Experiment Studies Of Flue Gas Desulfurization By Coal Slurry Catalytic Oxidation

Based on aqueous catalyzed oxidation, coal slurries were used to remove SO₂ from flue gas and, simultaneously, the content of pyrite sulfur in coal was reduced through the reaction between SO₂, O2 and coal pyrite. The catalyst, Fe³⁺/Fe²⁺, was produced in situ by leaching of coal pyrite. The coal was dried, smashed and screened. The particle size of coal used for the flue gas desulfurization(FGD) experiments was 0.20⁰.60mm. The influences of temperature, SO₂ and O₂ concentration on SO₂ removal efficiency and on the leaching of coal pyrite were studied. The coals used included high-sulfur raw-coal, low-sulfur raw-coal and middling coal.The result of high-sulfur raw-coal experiment showed that the SO₂ removal efficiency increased rapidly with the increasing of reaction temperature when it was below 40℃. However, SO₂ removal efficiency was not greatly influenced by temperature when it was above 40℃. As SO₂ concentration increased, the removal efficiency decreased, which was similar to that in wet limestone/lime FGD process. The removal efficiency was not greatly influenced by O₂ concentration, and, when O₂ concentration was in the range of 3%²0%, the removal efficiencies were all above 90%. So the O₂ concentration in actual flue gas can meet the demand of catalyzed oxidation.The pH value gradually decreased in the process of desulfurization. Especially, it decreased faster in the first 30 minutes. The fall of pH value increased as the concentration of SO₂ increased. Similarly, the amount of leached pyrite increased as the amount of SO₂ removed increased. So the coal pyrite sulfur can be decreased through flue gas desulfurization process.The experiment results of low-sulfur raw-coal slurry showed that, when the SO₂ concentration was 1520×10^-6 and the temperature was 20℃, the removal efficiency decreased as the reaction time was prolonged, which was consistent with that of high-sulfur raw-coal experiment. However, when the reaction temperature was increased to 42℃, the removal efficiency maintained above 97%. The variation of pH and the leaching of pyrite were similar to that of high-sulfurraw-coal experiments.Middling coal could also be used to removal SO2 from flue gas. When the SO2 concentration was 1370><10"6 and the reaction temperature was 42 °C, the removal efficiency maintained above 99.5%. The coal pyrite was continuously leached as the FGD process proceeded. The effect of the fall of pH value on SO2 removal was also slight.