【作者】 袁晓东；

【导师】 朱明； 夏东海；

【作者基本信息】 华中科技大学 ， 电子与通信工程， 2019， 硕士

【摘要】 固定污染源排放烟气中的颗粒物是大气污染物的重要组成部分,对大气环境、人体健康和人类的生活造成了不利的影响,如何对固定污染源排放的颗粒物进行连续在线监测引发了广泛的关注。本文基于Mie散射理论,设计实现了一种探测颗粒物粒径分布和浓度的光学系统。本文首先根据Mie散射理论,提出了一种利用单波长测量颗粒物浓度的方法,并根据这种方法完成了设备结构的设计和分析。通过分析,发现该方法在颗粒物粒径发生变化时对浓度的测量并不准确。固定污染源排放烟气中颗粒物的折射系数通常不会发生明显变化,根据Mie散射理论,散射光信号与颗粒物粒径分布、浓度和入射光波长有关。其中,粒径分布近似符合正态对数分布,可用中值粒径和标准差表达,此时需要求解中值粒径、标准差和颗粒物浓度三个参数,理论上需要三路不同波长的散射光信号来完成计算。于是本文又提出了一种三波长的探测方法,在利用探测器对三路散射光信号的响应实现对颗粒物粒径分布的探测后,根据其中一路的光强响应值探测颗粒物浓度。本文根据三波长的测量原理,通过对单波长设备的改进,设计了三波长测量粒径分布和浓度的设备,并对设备的气路进行了仿真分析。使用三波长结构的设备,不仅能获得颗粒物更多的信息,而且能够使浓度测量更加准确。本文尝试将该设备应用于对火电厂排放烟气中颗粒物的连续监测中,在完成对探测设备的设计之后,利用实验室的现有资源,设计了相关实验平台,使用已有的粒径测量设备和浓度测量设备作为参照,对本设备的测量准确性和稳定性做出了实验验证。该系统的实现最终促使资助课题通过了国家重点研发计划中期检查。更多还原

【Abstract】 Particulate matter in flue gas emitted by fixed pollution sources is an important part of atmospheric pollutants,it has detrimental effects on the atmospheric environment,human health and human life.Therefore,how to continuously monitor the particulate matter discharged from fixed pollution sources has caused widespread concern.In this paper we designed and implemented a device for detecting the particle size distribution and concentration of particles based on the Mie scattering theory.In this paper,we proposed a method for measuring the concentration of particulate matter by single-wavelength optical detector and completed the design and analysis of the equipment structure based on the single-wavelength method.We found that this method does not accurately measure the concentration when the particle size changes.Therefore,a three-wavelength detection method is proposed.Since the refractive index of particulate matter in the flue gas from a fixed source of pollution usually does not change significantly,the scattered light signal is related to the particle size distribution,concentration and wavelength of incident light.The particle size distribution is calculated by the detectors’ response to the three-channel scattered light signal.After the calculation of the size distribution,the mass concentration of the particles is detected based on the response of the light intensity of one of the channels.The device using a three-wavelength structure can not only obtain more information on the particles,but also make the concentration measurement more accurate.The device in this paper is applied to the continuous monitoring of particulate matter in flue gas from thermal power plants.After the design of the detection equipment,we used the existed resources to design an experimental platform to verify the accuracy and stability of the measurement of the equipment.As reference,we used existing particle size measuring equipment and concentration measuring equipment to measure the particle matters simultaneously.更多还原