【作者】 姚顺春；

【导师】 陆继东；

【作者基本信息】 华南理工大学 ， 电站系统及其控制， 2011， 博士

【摘要】 近年来,随着我国电力生产的快速发展和用电结构发生的重大变化,使电站锅炉面临来煤多变,煤质特性复杂多样,大范围的负荷变化等不利影响,导致运行中出现各种各样的问题,比如燃烧效率偏低、燃烧稳定性差、受热面积灰、结渣、磨损等,不利于机组的稳定控制,直接影响电站锅炉运行的安全性和经济性,也严重影响了电网运行安全。燃煤电站锅炉机组在线测量技术的缺乏已经成为制约火电机组优化运行技术发展的瓶颈问题之一。因此本文致力于探讨将激光诱导击穿光谱技术应用于电站锅炉的运行诊断中,以此作为论文的研究主题,针对粉煤灰未燃碳、燃煤结渣特性和灰分含量以及受热面失效趋势的快速分析和检测开展理论和实验研究。论文在粉煤灰未燃碳、燃煤结渣特性和灰分含量以及受热面失效分析的技术水平和研究现状基础上,阐述了本论文选题的背景和意义,并明确了本论文的研究内容。详细的介绍了激光诱导击穿光谱技术原理与搭建的实验系统,为实现激光器和光谱同步控制进行了触发信号控制系统改造。将多变量分析方法引入激光诱导击穿光谱技术的定性和定量分析中,在详细阐述各方法的数学原理和计算过程的基础上,结合实验研究验证了多元线性回归、主成分回归和偏最小二乘法回归方法在LIBS定量分析方面的潜力。对重要测量参数之一的激光能量对粉煤灰未燃碳分析的影响机制和规律进行了深入研究,探讨了在大气环境下利用深紫外区碳谱线定量分析未燃碳的可行性。针对基体效应影响定量分析的问题,引入了多元线性回归和多谱线强度和为内标的定量分析方法,对比了不同煤种的粉煤灰样品未燃碳含量的定量分析结果,验证了激光诱导击穿光谱技术分析粉煤灰未燃碳的煤种适应性能力。在深入研究样品形态和激光能量这两个重要参数对燃煤中主要的灰成分元素测量的影响机制和规律的基础上,对比分析了直接关系到现场应用的两种收光模式下的燃煤等离子体光谱信号,发展了一种基于单次光谱同时检测Si₂O和Al₂O₃的燃煤结渣特性评价方法。此外,针对传统方法由光谱数据先得到灰成分含量再计算灰分含量的测量精确度较差问题,引入了偏最小二乘法,发展了直接提取燃煤光谱数据分析得到灰分含量的新方法,并验证了其良好的灰分分析精确度。针对传统失效分析方法需要进行破坏性割管和无损检测方法只能分析裂纹等宏观缺陷的问题,提出了将激光诱导击穿光谱应用于受热面材料宏观缺陷出现前的失效趋势分析。在详细分析锅炉受热面材料失效特征的基础上,深入研究了不同金相组织和不同球化程度的受热面材料与激光相互作用的机制,揭示了谱线特征、等离子体温度和电子密度等激光等离子体特性随受热面材料不同状态的变化规律。并引入了主成分分析法,利用更多可以表征材料特性的光谱数据对不同组织的样品进行了归类。为发展受热面失效趋势分析的新方法和拓展激光诱导击穿光谱技术应用的新方向奠定了理论基础和实践依据。更多还原

【Abstract】 In recent years, with the rapid development of electric power production and the major changes of power consumption structure, the boiler will be affected by many adverse factors （e.g. coal changes, complex and diverse quality characteristics of coal, a wide range of load variability, etc.）. These adverse factors may lead to a series of problems, such as low combustion efficiency, poor combustion stability, fouling of heating surface, slagging, abrasion, etc. which are not conducive to the stability of the boiler control. There are not only direct impact on the safety of boiler operation and economy, but also seriously affect the power grid security. The lack of online measurement technology for coal-fired power plant boiler units’ has become one of bottleneck problems that limite the development of optimal operation of thermal power technology. The purpose of this thesis is to investigate the potential of laser-induced breakdown spectroscopy technology used in power station for boiler diagnosis, of particular interest to the theoretical analysis and experimental research of unburned carbon of fly ash, slagging characteristics of coal and ash content and the failure trend of heat exchange surface.Firstly, the research status of the measurement technology of unburned carbon of fly ash, slagging characteristics of coal and ash content and the failure trend of heat exchange surface were reviewed. The research contents of this thesis were details based on the representation of backgroung and purpose. Moreover, the principles of laser induced breakdown spectroscopy and the structures of the experimental system were detailed. The transformation of trigger signal for achieving simultaneous control of lasers and spectroscopy was also introduced. Then multivariate analysis method was introduced to the qualitative and quantitative analysis of laser-induced breakdown spectroscopy, the mathematical theory and calculation process of these methods were described in detail. At last, the potential of linear regression, principal component regression and partial least squares regression method for simultaneously quantitative analysis of nutrients in fertilizer was demonstrated by experiment.Secondly, the impact of laser energy on the measurement of fly ash carbon content was investigated. The analysis of unburned carbon in coal fly ash using laser-induced breakdown spectroscopy in deep UV was also discussed. Besides, in order to correct the adverse effect of matrix effects, the multiple linear Regression and multi-line intensities as the internal standard method were employed to quantitative analyze the unburned carbon in fly ash. The analysis shows that traditionally used univariate calibration in LIBS does not qualify quantitative analysis of fly ashes from different kinds of coal due to the presence of matrix effects. Instead, multivariate calibration has a better performance as the matrix effects can be taken into account with the influence of the spectroscopic signals of other components in fly ash. It is indicated that laser-induced breakdown spectroscopy is suitable for rapidly detect unburned carbon in fly ash with receptible applicability.Then, the effect law and influence mechanism of the sample morphology and the pulse laser energy on the measurement of the major elements in coal ash were analyzed. On this basis, the quantitative analysis results of SiO₂ and Al₂O₃ in different placement of focus len that was directly related to the application of LIBS in field were compared. The indicator of slagging characteristics （SiO₂/Al₂O₃） calculated by the measurement of laser induced breakdown spectroscopy was compared with that of routine laboratory analysis. Furthermore, the multivariate analysis method was employed to extracte coal ash content from LIBS spectral. These analysis results were compared with that provided by elemental analysis.At last, in order to develop nondestructive examination technology for analysis the failure tendency of boiler heat exchange surface before the appearance of macrography craze, LIBS was employed as a potential analysis technology. On the basis of the detail of characteristics of boiler heat exchange surface, the interaction mechanisms between laser and boiler heat exchange surface materials with different microstructure and pearlite spheroidization were analyzed. The variations of line intensity, plasma temperature and ablated crater of the pearlitic/ferritic and martensitic phases were investigated. Alternatively, principal component analysis method was employed to discriminate the pearlitic/ferritic from martensitic phases. Furthermore, the lines intensities, the intensity ratio of atomic and ionic lines, plasma temperature and electron density of raw material and different pearlite spheroidization samples were also investigated. It should be noted that there are good corresponding relationship between the intensity radio of atomic and ionic lines, electron density and the hardness of these samples.更多还原