Analysis of the influence of temperature on the adsorption characteristics of coal: Insights into low-temperature outburst prevention

Abstract

To investigate the impact of temperature reduction on the adsorption characteristics of coal gas, isothermal adsorption experiments were conducted with environmental temperature and moisture content as variables. The changing patterns of coal gas adsorption characteristics, adsorption theories, and the temperature response of gas expansion were analyzed. Furthermore, engineering measures for preventing gas outbursts in low-temperature frozen coal seams were discussed. The research findings indicate that the gas adsorption capacity of coal samples increases with decreasing temperature. When the temperature decreases from 20 to −20 °C, the gas adsorption capacity decreases from 34.48 to 19.90 cm3/g. At the same pressure, the adsorption capacity of coal is negatively correlated with temperature. The Langmuir theoretical model better reflects the adsorption law of coal gas under different environmental temperature conditions, wherein the adsorption constant “a” gradually decreases with the increase in environmental temperature. In a closed space, the gas pressure decreases with the decrease in coal sample temperature. Under the new adsorption equilibrium, the gas pressure in the coal sample tank decreases linearly with temperature. Coal samples with different moisture contents exhibit varying degrees of decrease in gas pressure at the same temperature, with higher moisture content resulting in a smaller decrease in gas pressure. Gas expansion energy decreases linearly with the decrease in coal temperature, indicating a proportional relationship between gas expansion energy and coal gas release pressure. As the temperature decreases, the gas pressure decreases. Based on the experimental results, a synergistic approach for preventing gas outbursts through low-temperature freezing is proposed.