155 / 2023-07-04 22:21:26

​Prevention and control techniques for spontaneous combustion of deep mine coal in the Ordos mining area

air leakage,oxygen concentration,oxidation zone,index gases,nitrogen injection

The Ordos mining area is mainly dominated by low-metamorphic coal, and some of the newly established mines, such as the Gaotouyao and Hujierte mines, are working deep seams, making it difficult to control spontaneous combustion of goaf. Three coal mines in Ordos were used as examples in this study, all of which employed a double-tunnel arrangement and comprehensive mechanized mining, and their main coal seam belonged to a seam prone to spontaneous combustion. Based on the field measurement and numerical simulation of the spontaneous combustion oxidation zone in the goaf, the corresponding prevention and control measures are formulated to improve the effect of the fire prevention work in the double-tunnel coal mine in Ordos, and to enhance the importance of the comprehensive fire prevention work in the coal seam prone to spontaneous combustion of Ordos mining area.

The oxygen concentration criteria and the shortest spontaneous combustion period of the spontaneous combustion oxidation zone of the coal seam were determined by the heating experiment, and the initial temperatures of the spontaneous combustion index gases C₂H₄, C₃H₈, C₂H₆ and C₂H₂ were determined by the experiment. Beam tube monitoring system was set up at three working faces to analyze the distribution of oxygen concentrations in the goaf. The air leakage rate in the work face was determined by measuring the wind speed and the closed air leakage rate in the transport tunnel was determined by SF₆. Based on hydrodynamic theory, 3D models of spontaneous combustion was developed by using the FLUENT numerical simulation software to simulate different leakage locations and leakage air volumes, as well as different nitrogen injection locations and nitrogen injection volumes in the goafs and transport tunnels. A specific fire prevention system was established, and through numerical simulation, it was determined that the air leakage in the connection tunnels had an inhibitory effect on the oxidation zone formed by the air leakage in the working faces, and the appropriate nitrogen injection position and volumes were determined. The specific techniques and methods for constructing positive pressure inert nitrogen chambers in transport tunnels to reduce air leakage. According to the identified index gases and its occurrence temperature, the beam tube monitoring system is established for daily monitoring.

With the treatment, the oxidation zone and minimum mining rate of the goafs were greatly reduced, which significantly reduced the risk of spontaneous combustion in the goafs, improved mine safety production levels, and provided technical experience to be used as a reference for deep mining operations in similar conditions in the Ordos mining area.