Tribo-aero-electrostatic Separator for Coarse Granular Insulating Materials

The tribo-aero-electrostatic separator achieves the selective sorting of mixed granular insulating materials in a fluidized bed affected by an electric field orthogonally oriented to the direction of the fluidization air. The aim of the present paper is to optimize the design and the operation of such a separator, i.e. maximize the total mass of the granules collected at the two electrodes that generate the electric field. The experiments were performed for four different electrode configurations. The granular mixtures to be separated were composed of Acrylonitrile Butadiene Styrene (ABS) and High Impact Polystyrene (HIPS) originating from the recycling of waste electric and electronic equipment (WEEE). The typical granule size was in the range 2 to 4.5 mm. The highest separation efficiency was obtained when the electric field in the active zone was intensified by the use of an additional electrode connected to the ground and when the collecting electrodes were covered by a thin insulating layer, preventing charge leakage from the particles in contact with them.