Effect of Regeneration Temperature on the Composition and Carbon Dioxide Sorption Ability of a K2CO3/Al2O3 Solid Sorbent in a Bubbling Fluidized Bed Reactor

The effect of the regeneration temperature (150°, 250°, and 350°C) during multiple CO₂ cyclic sorption-regeneration cycles of a K₂CO₃/Al₂O₃ solid sorbent in a bubbling fluidized bed reactor was evaluated in terms of the CO₂ capture capacity and chemical composition of the solid sorbent. The CO₂ capture capacity after regeneration at 150° and 250°C decreased with increasing cycle numbers, reaching approximately 57 and 78%, respectively, and 19.0 and 39.3%, respectively, of the original capacity after one and five regeneration cycles. This decline in the CO₂ capture capacity was due to the accumulation of KHCO₃ (at 150°C) and KAl(CO₃)₂(OH)₂ (150° and 250°C) from their incomplete degradation back to the K₂CO₃/Al₂O₃ solid sorbent. When regenerated at 350°C, the CO₂ capture capacity remained essentially constant in each cycle number because of complete desorption (no residual KHCO₃ and KAl(CO₃)₂(OH)₂). The formation mechanism of complex structure occurred similar to the one in a fixed bed reactor/thermogravimetric analyzer with lower regeneration temperature. The general operation conditions for K₂CO₃/Al₂O₃ solid sorbents are summarized.