Comparative Study on CO2 Capture Performance of Prewashed Agricultural Waste-Templated, CaO-based Pellets Subjected to Different Regeneration Conditions

Granulation is an effective method to mitigate the issue of CaO-based sorbent elutriation in the calcium looping process. To further enhance CO2 capture performance of CaO-based pellets, pore-forming templates are usually added. In this work, rice straw, wheat straw, and corn stalk were adopted as the pore-forming templates. The effect of different regeneration conditions (mild, moderately severe, and severe calcination conditions) on agricultural waste-templated, CaO-based pellets was comparatively investigated. Severe calcination conditions remarkably cause deactivation of the agricultural waste-templated, CaO-based pellets due to the accelerated sintering. Additionally, the existence of alkaline elements within agricultural wastes results in poor CO2 capture performance for agricultural waste-templated, CaO-based pellets. The pretreatment of water- and acid-washing can remove most of the alkaline elements within raw agricultural wastes. The CaO-based pellets added with 10 wt % of acid-washed rice straw exhibit the highest cumulative CO2 capture capacity of 2.074 g/g during 15 cycles, which is over 2.3 times that of those pellets added with 10 wt % raw rice straw. Therefore, water-washing and acid-washing are potential approaches to mitigate the adverse effect of alkaline elements within agricultural wastes, which consequently improves the CO2 capture performance for the agricultural waste-templated, CaO-based pellets.