Corona-assisted plate-type electrostatic separation process for granular plastic wastes

Plate-type electrostatic separators are commonly employed for the selective sorting of conductive and non-conductive granular materials. Unfortunately, the purity of the conductive products is often compromised by the fact that the trajectories of the non-conductive granules cannot be controlled. The aim of the present work is to validate a relative simple solution to this problem: subjecting the granules to a corona discharge during their sliding down the plate electrode. This discharge does not affect the conductive granules but charges the non-conductive ones, so that the electric force would tend to pin them to the surface of the grounded electrode. In this way, the friction forces between the granules and the plate increase and the inertia forces decrease. Design of experiments methodology is employed to identify the optimum high-voltage, relative position of the electrodes, and configuration of the collector. The conclusions of this study served at the optimum design of an industrial corona-assisted plate-type electrostatic separator for the recycling of metals and plastics from granular electric cable wastes.