【作者】 徐莹；

【导师】 孙锐；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2010， 硕士

【摘要】 燃煤污染物NO_x的排放将严重危害人类的身体健康，污染环境。随着我国对NO_x排放控制要求的提高，有效地控制燃煤过程中NO_x排放已是一项十分紧迫的任务。在众多的NO_x排放控制技术中，再燃被认为是最经济和最有应用前景的技术之一。本文对气体燃料再燃技术的影响因素和反应动力学机理做了分析和研究。为了实现反应和流动的耦合计算，对规模较大的详细反应动力学机理进行了简化，得到符合要求的骨架简化机理。本文基于典型的气体再燃实验工况，借助化学动力学软件Chemkin4.1，对主要的还原性气体CH₄、CO、H₂及其混合的生物质热解气再燃还原NO特性进行了模拟研究，分析了不同再燃燃料、再燃反应温度、再燃燃料量和入口氧气浓度对NO脱除效率的影响。结果表明，CH₄具有NO最佳的还原效率，1350¹400K是相应的脱硝率较高的反应温度。在混合热解气中CH₄对NO的还原起到了关键作用，主要是因为CH₄分解产生CHi和NO反应成为消减NO的主要途径。运用敏感性分析方法得出各气体燃料再燃还原NO情形下的主要基元反应。通过和实验结果的对照，证实了SKG03详细化学反应动力学模型对气体再燃还原NO的模拟具有较好的适用性。因此本文在SKG03详细化学反应动力学机理的基础上，运用直接关系图法（DRG）对详细反应机理进行了骨架机理的简化，得到了一个由37种组分，218个反应组成的骨架反应机理。通过和实验结果的对照分析证实了骨架机理模型对模拟三种主要还原性气体再燃还原NO良好的适用性。并在此基础上分析了骨架机理中物质之间的耦合作用关系和碳氢基团之间的转化关系。然后把简化的骨架反应动力学机理作为反应动力学部分带入Fluent软件中进行耦合计算。对CH₄再燃过程进行计算，结果表明对NO还原的预测趋势和实验结果一致，随着温度的升高，NO的出口浓度减少，脱硝率增加。燃料和氧化剂在反应过程中混合充分，CH₄和O₂迅速反应被消耗。对于气相反应，在Fluent中带入详细的化学反应动力学机理计算，时间上可行，计算准确度有待于进一步地提高。为预测实际工程应用中加入异相反应的再燃脱硝性能奠定了基础。更多还原

【Abstract】 NO_x emissions of pollutants from coal burning would seriously endangerhuman health, pollute the environment. Recently, China has specified more rigorouslimits for the NO_x emissions. Among the most recent developments for reducingNO_x emissions, reburning technology is considered to be one of the most promisingand cost-effective NO_x reduction strategies for coal combustion systems.The key influencing factors of the gaseous fuel reburning process and thereaction mechanism were analyzed and studied in this thesis. In order to achieve thecoupling of reaction and flow computing, the detailed reaction mechanism of largescale was reduced to the skeletal mechanism which meet the requirements of fluidcomputing.NO reburning process by the gaseous fuel of CH4、CO、H₂ and biomass pyrtedolysis gas was simulabased on the typical gas reburn experiments using chemicalkinetics software Chemkin4.1. The key influencing factors of reburning fuel type,reaction temperature, reburning fuel quantity and the inlet O₂ concentration werestudied. The research results indicate that, CH4 has the highest NO reductionefficiency compared to CO and H₂.The most appropriate temperature is 1350¹400Kfor CH4 as reburn fuel.CH4 has the most important effects on reducing NO in themixed prolysis gas because that the reactive radical CHi produced by thedecomposition of CH4 reacts with NO which is the major way to consume NO. Thekey elementary reactions of gaseous fuel reburning process were obtained withsensitivity method. Comparing to the experiment results, it confirmed the SKG03detailed chemical kinetic model has good applicability for the simulation of gasreburning NO reduction.Using the directed relation graph （DRG） method, a skeletal mechanism wasdeveloped from the SKG03 mechanism which contains 37 species and 218 reactions.The skeletal mechanism showed very good applicability for the simulation of thethree gases reburning NO compared to the detailed mechanism. The couplingrelationships between species and transforming relationships between hydrocarbonradicals in the mechanism were analyzed. The reduced skeletal mechanism wascoupled as the chemical model in the Fluent software. The CH4 reburn process hasbeen computed, the results showed that the Fluent simulation agree with theexperimental results on the forecast trends of NO reduction. The outlet NOconcentration decreased with the reaction temperature increased. The oxidizer andfuel mixed well.CH4 and O₂ reacted quickly and consumed in a short time. For thegas reaction, the calculations in Fluent coupled of detailed chemical kinetics are time possible. However the accuracy need to be further improved. It provided the basis ofpredicting the NO_x reburning performance in engineering applications addingheterogeneous reactions.更多还原