Continuous centrifugation

A new countercurrent continuous centrifugal extractor developed in the former USSR (214) has the feature that mechanical seals are replaced by Hquid seals with the result that operation and maintenance are simplified the mechanical seals are an operating weak point in most centrifugal extractors. The operating units range between 400 and 1200 mm in diameter, and a capacity of 70 m /h has been reported in service. The extractors have been appHed in coke-oven refining (see Coal conversion processes), erythromycin production, lube oil refining, etc. 

Crystallization batches range from 30,000 to 60,000 Hters for each pan. Continuous centrifugals are typically used for second, third, and affination steps continuous vacuum pans are less common but are used in the U.S. for intermediate strikes. Most horizontal batch crystallizers have been replaced by continuous units, and all are designed for controlled cooling of the massecuite to maintain supersaturation. 

The first three types, including the manual-discharge disk, are batch-feed centrifuges, whereas the latter three, including the intermittent and nozzle-discharge disks, are continuous centrifuges. 

Unless operating data on similar material are available from other sources, continuous centrifuges should be selected and sized only after tests on a centrifuge of identical configuration. 

The advantage of the modern continuous centrifuge is the rapidity with which it will separate both solids and emmiscible liquids. Another stems from the larger volume of oil it can handle in a given time. 

A continuous centrifugal separator separates NG from the spent acid. The centrifuge operates at 3200 rpm. For a unit with a capacity of 2500 /hr the quantity of NG in the separator bowl during operation is only 3.5 kg. The separated acid-free NG is emulsified immediately by a wash-jet to form a non-expl mixt and is removed continuously from the separator house to the NG wash-and-weigh house... 

A continuous centrifugal bioreactor, in which cells are fluidized in balance with centrifugal forces, has been designed to allow high density cell cultivation and superior aeration without elutriation of the suspended cells (van Wie et al., 1991). Reactor performance was hampered by elutriation of biomass by evolved gas in an anaerobic fermentation, indicating that it may not be suitable in its present state for three-phase fermentations. Immobilization of the cells on denser particles may overcome this problem. 

Countercurrent contactors, design of, 10 757 Countercurrent continuous centrifugal extractor, 10 781... 

The conversion of the process from batch treating to continuous centrifuging effected a marked improvement in the economy of the operation. The time of treatment and the quantity of acid required for treating were substantially reduced. The loss of oil to sludge was decreased and the sludge was less viscous than that obtained in batch operation and could be disposed of with less difficulty. 

Skim Milk. After all or most of the milk fat is removed from whole milk by continuous centrifugal separation, the resulting skim milk is fortified with 2000 International Units (IU) of vitamin A per quart and often with additional milk solids and vitamins, then pasteurized, packaged, and refrigerated until sold. The addition of vitamin D is optional but, when added, it must be not less than 400 IU/quart, and this must be shown on the label. 

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