Abstract
Coal and gas outburst is one of the major serious natural disasters during underground coal, and the shock air flow produced by outburst has a huge threat on the mine safety. In order to study the two-phase flow of a mixture of pulverized coal and gas of a mixture of pulverized coal and gas migration properties and its shock effect during the process of coal and gas outburst, the coal samples of the outburst coal seam in Yuyang Coal Mine, Chongqing, China were selected as the experimental subjects. By using the self-developed coal and gas outburst simulation test device, we simulated the law of two-phase flow of a mixture of pulverized coal and gas in the roadway network where outburst happened. The results showed that the air in the roadway around the outburst port is disturbed by the shock wave, where the pressure and temperature are abruptly changed. For the initial gas pressure of 0.35 MPa, the air pressure in different locations of the roadway fluctuated and eventually remain stable, and the overpressure of the outburst shock wave was about 20~35 kPa. The overpressure in the main roadway and the distance from the outburst port showed a decreasing trend. The highest value of temperature in the roadway increased by 0.25 °C and the highest value of gas concentration reached 38.12% during the experiment. With the action of shock air flow, the pulverized coal transportation in the roadway could be roughly divided into three stages, which are the accelerated movement stage, decelerated movement stage and the particle settling stage respectively. Total of 180.7 kg pulverized coal of outburst in this experiment were erupted, and most of them were accumulated in the main roadway. Through the analysis of the law of outburst shock wave propagation, a shock wave propagation model considering gas desorption efficiency was established. The relationships of shock wave overpressure and outburst intensity, gas desorption rate, initial gas pressure, cross section and distance of the roadway were obtained, which can provide a reference for the protection of coal and gas outburst and control of catastrophic ventilation.
Highlights
Coal and gas outburst accident is one of the most serious hazards to the safe production of underground coal mines
To achieve a reliable laboratory simulation test which analogies to the outburst in the field, the coal samples were selected from the outburst coal seam in Chongqing Yuyang Coal Mine, China, and high-purity CO2 was injected as the experimental gas
A self-developed coal and gas outburst simulation test device was constructed to simulate the law of coal-gas two phase flow in the roadway of the outburst process
Summary
Coal and gas outburst accident is one of the most serious hazards to the safe production of underground coal mines. The research on the outburst mechanism mainly focuses on analysis of its occurrence conditions, but few researches focus on the development process of coal and gas outburst, such as the lack of studies on the rule of coal and gas flow and the shock wave disaster effect in the roadway. When studying the propagation of shock wave and the two-phase flow of a mixture of pulverized coal and gas law of coal and gas outburst, researches were mostly based on the theoretical analysis and numerical simulation. This paper uses the self-developed experimental device of coal and gas outburst dynamic effects to carry out the laboratory simulation experiment of two-phase flow of a mixture of pulverized coal and gas in the outburst process. The research on the rules of shock wave propagation in roadway and pulverized coal migration characteristics can help to make further improvement for the theory of coal and gas outburst prediction and provide a reference for disaster protection and catastrophic ventilation design
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