OPTIMAL HIGH-VOLTAGE ENERGIZATION OF CORONA ELECTROSTATIC SEPARATORS

The selection of the high-voltage supply can play an important role in the optimization of electrostatic separation processes, This paper ai ms to evaluate the influence of the main high-voltage parameters (wave form, polarity, level) on the efficiency of electrostatic separation, in the case of insulation-metal granular mixtures. A roll-type laborat ory high-tension separator was employed for the experimental study, an d the tests were carried out with samples of granular materials taken from the technological flowsheet of a recycling plant for electric wir e scraps, The oscillograms of the voltage and of the current across th e separator proved to be of great use for studying the transition from corona to spark discharges, The experiments, performed under various operating conditions (roll speed, roll radius, high, voltage level, in terelectrode distance), show the existence of a strong interdependence between these parameters, the frequency of spark discharges, and the efficiency of the separation process, The reported results suggest tha t monitoring the frequency of the spark discharges could be of use for controlling the optimum operating voltage for a given electrostatic s eparation application, Although the full-wave rectifier allows for low er operating voltages than the half-wave rectifier, its general effect iveness in electrostatic separation processes is superior, Good insula tion-metal electrostatic separation can be achieved at either positive or negative polarity of the high-voltage supply, but negative electro de energization is recommended for most industrial applications, The m ethodology proposed in this paper might be successfully employed for e stablishing the optimal operating conditions of electrode energization for other applications, such as electrostatic precipitation, plasma c hemical purification of gases, or charge neutralization.