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The sectional view of a super-centrifuge shows how centrifugal force is applied to a mixture of two immiscible liquids containing a suspended solid that is heavier than the liquids.
The mixture enters the super-centrifuge through an inlet at the base of the machine and flows into a hollow cylindrical rotor featuring two different sets of openings on the upper part which allow the separated liquids to be discharged. The rotor turns at 17,000 rpm and generates a centrifugal force 13,000 times the force of gravity. This force separates the liquids and the solids into concentric cylindrical layers depending on their specific weights. The lighter liquid moves next to the centre of the rotor while the heavier liquid forms the external layer. At the same time, the solids are deposited against the rotor wall.
The super-centrifuge works on a continuous basis. The separated liquids are continuously displaced upwards by the incoming mixture, and discharged through their respective outlet ports at the top of the rotor. The layer of accumulated solids that builds up on the rotor wall is cleaned out when the centrifuge is turned off.
The feeding thrust sends the liquid into the rotor and it is discharged by overflowing from the outlet ports. The flow from the covers is therefore only determined by the force of gravity. This particular rotor - known as a "separator" - was designed to separate two liquids and simultaneously remove suspended solids. There are, however, many applications where suspended solids are required to be separated from one liquid only. Super-centrifuges for these applications are fitted out with just one set of discharge ports and are called "clarifiers". |
