Simulation of elevated temperature combined water gas shift and solid sorbent CO2 capture for pre-combustion applications using computational fluid dynamics

Abstract

Water gas shift reaction combined with CO2 adsorption is a novel promising technology for pre-combustion CO2 capture in IGCC applications. By combining the two processes in an IGCC, reduction in plant capital cost (by eliminating the separate shift reactors) and in heat rate (by reducing their steam injection rates) may be realized. CFD modeling was employed to predict the CO2 adsorption, desorption and shift reaction rates, CO2 loading, CO2 breakthrough curve and temperature distribution within the reactor. The model was validated against experimental data. It was shown that significant increase in temperature occurs near the bottom region of the combined catalyst and sorbent mixed zone because majority of the reaction occurs over a small region where the feed syngas contacts the WGS catalyst. Injection of liquid water between beds is investigated for temperature control. CFD simulation model of the combined WGS and CO2 capture would be useful in reactor design, developing thermal management strategies to avoid the high temperature zones, and developing IGCC overall plant design as well as in assessing the plant thermo-economics.