| The controlling of SO2is a difficulty point of the controlling of air pollution in our country. Wet desulfurization is a kind of common flue gas desulfurization technology which mainly includes:Sodium process, wet limestone/gypsum method, ammonium method, magnesium oxide method, etc. With the promotion of wet sulfur removal technology, the dealing problems of their by-products such as calcium sulfate, sodium sulfite, magnesium sulfate and ammonium sulfate have became the hot issues of the research in the field. Among them, the sodium process is an efficient technology which has no fouling, congestion problems fit for the desulfurization of small and medium-sized industrial boilers. There is theoretical and practical significance for the design and operation of wet desulfurization process system to research the oxidation reaction kinetics of its by-products-sodium sulfite under restrain conditions.Using laboratory bubbling reactor, the catalyzed and inhibited oxidation kinetics of sodium sulfite, magnesium sulfite, calcium sulfite and ammonium sulfite were studied respectively, emphasizes investigated the inhibiting oxidation dynamics of sodium sulfite.In study of inhibited oxidation kinetics, effects of six additives, such as ascorbic acid, tea polyphenol, hydroquinone, pyrocatechol, alcohol and sodium hyposulfite on the oxidation rate of different sulfite were studied respectively. It indicates that ascorbic acid has the most significant effect on the oxidation rate of magnesium sulfite, sodium sulfite, calcium sulfite and ammonium sulfite. In the research of inhibited oxidation reaction kinetics of sodium sulfite, tea polyphenols was an efficient inhibitor which was safe and non-toxic had good inhibition effect which was only second to ascorbic acid.On the base of above screening experiments, macroscopic oxidation kinetic and mechanism of sodium sulfite in presence of tea polyphenols was investigated by varying pH, inhibitor concentration, sodium sulfite concentration, oxygen partial pressure, airflow rate and temperature. The results indicate that the general reaction process was greatly influenced by tea polyphenols, oxygen partial pressure and temperature. The reaction orders for tea polyphenols, oxygen partial pressure, and magnesium sulfite are-0.46,1.96, and1.13respectively, and the apparent activation energy is13.095kJ.mol-1. Integrated with the three-phase reaction model, the general reaction rate was deduced to be controlled by the intrinsic reaction. In addition, effects of five additives including cobalt sulfate, manganese sulfate, copper sulfate, nickel sulfate. and ferrous sulfate on the oxidation rate of different desulphurization. byproduct were compared. The results show that cobalt sulfate is the most effective catalyst in the three sulfite oxidation systems including magnesium sulfite, sodium sulfite, and ammonium sulfite. However, manganese sulfate is the most effective in calcium sulfite oxidation system.The results showed that the additives were selective in different kinds of sulfites oxidation reaction system. It might be due to the cationic ions in sulfite that participate in the chain reaction. The regulation mechanism of the selectivity was analyzed in this theory. |
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