Study On Flow Field Simulation And Optimization Of SCR Denitrification Unit

With the accelerating economic and industrialization,the air pollution problem has become increasingly prominent,and the country has put forward higher requirements for the NOx emission index of coal-fired boilers.The original coal-fired boiler emission index of the company fail to meet the new requirements.Therefore,the denitrification reform is carried out.The focus of the transformation is to increase the SCR denitrification reactor.This paper uses the computer-aided analysis technology and the actual operation data to run the SCR denitrification reactor.Numerical simulations and analysis of denitrification effects are presented,and improvements are proposed for operating conditions.The model of the SCR denitrification reactor is modeled and networked,and then numerically simulated.The main analysis and improvement results are as follows:The speed deviation is 34.3%on the first layer of catalyst under the condition of the reactor empty tower.Then the original design scheme is numerically simulated.It is found that the inlet flue velocity deviation of the first layer of catalyst is significantly lower than that of the empty tower,but it was still high about 25.8%;Improvement,The speed deviation is 12.1%by improving the rectifier grille.It meet the engineering requirements.At the same time,the simulation results are compared with the actual operation results.The comparison find that both errors are within the specified range,indicating that the analysis results have practical significance.By analyzing the velocity and ammonia distribution of the variable cross-section of the flue gas,the results show that the velocity deviation and the ammonia concentration are greatly deviated,showing an "n" type variation,and the fly ash wears the deflector easily.Using the improved SCR denitrification reaction model,the mixture transport model and the finite rate chemical reaction model are used to simulate the mixing reaction of ammonia gas and flue gas,and the inlet section of the first layer of the catalyst layer under the same speed and improved adjustment is studied.The distribution of mass is found to be equal to a speed deviation greater than 5%,and the deviation after improved adjustment is less than 5%.Catalytic reactions are simulated for both cases.After the catalytic reaction,the ammonia slip amount is reduced from 3.2 ppm to 1.9 ppm,and the denitration efficiency is from 82.4%to 83.5%.Through the discrete phase model,the influence of particle diameter on the trajectory is studied.It is found that particles with a larger particle size are likely to be concentrated on the rear wall of the catalyst inlet,and the deposition density on the upper,middle,and lower catalysts is approximately the same,mainly concentrated between 14.3 and 42.2 g/m3,and the local area exceeds 112 g/m3 provides the basis for the arrangement of soot blowers.A "U" shaped flue appear at the tail of the SCR denitrification reactor and a significant fly ash deposition occur,which result in blockage of some of the flue.The ash bucket or other measures are installed at this place to remove the deposited ash in time.