The application of centrifugal force has proved an effective technique for the recovery of fine heavy minerals in recent years. The centrifugal force acting on a particle can be equal to or even higher than 50 times the force of gravity, significantly increasing the settling rate of a particle. The size of particles that can be captured becomes finer as the intensity of centrifugal forces generated is increased.
The Kneson centrifugal concentrator is an enhanced gravity device that generates a high gradient centrifugal field whereby the deposition and stratification of fine particles occur inside a smooth centrifugal wall. Feed slurry is introduced into a rotating rotor bowl and accelerated by an impeller as it flows on the inner wall of the rotor. The lower part of the rotor is inclined at a slight angle to provide a migration zone, while the cylindrical upper part acts as the retention zone. The strong centrifugal forces, normal to the wall, lead to the hindered settling and stratification of particles in the migration zone. The weak driving force, parallel to the inclined rotor surface, moves the stratified particles up towards the top. The lighter particles, on the outside of the bed, migrate out of the rotor assembly due to their lower specific gravity or small size. Heavy particles are retained in the concentrating (retention) zone where the concentrate is cleaned by fluidization water.