Electric potential distribution at the surface of insulating materials exposed to corona discharges from various electrode configurations

Higher and more uniform charging of insulating granules in electrostatic separators increases separation efficiency. The aim of this work is to analyze the effect of a metallic shield in the proximity of “dual-type” or “triode type” corona electrode configurations. The basic idea is to measure the electric potential at the surface of polyvinyl plates exposed to the corona discharge generated by these electrodes. A first set of experimental results clearly show that the presence of the metallic shield enlarges the distribution of charges generated by corona discharge and produces higher electrical potential values on the surface of polymers. A second experiment points out the efficiency of the shielded electrode system for the charging of granular insulating materials in electrostatic separators. These experiments are discussed in relation with the results of the numerical analysis of the electric field generated by the different electrode configurations, taking into account the presence of an insulating material on the surface of the collecting electrode.