Regenerable MgO-based sorbent for high temperature CO_2 removal from syngas: 3. CO_2 capture and sorbent enhanced water gas shift reaction

摘要

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 CO_2/N_2/H_2O mixture and simulated pre-combustion syngas environment. In CO_2/N_2/H_2O environment, the CO_2 absorption capacity of the sorbent increases with increasing temperatures from 6.7% at 350 ℃ to 9.5% 450 ℃. The sorbent is capable of achieving over 95% CO_2 capture and 40% conversion in the water gas shift (WGS) reaction, which should be attributed to positive effect of WGS reaction in producing CO_2 during the process. The sorbent reactivity and absorption capacity toward CO_2, as well as its WGS catalytic activity decreases with increasing temperature. The maximum pre-breakthrough WGS conversion occurs at 350 ℃, 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.