Experimental Investigation On Emission Of 300MW Dual Register Swirl Burner Pulverized Coal Boilier

The research of this thesis is based on a 300 MW sub-critical boiler with natural water circulation from unit 10 in a power plant in Hebei province.The boiler adopts wall fired combustion technology with dual register swirled burners.According to the comparison and analysis on the test data before and after the low NO_x retrofit,we can get the variation relationship between the coal characteristics and the changes of boiler furnace gas temperature and boiler exit gas temperature.Meanwhile,the research on the boiler efficiency and NO_x emission based on the oxygen content,the upper tertiary air ratio,the boiler load,the OFA flow ratio,the secondary air ratio,the OFA louvers opening,mill operation mode and the coal fineness was also executed.Based on the theoretical and experimental analysis,a new effective technique to reduce the NO_x emission is proposed.The test data is obtained by cold and hot state experiments.The measurements and analysis for flue gas emission characteristics,furnace flue gas temperature distribution and boiler thermal efficiency were executed under the various conditions,then the the variation relationship between the boiler efficiency and the characteristics of flue gas emission were obtained.By adjusting the oxygen content,the tertiary air ratio,the boiler load,the OFA flow ratio,the secondary air ratio,the OFA louvers opening and the fineness of the pulverized coal,the optimized boiler efficiency and NO_x emission can be obtained.Before the retrofit,the NO_x emissions at two airheaters outlets are 1073mg/Nm~3 and 1099.9 mg/Nm~3,after the retrofit,the NO_x emissions at two airheaters outlets are 933mg/Nm~3 and 952mg/Nm~3.The NO_x emissions has been reduced a lot,although it still did not achieve the target.The reason is that the increase of the nitrogen content and the fineness of pulverized coal cause the increase of NO_x emission.Based on the test data analysis,an effective technical method to reduce the NO_x emission is defined as follows: removing the refractory belt in lower burner furnace area to reduce the furnace temperature level and avoid slagging;raising the OFA nozzle location to reduce the excess air coefficient in the reduction zone.Based on the above methods,the NO_x emission can be optimized to the guarantee value.