【作者】 余亮英；

【导师】 陆继东；

【作者基本信息】 华中科技大学 ， 热能工程， 2005， 博士

【摘要】 火电厂发电成本中燃煤费用占了很大的比例,对入厂煤与入炉煤的煤质监测工作直接关系到电站锅炉运行的安全性及经济性。传统的煤质测量方法通常是进行离线测量,这种测量不能及时地反映送入炉膛的煤质的情况,远远不能满足锅炉燃烧调整和事故分析的需要,带有很大的局限性。由于检测手段的限制,使得实际需要与检测数据报出时间滞后的矛盾越来越突出,因此很有必要研究、实现煤质的快速在线检测。元素分析是煤质分析的一个重要手段。本文首先总结和分析了目前国际上在燃煤领域常用元素分析的主要技术方法,对不同的方法的优势及其存在的问题进行了分析和评价。同时,详细地分析了煤质对电厂锅炉各方面的影响,提出将一种新的光谱技术——激光感生击穿光谱技术——用于煤质快速分析的必要性。本论文主要从以下几个方面进行了有意义的研究: 重点介绍了激光等离子体的产生机理、特点,以及激光感生击穿光谱技术的原理。同时,分析了等离子体光谱连续背景的产生及其影响,最后详细描述了试验工作中搭建的激光感生击穿光谱实验系统。传统的光谱定量分析,在定量结果得出之前需要利用国际标准样品实验得到定标曲线。为了使光谱定量分析从传统的定量方法中解放出来,实现自由定标,本文介绍了激光感生击穿光谱的自由定标模型。为了更进一步地提高定量分析的精度,在自由定标模型的基础上,利用自吸收模型进行修正补充。根据激光感生击穿光谱对标准铜靶和大气的实验,对模型进行了验证,结果表明利用该模型计算出的结果与实际很吻合。分析了煤种等对激光等离子体的影响,而国外仅仅是以煤化程度低的褐煤为对象,本论文研究的煤种包括煤化程度高的无烟煤、烟煤和煤化程度低的褐煤等工业界广泛应用的动力用煤。研究发现煤化程度高的煤种产生的等离子体温度高,容易发生二次电离; 分析了煤样品的形态(片状和粉末状)对等离子体的影响,片状煤更多还原

【Abstract】 The cost of fuel takes significant importance in the power plant. Usually, the traditional method of coal quality analys is off-line. Therefore, the traditional measurements spent too much long time and analyze so slowly. So the results can’t represent the coal quality in time. The traditional technologies couldn’t meet the requirement of modern power plant due to the unavailable real-time data of coal quality. It is extremely urgent to find a new technology, which can analyze the coal quality on-line and quickly compared with the limitations of the off-line technologies. Element analysis is one of the most concerning in the assessment of coal quality. Firstly, the existing and potential technologies used for element analysis have been identified and assessed in this thesis. Meanwhile, the impact of coal on boiler of power plant was analyzed in detail,and then, put forward to the necessity of developing a new technology , know as Laser-induced Breakdown Spectroscopy(LIBS), which could analyze coal on-line. This thesis has carried on important researches from the several following respects mainly: The mechanism and character of laser plasma were introduced in detail. Meanwhile, the production theory and effect from continuous background of the plasma spectrum was analyzed, finally, the LIBS experiment system was described detail. Traditional spectrum quantitative analysis needs to utilize the standard sample experiment to get the calibration curve before the quantitative result is done. In order to make the quantitative analysis liberate from traditional quantitative method and realize the freedom calibration, this thesis put forward to a calibration-free model of LIBS. In order to improve the precision of quantitative analysis fatherly, a self-absorption model has been mentioned, which correct and complete the calibration-free model. According to the LIBS experiment of standard copper target and atmospheric pressure, the calibration-free model has been certified, the result shows the model was feasible. The anthracite coal, bituminite coal and lignite coal had been analysed in this paper, other researcher had studied the lignite coal only. The physical and chemical characters of coal effecting on the laser plasma have been studied in detail. With the high drgree of coalification, the plasma temperature is higher, and coal sample is easily to generate double ionization. The plasma intensity of chip sample is more higher than powder sample. In addition, the experimental results show that the plasma temperature and the analysis precision are higher with the smalle partical size. The effect of delay time on the calibration curves has been discussed too, the results indicate that the delay times are different for each element, the optimal times depend on the experiment. The experiments of laser-induced breakdown spectroscopy on a series of fly ash samples and the quantitative analysis of carbon contents have been carried out. The result shows that carbon content of fly ash measured by LIBS and method of Weight-Combustion are coincident well. It’s authenticated that LIBS can be used to measure carbon content of fly ash as a new method. A quantitative elements (C, H, O, N, S, Ca, Al, Si and Fe) analysis of coal samples were carried out with LIBS. Because of the self-absorbtion of laser plasma, the calibration curves of those elements shows that the curves has a trend of bend down when the concentration of the analyzed elements are higher. In addition, the quantitative measurement results shows that LIBS is a effective technology for quantitative analysis, and the relative error for each elements are almost less 5%. Finally, general summary and conclusion of the thesis as well as further development direction about research of LIBS in coal combustion are presented, and the context of on-going work is determined.更多还原