激光消光法粉尘浓度在线测量系统的研发

发布时间：2018-08-12 09:03

【摘要】：燃煤电厂产生的大量烟气是大气污染的主要原因之一。发展粉尘颗粒浓度监测技术是解决大气环境粉尘污染问题的首要任务之一。目前,现有的粉尘颗粒浓度测量系统,往往难以满足恶劣环境下在线监测要求。本文基于激光消光法原理,结合CCD相机和光纤成像技术,研发了一套粉尘浓度在线测量系统。首先,介绍了光散射基本理论,并在此基础上阐述了Mie散射理论、夫朗禾费衍射理论和全散射理论。根据全散射法的原理和颗粒粒径分布函数,采用平均粒径和平均消光系数,推导出了激光消光法的测量方程。该方法可以直接求解颗粒的质量浓度,而且极大地简化了测量系统结构的复杂性。其次,结合激光消光法的测量方程,研制了一套基于CCD和光纤成像的粉尘浓度在线测量系统。系统主要包括电源系统、发射光路系统、透射光采集系统、数据处理系统以及吹风装置。发射光路系统由激光器、空间滤波器、准直透镜和分束镜组成,实现激光的准直发射和杂散光的消除,提高入射光束的质量。透射光采集系统利用光纤传像束和CCD相机,实现光信号传输和采集功能。数据处理系统是一套基于MFC框架结构的应用程序,具有实时在线测量粉尘浓度、显示透射光强度和浓度动态曲线图,并具有数据存储等功能。吹风装置则利用干净的压缩空气清扫光学窗口以及防止烟气进入测量系统。五个系统高度集成,提高了测量系统的抗干扰性和稳定性。最后,设计了粉尘发生装置,用于测试粉尘浓度在线测量系统的性能。根据CCD相机的像素位深和激光器的输出功率,设定了相机最佳工作曝光时间,并分析了测量系统随机误差产生的因素。通过粉尘浓度测量结果与取样称重法标定结果比较,表明：系统的零点漂移的范围约为--10～10g/m3,在低浓度范围,在线测量系统测量精度较差；但在中高浓度范围,系统精度高,且稳定可靠。该系统能够实时在线测量粉尘浓度值,并且具备很好的灵敏性和稳定性。
[Abstract]:A large amount of flue gas produced by coal-fired power plants is one of the main causes of air pollution. The development of dust particle concentration monitoring technology is one of the most important tasks to solve the problem of dust pollution in atmospheric environment. At present, the existing dust particle concentration measurement system is often difficult to meet the requirements of on-line monitoring in harsh environment. Based on the principle of laser extinction, combined with CCD camera and optical fiber imaging technology, an on-line dust concentration measurement system is developed in this paper. Firstly, the basic theory of light scattering is introduced, and the Mie scattering theory, Fraunhofer diffraction theory and total scattering theory are expounded. According to the principle of total scattering method and particle size distribution function, the measurement equation of laser extinction method is derived by using average particle size and average extinction coefficient. This method can directly solve the mass concentration of particles and greatly simplify the complexity of the measurement system. Secondly, an on-line dust concentration measurement system based on CCD and optical fiber imaging is developed based on the measurement equation of laser extinction method. The system includes power supply system, transmission system, data processing system and blowing device. The system consists of a laser, a spatial filter, a collimation lens and a beam splitter, which realizes the collimation of the laser and the elimination of stray light, and improves the quality of the incident beam. The optical signal transmission and acquisition function is realized by using optical fiber image beam and CCD camera in the transmission optical acquisition system. The data processing system is a set of application program based on MFC frame structure. It can measure dust concentration in real time, display the dynamic curve of intensity and concentration of transmitted light, and have the function of data storage and so on. The blowing device uses clean compressed air to clean the optical window and prevent smoke from entering the measurement system. The five systems are highly integrated to improve the anti-interference and stability of the measurement system. Finally, a dust generator is designed to test the performance of the dust concentration measurement system. According to the pixel depth of the CCD camera and the output power of the laser, the optimal exposure time of the camera is set, and the factors causing the random error of the measurement system are analyzed. By comparing the dust concentration measurement results with the sampling and weighing calibration results, it is shown that the range of zero drift of the system is about -10 ~ 10g / m ~ 3, and the measurement accuracy of the on-line measurement system is poor in the low concentration range, but the system accuracy is high in the medium and high concentration range. And stable and reliable. The system can measure dust concentration in real time and has good sensitivity and stability.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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