High-voltage electrode position: a key factor of electrostatic separation efficiency

Industry application of electrostatic separation technologies still faces a major difficulty: good results can be obtained only by adequate control of a multitude of operating parameters. The aim of the present paper is to analyze a key factor of electrostatic separation efficiency: the position of the high-voltage electrodes. Experiments were performed with two types of granular materials: chopped electric wire wastes and foundry sands. The electrostatic separator employed for the tests was provided with a needle-type corona electrode, associated - in some experiments - with a tabular-type electrostatic electrode, at various angular and radial positions, with respect with a rotating roll electrode connected to the ground. The experimental data are discussed in relation with the results of the numerical analysis of the electric field, carried out with a charge simulation program. They show that the outcome of the separation process (i.e. the weight percentage of the conductor and non-conductor fractions, as well as the purity of the recovered materials) depend on the configuration of the electrode system. The position of the electrodes affects both the particles charging conditions on the surface of the roll electrode, and the trajectories of the charged particles in the high intensity electric field of the separator. Some recommendations could be formulated for the industrial application of the electrostatic separation technology.