Oxidation Macrokinetics of Sulfite in the Zinc-Based Wet Flue Gas Desulfurization Process

Abstract

The zinc oxide method is one of the most popular flue gas desulfurization processes, especially for the control of low-content sulfur dioxide. In this process, zinc sulfite can be oxidized to form a soluble zinc sulfate, which can solve the problems of scale formation and pipe plugging. This paper aims to study the oxidation kinetics of zinc sulfite in the zinc-based wet flue gas desulfurization (FGD) process by varying the zinc sulfite concentration, initial pH, oxygen partial pressure, temperature, stirring speed, gas flow rate, and particle size. The oxidation results indicate that there is a critical sulfite concentration of 7.5%, below which the reaction rate is 0.32 order dependence from sulfite, while above which the order turns to −0.78. Meanwhile, the reaction rate is 1.0 order in the oxygen partial pressure. The initial pH and particle size have little effect on the oxidation rate, while the oxidation rate increases with the stirring speed, gas flow rate, and temperature. Moreover, the apparent activation energy is calculated to be 15.85 kJ·mol−1. Integrated with the kinetic model, it is concluded that the oxidation rate of zinc sulfite is controlled by the mass transfer of oxygen in the liquid phase.