Numerical Simulation And Optimization Of Denitration In SNCR Furnace Of 330MW Coal-fired Boiler

At present,China's coal consumption is still dominated by coal-fired power generation,which accounts for 52%of the total coal consumption.The huge amount of coal burning directly leads to many environmental pollution problems that cannot be ignored,among which air pollution is the most serious.Under the environment of more and more strict national emission standards,the emission limits for in-service boiler sets in various provinces are constantly updated.The research object of this paper is a330MW coal-fired boiler of a power plant in Shanxi Province,whose emission value under BMCR condition reaches about 800 mg/Nm³?O₂=6%?.According to the latest announcement of special emission limit of atmospheric pollutants issued by the ministry of environmental protection,the NO_x emission standard of some existing coal-fired boilers in Shanxi Province is only 400 mg/Nm³?O₂=6%?.In order to achieve the reasonable emission value of the research object,considering the characteristics of the boiler in service for a long time,the limited scope of transformation,the original operating results are not suitable for the addition of SNCR denitrification system and so on,an economical,feasible and efficient transformation scheme of low-nitrogen combustion and denitrification in SNCR furnace is proposed.Numerical simulation software ICEM and Fluent were used to simulate the combustion process of the 330MW coal-fired boiler BMCR by combining the actual operation data.Through the analysis found that the boiler temperature calculated values and measured values change trend consistent and reasonable error,the furnace exit flue gas containing NO_x concentration calculation value is 807 mg/Nm³?O₂=6%?,measured in practical operation of emission limits,prove the modeling,model selection and calculation of this study has certain reliability,can satisfy the demand of practical engineering,at the same time there are tangential firing diameter slightly larger,part of the fire wall,furnace flame is full of poor,unable to provide reasonable SNCR reaction temperature window and other issues need to optimize the transformation.Through the boiler primary air vents,burning wind arrangement,different layer burner nozzle jet parameters such as Angle,the wind rate of low nitrogen after modification,the results of the simulation burning again shows that furnace outlet smoke temperature,reduced NO_x levels,which the NO_x emission was reduced by 15%,more stable and tangential firing,flame is relatively good,the temperature distribution more uniform,mean velocity of flue gas furnace top area decrease obviously,the residual rotation range is narrow,creates the SNCR reaction suitable reaction conditions.The denitrification system of SNCR was simulated with the results of boiler combustion calculation after low-nitrogen transformation as the initial environment.In this study,the denitrification characteristics of SNCR were studied using a strict single-variable control method.Results show that the unit SNCR furnace denitration system optimum operation condition for the ammonia nitrogen mole ratio equals 1.4,the boiler 52 m,55 m,58 m in cross section,respectively,set A,B,C three groups of nozzle at the speed of 10 m/s at the same time,the spray droplet size for an average of 90?m,the mass concentration of 10%urea solution,in order to get the furnace exit NO_x emission concentration of 337 mg/Nm³?O₂=6%?,compared with the original boiler NO_x removal efficiency reached 58%,ammonia leakage quantity is about 18 ppm?O₂=6%?,basic meet the discharge standard.