Study on the kinetics of S(iv) oxidation in the basic aluminum sulfate wet flue gas desulfurization process

Abstract

Through a laboratory-scale bubbling apparatus, the kinetics of S(IV) oxidation related to the basic aluminum sulfate (BAS) wet flue gas desulfurization (FGD) process were investigated by varying the components of the BAS solution, concentration of S(IV), temperature, air flow and oxygen partial pressure. The experimental findings showed that the oxidation rate of S(IV) slightly increased with pH as the basicity increased, while increasing the amount of aluminum could weaken the oxidation rate of sulfite. Moreover, the general reaction rate was found to be 0.21 order in S(IV) and first-order in oxygen, respectively. The apparent activation energy was calculated to be 24.5 kJ mol⁻¹. Combined with the kinetic model of S(IV) oxidation proposed, we found that the general oxidation rate of S(IV) in BAS rich solution was controlled by the mass transfer of oxygen accompanied with a rapid chemical reaction, which was verified by the Hatta number (around 1.4). As a result, the intrinsic kinetics were investigated, indicating the reaction orders with respect to S(IV) and oxygen to be 0.42 and 1.0, respectively. The results would be valuable for process optimization or industrial design during the BAS wet FGD process.