass tar was investigated over Ni/dolomite catalyst prepd. by the incipient wetness method using modified dolomite as precursor. Modified dolomite was prepd. by mixing Fe2O3 powders with natural dolomite powders to increase Fe2O3 content for higher activity of tar cracking. Four other catalysts (natural dolomite, modified dolomite, ICI-46-1, and Z409) were tested and compared with Ni/dolomite catalyst. The effects of temp., steam-to-carbon, and space velocity on tar conversion were explored. Ni/dolomite is shown to be very active and useful for tar removal. A 97% tar removal is easily obtained at catalyst temp. of 750 °C and space velocities of 12 000 h-1. The min. S/C ratio for Ni/dolomite was 2.5 at a catalyst temp. of 750 °C to prevent the formation of the coke on the catalyst. No obvious deactivation of catalyst was obsd. in 60 h onstream tests. Compared with the Ni-based catalysts (ICI-46-1, Z409), Ni/dolomite catalyst is cheap and has also excellent activity and anticoke ability.
  148. 148
    Miyazawa, T.; Kimura, T.; Nishikawa, J.; Kado, S.; Kunimori, K.; Tomishige, K. Catalytic Performance of Supported Ni Catalysts in Partial Oxidation and Steam Reforming of Tar Derived from the Pyrolysis of Wood Biomass. Catal. Today 2006, 115, 254– 262,  DOI: 10.1016/j.cattod.2006.02.055
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    Catalytic performance of supported Ni catalysts in partial oxidation and steam reforming of tar derived from the pyrolysis of wood biomass
    Miyazawa, Tomohisa; Kimura, Takeo; Nishikawa, Jin; Kado, Shigeru; Kunimori, Kimio; Tomishige, Keiichi
    Catalysis Today (2006), 115 (1-4), 254-262CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
    Activity test of Ni/Al2O3, Ni/ZrO2, Ni/TiO2, Ni/CeO2 and Ni/MgO catalysts in the partial oxidn. (POT) and steam reforming of tar (SRT) derived from the pyrolysis of cedar wood was performed. In these activity tests, the order of the performance in both reactions was similar. Catalyst characterization was also carried out by means of H2 adsorption, TPR and XRD. From the combination of catalyst characterization with the results of the activity tests, it was suggested that the conversion of tar in POT and SRT is mainly controlled by the no. of surface Ni metal. In addn., Ni/CeO2 showed smaller amt. of coke than other catalysts in the POT and SRT. From the TGA profiles of active carbon mixed with catalysts, it is found that Ni/CeO2 promoted the reaction of active carbon with O2 and steam. The function of the fluidized bed reactor in the POT with respect to coke and tar amt. was discussed.
  149. 149
    Furusawa, T.; Saito, K.; Kori, Y.; Miura, Y.; Sato, M.; Suzuki, N. Steam Reforming of Naphthalene/Benzene with Various Types of Pt-and Ni-Based Catalysts for Hydrogen Production. Fuel 2013, 103, 111– 121,  DOI: 10.1016/j.fuel.2011.09.026
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    Steam reforming of naphthalene/benzene with various types of Pt- and Ni-based catalysts for hydrogen production
    Furusawa, Takeshi; Saito, Katsuhiko; Kori, Yoshihiko; Miura, Yasutomo; Sato, Masahide; Suzuki, Noboru
    Fuel (2013), 103 (), 111-121CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    The influence of support on the catalytic performances of Pt and Ni based catalysts for the steam reforming of naphthalene/benzene as model tar compds. of biomass gasification was investigated. Pt/Al2O3 catalyst showed relatively high and stable activity in steam reforming for 30 h at 1023 K and 1073 K with steam/carbon (S/C) molar ratio of 3. However, this catalyst remarkably lost its activity after 1st step of oxidn. treatment during cycle test of steam reforming-oxidn. treatment. When hydrogen treatment was conducted as a regeneration method, Pt/Al2O3 catalyst showed stable performance for 5 cycles. Ni/Al2O3 and Pt/Al2O3 catalysts showed similar catalytic behaviors for steam reforming and cycle test. Pt/MgO catalyst exhibited stable activity at 1073 K for the steam reforming under steady state and cycle utilization test of steam reforming-oxidn. treatment. However, when the reaction temp. was reduced to 1023 K, Pt/MgO catalyst lost its activity for both cases. It is concluded from the above results that Al2O3 supported catalysts were excellent catalysts for the steam reforming of naphthalene/benzene to produce H2.
  150. 150
    Binte Mohamed, D. K.; Veksha, A.; Ha, Q. L. M.; Chan, W. P.; Lim, T. T.; Lisak, G. Advanced Ni Tar Reforming Catalysts Resistant to Syngas Impurities: Current Knowledge, Research Gaps and Future Prospects. Fuel 2022, 318, 123602,  DOI: 10.1016/j.fuel.2022.123602
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    Advanced Ni tar reforming catalysts resistant to syngas impurities: Current knowledge, research gaps and future prospects
    Binte Mohamed, Dara Khairunnisa; Veksha, Andrei; Ha, Quan Luu Manh; Chan, Wei Ping; Lim, Teik-Thye; Lisak, Grzegorz
    Fuel (2022), 318 (), 123602CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    A review. Catalytic reforming is a promising technol. for the removal of tar from syngas. However, due to the presence of other impurities such as H2S, HCl, HBr, siloxanes, alkali metals, and NH3, the lifetime, activity, and stability of commonly used Ni-based catalysts is limited. This review investigates the recent findings related to poisoning effects of both common and under-researched syngas impurities on nickel catalysts and achievements in the synthesis of poison tolerant catalysts. The source and content of impurities produced from the gasification of different feedstock are examd. As current catalysts used for tar reforming require further improvement to ensure tolerance to poisoning, two approaches for catalytic tar reforming gas products from gasification of biomass/solid waste with and without prior syngas pre-treatment are evaluated to emphasize the importance of developing poison-tolerant catalysts. The deactivation mechanisms of Ni catalysts by syngas impurities, regeneration techniques, and strategies for developing poison-tolerant catalysts are reviewed. Finally, limitations of current catalytic tar reforming processes and promising approaches for future works are further discussed.
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    Binte Mohamed, D. K.; Veksha, A.; Ha, Q. L. M.; Lim, T. T.; Lisak, G. Unravelling the Significance of Catalyst Reduction Stage for High Tar Reforming Activity in the Presence of Syngas Impurities. Appl. Catal. A Gen 2022, 642, 118711,  DOI: 10.1016/j.apcata.2022.118711
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    Unravelling the significance of catalyst reduction stage for high tar reforming activity in the presence of syngas impurities
    Binte Mohamed, Dara Khairunnisa; Veksha, Andrei; Ha, Quan Luu Manh; Lim, Teik-Thye; Lisak, Grzegorz
    Applied Catalysis, A: General (2022), 642 (), 118711CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Ni catalysts are used widely in tar reforming for syngas purifn. This study investigates the aim of the redn. stage toward Ni catalysts during tar reforming in the presence of syngas impurities. A NiAl2O4 catalyst was used for the reforming of a mixt. of tar model compds. (naphthalene, toluene, and styrene) in simulated syngas contg. 50 ppmv H2S and 500 ppmv HCl. The catalyst exhibited activity in tar reforming even without the pre-redn. treatment, but it was deactivated rapidly due to the favored reaction between H2S and Ni2+ species, causing increased Ni agglomeration and carbon deposition. Pre-redn. of catalysts enhanced the catalyst stability even in the presence of syngas impurities. Higher reforming activity was achieved by increasing the redn. temp. from 800°C to 900°C. However, transformation in the support structure at higher reducing temp. could lead to decreased exposure of Ni due to the collapse of pore structures.
  152. 152
    Sutton, D.; Kelleher, B.; Ross, J. R. H. Review of Literature on Catalysts for Biomass Gasification. Fuel Process. Technol. 2001, 73 (3), 155– 173,  DOI: 10.1016/S0378-3820(01)00208-9
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    Review of literature on catalysts for biomass gasification
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    Fuel Processing Technology (2001), 73 (3), 155-173CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Science B.V.)
    A review with refs. Biomass gasification is a possible alternative to the direct use of fossil fuel energy. Biomass, a CO2 neutral source of renewable fuel, can contribute to the demand for heat, electricity and synthesis gas. However, there are inefficiencies in the technol., which at present render biomass gasification economically unviable. The presence of condensable org. compds. and methane in the product gas renders the gas unsuitable for specific applications. Elimination of the condensable org. compds. and methane by a suitably cheap technol. will enhance the economic viability of biomass gasification. This paper contains an extensive literature review of the three main groups of catalysts, which have been evaluated for the elimination of these hydrocarbons. These three groups of catalysts are dolomite, alkali metals and nickel.
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    Valderrama Rios, M. L.; Gonzalez, A. M.; Lora, E. E. S.; Almazan del Olmo, O. A. Reduction of Tar Generated during Biomass Gasification: A Review. Biomass Bioenergy 2018, 108, 345– 370,  DOI: 10.1016/j.biombioe.2017.12.002
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    Reduction of tar generated during biomass gasification: A review
    Valderrama Rios, Martha Lucia; Gonzalez, Aldemar Martinez; Lora, Electo Eduardo Silva; Almazan del Olmo, Oscar Agustin
    Biomass and Bioenergy (2018), 108 (), 345-370CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    A review. One of the main problems that happen during biomass gasification is tar formation, which could make this technol. unsuccessfully from a com. point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, lab. and industrial methods and technologies for its redn.-removal, as well as research and development in this area are reviewed and evaluated in this paper.
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    Anis, S.; Zainal, Z. A. Tar Reduction in Biomass Producer Gas via Mechanical, Catalytic and Thermal Methods: A Review. Renewable and Sustainable Energy Reviews 2011, 15, 2355– 2377,  DOI: 10.1016/j.rser.2011.02.018
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    Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review
    Anis, Samsudin; Zainal, Z. A.
    Renewable & Sustainable Energy Reviews (2011), 15 (5), 2355-2377CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compns., which is assocd. with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar redn. are discussed.
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    Galadima, A.; Masudi, A.; Muraza, O. Catalyst Development for Tar Reduction in Biomass Gasification: Recent Progress and the Way Forward. J. Environ. Manage. 2022, 305, 114274,  DOI: 10.1016/j.jenvman.2021.114274
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    Catalyst development for tar reduction in biomass gasification: Recent progress and the way forward
    Galadima, Ahmad; Masudi, Ahmad; Muraza, Oki
    Journal of Environmental Management (2022), 305 (), 114274CODEN: JEVMAW; ISSN:0301-4797. (Elsevier Ltd.)
    A review. Biomass valorization via catalytic gasification is a potential technol. for commercizalization to industrial scale. However, the generated tar during biomass valorization posing numerous problems to the overall reaction process. Thus, catalytic tar removal via reforming, cracking and allied processes was among the priority areas to researchers in the recent decades. This paper reports new updates on the areas of catalyst development for tar redn. The catalyst survey include metallic and metal-promoted materials, nano-structured systems, mesoporous supports like zeolites and oxides, group IA and IIA compds. and natural catalysts based on dolomite, palygorskite, olivine, ilmenite, goethite and their modified derivs. The influence of catalyst properties and parameters such as reaction conditions, catalyst prepn. procedures and feedstock nature on the overall activity/selectivity/stability properties were simultaneously discussed. This paper not only cover to model compds., but also explore to real biomass-derived tar for consistency. The area that require further investigation was identified in the last part of this review.
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    Narnaware, S. L.; Panwar, N. L. Catalysts and Their Role in Biomass Gasification and Tar Abetment: A Review. Biomass Conv. Bioref. 2021,  DOI: 10.1007/s13399-021-01981-1
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    Bjorgaard, S. J. Characterization And Catalytic Cracking Of Tar Obtained In Coal/Biomass/Municipal Solid Waste Gasification: The Use Of Basic Mineral Catalysts And Miscibility, Properties, And Corrosivity Of Petroleum-Biofuel Oils And Blends For Application In Oil-Fired Power Stations. Doctoral Thesis, University of North Dakota, Grand Forks, ND, 2015.
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    Dou, B.; Gao, J.; Sha, X.; Baek, S. W. Catalytic Cracking of Tar Component from High-Temperature Fuel Gas. Appl. Therm. Eng. 2003, 23, 2229– 2239,  DOI: 10.1016/S1359-4311(03)00185-6
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    Catalytic cracking of tar component from high-temperature fuel gas
    Dou, Binlin; Gao, Jinsheng; Sha, Xingzhong; Baek, Seung Wook
    Applied Thermal Engineering (2003), 23 (17), 2229-2239CODEN: ATENFT; ISSN:1359-4311. (Elsevier Science Ltd.)
    The cracking removal of tar component in high-temp. fuel gas cleanup is one of the most crucial problems in developing cleanest advanced power technol. Five catalysts were evaluated to tar component removal from high-temp. fuel gas in a fixed-bed reactor. 1-Methylnaphthalene was chosen as a model of tar component. The Y-zeolite and NiMo catalysts were the most effective catalysts. Two catalysts almost removed 100% tar component at 550 °C. The process variables, temp. and space velocity, have very significant effects on tar component removal with catalysts. The long-term durability shows that two catalysts maintain more than 95% removal conversion at 550 °C in 168 h. The combustion study of coke deposited on catalysts by thermal gravimetric anal. technol. shows that very small amt. buildup of coke appears on two catalysts surface. Using a first-order kinetic model, the apparent energies of activation and pre-exponential factors for tar component removal reaction and coke combustion on catalysts were obtained for the most active catalysts.
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    Srinakruang, J.; Sato, K.; Vitidsant, T.; Fujimoto, K. Highly Efficient Sulfur and Coking Resistance Catalysts for Tar Gasification with Steam. Fuel 2006, 85, 2419– 2426,  DOI: 10.1016/j.fuel.2006.04.026
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    Highly efficient sulfur and coking resistance catalysts for tar gasification with steam
    Srinakruang, Jumluck; Sato, Kazuhiro; Vitidsant, Tharapong; Fujimoto, Kaoru
    Fuel (2006), 85 (17-18), 2419-2426CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Ni-on-dolomite catalysts were effective catalysts for coking resistance and promising sulfur tolerance for steam reforming of tar. Expts. were carried out in a fixed bed reactor at 730-850° with a short contact time (W/F: 0.55 g h/mol) and under atm. pressure. Toluene and naphthalene were selected as the model component of tar. The process variables such as calcination temp., reaction temp. and the content of nickel had substantial influence on promising sulfur tolerance in catalytic tar removal by Ni/Dolomite catalysts. Results were compared with the Ni/Al2O3, Ni/SiO2 as a representative of com. catalysts. The novel 15%Ni/Dolomite almost gasified tar component even at 770° and the presence of 100 ppm H2S in the feed. The poisoning effect of H2S was discovered to be reversible. The suppression of the catalytic activity by adding H2S was much lower for Ni/Dolomite than Ni/Al2O3. The TGA-DTA anal. of used catalysts revealed that Ni/Dolomite exhibited high resistance to coke deposition over those of the Ni/Al2O3, Ni/SiO2.
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    Li, C.; Hirabayashi, D.; Suzuki, K. A Crucial Role of O2– and O22– on Mayenite Structure for Biomass Tar Steam Reforming over Ni/Ca12Al14O33. Appl. Catal. B 2009, 88, 351– 360,  DOI: 10.1016/j.apcatb.2008.11.004
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    A crucial role of O2- and O22- on mayenite structure for biomass tar steam reforming over Ni/Ca12Al14O33
    Li, Chunshan; Hirabayashi, Daisuke; Suzuki, Kenzi
    Applied Catalysis, B: Environmental (2009), 88 (3-4), 351-360CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    Newly synthesized nickel calcium aluminum catalysts (Ni/Ca12Al14O33) were tested in a fixed bed reactor for biomass tar steam reforming, toluene as a tar decompn. model compd. Four catalysts (Ni/Ca12Al14O33) were prepd. with Ni loading amt. from 1, 3, 5 to 7%, even 1% loading catalyst also showed excellent performance. Catalysts aged expts. in the absence (60 h on stream) and presence of H2S were characterized by BET, XRD, and Raman spectra. Ni/Ca12Al14O33 showed excellent sustainability against coke formation due to the free oxygen in the catalysts. It also exhibited higher H2S-poisoning resistance property compared to the com. catalysts Ni/Al2O3 (5%) and Ni/CaO0.5/MgO0.5. Raman spectra revealed that free oxygen O2- and O22- in the structure of the catalysts could be substituted by sulfur then protected Ni poisoning on some degree, but reactivation expts. by O2 flowing showed that the sulfide Ni/Ca12Al14O33 was difficult to completely restore, incorporation of sulfur in the structure only partly regain by O2. The kinetic model proposes, as generally accepted, a 1st-order reaction for toluene with activation energy of 82.06 kJ mol-1 was coincident with the literature data. The Ni/Ca12Al14O33 catalyst was effective and relative cheap, which may be lead to redn. in the cost of hot gas cleaning process.
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    Tomishige, K.; Miyazawa, T.; Kimura, T.; Kunimori, K. Novel Catalyst with High Resistance to Sulfur for Hot Gas Cleaning at Low Temperature by Partial Oxidation of Tar Derived from Biomass. Catal. Commun. 2005, 6, 37– 40,  DOI: 10.1016/j.catcom.2004.10.007
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    Novel catalyst with high resistance to sulfur for hot gas cleaning at low temperature by partial oxidation of tar derived from biomass
    Tomishige, Keiichi; Miyazawa, Tomohisa; Kimura, Takeo; Kunimori, Kimio
    Catalysis Communications (2005), 6 (1), 37-40CODEN: CCAOAC; ISSN:1566-7367. (Elsevier B.V.)
    Rh/CeO2/SiO2 exhibited higher and more stable activity in the partial oxidn. of tar derived from the pyrolysis of cedar biomass even under the presence of high concn. (280 ppm) H2S than the steam reforming Ni catalyst at lower reaction temp. than conventional conditions.
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    Ammendola, P.; Piriou, B.; Lisi, L.; Ruoppolo, G.; Chirone, R.; Russo, G. Dual Bed Reactor for the Study of Catalytic Biomass Tars Conversion. Exp Therm Fluid Sci. 2010, 34 (3), 269– 274,  DOI: 10.1016/j.expthermflusci.2009.10.019
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    Dual bed reactor for the study of catalytic biomass tars conversion
    Ammendola, P.; Piriou, B.; Lisi, L.; Ruoppolo, G.; Chirone, R.; Russo, G.
    Experimental Thermal and Fluid Science (2010), 34 (3), 269-274CODEN: ETFSEO; ISSN:0894-1777. (Elsevier B.V.)
    A dual fixed bed lab. scale set up has been used to compare the activity of a novel Rh/LaCoO3/Al2O3 catalyst to that of dolomite, olivine and Ni/Al2O3, typical catalysts used in fluidized bed biomass gasification, to convert tars produced during biomass devolatilization stage. The exptl. app. allows the catalyst to be operated under controlled conditions of temp. and with a real gas mixt. obtained by the pyrolysis of the biomass carried out in a sep. fixed bed reactor operated under a selected and controlled heating up rate. The proposed catalyst exhibits much better performances than conventional catalysts tested. It is able to completely convert tars and also to strongly decrease coke formation due to its good redox properties.
  163. 163
    Iida, H.; Noguchi, K.; Numa, T.; Igarashi, A.; Okumura, K. Ru/12SrO-7Al2O3 (S12A7) Catalyst Prepared by Physical Mixing with Ru (PPh3)3Cl2 for Steam Reforming of Toluene. Catal. Commun. 2015, 72, 101– 104,  DOI: 10.1016/j.catcom.2015.09.018
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    Ru/12SrO-7Al2O3 (S12A7) catalyst prepared by physical mixing with Ru (PPh3)3Cl2 for steam reforming of toluene
    Iida, Hajime; Noguchi, Kazuhide; Numa, Takashi; Igarashi, Akira; Okumura, Kazu
    Catalysis Communications (2015), 72 (), 101-104CODEN: CCAOAC; ISSN:1566-7367. (Elsevier B.V.)
    Steam reforming of toluene as a model of aroms. was performed over various Ru/12SrO-7Al2O3 (S12A7) catalysts, and the effects of Ru precursor, calcination and pre-treatment conditions on the catalytic activity and durability of Ru/S12A7 catalysts were investigated. The catalytic activity of prepd. Ru/S12A7 catalysts exhibited higher than that of a com. Ru/Al2O3 (RA), despite low Ru loading. The catalysts prepd. by the phys. mixing of Ru (PPh3)3Cl2 and S12A7 (PPH) had higher catalytic activities than the catalysts prepd. by the impregnation with RuCl3 nH2O (CL). It is interesting that the N2 pre-treated PPH and CL catalysts esp. had higher catalytic activities than the H2 pre-treated PPH and CL catalysts. In their catalysts, there was a linear relationship between the catalytic activity and the Ru dispersion estd. by CO chemisorption. The catalytic activity of the N2 pre-treated PPH catalyst has little decreased with time on stream, whereas the catalytic activities of the N2 pre-treated CL catalyst and H2 pre-treated PPH catalyst gradually decreased with time on stream.
  164. 164
    Iida, H.; Deguchi, S.; Torigai, M.; Osawa, Y. Steam Reforming of Toluene over Ru/SrCO3-Al2O3 Catalyst under Extremely Low Steam-to-Carbon Ratio Conditions. Fuel 2020, 272, 117703,  DOI: 10.1016/j.fuel.2020.117703
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    Steam reforming of toluene over Ru/SrCO3-Al2O3 catalyst under extremely low steam-to-carbon ratio conditions
    Iida, Hajime; Deguchi, Shuntaro; Torigai, Miyu; Osawa, Yuki
    Fuel (2020), 272 (), 117703CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Ru/SrCO3-Al2O3 exhibited superior catalytic activity compared to Ru/CeO2 and Ru/Al2O3 for steam reforming of toluene under extremely low steam-to-carbon (S/C) ratio conditions that targeted chem. recovery of exhaust heat from vehicles. Ru/SrCO3-Al2O3 also exhibited good coking tolerance, unlike Ru/CeO2, even under a S/C ratio of 0.3. The efficiency of chem. heat recovery over Ru/SrCO3-Al2O3 was the highest among the examd. Ru catalysts, even under a low S/C ratio.
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    Tang, W.; Cao, J.-P.; Yang, F.-L.; Feng, X.-B.; Ren, J.; Wang, J.-X.; Zhao, X.-Y.; Zhao, M.; Cui, X.; Wei, X.-Y. Highly Active and Stable HF Acid Modified HZSM-5 Supported Ni Catalysts for Steam Reforming of Toluene and Biomass Pyrolysis Tar. Energy Convers. Manag. 2020, 212, 112799  DOI: 10.1016/j.enconman.2020.112799
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    Highly active and stable HF acid modified HZSM-5 supported Ni catalysts for steam reforming of toluene and biomass pyrolysis tar
    Tang, Wen; Cao, Jing-Pei; Yang, Fei-Long; Feng, Xiao-Bo; Ren, Jie; Wang, Jing-Xian; Zhao, Xiao-Yan; Zhao, Ming; Cui, Xin; Wei, Xian-Yong
    Energy Conversion and Management (2020), 212 (), 112799CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    This paper investigated the performance of HF modified HZSM-5 supported nickel catalysts (Ni/FZ5) in steam reforming of toluene (TSR) and biomass pyrolysis tar (BSR). The mesopores vol. of support increased from 0.021 to 0.061 cm3/g with decreasing acid amt. from 2.27 to 0.41 mmol/g after HF treatment. Catalysts with different Ni loadings were prepd. and characterized. The Ni/FZ5 with Ni loading of 9 wt% possesses relatively large sp. surface area (337 m2/g) and av. pore size (2.91 nm), as well as small Ni particle size (23 nm) and high dispersion. In the process of TSR, 9Ni/FZ5 was kept above 70% for 7 h. Owing to the calcd. lower apparent activation energy (30.76 KJ/mol), 9Ni/FZ5 exhibited the best performance in BSR at 650°C, achieving the largest H2 yield of 52.8 mmol/g and the highest selectivity of H2 at 72.8%. Addnl., only 1.6 mg/g catalyst of coke deposition was detected. Moreover, its high activity was still identified with excellent hydrothermal stability even after 7 times of regeneration. All findings suggest that 9Ni/FZ5 is a promising catalyst for biomass tar cracking.
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    Gu, J.; Wang, S.; Lu, T.; Wu, Y.; Yuan, H.; Chen, Y. Synthesis and Evaluation of Pyrolysis Waste Peat Char Supported Catalyst for Steam Reforming of Toluene. Renew Energy 2020, 160, 964– 973,  DOI: 10.1016/j.renene.2020.06.109
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    Synthesis and evaluation of pyrolysis waste peat char supported catalyst for steam reforming of toluene
    Gu, Jing; Wang, Shuxiao; Lu, Tao; Wu, Yufeng; Yuan, Haoran; Chen, Yong
    Renewable Energy (2020), 160 (), 964-973CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Pyrolytic char as a catalyst carrier has been widely used in tar removal. This paper aimed to develop a cost-effective and eco-friendly tar steam reforming approach by using waste peat char supported Ca catalysts in a lab. dual-stage reactor. Tar model compd. toluene was used in steam reforming expt. for facilitate fundamental research. The reaction temp., residence time, steam-to-carbon ratio and the molar ratios of H2, CO, CO2 and CH4 in the generated gas were investigated. Exptl. results show that the peat char supported Ca catalysts had good selectivity for H2, esp. the catalyst which activated by KOH and CO2. The catalyst demonstrated better catalytic activity with a higher residence time (0.6 s-0.7 s) and S/C ratio (S/C > 2.5). Under the optimized conditions, the toluene conversion and the mol% of H2 can reached 94.4% and 68.5%, resp. Meanwhile, the activity of the catalyst was proved by a variety of performance tests, and the deactivation and mechanism of catalysts were investigated. Finally, these cost-effective and green peat char-supported Ca catalysts could be used for tar removal.
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    Park, S. Y.; Oh, G.; Kim, K.; Seo, M. W.; Ra, H. W.; Mun, T. Y.; Lee, J. G.; Yoon, S. J. Deactivation Characteristics of Ni and Ru Catalysts in Tar Steam Reforming. Renew Energy 2017, 105, 76– 83,  DOI: 10.1016/j.renene.2016.12.045
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    Deactivation characteristics of Ni and Ru catalysts in tar steam reforming
    Park, Seo Yun; Oh, Gunung; Kim, Kwangyul; Seo, Myung Won; Ra, Ho Won; Mun, Tae Young; Lee, Jae Goo; Yoon, Sang Jun
    Renewable Energy (2017), 105 (), 76-83CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Tar formation resulting during lignocellulosic biomass gasification is a major impediment to utilizing biomass energy sources, in that it blocks and fouls the processing equipment; as such, any tar present in the produced syngas much be effectively removed. This study analyzes the ability of com. available Ni and Ru based CH4 reforming catalysts to effect tar removal and compares deactivation characteristics. Toluene was used as the model biomass tar at concns. of 30 and 100 g/Nm3. Several addnl. parameters were also tested, including reaction temps. (400-800°C), space velocities (5000-30,000 h-1), and the steam/toluene ratios (2-20). The variation of toluene conversion and product gas compn. with reaction conditions was analyzed. Overall, H2 and CO prodn. were favored by the Ru catalyst and generally increased with temp. Conversion also increased with temp., with conversions higher than 90% obtained at 800°C.
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    Xu, H.; Shen, Z.; Zhang, S.; Chen, G.; Pan, H.; Ge, Z.; Zheng, Z.; Wang, Y.; Wang, Y.; Li, X. Arming Wood Carbon with Carbon-Coated Mesoporous Nickel-Silica Nanolayer as Monolithic Composite Catalyst for Steam Reforming of Toluene. J. Colloid Interface Sci. 2021, 599, 650– 660,  DOI: 10.1016/j.jcis.2021.04.112
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    Arming wood carbon with carbon-coated mesoporous nickel-silica nanolayer as monolithic composite catalyst for steam reforming of toluene
    Xu, Haiyang; Shen, Zhangfeng; Zhang, Siqian; Chen, Gang; Pan, Hu; Ge, Zhigang; Zheng, Zheng; Wang, Yanqin; Wang, Yangang; Li, Xi
    Journal of Colloid and Interface Science (2021), 599 (), 650-660CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
    Steam reforming is an effective measure for biomass tar elimination as well as H2-rich syngas (H2 + CO) prodn. However, the granular or powdery Ni-based catalysts are prone to deactivation, which is caused by inappropriate mass transfer and clogging of catalyst bed. Herein, monolithic wood carbon (WC) with low-tortuosity microchannels is armed with a carbon-coated mesoporous nickel-silica nanocomposite (Ni-SiO2@C) layer via an evapn.-induced self-assembly and calcination procedure for toluene (tar model compd.) steam reforming. The quality of the Ni-SiO2@C layer growing on the surface of WC microchannel is affected by the molar ratios of Si/Ni feed. A uniform thin-layer coverage is obtained on the Ni-15SiO2@C/WC (Si/Ni = 15) catalyst, where highly dispersed Ni nanoparticles (av. size of 6.6 nm) with appropriate metal-support interaction and remarkable mech. strength are achieved. The mass transfer, coke resistance, and hydrothermal stability of the Ni-15SiO2@C/WC catalyst were significantly improved by the multilevel structure assembled from the WC microchannels and the secondary ordered SiO2 mesopores. A stable toluene conversion over 97% with an H2 yield of 135μmol/min was obtained at 600°C on the Ni-15SiO2@C/WC catalyst. This work opens a new window for facilely constructing high-performance wood carbon-based monolithic tar reforming catalyst.
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    Wang, X.-B.; Yang, S.-Q.; Xu, C.; Ma, H.-D.; Zhang, Z.-H.; Du, Z.-Y.; Li, W.-Y. Effect of Boron Doping on the Performance of Ni/Biochar Catalysts for Steam Reforming of Toluene as a Tar Model Compound. J. Anal Appl. Pyrolysis 2021, 155, 105033  DOI: 10.1016/j.jaap.2021.105033
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    Effect of boron doping on the performance of Ni/Biochar catalysts for steam reforming of toluene as a tar model compound
    Wang, Xing-Bao; Yang, Shi-Qi; Xu, Chen; Ma, Hong-Da; Zhang, Zhi-Hua; Du, Zhen-Yi; Li, Wen-Ying
    Journal of Analytical and Applied Pyrolysis (2021), 155 (), 105033CODEN: JAAPDD; ISSN:0165-2370. (Elsevier B.V.)
    Biochar-supported nickel (Ni/BC) catalysts have potential applications in steam reforming of tar during biomass gasification. However, the industrial application of Ni/BC catalysts is restricted by their rapid deactivation caused by the gasification of biochar support and deposition of carbon on the active Ni metal. In this study, the effect of boron doping was explored on the performance of Ni/BC catalysts in steam reforming of toluene as a tar model compd. A series of Ni/BC and boron-doped Ni/BC catalysts were prepd. by impregnating Ni salts on raw and acid-washed biomass as the starting materials and used in steam reforming of toluene as the tar model compd. It was found that boron doping significantly prolonged the lifetime of Ni/BC catalysts by interacting with Ni and the biochar support simultaneously. It is believed that boron doping lowered the gasification consumption rate of the biochar support in three ways: transforming the inherent K into more stable borates, inhibiting the desorption of CO and CO2, and forming B2O3 as the active site blocker. Furthermore, boron doping also reduced coke deposition on the Ni particles.
  170. 170
    Zhou, S.; Chen, Z.; Gong, H.; Wang, X.; Zhu, T.; Zhou, Y. Low-Temperature Catalytic Steam Reforming of Toluene as a Biomass Tar Model Compound over Three-Dimensional Ordered Macroporous Ni-Pt/ Ce 1–x Zr x O 2 Catalysts. Appl. Catal. A Gen. 2020, 607, 117859  DOI: 10.1016/j.apcata.2020.117859
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    Low-temperature catalytic steam reforming of toluene as a biomass tar model compound over three-dimensional ordered macroporous Ni-Pt/Ce1-xZrxO2 catalysts
    Zhou, Shuyu; Chen, Zezhi; Gong, Huijuan; Wang, Xiaoshu; Zhu, Tingting; Zhou, Yuchen
    Applied Catalysis, A: General (2020), 607 (), 117859CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Ceria-zirconia solid soln. (Ce1-xZrxO2) is a fascinating catalyst support in steam reforming reaction. In order to further improve the performance of Ni-based catalyst with Ce1-xZrxO2 as support for tar team reforming, three-dimensional ordered macroporous Ni-Pt/Ce1-xZrxO2 (Ni-Pt/C1-xZx-3DOM; x = 0.2, 0.3, 0.4) catalysts were prepd. by a colloidal crystal template method and their catalytic performances for toluene steam reforming were investigated in low temp. range. The Ni-Pt/C1-xZx-3DOM exhibited excellent catalytic performance, and toluene conversion of Ni-Pt/C0.8Z0.2-3DOM reached 90.4% at 500°C under 185μmol/min toluene flowrate and 10,000 h-1 GHSV. Besides, this catalyst showed good durability with 1.7 mg g-1cat h-1 carbon deposition rate during 30 h of operation at 600°C. The characterization results demonstrated the Ni-Pt/C1-xZx-3DOM exhibits desirable characteristics to promote the catalysis performance compared to non-porous Ni-Pt/C1-xZx, including more oxygen vacancies on catalyst surface, higher sp. surface areas, larger pore vols., more meso-pores, smaller cryst. size of active component and support, and better reducibility.
  171. 171
    He, L.; Hu, S.; Yin, X.; Xu, J.; Han, H.; Li, H.; Ren, Q.; Su, S.; Wang, Y.; Xiang, J. Promoting Effects of Fe-Ni Alloy on Co-Production of H 2 and Carbon Nanotubes during Steam Reforming of Biomass Tar over Ni-Fe/α-Al 2 O 3. Fuel 2020, 276, 118116  DOI: 10.1016/j.fuel.2020.118116
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    Promoting effects of Fe-Ni alloy on co-production of H2 and carbon nanotubes during steam reforming of biomass tar over Ni-Fe/α-Al2O3
    He, Limo; Hu, Song; Yin, Xiaofei; Xu, Jun; Han, Hengda; Li, Hanjian; Ren, Qiangqiang; Su, Sheng; Wang, Yi; Xiang, Jun
    Fuel (2020), 276 (), 118116CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Fe-modified Ni/Al2O3 catalysts with Fe/Ni molar ratios of 0, 0.5, 1 and 2 were prepd. to promote the co-prodn. of H2 and carbon nanotubes (CNTs) during steam reforming of toluene as a tar model compd. After the addn. of Fe, toluene conversion increased from 55.1% of Ni/Al2O3 to 73.6% of F1N1A (Fe/Ni ratio of 1), and H2 yield over F1N1A reached the max. of more than 2000 mmol/(g-cata). Multi-walled carbon nanotubes with av. diam. of 10-30 nm were generated and follow tip-growth mechanism. Compared with Ni/Al2O3, the addn. of Fe remarkably increased the amt. and quality of CNTs which had longer length and less tortuosity. These dual promoting effects on H2 and CNTs after the addn. of Fe were attributed to the strong interaction between Ni and Fe in Fe-Ni alloy. Fe-Ni alloy had the high activity for the decompn. performance of toluene and H2O to generate more H2 and intermediates for improving the reforming reaction. Meanwhile, the high catalytic decompn. activity supplied more carbon species and the formation of Fe-Ni alloy enhanced the generation of metal carbide for promoting CNTs growth. Besides, the deposition of amorphous carbon was suppressed and the interaction between Ni particle and catalyst support was weakened after the addn. of Fe, which kept the activity of catalyst and promoted the tip-growth of CNTs.
  172. 172
    Zou, X.; Chen, T.; Zhang, P.; Chen, D.; He, J.; Dang, Y.; Ma, Z.; Chen, Y.; Toloueinia, P.; Zhu, C.; Xie, J.; Liu, H.; Suib, S. L. High Catalytic Performance of Fe-Ni/Palygorskite in the Steam Reforming of Toluene for Hydrogen Production. Appl. Energy 2018, 226, 827– 837,  DOI: 10.1016/j.apenergy.2018.06.005
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    172
    High catalytic performance of Fe-Ni/Palygorskite in the steam reforming of toluene for hydrogen production
    Zou, Xuehua; Chen, Tianhu; Zhang, Ping; Chen, Dong; He, Junkai; Dang, Yanliu; Ma, Zhiyuan; Chen, Ye; Toloueinia, Panteha; Zhu, Chengzhu; Xie, Jingjing; Liu, Haibo; Suib, Steven L.
    Applied Energy (2018), 226 (), 827-837CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
    The inexpensive and abundant material, palygorskite, was used as a promising catalyst support to prep. Fe-Ni/Pal catalysts. Catalytic steam reforming of toluene as a biomass tar model compd. over these catalysts was investigated in a fixed-bed reactor under different parameters, including reaction temps. and S/C molar ratios. The stability and lifetime of Fe3Ni8/Palygorskite catalyst was evaluated under optimal conditions and its kinetic parameters were detd. as well. The fresh and used catalysts were characterized using X-ray diffraction (XRD), H2 temp.-programmed redn. (H2-TPR), transmission electron microscopy (TEM), and Raman spectra. The results showed that the Fe3Ni8/Palygorskite catalyst with high dispersion was successfully prepd. and exhibited superior catalytic performance compared with those of the monometallic catalysts (Fe3/Palygorskite and Ni8/Palygorskite) and the bare Palygorskite. Increasing the reaction temp. from 500 °C to 700 °C was beneficial for the toluene conversion and gaseous yields. The catalytic activity of Fe3Ni8/Palygorskite varied distinctly with the increase of S/C molar ratio and reached max. at the the S/C molar ratio of 1.0. The apparent activation energy of 41.55 kJ mol-1 and the pre-exponential factor of 1.35 × 103 m3 kg-1 h-1 were obtained for Fe3Ni8/Palygorskite in kinetic studies under optimal reaction conditions, resp. The carbon deposition anal. of the used catalysts revealed that the formation of graphitic carbon rather than amorphous carbon was the main reason for the deactivation of Fe3Ni8/Palygorskite catalysts. When ceased the injection of steam into the reaction system, the graphitic carbon would be accelerating formed on the surface of the Fe3Ni8/Palygorskite and decreased its catalytic activity for toluene conversion. But owing to the water gas shift reaction, the catalytic activity of Fe3Ni8/Palygorskite seemed to recover gradually to its optimum.
  173. 173
    Oh, G.; Park, S. Y.; Seo, M. W.; Ra, H. W.; Mun, T. Y.; Lee, J. G.; Yoon, S. J. Combined Steam-Dry Reforming of Toluene in Syngas over CaNiRu/Al 2 O 3 Catalysts. Int. J. Green Energy 2019, 16 (4), 333– 349,  DOI: 10.1080/15435075.2019.1566729
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    Combined steam-dry reforming of toluene in syngas over CaNiRu/Al2O3 catalysts
    Oh, Gunung; Park, Seo Yoon; Seo, Myung Won; Ra, Ho Won; Mun, Tae Young; Lee, Jae-Goo; Yoon, Sang Jun
    International Journal of Green Energy (2019), 16 (4), 333-349CODEN: IJGECR; ISSN:1543-5075. (Taylor & Francis, Inc.)
    Cracking, steam reforming, dry reforming, and combined steam and dry reforming of toluene in model syngas were performed using catalysts to simulate tar removal produced during biomass gasification. The catalysts were prepd. by adding Ru, Ca, and Mn to Ni-based catalysts, and their properties were measured using BET, pulse CO chemisorption, XRD and TG. In steam and dry reforming of toluene, a high toluene conversion was obsd. with increasing Ca content in the catalyst and catalysts contg. Ca showed a higher activity than those contg. Mn. In combined steam-dry reforming with syngas, 1%CaNiRu/Al2O3 indicated a conversion of 93.9% at 800°C.
  174. 174
    Yang, X.; Liu, X.; Guo, T.; Liu, C. Effects of Cu and Fe Additives on Low-Temperature Catalytic Steam Reforming of Toluene Over Ni/AC Catalysts. Catalysis Surveys from Asia 2019, 23 (2), 54– 63,  DOI: 10.1007/s10563-018-9260-7
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    Effects of Cu and Fe Additives on Low-Temperature Catalytic Steam Reforming of Toluene Over Ni/AC Catalysts
    Yang, Xiaoqin; Liu, Xuejing; Guo, Tong; Liu, Chuang
    Catalysis Surveys from Asia (2019), 23 (2), 54-63CODEN: CSAABF; ISSN:1571-1013. (Springer)
    Steam reforming of toluene, a model tar compd., was carried out at low temp. of 600°C using Cu-Ni and Fe-Ni bimetallic catalysts with different molar ratios supported on activated carbon (AC). For the Cu-Ni/AC catalysts, the carbon conversion of toluene rose and then decreased with the content of Cu increasing, and the best performance was achieved at the molar ratio of 0.2. However, the Fe-Ni/AC catalyst with the optimum compn. of Fe/Ni = 0.1 had a better catalytic performance for toluene steam reforming than the Cu-Ni/AC catalyst (Cu/Ni = 0.2). During the duration test of 20 h, the Fe-Ni/AC (Fe/Ni = 0.1) catalyst showed higher activity for the av. carbon conversion of toluene (93.8% vs. 92.9%) and better resistance. to carbon deposition than those of Ni/AC catalyst. Moreover, the metal av. sizes of the spent Ni/AC and 0.1-Fe-Ni/AC were estd. to be 30.0 nm and 19.0 nm, resp. Based on a variety of physiochem. characterization results, it is demonstrated that the addn. of iron into Ni/AC catalyst led to good dispersion of Ni, and few coke formation and limited aggregation of nickel particles during reaction.
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    Ahmed, T.; Xiu, S.; Wang, L.; Shahbazi, A. Investigation of Ni/Fe/Mg Zeolite-Supported Catalysts in Steam Reforming of Tar Using Simulated-Toluene as Model Compound. Fuel 2018, 211, 566– 571,  DOI: 10.1016/j.fuel.2017.09.051
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    Investigation of Ni/Fe/Mg zeolite-supported catalysts in steam reforming of tar using simulated-toluene as model compound
    Ahmed, Talal; Xiu, Shuangning; Wang, Lijun; Shahbazi, Abolghasem
    Fuel (2018), 211 (), 566-571CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Catalytic performance of Ni/zeolite, Ni-Fe/zeolite, and Ni-Fe-Mg/zeolite catalysts were investigated in steam reforming of toluene as a biomass tar model compd. to explore promotional effect of MgO and Fe on Ni/zeolite support. The Ni-Fe-Mg/zeolite catalysts with optimum metallic compn. showed higher catalytic performance over corresponding monometallic Ni and Fe catalysts and Ni-Fe/zeolite (bimetallic) catalysts. Addn. of Mg to Ni-Fe/zeolite catalyst enhanced the tar reforming reactions and increased the carbon deposition tolerance. The results suggest that Ni-Fe/zeolite and Ni-Fe-Mg/zeolite catalysts have great potential for application in the steam reforming of biomass tar.
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    Yin, F.; Tremain, P.; Yu, J.; Doroodchi, E.; Moghtaderi, B. An Experimental Investigation of the Catalytic Activity of Natural Calcium-Rich Minerals and a Novel Dual-Supported CaO–Ca12Al14O33_Al2O3 Catalyst for Biotar Steam Reforming. Energy Fuels 2018, 32, 4269– 4277,  DOI: 10.1021/acs.energyfuels.7b03201
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    An Experimental Investigation of the Catalytic Activity of Natural Calcium-Rich Minerals and a Novel Dual-Supported CaO-Ca12Al14O33/Al2O3 Catalyst for Biotar Steam Reforming
    Yin, Fengkui; Tremain, Priscilla; Yu, Jianglong; Doroodchi, Elham; Moghtaderi, Behdad
    Energy & Fuels (2018), 32 (4), 4269-4277CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Tar removal plays a key role in the process efficiency and viability of biomass gasification for syngas prodn. applications. Among currently available tar treatment technologies, catalytic cracking was found to be the most attractive due to minimal energy losses by avoiding cooling of the raw product gas. Naturally available calcium-based catalysts, particularly stone dust and dolomite, have been proven to be effective for biotar cracking; however, they have poor resistance to attrition and undergo deactivation after a few carbonation/calcination cycles. As such, these characteristics play a crit. role in detg. the viability of their application at a large-scale. Hence to overcome the shortcomings previously stated, a novel dual supported calcium-based catalyst which includes a stable support with great mech. strength (alumina, Al2O3, and mayenite, Ca12Al14O33) dosed with CaO nanoparticles was synthesized by wet impregnation of calcium on alumina particles with and without the assistance of ultrasonication, referred to as CA and CAU resp. The synthesized catalysts, as well as the naturally occurring calcium rich minerals stone dust and dolomite, were phys. and chem. characterized using a variety of anal. techniques. The synthesized catalysts showed superior mech. strength up to 5 times greater than the natural minerals. Each of the natural and synthesized catalysts was then investigated in a fixed bed reactor for steam reforming of biotars. In these expts., toluene was used as a model tar compd. to assess the catalytic activity of each and det. the best option in terms of catalytic activity, cost, and mech. strength. The synthesized CA catalyst without ultrasonic treatment exhibited better tar cracking performance in comparison to stone dust and dolomite in the temp. range of 600 to 800 °C. The synthesized CA catalyst also had the greatest performance in terms of superior surface area and mech. strength due to the core support of Al2O3. This makes it a potential bed material for further study of tar cracking in large-scale fluidized applications.
  177. 177
    Oh, G.; Park, S. Y.; Seo, M. W.; Kim, Y. K.; Ra, H. W.; Lee, J.-G.; Yoon, S. J. Ni/RueMn/Al 2 O 3 Catalysts for Steam Reforming of Toluene as Model Biomass Tar. Renew. Energy 2016, 86, 841– 847,  DOI: 10.1016/j.renene.2015.09.013
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    Ni/Ru-Mn/Al2O3 catalysts for steam reforming of toluene as model biomass tar
    Oh, Gunung; Park, Seo Yoon; Seo, Myung Won; Kim, Yong Ku; Ra, Ho Won; Lee, Jae-Goo; Yoon, Sang Jun
    Renewable Energy (2016), 86 (), 841-847CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    The catalytic steam reforming of the major biomass tar component, toluene, was studied over two com. Ni-based catalysts and two prepd. Ru-Mn-promoted Ni-base catalysts, in the temps. range 673-1073 K. Generally, the conversion of toluene and the H2 content in the product gas increased with temp. A H2-rich gas was generated by the steam reforming of toluene, and the CO and CO2 contents in the product gas were reduced by the reverse Boudouard reaction. A naphtha-reforming catalyst (46-5Q) exhibited better performance in the steam reforming of toluene at temps. over 873 K than a methane-reforming catalyst (Reformax 330). Ni/Ru-Mn/Al2O3 catalysts showed high toluene reforming performance at temps. over 873 K. The results indicate that the obsd. high stability and coking resistance may be attributed to the promotional effects of Mn on the Ni/Ru-Mn/Al2O3 catalyst.
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    De Castro, T. P.; Peguin, R. P. S.; Neto, R. C. R.; Borges, L. E. P.; Noronha, F. B. Steam Reforming of Toluene over Pt/Ce x Zr1-x O2/Al2O3 Catalysts. Top Catal 2016, 59 (2–4), 292– 302,  DOI: 10.1007/s11244-015-0443-4
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    Steam Reforming of Toluene Over Pt/CexZr1-xO2/Al2O3 Catalysts
    de Castro, T. P.; Peguin, R. P. S.; Neto, R. C. R.; Borges, L. E. P.; Noronha, F. B.
    Topics in Catalysis (2016), 59 (2-4), 292-302CODEN: TOCAFI; ISSN:1022-5528. (Springer)
    Steam reforming of toluene was investigated over Pt/CexZr1-xO2/Al2O3 catalysts with different ceria and zirconia content (x = 0.25, 0.50, 0.75, and 1.00). Toluene was used as model mol. representative of tar produced in biomass gasification. The main reactions over Pt/CexZr1-xO2/Al2O3 catalysts are the steam reforming of toluene and the water-gas shift. The dealkylation of toluene to benzene and methane takes place only at the beginning of the reaction. Toluene conversion significantly decreases during the reaction for all catalysts excepted for Pt/CeO2/Al2O3 catalyst. Catalyst deactivation was attributed to carbon deposition as revealed by Raman spectroscopy. A clear relation is obsd. between the acidity of the catalyst and the amt. of carbon formed over Pt/CexZr1-xO2/Al2O3 catalysts. Decreasing the Ce/Zr ratio increased the d. of acid sites as well as the amt. of carbon formed. This result suggests that the main route for carbon deposition proceeds by the oligomerization of toluene mol. on the acid sites of the support. Pt/CeO2/Al2O3 catalyst was quite stable during steam reforming of toluene without carbon deposition. For this catalyst, ceria covered the acid sites of alumina and did not introduce significant Lewis acid sites.
  179. 179
    Liu, X.; Yang, X.; Liu, C.; Chen, P.; Yue, X.; Zhang, S. Low-Temperature Catalytic Steam Reforming of Toluene over Activated Carbon Supported Nickel Catalysts. J. Taiwan Inst Chem. Eng. 2016, 65, 233– 241,  DOI: 10.1016/j.jtice.2016.05.006
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    Low-temperature catalytic steam reforming of toluene over activated carbon supported nickel catalysts
    Liu, Xuejing; Yang, Xiaoqin; Liu, Chuang; Chen, Peng; Yue, Xiaoming; Zhang, Shuangquan
    Journal of the Taiwan Institute of Chemical Engineers (2016), 65 (), 233-241CODEN: JTICA8; ISSN:1876-1070. (Elsevier B.V.)
    In order to decrease the reaction temp. of catalytic cracking of tar derived from biomass gasification and prolong the lifetime of catalyst, nickel supported on activated carbon (Ni/AC) catalysts were prepd. by impregnation method and used in steam reforming of toluene, a model tar compd., in a fixed bed reactor. The physiochem. properties of the catalysts were analyzed by N2 adsorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM), etc. The effects of nickel content, calcination temp. and reaction temp. on carbon conversion were investigated, and the catalytic performance of the Ni/AC catalyst was compared with those of Al2O3/olivine-supported nickel catalysts. The results showed that the Ni/AC catalyst with 10 wt. % of nickel loading and 600°C of calcination temp. had the best low-temp. catalytic activity at 600°C for toluene reforming, and the carbon conversion achieved about 99%. The high performance of the 600-10%Ni/AC catalyst was probably accounted for the AC support, which had a large BET surface area and unique porous structure, and therefore, a fine nickel particle size distribution on it. It also could be known by XRD anal. that nickel loaded on the surface of AC was in the form of metallic state after calcination, thus decreasing the use of hydrogen for redn. before reaction, so the catalyst prepn. process can be simplified and the cost will be saved.
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    Guo, F.; Liang, S.; Jia, X.; Peng, K.; Jiang, X.; Qian, L. One-Step Synthesis of Biochar-Supported Potassium-Iron Catalyst for Catalytic Cracking of Biomass Pyrolysis Tar. Int. J. Hydrogen Energy 2020, 45 (33), 16398– 16408,  DOI: 10.1016/j.ijhydene.2020.04.084
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    One-step synthesis of biochar-supported potassium-iron catalyst for catalytic cracking of biomass pyrolysis tar
    Guo, Feiqiang; Liang, Shuang; Jia, Xiaopeng; Peng, Kuangye; Jiang, Xiaochen; Qian, Lin
    International Journal of Hydrogen Energy (2020), 45 (33), 16398-16408CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    K-Fe bimetallic catalyst supported on porous biomass char was synthesized via a 1-step synthesis method by pyrolysis of biomass (peanut shells) after impregnation of a small amt. of K ferrate (PSC-K2FeO4), and was evaluated for the cracking of biomass pyrolysis tar. Control expts. using the pure char (PSC) and char-supported catalysts after impregnation of KOH (PSC-KOH) and FeCl3 (PSC-FeCl3) were also performed for comparison. The as-prepd. PSC-K2FeO4 possessed a porous structure with the dispersion of particles/clusters of Fe metal, K2CO3 and KFeO2 on the char support. Tar cracking expts. showed that the PSC-K2FeO4 exhibited excellent catalytic activity on the cracking of biomass pyrolysis tar at 600-800°, and the obtained tar conversion efficiencies were obviously higher than that in the control expts., particularly at relatively lower temps. (600 and 700°). The yields of combustible gas compds. including CO, H2 and CH4 increased significantly using PSC-K2FeO4 as the catalyst due to the enhanced tar cracking and reforming reactions. The porous structure and the active crystal structures of the spent catalyst were well retained, indicating the potential for efficient and long-term use of the catalyst in tar cracking. PSC-K2FeO4 exhibited excellent reusability during the 5 times reuse under the same conditions without regeneration, which showed almost no obvious decrease in the tar conversion efficiency and gas yields.
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    Frainetti, A. J.; Klinghoffer, N. B. Recent Experimental Advances on the Utilization of Biochar as a Tar Reforming Catalyst: A Review. International Journal of Hydrogen Energy. 2023, 48, 8022– 8044,  DOI: 10.1016/j.ijhydene.2022.11.127
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    Recent experimental advances on the utilization of biochar as a tar reforming catalyst
    Frainetti, Alexandra J.; Klinghoffer, Naomi B.
    International Journal of Hydrogen Energy (2023), 48 (22), 8022-8044CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Review. Biomass gasification to form syngas is a promising renewable energy prodn. process. Here, biomass is exposed to high temps. in an oxygen-controlled environment where volatiles react to form components of syngas that can be used for energy or chem. prodn. A limitation to the use of gasification is the generation of tars that condense in downstream equipment causing damage and halting prodn. Currently tars are removed by phys., thermal, or catalytic processes, all high-cost options. On the other hand, biochar is produced as a solid byproduct of gasification, characterized by high surface area, desirable adsorption properties, and relatively low cost. This review details the use of biochar as a catalyst to reform tars, while highlighting recent exptl. advances in evaluating the effects of biomass compn., gasification conditions, and pre-treatment and post-treatment options to improve catalytic function. It discusses tar degrdn. mechanisms and catalyst deactivation and recommends further areas for research.
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    Qian, K.; Kumar, A. Catalytic Reforming of Toluene and Naphthalene (Model Tar) by Char Supported Nickel Catalyst. Fuel 2017, 187, 128– 136,  DOI: 10.1016/j.fuel.2016.09.043
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    Catalytic reforming of toluene and naphthalene (model tar) by char supported nickel catalyst
    Qian, Kezhen; Kumar, Ajay
    Fuel (2017), 187 (), 128-136CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    The purpose of this study was to utilize gasification derived char as a catalyst support for tar removal. Red cedar char collected from downdraft bed gasification was chem. activated into activated carbon and impregnated with nickel acetate and nickel nitrate. The effects of nickel salts precursor, nitric acid treatment of support and redn. of nickel in hydrazine medium on catalyst performance were studied. It was found nickel nitrate was a better nickel precursor than nickel acetate for prepn. of char supported nickel catalyst. The catalyst impregnated with nickel nitrate was found more active in steam reforming of toluene than the catalyst impregnated with nickel acetate. TEM results indicated that nickel particle size of the catalyst impregnated with nickel nitrate was much smaller than that of the catalyst impregnated with nickel acetate. Toluene showed higher removal efficiency than naphthalene. The presence of naphthalene decreased the toluene removal.
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    Mani, S.; Kastner, J. R.; Juneja, A. Catalytic Decomposition of Toluene Using a Biomass Derived Catalyst. Fuel Process. Technol. 2013, 114, 118– 125,  DOI: 10.1016/j.fuproc.2013.03.015
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    Catalytic decomposition of toluene using a biomass derived catalyst
    Mani, Sudhagar; Kastner, James R.; Juneja, Ankita
    Fuel Processing Technology (2013), 114 (), 118-125CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Pine bark biochar generated by slow pyrolysis (950 °C) was used as a low cost catalyst to decomp. toluene (model tar compd.) over a temp. range of 600-900 °C. Relative to thermal cracking, fractional toluene conversion increased from 13 to 94% when increasing temps. from 600 to 900 °C (2500 ppmv, SV = 0.76 s-1, 3.8 g catalyst) and Arrhenius anal. indicated an activation energy of 91 kJ/mol, comparable to that of synthetic catalysts (e.g., 80.24 kJ/mol for Ni/Mayenite and 196 kJ/mol for olivine) and lower than that of thermal cracking (356 kJ/mol). The reaction rate for toluene decompn. increased linearly from 550 to 700 °C with a concn. range of 1000-4600 ppmv indicating a first order rate law with respect to toluene. Benzene was detected as a potential intermediate in the decompn. of toluene with selectivity ranging from 0 to 28% at temps. from 600 to 900 °C resp., and its formation increased with increasing toluene conversion. Toluene conversion ranged between 40 and 95% with benzene selectivity from 0 to 20% at 800 °C during catalyst longevity studies of 6 days. These results indicate that biochar generated from slow pyrolysis of pine bark at high temp. can be used as a low cost catalyst for tar removal from syngas. However, the tar removal rates using the biochar catalyst were lower than that of olivine and nickel based catalysts indicating the need to increase catalytic activity.
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    Lee, J.; Kim, K.-H.; Kwon, E. E. Biochar as a Catalyst. Renewable Sustainable Energy Rev. 2017, 77, 70– 79,  DOI: 10.1016/j.rser.2017.04.002
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    Biochar as a Catalyst
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    Renewable & Sustainable Energy Reviews (2017), 77 (), 70-79CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. Biochar is pyrogenic carbon rich material generated from carbon neutral sources (i.e., biomass). Being an environmentally benign means for soil amendment, it also offers principle strategies for carbon capture and storage (CCS). In addn., recent recognition of biochar as versatile media for catalytic applications has brought forth initial research exploring the catalytic capacity of biochar and mechanistic practices in various routes. Thus, to provide comprehensive information on the catalytic applications of biochar in the field of catalysis, this review focuses on the catalytic challenges and practices of biochar, e.g., biodiesel prodn., tar redn. in bio-oil and syngas (synthetic gas: H2 and CO), enhanced syngas prodn., conversion of biomass into chems. and biofuels, deNOx reactions, and microbial fuel cell electrodes. This review also provides an in-depth assessment on the catalytic properties of biochar with respect to prodn. recipes at the fundamental level. Lastly, the performance of various biochar catalysts is also evaluated in this review.
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    Kastner, J. R.; Mani, S.; Juneja, A. Catalytic Decomposition of Tar Using Iron Supported Biochar. Fuel Process. Technol. 2015, 130, 31– 37,  DOI: 10.1016/j.fuproc.2014.09.038
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    Catalytic decomposition of tar using iron supported biochar
    Kastner, James R.; Mani, Sudhagar; Juneja, Ankita
    Fuel Processing Technology (2015), 130 (), 31-37CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Iron supported biochar catalysts were used to decomp. toluene, a model tar compd., over a temp. range of 600-900 °C. Toluene conversion and decompn. rates increased linearly with increasing temp. and catalyst loading from 600 to 700 °C. Relative to biochar alone, the iron supported catalysts lowered the activation energy by 47% and decreased the formation of benzene, an intermediate in toluene decompn. At 800 °C for the 13 and 18.7 wt.% iron loaded catalyst, toluene conversion approached 100% and benzene selectivity (SB) was zero, compared to an SB of 0.025% and 0.35% for 10% iron and the biochar, resp. Time on stream studies with the 13 wt.% iron biochar catalyst, over the course of four days, resulted in a mean toluene conversion of 91% and benzene selectivity of 0.02%. These results indicate that inexpensive iron impregnated biochar catalysts could potentially be used to catalytically decomp. tar mols. in syngas generated via biomass gasification.
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    Abu El-Rub, Z.; Bramer, E. A.; Brem, G. Experimental Comparison of Biomass Chars with Other Catalysts for Tar Reduction. Fuel 2008, 87, 2243– 2252,  DOI: 10.1016/j.fuel.2008.01.004
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    Experimental comparison of biomass chars with other catalysts for tar reduction
    Abu El-Rub, Z.; Bramer, E. A.; Brem, G.
    Fuel (2008), 87 (10-11), 2243-2252CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    In this paper the potential of using biomass char as a catalyst for tar redn. is discussed. Biomass char is compared with other known catalysts used for tar conversion. Model tar compds., phenol and naphthalene, were used to test char and other catalysts. Tests were carried out in a fixed bed tubular reactor at a temp. range of 700-900° under atm. pressure and a gas residence time in the empty catalyst bed of 0.3 s. Biomass chars are compared with calcined dolomite, olivine, used fluid catalytic cracking (FCC) catalyst, biomass ash and com. nickel catalyst. The conversion of naphthalene and phenol over these catalysts was carried out in the atm. of CO2 and steam. At 900°, the conversion of phenol was dominated by thermal cracking whereas naphthalene conversion was dominated by catalytic conversion. Biomass chars gave the highest naphthalene conversion among the low cost catalysts used for tar removal. Further, biomass char is produced continuously during the gasification process, while the other catalysts undergo deactivation. A simple first order kinetic model is used to describe the naphthalene conversion with biomass char.
  187. 187
    Pereira Lopes, R.; Astruc, D. Astruc Didier. Biochar as a Support for Nanocatalysts and Other Reagents: Recent Advances and Applications. Coord. Chem. Rev. 2021, 426, 213585  DOI: 10.1016/j.ccr.2020.213585
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    Biochar as a support for nanocatalysts and other reagents: Recent advances and applications
    Pereira Lopes, Renata; Astruc, Didier
    Coordination Chemistry Reviews (2021), 426 (), 213585CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. The transformation and use of the biomass are of fundamental energetic and ecol. interest. The general objective of this review is to provide an overview of biochar (a major biomass product) as a support for nanocatalysts and other reagents, its mode of coordination and activation with nanoparticles and applications. This includes the physico-chem. characteristics of biochar, the advances in its prodn. processes, and its activation and functionalization in order to improve its phys. and chem. characteristics and applications as support in catalysis and environmental decontamination. Biochar is a byproduct produced by carbonization of biomass. In this process, the products of interest are syngas and bio-oil, due to their high calorific value and their diverse applications. However, biochar has interesting characteristics. It can be used as support, allowing to disperse nanoparticles of the catalysts, such as those of the transition metals: Fe, Ag, Ni, Pd, etc. bimetallic compns. such as Ru/Re, Fe/Ni, etc. and metal oxides such as Fe3O4, CO3O4, CuO, TiO2, etc. increasing the reactivity of the system, minimizing the leaching of the catalysts and allowing their re-use. These materials can be employed in the degrdn. of contaminants in aq. systems, soil and sediments, tar reforming reactions and synthesis of fine chems. This review will serve as the basis for new research aiming to add value to this important resource.
  188. 188
    Bhandari, P. N.; Kumar, A.; Bellmer, D. D.; Huhnke, R. L. Synthesis and Evaluation of Biochar-Derived Catalysts for Removal of Toluene (Model Tar) from Biomass-Generated Producer Gas. Renew Energy 2014, 66, 346– 353,  DOI: 10.1016/j.renene.2013.12.017
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    188
    Synthesis and evaluation of biochar-derived catalysts for removal of toluene (model tar) from biomass-generated producer gas
    Bhandari, Pushpak N.; Kumar, Ajay; Bellmer, Danielle D.; Huhnke, Raymond L.
    Renewable Energy (2014), 66 (), 346-353CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
    Challenges in removal of contaminants, esp. tars, from biomass-generated producer gas continue to hinder commercialization efforts in biomass gasification. The objectives of this study were to synthesize catalysts made from biochar, a byproduct of biomass gasification and to evaluate their performance for tar removal. The three catalysts selected for this study were original biochar, activated carbon, and acidic surface activated carbon derived from biochar. Expts. were carried out in a fixed bed tubular catalytic reactor at temps. of 700 and 800°C using toluene as a model tar compd. to measure effectiveness of the catalysts to remove tar. Steam was supplied to promote reforming reactions of tar. Results showed that all three catalysts were effective in toluene removal with removal efficiency of 69-92%. Activated carbon catalysts resulted in higher toluene removal because of their higher surface area (∼900 m2/g compared to less than 10 m2/g of biochar), larger pore diam. (19 A° compared to 15.5 A° of biochar) and larger pore vol. (0.44 cc/g compared to 0.085 cc/g of biochar). An increase in reactor temp. from 700 to 800 °C resulted in 3-10% increase in toluene removal efficiency. Activated carbons had higher toluene removal efficiency compared to biochar catalysts.
  189. 189
    Feng, D.; Zhao, Y.; Zhang, Y.; Sun, S. Effects of H2O and CO2 on the Homogeneous Conversion and Heterogeneous Reforming of Biomass Tar over Biochar. Int. J. Hydrogen Energy 2017, 42, 13070– 13084,  DOI: 10.1016/j.ijhydene.2017.04.018
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    189
    Effects of H2O and CO2 on the homogeneous conversion and heterogeneous reforming of biomass tar over biochar
    Feng, Dongdong; Zhao, Yijun; Zhang, Yu; Sun, Shaozeng
    International Journal of Hydrogen Energy (2017), 42 (18), 13070-13084CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    The effects of H2O and CO2 reforming agents on the homogeneous conversion and heterogeneous reforming of biomass tar were studied in the presence of a biochar catalyst to better understand the transformation pathway between tar and biochar. Catalysis was performed in a two-stage fluidized bed/fixed bed reactor while Raman anal. and Gas Chromatograph-Mass Spectrometry were used to investigate biochar and tar characteristics. The results show temps. of 700-900 °C are required for the homogeneous transformation of tar in the presence of H2O/CO2, which esp. affect polycyclic arom. hydrocarbons. The tar homogeneous reforming effect of 15 vol.% H2O is significantly higher than that of 29 vol.% CO2. During heterogeneous reforming of tar over biochar at 800 °C, the tar yield decreases in varying degrees with the H2O and CO2 concn. increasing. H2O and CO2 not only directly affect the tar transformation on biochar, but also indirectly influence the reforming of tar through changing the structure of biochar catalyst. The formation of addnl. oxygen-contg. functional groups and transformation of small arom. rings to larger arom. rings in the biochar structure are promoted with the concn. of H2O and CO2 increasing. Under a H2O/CO2 atmosphere, a higher degree of arom. ring heterogeneous reforming occurs over biochar than for non-arom. tar components. Heterogeneous reforming reactivity of tar is promoted by the biomass tar structure (e.g the substituents, large arom. ring size and five-carbon ring structures) over biochar under H2O/CO2 atmospheres. Further increasing H2O and CO2 concn. enhances this effect.
  190. 190
    Lang, L.; Yang, W.; Xie, J.; Yin, X.; Wu, C.; Lin, J. Y. S. Oxidative Filtration for Flyash & Tar Removal from 1.0 MWth Fixed-Bed Biomass Air Gasification. Biomass Bioenergy 2019, 122, 145– 155,  DOI: 10.1016/j.biombioe.2019.01.018
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    190
    Oxidative filtration for flyash & tar removal from 1.0 MWth fixed-bed biomass air gasification
    Lang, Lin; Yang, Wenshen; Xie, Jianjun; Yin, Xiuli; Wu, Chuangzhi; Lin, Jerry Y. S.
    Biomass and Bioenergy (2019), 122 (), 145-155CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    Exptl. campaigns were performed with the aim to study the hot gas filtration process during the pilot-scale biomass gasification at GIEC. This paper gives an overview of the continuous and steady filtration tests performed with stable pressure drop (ΔP) for over 200 h in 400-600°C, using wood chip and charcoal as the feedstock. The ceramic candles show good long-term filtration performance with a permanent cake layer serving as an extra filtration medium. Tar content is found to be the controlling resistance for the biomass gasification-filtration process. A novel oxidative filtration is reported to lead to a simultaneous removal of carbonaceous flyash particles (CFPs) and tars as well as a dramatic ΔP decrease with no obvious degrdn. in the heating value of the producer gas, in which a tiny amt. of addnl. air (≤5.5 vol%) is introduced into the producer gas. Under the optimum condition, the CFP removal efficiency is always >99.0% and the tar removal efficiency of 92.2% could be achieved, with ΔP kept within a range of 1000-2000 N m-2 at the gas superficial velocity of 1.5-2.0 cm s-1 and 0.5-1.5% oxygen content of the producer gas (O2%). It is found that filter candles could act as a reactor without any catalyst to partially oxidize tars and CFPs with a little heat generation when hot gas filtration is operated in the presence of low oxygen concn. in 400-600°C. The efficient CFP removal and tar redn. during the high-temp. oxidative filtration is beneficial for downstream units and their operability.
  191. 191
    Awais, M.; Li, W.; Arshad, A.; Haydar, Z.; Yaqoob, N.; Hussain, S. Evaluating Removal of Tar Contents in Syngas Produced from Downdraft Biomass Gasification System. Int. J. Green Energy 2018, 15 (12), 724– 731,  DOI: 10.1080/15435075.2018.1525557
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    191
    Evaluating removal of tar contents in syngas produced from downdraft biomass gasification system
    Awais, Muhammad; Li, Wei; Arshad, Arfan; Haydar, Zeeshan; Yaqoob, Nauman; Hussain, Sajjad
    International Journal of Green Energy (2018), 15 (12), 724-731CODEN: IJGECR; ISSN:1543-5075. (Taylor & Francis, Inc.)
    Biomass gasification is a process of converting solid biomass ingredients into a combustible gas which can be used in electricity generation. Regardless of their applications in many fields, biomass gasification technol. is still facing many cleaning issues of syngas. Tar prodn. in biomass gasification process is one of the biggest challenges for this technol. The aimed of this study is to evaluate the tar contents in syngas produced from wood chips and corn cobs as a biomass fuel and tar removal efficiency of different cleaning units integrated with gasifier. Performance of different cleaning units, i.e., cyclone separator, wet scrubber, biomass filter, and auxiliary filter was tested with two biomass fuels. Results of this study reported that wood chips produced less tar 6,600 mg/Nm3 as compared to corn cobs 7,500 mg/Nm3 in biomass reactor stage before cleaning. After passing through the whole cleaning system, the tar concn. in case wood chip reduced from 6,600 to 112 mg/Nm3, while in case of corn cob from 7,500 to 220 mg/Nm3. Overall tar removal efficiencies of cyclone separator, wet scrubber, biomass filter and auxiliary filter was noted as 72%, 63%, 74%, 35%, resp.
  192. 192
    Rapagnà, S.; Gallucci, K.; Foscolo, P. U. Olivine, Dolomite and Ceramic Filters in One Vessel to Produce Clean Gas from Biomass. Waste Manag 2018, 71, 792– 800,  DOI: 10.1016/j.wasman.2017.07.038
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    Olivine, dolomite and ceramic filters in one vessel to produce clean gas from biomass
    Rapagna, Sergio; Gallucci, Katia; Foscolo, Pier Ugo
    Waste Management (Oxford, United Kingdom) (2018), 71 (), 792-800CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
    Heavy org. compds. produced during almond shells gasification in a steam and/or air atm., usually called tar, are drastically reduced in the product gas by using simultaneously in one vessel a ceramic filter placed in the freeboard and a mixt. of olivine and dolomite particles in the fluidized bed of the gasifier. The content of tar in the product gas during a ref. gasification test with air, in presence of fresh olivine particles only, was 8600 mg/Nm3 of dry gas. By gasifying biomass with steam at the same temp. level of 820 °C in a bed of olivine and dolomite (20% by wt.), and in the presence of a catalytic ceramic filter inserted in the freeboard of the fluidized bed gasifier, the level of tar was brought down to 57 mg/Nm3 of dry product gas, with a decrease of more than two orders of magnitude.
  193. 193
    Surjosatyo, A.; Anggriawan, M. B.; Hermawan, A. A.; Dafiqurrohman, H. Comparison between Secondary Thermal Cracking Methods and Venturi Scrubber Filtering in Order to Reduce Tar in Biomass Gasification. Energy Procedia 2019, 158, 749– 754,  DOI: 10.1016/j.egypro.2019.01.200
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    193
    Comparison between secondary thermal cracking methods and venturi scrubber filtering in order to reduce tar in biomass gasification
    Surjosatyo, Adi; Anggriawan, Muhammad Barryl; Hermawan, Andika Akbar; Dafiqurrohman, Hafif
    Energy Procedia (2019), 158 (), 749-754CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
    Biomass Gasification is a potential technol. to overcome energy needs in the present time. However, one of the major challenges in using syngas as an elec. power is a tar problem in producer gas that can cause fouling in pipes. The purpose of this research, is to show the comparison between secondary thermal cracking and venturi scrubber in order to reduce tar concn. The performance of this method was tested in 10 kW rice husk biomass gasifier. The max. tar redn. efficiencies of venturi scrubber and secondary thermal cracking were found 89% and 74% resp. This is because as the ER increased, the temp. in the pyrolysis zone was also increased, hence, enhancing tar redn. with thermal cracking.
  194. 194
    Zhu, F.; Li, X.; Zhang, H.; Wu, A.; Yan, J.; Ni, M.; Zhang, H.; Buekens, A. Destruction of Toluene by Rotating Gliding Arc Discharge. Fuel 2016, 176, 78– 85,  DOI: 10.1016/j.fuel.2016.02.065
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    Destruction of toluene by rotating gliding arc discharge
    Zhu, Fengsen; Li, Xiaodong; Zhang, Hao; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Zhang, Hanwei; Buekens, Alfons
    Fuel (2016), 176 (), 78-85CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Non-thermal plasma is considered as an alternative treatment of tar present in the effluent from gasification processes. In this study, a novel rotating gliding arc (RGA) discharge reactor was developed for tar destruction. Toluene in nitrogen flow was used as a tar surrogate. The phys. features of RGA discharge and its application to toluene destruction are investigated at different input concns. and total gas flow rates. As a result, the highest destruction efficiency could exceed 95%, with a toluene concn. of 10 g/N m3 and a total flow rate of 0.24 N m3/h. The two major gaseous products are H2 and C2H2, with max. selectivity of 39.35% and 27.0%, resp. A higher input concn. slightly reduces this destruction efficiency but the energy efficiency further expanded, with a highest value of 16.61 g of toluene eliminated/kW h. In addn., the liq. and solid byproducts are collected downstream of the RGA reactor and detd. qual. and semi-quant. The amt. and structure of these byproducts is instructive for reaching a better comprehension of the chem. consequences of plasma treatment to the model compd. and to the carrier gas nitrogen.
  195. 195
    Wang, Y.; Yang, H.; Tu, X. Plasma Reforming of Naphthalene as a Tar Model Compound of Biomass Gasification. Energy Convers. Manag. 2019, 187, 593– 604,  DOI: 10.1016/j.enconman.2019.02.075
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    Plasma reforming of naphthalene as a tar model compound of biomass gasification
    Wang, Yaoling; Yang, Haiping; Tu, Xin
    Energy Conversion and Management (2019), 187 (), 593-604CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    The contamination of producer gas with tars from biomass gasification remains a significant challenge in the bioenergy industry and a crit. barrier, limiting the com. applications of biomass gasification. Non-thermal and non-equil. plasma offers an unconventional and emerging technol. for the effective redn. of problematic tars from gasification. In this study, we investigated plasma reforming of naphthalene as a two-ring tar model compd. using a gliding arc discharge (GAD) reactor with/without steam. The influence on the plasma conversion of naphthalene based on the inlet naphthalene concn., discharge power and steam-to-carbon ratio was examd. to understand the effects of these operating parameters on the destruction of tar, gas selectivity/yield and energy efficiency. Adding H2O in the plasma process generates oxidative OH radicals, creating addnl. reaction routes for the step-wised oxidn. of naphthalene and its fragments towards the CO, CO2 and water. The optimum ratio (2.0) of steam-to-carbon was identified to achieve the highest naphthalene conversion (84.8%), C2H2 yield (33.0%), total gas yield (72.2%) and energy efficiency (5.7 g/kWh). The effect of the amt. of steam on the plasma redn. of tars was dependent on the balance between two opposite effects due to the presence of steam: pos. effect of OH radicals and the neg. effect of electron attachment on water mols. Introducing an appropriate amt. of steam to the plasma redn. of naphthalene also substantially minimized the formation of byproducts and enhanced the carbon balance. Plausible reaction mechanisms for the plasma decompn. of naphthalene were proposed through a comprehensive anal. of gaseous and condensable products combined with plasma spectroscopic diagnostics.
  196. 196
    Zhang, H.; Zhu, F.; Li, X.; Xu, R.; Li, L.; Yan, J.; Tu, X. Steam Reforming of Toluene and Naphthalene as Tar Surrogate in a Gliding Arc Discharge Reactor. J. Hazard Mater. 2019, 369, 244– 253,  DOI: 10.1016/j.jhazmat.2019.01.085
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    Steam reforming of toluene and naphthalene as tar surrogate in a gliding arc discharge reactor
    Zhang, Hao; Zhu, Fengsen; Li, Xiaodong; Xu, Ruiyang; Li, Li; Yan, Jianhua; Tu, Xin
    Journal of Hazardous Materials (2019), 369 (), 244-253CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
    Steam reforming of mixed toluene and naphthalene as tar surrogate was studied in an a.c. gliding arc discharge plasma, with particular emphasis on better understanding the effect of steam and CO2 on the reaction performance. H2, C2H2 and CO are the major gas products in the plasma steam reforming of tar for energy recovery. The addn. of a small amt. of steam remarkably enhances the conversions of both toluene and naphthalene, from 60.4% to 76.1% and 57.6% to 67.4%, resp., as ·OH radicals formed by H2O dissocn. create more reaction pathways for the conversion of toluene, naphthalene and their fragments. However, introducing CO2 to this process has a neg. effect on the tar reforming. Optical emission spectroscopic diagnostics showed the formation of a variety of reactive species in the plasma process. Trace amts. of monocyclic and bicyclic arom. condensable byproducts are also detected. The destruction of toluene and naphthalene can be initiated through the collisions of tar surrogates with energetic electrons, N2 excited species, ·OH and O radicals etc. Further optimization of the plasma tar destruction is still needed because the complexity of the tar component in a practical gasifier could decrease the tar conversions.
  197. 197
    Xu, B.; Xie, J.; Zhan, H.; Yin, X.; Wu, C.; Liu, H. Removal of Toluene as a Biomass Tar Surrogate in a Catalytic Nonthermal Plasma Process. Energy Fuels 2018, 32 (10), 10709– 10719,  DOI: 10.1021/acs.energyfuels.8b02444
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    Removal of Toluene as a Biomass Tar Surrogate in a Catalytic Nonthermal Plasma Process
    Xu, Bin; Xie, Jianjun; Zhan, Hao; Yin, Xiuli; Wu, Chuangzhi; Liu, Hao
    Energy & Fuels (2018), 32 (10), 10709-10719CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    In this study, a packed-bed dielec. barrier discharge (DBD) reactor was developed to investigate the removal of biomass tar in a fuel gas atm. Toluene was used as the tar surrogate, and the catalyst used was a Nickel-based catalyst (Ni/γ-Al2O3) because of its high activity and low cost. In addn., another two kinds of packing materials (glass pellets and γ-Al2O3 pellets) were employed to make a comparison with the Ni/γ-Al2O3 catalyst. The research has focused on the removal efficiency of toluene and the effects of carrier gas, reaction temp., Ni loading, and concn. of toluene. The results indicated that two supplementary packing materials could not realize an effective removal of toluene. On the contrary, Ni/γ-Al2O3 combined with plasma showed a significant synergetic effect and hence a great toluene removal potential. On one hand, the removal efficiency initially decreased within the temp. range of 200-300 °C and then significantly increased within the temp. of 300-400 °C during plasma-catalytic process. At the optimal temp. of 400 °C, the toluene removal efficiency could reach the max. values of 80.2%, 91.7%, and 100.0% when the Ni loading was 3, 5, and 10 wt %, resp. On the other hand, an increase in the inlet toluene concn. slightly reduced removal efficiency but increased the energy efficiency, reaching the highest value of 16.8 g/kWh. The introduction of plasma enhanced the methanation reaction of the fuel gas occurring in the catalytic process, which was favorable at high temps. Based on these findings, the mechanisms and pathways of toluene destruction in the plasma-catalytic process were proposed and elucidated.
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    J, A.; Rao, L. Influence of Transitional and Turbulent Flow on Electrical, Optical, Morphological and Chemical Characteristics of a Nitrogen Rotating Gliding Arc. J. Phys. D Appl. Phys. 2022, 55 (24), 245202,  DOI: 10.1088/1361-6463/ac5bcc
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    Kim, S. W.; Park, H. S.; Kim, H. J. 100 KW Steam Plasma Process for Treatment of PCBs (Polychlorinated Biphenyls) Waste. Vacuum 2003, 70 (1), 59– 66,  DOI: 10.1016/S0042-207X(02)00761-3
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    100 kW steam plasma process for treatment of PCBs (polychlorinated biphenyls) waste
    Kim, Seok-Wan; Park, Hyun-Seo; Kim, Hyung-Jin
    Vacuum (2003), 70 (1), 59-66CODEN: VACUAV; ISSN:0042-207X. (Elsevier Science Ltd.)
    Non-transferred DC steam (H2O) plasma working with 100 kW was used to treat hazardous wastes to minimize the formation of toxic byproducts such as dioxins and furans usually assocd. with conventional incineration processes. In the steam plasma treatment of wastes contg. a mixt. of polychlorinated biphenyl (PCB), the content of combustible gas that can be used as gaseous fuel was about 30% based on wet gas. For the mixt. of 27% PCB and 73% CCl4, total toxic equiv. concn. of PCDD/PCDF was about 0.056 ng TEQ/N m3. It is concluded that the steam plasma torch process was more effective for waste-to-energy and hazardous waste treatment than the air plasma torch process injected steam and the conventional incineration process.
  200. 200
    Vecten, S.; Wilkinson, M.; Bimbo, N.; Dawson, R.; Herbert, B. M. J. Hydrogen-Rich Syngas Production from Biomass in a Steam Microwave-Induced Plasma Gasification Reactor. Bioresour. Technol. 2021, 337, 125324,  DOI: 10.1016/j.biortech.2021.125324
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    Hydrogen-rich syngas production from biomass in a steam microwave-induced plasma gasification reactor
    Vecten, Simon; Wilkinson, Michael; Bimbo, Nuno; Dawson, Richard; Herbert, Ben M. J.
    Bioresource Technology (2021), 337 (), 125324CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
    Substitution of fossil fuels by sustainable practices must be rapidly implemented to mitigate the impacts of climate change. The conversion of biomass into combustible gas is investigated in a microwave-induced plasma reactor using pure steam as the plasma working gas for the first time. The optimum results are achieved at the highest forward microwave power of 6 kW with biomass carbon conversion efficiency over 98% and complete biomass energy recovery in syngas. Unreacted steam is simply condensed out, leading to the prodn. of a syngas with low inert diln. and high calorific value in the range 10.5-12 MJ/Nm3. The syngas produced is rich in hydrogen, exceeding 60% by vol. The proposed process could aid in the transition to a carbon neutral economy as it has the potential to efficiently convert biomass to syngas that can be used for the sustainable generation of fuels, chems. and energy.
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    Mallick, R.; Vairakannu, P. Experimental Investigation of Acrylonitrile Butadiene Styrene Plastics Plasma Gasification. J. Environ. Manage 2023, 345, 118655,  DOI: 10.1016/j.jenvman.2023.118655
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    Experimental investigation of acrylonitrile butadiene styrene plastics plasma gasification
    Mallick, Roni; Vairakannu, Prabu
    Journal of Environmental Management (2023), 345 (), 118655CODEN: JEVMAW; ISSN:0301-4797. (Elsevier Ltd.)
    E-waste comprising plastics causes serious ecol. problems due to low degradability, but it is capable of producing a high amt. of energy by thermochem. conversion. Therefore, the current study focuses on generating clean syngas through plasma gasification of acrylonitrile butadiene styrene (ABS) based computer keyboard plastic waste (CKPW) using CO2 as a gasifying agent. The effect of feed rate, gas flow rate and plasma power on the syngas compn. was studied. In addn., a comprehensive investigation of energy, exergy, economic and environmental analyses along with characterization of the obtained products was conducted to evaluate the performance of the system. Based on the exptl. results, the optimum process parameters for producing syngas possessing a higher calorific value (15.80 MJ/m3) with a higher percentage of H2 (30.16 vol%) and CO (46.09 vol%) were estd. The optimum feed flow rates of solid fuel and CO2 gas and torch power were estd. as 40 g/10 min, 0.5 lpm and 1.12 kW, resp. At these conditions, the system could achieve a max. energy and exergy efficiency of 46.06% and 44.34%, resp., while the levelized cost of syngas (LCOSover) was estd. as 25.45 INR/kWh, including the social cost. Likewise, the lower values of the estd. global warming potential (370.19 gCO2eq/h) illustrate the better sustainability of the process. The obtained oil with the estd. LHV of 39.13 MJ/kg could be an alternative fuel for diesel and the residue contg. a higher proportion of TiO2 has medical applications upon further enrichment. The reaction mechanism of ABS conversion to syngas under plasma gasification conditions is proposed.
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    Chu, C.; Wang, P.; Boré, A.; Ma, W.; Chen, G.; Wang, P. Thermal Plasma Co-Gasification of Polyvinylchloride and Biomass Mixtures under Steam Atmospheres: Gasification Characteristics and Chlorine Release Behavior. Energy 2023, 262, 125385,  DOI: 10.1016/j.energy.2022.125385
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    Thermal plasma co-gasification of polyvinylchloride and biomass mixtures under steam atmospheres: Gasification characteristics and chlorine release behavior
    Chu, Chu; Wang, Ping; Bore, Abdoulaye; Ma, Wenchao; Chen, Guanyi; Wang, Pan
    Energy (Oxford, United Kingdom) (2023), 262 (Part_B), 125385CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    This study systematically explores the syngas characteristics and chlorine release behavior during plasma co-gasification of polyvinylchloride (PVC) and biomass through exptl. and thermodn. methods. The results indicate that carbon conversion rate and chlorine release ratio are pos. assocd. with power and steam/carbon ratio. Plasma co-gasification of PVC and biomass yields 4.96-16.95% higher H2 proportion and 1.84-41.41% lower chlorine release ratio than the weighted sum values of mono-gasification. The thermodn. calcn. also verifies the lower percentage (16.33-97.47 wt%) of gaseous chlorides (HCl(g), KCl(g), etc.) from plasma co-gasification than mono-gasification. The low level of av. relative error (0.059) of thermodn. simulation demonstrates its potential for quant. anal. of chlorine release behavior. Redundancy anal. reveals that temp. is the most significant factor of carbon conversion rate, H2 proportion, and chlorine release ratio. This study could provide theor. guidance for operational optimization and pollution control of plasma gasification.
  203. 203
    Cvetinović, D.; Milutinović, N.; Erić, A.; Škobalj, P.; Andjelković, J.; Bakić, V. Optimisation of the Operating Parameters of a Thermal Plasma System for the Conversion of Waste Containing Polychlorinated Biphenyls by Thermodynamic Modelling. Energy Convers. Manag. 2023, 292, 117358,  DOI: 10.1016/j.enconman.2023.117358
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    203
    Optimisation of the operating parameters of a thermal plasma system for the conversion of waste containing polychlorinated biphenyls by thermodynamic modelling
    Cvetinovic, Dejan; Milutinovic, Nada; Eric, Aleksandar; Skobalj, Predrag; Andjelkovic, Jovana; Bakic, Vukman
    Energy Conversion and Management (2023), 292 (), 117358CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    This paper proposes a math. modeling approach to det. the thermodn. equil. of chem. systems in order to optimize the operating parameters of the plasma chem. processes in a low-temp. thermal plasma pilot reactor with a d.c. elec. arc for the treatment of hazardous waste contg. polychlorinated biphenyls. The model is primarily based on the principles of mass action and min. Gibbs free energy. The obtained results can serve as a basis for multi-criteria optimization based on ecol. aspects, redn. of energy consumption and the possibility of using the produced synthetic gas for energy recovery in the process. The anal. carried out clearly showed the advantages of using water vapor as a plasma working medium and the appropriate mixing of the org. waste contg. polychlorinated biphenyls with used engine oil for enriched syngas prodn. The presented anal. dets. the optimal reactor temp. for an ecol. efficient treatment and shows possibilities for energy recovery in the process. The proposed model can also be used for other chem. reactors and for the treatment of other chem. substances.
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    Frolov, S. M. Organic Waste Gasification: A Selective Review. Fuels 2021, 2 (4), 556– 651,  DOI: 10.3390/fuels2040033
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    Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.; Chumak, A.; Beeckman, E.; Verstraeten, J. Pyrolysis of Waste Using a Hybrid Argon-Water Stabilized Torch. Vacuum 2006, 80 (11–12), 1132– 1137,  DOI: 10.1016/j.vacuum.2006.01.046
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    Pyrolysis of waste using a hybrid argon-water stabilized torch
    Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.; Chumak, A.; Beeckman, E.; Verstraeten, J.
    Vacuum (2006), 80 (11-12), 1132-1137CODEN: VACUAV; ISSN:0042-207X. (Elsevier B.V.)
    An exptl. plasmachem. reactor equipped with the novel IPP-ASCR hybrid gas-water stabilized DC torch (160 kW) has recently been started at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chem. valorization and to a redn. of the emission of greenhouse gases. Since the process energy is provided by direct heat transfer from plasma, gases of widely varying chem. compn. may be used. The use of elec. energy also reduces the gas flows and requirements for exhaust-gas treatment, and offers control over the chem. Pyrolysis of biomass was exptl. studied using wood chips as a model substance. Syngas with a high content of hydrogen and CO was produced. The influence of adding CO2 for increase of oxygen content in the reactor was investigated.
  206. 206
    Lin, B. J.; Chen, W. H. Sugarcane Bagasse Pyrolysis in a Carbon Dioxide Atmosphere with Conventional and Microwave-Assisted Heating. Front Energy Res. 2015, 3 (FEB), 4,  DOI: 10.3389/fenrg.2015.00004
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    Hlina, M.; Hrabovsky, M.; Kavka, T.; Konrad, M. Production of High Quality Syngas from Argon/Water Plasma Gasification of Biomass and Waste. Waste Management 2014, 34 (1), 63– 66,  DOI: 10.1016/j.wasman.2013.09.018
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    Production of high quality syngas from argon/water plasma gasification of biomass and waste
    Hlina, M.; Hrabovsky, M.; Kavka, T.; Konrad, M.
    Waste Management (Oxford, United Kingdom) (2014), 34 (1), 63-66CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
    Extremely hot thermal plasma was used for the gasification of biomass (spruce sawdust, wood pellets) and waste (waste plastics, pyrolysis oil). The plasma was produced by a plasma torch with DC elec. arc using unique hybrid stabilization. The torch input power of 100-110 kW and the mass flow rate of the gasified materials of tens kg/h was set up during expts. Produced synthetic gas featured very high content of hydrogen and carbon monoxide (together approx. 90%) that is in a good agreement with theory. High quality of the produced gas is given by extreme parameters of used plasma - compn., very high temp. and low mass flow rate.
  208. 208
    Shie, J. L.; Tsou, F. J.; Lin, K. L.; Chang, C. Y. Bioenergy and Products from Thermal Pyrolysis of Rice Straw Using Plasma Torch. Bioresour. Technol. 2010, 101 (2), 761– 768,  DOI: 10.1016/j.biortech.2009.08.072
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    Bioenergy and products from thermal pyrolysis of rice straw using plasma torch
    Shie Je-Lueng; Tsou Feng-Ju; Lin Kae-Long; Chang Ching-Yuan
    Bioresource technology (2010), 101 (2), 761-8 ISSN:.
    The aim of this work was to study the feasibility and operation performance of plasma torch pyrolysis of biomass wastes, taking rice straw as the target material. This novel method has several advantages including high heating rate, short heating time, no viscous tar and low residual char (7.45-13.78 wt.%) or lava. The productions of CO and H(2) are the major components (91.85-94.14 vol.%) in the gas products with relatively high reaction rates. The maximum concentrations of gaseous products occurring times are all below 1 min. Almost 90% of gaseous products were appeared in 4 min reaction time. The yield of H(2) increases with the increase of input power or temperature. With the increase of moisture (5-55 wt.%), the mass yields of H(2) and CO(2) also increase from the H(2)O decomposition. However, due to the CO(2) production, the accumulated volume fraction of syngas decreases with the increase of moisture.
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    Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T. Pyrolysis/Gasification of Biomass for Synthetic Fuel Production Using a Hybrid Gas-Water Stabilized Plasma Torch. Vacuum 2008, 83 (1), 209– 212,  DOI: 10.1016/j.vacuum.2008.03.084
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    209
    Pyrolysis/gasification of biomass for synthetic fuel production using a hybrid gas-water stabilized plasma torch
    Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.
    Vacuum (2008), 83 (1), 209-212CODEN: VACUAV; ISSN:0042-207X. (Elsevier B.V.)
    An exptl. plasma-chem. reactor equipped with a novel hybrid gas-water stabilized torch is available at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chem. valorization and to a redn. of the emission of greenhouse gases. Gasification/pyrolysis of biomass was exptl. studied using crushed wood as a model substance. The exptl. results demonstrate homogeneous heating of the reactor vol. and proper mixing of plasma with treated material in spite of the low plasma mass flow rate and constricted plasma jet. The conditions within the reactor ensure complete destruction of the tested substance. The economical viability, environmental performance and safety of biofuels/hydrogen produced from syngas resulting from the plasma-thermochem. gasification of a very broad range of second generation biomass feedstock will be investigated. The performance of several types of plasma torches and of possible combinations of torches will be compared. The final biofuels will be tested in the existing Internal Combustion Engine (ICE) test stands.
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    Murphy, A. B.; Farmer, A. J. D.; Horrigan, E. C.; Mcallister, T. Plasma Destruction of Ozone Depleting Substances. Plasma Chem. Prosma Process. 2002, 22 (3), 371,  DOI: 10.1023/A:1015365032020
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    Qi, H.; Xu, H.; Zhang, J.; Xu, Z.; Zhong, L.; Cui, P.; Zhu, Z.; Wang, Y. Thermodynamic and Techno-Economic Analyses of Hydrogen Production from Different Algae Biomass by Plasma Gasification. Int. J. Hydrogen Energy 2023, 48 (92), 35895– 35906,  DOI: 10.1016/j.ijhydene.2023.06.038
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    211
    Thermodynamic and techno-economic analyses of hydrogen production from different algae biomass by plasma gasification
    Qi, Huaqing; Xu, Hongwei; Zhang, Jifu; Xu, Zaifeng; Zhong, Limei; Cui, Peizhe; Zhu, Zhaoyou; Wang, Yinglong
    International Journal of Hydrogen Energy (2023), 48 (92), 35895-35906CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    In this study, hydrogen prodn. processes by plasma gasification of three different algae were proposed. The processes were comprehensively analyzed and evaluated in terms of thermodn. efficiency and economic benefits. The results showed that the hydrogen prodn. processes of Enteromorpha by plasma gasification had the best performance and the exergy efficiency of the plasma gasification was as high as 74.46%. The total efficiency of the hydrogen prodn. process of Enteromorpha by plasma gasification was 33.92%, which was 3.87% and 3.63% higher than that of the Cyanobacteria and Sargassum process, resp. The high exergy loss of the acid gas removal and plasma gasification unit accounted for 80.14%-83.53% of the total exergy loss. In addn., the Enteromorpha process also had better economic benefits compared to the other two processes, which was greatly affected by feedstock and electricity prices.
  212. 212
    Sikarwar, V. S.; Peela, N. R.; Vuppaladadiyam, A. K.; Ferreira, N. L.; Mašláni, A.; Tomar, R.; Pohořelý, M.; Meers, E.; Jeremiáš, M. Thermal Plasma Gasification of Organic Waste Stream Coupled with CO2-Sorption Enhanced Reforming Employing Different Sorbents for Enhanced Hydrogen Production. RSC Adv. 2022, 12 (10), 6122– 6132,  DOI: 10.1039/D1RA07719H
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    212
    Thermal plasma gasification of organic waste stream coupled with -sorption enhanced reforming employing different sorbents for enhanced hydrogen production
    Sikarwar, Vineet Singh; Peela, Nageswara Rao; Vuppaladadiyam, Arun Krishna; Ferreira, Newton Libanio; Maslani, Alan; Tomar, Ritik; Pohorely, Michael; Meers, Erik; Jeremias, Michal
    RSC Advances (2022), 12 (10), 6122-6132CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    In the past few years, rising concerns vis-a´-vis global climate change and clean energy demand have brought worldwide attention to developing the 'biomass/org. waste-to-energy' concept as a zero-emission, environment-friendly and sustainable pathway to simultaneously quench the global energy thirst and process diverse biomass/org. waste streams. Bioenergy with carbon capture and storage (BECCS) can be an influential technol. route to curb climate change to a significant extent by preventing CO2 discharge. One of the pathways to realize BECCS is via in situ CO2-sorption coupled with a thermal plasma gasification process. In this study, an equil. model is developed using RDF as a model compd. for plasma assisted CO2-sorption enhanced gasification to evaluate the viability of the proposed process in producing H2 rich syngas. Three different classes of sorbents are investigated namely, a high temp. sorbent (CaO), an intermediate temp. sorbent (Li4SiO4) and a low temp. sorbent (MgO). The distribution of gas species, H2 yield, dry gas yield and LHV are deduced with the varying gasification temp., reforming temp., steam-to-feedstock ratio and sorbent-to-feedstock for all three sorbents. Moreover, optimal values of different process variables are predicted. Maximum H2 is noted to be produced at 550°C for CaO (79 vol%), 500°C for MgO (29 vol%) and 700°C (55 vol%) for Li4SiO4 whereas the optimal SOR/F ratios are found to be 1.5 for CaO, 1.0 for MgO and 2.5 for Li4SiO4. The results obtained in the study are promising to employ plasma assisted CO2-sorption enhanced gasification as an efficacious pathway to produce clean energy and thus achieve carbon neutrality.
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    Kaushal, R.; Rohit; Dhaka, A. K. A Comprehensive Review of the Application of Plasma Gasification Technology in Circumventing the Medical Waste in a Post-COVID-19 Scenario. Biomass Convers. Biorefin. 2022,  DOI: 10.1007/s13399-022-02434-z
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    Zhang, H.; Zhu, F.; Li, X.; Du, C. Dynamic Behavior of a Rotating Gliding Arc Plasma in Nitrogen: Effects of Gas Flow Rate and Operating Current. Plasma Sci. Technol. 2017, 19 (4), 045401,  DOI: 10.1088/2058-6272/aa57f3
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    Dynamic behavior of a rotating gliding arc plasma in nitrogen: effects of gas flow rate and operating current
    Zhang, Hao; Zhu, Fengsen; Li, Xiaodong; Du, Changming
    Plasma Science & Technology (Bristol, United Kingdom) (2017), 19 (4), 045401/1-045401/6CODEN: PSTHC3; ISSN:1009-0630. (IOP Publishing Ltd.)
    The effects of feed gas flow rate and operating current on the elec. characteristics and dynamic behavior of a rotating gliding arc (RGA) plasma codriven by a magnetic field and tangential flow were investigated. The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge, particularly at flow rate = 21min-1. When the current was lower than 140 mA, sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be obsd. (flow rate = 21min-1). The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions. Increasing the flow rate from 8 to 121min-1 (at the same current) led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage (around 120-200 V). For a given flow rate, the redn. of current resulted in a nearly linear increase of voltage.
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    Diaz, G.; Leal-Quiros, E.; Smith, R. A.; Elliott, J.; Unruh, D. Syngas Generation from Organic Waste with Plasma Steam Reforming. J. Phys.: Conf. Ser. 2014, 511, 012081,  DOI: 10.1088/1742-6596/511/1/012081
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    Syngas generation from organic waste with plasma steam reforming
    Diaz, G.; Leal-Quiros, E.; Smith, R. A.; Elliott, J.; Unruh, D.
    Journal of Physics: Conference Series (2014), 511 (15th International Congress on Plasma Physics & 13th Latin American Workshop on Plasma Physics, 2010), 012081CODEN: JPCSDZ; ISSN:1742-6588. (IOP Publishing Ltd.)
    A plasma steam reforming system to process waste is in the process of being set up at the University of California, Merced. The proposed concept will use two different plasma regimes, i.e. glow discharge and arc torches to process a percentage of the total liq. waste stream generated at the campus together with shredded local org. solid waste. One of the main advantages of the plasma technol. to be utilized is that it uses graphite electrodes that can be fed to the reactor to achieve continuous operation, thus, electrode or nozzle life is not a concern. The waste to energy conversion process consists of two stages, one where a mixt. of steam and hydrogen is generated from the liq. in a glow-discharge cell, and a second stage where the mixt. of exhaust gases coming out of the first device are mixed with solid waste in a reactor operating in steam reforming mode interacting with a plasma torch to generate high-quality syngas. In this paper, the results of a thermodn. model developed for the two stages are shown. The syngas compn. obtained indicates that the fraction of CO2 present decreases with increasing temp. and the molar fractions of hydrogen and carbon monoxide become dominant. The fraction of water vapor present in the product gases coming out of the second stage needs to be condensed before the syngas can be utilized in a prime mover.
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    Yue, W.; Lei, W.; Dong, Y.; Shi, C.; Lu, Q.; Cui, X.; Wang, X.; Chen, Y.; Zhang, J. Toluene Degradation in Air/H2O DBD Plasma: A Reaction Mechanism Investigation Based on Detailed Kinetic Modelling and Emission Spectrum. J. Hazard. Mater. 2023, 448, 130894,  DOI: 10.1016/j.jhazmat.2023.130894
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    Toluene degradation in air/H2O DBD plasma: A reaction mechanism investigation based on detailed kinetic modeling and emission spectrum analysis
    Yue, Wenjing; Lei, Wentao; Dong, Yongheng; Shi, Chengjing; Lu, Qiancheng; Cui, Xin; Wang, Xinyu; Chen, Yumin; Zhang, Junying
    Journal of Hazardous Materials (2023), 448 (), 130894CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
    Non-thermal plasma (NTP) is emerging as an attractive method for decompg. volatile org. compds. (VOCs). In this paper, to study toluene degrdn. mechanism in air/H2O dielec. barrier discharge (DBD) plasma, optical emission spectrometry (OES) was employed to in-situ monitor active species in plasma, with the permanent degrdn. products being detected by online mass spectrometry under various operations. A detailed kinetic model of NTP with incorporation of non-const. electron filed and thermal effects has also been established. A toluene degrdn. efficiency > 82% could be achieved at P = 115 W, Cin, toluene = 1000 ppm. The relative spectrum intensity of excited OH, O, H and N2 (A3Σu+) increased with increase of discharge power and was decreased at higher gas flowrates. Toluene degrdn. was mainly induced by oxidn. of OH and O at afterglow stage, while part of toluene was decompd. by attack of electrons and reactive particles N2 (A3Σu+) in discharge stage. A toluene degrdn. pathway has been proposed as: toluene→benzyl→benzaldehyde→benzene→phenoxy→cyclopentadiene→polycarbenes/alkynol→CO2/H2O. Benzoquinone, benzaldehyde, cyclopentadiene and cyclopentadienyl are supposed to be important intermediates for the ring-opening of toluene. Clarification of toluene degrdn. behaviors at discharge and afterglowing stage could provide new insights for plasma-catalytic process in future.
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    Saleem, F.; Khoja, A. H.; Khan, A.; Rehman, A.; Naqvi, S. R.; Qazi, U. Y.; Zhang, K.; Harvey, A. Effect of Non-Thermal Plasma Dielectric Barrier Discharge Reactor on the Quality of Biomass Gasification Product Gas from the Gasifier. J. Energy Institute 2023, 108, 101228,  DOI: 10.1016/j.joei.2023.101228
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    Effect of non-thermal plasma dielectric barrier discharge reactor on the quality of biomass gasification product gas from the gasifier
    Saleem, Faisal; Khoja, Asif Hussain; Khan, Atif; Rehman, Abdul; Naqvi, Salman Raza; Qazi, Umair Yaqub; Zhang, Kui; Harvey, Adam
    Journal of the Energy Institute (2023), 108 (), 101228CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
    The primary goal of this research is to det. the effect of key processing paramters of dielec. barrier discharge (DBD) reactor on the components concn. of the fuel gas produced during the biomass gasification. By changing key processing parameters such as plasma input power, flow rate, and temp., the performance of the DBD reactor is assessed. When the power is increased from 5 to 40 W, the concns. of CO2 and H2 decrease to 12.9% and 18.5%, resp., while the concn. of CO increases to 17.2%. At 40 W and 65 mL/min, the amt. of tar compd. significantly drops from 33 g/Nm3 to less than 1 g/Nm3. However, as input power increases, the concn. of C1-C5 hydrocarbons also tends to rise. The highest concn. of C1-C5 was around 0.60% at 40 W. As the flow rate increases, the concn. of CO2 increases while the concn. of CO tends to decrease at all measured power levels, the max. concn. of CO2 was at 120 mL/min, whereas the min. concn. of CO is seen under same conditions. With an increase in flow rate, the concn. of CH4 shows a decreasing tendency. It is seen that at 40 W, the concn. of CO and H2 drops as the temp. rises up to 400°C. In contrast, there is a rising trend in the concn. of CO2, CH4, and tar compds. while inreasing temp. Hence, the DBD reactor appears to have a profound influence on a gas component produced during biomass gasification.
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    Dahiru, U. H.; Saleem, F.; Al-sudani, F. T.; Zhang, K.; Harvey, A. P. Decomposition of Benzene Vapour Using Non-Thermal Plasmas: The Effect of Moisture Content on Eliminating Solid Residue. J. Environ. Chem. Eng. 2022, 10, 107767,  DOI: 10.1016/j.jece.2022.107767
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    Decomposition of benzene vapor using non-thermal plasmas: The effect of moisture content on eliminating solid residue
    Dahiru, Usman H.; Saleem, Faisal; Al-sudani, Farah Talib; Zhang, Kui; Harvey, Adam P.
    Journal of Environmental Chemical Engineering (2022), 10 (3), 107767CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
    This study investigated the effect of power, carrier gases and moisture content on the removal of benzene in dry air and humidified air in a DBD plasma reactor. The influence of plasma power, carrier gases and humidity on benzene conversion and product selectivity were explored. The main decompn. products were CO, CO2, lower hydrocarbons (C1-C5) and solid residue in the reactor. This study reveals that benzene removal efficiency and the selectivity to CO2 increased with power in both dry and humidified air. In contrast, the selectivity to lower hydrocarbons decreased. The most important finding of this study was that the formation of solid residue in the plasma reactor can be removed in humidified air. As the amt. of water vapor increased from 0% to 35% at 20°C, the benzene removal efficiency and CO2 selectivity increased; O3 decreased from 7.3 ppm to 0.5 ppm; NOx and solid residue were eliminated. These effects are probably due to OH radicals, and the mechanism for the various effects are proposed. The max. benzene removal efficiency obsd. was 93.7%, and the max. selectivity to CO2 was 82.4% (both at a relative humidity of 35% at 20°C and 10 W). This study demonstrated that plasma-assisted benzene remediation operating in a humid condition can overcome the major drawback of plasma-assisted VOC conversion in the air by eliminating the solid residues in the reactor.
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    Shi, Y.; Ding, L.; Mei, D.; Fang, Z.; Liu, S. Toluene Conversion by Gliding Arc Discharge in the Simulated Gasified Product Gas. In Proceedings of the IEEE 5th International Electrical and Energy Conference (CIEEC), May 27–29, 2022, Nanjing, China; Institute of Electrical and Electronics Engineers Inc., 2022.  DOI: 10.1109/CIEEC54735.2022.9846294 .
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    Saleem, F.; Abbas, A.; Rehman, A.; Khoja, A. H.; Naqvi, S. R.; Arshad, M. Y.; Zhang, K.; Harvey, A. Decomposition of Benzene as a Biomass Gasification Tar in CH4 Carrier Gas Using Non-Thermal Plasma: Parametric and Kinetic Study. J. Energy Institute 2022, 102, 190– 195,  DOI: 10.1016/j.joei.2022.03.009
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    220
    Decomposition of benzene as a biomass gasification tar in CH4 carrier gas using non-thermal plasma and Parametric and kinetic study
    Saleem, Faisal; Abbas, Aumber; Rehman, Abdul; Khoja, Asif Hussain; Naqvi, Salman Raza; Arshad, Muhammad Yousaf; Zhang, Kui; Harvey, Adam
    Journal of the Energy Institute (2022), 102 (), 190-195CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
    In this work, the decompn. of benzene was studied with CH4 using a dielec. barrier discharge (DBD) reactor. The exptl. conditions such as input power, residence time, and concn. were varied to investigate the decompn. of benzene. The decompn. of benzene increased with increasing input power and residence time. The highest decompn. of benzene at 40 W and 2.86 s was 82.9. The major gaseous products were H2 and lower hydrocarbons (LHC) and the yield of these products also increases with input power and residence time. The percentage yield of H2 increases from 0.65 to 5.18by increasing input power from 5 to 40 W at 2.86 s. Similarly, the yield of LHC increases from 0.78 to 8.86for benzene under the same reaction conditions. Hence, input power promoted the decompn. of tar compds. and enhanced the yield of gaseous products. However, at higher concns. of the tar compd., decompn. efficiency and product yield decreased. The modified first-order kinetic model was used for the decompn. of tar model compd. and methane carrier gas.
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    Xu, R.; Zhu, F.; Zhang, H.; Ruya, P. M.; Kong, X.; Li, L.; Li, X. Simultaneous Removal of Toluene, Naphthalene, and Phenol as Tar Surrogates in a Rotating Gliding Arc Discharge Reactor. Energy Fuels 2020, 34 (2), 2045– 2054,  DOI: 10.1021/acs.energyfuels.9b03529
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    Simultaneous Removal of Toluene, Naphthalene, and Phenol as Tar Surrogates in a Rotating Gliding Arc Discharge Reactor
    Xu, Ruiyang; Zhu, Fengsen; Zhang, Hao; Ruya, Petric Marc; Kong, Xiangzhi; Li, Li; Li, Xiaodong
    Energy & Fuels (2020), 34 (2), 2045-2054CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    A rotating gliding arc (RGA) plasma reactor was studied for the decompn. of gasification derived tar. Toluene, naphthalene, and phenol were selected as tar surrogates to be simultaneously decompd. The effects of steam addn., preheating temp., tar, and CO2 concn. were studied and the decompn. pathways of tar model compds. were proposed. The optimum amt. of steam can facilitate tar destruction, enhance H2 yield, and, importantly, suppress the formation of C black. The conversions of toluene, naphthalene, and phenol can be up to 85.8, 76.4, and 93.4%, resp., when 8-12% steam is applied in the system. As expected, the increase of tar or CO2 concn. reduces the conversions of tar. Increasing the preheating temp. to 600° enhances the tar conversions but is then surprisingly followed by a slight drop with the subsequent increase in temp. The conversions of the 3 components decrease in the order of phenol > toluene > naphthalene under the studied conditions. Primary decompn. products of toluene, naphthalene, and phenol are benzyl, naphthyl, and phenoxy compds., which would be further degraded by active species such as N2 (A3.sum.u+), OH radicals, O radicals, etc. into smaller mols. like H2, CO, and CO2.
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    Capitelli, M.; Armenise, I.; Bisceglie, E.; Bruno, D.; Celiberto, R.; Colonna, G.; D’Ammando, G.; De Pascale, O.; Esposito, F.; Gorse, C.; Laporta, V.; Laricchiuta, A. Thermodynamics, Transport and Kinetics of Equilibrium and Non-Equilibrium Plasmas: A State-to-State Approach. Plasma Chemistry and Plasma Processing 2012, 32 (3), 427– 450,  DOI: 10.1007/s11090-011-9339-7
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    Thermodynamics, transport and kinetics of equilibrium and non-equilibrium plasmas. A state-to-state approach
    Capitelli, M.; Armenise, I.; Bisceglie, E.; Bruno, D.; Celiberto, R.; Colonna, G.; D'Ammando, G.; De Pascale, O.; Esposito, F.; Gorse, C.; Laporta, V.; Laricchiuta, A.
    Plasma Chemistry and Plasma Processing (2012), 32 (3), 427-450CODEN: PCPPDW; ISSN:0272-4324. (Springer)
    Thermal non-equil. plasmas were deeply investigated theor. by the state-to-state approach, offering the unique opportunity of a detailed information about internal distributions affecting thermodn., transport coeffs. and kinetics, properly accounting for the presence of excited states. The efforts made in the construction of knowledge on the dynamics of elementary processes occurring in the plasma with resoln. on internal degrees of freedom, required by the method, are discussed. Boltzmann equation is solved for electrons self-consistently coupled to the chem. species collisional dynamics, reproducing very interesting features of strongly non-equil. internal distributions, characterizing plasmas.
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    Cimerman, R.; Račková, D.; Hensel, K. Tars Removal by Non-Thermal Plasma and Plasma Catalysis. J. Phys. D Appl. Phys. 2018, 51 (27), 274003,  DOI: 10.1088/1361-6463/aac762
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    Cimerman, Richard; Rackova, Diana; Hensel, Karol
    Journal of Physics D: Applied Physics (2018), 51 (27), 274003/1-274003/13CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)
    The gasification of a fuel or biomass is an industrial process that is utilized for synthesis gas (syngas) prodn. The syngas can be used to generate electricity, but after gasification it is often polluted with tars and various other pollutants. Therefore, the syngas must be cleaned before further use. The objective of this paper was to investigate the potential of removing the tars by non-thermal plasma generated by atm. pressure dielec. barrier discharge in combination with various packing materials (TiO2, Pt/γ-Al2O3, γ-Al2O3, glass beads). Naphthalene was used as a model polyarom. tar compd. The effect of discharge power, carrier gas and packing material on naphthalene removal was investigated and gaseous and solid byproducts were analyzed by means of FTIR spectrometry. In ambient air, a naphthalene removal efficiency of 88% and 40% was achieved for 320 J l-1 with and without the catalyst, resp. The max. removal efficiency of almost 100% was obsd. with a TiO2 catalyst and oxygen carrier gas. CO, CO2, H2O and HCOOH were identified among the products, as well as more complex compds., such as 1,4-naphthoquinone and phthalic anhydride.
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    Fridman, A. Plasma Chemistry; Cambridge University Press: Cambridge, U.K., 2008.
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    Pathak, R. M.; Ananthanarasimhan, J.; Rao, L. Chemical Kinetics Simulation of Hydrogen Generation in Rotating Gliding Arc Plasma. IEEE Trans. Plasma Sci. 2022, 50 (8), 2482– 2488,  DOI: 10.1109/TPS.2022.3188338
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    Chemical kinetics simulation of hydrogen generation in rotating gliding arc plasma
    Pathak, Ram Mohan; Ananthanarasimhan, J.; Rao, Lakshminarayana
    IEEE Transactions on Plasma Science (2022), 50 (8), 2482-2488CODEN: ITPSBD; ISSN:1939-9375. (Institute of Electrical and Electronics Engineers)
    This work reports hydrogen (H2) formation using methane nitrogen gas mixt. as a feed stream in a rotating gliding arc (RGA) reactor. The H2 formation in the RGA was quantified by exptl. studies, and the results were validated by simulating plasma chem. kinetics using the Chem. Workbench software. The simulation was performed for an exptl. condition, where methane (1%) and nitrogen (99%) gas mixt. was fed to an RGA at 5, 10, 25, and 40 lpm. For these flow rates, the simulation predicted 1417, 802, 299, and 67 ppm of H2, resp. Also, the results show that at these flow rates, the reduced elec. field (E/N) of the discharge was 78, 83, 92, and 101 Td and the gas temp. was 3800, 4108, 4590, and 4975 K resp. The simulation result was in reasonable agreement with the exptl. data, which shows 1276, 717, 213, and 61 ppm of H2 in the product gas, resp., at 5, 10, 25, and 40 lpm. This work marks the first step toward process optimization through the simulation approach.
  227. 227
    Nair, S. A. Corona Plasma for Tar Removal. Doctoral Thesis, Technical University of Eindhoven, Eindhoven, Netherlands, 2004.
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    Fridman, A.; Chirokov, A.; Gutsol, A. Non-Thermal Atmospheric Pressure Discharges. J. Phys. D: Appl. Phys. 2005, 38, R1,  DOI: 10.1088/0022-3727/38/2/R01
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    Non-thermal atmospheric pressure discharges
    Fridman, A.; Chirokov, A.; Gutsol, A.
    Journal of Physics D: Applied Physics (2005), 38 (2), R1-R24CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)
    There has been considerable interest in non-thermal atm. pressure discharges over the past decade due to the increased no. of industrial applications. Diverse applications demand a solid phys. and chem. understanding of the operational principals of such discharges. This paper focuses on the four most important and widely used varieties of non-thermal discharges: corona, dielec. barrier, gliding arc and spark discharge. The physics of these discharges is closely related to the breakdown phenomena. The main players in elec. breakdown of gases: avalanches and streamers are also discussed in this paper. Although non-thermal atm. pressure discharges have been intensively studied for the past century, a clear phys. picture of these discharges is yet to be obtained.
  229. 229
    Zhang, H.; Xu, R.; J, A.; Zheng, J.; Wan, J.; Wang, K.; Lan, B.; Yan, J.; Li, X. Destruction of Biomass Tar Model Compound in a Rotating Gliding Arc Plasma Catalytic System: Contribution of Typical Transition Metals in Ni-Based Bimetallic Catalysts. Fuel 2022, 323, 124385,  DOI: 10.1016/j.fuel.2022.124385
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    Destruction of biomass tar model compound in a rotating gliding arc plasma catalytic system: Contribution of typical transition metals in Ni-based bimetallic catalyst
    Zhang, Hao; Xu, Ruiyang; J, Ananthanarasimhan; Zheng, Jiageng; Wan, Jieying; Wang, Kaiyi; Lan, Bingru; Yan, Jianhua; Li, Xiaodong
    Fuel (2022), 323 (), 124385CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    In this work, the destruction of toluene as a biomass tar model compd. has been investigated in a rotating gliding arc (RGA) plasma catalytic system focusing on understanding the contribution of typical transition metals (Fe, Co, Cu) in Ni-based bimetallic catalyst. Investigations were conducted to elucidate their synergy with plasma under simulated gasifier gas (SGG) to destruct toluene and their effect on value-added benefits such as the enhanced heat content of the reacted producer gas. Results showed that the N2 environment offered better performance than the SGG environment, esp. at high tar concn., due to a more abundance of N2 excited species. The loading of Ni on the Al2O3 catalyst remarkably enhanced the tar conversion from 80.7% to 93.1%. Except for the NiFe, the bimetallic catalysts improved conversion and reduced specific energy consumption (SEC). Primarily, the NiCu catalyst provided a max. tar conversion of up to 94.3% and significantly enhanced the heat content of the producer gas by 29% from that of the SGG. The min. SEC of 64.5 kWh/kg was achieved by the NiCo, which also showed the best sintering resistance. In the 24-h plasma-catalytic operation, NiCu and NiCo showed excellent stability with only a slight drop in the tar conversion (∼94% to ∼ 91%) after 10-12 h. Anal. of byproducts indicated back spillover of OH and O, which could help clean the metal surface. Thermogravimetric anal. of the spent catalyst indicated that the coke deposited is likely composed of the arom. compds. of b.p. in the range of 100°C to 300°C.
  230. 230
    Vreugdenhil, B. J.; Zwart, R. W. R. Tar Formation in Pyrolysis and Gasification; ECN-E--08-087; Energy Research Centre of the Netherlands: Petten, Netherlands, 2009.
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    Conrads, H.; Schmidt, M. Plasma Generation and Plasma Sources. Plasma Sources Sci. Technol. 2000, 9, 441– 454,  DOI: 10.1088/0963-0252/9/4/301
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    Plasma generation and plasma sources
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    Plasma Sources Science & Technology (2000), 9 (4), 441-454CODEN: PSTEEU; ISSN:0963-0252. (Institute of Physics Publishing)
    This paper reviews the most commonly used methods for the generation of plasmas with special emphasis on non-thermal, low-temp. plasmas for technol. applications. The authors also discuss various tech. realizations of plasma sources for selected applications. This paper is further limited to the discussion of plasma generation methods that employ elec. fields. The various plasmas described include d.c. glow discharges, either operated continuously (continuous-wave) or pulsed, capacitively and inductively coupled rf discharges, helicon discharges, and microwave discharges. Various examples of tech. realizations of plasmas in closed structures (cavities), in open structures (surfatron, planar plasma source), and in magnetic fields (ECR sources) are discussed in detail. Finally, the authors mention dielec. barrier discharges as convenient sources of non-thermal plasmas at high pressures (up to atm. pressure) and beam-produced plasmas. It is the main objective of this paper to give an overview of the wide range of diverse plasma generation methods and plasma sources and highlight the broad spectrum of plasma properties which, in turn, lead to a wide range of diverse technol. and tech. applications. 36 Refs.
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    Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Destruction of Biomass Tar Using a Gliding Arc Plasma Reformer. Int. J. Environ. Protection 2012, 2, 1– 8
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    Kogelschatz, U. Dielectric-Barrier Discharges: Their History, Discharge Physics, and Industrial Applications. Plasma Chem. Plasma Process. 2003, 23, 1– 46,  DOI: 10.1023/A:1022470901385
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    Dielectric-barrier discharges: their history, discharge physics, and industrial applications
    Kogelschatz, Ulrich
    Plasma Chemistry and Plasma Processing (2003), 23 (1), 1-46CODEN: PCPPDW; ISSN:0272-4324. (Kluwer Academic/Plenum Publishers)
    A review. Dielec.-barrier discharges (silent discharges) are used on a large industrial scale. They combine the advantages of non-equil. plasma properties with the ease of atm.-pressure operation. A prominent feature is the simple scalability from small lab. reactors to large industrial installations with megawatt input powers. Efficient and cost-effective all-solid-state power supplies are available. The preferred frequency range lies between 1 kHz and 10 MHz, the preferred pressure range between 10 kPa and 500 kPa. Industrial applications include ozone generation, pollution control, surface treatment, high power CO2 lasers, UV excimer lamps, excimer based mercury-free fluorescent lamps, and flat large-area plasma displays. Depending on the application and the operating conditions, the discharge can have pronounced filamentary structure or fairly diffuse appearance. History, discharge physics, and plasma chem. of dielec.-barrier discharges and their applications are discussed in detail.
  234. 234
    Mei, D.; Liu, S.; Yanik, J.; Lopez, G.; Olazar, M.; Fang, Z.; Tu, X. Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor. ACS Sustain Chem. Eng. 2022, 10 (27), 8958– 8969,  DOI: 10.1021/acssuschemeng.2c02495
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    234
    Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor
    Mei Danhua; Liu Shiyun; Fang Zhi; Mei Danhua; Tu Xin; Yanik Jale; Lopez Gartzen; Olazar Martin; Lopez Gartzen
    ACS sustainable chemistry & engineering (2022), 10 (27), 8958-8969 ISSN:2168-0485.
    Biomass gasification is a promising and sustainable process to produce renewable and CO2-neutral syngas (H2 and CO). However, the contamination of syngas with tar is one of the major challenges to limit the deployment of biomass gasification on a commercial scale. Here, we propose a hybrid plasma-catalytic system for steam reforming of tar compounds over honeycomb-based catalysts in a gliding arc discharge (GAD) reactor. The reaction performances were evaluated using the blank substrate and coated catalytic materials (γ-Al2O3 and Ni/γ-Al2O3). Compared with the plasma alone process, introducing the honeycomb materials in GAD prolonged the residence time of reactant molecules for collision with plasma reactive species to promote their conversions. The presence of Ni/γ-Al2O3 gave the best performance with the high conversion of toluene (86.3%) and naphthalene (75.5%) and yield of H2 (35.0%) and CO (49.1%), while greatly inhibiting the formation of byproducts. The corresponding highest overall energy efficiency of 50.9 g/kWh was achieved, which was 35.4% higher than that in the plasma alone process. Characterization of the used catalyst and long-term running indicated that the honeycomb material coated with Ni/γ-Al2O3 had strong carbon resistance and excellent stability. The superior catalytic performance of Ni/γ-Al2O3 can be mainly ascribed to the large specific surface area and the in situ reduction of nickel oxide species in the reaction process, which promoted the interaction between plasma reactive species and catalysts and generated the plasma-catalysis synergy.
  235. 235
    Liu, S. Y.; Mei, D. H.; Nahil, M. A.; Gadkari, S.; Gu, S.; Williams, P. T.; Tu, X. Hybrid Plasma-Catalytic Steam Reforming of Toluene as a Biomass Tar Model Compound over Ni/Al2O3 Catalysts. Fuel Process. Technol. 2017, 166, 269– 275,  DOI: 10.1016/j.fuproc.2017.06.001
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    235
    Hybrid plasma-catalytic steam reforming of toluene as a biomass tar model compound over Ni/Al2O3 catalysts
    Liu, S. Y.; Mei, D. H.; Nahil, M. A.; Gadkari, S.; Gu, S.; Williams, P. T.; Tu, X.
    Fuel Processing Technology (2017), 166 (), 269-275CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    In this study, plasma-catalytic steam reforming of toluene as a biomass tar model compd. was carried out in a coaxial dielec. barrier discharge (DBD) plasma reactor. The effect of Ni/Al2O3 catalysts with different nickel loadings (5-20 wt%) on the plasma-catalytic gas cleaning process was evaluated in terms of toluene conversion, gas yield, byproducts formation and energy efficiency of the plasma-catalytic process. Compared to the plasma reaction without a catalyst, the combination of DBD with the Ni/Al2O3 catalysts significantly enhanced the toluene conversion, hydrogen yield and energy efficiency of the hybrid plasma process, while significantly reduced the prodn. of org. byproducts. Increasing Ni loading of the catalyst improved the performance of the plasma-catalytic processing of toluene, with the highest toluene conversion of 52% and energy efficiency of 2.6 g/kWh when placing the 20 wt% Ni/Al2O3 catalyst in the plasma. The possible reaction pathways in the hybrid plasma-catalytic process were proposed through the combined anal. of both gas and liq. products.
  236. 236
    Zhu, F.; Zhang, H.; Yang, H.; Yan, J.; Li, X.; Tu, X. Plasma Reforming of Tar Model Compound in a Rotating Gliding Arc Reactor: Understanding the Effects of CO2 and H2O Addition. Fuel 2020, 259, 116271,  DOI: 10.1016/j.fuel.2019.116271
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    Plasma reforming of tar model compound in a rotating gliding arc reactor: Understanding the effects of CO2 and H2O addition
    Zhu, Fengsen; Zhang, Hao; Yang, Haiping; Yan, Jianhua; Li, Xiaodong; Tu, Xin
    Fuel (2020), 259 (), 116271CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    In this study, a rotating gliding arc (RGA) plasma reactor co-driven by a magnetic field and tangential flow has been investigated for the reforming of toluene as a tar surrogate from the gasification of biomass or waste. The effect of steam and CO2 addn. on the reaction performance of the plasma tar reforming process has been evaluated in terms of the conversion of toluene, gas prodn. and energy efficiency. The presence of CO2 in the reaction suppresses the conversion of toluene. By contrast, adding an appropriate amt. of steam to the reforming process significantly enhances the conversion of toluene, while further increasing steam concn. reduces the conversion of toluene. The max. toluene conversion of 85.2% is achieved at an optimal steam concn. of 16%. Optical emission spectroscopic (OES) diagnostics have been used to understand the generation of reactive species contributed to the conversion of toluene and reaction intermediates in the plasma reforming process. The possible reaction pathways and mechanisms have been discussed based on the anal. of gases and condensed liq. byproducts combined with the emission spectra of the plasma in the presence or absence of steam and CO2.
  237. 237
    Subrahmanyam, C.; Renken, A.; Kiwi-Minsker, L. Catalytic Non-Thermal Plasma Reactor for Abatement of Toluene. Chemical Engineering Journal 2010, 160 (2), 677– 682,  DOI: 10.1016/j.cej.2010.04.011
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    Catalytic non-thermal plasma reactor for abatement of toluene
    Subrahmanyam, Ch.; Renken, A.; Kiwi-Minsker, L.
    Chemical Engineering Journal (Amsterdam, Netherlands) (2010), 160 (2), 677-682CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    A non-thermal plasma rector with a catalytic electrode comprised of sintered metal fibers (SMF) was tested for the oxidative decompn. of a model volatile org. compd., toluene. Input energy was 160-295 J/L by varying the applied voltage from 12.5 to 22.5 kV at 200 Hz. The effect of various parameters (toluene concn., SMF modification by Mn and Co oxides, input energy, O3 formation) was examd. The plasma catalytic approach was very effective for total oxidn. of toluene at low input energy, esp. for toluene concns. ≤250 ppm and SMF modification by transition metal oxides; significantly increasing reactor performance. MnOx modification appeared to be a better than CoOx, which may be attributed to the in-situ decompn. of O3 leading to formation of more reactive oxidants, e.g., at. O.
  238. 238
    Xu, R.; Kong, X.; Zhang, H.; Ruya, P. M.; Li, X. Destruction of Gasification Tar over Ni Catalysts in a Modified Rotating Gliding Arc Reactor: Effect of Catalyst Position and Nickel Loading. Fuel 2021, 289, 119742,  DOI: 10.1016/j.fuel.2020.119742
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    238
    Destruction of gasification tar over Ni catalysts in a modified rotating gliding arc plasma reactor: Effect of catalyst position and nickel loading
    Xu, Ruiyang; Kong, Xiangzhi; Zhang, Hao; Ruya, Petric Marc; Li, Xiaodong
    Fuel (2021), 289 (), 119742CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    In this study, a modified rotating gliding arc (RGA) plasma reactor with fan-shaped swirl generator coupled with Ni/γ-Al2O3 catalyst was investigated for the steam reforming of gasification tar from waste materials, taking toluene as the tar surrogate. The system performance was evaluated in terms of tar conversion, energy efficiency, yield of product gas, as well as synergistic capability of plasma catalysis, with particular attention on the effects of specific energy input (SEI), positioning of the catalysts, and Ni loading of catalysts. Different characterizations of catalysts including N2 adsorption-desorption, XRD, H2-TPR, and TEM were conducted to study the properties of catalysts. Incorporation of catalyst placed sufficiently far from the anode increased toluene conversion which indicated the synergy between plasma and catalysis for tar conversion. A toluene conversion of up to 91.9% can be achieved with a distance of 62 mm between the catalyst and the anode, which was 21% higher than that in the plasma alone system. The toluene conversion can be further increased to 94.7% when the Ni loading was increased from 4% to 16%. The synergistic capability of plasma catalysis was demonstrated from an enhanced toluene conversion and the increased formation of value-added fuel gases such as H2, CO, and CH4, together with simultaneously a selective redn. in CO2 formation, esp. when the Ni loading was 4% and 8%. Identification of liq. byproducts also revealed the synergy between plasma and catalysis which transformed bi-radical HC=CH into gaseous products, prohibiting the formation of indene and naphthalene.
  239. 239
    Liu, Y.; Song, J.; Diao, X.; Liu, L.; Sun, Y. Removal of Tar Derived from Biomass Gasification via Synergy of Non-Thermal Plasma and Catalysis. Sci. Total Environ. 2020, 721, 137671,  DOI: 10.1016/j.scitotenv.2020.137671
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    239
    Removal of tar derived from biomass gasification via synergy of non-thermal plasma and catalysis
    Liu, Yawen; Song, Jianwei; Diao, Xungang; Liu, Lina; Sun, Yifei
    Science of the Total Environment (2020), 721 (), 137671CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
    In this study, the reforming of toluene, as a surrogate for tar, was investigated in plasma-alone (PA) and plasma-catalytic (PC) systems. The effects of feed gas oxygen content (O2/(O2 + N2) = 0, 3, 12, 21, or 30 vol%) and the discharge power (30, 75, or 90 W) on toluene conversion, the selectivity of syngas (H2 + CO), and undesirable liq. byproducts were evaluated using the PA system. A max. toluene conversion of 87.9% and a min. selectivity of undesirable liq. byproducts of 0.53% for ethylbenzene, and 1.24% for benzene, were obtained when the discharge power was 90 W and the oxygen content in the carrier gas was 3 vol%. However, a max. gas selectivity of 48.4% for H2 and 19.4% for CO was attained when the discharge power was 75 W and the oxygen content was 3 vol% and 12 vol%, resp. The effect of the steam/carbon molar ratio (S/C) on toluene reforming was investigated using the PC system with Ni/ZSM-5 catalyst under a discharge power of 75 W. The addn. of steam to the feed gas significantly enhanced the conversion of toluene to syngas. A max. toluene conversion of 88.5% was reached with a min. selectivity of liq. byproducts (1.9% for ethylbenzene and 5.2% for benzene) when S/C was 2. However, the highest selectivity of syngas (69.8% for H2 and 21.2% for CO) was achieved when S/C was 2.5. The catalyst employed in the plasma reforming of toluene exhibited excellent anti-carbon deposition performance. A possible reaction mechanism and pathway of toluene destruction was proposed based on anal. of both gaseous and liq. products.
  240. 240
    Xu, B.; Li, J.-q.; Xie, J.-j.; Huang, Y.-q.; Yin, X.-l.; Wu, C.-z. Performance Study on Simultaneous Tar Removal and Bio-Syngas Methanation by Combining Catalysis with Non-Thermal Plasma. J. Fuel Chem. Technol. 2021, 49 (7), 967– 977,  DOI: 10.1016/S1872-5813(21)60045-2
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    Petitpas, G.; Rollier, J. D.; Darmon, A.; Gonzalez-Aguilar, J.; Metkemeijer, R.; Fulcheri, L. A Comparative Study of Non-Thermal Plasma Assisted Reforming Technologies. Int. J. Hydrogen Energy 2007, 32 (14), 2848– 2867,  DOI: 10.1016/j.ijhydene.2007.03.026
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    A comparative study of non-thermal plasma assisted reforming technologies
    Petitpas, G.; Rollier, J.-D.; Darmon, A.; Gonzalez-Aguilar, J.; Metkemeijer, R.; Fulcheri, L.
    International Journal of Hydrogen Energy (2007), 32 (14), 2848-2867CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    A review of the setting up, feasibility and efficiency of the existing technologies for on-board H prodn. On-board H prodn. from hydrocarbons (reforming) for fuel cells is subject to problems when used with traditional catalysts. High device wt., a relatively long transient time and poisoning make the integration on-board a vehicle, complex. In response to these challenges, hydrocarbon reforming processes assisted by non-thermal plasmas for H prodn. was implemented. The characteristics of plasma reforming through various approaches are discussed. The performance of some of the systems are then compared against each other and discussed.
  242. 242
    Eliott, R. M.; Nogueira, M. F. M.; Silva Sobrinho, A. S.; Couto, B. A. P.; MacIel, H. S.; Lacava, P. T. Tar Reforming under a Microwave Plasma Torch. Energy Fuels 2013, 27 (2), 1174– 1181,  DOI: 10.1021/ef301399q
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    Tar Reforming under a Microwave Plasma Torch
    Eliott, Rodrigo Monteiro; Nogueira, Manoel F. M.; Silva Sobrinho, Argemiro S.; Couto, Bruno A. P.; Maciel, Homero S.; Lacava, Pedro T.
    Energy & Fuels (2013), 27 (2), 1174-1181CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    Because of the scarcity of nonrenewable natural resources, such as petroleum and natural gas, the use of biofuel is needed. Gasification is a major process used to obtain renewable fuels from biomass; however, the gas cleaning system is a constraint for its broad utilization. During the pyrolysis process, a mixt. of org. compds. in the gas phase is produced and must be removed from the gases before it is used in the most practical applications. In order to remove such org. compds., which are known as tar, large, sophisticated, problematic, and expensive gas cleaning systems are added to the gasifier gas exit. Previous papers have shown that the plasma torch has the potential to destroy produced tar, being a simpler and less-expensive system than traditional gas cleaners. This work presents a qual. and quant. evaluation of a microwave plasma system running on tar destruction and its reforming. In order to evaluate a 1 kW microwave plasma system performance, an app. was developed and installed at ITA Lab. of Plasmas and Processes (LPP-ITA). The system runs at atm. pressure with nitrogen and argon as carrier gas under a large range of flow rates. Expts. were performed using a gas mixt. of N2, H2O, ethanol, and tar at controlled concn. in order to simulate the gases produced by a gasifier. The injected tar was obtained from pine pyrolysis and characterized for energy purposes. In order to reduce tar viscosity, it was dild. in com. ethanol (92.5% ethanol and 7.5% water) and its concn. varied from 0.8 gtar/Nmgas3 to 4.2 gtar/Nmgas3. Species formed in the microwave plasma torch were identified using an optical spectrometer. The reactor exit gases had their compn. evaluated on tar content as well as for noncondensable gases. As a result, this paper shows that no tar content was detected at the reactor outlet, indicating that all supplied tar was destroyed in the plasma reactor. The main detected products were CO and solid carbon (C(s)). Furthermore, neither NO nor CO2 were detected, and an indication of H2 formation was obtained. This paper concludes that the microwave plasma system is capable of destroying and reforming tar efficiently and produces mainly H2, CO, O2, and C(s) as byproducts.
  243. 243
    Medeiros, H. S.; Pilatau, A.; Nozhenko, O. S.; Da Silva Sobrinho, A. S.; Petraconi Filho, G. Microwave Air Plasma Applied to Naphthalene Thermal Conversion. Energy Fuels 2016, 30 (2), 1510– 1516,  DOI: 10.1021/acs.energyfuels.5b02451
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    Microwave Air Plasma Applied to Naphthalene Thermal Conversion
    Medeiros, H. S.; Pilatau, A.; Nozhenko, O. S.; da Silva Sobrinho, A. S.; Petraconi Filho, G.
    Energy & Fuels (2016), 30 (2), 1510-1516CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    In this paper, a naphthalene (C10H8) thermal cracking model is presented. The model is based on a simple model that takes into account the microwave (MW) plasma thermal influence on naphthalene cracking, accompanying its steam reforming reactions. The temp. level of 1573 K was established for complete C10H8 cracking at 1.75 kW plasma power. High conversion efficiency of C10H8 is achieved varying the air flow rate in the range of 0.6-1.2 m3/h. The model approximates the characteristics of the considered MW plasma to thermal plasma in local thermodn. equil. Exptl. data have good agreement with calcd. data at the cited region of the air flow rate and power. Conversion efficiency up to 99.36% was obtained.
  244. 244
    Mista, W.; Kacprzyk, R. Decomposition of Toluene Using Non-Thermal Plasma Reactor at Room Temperature. Catal. Today 2008, 137 (2–4), 345– 349,  DOI: 10.1016/j.cattod.2008.02.009
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    Decomposition of toluene using non-thermal plasma reactor at room temperature
    Mista, W.; Kacprzyk, R.
    Catalysis Today (2008), 137 (2-4), 345-349CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
    A non-thermal, atm. pressure plasma using a direct-current (DC) back-corona discharge was used to examine abatement of toluene in air at room temp. Toluene removal efficiency applying wire-plate geometry increased with increasing applied voltage. Results indicated ∼93% toluene removal efficiency and very small NOx formation (∼10 ppm) was achieved for an air stream contg. 70 ppm toluene. The neg. corona current was larger than the pos. corona current at the same applied voltage (polarity effect), resulting in the higher efficiency of the plasma reactor at neg. discharge polarity.
  245. 245
    Van Durme, J.; Dewulf, J.; Sysmans, W.; Leys, C.; Van Langenhove, H. Abatement and Degradation Pathways of Toluene in Indoor Air by Positive Corona Discharge. Chemosphere 2007, 68 (10), 1821– 1829,  DOI: 10.1016/j.chemosphere.2007.03.053
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    Abatement and degradation pathways of toluene in indoor air by positive corona discharge
    Van Durme, J.; Dewulf, J.; Sysmans, W.; Leys, C.; Van Langenhove, H.
    Chemosphere (2007), 68 (10), 1821-1829CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
    Indoor air concns. of volatile org. compds. often exceed outdoor levels by a factor of 5. There is much interest in developing new technologies to improve indoor air quality. Non-thermal plasma (DC pos. corona discharge) is explored as an innovative technol. for indoor air purifn. An inlet gas stream of 10 L min-1 contg. 0.50 ± 0.02 ppm toluene was treated by the plasma reactor in atm. conditions. Toluene removal proved to be achievable with a characteristic energy d. ε0 of 50 J L-1. Removal efficiencies were higher for 26% relative humidity (ε0 = 35 J L-1), compared with those at increased humidities (50% relative humidity, ε0 = 49 J L-1). Reaction products such as formic acid, benzaldehyde, benzyl alc., 3-methyl-4-nitrophenol, 4-methyl-2-nitrophenol, 4-methyl-2-Pr furan, 5-methyl-2-nitrophenol, 4-nitrophenol, 2-methyl-4,6-dinitrophenol are identified by mass spectrometry. Based on these byproducts a toluene degrdn. mechanism is proposed.
  246. 246
    Bityurin, V. A.; Filimonova, E. A.; Naidis, G. V. Simulation of Naphthalene Conversion in Biogas Initiated by Pulsed Corona Discharges. IEEE Transactions on Plasma Science 2009, 37, 911– 919,  DOI: 10.1109/TPS.2009.2019756
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    Simulation of naphthalene conversion in biogas initiated by pulsed corona discharges
    Bityurin, Valentin A.; Filimonova, Elena A.; Naidis, George V.
    IEEE Transactions on Plasma Science (2009), 37 (6, Pt. 1), 911-919CODEN: ITPSBD; ISSN:0093-3813. (Institute of Electrical and Electronics Engineers)
    The numerical results on naphthalene removal in biogas are presented and compared with expt. Plasma-chem. processes in discharge and postdischarge stages are considered. The self-consistent approach for modeling of cleaning process on the basis of pulsed corona discharges is demonstrated. It has been revealed that the reaction of naphthalene (C10H8) with excited nitrogen mol. (N2(A3Σ)) is very important in the cleaning process in nitrogen-contg. mixts. The addn. to N2 of CO, CO2, and H2 results in the deterioration of treatment.
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    Nair, S. A.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.; Ptasinski, K. J.; Drinkenburg, A. A. H. Tar Removal from Biomass Derived Fuel Gas by Pulsed Corona Discharges: Chemical Kinetic Study II. Ind. Eng. Chem. Res. 2005, 44 (6), 1734– 1741,  DOI: 10.1021/ie049292t
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    Tar Removal from Biomass Derived Fuel Gas by Pulsed Corona Discharges: Chemical Kinetic Study II
    Nair, S. A.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.; Ptasinski, K. J.; Drinkenburg, A. A. H.
    Industrial & Engineering Chemistry Research (2005), 44 (6), 1734-1741CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Tar (heavy hydrocarbon or poly arom. hydrocarbon (PAH)) removal from biomass derived fuel gas is one of the biggest obstacles in its use for power generation. The authors have studied pulsed corona as a method for tar removal. The previous exptl. results indicate the energy consumption of 400 J/L for naphthalene removal (model tar compd.) from synthetic fuel gas (CO, CO2, H2, CH4, N2) at a temp. of 200 °C. The present study extends the work on exptl. and kinetic calcns. for temps. up to 500 °C. Radical yields are evaluated at various temps. According to the kinetic model and exptl. results the optimum temp. for tar removal is ∼400 °C. The energy consumption for tar removal at 400 °C is ∼200-250 J/L, whereas at 200 °C, this is ∼400-600 J/L.
  248. 248
    Kushwah, A.; Reina, T. R.; Short, M. Modelling Approaches for Biomass Gasifiers: A Comprehensive Overview. Sci. Total Environ. 2022, 834, 155243,  DOI: 10.1016/j.scitotenv.2022.155243
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    Modelling approaches for biomass gasifiers: A comprehensive overview
    Kushwah, A.; Reina, T. R.; Short, M.
    Science of the Total Environment (2022), 834 (), 155243CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
    A review. Biomass resources have the potential to become a viable renewable technol. and play a key role within the future renewable energy paradigm. Since CO2 generated in bio-energy prodn. is equal to the CO2 absorbed during the growth of the biomass, this renewable energy is a net zero emissions resource. Biomass gasification is a versatile method for transforming waste into energy in which biomass material is thermochem. converted within a reactor. Gasification's superior flexibility, including both in terms of biomass type and heat generation or energy prodn. alternatives, is what stimulates biomass gasification scientific and industrial potential. Downdraft gasifiers seem to be well-suited for small-scale generation of heat along with energy, whereas fluidised bed and entrained flow gasifiers currently attain significant economies of scale for fuel prodn. The operation of gasifiers is influenced by several factors, including operational parameters, feedstock types, and reactor design. Modeling is a valuable tool for building a unit based on the results of model predictions with different operational parameters and feedstock in such scenarios. Once verified, a suitable model may be used to assess the sensitivity of a gasifier's performance to changes in various operational and design factors. Effective models may help designers to theorise and predict the impacts of a variety of characteristics without the need for further empirical observations, which can help in the design and implementation of this technol. This work provides an overview of gasification technologies and a succinct guidance to the modeling decisions and modeling strategies for biomass gasification to enable a successful biomass to fuel conversion. A tech. description and crit. anal. of thermodn., kinetic, computational fluid dynamic and data-driven approaches is provided, including crucial modeling considerations that have not been explored in earlier studies. The review aims to aid researchers in the field to select the appropriate approach and guide future work.
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    Li, C.; Liu, R.; Zheng, J.; Zhang, Y. Thermodynamic Study on the Effects of Operating Parameters on CaO-Based Sorption Enhanced Steam Gasification of Biomass. Energy 2023, 273, 127208,  DOI: 10.1016/j.energy.2023.127208
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    Thermodynamic study on the effects of operating parameters on CaO-based sorption enhanced steam gasification of biomass
    Li, Chongcong; Liu, Rui; Zheng, Jinhao; Zhang, Yan
    Energy (Oxford, United Kingdom) (2023), 273 (), 127208CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    Sorption enhanced steam gasification of biomass (SESGB) is a promising route for the prodn. of H2-rich syngas. In this work, effects of some crit. parameters of SESGB on hydrogen prodn. are studied by means of thermodn. equil. modeling. To improve the model performance, modeling modifications are made by using the carbon conversion efficiency for carbon balance calcn. and by calibrating the equil. consts. of methane reforming, water-gas shift, and CaO carbonation reactions with the exptl. data. In addn., a new concept of CaO effective conversion rate is proposed to describe the influence of the CaO with different CO2 sorption capacity on hydrogen prodn. The root mean square error (RMSE) between the prediction results of the modified model and the exptl. results is less than 3.5%, indicating the validity of the modification method. And the prediction results show that increasing temp. and the mass ratio of steam/biomass from 823 K to 923 K and from 0.5 to 1.5 increases the concn. of H2 and gas yield, while increasing the molar ratio between CaO and carbon from 1 to 2 mainly increases the H2 concn.
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    Xiang, X.; Gong, G.; Shi, Y.; Cai, Y.; Wang, C. Thermodynamic Modeling and Analysis of a Serial Composite Process for Biomass and Coal Co-Gasification. Renewable Sustainable Energy Rev. 2018, 82, 2768– 2778,  DOI: 10.1016/j.rser.2017.10.008
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    Thermodynamic modeling and analysis of a serial composite process for biomass and coal co-gasification
    Xiang, Xianan; Gong, Guangcai; Shi, Ying; Cai, Youchan; Wang, Chenhua
    Renewable & Sustainable Energy Reviews (2018), 82 (Part_3), 2768-2778CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    This paper puts forward a new process for the co-gasification of biomass and coal. The process is divided into combustion stage and gasification stage. It provides thermal energy in the combustion stage and produces combustible gases in the gasification stage. The process is named as serial composite process for biomass and coal co-gasification, because of the biomass gasification react after coal gasification react in the gasification stage. A thermodn. equil. model is established for the process. The model is divided into two sub-models, one is the coal combustion sub-model, the other is the coal-biomass serial gasification sub-model. The coal combustion sub-model is divided into two stages including coal pyrolysis and combustion reaction. The coal-biomass serial gasification sub-model is also divided into two stages including coal char gasification reaction and biomass gasification reaction; the temp. of two stages is different; an empirical equation for the temp. relationship is estd. from the exptl. data. The model studies the effects of key parameters on gasification properties, including gasification temp., s/c, coal/biomass, and predicts the compn. of product gas, gas yield, gas calorific value and gasification efficiency of the process. Compared with the dual-fluidized bed gasification process, the process is stable, high gas yield, the medium calorific value gas can be produced. It is a new gasification technol. worthy to be popularized.
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    Puig-Arnavat, M.; Bruno, J. C.; Coronas, A. Review and Analysis of Biomass Gasification Models. Renewable and Sustainable Energy Reviews. 2010, 14, 2841– 2851,  DOI: 10.1016/j.rser.2010.07.030
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    Review and analysis of biomass gasification models
    Puig-Arnavat, Maria; Bruno, Joan Carles; Coronas, Alberto
    Renewable & Sustainable Energy Reviews (2010), 14 (9), 2841-2851CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. The use of biomass as a source of energy has been further enhanced in recent years and special attention has been paid to biomass gasification. Due to the increasing interest in biomass gasification, several models have been proposed in order to explain and understand this complex process, and the design, simulation, optimization and process anal. of gasifiers have been carried out. This paper presents and analyses several gasification models based on thermodn. equil., kinetics and artificial neural networks. The thermodn. models are found to be a useful tool for preliminary comparison and for process studies on the influence of the most important fuel and process parameters. They have the advantage of being independent of gasifier design, but they cannot give highly accurate results for all cases. The kinetic-based models are computationally more intensive but give accurate and detailed results. However, they contain parameters that limit their applicability to different plants.
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    Huang, H. J.; Ramaswamy, S. Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach. Appl. Biochem. Biotechnol. 2009, 154, 14– 25,  DOI: 10.1007/s12010-008-8483-x
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    Modeling biomass gasification using thermodynamic equilibrium approach
    Huang Hua-Jiang; Ramaswamy Shri
    Applied biochemistry and biotechnology (2009), 154 (1-3), 14-25 ISSN:.
    In this paper, the thermodynamic equilibrium models for biomass gasification applicable to various gasifier types have been developed, with and without considering char. The equilibrium models were then modified closely matching the CH(4) only or both CH(4) and CO compositions from experimental data. It is shown that the modified model presented here based on thermodynamic equilibrium and taking into account local heat and mass considerations can be used to simulate the performance of a downdraft gasifier. The model can also be used to estimate the equilibrium composition of the syngas. Depending on the gasifier type and internal fluid flow, heat and mass transfer characteristics, with proper modification of the equilibrium model, a simple tool to simulate the operation and performance of varying types of biomass gasifier can be developed.
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    Adil, A.; Shivapuji, A. M.; Rao, L. Thermodynamic Analysis for Methanol Synthesis Using Biomass-Derived Syngas. Biomass Convers Biorefin 2022, 12 (5), 1819– 1834,  DOI: 10.1007/s13399-022-02338-y
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    Thermodynamic analysis for methanol synthesis using biomass-derived syngas
    Adil, Anam; Shivapuji, Anand M.; Rao, Lakshminarayana
    Biomass Conversion and Biorefinery (2022), 12 (5), 1819-1834CODEN: BCBIBN; ISSN:2190-6823. (Springer)
    This study presents multi-variable anal. for prediction and optimization of the methanol yield from biomass-based syngas using a thermodn. model. The biomass-based syngas has a lower H2 content and higher CO2 than the typical syngas obtained from natural gas reforming which is used for the com. methanol synthesis process. Consequently, a thorough examn. was done to det. the working range for the input parameters for a biomass-derived syngas, so that the output of the process becomes comparable to the existing com. technologies. Two cases were examd., case 1 where the H2 enriched bio-syngas was used for methanol synthesis and case 2 where the methanol was directly synthesized by the bio-syngas obtained by oxy-steam gasification process. A multi-variable anal. of the selected parameters is first performed; then, surrogate model for the methanol yield is constructed for both the cases. A selective set of response surfaces from the surrogate math. model for both the cases were used to illustrate the mutual effect of two parameters by keeping the other parameters at the base values. The anal. indicated that the methanol yield is most sensitive to temp. followed by pressure, CO2/CO, and H2/(CO + CO2) molar ratios in both the cases. The optimized values of methanol yield obtained for case 1 and case 2 were 92.72% and 45.35%, resp., achieved at 473 K, 9 MPa. The CO2/CO and the H2/(CO+CO2) molar ratios were at 0.42 and 4.88 resp. for case 1 and for case 2; the values were 0.90 and 1.13 resp. The high-pressure anal. involves the use of equations of states (EoS) to account for the deviations from ideality. Although many equations of state (EoS) are available, there is no one equation that would predict the properties of all the substances under all the conditions. An attempt has been made in this work to address the use of three such equations of state, namely Peng-Robinsons, Soave-Redlich-Kwong EoS and Newton's universal curves, and to compare the results for the components involved in the methanol synthesis reaction. The results indicate that all three EoS provide similar correction factors in the studied temp. and pressure range for methanol synthesis.
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    Qi, J.; Wang, Y.; Hu, M.; Xu, P.; Yuan, H.; Chen, Y. A Reactor Network of Biomass Gasification Process in an Updraft Gasifier Based on the Fully Kinetic Model. Energy 2023, 268, 126642,  DOI: 10.1016/j.energy.2023.126642
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    A reactor network of biomass gasification process in an updraft gasifier based on the fully kinetic model
    Qi, Jingwei; Wang, Yijie; Hu, Ming; Xu, Pengcheng; Yuan, Haoran; Chen, Yong
    Energy (Oxford, United Kingdom) (2023), 268 (), 126642CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    Modeling gasification reactors by process simulation is a practical utility to evaluate gasification performance and assist device design. In this study, a fully kinetic model for the biomass gasification process within a pilot-scale updraft gasifier is proposed, which considers the effect of reactor dimensions, residence time, and temp. distribution on the gasification process compared with the thermodn. equil. method and kinetic method modeled by continuous stirring tank reactor blocks. The pyrolysis stage is defined by detailed solid biomass pyrolysis mechanisms and secondary gas reactions kinetic mechanisms. Moreover, the gas evolution effect in the pyrolysis stage is considered by transferring gas to the gasification zone and freeboard zone according to different temps. The gasification and combustion processes are modeled utilizing comprehensive homogeneous and heterogeneous rate-controlled reactions and the plug flow reactor is first used in modeling the updraft gasifier with the countercurrent characteristic. This proposed model is validated by several exptl. data and the predictive results agree well with exptl. data with the max. root-mean-square deviation of 2.6%. The effect of air or steam as gasification agents on gasification performance is evaluated by the proposed model. This model can provide guidance for industrial equipment design.
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    Loha, C.; Chattopadhyay, H.; Chatterjee, P. K. Three Dimensional Kinetic Modeling of Fluidized Bed Biomass Gasification. Chem. Eng. Sci. 2014, 109, 53– 64,  DOI: 10.1016/j.ces.2014.01.017
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    Three dimensional kinetic modeling of fluidized bed biomass gasification
    Loha, Chanchal; Chattopadhyay, Himadri; Chatterjee, Pradip K.
    Chemical Engineering Science (2014), 109 (), 53-64CODEN: CESCAC; ISSN:0009-2509. (Elsevier Ltd.)
    Biomass gasification in fluidized bed system by using air-steam mixt. as the gasifying agent is a promising way of utilizing biomass because it produces a gaseous fuel having relatively higher calorific value as well as higher hydrogen content with min. or no heat addn. to the gasifier. In the present work, a three dimensional numerical simulation of a bubbling fluidized bed biomass gasifier has been carried out. The numerical simulation is based on the Eulerian-Lagrangian approach where the fluid phase is solved by using a continuum approach and the solid is modeled by using Lagrangian computational particle model. The chem. reactions are coupled with the complex hydrodynamic calcn. of gas-solid fluidized bed. The simulations are performed by varying the gasification temp., equivalence ratio and steam-to-biomass ratio. Detail analyses of flow pattern, pressure distribution, and gas compn. distribution have been presented. The complex three dimensional flow structures are revealed by plotting the results in different planes. The results provide a detail insight into the gasifier's behavior including fluidization, thermal and chem. characteristics. Simulated outlet gas compns. are compared with our own exptl. data and a very good resemblance is obsd.
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    Horton, S. R.; Mohr, R. J.; Zhang, Y.; Petrocelli, F. P.; Klein, M. T. Molecular-Level Kinetic Modeling of Biomass Gasification. Energy Fuels 2016, 30 (3), 1647– 1661,  DOI: 10.1021/acs.energyfuels.5b01988
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    Molecular-Level Kinetic Modeling of Biomass Gasification
    Horton, Scott R.; Mohr, Rebecca J.; Zhang, Yu; Petrocelli, Francis P.; Klein, Michael T.
    Energy & Fuels (2016), 30 (3), 1647-1661CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
    A mol.-level kinetic model for biomass gasification was developed and tuned to exptl. data from the literature. The development was divided into two categories: the compn. of the feedstock and the construction of the reaction network. The compn. model of biomass was divided into three submodels for cellulose, hemicellulose, and lignin. Cellulose and hemicellulose compns. were modeled as linear polymers using Flory-Stockmayer statistics to represent the polymer size distribution. The compn. of lignin, a cross-linked polymer, was modeled using relative amts. of structural building blocks or attributes. When constructing the full biomass compn. model, the fractions of cellulose, hemicellulose, and lignin were optimized using literature-reported ultimate analyses. The reaction network model for biomass contained pyrolysis, gasification, and light-gas reactions. For cellulose and hemicellulose, the initial depolymn. was described using Flory-Stockmayer statistics. The derived monomers from cellulose and hemicellulose were subjected to a full pyrolysis and gasification network. The pyrolysis reactions included both reactions to decrease the mol. size, such as thermal cracking, and char formation reactions, such as Diels-Alder addn. Gasification reactions included incomplete combustion and steam reforming. For lignin, reactions occurred between attributes and included both pyrolysis and gasification reactions. The light-gas reactions included water-gas shift, partial oxidn. of methane, oxidn. of carbon monoxide, steam reforming of methane, and dry reforming of methane. The final reaction network included 1356 reactions and 357 species. The performance of the kinetic model was examd. using literature data that spanned six different biomass samples and had gas compns. as primary results. Three data sets from different biomass samples were used for parameter tuning, and parity plot results showed good agreement between the model and data (ypredicted = yobs0.928 + 0.0003). The predictive ability of the model was probed using three addnl. data sets. Again, the parity plot showed agreement between the model and exptl. results (ypredicted = yobs0.989 - 0.007).
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    Sharma, A.; Nath, R. H 2 -Rich Syngas Production from Gasification Involving Kinetic Modeling: RSM-Utility Optimization and Techno-Economic Analysis. RSC Adv. 2023, 13 (15), 10308– 10321,  DOI: 10.1039/D3RA00287J
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    H2-rich syngas production from gasification involving kinetic modeling: RSM-utility optimization and techno-economic analysis
    Sharma, Ajay; Nath, Ratnadeep
    RSC Advances (2023), 13 (15), 10308-10321CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    In this research article, H2 rich syngas prodn. is optimized using response surface methodol. (RSM) and a utility concept involving chem. kinetic modeling considering eucalyptus wood sawdust (CH1.63O1.02) as gasification feed stock. By adding water gas shift reaction, the modified kinetic model is validated with lab scale exptl. data (2.56 ≤ root mean square error ≤ 3.67). Four operating parameters (i.e., particle size "dp", temp. "T", steam to biomass ratio "SBR", and equivalence ratio "ER") of air-steam gasifier at three levels are used to frame the test cases. Single objective functions like H2 maximization and CO2 minimization are considered whereas for multi-objective function a utility parameter (80% H2 : 20% CO2) is considered. The regression coeffs. (RH22 = 0.89, RCO22 = 0.98 and RU2 = 0.90) obtained during the anal. of variance (ANOVA) confirm a close fitting of the quadratic model with the chem. kinetic model. ANOVA results indicate ER as the most influential parameter followed by T, SBR, and dp. RSM optimization gives H2|max = 51.75 vol%, CO2|min = 14.65 vol% and utility gives H2|opt. = 51.69 vol% (0.11%), CO2|opt. = 14.70 vol% (0.34%). The techno-economic anal. for a 200 m3 per day syngas prodn. plant (at industrial scale) assured a pay back period of 4.8 (≈5) years with a min. profit margin of 142% when syngas selling price is set as 43 INR (0.52 USD) per kg.
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    Njuguna, F.; Ndiritu, H.; Gathitu, B.; Hawi, M.; Munyalo, J. Kinetic Modeling and Optimization of Process Parameters for Gasification of Macadamia Nutshells with Air Preheating: A Combined Use of Aspen Plus and Response Surface Methodology (RSM). Bioresour Technol. Rep 2023, 22, 101477,  DOI: 10.1016/j.biteb.2023.101477
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    Kinetic modeling and optimization of process parameters for gasification of macadamia nutshells with air preheating: A combined use of Aspen Plus and response surface methodology (RSM)
    Njuguna, Fredrick; Ndiritu, Hiram; Gathitu, Benson; Hawi, Meshack; Munyalo, Jotham
    Bioresource Technology Reports (2023), 22 (), 101477CODEN: BTRICJ; ISSN:2589-014X. (Elsevier Ltd.)
    This study used Aspen Plus process simulation for sensitivity anal. to identify the range of parameters for subsequent optimization using response surface methodol., to maximize syngas combustible gases and higher heating value (HHV) while minimizing tar. From the anal. of variance, equivalence ratio (ER) was the most significant parameter affecting H2 and CH4 prodn., HHV and tar content while pressure contributed the least. Air temp. influenced CO prodn. the most while ER had the least effect. For a pressurized gasifier operating at 4 atm, optimal ER and air temp. was 0.16 and 575 °C resp., producing syngas with HHV and tar content of 4.3 MJ/Nm3 and 23.68 g/Nm3 resp. Optimal ER and air temp. for atm. pressure gasifier were 0.15 and 445 °C resp., resulting in syngas with HHV and tar content of 4.14 MJ/Nm3 and 29.17 g/Nm3 resp. The simulation results were in good agreement with the exptl. data.
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    Solar Energy (1993), 51 (1), 19-25CODEN: SRENA4; ISSN:0038-092X.
    A kinetic model for biomass gasification was developed based on the mechanism of surface reactions. The apparent rate consts. were calcd. by minimizing the differences between exptl. data and theor. results for different residence times and different temps. The kinetic model was validated by comparing exptl. data with theor. results for different equivalence ratios; the simulations agree well with the exptl. data. Simulations modeling the influence of char particle size on the time required to achieve 90% C conversion agree with results of tests performed by other investigators. Simulations were performed to evaluate the effects of type of oxidant, residence time, char particle size, temp., pressure, equivalence ratio, and moisture on biomass gasification.
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    Zhang, H.; Okuyama, K.; Higuchi, S.; Soon, G.; Lisak, G.; Law, A. W. K. CFD-DEM Simulations of Municipal Solid Waste Gasification in a Pilot-Scale Direct-Melting Furnace. Waste Management 2023, 162, 43– 54,  DOI: 10.1016/j.wasman.2023.03.008
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    Waste Management (Oxford, United Kingdom) (2023), 162 (), 43-54CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
    A multiphase CFD-DEM model was built to simulate the waste-to-energy gasifying and direct melting furnace in a pilot demonstration facility. The characterizations of feedstocks, waste pyrolysis kinetics, and charcoal combustion kinetics were first obtained in the lab. and used as model inputs. The d. and heat capacity of waste and charcoal particles were then modelled dynamically under different status, compn., and temp. A simplified ash melting model was developed to track the final fate of waste particles. The simulation results were in good agreement with the site observations in both temp. and slag/fly-ash generations, verifying the CFD-DEM model settings and gas-particle dynamics. More importantly, the 3-D simulations quantified and visualized the individual functioning zones in the direct-melting gasifier as well as the dynamic changes throughout the whole lifetime of waste particles, which is otherwise tech. unachievable for direct plant observations. Hence, the study demonstrates that the established CFD-DEM model together with the developed simulation procedures can be used as a tool for the optimization of operating conditions and scaled-up design for future prototype waste-to-energy gasifying and direct melting furnace.
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    Salem, A. M.; Paul, M. C. CFD Modelling of Spatiotemporal Evolution of Detailed Tar Species in a Downdraft Gasifier. Biomass Bioenergy 2023, 168, 106656,  DOI: 10.1016/j.biombioe.2022.106656
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    CFD modelling of spatiotemporal evolution of detailed tar species in a downdraft gasifier
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    Biomass and Bioenergy (2023), 168 (), 106656CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
    The rising demand for renewable energy around the world has sparked interest in biomass gasification. However, the technol. greatly suffers because of tar species produced during the gasification process, which limits direct use of the produced gas. To address this issue, the paper presents a novel piece of work that focuses on the formation and evolution of tar species consisting of benzene, naphthalene, toluene, and phenol. A two-dimensional numerical model for a downdraft biomass gasifier is developed with a total of 20 thermochem. kinetic reactions to investigate the formation of tar species in the gasifier with the effect of residence time. The model's predictions are validated with the exptl. and kinetic data and found to be in good agreement. Besides, the model's ability to simulate the producer gas prodn. from a downdraft gasifier is examd. Reaction rates for volatiles decompn., combustion, and gasification reactions under different working conditions are investigated. Overall, benzene has the highest concn. of the selected tar species, followed by naphthalene, and with relatively modest amts. of phenol and toluene.
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    Faridi, I. K.; Tsotsas, E.; Heineken, W.; Koegler, M.; Kharaghani, A. Spatio-Temporal Prediction of Temperature in Fluidized Bed Biomass Gasifier Using Dynamic Recurrent Neural Network Method. Appl. Therm Eng. 2023, 219, 119334,  DOI: 10.1016/j.applthermaleng.2022.119334
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    Investigation of factors affecting performance of a downdraft fixed bed gasifier using optimized MLP neural networks approach
    Hashem Samadi, Seyed; Ghobadian, Barat; Nosrati, Mohsen; Rezaei, Mahdi
    Fuel (2023), 333 (Part_1), 126249CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Biomass gasification will be a competitive renewable technol. to meet the world's energy demand in the near future. However, extremely time-consuming and costly exptl. investigations are still required to achieve the best gasification performance. Machine learning through artificial neural networks can be considered as a convenient and low-cost tool for predicting and optimizing gasification conditions. In this paper, MLP neural network was used to develop a predictive model for the fixed bed gasification properties. Several MLP models were developed to predict the compn. of the produced gas and the lower heating value based on the physicochem. compn. of the biomass and the reactor operating conditions. The results showed that the MLP architecture with the Levenberg-Marquardt algorithm by considering the range of 47 to 57 neurons in the hidden layer and the tansig activation function had reasonable accuracy in predicting the outputs. Performance of the MLP proposed model showed good agreement between the output and target values with a coeff. of detn. of R2 >0.952, root mean squared error, RMSE < 0.83, and relative root mean squared error, rRMSE < 6.5%. In addn., according to the results obtained, the MLP indicated the highest precision to model the fixed bed gasification over the other methods. Finally, after the implementation of the model, the sensitivity anal. of input data on output data was performed. The modeling results of this study showed that the MLP model can effectively replace the costly exptl. tests to study the gasification process.

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  • Abstract

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    Figure 1

    Figure 1. Route map of biomass and wastewater conversion into products through gasification.

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    Figure 2

    Figure 2. Gasifier configurations: (a) downdraft, (b) updraft, and (c) fluidized bed gasifier. (d) Picture of condensed tar stuck to the downstream component of a gasifier at Indian Institute of Science.

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    Figure 3

    Figure 3. Maturation and temperature ranges of tar classes.

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    Figure 4

    Figure 4. Tar concentration of different classes as a function of dew point temperatures: class 2 (□), class 3 (▲), class 4 (●), and class 5 (◆).

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    Figure 5

    Figure 5. Box plot of tar concentrations for the various gasifier types.

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    Figure 6

    Figure 6. Box plot showing the effect of wood, waste (RDF/MSW), and agroresidue on the tar concentration for air as a gasifying medium.

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    Figure 7

    Figure 7. Typical gasification temperature for various feedstocks and its influence on a few parameters.

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    Figure 8

    Figure 8. Tar tolerance limits for downstream applications of a gasifier.

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    Figure 9

    Figure 9. Comparison of the tar removal performance of scrubber, ESP, and OLGA: heavy tar (black bar), light tar (red bar), heterocyclic (orange), and dew point (●).

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    Figure 10

    Figure 10. Catalyst materials for tar cracking.

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    Figure 11

    Figure 11. Specific energy inputs for various plasma sources used for tar destruction.

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  • References

    This article references 265 other publications.

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      Migliaccio, R.; Brachi, P.; Montagnaro, F.; Papa, S.; Tavano, A.; Montesarchio, P.; Ruoppolo, G.; Urciuolo, M. Sewage Sludge Gasification in a Fluidized Bed: Experimental Investigation and Modeling. Ind. Eng. Chem. Res. 2021, 60 (13), 5034– 5047,  DOI: 10.1021/acs.iecr.1c00084
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      Performance assessment of gasification reactors for sustainable management of municipal solid waste
      Chanthakett Apinya; Arif M T; Oo Aman M T; Khan M M K
      Journal of environmental management (2021), 291 (), 112661 ISSN:.
      The issue of waste management has received considerable critical attention due to the increase of waste generation worldwide. One of the solutions for waste disposal that has been widely implemented is through the use of the landfill due to its economic benefits. Landfill, however, results in many adverse impacts on the environment and human health. Recycling can extract some useful materials from waste, however not every waste can be recycled and a significant volume of waste, particularly the municipal solid waste (MSW) goes to landfill even though it has extractable energy potentials. Extraction of energy from MSW has been a key focus of research due to the scope of energy recovery, environmental and economic benefits. The principal concept of waste to energy is to convert waste into energy through thermal and/or biological processes. In addition, thermochemical processes such as gasification have been found as a promising technology offering several benefits. This paper presents a critical assessment of waste to energy gasification technology for MSW on processing, energy recovery, environmental performance and economic perspectives. These aspects have been analyzed for the landfill as well. The review also explored and identified suitable simulation tools for optimizing gasification. Subsequently, an assessment and comparison of different gasification reactors were carried out which indicate that the plasma gasification can be a feasible technology for MSW management due to higher energy efficiency (816 kWh/tonne) with minimum emission and lowest residue. Although plasma gasification is an energy intensive application which has relatively higher investment cost, it can be built as a large system (up to several 1000 MW system), which can make it economically competitive too. Other technologies such as; fluidized bed gasifier, fixed bed gasifier also have good energy efficiency (547-571 kWh/tonne) however, they contribute to higher CO2 emission. Considering overall waste management, it was found that gasification technology is beneficial to economy, environment and energy extraction compared to the landfill option. A number of tools and their relevant properties have been identified to develop appropriate gasifier model. It is expected that this study will advance further research and innovation that will be helpful to manage waste efficiently as well as to improve the environment.
    11. 11
      Wang, B.; Gupta, R.; Bei, L.; Wan, Q.; Sun, L. A Review on Gasification of Municipal Solid Waste (MSW): Syngas Production, Tar Formation, Mineral Transformation and Industrial Challenges. Int. J. Hydrogen Energy 2023, 48, 26676– 26706,  DOI: 10.1016/j.ijhydene.2023.03.086
      11
      A review on gasification of municipal solid waste (MSW): Syngas production, tar formation, mineral transformation and industrial challenges
      Wang, Ben; Gupta, Rajender; Bei, Lei; Wan, Qianmin; Sun, Lushi
      International Journal of Hydrogen Energy (2023), 48 (69), 26676-26706CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      This review provides an overview of the research progress related to syngas quality, tar formation, and minerals transformation. In addn., this paper gives a detailed description of the current technol. under construction and com. applications. On this basis, the challenges and prospects for the com. operation are outlined. In general, different gasification agents have crit. temps. and attention should be paid to the temp. window of 700-850°C, between which free energy of Boudouard reaction is lower than that of water-gas reaction. Above the crit. temp., the reverse water-gas shift reaction will be promoted to inhibit H2 release. Oxidant/municipal solid waste (MSW) ratio has an optimal value, which is esp. obvious for air atm. The optimal equivalence ratio is usually in the range of 0.1-0.4, and the LHV of the synthetic gas is in 4-10 MJ/m3. Steam to MSW ratio usually varies in a wide range and excess steam may have little impact on syngas quality. Simulation evaluation of parameter wt. shows steam to MSW ratio in steam atm. is the most important influencing factor, while temp. in air atm. plays a decisive role in the conversion of syngas. High temp. in the air atm. and low temp. in the steam atm. are the best choice for MSW gasification. The existence form of tar in different atmospheres is also quite different, such as PAHs in CO2 atmosphere and chain hydrocarbons in steam atm. The development of efficient catalyst gradually becomes a tech. bottleneck. Non-volatile minerals usually retain in bottom slag during MSW gasification. Elements with high b.ps. are existed in the form of metal, while heavy metals with low b.ps. are captured in the fly ash. The steam atm. can promote the volatilization of heavy metals. Most of the toxic heavy metals enter into the fly ash, so the leaching ability of the bottom slag is significantly weakened. Apart from tech. bottlenecks such as unstable syngas quality, catalyst deactivation, fouling and slagging, and MSW treatment capacity, great effort should be given to lower its investment cost and operation costs such as syngas purifn. and reforming. At the same time, energy price regulatory and policy barriers that affect the market should be addressed.
    12. 12
      Erdiwansyah; Gani, A.; Zaki, M.; Mamat, R.; Nizar, M.; Rosdi, S. M.; Yana, S.; Sarjono, R. E. Analysis of Technological Developments and Potential of Biomass Gasification as a Viable Industrial Process: A Review. Case Stud. Chem. Environ. Eng. 2023, 8, 100439,  DOI: 10.1016/j.cscee.2023.100439
      12
      Analysis of technological developments and potential of biomass gasification as a viable industrial process: A review
      Erdiwansyah; Gani, Asri; Zaki, M.; Mamat, Rizalman; Nizar, Muhammad; Rosdi, S. M.; Yana, Syaifuddin; Sarjono, R. E.
      Case Studies in Chemical and Environmental Engineering (2023), 8 (), 100439CODEN: CSCED5; ISSN:2666-0164. (Elsevier Ltd.)
      - They use technologies for the thermochem. conversion of substances for biomass, like pyrolysis, torrefaction, gasification, and hydrothermal process. In recent years, the generation of synthetic gas has significantly developed. This is esp. true when assocd. with the biomass gasification processes, primarily related to syngas prodn. The review focuses on technologies for cleaning syngas, gasification processes, and simulation methods on procedure parameters. In conclusion, prospect growths and opportunities are investigated, and discussions culminate with the presentation of a novel hydrogen fabrication strategy predicated on utilizing a modified combustion process that operates with such an air deficit.
    13. 13
      Mishra, S.; Upadhyay, R. K. Review on Biomass Gasification: Gasifiers, Gasifying Mediums, and Operational Parameters. Mater. Sci. Energy Technol. 2021, 4, 329– 340,  DOI: 10.1016/j.mset.2021.08.009
      13
      Review on biomass gasification: Gasifiers, gasifying mediums, and operational parameters
      Mishra, Somya; Upadhyay, Rajesh Kumar
      Materials Science for Energy Technologies (2021), 4 (), 329-340CODEN: MSETBW; ISSN:2589-2991. (Elsevier B.V.)
      A review. The burning of fossil fuels causes the av. global surface temp. to rise every year by 0.6 to 0.9 K between 1906 and 2005 causing massive ecol. imbalance and an increase in global warming as reported by Intergovernmental Panel on Climate Change (IPCC). Biomass gasification is an enhanced and mature technol. that has the capability of replacing fossil fuels. Despite the presence of vast literature, biomass technol. still needs improvement. This paper discusses the crit. overview of biomass gasification, the technologies embedded, and the deciding parameters for producing valuable products such as syngas, bio-fuels, bio-char, power, heat, and fertilizer, which can be further utilized in power generation units, and fuel-cell technologies. The paper assimilates the information available in past studies of biomass gasification and presents a comprehensive of various gasifiers and gasifying mediums employed, followed by introducing supercrit. water (SCW) gasification. Future directions for readers are also discussed.
    14. 14
      Shivapuji, A. M.; Dasappa, S. Influence of Fuel Hydrogen Fraction on Syngas Fueled SI Engine: Fuel Thermo-Physical Property Analysis and in-Cylinder Experimental Investigations. Int. J. Hydrogen Energy 2015, 40 (32), 10308– 10328,  DOI: 10.1016/j.ijhydene.2015.06.062
      14
      Influence of fuel hydrogen fraction on syngas fueled SI engine: Fuel thermo-physical property analysis and in-cylinder experimental investigations
      Shivapuji, Anand M.; Dasappa, S.
      International Journal of Hydrogen Energy (2015), 40 (32), 10308-10328CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Hydrogen, either in pure form or as a gaseous fuel mixt. specie enhances the fuel conversion efficiency and reduce emissions in an internal combustion engine. This is due to the redn. in combustion duration attributed to higher laminar flame speeds. Hydrogen is also expected to increase the engine convective heat flux, attributed (directly or indirectly) to parameters like higher adiabatic flame temp., laminar flame speed, thermal cond. and diffusivity and lower flame quenching distance. These factors (adversely) affect the thermo-kinematic response and offset some of the benefits. The current work addresses the influence of mixt. hydrogen fraction in syngas on the engine energy balance and the thermo-kinematic response for close to stoichiometric operating conditions. Four different bio-derived syngas compns. with fuel calorific value varying from 3.14 MJ/kg to 7.55 MJ/kg and air fuel mixt. hydrogen fraction varying from 7.1% to 14.2% by vol. are used. The anal. comprises of (a) use of chem. kinetics simulation package CHEMKIN for quantifying the thermo-phys. properties (b) 0-D model for engine in-cylinder anal. and (c) in-cylinder investigations on a two-cylinder engine in open loop cooling mode for quantifying the thermo-kinematic response and engine energy balance.With lower adiabatic flame temp. for Syngas, the in-cylinder heat transfer anal. suggests that temp. has little effect in terms of increasing the heat flux. For typical engine like conditions (700 K and 25 bar at CR of 10), the laminar flame speed for syngas exceeds that of methane (55.5 cm/s) beyond mixt. hydrogen fraction of 11% and is attributed to the increase in H based radicals. This leads to a redn. in the effective Lewis no. and laminar flame thickness, potentially inducing flame instability and cellularity.Use of a thermodn. model to assess the isolated influence of thermal cond. and diffusivity on heat flux suggests an increase in the peak heat flux between 2% and 15% for the lowest (0.420 MW/m2) and highest (0.480 MW/m2) hydrogen contg. syngas over methane (0.415 MW/m2) fueled operation. Exptl. investigations indicate the engine cooling load for syngas fueled engine is higher by about 7% and 12% as compared to methane fueled operation; the losses are seen to increase with increasing mixt. hydrogen fraction. Increase in the gas to electricity efficiency is obsd. from 18% to 24% as the mixt. hydrogen fraction increases from 7.1% to 9.5%. Further increase in mixt. hydrogen fraction to 14.2% results in the redn. of efficiency to 23%; argued due to the changes in the initial and terminal stages of combustion. On doubling of mixt. hydrogen fraction, the flame kernel development and fast burn phase duration decrease by about 7% and 10% resp. and the terminal combustion duration, corresponding to 90%-98% mass burn, increases by about 23%. This increase in combustion duration arises from the cooling of the near wall mixt. in the boundary layer attributed to the presence of hydrogen. The enhancement in engine cooling load and subsequent redn. in the brake thermal efficiency with increasing hydrogen fraction is evident from the engine energy balance along with the cumulative heat release profiles.
    15. 15
      Moriconi, N.; Laranci, P.; D’Amico, M.; Bartocci, P.; D’Alessandro, B.; Cinti, G.; Baldinelli, A.; Discepoli, G.; Bidini, G.; Desideri, U.; Cotana, F.; Fantozzi, F. Design and Preliminary Operation of a Gasification Plant for Micro-CHP with Internal Combustion Engine and SOFC. Energy Procedia 2015, 81, 298– 308,  DOI: 10.1016/j.egypro.2015.12.100
      15
      Design and Preliminary Operation of a Gasification Plant for Micro-CHP with Internal Combustion Engine and SOFC
      Moriconi, N.; Laranci, P.; D'Amico, M.; Bartocci, P.; D'Alessandro, B.; Cinti, G.; Baldinelli, A.; Discepoli, G.; Bidini, G.; Desideri, U.; Cotana, F.; Fantozzi, F.
      Energy Procedia (2015), 81 (), 298-308CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
      A gasification plant was designed and built to test syngas prodn. from biomass for electricity generation on microscale. The plant is mainly composed by a downdraft reactor, a gas cleaning section with a cyclone and a wet scrubber, a blower for syngas extn. and an ICE (Internal Combustion Engine, Lombardini LGA 340), equipped with an alternator. A small quantity of producer was also eventually sent to a button cell SOFC (Solid Oxide Fuel Cell) for preliminary characterization. The plant was tested in a preliminary exptl. campaign to evaluate mass and energy balances and process efficiency. Woody biomass was used and the producer gas firstly passed through impingers bottles, to condense and measure tar concn. (according to CEN/TS 15439), and then the remaining uncondensed gas was analyzed with a micro-GC (Gas Chromatograph). The paper presents and discusses the results of the preliminary tests carried out.
    16. 16
      Sridhar, H. V.; Sridhar, G.; Dasappa, S.; Paul, P. J.; Mukunda, H. S. On the Operation of a High Pressure Biomass Gasifier with Gas Turbine; In Proceedings of the 15th European Biomass Conference Paper and Exhibition, Berlin, Germany, May 7–11, 2007; ETA-Florence Renewable Energies: Florence, Italy, 2007.
      There is no corresponding record for this reference.
    17. 17
      Proceedings of the 10th Asian Mining Congress 2023: Roadmap for Best Mining Practices Vis-À-VIS Global Transformation; Sinha, A., Sarkar, B. C., Mandal, P. K., Eds.; Springer Proceedings in Earth and Environmental Sciences; Springer, 2023.
      There is no corresponding record for this reference.
    18. 18
      Handbook of Climate Change Mitigation; Chen, W. Y., Seiner, J., Suzuki, T., Lackner, M., Eds.; Springer, 2012.  DOI: 10.1007/978-1-4419-7991-9 .
      There is no corresponding record for this reference.
    19. 19
      Sikarwar, V. S.; Zhao, M.; Clough, P.; Yao, J.; Zhong, X.; Memon, M. Z.; Shah, N.; Anthony, E. J.; Fennell, P. S. An Overview of Advances in Biomass Gasification. Energy Environ. Sci. 2016, 9, 2939,  DOI: 10.1039/C6EE00935B
      19
      An overview of advances in biomass gasification
      Sikarwar, Vineet Singh; Zhao, Ming; Clough, Peter; Yao, Joseph; Zhong, Xia; Memon, Mohammad Zaki; Shah, Nilay; Anthony, Edward J.; Fennell, Paul S.
      Energy & Environmental Science (2016), 9 (10), 2939-2977CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      Biomass gasification is a widely used thermochem. process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technol. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modeling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technol. into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technol. advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technol.
    20. 20
      Sharma, M.; N, R.; Dasappa, S. Solid Oxide Fuel Cell Operating with Biomass Derived Producer Gas: Status and Challenges. Renewable Sustainable Energy Rev. 2016, 60, 450– 463,  DOI: 10.1016/j.rser.2016.01.075
      20
      Solid oxide fuel cell operating with biomass derived producer gas: Status and challenges
      Sharma, Monikankana; N, Rakesh; Dasappa, S.
      Renewable & Sustainable Energy Reviews (2016), 60 (), 450-463CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      Solid oxide fuel cell as a conversion device is finding importance in the energy sector due to its high efficiency, low emissions and fuel flexibility. The use of producer gas as a fuel is gaining importance due to certain advantages over the conventional fuels while challenges lie in its usage due to the inherent contaminants present. This paper consolidates the efforts carried out using fossil fuels and highlights the challenges, and further, the progress made in the use of producer gas is critically examd. The effects of contaminants such as tar, particulate matter, H2S etc. on anode materials are highlighted, and the published results are consolidated to examine whether the max. tolerance limits of the contaminants be identified. However, it is obsd. that due to many inexorable factors viz., differences in the electrode material, microstructure, diverse operating conditions, the conclusions obtained are diverse and it is difficult to predict the general behavior of a particular contaminant. The need for a comprehensive study having both exptl. and theor. components focusing on the role of contaminants under the same operating conditions and using the same materials is highlighted as a major conclusion of this study.
    21. 21
      Hofmann, P.; Panopoulos, K. D.; Aravind, P. V.; Siedlecki, M.; Schweiger, A.; Karl, J.; Ouweltjes, J. P.; Kakaras, E. Operation of Solid Oxide Fuel Cell on Biomass Product Gas with Tar Levels > 10 g Nm −3. Int. J. Hydrogen Energy 2009, 34 (22), 9203– 9212,  DOI: 10.1016/j.ijhydene.2009.07.040
      21
      Operation of solid oxide fuel cell on biomass product gas with tar levels >10 g Nm-3
      Hofmann, Ph.; Panopoulos, K. D.; Aravind, P. V.; Siedlecki, M.; Schweiger, A.; Karl, J.; Ouweltjes, J. P.; Kakaras, E.
      International Journal of Hydrogen Energy (2009), 34 (22), 9203-9212CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      This work assesses exptl. the feasibility of feeding a high tar load product gas from biomass gasification to a planar solid oxide fuel cell (SOFC) for renewable electricity generation. The SOFC had a nickel gadolinium-doped ceria anode (Ni-GDC) and the gasifier was a pilot scale circulating fluidized bed, employing hot gas-cleaning to remove particulates, HCl and H2S. The SOFC operated for several hours on either pre-reformed gas (reduced tar levels < 0.5 g Nm-3) as well as on high tar-laden wood gas (tar levels > 10 g Nm-3) i.e. with no pre-reforming of tars. The tests were carried out at low fuel utilization Uf of around 20% at a c.d. j = 130 mA cm-2. In all cases stable continuous SOFC performance was established. Post exptl. examn. of the SOFC showed that the anode was not affected by carbon deposition or other impurity accumulation.
    22. 22
      Costa, P.; Pinto, F.; André, R. N.; Marques, P. Integration of Gasification and Solid Oxide Fuel Cells (SOFCs) for Combined Heat and Power (CHP). Processes 2021, 9, 254,  DOI: 10.3390/pr9020254
      22
      Integration of gasification and solid oxide fuel cells (SOFCs) for combined heat and power (CHP)
      Costa, Paula; Pinto, Filomena; Andre, Rui Neto; Marques, Paula
      Processes (2021), 9 (2), 254CODEN: PROCCO; ISSN:2227-9717. (MDPI AG)
      This paper reviews the most recent information about the main operations to produce energy from carbonaceous materials, namely biomass and wastes through the integration of gasification, syngas cleaning and solid oxide fuel cells (SOFCs), which have shown to be a good option for combined heat and power (CHP) prodn., due to high efficiency and low environmental impact. However, some challenges still need to be overcome, mainly when mixed feedstocks with high contents of hazardous contaminants are used, thus syngas cleaning and conditioning is of major importance. Another drawback is SOFC operation, hence new materials esp. for the anode has been proposed and tested. An overall process to produce CHP by gasification integration with SOFC is proposed.
    23. 23
      Recalde, M.; Woudstra, T.; Aravind, P. V. Gasifier, Solid Oxide Fuel Cell Integrated Systems for Energy Production From Wet Biomass. Front Energy Res. 2019, 7, 129,  DOI: 10.3389/fenrg.2019.00129
      There is no corresponding record for this reference.
    24. 24
      Karl, J.; Frank, N.; Karellas, S.; Saule, M.; Hohenwarter, U. Hohenwarter Ulrich. Conversion of Syngas From Biomass in Solid Oxide Fuel Cells. J. Fuel Cell Sci. Technol. 2009, 6, 021005,  DOI: 10.1115/1.2971172
      24
      Conversion of syngas from biomass in solid oxide fuel cells
      Karl, Jurgen; Frank, Nadine; Karellas, Sotirios; Saule, Mathilde; Hohenwarter, Ulrich
      Journal of Fuel Cell Science and Technology (2009), 6 (2), 021005/1-021005/6CODEN: JFCSAU; ISSN:1550-624X. (American Society of Mechanical Engineers)
      Conversion of biomass in syngas by means of indirect gasification offers the option to improve the economic situation of any fuel cell system due to lower costs for feedstock and higher power revenues in many European countries. The coupling of an indirect gasification of biomass and residues with highly efficient solid oxide fuel cell (SOFC) systems is therefore a promising technol. for reaching economic feasibility of small decentralized combined heat and power prodn. (CHP). The predicted efficiency of common high temp. fuel cell systems with integrated gasification of solid feedstock is usually significantly lower than the efficiency of fuel cells operated with hydrogen or methane. Addnl. system components like the gasifier as well as the gas cleaning reduce this efficiency. Hence common fuel cell systems with integrated gasification of biomass will hardly reach elec. efficiencies above 30%. An extraordinary efficient combination is achieved in case that the fuel cells waste heat is used in an indirect gasification system. A simple combination of a SOFC and an allothermal gasifier enables then elec. efficiencies above 50%. However, this system requires an innovative cooling concept for the fuel cell stack. Another significant question is the influence of impurities on the fuel cell degrdn. The European Research Project "BioCellus" focuses on both questions-the influence of the biogenous syngas on the fuel cells and an innovative cooling concept based on liq. metal heat pipes. First expts. showed that, in particular, higher hydrocarbons-the so-called tars-do not have any significant influence on the performance of SOFC membranes. The innovative concept of the TopCycle comprises to heat an indirect gasifier with the exhaust heat of the fuel cell by means of liq. metal heat-pipes. Internal cooling of the stack and the recirculation of waste heat increases the system efficiency significantly. This concept promises elec. efficiencies of above 50% even for small-scale systems without any combined processes.
    25. 25
      Song, H.; Yang, G.; Xue, P.; Li, Y.; Zou, J.; Wang, S.; Yang, H.; Chen, H. Recent Development of Biomass Gasification for H2 Rich Gas Production. Appl. Energy Combustion Sci. 2022, 10, 100059,  DOI: 10.1016/j.jaecs.2022.100059
      There is no corresponding record for this reference.
    26. 26
      Alptekin, F. M.; Celiktas, M. S. Review on Catalytic Biomass Gasification for Hydrogen Production as a Sustainable Energy Form and Social, Technological, Economic, Environmental, and Political Analysis of Catalysts. ACS Omega. 2022, 7, 24918– 24941,  DOI: 10.1021/acsomega.2c01538
      26
      Review on Catalytic Biomass Gasification for Hydrogen Production as a Sustainable Energy Form and Social, Technological, Economic, Environmental, and Political Analysis of Catalysts
      Alptekin, Fikret Muge; Celiktas, Melih Soner
      ACS Omega (2022), 7 (29), 24918-24941CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      A review. Sustainable energy prodn. is a worldwide concern due to the adverse effects and limited availability of fossil fuels, requiring the development of suitable environmentally friendly alternatives. Hydrogen is considered a sustainable future energy source owing to its unique properties as a clean and nontoxic fuel with high energy yield and abundance. Hydrogen can be produced through renewable and nonrenewable sources where the prodn. method and feedstock used are indicators of whether they are carbon-neutral or not. Biomass is one of the renewable hydrogen sources that is also available in large quantities and can be used in different conversion methods to produce fuel, heat, chems., etc. Biomass gasification is a promising technol. to generate carbon-neutral hydrogen. However, tar prodn. during this process is the biggest obstacle limiting hydrogen prodn. and commercialization of biomass gasification technol. This review focuses on hydrogen prodn. through catalytic biomass gasification. The effect of different catalysts to enhance hydrogen prodn. is reviewed, and social, technol., economic, environmental, and political (STEEP) anal. of catalysts is carried out to demonstrate challenges in the field and the development of catalysts.
    27. 27
      Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G. A Review of the Primary Measures for Tar Elimination in Biomass Gasification Processes. Biomass Bioenergy 2003, 24 (2), 125– 140,  DOI: 10.1016/S0961-9534(02)00102-2
      27
      A review of the primary measures for tar elimination in biomass gasification processes
      Devi, Lopamudra; Ptasinski, Krzysztof J.; Janssen, Frans J. J. G.
      Biomass and Bioenergy (2003), 24 (2), 125-140CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
      A review. Tar formation is one of the major problems to deal with during biomass gasification. Tar condenses at reduced temp., thus blocking and fouling process equipments such as engines and turbines. Considerable efforts have been directed on tar removal from fuel gas. Tar removal technologies can broadly be divided into two approaches; hot gas cleaning after the gasifier (secondary methods), and treatments inside the gasifier (primary methods). Although secondary methods are proven to be effective, treatments inside the gasifier are gaining much attention as these may eliminate the need for downstream cleanup. In primary treatment, the gasifier is optimized to produce a fuel gas with min. tar concn. The different approaches of primary treatment are (a) proper selection of operating parameters, (b) use of bed additive/catalyst, and (c) gasifier modifications. The operating parameters such as temp., gasifying agent, equivalence ratio, residence time, etc. play an important role in formation and decompn. of tar. There is a potential of using some active bed additives such as dolomite, olivine, char, etc. inside the gasifier. Ni-based catalyst are reported to be very effective not only for tar redn., but also for decreasing the amt. of nitrogenous compds. such as ammonia. Also, reactor modification can improve the quality of the product gas. The concepts of two-stage gasification and secondary air injection in the gasifier are of prime importance. Some aspects of primary methods and the research and development in this area are reviewed and cited in the present paper.
    28. 28
      Asadullah, M. Barriers of Commercial Power Generation Using Biomass Gasification Gas: A Review. Renewable and Sustainable Energy Reviews 2014, 29, 201– 215,  DOI: 10.1016/j.rser.2013.08.074
      28
      Barriers of commercial power generation using biomass gasification gas: A review
      Asadullah, Mohammad
      Renewable & Sustainable Energy Reviews (2014), 29 (), 201-215CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Gasification is one of the promising technologies to convert biomass to gaseous fuels for distributed power generation. However, the com. exploitation of biomass energy suffers from a no. of logistics and technol. challenges. In this review, the barriers in each of the steps from the collection of biomass to electricity generation are highlighted. The effects of parameters in supply chain management, pretreatment and conversion of biomass to gas, and cleaning and utilization of gas for power generation are discussed. Based on the studies, until recently, the gasification of biomass and gas cleaning are the most challenging part. For electricity generation, either using engine or gas turbine requires a stringent specification of gas compn. and tar concn. in the product gas. Different types of updraft and downdraft gasifiers have been developed for gasification and a no. of phys. and catalytic tar sepn. methods have been investigated. However, the most efficient and popular one is yet to be developed for com. purpose. In fact, the efficient gasification and gas cleaning methods can produce highly burnable gas with less tar content, so as to reduce the total consumption of biomass for a desired quantity of electricity generation. According to the recent report, an advanced gasification method with efficient tar cleaning can significantly reduce the biomass consumption, and thus the logistics and biomass pretreatment problems can be ultimately reduced.
    29. 29
      Meng, X. Biomass Gasification: The Understanding of Sulfur, Tar, and Char Reaction in Fluidized Bed Gasifiers. Doctoral Thesis, Tianjin University, Tianjin, China, 2012.
      There is no corresponding record for this reference.
    30. 30
      Abdoulmoumine, N.; Adhikari, S.; Kulkarni, A.; Chattanathan, S. A Review on Biomass Gasification Syngas Cleanup. Appl. Energy 2015, 155, 294– 307,  DOI: 10.1016/j.apenergy.2015.05.095
      30
      A review on biomass gasification syngas cleanup
      Abdoulmoumine, Nourredine; Adhikari, Sushil; Kulkarni, Avanti; Chattanathan, Shyamsundar
      Applied Energy (2015), 155 (), 294-307CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
      Energy, fuel and chem. prodn. from biomass is increasingly attracting interest in the world. Gasification of biomass can produce raw syngas which contains CO, CO2, H2 and CH4. In addn., raw syngas contains minor but significant quantities of undesirable impurities - collectively known as syngas contaminants. Syngas contaminants are composed of tars, nitrogen based compds. (NH3, HCN, etc.), sulfur based compds. (H2S, COS, etc.), hydrogen halides (HCl, HF, etc.) and trace metals (Na, K, etc.). Raw syngas cleanup is an essential step prior to syngas utilization in downstream applications. In recent years, significant research attention has been devoted to syngas cleanup to reduce contaminants below tolerable limits. The present paper is a comprehensive review of cold gas and hot gas syngas cleanup for major contaminants in syngas (tar, NH3, H2S, HCl and trace metals). This review organizes and discusses investigations on syngas for all major contaminants, critically reviews important challenges in syngas cleanup and discusses recent advancements in hot and cold gas cleanup.
    31. 31
      Rakesh N; Dasappa, S. A Critical Assessment of Tar Generated during Biomass Gasification - Formation, Evaluation, Issues and Mitigation Strategies. Renewable Sustainable Energy Rev. 2018, 91, 1045– 1064,  DOI: 10.1016/j.rser.2018.04.017
      31
      A critical assessment of tar generated during biomass gasification - Formation, evaluation, issues and mitigation strategies
      Rakesh N; Dasappa, S.
      Renewable & Sustainable Energy Reviews (2018), 91 (), 1045-1064CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      Biomass gasification receives attention as a promising method to utilize biomass, a fuel which is carbon neutral. The producer gas/syngas which is an energy carrier obtained through this method finds use in engines, fuel cells, Fischer-Tropsch reactors, methanol synthesis and as an input for chem. industries, after the required quality levels for the above applications are achieved. To use the producer gas/syngas for power generation on a com. scale, the required gas quality has to be established. Producer gas obtained from biomass gasification has several contaminants like particulate matter, tar and gaseous species like H2S, NH3. The contaminants present in the producer gas, depending upon their nature and the amt., pose issues to power generation systems. Tar, which is a mixt. of varying mol. wt. hydrocarbon mols., generated from the thermo-chem. conversion processes of org. materials, could condense at low temps., and lead to clogging or blockage in end-use application devices, filters, and fuel lines. So, it is essential to reduce or transform the tar present in the producer gas to utilize the biomass gasification systems for power generation. This paper attempts to provide a crit. assessment of tar generated during biomass gasification, covering the sundry aspects of formation, evaluation, issues and mitigation strategies. The paper gives an introduction to biomass gasification systems, followed by a detailed description of tar, including the definition and the chem. of formation and destruction. An explanation of the various aspects of tar sampling, characterization and anal., is presented next. The suitability of different tar anal. approaches is compared from an end-use device perspective. Then the multifarious issues posed by the presence of tar in the syngas on the end-use devices is discussed. The last part of the paper describes several tar mitigation strategies used by researchers.
    32. 32
      Balas, M.; Lisy, M.; Kubicek, J.; Pospisil, J. Syngas Cleaning by Wet Scrubber. WSEAS Trans. Heat Mass Transfer 2014, 9, 195– 204
      There is no corresponding record for this reference.
    33. 33
      Basu, P. Biomass Gasification and Pyrolysis: Practical Design and Theory; Academic Press, 2010.  DOI: 10.1016/C2009-0-20099-7 .
      There is no corresponding record for this reference.
    34. 34
      Kinoshita, C. M.; Wang, Y.; Zhou, J. Tar Formation under Different Biomass Gasification Conditions. J. Anal Appl. Pyrolysis 1994, 29, 169– 181,  DOI: 10.1016/0165-2370(94)00796-9
      34
      Tar formation under different biomass gasification conditions
      Kinoshita, C. M.; Wang, Y.; Zhou, J.
      Journal of Analytical and Applied Pyrolysis (1994), 29 (2), 169-81CODEN: JAAPDD; ISSN:0165-2370.
      Parametric tests on tar formation, varying temp., equivalence ratio, and residence time, were performed on a bench-scale, indirectly-heated fluidized bed gasifier. Prepd. tar samples were analyzed in a gas chromatograph (GC) with a flame ionization detector, using a capillary column. Std. test mixts. contg. the dominant tar species were prepd. for GC calibration. The identified peaks included single-ring hydrocarbons, such as benzene, to five-ring hydrocarbons, such as perylene; these compds. represent about 70-90% (mass basis) of the tar constituents. The influences of the above-mentioned gasification parameters on tar formation were analyzed.
    35. 35
      Lv, P.; Yuan, Z.; Wu, C.; Ma, L.; Chen, Y.; Tsubaki, N. Bio-Syngas Production from Biomass Catalytic Gasification. Energy Convers Manag 2007, 48 (4), 1132– 1139,  DOI: 10.1016/j.enconman.2006.10.014
      35
      Bio-syngas production from biomass catalytic gasification
      Lv, Pengmei; Yuan, Zhenhong; Wu, Chuangzhi; Ma, Longlong; Chen, Yong; Tsubaki, Noritatsu
      Energy Conversion and Management (2007), 48 (4), 1132-1139CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      A promising application for biomass is liq. fuel synthesis, such as methanol or di-Me ether (DME). Previous studies have studied syngas prodn. from biomass-derived char, oil and gas. This study intends to explore the technol. of syngas prodn. from direct biomass gasification, which may be more economically viable. The ratio of H/CO is an important factor that affects the performance of this process. In this study, the characteristics of biomass gasification gas, such as H/CO and tar yield, as well as its potential for liq. fuel synthesis is explored. A fluidized bed gasifier and a downstream fixed bed are employed as the reactors. Two kinds of catalysts: dolomite and Ni based catalyst are applied, and they are used in the fluidized bed and fixed bed, resp. The gasifying agent used is an air-steam mixt. The main variables studied are temp. and wt. hourly space velocity in the fixed bed reactor. Over the ranges of operating conditions examd., the max. H content reaches 52.47 vol.%, while the ratio of H/CO varies between 1.87 and 4.45. The results indicate that an appropriate temp. (750° for this study) and more catalyst are favorable for getting a higher H/CO ratio. Using a simple 1st order kinetic model for the overall tar removal reaction, the apparent activation energies and pre-exponential factors are obtained for nickel based catalysts. The results indicate that biomass gasification gas has great potential for liq. fuel synthesis after further processing.
    36. 36
      Anis, S.; Zainal, Z. A. Tar Reduction in Biomass Producer Gas via Mechanical, Catalytic and Thermal Methods: A Review. Renewable and Sustainable Energy Reviews 2011, 15 (5), 2355– 2377,  DOI: 10.1016/j.rser.2011.02.018
      36
      Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review
      Anis, Samsudin; Zainal, Z. A.
      Renewable & Sustainable Energy Reviews (2011), 15 (5), 2355-2377CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compns., which is assocd. with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar redn. are discussed.
    37. 37
      Zhang, W.; Liu, H.; Ul Hai, I.; Neubauer, Y.; Schröder, P.; Oldenburg, H.; Seilkopf, A.; Kolling, A. Gas Cleaning Strategies for Biomass Gasification Product Gas. International Journal of Low-Carbon Technologies 2012, 7 (2), 69– 74,  DOI: 10.1093/ijlct/ctr046
      37
      Gas cleaning strategies for biomass gasification product gas
      Zhang, Wenbin; Liu, Hao; Ul Hai, Irfan; Neubauer, York; Schroeder, Philipp; Oldenburg, Holger; Seilkopf, Alexander; Koelling, Axel
      International Journal of Low-Carbon Technologies (2012), 7 (2), 69-74CODEN: IJLTAR; ISSN:1748-1317. (Oxford University Press)
      A review. In general, the raw product gas of biomass gasification contains a range of minor species and contaminants, including particles, tar, alkali metals, chlorine, nitrogen compds. and sulfur compds. This study reviews the recent developments in product gas cleaning technologies for these species and summarizes the findings of the research project Mop fan and electrofilter: an innovative approach for cleaning product gases from biomass gasification' which was recently carried out by the authors. The results of the project showed that combination of mop fan and electrofilter (ESP) has great potential in removing fine particles, tars and chem. contaminants in the product gas.
    38. 38
      Adamovich, I.; Baalrud, S. D.; Bogaerts, A.; Bruggeman, P. J.; Cappelli, M.; Colombo, V.; Czarnetzki, U.; Ebert, U.; Eden, J. G.; Favia, P.; Graves, D. B.; Hamaguchi, S.; Hieftje, G.; Hori, M.; Kaganovich, I. D.; Kortshagen, U.; Kushner, M. J.; Mason, N. J.; Mazouffre, S.; Thagard, S. M.; Metelmann, H. R.; Mizuno, A.; Moreau, E.; Murphy, A. B.; Niemira, B. A.; Oehrlein, G. S.; Petrovic, Z. L.; Pitchford, L. C.; Pu, Y. K.; Rauf, S.; Sakai, O.; Samukawa, S.; Starikovskaia, S.; Tennyson, J.; Terashima, K.; Turner, M. M.; Van De Sanden, M. C. M.; Vardelle, A. The 2017 Plasma Roadmap: Low Temperature Plasma Science and Technology. J. Phys. D Appl. Phys. 2017, 50 (32), 323001,  DOI: 10.1088/1361-6463/aa76f5
      38
      The 2017 Plasma Roadmap: Low temperature plasma science and technology
      Adamovich, I.; Baalrud, S. D.; Bogaerts, A.; Bruggeman, P. J.; Cappelli, M.; Colombo, V.; Czarnetzki, U.; Ebert, U.; Eden, J. G.; Favia, P.; Graves, D. B.; Hamaguchi, S.; Hieftje, G.; Hori, M.; Kaganovich, I. D.; Kortshagen, U.; Kushner, M. J.; Mason, N. J.; Mazouffre, S.; Thagard, S. Mededovic; Metelmann, H.-R.; Mizuno, A.; Moreau, E.; Murphy, A. B.; Niemira, B. A.; Oehrlein, G. S.; Petrovic, Z. Lj.; Pitchford, L. C.; Pu, Y.-K.; Rauf, S.; Sakai, O.; Samukawa, S.; Starikovskaia, S.; Tennyson, J.; Terashima, K.; Turner, M. M.; van de Sanden, M. C. M.; Vardelle, A.
      Journal of Physics D: Applied Physics (2017), 50 (32), 323001/1-323001/46CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)
      Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temp. plasma science and technol. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temp. plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temp. plasma field in the development of plasmas as an enabling technol. for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technol. challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.
    39. 39
      Bogaerts, A.; Neyts, E. C. Plasma Technology: An Emerging Technology for Energy Storage. ACS Energy Lett. 2018, 3 (4), 1013– 1027,  DOI: 10.1021/acsenergylett.8b00184
      39
      Plasma Technology: An Emerging Technology for Energy Storage
      Bogaerts, Annemie; Neyts, Erik C.
      ACS Energy Letters (2018), 3 (4), 1013-1027CODEN: AELCCP; ISSN:2380-8195. (American Chemical Society)
      Plasma technol. is gaining increasing interest for gas conversion applications, such as CO2 conversion into value-added chems. or renewable fuels, and N2 fixation from the air, to be used for the prodn. of small building blocks for, e.g., mineral fertilizers. Plasma is generated by elec. power and can easily be switched on/off, making it, in principle, suitable for using intermittent renewable electricity. In this Perspective article, we explain why plasma might be promising for this application. We briefly present the most common types of plasma reactors with their characteristic features, illustrating why some plasma types exhibit better energy efficiency than others. We also highlight current research in the fields of CO2 conversion (including the combined conversion of CO2 with CH4, H2O, or H2) as well as N2 fixation (for NH3 or NOx synthesis). Finally, we discuss the major limitations and steps to be taken for further improvement.
    40. 40
      Gimžauskaitė, D.; Aikas, M.; Tamošiu̅nas, A. Recent Progress in Thermal Plasma Gasification of Liquid and Solid Wastes. Recent Adv. Renewable Energy Technol. 2022, 2, 155– 196,  DOI: 10.1016/B978-0-12-823532-4.00007-0
      There is no corresponding record for this reference.
    41. 41
      Sanjaya, E.; Abbas, A. Plasma Gasification as an Alternative Energy-from-Waste (EFW) Technology for the Circular Economy: An Environmental Review. Resour., Conserv. Recycl. 2023, 189, 106730,  DOI: 10.1016/j.resconrec.2022.106730
      There is no corresponding record for this reference.
    42. 42
      Mukunda, H. S. Understanding Clean Energy and Fuels from Biomass; Wiley, 2010.
      There is no corresponding record for this reference.
    43. 43
      Dasappa, S. Potential of Biomass Energy for Electricity Generation in Sub-Saharan Africa. Energy for Sustainable Development 2011, 15 (3), 203– 213,  DOI: 10.1016/j.esd.2011.07.006
      There is no corresponding record for this reference.
    44. 44
      Dasappa, S.; Paul, P. J.; Mukunda, H. S.; Rajan, N. K. S.; Sridhar, G.; Sridhar, H. V. Biomass Gasification Technology-a Route to Meet Energy Needs. Curr. Sci. 2004, 87 (7), 908– 916
      44
      Biomass gasification technology - a route to meet energy needs
      Dasappa, S.; Paul, P. J.; Mukunda, H. S.; Rajan, N. K. S.; Sridhar, G.; Sridhar, H. V.
      Current Science (2004), 87 (7), 908-916CODEN: CUSCAM; ISSN:0011-3891. (Current Science Association)
      A review. The paper addresses a distributed power generation system that has evolved at the Indian Institute of Science, Bangalore. The technol. and field-related experience pertaining to open top re-burn down draft biomass gasification system coupled with the internal combustion engine or thermal device are brought out. The gasifier reactor design uses dual air entry - air nozzles and open top to help in establishing a thick high temp. zone to remove the contaminants in the product gas; a gas clean-up system to further refine the gas to ultra-pure quality. These elements are integrated with other sub-systems, namely feedstock prepn., ash handling, water treatment, process automation and other accessories to form an Independent Power Producer. Based on this technol. there are over 30 units operating in-India and abroad, with an accumulated capacity of over 20 MW. Over 80,000 h of operation of these systems have resulted in a saving of about 350 tons of fossil fuel, implying a saving of about 1120 tons of CO2 - a promising candidate for Clean Development Mechanisms (CDMs), other than redn. in toxic gases like NOx and SOx.
    45. 45
      Ravindranath, N. H.; Somashekar, H. I.; Dasappa, S.; Reddy, C. N. J. Sustainable Biomass Power for Rural India: Case Study of Biomass Gasifier for Village Electrification. Curr. Sci. 2004, 87 (7), 932– 941
      There is no corresponding record for this reference.
    46. 46
      Sandeep, K.; Dasappa, S. First and Second Law Thermodynamic Analysis of Air and Oxy-Steam Biomass Gasification. Int. J. Hydrogen Energy 2014, 39 (34), 19474– 19484,  DOI: 10.1016/j.ijhydene.2014.09.134
      46
      First and second law thermodynamic analysis of air and oxy-steam biomass gasification
      Sandeep, K.; Dasappa, S.
      International Journal of Hydrogen Energy (2014), 39 (34), 19474-19484CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Gasification is an energy transformation process in which solid fuel undergoes thermochem. conversion to produce gaseous fuel, and the two most important criteria involved in such process to evaluate the performance, economics, and sustainability of the technol. are: the total available energy (exergy) and the energy conserved (energy efficiency). Current study focuses on the energy and exergy anal. of the oxy-steam gasification and comparing with air gasification to optimize the H2 yield, efficiency and syngas energy d. Casuarina wood is used as a fuel, and mixt. of oxygen and steam in different proportion and amt. are used as a gasifying media. The results are analyzed with respect to varying equivalence ratio and steam to biomass ratio (SBR). Elemental mass balance technique is employed to ensure the validity of results. First and second law thermodn. anal. is used towards time evaluation of energy and exergy anal. Different component of energy input and output has been studied carefully to understand the effect of varying SBR on the availability of energy and irreversibility in the system to minimize the losses with change in input parameters for optimum performance. The energy and exergy losses (irreversibility) for oxy-steam gasification system are compared with the results of air gasification, and losses are found to be lower in oxy-steam thermal conversion; which has been argued and reasoned due to the presence of N2 in the air-gasification. The max. exergy efficiency of 85% with energy efficiency of 82% is achieved at SBR of 0.75 on the molar basis. It has been obsd. that increase in SBR results in lower exergy and energy efficiency, and it is argued to be due to the high energy input in steam generation and subsequent losses in the form of phys. exergy of steam in the product gas, which alone accounts for over 18% in exergy input and 8.5% in exergy of product gas at SBR of 2.7. Carbon boundary point (CBP), is identified at the SBR of 1.5, and water gas shift (WGS) reaction plays a crucial role in H2 enrichment after carbon boundary point (CBP) is reached. Effects of SBR and CBP on the H2/CO ratio is analyzed and discussed from the perspective of energy as well as the reaction chem. Energy d. of syngas and energy efficiency is favored at lower SBR but higher SBR favors H2 rich gas at the expense of efficiency.
    47. 47
      Sandeep, K.; Dasappa, S. Oxy–Steam Gasification of Biomass for Hydrogen Rich Syngas Production Using Downdraft Reactor Configuration. Int. J. Energy Res. 2014, 38 (2), 174– 188,  DOI: 10.1002/er.3019
      47
      Oxy-steam gasification of biomass for hydrogen rich syngas production using downdraft reactor configuration
      Sandeep, K.; Dasappa, S.
      International Journal of Energy Research (2014), 38 (2), 174-188CODEN: IJERDN; ISSN:0363-907X. (John Wiley & Sons Ltd.)
      SUMMARY : The paper focuses on the use of oxygen and steam as the gasification agents in the thermochem. conversion of biomass to produce hydrogen rich syngas, using a downdraft reactor configuration. Performance of the reactor is evaluated for different equivalence ratios (ER), steam to biomass ratios (SBR) and moisture content in the fuel. The results are compared and evaluated with chem. equil. anal. and reaction kinetics along with the results available in the literature. Parametric study suggests that, with increase in SBR, hydrogen fraction in the syngas increases but necessitates an increase in the ER to maintain reactor temp. toward stable operating conditions. SBR is varied from 0.75 to 2.7 and ER from 0.18 to 0.3. The peak hydrogen yield is found to be 104 g/kg of biomass at SBR of 2.7. Further, significant enhancement in H2 yield and H2 to CO ratio is obsd. at higher SBR (SBR = 1.5-2.7) compared with lower range SBR (SBR = 0.75-1.5). Expts. were conducted using wet wood chips to induce moisture into the reacting system and compare the performance with dry wood with steam. The results clearly indicate the both hydrogen generation and the gasification efficiency (ηg) are better in the latter case. With the increase in SBR, gasification efficiency (ηg) and lower heating value (LHV) tend to reduce. Gasification efficiency of 85.8% is reported with LHV of 8.9 MJ Nm-3 at SBR of 0.75 compared with 69.5% efficiency at SBR of 2.5 and lower LHV of 7.4 at MJ Nm-3 at SBR of 2.7. These are argued on the basis of the energy required for steam generation and the extent of steam consumption during the reaction, which translates subsequently in the LHV of syngas. From the anal. of the results, it is evident that reaction kinetics plays a crucial role in the conversion process. The study also presents the importance of reaction kinetics, which controls the overall performance related to efficiency, H2 yield, H2 to CO fraction and LHV of syngas, and their dependence on the process parameters SBR and ER. Copyright © 2013 John Wiley & Sons, Ltd.
    48. 48
      Sharma, S. K.; Shivapuji, A. M.; Dasappa, S. Char Reactivity Assessment with Steam in Packed Bed and Pilot Scale under Oxy-Steam Environment. Fuel 2023, 344, 128086  DOI: 10.1016/j.fuel.2023.128086
      48
      Char reactivity assessment with steam in packed bed and pilot scale under oxy-steam environment
      Sharma, Shirish Kumar; Shivapuji, Anand M.; Dasappa, S.
      Fuel (2023), 344 (), 128086CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      This paper focuses on char gasification in steam towards generating syngas as a part of two-stage gasification technol. developed inhouse to handle high-ash coal. Controlled expts. in a small-scale packed bed reactor are used to arrive at the dependence of char reactivity using parametric studies like the evolution of temp., gas compn., flow rate, and carbon conversion rate with time and are compared for different particle sizes. The vol. percentages of CO, CO2, CH4, and H2 were 7, 26, 1, and 66, resp., in steam char expts., over a particle size range from 1 mm to 4 mm. If the CO2 is sepd., the H2 vol. percentage reaches 90%. In small-scale expts., the gas compn. for all the particle sizes was invariable; however, the reactivity of small particles is higher than the bigger particles, i.e., 0.5 g/g-hr as against 0.38 g/g-hr for bigger particles due to the transition from diffusion to the kinetic regime, which establishes the suitability of small particles for pilot-scale operations. Finally, the expts. were carried out on pilot-scale char gasification in an oxy-steam environment, and the results were compared with simulated expts. for small-size particles. The consequences of adding oxygen with steam to keep the system auto-thermal are discussed. In the pilot scale under oxy-steam conditions, the volumetric concns. of CO, CO2, CH4, and H2 were 10.8, 39.9, 4.7, and 44.6%, resp. In contrast, the reactivity increased from 0.46 to 0.90 g/g-hr with a decrease in the calorific value of gas from 9.7 to 8.6 MJ/Nm3.
    49. 49
      Park, S. W.; Lee, S. Y.; Jeong, Y. O.; Han, G. H.; Seo, Y. C. Effects of Oxygen Enrichment in Air Oxidants on Biomass Gasification Efficiency and the Reduction of Tar Emissions. Energies (Basel) 2018, 11 (10), 2664,  DOI: 10.3390/en11102664
      49
      Effects of oxygen enrichment in air oxidants on biomass gasification efficiency and the reduction of tar emissions
      Park, Se-Won; Lee, Sang-Yeop; Jeong, Yean-Ouk; Han, Gun-Ho; Seo, Yong-Chil
      Energies (Basel, Switzerland) (2018), 11 (10), 2664/1-2664/13CODEN: ENERGA; ISSN:1996-1073. (MDPI AG)
      This study applied oxygen-enrichment conditions to remove tar (the main problem in biomass gasification) and increase gasification efficiency. Expts. on oxygen-enrichment conditions were conducted at oxygen concns. of 21%, 25%, 30%, and 35% in oxidants. This was expected to increase the partial oxidn. reaction in gasification reactions, thus leading to thermal decompn. of tar in producer gas. The decompd. tar was expected to be converted into syngas or combustible gases in the producer gas. The results were as follows: Tar-redn. efficiency was 72.46% at 30% oxygen enrichment compared to the std. 21% enrichment condition. In addn., the concns. of syngas and combustible gases in the producer gas tended to increase. Therefore, the 30% oxygen-enrichment condition was optimal, resulting in 78.00% for cold gas efficiency and 80.24% for carbon conversion efficiency. The application of oxygen enrichment into the lab-scale gasification system clearly reduced the concn. of tar and tended to increase some indexes of gasification efficiency, thus suggesting the usefulness of this technique in large-scale biomass gasification operations.
    50. 50
      Cao, Y.; Wang, Q.; Du, J.; Chen, J. Oxygen-Enriched Air Gasification of Biomass Materials for High-Quality Syngas Production. Energy Convers. Manag. 2019, 199, 111628,  DOI: 10.1016/j.enconman.2019.05.054
      50
      Oxygen-enriched air gasification of biomass materials for high-quality syngas production
      Cao, Y.; Wang, Q.; Du, J.; Chen, J.
      Energy Conversion and Management (2019), 199 (), 111628CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      The oxygen-enriched gasification of five biomasses (pine sawdust, rice husk, corn core, legume straw and wood chips) for high-quality gas prodn. was studied using Aspen Plus software. At first, in order to ensure the model accuracy, the simulation results performed at different temps. were compared with the exptl. data, and a good agreement was obtained. The performance of the process was evaluated based on the yield of producer gas, lower heating value of the fuel gas (LHVFG) and the tar yield. The simulation results indicated that temp. was the most important parameter in the process; higher temp. contributed to higher gas prodn. and lower tar yield. The gas yield also increased with the increase of equivalence ratio (ER), while the LHVFG and tar yield significantly reduced. Results also showed that the use of oxygen-enriched air was more favorable for gas quality and tar cracking; however, it lowered the gas yield. As ER increased from 0.19 to 0.27, the tar yields decreased markedly which is attributed to the thermal conversion of volatiles with the rise of oxidant. As a result, gasification of all the biomasses was feasible; however, gasification of pine sawdust showed the highest gas yield and gas heating value. The lowest tar yield was obtained from gasification of rice husk.
    51. 51
      Liu, W.; Tian, Y.; Yan, H.; Zhou, X.; Tan, Y.; Yang, Y.; Li, Z.; Yuan, L. Gasification of Biomass Using Oxygen-Enriched Air as Gasification Agent: A Simulation Study. Biomass Convers. Biorefin. 2023, 13, 15993,  DOI: 10.1007/s13399-021-02035-2
      51
      Gasification of biomass using oxygen-enriched air as gasification agent: a simulation study
      Liu, Wentao; Tian, Ye; Yan, Hui; Zhou, Xiong; Tan, Yu; Yang, Yu; Li, Zheng; Yuan, Liang
      Biomass Conversion and Biorefinery (2023), 13 (17), 15993-16000CODEN: BCBIBN; ISSN:2190-6823. (Springer)
      A steady-state Aspen Plus model was established to numerically study biomass (ramie residues) gasification using air as gasification agent. This study proposed a comprehensive model which used the thermodn. equil. and chem. kinetics to accurately simulate the char combustion and char/volatiles gasification, resp., to search for optimal gasifier operating conditions. The proposed model correctly predicted the products yield, gasifier performance and the compn. of the produced syngas, and therefore the higher heating value (HHV). The effects of air temp. and oxygen content in gasification agent on the gasification characteristics were discussed. The gas yield slightly increased with the increase of air temp., while char conversion efficiency (CCE) firstly increased and then declined attributing to the slight increase of tar cracking with the increase of air temp. The results also indicate that higher oxygen ratio (OR) leads to higher H2 prodn. and lower tar yield. Compared to the max. H2 content (11.17 vol%) and the syngas HHV (6.22 MJ/Nm3) at OR = 31.4%, they are resp. reduced to about 35.45% and 21.7% when OR drops to 21%. The present model opens the possibility of predicting the gasification characteristics using different gasification agents and feedstocks based on their chem. compns.
    52. 52
      Banerjee, S.; Tiarks, J. A.; Kong, S. C. Modeling Biomass Gasification System Using Multistep Kinetics under Various Oxygen-Steam Conditions. Environ. Prog. Sustain Energy 2015, 34 (4), 1148– 1155,  DOI: 10.1002/ep.12109
      There is no corresponding record for this reference.
    53. 53
      Di Giuliano, A.; Capone, S.; Anatone, M.; Gallucci, K. Chemical Looping Combustion and Gasification: A Review and a Focus on European Research Projects. Ind. Eng. Chem. Res. 2022, 61 (39), 14403– 14432,  DOI: 10.1021/acs.iecr.2c02677
      53
      Chemical looping combustion and gasification, and review and focus on European research projects
      Di Giuliano, Andrea; Capone, Serena; Anatone, Michele; Gallucci, Katia
      Industrial & Engineering Chemistry Research (2022), 61 (39), 14403-14432CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      A review. Climate change has driven attention toward promoting sustainable policies and processes to contain global warming below +1.5°C. Neg. emission technologies (NET)-bioenergy with carbon capture and storage in particular (BECCS)-are expected to contribute to the achievement of that target. Recent research and development concerning NET focused on chem. looping combustion (CLC) and chem. looping gasification (CLG), as they should limit cost- and energy-penalties assocd. with carbon capture and storage thanks to solid materials known as oxygen carriers (OCs). This review aims to provide an introductory tool about CLC and CLG and their possible role as NET if fed with biomasses to obtain BECCS. A crit. overlook is proposed concerning chem. looping reactions, fuels, types of OCs, and reactor systems developed at different scales, focusing on recent and current European research projects and remarks on the subsequent developments.
    54. 54
      Coppola, A.; Scala, F. Chemical Looping for Combustion of Solid Biomass: A Review. Energy and Fuels. 2021, 35, 19248– 19265,  DOI: 10.1021/acs.energyfuels.1c02600
      54
      Chemical Looping for Combustion of Solid Biomass: A Review
      Coppola, Antonio; Scala, Fabrizio
      Energy & Fuels (2021), 35 (23), 19248-19265CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      A review. Chem. looping combustion of solid biomass has the unique potential to generate energy with neg. carbon emissions, while entailing an energy penalty compared to traditional combustion that is lower than that of the competing carbon capture technologies. In spite of these attractive features, research is still needed to bring the technol. to a fully com. level. The reason relies on a no. of technol. challenges mostly related to the oxygen carrier performance, its possible detrimental interaction with the biomass ash components, and the efficiency of the gas-solid contact with the biomass volatiles. This review is focused on these specific challenges which are particularly relevant when firing biomass rather than coal in a solid-based chem. looping combustion process. Special attention will be given to the most recent findings published on these aspects. Related performance evaluation by modeling, system integration, and techno-economic anal. will also be briefly reviewed.
    55. 55
      Woolcock, P. J.; Brown, R. C. A Review of Cleaning Technologies for Biomass-Derived Syngas. Biomass and Bioenergy. 2013, 52, 54– 84,  DOI: 10.1016/j.biombioe.2013.02.036
      55
      A review of cleaning technologies for biomass-derived syngas
      Woolcock, Patrick J.; Brown, Robert C.
      Biomass and Bioenergy (2013), 52 (), 54-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      A review. Syngas from gasification of carbonaceous feedstocks is used for power prodn. and synthesis of fuels and commodity chems. Impurities in gasification feedstocks, esp. sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temp. exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the tech. difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
    56. 56
      Lyngfelt, A. Chemical Looping Combustion: Status and Development Challenges. Energy and Fuels. 2020, 34, 9077– 9093,  DOI: 10.1021/acs.energyfuels.0c01454
      56
      Chemical Looping Combustion: Status and Development Challenges
      Lyngfelt, Anders
      Energy & Fuels (2020), 34 (8), 9077-9093CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      A review. Because the CO2 capture is inherent in chem. looping combustion (CLC), thus ideally avoiding costly gas sepn., this process has potential for uniquely low costs of CO2 capture. The review reports on operational experiences with different oxygen carriers in CLC pilot operation. Further, the application to solid fuels is discussed in terms of technol. challenges, routes for upscaling to com. size, downstream gas treatment, options for achieving adequate circulation, and the use of biofuels in CLC to reach neg. emissions. It is concluded that the necessary elements for a scale-up are at hand. Oxygen carrier materials of low cost have been tested in extended operation and found to have reasonable performance with respect to reactivity and lifetime. Designs for large-scale units have been performed, indicating that the process is tech. realistic and should have a low cost of CO2 capture. A scale-up strategy to minimize risk and costs has been suggested.
    57. 57
      Prando, D.; Shivananda Ail, S.; Chiaramonti, D.; Baratieri, M.; Dasappa, S. Characterisation of the Producer Gas from an Open Top Gasifier: Assessment of Different Tar Analysis Approaches. Fuel 2016, 181, 566– 572,  DOI: 10.1016/j.fuel.2016.04.104
      57
      Characterisation of the producer gas from an open top gasifier: Assessment of different tar analysis approaches
      Prando, D.; Shivananda Ail, S.; Chiaramonti, D.; Baratieri, M.; Dasappa, S.
      Fuel (2016), 181 (), 566-572CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      The paper addresses a comprehensive screening procedure of the tar present in the raw producer gas generated by an open top downdraft gasifier developed at the Indian Institute of Science (IISc), Bangalore. The main objectives of this research are the comparison of different approaches for the sampling and anal. of tar (i.e. GC-MS and gravimetric methods), and the assessment of the capability of this gasifier to produce low-tar producer gas. The results of the GC-MS anal. of the collected samples showed that tar is mainly composed of light arom. compds., where benzene and toluene account for about 70% of the total detected tar. Contrastingly, the gravimetric tar is roughly one order of magnitude lower than the total tar that was detd. by GC-MS anal. on the collected samples. The light and heavy polycyclic arom. hydrocarbons (PAH) compds. that have a mol. wt. higher than 150 g mol-1 account for the gravimetric tars, but the main fraction is GC-undetectable. The two approaches for the anal. of tar have different capabilities and the choice of either the approaches would strongly depend on the selected gasification technol. The detailed exptl. anal. evidenced that the IISc open-top reactor design results in a low tar content in the producer gas. The gravimetric tar in the raw gas were measured at 50-80 mg N m-3, with min. dependence on the choice of the feedstock used (i.e. Casuarina wood chip or coconut shell).
    58. 58
      Milne, T. A.; Evans, R. J.; Abatzoglou, N. Biomass Gasifier “Tars”: Their Nature, Formation, and Conversion; NREL/TP-570-25357; National Renewable Energy Laboratory: Golden, CO, 1998.
      There is no corresponding record for this reference.
    59. 59
      Calvo, L. F.; Gil, M. V; Otero, M.; Morán, A.; García, A. I. Gasification of Rice Straw in a Fluidized-Bed Gasifier for Syngas Application in Close-Coupled Boiler-Gasifier Systems. Bioresource Technol. 2012, 109, 206– 214,  DOI: 10.1016/j.biortech.2012.01.027
      59
      Gasification of rice straw in a fluidized-bed gasifier for syngas application in close-coupled boiler-gasifier systems
      Calvo, L. F.; Gil, M. V.; Otero, M.; Moran, A.; Garcia, A. I.
      Bioresource Technology (2012), 109 (), 206-214CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
      The feasibility and operation performance of the gasification of rice straw in an atm. fluidized-bed gasifier was studied. The gasification was carried out between 700 and 850 °C. The stoichiometric air-fuel ratio (A/F) for rice straw was 4.28 and air supplied was 7-25% of that necessary for stoichiometric combustion. Mass and power balances, tar concn., produced gas compn., gas phase ammonia, chloride and potassium concns., agglomeration tendencies and gas efficiencies were assessed. Agglomeration was avoided by replacing the normal alumina-silicate bed by a mixt. of alumina-silicate sand and MgO. It was shown that it is possible to produce high quality syngas from the gasification of rice straw. Under the exptl. conditions used, the higher heating value (HHV) of the produced gas reached 5.1 MJ Nm-3, the hot gas efficiency 61% and the cold gas efficiency 52%. The obtained results prove that rice straw may be used as fuel for close-coupled boiler-gasifier systems.
    60. 60
      Li, J.; Yin, Y.; Zhang, X.; Liu, J.; Yan, R. Hydrogen-Rich Gas Production by Steam Gasification of Palm Oil Wastes over Supported Tri-Metallic Catalyst. Int. J. Hydrogen Energy 2009, 34, 9108– 9115,  DOI: 10.1016/j.ijhydene.2009.09.030
      60
      Hydrogen-rich gas production by steam gasification of palm oil wastes over supported tri-metallic catalyst
      Li, Jianfen; Yin, Yanfang; Zhang, Xuanming; Liu, Jianjun; Yan, Rong
      International Journal of Hydrogen Energy (2009), 34 (22), 9108-9115CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      The catalytic steam gasification of palm oil wastes for hydrogen-rich gas prodn. was exptl. investigated in a combined fixed bed reactor using the newly developed tri-metallic catalyst. The results indicated that the supported tri-metallic catalyst had greater activity for the cracking of hydrocarbons and tar in vapor phase and higher hydrogen yield than the calcined dolomite in catalytic steam gasification of palm oil wastes. A series of expts. have been performed to explore the effects of temp., steam to biomass ratio (S/B) and biomass particle size on gas compn., gas yield, low heating value (LHV) and hydrogen yield. The expts. demonstrated that temp. was the most important factor in this process; higher temp. contributed to higher hydrogen prodn. and gas yield, however, it lowered gas heating value. Comparing with biomass catalytic gasification, the introduction of steam improved gas quality and yield, the optimal value of S/B was found to be 1.33 under the present operating condition. It was also shown that a smaller particle size was more favorable for gas quality and yield. However, the LHV of fuel gas decreased with the increasing S/B ratio and the decreasing biomass particle size.
    61. 61
      Skoulou, V.; Zabaniotou, A.; Stavropoulos, G.; Sakelaropoulos, G. Syngas Production from Olive Tree Cuttings and Olive Kernels in a Downdraft Fixed-Bed Gasifier. Int. J. Hydrogen Energy 2008, 33 (4), 1185– 1194,  DOI: 10.1016/j.ijhydene.2007.12.051
      61
      Syngas production from olive tree cuttings and olive kernels in a downdraft fixed-bed gasifier
      Skoulou, V.; Zabaniotou, A.; Stavropoulos, G.; Sakelaropoulos, G.
      International Journal of Hydrogen Energy (2008), 33 (4), 1185-1194CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Fixed-bed gasification of olive kernels and olive tree cuttings was studied on lab. scale. Gasification took place with air at 750-950°, for various air equivalence ratios (0.14-0.42) and under atm. pressure. In each run, the main components of the gas phase were CO, CO2, H2 and CH4. Gasification with air at 950° favored gas yields. Syngas prodn. increased with reactor temp., while CO2, CH4, light hydrocarbons and tar followed an opposite trend. An increase of the air equivalence ratio decreased syngas prodn. and lowered the product gas heating value, but favoring tar destruction. Gas from olive tree cuttings at 950° and with an air equivalence ratio of 0.42 had a higher LHV (9.41 MJ/Nm3) in comparison to olive kernels (8.60 MJ/Nm3). Olive kernels produced more char with a higher content of fixed C (16.39 wt./wt.%) than olive tree cuttings; thus, they might be considered an attractive source for carbonaceous material prodn.
    62. 62
      Fazil, A.; Kumar, S.; Mahajani, S. M. Gasification and Co-Gasification of Paper-Rich, High-Ash Refuse-Derived Fuel in Downdraft Gasifier. Energy 2023, 263, 125659,  DOI: 10.1016/j.energy.2022.125659
      62
      Gasification and Co-gasification of paper-rich, high-ash refuse-derived fuel in downdraft gasifier
      Fazil, A.; Kumar, Sandeep; Mahajani, Sanjay M.
      Energy (Oxford, United Kingdom) (2023), 263 (Part_A), 125659CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      Among the various waste-to-energy conversion methods, gasification is a tech. feasible option for municipal solid waste valorization, meeting current emission limits and reducing landfill disposal burden. This work investigates the potential of paper rich ( 76% wt.) com. refuse-derived fuel (RDF) having high ash content (/// 17% wt.) for gasification and co-gasification in downdraft gasifier. The ash formed from RDF, with higher proportion of alk. earth metals (Ca and Mg) and lower proportion of alkali metals (Na and K), can effectively av.
    63. 63
      Seggiani, M.; Puccini, M.; Raggio, G.; Vitolo, S. Effect of Sewage Sludge Content on Gas Quality and Solid Residues Produced by Cogasification in an Updraft Gasifier. Waste Management 2012, 32 (10), 1826– 1834,  DOI: 10.1016/j.wasman.2012.04.018
      63
      Effect of sewage sludge content on gas quality and solid residues produced by cogasification in an updraft gasifier
      Seggiani, Maurizia; Puccini, Monica; Raggio, Giovanni; Vitolo, Sandra
      Waste Management (Oxford, United Kingdom) (2012), 32 (10), 1826-1834CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
      In the present work, the gasification with air of dehydrated sewage sludge (SS) with 20 wt.% moisture mixed with conventional woody biomass was investigated using a pilot fixed-bed updraft gasifier. Attention was focused on the effect of the SS content on the gasification performance and on the environmental impact of the process. The results showed that it is possible to co-gasify SS with wood pellets (WPs) in updraft fixed-bed gasification installations. However, at high content of sewage sludge the gasification process can become instable because of the very high ash content and low ash fusion temps. of SS. At an equiv. ratio of 0.25, compared with wood pellets gasification, the addn. of sewage sludge led to a redn. of gas yield in favor of an increase of condensate prodn. with consequent cold gas efficiency decrease. Low concns. of dioxins/furans and PAHs were measured in the gas produced by SS gasification, well below the limiting values for the exhaust gaseous emissions. NH3, HCl and HF contents were very low because most of these compds. were retained in the wet scrubber systems. On the other hand, high H2S levels were measured due to high sulfur content of SS. Heavy metals supplied with the feedstocks were mostly retained in gasification solid residues. The leachability tests performed according to European regulations showed that metals leachability was within the limits for landfilling inert residues. On the other hand, sulfate and chloride releases were found to comply with the limits for non-hazardous residues.
    64. 64
      Chen, G.; Liu, F.; Guo, X.; Zhang, Y.; Yan, B.; Cheng, Z.; Xiao, L.; Ma, W.; Hou, L. Co-Gasification of Acid Hydrolysis Residues and Sewage Sludge in a Downdraft Fixed Gasifier with CaO as an In-Bed Additive. Energy Fuels 2018, 32 (5), 5893– 5900,  DOI: 10.1021/acs.energyfuels.7b03960
      64
      Co-gasification of Acid Hydrolysis Residues and Sewage Sludge in a Downdraft Fixed Gasifier with CaO as an In-Bed Additive
      Chen, Guanyi; Liu, Fang; Guo, Xiang; Zhang, Yanru; Yan, Beibei; Cheng, Zhanjun; Xiao, Lin; Ma, Wenchao; Hou, Li-an
      Energy & Fuels (2018), 32 (5), 5893-5900CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Co-gasification expts. of acid hydrolysis residues (AHR) and sewage sludge (SS) both derived from a lignocellulosic ethanol plant were preliminarily investigated in a downdraft fixed gasifier at atm. pressure. Attention was focused on the effects of the gasifier bed temp. (600-800 °C), SS content (0-100 wt %), and equivalence ratio (ER, 0.15-0.30) on the gas quality and cold gas efficiency (CGE). The results showed that the optimal low heating value (LHV) of fuel gas of 6.83 MJ/Nm3, CGE of 70.68%, and low tar content of 5.84 g/Nm3 were obtained at 800 °C, SS content of 50 wt %, CaO/C (molar ratio) of 1.0, and ER of 0.22. A high temp. was favorable for high-quality gas prodn., and the optimum temp. was 800 °C, at which CaO mainly played the catalyst role but not the CO2 sorbent. Synergetic effects occurred in the co-gasification, and gas quality could be improved in an appropriate proportion by blending 50 wt % SS with AHR. ER ranging from 0.20 to 0.22 improved gas quality and CGE; however, a higher ER favored the decrease of the tar content, and the optimal tar content of 4.00 g/Nm3 was obtained with ER = 0.30. The results indicated the potential technol. for air co-gasification of AHR and SS as an option for energy recovery and waste disposal as well as for light industry with agricultural feedstock.
    65. 65
      Pfeifer, C.; Koppatz, S.; Hofbauer, H. Steam Gasification of Various Feedstocks at a Dual Fluidised Bed Gasifier: Impacts of Operation Conditions and Bed Materials. Biomass Convers Biorefin 2011, 1 (1), 39– 53,  DOI: 10.1007/s13399-011-0007-1
      65
      Steam gasification of various feedstocks at a dual fluidised bed gasifier: Impacts of operation conditions and bed materials
      Pfeifer, Christoph; Koppatz, Stefan; Hofbauer, Hermann
      Biomass Conversion and Biorefinery (2011), 1 (1), 39-53CODEN: BCBIBN; ISSN:2190-6823. (Springer)
      Gasification of biomass is an attractive technol. for combined heat and power prodn. as well as for synthesis processes such as prodn. of liq. and gaseous biofuels. Dual fluidized bed (DFB) technol. offers the advantage of a nearly nitrogen-free product gas mainly consisting of H2, CO, CO2 and CH4. The DFB steam gasification process has been developed at Vienna University of Technol. over the last 15 years using cold flow models, lab. units, math. modeling and simulation. The main findings of the exptl. work at a 100-kW pilot scale unit are presented. Different fuels (wood pellets, wood chips, lignite, coal, etc.) and different bed materials (natural minerals such as olivine, limestones, calcites, etc. as well as modified olivines) have been tested and the influence on tar content as well as gas compn. was measured and compared among the different components. Moreover, the influence of operating parameters such as fuel moisture content, steam/fuel ratio and gasification temp. on the product gas has been investigated. DFB steam gasification of solid biomass coupled with CO2 capture, the so-called absorption enhanced reforming (AER) process, is highlighted. The expts. in pilot scale led to com. realization of this technol. in demonstration scale. Summarising, the DFB system offers excellent fuel flexibility to be used in advanced power cycles as well as in polygeneration applications.
    66. 66
      Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G.; Van Paasen, S. V. B.; Bergman, P. C. A.; Kiel, J. H. A. Catalytic Decomposition of Biomass Tars: Use of Dolomite and Untreated Olivine. Renew Energy 2005, 30 (4), 565– 587,  DOI: 10.1016/j.renene.2004.07.014
      66
      Catalytic decomposition of biomass tars: use of dolomite and untreated olivine
      Devi, Lopamudra; Ptasinski, Krzysztof J.; Janssen, Frans J. J. G.; van Paasen, Sander V. B.; Bergman, Patrick C. A.; Kiel, Jacob H. A.
      Renewable Energy (2005), 30 (4), 565-587CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Although biomass is getting increased attention as a renewable energy source, one of the remaining problems still to be solved is the redn. of the high level of tar present in the product gas from gasification of biomass. The purpose of the present work is to study the activity of olivine and dolomite for tar destruction. Some researchers investigated olivine as bed material for biomass gasification. But it is not yet known how tars behave in the presence of olivine and whether olivine has some activity towards tar destruction. A slipstream from a lab-scale atm. bubbling-fluidized-bed gasifier (located at ECN) is passed through a secondary fixed-bed reactor where the additives are placed. For easy understanding, the results are represented in terms of the following tar classes; GC-undetectable tars (class 1), heterocyclic compds. (class 2), arom. compds. (class 3), light polyarom. compds. (class 4), heavy polyarom. compds. (class 5). The general observation is that the conversion of all tar classes increases as the temp. was raised from 800 to 900°C for both additives. The water-sol. heterocyclic compds. can be easily converted by thermal treatment. At the temp. of 900°C, the water-sol. heterocyclic compds. are completely converted. A 48% decrease in heavy PAHs is obsd. with pure sand. Addn. of 17 wt% olivine to the sand leads to a 71% decrease of PAHs at 900°C, whereas addn. of 17 wt% (pre-calcined) dolomite converted 90%. Also improvement in conversion of other tar classes is obsd. when olivine and dolomite are added during hot gas cleaning. A total tar amt. of 4.0 g m0-3 could be reduced to 1.5 and 2.2 g m0-3 using dolomite and olivine, resp., at a temp. of 900°C. Inspite of this redn. in total tar concn., a limited impact on the tar dew point is obsd.
    67. 67
      Mohammed, M.; Salmiaton, A.; Wan Azlina, W.; Mohammad Amran, M.; Fakhru'l-Razi, A. Air Gasification of Empty Fruit Bunch for Hydrogen-Rich Gas Production in a Fluidized-Bed Reactor. Energy Convers. Manage. 2011, 52, 1555– 1561,  DOI: 10.1016/j.enconman.2010.10.023
      There is no corresponding record for this reference.
    68. 68
      Luo, S.; Xiao, B.; Guo, X.; Hu, Z.; Liu, S.; He, M. Hydrogen-Rich Gas from Catalytic Steam Gasification of Biomass in a Fixed Bed Reactor: Influence of Particle Size on Gasification Performance. Int. J. Hydrogen Energy 2009, 34 (3), 1260– 1264,  DOI: 10.1016/j.ijhydene.2008.10.088
      68
      Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of particle size on gasification performance
      Luo, Siyi; Xiao, Bo; Guo, Xianjun; Hu, Zhiquan; Liu, Shiming; He, Maoyun
      International Journal of Hydrogen Energy (2009), 34 (3), 1260-1264CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      The catalytic steam gasification of biomass was carried out in a lab-scale fixed bed reactor in order to evaluate the effects of particle size at different bed temps. on the gasification performance. The bed temp. was varied from 600 to 900 °C and the biomass was sepd. into five different size fractions (below 0.075 mm, 0.075-0.15 mm, 0.15-0.3 mm, 0.3-0.6 mm and 0.6-1.2 mm). The results show that with decreasing particle size, the dry gas yield, carbon conversion efficiency and H2 yield increased, and the content of char and tar decreased. And the differences due to particle sizes in gasification performance practically disappear as the higher temp. bound is approached. Hydrogen and carbon monoxide contents in the produced gas increase with decreasing particle size at 900 °C, reaching to 51.2% and 22.4%, resp.
    69. 69
      Lv, P. M.; Xiong, Z. H.; Chang, J.; Wu, C. Z.; Chen, Y.; Zhu, J. X. An Experimental Study on Biomass Air-Steam Gasification in a Fluidized Bed. Bioresource Technol. 2004, 95, 95– 101,  DOI: 10.1016/j.biortech.2004.02.003
      69
      An experimental study on biomass air-steam gasification in a fluidized bed
      Lv P M; Xiong Z H; Chang J; Wu C Z; Chen Y; Zhu J X
      Bioresource technology (2004), 95 (1), 95-101 ISSN:0960-8524.
      The characteristics of biomass air-steam gasification in a fluidized bed are studied in this paper. A series of experiments have been performed to investigate the effects of reactor temperature, steam to biomass ratio (S/B), equivalence ratio (ER) and biomass particle size on gas composition, gas yield, steam decomposition, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the fuel gas yield varied between 1.43 and 2.57 Nm3/kg biomass and the LHV of the fuel gas was between 6741 and 9143 kJ/Nm3. The results showed that higher temperature contributed to more hydrogen production, but too high a temperature lowered gas heating value. The LHV of fuel gas decreased with ER. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality. It was also shown that a smaller particle was more favorable for higher gas LHV and yield.
    70. 70
      Wongsiriamnuay, T.; Kannang, N.; Tippayawong, N. Effect of Operating Conditions on Catalytic Gasification of Bamboo in a Fluidized Bed. Int. J. Chem. Eng. 2013, 2013, 1,  DOI: 10.1155/2013/297941
      There is no corresponding record for this reference.
    71. 71
      Jeong, Y. S.; Choi, Y. K.; Park, K. B.; Kim, J. S. Air Co-Gasification of Coal and Dried Sewage Sludge in a Two-Stage Gasifier: Effect of Blending Ratio on the Producer Gas Composition and Tar Removal. Energy 2019, 185, 708– 716,  DOI: 10.1016/j.energy.2019.07.093
      71
      Air co-gasification of coal and dried sewage sludge in a two-stage gasifier: Effect of blending ratio on the producer gas composition and tar removal
      Jeong, Yong-Seong; Choi, Young-Kon; Park, Ki-Bum; Kim, Joo-Sik
      Energy (Oxford, United Kingdom) (2019), 185 (), 708-716CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      The co-gasification of coal and dried sewage sludge (DSS) was conducted using a two-stage gasifier consisting of a fluidized bed gasifier and a tar-cracking reactor. In this study, the effect of the blending ratio of coal and DSS was investigated. Producer gases that were obtained from the tar-cracking reactor filled with active carbon contained high levels of hydrogen (max. H2: 27.7 vol%) and low tar contents (min. tar: 0 mg/Nm3). Upon gasification of the coal/DSS blends, the hydrogen content decreased and tar content increased with increasing DSS. Blends with coal/DSS ratios of 70/30 and 50/50 showed a synergetic effect on tar redn., which could be attributed to the high ash content of the DSS. The gasification of the 70% DSS blend increased the condensed tar yield by only 0.1 wt%, compared to coal gasification. Lastly, a hot filter filled with Fe-impregnated active carbon was applied to completely remove tar from producer gas, which led to the prodn. of a tar-free and hydrogen-rich gas (30 vol%). Furthermore, the Fe-impregnated active carbon reduced the H2S content to 229 ppmv. In summary, it was possible to produce a clean gas from coal and DSS blends in the UOS gasification process.
    72. 72
      García, G.; Campos, E.; Fonts, I.; Sánchez, J. L.; Herguido, J. Gas Catalytic Upgrading in a Two-Zone Fluidized Bed Reactor Coupled to a Cogasification Plant. Energy Fuels 2013, 27 (5), 2835– 2845,  DOI: 10.1021/ef400227z
      72
      Gas catalytic upgrading in a two-zone fluidized bed reactor coupled to a cogasification plant
      Garcia, G.; Campos, E.; Fonts, I.; Sanchez, J. L.; Herguido, J.
      Energy & Fuels (2013), 27 (5), 2835-2845CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      An integrated system has been designed and started up for sewage sludge and coal cogasification + desulfurization + gas reforming in a two-zone fluidized bed reactor (TZFBR). The system is capable of reforming tar compds. to nondetectable levels and improving gasification gas quality in terms of higher H2 and CO concns. The use of a TZFBR enables both the catalytic upgrading of the gasification gas and the regeneration of the catalyst deactivated by coke deposition in a single vessel. Both an increase of 37% of gas LHV and a redn. of tar compds. to nondetectable levels are achieved in the best conditions used, with a 2 vol % of oxygen in the regeneration flow. Dolomite was used in the desulfurization unit at 800 °C, allowing the redn. of the H2S content in the produced gas from 1100 ppm to less than 300 ppm, and a tar redn. from 15 g/m3(STP) to 0.2 g/m3(STP). With this novel integrated system, the catalytic cracking and reforming of a real gasification gas stream produced in the cogasification of sewage sludge and coal has been achieved, operating in a stable mode.
    73. 73
      Pan, Y. G.; Velo, E.; Roca, X.; Manyà, J. J.; Puigjaner, L. Fluidized-Bed Co-Gasification of Residual Biomass/Poor Coal Blends for Fuel Gas Production. Fuel 2000, 79, 1317– 1326,  DOI: 10.1016/S0016-2361(99)00258-6
      73
      Fluidized-bed co-gasification of residual biomass/poor coal blends for fuel gas production
      Pan, Y. G.; Velo, E.; Roca, X.; Manya, J. J.; Puigjaner, L.
      Fuel (2000), 79 (11), 1317-1326CODEN: FUELAC; ISSN:0016-2361. (Elsevier Science Ltd.)
      Expts. involving the co-gasification of residual biomass/poor coal blends and gasification of individual feedstocks used in the blends were performed in a bench scale, continuous fluidized-bed working at atm. pressure. Two types of blends were prepd., mixing pine chips (from Valcabadillo, Spain) with black coal, a low-grade coal from Escatron, Spain, and Sabero coal, a refuse coal from Sabero, Spain, in the ratio range of 0/100-100/0. Exptl. tests were carried out by using as a gasification agent mixts. of air and steam with dew points of 74-85°C at gasification temps. of 840-910°C and superficial fluidized gas velocities of 0.7-1.4 m/s. Feasibility studies were very pos., showing that blending effectively improved the performance of fluidized-bed co-gasification of the low-grade coal, and the possibility of converting the refuse coal to a low-Btu fuel gas. This study indicates that a blend ratio with no less than 20% pine chips for the low-grade coal and 40% pine chips for the refuse coal are the most appropriate. The dry product gas low heating value augments with increasing blend ratio from 3700 to 4560 kJ/N m3 for pine chips/low-grade coal, and from 4000 to 4750 kJ/N m3 for pine chips/refuse coal. Dry product gas yield rises with the increase of the blend ratio from 1.80 to 3.20 N m3/kg (pine chips/low-grade coal), and from 0.75 to 1.75 N m3/kg (pine chips/refuse coal), resp. About 50% co-gasification process overall thermal efficiency can be achieved for the two types of blend.
    74. 74
      Cao, Y.; Fu, L.; Mofrad, A. Combined-Gasification of Biomass and Municipal Solid Waste in a Fluidized Bed Gasifier. Journal of the Energy Institute 2019, 92 (6), 1683– 1688,  DOI: 10.1016/j.joei.2019.01.006
      74
      Combined-gasification of biomass and municipal solid waste in a fluidized bed gasifier
      Cao, Yan; Fu, Leijie; Mofrad, Amir
      Journal of the Energy Institute (2019), 92 (6), 1683-1688CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
      Due to the environmental problems assocd. with burning of fossil fuels and population growth, more attention has been paid to develop renewable energies in recent years. Among all options for renewable energy utilization, biomass gasification is more popular because of environmental benefits and economic issues. In the present study, a series of expts. were carried out to study the influence of blending ratio, reaction temp., equivalence ratio (ER) on co-gasification characteristics of pine sawdust (SD) and municipal solid waste (MSW). By increasing the blending ratio from 100% SD to 100% MSW, CO and CH4 resp. increased from 16.7 to 18.8 vol% and from 4.1 to 5.1 vol%, while an opposite trend was found for H2 and CO2. Over the ranges of the exptl. conditions used, the tar content and gas yield varied from 5.4 to 10.1 g/Nm3 and 1.34 to 1.15 Nm3/kg, resp.
    75. 75
      Bhoi, P. R.; Huhnke, R. L.; Kumar, A.; Indrawan, N.; Thapa, S. Co-Gasification of Municipal Solid Waste and Biomass in a Commercial Scale Downdraft Gasifier. Energy 2018, 163, 513– 518,  DOI: 10.1016/j.energy.2018.08.151
      75
      Co-gasification of municipal solid waste and biomass in a commercial scale downdraft gasifier
      Bhoi, Prakashbhai R.; Huhnke, Raymond L.; Kumar, Ajay; Indrawan, Natarianto; Thapa, Sunil
      Energy (Oxford, United Kingdom) (2018), 163 (), 513-518CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      In this study, municipal solid waste was gasified with switchgrass, i.e., co-gasification, using a com.-scale downdraft gasifier to produce power. The expts. were performed using a com.-scale 100 kg/h downdraft gasifier at co-gasification ratios of 0, 20 and 40%. The hot and cold gas efficiencies, syngas compns., heating value and yield, gasifier temps. and tar content were measured and analyzed. The results indicate that co-gasification of up to 40% MSW performed satisfactorily. The heating values of syngas were 6.2, 6.5 and 6.7 MJ/Nm3 for co-gasification ratios of 0, 20 and 40%, resp. The cold and hot gas efficiencies were 60.1, 51.1 and 60.0% and 65.0, 55.2 and 64.4% for co-gasification ratios of 0, 20 and 40%, resp.
    76. 76
      Zhu, H. L.; Zhang, Y. S.; Materazzi, M.; Aranda, G.; Brett, D. J. L.; Shearing, P. R.; Manos, G. Co-Gasification of Beech-Wood and Polyethylene in a Fluidized-Bed Reactor. Fuel Process. Technol. 2019, 190, 29– 37,  DOI: 10.1016/j.fuproc.2019.03.010
      76
      Co-gasification of beech-wood and polyethylene in a fluidized-bed reactor
      Zhu, Hua Lun; Zhang, Ye Shui; Materazzi, Massimiliano; Aranda, Guadalupe; Brett, Dan J. L.; Shearing, Paul R.; Manos, George
      Fuel Processing Technology (2019), 190 (), 29-37CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      The co-gasification of beech-wood and polyethylene has been investigated in a lab-scale fluidized-bed reactor in the presence of four different types of bed materials (silica sand, olivine, Na-Y zeolite and ZSM-5 zeolite). ZSM-5 zeolite is very effective as a catalytic bed material in fluidized-bed reactor for wood-only gasification and co-gasification in terms of high hydrogen prodn.and CGE. Na-Y zeolite is more effective compared with ZSM-5 zeolite in co-gasification of the beech-wood and polyethylene process. The catalytic activity in co-gasification of beech-wood and polyethylene can be ranked accordingly: Na-Y zeolite > ZSM-5 zeolite > olivine. In general, higher amts.of steam injected in the fluidized-bed reactor and more polyethylene would lead to higher hydrogen prodn.in the co-gasification process.
    77. 77
      Zhao, Y.; Sun, S.; Zhou, H.; Sun, R.; Tian, H.; Luan, J.; Qian, J. Experimental Study on Sawdust Air Gasification in an Entrained-Flow Reactor. Fuel Process. Technol. 2010, 91, 910– 914,  DOI: 10.1016/j.fuproc.2010.01.012
      77
      Experimental study on sawdust air gasification in an entrained-flow reactor
      Zhao, Yi-Jun; Sun, Shao-Zeng; Zhou, Hao; Sun, Rui; Tian, Hong-Ming; Luan, Ji-Yi; Qian, Juan
      Fuel Processing Technology (2010), 91 (8), 910-914CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Expts. were performed in an entrained-flow reactor to better understand the processes involved in biomass air gasification. Effects of the reaction temps. (700°, 800°, 900°, and 1000°), residence time and the equivalence ratio in the range of 0.22-0.34 on the gasification process were investigated. The behavior of biomass gasification was discussed in terms of compn. of produced gas. Four parameters, i.e. the low heating value, fuel gas prodn., carbon conversion and cold gas efficiency were used to evaluate the gasification. The results show that CO, CO2, and H2 are the main gasification products, while hydrocarbons (CH4 and C2H4) are the minor ones. With the increase of the reaction temp., the concn. of CO decreases, while the concns. of CO2 and H2 increase. The concns. of CH4 and C2H4 reach their max. value when the reaction temp. is 800°. The optimal reaction temp. is considered to be 800° and the optimal equivalence ratio is 0.28 in that the low heating value of the produced gas, carbon conversion and cold gas efficiency achieve their max. values. The kinetic parameters of sawdust air gasification are calcd. basing on the Arrhenius correlation.
    78. 78
      Reed, T. B.; Das, A. Handbook of Biomass Downdraft Gasifier Engine Systems; Solar Energy Research Institute: Golden, CO, 1988.
      There is no corresponding record for this reference.
    79. 79
      Van De Kamp, W.; De Wild, P.; Zielke, U.; Suomalainen, M.; Knoef, H.; Good, J.; Liliedahl, T.; Unger, C.; Whitehouse, M.; Neeft, J.; Van De Hoek, H.; Kiel, J. Tar Measurement Standard for Sampling and Analysis of Tars and Particles in Biomass Gasification Product Gas. In Proceedings of the 14th European Biomass Conference and Exhibition, Paris, France, October 17–21, 2005; Energy Research Centre of the Netherlands: Petten, Netherlands, 2005.
      There is no corresponding record for this reference.
    80. 80
      Eghtedaei, R.; Mirhosseini, S. A.; Esfahani, M. J.; Foroughi, A.; Akbari, H. Co-Gasification of Biomass and Municipal Solid Waste for Hydrogen-Rich Gas Production. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects 2017, 39 (14), 1491– 1496,  DOI: 10.1080/15567036.2017.1315757
      80
      Co-gasification of biomass and municipal solid waste for hydrogen-rich gas production
      Eghtedaei, R.; Mirhosseini, S. A.; Esfahani, M. J.; Foroughi, A.; Akbari, H.
      Energy Sources, Part A: Recovery, Utilization, and Environmental Effects (2017), 39 (14), 1491-1496CODEN: ESPACB; ISSN:1556-7036. (Taylor & Francis, Inc.)
      Gasification is a high-temp. thermochem. process to generate a clean syngas which can be used as an alternative method for fuel conversion. In this article, a kinetic model of co-gasification of biomass and municipal solid waste (MSW) was developed to study the influence of several crit. parameters such as biomass/MSW ratio, reactor temp., and steam/fuel ratio on gas compn., hydrogen yield, and tar content. Results showed that the H2 concn. significantly varies in the produced syngas with changing the MSW/biomass ratio may be due to limited water gas shift and tar cracking reactions. Also, it was found that the tar content does not change significantly with av. values of steam/fuel ratio probably due to the slow kinetics of the hydrocarbon steam reforming reactions at a const. temp.
    81. 81
      Qin, Y. H.; Campen, A.; Wiltowski, T.; Feng, J.; Li, W. The Influence of Different Chemical Compositions in Biomass on Gasification Tar Formation. Biomass Bioenergy 2015, 83, 77– 84,  DOI: 10.1016/j.biombioe.2015.09.001
      81
      The influence of different chemical compositions in biomass on gasification tar formation
      Qin, Yu Hong; Campen, Adam; Wiltowski, Tomasz; Feng, Jie; Li, Wenying
      Biomass and Bioenergy (2015), 83 (), 77-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      To elucidate the relationship between biomass compn. and tar formation, forest residue sawdust, rich in lignin, and agriculture waste cornstalks, rich in cellulose, were gasified in a spout-fluidized bed reactor from 700 °C to 900 °C. Gel permeation chromatog. (GPC) coupled with a photodiode array detector (PDA) and gas chromatog. - mass spectrometry (GC-MS) were used to analyze the tar character. The GPC results showed that the mol. mass distribution of the gasified tars were unchanged, only the amt. of each component changed when the temp. increased during gasification. The amt. of heaviest mol. mass components decreased, while the lighter components increased with temp. Sawdust tar and cornstalks tar both showed arom. character, while cornstalks tar contained more aliph. compds. than sawdust tar. The tar formation mechanism has been proposed from the exptl. data anal.
    82. 82
      Guangul, F. M.; Sulaiman, S. A.; Raghavan, V. R. Gasification and Effect of Gasifying Temperature on Syngas Quality and Tar Generation: A Short Review. AIP Conf. Proc. 2012, 1440, 491– 498,  DOI: 10.1063/1.4704254
      82
      Gasification and effect of gasifying temperature on syngas quality and tar generation: A short review
      Guangul, Fiseha Mekonnen; Sulaiman, Shaharin Anwar; Raghavan, Vijay R.
      AIP Conference Proceedings (2012), 1440 (Pt. 1, 4th International Meeting of Advances in Thermofluids, 2011), 491-498CODEN: APCPCS; ISSN:0094-243X. (American Institute of Physics)
      A review. Corrosion, erosion and plugging of the downstream equipments by tar and ash particle and, low energy content of syngas are the main problems of biomass gasification process. This paper attempts to review the findings of literature on the effect of temp. on syngas quality, and in alleviating the tar and ash problems in the gasification process. The review of literature indicates that as the gasification temp. increases, concn. of the resulting H2 and carbon conversion efficiency increase, the amt. of tar in the syngas decreases. For the same condition, CH4 and CO concn. do not show consistent trend when the feedstock and gasification process varies. These necessitate the need for conducting an expt. for a particular gasification process and feedstock to understand fully the benefits of controlling the gasification temp. This paper also tries to propose a method to improve the syngas quality and to reduce the tar amt. by using preheated air and superheated steam as a gasifying media for oil palm fronds (OPF) gasification. (c) 2012 American Institute of Physics.
    83. 83
      Chen, Y.; Luo, Y. H.; Wu, W. G.; Su, Y. Experimental Investigation on Tar Formation and Destruction in a Lab-Scale Two-Stage Reactor. Energy Fuels 2009, 23 (9), 4659– 4667,  DOI: 10.1021/ef900623n
      83
      Experimental Investigation on Tar Formation and Destruction in a Lab-Scale Two-Stage Reactor
      Chen, Yi; Luo, Yong-hao; Wu, Wen-guang; Su, Yi
      Energy & Fuels (2009), 23 (9), 4659-4667CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      A lab-scale two-stage reactor has been constructed for studying the release and destruction of tars in the two-stage gasifier. First, the pyrolysis characteristics of three fuel samples are investigated only using the single stage reactor. The results show that the max. value of tar yield is: rice straw 25%, corn straw 22%, and fir sawdust 31% of the initial fuel. Then, the exptl. program is extended to investigate the effect of operating conditions in the second stage of the reactor on tar removal. The effects of temp., residence time, char particle size, char type, fuel type, and dild. air feeding to throat on tar emission has been studied. The results show that the tar decreased with increasing temp. and residence time and with decreasing char particle size. The char type has little effect on tar redn. Tar emission with limited dild. air feeding is obviously less than that with empty second stage due to the more reactive radicals produced in oxidative conditions. The straw tars appear to have a different suite of compds. than the other two samples of derived material and presumably have different cracking pathways. The tars collected from first stage and second stage have been characterized by gas chromatog./mass spectrometry (GC/MS) and gel permeation chromatog. The results indicate that tar after pyrolysis contains a large amt. of oxygenated constituents. With the increasing of reaction severity (from the empty heated second stage to heated second stage with char bed), the tar compds. reacted further (polymd.) to form larger mol. mass material. It is clear that the material characterized by GC/MS represents a very small part of the total tar. The results have shown that the tar emission from two-stage gasifier can be reduced to low levels using optimized operating conditions, but complete tar removal is difficult to realize due to manipulation of operating parameters and fuel type.
    84. 84
      Knight, R. A. Experience with Raw Gas Analysis from Pressurized Gasification of Biomass. Biomass Bioenergy 2000, 18 (1), 67– 77,  DOI: 10.1016/S0961-9534(99)00070-7
      There is no corresponding record for this reference.
    85. 85
      Williams, P. T.; Besler, S. Polycyclic Aromatic Hydrocarbons in Waste Derived Pyrolytic Oils. J. Anal Appl. Pyrolysis 1994, 30 (1), 17– 33,  DOI: 10.1016/0165-2370(94)00802-7
      85
      Polycyclic aromatic hydrocarbons in waste derived pyrolytic oils
      Williams, Paul T.; Besler, Serpil
      Journal of Analytical and Applied Pyrolysis (1994), 30 (1), 17-33CODEN: JAAPDD; ISSN:0165-2370.
      Waste material in the form of wood waste, municipal solid waste and rice husks was pyrolyzed in a gas-purged static batch reactor and a fluidized bed reactor. The condensed pyrolytic oils were analyzed for their content of polycyclic arom. hydrocarbons (PAH). The oils were fractionated into chem. classes using mini-column liq. chromatog. followed by anal. using GC/FID and GC/MS for identification and quantitation of PAH. The waste derived oils were found to contain substantial concns. of PAH, which were formed via secondary Diels-Alder and deoxygenation reactions. The concns. of PAH were influenced by reactor temp. and residence time. The PAH consisted mainly of naphthalene, fluorene and phenanthrene and their alkylated homologues, but also included some PAH which were of known carcinogenic or mutagenic activity.
    86. 86
      Nemanova, V.; Engvall, K. Tar Variability in the Producer Gas in a Bubbling Fluidized Bed Gasification System. Energy Fuels 2014, 28 (12), 7494– 7500,  DOI: 10.1021/ef5015617
      86
      Tar Variability in the Producer Gas in a Bubbling Fluidized Bed Gasification System
      Nemanova, Vera; Engvall, Klas
      Energy & Fuels (2014), 28 (12), 7494-7500CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Previous studies in an atm. bubbling fluidized bed (BFB) gasification system indicated significant tar variability along the system. In this paper, the exptl. procedure has been improved for reliable results and understanding of tar variability in the producer gas. By introducing a new sample point for tar anal. to the system, expts. indicated tar redn. in the gasifier, probably due to continuous accumulation of char and ash in the bed, as well as in the ceramic filter because of thermo- and catalytic effects. Thermogravimetric anal. of the filter sample indicated 14% of volatile inorg. compds., and addnl. anal. of inorg. parts showed alkali and alk. earth metal content, well-known as tar breakdown catalysts.
    87. 87
      Dabai, F.; Paterson, N.; Millan, M.; Fennell, P.; Kandiyoti, R. Tar Formation and Destruction in a Fixed-Bed Reactor Simulating Downdraft Gasification: Equipment Development and Characterization of Tar-Cracking Products. Energy Fuels 2010, 24, 4560– 4570,  DOI: 10.1021/ef100681u
      87
      Tar Formation and Destruction in a Fixed-Bed Reactor Simulating Downdraft Gasification: Equipment Development and Characterization of Tar-Cracking Products
      Dabai, Fadimatu; Paterson, Nigel; Millan, Marcos; Fennell, Paul; Kandiyoti, Rafael
      Energy & Fuels (2010), 24 (8), 4560-4570CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      The aim of the present study is to examine operating parameters that would reduce the residual tar content in the fuel gas in downdraft gasifiers and eventually eliminate it altogether. A two-stage fixed-bed reactor was employed to simulate elements of tar cracking in a downdraft gasifier. In this reactor, tar is generated by pyrolysis in the first stage and cracking and gasification take place in the second stage. Modifications to a previous configuration of this reactor are described, which have enabled the use of smaller char particle sizes in the second stage and the generation of a more complete inventory of the reaction products. In this work, the effect of the temp. and the presence of char on product distributions are reported. Increasing the temp. from 700 to 1000°C resulted in a decrease in the quantity of tar recovered and an increase in the total amt. of CO released. The amt. of CH4 released increased between 700 and 800°C before remaining steady up to 1000°C. The CO2 content of the gas was relatively const. between 700 and 800°C and increased as the temp. increased from 800 to 1000°C. The amt. of water and light hydrocarbons (C2-C5 alkanes and alkenes) sharply decreased at 1000°C. The presence of char in the second stage had significant effects on tar cracking and product distributions. These effects were more obvious on the concns. of CO, CO2, and H2O, which may be a result of redn. reactions taking place with the carbon in the packed char bed. These reactions appear to be more significant at temps. between 900 and 1000°C, where the rates of gasification are expected to increase.
    88. 88
      Atnaw, S. M.; Kueh, S. C.; Sulaiman, S. A. Study on Tar Generated from Downdraft Gasification of Oil Palm Fronds. Sci. World J. 2014, 2014, 497830,  DOI: 10.1155/2014/497830
      There is no corresponding record for this reference.
    89. 89
      Mahapatra, S.; Dasappa, S. Influence of Surface Area to Volume Ratio of Fuel Particles on Gasification Process in a Fixed Bed. Energy for Sustainable Development 2014, 19 (1), 122– 129,  DOI: 10.1016/j.esd.2013.12.013
      89
      Influence of surface area to volume ratio of fuel particles on gasification process in a fixed bed
      Mahapatra, Sadhan; Dasappa, S.
      Energy for Sustainable Development (2014), 19 (), 122-129CODEN: ESDEFY; ISSN:0973-0826. (Elsevier B.V.)
      The paper addresses the effect of particle size on tar generation in a fixed bed gasification system. Pyrolysis, a diffusion limited process, depends on the heating rate and the surface area of the particle influencing the release of the volatile fraction leaving behind residual char. The flaming time has been estd. for different biomass samples. It is found that the flaming time for wood flakes is almost one fourth than that of coconut shells for same equiv. diam. fuel samples. The particle d. of the coconut shell is more than twice that of wood spheres, and almost four times compared with wood flakes; having a significant influence on the flaming time. The ratio of the particle surface area to that of an equiv. diam. is nearly two times higher for flakes compared with wood pieces. Accounting for the d. effect, on normalizing with d. of the particle, the flaming rate is double in the case of wood flakes or coconut shells compared with the wood sphere for an equiv. diam. This is due to increased surface area per unit vol. of the particle. Expts. are conducted on estn. of tar content in the raw gas for wood flakes and std. wood pieces. It is obsd. that the tar level in the raw gas is about 80% higher in the case of wood flakes compared with wood pieces. The anal. suggests that the time for pyrolysis is lower with a higher surface area particle and is subjected to fast pyrolysis process resulting in higher tar fraction with low char yield. Increased residence time with staged air flow has a better control on residence time and lower tar in the raw gas.
    90. 90
      Surjosatyo, A.; Vidian, F.; Nugroho, Y. S. Experimental Gasification of Biomass in an Updraft Gasifier with External Recirculation of Pyrolysis Gases. J. Combustion 2014, 2014, 832989,  DOI: 10.1155/2014/832989
      There is no corresponding record for this reference.
    91. 91
      Font Palma, C. Model for Biomass Gasification Including Tar Formation and Evolution. Energy Fuels 2013, 27, 2693– 2702,  DOI: 10.1021/ef4004297
      91
      Model for Biomass Gasification Including Tar Formation and Evolution
      Font Palma, Carolina
      Energy & Fuels (2013), 27 (5), 2693-2702CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Since tar elimination from the product gas is necessary to make gasification an attractive option, the presence of tar was included in a kinetic model. Lignin was assumed as the main precursor of tars due to its arom. nature; therefore, the lignin content of biomass was considered as part of the fuel characterization. This work shows the results from the simulation of the fluidized bed gasifier that incorporates the proposed mechanism for tar formation and evolution into the kinetic model. Model results were compared with exptl. data from wood gasification. The comparison showed that the model was consistent with what was expected during the evolution of primary tars according to exptl. work from previous reports. However, the model overestimated tars of class 2 and the total tar concn.
    92. 92
      Qian, K.; Kumar, A.; Patil, K.; Bellmer, D.; Wang, D.; Yuan, W.; Huhnke, R. L. Effects of Biomass Feedstocks and Gasification Conditions on the Physiochemical Properties of Char. Energies 2013, 6 (8), 3972– 3986,  DOI: 10.3390/en6083972
      92
      Effects of biomass feedstocks and gasification conditions on the physiochemical properties of char
      Qian, Kezhen; Kumar, Ajay; Patil, Krushna; Bellmer, Danielle; Wang, Donghai; Yuan, Wenqiao; Huhnke, Raymond L.
      Energies (Basel, Switzerland) (2013), 6 (), 3972-3986CODEN: ENERGA; ISSN:1996-1073. (MDPI AG)
      Char is a low-value byproduct of biomass gasification and pyrolysis with many potential applications, such as soil amendment and the synthesis of activated carbon and carbon-based catalysts. Considering these high-value applications, char could provide economic benefits to a biorefinery utilizing gasification or pyrolysis technologies. However, the properties of char depend heavily on biomass feedstock, gasifier design and operating conditions. This paper reports the effects of biomass type (switchgrass, sorghum straw and red cedar) and equivalence ratio (0.20, 0.25 and 0.28), i.e., the ratio of air supply relative to the air that is required for stoichiometric combustion of biomass, on the physiochem. properties of char derived from gasification. Results show that the Brunauer-Emmett-Teller (BET) surface areas of most of the char were 1-10 m2/g and increased as the equivalence ratio increased. Char moisture and fixed carbon contents decreased while ash content increased as equivalence ratio increased. The corresponding Fourier Transform IR spectra showed that the surface functional groups of char differed between biomass types but remained similar with change in equivalence ratio.
    93. 93
      Hwang, I. H.; Kobayashi, J.; Kawamoto, K. Characterization of Products Obtained from Pyrolysis and Steam Gasification of Wood Waste, RDF, and RPF. Waste Management 2014, 34 (2), 402– 410,  DOI: 10.1016/j.wasman.2013.10.009
      93
      Characterization of products obtained from pyrolysis and steam gasification of wood waste, RDF, and RPF
      Hwang, In-Hee; Kobayashi, Jun; Kawamoto, Katsuya
      Waste Management (Oxford, United Kingdom) (2014), 34 (2), 402-410CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
      Pyrolysis and steam gasification of woody biomass chip (WBC) obtained from construction and demolition wastes, refuse-derived fuel (RDF), and refuse paper and plastic fuel (RPF) were performed at various temps. using a lab-scale instrument. The gas, liq., and solid products were examd. to det. their generation amts., properties, and the carbon balance between raw material and products.The amt. of product gas and its hydrogen concn. showed a considerable difference depending on pyrolysis and steam gasification at higher temp. The reaction of steam and solid product, char, contributed to an increase in gas amt. and hydrogen concn. The amt. of liq. products generated greatly depended on temp. rather than pyrolysis or steam gasification. The compns. of liq. product varied relying on raw materials used at 500 °C but the polycyclic arom. hydrocarbons became the major compds. at 900 °C irresp. of the raw materials used. Almost fixed carbon (FC) of raw materials remained as solid products under pyrolysis condition whereas FC started to decomp. at 700 °C under steam gasification condition.For WBC, both char utilization by pyrolysis at low temp. (500 °C) and syngas recovery by steam gasification at higher temp. (900 °C) might be practical options. From the results of carbon balance of RDF and RPF, it was confirmed that the carbon conversion to liq. products conspicuously increased as the amt. of plastic increased in the raw material. To recover feedstock from RPF, pyrolysis for oil recovery at low temp. (500 °C) might be one of viable options. Steam gasification at 900 °C could be an option but the method of tar reforming (e.g. catalyst utilization) should be considered.
    94. 94
      Norisada, K.; Murakami, T.; Yasuda, H. New Approach to Analysis of Tar Components in Syngas Generated by Steam Gasification of Lignite in Fluidized Bed Gasifier. Energy Fuels 2017, 31 (1), 249– 254,  DOI: 10.1021/acs.energyfuels.6b02210
      94
      New Approach to Analysis of Tar Components in Syngas Generated by Steam Gasification of Lignite in Fluidized Bed Gasifier
      Norisada, Kazushi; Murakami, Takahiro; Yasuda, Hajime
      Energy & Fuels (2017), 31 (1), 249-254CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Lignite is a low-rank coal that is not used as a fuel in Japan. However, the effective use of this resource could be enabled by prodn. of syngas (hydrogen, carbon monoxide, etc.) from lignite through gasification. Tar in the syngas generated using the fluidized bed gasifier must be removed, and the tar compn. should be considered for the design of effective tar removal equipment. A new anal. and anal. methods of the tar were developed herein. Gas chromatograph mass spectrometry (GC/MS) and field desorption mass spectrometry (FD-MS) were used in combination to analyze the tar obtained during steam gasification of lignite at 1123 K using a lab.-scale fluidized bed gasifier. The low-boiling-point components were previously identified by GC/MS. However, the combined use of GC/MS and FD-MS in the new approach presented herein enabled elucidation of the overall compn. of tar, including the high-boiling-point components.
    95. 95
      Rakesh, N.; Dasappa, S. Analysis of Tar Obtained from Hydrogen-Rich Syngas Generated from a Fixed Bed Downdraft Biomass Gasification System. Energy Convers Manag 2018, 167, 134– 146,  DOI: 10.1016/j.enconman.2018.04.092
      95
      Analysis of tar obtained from hydrogen-rich syngas generated from a fixed bed downdraft biomass gasification system
      Rakesh, N.; Dasappa, S.
      Energy Conversion and Management (2018), 167 (), 134-146CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      This paper focuses on the development of a test protocol for the anal. of tar collected from an oxy-steam gasification system with a downdraft reactor configuration using biomass. A 10 kg·h-1 oxy-steam gasification system developed at the Indian Institute of Science, Bangalore was used for the studies. The present work involves qual. and quant. analyses to est. the amt. and nature of the tar present in the gas produced. The major focus of the work has been towards establishing protocols to est. the content and concn. of various species present in the raw and clean gas. The method uses internal std. alongside external stds. while analyzing compds. using GC-MS and GC-FID. The study clearly establishes the need for using different ref. compds. like naphthalene and phenol for the quantification process depending upon the nature of compds. manifesting as tar mols. Further, it has been established that the conventionally used gravimetric anal. has limitations towards estg. the total amt. of tar. GC-MS is used for the identification of the compds. The results from the study indicate that the av. values obtained for clean gas and raw gas are 2.7 mg·Nm-3 and 168 mg·Nm-3 with gravimetric anal. and 37.6mg·Nm-3 and 267 mg·Nm-3 with GC-MS/FID method. The lower hydrocarbons, having the no. of carbon atoms in the range of 1-5, which are not considered as tar compds., are absent in the clean gas and are quantified to be 10.6mg·Nm-3 in the raw gas. Finally, the study also captures a technique of anal. and quantification which is of general nature, used generally in org. compd. estn., and therefore can be applied as a generic procedure. The results indicate that the level of tar in the clean gas is low, making the gas suitable for a variety of applications, and the effluent treatment process simpler. The anal. presents an est. of the tar level obtained with the GC-FID technique using both internal and external calibration curves. These results are compared with results from a similar approach using GC-MS for quantification and from the external calibration curves using GC-FID and GC-MS. These studies confirm that the approach presented here is suitable for the present research activity.
    96. 96
      Meng, X.; Mitsakis, P.; Mayerhofer, M.; de Jong, W.; Gaderer, M.; Verkooijen, A. H.M.; Spliethoff, H. Spliethoff Hartmut. Tar Formation in a Steam-O 2 Blown CFB Gasifier and a Steam Blown PBFB Gasifier (BabyHPR): Comparison between Different on-Line Measurement Techniques and the off-Line SPA Sampling and Analysis Method. Fuel Process. Technol. 2012, 100, 16– 29,  DOI: 10.1016/j.fuproc.2012.03.002
      96
      Tar formation in a steam-O2 blown CFB gasifier and a steam blown PBFB gasifier (BabyHPR): Comparison between different on-line measurement techniques and the off-line SPA sampling and analysis method
      Meng, Xiangmei; Mitsakis, Panagiotis; Mayerhofer, Matthias; de Jong, Wiebren; Gaderer, Matthias; Verkooijen, Adrian H. M.; Spliethoff, Hartmut
      Fuel Processing Technology (2012), 100 (), 16-29CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Two online tar measurement campaigns were carried out using an atm. pressure 100 ""kWth steam-O2 blown circulating fluidized bed (CFB) gasifier at the Delft University of Technol. (TUD) and a 30-40kWth steam blown pressurized bubbling fluidized bed (PBFB) gasifier BabyHPR (Heatpipe Reformer) at the Tech. University Munich (TUM). Agrol, willow and Dry Distiller's Grains with Solubles (DDGS) were used. An FID based online tar analyzer (OTA), an induced fluorescence spectroscopy (LIFS) based online laser instrument, and off-line solid phase adsorption (SPA) were used to quantify tar content. In general, there was a fairly good agreement between the measured results of the 10 corresponding individual tar compds. obtained from Agrol and willow CFB and PBFB atm. pressure tests using the SPA and LIFS methods. The measured tar concn. difference between these two methods was less than 10%. However, a higher difference (up to 30%) was obsd. for fluoranthene and pyrene obtained from DDGS CFB test as well as those obtained from willow PBFB under pressure test. The total tar concn. measured by the LIFS, SPA and OTA methods varied in a comparable way with changing process parameters. Both the LIFS and OTA methods can be used as indicators to observe gasifier's performance change in real time, but a regular calibration of the OTA analyzer is required to achieve good and reliable results.
    97. 97
      Sun, R.; Zobel, N.; Neubauer, Y.; Cardenas Chavez, C.; Behrendt, F. Analysis of Gas-Phase Polycyclic Aromatic Hydrocarbon Mixtures by Laser-Induced Fluorescence. Opt. Lasers Eng. 2010, 48, 1231– 1237,  DOI: 10.1016/j.optlaseng.2010.06.009
      There is no corresponding record for this reference.
    98. 98
      Li, C.; Suzuki, K. Tar Property, Analysis, Reforming Mechanism and Model for Biomass Gasification-An Overview. Renewable Sustainable Energy Rev. 2009, 594– 604,  DOI: 10.1016/j.rser.2008.01.009
      98
      Tar property, analysis, reforming mechanism and model for biomass gasification-An overview
      Li, Chunshan; Suzuki, Kenzi
      Renewable & Sustainable Energy Reviews (2009), 13 (3), 594-604CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review, with 41 refs. Biomass becomes an important primary energy source as well as renewable energy source. As the most promising biomass use method, biomass gasification is gaining attention as a route for biomass energy prodn., but producer gas from this process usually contains unacceptable levels of tar. The tar control and convert is a key issue for a successful application of biomass-derived producer gas. A detail overview on tar chem. and phys. properties, reforming mechanism and reaction kinetic model are summarized.
    99. 99
      Carpenter, D. L.; Deutch, S. P.; French, R. J. Quantitative Measurement of Biomass Gasifier Tars Using a Molecular-Beam Mass Spectrometer: Comparison with Traditional Impinger Sampling. Energy Fuels 2007, 21 (5), 3036– 3043,  DOI: 10.1021/ef070193c
      99
      Quantitative Measurement of Biomass Gasifier Tars Using a Molecular-Beam Mass Spectrometer: Comparison with Traditional Impinger Sampling
      Carpenter, Daniel L.; Deutch, Steve P.; French, Richard J.
      Energy & Fuels (2007), 21 (5), 3036-3043CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Removal of tars produced during biomass gasification continues to be a tech. barrier confronted by developers of com. thermochem. conversion systems. Quant. measurement of tar in the synthesis gas (syngas) stream is important to assess the effectiveness of cleanup and conditioning processes and verify the suitability of the cleaned syngas for its intended downstream use (e.g., catalytic conversion to liq. fuels, hydrogen recovery, or electricity prodn.). In an effort to advance the art of gasifier tar measurement and address some limitations of traditional impinger sampling, the use of a mol.-beam mass spectrometer (MBMS) sampling system was investigated as an alternative method for quantifying real-time tar concns. in biomass gasifier-derived syngas. The 0.5 ton/day pilot-scale biomass gasification system of the National Renewable Energy Lab. (NREL) was used to make direct comparisons between MBMS sampling and replicate impinger sampling during continuous operations. Some systematic differences between the methods were obsd., although they do appear correlated. Using a synthetic tar mixt., as well as actual corn-stover-derived syngas, expts. were carried out to compare the accuracy of the two methods. Both methods demonstrated good reproducibility, but the MBMS measurements appear to be more accurate. Tar concns. detd. from impinger sampling averaged 11-21% lower than expected, depending upon the compd. Av. MBMS measurements were within 6% of the known values, demonstrating that the MBMS can be used to improve quant., continuous, real-time monitoring of gasifier tar.
    100. 100
      Brage, C.; Yu, Q.; Chen, G.; Sjöström, K. Use of Amino Phase Adsorbent for Biomass Tar Sampling and Separation. Fuel 1997, 76 (2), 137– 142,  DOI: 10.1016/S0016-2361(96)00199-8
      100
      Use of amino phase adsorbent for biomass tar sampling and separation
      Brage, Claes; Yu, Qizhuang; Chen, Guanxing; Sjoestroem, Krister
      Fuel (1997), 76 (2), 137-142CODEN: FUELAC; ISSN:0016-2361. (Elsevier)
      To reduce sampling and sample sepn. time, a highly efficient gas chromatog. method was designed based on solid-phase adsorption (SPA) on an aminopropylsilane-silica gel column. The method was suitable for intermittent trapping of tar compds., ranging from benzene to coronene, prevailing in product gases from thermal decompn. of biomass at 700-1000°. Using eluotropic elution, adsorbates were selectively desorbed into arom. and phenolic fractions and then detd. by gas chromatog. with flame-ionization detection. Use of this sampling step resulted in collection of one to three samples per min, compared with one or two samples per h using conventional cold trapping techniques. Thus, the progress of pyrolysis and gasification processes in terms of mol. distribution is easily followed. Furthermore, the method can be readily applied to establish cold-trap and filter performance and for industrial emission control. The method also compared favorably with a novel solid-phase micro extn. technique with respect to analyte discrimination and speed.
    101. 101
      Morf, P.; Hasler, P.; Nussbaumer, T. Mechanisms and Kinetics of Homogeneous Secondary Reactions of Tar from Continuous Pyrolysis of Wood Chips. Fuel 2002, 81 (7), 843– 853,  DOI: 10.1016/S0016-2361(01)00216-2
      101
      Mechanisms and kinetics of homogeneous secondary reactions of tar from continuous pyrolysis of wood chips
      Morf, Philipp; Hasler, Philipp; Nussbaumer, Thomas
      Fuel (2002), 81 (7), 843-853CODEN: FUELAC; ISSN:0016-2361. (Elsevier Science Ltd.)
      The change of mass and compn. of biomass tar due to homogeneous secondary reactions was exptl. studied by a lab reactor system that allows the spatially sepd. prodn. and conversion of biomass tar. A tarry pyrolysis gas was continuously produced by pyrolysis of wood chips (fir and spruce, 10-40 mm diam.) under fixed-bed biomass gasification conditions. Homogeneous secondary tar reactions without the external supply of oxidizing agents were studied in a tubular flow reactor operated at 500-1000° and with space times <0.2 s. Extensive chem. anal. of wet chem. tar samples provided quant. data about the mass and compn. of biomass tar during homogeneous conversion. These data were used to study the kinetics of the conversion of gravimetric tar and the formation of PAH compds., like naphthalene. Under the reactions conditions chosen for the expts., homogeneous secondary tar reactions become important at temps. >650, which is indicated by the increasing concns. of the gases CO, CH, and H in the pyrolysis gas. The gravimetric tar yield decreases with increasing reactor temps. during homogeneous tar conversion. The highest conversion reached in the expts. was 88% at a ref. temp. of 990° and isothermal space time of 0.12 s. Hydrogen is a good indicator for reactions that convert the primary tar into aroms., esp. PAH. Soot appears to be a major product from homogeneous secondary tar reactions.
    102. 102
      Valderrama Rios, M. L.; González, A. M.; Lora, E. E. S.; Almazán del Olmo, O. A. Reduction of Tar Generated during Biomass Gasification: A Review. Biomass Bioenergy 2018, 108, 345– 370,  DOI: 10.1016/j.biombioe.2017.12.002
      102
      Reduction of tar generated during biomass gasification: A review
      Valderrama Rios, Martha Lucia; Gonzalez, Aldemar Martinez; Lora, Electo Eduardo Silva; Almazan del Olmo, Oscar Agustin
      Biomass and Bioenergy (2018), 108 (), 345-370CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      A review. One of the main problems that happen during biomass gasification is tar formation, which could make this technol. unsuccessfully from a com. point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, lab. and industrial methods and technologies for its redn.-removal, as well as research and development in this area are reviewed and evaluated in this paper.
    103. 103
      Bosmans, A.; Wasan, S.; Helsen, L. Waste-to-Clean Syngas: Avoiding Tar Problems. In Proceedings of the 2nd International Academic Symposium on Enhanced Landfill Mining, Houthalen-Helchteren, Belgium, October 14–16, 2013; .EURELCO: Leuven, Belgium, 2013.
      There is no corresponding record for this reference.
    104. 104
      Delgado, J.; Aznar, M. P.; Corella, J. Biomass Gasification with Steam in Fluidized Bed: Effectiveness of CaO, MgO, and CaO-MgO for Hot Raw Gas Cleaning. Ind. Eng. Chem. Res. 1997, 36, 1535– 1543,  DOI: 10.1021/ie960273w
      104
      Biomass Gasification with Steam in Fluidized Bed: Effectiveness of CaO, MgO, and CaO-MgO for Hot Raw Gas Cleaning
      Delgado, Jesus; Aznar, Maria P.; Corella, Jose
      Industrial & Engineering Chemistry Research (1997), 36 (5), 1535-1543CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      The upgrading of the raw hot gas from a bubbling fluidized bed biomass gasifier is studied using cheap calcined minerals or rocks downstream from the gasifier. Biomass gasification is made with steam (not air) at 750-780° and about 0.5-1.0 kg of biomass/h. Calcined solids used are dolomite (MgO-CaO), pure calcite (CaO), and pure magnesite (MgO). Variables studied have been temp. of the secondary bed (780-910°), time of contact or space-time of the gas (0.08-0.32 kg·h/m3n), and particle diam. (1-4 mm) and type of mineral. Their effects on tar conversion, tar amt. in the exit gas, product distribution, and gas compn. are presented. Using a macro-kinetic model for the tar disappearance network, the activities of the stones are expressed by their apparent kinetic const. Apparent energies of activation for tar elimination (42-47 kJ/mol) and preexponential and effectiveness factors are given for all tested solids of which the most active is the calcined dolomite.
    105. 105
      Van Paasen, S. V. B.; Neeft, J. P. A.; Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G.; Meijer, R.; Berends, R. H.; Temmink, H. M. G.; Brem, G.; Padban, N.; Bramer, E A. Primary Measures to Reduce Tar Formation in Fluidised-Bed Biomass Gasifiers; Final Report SDE project P1999-012; Kiel, J. H. A., Ed.; Energy Research Centre of the Netherlands: Petten, Netherlands, 2004.
      There is no corresponding record for this reference.
    106. 106
      Cortazar, M.; Santamaria, L.; Lopez, G.; Alvarez, J.; Zhang, L.; Wang, R.; Bi, X.; Olazar, M. A Comprehensive Review of Primary Strategies for Tar Removal in Biomass Gasification. Energy Convers Manag 2023, 276, 116496  DOI: 10.1016/j.enconman.2022.116496
      106
      A comprehensive review of primary strategies for tar removal in biomass gasification
      Cortazar, M.; Santamaria, L.; Lopez, G.; Alvarez, J.; Zhang, L.; Wang, R.; Bi, X.; Olazar, M.
      Energy Conversion and Management (2023), 276 (), 116496CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      A review. In the current energy scenario, the prodn. of heat, power and biofuels from biomass have become of major interest. Amongst diverse thermochem. routes, gasification has stood out as a key technol. for the large-scale application of biomass. However, the development of biomass gasification is subjected to the efficient conversion of biochar and the mitigation of troublesome byproducts, such as tar. Syngas with high tar content can cause pipeline fouling, downstream corrosion, catalyst deactivation, as well as adverse impact on health and environment, which obstruct the commercialization of biomass gasification technologies. Since the redn. of tar formation is a key challenge in biomass gasification, a comprehensive overview is provided on the following aspects, which particularly include the definition and complementary classifications of tar, as well as possible tar formation and transformation mechanisms. Moreover, the adverse effects of tar on downstream applications, human health or environment, and tar analyzing techniques (online and off-line) are discussed. Finally, the primary tar removal strategies are summarized. In this respect, the effect of key operation parameters (temp., ER and S/B), catalysts utilization (natural and supported metal catalysts) and the improvement of reactor design on tar formation and elimination was thoroughly analyzed.
    107. 107
      Nobre, C.; Longo, A.; Vilarinho, C.; Goncalves, M. Gasification of Pellets Produced from Blends of Biomass Wastes and Refuse Derived Fuel Chars. Renew Energy 2020, 154, 1294– 1303,  DOI: 10.1016/j.renene.2020.03.077
      107
      Gasification of pellets produced from blends of biomass wastes and refuse derived fuel chars
      Nobre, Catarina; Longo, Andrei; Vilarinho, Candida; Goncalves, Margarida
      Renewable Energy (2020), 154 (), 1294-1303CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Refuse derived fuel (RDF) was carbonized at 300°C for 30 min and the resulting RDF char was used as additive for biomass pellets. Pine waste pellets with 0, 5 and 10% incorporation of RDF char were prepd. and characterized. RDF char incorporation caused an increase in fixed carbon and ash contents of the pellets. The pellets were subjected to gasification in a 1 kg/h bubbling-fluidized-bed gasifier at different temps. (800 and 850°C) and equivalence ratios (0.25 and 0.30). The producer gas yield varied from 1.5 to 2.5 m3/kg and was higher for an ER of 0.25. Carbon conversion and cold gas efficiency presented values between 60.4% - 96.1% and 42.3%-73.7%, resp. Concns. of CO, CO2, H2 and CH4 reached values between 13.3-17.4 vol% dry for CO, 13.1-14.7 vol% dry for CO2, 4.9-11.1 vol% dry for H2 and 3.5-4.4 vol% dry for CH4. Tars produced during gasification contained mainly arom. hydrocarbons and phenols, showing an increase in heavy PAHs concn. with higher RDF char incorporation. The RDF char can be used as a gasification additive at moderate incorporation ratios.
    108. 108
      Mastellone, M. L.; Zaccariello, L.; Arena, U. Co-Gasification of Coal, Plastic Waste and Wood in a Bubbling Fluidized Bed Reactor. Fuel 2010, 89, 2991– 3000,  DOI: 10.1016/j.fuel.2010.05.019
      108
      Co-gasification of coal, plastic waste and wood in a bubbling fluidized bed reactor
      Mastellone, Maria Laura; Zaccariello, Lucio; Arena, Umberto
      Fuel (2010), 89 (10), 2991-3000CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Seven mixts. of coals, plastics and wood have been pelletized and fed into a pre-pilot scale fluidized bed gasifier in order to investigate the main aspects of the co-gasification of these materials. The main components of the obtained syngas (CO, H2, CO2, N2, CH4, CnHm) were measured by means of online analyzers and a gas cromatograph. The performance of the gasifier was evaluated on the basis of syngas compn., carbon conversion efficiency, energy content of syngas, cold gas efficiency and yield of undesired byproducts (tar and soot-like particulate). The results of a first series of exptl. tests showed the effect of gas fluidizing velocity and that of equivalence ratio on the main performance parameters for a specific coal-plastics mixt. A second series of tests has been carried out by changing the mixt. compn. keeping fixed the gas velocity and equivalence ratio. The presence of wood and coal in the mixt. with plastics contributed to reduce the tar prodn. even though it is accompanied by a lower syngas specific energy.
    109. 109
      Kostyniuk, A.; Grilc, M.; Likozar, B. Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds to Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures. Ind. Eng. Chem. Res. 2019, 58 (19), 7690– 7705,  DOI: 10.1021/acs.iecr.9b01219
      109
      Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds To Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures
      Kostyniuk, Andrii; Grilc, Miha; Likozar, Blaz
      Industrial & Engineering Chemistry Research (2019), 58 (19), 7690-7705CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      A review. The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chem. substances, and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodol. unsuccessfully due to the blockage of sepg. particle filters, fuel line flow, and substantial transfer losses. Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, it is still highly desirable to enhance the catalysts' activity kinetics, selectivity, stability, resistance to (ir)reversible coke deposition, and regeneration solns. The purpose of this review is to provide a comparative systematic evaluation of the various natural, synthetic, and hybrid ways to convert the model mol. compds. into benzene, toluene, xylene, (poly)aroms., syngas, and others. The recent scientific progress, including calcite, dolomite, lime, magnesite, olivine, char, nonmetallic activated carbons, supported alkali, noble, and transition metals, and (metal-promoted) zeolites, is presented. A special concd. attention is paid to effectiveness, related to hydrogenation, peculiar pore structure, and formulations' suitable acidity. The role of catalysis is described, recommendations for prospective catalyzed mechanisms are provided, and future tech. feasibility is discussed as well.
    110. 110
      Zhen, H.; Wang, Y.; Fang, S.; Lin, Y.; Song, D.; Zhao, K.; Zhang, Y.; Xia, H.; Zhao, Z.; Huang, H. Chemical Looping Gasification of Benzene as a Biomass Tar Model Compound Using Hematite Modified by Ni as an Oxygen Carrier. Appl. Energy Combust. Sci. 2023, 15, 100172,  DOI: 10.1016/j.jaecs.2023.100172
      There is no corresponding record for this reference.
    111. 111
      Simell, P. A.; Hirvensalo, E. K.; Smolander, V. T.; Krause, A. O. I. Steam Reforming of Gasification Gas Tar over Dolomite with Benzene as a Model Compound. Ind. Eng. Chem. Res. 1999, 38, 1250– 1257,  DOI: 10.1021/ie980646o
      111
      Steam Reforming of Gasification Gas Tar over Dolomite with Benzene as a Model Compound
      Simell, Pekka A.; Hirvensalo, Elisa K.; Smolander, Visa T.; Krause, A. Outi I.
      Industrial & Engineering Chemistry Research (1999), 38 (4), 1250-1257CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      Tar decompn. over a dolomite catalyst in gasification conditions was modeled using benzene as a tar model compd. The reactions of the gas main components were included in the models studied. Kinetic studies were carried out at 750-925 °C and under ambient pressure in a plug flow reactor using a mixt. of simulated gasification gas. Operation conditions without external or internal mass-transfer limitations were applied. Mechanistic models of the Langmuir-Hinshelwood type describing benzene decompn. were developed and tested. Exptl. results could be best described by a kinetic rate equation based on the assumption that single-site adsorption of benzene was the rate-detg. step and that adsorption of hydrogen inhibited benzene decompn.
    112. 112
      Colby, J. L.; Wang, T.; Schmidt, L. D. Steam Reforming of Benzene as a Model for Biomass-Derived Syngas Tars over Rh-Based Catalysts. Energy Fuels 2010, 24 (2), 1341– 1346,  DOI: 10.1021/ef901033d
      112
      Steam Reforming of Benzene As a Model for Biomass-Derived Syngas Tars over Rh-Based Catalysts
      Colby, Joshua L.; Wang, Tao; Schmidt, Lanny D.
      Energy & Fuels (2010), 24 (2), 1341-1346CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      The ability of Rh based catalysts to remove undesired tars from biomass-derived syngas was examd. under realistic operating conditions. Expts. were performed in a fixed bed reactor at temps. of 650-850°C and atm. pressure using C6H6 as a model tar compd. Benzene conversion exhibited a strong dependence on temp. and H2O concn. in the feed. Significantly better catalyst performance was obsd. upon addn. of Ce to the catalyst, which increased Rh dispersion and stability. The concn. of C6H6 in the feed had little effect on catalyst performance. CO2, H2, and CO cofeeds had pos., neutral, and neg. effects, resp., on C6H6 conversion. A representative biomass-derived syngas mixt. of N2, H2, CO, CO2, H2O, and C6H6 was tested on the Rh-Ce catalyst at 850°C and 2 SLPM total flow rate, resulting in almost complete C6H6 conversion to a near equil. product stream.
    113. 113
      Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Removal Characteristics of Tar Benzene Using the Externally Oscillated Plasma Reformer. Chemical Engineering and Processing: Process Intensification 2012, 57–58, 65– 74,  DOI: 10.1016/j.cep.2012.03.007
      There is no corresponding record for this reference.
    114. 114
      Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Decomposition of Benzene as a Surrogate Tar in a Gliding Arc Plasma. Environ. Prog. Sustain Energy 2013, 32 (3), 837– 845,  DOI: 10.1002/ep.11663
      There is no corresponding record for this reference.
    115. 115
      Park, H. J.; Park, S. H.; Sohn, J. M.; Park, J.; Jeon, J.-K.; Kim, S.-S.; Park, Y.-K. Steam Reforming of Biomass Gasification Tar Using Benzene as a Model Compound over Various Ni Supported Metal Oxide Catalysts. Bioresour. Technol. 2010, 101, S101– S103,  DOI: 10.1016/j.biortech.2009.03.036
      There is no corresponding record for this reference.
    116. 116
      Saleem, F.; Khoja, A. H.; Umer, J.; Ahmad, F.; Abbas, S. Z.; Zhang, K.; Harvey, A. Removal of Benzene as a Tar Model Compound from a Gas Mixture Using Non-Thermal Plasma Dielectric Barrier Discharge Reactor. J. Energy Institute 2021, 96, 97– 105,  DOI: 10.1016/j.joei.2021.02.008
      116
      Removal of benzene as a tar model compound from a gas mixture using non-thermal plasma dielectric barrier discharge reactor
      Saleem, Faisal; Khoja, Asif Hussain; Umer, Jamal; Ahmad, Farhan; Abbas, Syed Zaheer; Zhang, Kui; Harvey, Adam
      Journal of the Energy Institute (2021), 96 (), 97-105CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
      In the present work, the decompn. of benzene as a tar model compd. was studied in a gas mixt. (CO2, H2, CO, and CH4) using a dielec. barrier discharge (DBD) non-thermal plasma reactor. The combined effect of temp. and power was studied to investigate the performance of the DBD reactor. The decompn. of tar compd. increased from 49.9 to 96% with increasing specific input energy (SIE) from 2.05 to 16.4 kWh/m3. The major products were lower hydrocarbons (C2-C5) and solid residues. The higher temp. (400°C) in the presence of plasma (40 W), decreased the conversion of tar compd. from 96 to 78%. However, the selectivity of lower hydrocarbons increases substantially to 52%, and the formation of solid residues is significantly reduced. Hence, the problematic solid residues formation can be controlled at a higher temp. during the treatment of gasifier product gas using non-thermal plasma.
    117. 117
      Pan, W.; Meng, J.; Gu, T.; Zhang, Q.; Zhang, J.; Wang, X.; Bu, C.; Liu, C.; Xie, H.; Piao, G. Plasma Catalytic Steam Reforming of Benzene as a Tar Model Compound over Ni-HAP and Ni-GammaAl2O3 Catalysts: Insights into the Importance of Steam and Catalyst Support. Fuel 2023, 339, 127327,  DOI: 10.1016/j.fuel.2022.127327
      117
      Plasma-catalytic steam reforming of benzene as a tar model compound over Ni-HAP and Ni-γAl2O3 catalysts: Insights into the importance of steam and catalyst support
      Pan, Wei; Meng, Junguang; Gu, Tingting; Zhang, Qian; Zhang, Jubing; Wang, Xinye; Bu, Changsheng; Liu, Changqi; Xie, Hao; Piao, Guilin
      Fuel (2023), 339 (), 127327CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Non-thermal plasma (NTP) coupled Ni-based catalysts are a promising method for tar steam reforming to syngas. In this work, Ni-based catalysts supported on hydroxyapatite (Ni-HAP) and γAl2O3 (Ni-γAl2O3) coupled with a coaxial dielec. barrier discharge (DBD) plasma were used to degrade biomass tar, and benzene was selected as a typical unbranched benzene ring structured tar model compd. In the NTP alone system, an increase in discharge power leads to benzene deep cracking to carbon deposition. In the NTP-catalytic system, the reaction temp. is a crit. factor for catalysis, and the catalyst leads to a significant increase in benzene conversion and total gas yield, prompting the conversion of more cracking intermediates to gaseous products. Steam in the system has both pos. and neg. effects: a certain amt. of steam can increase the amt. of H. and .OH, promoting benzene decompn. and carbon deposit elimination; excessive steam will compete for energetic electrons or oxidize the active metal in the catalyst, inhibiting benzene conversion. The Ni3-HAP catalyst exhibits the max. benzene conversion (92.13%) and energy efficiency (8.49 g/kWh), thanks to the formed Ni2+[I] and Ni2+[II] in the lattice due to the flexible ion exchange properties of the HAP support. The main reason for the catalyst activity degrdn. is carbon deposition rather than catalyst sintering. A good match among tar conversion rate, degree of decompn., steam content and steam decompn. rate is crit. for efficient and stable operation of the NTP-catalytic system.
    118. 118
      Han, J.; Kim, H. The Reduction and Control Technology of Tar during Biomass Gasification/Pyrolysis: An Overview. Renewable and Sustainable Energy Reviews 2008, 12 (2), 397– 416,  DOI: 10.1016/j.rser.2006.07.015
      118
      The reduction and control technology of tar during biomass gasification/pyrolysis: An overview
      Han, Jun; Kim, Heejoon
      Renewable & Sustainable Energy Reviews (2007), 12 (2), 397-416CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review, with 127 refs. Biomass is an important primary energy source as well as renewable energy source. As the most promising biomass use method, gasification/pyrolysis produces not only useful fuel gases, char and chems., but also some byproducts like fly ash, NOx, SO2 and tar. Tar in the product gases will condense at low temp., and lead to clogged or blockage in fuel lines, filters and engines. Also, too much tar in product gases will reduce the use efficiency of biomass. Therefore, the redn. or decompn. of tar in biomass derived fuel gases is one of the biggest obstacles in its use for power generation. The authors review the literatures pertaining to tar redn. or destruction methods during biomass gasification/pyrolysis. From their characteristics, the current tar redn. or destruction methods can be broadly divided into 5 main groups: mechanism methods, self-modification, thermal cracking, catalyst cracking and plasma methods.
    119. 119
      Gong, X.; Lin, Y.; Li, X.; Wu, A.; Zhang, H.; Yan, J.; Du, C. Decomposition of Volatile Organic Compounds Using Gliding Arc Discharge Plasma. J. Air Waste Manage. Assoc. 2020, 70, 138– 157,  DOI: 10.1080/10962247.2019.1698476
      119
      Decomposition of volatile organic compounds using gliding arc discharge plasma
      Gong, Xiangjie; Lin, Yanchun; Li, Xiaodong; Wu, Angjian; Zhang, Hao; Yan, Jianhua; Du, Changming
      Journal of the Air & Waste Management Association (2020), 70 (2), 138-157CODEN: JAWAFC; ISSN:1096-2247. (Taylor & Francis Ltd.)
      A review. This work provides a systematic review on the decompn. of volatile org. pollutants in flue gas through the gliding arc (GA) plasma technol. To begin with, the basic mechanisms of GA plasma generation are summarized and three characteristic stages existed during the GA plasma generation process are revealed: gas breakdown stage, equil. stage, and non-equil. stage. Then, the types of GA reactors are comparatively illustrated. Possible destruction mechanisms of volatile org. compds. (VOCs) by GA plasma are discussed by taking chloroform, benzene, and methanol as examples. Furthermore, the effects of many operating parameters on the VOCs destruction efficiency are comprehensively analyzed. Simultaneously, the product distribution, energy cost, tech. and economic during the whole decompn. process are considered. Finally, the advantages and disadvantages of GA plasma and its further development trend are concluded from the academic and industrial application of GA plasma in VOCs decompn. Implications: This paper comprehensively describes the principle, characteristics, research progress and engineering application examples of the degrdn. of volatile orgs. by gliding arc discharge plasma, so that readers can fully understand the degrdn. of volatile orgs. by gliding arc discharge plasma and provide theor. basis for the industrial application of the degrdn. of volatile orgs. by gliding arc discharge plasma.
    120. 120
      Shao, S.; Ye, Z.; Sun, J.; Liu, C.; Yan, J.; Liu, T.; Li, X.; Zhang, H.; Xiao, R. A Review on the Application of Non-Thermal Plasma (NTP) in the Conversion of Biomass: Catalyst Preparation, Thermal Utilization and Catalyst Regeneration. Fuel 2022, 330, 125420,  DOI: 10.1016/j.fuel.2022.125420
      120
      A review on the application of non-thermal plasma (NTP) in the conversion of biomass: Catalyst preparation, thermal utilization and catalyst regeneration
      Shao, Shanshan; Ye, Zian; Sun, Jiayuan; Liu, Chengyue; Yan, Jinlong; Liu, Tieyi; Li, Xiaohua; Zhang, Huiyan; Xiao, Rui
      Fuel (2022), 330 (), 125420CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      A review. A brief review of non-thermal plasma (NTP) technol. as a new technol. for the thermal conversion of biomass is presented in this paper. Three aspects of the entire process are generally considered from the viewpoint of (i) biomass pretreatment, catalyst prepn. assisted by NTP prior to the thermochem. conversion; (ii) thermochem. conversion of biomass or its derivates assisted by NTP; and (iii) regeneration of deactivated catalyst after thermochem. conversion. A stable catalyst is a requisite for any industrial application of catalysis to make it com. viable. However, there is still a challenge to achieving a controlled morphol., which majorly affects the catalytic performance in the thermochem. conversion of biomass or its derivates, and template removal and metal loading by NTP are focused. At the same time, the reforming of tar, catalytic pyrolysis of biomass, gasification of biomass, and upgrading of bio-oil assisted by NTP are given great attention, including the reaction mechanism, product distribution, etc. In the thermochem. conversion of biomass, the deactivation of catalysts easily occurs in the process due to sintering, coke accumulation, and other reasons. The deposited coke is oxidized to generate gaseous products by introducing oxidizing gas, which is generally used in the regeneration of catalysts. Generally, this article reviews the plasma-assisted prepn. of catalysts used in the thermochem. conversion of biomass, the application of plasma technol. in the thermal conversion of biomass, and the regeneration of deactivated catalysts in plasma-assisted thermochem. conversion of biomass.
    121. 121
      Kawi, S.; Ashok, J.; Dewangan, N.; Pati, S.; Junmei, C. Recent Advances in Catalyst Technology for Biomass Tar Model Reforming: Thermal, Plasma and Membrane Reactors. Waste Biomass Valor. 2022, 13, 1– 30,  DOI: 10.1007/s12649-021-01446-6
      There is no corresponding record for this reference.
    122. 122
      Yu, X.; Dang, X.; Li, S.; Zhang, J.; Zhang, Q.; Cao, L. A Comparison of In- and Post-Plasma Catalysis for Toluene Abatement through Continuous and Sequential Processes in Dielectric Barrier Discharge Reactors. J. Clean Prod 2020, 276, 124251  DOI: 10.1016/j.jclepro.2020.124251
      There is no corresponding record for this reference.
    123. 123
      Trushkin, A. N.; Kochetov, I. V. Simulation of Toluene Decomposition in a Pulse-Periodic Discharge Operating in a Mixture of Molecular Nitrogen and Oxygen. Plasma Physics Reports 2012, 38 (5), 407– 431,  DOI: 10.1134/S1063780X12040083
      123
      Simulation of toluene decomposition in a pulse-periodic discharge operating in a mixture of molecular nitrogen and oxygen
      Trushkin, A. N.; Kochetov, I. V.
      Plasma Physics Reports (2012), 38 (5), 407-431CODEN: PPHREM; ISSN:1063-780X. (MAIK Nauka/Interperiodica)
      The kinetic model of toluene decompn. in nonequil. low-temp. plasma generated by a pulse-periodic discharge operating in a mixt. of nitrogen and oxygen is developed. The results of numerical simulation of plasma-chem. conversion of toluene are presented; the main processes responsible for C6H5CH3 decompn. are identified; the contribution of each process to total removal of toluene is detd.; and the intermediate and final products of C6H5CH3 decompn. are identified. It was shown that toluene in pure nitrogen is mostly decompd. in its reactions with metastable N2(A3Σu+) and N2(a'1Σu+) mols. In the presence of oxygen, in the N2:O2 gas mixt., the largest contribution to C6H5CH3 removal is made by the hydroxyl radical OH which is generated in this mixt. exclusively due to plasma-chem. reactions between toluene and oxygen decompn. products. Numerical simulation showed the existence of an optimum oxygen concn. in the mixt., at which toluene removal is max. at a fixed energy deposition.
    124. 124
      Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Y. S. Decomposition of Toluene in a Steady-State Atmospheric-Pressure Glow Discharge. Plasma Physics Reports 2013, 39 (2), 167– 182,  DOI: 10.1134/S1063780X13020025
      124
      Decomposition of toluene in a steady-state atmospheric-pressure glow discharge
      Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.
      Plasma Physics Reports (2013), 39 (2), 167-182CODEN: PPHREM; ISSN:1063-780X. (MAIK Nauka/Interperiodica)
      Results are presented from exptl. studies of decompn. of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atm. pressure glow discharge at different water vapor contents in the working gas. The exptl. results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chem. decompn. of toluene in the N2: O2: H2O gas mixt. A substantial influence of the gas flow humidity on toluene decompn. in the atm. pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decompn. are detd. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chem. decompn. of C6H5CH3 is established. Based on the results of computer simulations, the compn. of the products of plasma chem. reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.
    125. 125
      Wang, Y.; Yang, H.; Tu, X. Plasma Reforming of Naphthalene as a Tar Model Compound of Biomass Gasification. Energy Convers. Manag. 2019, 187, 593– 604,  DOI: 10.1016/j.enconman.2019.02.075
      125
      Plasma reforming of naphthalene as a tar model compound of biomass gasification
      Wang, Yaoling; Yang, Haiping; Tu, Xin
      Energy Conversion and Management (2019), 187 (), 593-604CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      The contamination of producer gas with tars from biomass gasification remains a significant challenge in the bioenergy industry and a crit. barrier, limiting the com. applications of biomass gasification. Non-thermal and non-equil. plasma offers an unconventional and emerging technol. for the effective redn. of problematic tars from gasification. In this study, we investigated plasma reforming of naphthalene as a two-ring tar model compd. using a gliding arc discharge (GAD) reactor with/without steam. The influence on the plasma conversion of naphthalene based on the inlet naphthalene concn., discharge power and steam-to-carbon ratio was examd. to understand the effects of these operating parameters on the destruction of tar, gas selectivity/yield and energy efficiency. Adding H2O in the plasma process generates oxidative OH radicals, creating addnl. reaction routes for the step-wised oxidn. of naphthalene and its fragments towards the CO, CO2 and water. The optimum ratio (2.0) of steam-to-carbon was identified to achieve the highest naphthalene conversion (84.8%), C2H2 yield (33.0%), total gas yield (72.2%) and energy efficiency (5.7 g/kWh). The effect of the amt. of steam on the plasma redn. of tars was dependent on the balance between two opposite effects due to the presence of steam: pos. effect of OH radicals and the neg. effect of electron attachment on water mols. Introducing an appropriate amt. of steam to the plasma redn. of naphthalene also substantially minimized the formation of byproducts and enhanced the carbon balance. Plausible reaction mechanisms for the plasma decompn. of naphthalene were proposed through a comprehensive anal. of gaseous and condensable products combined with plasma spectroscopic diagnostics.
    126. 126
      Liu, S.; Zhou, J.; Liu, W.; Zhang, T. Removal of Toluene in Air by a Non-Thermal Plasma-Catalytic Reactor Using MnOx/ZSM-5. Catal. Lett. 2022, 152 (1), 239– 253,  DOI: 10.1007/s10562-021-03629-1
      126
      Removal of Toluene in Air by a Non-thermal Plasma-Catalytic Reactor Using MnOx/ZSM-5
      Liu, Su; Zhou, Jiabin; Liu, Wenbo; Zhang, Tianlei
      Catalysis Letters (2022), 152 (1), 239-253CODEN: CALEER; ISSN:1011-372X. (Springer)
      Dielec. barrier discharge (DBD) reactor at non-thermal plasma (NTP) in combination with catalysts was used to remove toluene in air. Several manganese oxides catalysts with ZSM-5 zeolite as the carrier were prepd. for plasma-catalytic degrdn. of toluene. The prepd. catalysts were characterized utilizing the SEM, transmission electron microscope (TEM), H2 temp.-programmed redn. (H2-TPR), x-ray diffraction (x-ray diffraction), and N2 adsorption-desorption. And the residence time, plasma power, toluene concn. and specific input energy, which are crit. operating factors in this process, were investigated. The expt. proved that the catalysts significantly improved the degrdn. effect of NTP, the conversion increased from 58 to 91.5% after loading MnOx/ZSM-5-300 at 750 ppm, and the improving trend became more obvious with the increase of concn. The degrdn. of toluene can reach 92.4% at the optimal process parameters of residence time 5.8 s, initial concn. 1000 ppm, input power 30 W, SIE 6000 J/L. The results of the evaluation indicate that it is effective to use MnOx/ZSM-5 catalyst combined with DBD-plasma for synergistic degrdn. of toluene at room temp. and a relatively low energy consumption.
    127. 127
      Wang, C.; Zhu, L.; Zhao, F.; Xu, D. The Chemistry of Gaseous Benzene Degradation Using Non-Thermal Plasma. Environmental Science and Pollution Research 2021, 28, 1565– 1573,  DOI: 10.1007/s11356-020-10506-8
      127
      The chemistry of gaseous benzene degradation using non-thermal plasma
      Wang, Chunyu; Zhu, Ling; Zhao, Fei; Xu, Danyun
      Environmental Science and Pollution Research (2021), 28 (2), 1565-1573CODEN: ESPLEC; ISSN:0944-1344. (Springer)
      In this study, the abatement of benzene in a dielec. barrier discharge (DBD) reactor was studied. The efficiency was investigated in terms of benzene conversion and product formation. The compn. of gas-liq.-solid three-phase product produced during degrdn. was obsd. by GC-MS. Under the optimal SED, the solid-phase product was analyzed by FT-IR, SEM, and EDS. The results suggested that the product were mainly benzonitriles, benzenedicarbonitrile, phenols, esters, and amides. The wt% of C in product decreased as SED increased, demonstrating that the high discharge voltage facilitated the conversion of VOCs to gaseous intermediate product and CO2. Possible degrdn. mechanism and pathways of benzene destruction in the DBD reactor were proposed.
    128. 128
      Zhu, F.; Li, X.; Zhang, H.; Wu, A.; Yan, J.; Ni, M.; Zhang, H.; Buekens, A. Destruction of Toluene by Rotating Gliding Arc Discharge. Fuel 2016, 176, 78– 85,  DOI: 10.1016/j.fuel.2016.02.065
      128
      Destruction of toluene by rotating gliding arc discharge
      Zhu, Fengsen; Li, Xiaodong; Zhang, Hao; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Zhang, Hanwei; Buekens, Alfons
      Fuel (2016), 176 (), 78-85CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Non-thermal plasma is considered as an alternative treatment of tar present in the effluent from gasification processes. In this study, a novel rotating gliding arc (RGA) discharge reactor was developed for tar destruction. Toluene in nitrogen flow was used as a tar surrogate. The phys. features of RGA discharge and its application to toluene destruction are investigated at different input concns. and total gas flow rates. As a result, the highest destruction efficiency could exceed 95%, with a toluene concn. of 10 g/N m3 and a total flow rate of 0.24 N m3/h. The two major gaseous products are H2 and C2H2, with max. selectivity of 39.35% and 27.0%, resp. A higher input concn. slightly reduces this destruction efficiency but the energy efficiency further expanded, with a highest value of 16.61 g of toluene eliminated/kW h. In addn., the liq. and solid byproducts are collected downstream of the RGA reactor and detd. qual. and semi-quant. The amt. and structure of these byproducts is instructive for reaching a better comprehension of the chem. consequences of plasma treatment to the model compd. and to the carrier gas nitrogen.
    129. 129
      Shen, Y.; Wang, J.; Ge, X.; Chen, M. By-Products Recycling for Syngas Cleanup in Biomass Pyrolysis – An Overview. Renewable and Sustainable Energy Reviews 2016, 59, 1246– 1268,  DOI: 10.1016/j.rser.2016.01.077
      129
      By-products recycling for syngas cleanup in biomass pyrolysis - An overview
      Shen, Yafei; Wang, Junfeng; Ge, Xinlei; Chen, Mindong
      Renewable & Sustainable Energy Reviews (2016), 59 (), 1246-1268CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      Bio-char and bio-oil have a potential to be used for gas cleaning in biomass pyrolysis/gasification. On one hand, tar in producer gas could be removed by phys. treatment, such as oil absorption and char adsorption; on the other hand, tar could be eliminated by chem. treatment, such as catalytic conversion over char-supported catalysts. This paper reviewed the recent progress in gas cleaning esp. for tar removal during biomass pyrolysis/gasification by using the byproducts (i.e. bio-char, bio-oil, low-viscosity tar). In general, bio-char could effectively adsorb the light tar compds. such as volatile org. compds. (VOCs), while bio-oil is normally benefit for the absorption of heavy tars. Addnl., catalytic reforming is considered as one of the promising alternatives for the removal of tars, because it converts the tars into the addnl. gas products. Bio-char could be used as a carbon catalyst or support with fair performance in tar removal. It is noteworthy that the char-supported catalysts could be gasified to recover energy of char without the need of frequent regeneration after deactivation. Furthermore, the carbon-based catalysts derived from bio-chars could be urgently developed for the removal of contaminants including NH3, H2S and tar simultaneously in the producer gas from the real biomass gasification processes.
    130. 130
      Liu, M.; Aravind, P. V. The Fate of Tars under Solid Oxide Fuel Cell Conditions: A Review. Appl. Therm Eng. 2014, 70 (1), 687– 693,  DOI: 10.1016/j.applthermaleng.2014.05.068
      130
      The fate of tars under solid oxide fuel cell conditions: A review
      Liu, Ming; Aravind, P. V.
      Applied Thermal Engineering (2014), 70 (1), 687-693CODEN: ATENFT; ISSN:1359-4311. (Elsevier Ltd.)
      A review. Biomass is a renewable and low-carbon energy source. Its use via gasification is an attractive way for solid oxide fuel cells (SOFCs). However, tars are the major bottleneck as tars produced from biomass gasification may have detrimental effects on the SOFC. This work comprehensively reviews the fate of tars under SOFC conditions. Specifically, it summarizes tar evolution during biomass gasification, discusses currently available studies on the interaction between tars and SOFC anodes or anode materials. In addn., readily available gas cleaning technologies for reducing tar content are discussed. Future research perspectives are also addressed.
    131. 131
      Singh, R. N.; Singh, S. P.; Belwanshi, J. B. Tar Removal from Producer Gas: A Review. Res. J. Eng. Sci. 2014, 3 (10), 16– 22
      131
      Tar removal from producer gas: a review
      Singh, R. N.; Singh, S. P.; Balwanshi, J. B.
      Research Journal of Engineering Sciences (2014), 3 (10), 16-22CODEN: RJESCM; ISSN:2278-9472. (International Science Congress Association)
      A review. Gasification is the most appropriate technol. for conversion of solid fuel (biomass) into a gaseous fuel, known as producer gas. Producer gas is a mixt. of gases which consists of hydrogen, carbon monoxide, methane, carbon dioxide, water vapor, nitrogen, tar and suspended particulate matter. For motive applications such as internal combustion engines, the tar present in producer gas may create problem, if the tar content in the producer gas is above 50-100 mg/Nm3. A tar-free gaseous fuel can be obtained in a suitably designed producer gas conditioning unit whose sole purpose is to provide clean producer gas. Gas cleaning and conditioning systems to control tar levels are being continuously modified for better efficiency and cost effectiveness. Major techniques used in tar cleaning are thermal cracking, catalytic cracking and phys. removal of tar. Many a times, combination of these techniques are used for better cleaning of producer gas. The following paper critically reviews the different techniques used for collection, identification and quantification of tars in producer gas obtained from biomass.
    132. 132
      Woolcock, P. J.; Brown, R. C. A Review of Cleaning Technologies for Biomass-Derived Syngas. Biomass Bioenergy 2013, 52, 54– 84,  DOI: 10.1016/j.biombioe.2013.02.036
      132
      A review of cleaning technologies for biomass-derived syngas
      Woolcock, Patrick J.; Brown, Robert C.
      Biomass and Bioenergy (2013), 52 (), 54-84CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      A review. Syngas from gasification of carbonaceous feedstocks is used for power prodn. and synthesis of fuels and commodity chems. Impurities in gasification feedstocks, esp. sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temp. exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the tech. difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
    133. 133
      Hasler, P.; Nussbaumer, T. Gas Cleaning for IC Engine Applications from Fixed Bed Biomass Gasification. Biomass Bioenergy 1999, 16 (6), 385– 395,  DOI: 10.1016/S0961-9534(99)00018-5
      133
      Gas cleaning for IC engine applications from fixed bed biomass gasification
      Hasler, P.; Nussbaumer, Th.
      Biomass and Bioenergy (1999), 16 (6), 385-395CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
      Gas cleaning for tar and particle removal is necessary for internal combustion (IC) engine applications of producer gas from fixed bed biomass gasifiers which are usually in the capacity range from 100 kW up to 5000 kW. In the present investigation, tar and particle collection efficiencies have been detd. in a sand bed filter, a wash tower, two different fabric filters, and a rotational particle separator in different test runs with fixed bed gasifiers. Tar adsorption on coke has been investigated in a fixed bed batch reactor. Furthermore data from literature for catalytic tar crackers, venturi scrubbers, a rotational atomizer, and a wet electrostatic precipitator (ESP) are given. Based on the presented gas cleaning efficiencies and the investment cost, an assessment of gas cleaning systems is made for IC engine applications from cocurrent gasifiers. The postulated gas quality requirements for IC engines cannot be safely achieved with state-of-the-art gas cleaning techniques and that 90% particle removal is easier to achieve than 90% tar removal. Except for the catalytic tar crackers which are considered as an option for applications above several MW and for gases with a high tar level, none of the investigated gas cleaning systems can securely meet a tar redn. exceeding 90%. Therefore one of the key issues for a successful application of biomass derived producer gas from small scale gasifiers is the tar removal, where further development is needed.
    134. 134
      Boerrigter, H.; Van Paasen, S. V. B.; Bergman, P. C. A.; Könemann, J. W.; Emmen, R.; Wijnands, A. OLGA Tar Removal Technology. Proof-of-Concept (PoC) for Application in Integrated Biomass Gasification Combined Heat and Power (CHP) Systems; ECN-RX-05-009; Energy Research Centre of the Netherlands: Petten, Netherlands, 2005.
      There is no corresponding record for this reference.
    135. 135
      Fjellerup, J.; Ahrenfeldt, J.; Henriksen, U.; Go̷bel, B. Formation, Decomposition and Cracking of Biomass Tars in Gasification; Technical University of Denmark: Lyngby, Denmark, 2005.
      There is no corresponding record for this reference.
    136. 136
      Coll, R.; Salvadó, J.; Farriol, X.; Montané, D. Steam Reforming Model Compounds of Biomass Gasification Tars: Conversion at Different Operating Conditions and Tendency towards Coke Formation. Fuel Process. Technol. 2001, 74 (1), 19– 31,  DOI: 10.1016/S0378-3820(01)00214-4
      136
      Steam reforming model compounds of biomass gasification tars: conversion at different operating conditions and tendency towards coke formation
      Coll, Roberto; Salvado, Joan; Farriol, Xavier; Montane, Daniel
      Fuel Processing Technology (2001), 74 (1), 19-31CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Science B.V.)
      The purifn. of biomass-derived syngas via tar abatement by catalytic steam reforming has been investigated using benzene, toluene, naphthalene, anthracene and pyrene as surrogated mols. The effects of temp. and steam-to-carbon (S/C) ratio on conversion, and the tendency towards coke formation were explored for each model compd. Two com. nickel-based catalysts, the UCI G90-C and the ICI 46-1, were evaluated. The five tar model compds. had very different reaction rates. Naphthalene was the most difficult compd. to steam reform, with conversions from 0.008 gorg_conv/gcat min (790 °C) to 0.022 gorg_conv/gcat min (890 °C) at an S/C ratio of 4.2. The most reactive compd. was benzene, with a conversion of 1.1 gorg_conv/gcat min at 780 °C and an S/C ratio of 4.3. The tendency towards coke formation grew as the mol. wt. of the arom. increased. The min. S/C ratio for toluene was 2.5 at a catalyst temp. of 725 °C, and for pyrene at 790 °C, it was 8.4. In general, catalyst temps. and S/C ratios need to be higher than for naphtha in order to prevent the formation of coke on the catalyst.
    137. 137
      Developments in Thermochemical Biomass Conversion; Bridgwater, A. V., Boocock, D. G. B., Eds.; Springer, 1997.
      There is no corresponding record for this reference.
    138. 138
      Brandt, P.; Larsen, E.; Henriksen, U. High Tar Reduction in a Two-Stage Gasifier. Energy Fuels 2000, 14 (4), 816– 819,  DOI: 10.1021/ef990182m
      138
      High Tar Reduction in a Two-Stage Gasifier
      Brandt, Peder; Larsen, Elfinn; Henriksen, Ulrik
      Energy & Fuels (2000), 14 (4), 816-819CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      The work with a 100-kWth two-stage gasifier at the Tech. University of Denmark (DTU) has resulted in a gas with a very low tar content. The redn. in tar has come about by combining the partial oxidn. of the pyrolysis gas with the reactions that follow on a charcoal bed in the char gasification unit. Tar is defined as org. contaminants which have retention times equal to or greater than those of phenol on a nonpolar GC column. Two test series were made with wood chips as feedstock, before and after the gasifier was optimized. The effect on tar redn. of a charcoal bed has been investigated by measuring the tar content and compn. of the gas after the partial oxidn. (above the charcoal bed) and after the passage of the gas through the charcoal. By introducing the correct supply of air, the tar content in the gas after its partial oxidn. was about 3000 mg/kg dry wood chips. Furthermore, a conclusive high tar redn. of the arom. hydrocarbons including PAH was obtained by avoiding bypasses of the charcoal bed. A gas was produced with a tar content as low as 10-40 mg/kg dry wood.
    139. 139
      Shen, Y.; Yoshikawa, K. Recent Progresses in Catalytic Tar Elimination during Biomass Gasification or Pyrolysis - A Review. Renewable and Sustainable Energy Reviews. 2013, 21, 371– 392,  DOI: 10.1016/j.rser.2012.12.062
      139
      Recent progresses in catalytic tar elimination during biomass gasification or pyrolysis-A review
      Shen, Yafei; Yoshikawa, Kunio
      Renewable & Sustainable Energy Reviews (2013), 21 (), 371-392CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Biomass gasification is an interesting technol. in the future development of a worldwide sustainable energy system, which can help to decrease our current dependence on fossil fuels. Biomass gasification is a thermal process where solid fuel is converted into a useful gas using several gasifying agents such as air, and steam. The producer gas has a great no. of applications. The most important is being combustion for power and heat generation as well as raw gas for prodn. of fuels or chems. This review mainly presents the recent progresses on tar elimination during the biomass gasification. Then, novel non-catalytic absorption and adsorption methods of tar removal under ambient temp. conducted by our lab. members were also explained. In our opinion, the tar removal can be conducted by combination of catalytic reforming in the gasifier and oil materials adsorption in the scrubber. Furthermore, the tar catalytic reforming is a most significant step during biomass gasification or pyrolysis. Thus, the development of reasonable catalysts for tar elimination has been faced with a significant challenge in current society.
    140. 140
      Huang, Q.; Lu, P.; Hu, B.; Chi, Y.; Yan, J. Cracking of Model Tar Species from the Gasification of Municipal Solid Waste Using Commercial and Waste-Derived Catalysts. Energy Fuels 2016, 30 (7), 5740– 5748,  DOI: 10.1021/acs.energyfuels.6b00711
      140
      Cracking of Model Tar Species from the Gasification of Municipal Solid Waste Using Commercial and Waste-Derived Catalysts
      Huang, Qunxing; Lu, Peng; Hu, Binhang; Chi, Yong; Yan, Jianhua
      Energy & Fuels (2016), 30 (7), 5740-5748CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      The cracking of model tar species from municipal solid waste gasification using dried sewage sludge char (DSS char) and bottom ash catalyst (BAC) was investigated, and the catalytic performance was compared to that of well-studied calcined dolomite, NiO/γ-Al2O3, and non-catalytic thermal cracking. The effects of the temp., internal structure, chem. compn., and functional groups on the performance of tar cracking were characterized. , When toluene was selected as the model tar species, conversion ratios for all catalysts were over 94% at 950°. The cracking efficiency was ordered as NiO/γ-Al2O3 > calcined dolomite > DSS char > BAC > thermal cracking. When the temp. increased from 750 to 850°, the conversion ratios for DSS char and BAC increased from 68.8 and 40.1% to 81.5 and 63.2%, resp. H2 and coke were the major products of toluene cracking, and catalysts promoted the yield of hydrogen. The lower heating value of the product gas followed the same rules of the conversion ratio. Coke deposition from toluene cracking will decrease the Brunauer-Emmett-Teller surface area of the catalysts, inevitably leading to the deactivation.
    141. 141
      Min, Z.; Yimsiri, P.; Zhang, S.; Wang, Y.; Asadullah, M.; Li, C. Z. Catalytic Reforming of Tar during Gasification. Part III. Effects of Feedstock on Tar Reforming Using Ilmenite as a Catalyst. Fuel 2013, 103, 950– 955,  DOI: 10.1016/j.fuel.2012.09.019
      141
      Catalytic reforming of tar during gasification. Part III. Effects of feedstock on tar reforming using ilmenite as a catalyst
      Min, Zhenhua; Yimsiri, Piyachat; Zhang, Shu; Wang, Yi; Asadullah, Mohammad; Li, Chun-Zhu
      Fuel (2013), 103 (), 950-955CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Australia mallee wood, bark and leaf samples (Eucalyptus loxophleba, subspecies lissophloia) were pyrolyzed to produce volatiles for in situ catalytic steam reforming with ilmenite as a catalyst. The results demonstrated that the properties of biomass feedstock (wood, bark and leaves) significantly influenced their product yields and properties. Bark produced the highest amts. of solid products, whereas leaf generated the highest amts. of tar during pyrolysis. The differences in the chem. compn. and the tar yields among wood, bark and leaf decreased with increasing temp. Ilmenite showed good activity for the reforming of all tars from different parts of mallee trees. However, its activity for reforming tar from bark and leaf decreased with prolonging feeding time due to their high gradual coke deposits. Compared with sintering, the accumulated coke deposited on ilmenite is a dominant factor to its deactivation during the steam reforming process. Burning coke is an effective method to regenerate the catalyst activity of ilmenite.
    142. 142
      Nordgreen, T.; Liliedahl, T.; Sjöström, K. Metallic Iron as a Tar Breakdown Catalyst Related to Atmospheric, Fluidised Bed Gasification of Biomass. Fuel 2006, 85 (5–6), 689– 694,  DOI: 10.1016/j.fuel.2005.08.026
      142
      Metallic iron as a tar breakdown catalyst related to atmospheric, fluidised bed gasification of biomass
      Nordgreen, Thomas; Liliedahl, Truls; Sjoestroem, Krister
      Fuel (2006), 85 (5-6), 689-694CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Tar formation is a major drawback when biomass is converted in a gasifier to obtain gas aimed for utilization in power prodn. plants or for prodn. of chems. Catalytic cracking is an efficient method to diminish the tar content in the gas mixt. In this study, the capability of metallic iron and iron oxides to catalytically crack tars has been exptl. examd. To obtain metallic iron, small grains of hematite (Fe2O3) were placed in a secondary reactor downstream the gasifier and reduced in situ prior to catalytic operation. The fuel used in the atm. fluidized bed gasifier was Swedish birch with a moisture content of approx. 7 wt%. The influence of temp. in the range 700-900 °C and λ values (i.e. equivalence ratio, ER) between 0 and 0.20 have been investigated. In essence, the results show that raising the temp. in the catalytic bed to approx. 900 °C yields almost 100% tar breakdown. Moreover, increasing the λ value also improves the overall tar cracking activity. The iron oxides did not demonstrate any catalytic activity.
    143. 143
      Miyazawa, T.; Kimura, T.; Nishikawa, J.; Kunimori, K.; Tomishige, K. Catalytic Properties of Rh/CeO2/SiO2 for Synthesis Gas Production from Biomass by Catalytic Partial Oxidation of Tar. Sci. Technol. Adv. Mater. 2005, 6 (6), 604– 614,  DOI: 10.1016/j.stam.2005.05.019
      143
      Catalytic properties of Rh/CeO2/SiO2 for synthesis gas production from biomass by catalytic partial oxidation of tar
      Miyazawa, Tomohisa; Kimura, Takeo; Nishikawa, Jin; Kunimori, Kimio; Tomishige, Keiichi
      Science and Technology of Advanced Materials (2005), 6 (6), 604-614CODEN: STAMCV; ISSN:1468-6996. (Elsevier Ltd.)
      Performance of Rh/CeO2/SiO2 in the partial oxidn. of tar from the pyrolysis of wood biomass (architectural salvage) was investigated and compared with various materials such as steam reforming Ni catalyst, active clay, USY zeolite, MS-13X, dolomite, alumina, silica sand, fluorite and non-catalyst. Rh/CeO2/SiO2 and the steam reforming Ni catalyst exhibited much higher performance than any other materials in terms of hydrogen prodn. and the amt. of tar. Therefore, the performance of Rh/CeO2/SiO2 and steam reforming Ni catalyst was particularly compared. From the result on the dependence of reaction temp., equivalence ratio, and biomass feeding rate, Rh/CeO2/SiO2 exhibited higher performance than the Ni catalyst, esp. in terms of tar and coke amt. Furthermore, Rh/CeO2/SiO2 was also more stable than the Ni catalyst. The catalyst deactivation can be related to the amt. of coke deposition. The results indicate that Rh/CeO2/SiO2 has high resistance to coke formation, and this is related to higher combustion activity of Rh/CeO2/SiO2 than the Ni catalyst. Furthermore, from the TPR profiles, Rh/CeO2/SiO2 had higher reducibility than the Ni catalyst. The combination of high combustion activity with high reducibility and reforming activity can be related to high performance of tar conversion in the fluidized bed reactor.
    144. 144
      Asadullah, M.; Miyazawa, T.; Ito, S. I.; Kunimori, K.; Yamada, M.; Tomishige, K. Catalyst Development for the Gasification of Biomass in the Dual-Bed Gasifier. Appl. Catal. A Gen 2003, 255 (2), 169– 180,  DOI: 10.1016/S0926-860X(03)00539-8
      144
      Catalyst development for the gasification of biomass in the dual-bed gasifier
      Asadullah, Mohammad; Miyazawa, Tomohisa; Ito, Shin-ichi; Kunimori, Kimio; Yamada, Muneyoshi; Tomishige, Keiichi
      Applied Catalysis, A: General (2003), 255 (2), 169-180CODEN: ACAGE4; ISSN:0926-860X. (Elsevier Science B.V.)
      A dual-bed gasifier system combined with catalysts was evaluated in the catalytic gasification of cedar wood at low temps. (823-973 °K). The dual-bed gasifier consisted of a primary-bed section for pyrolysis of biomass and sepn. of pyrolyzed gas and tar from solid products and a secondary-catalytic tar reformer. Catalyst development was carried out from Rh/CeO2/SiO2, which was developed for the higher conversion of carbon to gas and higher yield of CO + H2 + CH4. The authors have also carried out the optimization of reaction conditions. Esp., the tar derived from max. of 250 mg biomass/min can be totally converted to the gas product by 3 g catalyst in this system using ER = 0.25 of total carbon present in the biomass. This performance was much higher than that over com. steam reforming catalyst. The amt. of coke deposited on Rh/CeO2/SiO2 was much smaller. In the dual-bed system combined with excellent catalysts, almost all the tar can be converted to syngas at lower temp. than that needed by the conventional method with high energy efficiency.
    145. 145
      Asadullah, M.; Miyazawa, T.; Ito, S. I.; Kunimori, K.; Koyama, S.; Tomishige, K. A Comparison of Rh/CeO2/SiO2 Catalysts with Steam Reforming Catalysts, Dolomite and Inert Materials as Bed Materials in Low Throughput Fluidized Bed Gasification Systems. Biomass Bioenergy 2004, 26 (3), 269– 279,  DOI: 10.1016/S0961-9534(03)00105-3
      145
      A comparison of Rh/CeO2/SiO2 catalysts with steam reforming catalysts, dolomite and inert materials as bed materials in low throughput fluidized bed gasification systems
      Asadullah, Mohammad; Miyazawa, Tomohisa; Ito, Shin-ichi; Kunimori, Kimio; Koyama, Shuntarou; Tomishige, Keiichi
      Biomass and Bioenergy (2004), 26 (3), 269-279CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Science Ltd.)
      The gasification of cedar wood in the presence of Rh/CeO2/SiO2 has been conducted in the lab. scale fluidized bed reactor using air as a gasifying agent at low temps. (823-973 K) in order to produce high-quality fuel gas for gas turbine for power generation. The performance of the Rh/CeO2/SiO2 catalyst has been compared with conventional catalysts such as com. steam reforming catalyst G-91, dolomite and noncatalyst systems by measurements of the cold gas efficiency, tar concn., carbon conversion to gas and gas compn. The tar concn. was completely negligible in the Rh/CeO2/SiO2-catalyzed product gas whereas it was about 30, 113, and 139 g/m3 in G-91, dolomite and noncatalyzed product gas, resp. Since the carbon conversion to useful gas such as CO, H2, and CH4 are much higher on Rh/CeO2/SiO2 catalyst than others at 873 K, the cold gas efficiency is much higher (71%) in this case than others. The hydrogen content in the product gas is much higher (>24 vol%) than the specified level (>10 vol%) for efficient combustion in the gas turbine engine. The char and coke formation is also very low on Rh/CeO2/SiO2 catalyst than on the conventional catalysts. Although the catalyst surface area was slightly decreased after using the same catalyst in at least 20 expts., the deactivation problem was not severe.
    146. 146
      Zhao, Z.; Lakshminarayanan, N.; Kuhn, J. N.; Senefeld-Naber, A.; Felix, L. G.; Slimane, R. B.; Choi, C. W.; Ozkan, U. S. Optimization of Thermally Impregnated Ni-Olivine Catalysts for Tar Removal. Appl. Catal. A 2009, 363, 64– 72,  DOI: 10.1016/j.apcata.2009.04.042
      146
      Optimization of thermally impregnated Ni-olivine catalysts for tar removal
      Zhao, Zhongkui; Lakshminarayanan, Nandita; Kuhn, John N.; Senefeld-Naber, Allyson; Felix, Larry G.; Slimane, Rachid B.; Choi, Chun W.; Ozkan, Umit S.
      Applied Catalysis, A: General (2009), 363 (1-2), 64-72CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Thermally impregnated Ni-olivines are potential catalysts for hot cleanup of tars generated in fluidized bed biomass gasifiers. The present study examd. the influence of synthesis parameters, namely Ni precursor, prepn. temp., and olivine support upon the physicochem. and catalytic properties of Ni-olivine catalysts prepd. by thermal impregnation. Catalytic activity and stability was monitored by reforming naphthalene, a model tar compd. in simulated biomass-derived syngas and by reforming methane. Physicochem. properties, which include both structural (x-ray diffraction, temp. programmed redn., and Raman spectroscopy) and surface measurements (BET surface area and XPS), were evaluated for both fresh and spent catalysts. Choice of Ni precursor (NiO or Ni) demonstrated minimal influence upon physicochem. properties and catalytic activity and stability for naphthalene and methane steam reforming. The synthesis temp. (1100 and 1400°) and olivine support, however, did have an impact. Large structural changes and deactivation were obsd. when lower synthesis temps. were used, which indicated that this formulation was not desirable. The use of the Washington olivine as the support demonstrated improved catalytic performance and stability compared to two other olivine supports and further characterization showed that treatments are important in detg. the final structural features.
    147. 147
      Wang, T.; Chang, J.; Lv, P.; Zhu, J. Novel Catalyst for Cracking of Biomass Tar. Energy Fuels 2005, 19 (1), 22– 27,  DOI: 10.1021/ef030116r
      147
      Novel Catalyst for Cracking of Biomass Tar
      Wang, Tiejun; Chang, Jie; Lu, Pengmei; Zhu, Jingxu
      Energy & Fuels (2005), 19 (1), 22-27CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Cracking of biomass tar was investigated over Ni/dolomite catalyst prepd. by the incipient wetness method using modified dolomite as precursor. Modified dolomite was prepd. by mixing Fe2O3 powders with natural dolomite powders to increase Fe2O3 content for higher activity of tar cracking. Four other catalysts (natural dolomite, modified dolomite, ICI-46-1, and Z409) were tested and compared with Ni/dolomite catalyst. The effects of temp., steam-to-carbon, and space velocity on tar conversion were explored. Ni/dolomite is shown to be very active and useful for tar removal. A 97% tar removal is easily obtained at catalyst temp. of 750 °C and space velocities of 12 000 h-1. The min. S/C ratio for Ni/dolomite was 2.5 at a catalyst temp. of 750 °C to prevent the formation of the coke on the catalyst. No obvious deactivation of catalyst was obsd. in 60 h onstream tests. Compared with the Ni-based catalysts (ICI-46-1, Z409), Ni/dolomite catalyst is cheap and has also excellent activity and anticoke ability.
    148. 148
      Miyazawa, T.; Kimura, T.; Nishikawa, J.; Kado, S.; Kunimori, K.; Tomishige, K. Catalytic Performance of Supported Ni Catalysts in Partial Oxidation and Steam Reforming of Tar Derived from the Pyrolysis of Wood Biomass. Catal. Today 2006, 115, 254– 262,  DOI: 10.1016/j.cattod.2006.02.055
      148
      Catalytic performance of supported Ni catalysts in partial oxidation and steam reforming of tar derived from the pyrolysis of wood biomass
      Miyazawa, Tomohisa; Kimura, Takeo; Nishikawa, Jin; Kado, Shigeru; Kunimori, Kimio; Tomishige, Keiichi
      Catalysis Today (2006), 115 (1-4), 254-262CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
      Activity test of Ni/Al2O3, Ni/ZrO2, Ni/TiO2, Ni/CeO2 and Ni/MgO catalysts in the partial oxidn. (POT) and steam reforming of tar (SRT) derived from the pyrolysis of cedar wood was performed. In these activity tests, the order of the performance in both reactions was similar. Catalyst characterization was also carried out by means of H2 adsorption, TPR and XRD. From the combination of catalyst characterization with the results of the activity tests, it was suggested that the conversion of tar in POT and SRT is mainly controlled by the no. of surface Ni metal. In addn., Ni/CeO2 showed smaller amt. of coke than other catalysts in the POT and SRT. From the TGA profiles of active carbon mixed with catalysts, it is found that Ni/CeO2 promoted the reaction of active carbon with O2 and steam. The function of the fluidized bed reactor in the POT with respect to coke and tar amt. was discussed.
    149. 149
      Furusawa, T.; Saito, K.; Kori, Y.; Miura, Y.; Sato, M.; Suzuki, N. Steam Reforming of Naphthalene/Benzene with Various Types of Pt-and Ni-Based Catalysts for Hydrogen Production. Fuel 2013, 103, 111– 121,  DOI: 10.1016/j.fuel.2011.09.026
      149
      Steam reforming of naphthalene/benzene with various types of Pt- and Ni-based catalysts for hydrogen production
      Furusawa, Takeshi; Saito, Katsuhiko; Kori, Yoshihiko; Miura, Yasutomo; Sato, Masahide; Suzuki, Noboru
      Fuel (2013), 103 (), 111-121CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      The influence of support on the catalytic performances of Pt and Ni based catalysts for the steam reforming of naphthalene/benzene as model tar compds. of biomass gasification was investigated. Pt/Al2O3 catalyst showed relatively high and stable activity in steam reforming for 30 h at 1023 K and 1073 K with steam/carbon (S/C) molar ratio of 3. However, this catalyst remarkably lost its activity after 1st step of oxidn. treatment during cycle test of steam reforming-oxidn. treatment. When hydrogen treatment was conducted as a regeneration method, Pt/Al2O3 catalyst showed stable performance for 5 cycles. Ni/Al2O3 and Pt/Al2O3 catalysts showed similar catalytic behaviors for steam reforming and cycle test. Pt/MgO catalyst exhibited stable activity at 1073 K for the steam reforming under steady state and cycle utilization test of steam reforming-oxidn. treatment. However, when the reaction temp. was reduced to 1023 K, Pt/MgO catalyst lost its activity for both cases. It is concluded from the above results that Al2O3 supported catalysts were excellent catalysts for the steam reforming of naphthalene/benzene to produce H2.
    150. 150
      Binte Mohamed, D. K.; Veksha, A.; Ha, Q. L. M.; Chan, W. P.; Lim, T. T.; Lisak, G. Advanced Ni Tar Reforming Catalysts Resistant to Syngas Impurities: Current Knowledge, Research Gaps and Future Prospects. Fuel 2022, 318, 123602,  DOI: 10.1016/j.fuel.2022.123602
      150
      Advanced Ni tar reforming catalysts resistant to syngas impurities: Current knowledge, research gaps and future prospects
      Binte Mohamed, Dara Khairunnisa; Veksha, Andrei; Ha, Quan Luu Manh; Chan, Wei Ping; Lim, Teik-Thye; Lisak, Grzegorz
      Fuel (2022), 318 (), 123602CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      A review. Catalytic reforming is a promising technol. for the removal of tar from syngas. However, due to the presence of other impurities such as H2S, HCl, HBr, siloxanes, alkali metals, and NH3, the lifetime, activity, and stability of commonly used Ni-based catalysts is limited. This review investigates the recent findings related to poisoning effects of both common and under-researched syngas impurities on nickel catalysts and achievements in the synthesis of poison tolerant catalysts. The source and content of impurities produced from the gasification of different feedstock are examd. As current catalysts used for tar reforming require further improvement to ensure tolerance to poisoning, two approaches for catalytic tar reforming gas products from gasification of biomass/solid waste with and without prior syngas pre-treatment are evaluated to emphasize the importance of developing poison-tolerant catalysts. The deactivation mechanisms of Ni catalysts by syngas impurities, regeneration techniques, and strategies for developing poison-tolerant catalysts are reviewed. Finally, limitations of current catalytic tar reforming processes and promising approaches for future works are further discussed.
    151. 151
      Binte Mohamed, D. K.; Veksha, A.; Ha, Q. L. M.; Lim, T. T.; Lisak, G. Unravelling the Significance of Catalyst Reduction Stage for High Tar Reforming Activity in the Presence of Syngas Impurities. Appl. Catal. A Gen 2022, 642, 118711,  DOI: 10.1016/j.apcata.2022.118711
      151
      Unravelling the significance of catalyst reduction stage for high tar reforming activity in the presence of syngas impurities
      Binte Mohamed, Dara Khairunnisa; Veksha, Andrei; Ha, Quan Luu Manh; Lim, Teik-Thye; Lisak, Grzegorz
      Applied Catalysis, A: General (2022), 642 (), 118711CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Ni catalysts are used widely in tar reforming for syngas purifn. This study investigates the aim of the redn. stage toward Ni catalysts during tar reforming in the presence of syngas impurities. A NiAl2O4 catalyst was used for the reforming of a mixt. of tar model compds. (naphthalene, toluene, and styrene) in simulated syngas contg. 50 ppmv H2S and 500 ppmv HCl. The catalyst exhibited activity in tar reforming even without the pre-redn. treatment, but it was deactivated rapidly due to the favored reaction between H2S and Ni2+ species, causing increased Ni agglomeration and carbon deposition. Pre-redn. of catalysts enhanced the catalyst stability even in the presence of syngas impurities. Higher reforming activity was achieved by increasing the redn. temp. from 800°C to 900°C. However, transformation in the support structure at higher reducing temp. could lead to decreased exposure of Ni due to the collapse of pore structures.
    152. 152
      Sutton, D.; Kelleher, B.; Ross, J. R. H. Review of Literature on Catalysts for Biomass Gasification. Fuel Process. Technol. 2001, 73 (3), 155– 173,  DOI: 10.1016/S0378-3820(01)00208-9
      152
      Review of literature on catalysts for biomass gasification
      Sutton, D.; Kelleher, B.; Ross, J. R. H.
      Fuel Processing Technology (2001), 73 (3), 155-173CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Science B.V.)
      A review with refs. Biomass gasification is a possible alternative to the direct use of fossil fuel energy. Biomass, a CO2 neutral source of renewable fuel, can contribute to the demand for heat, electricity and synthesis gas. However, there are inefficiencies in the technol., which at present render biomass gasification economically unviable. The presence of condensable org. compds. and methane in the product gas renders the gas unsuitable for specific applications. Elimination of the condensable org. compds. and methane by a suitably cheap technol. will enhance the economic viability of biomass gasification. This paper contains an extensive literature review of the three main groups of catalysts, which have been evaluated for the elimination of these hydrocarbons. These three groups of catalysts are dolomite, alkali metals and nickel.
    153. 153
      Valderrama Rios, M. L.; Gonzalez, A. M.; Lora, E. E. S.; Almazan del Olmo, O. A. Reduction of Tar Generated during Biomass Gasification: A Review. Biomass Bioenergy 2018, 108, 345– 370,  DOI: 10.1016/j.biombioe.2017.12.002
      153
      Reduction of tar generated during biomass gasification: A review
      Valderrama Rios, Martha Lucia; Gonzalez, Aldemar Martinez; Lora, Electo Eduardo Silva; Almazan del Olmo, Oscar Agustin
      Biomass and Bioenergy (2018), 108 (), 345-370CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      A review. One of the main problems that happen during biomass gasification is tar formation, which could make this technol. unsuccessfully from a com. point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, lab. and industrial methods and technologies for its redn.-removal, as well as research and development in this area are reviewed and evaluated in this paper.
    154. 154
      Anis, S.; Zainal, Z. A. Tar Reduction in Biomass Producer Gas via Mechanical, Catalytic and Thermal Methods: A Review. Renewable and Sustainable Energy Reviews 2011, 15, 2355– 2377,  DOI: 10.1016/j.rser.2011.02.018
      154
      Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review
      Anis, Samsudin; Zainal, Z. A.
      Renewable & Sustainable Energy Reviews (2011), 15 (5), 2355-2377CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Biomass gasification presents highly interesting possibilities for expanding the utilization of biomass as power generation using internal combustion engines or turbines. However, the need to reduce the tar in the producer gas is very important. The successful application of producer gas depends not only on the quantity of tar, but also on its properties and compns., which is assocd. with the dew-point of tar components. Class 5, 4, and 2 tar become a major cause of condensation which can foul the engines and turbines. Hence, the selectivity of tar treatment method to remove or convert class 5, 4, and 2 tar is a challenge in producer gas utilization. This review was conducted to present the recent studies in tar treatment from biomass gasification. The new technologies with their strengths and the weaknesses in term of tar redn. are discussed.
    155. 155
      Galadima, A.; Masudi, A.; Muraza, O. Catalyst Development for Tar Reduction in Biomass Gasification: Recent Progress and the Way Forward. J. Environ. Manage. 2022, 305, 114274,  DOI: 10.1016/j.jenvman.2021.114274
      155
      Catalyst development for tar reduction in biomass gasification: Recent progress and the way forward
      Galadima, Ahmad; Masudi, Ahmad; Muraza, Oki
      Journal of Environmental Management (2022), 305 (), 114274CODEN: JEVMAW; ISSN:0301-4797. (Elsevier Ltd.)
      A review. Biomass valorization via catalytic gasification is a potential technol. for commercizalization to industrial scale. However, the generated tar during biomass valorization posing numerous problems to the overall reaction process. Thus, catalytic tar removal via reforming, cracking and allied processes was among the priority areas to researchers in the recent decades. This paper reports new updates on the areas of catalyst development for tar redn. The catalyst survey include metallic and metal-promoted materials, nano-structured systems, mesoporous supports like zeolites and oxides, group IA and IIA compds. and natural catalysts based on dolomite, palygorskite, olivine, ilmenite, goethite and their modified derivs. The influence of catalyst properties and parameters such as reaction conditions, catalyst prepn. procedures and feedstock nature on the overall activity/selectivity/stability properties were simultaneously discussed. This paper not only cover to model compds., but also explore to real biomass-derived tar for consistency. The area that require further investigation was identified in the last part of this review.
    156. 156
      Narnaware, S. L.; Panwar, N. L. Catalysts and Their Role in Biomass Gasification and Tar Abetment: A Review. Biomass Conv. Bioref. 2021,  DOI: 10.1007/s13399-021-01981-1
      There is no corresponding record for this reference.
    157. 157
      Bjorgaard, S. J. Characterization And Catalytic Cracking Of Tar Obtained In Coal/Biomass/Municipal Solid Waste Gasification: The Use Of Basic Mineral Catalysts And Miscibility, Properties, And Corrosivity Of Petroleum-Biofuel Oils And Blends For Application In Oil-Fired Power Stations. Doctoral Thesis, University of North Dakota, Grand Forks, ND, 2015.
      There is no corresponding record for this reference.
    158. 158
      Dou, B.; Gao, J.; Sha, X.; Baek, S. W. Catalytic Cracking of Tar Component from High-Temperature Fuel Gas. Appl. Therm. Eng. 2003, 23, 2229– 2239,  DOI: 10.1016/S1359-4311(03)00185-6
      158
      Catalytic cracking of tar component from high-temperature fuel gas
      Dou, Binlin; Gao, Jinsheng; Sha, Xingzhong; Baek, Seung Wook
      Applied Thermal Engineering (2003), 23 (17), 2229-2239CODEN: ATENFT; ISSN:1359-4311. (Elsevier Science Ltd.)
      The cracking removal of tar component in high-temp. fuel gas cleanup is one of the most crucial problems in developing cleanest advanced power technol. Five catalysts were evaluated to tar component removal from high-temp. fuel gas in a fixed-bed reactor. 1-Methylnaphthalene was chosen as a model of tar component. The Y-zeolite and NiMo catalysts were the most effective catalysts. Two catalysts almost removed 100% tar component at 550 °C. The process variables, temp. and space velocity, have very significant effects on tar component removal with catalysts. The long-term durability shows that two catalysts maintain more than 95% removal conversion at 550 °C in 168 h. The combustion study of coke deposited on catalysts by thermal gravimetric anal. technol. shows that very small amt. buildup of coke appears on two catalysts surface. Using a first-order kinetic model, the apparent energies of activation and pre-exponential factors for tar component removal reaction and coke combustion on catalysts were obtained for the most active catalysts.
    159. 159
      Srinakruang, J.; Sato, K.; Vitidsant, T.; Fujimoto, K. Highly Efficient Sulfur and Coking Resistance Catalysts for Tar Gasification with Steam. Fuel 2006, 85, 2419– 2426,  DOI: 10.1016/j.fuel.2006.04.026
      159
      Highly efficient sulfur and coking resistance catalysts for tar gasification with steam
      Srinakruang, Jumluck; Sato, Kazuhiro; Vitidsant, Tharapong; Fujimoto, Kaoru
      Fuel (2006), 85 (17-18), 2419-2426CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Ni-on-dolomite catalysts were effective catalysts for coking resistance and promising sulfur tolerance for steam reforming of tar. Expts. were carried out in a fixed bed reactor at 730-850° with a short contact time (W/F: 0.55 g h/mol) and under atm. pressure. Toluene and naphthalene were selected as the model component of tar. The process variables such as calcination temp., reaction temp. and the content of nickel had substantial influence on promising sulfur tolerance in catalytic tar removal by Ni/Dolomite catalysts. Results were compared with the Ni/Al2O3, Ni/SiO2 as a representative of com. catalysts. The novel 15%Ni/Dolomite almost gasified tar component even at 770° and the presence of 100 ppm H2S in the feed. The poisoning effect of H2S was discovered to be reversible. The suppression of the catalytic activity by adding H2S was much lower for Ni/Dolomite than Ni/Al2O3. The TGA-DTA anal. of used catalysts revealed that Ni/Dolomite exhibited high resistance to coke deposition over those of the Ni/Al2O3, Ni/SiO2.
    160. 160
      Li, C.; Hirabayashi, D.; Suzuki, K. A Crucial Role of O2– and O22– on Mayenite Structure for Biomass Tar Steam Reforming over Ni/Ca12Al14O33. Appl. Catal. B 2009, 88, 351– 360,  DOI: 10.1016/j.apcatb.2008.11.004
      160
      A crucial role of O2- and O22- on mayenite structure for biomass tar steam reforming over Ni/Ca12Al14O33
      Li, Chunshan; Hirabayashi, Daisuke; Suzuki, Kenzi
      Applied Catalysis, B: Environmental (2009), 88 (3-4), 351-360CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Newly synthesized nickel calcium aluminum catalysts (Ni/Ca12Al14O33) were tested in a fixed bed reactor for biomass tar steam reforming, toluene as a tar decompn. model compd. Four catalysts (Ni/Ca12Al14O33) were prepd. with Ni loading amt. from 1, 3, 5 to 7%, even 1% loading catalyst also showed excellent performance. Catalysts aged expts. in the absence (60 h on stream) and presence of H2S were characterized by BET, XRD, and Raman spectra. Ni/Ca12Al14O33 showed excellent sustainability against coke formation due to the free oxygen in the catalysts. It also exhibited higher H2S-poisoning resistance property compared to the com. catalysts Ni/Al2O3 (5%) and Ni/CaO0.5/MgO0.5. Raman spectra revealed that free oxygen O2- and O22- in the structure of the catalysts could be substituted by sulfur then protected Ni poisoning on some degree, but reactivation expts. by O2 flowing showed that the sulfide Ni/Ca12Al14O33 was difficult to completely restore, incorporation of sulfur in the structure only partly regain by O2. The kinetic model proposes, as generally accepted, a 1st-order reaction for toluene with activation energy of 82.06 kJ mol-1 was coincident with the literature data. The Ni/Ca12Al14O33 catalyst was effective and relative cheap, which may be lead to redn. in the cost of hot gas cleaning process.
    161. 161
      Tomishige, K.; Miyazawa, T.; Kimura, T.; Kunimori, K. Novel Catalyst with High Resistance to Sulfur for Hot Gas Cleaning at Low Temperature by Partial Oxidation of Tar Derived from Biomass. Catal. Commun. 2005, 6, 37– 40,  DOI: 10.1016/j.catcom.2004.10.007
      161
      Novel catalyst with high resistance to sulfur for hot gas cleaning at low temperature by partial oxidation of tar derived from biomass
      Tomishige, Keiichi; Miyazawa, Tomohisa; Kimura, Takeo; Kunimori, Kimio
      Catalysis Communications (2005), 6 (1), 37-40CODEN: CCAOAC; ISSN:1566-7367. (Elsevier B.V.)
      Rh/CeO2/SiO2 exhibited higher and more stable activity in the partial oxidn. of tar derived from the pyrolysis of cedar biomass even under the presence of high concn. (280 ppm) H2S than the steam reforming Ni catalyst at lower reaction temp. than conventional conditions.
    162. 162
      Ammendola, P.; Piriou, B.; Lisi, L.; Ruoppolo, G.; Chirone, R.; Russo, G. Dual Bed Reactor for the Study of Catalytic Biomass Tars Conversion. Exp Therm Fluid Sci. 2010, 34 (3), 269– 274,  DOI: 10.1016/j.expthermflusci.2009.10.019
      162
      Dual bed reactor for the study of catalytic biomass tars conversion
      Ammendola, P.; Piriou, B.; Lisi, L.; Ruoppolo, G.; Chirone, R.; Russo, G.
      Experimental Thermal and Fluid Science (2010), 34 (3), 269-274CODEN: ETFSEO; ISSN:0894-1777. (Elsevier B.V.)
      A dual fixed bed lab. scale set up has been used to compare the activity of a novel Rh/LaCoO3/Al2O3 catalyst to that of dolomite, olivine and Ni/Al2O3, typical catalysts used in fluidized bed biomass gasification, to convert tars produced during biomass devolatilization stage. The exptl. app. allows the catalyst to be operated under controlled conditions of temp. and with a real gas mixt. obtained by the pyrolysis of the biomass carried out in a sep. fixed bed reactor operated under a selected and controlled heating up rate. The proposed catalyst exhibits much better performances than conventional catalysts tested. It is able to completely convert tars and also to strongly decrease coke formation due to its good redox properties.
    163. 163
      Iida, H.; Noguchi, K.; Numa, T.; Igarashi, A.; Okumura, K. Ru/12SrO-7Al2O3 (S12A7) Catalyst Prepared by Physical Mixing with Ru (PPh3)3Cl2 for Steam Reforming of Toluene. Catal. Commun. 2015, 72, 101– 104,  DOI: 10.1016/j.catcom.2015.09.018
      163
      Ru/12SrO-7Al2O3 (S12A7) catalyst prepared by physical mixing with Ru (PPh3)3Cl2 for steam reforming of toluene
      Iida, Hajime; Noguchi, Kazuhide; Numa, Takashi; Igarashi, Akira; Okumura, Kazu
      Catalysis Communications (2015), 72 (), 101-104CODEN: CCAOAC; ISSN:1566-7367. (Elsevier B.V.)
      Steam reforming of toluene as a model of aroms. was performed over various Ru/12SrO-7Al2O3 (S12A7) catalysts, and the effects of Ru precursor, calcination and pre-treatment conditions on the catalytic activity and durability of Ru/S12A7 catalysts were investigated. The catalytic activity of prepd. Ru/S12A7 catalysts exhibited higher than that of a com. Ru/Al2O3 (RA), despite low Ru loading. The catalysts prepd. by the phys. mixing of Ru (PPh3)3Cl2 and S12A7 (PPH) had higher catalytic activities than the catalysts prepd. by the impregnation with RuCl3 nH2O (CL). It is interesting that the N2 pre-treated PPH and CL catalysts esp. had higher catalytic activities than the H2 pre-treated PPH and CL catalysts. In their catalysts, there was a linear relationship between the catalytic activity and the Ru dispersion estd. by CO chemisorption. The catalytic activity of the N2 pre-treated PPH catalyst has little decreased with time on stream, whereas the catalytic activities of the N2 pre-treated CL catalyst and H2 pre-treated PPH catalyst gradually decreased with time on stream.
    164. 164
      Iida, H.; Deguchi, S.; Torigai, M.; Osawa, Y. Steam Reforming of Toluene over Ru/SrCO3-Al2O3 Catalyst under Extremely Low Steam-to-Carbon Ratio Conditions. Fuel 2020, 272, 117703,  DOI: 10.1016/j.fuel.2020.117703
      164
      Steam reforming of toluene over Ru/SrCO3-Al2O3 catalyst under extremely low steam-to-carbon ratio conditions
      Iida, Hajime; Deguchi, Shuntaro; Torigai, Miyu; Osawa, Yuki
      Fuel (2020), 272 (), 117703CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Ru/SrCO3-Al2O3 exhibited superior catalytic activity compared to Ru/CeO2 and Ru/Al2O3 for steam reforming of toluene under extremely low steam-to-carbon (S/C) ratio conditions that targeted chem. recovery of exhaust heat from vehicles. Ru/SrCO3-Al2O3 also exhibited good coking tolerance, unlike Ru/CeO2, even under a S/C ratio of 0.3. The efficiency of chem. heat recovery over Ru/SrCO3-Al2O3 was the highest among the examd. Ru catalysts, even under a low S/C ratio.
    165. 165
      Tang, W.; Cao, J.-P.; Yang, F.-L.; Feng, X.-B.; Ren, J.; Wang, J.-X.; Zhao, X.-Y.; Zhao, M.; Cui, X.; Wei, X.-Y. Highly Active and Stable HF Acid Modified HZSM-5 Supported Ni Catalysts for Steam Reforming of Toluene and Biomass Pyrolysis Tar. Energy Convers. Manag. 2020, 212, 112799  DOI: 10.1016/j.enconman.2020.112799
      165
      Highly active and stable HF acid modified HZSM-5 supported Ni catalysts for steam reforming of toluene and biomass pyrolysis tar
      Tang, Wen; Cao, Jing-Pei; Yang, Fei-Long; Feng, Xiao-Bo; Ren, Jie; Wang, Jing-Xian; Zhao, Xiao-Yan; Zhao, Ming; Cui, Xin; Wei, Xian-Yong
      Energy Conversion and Management (2020), 212 (), 112799CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      This paper investigated the performance of HF modified HZSM-5 supported nickel catalysts (Ni/FZ5) in steam reforming of toluene (TSR) and biomass pyrolysis tar (BSR). The mesopores vol. of support increased from 0.021 to 0.061 cm3/g with decreasing acid amt. from 2.27 to 0.41 mmol/g after HF treatment. Catalysts with different Ni loadings were prepd. and characterized. The Ni/FZ5 with Ni loading of 9 wt% possesses relatively large sp. surface area (337 m2/g) and av. pore size (2.91 nm), as well as small Ni particle size (23 nm) and high dispersion. In the process of TSR, 9Ni/FZ5 was kept above 70% for 7 h. Owing to the calcd. lower apparent activation energy (30.76 KJ/mol), 9Ni/FZ5 exhibited the best performance in BSR at 650°C, achieving the largest H2 yield of 52.8 mmol/g and the highest selectivity of H2 at 72.8%. Addnl., only 1.6 mg/g catalyst of coke deposition was detected. Moreover, its high activity was still identified with excellent hydrothermal stability even after 7 times of regeneration. All findings suggest that 9Ni/FZ5 is a promising catalyst for biomass tar cracking.
    166. 166
      Gu, J.; Wang, S.; Lu, T.; Wu, Y.; Yuan, H.; Chen, Y. Synthesis and Evaluation of Pyrolysis Waste Peat Char Supported Catalyst for Steam Reforming of Toluene. Renew Energy 2020, 160, 964– 973,  DOI: 10.1016/j.renene.2020.06.109
      166
      Synthesis and evaluation of pyrolysis waste peat char supported catalyst for steam reforming of toluene
      Gu, Jing; Wang, Shuxiao; Lu, Tao; Wu, Yufeng; Yuan, Haoran; Chen, Yong
      Renewable Energy (2020), 160 (), 964-973CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Pyrolytic char as a catalyst carrier has been widely used in tar removal. This paper aimed to develop a cost-effective and eco-friendly tar steam reforming approach by using waste peat char supported Ca catalysts in a lab. dual-stage reactor. Tar model compd. toluene was used in steam reforming expt. for facilitate fundamental research. The reaction temp., residence time, steam-to-carbon ratio and the molar ratios of H2, CO, CO2 and CH4 in the generated gas were investigated. Exptl. results show that the peat char supported Ca catalysts had good selectivity for H2, esp. the catalyst which activated by KOH and CO2. The catalyst demonstrated better catalytic activity with a higher residence time (0.6 s-0.7 s) and S/C ratio (S/C > 2.5). Under the optimized conditions, the toluene conversion and the mol% of H2 can reached 94.4% and 68.5%, resp. Meanwhile, the activity of the catalyst was proved by a variety of performance tests, and the deactivation and mechanism of catalysts were investigated. Finally, these cost-effective and green peat char-supported Ca catalysts could be used for tar removal.
    167. 167
      Park, S. Y.; Oh, G.; Kim, K.; Seo, M. W.; Ra, H. W.; Mun, T. Y.; Lee, J. G.; Yoon, S. J. Deactivation Characteristics of Ni and Ru Catalysts in Tar Steam Reforming. Renew Energy 2017, 105, 76– 83,  DOI: 10.1016/j.renene.2016.12.045
      167
      Deactivation characteristics of Ni and Ru catalysts in tar steam reforming
      Park, Seo Yun; Oh, Gunung; Kim, Kwangyul; Seo, Myung Won; Ra, Ho Won; Mun, Tae Young; Lee, Jae Goo; Yoon, Sang Jun
      Renewable Energy (2017), 105 (), 76-83CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Tar formation resulting during lignocellulosic biomass gasification is a major impediment to utilizing biomass energy sources, in that it blocks and fouls the processing equipment; as such, any tar present in the produced syngas much be effectively removed. This study analyzes the ability of com. available Ni and Ru based CH4 reforming catalysts to effect tar removal and compares deactivation characteristics. Toluene was used as the model biomass tar at concns. of 30 and 100 g/Nm3. Several addnl. parameters were also tested, including reaction temps. (400-800°C), space velocities (5000-30,000 h-1), and the steam/toluene ratios (2-20). The variation of toluene conversion and product gas compn. with reaction conditions was analyzed. Overall, H2 and CO prodn. were favored by the Ru catalyst and generally increased with temp. Conversion also increased with temp., with conversions higher than 90% obtained at 800°C.
    168. 168
      Xu, H.; Shen, Z.; Zhang, S.; Chen, G.; Pan, H.; Ge, Z.; Zheng, Z.; Wang, Y.; Wang, Y.; Li, X. Arming Wood Carbon with Carbon-Coated Mesoporous Nickel-Silica Nanolayer as Monolithic Composite Catalyst for Steam Reforming of Toluene. J. Colloid Interface Sci. 2021, 599, 650– 660,  DOI: 10.1016/j.jcis.2021.04.112
      168
      Arming wood carbon with carbon-coated mesoporous nickel-silica nanolayer as monolithic composite catalyst for steam reforming of toluene
      Xu, Haiyang; Shen, Zhangfeng; Zhang, Siqian; Chen, Gang; Pan, Hu; Ge, Zhigang; Zheng, Zheng; Wang, Yanqin; Wang, Yangang; Li, Xi
      Journal of Colloid and Interface Science (2021), 599 (), 650-660CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
      Steam reforming is an effective measure for biomass tar elimination as well as H2-rich syngas (H2 + CO) prodn. However, the granular or powdery Ni-based catalysts are prone to deactivation, which is caused by inappropriate mass transfer and clogging of catalyst bed. Herein, monolithic wood carbon (WC) with low-tortuosity microchannels is armed with a carbon-coated mesoporous nickel-silica nanocomposite (Ni-SiO2@C) layer via an evapn.-induced self-assembly and calcination procedure for toluene (tar model compd.) steam reforming. The quality of the Ni-SiO2@C layer growing on the surface of WC microchannel is affected by the molar ratios of Si/Ni feed. A uniform thin-layer coverage is obtained on the Ni-15SiO2@C/WC (Si/Ni = 15) catalyst, where highly dispersed Ni nanoparticles (av. size of 6.6 nm) with appropriate metal-support interaction and remarkable mech. strength are achieved. The mass transfer, coke resistance, and hydrothermal stability of the Ni-15SiO2@C/WC catalyst were significantly improved by the multilevel structure assembled from the WC microchannels and the secondary ordered SiO2 mesopores. A stable toluene conversion over 97% with an H2 yield of 135μmol/min was obtained at 600°C on the Ni-15SiO2@C/WC catalyst. This work opens a new window for facilely constructing high-performance wood carbon-based monolithic tar reforming catalyst.
    169. 169
      Wang, X.-B.; Yang, S.-Q.; Xu, C.; Ma, H.-D.; Zhang, Z.-H.; Du, Z.-Y.; Li, W.-Y. Effect of Boron Doping on the Performance of Ni/Biochar Catalysts for Steam Reforming of Toluene as a Tar Model Compound. J. Anal Appl. Pyrolysis 2021, 155, 105033  DOI: 10.1016/j.jaap.2021.105033
      169
      Effect of boron doping on the performance of Ni/Biochar catalysts for steam reforming of toluene as a tar model compound
      Wang, Xing-Bao; Yang, Shi-Qi; Xu, Chen; Ma, Hong-Da; Zhang, Zhi-Hua; Du, Zhen-Yi; Li, Wen-Ying
      Journal of Analytical and Applied Pyrolysis (2021), 155 (), 105033CODEN: JAAPDD; ISSN:0165-2370. (Elsevier B.V.)
      Biochar-supported nickel (Ni/BC) catalysts have potential applications in steam reforming of tar during biomass gasification. However, the industrial application of Ni/BC catalysts is restricted by their rapid deactivation caused by the gasification of biochar support and deposition of carbon on the active Ni metal. In this study, the effect of boron doping was explored on the performance of Ni/BC catalysts in steam reforming of toluene as a tar model compd. A series of Ni/BC and boron-doped Ni/BC catalysts were prepd. by impregnating Ni salts on raw and acid-washed biomass as the starting materials and used in steam reforming of toluene as the tar model compd. It was found that boron doping significantly prolonged the lifetime of Ni/BC catalysts by interacting with Ni and the biochar support simultaneously. It is believed that boron doping lowered the gasification consumption rate of the biochar support in three ways: transforming the inherent K into more stable borates, inhibiting the desorption of CO and CO2, and forming B2O3 as the active site blocker. Furthermore, boron doping also reduced coke deposition on the Ni particles.
    170. 170
      Zhou, S.; Chen, Z.; Gong, H.; Wang, X.; Zhu, T.; Zhou, Y. Low-Temperature Catalytic Steam Reforming of Toluene as a Biomass Tar Model Compound over Three-Dimensional Ordered Macroporous Ni-Pt/ Ce 1–x Zr x O 2 Catalysts. Appl. Catal. A Gen. 2020, 607, 117859  DOI: 10.1016/j.apcata.2020.117859
      170
      Low-temperature catalytic steam reforming of toluene as a biomass tar model compound over three-dimensional ordered macroporous Ni-Pt/Ce1-xZrxO2 catalysts
      Zhou, Shuyu; Chen, Zezhi; Gong, Huijuan; Wang, Xiaoshu; Zhu, Tingting; Zhou, Yuchen
      Applied Catalysis, A: General (2020), 607 (), 117859CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Ceria-zirconia solid soln. (Ce1-xZrxO2) is a fascinating catalyst support in steam reforming reaction. In order to further improve the performance of Ni-based catalyst with Ce1-xZrxO2 as support for tar team reforming, three-dimensional ordered macroporous Ni-Pt/Ce1-xZrxO2 (Ni-Pt/C1-xZx-3DOM; x = 0.2, 0.3, 0.4) catalysts were prepd. by a colloidal crystal template method and their catalytic performances for toluene steam reforming were investigated in low temp. range. The Ni-Pt/C1-xZx-3DOM exhibited excellent catalytic performance, and toluene conversion of Ni-Pt/C0.8Z0.2-3DOM reached 90.4% at 500°C under 185μmol/min toluene flowrate and 10,000 h-1 GHSV. Besides, this catalyst showed good durability with 1.7 mg g-1cat h-1 carbon deposition rate during 30 h of operation at 600°C. The characterization results demonstrated the Ni-Pt/C1-xZx-3DOM exhibits desirable characteristics to promote the catalysis performance compared to non-porous Ni-Pt/C1-xZx, including more oxygen vacancies on catalyst surface, higher sp. surface areas, larger pore vols., more meso-pores, smaller cryst. size of active component and support, and better reducibility.
    171. 171
      He, L.; Hu, S.; Yin, X.; Xu, J.; Han, H.; Li, H.; Ren, Q.; Su, S.; Wang, Y.; Xiang, J. Promoting Effects of Fe-Ni Alloy on Co-Production of H 2 and Carbon Nanotubes during Steam Reforming of Biomass Tar over Ni-Fe/α-Al 2 O 3. Fuel 2020, 276, 118116  DOI: 10.1016/j.fuel.2020.118116
      171
      Promoting effects of Fe-Ni alloy on co-production of H2 and carbon nanotubes during steam reforming of biomass tar over Ni-Fe/α-Al2O3
      He, Limo; Hu, Song; Yin, Xiaofei; Xu, Jun; Han, Hengda; Li, Hanjian; Ren, Qiangqiang; Su, Sheng; Wang, Yi; Xiang, Jun
      Fuel (2020), 276 (), 118116CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Fe-modified Ni/Al2O3 catalysts with Fe/Ni molar ratios of 0, 0.5, 1 and 2 were prepd. to promote the co-prodn. of H2 and carbon nanotubes (CNTs) during steam reforming of toluene as a tar model compd. After the addn. of Fe, toluene conversion increased from 55.1% of Ni/Al2O3 to 73.6% of F1N1A (Fe/Ni ratio of 1), and H2 yield over F1N1A reached the max. of more than 2000 mmol/(g-cata). Multi-walled carbon nanotubes with av. diam. of 10-30 nm were generated and follow tip-growth mechanism. Compared with Ni/Al2O3, the addn. of Fe remarkably increased the amt. and quality of CNTs which had longer length and less tortuosity. These dual promoting effects on H2 and CNTs after the addn. of Fe were attributed to the strong interaction between Ni and Fe in Fe-Ni alloy. Fe-Ni alloy had the high activity for the decompn. performance of toluene and H2O to generate more H2 and intermediates for improving the reforming reaction. Meanwhile, the high catalytic decompn. activity supplied more carbon species and the formation of Fe-Ni alloy enhanced the generation of metal carbide for promoting CNTs growth. Besides, the deposition of amorphous carbon was suppressed and the interaction between Ni particle and catalyst support was weakened after the addn. of Fe, which kept the activity of catalyst and promoted the tip-growth of CNTs.
    172. 172
      Zou, X.; Chen, T.; Zhang, P.; Chen, D.; He, J.; Dang, Y.; Ma, Z.; Chen, Y.; Toloueinia, P.; Zhu, C.; Xie, J.; Liu, H.; Suib, S. L. High Catalytic Performance of Fe-Ni/Palygorskite in the Steam Reforming of Toluene for Hydrogen Production. Appl. Energy 2018, 226, 827– 837,  DOI: 10.1016/j.apenergy.2018.06.005
      172
      High catalytic performance of Fe-Ni/Palygorskite in the steam reforming of toluene for hydrogen production
      Zou, Xuehua; Chen, Tianhu; Zhang, Ping; Chen, Dong; He, Junkai; Dang, Yanliu; Ma, Zhiyuan; Chen, Ye; Toloueinia, Panteha; Zhu, Chengzhu; Xie, Jingjing; Liu, Haibo; Suib, Steven L.
      Applied Energy (2018), 226 (), 827-837CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
      The inexpensive and abundant material, palygorskite, was used as a promising catalyst support to prep. Fe-Ni/Pal catalysts. Catalytic steam reforming of toluene as a biomass tar model compd. over these catalysts was investigated in a fixed-bed reactor under different parameters, including reaction temps. and S/C molar ratios. The stability and lifetime of Fe3Ni8/Palygorskite catalyst was evaluated under optimal conditions and its kinetic parameters were detd. as well. The fresh and used catalysts were characterized using X-ray diffraction (XRD), H2 temp.-programmed redn. (H2-TPR), transmission electron microscopy (TEM), and Raman spectra. The results showed that the Fe3Ni8/Palygorskite catalyst with high dispersion was successfully prepd. and exhibited superior catalytic performance compared with those of the monometallic catalysts (Fe3/Palygorskite and Ni8/Palygorskite) and the bare Palygorskite. Increasing the reaction temp. from 500 °C to 700 °C was beneficial for the toluene conversion and gaseous yields. The catalytic activity of Fe3Ni8/Palygorskite varied distinctly with the increase of S/C molar ratio and reached max. at the the S/C molar ratio of 1.0. The apparent activation energy of 41.55 kJ mol-1 and the pre-exponential factor of 1.35 × 103 m3 kg-1 h-1 were obtained for Fe3Ni8/Palygorskite in kinetic studies under optimal reaction conditions, resp. The carbon deposition anal. of the used catalysts revealed that the formation of graphitic carbon rather than amorphous carbon was the main reason for the deactivation of Fe3Ni8/Palygorskite catalysts. When ceased the injection of steam into the reaction system, the graphitic carbon would be accelerating formed on the surface of the Fe3Ni8/Palygorskite and decreased its catalytic activity for toluene conversion. But owing to the water gas shift reaction, the catalytic activity of Fe3Ni8/Palygorskite seemed to recover gradually to its optimum.
    173. 173
      Oh, G.; Park, S. Y.; Seo, M. W.; Ra, H. W.; Mun, T. Y.; Lee, J. G.; Yoon, S. J. Combined Steam-Dry Reforming of Toluene in Syngas over CaNiRu/Al 2 O 3 Catalysts. Int. J. Green Energy 2019, 16 (4), 333– 349,  DOI: 10.1080/15435075.2019.1566729
      173
      Combined steam-dry reforming of toluene in syngas over CaNiRu/Al2O3 catalysts
      Oh, Gunung; Park, Seo Yoon; Seo, Myung Won; Ra, Ho Won; Mun, Tae Young; Lee, Jae-Goo; Yoon, Sang Jun
      International Journal of Green Energy (2019), 16 (4), 333-349CODEN: IJGECR; ISSN:1543-5075. (Taylor & Francis, Inc.)
      Cracking, steam reforming, dry reforming, and combined steam and dry reforming of toluene in model syngas were performed using catalysts to simulate tar removal produced during biomass gasification. The catalysts were prepd. by adding Ru, Ca, and Mn to Ni-based catalysts, and their properties were measured using BET, pulse CO chemisorption, XRD and TG. In steam and dry reforming of toluene, a high toluene conversion was obsd. with increasing Ca content in the catalyst and catalysts contg. Ca showed a higher activity than those contg. Mn. In combined steam-dry reforming with syngas, 1%CaNiRu/Al2O3 indicated a conversion of 93.9% at 800°C.
    174. 174
      Yang, X.; Liu, X.; Guo, T.; Liu, C. Effects of Cu and Fe Additives on Low-Temperature Catalytic Steam Reforming of Toluene Over Ni/AC Catalysts. Catalysis Surveys from Asia 2019, 23 (2), 54– 63,  DOI: 10.1007/s10563-018-9260-7
      174
      Effects of Cu and Fe Additives on Low-Temperature Catalytic Steam Reforming of Toluene Over Ni/AC Catalysts
      Yang, Xiaoqin; Liu, Xuejing; Guo, Tong; Liu, Chuang
      Catalysis Surveys from Asia (2019), 23 (2), 54-63CODEN: CSAABF; ISSN:1571-1013. (Springer)
      Steam reforming of toluene, a model tar compd., was carried out at low temp. of 600°C using Cu-Ni and Fe-Ni bimetallic catalysts with different molar ratios supported on activated carbon (AC). For the Cu-Ni/AC catalysts, the carbon conversion of toluene rose and then decreased with the content of Cu increasing, and the best performance was achieved at the molar ratio of 0.2. However, the Fe-Ni/AC catalyst with the optimum compn. of Fe/Ni = 0.1 had a better catalytic performance for toluene steam reforming than the Cu-Ni/AC catalyst (Cu/Ni = 0.2). During the duration test of 20 h, the Fe-Ni/AC (Fe/Ni = 0.1) catalyst showed higher activity for the av. carbon conversion of toluene (93.8% vs. 92.9%) and better resistance. to carbon deposition than those of Ni/AC catalyst. Moreover, the metal av. sizes of the spent Ni/AC and 0.1-Fe-Ni/AC were estd. to be 30.0 nm and 19.0 nm, resp. Based on a variety of physiochem. characterization results, it is demonstrated that the addn. of iron into Ni/AC catalyst led to good dispersion of Ni, and few coke formation and limited aggregation of nickel particles during reaction.
    175. 175
      Ahmed, T.; Xiu, S.; Wang, L.; Shahbazi, A. Investigation of Ni/Fe/Mg Zeolite-Supported Catalysts in Steam Reforming of Tar Using Simulated-Toluene as Model Compound. Fuel 2018, 211, 566– 571,  DOI: 10.1016/j.fuel.2017.09.051
      175
      Investigation of Ni/Fe/Mg zeolite-supported catalysts in steam reforming of tar using simulated-toluene as model compound
      Ahmed, Talal; Xiu, Shuangning; Wang, Lijun; Shahbazi, Abolghasem
      Fuel (2018), 211 (), 566-571CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Catalytic performance of Ni/zeolite, Ni-Fe/zeolite, and Ni-Fe-Mg/zeolite catalysts were investigated in steam reforming of toluene as a biomass tar model compd. to explore promotional effect of MgO and Fe on Ni/zeolite support. The Ni-Fe-Mg/zeolite catalysts with optimum metallic compn. showed higher catalytic performance over corresponding monometallic Ni and Fe catalysts and Ni-Fe/zeolite (bimetallic) catalysts. Addn. of Mg to Ni-Fe/zeolite catalyst enhanced the tar reforming reactions and increased the carbon deposition tolerance. The results suggest that Ni-Fe/zeolite and Ni-Fe-Mg/zeolite catalysts have great potential for application in the steam reforming of biomass tar.
    176. 176
      Yin, F.; Tremain, P.; Yu, J.; Doroodchi, E.; Moghtaderi, B. An Experimental Investigation of the Catalytic Activity of Natural Calcium-Rich Minerals and a Novel Dual-Supported CaO–Ca12Al14O33_Al2O3 Catalyst for Biotar Steam Reforming. Energy Fuels 2018, 32, 4269– 4277,  DOI: 10.1021/acs.energyfuels.7b03201
      176
      An Experimental Investigation of the Catalytic Activity of Natural Calcium-Rich Minerals and a Novel Dual-Supported CaO-Ca12Al14O33/Al2O3 Catalyst for Biotar Steam Reforming
      Yin, Fengkui; Tremain, Priscilla; Yu, Jianglong; Doroodchi, Elham; Moghtaderi, Behdad
      Energy & Fuels (2018), 32 (4), 4269-4277CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Tar removal plays a key role in the process efficiency and viability of biomass gasification for syngas prodn. applications. Among currently available tar treatment technologies, catalytic cracking was found to be the most attractive due to minimal energy losses by avoiding cooling of the raw product gas. Naturally available calcium-based catalysts, particularly stone dust and dolomite, have been proven to be effective for biotar cracking; however, they have poor resistance to attrition and undergo deactivation after a few carbonation/calcination cycles. As such, these characteristics play a crit. role in detg. the viability of their application at a large-scale. Hence to overcome the shortcomings previously stated, a novel dual supported calcium-based catalyst which includes a stable support with great mech. strength (alumina, Al2O3, and mayenite, Ca12Al14O33) dosed with CaO nanoparticles was synthesized by wet impregnation of calcium on alumina particles with and without the assistance of ultrasonication, referred to as CA and CAU resp. The synthesized catalysts, as well as the naturally occurring calcium rich minerals stone dust and dolomite, were phys. and chem. characterized using a variety of anal. techniques. The synthesized catalysts showed superior mech. strength up to 5 times greater than the natural minerals. Each of the natural and synthesized catalysts was then investigated in a fixed bed reactor for steam reforming of biotars. In these expts., toluene was used as a model tar compd. to assess the catalytic activity of each and det. the best option in terms of catalytic activity, cost, and mech. strength. The synthesized CA catalyst without ultrasonic treatment exhibited better tar cracking performance in comparison to stone dust and dolomite in the temp. range of 600 to 800 °C. The synthesized CA catalyst also had the greatest performance in terms of superior surface area and mech. strength due to the core support of Al2O3. This makes it a potential bed material for further study of tar cracking in large-scale fluidized applications.
    177. 177
      Oh, G.; Park, S. Y.; Seo, M. W.; Kim, Y. K.; Ra, H. W.; Lee, J.-G.; Yoon, S. J. Ni/RueMn/Al 2 O 3 Catalysts for Steam Reforming of Toluene as Model Biomass Tar. Renew. Energy 2016, 86, 841– 847,  DOI: 10.1016/j.renene.2015.09.013
      177
      Ni/Ru-Mn/Al2O3 catalysts for steam reforming of toluene as model biomass tar
      Oh, Gunung; Park, Seo Yoon; Seo, Myung Won; Kim, Yong Ku; Ra, Ho Won; Lee, Jae-Goo; Yoon, Sang Jun
      Renewable Energy (2016), 86 (), 841-847CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      The catalytic steam reforming of the major biomass tar component, toluene, was studied over two com. Ni-based catalysts and two prepd. Ru-Mn-promoted Ni-base catalysts, in the temps. range 673-1073 K. Generally, the conversion of toluene and the H2 content in the product gas increased with temp. A H2-rich gas was generated by the steam reforming of toluene, and the CO and CO2 contents in the product gas were reduced by the reverse Boudouard reaction. A naphtha-reforming catalyst (46-5Q) exhibited better performance in the steam reforming of toluene at temps. over 873 K than a methane-reforming catalyst (Reformax 330). Ni/Ru-Mn/Al2O3 catalysts showed high toluene reforming performance at temps. over 873 K. The results indicate that the obsd. high stability and coking resistance may be attributed to the promotional effects of Mn on the Ni/Ru-Mn/Al2O3 catalyst.
    178. 178
      De Castro, T. P.; Peguin, R. P. S.; Neto, R. C. R.; Borges, L. E. P.; Noronha, F. B. Steam Reforming of Toluene over Pt/Ce x Zr1-x O2/Al2O3 Catalysts. Top Catal 2016, 59 (2–4), 292– 302,  DOI: 10.1007/s11244-015-0443-4
      178
      Steam Reforming of Toluene Over Pt/CexZr1-xO2/Al2O3 Catalysts
      de Castro, T. P.; Peguin, R. P. S.; Neto, R. C. R.; Borges, L. E. P.; Noronha, F. B.
      Topics in Catalysis (2016), 59 (2-4), 292-302CODEN: TOCAFI; ISSN:1022-5528. (Springer)
      Steam reforming of toluene was investigated over Pt/CexZr1-xO2/Al2O3 catalysts with different ceria and zirconia content (x = 0.25, 0.50, 0.75, and 1.00). Toluene was used as model mol. representative of tar produced in biomass gasification. The main reactions over Pt/CexZr1-xO2/Al2O3 catalysts are the steam reforming of toluene and the water-gas shift. The dealkylation of toluene to benzene and methane takes place only at the beginning of the reaction. Toluene conversion significantly decreases during the reaction for all catalysts excepted for Pt/CeO2/Al2O3 catalyst. Catalyst deactivation was attributed to carbon deposition as revealed by Raman spectroscopy. A clear relation is obsd. between the acidity of the catalyst and the amt. of carbon formed over Pt/CexZr1-xO2/Al2O3 catalysts. Decreasing the Ce/Zr ratio increased the d. of acid sites as well as the amt. of carbon formed. This result suggests that the main route for carbon deposition proceeds by the oligomerization of toluene mol. on the acid sites of the support. Pt/CeO2/Al2O3 catalyst was quite stable during steam reforming of toluene without carbon deposition. For this catalyst, ceria covered the acid sites of alumina and did not introduce significant Lewis acid sites.
    179. 179
      Liu, X.; Yang, X.; Liu, C.; Chen, P.; Yue, X.; Zhang, S. Low-Temperature Catalytic Steam Reforming of Toluene over Activated Carbon Supported Nickel Catalysts. J. Taiwan Inst Chem. Eng. 2016, 65, 233– 241,  DOI: 10.1016/j.jtice.2016.05.006
      179
      Low-temperature catalytic steam reforming of toluene over activated carbon supported nickel catalysts
      Liu, Xuejing; Yang, Xiaoqin; Liu, Chuang; Chen, Peng; Yue, Xiaoming; Zhang, Shuangquan
      Journal of the Taiwan Institute of Chemical Engineers (2016), 65 (), 233-241CODEN: JTICA8; ISSN:1876-1070. (Elsevier B.V.)
      In order to decrease the reaction temp. of catalytic cracking of tar derived from biomass gasification and prolong the lifetime of catalyst, nickel supported on activated carbon (Ni/AC) catalysts were prepd. by impregnation method and used in steam reforming of toluene, a model tar compd., in a fixed bed reactor. The physiochem. properties of the catalysts were analyzed by N2 adsorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM), etc. The effects of nickel content, calcination temp. and reaction temp. on carbon conversion were investigated, and the catalytic performance of the Ni/AC catalyst was compared with those of Al2O3/olivine-supported nickel catalysts. The results showed that the Ni/AC catalyst with 10 wt. % of nickel loading and 600°C of calcination temp. had the best low-temp. catalytic activity at 600°C for toluene reforming, and the carbon conversion achieved about 99%. The high performance of the 600-10%Ni/AC catalyst was probably accounted for the AC support, which had a large BET surface area and unique porous structure, and therefore, a fine nickel particle size distribution on it. It also could be known by XRD anal. that nickel loaded on the surface of AC was in the form of metallic state after calcination, thus decreasing the use of hydrogen for redn. before reaction, so the catalyst prepn. process can be simplified and the cost will be saved.
    180. 180
      Guo, F.; Liang, S.; Jia, X.; Peng, K.; Jiang, X.; Qian, L. One-Step Synthesis of Biochar-Supported Potassium-Iron Catalyst for Catalytic Cracking of Biomass Pyrolysis Tar. Int. J. Hydrogen Energy 2020, 45 (33), 16398– 16408,  DOI: 10.1016/j.ijhydene.2020.04.084
      180
      One-step synthesis of biochar-supported potassium-iron catalyst for catalytic cracking of biomass pyrolysis tar
      Guo, Feiqiang; Liang, Shuang; Jia, Xiaopeng; Peng, Kuangye; Jiang, Xiaochen; Qian, Lin
      International Journal of Hydrogen Energy (2020), 45 (33), 16398-16408CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      K-Fe bimetallic catalyst supported on porous biomass char was synthesized via a 1-step synthesis method by pyrolysis of biomass (peanut shells) after impregnation of a small amt. of K ferrate (PSC-K2FeO4), and was evaluated for the cracking of biomass pyrolysis tar. Control expts. using the pure char (PSC) and char-supported catalysts after impregnation of KOH (PSC-KOH) and FeCl3 (PSC-FeCl3) were also performed for comparison. The as-prepd. PSC-K2FeO4 possessed a porous structure with the dispersion of particles/clusters of Fe metal, K2CO3 and KFeO2 on the char support. Tar cracking expts. showed that the PSC-K2FeO4 exhibited excellent catalytic activity on the cracking of biomass pyrolysis tar at 600-800°, and the obtained tar conversion efficiencies were obviously higher than that in the control expts., particularly at relatively lower temps. (600 and 700°). The yields of combustible gas compds. including CO, H2 and CH4 increased significantly using PSC-K2FeO4 as the catalyst due to the enhanced tar cracking and reforming reactions. The porous structure and the active crystal structures of the spent catalyst were well retained, indicating the potential for efficient and long-term use of the catalyst in tar cracking. PSC-K2FeO4 exhibited excellent reusability during the 5 times reuse under the same conditions without regeneration, which showed almost no obvious decrease in the tar conversion efficiency and gas yields.
    181. 181
      Frainetti, A. J.; Klinghoffer, N. B. Recent Experimental Advances on the Utilization of Biochar as a Tar Reforming Catalyst: A Review. International Journal of Hydrogen Energy. 2023, 48, 8022– 8044,  DOI: 10.1016/j.ijhydene.2022.11.127
      181
      Recent experimental advances on the utilization of biochar as a tar reforming catalyst
      Frainetti, Alexandra J.; Klinghoffer, Naomi B.
      International Journal of Hydrogen Energy (2023), 48 (22), 8022-8044CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Review. Biomass gasification to form syngas is a promising renewable energy prodn. process. Here, biomass is exposed to high temps. in an oxygen-controlled environment where volatiles react to form components of syngas that can be used for energy or chem. prodn. A limitation to the use of gasification is the generation of tars that condense in downstream equipment causing damage and halting prodn. Currently tars are removed by phys., thermal, or catalytic processes, all high-cost options. On the other hand, biochar is produced as a solid byproduct of gasification, characterized by high surface area, desirable adsorption properties, and relatively low cost. This review details the use of biochar as a catalyst to reform tars, while highlighting recent exptl. advances in evaluating the effects of biomass compn., gasification conditions, and pre-treatment and post-treatment options to improve catalytic function. It discusses tar degrdn. mechanisms and catalyst deactivation and recommends further areas for research.
    182. 182
      Qian, K.; Kumar, A. Catalytic Reforming of Toluene and Naphthalene (Model Tar) by Char Supported Nickel Catalyst. Fuel 2017, 187, 128– 136,  DOI: 10.1016/j.fuel.2016.09.043
      182
      Catalytic reforming of toluene and naphthalene (model tar) by char supported nickel catalyst
      Qian, Kezhen; Kumar, Ajay
      Fuel (2017), 187 (), 128-136CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      The purpose of this study was to utilize gasification derived char as a catalyst support for tar removal. Red cedar char collected from downdraft bed gasification was chem. activated into activated carbon and impregnated with nickel acetate and nickel nitrate. The effects of nickel salts precursor, nitric acid treatment of support and redn. of nickel in hydrazine medium on catalyst performance were studied. It was found nickel nitrate was a better nickel precursor than nickel acetate for prepn. of char supported nickel catalyst. The catalyst impregnated with nickel nitrate was found more active in steam reforming of toluene than the catalyst impregnated with nickel acetate. TEM results indicated that nickel particle size of the catalyst impregnated with nickel nitrate was much smaller than that of the catalyst impregnated with nickel acetate. Toluene showed higher removal efficiency than naphthalene. The presence of naphthalene decreased the toluene removal.
    183. 183
      Mani, S.; Kastner, J. R.; Juneja, A. Catalytic Decomposition of Toluene Using a Biomass Derived Catalyst. Fuel Process. Technol. 2013, 114, 118– 125,  DOI: 10.1016/j.fuproc.2013.03.015
      183
      Catalytic decomposition of toluene using a biomass derived catalyst
      Mani, Sudhagar; Kastner, James R.; Juneja, Ankita
      Fuel Processing Technology (2013), 114 (), 118-125CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Pine bark biochar generated by slow pyrolysis (950 °C) was used as a low cost catalyst to decomp. toluene (model tar compd.) over a temp. range of 600-900 °C. Relative to thermal cracking, fractional toluene conversion increased from 13 to 94% when increasing temps. from 600 to 900 °C (2500 ppmv, SV = 0.76 s-1, 3.8 g catalyst) and Arrhenius anal. indicated an activation energy of 91 kJ/mol, comparable to that of synthetic catalysts (e.g., 80.24 kJ/mol for Ni/Mayenite and 196 kJ/mol for olivine) and lower than that of thermal cracking (356 kJ/mol). The reaction rate for toluene decompn. increased linearly from 550 to 700 °C with a concn. range of 1000-4600 ppmv indicating a first order rate law with respect to toluene. Benzene was detected as a potential intermediate in the decompn. of toluene with selectivity ranging from 0 to 28% at temps. from 600 to 900 °C resp., and its formation increased with increasing toluene conversion. Toluene conversion ranged between 40 and 95% with benzene selectivity from 0 to 20% at 800 °C during catalyst longevity studies of 6 days. These results indicate that biochar generated from slow pyrolysis of pine bark at high temp. can be used as a low cost catalyst for tar removal from syngas. However, the tar removal rates using the biochar catalyst were lower than that of olivine and nickel based catalysts indicating the need to increase catalytic activity.
    184. 184
      Lee, J.; Kim, K.-H.; Kwon, E. E. Biochar as a Catalyst. Renewable Sustainable Energy Rev. 2017, 77, 70– 79,  DOI: 10.1016/j.rser.2017.04.002
      184
      Biochar as a Catalyst
      Lee, Jechan; Kim, Ki-Hyun; Kwon, Eilhann E.
      Renewable & Sustainable Energy Reviews (2017), 77 (), 70-79CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. Biochar is pyrogenic carbon rich material generated from carbon neutral sources (i.e., biomass). Being an environmentally benign means for soil amendment, it also offers principle strategies for carbon capture and storage (CCS). In addn., recent recognition of biochar as versatile media for catalytic applications has brought forth initial research exploring the catalytic capacity of biochar and mechanistic practices in various routes. Thus, to provide comprehensive information on the catalytic applications of biochar in the field of catalysis, this review focuses on the catalytic challenges and practices of biochar, e.g., biodiesel prodn., tar redn. in bio-oil and syngas (synthetic gas: H2 and CO), enhanced syngas prodn., conversion of biomass into chems. and biofuels, deNOx reactions, and microbial fuel cell electrodes. This review also provides an in-depth assessment on the catalytic properties of biochar with respect to prodn. recipes at the fundamental level. Lastly, the performance of various biochar catalysts is also evaluated in this review.
    185. 185
      Kastner, J. R.; Mani, S.; Juneja, A. Catalytic Decomposition of Tar Using Iron Supported Biochar. Fuel Process. Technol. 2015, 130, 31– 37,  DOI: 10.1016/j.fuproc.2014.09.038
      185
      Catalytic decomposition of tar using iron supported biochar
      Kastner, James R.; Mani, Sudhagar; Juneja, Ankita
      Fuel Processing Technology (2015), 130 (), 31-37CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Iron supported biochar catalysts were used to decomp. toluene, a model tar compd., over a temp. range of 600-900 °C. Toluene conversion and decompn. rates increased linearly with increasing temp. and catalyst loading from 600 to 700 °C. Relative to biochar alone, the iron supported catalysts lowered the activation energy by 47% and decreased the formation of benzene, an intermediate in toluene decompn. At 800 °C for the 13 and 18.7 wt.% iron loaded catalyst, toluene conversion approached 100% and benzene selectivity (SB) was zero, compared to an SB of 0.025% and 0.35% for 10% iron and the biochar, resp. Time on stream studies with the 13 wt.% iron biochar catalyst, over the course of four days, resulted in a mean toluene conversion of 91% and benzene selectivity of 0.02%. These results indicate that inexpensive iron impregnated biochar catalysts could potentially be used to catalytically decomp. tar mols. in syngas generated via biomass gasification.
    186. 186
      Abu El-Rub, Z.; Bramer, E. A.; Brem, G. Experimental Comparison of Biomass Chars with Other Catalysts for Tar Reduction. Fuel 2008, 87, 2243– 2252,  DOI: 10.1016/j.fuel.2008.01.004
      186
      Experimental comparison of biomass chars with other catalysts for tar reduction
      Abu El-Rub, Z.; Bramer, E. A.; Brem, G.
      Fuel (2008), 87 (10-11), 2243-2252CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      In this paper the potential of using biomass char as a catalyst for tar redn. is discussed. Biomass char is compared with other known catalysts used for tar conversion. Model tar compds., phenol and naphthalene, were used to test char and other catalysts. Tests were carried out in a fixed bed tubular reactor at a temp. range of 700-900° under atm. pressure and a gas residence time in the empty catalyst bed of 0.3 s. Biomass chars are compared with calcined dolomite, olivine, used fluid catalytic cracking (FCC) catalyst, biomass ash and com. nickel catalyst. The conversion of naphthalene and phenol over these catalysts was carried out in the atm. of CO2 and steam. At 900°, the conversion of phenol was dominated by thermal cracking whereas naphthalene conversion was dominated by catalytic conversion. Biomass chars gave the highest naphthalene conversion among the low cost catalysts used for tar removal. Further, biomass char is produced continuously during the gasification process, while the other catalysts undergo deactivation. A simple first order kinetic model is used to describe the naphthalene conversion with biomass char.
    187. 187
      Pereira Lopes, R.; Astruc, D. Astruc Didier. Biochar as a Support for Nanocatalysts and Other Reagents: Recent Advances and Applications. Coord. Chem. Rev. 2021, 426, 213585  DOI: 10.1016/j.ccr.2020.213585
      187
      Biochar as a support for nanocatalysts and other reagents: Recent advances and applications
      Pereira Lopes, Renata; Astruc, Didier
      Coordination Chemistry Reviews (2021), 426 (), 213585CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. The transformation and use of the biomass are of fundamental energetic and ecol. interest. The general objective of this review is to provide an overview of biochar (a major biomass product) as a support for nanocatalysts and other reagents, its mode of coordination and activation with nanoparticles and applications. This includes the physico-chem. characteristics of biochar, the advances in its prodn. processes, and its activation and functionalization in order to improve its phys. and chem. characteristics and applications as support in catalysis and environmental decontamination. Biochar is a byproduct produced by carbonization of biomass. In this process, the products of interest are syngas and bio-oil, due to their high calorific value and their diverse applications. However, biochar has interesting characteristics. It can be used as support, allowing to disperse nanoparticles of the catalysts, such as those of the transition metals: Fe, Ag, Ni, Pd, etc. bimetallic compns. such as Ru/Re, Fe/Ni, etc. and metal oxides such as Fe3O4, CO3O4, CuO, TiO2, etc. increasing the reactivity of the system, minimizing the leaching of the catalysts and allowing their re-use. These materials can be employed in the degrdn. of contaminants in aq. systems, soil and sediments, tar reforming reactions and synthesis of fine chems. This review will serve as the basis for new research aiming to add value to this important resource.
    188. 188
      Bhandari, P. N.; Kumar, A.; Bellmer, D. D.; Huhnke, R. L. Synthesis and Evaluation of Biochar-Derived Catalysts for Removal of Toluene (Model Tar) from Biomass-Generated Producer Gas. Renew Energy 2014, 66, 346– 353,  DOI: 10.1016/j.renene.2013.12.017
      188
      Synthesis and evaluation of biochar-derived catalysts for removal of toluene (model tar) from biomass-generated producer gas
      Bhandari, Pushpak N.; Kumar, Ajay; Bellmer, Danielle D.; Huhnke, Raymond L.
      Renewable Energy (2014), 66 (), 346-353CODEN: RNENE3; ISSN:0960-1481. (Elsevier Ltd.)
      Challenges in removal of contaminants, esp. tars, from biomass-generated producer gas continue to hinder commercialization efforts in biomass gasification. The objectives of this study were to synthesize catalysts made from biochar, a byproduct of biomass gasification and to evaluate their performance for tar removal. The three catalysts selected for this study were original biochar, activated carbon, and acidic surface activated carbon derived from biochar. Expts. were carried out in a fixed bed tubular catalytic reactor at temps. of 700 and 800°C using toluene as a model tar compd. to measure effectiveness of the catalysts to remove tar. Steam was supplied to promote reforming reactions of tar. Results showed that all three catalysts were effective in toluene removal with removal efficiency of 69-92%. Activated carbon catalysts resulted in higher toluene removal because of their higher surface area (∼900 m2/g compared to less than 10 m2/g of biochar), larger pore diam. (19 A° compared to 15.5 A° of biochar) and larger pore vol. (0.44 cc/g compared to 0.085 cc/g of biochar). An increase in reactor temp. from 700 to 800 °C resulted in 3-10% increase in toluene removal efficiency. Activated carbons had higher toluene removal efficiency compared to biochar catalysts.
    189. 189
      Feng, D.; Zhao, Y.; Zhang, Y.; Sun, S. Effects of H2O and CO2 on the Homogeneous Conversion and Heterogeneous Reforming of Biomass Tar over Biochar. Int. J. Hydrogen Energy 2017, 42, 13070– 13084,  DOI: 10.1016/j.ijhydene.2017.04.018
      189
      Effects of H2O and CO2 on the homogeneous conversion and heterogeneous reforming of biomass tar over biochar
      Feng, Dongdong; Zhao, Yijun; Zhang, Yu; Sun, Shaozeng
      International Journal of Hydrogen Energy (2017), 42 (18), 13070-13084CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      The effects of H2O and CO2 reforming agents on the homogeneous conversion and heterogeneous reforming of biomass tar were studied in the presence of a biochar catalyst to better understand the transformation pathway between tar and biochar. Catalysis was performed in a two-stage fluidized bed/fixed bed reactor while Raman anal. and Gas Chromatograph-Mass Spectrometry were used to investigate biochar and tar characteristics. The results show temps. of 700-900 °C are required for the homogeneous transformation of tar in the presence of H2O/CO2, which esp. affect polycyclic arom. hydrocarbons. The tar homogeneous reforming effect of 15 vol.% H2O is significantly higher than that of 29 vol.% CO2. During heterogeneous reforming of tar over biochar at 800 °C, the tar yield decreases in varying degrees with the H2O and CO2 concn. increasing. H2O and CO2 not only directly affect the tar transformation on biochar, but also indirectly influence the reforming of tar through changing the structure of biochar catalyst. The formation of addnl. oxygen-contg. functional groups and transformation of small arom. rings to larger arom. rings in the biochar structure are promoted with the concn. of H2O and CO2 increasing. Under a H2O/CO2 atmosphere, a higher degree of arom. ring heterogeneous reforming occurs over biochar than for non-arom. tar components. Heterogeneous reforming reactivity of tar is promoted by the biomass tar structure (e.g the substituents, large arom. ring size and five-carbon ring structures) over biochar under H2O/CO2 atmospheres. Further increasing H2O and CO2 concn. enhances this effect.
    190. 190
      Lang, L.; Yang, W.; Xie, J.; Yin, X.; Wu, C.; Lin, J. Y. S. Oxidative Filtration for Flyash & Tar Removal from 1.0 MWth Fixed-Bed Biomass Air Gasification. Biomass Bioenergy 2019, 122, 145– 155,  DOI: 10.1016/j.biombioe.2019.01.018
      190
      Oxidative filtration for flyash & tar removal from 1.0 MWth fixed-bed biomass air gasification
      Lang, Lin; Yang, Wenshen; Xie, Jianjun; Yin, Xiuli; Wu, Chuangzhi; Lin, Jerry Y. S.
      Biomass and Bioenergy (2019), 122 (), 145-155CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      Exptl. campaigns were performed with the aim to study the hot gas filtration process during the pilot-scale biomass gasification at GIEC. This paper gives an overview of the continuous and steady filtration tests performed with stable pressure drop (ΔP) for over 200 h in 400-600°C, using wood chip and charcoal as the feedstock. The ceramic candles show good long-term filtration performance with a permanent cake layer serving as an extra filtration medium. Tar content is found to be the controlling resistance for the biomass gasification-filtration process. A novel oxidative filtration is reported to lead to a simultaneous removal of carbonaceous flyash particles (CFPs) and tars as well as a dramatic ΔP decrease with no obvious degrdn. in the heating value of the producer gas, in which a tiny amt. of addnl. air (≤5.5 vol%) is introduced into the producer gas. Under the optimum condition, the CFP removal efficiency is always >99.0% and the tar removal efficiency of 92.2% could be achieved, with ΔP kept within a range of 1000-2000 N m-2 at the gas superficial velocity of 1.5-2.0 cm s-1 and 0.5-1.5% oxygen content of the producer gas (O2%). It is found that filter candles could act as a reactor without any catalyst to partially oxidize tars and CFPs with a little heat generation when hot gas filtration is operated in the presence of low oxygen concn. in 400-600°C. The efficient CFP removal and tar redn. during the high-temp. oxidative filtration is beneficial for downstream units and their operability.
    191. 191
      Awais, M.; Li, W.; Arshad, A.; Haydar, Z.; Yaqoob, N.; Hussain, S. Evaluating Removal of Tar Contents in Syngas Produced from Downdraft Biomass Gasification System. Int. J. Green Energy 2018, 15 (12), 724– 731,  DOI: 10.1080/15435075.2018.1525557
      191
      Evaluating removal of tar contents in syngas produced from downdraft biomass gasification system
      Awais, Muhammad; Li, Wei; Arshad, Arfan; Haydar, Zeeshan; Yaqoob, Nauman; Hussain, Sajjad
      International Journal of Green Energy (2018), 15 (12), 724-731CODEN: IJGECR; ISSN:1543-5075. (Taylor & Francis, Inc.)
      Biomass gasification is a process of converting solid biomass ingredients into a combustible gas which can be used in electricity generation. Regardless of their applications in many fields, biomass gasification technol. is still facing many cleaning issues of syngas. Tar prodn. in biomass gasification process is one of the biggest challenges for this technol. The aimed of this study is to evaluate the tar contents in syngas produced from wood chips and corn cobs as a biomass fuel and tar removal efficiency of different cleaning units integrated with gasifier. Performance of different cleaning units, i.e., cyclone separator, wet scrubber, biomass filter, and auxiliary filter was tested with two biomass fuels. Results of this study reported that wood chips produced less tar 6,600 mg/Nm3 as compared to corn cobs 7,500 mg/Nm3 in biomass reactor stage before cleaning. After passing through the whole cleaning system, the tar concn. in case wood chip reduced from 6,600 to 112 mg/Nm3, while in case of corn cob from 7,500 to 220 mg/Nm3. Overall tar removal efficiencies of cyclone separator, wet scrubber, biomass filter and auxiliary filter was noted as 72%, 63%, 74%, 35%, resp.
    192. 192
      Rapagnà, S.; Gallucci, K.; Foscolo, P. U. Olivine, Dolomite and Ceramic Filters in One Vessel to Produce Clean Gas from Biomass. Waste Manag 2018, 71, 792– 800,  DOI: 10.1016/j.wasman.2017.07.038
      192
      Olivine, dolomite and ceramic filters in one vessel to produce clean gas from biomass
      Rapagna, Sergio; Gallucci, Katia; Foscolo, Pier Ugo
      Waste Management (Oxford, United Kingdom) (2018), 71 (), 792-800CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
      Heavy org. compds. produced during almond shells gasification in a steam and/or air atm., usually called tar, are drastically reduced in the product gas by using simultaneously in one vessel a ceramic filter placed in the freeboard and a mixt. of olivine and dolomite particles in the fluidized bed of the gasifier. The content of tar in the product gas during a ref. gasification test with air, in presence of fresh olivine particles only, was 8600 mg/Nm3 of dry gas. By gasifying biomass with steam at the same temp. level of 820 °C in a bed of olivine and dolomite (20% by wt.), and in the presence of a catalytic ceramic filter inserted in the freeboard of the fluidized bed gasifier, the level of tar was brought down to 57 mg/Nm3 of dry product gas, with a decrease of more than two orders of magnitude.
    193. 193
      Surjosatyo, A.; Anggriawan, M. B.; Hermawan, A. A.; Dafiqurrohman, H. Comparison between Secondary Thermal Cracking Methods and Venturi Scrubber Filtering in Order to Reduce Tar in Biomass Gasification. Energy Procedia 2019, 158, 749– 754,  DOI: 10.1016/j.egypro.2019.01.200
      193
      Comparison between secondary thermal cracking methods and venturi scrubber filtering in order to reduce tar in biomass gasification
      Surjosatyo, Adi; Anggriawan, Muhammad Barryl; Hermawan, Andika Akbar; Dafiqurrohman, Hafif
      Energy Procedia (2019), 158 (), 749-754CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
      Biomass Gasification is a potential technol. to overcome energy needs in the present time. However, one of the major challenges in using syngas as an elec. power is a tar problem in producer gas that can cause fouling in pipes. The purpose of this research, is to show the comparison between secondary thermal cracking and venturi scrubber in order to reduce tar concn. The performance of this method was tested in 10 kW rice husk biomass gasifier. The max. tar redn. efficiencies of venturi scrubber and secondary thermal cracking were found 89% and 74% resp. This is because as the ER increased, the temp. in the pyrolysis zone was also increased, hence, enhancing tar redn. with thermal cracking.
    194. 194
      Zhu, F.; Li, X.; Zhang, H.; Wu, A.; Yan, J.; Ni, M.; Zhang, H.; Buekens, A. Destruction of Toluene by Rotating Gliding Arc Discharge. Fuel 2016, 176, 78– 85,  DOI: 10.1016/j.fuel.2016.02.065
      194
      Destruction of toluene by rotating gliding arc discharge
      Zhu, Fengsen; Li, Xiaodong; Zhang, Hao; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Zhang, Hanwei; Buekens, Alfons
      Fuel (2016), 176 (), 78-85CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Non-thermal plasma is considered as an alternative treatment of tar present in the effluent from gasification processes. In this study, a novel rotating gliding arc (RGA) discharge reactor was developed for tar destruction. Toluene in nitrogen flow was used as a tar surrogate. The phys. features of RGA discharge and its application to toluene destruction are investigated at different input concns. and total gas flow rates. As a result, the highest destruction efficiency could exceed 95%, with a toluene concn. of 10 g/N m3 and a total flow rate of 0.24 N m3/h. The two major gaseous products are H2 and C2H2, with max. selectivity of 39.35% and 27.0%, resp. A higher input concn. slightly reduces this destruction efficiency but the energy efficiency further expanded, with a highest value of 16.61 g of toluene eliminated/kW h. In addn., the liq. and solid byproducts are collected downstream of the RGA reactor and detd. qual. and semi-quant. The amt. and structure of these byproducts is instructive for reaching a better comprehension of the chem. consequences of plasma treatment to the model compd. and to the carrier gas nitrogen.
    195. 195
      Wang, Y.; Yang, H.; Tu, X. Plasma Reforming of Naphthalene as a Tar Model Compound of Biomass Gasification. Energy Convers. Manag. 2019, 187, 593– 604,  DOI: 10.1016/j.enconman.2019.02.075
      195
      Plasma reforming of naphthalene as a tar model compound of biomass gasification
      Wang, Yaoling; Yang, Haiping; Tu, Xin
      Energy Conversion and Management (2019), 187 (), 593-604CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      The contamination of producer gas with tars from biomass gasification remains a significant challenge in the bioenergy industry and a crit. barrier, limiting the com. applications of biomass gasification. Non-thermal and non-equil. plasma offers an unconventional and emerging technol. for the effective redn. of problematic tars from gasification. In this study, we investigated plasma reforming of naphthalene as a two-ring tar model compd. using a gliding arc discharge (GAD) reactor with/without steam. The influence on the plasma conversion of naphthalene based on the inlet naphthalene concn., discharge power and steam-to-carbon ratio was examd. to understand the effects of these operating parameters on the destruction of tar, gas selectivity/yield and energy efficiency. Adding H2O in the plasma process generates oxidative OH radicals, creating addnl. reaction routes for the step-wised oxidn. of naphthalene and its fragments towards the CO, CO2 and water. The optimum ratio (2.0) of steam-to-carbon was identified to achieve the highest naphthalene conversion (84.8%), C2H2 yield (33.0%), total gas yield (72.2%) and energy efficiency (5.7 g/kWh). The effect of the amt. of steam on the plasma redn. of tars was dependent on the balance between two opposite effects due to the presence of steam: pos. effect of OH radicals and the neg. effect of electron attachment on water mols. Introducing an appropriate amt. of steam to the plasma redn. of naphthalene also substantially minimized the formation of byproducts and enhanced the carbon balance. Plausible reaction mechanisms for the plasma decompn. of naphthalene were proposed through a comprehensive anal. of gaseous and condensable products combined with plasma spectroscopic diagnostics.
    196. 196
      Zhang, H.; Zhu, F.; Li, X.; Xu, R.; Li, L.; Yan, J.; Tu, X. Steam Reforming of Toluene and Naphthalene as Tar Surrogate in a Gliding Arc Discharge Reactor. J. Hazard Mater. 2019, 369, 244– 253,  DOI: 10.1016/j.jhazmat.2019.01.085
      196
      Steam reforming of toluene and naphthalene as tar surrogate in a gliding arc discharge reactor
      Zhang, Hao; Zhu, Fengsen; Li, Xiaodong; Xu, Ruiyang; Li, Li; Yan, Jianhua; Tu, Xin
      Journal of Hazardous Materials (2019), 369 (), 244-253CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
      Steam reforming of mixed toluene and naphthalene as tar surrogate was studied in an a.c. gliding arc discharge plasma, with particular emphasis on better understanding the effect of steam and CO2 on the reaction performance. H2, C2H2 and CO are the major gas products in the plasma steam reforming of tar for energy recovery. The addn. of a small amt. of steam remarkably enhances the conversions of both toluene and naphthalene, from 60.4% to 76.1% and 57.6% to 67.4%, resp., as ·OH radicals formed by H2O dissocn. create more reaction pathways for the conversion of toluene, naphthalene and their fragments. However, introducing CO2 to this process has a neg. effect on the tar reforming. Optical emission spectroscopic diagnostics showed the formation of a variety of reactive species in the plasma process. Trace amts. of monocyclic and bicyclic arom. condensable byproducts are also detected. The destruction of toluene and naphthalene can be initiated through the collisions of tar surrogates with energetic electrons, N2 excited species, ·OH and O radicals etc. Further optimization of the plasma tar destruction is still needed because the complexity of the tar component in a practical gasifier could decrease the tar conversions.
    197. 197
      Xu, B.; Xie, J.; Zhan, H.; Yin, X.; Wu, C.; Liu, H. Removal of Toluene as a Biomass Tar Surrogate in a Catalytic Nonthermal Plasma Process. Energy Fuels 2018, 32 (10), 10709– 10719,  DOI: 10.1021/acs.energyfuels.8b02444
      197
      Removal of Toluene as a Biomass Tar Surrogate in a Catalytic Nonthermal Plasma Process
      Xu, Bin; Xie, Jianjun; Zhan, Hao; Yin, Xiuli; Wu, Chuangzhi; Liu, Hao
      Energy & Fuels (2018), 32 (10), 10709-10719CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      In this study, a packed-bed dielec. barrier discharge (DBD) reactor was developed to investigate the removal of biomass tar in a fuel gas atm. Toluene was used as the tar surrogate, and the catalyst used was a Nickel-based catalyst (Ni/γ-Al2O3) because of its high activity and low cost. In addn., another two kinds of packing materials (glass pellets and γ-Al2O3 pellets) were employed to make a comparison with the Ni/γ-Al2O3 catalyst. The research has focused on the removal efficiency of toluene and the effects of carrier gas, reaction temp., Ni loading, and concn. of toluene. The results indicated that two supplementary packing materials could not realize an effective removal of toluene. On the contrary, Ni/γ-Al2O3 combined with plasma showed a significant synergetic effect and hence a great toluene removal potential. On one hand, the removal efficiency initially decreased within the temp. range of 200-300 °C and then significantly increased within the temp. of 300-400 °C during plasma-catalytic process. At the optimal temp. of 400 °C, the toluene removal efficiency could reach the max. values of 80.2%, 91.7%, and 100.0% when the Ni loading was 3, 5, and 10 wt %, resp. On the other hand, an increase in the inlet toluene concn. slightly reduced removal efficiency but increased the energy efficiency, reaching the highest value of 16.8 g/kWh. The introduction of plasma enhanced the methanation reaction of the fuel gas occurring in the catalytic process, which was favorable at high temps. Based on these findings, the mechanisms and pathways of toluene destruction in the plasma-catalytic process were proposed and elucidated.
    198. 198
      J, A.; Rao, L. Influence of Transitional and Turbulent Flow on Electrical, Optical, Morphological and Chemical Characteristics of a Nitrogen Rotating Gliding Arc. J. Phys. D Appl. Phys. 2022, 55 (24), 245202,  DOI: 10.1088/1361-6463/ac5bcc
      There is no corresponding record for this reference.
    199. 199
      Kim, S. W.; Park, H. S.; Kim, H. J. 100 KW Steam Plasma Process for Treatment of PCBs (Polychlorinated Biphenyls) Waste. Vacuum 2003, 70 (1), 59– 66,  DOI: 10.1016/S0042-207X(02)00761-3
      199
      100 kW steam plasma process for treatment of PCBs (polychlorinated biphenyls) waste
      Kim, Seok-Wan; Park, Hyun-Seo; Kim, Hyung-Jin
      Vacuum (2003), 70 (1), 59-66CODEN: VACUAV; ISSN:0042-207X. (Elsevier Science Ltd.)
      Non-transferred DC steam (H2O) plasma working with 100 kW was used to treat hazardous wastes to minimize the formation of toxic byproducts such as dioxins and furans usually assocd. with conventional incineration processes. In the steam plasma treatment of wastes contg. a mixt. of polychlorinated biphenyl (PCB), the content of combustible gas that can be used as gaseous fuel was about 30% based on wet gas. For the mixt. of 27% PCB and 73% CCl4, total toxic equiv. concn. of PCDD/PCDF was about 0.056 ng TEQ/N m3. It is concluded that the steam plasma torch process was more effective for waste-to-energy and hazardous waste treatment than the air plasma torch process injected steam and the conventional incineration process.
    200. 200
      Vecten, S.; Wilkinson, M.; Bimbo, N.; Dawson, R.; Herbert, B. M. J. Hydrogen-Rich Syngas Production from Biomass in a Steam Microwave-Induced Plasma Gasification Reactor. Bioresour. Technol. 2021, 337, 125324,  DOI: 10.1016/j.biortech.2021.125324
      200
      Hydrogen-rich syngas production from biomass in a steam microwave-induced plasma gasification reactor
      Vecten, Simon; Wilkinson, Michael; Bimbo, Nuno; Dawson, Richard; Herbert, Ben M. J.
      Bioresource Technology (2021), 337 (), 125324CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
      Substitution of fossil fuels by sustainable practices must be rapidly implemented to mitigate the impacts of climate change. The conversion of biomass into combustible gas is investigated in a microwave-induced plasma reactor using pure steam as the plasma working gas for the first time. The optimum results are achieved at the highest forward microwave power of 6 kW with biomass carbon conversion efficiency over 98% and complete biomass energy recovery in syngas. Unreacted steam is simply condensed out, leading to the prodn. of a syngas with low inert diln. and high calorific value in the range 10.5-12 MJ/Nm3. The syngas produced is rich in hydrogen, exceeding 60% by vol. The proposed process could aid in the transition to a carbon neutral economy as it has the potential to efficiently convert biomass to syngas that can be used for the sustainable generation of fuels, chems. and energy.
    201. 201
      Mallick, R.; Vairakannu, P. Experimental Investigation of Acrylonitrile Butadiene Styrene Plastics Plasma Gasification. J. Environ. Manage 2023, 345, 118655,  DOI: 10.1016/j.jenvman.2023.118655
      201
      Experimental investigation of acrylonitrile butadiene styrene plastics plasma gasification
      Mallick, Roni; Vairakannu, Prabu
      Journal of Environmental Management (2023), 345 (), 118655CODEN: JEVMAW; ISSN:0301-4797. (Elsevier Ltd.)
      E-waste comprising plastics causes serious ecol. problems due to low degradability, but it is capable of producing a high amt. of energy by thermochem. conversion. Therefore, the current study focuses on generating clean syngas through plasma gasification of acrylonitrile butadiene styrene (ABS) based computer keyboard plastic waste (CKPW) using CO2 as a gasifying agent. The effect of feed rate, gas flow rate and plasma power on the syngas compn. was studied. In addn., a comprehensive investigation of energy, exergy, economic and environmental analyses along with characterization of the obtained products was conducted to evaluate the performance of the system. Based on the exptl. results, the optimum process parameters for producing syngas possessing a higher calorific value (15.80 MJ/m3) with a higher percentage of H2 (30.16 vol%) and CO (46.09 vol%) were estd. The optimum feed flow rates of solid fuel and CO2 gas and torch power were estd. as 40 g/10 min, 0.5 lpm and 1.12 kW, resp. At these conditions, the system could achieve a max. energy and exergy efficiency of 46.06% and 44.34%, resp., while the levelized cost of syngas (LCOSover) was estd. as 25.45 INR/kWh, including the social cost. Likewise, the lower values of the estd. global warming potential (370.19 gCO2eq/h) illustrate the better sustainability of the process. The obtained oil with the estd. LHV of 39.13 MJ/kg could be an alternative fuel for diesel and the residue contg. a higher proportion of TiO2 has medical applications upon further enrichment. The reaction mechanism of ABS conversion to syngas under plasma gasification conditions is proposed.
    202. 202
      Chu, C.; Wang, P.; Boré, A.; Ma, W.; Chen, G.; Wang, P. Thermal Plasma Co-Gasification of Polyvinylchloride and Biomass Mixtures under Steam Atmospheres: Gasification Characteristics and Chlorine Release Behavior. Energy 2023, 262, 125385,  DOI: 10.1016/j.energy.2022.125385
      202
      Thermal plasma co-gasification of polyvinylchloride and biomass mixtures under steam atmospheres: Gasification characteristics and chlorine release behavior
      Chu, Chu; Wang, Ping; Bore, Abdoulaye; Ma, Wenchao; Chen, Guanyi; Wang, Pan
      Energy (Oxford, United Kingdom) (2023), 262 (Part_B), 125385CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      This study systematically explores the syngas characteristics and chlorine release behavior during plasma co-gasification of polyvinylchloride (PVC) and biomass through exptl. and thermodn. methods. The results indicate that carbon conversion rate and chlorine release ratio are pos. assocd. with power and steam/carbon ratio. Plasma co-gasification of PVC and biomass yields 4.96-16.95% higher H2 proportion and 1.84-41.41% lower chlorine release ratio than the weighted sum values of mono-gasification. The thermodn. calcn. also verifies the lower percentage (16.33-97.47 wt%) of gaseous chlorides (HCl(g), KCl(g), etc.) from plasma co-gasification than mono-gasification. The low level of av. relative error (0.059) of thermodn. simulation demonstrates its potential for quant. anal. of chlorine release behavior. Redundancy anal. reveals that temp. is the most significant factor of carbon conversion rate, H2 proportion, and chlorine release ratio. This study could provide theor. guidance for operational optimization and pollution control of plasma gasification.
    203. 203
      Cvetinović, D.; Milutinović, N.; Erić, A.; Škobalj, P.; Andjelković, J.; Bakić, V. Optimisation of the Operating Parameters of a Thermal Plasma System for the Conversion of Waste Containing Polychlorinated Biphenyls by Thermodynamic Modelling. Energy Convers. Manag. 2023, 292, 117358,  DOI: 10.1016/j.enconman.2023.117358
      203
      Optimisation of the operating parameters of a thermal plasma system for the conversion of waste containing polychlorinated biphenyls by thermodynamic modelling
      Cvetinovic, Dejan; Milutinovic, Nada; Eric, Aleksandar; Skobalj, Predrag; Andjelkovic, Jovana; Bakic, Vukman
      Energy Conversion and Management (2023), 292 (), 117358CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      This paper proposes a math. modeling approach to det. the thermodn. equil. of chem. systems in order to optimize the operating parameters of the plasma chem. processes in a low-temp. thermal plasma pilot reactor with a d.c. elec. arc for the treatment of hazardous waste contg. polychlorinated biphenyls. The model is primarily based on the principles of mass action and min. Gibbs free energy. The obtained results can serve as a basis for multi-criteria optimization based on ecol. aspects, redn. of energy consumption and the possibility of using the produced synthetic gas for energy recovery in the process. The anal. carried out clearly showed the advantages of using water vapor as a plasma working medium and the appropriate mixing of the org. waste contg. polychlorinated biphenyls with used engine oil for enriched syngas prodn. The presented anal. dets. the optimal reactor temp. for an ecol. efficient treatment and shows possibilities for energy recovery in the process. The proposed model can also be used for other chem. reactors and for the treatment of other chem. substances.
    204. 204
      Frolov, S. M. Organic Waste Gasification: A Selective Review. Fuels 2021, 2 (4), 556– 651,  DOI: 10.3390/fuels2040033
      There is no corresponding record for this reference.
    205. 205
      Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.; Chumak, A.; Beeckman, E.; Verstraeten, J. Pyrolysis of Waste Using a Hybrid Argon-Water Stabilized Torch. Vacuum 2006, 80 (11–12), 1132– 1137,  DOI: 10.1016/j.vacuum.2006.01.046
      205
      Pyrolysis of waste using a hybrid argon-water stabilized torch
      Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.; Chumak, A.; Beeckman, E.; Verstraeten, J.
      Vacuum (2006), 80 (11-12), 1132-1137CODEN: VACUAV; ISSN:0042-207X. (Elsevier B.V.)
      An exptl. plasmachem. reactor equipped with the novel IPP-ASCR hybrid gas-water stabilized DC torch (160 kW) has recently been started at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chem. valorization and to a redn. of the emission of greenhouse gases. Since the process energy is provided by direct heat transfer from plasma, gases of widely varying chem. compn. may be used. The use of elec. energy also reduces the gas flows and requirements for exhaust-gas treatment, and offers control over the chem. Pyrolysis of biomass was exptl. studied using wood chips as a model substance. Syngas with a high content of hydrogen and CO was produced. The influence of adding CO2 for increase of oxygen content in the reactor was investigated.
    206. 206
      Lin, B. J.; Chen, W. H. Sugarcane Bagasse Pyrolysis in a Carbon Dioxide Atmosphere with Conventional and Microwave-Assisted Heating. Front Energy Res. 2015, 3 (FEB), 4,  DOI: 10.3389/fenrg.2015.00004
      There is no corresponding record for this reference.
    207. 207
      Hlina, M.; Hrabovsky, M.; Kavka, T.; Konrad, M. Production of High Quality Syngas from Argon/Water Plasma Gasification of Biomass and Waste. Waste Management 2014, 34 (1), 63– 66,  DOI: 10.1016/j.wasman.2013.09.018
      207
      Production of high quality syngas from argon/water plasma gasification of biomass and waste
      Hlina, M.; Hrabovsky, M.; Kavka, T.; Konrad, M.
      Waste Management (Oxford, United Kingdom) (2014), 34 (1), 63-66CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
      Extremely hot thermal plasma was used for the gasification of biomass (spruce sawdust, wood pellets) and waste (waste plastics, pyrolysis oil). The plasma was produced by a plasma torch with DC elec. arc using unique hybrid stabilization. The torch input power of 100-110 kW and the mass flow rate of the gasified materials of tens kg/h was set up during expts. Produced synthetic gas featured very high content of hydrogen and carbon monoxide (together approx. 90%) that is in a good agreement with theory. High quality of the produced gas is given by extreme parameters of used plasma - compn., very high temp. and low mass flow rate.
    208. 208
      Shie, J. L.; Tsou, F. J.; Lin, K. L.; Chang, C. Y. Bioenergy and Products from Thermal Pyrolysis of Rice Straw Using Plasma Torch. Bioresour. Technol. 2010, 101 (2), 761– 768,  DOI: 10.1016/j.biortech.2009.08.072
      208
      Bioenergy and products from thermal pyrolysis of rice straw using plasma torch
      Shie Je-Lueng; Tsou Feng-Ju; Lin Kae-Long; Chang Ching-Yuan
      Bioresource technology (2010), 101 (2), 761-8 ISSN:.
      The aim of this work was to study the feasibility and operation performance of plasma torch pyrolysis of biomass wastes, taking rice straw as the target material. This novel method has several advantages including high heating rate, short heating time, no viscous tar and low residual char (7.45-13.78 wt.%) or lava. The productions of CO and H(2) are the major components (91.85-94.14 vol.%) in the gas products with relatively high reaction rates. The maximum concentrations of gaseous products occurring times are all below 1 min. Almost 90% of gaseous products were appeared in 4 min reaction time. The yield of H(2) increases with the increase of input power or temperature. With the increase of moisture (5-55 wt.%), the mass yields of H(2) and CO(2) also increase from the H(2)O decomposition. However, due to the CO(2) production, the accumulated volume fraction of syngas decreases with the increase of moisture.
    209. 209
      Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T. Pyrolysis/Gasification of Biomass for Synthetic Fuel Production Using a Hybrid Gas-Water Stabilized Plasma Torch. Vacuum 2008, 83 (1), 209– 212,  DOI: 10.1016/j.vacuum.2008.03.084
      209
      Pyrolysis/gasification of biomass for synthetic fuel production using a hybrid gas-water stabilized plasma torch
      Van Oost, G.; Hrabovsky, M.; Kopecky, V.; Konrad, M.; Hlina, M.; Kavka, T.
      Vacuum (2008), 83 (1), 209-212CODEN: VACUAV; ISSN:0042-207X. (Elsevier B.V.)
      An exptl. plasma-chem. reactor equipped with a novel hybrid gas-water stabilized torch is available at IPP Prague for the innovative and environmentally friendly plasma treatment of waste streams with a view to their sustainable energetic and chem. valorization and to a redn. of the emission of greenhouse gases. Gasification/pyrolysis of biomass was exptl. studied using crushed wood as a model substance. The exptl. results demonstrate homogeneous heating of the reactor vol. and proper mixing of plasma with treated material in spite of the low plasma mass flow rate and constricted plasma jet. The conditions within the reactor ensure complete destruction of the tested substance. The economical viability, environmental performance and safety of biofuels/hydrogen produced from syngas resulting from the plasma-thermochem. gasification of a very broad range of second generation biomass feedstock will be investigated. The performance of several types of plasma torches and of possible combinations of torches will be compared. The final biofuels will be tested in the existing Internal Combustion Engine (ICE) test stands.
    210. 210
      Murphy, A. B.; Farmer, A. J. D.; Horrigan, E. C.; Mcallister, T. Plasma Destruction of Ozone Depleting Substances. Plasma Chem. Prosma Process. 2002, 22 (3), 371,  DOI: 10.1023/A:1015365032020
      There is no corresponding record for this reference.
    211. 211
      Qi, H.; Xu, H.; Zhang, J.; Xu, Z.; Zhong, L.; Cui, P.; Zhu, Z.; Wang, Y. Thermodynamic and Techno-Economic Analyses of Hydrogen Production from Different Algae Biomass by Plasma Gasification. Int. J. Hydrogen Energy 2023, 48 (92), 35895– 35906,  DOI: 10.1016/j.ijhydene.2023.06.038
      211
      Thermodynamic and techno-economic analyses of hydrogen production from different algae biomass by plasma gasification
      Qi, Huaqing; Xu, Hongwei; Zhang, Jifu; Xu, Zaifeng; Zhong, Limei; Cui, Peizhe; Zhu, Zhaoyou; Wang, Yinglong
      International Journal of Hydrogen Energy (2023), 48 (92), 35895-35906CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      In this study, hydrogen prodn. processes by plasma gasification of three different algae were proposed. The processes were comprehensively analyzed and evaluated in terms of thermodn. efficiency and economic benefits. The results showed that the hydrogen prodn. processes of Enteromorpha by plasma gasification had the best performance and the exergy efficiency of the plasma gasification was as high as 74.46%. The total efficiency of the hydrogen prodn. process of Enteromorpha by plasma gasification was 33.92%, which was 3.87% and 3.63% higher than that of the Cyanobacteria and Sargassum process, resp. The high exergy loss of the acid gas removal and plasma gasification unit accounted for 80.14%-83.53% of the total exergy loss. In addn., the Enteromorpha process also had better economic benefits compared to the other two processes, which was greatly affected by feedstock and electricity prices.
    212. 212
      Sikarwar, V. S.; Peela, N. R.; Vuppaladadiyam, A. K.; Ferreira, N. L.; Mašláni, A.; Tomar, R.; Pohořelý, M.; Meers, E.; Jeremiáš, M. Thermal Plasma Gasification of Organic Waste Stream Coupled with CO2-Sorption Enhanced Reforming Employing Different Sorbents for Enhanced Hydrogen Production. RSC Adv. 2022, 12 (10), 6122– 6132,  DOI: 10.1039/D1RA07719H
      212
      Thermal plasma gasification of organic waste stream coupled with -sorption enhanced reforming employing different sorbents for enhanced hydrogen production
      Sikarwar, Vineet Singh; Peela, Nageswara Rao; Vuppaladadiyam, Arun Krishna; Ferreira, Newton Libanio; Maslani, Alan; Tomar, Ritik; Pohorely, Michael; Meers, Erik; Jeremias, Michal
      RSC Advances (2022), 12 (10), 6122-6132CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      In the past few years, rising concerns vis-a´-vis global climate change and clean energy demand have brought worldwide attention to developing the 'biomass/org. waste-to-energy' concept as a zero-emission, environment-friendly and sustainable pathway to simultaneously quench the global energy thirst and process diverse biomass/org. waste streams. Bioenergy with carbon capture and storage (BECCS) can be an influential technol. route to curb climate change to a significant extent by preventing CO2 discharge. One of the pathways to realize BECCS is via in situ CO2-sorption coupled with a thermal plasma gasification process. In this study, an equil. model is developed using RDF as a model compd. for plasma assisted CO2-sorption enhanced gasification to evaluate the viability of the proposed process in producing H2 rich syngas. Three different classes of sorbents are investigated namely, a high temp. sorbent (CaO), an intermediate temp. sorbent (Li4SiO4) and a low temp. sorbent (MgO). The distribution of gas species, H2 yield, dry gas yield and LHV are deduced with the varying gasification temp., reforming temp., steam-to-feedstock ratio and sorbent-to-feedstock for all three sorbents. Moreover, optimal values of different process variables are predicted. Maximum H2 is noted to be produced at 550°C for CaO (79 vol%), 500°C for MgO (29 vol%) and 700°C (55 vol%) for Li4SiO4 whereas the optimal SOR/F ratios are found to be 1.5 for CaO, 1.0 for MgO and 2.5 for Li4SiO4. The results obtained in the study are promising to employ plasma assisted CO2-sorption enhanced gasification as an efficacious pathway to produce clean energy and thus achieve carbon neutrality.
    213. 213
      Kaushal, R.; Rohit; Dhaka, A. K. A Comprehensive Review of the Application of Plasma Gasification Technology in Circumventing the Medical Waste in a Post-COVID-19 Scenario. Biomass Convers. Biorefin. 2022,  DOI: 10.1007/s13399-022-02434-z
      There is no corresponding record for this reference.
    214. 214
      Zhang, H.; Zhu, F.; Li, X.; Du, C. Dynamic Behavior of a Rotating Gliding Arc Plasma in Nitrogen: Effects of Gas Flow Rate and Operating Current. Plasma Sci. Technol. 2017, 19 (4), 045401,  DOI: 10.1088/2058-6272/aa57f3
      214
      Dynamic behavior of a rotating gliding arc plasma in nitrogen: effects of gas flow rate and operating current
      Zhang, Hao; Zhu, Fengsen; Li, Xiaodong; Du, Changming
      Plasma Science & Technology (Bristol, United Kingdom) (2017), 19 (4), 045401/1-045401/6CODEN: PSTHC3; ISSN:1009-0630. (IOP Publishing Ltd.)
      The effects of feed gas flow rate and operating current on the elec. characteristics and dynamic behavior of a rotating gliding arc (RGA) plasma codriven by a magnetic field and tangential flow were investigated. The operating current has been shown to significantly affect the time-resolved voltage waveforms of the discharge, particularly at flow rate = 21min-1. When the current was lower than 140 mA, sinusoidal waveforms with regular variation periods of 13.5-17.0 ms can be obsd. (flow rate = 21min-1). The restrike mode characterized by serial sudden drops of voltage appeared under all studied conditions. Increasing the flow rate from 8 to 121min-1 (at the same current) led to a shift of arc rotation mode which would then result in a significant drop of discharge voltage (around 120-200 V). For a given flow rate, the redn. of current resulted in a nearly linear increase of voltage.
    215. 215
      Diaz, G.; Leal-Quiros, E.; Smith, R. A.; Elliott, J.; Unruh, D. Syngas Generation from Organic Waste with Plasma Steam Reforming. J. Phys.: Conf. Ser. 2014, 511, 012081,  DOI: 10.1088/1742-6596/511/1/012081
      215
      Syngas generation from organic waste with plasma steam reforming
      Diaz, G.; Leal-Quiros, E.; Smith, R. A.; Elliott, J.; Unruh, D.
      Journal of Physics: Conference Series (2014), 511 (15th International Congress on Plasma Physics & 13th Latin American Workshop on Plasma Physics, 2010), 012081CODEN: JPCSDZ; ISSN:1742-6588. (IOP Publishing Ltd.)
      A plasma steam reforming system to process waste is in the process of being set up at the University of California, Merced. The proposed concept will use two different plasma regimes, i.e. glow discharge and arc torches to process a percentage of the total liq. waste stream generated at the campus together with shredded local org. solid waste. One of the main advantages of the plasma technol. to be utilized is that it uses graphite electrodes that can be fed to the reactor to achieve continuous operation, thus, electrode or nozzle life is not a concern. The waste to energy conversion process consists of two stages, one where a mixt. of steam and hydrogen is generated from the liq. in a glow-discharge cell, and a second stage where the mixt. of exhaust gases coming out of the first device are mixed with solid waste in a reactor operating in steam reforming mode interacting with a plasma torch to generate high-quality syngas. In this paper, the results of a thermodn. model developed for the two stages are shown. The syngas compn. obtained indicates that the fraction of CO2 present decreases with increasing temp. and the molar fractions of hydrogen and carbon monoxide become dominant. The fraction of water vapor present in the product gases coming out of the second stage needs to be condensed before the syngas can be utilized in a prime mover.
    216. 216
      Yue, W.; Lei, W.; Dong, Y.; Shi, C.; Lu, Q.; Cui, X.; Wang, X.; Chen, Y.; Zhang, J. Toluene Degradation in Air/H2O DBD Plasma: A Reaction Mechanism Investigation Based on Detailed Kinetic Modelling and Emission Spectrum. J. Hazard. Mater. 2023, 448, 130894,  DOI: 10.1016/j.jhazmat.2023.130894
      216
      Toluene degradation in air/H2O DBD plasma: A reaction mechanism investigation based on detailed kinetic modeling and emission spectrum analysis
      Yue, Wenjing; Lei, Wentao; Dong, Yongheng; Shi, Chengjing; Lu, Qiancheng; Cui, Xin; Wang, Xinyu; Chen, Yumin; Zhang, Junying
      Journal of Hazardous Materials (2023), 448 (), 130894CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
      Non-thermal plasma (NTP) is emerging as an attractive method for decompg. volatile org. compds. (VOCs). In this paper, to study toluene degrdn. mechanism in air/H2O dielec. barrier discharge (DBD) plasma, optical emission spectrometry (OES) was employed to in-situ monitor active species in plasma, with the permanent degrdn. products being detected by online mass spectrometry under various operations. A detailed kinetic model of NTP with incorporation of non-const. electron filed and thermal effects has also been established. A toluene degrdn. efficiency > 82% could be achieved at P = 115 W, Cin, toluene = 1000 ppm. The relative spectrum intensity of excited OH, O, H and N2 (A3Σu+) increased with increase of discharge power and was decreased at higher gas flowrates. Toluene degrdn. was mainly induced by oxidn. of OH and O at afterglow stage, while part of toluene was decompd. by attack of electrons and reactive particles N2 (A3Σu+) in discharge stage. A toluene degrdn. pathway has been proposed as: toluene→benzyl→benzaldehyde→benzene→phenoxy→cyclopentadiene→polycarbenes/alkynol→CO2/H2O. Benzoquinone, benzaldehyde, cyclopentadiene and cyclopentadienyl are supposed to be important intermediates for the ring-opening of toluene. Clarification of toluene degrdn. behaviors at discharge and afterglowing stage could provide new insights for plasma-catalytic process in future.
    217. 217
      Saleem, F.; Khoja, A. H.; Khan, A.; Rehman, A.; Naqvi, S. R.; Qazi, U. Y.; Zhang, K.; Harvey, A. Effect of Non-Thermal Plasma Dielectric Barrier Discharge Reactor on the Quality of Biomass Gasification Product Gas from the Gasifier. J. Energy Institute 2023, 108, 101228,  DOI: 10.1016/j.joei.2023.101228
      217
      Effect of non-thermal plasma dielectric barrier discharge reactor on the quality of biomass gasification product gas from the gasifier
      Saleem, Faisal; Khoja, Asif Hussain; Khan, Atif; Rehman, Abdul; Naqvi, Salman Raza; Qazi, Umair Yaqub; Zhang, Kui; Harvey, Adam
      Journal of the Energy Institute (2023), 108 (), 101228CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
      The primary goal of this research is to det. the effect of key processing paramters of dielec. barrier discharge (DBD) reactor on the components concn. of the fuel gas produced during the biomass gasification. By changing key processing parameters such as plasma input power, flow rate, and temp., the performance of the DBD reactor is assessed. When the power is increased from 5 to 40 W, the concns. of CO2 and H2 decrease to 12.9% and 18.5%, resp., while the concn. of CO increases to 17.2%. At 40 W and 65 mL/min, the amt. of tar compd. significantly drops from 33 g/Nm3 to less than 1 g/Nm3. However, as input power increases, the concn. of C1-C5 hydrocarbons also tends to rise. The highest concn. of C1-C5 was around 0.60% at 40 W. As the flow rate increases, the concn. of CO2 increases while the concn. of CO tends to decrease at all measured power levels, the max. concn. of CO2 was at 120 mL/min, whereas the min. concn. of CO is seen under same conditions. With an increase in flow rate, the concn. of CH4 shows a decreasing tendency. It is seen that at 40 W, the concn. of CO and H2 drops as the temp. rises up to 400°C. In contrast, there is a rising trend in the concn. of CO2, CH4, and tar compds. while inreasing temp. Hence, the DBD reactor appears to have a profound influence on a gas component produced during biomass gasification.
    218. 218
      Dahiru, U. H.; Saleem, F.; Al-sudani, F. T.; Zhang, K.; Harvey, A. P. Decomposition of Benzene Vapour Using Non-Thermal Plasmas: The Effect of Moisture Content on Eliminating Solid Residue. J. Environ. Chem. Eng. 2022, 10, 107767,  DOI: 10.1016/j.jece.2022.107767
      218
      Decomposition of benzene vapor using non-thermal plasmas: The effect of moisture content on eliminating solid residue
      Dahiru, Usman H.; Saleem, Faisal; Al-sudani, Farah Talib; Zhang, Kui; Harvey, Adam P.
      Journal of Environmental Chemical Engineering (2022), 10 (3), 107767CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
      This study investigated the effect of power, carrier gases and moisture content on the removal of benzene in dry air and humidified air in a DBD plasma reactor. The influence of plasma power, carrier gases and humidity on benzene conversion and product selectivity were explored. The main decompn. products were CO, CO2, lower hydrocarbons (C1-C5) and solid residue in the reactor. This study reveals that benzene removal efficiency and the selectivity to CO2 increased with power in both dry and humidified air. In contrast, the selectivity to lower hydrocarbons decreased. The most important finding of this study was that the formation of solid residue in the plasma reactor can be removed in humidified air. As the amt. of water vapor increased from 0% to 35% at 20°C, the benzene removal efficiency and CO2 selectivity increased; O3 decreased from 7.3 ppm to 0.5 ppm; NOx and solid residue were eliminated. These effects are probably due to OH radicals, and the mechanism for the various effects are proposed. The max. benzene removal efficiency obsd. was 93.7%, and the max. selectivity to CO2 was 82.4% (both at a relative humidity of 35% at 20°C and 10 W). This study demonstrated that plasma-assisted benzene remediation operating in a humid condition can overcome the major drawback of plasma-assisted VOC conversion in the air by eliminating the solid residues in the reactor.
    219. 219
      Shi, Y.; Ding, L.; Mei, D.; Fang, Z.; Liu, S. Toluene Conversion by Gliding Arc Discharge in the Simulated Gasified Product Gas. In Proceedings of the IEEE 5th International Electrical and Energy Conference (CIEEC), May 27–29, 2022, Nanjing, China; Institute of Electrical and Electronics Engineers Inc., 2022.  DOI: 10.1109/CIEEC54735.2022.9846294 .
      There is no corresponding record for this reference.
    220. 220
      Saleem, F.; Abbas, A.; Rehman, A.; Khoja, A. H.; Naqvi, S. R.; Arshad, M. Y.; Zhang, K.; Harvey, A. Decomposition of Benzene as a Biomass Gasification Tar in CH4 Carrier Gas Using Non-Thermal Plasma: Parametric and Kinetic Study. J. Energy Institute 2022, 102, 190– 195,  DOI: 10.1016/j.joei.2022.03.009
      220
      Decomposition of benzene as a biomass gasification tar in CH4 carrier gas using non-thermal plasma and Parametric and kinetic study
      Saleem, Faisal; Abbas, Aumber; Rehman, Abdul; Khoja, Asif Hussain; Naqvi, Salman Raza; Arshad, Muhammad Yousaf; Zhang, Kui; Harvey, Adam
      Journal of the Energy Institute (2022), 102 (), 190-195CODEN: JEIOB8; ISSN:1743-9671. (Elsevier Ltd.)
      In this work, the decompn. of benzene was studied with CH4 using a dielec. barrier discharge (DBD) reactor. The exptl. conditions such as input power, residence time, and concn. were varied to investigate the decompn. of benzene. The decompn. of benzene increased with increasing input power and residence time. The highest decompn. of benzene at 40 W and 2.86 s was 82.9. The major gaseous products were H2 and lower hydrocarbons (LHC) and the yield of these products also increases with input power and residence time. The percentage yield of H2 increases from 0.65 to 5.18by increasing input power from 5 to 40 W at 2.86 s. Similarly, the yield of LHC increases from 0.78 to 8.86for benzene under the same reaction conditions. Hence, input power promoted the decompn. of tar compds. and enhanced the yield of gaseous products. However, at higher concns. of the tar compd., decompn. efficiency and product yield decreased. The modified first-order kinetic model was used for the decompn. of tar model compd. and methane carrier gas.
    221. 221
      Xu, R.; Zhu, F.; Zhang, H.; Ruya, P. M.; Kong, X.; Li, L.; Li, X. Simultaneous Removal of Toluene, Naphthalene, and Phenol as Tar Surrogates in a Rotating Gliding Arc Discharge Reactor. Energy Fuels 2020, 34 (2), 2045– 2054,  DOI: 10.1021/acs.energyfuels.9b03529
      221
      Simultaneous Removal of Toluene, Naphthalene, and Phenol as Tar Surrogates in a Rotating Gliding Arc Discharge Reactor
      Xu, Ruiyang; Zhu, Fengsen; Zhang, Hao; Ruya, Petric Marc; Kong, Xiangzhi; Li, Li; Li, Xiaodong
      Energy & Fuels (2020), 34 (2), 2045-2054CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      A rotating gliding arc (RGA) plasma reactor was studied for the decompn. of gasification derived tar. Toluene, naphthalene, and phenol were selected as tar surrogates to be simultaneously decompd. The effects of steam addn., preheating temp., tar, and CO2 concn. were studied and the decompn. pathways of tar model compds. were proposed. The optimum amt. of steam can facilitate tar destruction, enhance H2 yield, and, importantly, suppress the formation of C black. The conversions of toluene, naphthalene, and phenol can be up to 85.8, 76.4, and 93.4%, resp., when 8-12% steam is applied in the system. As expected, the increase of tar or CO2 concn. reduces the conversions of tar. Increasing the preheating temp. to 600° enhances the tar conversions but is then surprisingly followed by a slight drop with the subsequent increase in temp. The conversions of the 3 components decrease in the order of phenol > toluene > naphthalene under the studied conditions. Primary decompn. products of toluene, naphthalene, and phenol are benzyl, naphthyl, and phenoxy compds., which would be further degraded by active species such as N2 (A3.sum.u+), OH radicals, O radicals, etc. into smaller mols. like H2, CO, and CO2.
    222. 222
      Capitelli, M.; Armenise, I.; Bisceglie, E.; Bruno, D.; Celiberto, R.; Colonna, G.; D’Ammando, G.; De Pascale, O.; Esposito, F.; Gorse, C.; Laporta, V.; Laricchiuta, A. Thermodynamics, Transport and Kinetics of Equilibrium and Non-Equilibrium Plasmas: A State-to-State Approach. Plasma Chemistry and Plasma Processing 2012, 32 (3), 427– 450,  DOI: 10.1007/s11090-011-9339-7
      222
      Thermodynamics, transport and kinetics of equilibrium and non-equilibrium plasmas. A state-to-state approach
      Capitelli, M.; Armenise, I.; Bisceglie, E.; Bruno, D.; Celiberto, R.; Colonna, G.; D'Ammando, G.; De Pascale, O.; Esposito, F.; Gorse, C.; Laporta, V.; Laricchiuta, A.
      Plasma Chemistry and Plasma Processing (2012), 32 (3), 427-450CODEN: PCPPDW; ISSN:0272-4324. (Springer)
      Thermal non-equil. plasmas were deeply investigated theor. by the state-to-state approach, offering the unique opportunity of a detailed information about internal distributions affecting thermodn., transport coeffs. and kinetics, properly accounting for the presence of excited states. The efforts made in the construction of knowledge on the dynamics of elementary processes occurring in the plasma with resoln. on internal degrees of freedom, required by the method, are discussed. Boltzmann equation is solved for electrons self-consistently coupled to the chem. species collisional dynamics, reproducing very interesting features of strongly non-equil. internal distributions, characterizing plasmas.
    223. 223
      Roth, J. R. Industrial Plasma Engineering, Vol. 1; CRC Press: Boca Raton, FL, 1995.  DOI: 10.1201/9780367802615 .
      There is no corresponding record for this reference.
    224. 224
      Cimerman, R.; Račková, D.; Hensel, K. Tars Removal by Non-Thermal Plasma and Plasma Catalysis. J. Phys. D Appl. Phys. 2018, 51 (27), 274003,  DOI: 10.1088/1361-6463/aac762
      224
      Tars removal by non-thermal plasma and plasma catalysis
      Cimerman, Richard; Rackova, Diana; Hensel, Karol
      Journal of Physics D: Applied Physics (2018), 51 (27), 274003/1-274003/13CODEN: JPAPBE; ISSN:0022-3727. (IOP Publishing Ltd.)
      The gasification of a fuel or biomass is an industrial process that is utilized for synthesis gas (syngas) prodn. The syngas can be used to generate electricity, but after gasification it is often polluted with tars and various other pollutants. Therefore, the syngas must be cleaned before further use. The objective of this paper was to investigate the potential of removing the tars by non-thermal plasma generated by atm. pressure dielec. barrier discharge in combination with various packing materials (TiO2, Pt/γ-Al2O3, γ-Al2O3, glass beads). Naphthalene was used as a model polyarom. tar compd. The effect of discharge power, carrier gas and packing material on naphthalene removal was investigated and gaseous and solid byproducts were analyzed by means of FTIR spectrometry. In ambient air, a naphthalene removal efficiency of 88% and 40% was achieved for 320 J l-1 with and without the catalyst, resp. The max. removal efficiency of almost 100% was obsd. with a TiO2 catalyst and oxygen carrier gas. CO, CO2, H2O and HCOOH were identified among the products, as well as more complex compds., such as 1,4-naphthoquinone and phthalic anhydride.
    225. 225
      Fridman, A. Plasma Chemistry; Cambridge University Press: Cambridge, U.K., 2008.
      There is no corresponding record for this reference.
    226. 226
      Pathak, R. M.; Ananthanarasimhan, J.; Rao, L. Chemical Kinetics Simulation of Hydrogen Generation in Rotating Gliding Arc Plasma. IEEE Trans. Plasma Sci. 2022, 50 (8), 2482– 2488,  DOI: 10.1109/TPS.2022.3188338
      226
      Chemical kinetics simulation of hydrogen generation in rotating gliding arc plasma
      Pathak, Ram Mohan; Ananthanarasimhan, J.; Rao, Lakshminarayana
      IEEE Transactions on Plasma Science (2022), 50 (8), 2482-2488CODEN: ITPSBD; ISSN:1939-9375. (Institute of Electrical and Electronics Engineers)
      This work reports hydrogen (H2) formation using methane nitrogen gas mixt. as a feed stream in a rotating gliding arc (RGA) reactor. The H2 formation in the RGA was quantified by exptl. studies, and the results were validated by simulating plasma chem. kinetics using the Chem. Workbench software. The simulation was performed for an exptl. condition, where methane (1%) and nitrogen (99%) gas mixt. was fed to an RGA at 5, 10, 25, and 40 lpm. For these flow rates, the simulation predicted 1417, 802, 299, and 67 ppm of H2, resp. Also, the results show that at these flow rates, the reduced elec. field (E/N) of the discharge was 78, 83, 92, and 101 Td and the gas temp. was 3800, 4108, 4590, and 4975 K resp. The simulation result was in reasonable agreement with the exptl. data, which shows 1276, 717, 213, and 61 ppm of H2 in the product gas, resp., at 5, 10, 25, and 40 lpm. This work marks the first step toward process optimization through the simulation approach.
    227. 227
      Nair, S. A. Corona Plasma for Tar Removal. Doctoral Thesis, Technical University of Eindhoven, Eindhoven, Netherlands, 2004.
      There is no corresponding record for this reference.
    228. 228
      Fridman, A.; Chirokov, A.; Gutsol, A. Non-Thermal Atmospheric Pressure Discharges. J. Phys. D: Appl. Phys. 2005, 38, R1,  DOI: 10.1088/0022-3727/38/2/R01
      228
      Non-thermal atmospheric pressure discharges
      Fridman, A.; Chirokov, A.; Gutsol, A.
      Journal of Physics D: Applied Physics (2005), 38 (2), R1-R24CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)
      There has been considerable interest in non-thermal atm. pressure discharges over the past decade due to the increased no. of industrial applications. Diverse applications demand a solid phys. and chem. understanding of the operational principals of such discharges. This paper focuses on the four most important and widely used varieties of non-thermal discharges: corona, dielec. barrier, gliding arc and spark discharge. The physics of these discharges is closely related to the breakdown phenomena. The main players in elec. breakdown of gases: avalanches and streamers are also discussed in this paper. Although non-thermal atm. pressure discharges have been intensively studied for the past century, a clear phys. picture of these discharges is yet to be obtained.
    229. 229
      Zhang, H.; Xu, R.; J, A.; Zheng, J.; Wan, J.; Wang, K.; Lan, B.; Yan, J.; Li, X. Destruction of Biomass Tar Model Compound in a Rotating Gliding Arc Plasma Catalytic System: Contribution of Typical Transition Metals in Ni-Based Bimetallic Catalysts. Fuel 2022, 323, 124385,  DOI: 10.1016/j.fuel.2022.124385
      229
      Destruction of biomass tar model compound in a rotating gliding arc plasma catalytic system: Contribution of typical transition metals in Ni-based bimetallic catalyst
      Zhang, Hao; Xu, Ruiyang; J, Ananthanarasimhan; Zheng, Jiageng; Wan, Jieying; Wang, Kaiyi; Lan, Bingru; Yan, Jianhua; Li, Xiaodong
      Fuel (2022), 323 (), 124385CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      In this work, the destruction of toluene as a biomass tar model compd. has been investigated in a rotating gliding arc (RGA) plasma catalytic system focusing on understanding the contribution of typical transition metals (Fe, Co, Cu) in Ni-based bimetallic catalyst. Investigations were conducted to elucidate their synergy with plasma under simulated gasifier gas (SGG) to destruct toluene and their effect on value-added benefits such as the enhanced heat content of the reacted producer gas. Results showed that the N2 environment offered better performance than the SGG environment, esp. at high tar concn., due to a more abundance of N2 excited species. The loading of Ni on the Al2O3 catalyst remarkably enhanced the tar conversion from 80.7% to 93.1%. Except for the NiFe, the bimetallic catalysts improved conversion and reduced specific energy consumption (SEC). Primarily, the NiCu catalyst provided a max. tar conversion of up to 94.3% and significantly enhanced the heat content of the producer gas by 29% from that of the SGG. The min. SEC of 64.5 kWh/kg was achieved by the NiCo, which also showed the best sintering resistance. In the 24-h plasma-catalytic operation, NiCu and NiCo showed excellent stability with only a slight drop in the tar conversion (∼94% to ∼ 91%) after 10-12 h. Anal. of byproducts indicated back spillover of OH and O, which could help clean the metal surface. Thermogravimetric anal. of the spent catalyst indicated that the coke deposited is likely composed of the arom. compds. of b.p. in the range of 100°C to 300°C.
    230. 230
      Vreugdenhil, B. J.; Zwart, R. W. R. Tar Formation in Pyrolysis and Gasification; ECN-E--08-087; Energy Research Centre of the Netherlands: Petten, Netherlands, 2009.
      There is no corresponding record for this reference.
    231. 231
      Conrads, H.; Schmidt, M. Plasma Generation and Plasma Sources. Plasma Sources Sci. Technol. 2000, 9, 441– 454,  DOI: 10.1088/0963-0252/9/4/301
      231
      Plasma generation and plasma sources
      Conrads, H.; Schmidt, M.
      Plasma Sources Science & Technology (2000), 9 (4), 441-454CODEN: PSTEEU; ISSN:0963-0252. (Institute of Physics Publishing)
      This paper reviews the most commonly used methods for the generation of plasmas with special emphasis on non-thermal, low-temp. plasmas for technol. applications. The authors also discuss various tech. realizations of plasma sources for selected applications. This paper is further limited to the discussion of plasma generation methods that employ elec. fields. The various plasmas described include d.c. glow discharges, either operated continuously (continuous-wave) or pulsed, capacitively and inductively coupled rf discharges, helicon discharges, and microwave discharges. Various examples of tech. realizations of plasmas in closed structures (cavities), in open structures (surfatron, planar plasma source), and in magnetic fields (ECR sources) are discussed in detail. Finally, the authors mention dielec. barrier discharges as convenient sources of non-thermal plasmas at high pressures (up to atm. pressure) and beam-produced plasmas. It is the main objective of this paper to give an overview of the wide range of diverse plasma generation methods and plasma sources and highlight the broad spectrum of plasma properties which, in turn, lead to a wide range of diverse technol. and tech. applications. 36 Refs.
    232. 232
      Chun, Y. N.; Kim, S. C.; Yoshikawa, K. Destruction of Biomass Tar Using a Gliding Arc Plasma Reformer. Int. J. Environ. Protection 2012, 2, 1– 8
      There is no corresponding record for this reference.
    233. 233
      Kogelschatz, U. Dielectric-Barrier Discharges: Their History, Discharge Physics, and Industrial Applications. Plasma Chem. Plasma Process. 2003, 23, 1– 46,  DOI: 10.1023/A:1022470901385
      233
      Dielectric-barrier discharges: their history, discharge physics, and industrial applications
      Kogelschatz, Ulrich
      Plasma Chemistry and Plasma Processing (2003), 23 (1), 1-46CODEN: PCPPDW; ISSN:0272-4324. (Kluwer Academic/Plenum Publishers)
      A review. Dielec.-barrier discharges (silent discharges) are used on a large industrial scale. They combine the advantages of non-equil. plasma properties with the ease of atm.-pressure operation. A prominent feature is the simple scalability from small lab. reactors to large industrial installations with megawatt input powers. Efficient and cost-effective all-solid-state power supplies are available. The preferred frequency range lies between 1 kHz and 10 MHz, the preferred pressure range between 10 kPa and 500 kPa. Industrial applications include ozone generation, pollution control, surface treatment, high power CO2 lasers, UV excimer lamps, excimer based mercury-free fluorescent lamps, and flat large-area plasma displays. Depending on the application and the operating conditions, the discharge can have pronounced filamentary structure or fairly diffuse appearance. History, discharge physics, and plasma chem. of dielec.-barrier discharges and their applications are discussed in detail.
    234. 234
      Mei, D.; Liu, S.; Yanik, J.; Lopez, G.; Olazar, M.; Fang, Z.; Tu, X. Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor. ACS Sustain Chem. Eng. 2022, 10 (27), 8958– 8969,  DOI: 10.1021/acssuschemeng.2c02495
      234
      Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor
      Mei Danhua; Liu Shiyun; Fang Zhi; Mei Danhua; Tu Xin; Yanik Jale; Lopez Gartzen; Olazar Martin; Lopez Gartzen
      ACS sustainable chemistry & engineering (2022), 10 (27), 8958-8969 ISSN:2168-0485.
      Biomass gasification is a promising and sustainable process to produce renewable and CO2-neutral syngas (H2 and CO). However, the contamination of syngas with tar is one of the major challenges to limit the deployment of biomass gasification on a commercial scale. Here, we propose a hybrid plasma-catalytic system for steam reforming of tar compounds over honeycomb-based catalysts in a gliding arc discharge (GAD) reactor. The reaction performances were evaluated using the blank substrate and coated catalytic materials (γ-Al2O3 and Ni/γ-Al2O3). Compared with the plasma alone process, introducing the honeycomb materials in GAD prolonged the residence time of reactant molecules for collision with plasma reactive species to promote their conversions. The presence of Ni/γ-Al2O3 gave the best performance with the high conversion of toluene (86.3%) and naphthalene (75.5%) and yield of H2 (35.0%) and CO (49.1%), while greatly inhibiting the formation of byproducts. The corresponding highest overall energy efficiency of 50.9 g/kWh was achieved, which was 35.4% higher than that in the plasma alone process. Characterization of the used catalyst and long-term running indicated that the honeycomb material coated with Ni/γ-Al2O3 had strong carbon resistance and excellent stability. The superior catalytic performance of Ni/γ-Al2O3 can be mainly ascribed to the large specific surface area and the in situ reduction of nickel oxide species in the reaction process, which promoted the interaction between plasma reactive species and catalysts and generated the plasma-catalysis synergy.
    235. 235
      Liu, S. Y.; Mei, D. H.; Nahil, M. A.; Gadkari, S.; Gu, S.; Williams, P. T.; Tu, X. Hybrid Plasma-Catalytic Steam Reforming of Toluene as a Biomass Tar Model Compound over Ni/Al2O3 Catalysts. Fuel Process. Technol. 2017, 166, 269– 275,  DOI: 10.1016/j.fuproc.2017.06.001
      235
      Hybrid plasma-catalytic steam reforming of toluene as a biomass tar model compound over Ni/Al2O3 catalysts
      Liu, S. Y.; Mei, D. H.; Nahil, M. A.; Gadkari, S.; Gu, S.; Williams, P. T.; Tu, X.
      Fuel Processing Technology (2017), 166 (), 269-275CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      In this study, plasma-catalytic steam reforming of toluene as a biomass tar model compd. was carried out in a coaxial dielec. barrier discharge (DBD) plasma reactor. The effect of Ni/Al2O3 catalysts with different nickel loadings (5-20 wt%) on the plasma-catalytic gas cleaning process was evaluated in terms of toluene conversion, gas yield, byproducts formation and energy efficiency of the plasma-catalytic process. Compared to the plasma reaction without a catalyst, the combination of DBD with the Ni/Al2O3 catalysts significantly enhanced the toluene conversion, hydrogen yield and energy efficiency of the hybrid plasma process, while significantly reduced the prodn. of org. byproducts. Increasing Ni loading of the catalyst improved the performance of the plasma-catalytic processing of toluene, with the highest toluene conversion of 52% and energy efficiency of 2.6 g/kWh when placing the 20 wt% Ni/Al2O3 catalyst in the plasma. The possible reaction pathways in the hybrid plasma-catalytic process were proposed through the combined anal. of both gas and liq. products.
    236. 236
      Zhu, F.; Zhang, H.; Yang, H.; Yan, J.; Li, X.; Tu, X. Plasma Reforming of Tar Model Compound in a Rotating Gliding Arc Reactor: Understanding the Effects of CO2 and H2O Addition. Fuel 2020, 259, 116271,  DOI: 10.1016/j.fuel.2019.116271
      236
      Plasma reforming of tar model compound in a rotating gliding arc reactor: Understanding the effects of CO2 and H2O addition
      Zhu, Fengsen; Zhang, Hao; Yang, Haiping; Yan, Jianhua; Li, Xiaodong; Tu, Xin
      Fuel (2020), 259 (), 116271CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      In this study, a rotating gliding arc (RGA) plasma reactor co-driven by a magnetic field and tangential flow has been investigated for the reforming of toluene as a tar surrogate from the gasification of biomass or waste. The effect of steam and CO2 addn. on the reaction performance of the plasma tar reforming process has been evaluated in terms of the conversion of toluene, gas prodn. and energy efficiency. The presence of CO2 in the reaction suppresses the conversion of toluene. By contrast, adding an appropriate amt. of steam to the reforming process significantly enhances the conversion of toluene, while further increasing steam concn. reduces the conversion of toluene. The max. toluene conversion of 85.2% is achieved at an optimal steam concn. of 16%. Optical emission spectroscopic (OES) diagnostics have been used to understand the generation of reactive species contributed to the conversion of toluene and reaction intermediates in the plasma reforming process. The possible reaction pathways and mechanisms have been discussed based on the anal. of gases and condensed liq. byproducts combined with the emission spectra of the plasma in the presence or absence of steam and CO2.
    237. 237
      Subrahmanyam, C.; Renken, A.; Kiwi-Minsker, L. Catalytic Non-Thermal Plasma Reactor for Abatement of Toluene. Chemical Engineering Journal 2010, 160 (2), 677– 682,  DOI: 10.1016/j.cej.2010.04.011
      237
      Catalytic non-thermal plasma reactor for abatement of toluene
      Subrahmanyam, Ch.; Renken, A.; Kiwi-Minsker, L.
      Chemical Engineering Journal (Amsterdam, Netherlands) (2010), 160 (2), 677-682CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      A non-thermal plasma rector with a catalytic electrode comprised of sintered metal fibers (SMF) was tested for the oxidative decompn. of a model volatile org. compd., toluene. Input energy was 160-295 J/L by varying the applied voltage from 12.5 to 22.5 kV at 200 Hz. The effect of various parameters (toluene concn., SMF modification by Mn and Co oxides, input energy, O3 formation) was examd. The plasma catalytic approach was very effective for total oxidn. of toluene at low input energy, esp. for toluene concns. ≤250 ppm and SMF modification by transition metal oxides; significantly increasing reactor performance. MnOx modification appeared to be a better than CoOx, which may be attributed to the in-situ decompn. of O3 leading to formation of more reactive oxidants, e.g., at. O.
    238. 238
      Xu, R.; Kong, X.; Zhang, H.; Ruya, P. M.; Li, X. Destruction of Gasification Tar over Ni Catalysts in a Modified Rotating Gliding Arc Reactor: Effect of Catalyst Position and Nickel Loading. Fuel 2021, 289, 119742,  DOI: 10.1016/j.fuel.2020.119742
      238
      Destruction of gasification tar over Ni catalysts in a modified rotating gliding arc plasma reactor: Effect of catalyst position and nickel loading
      Xu, Ruiyang; Kong, Xiangzhi; Zhang, Hao; Ruya, Petric Marc; Li, Xiaodong
      Fuel (2021), 289 (), 119742CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      In this study, a modified rotating gliding arc (RGA) plasma reactor with fan-shaped swirl generator coupled with Ni/γ-Al2O3 catalyst was investigated for the steam reforming of gasification tar from waste materials, taking toluene as the tar surrogate. The system performance was evaluated in terms of tar conversion, energy efficiency, yield of product gas, as well as synergistic capability of plasma catalysis, with particular attention on the effects of specific energy input (SEI), positioning of the catalysts, and Ni loading of catalysts. Different characterizations of catalysts including N2 adsorption-desorption, XRD, H2-TPR, and TEM were conducted to study the properties of catalysts. Incorporation of catalyst placed sufficiently far from the anode increased toluene conversion which indicated the synergy between plasma and catalysis for tar conversion. A toluene conversion of up to 91.9% can be achieved with a distance of 62 mm between the catalyst and the anode, which was 21% higher than that in the plasma alone system. The toluene conversion can be further increased to 94.7% when the Ni loading was increased from 4% to 16%. The synergistic capability of plasma catalysis was demonstrated from an enhanced toluene conversion and the increased formation of value-added fuel gases such as H2, CO, and CH4, together with simultaneously a selective redn. in CO2 formation, esp. when the Ni loading was 4% and 8%. Identification of liq. byproducts also revealed the synergy between plasma and catalysis which transformed bi-radical HC=CH into gaseous products, prohibiting the formation of indene and naphthalene.
    239. 239
      Liu, Y.; Song, J.; Diao, X.; Liu, L.; Sun, Y. Removal of Tar Derived from Biomass Gasification via Synergy of Non-Thermal Plasma and Catalysis. Sci. Total Environ. 2020, 721, 137671,  DOI: 10.1016/j.scitotenv.2020.137671
      239
      Removal of tar derived from biomass gasification via synergy of non-thermal plasma and catalysis
      Liu, Yawen; Song, Jianwei; Diao, Xungang; Liu, Lina; Sun, Yifei
      Science of the Total Environment (2020), 721 (), 137671CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
      In this study, the reforming of toluene, as a surrogate for tar, was investigated in plasma-alone (PA) and plasma-catalytic (PC) systems. The effects of feed gas oxygen content (O2/(O2 + N2) = 0, 3, 12, 21, or 30 vol%) and the discharge power (30, 75, or 90 W) on toluene conversion, the selectivity of syngas (H2 + CO), and undesirable liq. byproducts were evaluated using the PA system. A max. toluene conversion of 87.9% and a min. selectivity of undesirable liq. byproducts of 0.53% for ethylbenzene, and 1.24% for benzene, were obtained when the discharge power was 90 W and the oxygen content in the carrier gas was 3 vol%. However, a max. gas selectivity of 48.4% for H2 and 19.4% for CO was attained when the discharge power was 75 W and the oxygen content was 3 vol% and 12 vol%, resp. The effect of the steam/carbon molar ratio (S/C) on toluene reforming was investigated using the PC system with Ni/ZSM-5 catalyst under a discharge power of 75 W. The addn. of steam to the feed gas significantly enhanced the conversion of toluene to syngas. A max. toluene conversion of 88.5% was reached with a min. selectivity of liq. byproducts (1.9% for ethylbenzene and 5.2% for benzene) when S/C was 2. However, the highest selectivity of syngas (69.8% for H2 and 21.2% for CO) was achieved when S/C was 2.5. The catalyst employed in the plasma reforming of toluene exhibited excellent anti-carbon deposition performance. A possible reaction mechanism and pathway of toluene destruction was proposed based on anal. of both gaseous and liq. products.
    240. 240
      Xu, B.; Li, J.-q.; Xie, J.-j.; Huang, Y.-q.; Yin, X.-l.; Wu, C.-z. Performance Study on Simultaneous Tar Removal and Bio-Syngas Methanation by Combining Catalysis with Non-Thermal Plasma. J. Fuel Chem. Technol. 2021, 49 (7), 967– 977,  DOI: 10.1016/S1872-5813(21)60045-2
      There is no corresponding record for this reference.
    241. 241
      Petitpas, G.; Rollier, J. D.; Darmon, A.; Gonzalez-Aguilar, J.; Metkemeijer, R.; Fulcheri, L. A Comparative Study of Non-Thermal Plasma Assisted Reforming Technologies. Int. J. Hydrogen Energy 2007, 32 (14), 2848– 2867,  DOI: 10.1016/j.ijhydene.2007.03.026
      241
      A comparative study of non-thermal plasma assisted reforming technologies
      Petitpas, G.; Rollier, J.-D.; Darmon, A.; Gonzalez-Aguilar, J.; Metkemeijer, R.; Fulcheri, L.
      International Journal of Hydrogen Energy (2007), 32 (14), 2848-2867CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      A review of the setting up, feasibility and efficiency of the existing technologies for on-board H prodn. On-board H prodn. from hydrocarbons (reforming) for fuel cells is subject to problems when used with traditional catalysts. High device wt., a relatively long transient time and poisoning make the integration on-board a vehicle, complex. In response to these challenges, hydrocarbon reforming processes assisted by non-thermal plasmas for H prodn. was implemented. The characteristics of plasma reforming through various approaches are discussed. The performance of some of the systems are then compared against each other and discussed.
    242. 242
      Eliott, R. M.; Nogueira, M. F. M.; Silva Sobrinho, A. S.; Couto, B. A. P.; MacIel, H. S.; Lacava, P. T. Tar Reforming under a Microwave Plasma Torch. Energy Fuels 2013, 27 (2), 1174– 1181,  DOI: 10.1021/ef301399q
      242
      Tar Reforming under a Microwave Plasma Torch
      Eliott, Rodrigo Monteiro; Nogueira, Manoel F. M.; Silva Sobrinho, Argemiro S.; Couto, Bruno A. P.; Maciel, Homero S.; Lacava, Pedro T.
      Energy & Fuels (2013), 27 (2), 1174-1181CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      Because of the scarcity of nonrenewable natural resources, such as petroleum and natural gas, the use of biofuel is needed. Gasification is a major process used to obtain renewable fuels from biomass; however, the gas cleaning system is a constraint for its broad utilization. During the pyrolysis process, a mixt. of org. compds. in the gas phase is produced and must be removed from the gases before it is used in the most practical applications. In order to remove such org. compds., which are known as tar, large, sophisticated, problematic, and expensive gas cleaning systems are added to the gasifier gas exit. Previous papers have shown that the plasma torch has the potential to destroy produced tar, being a simpler and less-expensive system than traditional gas cleaners. This work presents a qual. and quant. evaluation of a microwave plasma system running on tar destruction and its reforming. In order to evaluate a 1 kW microwave plasma system performance, an app. was developed and installed at ITA Lab. of Plasmas and Processes (LPP-ITA). The system runs at atm. pressure with nitrogen and argon as carrier gas under a large range of flow rates. Expts. were performed using a gas mixt. of N2, H2O, ethanol, and tar at controlled concn. in order to simulate the gases produced by a gasifier. The injected tar was obtained from pine pyrolysis and characterized for energy purposes. In order to reduce tar viscosity, it was dild. in com. ethanol (92.5% ethanol and 7.5% water) and its concn. varied from 0.8 gtar/Nmgas3 to 4.2 gtar/Nmgas3. Species formed in the microwave plasma torch were identified using an optical spectrometer. The reactor exit gases had their compn. evaluated on tar content as well as for noncondensable gases. As a result, this paper shows that no tar content was detected at the reactor outlet, indicating that all supplied tar was destroyed in the plasma reactor. The main detected products were CO and solid carbon (C(s)). Furthermore, neither NO nor CO2 were detected, and an indication of H2 formation was obtained. This paper concludes that the microwave plasma system is capable of destroying and reforming tar efficiently and produces mainly H2, CO, O2, and C(s) as byproducts.
    243. 243
      Medeiros, H. S.; Pilatau, A.; Nozhenko, O. S.; Da Silva Sobrinho, A. S.; Petraconi Filho, G. Microwave Air Plasma Applied to Naphthalene Thermal Conversion. Energy Fuels 2016, 30 (2), 1510– 1516,  DOI: 10.1021/acs.energyfuels.5b02451
      243
      Microwave Air Plasma Applied to Naphthalene Thermal Conversion
      Medeiros, H. S.; Pilatau, A.; Nozhenko, O. S.; da Silva Sobrinho, A. S.; Petraconi Filho, G.
      Energy & Fuels (2016), 30 (2), 1510-1516CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      In this paper, a naphthalene (C10H8) thermal cracking model is presented. The model is based on a simple model that takes into account the microwave (MW) plasma thermal influence on naphthalene cracking, accompanying its steam reforming reactions. The temp. level of 1573 K was established for complete C10H8 cracking at 1.75 kW plasma power. High conversion efficiency of C10H8 is achieved varying the air flow rate in the range of 0.6-1.2 m3/h. The model approximates the characteristics of the considered MW plasma to thermal plasma in local thermodn. equil. Exptl. data have good agreement with calcd. data at the cited region of the air flow rate and power. Conversion efficiency up to 99.36% was obtained.
    244. 244
      Mista, W.; Kacprzyk, R. Decomposition of Toluene Using Non-Thermal Plasma Reactor at Room Temperature. Catal. Today 2008, 137 (2–4), 345– 349,  DOI: 10.1016/j.cattod.2008.02.009
      244
      Decomposition of toluene using non-thermal plasma reactor at room temperature
      Mista, W.; Kacprzyk, R.
      Catalysis Today (2008), 137 (2-4), 345-349CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
      A non-thermal, atm. pressure plasma using a direct-current (DC) back-corona discharge was used to examine abatement of toluene in air at room temp. Toluene removal efficiency applying wire-plate geometry increased with increasing applied voltage. Results indicated ∼93% toluene removal efficiency and very small NOx formation (∼10 ppm) was achieved for an air stream contg. 70 ppm toluene. The neg. corona current was larger than the pos. corona current at the same applied voltage (polarity effect), resulting in the higher efficiency of the plasma reactor at neg. discharge polarity.
    245. 245
      Van Durme, J.; Dewulf, J.; Sysmans, W.; Leys, C.; Van Langenhove, H. Abatement and Degradation Pathways of Toluene in Indoor Air by Positive Corona Discharge. Chemosphere 2007, 68 (10), 1821– 1829,  DOI: 10.1016/j.chemosphere.2007.03.053
      245
      Abatement and degradation pathways of toluene in indoor air by positive corona discharge
      Van Durme, J.; Dewulf, J.; Sysmans, W.; Leys, C.; Van Langenhove, H.
      Chemosphere (2007), 68 (10), 1821-1829CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
      Indoor air concns. of volatile org. compds. often exceed outdoor levels by a factor of 5. There is much interest in developing new technologies to improve indoor air quality. Non-thermal plasma (DC pos. corona discharge) is explored as an innovative technol. for indoor air purifn. An inlet gas stream of 10 L min-1 contg. 0.50 ± 0.02 ppm toluene was treated by the plasma reactor in atm. conditions. Toluene removal proved to be achievable with a characteristic energy d. ε0 of 50 J L-1. Removal efficiencies were higher for 26% relative humidity (ε0 = 35 J L-1), compared with those at increased humidities (50% relative humidity, ε0 = 49 J L-1). Reaction products such as formic acid, benzaldehyde, benzyl alc., 3-methyl-4-nitrophenol, 4-methyl-2-nitrophenol, 4-methyl-2-Pr furan, 5-methyl-2-nitrophenol, 4-nitrophenol, 2-methyl-4,6-dinitrophenol are identified by mass spectrometry. Based on these byproducts a toluene degrdn. mechanism is proposed.
    246. 246
      Bityurin, V. A.; Filimonova, E. A.; Naidis, G. V. Simulation of Naphthalene Conversion in Biogas Initiated by Pulsed Corona Discharges. IEEE Transactions on Plasma Science 2009, 37, 911– 919,  DOI: 10.1109/TPS.2009.2019756
      246
      Simulation of naphthalene conversion in biogas initiated by pulsed corona discharges
      Bityurin, Valentin A.; Filimonova, Elena A.; Naidis, George V.
      IEEE Transactions on Plasma Science (2009), 37 (6, Pt. 1), 911-919CODEN: ITPSBD; ISSN:0093-3813. (Institute of Electrical and Electronics Engineers)
      The numerical results on naphthalene removal in biogas are presented and compared with expt. Plasma-chem. processes in discharge and postdischarge stages are considered. The self-consistent approach for modeling of cleaning process on the basis of pulsed corona discharges is demonstrated. It has been revealed that the reaction of naphthalene (C10H8) with excited nitrogen mol. (N2(A3Σ)) is very important in the cleaning process in nitrogen-contg. mixts. The addn. to N2 of CO, CO2, and H2 results in the deterioration of treatment.
    247. 247
      Nair, S. A.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.; Ptasinski, K. J.; Drinkenburg, A. A. H. Tar Removal from Biomass Derived Fuel Gas by Pulsed Corona Discharges: Chemical Kinetic Study II. Ind. Eng. Chem. Res. 2005, 44 (6), 1734– 1741,  DOI: 10.1021/ie049292t
      247
      Tar Removal from Biomass Derived Fuel Gas by Pulsed Corona Discharges: Chemical Kinetic Study II
      Nair, S. A.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.; Ptasinski, K. J.; Drinkenburg, A. A. H.
      Industrial & Engineering Chemistry Research (2005), 44 (6), 1734-1741CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      Tar (heavy hydrocarbon or poly arom. hydrocarbon (PAH)) removal from biomass derived fuel gas is one of the biggest obstacles in its use for power generation. The authors have studied pulsed corona as a method for tar removal. The previous exptl. results indicate the energy consumption of 400 J/L for naphthalene removal (model tar compd.) from synthetic fuel gas (CO, CO2, H2, CH4, N2) at a temp. of 200 °C. The present study extends the work on exptl. and kinetic calcns. for temps. up to 500 °C. Radical yields are evaluated at various temps. According to the kinetic model and exptl. results the optimum temp. for tar removal is ∼400 °C. The energy consumption for tar removal at 400 °C is ∼200-250 J/L, whereas at 200 °C, this is ∼400-600 J/L.
    248. 248
      Kushwah, A.; Reina, T. R.; Short, M. Modelling Approaches for Biomass Gasifiers: A Comprehensive Overview. Sci. Total Environ. 2022, 834, 155243,  DOI: 10.1016/j.scitotenv.2022.155243
      248
      Modelling approaches for biomass gasifiers: A comprehensive overview
      Kushwah, A.; Reina, T. R.; Short, M.
      Science of the Total Environment (2022), 834 (), 155243CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)
      A review. Biomass resources have the potential to become a viable renewable technol. and play a key role within the future renewable energy paradigm. Since CO2 generated in bio-energy prodn. is equal to the CO2 absorbed during the growth of the biomass, this renewable energy is a net zero emissions resource. Biomass gasification is a versatile method for transforming waste into energy in which biomass material is thermochem. converted within a reactor. Gasification's superior flexibility, including both in terms of biomass type and heat generation or energy prodn. alternatives, is what stimulates biomass gasification scientific and industrial potential. Downdraft gasifiers seem to be well-suited for small-scale generation of heat along with energy, whereas fluidised bed and entrained flow gasifiers currently attain significant economies of scale for fuel prodn. The operation of gasifiers is influenced by several factors, including operational parameters, feedstock types, and reactor design. Modeling is a valuable tool for building a unit based on the results of model predictions with different operational parameters and feedstock in such scenarios. Once verified, a suitable model may be used to assess the sensitivity of a gasifier's performance to changes in various operational and design factors. Effective models may help designers to theorise and predict the impacts of a variety of characteristics without the need for further empirical observations, which can help in the design and implementation of this technol. This work provides an overview of gasification technologies and a succinct guidance to the modeling decisions and modeling strategies for biomass gasification to enable a successful biomass to fuel conversion. A tech. description and crit. anal. of thermodn., kinetic, computational fluid dynamic and data-driven approaches is provided, including crucial modeling considerations that have not been explored in earlier studies. The review aims to aid researchers in the field to select the appropriate approach and guide future work.
    249. 249
      Li, C.; Liu, R.; Zheng, J.; Zhang, Y. Thermodynamic Study on the Effects of Operating Parameters on CaO-Based Sorption Enhanced Steam Gasification of Biomass. Energy 2023, 273, 127208,  DOI: 10.1016/j.energy.2023.127208
      249
      Thermodynamic study on the effects of operating parameters on CaO-based sorption enhanced steam gasification of biomass
      Li, Chongcong; Liu, Rui; Zheng, Jinhao; Zhang, Yan
      Energy (Oxford, United Kingdom) (2023), 273 (), 127208CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      Sorption enhanced steam gasification of biomass (SESGB) is a promising route for the prodn. of H2-rich syngas. In this work, effects of some crit. parameters of SESGB on hydrogen prodn. are studied by means of thermodn. equil. modeling. To improve the model performance, modeling modifications are made by using the carbon conversion efficiency for carbon balance calcn. and by calibrating the equil. consts. of methane reforming, water-gas shift, and CaO carbonation reactions with the exptl. data. In addn., a new concept of CaO effective conversion rate is proposed to describe the influence of the CaO with different CO2 sorption capacity on hydrogen prodn. The root mean square error (RMSE) between the prediction results of the modified model and the exptl. results is less than 3.5%, indicating the validity of the modification method. And the prediction results show that increasing temp. and the mass ratio of steam/biomass from 823 K to 923 K and from 0.5 to 1.5 increases the concn. of H2 and gas yield, while increasing the molar ratio between CaO and carbon from 1 to 2 mainly increases the H2 concn.
    250. 250
      Xiang, X.; Gong, G.; Shi, Y.; Cai, Y.; Wang, C. Thermodynamic Modeling and Analysis of a Serial Composite Process for Biomass and Coal Co-Gasification. Renewable Sustainable Energy Rev. 2018, 82, 2768– 2778,  DOI: 10.1016/j.rser.2017.10.008
      250
      Thermodynamic modeling and analysis of a serial composite process for biomass and coal co-gasification
      Xiang, Xianan; Gong, Guangcai; Shi, Ying; Cai, Youchan; Wang, Chenhua
      Renewable & Sustainable Energy Reviews (2018), 82 (Part_3), 2768-2778CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      This paper puts forward a new process for the co-gasification of biomass and coal. The process is divided into combustion stage and gasification stage. It provides thermal energy in the combustion stage and produces combustible gases in the gasification stage. The process is named as serial composite process for biomass and coal co-gasification, because of the biomass gasification react after coal gasification react in the gasification stage. A thermodn. equil. model is established for the process. The model is divided into two sub-models, one is the coal combustion sub-model, the other is the coal-biomass serial gasification sub-model. The coal combustion sub-model is divided into two stages including coal pyrolysis and combustion reaction. The coal-biomass serial gasification sub-model is also divided into two stages including coal char gasification reaction and biomass gasification reaction; the temp. of two stages is different; an empirical equation for the temp. relationship is estd. from the exptl. data. The model studies the effects of key parameters on gasification properties, including gasification temp., s/c, coal/biomass, and predicts the compn. of product gas, gas yield, gas calorific value and gasification efficiency of the process. Compared with the dual-fluidized bed gasification process, the process is stable, high gas yield, the medium calorific value gas can be produced. It is a new gasification technol. worthy to be popularized.
    251. 251
      Puig-Arnavat, M.; Bruno, J. C.; Coronas, A. Review and Analysis of Biomass Gasification Models. Renewable and Sustainable Energy Reviews. 2010, 14, 2841– 2851,  DOI: 10.1016/j.rser.2010.07.030
      251
      Review and analysis of biomass gasification models
      Puig-Arnavat, Maria; Bruno, Joan Carles; Coronas, Alberto
      Renewable & Sustainable Energy Reviews (2010), 14 (9), 2841-2851CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. The use of biomass as a source of energy has been further enhanced in recent years and special attention has been paid to biomass gasification. Due to the increasing interest in biomass gasification, several models have been proposed in order to explain and understand this complex process, and the design, simulation, optimization and process anal. of gasifiers have been carried out. This paper presents and analyses several gasification models based on thermodn. equil., kinetics and artificial neural networks. The thermodn. models are found to be a useful tool for preliminary comparison and for process studies on the influence of the most important fuel and process parameters. They have the advantage of being independent of gasifier design, but they cannot give highly accurate results for all cases. The kinetic-based models are computationally more intensive but give accurate and detailed results. However, they contain parameters that limit their applicability to different plants.
    252. 252
      Huang, H. J.; Ramaswamy, S. Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach. Appl. Biochem. Biotechnol. 2009, 154, 14– 25,  DOI: 10.1007/s12010-008-8483-x
      252
      Modeling biomass gasification using thermodynamic equilibrium approach
      Huang Hua-Jiang; Ramaswamy Shri
      Applied biochemistry and biotechnology (2009), 154 (1-3), 14-25 ISSN:.
      In this paper, the thermodynamic equilibrium models for biomass gasification applicable to various gasifier types have been developed, with and without considering char. The equilibrium models were then modified closely matching the CH(4) only or both CH(4) and CO compositions from experimental data. It is shown that the modified model presented here based on thermodynamic equilibrium and taking into account local heat and mass considerations can be used to simulate the performance of a downdraft gasifier. The model can also be used to estimate the equilibrium composition of the syngas. Depending on the gasifier type and internal fluid flow, heat and mass transfer characteristics, with proper modification of the equilibrium model, a simple tool to simulate the operation and performance of varying types of biomass gasifier can be developed.
    253. 253
      Adil, A.; Shivapuji, A. M.; Rao, L. Thermodynamic Analysis for Methanol Synthesis Using Biomass-Derived Syngas. Biomass Convers Biorefin 2022, 12 (5), 1819– 1834,  DOI: 10.1007/s13399-022-02338-y
      253
      Thermodynamic analysis for methanol synthesis using biomass-derived syngas
      Adil, Anam; Shivapuji, Anand M.; Rao, Lakshminarayana
      Biomass Conversion and Biorefinery (2022), 12 (5), 1819-1834CODEN: BCBIBN; ISSN:2190-6823. (Springer)
      This study presents multi-variable anal. for prediction and optimization of the methanol yield from biomass-based syngas using a thermodn. model. The biomass-based syngas has a lower H2 content and higher CO2 than the typical syngas obtained from natural gas reforming which is used for the com. methanol synthesis process. Consequently, a thorough examn. was done to det. the working range for the input parameters for a biomass-derived syngas, so that the output of the process becomes comparable to the existing com. technologies. Two cases were examd., case 1 where the H2 enriched bio-syngas was used for methanol synthesis and case 2 where the methanol was directly synthesized by the bio-syngas obtained by oxy-steam gasification process. A multi-variable anal. of the selected parameters is first performed; then, surrogate model for the methanol yield is constructed for both the cases. A selective set of response surfaces from the surrogate math. model for both the cases were used to illustrate the mutual effect of two parameters by keeping the other parameters at the base values. The anal. indicated that the methanol yield is most sensitive to temp. followed by pressure, CO2/CO, and H2/(CO + CO2) molar ratios in both the cases. The optimized values of methanol yield obtained for case 1 and case 2 were 92.72% and 45.35%, resp., achieved at 473 K, 9 MPa. The CO2/CO and the H2/(CO+CO2) molar ratios were at 0.42 and 4.88 resp. for case 1 and for case 2; the values were 0.90 and 1.13 resp. The high-pressure anal. involves the use of equations of states (EoS) to account for the deviations from ideality. Although many equations of state (EoS) are available, there is no one equation that would predict the properties of all the substances under all the conditions. An attempt has been made in this work to address the use of three such equations of state, namely Peng-Robinsons, Soave-Redlich-Kwong EoS and Newton's universal curves, and to compare the results for the components involved in the methanol synthesis reaction. The results indicate that all three EoS provide similar correction factors in the studied temp. and pressure range for methanol synthesis.
    254. 254
      Qi, J.; Wang, Y.; Hu, M.; Xu, P.; Yuan, H.; Chen, Y. A Reactor Network of Biomass Gasification Process in an Updraft Gasifier Based on the Fully Kinetic Model. Energy 2023, 268, 126642,  DOI: 10.1016/j.energy.2023.126642
      254
      A reactor network of biomass gasification process in an updraft gasifier based on the fully kinetic model
      Qi, Jingwei; Wang, Yijie; Hu, Ming; Xu, Pengcheng; Yuan, Haoran; Chen, Yong
      Energy (Oxford, United Kingdom) (2023), 268 (), 126642CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      Modeling gasification reactors by process simulation is a practical utility to evaluate gasification performance and assist device design. In this study, a fully kinetic model for the biomass gasification process within a pilot-scale updraft gasifier is proposed, which considers the effect of reactor dimensions, residence time, and temp. distribution on the gasification process compared with the thermodn. equil. method and kinetic method modeled by continuous stirring tank reactor blocks. The pyrolysis stage is defined by detailed solid biomass pyrolysis mechanisms and secondary gas reactions kinetic mechanisms. Moreover, the gas evolution effect in the pyrolysis stage is considered by transferring gas to the gasification zone and freeboard zone according to different temps. The gasification and combustion processes are modeled utilizing comprehensive homogeneous and heterogeneous rate-controlled reactions and the plug flow reactor is first used in modeling the updraft gasifier with the countercurrent characteristic. This proposed model is validated by several exptl. data and the predictive results agree well with exptl. data with the max. root-mean-square deviation of 2.6%. The effect of air or steam as gasification agents on gasification performance is evaluated by the proposed model. This model can provide guidance for industrial equipment design.
    255. 255
      Loha, C.; Chattopadhyay, H.; Chatterjee, P. K. Three Dimensional Kinetic Modeling of Fluidized Bed Biomass Gasification. Chem. Eng. Sci. 2014, 109, 53– 64,  DOI: 10.1016/j.ces.2014.01.017
      255
      Three dimensional kinetic modeling of fluidized bed biomass gasification
      Loha, Chanchal; Chattopadhyay, Himadri; Chatterjee, Pradip K.
      Chemical Engineering Science (2014), 109 (), 53-64CODEN: CESCAC; ISSN:0009-2509. (Elsevier Ltd.)
      Biomass gasification in fluidized bed system by using air-steam mixt. as the gasifying agent is a promising way of utilizing biomass because it produces a gaseous fuel having relatively higher calorific value as well as higher hydrogen content with min. or no heat addn. to the gasifier. In the present work, a three dimensional numerical simulation of a bubbling fluidized bed biomass gasifier has been carried out. The numerical simulation is based on the Eulerian-Lagrangian approach where the fluid phase is solved by using a continuum approach and the solid is modeled by using Lagrangian computational particle model. The chem. reactions are coupled with the complex hydrodynamic calcn. of gas-solid fluidized bed. The simulations are performed by varying the gasification temp., equivalence ratio and steam-to-biomass ratio. Detail analyses of flow pattern, pressure distribution, and gas compn. distribution have been presented. The complex three dimensional flow structures are revealed by plotting the results in different planes. The results provide a detail insight into the gasifier's behavior including fluidization, thermal and chem. characteristics. Simulated outlet gas compns. are compared with our own exptl. data and a very good resemblance is obsd.
    256. 256
      Horton, S. R.; Mohr, R. J.; Zhang, Y.; Petrocelli, F. P.; Klein, M. T. Molecular-Level Kinetic Modeling of Biomass Gasification. Energy Fuels 2016, 30 (3), 1647– 1661,  DOI: 10.1021/acs.energyfuels.5b01988
      256
      Molecular-Level Kinetic Modeling of Biomass Gasification
      Horton, Scott R.; Mohr, Rebecca J.; Zhang, Yu; Petrocelli, Francis P.; Klein, Michael T.
      Energy & Fuels (2016), 30 (3), 1647-1661CODEN: ENFUEM; ISSN:0887-0624. (American Chemical Society)
      A mol.-level kinetic model for biomass gasification was developed and tuned to exptl. data from the literature. The development was divided into two categories: the compn. of the feedstock and the construction of the reaction network. The compn. model of biomass was divided into three submodels for cellulose, hemicellulose, and lignin. Cellulose and hemicellulose compns. were modeled as linear polymers using Flory-Stockmayer statistics to represent the polymer size distribution. The compn. of lignin, a cross-linked polymer, was modeled using relative amts. of structural building blocks or attributes. When constructing the full biomass compn. model, the fractions of cellulose, hemicellulose, and lignin were optimized using literature-reported ultimate analyses. The reaction network model for biomass contained pyrolysis, gasification, and light-gas reactions. For cellulose and hemicellulose, the initial depolymn. was described using Flory-Stockmayer statistics. The derived monomers from cellulose and hemicellulose were subjected to a full pyrolysis and gasification network. The pyrolysis reactions included both reactions to decrease the mol. size, such as thermal cracking, and char formation reactions, such as Diels-Alder addn. Gasification reactions included incomplete combustion and steam reforming. For lignin, reactions occurred between attributes and included both pyrolysis and gasification reactions. The light-gas reactions included water-gas shift, partial oxidn. of methane, oxidn. of carbon monoxide, steam reforming of methane, and dry reforming of methane. The final reaction network included 1356 reactions and 357 species. The performance of the kinetic model was examd. using literature data that spanned six different biomass samples and had gas compns. as primary results. Three data sets from different biomass samples were used for parameter tuning, and parity plot results showed good agreement between the model and data (ypredicted = yobs0.928 + 0.0003). The predictive ability of the model was probed using three addnl. data sets. Again, the parity plot showed agreement between the model and exptl. results (ypredicted = yobs0.989 - 0.007).
    257. 257
      Sharma, A.; Nath, R. H 2 -Rich Syngas Production from Gasification Involving Kinetic Modeling: RSM-Utility Optimization and Techno-Economic Analysis. RSC Adv. 2023, 13 (15), 10308– 10321,  DOI: 10.1039/D3RA00287J
      257
      H2-rich syngas production from gasification involving kinetic modeling: RSM-utility optimization and techno-economic analysis
      Sharma, Ajay; Nath, Ratnadeep
      RSC Advances (2023), 13 (15), 10308-10321CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      In this research article, H2 rich syngas prodn. is optimized using response surface methodol. (RSM) and a utility concept involving chem. kinetic modeling considering eucalyptus wood sawdust (CH1.63O1.02) as gasification feed stock. By adding water gas shift reaction, the modified kinetic model is validated with lab scale exptl. data (2.56 ≤ root mean square error ≤ 3.67). Four operating parameters (i.e., particle size "dp", temp. "T", steam to biomass ratio "SBR", and equivalence ratio "ER") of air-steam gasifier at three levels are used to frame the test cases. Single objective functions like H2 maximization and CO2 minimization are considered whereas for multi-objective function a utility parameter (80% H2 : 20% CO2) is considered. The regression coeffs. (RH22 = 0.89, RCO22 = 0.98 and RU2 = 0.90) obtained during the anal. of variance (ANOVA) confirm a close fitting of the quadratic model with the chem. kinetic model. ANOVA results indicate ER as the most influential parameter followed by T, SBR, and dp. RSM optimization gives H2|max = 51.75 vol%, CO2|min = 14.65 vol% and utility gives H2|opt. = 51.69 vol% (0.11%), CO2|opt. = 14.70 vol% (0.34%). The techno-economic anal. for a 200 m3 per day syngas prodn. plant (at industrial scale) assured a pay back period of 4.8 (≈5) years with a min. profit margin of 142% when syngas selling price is set as 43 INR (0.52 USD) per kg.
    258. 258
      Njuguna, F.; Ndiritu, H.; Gathitu, B.; Hawi, M.; Munyalo, J. Kinetic Modeling and Optimization of Process Parameters for Gasification of Macadamia Nutshells with Air Preheating: A Combined Use of Aspen Plus and Response Surface Methodology (RSM). Bioresour Technol. Rep 2023, 22, 101477,  DOI: 10.1016/j.biteb.2023.101477
      258
      Kinetic modeling and optimization of process parameters for gasification of macadamia nutshells with air preheating: A combined use of Aspen Plus and response surface methodology (RSM)
      Njuguna, Fredrick; Ndiritu, Hiram; Gathitu, Benson; Hawi, Meshack; Munyalo, Jotham
      Bioresource Technology Reports (2023), 22 (), 101477CODEN: BTRICJ; ISSN:2589-014X. (Elsevier Ltd.)
      This study used Aspen Plus process simulation for sensitivity anal. to identify the range of parameters for subsequent optimization using response surface methodol., to maximize syngas combustible gases and higher heating value (HHV) while minimizing tar. From the anal. of variance, equivalence ratio (ER) was the most significant parameter affecting H2 and CH4 prodn., HHV and tar content while pressure contributed the least. Air temp. influenced CO prodn. the most while ER had the least effect. For a pressurized gasifier operating at 4 atm, optimal ER and air temp. was 0.16 and 575 °C resp., producing syngas with HHV and tar content of 4.3 MJ/Nm3 and 23.68 g/Nm3 resp. Optimal ER and air temp. for atm. pressure gasifier were 0.15 and 445 °C resp., resulting in syngas with HHV and tar content of 4.14 MJ/Nm3 and 29.17 g/Nm3 resp. The simulation results were in good agreement with the exptl. data.
    259. 259
      Yu, J.; Smith, J. D. Validation and Application of a Kinetic Model for Biomass Gasification Simulation and Optimization in Updraft Gasifiers. Chemical Engineering and Processing - Process Intensification 2018, 125, 214– 226,  DOI: 10.1016/j.cep.2018.02.003
      There is no corresponding record for this reference.
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      Wang, Y.; Kinoshita, C. M. Kinetic Model of Biomass Gasification. Sol. Energy 1993, 51 (1), 19– 25,  DOI: 10.1016/0038-092X(93)90037-O
      260
      Kinetic model of biomass gasification
      Wang, Y.; Kinoshita, C. M.
      Solar Energy (1993), 51 (1), 19-25CODEN: SRENA4; ISSN:0038-092X.
      A kinetic model for biomass gasification was developed based on the mechanism of surface reactions. The apparent rate consts. were calcd. by minimizing the differences between exptl. data and theor. results for different residence times and different temps. The kinetic model was validated by comparing exptl. data with theor. results for different equivalence ratios; the simulations agree well with the exptl. data. Simulations modeling the influence of char particle size on the time required to achieve 90% C conversion agree with results of tests performed by other investigators. Simulations were performed to evaluate the effects of type of oxidant, residence time, char particle size, temp., pressure, equivalence ratio, and moisture on biomass gasification.
    261. 261
      Yang, M.. CFD Modeling of Biomass Combustion and Gasification in Fluidized Bed Reactors. Doctoral Dissertation, Lund University, Lund, Sweden, 2023.
      There is no corresponding record for this reference.
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      Zhang, H.; Okuyama, K.; Higuchi, S.; Soon, G.; Lisak, G.; Law, A. W. K. CFD-DEM Simulations of Municipal Solid Waste Gasification in a Pilot-Scale Direct-Melting Furnace. Waste Management 2023, 162, 43– 54,  DOI: 10.1016/j.wasman.2023.03.008
      262
      CFD-DEM simulations of municipal solid waste gasification in a pilot-scale direct-melting furnace
      Zhang, Hui; Okuyama, Keiichi; Higuchi, Shinji; Soon, Genevieve; Lisak, Grzegorz; Law, Adrian Wing-Keung
      Waste Management (Oxford, United Kingdom) (2023), 162 (), 43-54CODEN: WAMAE2; ISSN:0956-053X. (Elsevier Ltd.)
      A multiphase CFD-DEM model was built to simulate the waste-to-energy gasifying and direct melting furnace in a pilot demonstration facility. The characterizations of feedstocks, waste pyrolysis kinetics, and charcoal combustion kinetics were first obtained in the lab. and used as model inputs. The d. and heat capacity of waste and charcoal particles were then modelled dynamically under different status, compn., and temp. A simplified ash melting model was developed to track the final fate of waste particles. The simulation results were in good agreement with the site observations in both temp. and slag/fly-ash generations, verifying the CFD-DEM model settings and gas-particle dynamics. More importantly, the 3-D simulations quantified and visualized the individual functioning zones in the direct-melting gasifier as well as the dynamic changes throughout the whole lifetime of waste particles, which is otherwise tech. unachievable for direct plant observations. Hence, the study demonstrates that the established CFD-DEM model together with the developed simulation procedures can be used as a tool for the optimization of operating conditions and scaled-up design for future prototype waste-to-energy gasifying and direct melting furnace.
    263. 263
      Salem, A. M.; Paul, M. C. CFD Modelling of Spatiotemporal Evolution of Detailed Tar Species in a Downdraft Gasifier. Biomass Bioenergy 2023, 168, 106656,  DOI: 10.1016/j.biombioe.2022.106656
      263
      CFD modelling of spatiotemporal evolution of detailed tar species in a downdraft gasifier
      Salem, Ahmed M.; Paul, Manosh C.
      Biomass and Bioenergy (2023), 168 (), 106656CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
      The rising demand for renewable energy around the world has sparked interest in biomass gasification. However, the technol. greatly suffers because of tar species produced during the gasification process, which limits direct use of the produced gas. To address this issue, the paper presents a novel piece of work that focuses on the formation and evolution of tar species consisting of benzene, naphthalene, toluene, and phenol. A two-dimensional numerical model for a downdraft biomass gasifier is developed with a total of 20 thermochem. kinetic reactions to investigate the formation of tar species in the gasifier with the effect of residence time. The model's predictions are validated with the exptl. and kinetic data and found to be in good agreement. Besides, the model's ability to simulate the producer gas prodn. from a downdraft gasifier is examd. Reaction rates for volatiles decompn., combustion, and gasification reactions under different working conditions are investigated. Overall, benzene has the highest concn. of the selected tar species, followed by naphthalene, and with relatively modest amts. of phenol and toluene.
    264. 264
      Faridi, I. K.; Tsotsas, E.; Heineken, W.; Koegler, M.; Kharaghani, A. Spatio-Temporal Prediction of Temperature in Fluidized Bed Biomass Gasifier Using Dynamic Recurrent Neural Network Method. Appl. Therm Eng. 2023, 219, 119334,  DOI: 10.1016/j.applthermaleng.2022.119334
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      Hashem Samadi, S.; Ghobadian, B.; Nosrati, M.; Rezaei, M. Investigation of Factors Affecting Performance of a Downdraft Fixed Bed Gasifier Using Optimized MLP Neural Networks Approach. Fuel 2023, 333, 126249,  DOI: 10.1016/j.fuel.2022.126249
      265
      Investigation of factors affecting performance of a downdraft fixed bed gasifier using optimized MLP neural networks approach
      Hashem Samadi, Seyed; Ghobadian, Barat; Nosrati, Mohsen; Rezaei, Mahdi
      Fuel (2023), 333 (Part_1), 126249CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Biomass gasification will be a competitive renewable technol. to meet the world's energy demand in the near future. However, extremely time-consuming and costly exptl. investigations are still required to achieve the best gasification performance. Machine learning through artificial neural networks can be considered as a convenient and low-cost tool for predicting and optimizing gasification conditions. In this paper, MLP neural network was used to develop a predictive model for the fixed bed gasification properties. Several MLP models were developed to predict the compn. of the produced gas and the lower heating value based on the physicochem. compn. of the biomass and the reactor operating conditions. The results showed that the MLP architecture with the Levenberg-Marquardt algorithm by considering the range of 47 to 57 neurons in the hidden layer and the tansig activation function had reasonable accuracy in predicting the outputs. Performance of the MLP proposed model showed good agreement between the output and target values with a coeff. of detn. of R2 >0.952, root mean squared error, RMSE < 0.83, and relative root mean squared error, rRMSE < 6.5%. In addn., according to the results obtained, the MLP indicated the highest precision to model the fixed bed gasification over the other methods. Finally, after the implementation of the model, the sensitivity anal. of input data on output data was performed. The modeling results of this study showed that the MLP model can effectively replace the costly exptl. tests to study the gasification process.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.3c04425.

    • Typical tar levels reported in literature for various operating conditions (PDF)


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