Selection based on the characteristics of solid particles
Particle size
If the solid particles are large (e.g., larger than 1mm in diameter), such as concrete mixing wastewater containing large stones and sand in the construction industry, a filter centrifuge or a low-speed centrifuge may be a better choice. A filter centrifuge can intercept these large particles with a simple sieve, while a low-speed centrifuge can use relatively small centrifugal forces to separate large particles through rapid sedimentation. For smaller particles (between 1 – 100μm in diameter), such as some fine powder suspensions in chemical production, a high-speed centrifuge or a sedimentation centrifuge is more suitable because they can provide sufficient centrifugal force to settle and separate these fine particles. For very fine particles (less than 1μm in diameter), such as solid-liquid separation in some nanomaterial production, an ultracentrifuge or a disc centrifuge may be the only equipment that can achieve effective separation.
Particle shape
When solid particles have a regular shape, such as spherical or nearly spherical, filter centrifuges are known to perform better. This is because such particles are less likely to clog the filter media and can easily pass through the pores of the screen or filter cloth. For instance, when filtering a mixture of spherical glass beads and liquid, filter centrifuges can efficiently separate solids from liquids. However, in cases of irregular and angular particles, such as the sharp-edged metal scraps produced during metal processing, a decanter centrifuge might be a more appropriate choice. This is because such particles tend to clog the filter media, making a decanter centrifuge the preferred option which utilizes centrifugal force for direct separation. In certain instances, where effective separation is crucial, like in nanomaterial production, an ultracentrifuge or a disc centrifuge may be the only equipment capable of achieving it.
Particle density
For optimal separation, it is important to consider the density difference between solid particles and liquid. In cases where the difference is large, such as in oil sand mining, a centrifuge with lower speed can achieve superior results. However, when the density difference is small, such as in the separation of micro-particle organic matter in certain organic solutions, a high-speed or ultra-high-speed centrifuge is necessary to provide enough centrifugal force to overcome the effects of the small density difference and achieve successful separation.
Selection based on liquid properties
Liquid Viscosity
For liquids with low viscosity, like water or low concentration aqueous solutions, various types of centrifuges can be utilized with great efficiency. However, when the viscosity of the liquid is high, such as with concentrated syrup or viscous oil, the separation process of the centrifuge may be negatively impacted. In such cases, a sedimentation or disc centrifuge might be a more appropriate option for solid-liquid separation in high viscosity liquids. These centrifuges do not require the use of filter media, but instead utilize centrifugal force to settle or separate solid particles from the liquid. This method avoids the potential issue of the liquid passing through the filter medium at a slower speed or even clogging it.
The nature of the liquid (whether it is an emulsion, etc.)
When dealing with non-emulsified substances, like a basic solid-liquid mixture, you have the option of filtration, sedimentation, or a high-speed centrifuge, depending on the characteristics of the solid particles. However, for emulsions such as milk or those containing chemicals, a disc centrifuge is the optimal choice. This specialized machine utilizes centrifugal force and a unique disc structure to efficiently separate the oil phase, water phase, and solid impurities found in emulsions, directing them to different outlets.