Screening of Naturally Al/Si-Based Mineral Binders to Modify CaO-Based Pellets for CO2 Capture

CO 2 removal in the calcium looping process is achieved by circulating the CaO-based sorbents between two interconnected fluidized-bed reactors. During the cyclic CO 2 capture process, severe attrition easily emerged for CaO-based sorbents. Therefore, the preparation of CaO-based pellets with a high antiattrition ability is important. In this work, a range of inert aluminosilicate binders (i.e., diatomite, rectorite, montmorillonite, attapulgite, vermiculite, pumice, and bauxite) were added to the extruded-spheronized CaO-based pellets aiming to improve their attrition-resisting properties. Two modifying modes of binder (dry-mixing and hydration-mixing) were compared in order to confirm the more suitable one for the preparation of binder-bound pellets. It is found that the pumice-bound pellets containing 10 wt % of pumice prepared via hydration-mixing exhibit the highest cumulative CO 2 capture capacity of 11.13 g of CO 2 /g of CaO during 25 cycles and a promising antiattrition ability (a weight loss of 0.77% after 3000 rotations). The formed Ca 3 Al 2 O 6 acting as the skeleton structure can alleviate sorbent sintering, thus resulting in the superior CO 2 capture performance. The high antiattrition ability is mainly attributed to the uniformly distributed pumice particles, the high binding force of hydrate lime, and the formation of calcium carbonate during air drying process.