Carbon monoxide sensor for coal mine thermodynamic disaster monitoring

The thermodynamic disasters of coal mines are mainly divided into two kinds:gas explosion and coal sponta⁃ neous combustion，which are not independent in the mine goaf. In the case of coal spontaneous combustion，the car⁃ bon monoxide concentration is low，and the high sensitivity carbon monoxide sensor is needed. In the case of gas explosion warning，the methane sensor with fast response and large range is needed. TDLAS(Tunable diode laser absorption spectroscopy) with narrow line⁃width laser has better selectivity，so it is suitable for coal mine environment with complex background gas. However，in the face of the monitoring of multiple disasters，the absorption line strength of carbon mon⁃ oxide in the near⁃infrared band is relatively weak，and it is easy to be covered by the absorption line of other back⁃ ground gases in the goaf(ethane，ethylene，carbon dioxide，water vapor)，leading to false alarm. Therefore，the absorption line of carbon monoxide at 2 330 nm was selected. The line strength of carbon monoxide absorption line in this band is high，and high sensitivity detection can be achieved. Secondly，the absorption line of water vapor in this band is weak， so interference can be avoided as long as methane and carbon monoxide are identified. According to the high⁃resolu⁃ tion transmission molecular absorption database(HITRAN)，the absorption coefficients of the carbon monoxide character⁃ istic absorption peaks in this band and the absorption coefficients of the adjacent methane characteristic absorption peaks were searched and calculated. Based on TDLAS，a carbon monoxide sensor was developed by using a 2 330 nm laser， a compact chamber and a phase⁃locked module. The results show that the 1σ detection limit of carbon monoxide is 2.14×10-7 and the 3σ detection limit is 6.4×10-7. The linearity in the measurement range of 0-5×10-4 is better than 2%. Gas with different concentrations was filled into the sensor，the flow rate was controlled to be 10 mL / min，and the sensor re⁃ sponse time T90 was 6 s after testing. In order to realize the accurate detection of carbon monoxide in the background of mixed gas in goaf，a component intelligent identification method was proposed. The wavelength scanning range of the laser was increased. Carbon monoxide and its adjacent methane spectrum lines were scanned simultaneously， and the composition and concentration information of background gas were obtained at the same time. The detection limit of methane was 1×10-6，which was consistent with the calculation results of HITRAN database. Mixed gas was used for verification. The test results show that the method can realize the identification of carbon monoxide and methane compo⁃ nents，avoid the cross interference of complex gases as background，and realize the rapid and high sensitivity measure⁃ ment of carbon monoxide gas，which can meet the needs of goaf disaster monitoring.