Experimental Research On Low NO_X Combustion Technology Reform By SOFA Method Of A 420t/h Boiler

With the acceleration of industrialization process and the development of the power industry, the consumption of coal was increasing year by year. The combustion of fuels generate more and more NO_X emission, which can lead to serious atmosphere pollution. Control of the combustion and pollution of power plant were important for the sustainable development of our country.A Corner-tangential-boiler of 420t/h in Xiaoshan thermal power plant was studied in the thesis by means of experiments and field tests and numerical simulation, then the low NO_X Combustion Technology reform sheme by SOFA method was designed.Through the method of the thermo gravimetric analysis, studied the factor that influencing the coal combustion characteristic, including the ignition and combustion characteristic, analyzed the coal kind and elevation of temperature speed. The results revealed that the ignition temperature,steady combustion numeric and burnout index of different coal types had obvious difference.The ignition-temperature of dahun35002 was 363°C ,which was the lowest one of the coal samples, The ignition-temperature of dahun35007 was 424℃,which was the highest one of the coal samples,the discrepancy between them was greater than 60℃;The law of steady combustion numeric was the same as The law of ignition-temperature. The burnout index of dahun35007 was 145.31, which was the highest one of the coal samples,the burnout index of dahun106 and zhunhun was 120.31 and 124.40 respectively,The Combustion Efficiency of dahun35002 was the poorest, The burnout index of it was only 71.03.The Experimental Investigation on the influence of different excess air factor and temperature on the NO_x emission characteristics of different coal types was carried out on subsiding furnace, and their causes analyzed. By comprehensive consideration of NO_x emission and the coke burnout,the excess air factor in the main combustion zone was controlled at 0.85.When the furnace temperature was over 1300℃,the NO_x emission was greatly increased either in the oxidizing atmosphere or in the reducing atmosphere,so the temperature of main combustion zone had best controlled below 1300℃.Hot state tests on the NO_X emission of the boiler was carried out. When the boiler operated at low load,the oxygen concentration was over high,then causing NO_X emission too highly.When two coal mills operated, Tertiary-Air Coal Rebuming reduced NO_X Release.When the oxygen concentration was below 3%,NO_X emission increased greatly as the oxygen concentration rised. When the oxygen concentration was above 3%,the increasing rate was easting up.For the existing burner, pulverized coal distribution had little influence on NO_X emission. Ensuring primary air Stable,on this premise,low primary air velocity can lower the NO_X emission. For the existing burner, optimizing air distribution only had limited influence on NO_X emission.Based on the test result,two low NO_X and combined with practical boiler operation,two low NO_X reform schemes was desighed,then a predicton of reform scheme combustion and NO_X emission was made by numerical simulation.The simulation results showed that the boiler operated stably; the temperature field was uniformity; complete combustion was reached, NO_x emission reduced greatly,and the scheme one had better reconstruction effect than the scheme two.