An apparatus for tribocharging particles of electrically insulating materials
has a rotatable drum (1), made of a metallic material, for containing the
particles. The drum has an inlet (11), for charging material, and an outlet
(13), for discharging material. The drum further has means (7) for
rotating the drum about an axis of rotation, the orientation of the axis of rotation
being such that, in operation of the apparatus, the particles tumble against each
other and against the walls of the vessel, thereby becoming tribocharged. A fines
removal mesh screening means (10) is attached to an outer surface of the
drum, allowing fines to escape from the drum. An electrostatic separation tower
(20), having tapering walls and at least one pair of electrodes (24)
arranged on opposite walls of the tower, is aligned to receive discharged material
from the drum. The tower separates the particles, falling from the drum into the
tower (20), in an electric field generated between the electrodes (24).
