Quantitative analysis of SO₂, NO₂ and NO mixed gases based on ultraviolet absorption spectrum

SO₂, NO₂ and NO are the main atmospheric pollutants produced by the combustion of fossil fuel. Detecting these gases is of great significance for atmospheric protection and the online concentration detection of pollutants. In this study, the concentration retrieval methods of NO, NO₂ and SO₂ and their mutual effects were studied in the wavelength range of 192.3-254.4 nm. In this band, NO, NO₂ and SO₂ have large absorption cross-sections; however, their spectrum superpositions were serious. A novel method was proposed to separate the superposed absorption spectra of NO and SO₂ or NO₂. The advantage of this method is that it can remove the influence of SO₂ and NO₂ on NO concentration retrieval. The fast Fourier transform (FFT) amplitude method was used to calculate the concentrations of SO₂ and NO₂, and the direct absorption spectroscopy method was used to calculate NO concentration. Via these methods, the gas concentrations of SO₂, NO₂ and NO can be calculated in ternary-gas mixtures. The experimental results show that these methods can effectively remove the mutual interferences between the concentration retrieval of NO, NO₂ and SO₂. The maximum absolute values of the relative deviations for the concentration retrieval of SO₂, NO₂ and NO in ternary-gas mixtures are 3.868%, 4.740% and 5.008%, respectively. These methods have high detection precision and good adaptability and are suitable for online flue detection equipment.