Mass transfer enhanced CaO pellets for CO2 sorption: Utilization of CO2 emitted from CaCO3 pellets during calcination

Abstract

• Mass transfer enhanced CaO pellets were prepared and applied to capture CO 2 . • CO 2 evacuation from CaCO 3 pellets created mass transfer channels. • Developed channels significantly enhanced CO 2 sorption kinetics. • Enhanced mass transfer caused fast regeneration of CaO pellets after CO 2 sorption. In the preparation of CaO-based CO 2 sorbents, particle densification during pelletization significantly limits the mass transfer of CO 2 , thereby decreasing the CO 2 sorption performance. In this study, mass transfer enhanced CaO pellets (CaO–PC) were prepared through the formation of channels using CO 2 evacuation from the inside of the pellets. Calcination of CaCO 3 pellets induced CO 2 evacuation and the remaining evacuation pathways provided excellent mass transfer channels for CaO–PC. Conventional CaO pellets (CaO–CP) were also prepared for comparison. Unlike the severely agglomerated (or blocked) morphology of CaO–CP, well-developed channels were observed in CaO–PC. It was experimentally confirmed that these channels directly contributed to the initial stage of CO 2 sorption in CaO–PC, which significantly accelerated the CO 2 sorption kinetics. CaO–PC had increased CO 2 sorption uptakes of 58.9, 65.1, and 67.0 wt% at 500, 600, and 700 °C, respectively, whereas those for CaO–CP were 47.6, 55.4, and 56.8 wt%. In addition to CO 2 sorption, enhanced mass transfer had a positive effect on CO 2 release after capture. Under CO 2 flow, the regeneration of CaO–PC was faster than that of CaO–CP, even at lower temperatures. Both the fast CO 2 sorption and regeneration kinetics of CaO–PC significantly enhance the energy efficiency of continuous CO 2 capture processes. These improvements were accomplished easily without the need of any additional energy-consuming treatments other than the conventional preparation methods.