What is a cyclone?

It is a continuously operating classifying device that utilises centrifugal force to accelerate the settling rate of particles. It is one of the most important devices in the minerals industry, its main use in mineral processing being as a classifier, which has proved extremely efficient at fine separation sizes.

Where is cyclones used?

It is widely used in closed-circuit grinding operations. It has also many other uses, such as de-sliming, de-gritting, and thickening. It has replaced mechanical classifiers in many applications. The advantages of cyclones are simplicity and high capacity relative to its size.

How does cyclone works?



A typical hydrocyclone consists of a conically shaped vessel open at its apex through which the underflow comes out. On the top side of the conical vessel it is joined to a cylindrical section, which has a tangential feed inlet. The top of the cylindrical section is closed with a plate through which passes an axially mounted overflow pipe. The pipe is extended into the body of the cyclone by a short, removable section known as the vortex finder, which prevents short-circuiting of feed directly into the overflow.

The feed is introduced under pressure through the tangential entry which imparts a swirling motion to the pulp. This generates a vortex in the cyclone, with a low-pressure zone along the vertical axis. An air core develops along the axis, normally connected to the atmosphere through the apex opening, but in part created by dissolved air coming out of solution in the zone of low pressure.

The hydrocyclone acts in the principle that particles within the flow pattern are subjected to two opposing forces- an outward centrifugal force and an inwardly acting drag force. The centrifugal force developed accelerates the settling rate of the particles thereby separating particles according to size, shape, and specific gravity. Faster settling particles move to the wall of the cyclone, where the velocity is lowest, and migrate to the apex opening. Due to the action of the drag force, the slower-settling particles move towards the zone of low pressure along the axis and are carried upward through the vortex-finder to the overflow.