【作者】 李莉；

【导师】 陆继东；

【作者基本信息】 华南理工大学 ， 工程热物理， 2010， 硕士

【摘要】 近年来,我国水泥工业的迅猛发展,已经成为我国居火力发电、汽车尾气之后的第三大氮氧化物排放来源,严重影响大气环境质量,并成为水泥工业可持续发展的主要制约因素之一。因此减少和控制水泥工业的氮氧化物排放已经成为制约水泥工业可持续发展的紧迫课题。水泥分解炉是水泥工业NOx排放的主要设备之一,本文针对水泥分解炉内的低温、高浓度CO2、复杂多变气氛、大量水泥生料分解和煤粉燃烧过程相互耦合等特点,研究分解炉内特殊工况条件下煤粉燃烧过程中燃料NOx的释放特性和生成机理。采用实验研究方法研究炉内低温、高浓度CO2、水泥生料分解和煤粉燃烧过程相互耦合等因素对煤粉及煤焦燃烧过程中NOx释放特性的影响及作用规律。采用化学反应机理模拟研究方法,从化学反应动力学的角度研究分解炉内低温高浓度CO2和复杂多变气氛下NOx的转化机理及动力学反应过程,为有效预测水泥分解炉内NOx排放及发展水泥工业NOx减排和控制技术提供理论依据和实验基础。本论文的研究内容主要围绕以下几章展开:首先介绍了水泥生产工业特点及其NOx产生的主要来源,分析研究水泥分解炉内NOx释放特性及转化机理的研究意义,总结国内外普通电站煤粉锅炉NOx转化机理的研究现状,为后续的实验设计、分析及模拟研究提供参考和理论基础,最后提出本文的主要研究内容。针对水泥分解炉条件下低温、高浓度CO2、水泥生料存在特点,展开煤粉燃烧过程中的NOx释放特性的实验研究,探索分解炉内特殊工况条件下燃煤过程中燃料NOx的释放规律,分析水泥分解炉内煤粉低温悬浮燃烧过程中高浓度CO2和水泥生料存在对燃料NOx释放的影响程度和影响机理。详细介绍化学反应动力学机理模拟研究的计算方法、计算原理和模型,分析了对燃烧过程进行详细气相反应动力学研究的重要意义,同时总结了自上世界80年代以来,国内外应用Chemkin研究燃烧领域详细反应动力学的具体发展过程和主要研究内容,为后续研究分解炉内NOx气相转化详细反应动力学提供理论计算依据。从化学动力学的角度,采用气相化学反应动力学模拟研究方法,研究分解炉内低温、高浓度CO2、复杂气氛条件下煤粉挥发份燃烧过程中挥发份中含氮前驱化合物HCN转化生成NO的转化机理,采用生成速率分析方法和反应路径分析方法分析各影响因素对NOx生成的作用机制,得出分解炉内低温、高浓度CO2、多变气氛条件下煤粉挥发份中HCN转化生成NO的化学动力学机理过程和主要反应路径,为有效预测分解炉内NOx排放提供理论指导意义。最后,对全文进行了总结,同时对现有工作的不足和进一步的研究内容提出了展望。更多还原

【Abstract】 Large coal consumption in cement industry results in a significant NOx emission, and with the increasing prosperity of the cement industry in recent years, it has come to be one of major sources for NOx emission in addition to thermal power industries and the automobile industry. So how to deduct and control NOx emission in cement prodiction process has become a critical problem affecting the quality of atmospheric environment and the development of cement industry.Cement precalciner is one of the important equipment for NOx emission in cement factories. The objective of this work is to explore the characteristics of NOx emission and the mechanism of NOx formation on account for the special characteristics such as low temperature/high concentration of CO2/complex and astable atmosphere/ pre-decomposition of raw materials in cement precalciner. Experiments have been taken in the desigened gas-solid reactor to investigate the characteristics of NOx emission during coal combustion under cement precalciner condition. The mechanism of nitric oxide (NO) formation from the oxidation of hydrogen cyanide (HCN) during the combustion of volatile from pulverized coal under cement precalciner conditions has been studied in terms of a chemical kinetic model. All studies in this thesis provide the foundation of experiment and theory for the effectual strategy to control and deduct the NO emission in cement factories. The main contents of this thesis are as follows:Firstly, the characteristics of cement industry and the main source of NO emission in cement factories have been introduced. The significance of researches on the characteristics of NOx emission and the mechanism of NOx formation has been analyzed. Than the study situation on the characteristics of NOx emission and the mechanisim of NOx conversion dring coal combustion in ordinary pulverized coal fired boilers has been summarized. All the above contents provide the foundation of experiment and theory for the following experiments studies and kinetic modeling. And the main contents of this paper are put forward.The characteristics of NOx emission from coal combustion in cement precalciner has been investigated in a desigened gas-solid reactor under the suspension and spray condition of industry precalciner. Based on experiments stuies, the release characteristics of NOx emission have been obtained and the effect mechanisms of the special working condition such as high concentration of CO2 and the presence of cement raw meal in cement precalciner on NOx emission have been analyzed.The calculation principles/methods and models of kinetic modeling have been introduced which provide theoretical basis for the studies of detail kinetic modeling of NOx formatin, and the significance of kinetic modeling studies on the process of combustion has been analyzed. The development history of kinetic modeling studies and the main resesrch content of detailed kinetic study on combustion using Chemkin modeling have been summaried.The mechanism of nitric oxide (NO) formation from the oxidation of hydrogen cyanide (HCN) during the combustion of volatile from pulverized coal under cement precalciner conditions has been studied in terms of a chemical kinetic model. By using the rate of production (ROP) and pathway analyses, the detail kinetics modeling of volatile NO formation has been established and the specific chemical effect of high concentration of CO2 in cement precalciner on volatile NO formation was identified in different excess air coefficients during coal volatile combustion. Specifically,the major reaction pathways of volatile NO formation from HCN under cement precalciner conditions are identified. And the numerical results of this study proposed a theoretical guidance for effectual predictive control of NOx emission in cement precalciner.Finally, the whole research work was summarized and the prospects for the further studies on coal analysis were suggested.更多还原