CO_(2)和H_(2)O气氛下甲烷MILD富氧燃烧NO和CO生成机理

NO and CO Formation Mechanisms for Methane MILD-Oxyfuel Combustion Under CO_(2)and H_(2)O Atmospheres

利用Chemkin软件中对冲火焰模型对CO_(2)和H_(2)O气氛下甲烷MILD富氧燃烧进行详细数值模拟,对比了两种气氛下NO和CO的排放规律和生成机理.结果表明,MILD-CO_(2)燃烧模式下CO排放浓度约为MILDH_(2)O燃烧模式下的3倍.敏感性分析发现CO_(2)的分解会增加CO排放浓度,而MILD-H_(2)O燃烧模式下H_(2)O分解生成的OH基团促进了CO的氧化,降低了CO的排放浓度.同时,MILD-CO_(2)燃烧模式下NO排放浓度约为MILD-H_(2)O燃烧时的4倍,且MILD-H_(2)O燃烧模式下NO生成对氧化剂进口温度的变化不敏感.通过分离NO生成路径发现,两种气氛下N_(2)O中间体路径主导了NO的生成,NO再燃可以消耗20%以上生成的NO,其余路径相对不重要.结果表明MILD-H_(2)O燃烧比MILD-CO_(2)燃烧更有利于降低CO和NO排放.

A detailed numerical simulation of methane MILD-oxyfuel combustion under CO_(2)and H_(2)O atmos-pheres was carried out by using the opposed flow flame model in Chemkin software.The formation mechanism and emission characteristics of NO and CO under the two atmospheres were compared.The results show that the emis-sion of CO in MILD-CO_(2)combustion mode is about three times that in MILD-H_(2)O combustion mode.The sensitiv-ity analysis shows that the decomposition of CO_(2)increases the concentration of CO emission.In MILD-H_(2)O com-bustion mode,the generation of OH radicals by the decomposition of H_(2)O promotes the oxidation of CO and re-duces the emission of CO.The NO emission concentration in MILD-CO_(2)combustion mode is about four times that in MILD-H_(2)O combustion mode,and the NO generation in MILD-H_(2)O combustion mode is not sensitive to the variation of initial oxidant temperature.It is found that the N_(2)O intermediate route dominates the NO generation under the two atmospheres through path separation,the NO reburning can consume more than 20%of the gener-ated NO,and the other paths are relatively unimportant.In contrast,MILD-H_(2)O combustion is more beneficial to the reduction of CO and NO emissions than MILD-CO_(2)combustion.