Electrostatic separation of Al/Cu/PVC mixture using a cascade of flat horizontal discs

Abstract

This paper presents a new configuration of an induction-type electrostatic separator aimed at metal/insulator recovery. The proposed setup features two flat, horizontal rotating discs, each connected to a different voltage amplitude. This design is intended to separate aluminum (Al) and copper (Cu) metals from a ternary mixture of aluminum, copper, and PVC (Al/Cu/PVC). The metallic particles moving under the two discs, placed in cascade, are attracted toward the first or the second disc depending on their weight. The first disc is intended to attract light aluminum particles, whereas the second disc with a higher voltage attracts copper particles. The required voltage for aluminum is approximately 5 kV, nearly the half of the required voltage for copper, which is 11 kV. Once the particles are attracted to the discs, they are radially ejected when they reach its surface. The collecting boxes, located on both sides of the discs, capture the separated materials. The separator is equipped with five boxes: two for aluminum, two for copper, and one for PVC, which remains on the conveyor and is recovered at the end. The separator is modeled and optimized using the design of experiments methodology. The main influencing factors were the voltages and the rotation speeds of the two discs. With optimal parameter values—U_Al = 5.60 kV, U_Cu = 11.92 kV, and a speed of 149.7 rpm—the separator achieves a 100 % recovery rate and high purity: over 93 % for aluminum, 94 % for copper, and 100 % for PVC.