SEWGS process cycle optimization

AbstractSorption-enhanced water-gas shift (SEWGS) is a technology for pre-combustion CO2 capture, which can be integrated in an IGCC plant. A computer model is used to simulate the SEWGS unit, using a counter-current steam rinse cycle with one equalization step. The sensitivity of the CO2 recovery and the purity of the CO2 stream with respect to the feed flow rate, rinse flow rate, purge flow rate and cycle time has been investigated at an initial operating point. One at a time variations show that the CO2 recovery increases with increasing purge flow rate and decreases with increasing feed flow rate, cycle time and rinse flow, in order of decreasing sensitivity. The CO2 purity is much less sensitive to changes of these conditions, unless either the rinse flow rate or the cycle time drop below certain values, which are determined by the ratio of the pressures at the end of the rinse and equalization steps. The optimum rinse flow, purge flow and cycle time have been determined with respect to the efficiency penalty due to the rinse and purge steam requirements, with a CO2 recovery of 90% and a dry CO2 purity of 98% as constraints, for a given feed flow rate, feed flow composition, operating pressure, reactor sizing and configuration. Minimum steam-to-carbon ratios are 0.55 for the rinse and 1.3 for the purge gas