Study On Online Synchronous Measurement System Of Gas And Particle Concentration

Pollutants which come from combustion of coal and other fossil fuels,such as carbon oxides,nitrogen oxides and soot particles are the main inducing factors of air pollution.In 2015,the ultra low emission standards of thermal power plants were fully implemented,and the emission concentration of soot,SO2 and NOx was not more than 5 mg/m~3,35 mg/m~3 and 50mg/m~3 respectively.The research on technology and equipment that can accurately and quickly measure the concentration of gas components and particles,is of great significance for the environmental protection departments to supervise and control the discharge of pollutants.The instrument for measuring gas concentration and particle concentration synchronously is still in blank state.In this paper,a design concept of on-line synchronous measurement system for gas concentration and particle concentration is proposed,in view of the measurement problem in flue gas emission,which provides a solution for the simultaneous detection of gas component concentration and particle concentration.To solving the above problems,the following research works have been carried out in this paper:1.The principle of simultaneous measurement of gas concentration and particle concentration is put forward.According to the characteristics of gas concentration measurement and particle concentration measurement,the optical path of gas concentration measurement and particle concentration measurement are coupled.The measurement of gas concentration and particle concentration by a single optical path is designed.The methane concentration in the presence of particulate matter is measured through experiments.The independence of gas and particle concentration measurement is proved,which provides experimental basis for synchronous measurement principle.2.A measurement method of particle concentration based on modulating scattered light is proposed.The amplitude of scattered light signal is modulated to high frequency,and the amplitude of scattered light is obtained by orthogonal demodulation,which overcomes the disadvantage that the traditional particle measurement device is easily interfered by external interference in the process of measuring the concentration of particles with stable light intensity.The effect of light scattering on the measurement of the extinction effect in the process of particle concentration is simulated.The simulation shows that in the range of low particle concentration,that is,the concentration range of the object is measured in this paper0.1~10mg/m3.The light intensity loss caused by the extinction effect is only 0.495%,and the effect is less.3.The hardware and software of online synchronous measurement system of gas concentration and particle concentration based on FPGA as the core of data processing and control is researched and designed.The hardware circuit has completed including temperature-control and current-driver circuit for DFB laser,the DDS signal generator circuit and the FPGA data processing control system.The Ethernet transmission circuit is added to realize the interaction with other devices.The main circuit is integrated on a printed circuit board in a compact way,which realizes the miniaturization of the system.The development of software realized DDS signal generating function and the orthogonal demodulation of signal.In the implementation of the low pass filter by FPGA,the dual channel low pass filter is adopted to solve the balance problem between the processing speed and the resource occupancy.Ping Pong operation is applied in data stream processing,which realizes seamless cache and processing of data flow.4.The work of test and debug combining software and hardware is accomplished.The experiment of measuring the concentration of gas and the concentration of particles has been completed.The experiment shows that the stability of the measuring system is stable,and it can show good performance for the measurement of gas concentration and particle concentration.