Continuous CO2 capture performance of K2CO3/Al2O3 sorbents in a novel two-stage integrated bubbling-transport fluidized reactor

Post-combustion CO2 capture with solid sorbents is a promising technology. The feature of temperature swing adsorption for such process requires sufficient gas-sorbent contact, sustained driving force for adsorption and adjustable sorbent circulation between reactors. This, however, is hard to fully realize by traditional single regime fluidized reactors. In view of this, we proposed a novel two-stage integrated bubbling-transport bed reactor and examined its CO2 capture performance using K2CO3/Al2O3 sorbents. The results show that the optimal adsorption temperature ranges from 60 degrees C to 100 degrees C, much wider than that of traditional reactors. The CO2 capture efficiency increases with both sorbent circulation rate and desorption temperature. Better CO2 capture performance was observed when using air instead of CO2 as the desorption gas. Nevertheless, the difference is negligible as the desorption temperature exceeds 200 degrees C. Stage I is the region where CO2 adsorption mainly takes place, owing to the over-adsorption of water vapor. This limits the CO2 capture performance of the entire system. To this regard, water vapor step-feeding was carried out, acting as an in-situ activation of sorbents. It enhances the maximum CO2 capture efficiency from 87% to 96%, meanwhile showing a strong anti-interference ability for water vapor fluctuation even at a fixed total water vapor. The 24 h continuous test verifies the superiority of the present system as the CO2 capture efficiency maintains around 93% and the desorption CO2 purity keeps above 98%.