Concentration Detection Of SO₂ And NO Mixed Gas Based On Ultraviolet Absorption Spectroscopy

Air pollution is becoming a hot issue in the country's financial growth and the general public's livelihood. The new atmosphere control law has formulated clear regulations on various pollutants emission standards. Real time monitoring of major pollutants is the necessary technical basis for the implementation of the policy of total pollutant emission control. This paper is based on the UV absorption spectrometry principium, where the experimentation was conducted on the absorption spectrum analysis of SO₂ and NO admixture and concentration measurement method of various components in the mixed gases. This article's main substance include:?1? The theoretical foundation for the identification of the gas categories and the quantitative calculation of gas concentration in various kinds of polluted gases by DOAS technology was studied. Firstly, combined with the axiom of ray scattering, various scattering extinction, such as Mie scattering and Rayleigh coefficient, is added to the measurement model, which modified the theoretical model of Lambert-Bill law under the circumstances of practical measure. Then, by using the principle of UV differential optical absorption spectroscopy, this paper design the DOAS technology process of absorption spectral data.?2? The study of sulfur dioxide absorption spectrum and concentration measurement was launched. In view of the characteristics of the continuous shock absorption spectrum of sulfur dioxide gas, the 284nm-314 nm band, which is influenced by other interfering gases, is selected as the concentration measurement band of sulfur dioxide gas. In view of the standard absorption cross section of the gas directly influences the accuracy of the gas concentration by using DOAS technique, the calibration of SO₂ standard absorption cross section is carried out by using a higher concentration SO₂ standard sample gas. The researches of on-line monitoring experiments on single SO₂ gas and SO₂ gas with the interference of NO gas were respectively conducted. The experimental results show that selecting 284nm-314 nm band for the concentration inversion of SO₂ gas of can achieve good results.?3? The study of nitric oxide absorption spectrum and concentration inversion was conducted. Because the NO gas has three strong absorption peaks in the ultraviolet band, while the main interfering gas SO₂ absorption is relatively weak in the vicinity of 226 nm, so the absorption crest in nearby 226 nm is usually selected to study the concentration measurement of NO gas. According to the overlap of NO gas absorption spectrum and SO₂ gas absorption spectrum, the subsection computational arithmetic and discrete wavelet decomposition arithmetic of NO absorption spectrum are proposed. The two method is based on separating the NO absorption spectrum signal from the mixed spectra. Then the function between the NO gas concentration and the optical density of NO gas were established. The experimental results indicate that the subsection algorithm and the wavelet decomposition algorithm can obtain good experimental effects. In contrast with the algorithm of subsection computation, the multi scale wavelet discrete decomposition method directly abtaines the NO absorption signal which is stripped from the mixed gas spectra, and the algorithm is independent.