Experimental study on fine particle separation in a wet electrostatic classifier

Fine particles were separated by applying an electrostatic field in a designed wet classifier to improve the classification performance. Separation experiments were performed using fine silica particles with a size range from 0.21 to 8.71 μm based on the zeta potential of the suspended particles in the water. The effects of feed flow rate, electrode voltage, and feed particle concentration on separation performance were discussed. The results show that partial separation efficiency increased with feed flow rate and feed particle concentration, but decreased with electrode voltage. Maximum total separation efficiency was achieved at a given feed flow rate, a given electrode voltage, and a given feed particle concentration. The total separation efficiency reached 61.9 % when the nozzle diameter was 1.0 mm, the feed flow rate was 46.2 mL/min, and the electrode voltage was 150 V, which was higher by approximately 11.1 % compared to gravity settling. The separation factor for electrostatic wet classification reached 44,000 for 0.5 μm particles. The 50 % cut size decreased linearly with the increase in electrode voltage and a minimum 50 % cut size of 1.033 μm was obtained. Particle agglomeration effect, fishhook effect, and strong reverse flow should be considered when wet classification technology is employed in engineering applications.