Tribo-electrostatic separation of two or more plastics contained in granular mixtures originating from WEEE

Abstract

Electrostatic separation is able to process mixtures of plastics from waste electrical and electronic equipment. The efficiency and quality of the electrostatic separation depends on the electric charge acquired by the particles in the appropriate tribocharging devices. The aim of the present work is to validate the possibility of using an electrostatic drum separator to separate mixtures of particles which are difficult to separate by other separation techniques. In this type of separator, the plastic particles are charged by triboelectric effect. Two types of tribocharging device have been used: fluidized bed and rotating multicylinders. Two series of experiments were performed with samples composed in equal proportions of: (1) acrylonitrile butadiene styrene (ABS) and polystyrene (PS); (2) polypropylene (PP) and polyethylene (PE). A third series of experiments were carried out with a mixture of three plastics in equal proportions of: polypropylene (PP), polyethylene (PE) and acrylonitrile butadiene styrene (ABS), with an average particle diameter ranginig between 3 mm and 6 mm. The efficiency of the electrostatic separation was evaluated by measuring the charge, the purity and the recovery of the granules collected at the outlet of the electrostatic separation. The results confirm that the separation of ABS / PS and PP / PE mixtures is feasible and the best separation results were obtained using the fluidized bed tribocharger.