On the correspondence of hilt's rule to metamorphic transformations of coal seams

Abstract

Purpose. Prove the compliance of Hilt's rule for all coal seams, if instead of the release of volatile matter yield to determine the degree of metamorphism, indicators are used that directly characterize changes in the composition of the organic mass. Methodology. Provides for consideration of experimental data, on the basis of which deviations from the Hilt's rule were established for the seams of ten mines using the indicator of volatile matter yield (Vdaf). Comparing the geometric arrangement of coal seams and their metamorphic characteristics, respectively, in indicators of Vdaf and Со, it is possible to analyze the compliance of each coal seam with the Hilt rule. Findings. With the help of the indicator of the release of volatile matter yield, it is not possible to reveal the picture of metamorphic transformations of coal seams. One indicator of metamorphic transformations of coal seams cannot single-handedly and comprehensively characterize simultaneously changes in both the composition and properties of coals. The elemental content of carbon in the organic mass is one of the more informative indicators in determining the hazardous properties of coal seams compared to the release of volatile matter yield. Compliance with the Hilt rule, established by the volatile matter yield and carbon content, is, according to both indicators, random. The absolute maximum non-compliance with the Hilt rule for the release of volatile matter yield is 7.84%, and the relative one is 23.08%. The maximum absolute and relative deviations from the Hilt rule for carbon content do not exceed 4%, which is largely due to sampling in different parts of the mine fields. Moisture, together with the release of volatile substances and carbon content, is an indicator of metamorphic transformations of coal seams, including determining their dangerous properties. The content of mineral impurities for individual coal seams is random. When developing regulatory documents for the safe conduct of mining operations, in addition to the indicators of metamorphic transformations that characterize the composition and properties of coal, it is necessary to consider the mining-geological and mining-technical conditions for mining coal seams. Originality. For the first time it has been established that the discrepancy between the metamorphic transformations of coal mine seams and the Hilt rule is eliminated if the carbon content in the organic mass is used instead of the indicator of the release of volatile matter yield. In this case, the absolute and relative deviations from the Hilt rule do not exceed 4%, which corresponds to the accuracy of determining the carbon content in different parts of the mine field. Practical implications. The research results make it possible to develop proposals for improving the regulatory framework in terms of predicting the manifestation of hazardous properties of coal seams during mining operations.