Decanter centrifuges utilize centrifugal force to speed the dewatering or thickening of slurries and suspensions in many industrial and commercial applications. While these centrifuges, like others, may also be used to separate liquids from liquids, they are more applicable in situations that require the separation of liquids from appreciable amounts of suspended solids.
Food and beverage, water treatment, oil, gas and pharmaceutical industries commonly employ decanter centrifuges for the classification of solids based on the sedimentation principle as well as the clarification of fluids resulting from the settling out of debris. Other industrial uses for decantation include solids recovery which enables many manufacturing facilities to recover and reuse valuable materials that would otherwise be disposed of along with wastewater.
While gravity alone is sometimes used, decanter centrifuges are essential in applications where the density difference of elements within a heterogeneous mixture is too small or the particles themselves are too small. Whereas normal gravity could take ages to sort these materials, the centrifugal force generated by industrial centrifuges speeds the process while producing drier solids.
Dryness is important as both dewatering and drying materials helps to provide raw or processed substances that are lighter in weight than their immersed counterparts making for easier handling and lower transportation costs.
The operation of a decanter centrifuge can be either batch or continuous and is not altogether dissimilar to other types of centrifuges. A metal or plastic cylinder fixed along a central axis houses the materials or solutions to be sorted. When a motor engages the axis perpendicular to this, it creates a rotational movement capable of creating gravitational pulls up to twenty thousand times that of normal gravity.
This causes larger particles to separate out first in a radial direction allowing them to move toward the bottom of the cylinder while lighter materials move toward the top. In some decanter centrifuges a mesh is used to collect solids with liquids passing through to the outer area of the cylinder before being drained. In other models a helical extraction screw directs solids to one end and liquids to the other.
If high enough acceleration is reached, the solids may even become compressed for easy removal. Both new and used centrifuges are available to purchase. As adjustable and fixed acceleration models are widely available, it is important to consider the parameters of a specific application before purchasing a decanter centrifuge. Capacity should also be considered with regard to the intended use as should the design and material construct of a decanter centrifuge as these materials must be compatible with both process liquids and solids to be sorted.