The Influence of the Permeability of the Fractures Zone Around the Heading on the Concentration and Distribution of Methane

Abstract

One of the main problems related to the excavation of dog headings in coal beds is the emission of methane during this process. To prevent the occurrence of dangerous concentration levels of this gas, it is necessary to use an appropriate ventilation system. The operation effectiveness of such a system depends on a number of mining, geological, technical and organizational factors. One of them includes the size and permeability of the fractures zone formed around the excavated dog heading. The primary objective of the paper is to determine the influence of this zone on the ventilation parameters, including the concentration and distribution of methane in the excavated dog heading. In order to achieve the assumed objective, multivariate model-based tests were carried out, which reproduce a real-world dog heading. Literature data and test results in actual conditions were used to determine the size and permeability of the fractures zone around the excavated heading. These data served as the basis to develop a model of the region under analysis and adopt boundary conditions. The analyses were carried out for four permeability values of the fractures zone and for two volumetric flow rates of the air stream supplied to the heading. The results were used to determine the influence of the fractures zone on the distribution and concentration of methane in the heading under analysis. The model-based tests were performed using ANSYS Fluent software. The idea to take into account the fractures zone around the heading represents a new approach to the analysis of ventilation parameters in underground mine headings. The results clearly indicate that this zone affects the ventilation parameters in the heading, including the distribution and concentration of methane. The knowledge obtained from the tests should be used to optimize the ventilation process of dog headings. All authors have read and agreed to the published version of the manuscript.Sustainability 2020, 12, 16 2 of 24 very expensive, equipment makes it necessary to provide adequate ventilation to such headings. The ventilation system must ensure proper temperature and chemical composition of air, so that the employees could freely and safely perform their work [6][7][8][9][10][11][12][13][14][15].Sustainability 2020, 12, x FOR PEER REVIEW 2 of 24 employees could freely and safely perform their work [6][7][8][9][10][11][12][13][14][15].to prevent the occurrence of dangerous methane concentration levels in those headings [7][8][9][10][11][12][13][14][15]. 50 Unfortunately, the coal beds currently excavated in Poland contain high methane deposits. As a 51 result, the dog headings mined in those coal beds are susceptible to high methane emissions. To 52 guarantee working safety for the crew and proper effectiveness of the excavation process, dangerous 53 methane concentration levels are not acceptable in such headings. This is because they may lead to 54 the combustion and/or explosion of this gas. Both of these phenomena are amongst the most 55 dangerous in the mining ...

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