A systematic approach to the modeling and simulation of a Sorption Enhanced Water Gas Shift (SEWGS) process for CO2 capture

Abstract

Dynamic operation of a multi-train Sorption Enhanced Water Gas Shift (SEWGS) system, based on a Pressure Swing Adsorption (PSA) process, is investigated by a detailed dynamic modeling and simulation. The multi-train SEWGS system, which consists of eight reactors in each train, operating in parallel, treats the feed syngas being produced continuously in a gasifier of an Integrated Gasification Combined Cycle (IGCC). Syngas is converted to a H2-rich product and a separate CO2-rich stream is also produced. The SEWGS system is designed for pre-combustion CO2 capture in the IGCC power plant. Therefore dynamic characteristic of the system at different loads of feed syngas is interesting for investigation of the performance of IGCC power plant at different Gas Turbine (GT) load levels. Simulation results reveal performance of the system in terms of components breakthrough curves and steam consumption of the system with a CO2 recovery rate of 95% and 99% purity of the recovered CO2. The H2-rich product purity achieved is around 81%. It is found that changing the rinse and purge steam amount affects the CO2 purity and recovery rate. However, the H2-rich product purity remains almost unchanged. Simulation results at different loads of feed syngas shows that to maintain the CO2 recovery and purity of the design case as the target performance, in addition to changing the rinse and purge steam loads, duration of the feed step and thus the cycle time should be varied as well. The H2-rich stream flow rate is found to undergo a periodic fluctuation of around ±33%, which should be minimized due to the GT requirements. It is tried to reduce the fluctuations by scheduling operation of the trains with time lags. Operation of the SEWGS system under two different scheduled operation scheme is investigated. H2-rich stream flow rate fluctuations are decreased from ∼±33% in the basic operation scheme to ∼±14% and ∼±11% in the first and second scheme. However, compared to the basic scheme, the H2-rich stream overall production rate drops around 5.5% and 6.2% on average, respectively.