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and char. Volatiles and char from the pyrolysis process are further converted into
gases during the gasification process. Although the exact chemical reactions and
kinetics are complex and not yet fully-understood, biomass gasification includes the
(1) Combustion
(biomass volatiles/char) + O 2
CO 2
(2) Partial oxidation
(biomass volatiles/char) + O 2
(3) Methanation
(biomass volatiles/char) + H 2
CH 4
(4) Water-gas shift
CO + H 2 O
CO 2 +H 2
(5) CO methanation
CO + 3H 2
CH 4 +H 2 O
(6) Steam-carbon reaction
(biomass volatiles/char) + H 2 O
CO + H 2
(7) Boudouard reaction
(biomass volatiles/char) + CO 2
The major components of typical syngas generated from wood are listed in
Table 3, and it is evident that output variation occurs, even in the same type of gasi-
fier as gasification conditions (temperature, pressure, O 2, and steam levels) typically
impact the syngas composition.
5.3 Liquid Fuels - FT Liquids (Diesel), Ethanol
or Butanol, Chemicals
Technically, a variety of different liquid fuels and chemicals can be made from high
quality syngas (Fig. 4). The production of liquid fuel, either a thermochemical-
catalyzed conversion or a microbial fermentation process (under development),
Fig. 4 A diversity of chemicals can be produced from syngas (from page 3 of Drs. Spath and
Dayton's 2003 NREL Technical Report, NREL/TP-510-34929, with modification)
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