Process Optimization Of Flue Gas De-NO_x System In Waste-to-Energy And Engineering Application

NO_x produced by waste incinerators has become one of the main sources of NO_x emissions in China.With the emission standard of flue gas raised in China,it is how to reduce NO_x emissions from waste incinerators that has become an urgent and critical problem.In order to reach the emission standard of flue gas NO_x,the existing SNCR De-NO_x system no longer meets the requirement,and the flue gas system needs to be upgraded and an SCR De-NO_x system should be added.In this paper,we use a computational fluid dynamics software,Fluent,to simplify,model,and numerically calculate the system;we optimize the process design of the SCR De-NO_x system and the catalyst thermal regeneration system,carry out a technical transformation,and run them.Our work provides a theoretical base and design reference to advance related devices.In this paper,we model the main equipment of the SCR De-NO_x system with CFD,analyze the influence of the flue gas on the temperature field,velocity field,ammonia diffusion,and pressure distribution in the flue and reaction tower,and optimize the design of SCR denitrification process system as well as the structure optimization and selection of main equipment.The simulation results demonstrate that,with the deflector arrangement and rectifier distribution enhanced,the error of the flue gas temperature is lower than 1.5℃,the disparity of the velocity is 16%,the variance of the flue gas incident angle is 8°,and the pressure difference of catalyst pressure is maintained at about 200Pa.Through structural optimization,the uniformity of the flow field distribution of flue gas in the equipment is better than that of the device before transformation,which is conducive to the blending of flue gas and reducing agent.To deal with the difficulty in controlling the temperature rise of the in-situ regeneration system,the design of the catalyst thermal regeneration system is optimized.Specifically,considering the power of the regeneration fan and the supporting electric heater,the inlet of the circulation pipeline,the thickness of the reactor tower’s insulation layer,and the isolation and heat dissipation points,we seek the balance between air volume and heating power and obtain the optimal device configuration.In accordance with the results,when the circulating air volume is 10000m3/h and the power of the electric heater is 220kW,the temperature in the reaction tower can reach and stabilize at 320℃,which meets the requirement of catalyst thermal regeneration.We technically transform the SCR denitrification system and thermal regeneration system and carry out the comparative evaluation of operation data for 6 months.The outcome of the actual operation shows the effectiveness of flue gas diversion and the ammonia injection device that has been optimized and technically transformed:the temperature error of the flue gas which enters the reaction tower is within 8℃,shown by the temperature measurement;when the SNCR De-NO_x system is running,and the NO_x at the inlet of the SCR system is 250 mg/Nm3,the denitrification efficiency can be smoothly stabilized at about 80%,and the ammonia escape is lower than 3 mg/Nm3,the actual consumption of ammonia water is 29.2L/h,and the outlet NO_x emission value is under 50 mg/Nm3,meeting the current emission standard of national nitrogen.After the optimization and renovation of the regeneration device,the results show that the catalyst regeneration can be completed within 48 hours,which is 48 hours less;after the regeneration system is in operation,the test records of the actual operation data of the SCR DeNO_x system show that the catalyst pressure drop can be reduced by 50%,the NO_x emission at the outlet can be reduced by about 60%,the denitrification efficiency can be increased by 50%,and the consumption of ammonia water can drop by 40%.