一次风速对高浓度煤粉预燃式低氮燃烧器性 能影响的数值模拟

The high-concentration pulverized coal burner can stabilize the combustion and significantly reduce N()v emissions,which is a very economical and environmentally friendly combustion technology. Its primary wind speed has a very important impact on the ignition delay in the furnace,the stability of pulverized coal combustion and the N()v emissions. In order to determine the primary wind speed suit¬able for the new high-concentration coal pre-combustion low-nitrogen burner,and provide guidance for the on-site experiment and actual operation of the burner, ANSYS Fluent software was used to simulate and calculate the influence of primary wind speed on the combustion stability of pulverized coal and N()v emissions. In this paper,a grid-independent test was performed first,and a 25 t/h full-scale pulver¬ized coal industrial boiler was tested to verify the accuracy of the model. The numerical simulation results show that the new high-concen¬tration coal pre-combustion low-nitrogen burner can form two recirculation zones in the pre-combustion chamber and the furnace. The re¬circulation zone in the pre-combustion chamber ensures stable combustion of pulverized coal,and the recirculation zone in the furnace re¬duces N()v. When the primary wind speed is too low, the later mixing of primary and secondary air weakens, the combustion of pulver¬ized coal is unstable,and N()v emission increases slightly. Also,when the primary wind speed is too high,the mixing of the secondary air nd the pulverized coal is weakened,and the combustion of pulverized coal is unstable,resulting in a significant decrease in the coke con¬version rate and a significant increase in N()v emissions. The primary wind speed increases from 17 m/s to 20 m/s,and the N()v concentra¬tion in the outlet section increases by about 10%. An appropriate primary wind speed can not only stabilize the ignition and combustion of pulverized coal,but also achieve low N()v emissions. The best primary wind speed of the burner studied is between 14-17 m/s.