Experimental investigation on lifting criteria of an induction-charged spherical particle in a field with horizontally set parallel plate electrodes

The lifting criteria of an induction-charged spherical particle in a field with horizontally set parallel plate electrodes is investigated by an experimental approach, using alumina, silica, and polyurethane powders. The present paper gives 0.25 kV/mm as the minimum lifting intensity of the electric field. The experiment proves that electrical conductivity of a particle is an important factor in governing lifting criteria so that powders with high conductivity, over 10(-8)(Ohm m)(-1), could easily be lifted up. Polyurethane powders with below 1% water fraction on the surface of the particles cannot be lifted up even under a high electric field intensity, because of their low conductivity. By adding water to the powders, the conductivity increases so that the particles are lifted up in over 3% water fraction. But at over 10% water fraction, the binding force of the water bridge between particles governs the total force balance. With considerations of the electrostatic upward force of the particle and the capillary binding force of the water bridge between particles and the gravity force as downward forces, estimations of lifting criteria by a theoretical approach are identical with the experimental results.