空气深度分级燃烧NO_x排放特性的CHEMKIN模拟研究

CHEMKIN Simulation of NO_x Emission of Deep Air-Staged Combustion

利用两段PFR反应器构建模型在CHEMKIN中模拟,研究空气深度分级燃烧中各个影响因素,使用生成速率分析和敏感性分析,探求燃料N向NOx的转化路径及原因.模拟结果表明,主燃区α对NOx转化率影响较大,高温强还原氛围能明显降低NOx排放;改变燃烧温度降低NOx排放,应当考虑主燃区,而非燃尽区;当主燃区温度小于1500℃,燃尽风比率为35%左右时,NOx排放最低;富燃条件下O2/CO2燃烧增大了OH/H,促进NOx生成;燃尽风位置向后移会降低NOx转化率,改变燃尽风氧浓度NOx转化率几乎不变.本文不仅扩大了前人对空气分级燃烧的研究范围,而且对于前人没有研究的影响因素给出了结果,并且进行了化学反应动力学分析,对实际锅炉运行过程中减少NOx排放具有指导意义.

A model is established with two-stage PFR in CHEMKIN to study the fuel-N conversion in deep airstaged combustion including all the factors,and the results are analyzed by production rate and sensitivity analysis.The results show that the stoichiometric ratio of main combustion zone affects NOx emission significantly,especially under high temperature and strong reducing atmosphere.The temperature of main combustion zone should be considered to decrease NOx formation rather than that of burnout zone.The NOx emission is the lowest when the temperature of main combustion zone is lower than 1500℃and the rate of overfire air is 35%.The staged O2/CO2 combustion under a fuel-rich condition increases OH/H ratio,leading to more NOx production.The NOx conversion rate will be reduced when the position of overfire air moves backward,but it will be hardly changed when the oxygen concentration of overfire air is changed.The paper not only expands the range of previous research,but also obtains the results that have not been reparted,which are analyzed by chemical reaction kinetics and helpful in reducing NOx emissions when the boiler is in practical operation.