【作者】 冯荣；

【导师】 徐明厚；

【作者基本信息】 华中科技大学 ， 热能工程， 2004， 硕士

【摘要】 煤作为一次能源在我国的利用方式主要就是燃烧,而煤的燃烧是造成我国生态环境破坏的最大污染源。燃煤污染已成为制约我国国民经济和社会持续发展的一个重要因素。在燃煤造成的污染物中,除二氧化硫、氮氧化物和二氧化碳外,有关痕量元素及其化合物的排放已经成为燃烧污染中的一个新兴而前沿的研究领域,成为愈来愈关切的热点。本文首先对痕量元素进行了综述,从痕量元素的定义、来源、危害、煤中的含量、分类、煤燃烧过程中的转化机理以及研究现状等方面进行了介绍;然后阐述了痕量元素化学热力学的研究,采用化学热力学软件F*A*C*T预报了煤中汞、镉、砷、铅、铬、镍六种痕量元素在煤燃烧过程中的的化学形态分布,模型中特别增加了硫的氧化作用以及矿物质钙和硅对于痕量元素转化的影响;接着阐述了痕量元素化学动力学的研究,使用CHEMKIN-III软件包对汞和铬的化学动力学进行计算,建立了均相汞氧化模型和铬氧化模型,动力学模拟计算结果与Mamani-Paco 和 Widmer等人的实验数值吻合较好。最后,论文叙述了化学热力学与化学动力学的结合,并以汞和铬为例对上述两种研究方法进行了比较与分析。总体而言,化学热力学模型的计算有助于动力学模型的建立;两种方法的计算结果在生成物的趋势上是相似的。两种方法计算结果存在误差的可能原因是:(1)痕量元素氧化机理的动力学参数本身存在误差;(2)热力学分析中反应时间取值的误差;(3)热力学平衡计算中的误差。更多还原

【Abstract】 The main way to utilize coal, which is a main kind of energy source in China, is burning. But coal combustion will bring great pollution to the environment and do harm to the health of human beings and life of wild plant and animals, and it will even affect the progress of sustainable economic development in China. Emission and control of trace element (TE) from coal combustion is now an emerging and frontier area and going to attract more attention in future. In this paper, the trace elements was comprehensively presented at first from seven aspects, such as definition, origination, harm, content in coal, kind, transform mechanisms and lately study progress. The thesis then introduced the method of chemical equilibrium analysis, and F*A*C*T, the software of chemical thermodynamics was used to predict the speciation of six kinds of trace elements, that is mercury, cadmium, arsenic, lead, chromium and nickel in flue gases during coal combustion. Especially, oxidant of sulfur and minerals of calcium and silicon were taken into account to include in the models of equilibrium. At the same time, the theory of chemical kinetics was also referred and the procedure CHEMKIN-III , just programmed according to the theory, was utilized to describe accurately reaction products and their concentrations-time correlation of mercury and chromium. Speciation of mercury and chromium in combustion-generated flue gases was modeled by detailed kinetic model. The results from the model kinetic calculation are in reasonable agreement with Mamani-Paco and Widmer’s experimental data.Finally, the results of models of chemical thermodynamics and kinetics were combined and compared for the example of mercury and chromium. The thermodynamic calculation help to set up the kinetic models. The results of the two were similar and errors maybe were caused by: (1) the errors of the kinetic parameters in oxidation mechanism; (2) the errors of choice of reaction time in the thermodynamic analysis; (3) the errors of the equilibrium calculation.更多还原