解耦燃烧技术在煤粉工业锅炉高速燃烧器中的应用研究

Applied research of decoupling combustion in pulverized coal industrial boilers equipped with high-speed burner

煤粉解耦燃烧降低NO_(x)排放的同时能够保持较高的燃烧效率,但存在着飞灰残碳随着过量空气系数降低而升高的现象,即飞灰含碳量仍超过10%,因此采用数值模拟的方法拓展解耦燃烧在煤粉工业锅炉高速燃烧器中的应用范围。以高速煤粉燃烧器作为研究对象,先从理论上研究焦炭氮集中释放与还原的煤粉解耦低氮燃烧关键技术,再采用数值计算的方法对比10种不同的工况,重点研究二次风温度、旋流强度、二次风过量空气系数等常规参数对燃烧器内燃烧的影响。研究发现:高速煤粉燃烧器解耦燃烧需进一步提高燃烧器内的碳转化率以降低氮氧化物排放,提高旋流强度和二次风温度均有利于提高燃烧器内的碳转化率;当过量空气系数降低时,燃烧器内的还原性气氛增强且碳转化率降低,提高一次风量至15%则燃烧器内碳转化率可达到99%,能够保证焦炭氮快速集中释放。

Pulverized coal decoupling combustion can reduce NO_(x) emission and maintain high combustion efficiency while the residual carbon in fly ash increases with the decreasing of excessive air coefficient.In fact,the residual carbon content of fly ash is still more than 10%,so numerical simulation method was applied to study decoupling combustion technology which would expand the using scope of pulverized coal boilers’s high-speed burner.Firstly,it was theoretically illuminated that the key decoupling low nitrogen combustion technology was the release and reduction of coke coal nitrogen in high-speed pulverized coal burner.Then numerical simulation method was adopted to analyze 10 different kinds of working conditions.The secondary air temperature,swirl intensity and secondary excess air coefficient were focused to study their influence on combustion inside the burner.It is found that pulverized coal decoupling combustion equipped with high-speed burner should increase the carbon conversion rate in burner furtherly in order to reduce the NOx emission.The increase of swirl intensity and secondary temperature will be beneficial to promote the carbon conversion rate.When the excessive air coefficient decreases,the reductive atmosphere in burner will increase but the carbon conversion rate will decrease.When the first air ratio is increased to 15%,the carbon conversion will be increased to 99%.Therefore,the rapid emission of coke nitrogen can be acquired.