CaO-based sorbents represent a highly viable solution for post-combustion CO 2 capture, with granulation commonly employed to mitigate elutriation in fluidized-bed reactors. Nonetheless, granulation markedly increases the density of these sorbents, thereby impairing their CO 2 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 CO 2 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 (CaAl 4 Si 2 O 11 ). The first two factors markedly enhance the diffusion kinetics conditions and thus improving the CO 2 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 CO 2 adsorption performance and durability of CaO-based particles.
Yi Fang,Yingjie Li,Jigang Zhang,Youhao Zhang,Zhiwei Chu,Kuihua Han
CaO/CaCO 3 heat storage is considered a promising technology to solve the intermittency of solar energy. Fluidized-bed reactor is commonly used as calciner/carbonator to efficiently achieve heat storage. In the fluidized-bed reactor, the particle cohesion impedes fluidization of CaO/CaCO 3 particles, adversely impacting heat storage. However, the current research rarely focuses on the cohesive behavior of CaO-based particles in fluidization during CaO/CaCO 3 heat storage process. Furthermore, current research on cohesive behavior primarily focuses on experimental studies, lacking an explanation of the underlying mechanisms at the molecular level. In this work, the cohesive behavior of CaO-based particles in CaO/CaCO 3 heat storage process was studied on a fluidized-bed reactor. The particle cohesion is reflected by the tensile yield strength during the transition from static state to fluidization state. The results indicate that the cohesive behavior of CaCO 3 particles gradually is strengthened with increasing temperature. The tensile yield strength of CaCO 3 particles at 800 °C is 1770 Pa, which is 200 % higher than that at 500 °C. Additionally, the carbonation enhances the cohesive behavior of CaO particles. The tensile yield strength of CaO particles after the carbonation is 55 % higher than that of before the carbonation. The enhanced cohesive behavior of CaO particles during the carbonation results in the defluidization. Molecular dynamics simulation shows that the formation of sintering necks at above 650 °C in the carbonation stage results in cohesive behavior of CaO particles. The introduction of 5 % Al 2 O 3 fines (50–75 μm) as lubricant effectively improves the fluidization quality of CaO particles in the carbonation stage, thereby enhancing the exothermic performance of CaO particles. These findings provide valuable insights for the industrial application of CaO/CaCO 3 heat storage in fluidization.
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