PURPOSE: To omit or simplify muddy waste water treatment and dehydrating and drying stages by fluidizing the particles of fine powder, charging these particles electrostatically by the friction among powder particles, 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. Since the charger has a gas distributor 28 in the lower stage in a cylindrical vessel, an overflow pipe 29, and a non-combustible gas blow port 30 communicating with the lower part of the distributor 28, the pluverized coal blown through a powder blow port 31 is fluidized by the flow of the non-combustible gas from the lower part to form fluidized beds. It is electrostatically charged by the friction among the powder particles and is sent from th overflow pipe to an electrostatic separator. The separator generates a DC electric field between electrode plates 34A and 34B facing each other. Since this electric field is moved by applying multiphase AC voltages to an electrode plate 35, charged powder is separated under conveyance according to the respective polarities and electrostatic charge guantity, and is conducted to capturing pipes 36W38.