Improvement of the Industrial Pilot of a Tribo-aero- electrostatic Separator for Binary Mixtures of Granular Insulating Materials

New electrostatic separation processes have been developed for the treatment of waste electrical and electronic equipment (WEEE), the amounts of which are increasing from year to year. The objective of this paper is to analyze two possibilities for improving the performance of a semi-industrial tribo-aero-electrostatic separator for insulating granules: decrease the section or modify the wall material of the fluidized bed. The electric field of the separator is generated between two metallic belt conveyors connected to two DC high voltage supplies of opposite polarities and is orthogonal to the direction of the fluidized air. The experiments were performed on a insulating granular mixture consisting of acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS), average size 2 mm, originating from the processing of WEEE. The first series of experiments was conducted for two sections of the fluidized bed (42 cm x 15 cm and 30 cm x 15 cm, respectively) in similar environmental conditions (temperature: 18 degrees C, relative humidity: 40% +/- 1). The decrease of the surface of the fluid bed was accompanied by an increase in the mass of products recovered in the collecting boxes: 52% for ABS and over 14% for HIPS. The second series of tests demonstrated the role of the lateral walls of the fluidized bed. The walls of polymethyl metracrylate-(PMMA) promote the separation of ABS, while those in acetate improve the recovery of HIPS.