Centrifugation and decantation

Among the processes used for mechanical treatment of liquids, sedimentation and centrifugation are based on the difference in density of the phases present. The physical phenomena involved and the resulting forces characterize these two processes.

Sedimentation uses the field of terrestrial acceleration, while centrifugation uses the field of centrifugal acceleration.

The forces involved are gravitational and centrifugal.

After a brief review of the principles of sedimentation and decantation, this dossier focuses on centrifugation, which can be defined as the operation used to separate :

• two liquid phases ;

• a solid phase suspended in a liquid phase;

• two liquid phases containing a third solid phase.

There are two main categories of centrifuge:

• Vertical-axis centrifuges, commonly known as clarifiers or centrifugal separators (with a bowl of plates or chambers that rotates on a vertical axis);

• horizontal-axis centrifuges, commonly known as decanter centrifuges (with a cylindro-conical bowl that rotates on a horizontal axis, and a screw located inside the bowl for sediment removal).

These construction provisions partly determine the areas of use for this equipment.