Tribo-aero-electrostatic separation of micronized mixtures of insulating materials using “back-and-forth” moving vertical electrodes

The existing industrial tribo-electrostatic separators have proved their efficiency for sorting mixtures of millimeter-sized granular plastics. The objective of this paper is to validate a new tribo-aero-electrostatic separator designed for processing granular mixtures of insulating materials (average size: 10-100 μm). The device consists of two vertical plate electrodes of dimensions 20 cm × 30 cm, connected to two DC high voltage supplies of opposite polarities. Both electrodes perform “back-and-forth” motions inside a fluidized bed containing the micronized materials to be separated. Fluidization is achieved by injection of air using a variable speed air blower. The experimental study is carried out with samples of white PVC and gray PVC having an average size of 50 μm, and enables the analysis of the effects of several factors on the separation efficiency: the linear speed of the electrodes, the electric field, the mass of processed materials and the fluidization air flow rate. The new separation process is characterized by high product recovery rates. The purity of the separated products, estimated by visual examination, exceeds 90% in all experiments.