The degree indicators of coal metamorphism for predicting the coal seams hazardous properties during the mining

Abstract Metamorphic processes in natural conditions reached a certain stage of the original organic matter transformation at temperatures no more than 650 °C. Analyzes of the coal physical and chemical characteristics are carried out at higher temperatures. Thermal decomposition processes determine the properties of coals during their further transformation, which is important for establishing their consumer properties. The quantitative and qualitative composition of the formed volatiles is not directly related to the fluids, previously removed from coal seams in natural conditions. The thermal decomposition products of coals are the result of a new stage in the initial organic matter transformation. It is shown that the method for determining the yield of volatile substances on a ash-free dry mass when establishing technological properties does not reflect the state of coal seams in natural conditions. Analysis of the results indicates that at present there are no methods for complete the coal sample demineralization. Obtaining an accurate value for the yield of volatile substances per ash-free dry organic mass leads to an overestimation of this indicator. Significant differences in the balances between the metamorphic processes occurring in coal seams and during the thermal decomposition of coal are caused by different conditions for their determination. The products assignment of thermal decomposition processes to a ash-free dry organic mass according to industrial classifications doesn’t allow to use of their consumer properties indicators to characterize the hazardous properties of coal seams in natural conditions. It is proposed to develop the basic principles of the methodology for predicting the hazardous properties of coal seams based on the deviation of the content of organic matter main components, including moisture and sulfur, from their average indicators.