Efficient Inhibition of S(IV) Oxidation in a Novel Basic Aluminum Sulfate Regenerative Flue Gas Desulfurization Process by Ethylene Glycol: Kinetics and Reaction Mechanism

For the regenerative flue gas desulfurization method based on basic aluminum sulfate (BAS), efficiently inhibiting the oxidation of desulfurization by-products is extremely critical to reuse the absorbents and recover SO2. In this paper, the macrokinetics of S(IV) antioxidation procedure was systematically investigated by varying inhibitors, aluminum content, pH, S(IV) concentration, ethylene glycol (EG) concentration, temperature, oxygen partial pressure, and air flow in a bubbling reactor with magnetic stirring. EG was environmentally considered to be an ideal inhibitor by screening. Furthermore, the S(IV) oxidization speed inhibited by EG was significantly accelerated when the aluminum content rose and was correlated to 10(-0.6pH) with a coefficient of 0.98. The general oxidization speed of S(IV) was determined to be 1.1, -2.4, and 0.96 order in oxygen partial pressure, EG content, and total S(IV) level, respectively. The apparent activity energy of S(IV) oxidation process was obtained to be 52.0 kJ/mol. On the basis of a two-step model, kinetic analysis proved that the general S(IV) oxidation rate in the BAS desulfurization liquid was decided by the intrinsic oxidation reaction. Meanwhile, the mechanism of S(IV) oxidation reaction with EG was demonstrated and the products in reaction solution were detected by gas chromatography-mass spectrometry. The experimental findings will contribute to industrial design and procedure optimization related to the BAS regenerative desulfurization process.