Research On The Key Technology Of Methane Concentration Detection System Based On TDLAS

The demand for high-sensitivity,high-precision,non-contact methane gas real-time detection systems is urgent in the fields of industrial production and environmental monitoring.Aiming at the low sensitivity,insufficient resolution,long measurement time and poor antiinterference ability of traditional gas detection technology,the real-time detection system of methane concentration based on tunable semiconductor laser absorption spectroscopy technology has the advantage of high selectivity,high resolution,high precision and short response time,and has become the main research direction of gas detection methods.Under the background of the application of TDLAS methane concentration detection system,the three key technologies of semiconductor laser drive,harmonic detection technology and semiconductor laser constant temperature control system were deeply studied.Based on molecular spectroscopy theory and Lambert Beer's law,the theoretical application of TDLAS technology in gas concentration detection was carried out,and the design scheme of TDLAS methane gas detection system combining wavelength modulation technology and harmonic detection technology was determined.Based on the molecular characteristics of methane gas,the overall design of the methane concentration detection system based on TDLAS technology was completed.The design of the semiconductor laser drive circuit,the preamplifier circuit design of the photodetector,the design of the lock-in amplifier circuit,the design of the laser thermostatic control module,and the design of the air chamber and the optical path were realized.The design and simulation of the software related to system were completed by FPGA.The experimental platform for TDLAS methane concentration detection system was constructed,and the laser drive circuit was tested for frequency accuracy and signal stability of the drive signal to verify the correctness of the laser drive module.Then,the thermostatic control module was tested to verify its temperature control accuracy and temperature stability.Finally,the system was tested by standard gas chamber,and the second harmonic amplitude at different concentrations was measured.The expression of gas concentration was obtained,and the on-line detection of methane concentration was realized.