Abstract: In order to improve the flue gas flow uniformity of SCR system,improve the catalytic efficiency of SCR reactor,reduce the erosion and loss of catalyst,increase the service life of catalyst and improve the contact degree of reactants,in this study,the flow field of SCR reactor was simulated and the structure optimization of guide plate and rectifier plate was carried out.The purpose of the study is that through the simulation of velocity field of full scale SCR reactor model,Realizable k-ε model and porous medium model were used to study the effects of diversion plate structure,number of rectifier plates and fly ash deposition on the flow field organization and the air flow uniformity of SCR denitrification system.At the same time,the influence of fly ash particles on the flow field was studied by simulating the particle distribution in the SCR reactor.By calculating the relative velocity deviation of the section in front of the rectifier plate and analyzing the velocity field of SCR reactor under different optimization schemes,the diversion effect of the guide plate and the rectifier plate was evaluated,and then the best scheme was determined.The results show that the " straight arc" guide plate has the best effect among the four kinds of deflector schemes,because the horizontal straight plate and vertical straight plate in front of the arc guide plate can better guide the air flow.According to the geometric characteristics of inclined top design in reactor,the shape optimization of the right guide plate can significantly improve the velocity uniformity,which can significantly optimize the air distribution of flue gas and reduce the energy dissipation at the turning.The rectifier plate in front of the homogeneous catalyst layer can further guide the flow of airflow and greatly improve the uniformity of airflow.However,too many rectifiers increase the gas flow resistance near the wall,aggravate the energy dissipation and velocity inhomogeneity and reduce the rectifying effect of the rectifiers.In this model,the appropriate number of rectifiers is 15.Ultimately,the deviation of upper catalyst velocity is reduced to 6. 68%,which meets the industrial requirements. The analysis of the flue gas particle field shows that the fly ash particles are deposited on the right wall of the flue and the upper wall of the ascending channel,and the necessary fly ash treatment at the particle deposition can reduce the erosion effect of the fly ash on the catalyst.