Methane And Hydrogen Trace Gases Detection Based On Quartz Detection Spectroscopy Technology

With the advent of the new times,people have begun to have an increasing demand for atmospheric environment monitoring,coal mine production safety,characteristic gas analysis of electrical equipment failure,and medical diagnosis of exhaled gas.Therefore,the development of ultra-sensitive trace gas detection research is of great significance to the development of society.Quartz-enhanced photoacoustic spectroscopy(QEPAS)is a widely used trace gas detection technology.Unlike traditional photoacoustic spectroscopy technology,the core component of QEPAS technology is the quartz tuning fork.First of all,this paper calculated the first ten vibration modes of the quartz tuning fork by using the COMSOL software simulation,and compared the result obtained by the simulation,the result calculated by the formula and the result measured by the experiment.Next,a simulation study of the vibration amplitude of the tuning fork was carried out.Finally,the simulation calculation obtained the optimal resonant tube length to be 5 mm,and the optimal laser excitation position that maximized the vibration amplitude of the tuning fork was obtained.In the experimental part,in view of the low sensitivity of traditional photoacoustic spectroscopy detection systems to methane gas detection,this paper used a high-power near-infrared tunable distributed feedback laser as the excitation light source for photoacoustic spectroscopy.In order to improve system detection performance,the modulation depth was optimized and the acoustic resonance tube was coupled.Finally,the signal amplitude was increased by adding water vapor to increase the relaxation rate of gas molecules.In this experiment,the detected QEPAS signal was3.23 mV and the minimum detection limit was 7.9 ppm.Experimental results proved that the QEPAS sensing system had a good linear concentration response to different concentrations of methane gas.In terms of the problem of insufficient detection of corrosive gases in the QEPAS detection system,light-induced thermoelastic spectroscopy(LITES)was proposed.In this experiment,the corrosive gas hydrogen chloride(HCl)was detected.The detection performance of the LITES sensing system was improved by optimizing the laser excitation position and modulation depth.Finally,the maximum amplitude of the detected LITES signal was 2.99 mV,and the minimum detection limit of the system reached 410 ppb.The experimental results proved that the LITES sensing system had a good linear concentration response to different concentrations of HCl gas,and also had a good linear power response under different laser powers.