Mining high-gas coal seams in China has the characteristics mining of deep, high storage and low permeability, and low drainage efficiency, which seriously restrict the efficient prevention and control of mine gas disasters. Based on the characteristics of low viscosity and permeability, phase change pressurization, and strong adsorption potential energy of liquid CO₂, the technology system of liquid CO₂ displacement for high-gas and low-permeability coal seam was developed, and field industrial of low-pressure (0.52.5MPa) and medium-pressure (2.515.0MPa) combined injection test was carried out. In this test, the mode of injection followed by drainage was adopted, and the gas drainage effect was investigated for 30 days. The test results show that the effective influence radius of CO₂ in this test is 20m, and the liquid seepage radius is 5 to 7m. After the injection of liquid CO₂ into coal seam, the average gas drainage concentration and drainage purity of all drainage holes were increased by 3.2 and 3.4 times, respectively, and the gas promotion effect was significant. Taking the liquid CO₂ low-medium-pressure displacement gas test area as the calculation unit, from the comprehensive benefit analysis, compared with the original drainage mode, the liquid CO₂-combined pressure injection process can save 34.7 of the engineering cost and shorten the gas drainage standard time by 45.9. Therefore, the application of this technology has important technical support and reference significance for the efficient management of gas in the same type of mine.

Coal mine gas disasters have severely restricted production safety. Improving gas extraction efficiency can effectively reduce disasters. Scholars have confirmed that CO₂ successfully displaces coal seam CH₄. This study conducted displacement and in situ experiments and compared gas drainage under different injection pressures. The displacement experiments indicated that CH₄ production rates increased under increased pressures while the displacement ratios decreased. The pressure had a positive effect on sweep efficiency. The in situ experiment showed that CH₄ and CO₂ concentration trends in the inspection hole remained consistent. Through observing the data of the original and inspection holes, the average gas drainage concentration during low- and medium-pressure injections increased by 0.61 times and 1.17 times, respectively. The low-pressure average gas drainage scalar was increased by 1.08 times. During the medium-pressure injection, the average gas drainage purity increased by 1.94 times. The diffusion ranges of CO₂ under low- and medium-pressure injections were 20–25 m and 25–30 m, respectively. The sweep efficiency of medium-pressure injection was 26% better than that of the low-pressure injection, with average pressures of 2.8 MPa and 1.4 MPa, respectively, for sweep efficiency. This study proposes an effective method for improving coal mine gas drainage efficiency.

To mitigate coal spontaneous combustion in the fully mechanized caving face at the boundary of Jining No. 2 coal mine, the accurate prediction of the location and degree of coal spontaneous combustion was realized through theoretical analysis, experimental prediction, and field observations. The concentration changes of CO, C₂H₆, and C₂H₄ during coal oxidation and heating were analyzed. By combining a mathematical prediction model with CO generation rates for different temperature thresholds, the CO concentration in the return air corner was predicted to assess the coal spontaneous combustion degree in the goaf. Through the analysis of the coal spontaneous combustion oxygen concentration limit and three zones, the spontaneous combustion position in the goaf was obtained and verified by drilling. Moreover, based on the mine’s existing glue injection system, we proposed a new system with long-distance and large-flow transportation, flowrate control, and precise slurry concentration control. The results showed that the remaining coal temperature in the goaf reached the critical temperature (60–80 C). The highest temperature point in the goaf was located 12 m behind support #10. The proposed glue injection system increased the efficiency of coal spontaneous combustion prevention and control.