Some of the impurities (Br, Cl, Fuel-N, and S) in fuels can reduce the radicals (O, H, and OH) formed in the flames on combustion, thus lowering the radical mole fraction. The variation in the radical mole fraction affects the NO_x emissions. In this study, the radical reducing effects caused by these impurities were modeled based on measurements of the radical mole fractions. Linear relationships were obtained between the mole fractions of the impurities in the flames and the reciprocals of the radical mole fractions. The slope of this straight line was defined as the radical reducing effect coefficient (α). The value of α for each radical was determined for fuels containing HBr, CH₃Br, HCl, CCl₄, CH₃NH₂, NH₃, H₂S, and CS₂ impurities. The OH radical was the most susceptible to the reducing effects of the fuel-N impurity. However, the calculated radical mole fractions (CH₄–NH₃ flame) by detailed chemical kinetics did not agree with the experimental results, and the O atom radicals were, in fact, most susceptible to the fuel-N impurities. The calculations overestimated the OH mole fraction and fuel-N conversion to NO_x. The α value calculated for the OH radical was 19.4 times smaller than that obtained experimentally. The contributions of OH radicals to fuel-NO_x generation for methane–ammonia and hydrogen–ammonia cocombustion were investigated by using a simplified reaction scheme for fuel-NO_x. If the OH radical was a controlling factor in fuel-NO_x generation, the difference in NO_x conversion between experiment and calculation could be explained. On the basis of the results, the reaction scheme was extended to the solid fuel combustion of coal and biomass. The NO_x conversion for the cocombustion of coal and ammonia was lower than that for the methane–ammonia cocombustion. The effect of Cl impurities on biomass combustion was also investigated. If the OH radical mole fraction was lowered by the presence of Cl in the biomass fuel, the NO_x conversion tended to be low. However, if the OH mole fraction was too low to decompose ammonia in the flame, the NO_x conversion tended to be high.

中文翻译：

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OH自由基在氨与氢，甲烷，煤和生物质共燃过程中在燃料NOx形成中的作用

燃料中的某些杂质（Br，Cl，Fuel-N和S）可以减少燃烧时火焰中形成的自由基（O，H和OH），从而降低自由基的摩尔分数。自由基摩尔分数的变化影响NO _x排放。在这项研究中，由这些杂质引起的自由基还原作用是基于自由基摩尔分数的测量建模的。在火焰中杂质的摩尔分数与自由基摩尔分数的倒数之间获得线性关系。将该直线的斜率定义为自由基减少效果系数（α）。对于包含HBr，CH ₃ Br，HCl，CCl ₄，CH ₃ NH ₂，NH的燃料，确定每个自由基的α值₃，H ₂ S和CS ₂杂质。OH自由基最易受到燃料-N杂质的还原作用的影响。但是，通过详细的化学动力学计算得出的自由基摩尔分数（CH ₄ -NH ₃火焰）与实验结果不一致，事实上，O原子自由基最容易受到燃料-N杂质的影响。该计算高估了OH的摩尔分数和燃料-N向NO _x的转化。计算出的OH基的α值比实验获得的小19.4倍。OH自由基对燃料NO _x的贡献通过使用简化的燃料-NO _x反应方案，研究了甲烷-氨和氢-氨共燃烧的产生。如果OH自由基是燃料NO _x生成的控制因素，则可以解释实验与计算之间的NO _x转化率差异。根据结果​​，反应方案扩展到了煤和生物质的固体燃料燃烧。的NO _X煤和氨的cocombustion转化率比用于甲烷的氨cocombustion低。还研究了Cl杂质对生物质燃烧的影响。如果通过在生物质燃料中存在Cl降低OH自由基摩尔分数，则NO _x转化率往往较低。然而，如果OH摩尔分数太低而不能在火焰中分解氨，则NO _x转化率趋于高。