K₂CO₃/Al₂O₃ for Capturing CO₂ in Flue Gas from Power Plants. Part 3: CO₂ Capture Behaviors of K₂CO₃/Al₂O₃ in a Bubbling Fluidized-Bed Reactor

K 2 CO 3 /Al 2 O 3 used for capturing CO 2 in flue gas is thoroughly investigated. The present paper focuses on the CO 2 capture behaviors of K 2 CO 3 /Al 2 O 3 in a bubbling fluidized-bed reactor. It is found that K 2 CO 3 /Al 2 O 3 shows a higher CO 2 capture capacity than other potassium-based sorbents. The carbonation reaction capacities are in the range of 290–319 mg of CO 2 /g of K 2 CO 3 for K 2 CO 3 /Al 2 O 3 with loading amounts of 12.8–36.8%. It is abruptly decreased to 148.98 mg of CO 2 /g of K 2 CO 3 when the loading amount of K 2 CO 3 increases to 45.1%. The reason is attributed to the change of the active component distribution behavior. The total CO 2 sorption capacity maintains a high level when the carbonation temperature is in the range of 60–80 °C. The CO 2 capture behavior is significantly affected by the changing H 2 O concentration and the process of water pretreatment for the sorbent. The effect of the CO 2 concentration is not significant on the carbonation conversion when it is in the range of 10–30%. The sorbent is completely regenerated when the final temperature is higher than 300 °C in a slow heating process, and the temperature for 100% regeneration of the sorbent is 350 °C in a rapid heating process. The carbonation conversion of K 2 CO 3 /Al 2 O 3 decreases from 91 to 79.6% after 80 cycles. The surface area and pore volume of the sorbent keep a stable value, and the pore size distribution behavior is not changed after 80 cycles.