Research On Catalyst And Urea Control For Selective Catalytic Reduction

SCR technology has been considered as the most effective method of purification of NOx. However, vanadium-based SCR currently has widely used as the SCR catalyst currently. Although the performance of vanadium-based SCR catalysts are very good, vanadium belongs to a highly toxic substance, and the efficiency of vanadium-based catalyst is bad at very low and high temperature in the SCR reaction. It makes the replacement of the SCR catalyst to be a research hotspot all over the world. And the zeolite SCR catalyst is the highlight in SCR catalyst field. It has a very wide temperature window and good thermal stability, so it is considered to be the most potential selection for the SCR catalyst.In this paper, the SCR catalyst types and catalyst characteristics are studied at first. And the SCR reaction principle is also analyzed. Then the zeolite SCR catalyst is researched by the engine test. It is analyzed the impact for different temperatures and NH3/NOx molar ratio to reduce NOx emissions. And the test is focused on the impact of different temperature and NH3/NOx molar ratio to the NOx conversion efficiency when the catalyst is under the a stable catalyst airspeed (40000h-1), and the temperature is at200℃,250℃,300℃,350℃. It is also analyzed the impact of the operating temperature of diesel engine and NH3/NOx molar ratio to the SCR NOx conversion efficiency. And the zeolite catalyst ammonia storage characteristics pilot is also researched by the engine test in this paper. By the contrast test result of vanadium-based catalyst, the injection quantity of urea and NOx conversion efficiency of the zeolite catalyst are analyzed. According to the GB17691-2005, the NOx emission performance of original diesel engine is researched. The NOx emission values and the supply of urea solution at different ESC conditions is obtained by the engine emission experiment, and the urea control strategy of vanadium-based catalyst and zeolite catalyst which can be meet the national IV/V emission regulation is obtained. The zeolite SCR catalyst is researched on the engine test, and the impact of different temperatures and NH3/NOx molar ratio for the performance of zeolite catalyst are analyzed. The NOx conversion efficiency of the zeolite catalyst is also analyzed.The result of this paper, which is about the research of zeolite SCR catalyst and the urea control strategy, has a guiding significance for the zeolite SCR catalyst popularizing in the future domestic market. And it also has a engineering significance in purification of NOx.