Modelling Of Tribo-electrostatic Separation For Industrial By-products Recycling

Tribo-electrostatic separation is a dry technology which allows the elimination of impurities from industrial wastes on the basis of their surface charging characteristics. In this paper results of investigations aiming to numerically simulate the tribo-electrostatic separation of fine particles for industrial by-products recycling are described. After charging in a pneumatic transport line, the mixture of the particles to be separated is injected in a separation chamber where a DC electric field is created using two parallel plate electrodes. The particle/gas flow inside the chamber was simulated using an extended commercial computational fluid dynamics (CFD) code. The three-dimensional turbulent flow was calculated. Based on the Lagrangian approach, the trajectories of the powder particles (< 100 microns) were modelled considering electric and aerodynamic forces. Comparison of the simulation results with experiments carried out with a bench-scale separation unit are presented for the case of silica beads, whose electric characteristics resemble those of coal fly ashes. The effects of particle charge, electric field and injection velocity were investigated, revealing that a proper choice of separator geometry and flow parameters allows unwanted fine particles in industrial wastes like fly ash to be efficiently removed.