;The low nitrogen combustion technology of pulverized coal pre-combustion can balance stable combustion and NOx emis-sion control,which has great application potential in the field of flexible peak shaving and stable combustion of coal-fired boilers.Based on the 5 MW combustion test rig,the operation performance of a high-concentration pulverized coal pre-combustion low-nitrogen burner with a small pre-combustion chamber developed by the authors'team was studied.The effects of primary air rate,internal and external seconda-ry air distribution and separate over-fire air(SOFA)on the combustion performance and pollutant emission of the burner were systemati-cally studied by CFD numerical simulation.The combustion model was verified by the test results of the 5 MW combustion test rig.The maximum deviation between the actual temperature and the numerical calculation results is 44 ℃,and the error range is±3.3%,which proves the accuracy of the selected combustion model.The results show that the primary air rate is the key factor affecting the backflow zone of the pre-combustion chamber,and too low or too high primary air rate will affect the combustion stability and nitrogen reduction ability respectively.Under the condition of 8.8%primary air rate,sufficient backflow can be guaranteed,which is conducive to the ignition and emission control of pulverized coal.Increasing the internal secondary air rate can entrain more high-temperature flue gas in the fur-nace,which is conducive to the burning of pulverized coal.However,the increase of the high-temperature oxidizing atmosphere area in the furnace will lead to the increase of pollutant emission.The internal secondary air rate of about 43.5%can both stabilize combustion and re-duce nitrogen.Replacing the external secondary air with an appropriate proportion of SOFA can make the nitrogen-containing compounds in the combustion area more easily reduced,thus reducing emissions.At 23%SOFA rate,a significant nitrogen reduction effect was ob-served,with NOx emissions of 72 mg/m3(6%O2),a reduction of about 67%compared to 0%SOFA rate.
pre-combustion low nitrogen combustionburnerair distribution optimizationnumerical simulationNOx emission