Research And Optimization Of Internal Strucre Performance Of SCR System

With the increasingly strict emission regulations at home and abroad,energy conservation and emission reduction are imperative.The emission requirements for nitrogen oxides（NO_x）in diesel engine exhaust are very strict.Due to the excellent performance of diesel engines,they are widely used in industries,agriculture,navigation,and aerospace,resulting in a sharp increase in the amount of NO_x emitted by diesel engines.In order to reduce NO_x emissions,countries around the world are adopting various internal and external post-treatment technologies.Among these technologies,selective catalytic reduction（SCR）technology can be used as a relatively mature technology for treating NO_x emissions.Due to the limited installation space of the SCR system,high cost of catalyst use,and low denitrification efficiency,it is particularly important to improve the performance of the SCR system and save economic costs.This article analyzes the characteristics of SCR reaction,studies and optimizes the internal structure of the SCR system,and identifies key factors that affect SCR performance,in order to improve the denitrification performance of the SCR system,reduce pressure drop,and reduce the amount of catalyst coating.The main content and innovative points of this study are as follows:（1）Firstly,based on the understanding of the reaction mechanism of SCR system and the main factors affecting SCR performance,a single channel reaction model of SCR reactor was established by using computational fluid dynamics（CFD）simulation software.By changing the shape of a single channel in the SCR system,the effect of different shapes of single channels on the flow,heat transfer,mass transfer,and denitrification efficiency inside the channel is studied.The relatively optimal channel shape with performance is determined through comprehensive comparison and analysis.The results indicate that compared to other channels,circular channels have better mass and heat transfer performance.In addition,the influence of channel shape,NO/NO_x,and channel inlet velocity on the performance of the SCR system was analyzed through orthogonal experimental methods.The results indicate that the channel inlet speed has the greatest impact.（2）Then,on the basis of studying single channels,study the performance of a complete SCR reactor.By establishing a radial non-uniform catalyst coating model for the SCR system,the catalytic reaction area was radially divided into three different regions.The effect of changing the radial coating distribution of catalysts in each region on SCR denitrification performance and pressure drop was studied.This chapter uses response surface methodology to optimize the structural parameters of a multi parameter SCR reactor,with the objectives of denitrification efficiency and pressure drop.The optimal combination of structural parameters for the optimized reactor:the radius R₁ of region 1 is 50mm,the radius R₂ of region 2 is 100mm,and the porosity isε₁ is 0.47,porosityε₂ is 0.7.Its de-NO_x efficiency increased by 3.74%and the pressure drop decreased by 15.75%compared to the uniform distribution of catalysts.（3）Finally,investigate the effect of axial non-uniform distribution of catalysts on the performance of SCR systems.Divide the SCR reactor into two support reaction sections axially,keeping the total reaction zone length unchanged,and achieve the axial non-uniform distribution of the catalyst by changing the axial length and porosity of the two supports,in order to study the impact of the axial non-uniform distribution of the catalyst on the performance of the SCR system.Use the fuzzy grey correlation analysis method to calculate the comprehensive effect of the axial length and porosity of the dual carrier on the pressure drop and denitrification efficiency of the SCR system.The results indicate that the axial length l₁ of the carrier has a significant impact on the de-NO_xefficiency,and the carrier porosityδ₂ has a significant impact on pressure drop.In this paper,this article proposes an optimization plan to improve SCR performance by studying the internal channel shape of the SCR system and the non-uniform coating of the catalyst.This study can provide theoretical and engineering references for the design of SCR channels and the improvement and progress of catalyst coating processes.