The basic separation principle of centrifuges

A centrifuge is a separation machine that uses centrifugal force to separate suspensions or emulsions. The main coarse part of the centrifuge is a high-speed rotating drum that generates a centrifugal force field, in which the material to be separated is placed.

According to the different separation principles, centrifuges can be divided into two categories: settling type and filtering type.

A filter centrifuge is used for separating suspensions, with small holes on the drum wall and a filter screen or cloth inside the drum. According to the different materials, they should be added when the drum is stationary or rotating. When the drum rotates, the liquid in the suspension is thrown out of the drum through the filter screen and small holes on the drum wall under centrifugal force, while the solid phase is trapped on the filter mesh to form a layer of filter residue. The filter residue can be manually discharged after the drum stops, or mechanically discharged when the drum rotates.

A settling centrifuge can separate both suspension and emulsion, with no pores on the drum wall. When the drum rotates, components with different densities are separated from each other under the action of centrifugal force. When separating the suspension, the solid phase deposits on the drum wall, and the surface of the solid phase is a liquid distributed in a circular pattern; When separating emulsion, the material is divided into two concentric liquid rings, the outer ring is a liquid with higher density, and the inner ring is a liquid with lower density saddle. When separating the suspension, the material is added after the centrifuge is started, and the unloading situation is the same as that of a filter centrifuge. When separating the emulsion, the feeding and unloading of the separated material are both carried out continuously while the drum is rotating.

The separation factor f is the multiple of the centrifugal acceleration of the material during centrifugal separation to the gravitational acceleration of the Earth: f=Rw2/g,

In the formula: R: Inner radius of the governing drum (meters)

w: The angular velocity of the drum (radians/second)

g: Earth's gravitational acceleration (meters/second)

The centrifugal separation operation intensity of a centrifuge is directly proportional to the separation factor.