On determining coal classification indicators for establishing dangerous properties of mines

Abstract

Currently, more than 20 qualification indicators are known by which degree of metamorphic coal transformations are established. Most of these indicators are designed for determining technological properties with industrial use of coal in mind. Due to sufficient knowledge of the indicators used, industrial classifications are constantly being improved. The modern classification by genetic and technological parameters groups the coals by the grades based on ten indicators. Of these, only one - the mass yield of volatile substances during the thermal decomposition of coal - is used as the main indicator of the manifestation of dangerous properties of coal seams without due scientific justification. Dangerous properties of coal seams during mining include: gas content of coal, a tendency to gas-dynamic phenomena and spontaneous combustion, dust forming ability and explosiveness of coal dust. In industrial classifications, the main indicator is determined for the dry ash-free state of organic matter. Manifestation of dangerous properties of coal seams occurs in the presence of both moisture and mineral impurities. This fact is not taken into account by other auxiliary indicators used to predict the hazardous properties of coal seams. Moisture in coal seams is in at least four states, and it is completely removed while analyzing the samples and is not taken into account in volatile products of thermal decomposition of coal. Thus, when using the indicator of mass output of volatile substances, influence of moisture in any form of its presence in coal on the occurrence of emergency situations is automatically ignored. The probability of emergencies during mining is largely determined by the ratio between components of organic mass (C, O, H, S, N) and mineral impurities. It is also not taken into account in normative documents which regulate safety of coal seam mining. The classification indicators defined in different ways characterize different aspects of coal conversion in metamorphic processes. Volatiles yield and average vitrine reflectance, well studied in industrial applications, correspond to different aspects of degree of conversion of starting organic matter. In order to establish dangerous properties of coal seams, their mutual substitution is unacceptable, which is confirmed by nonlinear connection between them. The existence of a genetic relationship between the outburst and fire hazard of coal seams has been established. This indicates the need to develop a unified classification of the hazardous properties of coal seams by genetic, mining engineering and geological parameters. The scientifically substantiated use in regulatory documents of a set of classification indicators that directly characterize the manifestations of the hazardous properties of coal seams will help to reduce number of accidents and injuries in coal mines.