Facile and economic modified method for CaO-based particles with straw as additive: Improving CO2 adsorption performance and cyclic stability

Abstract

CaO-based sorbents represent a highly viable solution for post-combustion CO₂ capture, with granulation commonly employed to mitigate elutriation in fluidized-bed reactors. Nonetheless, granulation markedly increases the density of these sorbents, thereby impairing their CO₂ uptakes and cyclic stability. In this study, a cost-effective strategy was developed by incorporating various pore-forming agents (agar, urea, straw, and biochar) into CaO-based particles (denoted as CaO+C+A, CaO+C+U, CaO+C+S, and CaO+C+B) to enhance their adsorption performance and durability. The findings revealed that the mechanical strength of uncalcined CaO-based particles remained unaltered by the incorporation of additives, whereas only the CaO+C+S particle maintained acceptable compressive strength (17.1 N) and a low attrition rate (6.6 %) after calcination. Compared with the CaO+C+A particle, the compressive strength of CaO+C+S particle was increased by 87.5 % and the attrition rate was decreased by 22.8 %. Meanwhile, the CaO+C+S particle exhibited the highest CO₂ adsorption performance, achieving 541 mg/g within 10 min, alongside outstanding cyclic stability, maintaining 217 mg/g after 20 cycles. This represents a 17.4 % increase in initial adsorption and a 25.3 % improvement in long-term stability compared to the control particle. These advancements are attributed to straw’s role in facilitating pore formation, refining CaO crystal size, and increasing the proportion of high-melting-phase (CaAl₄Si₂O₁₁). The first two factors markedly enhance the diffusion kinetics conditions and thus improving the CO₂ adsorption performance of CaO-based particles. Combined, these three factors enhance resistance to sintering by creating spatial physical barriers and increasing the melting point. This study offers a straightforward and cost-efficient modification approach to improve the CO₂ adsorption performance and durability of CaO-based particles.