Research On Furnace Characteristics After DeNO_x Burner Retrofit For 660MW Supercritical Pressure Boiler

In this paper,the combustion process in four tangentially fired furnace of a 660 MW supercritical pressure boiler is simulated by using the fluent numerical simulation software,and the simulation results are analyzed in various conditions,the process of data analysis combine with the actual operation,some problems are pointed out in the process of simulation,and the results can more truly reflect the running state of the boiler.Firstly,Gambit software is used to carry out the full scale modeling of the boiler body.In view of the four corner tangential combustion mode,the grid is divided in different regions and the grid direction is consistent with the direction of pulverized coal jet.The occurrence of pseudo diffusion is effectively reduced in this method.According to the boiler furnace type,the arrangement of the burner and the distribution of wind,as the basis for selecting the mathematical physical model.Among them,the turbulence model use RNG k-epsilon mode.The Lagrange method is used to solve the problems in the process of gas solid two phase turbulent flow.A stochastic trajectory model is used in the tracking of pulverized coal particles,equilibrium mixed fraction /PDF model is used in the volatile combustion model,coke combustion model is a kind of kinetic / diffusion reaction rate model.Radiation heat transfer model is the P-1 radiation model.The method of post-processing is used to calculate the NO_x generation.The results of combustion simulation under different working conditions include the velocity field,concentration field of oxygen,carbon dioxide,NO_x and temperature field in the furnace under three different kinds of load.The flow and combustion characteristics of different zones in the furnace are analyzed under three conditions,the results indicate that a thermal deviation phenomenon exists in the lower wind zone under full load and the pulverized coal flow flush the walls in the upper CFS wind zone.Changing the oxygen content in the furnace,analyzing the combustion conditions of the four kinds of excess air coefficient,comparing the speed field and temperature distribution in the furnace under the four conditions,and find out the appropriate excess air coefficient is 1.15.Changing the SOFA horizontally offset angle will reduce the coking problem near the heated surface and improve the steam temperature regulation performance.The NO_x concentration in the furnace and outlet will be reduced within certain range through decreacing the baffle opening of CCOFA and CFS.In this paper,various conditions are simulated,and the results are analyzed objectively,and the analysis results are compared with the measured data and the actual operating conditions,the simulation results can reflect the actual situation.It provides practical reference value for the combustion adjustment of supercritical pressure boiler and reduction of NO_x.