Design and optimization of free‐fall electrostatic separators for plastics recycling

Abstract

AbstractElectrostatic separation is a promising technique for separating a mix of plastics, which can acquire different sign charges through triboelectrification. A particular application of growing importance is the separation of plastics with overlapping densities from a waste stream of electronic products. Particle charging, which plays an important role in separation efficiency, has been the topic of much research. However, no systematic method has been proposed for design and optimization of the separation process itself, a gap that this research seeks to fill. The aim is to compare several design options for free‐fall electrostatic separators, taking into account the distribution of the particle charge and initial position. Particle trajectory and recovery models are derived under a set of simplifying assumptions that are carefully analyzed. Optimization models are developed that trade off the strength of the electric field with the size and number of stages of the free‐fall separator. Several different configurations are optimized and compared under various conditions (mean value and standard deviation of particle charges, feed rate, and product prices). Finally, a general guide is proposed for selecting an appropriate design.