Hydrocyclone

A hydrocyclone (often referred to by the shortened form cyclone) is a device to classify, separate or sort particles in a liquid suspension based on the ratio of their centripetal force to fluid resistance. This ratio is high for dense (where separation by density is required) and coarse (where separation by size is required) particles, and low for light and fine particles. Hydrocyclones also find application in the separation of liquids of different densities.

A different description: A hydrocyclone is a mechanical device designed to reduce or increase the concentration of a dispersed phase, solid, liquid or gas of different density, by means of centripetal forces or centrifugal forces within a vortex.

The mixture is injected into the hydrocyclone in such a way as to create the vortex and, depending upon the relative densities of the two phases, the centrifugal acceleration will cause the dispersed phase to move away from or towards the central core of the vortex.

A hydrocyclone will normally have a cylindrical section at the top where liquid is being fed tangentially, and a conical base. The angle, and hence length of the conical section, plays a role in determining operating characteristics.

A hydrocyclone is a classifier that has two exits on the axis: one on the bottom (underflow or reject) and one at the top (overflow or accept). The underflow is generally the denser or coarser fraction, while the overflow is the lighter or finer fraction. It has no moving parts and its operation depends two major parameters:

The characteristics of the feed stream include size distribution of solids in the feed stream, pulp density (percent solids in the slurry), pulp viscosity and the inlet pressure for solid/liquid separation. In liquid/liquid feed streams, for example in oily water, the main feed characteristics are based on oil droplet size and distribution, oil density, water density, oil concentration, viscosity and temperature.

The geometry of the cyclone involves-inlet shape and area, cyclone dimensions (cone angle, length of cylindrical section and total length of the cyclone) and inlet, vortex and apex diameters.

Internally, inertia is countered by the resistance of the liquid, with the effect that larger or denser particles are transported to the wall for eventual exit at the underflow side with a limited amount of liquid, while the finer, or less dense particles, remain in the liquid and exit at the overflow side through a tube extending slightly into the body of the cyclone at the center.

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Wikipedia