Research On High Sensitivity Spectroscopic Detection Of Trace Components In Natural Gas

As a kind of clean energy,natural gas accounts for a large proportion of China's energy structure.The impurities and leakage of natural gas in the process of mining,production and transportation have a great impact on the safety production of the natural gas industry.At present,the proportion of high-end analytical instruments imported by the natural gas industry is too large.Therefore,there is a huge market demand for the development of trace gas component detection instruments in natural gas,and the prospects are very broad.This paper focuses on the analysis of natural gas trace components,to develop high sensitivity laser spectrum detection technology and application research.The main research results and innovations of this paper are as follows:1.A two-component CH4/C2H6 gas measurement system is built by using a tunable diode laser with a central wavelength of 1.653 ?m(CH4)and 1.684?m(C2H6)as the light source.The high sensitivity detection of CH4/C2H6 is realized by using a home-made long optical path multipass cell combined with wavelength modulation absorption spectroscopy and background subtraction technology.When the average time of the system is 140 s,the minimum detection concentration limit of CH4 is 1.5 ppb;when the average time of the system is 200 s,the minimum detection concentration limit of C2H6 is 100 ppb.The results show that the two-component CH4/C2H6 sensor based on TDLAS can be used to identify natural gas and biogas.2.Research on high sensitivity measurement technology of H2O and CH4 based on off-axis integral cavity technology.An off-axis integral cavity with an effective absorption path of 8.626 km is established by two high reflectivity cavity mirrors with a reflectivity of 99.9976%.When the average time is 100 s,the minimum detectable concentration sensitivity of CH4 is 7.5 ppb.The system's optimal average detection time for H2O is 200 s,and the minimum detectable concentration limit is 55 ppm.Kalman filtering method is adopted to further improve the measurement precision of the system.Kalman filtering significantly shortens the response time of the system compared with the multiple averaging method.3.High sensitivity detection of H2S gas is studied by wavelength modulation spectroscopy.When the average measurement time of the system is 300 s,the minimum detection sensitivity of H2S that can be achieved is 13 ppb.Simultaneous detection of H2S and CO2 is achieved by off-axis cavity enhanced absorption spectroscopy.When the system integration time is 171 s,the minimum detectable concentration of H2S is 150 ppb.When the acquisition time is 209 s,the corresponding minimum detectable concentration of CO2 is 1.03 ppm.