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Centrifuge working principle

Oct 31, 2019

The working principle of the centrifuge:

A centrifuge is a separation machine that separates a mixture of solid and liquid (liquid and liquid) to obtain solids and liquids (or liquids and liquids), respectively. The working principle of the centrifuge is to have a different Natural stratification occurs when the density mixture is allowed to stand. The solids generally settle to the bottom layer, while the upper layer forms a clear liquid. The stratification relies on the gravitational acceleration of the Earth. In order to meet the needs of industrial production, people need to separate some of the mixture faster and more, thus creating a centrifuge.


The centrifuge rotates at high speed to generate powerful centrifugal force. The centrifugal separation coefficient is usually hundreds of times, thousands of times and 10,000 times of the gravity acceleration. Therefore, the separation speed is very fast, but due to the great difference in material properties, various types have been formed. Centrifuges of different specifications, generally centrifuges with solid and liquid separation speeds below 3000 rpm, finer particles, and smaller density differences require centrifuges with speeds between 8,000 and 30,000 to separate, like uranium Concentrated separation requires a higher speed centrifuge. 

The main principle of the centrifuge is to accelerate the liquid phase in the solid-liquid mixture to the drum by the centrifugal force generated by the high-speed centrifugal drum (with appropriate filter material), and leave the solid phase in the drum to reach The effect of separating solids and liquids, or the effect of dehydration.


When the suspension containing fine particles is left stationary, the suspended particles gradually sink due to the action of the gravitational field. The heavier the particles, the faster the sinking, whereas the particles with a lower density than the liquid will float. The rate at which particles move under the gravitational field is related to the size, morphology, and density of the particles, and is related to the strength of the gravitational field and the viscosity of the liquid. Particles of the size of red blood cells, a few micrometers in diameter, can be observed under normal gravity.


The main principle of the decanter centrifuge is to accelerate the sedimentation velocity of different specific gravity components (solid phase or liquid phase) in the mixture by the powerful centrifugal force generated by the high-speed rotation of the rotor, and to separate the different sedimentation coefficients and buoyant density substances in the sample.


In addition, the substance is accompanied by a diffusion phenomenon when it settles in the medium. Diffusion is unconditional and absolute. The diffusion is inversely proportional to the mass of the material, and the smaller the particle, the more severe the diffusion. The settlement is relative, and if it is conditional, it must be subjected to external forces to move. The settlement is proportional to the weight of the object, and the larger the particle, the faster the sedimentation. For particles smaller than a few micrometers such as viruses or proteins, they are in a colloidal or semi-colloidal state in solution, and it is impossible to observe the sedimentation process by gravity alone. The smaller the particles, the slower the sedimentation, and the more severe the diffusion phenomenon. Therefore, it is necessary to use a centrifugal machine to generate a strong centrifugal force in order to force these particles to overcome the diffusion to produce a settling motion.