Water Gas Catalytic Reduction Of Sulfur In Sulfur Dioxide Flue Gas Recovery

Sulfur dioxide (SO2) is serious pollutant in the earth's atmosphere in the sense that they are one of the main sources of acid rain and the damage of sulfur dioxide to human being and the environment is getting worse and worse. So to accelerate the step of FGD is gradually important and urgent. Directly reducing sulfur dioxide in exhaust gases to elemental over a catalyst is attractive, because it produces a salable product without any solid waste to dispose of. In this paper, the best catalyst and optimum conditions for reduction of SO2 to sulfur in the flue gas produced in metallurgical was investigated over catalysts of transition metal oxide. Additionally, the mechanism of this catalytic reduction reaction was also explored.Series of transition metal oxide catalyst(sCu,Co,Fe,Ni) were produced by impregnation process with alumina as carrier. The effect of active components, content of active metal, reaction temperature, airspeed, gas ratio, sulfide processing and response time on conversion rate of sulfur dioxide and yield of sulfur were investigated. The effect of rare earth components, content of RE impregnation method of catalyst on catalytic of Fe/Al2O3 was also studied by adding rare earth catalyst.The experimental results indicate that iron oxide catalyst is the best catalyst. The optimal content of ferrous is 14 wt% in the catalyst of Fe/Al2O3 that the yield of sulfur achieves 81.92% when the reaction temperature is 400℃. Conversion rate of sulfur dioxide and sulfur yield were increased with the increase of temperature but selection would deteriorate when the temperature is too high, resulting in decreased yield of sulfur. It's not conducive to the conduct of the response that airspeed is too large or too small and the higher temperature the smaller influence of airspeed. The influence of gas ratio on reaction is great and the ratio of SO2 in the flue gas produced in metallurgical to water-gas should be controlled at about 1.7. Different rare earth imposed different effect on the activity of the Fe/Al2O3 catalyst. Especially, the addition of Sm and Dy greatly improved the catalytic activity. The yield of sulfur over SmFe/Al2O3 was 40.5% higher than that over Fe/Al2O3 at 360℃and the sulfur yield over DyFe/Al2O3 was 26.4% higher than that over Fe/Al2O3 at 400℃. Rare earth plays a role of additives in Fe/Al2O3 catalyst. For SmFe/Al2O3, the content of Sm was optimized to be about 1.0 wt%. The rare earth catalyst prepared with different methods also showed varied activity. The yield of sulfur over rare earth transition metal catalyst follows the order: Sm and Fe solution mixing impregnation>Sm first, then Fe solution impregnation>Fe first, then Sm solution impregnation. The metal sulfide is the active phase for catalytic reduction of sulfur dioxide and the reaction mechanism was proposed to be an intermediate mechanism.