The Study Of TWC Catalytic Removal NOx From Waste Incineration Flue Gas

The increasing production of the flue gas of the refuse incineration power plants not only seriously affects the quality of the environment but also destroys atmosphere, soil, water and other things. NOX is one pollutant of the atmospheric hazards, and is an important factor in the formation of Acid rain, photochemical smog. The traditional flue gas denitrification technologies need classification, and because of the high investment and large area needing, they cannot meet the amount of refuse incineration power plants flue gas increasing and pollution control requirements. As a effective method for NO_x removal, TWC Catalytic Reduction is widely used. So there are very important environmental, economic and social benefits to research and develop the appropriate technology TWC denitrification.In this dissertation, six kinds of Ce_0.5Zr_0.5O₂ /γ-Al₂O₃ samples were respectively prepared by impregnation and co-precipitation, the influence of Ce_0.5Zr_0.5O₂ doping content and preparation methods were studied and system researched combining with BET, XRD, and SEM. Then the complex supports which have better performance were selected out. Finally, XRD and H₂-TPR as the activity judge methods were used to separately investigate and study the optimal selection of the catalysts after optimization. And through the gas distribution simulation waste incineration flue gas composition revealed the simulation under the condition of TWC catalyst for NO_x catalytic removal reaction rule.The characterization results of BET showed that the specific surface area of the supports decline following the increase of Ce_0.5Zr_0.5O₂ doping content, and Ce_0.5Zr_0.5O₂ doping was beneficial to the inhibition of the sintering of the catalysts, particles. Composite supports which contains 30wt%-50wt% Ce_0.5Zr_0.5O₂ were comparatively better at the specific surface area, anti-aging properties and high temperature stability. The series of supports prepared by co-precipitation, no matter fresh or aged, all have lager specific surface area than these which were prepared by impregnation. And at the same time, they also have better anti-aging properties and thermal stability.0.5wt% Pd supported on the composite supports containing 30wt%-50wt% Ce_0.5Zr_0.5O₂ which prepared by impregnation and co-precipitation and then these catalysts were characterized by XRD and H₂-TPR. Comparing the results, the fresh and aged catalysts which were prepared by co-precipitation all had a cubic structure similar to Ce_0.5Zr_0.5O₂ and grains growth to a lesser extent after being aged. The fresh catalysts, whose supports were prepared by co-precipitation, have a certain degree of redox activity. But the redox activity of these catalysts decreased after being aged. This means that this series of catalysts have a better ability of anti-sintering. However the fresh catalysts, whose supports were prepared by impregnation, have dispersing diffraction peaks and incomplete crystal form, and the grains growth to a more extent after being aged. This series of fresh catalysts whose supports were prepared by impregnation have a worse redox active than these whose supports were prepared by co-precipitation. And after being aged at 1100oC, the redox activity of this series of catalysts almost disappeared, indicating that the sintering situation is very serious.The active test of #P5 has studied under the different temperature and the different speed of flow and the different oxygen concentration, to study the conversion of NO_x. The results showed that temperature, speed of flow, oxygen concentration were all gave large influences on the conversion of NO_x. When the operating temperature in 150oC, the oxygen concentration is 10%, the entrance speed of flow establishment is 300mL/min, the gas residence time for 6×10^-4 sec, catalyst activeness achieves gradually best, the NO_x conversion rate could reach 94%. About catalysts for the Pd support on CZA, Composite supports which contains 30wt%-50wt% Ce_0.5Zr_0.5O₂, no matter fresh or aged, are maintained in the solid solution of cubic structure and have the better redox activity. These catalysts can be used during waste incineration flue gas purification.