Enhancement of CO2 capture and microstructure evolution of the spent calcium-based sorbent by the self-reactivation process

The effect of self-reactivation on the CO2 capture capacity of the spent calcium based sorbent was investigated in a dual-fixed bed reactor. The sampled sorbents from the dual-fixed bed reactor were sent for XRD, SEM and N-2 adsorption analysis to explain the self-reactivation mechanism. The results show that the CaO in the spent sorbent discharged from the calciner absorbs the vapor in the air to form Ca(OH)(2) and further Ca(OH)(2 center dot)2H(2)O under environmental conditions, during which process the CO2 capture capacity of the spent sorbent can be self-reactivated. The microstructure of the spent sorbent is improved by the self-reactivation process, resulting in more porous microstructure, higher BET surface area and pore volume. Compared with the calcined spent sorbent that has experienced 20 cycles, the pore volume and BET surface area are increased by 6.69 times and 56.3% after self-reactivation when phi = 170%. The improved microstructure makes it easier for the CO2 diffusion and carbonation reaction in the sorbent. Therefore, the CO2 capture capacity of the spent sorbent is enhanced by self-reactivation process. A self-reactivation process coupled with calcium looping process was proposed to reuse the discharged spent calcium based sorbent from the calciner. Higher average carbonation conversion and CO2 capture efficiency can be achieved when self-reactivated spent sorbent is used as supplementary sorbent in the calciner rather than fresh CaCO3 under the same conditions. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.