氧煤MILD燃烧条件下NO生成的动力学模拟

Chemical-kinetic simulation of NO production in oxy-coal MILD combustion

利用CHEMKIN研究氧化剂与内回流烟气之间的掺混温度和氧气体积分数两个关键因素对氧煤MILD燃烧条件下NO生成的影响,选取氧化剂气氛为5%O2/90%CO2/5%H2O,10%O2/85%CO2/5%H2O,15%O2/80%CO2/5%H2O和25%O2/70%CO2/5%H2O,温度为1 273,1 373和1473 K。结果表明：NH2是一关键的前驱组分,反应NH2＋OH=NH＋H2O对促进NO生成影响最大,而反应NH2＋NO=N2＋H2O对抑制NO生成影响最大,两者影响力随着氧气体积分数降低而加大;提高掺混温度和氧气体积分数可增大燃料N→NO的转化率和OH基团的平衡浓度,氧气体积分数10%～15%是一个可兼顾CO和NO排放的较合理区间,且氧气体积分数的改变对污染物排放的影响与掺混温度的关系不大;NO还原路径的反应速率在低氧气体积分数下反而有不同程度的增大,在MILD燃烧条件下,还原反应的趋势增强,从而延长反应进程,增加系统的整体复杂性。

The influence of mixing temperature and oxygen concentration between oxidizer and inner-recirculated flue gas on NO production in oxy-coal MILD combustion was studied through CHEMKIN simulation. The temperature was chosen as 1 273,1 373 and 1 473 K,besides,the atmosphere was 5% O2/90% CO2/5% H2 O,10% O2/85% CO2/5%H2O,15% O2/80% CO2/5% H2 O and 25% O2/70% CO2/5% H2 O. The results show： NH2 is a crucial precursor that the reaction NH2＋ OH = NH ＋ H2 O is predominantly sensitive to the formation of NO,while the reaction NH2＋ NO =N2＋ H2 O is predominantly sensitive to the consumption of NO,both become more important as the oxygen concentration decreases; the fuel-N→NO transfer rate and OH radical equilibrium concentration become larger as temperature and oxygen concentration increase; the mixing oxygen concentration of 10%- 15% is a reasonable range for balancing NO and CO emissions,besides,there is little relationship between the mixing temperature and the influence of oxygen concentration on pollutant emissions; the reaction rate corresponding to NO reduction path increases under low oxygen concentration,indicating that the trend of reduction is enhanced,therefore,the reaction progress extends and the overall complexity develops in MILD combustion.