Regenerable MgO-based sorbent for high temperature CO2 removal from syngas: 3. CO2 capture and sorbent enhanced water gas shift reaction

Abstract

Regenerable MgO-based sorbent, which was prepared and evaluated in the thermogravimetric analyzer (TGA) in part 1, was also evaluated in high-pressure packed-bed unit in CO2/N2/H2O mixture and simulated pre-combustion syngas environment. In CO2/N2/H2O environment, the CO2 absorption capacity of the sorbent increases with increasing temperatures from 6.7% at 350°C to 9.5% 450°C. The sorbent is capable of achieving over 95% CO2 capture and 40% conversion in the water gas shift (WGS) reaction, which should be attributed to positive effect of WGS reaction in producing CO2 during the process. The sorbent reactivity and absorption capacity toward CO2, as well as its WGS catalytic activity decreases with increasing temperature. The maximum pre-breakthrough WGS conversion occurs at 350°C, which diminishes as the sorbent is carbonated. The variable diffusivity shrinking core reaction model coupled with the two-fluid computational fluid dynamics (CFD) model was shown to accurately predict the break-through gas compositions at different operating conditions.