Detection Of Low Concentration Hydrogen Sulfide Gas Based On Differential Absorption

The sulfur-containing oil and gas fields are mostly in the west and south of China.The rugged terrain makes it difficult for the hydrogen sulfide gas produced to spread rapidly,which seriously threatens people's life safety.Therefore,the research on the detection of low concentration hydrogen sulfide gas is of great significance.The research content of this paper comes from the national natural fund project(41474121).In the Simulink simulation platform,the differential absorption detection system is modeled and simulated.The light signal after passing through the gas chamber is mixed with interference signal,which results in the influence of gas detection results.The signal can not only extract the amplitude signal,but also filter out the aperiodic signal and noise,which improves the anti-interference ability of the system.Therefore,in the process of modeling,the orthogonal phase-locked amplifier is designed.Two amplitude signals are obtained by the quadrature lock-in amplifier,and the amplitude ratio is obtained by comparing the two amplitude signals,so as to reverse the gas concentration.By changing the concentration of hydrogen sulfide several times,the relationship between the gas concentration and the amplitude ratio is obtained.In this paper,the differential absorption detection system for hydrogen sulfide is designed.LED is used as light source,which has simple structure and low price.The application of filtering technology improves the quality of light output and reduces the error caused by the fluctuation of light source.Using fiber grating instead of traditional filter to modulate the light source,and combining the intensity modulation technology of light source and lock-in amplification technology,the interference of optical path and the influence of intensity fluctuation of light source are eliminated,and the detection sensitivity is improved.The air chamber is improved so that the incident light can be reflected back and forth in the air chamber,thus increasing the length of the optical path.At the same time,the hardware part of the detection system is designed.The single chip microcomputer transmits the data to the upper computer through serial communication for display.Finally,the gas detection platform is built to detect the hydrogen sulfide gas of different concentrations.The results show that the new method based on differential absorption can reduce a series of errors caused by light source fluctuation and light path strength,and improve the accuracy of gas detection.It is found that when the concentration of hydrogen sulfide gas is too high,the detection error will increase,and the output error of the system is within the acceptable range,so the detection system is suitable for the detection of low concentration hydrogen sulfide gas.This study can be applied to oil and gas field exploitation,and provides a good theoretical basis for the detection of low concentration hydrogen sulfide gas.