PURPOSE: To eliminate or simplify a sludge treatment, a dehydrating and a drying processes by a method wherein a powder mixture consisting of two kinds or more of components is charged by a vibration screen type electrically charging apparatus and, after charging, classified and extracted in an electrostatic classifying apparatus into specific components.

CONSTITUTION: A ground and dried raw coal fine powder is thrown into a vibration screen type charging apparatus from a hood 117. A frame body 111 of the charging apparatus is hung from an enclosure 14 by a vibration plate 112 and a spring 113 and vibration is imparted thereto by a coil 115. To the frame body 111, a charging body having a fine pore group to a vertical direction thereof is provided and earthed through the frame body. The powder is charged by friction with the inner wall thereof while fallen through the fine pore group by vibration. The charged powder is introduced into an electrostatic classification apparatus to which a D.C. electric field B is impressed by applying high voltage to electrode plates 121, 122 and the positively charged high carbonaceous component therein is classified into the collecting port 124a of a hopper, the negatively charged ash component therein into the collecting port 124C thereof and a mixed component having no polarity into the collecting port 124b thereof. Those adhered to the electrode plates are respectively scraped off to collecting ports.