Corona-discharge electrodes for improved electrostatic separation of electroinsulating materials

Two sets of corona-discharge electrodes, wire and needle type, have been tested on laboratory electroseparators. As compared to needle-type electrodes, the wire-type ones are characterized by: (i) a larger possibility of adjusting the parameters which determine the field in the active zone of the separator; (ii) a less complicated manufacturing technology; and (iii) smaller quantities of ozone generated during corona discharge. Needle-type electrodes, on the other hand, have at least three favorable characteristics: (i) not being affected by vibrations; (ii) lower corona voltages; and (iii) higher slopes of V-A digrams (which means an increased corona effect). Based on these facts, the authors have used this kind of electrode with the ELSIM-2 insulation-metal electroseparator. Pilot-plant tests of electroseparation were effected on chopped PVC-insulated copper wire scrap and on a mica-feldspar-quartz mixture, using various field configurations, to validate the efficacy of the design. High-purity electroinsulating materials were obtained and then incorporated into different types of electrical insulation.