Carbon dioxide removal in indirect gasification - SGC

SGC Rapport 2013:277
Figure 25. Representation of the changes in chemical energy with reaction.
Much of the chemical energy on the conversion side is lost in the same stages,
there are however some differences in the separation and methanation stages. A
summary of the inputs and outputs in the pre-methanation separation case may be
viewed in Table 15.
Table 15. Summary of inputs and outputs from the 100 MWth system, premethanation
separation.
Water scrubber Amine scrubber
Input
Biomass 100 MWth (46 MWee) 100 MWth (46 MWee)
Power 3.3 MWee 0.6 MWee
LPG 10.80 MWth (5.4 MWee) 0.41 MWth (0.2 MWee)
Output
SNG 67.85 MWth (33.9 MWee) 68.38 MWth (34.2 MWee)
SNG+LPG 78.65 MWth (39.3 MWee) 68.79 MWth (34.4 MWee)
Heat 23.22 MWth (2.3 MWee) 3.91 MWth (0.4 MWee)
The same exercise as in the pre-methanation case has been performed for the
case with post-methanation purification. The results from the separations are
shown in table 16 for water and amine scrubbing respectively.
Table 16. Gas compositions and other properties in the 100 MWth case after upgrading
post-methanation, on a dry-gas basis.
Water scrubbing Amine scrubbing
Component (Vol-%)
CO2 1.0 0.2
CH4 90.8 92.8
CO 1.81*10 -4
1.9*10 -4
H2 3.9 3.9
C2Hx
1.46*10 -3
1.53*10 -3
C6H6 0 0
N2 3.9 3.1
O2 0.4 0
Methane slip (% of inlet) 1 0.05
Propane required for Wobbe indexLHV
45.5 (kg/Nm 3 ) 0.04 0.002
The SNG-efficiency (ηSNG) for the cases with post-methanation CO2-removal has
been calculated to 68.1% and 68.7% for water and amine scubbing respectively.
The amount of propane which is requried for reaching the taget Wobbe index is
however significantly lower in the water scrubber post-methanation case
compared to the pre-methanation case (0.04 kg/Nm 3 compared to 0.11 kg/Nm 3 ).
The electricity consumption of the gasification system was set to 1.5% of the
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