Non-catalytic oxidation kinetics of calcium sulfite in wet limestone-gypsum FGD process

A study on non-catalytic oxidation kinetics of calcium sulfite is presented under typical conditions of wet flue gas desulfurization (FGD). A laboratory-scale mechanically stirred tank reactor is used with continuous feed of both gas and liquid phase. The results show that increasing CaSO₃ load from a lower value, the reaction rate increases and is limited by solid sulfite dissolution. The oxidation rate limitation is observed at loads exceeding certain concentration. The rate limitation is possibly caused by solid sulfite solubility or oxygen gas-liquid diffusion. The experimental conclusions are useful for design and operation of the holding tank in forced-oxidation wet FGD.