The invention relates to mining of fossil energy minerals and can be applied to the beneficiation and utilization of various kinds of coal and shale oil as a solid fuel for thermoelectric power stations. The object of the invention is to reduce the energy consumption of mining energy generation, to eliminate solid fuel loss, to reduce water consumption and to protect the environment. To this end, the beneficiation process is performed underground, in the immediate proximity to the place of beneficiation waste stowing, using aqueous salt solution with a density intermediate between those of the target component and waste rock. The regeneration of heavy liquid from final beneficiation tailings is performed by washing with non-aqueous volatile liquid, with subsequent drying by the subsurface heat after placing these tailings in the worked-out space. The resulting vapors are compressed and condensed; thus regenerated non-aqueous liquid is returned for washing the beneficiation tailings, while effluents produced by washing are separated into aqueous and non-aqueous components by heat released at the liquefaction of the non- aqueous liquid vapors. The enriched solid fuel remaining in the floatable state is delivered by its flow to the thermo not electric power plant, where it is separated hydromechanically from liquid component, washed with water, dried and directed to combustion. The effluents from washing with water are evaporated with heat released at the condensation of the working medium of the power station thermodynamic cycle. Then they are mixed with drains from solid fuel delivered to the destination, and returned to the starting point of the process.