Experimental investigation of a new-electrostatic separation process for micronized plastics

Tribo-electrostatic separation of mm-size granular insulating materials is a process widely used in plastics recycling industry. However, the separation of micronized plastics is still inefficient because the adhesion and aerodynamic forces of such particles are most often stronger than the electrostatic forces. The aim of this paper is an experimental investigation of a new separation process for micronized mixed plastics based on a fluidized bed tribocharging system and ADC high voltage cylinder rotating electrode is placed at 3 cm above the fluidized bed. The micronized insulating materials to be separated (white and grey PVC particles of average size 20 μm) are tribocharged using a fluidization air provided at variable-speed blower. The charged particles are pinned to the rotating electrode of opposite polarity. This process allows the sorting of one product while the other materials are left in the fluidized bed. The separation outcome, in terms of recovery and purity, depends on several factors and has been found to be optimal for a voltage of 35 kV and a rotation speed of 60 rpm. This new process has also been tested for ternary samples and the obtained results demonstrate its effectiveness for screening a targeted product, according to the voltage polarity, leaving the other products in the bed.