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利用数值模拟方法对空气分级燃烧下NOx的生成特性进行了研究,分析了燃烧器附近局部区域和炉膛整体区域NOx的反应速率,得到了不同燃尽风率下NOx的生成特性.结果表明:NOx主要产生于燃烧初期,当燃料与O2混合不充分时会发生NOx的还原反应;从炉膛整体来看,燃料型NOx的生成速率明显大于热力型NOx,主燃区和燃尽区均生成燃料型NOx,而热力型NOx几乎只在温度很高的主燃区生成,且对O2体积分数的敏感性弱于燃料型NOx;主燃区和燃尽区NOx反应速率的主要控制因素分别为O2体积分数和焦炭燃烧速率;燃尽风率增大,主燃区NOx生成速率和生成区域减小,还原区域增大,NOx排放质量浓度明显减小.
The formation characteristics of NOx under air staged combustion were studied by numerical simulation, and the reaction rates of NOx in the local area around the burner and in the whole area of the furnace were analyzed, and the formation characteristics of NOx at different burnout rates were obtained.The results showed that NOx Mainly from the early stage of combustion. When the mixture of fuel and O2 is not sufficient, the NOx reduction reaction will occur. From the perspective of the furnace, the formation rate of fuel NOx is significantly greater than that of thermal NOx, and both the main combustion zone and the burnout zone generate fuel NOx, while the thermal NOx is almost only generated in the main combustion zone at high temperature, and its sensitivity to the O2 volume fraction is weaker than that of the fuel NOx. The main control factors of the NOx reaction rate in the main combustion zone and the burnout zone are O2 volume Fraction and coke combustion rate. When the burnout wind rate increases, the NOx formation rate and formation area in the main combustion zone decreases, the reduction area increases, and the NOx emission concentration decreases significantly.