Research On Optimization Of SNCR Denitration Characteristics And Safety Of Waste Incinerator

At present,the waste incineration power generation method has become the international mainstream waste treatment method,but the secondary pollution caused by incineration is still serious.SNCR technology is widely used in the denitrification treatment of waste incineration flue gas.However,it is faced with the problems of high nitrogen oxide emissions,low denitrification efficiency,large ammonia escape amount and so on,which seriously threatens the environmental safety and human health.Therefore,it is necessary to further study the denitrification characteristics and put forward the optimization scheme.At the same time,as the core device of the incineration process,the waste incinerator may have a variety of failure modes due to the complex working environment,which will affect the safety of the entire system.In view of the above problems,this paper takes a 750t/d waste incinerator in a waste incineration power plant in Guangzhou as the research object,and uses on-site investigation,data monitoring,numerical simulation and other methods to study the denitration characteristics and safety of the incinerator.The main research contents are as follows:The numerical model of incinerator combustion and denitration was established and the physical model was constructed.Fluent was used to simulate the combustion process of gas-phase components,and the distribution state of NO_x was obtained by the post-processing method.Then,the denitration process of SNCR was simulated based on the combustion results,and the variation rules of temperature field,velocity field and group fraction field in the furnace before and after denitration were analyzed.The results show that the temperature in flue area and the average velocity of flue gas in jet plane are slightly increased after denitration.The O₂volume fraction in flue area and outlet decreased slightly,and the NO_x concentration at the outlet decreased from 266.72mg/m³ to 121.11mg/m³,the denitration efficiency was 54.59%,NH₃ was mainly concentrated near the spray gun,and the outflow of ammonia was 7.41ppm.Combined with the actual monitoring data,the accuracy of the numerical simulation is verified.The influences of three distribution parameters and four injection parameters on the denitrification characteristics were studied,and the distribution of NO_x and NH₃,denitrification efficiency and ammonia escape amount in the flue area were analyzed.The results show that the spray height,the length of the spray gun into the furnace,the molar ratio of ammonia to nitrogen and the particle size of liquid droplets have a great influence on the distribution of NO_xand the denitration efficiency in the flue area.When the molar ratio of ammonia to nitrogen is1.6,the escape amount of ammonia exceeds the limit,while the number of spray guns,ammonia water injection speed and Angle have little influence.The optimal conditions are as follows:only the first layer spray gun is opened,the number of spray guns is kept as 7,the spray gun extends into the furnace with 0.75m,the molar ratio of ammonia to nitrogen is set as 1.3,the particle size of liquid drops is 400μm,the spray velocity and Angle are 19.6m/s and 60°respectively.Under this condition,the denitration efficiency is 68.03%,which is 24.62%higher than the original condition,and the ammonia escape is 4.64ppm,which is 37.38%lower than the original condition.After denitration,the flow field,temperature field and reducing atmosphere in the flue area are the important factors that cause the corrosion of water wall.The traditional FMECA method and the fuzzy FMECA method based on AHP-entropy weight were used to analyze the safety of 15 possible failure modes of incinerators.It is found that the thinning of water-wall pipe,the wear of grate plate and the rupture of water-wall pipe are the three most dangerous fault modes,so the safety measures and suggestions are put forward.