Numerical Simulation And Optimization Of SCR Reaction

So far, thermal power is an important component of the power source in China.In the case of environmental protection has become increasingly harsh,the requirement of the flue gas denitrification becomes higher.SCR denitrification is a technology,which is efficient,cost-effective,applied widely. Catalytic reaction is the most important in the SCR denitrification technology.Study influence factors of SCR reaction will be of great importance.This paper focus on the SCR reaction,the reaction kinetics and process with Comsol software and Aspen software were used to research it:(1)Side reaction were increased on the basis of the standard reaction,reaction kinetics was simulated and examined firstly for simulating three-dimensional channel,then kinetics,heat and mass transfer, and flow distribution were coupled on three-dimensional channel,building model.Investigating the effect of temperature,smoke flow speed,mole ratio of NH3/NOx,and channel volume on the efficiency of denitrification and optional parameters.Temperature and concentration distribution on the different cross section were analyzed. Optimum mole ratio of NH3/NOx is1.1,optimum reaction temperature is about 650 K.(2)The effect of shape parameters of catalyst on the denitration efficiency was studied.Shape parameters of catalyst are orifice throat length and channel diameter.Efficiency of denitrification is proportional to surface area of catalyst.Reaction has finished at 300 mm orifice throat length.The length of channel increase of 100 mm, the efficiency increased by about 4%.The length of channel diameter increase of 2mm,the efficiency increased by about 10%.After the simple shape simulation,velocity and reaction rate as the optimization objectives respectively,the optimization was carried out using SNOPT method.Finally, the optimized regular shape is obtained.(3)The SCR reaction was simulated in the view of the process.Firstly,simulated SCR reactor using Aspen software,analyzed the effect of different operating parameters on the efficiency of denitrification.Reactor in the radius of 0.5m, the length of 1 meters will be able to complete the reaction. The effect of oxygen content greater than 10% on the efficiency of denitrification is weakened.When the oxygen concentration is greater than 15%, there is no effect. Different physical methods have effect on the efficiency of denitrification,especially UNIFAC.With the increase oftemperature, the efficiency of denitrification increases first and then decreases, the optimal value is about 520 K. The higher the parameter P value of the PID dynamic simulation, the better the control,the higher the I value, the greater the deviation,faster to achieve stability. With the control of the reactor, the reactor concentration tends to be uniform.(4) The effect of operating parameters on the efficiency of the denitration efficiency was studied with the fast SCR reaction,especially the NO2 content,also including the effect of oxygen content, and water vapor content on the efficiency of denitrification.When the concentration of O2 was more than 2%, there was nearly no effect on the denitration efficiency.However, when the oxygen concentration is less than 2%, the denitrification efficiency of SCR increases with the increase of the concentration of oxygen.The denitrification efficiency of SCR decreases with the increase of the concentration of water vapor.with the enough NH3.When the molar ratio of NO2 to NO is 1, the efficiency of denitrification is optimal.