Study on aging characteristics and failure mechanism of CO₂ absorbents for optical interference methane detector in underground coal mines

After a mine fire or gas explosion, accurate detection of methane concentration is critical for disaster relief decisions. However, high-concentration CO₂ from fires causes measurement deviations in optical interference methane detectors, as the CO₂ absorption capacity of soda lime absorbent degrades over time. To investigate factors affecting detection accuracy in underground coal mine disaster areas, a simulation system was built to test soda lime's CO₂ absorption under varied conditions. This revealed its time-dependent performance characteristics, failure mechanism, and enabled the establishment of a methane concentration correction model for CO₂-rich atmospheres. The results show that soda lime's effective CO₂ absorption cycles are negatively correlated with CO₂ concentration. With CO₂ concentrations of 5 %, 10 %, 15 %, 20.99 %, 27.18 %, and 32.09 % in the gas mixture, the effective absorption cycles are 20, 18, 12, 8, 5, and 3 times, respectively. The CO₂ absorption time-efficiency curves exhibit an "S"-shaped nonlinear pattern under different concentrations and flow rates. Higher CO₂ concentrations and gas flow rates increase absorption per unit time, shorten the high-efficiency duration, accelerate saturation/failure, and reduce the effective absorption time. Therefore, adjusting soda lime dosage and optimizing sampling flow rates are key to improving detection accuracy in high-CO₂ environments.