Dust Concentration On-line Monitoring Device Based On Oscillation Balance Method

With the rapid development of all walks of life in China,air quality is getting worse and worse,which is a serious threat to people's health.Stationary source emissions is one of the main factors of air pollution,it has become a key indicator in the monitoring of the national environmental protection department.In order to meet the requirements of the state for the monitoring of ultra low concentration emissions from stationary sources.This paper presents a smoke concentration on-line monitoring device based on oscillation balance method,its core idea is to use a certain fixed function relationship between the natural frequency of the object and its own quality,thus by determining the natural frequency of the object we can obtain the weight of the object indirectly.The natural frequency of the oscillating tube before and after sampling is measured by the high precision frequency measurement circuit,and the quality of the smoke particles is obtained by calculation.The main work of this paper is as follows:(1)The design of on line monitoring system for soot concentration based on oscillation balance method.By using fuzzy PID algorithm,the sampling velocity of flue gas is realized in the smoke sampling part.The principle of oscillating balance method is adopted in the continuous weighing part of smoke and dust.The temperature and pressure compensation and the oxygen content conversion are realized in the smoke and gas detection part.The data display part realizes the real-time monitoring of the key data,such as the smokeconcentration and so on.The system can realize the real-time monitoring of the smoke concentration under the ultra low concentration emission.(2)Using the finite element analysis software ANSYS,the dynamic modeling and Simulation of the core element of the mass balance sensor of the oscillating balance method.The oscillation characteristics of different parameters of oscillating tube for the detailed simulation,we get the relationship between these parameters and the oscillation characteristics,determine the optimal design of the structure of the oscillating tube,the oscillation tube under the scheme of high measurement sensitivity,meet the requirements of low concentration detection.(3)The hardware circuit of the mass sensor based on the oscillating balance method is designed.Using DDS chip AD9832 to generate frequency adjustable excitation signal.The method of phase difference detection is used to capture the natural frequency of the oscillator,and the accuracy of the frequency measurement circuit affects the accuracy of the weighing.According to the principle of equal precision frequency measurement method,using the FPGA with 100 MHz crystal,to achieve the detection signal frequency measurement,the measurement accuracy can reach 0.001 Hz.By comparing the test results of the mass balance and the analytical balance,the relative error of the measurement data is relatively low,and the soot particles of 0.1mg can be accurately measured.The mass sensor module is added to the on-line monitoring device of the smoke concentration,and the measurement results are in good agreement with the measured results of the off-line filter membrane weighing sampling method.The smoke concentration online monitoring device based on oscillation balance method has the use value,I believe that through continuous exploration and improvement,the application prospect of this product is widely used in industry,agriculture,energy and the environment quality of social life of the domain.