Hydrocyclone

After the fan pump the stock is cleaned in small cyclones: hydrocyclones. The reason why the hydrocyclones are so small, is that the smaller the diameter, the better it separates very small impurities. A hydrocyclone is cone-shaped (click image twice to enlarge). The incoming stock, the inject, is fed into the thick end.

The stock, when it comes into the cyclone, starts rotating. The quicker the stock rotates, the more the centrifugal force will influence the stock.

The centrifugal force influences particles with a high density more, than particles with a low density. The higher the density, the higher the force driving the particles towards the cyclone wall will be.

Closest to the wall the stock streams in a downwards spiral. The heavy particles come along in the stream and leave the cyclone as reject. However, in the centre of the cyclone the flow spiral is directed upwards and its content, the accept, leaves the cyclone.

Source : MURATA KOGYO Co,Ltd. (picture)