A New Electrostatic Separator and Sizer for Small Particles

Experimental results are obtained with a new apparatus developed at The University of Western Ontario, Canada, for the separation and sizing of particles in the 90-700-¿m diameter range. The apparatus consists of two plane electrodes set at an angle and mounted on a vibratory feeder. Experiments were carried out both with specially prepared small particle mixtures and with fly ash containing unburned carbon particles as collected from electrostatic precipitators in power plants. The upper electrode was maintained at a high voltage ac potential of various frequencies from 10 to 200 Hz. The results show that by optimizing the voltage and the frequency of the ac electric field, one can effectively separate and/or size small particles. As a typical example, starting with a synthetic mixture of copper particles consisting of approximately 50 percent by weight small particles (90-120 ¿m) and approximately 50 percent by weight large particles (594-700 ¿m), in a separated fraction containing 40 percent of the mass, one finds 83 percent of all the particles in the range of 594-700- ¿m diameter. The experiments with fly ash show an effective separation of carbon-rich fractions containing as high as 60 percent carbon.