Temperature evolution in abandoned mines and the effect on gas adsorption properties of residual coal

ABSTRACTAbandoned mines contain a large amount of residual coal and gas resources for development and utilization. In order to accurately establish the calculation model of gas reserves and lay a foundation for the exploitation of gas resources in abandoned mines, based on the analysis of temperature evolution of abandoned mines, gas adsorption experiments and molecular simulations were carried out at temperatures of 30, 60, 90, 120, 150 °C and five different adsorption equilibrium pressures (0.5∼2.5 MPa). The test results show that the attenuation rates of gas adsorption at 30∼60 °C, 60∼90 °C, 90∼120 °C, and 120∼150 °C are 8.53%, 7.89%, 5.55%, and 1.55%, respectively. High temperature inhibits the increase of gas adsorption by residual coal, but its inhibition has a certain limit. At high adsorption equilibrium pressure, the initial adsorption rate increases with the rise of temperature. When the pressure is 2.5 MPa, the initial adsorption rates at 30, 60, and 90 °C is 1.25, 2.22, and 2.32 ml▪g−1▪min−1, respectively. Temperature affects the gas adsorption characteristics of residual coal. Therefore, the influence of temperature should be considered when establishing the gas reserves model of abandoned mines.HighlightsThe inhibition effect of high temperature on adsorption is limited.Initial adsorption rate increases with the rising temperature at high pressure.The temperature factor should be added to the gas reserves model of abandoned mines.KEYWORDS: Abandoned minesresidual coaltemperature evolutionadsorption rateattenuation rate AcknowledgmentsThis research was supported by the National Natural Science Foundation of China (No. 52074105), the Key R & D and Extension Projects of Henan Province (No. 202102310223, No. 222102320017),The Key Scientific Research Projects of Colleges and Universities in Henan Province (No.22B620002), the Doctoral Foundation of Henan Polytechnic University (B2021-7), the Key Science and Technology Project of Henan Province (No. 222102320017), the State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University) (No.WS2021A06).Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by the Doctoral Foundation of Henan Polytechnic University: [Grant Number B2021-7]; the Key Science and Technology Project of Henan Province: [Grant Number No. 222102320017]; the State Key Laboratory Cultivation Base for Gas Geology and Gas Control: [Grant Number No.WS2021A06]; Key R & D and Extension Projects of Henan Province: [Grant Number No. 202102310223, No. 222102320017]; National Natural Science Foundation of China: [Grant Number No. 52074105].