Abstract
In the last decades, rigorous research has been carried out with the end of understanding the gas dynamic phenomenon and although different preventive techniques have been employed, even today there are numerous accidents even with the loss of life. This work analyses an alternative and innovative method of fracturing and degassing coal, by generating CO2 with a pyrotechnic device called PYROC (Pyrotechnic Break Cartridges). Medium-scale tests of generation of CO2 into coal samples are carried out and their effect is analysed comparing the initial and final permeabilities of the coal samples once the generation of CO2 has finished. These permeabilities are calculated by injecting methane. Besides, the influence of different parameters as the length of the boreholes, the pressure of the gas or the initial permeability of the coal have been analysed with a numerical simulation of one face of one of the sublevels of a mine. The results show that the method increases the safety in mining operations because it fractures and degasses the coal, increases the permeability of the coal in the borehole of injection from 9.5 mD to 31 mD, decreases the methane gas pressure below pre-detonation levels for 1 min, achieves decompressed lengths between 8 and 10 m ahead of the face with pressures of injection of 50 MPa, relaxes the total length of the borehole for initial coal permeability values equal to or greater than 0.002 mD, and allows to work with low permeable coals with high induced stresses and high methane concentrations.
Highlights
Received: 5 July 2021Accepted: 18 August 2021Published: 23 August 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.One of the most important problems in underground coal mining is the Gas DynamicPhenomenon (GDP)
At the end of the 20th century, due to an increase in the depth of mining operations and their mechanisation, there has been an increase in Gas DynamicPhenomenon (GDP), resulting in numerous instances of material and human damage
After the discussion of the results, it is possible to say that the PYROC system is effective in degassing coal and increases safety in mining operations
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The last preventive technique, the injection of water, is used with the end of increasing the level of moisture and reducing the capacity of the coal to accumulate elastic deformation energy and increasing its plastic deformation energy [11,12]. This is because when the humidity of coal under high-pressure increases, water molecules try to occupy the empty spaces and displace the methane molecules, reducing the gas content. To verify the effect of high-pressure CO2 generation on medium-scale coal samples, the front face of one of the sublevels of a mining operation has been numerically simulated with a hydromechanical using the FLAC-2D software application. After the discussion of the results, it is possible to say that the PYROC system is effective in degassing coal and increases safety in mining operations
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