Study On Catalytic Oxidation Of SO₂ In Flue Gas By Thiobacillus Ferrooxidans

FGD (Flue Gas Desulfurization) is one of the most important methods for SO₂ pollution controlling. Flue Gas Desulfurization by microorganism, with advantages of flexible operational conditions, low cost, no secondary pollutions, etc., will be a new developing direction of FGD technologies.T.f (Thiobacillus ferrooxidans) is one of the most important bacteria species in biological desulfurization for its dual oxidation property. In the recent, most of the studies are still focused on the theoretical study. Based on biologically desulfurizing theory, this paper studied the effects of different reaction conditions to desulfurizing efficiency and acid-producing action, the reaction mechanisms of catalytic oxidation of SO₂ by T.f, the optimal reaction conditions and the reaction kinetics, for prompting biological desulfurizing technology to a great progress.Contrasting desulfurizing effects of pure water, water containing Fe²⁺, water containing Fe³⁺, bacteria liquor and bacterium culture medium liquor, it can be conclude that T.f has the capacities of direct biologic oxidation and indirect catalytic oxidation property to SO₂, T.f can directly oxidize low-valence sulfur into SO₄^2-, meanwhile, under acid conditions, can quickly oxidize Fe²⁺ into Fe³⁺ which increase the catalytic oxidation capacity of SO₂. After further study on single factor-based experiments, the results indicated that desulfurization rate can be affected by the operational conditions, such as the initial concentration of Fe³⁺, the initial concentration of Fe²⁺, the concentration of SO₂, the reaction temperature, and the ratio of liquid and gas etc., Perfect desulfurization effect can be only obtained in proper temperature (30℃⁴0℃) and pH. So, selecting and taming more adaptiveand steady T.f is absolutely necessary to increase desulfurization effect. The higher initial concentration of Fe3+and Fe2+, the more effective of desulfurization, which shown that indirect catalytic oxidation by T.f play dominate role in the process of catalytic oxidation of SO2.In the end, a reaction kinetics equation that can be used in the system of T.f and Fe3+ cooperative catalytic oxidation of SO2 is given out:2--r = d[S°4 ] = 11.236x 10-5[Fg3+]035[S<942-]005 dtThe given equation can effectively describe acid-producing characteristics, with the existence of T.f, in the process of Fe catalytic oxidation of SO2.