| Selective catalytic reduction(SCR)technology was widely used as an efficient and pollution-free denitration technology.The key of SCR technology was efficient catalyst.However,the vanadium based catalysts on the market have low efficiency at low temperature and produce toxic components at high temperature.The cost of precious metals used in molecular sieve catalysts is high,and both technologies were monopolized by foreign countries.Compared with vanadium based and molecular sieve catalysts,rare earth based SCR catalysts have wide activity temperature window,excellent performance,abundant rare earth resources and low manufacturing cost in China.Therefore,the development and application of rare earth based SCR catalysts was more in line with China’s national conditions.In this paper,the catalytic performance of rare earth catalyst and its matching application with diesel vehicle are studied(1)Rare earth catalyst formulation design and mixer optimization.A series of microporous Ce WTi-X catalysts with different proportions were prepared by template method.The rare earth catalysts were characterized by Ce WTi-X activity test,crystal structure analysis and surface element analysis.The catalytic performance and hydrothermal aging resistance of different rare earth catalysts were compared,and the influencing factors of catalytic performance and resistance of rare earth catalysts were analyzed.And then determine the optimal catalyst formula;prepare honeycomb rare earth catalysts with different mesh number and wall thickness,explore the influence of mesh number and wall thickness of catalyst on catalytic performance through experiments,and determine its structural parameters;explore the catalytic characteristics of catalyst through activity test,ammonia storage test and selectivity test,and analyzed the degradation degree of its performance after aging;finally,combined with simulation and bench test The mixer of SCR system was optimized to improve the performance of SCR system.(2)SCR reaction mechanism model building and parameter identification.Firstly,the reaction mechanism of SCR system was introduced.On this basis,the reaction mechanism model of SCR system is built.The effects of temperature,space velocity and ammonia nitrogen ratio on the catalytic reaction of rare earth catalyst are compared and analyzed,and the main influencing factors of catalytic reaction are explored.The kinetic parameters of the model were identified through the experimental data to provide accurate SCR reaction mechanism for the subsequent control system design Model.(3)Simulation and experimental study on control model of rare earth SCR system.Based on the SCR reaction mechanism model,the model predictive control method was used to build the urea injection control model of rare earth SCR system.The controller was designed with urea injection as output,NH3 coverage as input and NH3 escape as constraint input.The target ammonia coverage map was obtained by the rare earth SCR reaction mechanism model simulation,and the urea injection quantity was obtained by the simulation research under the engine WHSC/WHTC cycle condition;the control effect of NOx and NH3 in the rare earth SCR system was verified by bench test,which can meet the national six emission standards.This paper adopts the research method of combining bench test and simulation analysis.The catalytic characteristics of rare earth SCR catalyst are analyzed;the reaction mechanism model of rare earth SCR catalyst and the control model of urea injection quantity are constructed;and the emission verification is carried out on the bench to realize the matching application of rare earth catalyst and vehicle diesel engine. |
