Modelling of conducting particle behaviour in plate-type electrostatic separators

Abstract

The charging of conductive particles in contact with an electrode affected by a non-uniform electric field is a physical mechanism of paramount importance for various electrostatic technologies, including the separation of particulate mixtures. The aim of this paper is to model the behaviour of such charged particles in plate-type electrostatic separators. A computer program based on the boundary element method enabled the evaluation of the electric field strength at the surface of the plate electrode of these installations. The results of field computation were then employed for estimating the charge of perfectly-conducting spherical particles, as well as their position on the plate electrode, at the moment of detachment under the action of the electric force acting on them. The data reported in the paper point out the following factors which affect particle detachment and hence the efficiency of the electrostatic separation: the size and specific mass of the particles; the slope of the plate electrode; the dimensions and relative position of the high-voltage electrode; and the level of the high voltage applied to the electrode system. Experiments carried out with two kinds of particles (silver-plated polyamide spheres of radius 1.5 mm and mass 0.0192 g; and steel balls of radius 0.2-0.25 mm and average mass 0.000 45 g) confirmed the conclusions of numerical simulations. The modelling of particle behaviour in contact with plate electrodes facilitates the feasibility studies and can guide the experimental tests, which are needed for the development of any new application of the electrostatic separation method.