Study on Online Detection Method of Methane Gas in Coal Mine Based on TDLAS Technology

Tunable diode laser absorption spectroscopy (TDLAS) provides a reliable method for detection of methane in coal mine. To study the influence of temperature and pressure on methane concentration detection, 1653.7 nm was selected as the center wavelength of methane according to the HITRAN database (explain what is this database), and then methane online detection system was designed using long path reflection structure detection technology combined with wavelength modulation and harmonic. The standard methane concentrations of 50.0, 99.8 and 200.0 ppm were adopted to study the influence of different temperature and pressure on the methane concentration within the range of −5 to 50 °C and 0–75 kPa. The results indicated that with the increase of temperature, methane concentration gradually decreased at the same pressure. Simultaneously, with the increase of pressure, the methane concentration also gradually decreased at the same temperature. Based on the above results, the temperature and pressure effects of different concentrations were combined to obtain the correction formula. The feasibility of the formula was verified by correcting the methane concentration at different temperatures and pressures. The corrected maximum relative error was 2%, which greatly improves the measurement accuracy and enables the system to meet the needs of methane detection during coal mine production.