Filtration centrifuges basket centrifuge

The scale-up of filtration centrifuges is usually done on an area basis, based on small-scale tests. Buchner funnel-type tests are not of much value here because the driving force for filtration is not only due to the static head but also due to the centrifugal forces on the Hquid in the cake. A test procedure has been described with a specially designed filter beaker to measure the intrinsic permeabiHty of the cake (7). The best test is, of course, with a small-scale model, using the actual suspension. Many manufacturers offer small laboratory models for such tests. The scale-up is most reHable if the basket diameter does not increase by a factor of more than 2.5 from the small scale. 

The final pH of the initial extract from the vibrating screen was 7.5 but this increased to pH 9.6 and 10.2 for fababean and field pea, resp., during the second extraction. The filtrates were combined and centrifuged on a Fletcher basket centrifuge at 3400 rpm (1800 x g) to separate the starch and protein (Figure 2). 

In contrast to the caseins, whey proteins retain their solubility in the pH 4.5-5.0 range, provided they have not been denatured. It is therefore relatively difficult to recover and purify undenatured protein concentrates on a commercial scale. Processes that separate the whey proteins from the low molecular weight, nonprotein components of whey have been used with only moderate success to date (18). Such processes utilize ultrafil-tration/reverse osmosis membrane technology, gel filtration by the basket centrifuge technique, polyvalent ion precipitating agents... 

Larger oligonucleotide solutions can be desalted on DEAE-cellu-lose and the desalted solution concentrated by rotary evaporation, freeze drying, dialysis against Ficoll or gel filtration in a basket centrifuge depending on what apparatus is available. These methods are described below. 

Mechanical Design The vertical basket centrifuge is equipped with a cylindrical basket rotating about the vertical axis. The basket shell is normally perforated and lined with filtration media consisting of filter cloth, and backing screens to provide liquid drainage paths to the basket holes. Securing the filter cloth may be by hook and loop attachment or with snap-in retainers. 

FIG. 18-178 Pressure distribution in a basket centrifuge under bulk filtration. 

Diaphragm pumps. These offer very gentle handling of slurries and are inexpensive and mobile. However, the pulsating flow can cause feeding and distribution problems in some types of filtration systems, e.g., conventional basket centrifuges. They can also interfere with process instrumentation e.g., flowmeters and loadcells. 

Vertical basket centrifuges have been the work horse for the pharmaceutical industry for many years for intermediate and final filtration steps. Chemical and specialty chemical productions use this type of equipment in a wide range of applications... 

Wright, J., Practical Guide to the Selection and Operation of Batch-type Filtering Basket Centrifuges, Filtration and Separation, pp. 647-652, (Nov 1993)... 

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