| SO2 and NO produced in industrial production are one of significant causes of atmospheric pollution.The government has formulated strict SO2,NO emission standards and requirements for monitoring equipment of pollutant gas concentration.This paper focuses on the accurate detection of low concentration SO2 and NO.According to HJ 75-2017 and HJ 76-2017 standards,the detection principle and method of SO2 and NO are studied.The structure design of ultraviolet differential low concentration flue gas analyzer is carried out,and the experiment is carried out.The accurate detection of low concentration SO2 and NO is realized.The major research contents and key techniques are composed of the following three parts:1.Based on ultraviolet differential absorption spectroscopy?UV-DOAS?,a method for the determination of SO2 and NO in low concentration is designed.To improve the resolution of the system,a long distance gas cell with a right angle prism is designed.According to the detection principle,the absorption characteristics of the gas to be measured and the detection requirements,the key components are reasonably selected.2.According to the absorption characteristics of SO2,the absorption characteristics frequency domain expressing algorithm is proposed to obtain the absorption characteristics of SO2 in the frequency domain cooperate with PCA.To improve the accuracy and stability of the algorithm,band selection algorithm for SO2detection based on absorption characteristics frequency domain expressing algorithm is studied.3.Based on UV-DOAS,the traditional differential algorithm is optimized.DB11wavelet is selected as the wavelet basis to study the characteristics of each layer after wavelet decomposition of the differential absorption spectrum of NO.A frequency domain representation based on wavelet decomposition is proposed to extract the absorption characteristics of NO on the D6 component of differential absorption spectrum after wavelet decomposition. |
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