National University of Science and Technology ‘MISIS’, Moscow, Russia:

S. A. Epshtein, Head of Scientific-educational Laboratory of Physics and Chemistry of Coals, Doctor, e-mail: apshtein@yandex.ru
E. L. Kossovich, Senior Researcher, Candidate of Engineering Sciences
V. A. Prosina, Student, Laboratory Assistant
N. N. Dobryakova, Leading Engineer, Candidate of Engineering Sciences

This article is dedicated to the studying of the features of structure and mechanical properties (including strength) of coals extracted from the same seam but originating from packs that differ with respect to potential outburst hazards. One of such packs was related to potentially prone to outbursts, another was characterized as non-hazardous. It was found that the vitrinite of coal from the pack that is potentially prone to outbursts is highly heterogenous and is represented by detrital organic substance with the pronounced distinct boundaries. On the other hand, vitrinite of coal from a non-hazardous pack is characterized by a rather homogeneous structure. The latter is found not to contain any signs of undecomposed plant material. The differences in microstructures, also microhardness and the vitrinite reflection index between these coals made it possible to attribute them to different genetic types with respect to the degree of reduction. High heterogeneity of the organic matter of coal from the pack that is potentially prone to outbursts, as well as the lower density of its structural constituents crosslinking determine the nature of strength degradation reasoned by sorption softening. Dimethylformamide sorption by this coal leads to the active disintegration of its particles’ surfaces and formation of a large number of fine (several hundreds of micrometers) classes. The obtained data indicate that the microstructe features of the coals have a significant impact on their strength and may determine their ability to form fine particles upon destruction, including those that may transfer to a fine (aerosol) dust. It may be added that studying of structural and textural characteristics of coals at microscale may be used as complementary indicators for prediction of the seams and packs outburst hazards along with the traditionally used criteria.
The work was financially supported by the Russian Science Foundation (grant No. 16–17–10217).

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