Fundamental study of heterogeneous KCl sulfation under oxy-fuel combustion conditions

Under oxy-fuel combustion condition, SO2 in the flue gas would be accumulated by recirculation, which is conducive to the heterogeneous sulfation reaction of alkali metals. In the present study, experiments were conducted in a fixed bed to investigate the effects of operating parameters and mineral additives (SiO2, CaO, and Fe2O3) on the heterogeneous sulfation of potassium chloride under oxy-fuel combustion atmosphere. According to the results here, the heterogeneous sulfation reaction was a kinetically controlled process, with the activation energy of 93.6 kJ/mol. The reaction orders with respect to SO2, O-2, and H2O were determined as 1, 0.6 and 0 (H2O involved in the reaction). While the reaction would be promoted obviously in the absence of H2O. The rate law of heterogeneous sulfation of potassium chloride was derived based on the experimental data. Compared with air combustion, the heterogeneous sulfation rate was lower under oxy-fuel combustion. All the mineral additives employed would affect the sulfation reaction. The sulfation reaction can be catalyzed by Fe2O3. While CaO would suppress the reaction by competing for SO2 with KCl. The reaction between CaO and SO2 could also be catalyzed by Fe2O3. Besides, SO2 was more reactive towards CaO than KCl.