(478b) CO2 Sorption Capacity and Cyclic Performance of Calcined Limestone (CaO) during Carbonation: Effects of Temperature, Steam, and Syngas (CO & H2) Addition

Advanced gasification technologies like sorption-enhanced gasification featuring in situ carbon capture offer a promising avenue for clean H₂ production, potentially enabling the permanent sequestration of CO₂ stemming from biomass-to-H₂ using solid sorbents (e.g., lime, CaO). Despite extensive studies on CaO-based sorbents for CO₂ sorption, current studies have not clarified the effects of syngas during carbonation, and more work is required to address these effects. In this contribution, we investigate the impact of steam injection and the presence of syngas (CO and H₂) during carbonation on the sorption performance of CaO derived from commercially available limestone (CaCO₃). This work investigates CO₂ absorption capacity of CaO at different temperatures with or without steam injection during carbonation. Furthermore, the effects of CO and H₂ addition during carbonation are investigated in both conditions.

Our results demonstrate that steam addition positively affects the sorption activity of CaO under conditions suitable for in situ CO₂ capture in gasification, owing to the formation of cracks, an increase in porosity, and enhanced solid-state CO₂ diffusion through the carbonate layer. On the contrary, syngas introduction during carbonation significantly reduces the sorption performance of CaO in dry and wet conditions. It is hypothesized that competitive adsorption at CaO active sites, formation and deposition of C from the Boudouard reaction, and other competitive reactions are favorable at the same conditions as the carbonation reaction can be attributed to these inhibitory effects of syngas addition during carbonation. Furthermore, cyclic carbonation tests at these conditions are performed to understand sorbent activity and decay profiles over multiple cycles. Understanding these interactions is crucial for optimizing the performance of CaO-based sorbents for in situ CO₂ capture during biomass gasification.