【作者】 魏砾宏；

【导师】 姜秀民；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2007， 博士

【摘要】 超细煤粉燃烧技术是一种新型的低NOx燃烧技术，一些国家将其列为减少NOx排放的重要技术之一。超细煤粉燃烧不仅有降低NOx排放的作用，在燃烧特性方面也表现出着火温度低、燃尽率高、减弱或消除飞灰在炉内受热面上的沉积与结渣等特点。我国对此开展了研究，其中不乏工业试验，但在燃烧机理方面的研究仍然不够深入和透彻。本文针对超细煤粉的热解机理、热解过程氮、硫化物的析出特性、超细煤粉燃烧机理及燃烧过程污染物的析出特性、金属矿物质对NO的催化还原机理等内容进行了较为系统深入的研究。旨在为燃用超细煤粉锅炉的设计和运行提供基础数据和技术支撑，对提高煤的燃烧效率和降低大气污染物的排放技术的研究提供理论依据。本文首先利用热天平研究了超细煤粉的热解特性，采用非等温热重分析方法，研究了煤种和升温速率对细化和超细化煤粉的热解特性和热解动力学特性。同时利用气相色谱质谱联用仪研究了细化和超细煤粉热解过程中含氮和含硫化合物的析出特性，分析了上述因素对其的影响。对深入理解细化和超细化煤粉燃烧前的行为特点具有重要意义。结果表明，超细化改变了煤粉挥发分的析出特性，有利于挥发分的析出；当粒径在10μm以上时，热解过程含氮气体释放量与煤中含氮量成正相关；煤热解中硫的析出并不完全受煤中含硫总量控制，而主要由煤中硫的形态和含量、酸洗矿物质和碱性矿物质的含量、氢的含量、以及其它一些外部条件所决定。为进一步了解细化和超细化煤粉燃烧过程的特点和污染物析出特性，本文利用热分析天平研究了细化和超细煤粉的着火特性、最大燃烧速率和燃尽特性，分析了粒度、升温速率和氧气浓度对着火特性和综合燃烧特性的影响。利用气相色谱质谱联用仪研究了燃煤而产生的大气主要污染物SO2和NOx的生成特性，深入探讨了粒径、升温速率、氧气浓度和煤种对SO2和NOx生成的影响，对了解控制污染性气体的排放因素和机理，对煤粉锅炉的优化运行有一定的指导意义。煤中矿物质是影响细化和超细煤粉燃烧的重要因素，目前对此进行的研究较少，本文进行了较为系统的研究。主要的研究方法是先对细化和超细煤粉进行脱灰处理，再向脱灰样品中加入Ca、Mg、Na、K、Al、Fe的氧化物和氢氧化物，研究其代表的相应矿物组成对细化和超细煤粉燃烧特性和污染物析出特性的影响，分析其可能原因。结果表明，适量的KOH和NaOH能改善细化和超细煤粉的燃烧特性，降低表观活化能。细化和超细化3种原煤在燃烧过程中SO2的释放曲线是3峰曲线，而脱灰样品SO2的释放曲线是双峰曲线，并且出现峰值的温度范围不尽相同。其中Na的催化还原能力最强，并且催化还原能力大小还与煤种有关。NO的催化还原是烟气脱硝的一种重要方法，许多学者也对此进行研究。但燃烧过程中NO的催化还原相对复杂，目前尚未见报道。本文采用量子化学的研究手段，以用较小尺度的MgO簇模型Mg5O5为对象，研究了焦炭催化还原NO的机理，分析了NO的分解途径，为燃烧过程中NO的脱除技术提供理论依据。本文再最后部分提出了细化和超细化煤粉的原煤和半焦的表面特性。鹤岗煤、铁法煤和准噶尔煤三种原煤样品的表面分维数分别为2.3459、2.2942和2.7267。3种煤的表面分维均在2与3之间，并且随着粒径的减小，煤粉颗粒的比表面积增大，表面分析维数增大。说明随着煤颗粒粒度的减小，表面结构愈复杂，其分析维数愈高，对燃烧愈有利。更多还原

【Abstract】 Micro-pulverised coal combustion technology is a new combustion technology with low NOX. It is regarded as one of important technology reducing NOX emission in some countries. Combustion of micro-pulverised coal has not only the function of decreasing NOX emission, but also represents some combustion characteristics such as low ignition temperature, high burn-off rate, reduction or removal of settling and slag-off made of fly ash on heating surface in furnace. In China, study on this technology was just started. Experimental studies in industrial sector have been conducted, however, the study on combustion mechanism is not deep and intensive. In this article, based on the pyrolysis mechanism of micro-pulverised coal, the emission characteristics of Nitrogen and sulphide in process of pyrolysis, the combustion mechanism of micro-pulverised coal and the emission characteristics of pollutants in process of combustion, the catalysis and reduction mechanism of metal mineral to NO, the author studies systematically the combustion mechanism of micro-pulverised coal. The purpose of study is to provide valuable parameters for design and operation of furnace burning micro-pulverised coal and to provide theoretical basis for technical study on increasing combustion rate of coal and reducing emission of air pollutants.First, the author studies the pyrolysis characteristics of micro-pulverised coal by thermobalance, studies the effects on pyrolysis characteristics and pyrolysis dynamics characteristics of pulverised and micro-pulverised coal from different type, size of coal and temperature raise speed through the method of non-isothermal thermogravimetric analysis. Meanwhile, by using gas chromatography/mass spetrometer, the author studies the precipitation characteristics of nitrogen- and sulphide-containing compound in pyrolysis process of pulverised and micro-pulverised coal and analyses the influences on precipitation by the above-mentioned factors. This study is meaningful to understand in-depth the behaviour characteristics of pulverised and micro-pulverised coal before combustion. The result shows that micro-pulverisation change the precipitation characteristics of volatile content of coal and micro-pulverisation helps precipitation of volatile content; when the size is over 10μm, emission amount of nitrogen-containing gas has positive correlation with nitrogen amount contained in coal in process of pyrolysis; sulphide precipitation in process of coal pyrolysis is not completely controlled by total nitrogen amount, but controlled by form and content of sulphide in coal, by content of acidwashing minerals and alkali minerals, content of hydrogen and other exterior conditions.In order to understand further the characteristics of pulverised and micro-pulverised coal in process of combustion and the precipitation characteristics of pollutants, the author studies the ignition characteristics of pulverised and micro-pulverised coal by using thermal analysis scale, the maximum combustion speed rate and combustion characteristics, analyses the effects to ignition characteristics and general combustion characteristics by different size, temperature raise speed and oxygen concentration, studies the generation characteristics of SO2 and NOx which are main pollutants in coal air by gas chromatography/mass spetrometer, probe into effects to SO2 and NOx generation by different size, temperature raise speed and oxygen concentration and type of coal and find out the factor and mechanism controlling emission of pollution air. The study is meaningful to optimised operation of coal furnace.Mineral substance in coal is the important factor effecting combustion of pulverised and micro-pulverised coal. It is a hot study point at present as well. The author makes further study on this point, too. The main study method is to first de-ash pulverised and micro-pulverised coal, then add oxidate and hydroxide of Ca, Mg, Na, K, Al, Fe into deashed sample to study the influence to combustion characteristics of pulverised and micro-pulverised coal and precipitation characteristics of pollutants by corresponding mineral groups and to analyse possible reasons. The result shows that proper quantity of KOH and NaOH can improve the combustion characteristics of pulverised and micro-pulverised coal and reduce apparent activated energy. Three kinds of pulverised and micro-pulverised coal show 3-peak SO2 emission course in process of combustion, but SO2 emission course of deashed sample is double peak course. Temperature range for peak value occurring is not same neither. It is found that Na has strongest catalysis and reduction capacity relating to type of coal.NO catalysis and reduction is an important way of oxygen denitration. It has been studied by many researchers. However, catalysis and reduction of NO in combustion process in relatively complex, so far there is no any report on this study. The author uses quantum chemistry study and takes Mg5O5 of small-scaled MgO cluster model as objective to study the mechanism of catalysis reaction between coke NO and analyse NO decomposition approach. The study provides theoretical basis for de-NO technology in process of combustion. In the last part of article, the author studies the surface characteristics of raw coal and semicoke of pulverised and micro-pulverised coal. The surface fractional dimension number of sample of raw coals from Hegang, Tiefa and Zhungaer area is 2.3459, 2.2942 and 2.7267, respectively. The surface fractional dimension value of three coals is between 2 and 3. With reduction of particle size, specific area of pulverised coal increases and surface analysis dimension increases. That means with reduction of particle size of coal, the surface structure gets complex and analysis dimension gets high, therefore, it is helpful for combustion.更多还原