The invention is a process for the beneficiation and utilization of various kinds of coal and shale oil as a solid fuel for thermoelectric power stations. The beneficiation process is performed underground, near to the place of beneficiation waste stowing, using aqueous salt solution with a density 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-electric power plant.