Conclusions to Chapter 4

1. HV monitoring could provide useful information for electrostatic separation process control. By comparing the measured value of the high-voltage to the imposed level, any unconformable operation could be readily detected. In case that spark discharges are too frequent, the applied voltage should be reduced, in order to avoid these events that affect the outcome of the separation process.

2. In spite of the fact that the electronic HV supplies employed with modern separators are provided with protections against sparkover, not all of them are adequate for applications characterized by frequent sparks between the electrodes in the presence of the processed material. The restoration of the high-voltage at the level it had before sparkover may require a relatively long time (up to 1 s!), imposed by the electronic scheme of the supply. The shorter this time, the more appropriate the high-voltage supply is for energizing the electrodes of an insulator/metal separator, where spark discharges between the electrodes cannot be completely avoided.

3. The most interesting result of this work is the linear correlation that was evidenced between the standard deviation of the measured high-voltage (σHV) and the composition of the material passing through the active zone of the separator. A change in the measured σHV could point out an alteration in the composition of the processed material, and indicate that appropriate corrections should be made for optimal operation of the overall system.