【作者】 张珂；

【导师】 乔瑜；

【作者基本信息】 华中科技大学 ， 热能工程， 2017， 硕士

【摘要】 燃煤火电厂作为大气污染的排放大户,控制各项主要污染物的排放是我国环境治理必须研究的重要课题。控制大气污染物包括氮氧化物(NO_X)等的排放成为急需解决的难题。为应对我国严峻的环境污染态势,新国标严格限定燃煤锅炉NO_X排放值并设定整改期限,现存的燃煤锅炉中一部分为老机组,它们并没有任何减排NO_X的措施,对这些锅炉进行低氮改造势在必行。本文对典型的4类原煤的基础特性进行了测试分析,选取其中有代表性的八种进行了沉降炉的燃烧和热解实验,探讨了NO_X的生成机理及条件,发现降低燃烧区氧气浓度和煤粉在高温区的停留时间是抑制NO_X生成的主要因素。为了进一步考察氮在煤中的的赋存形态,对四种煤及其焦样进行了X射线光电子能谱扫描(XPS)实验研究,发现煤中含氮物质主要为吡啶和吡咯,其热稳定性较强,在热解过程中其他含氮官能团有向这两种物质转化的趋势。为了减少某电厂150MW锅炉NO_X的排放,对其进行了低氮燃烧的改造。改造后的锅炉进行了冷态空气动力场实验和热态的运行调试实验。实验结果表明,此次低氮燃烧改造效果良好,炉膛出口NO_X浓度由改造前的700 mg/m~3(干态,6%氧量)降低为改造后的250 mg/m~3(干态,6%氧量)。改造后的试验结果表明:本次改造工程有效降低了锅炉NO_X的排放,此外还有效缓解炉膛结焦的问题。锅炉过热器减温水和再热汽减温水用量大幅度减小。在燃用适烧煤种时,锅炉效率可以达到目标值91.85以上,总体上达到了很好的环保效益和经济效益。本文选取了几种典型的中国煤,对它们的燃烧特性和NO_X排放规律进行了研究,并对某电厂150MW燃煤锅炉进行了氮碳改造,改造后的测试结果表明,经分级燃烧改造后的锅炉实现了低氮燃烧并稳定高效运行,对其他电厂燃煤锅炉的低氮燃烧改造工程提供了借鉴意义。更多还原

【Abstract】 Coal-fired power plants,as one of the major sources of air pollution,discharge large amounts of atmospheric pollutants.The control of the emission of all major pollutants has become an important subject for the environmental governance of our country.In order to deal with the Severe environmental pollution problem,a new national standard had been issued stipulating a stricter emission limits.Thus,it is imperative toTransform Existing coal-fired boilers to low-nitrogen combustion model.In this paper,the basic characteristics of the four types of coal are analyzed.The combustion and pyrolysis experiment of eight representative samples are conducted on the subsidence furnace.The mechanism and conditions of the forming of NO_X are discussed,finding that the oxygen concentration of burning zone and the dwell time of coal powder burning in the high-temperature zone are the main factors inhibit NO_X generation.For further study of mode of occurrence of nitrogen in coal,X-Ray Photoelectron Spectra(XPS)research had been conducted on three kinds of coal and their corresponding char.It is found that the nitrogen in coal is mainly pyridine and pyrrole.They both possess strong thermal stability.Other nitrogen-containing functional groups tend to convert to pyridine and pyrrole during pyrolysis.The transformation of low nitrogen combustion was carried out on a 150MW coal-fire boiler aiming at reduce the exhaust fo pollutant.After the transformation project,the cold air power field experiment and operating experiment were carried out.The results showed that the project had achieved its goal.The Concentration of NOX had droped from700mg/m~3(dry state 6%oxygen)to 250mg/m~3(dry state 6%oxygen).According to the results of the experiments,the transformation project had effectively reduced the emission of NO_X.Besides,the project alleviated the problem of the furnace coking,reduced the amount of attemperation water of superheater and reheater.The boiler efficiency can reach above 91.85%as long as proper coal is used.The boiler had achieved excellent environmental and economic benefits.This paper studies the combustion characteristics and NO_X emission pattern of typical coal powder in China.A low-nitrogen combustion transformation project had been conducted.The boiler than experienced a few tests in order to examine the amount of NOX emission and operating parameter.The test showed that the boiler can realize low-nitrogen combustion and a stable and high effective operation.This study is useful for both reducing the NO_X emission of the power plant and improving the operating efficiency of the power plant.更多还原