Effect of Preparation Temperature on Cyclic CO2 Capture and Multiple Carbonation−Calcination Cycles for a New Ca-Based CO2 Sorbent

Abstract

The cyclic CO 2 capture, transient phases change, and microstructure appearance of a new kind of Ca-based regenerable CO 2 sorbent, CaO/Ca 12 Al 14 O 33, obtained by the integration of CaO as solid reactant with a composite metal oxide of Ca 12 Al 14 O 33 as a binder, were investigated by thermogravimetric analysis, XRD, and SEM at different preparation calcination temperatures. When the calcination temperature in the preparation stage is higher than 1000 °C, the cyclic CO 2 capture of this new sorbent declines. The lowered CO 2 capture may mainly be attributed to the formation of Ca 3 Al 2 O 6, which decreases the ratio of CaO to binder in sorbent, and the severe sintering of sorbent occurs when calcined at such high temperatures in the preparation processes. These results suggest that the calcination temperature for this new sorbent should not be higher than 1000 °C in order to obtain its high reactivity. The performance of the new sorbent over 50 cycles was evaluated under mild and severe regeneration conditions, respectively. CaO/Ca 12 Al 14 O 33 attained 41 wt % CO 2 capture after 50 carbonation−calcination cycles under mild calcination conditions (850 °C, 100% N 2 ), and the results obtained here indicate that the new sorbent, CaO/Ca 12 Al 14 O 33, has significantly improved CO 2 capture and cyclic reaction stability over multiple carbonation−calcination cycles compared with limestone and dolomite under mild calcination conditions. When more severe calcination conditions (980 °C, 100% CO 2 ) were used, the capture of CaO/Ca 12 Al 14 O 33 decreased from 52 wt % in the first cycle to about 22 wt % in the 56th cycle; however, the capture of CaO/Ca 12 Al 14 O 33 sorbent over 56 cycles is still higher than that of dolomite and limestone under the same severe calcination conditions.