Sulphide Gas Detection Based On Photochemical Conversion And Differential Absorption Spectroscopy

Sulphides are widely present in production and life in the natural environment,industrial production,and medical and health.The discharge into the air will eventually form acid rain,which will cause harm to human health and equipment.Therefore,the measurement of sulphide content and related parameters will help ensure equipment.Normal operation and safety of people's lives.Optical detection methods have been gradually applied to sulphide detection due to their advantages such as high sensitivity and strong online detection capability.This paper mainly uses ultraviolet differential absorption spectroscopy technology to combine the photolysis and redox chemical reactions under the action of ultraviolet light to carry out research on the measurement of sulphide content and related parameters.It mainly solves the problem of mutual interference caused by spectral overlap in spectrum detection.The problem that the differential absorption spectroscopy technique cannot be applied due to variable absorption characteristics and the problem of unstable gas measurement during the photochemical reaction process.Firstly,based on the combination of segmented differential absorption spectroscopy technology and photocatalytic reaction,trace H2S gas concentration measurement was realized.H₂S gas has a slowly changing absorption characteristic in the vacuum ultraviolet band below 200 nm,leading to the need to protect with nitrogen to prevent the absorption of ultraviolet light by H₂S gas measurement.In addition,the absorption spectrum of H₂S and the absorption spectrum of SO₂ gas at 180?230 nm The existence of spectral overlaps causes SO₂ to interfere with H₂S measurement when measuring H₂S and SO₂ mixed gas.In order to solve the problems in H2S gas measurement,this paper uses photocatalytic conversion to convert H₂S to SO₂,uses segmented differential absorption spectroscopy to measure SO2 gas concentration changes to achieve H2S gas concentration measurement.In a mixed gas of H2S and SO2,the SO2 gas concentration is first measured using segmented differential absorption spectroscopy;after that,a small amount of oxygen is injected into the mixed gas,and O2 is converted to O3 under the irradiation of ultraviolet light,and reacts with H₂S to produce SO₂.The concentration of SO₂ gas changes its concentration,and the concentration of H2S gas can be obtained according to the conservation of S element.In order to increase the detection limits of H₂S and SO₂,we propose a segmented differential absorption spectroscopy technique.According to the characteristics of SO₂absorption,the SO₂ absorption is divided into positive and negative parts.This method can effectively reduce the influence of electronic noise on the measurement results.Secondly,based on the photolysis of CS₂ gas,the measurement of CS absorption cross section of unstable gas was realized.CS is widely used in the detection of S content in coal,petroleum,etc.Due to its unstable chemical properties,the survival time at room temperature and pressure is extremely short,and its absorption cross-section data has not been given in previous studies.This paper proposes a CS absorption cross-section measurement method based on CS₂ photolysis dynamic equilibrium.It is established under low incident light intensity and high gas flow rate.The relationship between the concentration of CS₂ and the best estimated coefficient was obtained,and then the gas concentration of the generated CS was obtained from the conservation of S element under strong incident light intensity and low gas velocity.Based on Lambert's law,the CS was calculated at 250 nm.Value of the absorption cross section at 250?258 nm.Finally,the study of CS2 gas concentration measurement in the presence of photolysis was carried out.O₂ can produce O₃ under ultraviolet light,which leads to the formation of SO₂ by CS₂ and CS under the oxidation of O₃.By measuring the concentration of SO₂ and obtaining the converted CS₂ concentration based on the conservation of S element,the correction of the concentration of CS₂ can be achieved.The adsorption effect of SO₂ on the inner wall of the gas chamber establishes the adsorption compensation function of SO₂concentration over time,and corrects the measured value of SO2 accordingly.In the flowing state,the elemental C is conserved,the concentration of CS₂ gas is corrected based on the concentration of CS gas,and the photolysis rate of CS₂ under different gas concentrations is analyzed.