Abstract
In order to effectively prevent and control spontaneous combustion of residual coal in the goaf and reduce the waste of nitrogen caused by setting the position of nitrogen injection, 1303 fully mechanized coal caving faces of the Jinniu Mine are studied. By deploying a bundle tube monitoring system in the inlet air side and return air side of the goaf, changes in gas concentration in the goaf are continuously monitored. In addition, the distribution area for spontaneous combustion three-zone in the goaf is divided into heat dissipation zone, oxidized spontaneous combustion zone, and suffocation zone. Simulations from the COMSOL Multiphysics 5.3 software provide insight based on the three zones division standard of spontaneous combustion in the goaf. The gradual deepening of the nitrogen injection position into the goaf affects the lower limit of the oxidized spontaneous combustion zone significantly, but the impact on the upper limit of the oxidized spontaneous combustion zone is not obvious and is negligible. With regard to the width of the oxidized spontaneous combustion zone, it initially decreases followed by a gradual increase. Numerical calculations suggest the optimal nitrogen injection position is 40 m from the roof cutting line, with an oxidized spontaneous combustion zone width of 28 m. Based on the simulation analysis results, nitrogen injection controlling measures have been adopted for spontaneous combustion of residual coal in the goaf of the 1303 fully mechanized coal caving faces, and coal self-ignition in the goaf has been successfully extinguished.
Highlights
Coal mine fires affect the safety of mines
The three zones of spontaneous combustion divided by the oxygen concentration and the numerical calculation of the air leakage velocity are in agreement with the numerical simulation
As of January 2018, the 1303 fully mechanized coal caving faces had been successfully pushed forward for over 600 meters, and no spontaneous combustion of coal occurred in the goaf. These results highlight the efficacy of the nitrogen injection control measures for the spontaneous combustion of residual coal in the goaf of 1303 fully mechanized coal caving faces
Summary
Coal mine fires affect the safety of mines. Among coal mine fires, 85% stem from the spontaneous combustion of coal in the goaf [1,2,3]. Thanks to "The National Natural Science Foundation of China (Grant: 51274113); Key special-funded projects of the State key R & D program (2018YFC0807900)" for the financial support The recipient of these funds is Qi Qingjie. Li Zongxiang et al [9] combined the finite element numerical method with computer graphics technology to simulate the change process of the boundary of nitrogen injection control zone with the amount of nitrogen injection. Zhu Hongqing et al [11] studied the law of spontaneous combustion and temperature rise in the context of nitrogen injection and fire prevention using the Fluent software. These studies only focused on nitrogen injection in the context of fire prevention principles and the nitrogen injection process They did not consider the effects of coal oxidation and gas emission in the goaf area. Based on the results of the simulation analysis, the proposed nitrogen injection scheme could hold significant benefits industrial settings
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