High-voltage energizing of corona electrodes
Electrostatic separation is based on the electrical forces acting on charged or polarized particles in an electric field [45, 48, 54, 101], generated by an electrode system connected to a high-voltage supply. Applied high voltage (HV) should be adjusted close to the threshold beyond which spark discharges could occur between the electrodes, in the presence of the processed material . In this way, one ensures the highest possible intensity of the electric field, which implies best particle charging conditions, and most effective electric separation forces [21, 22, 59].
Indeed, electrostatic induction, which is the prevalent charging mechanism of conductive particles in roll-type separators (Figure 4.1), depends directly of the electric field strength at the surface of the electrode carrier . Corona charging, which affects both conductors and insulators, is also proportional with the electric field strength, and hence with the voltage applied to the electrode system .