基于吸收光谱技术的工业气体监测关键技术研究

发布时间：2018-07-24 12:27

【摘要】：近年来随着工业的发展，大气污染问题日益突出，不仅严重影响了人们的日常生活，而且也极大地制约了社会的可持续发展。一氧化碳是污染气体中的重要成分，广泛存在于人们的生活环境中，该气体浓度过高时将严重威胁人类健康，因此对一氧化碳气体排放进行监测和控制显得十分紧迫。目前一氧化碳气体的检测方法已经比较成熟，，但是尚不能满足复杂工业现场中在线监测、高灵敏度测量等要求。可调谐半导体激光吸收光谱技术具有高选择性、在线测量、高灵敏度、响应速度快等优点，经过近30年的发展，已广泛应用于大气化学研究和污染气体监测中，成为常用的大气痕量气体高灵敏度监测技术，并且各知名仪器制造商也都对激光气体分析仪展开了研发。开发具有自主知识产权的基于吸收光谱技术的一氧化碳监测系统是本文的主要研究内容，不仅从理论上验证了基于吸收光谱技术进行气体浓度监测的可行性，给出了严密的数学推导，而且设计了基于吸收光谱技术的气体浓度监测实验系统。本文的研究工作主要从三个方面开展：一、对基于吸收光谱技术的气体浓度监测方法理论进行研究，从分子的角度阐明了激光光强信号被气体分子吸收的机理，并介绍了吸收光谱技术的理论基础：朗伯-比尔定律；二、介绍基于吸收光谱技术的一氧化碳浓度监测系统的设计方案。首先，对该系统的设计思想、工作原理和硬件构成进行介绍，并着重对主控单元和光源模块进行阐述；其次，针对单中央处理芯片运算速度慢，难以满足本系统多通道采样、多参数复杂运算的要求，本文采用了双中央处理器的设计模式来提高系统的可靠性和系统的运行速度；再次，本系统通过对二次谐波信号进行数据处理，得到被测气体的浓度信息，设计了更符合工程实际的气体浓度计算方法；最后，针对低浓度气体的二次谐波信号信噪比较低的情况，设计了基于傅立叶变换的二次谐波滤波算法，并针对高温高压的复杂工业现场，设计了温度压力补偿算法；三、利用本系统对一氧化碳气体进行实际测量，并将采集得到的一氧化碳气体的二次谐波信号进行数据处理，浓度测量结果表明：本文设计的基于吸收光谱技术的气体浓度监测系统能够准确测量一氧化碳气体浓度。本文设计了基于吸收光谱技术的一氧化碳气体浓度监测系统，并通过已知浓度的一氧化碳气体对该系统的精度进行检测，通过气体浓度反演结果表明该系统浓度监测结果的准确性。最后，针对激光气体分析仪如何完成从实验室的实验验证到工业现场的实际应用的转换问题，提出了可行的建议。
[Abstract]:In recent years, with the development of industry, the problem of air pollution has become increasingly prominent, which not only seriously affects people's daily life, but also greatly restricts the sustainable development of society. Carbon monoxide (CO) is an important component of the polluted gas, which widely exists in people's living environment. When the concentration of carbon monoxide is too high, it will seriously threaten human health, so it is very urgent to monitor and control the emission of carbon monoxide. At present, the detection method of carbon monoxide gas is mature, but it can not meet the requirements of on-line monitoring and high sensitivity measurement in complex industrial field. The tunable semiconductor laser absorption spectroscopy has the advantages of high selectivity, on-line measurement, high sensitivity and fast response. It has been widely used in atmospheric chemistry research and pollution gas monitoring after nearly 30 years of development. It has been widely used as a sensitive monitoring technique for trace atmospheric gases, and laser gas analyzer has been developed by many famous instrument manufacturers. The development of carbon monoxide monitoring system based on absorption spectrum technology with independent intellectual property rights is the main research content of this paper, which not only proves theoretically the feasibility of gas concentration monitoring based on absorption spectrum technology. A strict mathematical derivation is given, and an experimental system of gas concentration monitoring based on absorption spectrum technology is designed. The research work in this paper is mainly carried out in three aspects: first, the theory of gas concentration monitoring based on absorption spectrum technology is studied, and the mechanism of laser intensity signal absorbed by gas molecule is explained from the molecular point of view. The theoretical basis of absorption spectrum technology: Lambert-Beer 's law and the design scheme of carbon monoxide concentration monitoring system based on absorption spectrum technology are introduced. Firstly, the design idea, working principle and hardware structure of the system are introduced, and the main control unit and light source module are emphasized. Secondly, because of the slow operation speed of single central processing chip, it is difficult to satisfy the multi-channel sampling of the system. In order to improve the reliability of the system and the running speed of the system, the design mode of dual central processor is adopted to improve the reliability and the speed of the system. Thirdly, the data processing of the second harmonic signal is carried out in the system. The concentration information of the measured gas is obtained, and the calculation method of the gas concentration is designed, which is more in line with the engineering practice. Finally, the signal to noise ratio of the second harmonic signal of the low concentration gas is low. The second harmonic filter algorithm based on Fourier transform is designed, and the temperature and pressure compensation algorithm is designed for the complex industrial field of high temperature and high pressure. The data of the second harmonic signal of carbon monoxide gas are processed. The concentration measurement results show that the gas concentration monitoring system based on absorption spectrum technology can accurately measure the concentration of carbon monoxide gas. In this paper, a carbon monoxide concentration monitoring system based on absorption spectrum technology is designed, and the accuracy of the system is measured by the known concentration of carbon monoxide gas. The results of gas concentration inversion show the accuracy of the system concentration monitoring results. Finally, some feasible suggestions are put forward to solve the problem of how to convert the laser gas analyzer from experimental verification in laboratory to practical application in industrial field.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP274

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