烟气再循环对天然气非预混燃烧NO_x排放特性的影响

Effect of Flue Gas Recirculation on NO_x Emission Characteristics of Natural Gas Non-Premixed Combustion

天然气在燃烧过程中生成NO_x的浓度主要受温度影响.烟气再循环不仅能降低燃烧温度,而且减小了燃烧高温区域,使污染物排放降低.为减少NO_x排放,采用一台标定功率为800,k W的非预混燃烧器进行了烟气再循环非预混燃烧试验,主要研究了燃烧负荷、过量空气系数、烟气再循环率对NO_x生成的影响.同时,采用FLUENT6.3软件模拟计算燃烧火焰温度分布和NO_x质量浓度分布.结果表明:燃烧器热负荷的增加,会使烟气中NO_x质量浓度增加;过量空气系数?在1.0~1.15之间时,有利于降低NO_x排放;烟气再循环量增加能有效降低NO_x排放,在?为1.1和1.15时、烟气再循环率为20%,时,NO_x质量浓度为40~50,mg/m3.

The generation of nitrogen oxides during the combustion of nature gas is affected by the temperature. Flue gas recirculation（FGR）reduces not only the combustion temperature but also the high temperature area of combustion,which leads to the reduction of pollutant emissions.In order to reduce the emission of NOx,a nonpremixed fundamental experiment with exhaust gas recirculation was done in a non-premixed burner whose rated power was 800,k W.The influences of thermal load,excess air coefficient and exhaust gas recirculation rate on the formation of NOx were analyzed.Meanwhile,the FLUENT 6.3 software was used to simulate the distributions of flame temperature and the mass concentration of NOx emissions.Results show that with the increase of burner thermal load,the NOx content in the exhaust gas increased;The excessive air coefficient with the range of 1.0—1.15 was beneficial to the reduction of NOx emission;the emission of NOx was reduced with the increase of exhaust gas recirculation rate,and when the flue gas recirculation rate was 20%, under ？=1.1,1.15,the mass concentration of NOx was 40—50mg/m^3.