Carbon dioxide removal in indirect gasification - SGC

SGC Rapport 2013:277
Table 14b. Gas compositions and other properties in the 100 MW th case after upgrading
pre-methanation with amine scrubbing, on a dry-gas basis.
After separation After methanation
Component (Vol-%)
CO2 0.1 0.2
CH4 37.9 92.7
CO 15.2 9.3*10 -3
H2 45.17 4.0
C2Hx
C6H6
6.4*10 -4
2.1*10 -6
7.9*10 -4
0
N2 1.7 3.1
O2 0 0
Methane slip (% of inlet) 0.05 N/A
Propane required for Wobbe indexLHV
45.5 (kg/Nm 3 ) N/A 0.004
The SNG-efficiency (ηSNG) for the cases with pre-methanation CO2-removal has
been calculated to 67.9% and 68.4% for water and amine scubbing respectively.
The amount of propane which is requried for reaching the taget Wobbe index is
however significantly higher in the water scrubber case. This is due to the high
level of nitrogen which the separation method results in, which is further
emphasised by the gas volume reduction over the methanation stage. The
electricity consumption of the gasification system was set to 1.5% of the overall
biomass input or 1.5 MW [89]. The water scrubber consumed 5.1 MW while the
amine scrubber consumed 2.5 MW; in both cases 3.4 MW electricity was
produced in the system. In Figure 25 the changes in chemical energy is visualised
in the pre-methanation separation case, please note that the red and blue arrows
add up to the inlet 100 MW th and that the power is the net input, some electricity is
generated internally.
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