Web Release Date: March 14,
The Art, Science, and Technology of Charcoal Production
Hawaii Natural Energy Institute, University of Hawaii at Manoa, Honolulu, Hawaii 96822
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SINTEF Energy Research, Thermal Energy, 7465 Trondheim, Norway
Received for review October 7, 2002
Revised manuscript received January 13, 2003
Accepted January 15, 2003
Contents- Introduction
- Charcoal Properties and Yields
- Effects of Thermal Pretreatments, Heating Rate, and Final (Peak) Temperature
- Thermal Pretreatments
- Heating Rate
- Peak Temperature
- Carbonization
- Effects of the Gas Environment
- Moisture
- Vapor-Phase Residence Time
- Pressure
- Effects of Feedstock Properties
- Reactivity
- Pyrophoricity
- Chemisorption
- Ignition
- Combustion
- Industrial Processes
- Conclusions
Abstract:
In this review, we summarize the knowledge of the production and properties of charcoal that has been accumulated over the past 38 millenia. The manipulation of pressure, moisture content, and gas flow enables biomass carbonization with fixed-carbon yields that approach-or attain-the theoretical limit after reaction times of a few tens of minutes. Much of the heat needed to carbonize the feed is released by vigorous, exothermic secondary reactions that reduce the formation of unwanted tars by augmenting the charcoal yield in a well-designed carbonizer. As a renewable fuel, charcoal has many attractive features: it contains virtually no sulfur or mercury and is low in nitrogen and ash; it is highly reactive yet easy to store and handle. Carbonized charcoal can be a good adsorbent with a large surface area and a semimetal with an electrical resistivity comparable to that of graphite. Recent advances in knowledge about the production and properties of charcoal presage its expanded use as a renewable fuel, reductant, adsorbent, and soil amendment.
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