Effect of sulfation on CO2 capture of CaO-based sorbents during calcium looping cycle

Calcium looping cycle is considered as one of the most promising post combustion CO2 capture technologies that can curb CO2 emissions from power plants fired with fossil fuel. However the presence of SO2 and steam in the flue gas leads to the sulfation of CaO-based sorbents, and thus reduces the sorbents' capacity for CO2 capture. In this study, the effect of sorbent sulfation during both carbonation and calcination stage on the cyclic CO2 capture performance was investigated. The results showed that the reaction time, SO2 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 SO2 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 CO2 capture capacities than natural limestone sorbent whether in conditions without SO2 or with SO2 and steam. Microscopic images showed that after multiple cycles in the presence of SO2 and steam, the porous structure of the synthetic sorbent could be retained while limestone experienced serious pore blockage and agglomeration of grains.