Magnetite powder is used as weighting material in heavy coal preparation, and the medium density is determined according to the product quality requirements. When the density of the object is greater than that of the medium, the minerals sink. When the density of an object is less than that of a medium, minerals float. In this way, minerals are divided into two products: light products (clean coal) and heavy products (coal gangue).

The process flow of dense medium coal preparation is shown in the following figure: