Mechanism and Effect of a Phenol Inhibitor on the Oxidation Kinetics of Magnesium Sulfite

Magnesium sulfite oxidation is an important step in the wet magnesia flue gas desulphurization process. In this paper, a novel phenol inhibitor, T, is selected by comparison experiments that could slow down the oxidation rate of magnesium sulfite greatly. Effects of inhibitor concentration, magnesium sulfite concentration, oxygen partial pressure, pH and temperature, on the oxidation rate were studied under the condition close to the practical. The results show that the reaction orders for inhibitor T, dissolved oxygen and magnesium sulfite are -0.25, 0.5 and 0, respectively. And the apparent activation energy is 48.2 kJ.mol(-1). Integrated with the three-phase reaction model, the general reaction process was deduced. It is concluded that the intrinsic chemical reaction takes place in the poor oxygen zone and the general reaction rate is controlled by the oxygen diffusion. Compared with the results under the uninhibited conditions, the presence of T delays the intrinsic reaction rate, resulting in the decrease of oxygen diffusion rate. Thus the result provides a useful reference for recycle of byproduct by inhibited oxidation in magnesia desulphurization.