【作者】 陆方；

【导师】 罗永浩；

【作者基本信息】 上海交通大学 ， 热能工程， 2009， 博士

【摘要】 以煤为主的能源结构在我国相当长一段时期内将长期存在,煤粉锅炉产生的大量氮氧化物是当前亟待解决的环境污染问题。本文针对我国目前煤粉锅炉的主流炉型和氮氧化物排放浓度现状,结合国家和地方日趋严格的排放标准以及发展趋势,分析研究系列化低NOx燃烧技术,以满足不同阶段相应的排放标准,为我国分阶段实施氮氧化物减排提供解决方案。本文以数值模拟、实验研究及化学动力学分析方法为研究手段,对整体空气分级、燃料再燃及高级再燃这一系列低NOx燃烧技术进行全面深入的研究,揭示脱除NOx的基本机理、提出对现有煤粉锅炉实施低NOx燃烧技术改造的设计方法和原则、总结分析先进低NOx燃烧技术的影响因素并对还原NOx所需的反应机理模型进行了探讨。本文根据NOx生成机理分析了低NOx煤粉燃烧器的各种影响因素及优化原则,并以具有代表性的煤粉锅炉为例,对整体空气分级低NOx燃烧技术中的关键因素进行深入分析。针对国家和地方新的NOx排放标准,得出整体空气分级低NOx燃烧技术是有效而低成本的改造现有电站煤粉锅炉的先进技术方案,并采用数值模拟进行改造设计和优化运行。面对更严格的NOx排放标准,可在整体空气分级基础上,采用燃料再燃低NOx燃烧技术进一步降低NOx排放。本文对以天然气和石油气为再燃燃料的燃料再燃低NOx燃烧技术进行了研究,研究结果表明:对于天然气再燃,HCCO、CH2及CH3自由基是还原NO的主要活性物质,反应温度及OH、H、O基团是生成这些活性物质的关键因素;在相同的条件下石油气再燃还原NO的效果明显优于天然气,主要原因是石油气再燃还原NO过程中大量HCCO自由基及H、OH活性基团参与反应。在燃料再燃的基础上,采用高级再燃低NOx燃烧技术可实现与SCR同等级的大幅度降低NOx排放的效果。反应时间、反应温度、再燃区过量空气系数及喷入氨剂量与当地NO化学当量比NSR等是高级再燃还原NO的主要影响因素;为模拟高级再燃条件下NO沿反应器长度的分布规律,尝试采用GRI-SNCR反应机理模型,得到实验验证,并用此反应机理模型对高级再燃进行深入的机理分析;从反应物的生成率分析可以看出,在还原性气氛下,NH2是还原NO的主要活性基团,在氧化性气氛下,NH2大部分氧化为HNO,最终生成NO,所以在高级再燃中NH2自由基与NO的反应是强烈依赖于气氛的竞争反应,既可以将NO还原为N2,也可以自身氧化为NO。更多还原

【Abstract】 In China, coal-dominated energy structure would exist for a long period of time. Nitrogen oxides produced by coal-fired boilers leads to serious environmental pollution, which have to be solved urgently. In this paper, a serious of low NOx combustion technologies is presented, by taking account of China’s main coal-fired boiler furnace and the concentration of nitrogen oxides emission, combined with increasingly stringent emission standards as well as the development trend for both state and local government. These technologies will meet different stages of the corresponding emission standards and provide solutions for China’s incremental stages for the implementation of the nitrogen oxide emission reduction. Numerical simulation, laboratory research and chemical kinetics analysis methods are used to conduct a comprehensive in-depth study on a series of low-NOx combustion technology such as the separated over fire air, fuel reburning and advanced reburning. Mechanism of NOx reduction, the design methods and principles for low NOx technologic l upgrading on existed coal-fired boiler are presented. In addition, advanced low-NOx combustion technology and the impact of the factors required for NOx reduction reaction mechanism model are discussed.Based on the mechanism of NOx production, a variety of factors and optimization principle are analyzed. A representative coal- fired boiler is set as a case, key factors on separated over fire air low NOx combustion technology is analyzed in deep. According to the new NOx emissions standards for state and local, it is proposed that SOFA is an effective and low-cost transformation of technologic l upgrading on existed coal-fired boiler, hence, numerical simulation method for the design and modification of the optimal operation is provided.Facing to the more stringent NOx emissions standards, use low-NOx reburning fuel combustion technology on overall classification on the basis of the air will further reduce NOx emissions. Different fuels for reburning are studied such as natural gas, petroleum gas and biomass gasification gas with tar. Results show that: For natural gas reburning, HCCO, CH2 and CH3 radical is the main active substance on NO reduction. Reaction temperature and OH, H, O are key factors for a group of active substances production; Under the same conditions, NO restore by petroleum gas reburning are better than natural gas reburning. This is because a large number of free radicals HCCO and H, OH active groups involved in the reaction during petroleum gas reburning for NOx reduction.On the basis of fuel reburning, advanced reburning can achieve the same level of a significant reduction as SCR does in NOx emissions. Reaction time, reaction temperature, excess air ratio in reburning zone and NSR, are the main factors for NO reduction; In order to simulate the NO distribution discipline along the length of reactor, GRI-SNCR reaction mechanism model is been tried and proved by experiment. Then, this reaction mechanism can be used to carry out in-depth analysis of advanced reburning; It can be seen from reactant generation rate analysis: Under rich fuel condition, NH2 is the main activity radical for NO reduction. Under oxidizing atmosphere, most NH2 are oxidized to HNO, and finally to NO. Therefore, during advanced reburning, reaction between NH2 radical and NO is competitive reaction strongly dependent on the atmosphere, NH2 can reduced NO to N2, and also be oxidized to NO.更多还原