PURPOSE: To prevent the loss of a heavy liq. material and to reduce the cost of equipment by utilizing part of product coal or raw coal as the heavy liq. material used in specific gravity separation.

CONSTITUTION: Part of product coal or raw coal is utilized as a heavy liq. material used in specific gravity separation and the heavy liq. material is circulated and used so that the material discharged from a system by sticking to a product can be replenished. By this method, raw coal is not damaged, a heavy liq. recovering system is not complexed and the cost of equipment can be reduced.