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94 Biofuels for a More Sustainable Future
12 Syngas conditioning
After the removal of unwanted compounds, syngas presents elevated purity,
but adjustments are still necessary in its composition before its utilization in
the production of FT fuels. These adjustments consist of the conversion of
the methane present in the gas into CO and H 2 , and of the increase of the
ratio between the concentrations of hydrogen and carbon monoxide (ratio
H 2 /CO) closer to a 2.01 value in accordance with the requirements of the
FT synthesis (Tijmensen et al., 2002).
13 Fischer-Tropsch synthesis
In the FT synthesis step, fuels are produced from syngas, through the con-
version of carbon monoxide and hydrogen into water and the CH2 mono-
mer, which will form the hydrocarbon chain, as shown by reaction (4.1),
called polymerization reaction. Iron-based catalysts are utilized, as these
do not suffer poisoning as occurs with CO 2 (Tijmensen et al., 2002).
°
CO + 2H 2 ! CH 2 +H 2 O ΔH 165:0MJ=kmol (4.1)
298
Fig. 4.14 presents the mass balance of the adjustment of syngas condi-
tioning and FT synthesis.
Table 4.5 summarizes the processes contemplated by gasification and FT
synthesis.
Fig. 4.14 Mass and energy balance for the FT synthesis.
