采用详细化学反应机理研究煤富氧燃烧NO_x生成机制

Modeling NO_x Formation in Pulverized Coal Oxy-Fuel Combustion by Detailed Chemical Reaction Mechanism

本文采用详细化学反应机理,建立氧煤燃烧气固反应模型,分析煤在富氧燃烧条件下NO_x生成机制,研究不同O_2浓度和分级燃烧对NO_x排放的影响。富氧燃烧时,NO_x生成主要路径为:HCN→CN→NCO→NO和HCN→CN→NCO→HNCO→HN_2→NH→HNO→NO。初始O_2增大,挥发分和HCN析出时间提前,高的O_2初始浓度对燃料N转化率有促进作用;煤富氧分级燃烧时,主燃区还原气氛有利于NO还原为N_2,其主要还原路径如下:NO+CO→N+CO_2、NO+H→N+OH和NO+N→N_2+O,当主燃区过量空气系数SR_1从1.15减小到0.6,N最终转化率(t=1000 ms)只是从0.379减小到0.339,相对于未分级燃烧时变化了10.55%,与煤空气分级燃烧相比,煤富氧分级燃烧对N转化率影响较小。

Gas-solid reaction model of pulverized coal was established based on detailed chemical reac- tiou mechanism, the NOx formation mechanism in oxy-coal combustion was analyzed, and the effects of 02 concentration and air staged combustion on NOx emission were investigated. NOx formation paths in oxy-coal combustion are HCN→CN→NCO→NO and HCN→CN→NCO→HNCO→HN2 →NH→HNO →NO. The increase of initial O2 concentration makes the release of volatile and HCN ahead, and increasing initial concentration of O2 promotes the conversion rate of fuel N. In Oxy-coal staged combustion, the reducing atmosphere in primary combustion zone is conducive to NO reduction to N2, and the main reaction paths are NO＋CO→N＋CO2, NO＋H→N＋OH and NO＋N→N2＋O. N conversion rate decreases from 0.379 to 0.339 when the excessive air rate decreases from 1.15 to 0.6, and it decreases 10.55% as compared that of unstaged combustion. Oxy-eoal combustion has slightly influence on N conversion rate as compared that of air-coal combustion.