O_2/CO_2气氛下NO_x前驱物的转化机理

Homogeneous reaction mechanism of NO_x precursors under O_2/CO_2 atmosphere

从化学反应动力学角度,基于实验数据选择了最佳基元反应模型,采用CHEMKIN软件包研究了O2/CO2气氛及空气气氛下甲烷火焰中NOx前驱物的转化机理,探讨了多种影响因素对NOx前驱物转化过程的影响规律,比较了2种气氛下NOx前驱物转化机理的异同,考察了重要基元反应在2种气氛下生成率的区别以及高体积分数CO2气氛对主要基元反应的影响,得到了不同气氛下NOx前驱物的转化历程,从微观反应动力学的角度解释了2种气氛下NOx前驱物转化行为的差异.结果表明NOx前驱物HCN和NH3在2种气氛下的反应历程是不相同的.其中:O2/CO2气氛富燃条件下NOx前驱物的主要转化历程为HCN→NCO→N2O→N2,NH3→NH2→N2;O2/CO2气氛贫燃条件下NOx前驱物的主要反应历程为HCN→NCO→N2O→N2,NH3→NH2→NNH→N2.

Most studies find significantly lower NO, emissions during oxy-coal combustion. Methane （CH4） was used as fuel, with hydrogen cyanide （HCN） and ammonia （NH3） being added as fuel-ni- trogen sources. Numerical simulations using Chemkin to model N-conversion through homogeneous gas phase reactions were reported. A suitable reaction mechanism was chosen based on comparison of the calculations to experimental data which accurately predicts NO concentrations over the range of equivalence ratios. The influence of various parameters （temperature, pressure, equivalence ratio, CO2 concentration） on NO formation was investigated. The effects of high concentration of CO2 were emphasized through mechanism analysis. In addition, a sensitivity analysis was performed in an attempt to identify the most important reactions pertinent under the relevant conditions of study. According to this study, under O2/CO2 atmosphere, NOw precursors mainly proceeds via reaction： HC→NCO→ N2O→N2, and NH3→NH2→N2 （fuel-rich condition）, while conversion of NOx precursors mainly pro- ceeds via reaction： HCN→NCO→N2O→N2, and NH3→NH2→NNH→N2 （fuel-lean condition）.