Delineation and Prevention of the Spontaneous Combustion Dangerous Area of Coal in a Regenerated Roof: A Case Study in the Zhoujing Coal Mine, China
2020
Lu, Yi | Yan, Zhihong | Shi, Shiliang | Wang, Geoff | Li, He | Niu, Huiyong | Guo, Zhiguo | Wang, Ping
Spontaneous coal combustion in a regenerated roof is difficult to find, and the awareness of prevention is relatively weak. To effectively delineate the range of the danger area, the characteristic parameters of spontaneous coal combustion were tested. The result shows that carbon monoxide (CO) was chosen as the index gas, and the relationship between the oxygen consumption rate and oxygen concentration was fitted linearly. Mathematical models of the air speed field and oxygen concentration field were derived, and a physical model of the regenerated roof was established. On the basis of COMSOL Multiphysics simulation, the test value and predicted value of air speed and oxygen concentration were compared with good similarity. The danger area of spontaneous coal combustion was determined by the two indices of oxygen concentration and air speed with ranges of 1.35–6 and 0.60–3.02 m, respectively. A polyacrylamide–particle-stabilized foam (PPSF) with an average pore size of 165 μm and pore wall thickness of 30.5 μm was prepared in batch mode using a homemade foam-generating device. Optical microstructure characterization showed that the mixed powder can be distributed evenly in the liquid film and that polyacrylamide as a vesicular liquid membrane carrier presented a network structure. The formation mechanism of the foam was presented in a schematic diagram. The PPSF was injected into the delineated danger area of 350 m³, and the temperature and concentration of CO decreased to 32 and 29 °C and 5 and 22 ppm, respectively. All of these results indicated that PPSF can effectively inhibit spontaneous coal combustion in the regenerated roof.
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