Environmental Engineering Reference
In-Depth Information
Gas
cleaning
Gas turbine/Generator
Biomass
Gasifier
Clean
Syngas
H
2
+CO
~
H
2
Separation
of H
2
from
CO
2
Shift reaction
CO + H
2
O
Æ
H
2
+ CO
2
Methanation
CO + 3H
2
Æ
CH
4
+ H
2
O2H
2
+ CO
Æ
CH
3
OH
Methanol synthesis
Fischer-Tropsch
H
2
2nH
2
+ nCO
Æ
(-CH-)
n
+ nH
2
O
Fuel cell
NH
3
Transportation
fuels
Acetic acid
Formaldehyde
MTBE
DME
M-100
M-85
DMFC
Feedstocks for
chemical
industry
MTBE: Methyl tert-butyl ether
DME: Dimethyl ether
DMFC: Direct-methanol fuel cells
M-100: 100% pure methanol
M-85: 85% methanol with 15% unleaded premium gasoline
Figure 14.3
Potential products and applications from syngas produced from biomass.
Adapted from Spath and Dayton, 2003.
and
Acetobacterium woodii,
have the capability of uptaking carbon monoxide and hydrogen
and converting into ethanol (Munasinghe and Khanal, 2010) or other solvents including iso-
propyl alcohol, acetic acid, and butanol (Kundiyana et al., 2010).
Unfortunately, the technology is still in the research phase and is not problem free. The
main limitations of microbial fermentation using carbon monoxide and hydrogen as substrates
are as follows (Munasinghe and Khanal, 2010):
1. The presence of inhibitory compounds including ethylene, ethane, acetylene, tar, ash, char
particles, and sulfur and nitrogen compounds.
2. Limited gas-liquid mass transfer.
3. Need of growth media that includes minerals, trace elements, vitamins, and reducing
agents
4. Low yields.
Syngas can be transformed into liquid hydrocarbons via a chemical route using the Fischer-
Tropsch process. However, the process has its limitations. When using syngas from biomass,
the presence of impurities deactivates catalysts and produces corrosion in downstream equip-
ment. Some of the main contaminants are sulfur compounds, including hydrogen sulfide and
