Study On Optical Scattering System Of On-line Monitoring Instrument For Particle Concentration And Particle Size Spectrum

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.