Research On CS₂ And SO₂ Gas Detection Base On Adaptive Differential Absorption Spectroscopy Technology

As an organic solvent and chemical raw material,CS₂is widely used in chemical industry,manufacturing industry and laboratory research.As a combustion product of coal and petroleum,SO₂is one of the main atmospheric sulfur pollutants in China,and the emission of SO₂deteriorates the air quality of cities and poses a great threat to soil,water bodies and forest land.In addition,CS₂and SO₂have also been confirmed to have important application value in the field of high-voltage insulated electrical equipment fault diagnosis.Therefore,it is especially important to realize the high-precision detection of CS₂and SO₂in the fields of environmental protection and power grid safety.In this paper,we introduced an adaptive sliding window in DOAS,developed A-DOAS,solved the nonlinearity of DOAS measurement gas in a wide concentration range,and measured the CS₂absorption cross section using CS₂conversion equilibrium relationship under photocatalysis.The main research includes.（1）The absorption cross section of CS₂was measured in the range of 188-215 nm at room temperature and atmospheric pressure.CS₂absorption cross section is an important spectral data for gas concentration inversion based on DOAS.In this paper,the effect of CS₂conversion on absorption cross section measurement was eliminated by controlling the light intensity and gas flow rate,and accurate CS₂absorption cross section was obtained.Firstly,the experimental setup for CS₂absorption cross section measurement was built,and secondly,the method of CS₂absorption cross section and CS₂concentration inversion was established.Finally,by setting different incident light intensities and gas flow rates,the relationships between the effects of light intensity and flow rate on CS₂adsorption and conversion were established.By setting reasonable parameters,the influence of CS₂absorption and conversion on the absorption cross section was weakened.Base on the optimization of the parameters,the CS₂absorption cross section in the wavelength range of 188-215 nm under normal pressure was given.（2）A study of CS₂measurement was carried out based on the adaptive DOAS,which solved the nonlinearity problem of CS₂measurement in the wide concentration range and balanced the measurement sensitivity at high concentration of CS₂measurement and the measurement accuracy at low concentration measurement.First,the spectral absorption characteristics of CS₂in the concentration range of 2.5-50 ppm were investigated based on the broad absorption band of 195-215 nm and the narrow absorption band of 211-215 nm for CS₂.Research shown that good accuracy is obtained in the range of 2.5-50 ppm for CS₂measurements in the broad absorption band,but there is a non-linearity between the concentration and absorption parameters at high concentrations,which reduces the sensitivity.When measuring CS₂in narrow band,a linear relationship exists in the range of2.5 to 50 ppm,and consistent measurement sensitivity can be obtained,but at low concentrations,measurement accuracy cannot be guaranteed.In order to take into account the measurement accuracy and sensitivity of a wide concentration range measurement,an adaptive sliding window is introduced,which intercepts different absorption bands according to different concentrations to evaluate the concentration of CS₂.Based on the A-DOAS measurements of CS₂gas at concentrations from 2.5 to 50 ppm,the results showed that the method can guarantee accuracy at low concentrations and eliminate nonlinearity and ensure sensitivity at high concentrations.（3）A study of SO₂concentration measurement based on A-DOAS was carried out.Firstly,the characteristic spectra of SO₂in the 200-230 nm and 290-310 nm absorption bands were investigated,and the 200-230 nm band was adopted for SO₂gas detection performance study.Secondly,the adaptive sliding window was designed for intercepting different bands according to SO₂concentration.The results showed that the full band of200-230 nm is suitable for the evaluation of low concentration of SO₂with good stability and accuracy,and the band of 225-230 nm is suitable for the evaluation of high concentration of SO₂,which can eliminate the nonlinearity and ensure the sensitivity at high concentration.Finally,the A-DOAS was used to measure several groups of SO₂at different concentrations,and the results showed that the A-DOAS is also suitable for SO₂detection in a wide concentration range.