PURPOSE: To omit or simplify muddy waste water treatment and dehydrating and drying stages by fluidizing the particles of fine powder, charging these particles electrostaticlly by the friction with an electrostatic charger, passing the same through the inside of an electric field and separating these by the electrical properties of the particles.

CONSTITUTION: The pulverized coal which is ground and dried is mixed with a non- combustible gas and is blown into an electrostatic charger. The charger assumes the shape of a cyclone, has a powder blow port 28 in the upper part of a metallic cylindrical vessel 27 and a blow-out port 29 in the central part and is coated with an electrostatic charging member 30 on the inside wall surface of the vessel 27 and the outside circumferential surface of the port 29; therefore, the fine powder blown therein falls while swirling in the vessel 27, and is charged by the contact and friction with the member 30. This powder is discharged from the lower part of the vessel and is fed to an electrostatic separator. The separator generates a DC electric field between electrode plates 34A and 34B facing each other and generates a moving electric field by applying multiphase AC voltages to an electrode plate 35; therefore, the charged powder is separated under conveyance according to the respective polarities and charge quantity and is conducted to capturing pipes 36W38.