Carbon dioxide removal in indirect gasification - SGC

SGC Rapport 2013:277
Table 10. Gas compositions and other properties in the 10 MW th case after upgrading,
on a dry-gas basis.
Using water Using amine
scrubbing scrubbing
Component (Vol-%)
CO2 1 0.2
CH4 93.4 96.3
CO 3.45*10 -5
8.4*10 -5
H2 3.4 3.5
C2Hx 0 0
C6H6 0 0
N2 1.4 0
O2 0.8 0
Methane slip (% of inlet) 1 0.05
Propane required for Wobbe indexLHV
45.5 (kg/Nm 3 ) 0.007 0
The major difference between the two systems is the operating pressure. The water
scrubber system operate at 7 bar(a) while the amine scrubber system operate
close to 1 bar(a). The use of air as stripper gas in the CO2 stripping system and
the rather high water pump-around rate is the explanation for the nitrogen and oxygen
in the gas after purification in the water scrubber case. There is no need for
propane addition in the amine purification case while there is a small requirement
in the air separation case (0.007 kg/Nm 3 ). Taking the methane losses into account
over the purification stage, the ηSNG becomes 61.2% in the amine scrubber case
and 60.6% in the water scrubber case. In Figure 24, the changes in chemical energy
are visualized; please note that the blue and red arrows add up to the inlet 10
MWth biomass.
Figure 24. Representation of the changes in chemical energy with reaction.
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