燃尽风率变化对电站锅炉NOx排放特性影响的数值模拟

Numerical simulation of the effect of over-fire air rate on NO_x emission in utility boiler

燃尽风率是决定燃尽风技术降低NOx排放量的关键因素。对一300 MW机组四角切圆锅炉炉内煤粉燃烧过程进行了不同燃尽风率条件下的数值模拟。分析研究了燃尽风率对炉内温度、O2、CO浓度分布、NOx排放特性和飞灰含碳的影响规律。分析结果表明:随着燃尽风率的增加,炉内温度水平会降低,在煤粉燃烧区域氧浓度降低,CO浓度升高,炉内NOx浓度明显下降,炉膛出口NOx排放量线性降低;在燃尽风率为5.5%到8.5%之间时,燃尽风率增大飞灰含碳量降低,当燃尽风率增大到8.5%以上时会引起飞灰含碳量的升高。

Over-fire air rate is a key factor to the over - fire air technology on reducing mass of emitted NOx. The numerical simulations were made on the combustion of a 300 MW pulverized coal boiler with different over - fire air rate. It was analysed that the influence of over- fire air rate on temperature , concentration of O2 and CO, NOx emission and carbon in fly ash. The results indicate that when the Over-fire air rate increases, the temperature and the concentration of 02, NO, will reduce in boiler, the concentration of CO will increase, the mass of emitted NOx will reduce linearly in furnace outlet. When the over-fire air rate increases from 5.5% to 8.5%, the carbon in fly ash will reduce. When the over- fire air rate is over 8.5 %, the carbon in fly ash will increase.