不同煤种及其燃烧特性对NO_x排放浓度的影响

Effect of different coals and their combustion characteristics on NO_x emission

选择了11个不同煤种,分别用4个单煤和4组配煤在1台600MW超临界机组锅炉上进行了低NOx燃烧试验,在其他运行参数相同的条件下,研究入炉煤煤质特性、燃烧特性(热分析)、炉膛温度等与NOx排放浓度之间的关系。结果表明:随着燃料比率的增加,NOx排放浓度逐渐减小,当燃料比大于0.48后,下降趋势趋于平缓,而煤的含N量对NOx排放浓度没有明显影响;煤粉的着火温度对NOx排放浓度没有明显影响,但随着燃尽温度的增加,NOx排放浓度增加,主燃烧器上部区域炉膛温度也增加,说明火焰中心上移;主燃区下部由于还原性气氛减弱、空气分级深度减小、还原区炉膛温度升高等的共同作用,NOx排放浓度呈明显增加趋势。

To study the relationships between coal quality,coal combustion characteristics(thermal analysis),furnace temperature and NOx emission,low NOx combustion experiment in a 600 MW supercritical boiler was conducted,firing four single coals and four blending coal mixtures,with constant operation parameters.The results show that:the NOx concentration gradually dropped with the increasing fuel ratio,and changed smoothly once the fuel ratio exceeded 0.48;the content of N in coal had no significant effect on the NOx emission;the NOx emission changed little with the coal ignition temperature but increased with the raising burnout temperature;moreover,the furnace temperature at upper region of the main burner also increased with the raising burnout temperature,indicating the flame center moved up;due to the weakening reducing atmosphere,reducing air staging depth and increasing furnace temperature at reducing region,the NOx emission showed a dramatic growth tendency.