Simultaneous CO2/SO2 Adsorption Performance of Carbide Slag in Adsorption/Desorption Cycles

Simultaneous CO2/SO2 adsorption performance of CaO derived from carbide slag (an industrial waste product from a chlor-alkali plant) in multiple adsorption/desorption cycles was investigated in a dual fixed-bed reactor. The effects of adsorption duration, SO2 concentration, adsorption temperature, desorption conditions, and particle size on carbonation conversion, cumulative sulphation conversion, and total Ca utilization of the carbide slag over multiple cycles were discussed. SO2 presence appreciably impedes the cyclic CO2 adsorption capacity of the carbide slag. A longer adsorption duration causes a sharper drop in the carbonation conversion due to the adverse effect of SO2. The presence of SO2 intensifies the effect of adsorption temperature on the carbonation conversion of the carbide slag. The optimum adsorption temperature for cyclic simultaneous CO2/SO2 adsorption by the carbide slag is 700 degrees C. The high desorption temperature and CO2 concentration (950 degrees C, 0.9999 L/L CO2) are not beneficial to cyclic CO2/SO2 adsorption. Both the carbonation conversion and cumulative sulphation conversion of the carbide slag decrease with increasing sorbent particle size in the cycles. The compact CaSO4 product layer covers the surface of CaO derived from the carbide slag during the multiple cycles, which results in a sharp drop in the surface area and pore volume with the cycle number. Compared with limestone, the carbide slag exhibits higher SO2 adsorption capacity and similar CO2 adsorption capacity during the cyclic simultaneous CO2/SO2 adsorption.