About authors: S.A. Silyutin, Cand. Sci. (Eng.), JSC Siberian Coal and Energy Company (SUEK), Moscow, Russia, e-mail: silutinsa@suek.ru,
S.A. Epshtein, Dr. Sci. (Eng.), Head of Scientific and Educational Testing Laboratory «Physics and Chemistry of Coals», National University of Science and Technology «MISiS», 119049, Moscow, Russia, e-mail: apshtein@yandex.ru.