Micropores of Fossil Coals and Hazardous Properties of Coal Seams During Mining Operations

Purpose: to establish the closeness of the correlation relationship for the majority of coal seams of the Donetsk and Lviv-Volyn basins between the release of volatile substances during thermal decomposition of coals without air access and the volume of micropores determined on the basis of experimental isotherms of methane sorption. Methodology: the study is based on the analysis of coal sorption isotherms established experimentally in laboratory conditions. The research methodology involves statistical processing of micropore volume values using the least squares method and establishing their empirical dependence on the yield of volatile substances. Results: based on statistical processing, an empirical dependence of the micropore volume indicators on the degree of metamorphic transformations of coal seams was obtained. The change in the micropore volume as the influence of metamorphic processes increases (reduction in the yield of volatile substances) is ambiguous. When moving from low-metamorphosed coal to an average degree of metamorphism, there is a slight reduction in the micropore volume. With further intensification of the influence of metamorphic processes, the micropore volume increases. Such a change in the micropore volume during metamorphic transformations of coal seams is characterized by high indicators of the closeness of the correlation for a second-order polynomial. It should be noted that the criterion of the yield of volatile substances only indirectly characterizes the degree of metamorphic transformations of coal seams. The presence of methane in coal compared to metamorphic transformations of coal seams obviously characterizes their tendency to manifest gas-dynamic phenomena. Scientific novelty: for the first time, based on statistical processing of experimental data, the formation of micropores has been proven, mainly at the stage of metamorphic transformations of coal seams. This is confirmed by the close correlation between the volume of micropores and the release of volatile substances for a set of 776 coal seams. It has been proven that at the stage of coalification, a structure is formed that is optimal for sorption processes. Practical value: the research results make it possible to develop proposals for improving the regulatory framework for safe mining operations in terms of predicting the manifestation of hazardous properties of coal seams.