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

K2CO3/Al2O3 used for capturing CO2 in flue gas is thoroughly investigated. The present paper focuses on the CO2 capture behaviors of K2CO3/Al2O3 in a bubbling fluidized-bed reactor. It is found that K2CO3/Al2O3 shows a higher CO2 capture capacity than other potassium-based sorbents. The carbonation reaction capacities are in the range of 290-319 mg of CO2/g of K2CO3 for K2CO3/Al2O3 with loading amounts of 12.8-36.8%. It is abruptly decreased to 148.98 mg of CO2/g of K2CO3 when the loading amount of K2CO3 increases to 45.1%. The reason is attributed to the change of the active component distribution behavior. The total CO2 sorption capacity maintains a high level when the carbonation temperature is in the range of 60-80 degrees C. The CO2 capture behavior is significantly affected by the changing H2O concentration and the process of water pretreatment for the sorbent. The effect of the CO2 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 degrees C in a slow heating process, and the temperature for 100% regeneration of the sorbent is 350 degrees C in a rapid heating process. The carbonation conversion of K2CO3/Al2O3 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.