| Thermal hazard and fire disaster in mining regions have long been the major threats to the safe production of coal mine, though there exists many researches on heat damage and coal spontaneous combustion problems, relevant accidents still often occur. With the increase of mining depth, it results in temperature of gateway and working face becoming higher. On the one hand, high temperature causes severe damage to the workers’physical and mental health; On the other hand, it makes a surge in mine accidents. Therefore, it is necessary to investigate the temperature field in deep coal bed with combining large-scale geothermal field by developing a FORTRAN program.Firstly, based on the transport equation and filtration equation, a two-dimensional mathematical model of coal bed temperature field was developed, and then the FEM equation is deduced by applying Galerkin Method. Based on the FEM equation, the numerical computed program for two-dimensional coal bed temperature field analysis was implemented in FORTRAN language. The program consists of grid generation, anomalous region delineation, matrix establishments, boundary conditions and temperature field calculations.Secondly, referencing published experimental data and calculated results reported in literatures, the mathematical model built in this paper is verified. The simulation results are consistent with the literature data approximately, which shows that this model is suitable for analysis of geothermal field and the mining coal bed under the influence of the temperature field. In the first case, the study took the geological structure and surface relief of the investigated area into consideration, which was based on the measured data of Nowa Ruda coal mining in Poland. After setting the isothermal anomalous region, then the established mathematical model was applied for computing the temperature field distribution around the abandoned mine by ignoring the fluid flow. In the second case, thermal effect of groundwater basin under a regional scale system is simulated. According to the size of rock permeability, groundwater basin thermal regime can be divided into conduction and convection, and the groundwater basin thermal distribution state was calculated by the corresponding model under different permeability under the influence of seepage.Finally, the study introduced the method in dealing with the anomalous region of the geothermal field to temperature field of the coal deposits, which means taking the working face and goaf as the anomalous region. The temperature distribution of the coal deposits is simulated under the effect of airflow by developed FORTRAN program. The results show that the temperature gradient is relatively large in the first half of the working face, and the temperature of airflow increases along with the flow direction; But in the second half, the temperature of airflow increases slowly and tends to be stable. And the penetration flow of the goaf accounts for a much weaker effect compared with the heat flux, which was considered as a dominant factor. For deep coal deposits mining, working temperature exceeds the ’regulation’ provisions of 26 ℃ due to geothermal effect, which can not meet the requirements of safety in production of coal mine and need to artificial cooling. The results can be further applied for cooling mines as well as preventing the spontaneous combustion of remaining coals. |
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