Kinetic analysis of cyclic carbonation of carbide slag during chemical reaction‐controlled stage under fluidization conditions

Abstract

Carbide slag, as a kind of typical industrial waste, was proposed as a CO2 sorbent in the calcium looping process. The CO2 capture performance of carbide slag was investigated in a bubbling fluidized bed reactor (BFBR) under fluidization conditions. A surface reaction‐controlled kinetic model was employed to describe the carbonation kinetics of carbide slag during the chemical reaction‐controlled stage. The results show that the values of k, tcrcs, and Xu, which respectively denote the reaction rate constant, duration time, and final carbonation conversion in the chemical reaction‐controlled stage, decrease with the cycle number, due to the sintering of the sorbents. The microstructure of calcined carbide slag leads to higher CO2 diffusion resistance in carbide slag than that in limestone, causing lower k and longer tcrcs compared with limestone. The larger BET areas and pore areas of calcined carbide slag provide additional surface for the reaction of CaO and CO2. Therefore, the Xu values of carbide slag are higher than those of limestone after 5 cycles. Reaction conditions have a significant effect on the carbonation process of carbide slag. 850–900 °C is the optimum temperature range for the calcination of carbide slag. The gas‐solid transfer is strengthened at a higher fluidization number, enhancing the CO2 capture of carbide slag. The pores of the larger particles are more easily blocked due to the formation of CaCO3 layer, and the Xu of the carbide slag with a larger particle size is lower.