Influence Of Annular Separation Secondaryair Of Burner On Flow And Combustion Characteristics Of 30MW Precombustion Chamber Burner

In China,coal is the main energy production capacity,but the products of coal combustion will have a negative impact on the ecological environment.In order to reduce the emission of high nitrogen oxides from coal-fired boilers,Harbin Institute of technology proposed a new type of low nitrogen pulverized coal combustion technology.Its unique arrangement of secondary air separation realizes the staged combustion from the inner diameter of the boiler to the air,which can effectively reduce the emission of nitrogen oxides from the boiler.However,there are few researches on the arrangement of separated secondary air.In this paper,fluent software is used to simulate the basic structure and coal quality parameters of a 30MW low concentration precombustion chamber burner used in a coal-fired boiler,and the selection of parameters is described when using fluent to simulate the influence of flow,combustion and NO_xgeneration characteristics in a30MW industrial boiler,and the independence of the grid is verified.The accuracy of the model selection is verified by comparing the measured data of industrial test with the simulated data at 9mw.By changing the structure parameters of the secondary air nozzle,with the increase of the diameter of the locating circle,the effect of the secondary air on the inward convergence of the mixed flow in the furnace is stronger,and the length of the reflux zone is longer.Moreover,with the increase of the diameter of the locating circle,the temperature change in the furnace is more violent.Combined with the tail outlet parameters,the effect of the diameter of the locating circle of the secondary air on the nitrogen oxides in the tail is smaller,When d=1.29d or 1.43d,the NO_xin the furnace is lower and the burnout rate of pulverized coal is higher,which is the best working condition.With the increase of the number of separated secondary air nozzles,the wrapping effect of separated secondary air on the mixed gas flow in the furnace is stronger,the pulverized coal combustion in the later stage is more uniform,and the combustion is more sufficient,which is conducive to control the formation of nitrogen oxides,When n=32,the burnout rate of pulverized coal is the highest and the NO_xemission is the lowest.The NO_xemission in the furnace decreases by 15.2mg/m³（O₂=9%）,which is the best working condition.Changing the operating parameters of the secondary air separation nozzle,the secondary air separation rate has little effect on the mixing of the precombustion chamber and the secondary air separation.With the increase of the secondary air separation rate,the nitrogen oxide concentration in the furnace becomes lower and lower.When the secondary air separation rate is 55%,the nitrogen oxide concentration in the furnace decreases significantly,28.2mg/m³（O₂=9%）.With the increase of the temperature of the secondary air,the area of the high temperature area in the furnace increases gradually,and the combustion with the return flue gas is more sufficient,and the NO_xemission in the tail is lower.When the air temperature is 573K,the NO_xin the furnace decreases by 13.5mg/m³（O₂=9%）.The results show that the best condition is55%of the secondary air separation rate and 573K of the air temperature.Considering all the factors,it is recommended that when d=1.29d or 1.43d,32pieces of secondary air are arranged,the air rate is 55%,and the air temperature is 623k,the staged combustion effect of pulverized coal in the furnace is the best,and the nitrogen oxide concentration of pulverized coal at the outlet is the lowest,which is the best working condition.