Effect of sulfation on CO_2 capture of CaO-based sorbents during calcium looping cycle

摘要

Calcium looping cycle is considered as one of the most promising post combustion CO_2 capture technologies that can curb CO_2 emissions from power plants fired with fossil fuel. However the presence of SO_2 and steam in the flue gas leads to the sulfation of CaO-based sorbents, and thus reduces the sorbents' capacity for CO_2 capture. In this study, the effect of sorbent sulfation during both carbonation and calcination stage on the cyclic CO_2 capture performance was investigated. The results showed that the reaction time, SO_2 concentrations and steam greatly influenced the capacity of CaO-based sorbent. The sulfation degree of the sorbent decreased with the reduction of carbonation and calcination time per cycle. High SO_2 concentration present with steam led to a rapid loss in capacity of the sorbent within a few cycles. Furthermore, the synthetic sorbent derived from a sol-gel process had much higher cyclic CO_2 capture capacities than natural limestone sorbent whether in conditions without SO_2 or with SO_2 and steam. Microscopic images showed that after multiple cycles in the presence of SO_2 and steam, the porous structure of the synthetic sorbent could be retained while limestone experienced serious pore blockage and agglomeration of grains.