Research On Measurement Method Of Hydrogen Sulfide Gas Concentration Based On TDLAS Technology

In the exploitation of petroleum and other industrial raw materials,it is very likely to produce highly toxic hydrogen sulfide gas.Once the gas leaks,it will not only corrode industrial materials and explode when exposed to open flames,but also cause huge damage to the human body and even cause death.As a new detection technology,Tunable Diode Laser Absorption Spectroscopy(TDLAS)has the advantages of fast response and strong adaptability,which can realize the real-time measurement of hydrogen sulfide gas concentration under harsh conditions.The theoretical basis of TDLAS detection technology is studied.The principle of gas molecular absorption,the generation of spectrum and the spectral line function of absorption spectrum are deeply analyzed.The absorption spectrum line of hydrogen sulfide gas is analyzed in detail.Finally,1.578μm is selected as the absorption wavelength of hydrogen sulfide gas.With the help of Lambert-Beer law,combined with wavelength modulation technology and harmonic detection technology,detailed analysis and mathematical derivation are carried out to provide a perfect theoretical basis for the research of detection system.On the basis of theoretical research,the whole system simulation is completed.The simulation process is divided into independent links,and each link is simulated and analyzed,and the simulation performance is tested by adding interference noise.The simulation results verify the feasibility of the technology,which plays an important role in guiding the design of the system.The hydrogen sulfide gas detection system is designed,and each module is optimized from the aspects of filtering noise and increasing signal strength.The system design mainly includes the following modules: the laser selection,the drive and temperature control of the light source control module,the F-P filter and gas absorption cell design of the gas absorption module,the selection and preprocessing of the photodetector of the signal receiving module,the lock-in amplifier module and the design of human-computer interaction system.In particular,based on the design of long optical path gas absorption cell,in order to meet the needs of miniaturization of the system and improve the utilization rate,a gas absorption cell with single gas chamber and double optical path is designed,which can realize the selection of two optical paths,meet the different accuracy requirements of hydrogen sulfide gas detection in different environments,and can also be used for mixed gas detection.In addition,the digital phase-locked amplifier is designed,and the algorithm is used to extract the second harmonic,which solves the error problem caused by the traditional analog lock-in amplifier,with low cost,small volume and convenient maintenance.Finally,the hydrogen sulfide detection system is calibrated,and the whole system is analyzed from two aspects of system error and stability.Through experiments,it can be concluded that the detection error of the gas detection system within the measured concentration range is less than 2%,and it has good stability and meets the requirements of hydrogen sulfide gas detection.