【作者】 刘汉周；

【导师】 辛明道；

【作者基本信息】 重庆大学 ， 工程热物理， 2006， 博士

【摘要】 煤粉燃烧过程中释放的NOx是主要大气污染物之一,对环境、气候和人类健康带来严重影响。随着我国燃煤电站锅炉的装机容量不断增加,NOx排放带来的环境污染问题也越来越严重。为了解决电站煤粉锅炉NOx排放污染问题,许多学者开始了对NOx生成与破坏机理的研究、并研究出低氮燃烧器、空气分级、燃料再燃、烟气再循环、选择性催化还原以及选择性非催化还等诸多NOx控制方法。其中,天然气再燃具有投资小、运行费用低,脱硝效率高等优点。采用天然气再燃技术降低煤粉锅炉NOx排放具有重要的工程实用价值。目前,欧美等先进工业国家在已有比较成熟的天然气再燃示范工程应用,然而,其应用的关键性技术未见有公开报道,并且也未见有系统性的研究。因此,要将该技术应用于国内煤粉锅炉上,必须进行系统性的研究,以掌握其中关键技术并进行应用推广。以我国典型的切圆煤粉锅炉为研究对象,进行天然气再燃的系统性的试验和数值模拟,探索和弄清再燃气流在炉内的混合特性、燃烧特性,研究开发再燃系统工业装置,将充实和推动再燃技术的学术研究,也将促进再燃低NOx技术应用的创新及推广。文中在深入分析国内外煤粉锅炉再燃技术发展及现状的基础上,通过理论分析和试验相结合的方法首次系统深入地探讨了利用天然气再燃技术降低四角切圆燃烧煤粉锅炉NOx排放的关键性影响因素,重点研究了再燃射流在炉内的混合机理,并首次提出了四角切圆煤粉锅炉上前后墙对冲喷射再燃燃料和燃尽风的技术,强化了炉内气流混合并降低了炉膛出口气流的扭转残余。文中的具体研究工作包括再燃喷气在炉内的混合特性试验与数值模拟、一维试验炉再燃热态数值模拟与试验以及天然气再燃工业应用及优化研究。①针对在煤粉锅炉再燃低NOx技术影响因素研究的文献中,未见有关于再燃气体混合机理的具体报道,首次采用不等温射流试验方法,进行了较为系统的冷态试验研究,模拟了再燃射流和燃尽风射流与炉内主气流的混合特性。采用炉内温度场模拟炉内气流混合状况的试验方案,分析了再燃气流流量、再燃气流喷口布置方式、再燃气流喷口安装高度、燃尽风流量、燃尽风喷口布置方式、燃尽风喷口安装高度等参数对炉内气流混合特性(温度分布)的影响。试验结果表明射流流量、喷口布置方式、喷口在炉膛上的安装高度之间存在最佳配置方式。②针对试验研究的局限性,采用计算机数值计算模拟了煤粉锅炉进行再燃改造后的炉内气流混合状况。文中首先通过模拟横向单喷口射流与垂直主气流之间的混合特性,得出了单喷口横向射流在炉内的速度、温度、浓度分布特性,进一更多还原

【Abstract】 NOx emission from the coal burning is one of the major pollutant sources for atmosphere, and it is a threat to environment, climate and human health. The pollutant problem of NOx emission becomes more and more serious with coal fired boilers increasing. Many scholars begin to research the forming and destroying mechanism of NOx for resolving the problem of NOx emission from coal fired boilers in power plants, and a good many NOx controlling methods are invented such as Low-NOx Burners, Air Staging, Fuel Reburning, Flue Gas Recirculation, Selective Catalytic Reduction and Selective Noncatalytic Reduction. Therefinto, Natural Gas Reburning (NGR) has the advantage of lower investment, low operating expenses and high NOx reduction efficiency. It has very important value of engineering application for reducing NOx emission with Natural Gas Reburning.Now, NGR technology have been proven to be an available technology by all industrial demonstrations in USA and Europe, but the critical technologies haven’t been openly reported and the systemic research hasn’t been found. So, before applied NGR technology to pulverized coal boilers in China, the systemic research must been carried for mastering the critical technologies and industrial demonstrating. Using the typical tangentially fired boilers in China as researching object, numerical and experimental investigation on NGR technology for NOx reduction, to explore and understand the mixing characteristic, burning characteristic and to exploit the industrial equipments, all of which will enrich and promote the academic researches and carry forward the technological innovations and engineering applications of NGR technology.This paper is in allusion to the development and actuality reburning technologies of coal fired boilers in china and foreign countries. It is firstly to more deeply investigate the critical influencing factors on reducing NOx emission of tangentially coal fired boilers with NGR technology combined numerical and experimental methods. The mixing mechanism of the reburning injection in furnace was emphasis in this paper, and the methods on oppositely injecting reburning gas and over firing air (OFA) in the front and rear walls in tangentially coal fired boiler is the firstly brought forward, which can strengthen the gas flow mixing in furnace and reducing the gas flow swirling remains at the furnace outlet.The researches include the cold experimental and numerical studies on mixing更多还原