Filtration centrifuge filters

It does not matter, from the fundamental point of view, how the pressure drop is generated in the filter. In the case of the centrifugal filters there is an additional phenomenon of the mass forces acting on the Hquid within the cake. The conventional filtration theory must be amended to include this effect (2). 

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. 

After thickening, a variety of sludge handling and disposal options are available. For example, the thickened sludge can be applied directly to land. If liquid disposal is not applicable to a specific project, the thickened sludge can be dewatered by centrifugation, vacuum filtration, or filter pressing. The dewatered residue can then be land fill or incinerated. These options are discussed further on. 

Weigh 50 g of the potato sample into a 250-mL centrifuge vial and homogenize with 100 mL of acetone. After centrifugation at 1500-2000 rpm for 5 min, decant the supernatant over filter paper filled with Celite and collect in a 500-mL evaporation flask. Repeat extraction with 80 mL of acetone, centrifuge, filter and combine the extracts. Rinse Celite with 20 mL of acetone into the combined filtrates. 

Centrifugal filters use centrifugal force to drive the filtrate through the filter cake. The equipment used is described in the next section. 

Fifty-microlitre aliquots of standards, QC material or neat CSF are injected directly onto the F1PLC system. Blood-contaminated CSF should be filtered using a 10,000-molecular-weight (MW) centrifugal filtration system (e.g. Millipore Ultrafree-MC centrifugal filters) prior to injection. 

Cell walls, total membrane-bound components, and ribosomes were separated and assayed for cellulase activity to study the subcellular localization of the enzymes as follows. Segments (approx. 5 g fresh wt) were ground in two volumes of extraction medium containing 0.4M sucrose (ribonuclease-free), 5mM Mg acetate, lOmM Tris-HCl (pH 7.5 at 22°C), 20mM KC1 and 5mM / -mercaptoethanol. The brei was filtered and the filtrate centrifuged at 500 Xg for 20 min. The post-500 Xg supernatant was fractionated essentially as previously described (28). Aliquots (7 mL) of the supernatant were layered on a discontinuous gradient composed of 2 mL 70% (w/v) sucrose and 3 mL 15% (w/v) sucrose both in lOmM Tris-HCl (pH 7.5 at 22°C), lOmM KC1, 2.5mM Mg acetate and ImM / -mercaptoethanol. The tubes were centrifuged at... 

In operationally defined speciation the physical or chemical fractionation procedure applied to the sample defines the fraction isolated for measurement. For example, selective sequential extraction procedures are used to isolate metals associated with the water/acid soluble , exchangeable , reducible , oxidisable and residual fractions in a sediment. The reducible, oxidisable and residual fractions, for example, are often equated with the metals associated, bound or adsorbed in the iron/manganese oxyhydroxide, organic matter/sulfide and silicate phases, respectively. While this is often a convenient concept it must be emphasised that these associations are nominal and can be misleading. It is, therefore, sounder to regard the isolated fractions as defined by the operational procedure. Physical procedures such as the division of a solid sample into particle-size fractions or the isolation of a soil solution by filtration, centrifugation or dialysis are also examples of operational speciation. Indeed even the distinction between soluble and insoluble species in aquatic systems can be considered as operational speciation as it is based on the somewhat arbitrary definition of soluble as the ability to pass a 0.45/Am filter. 

The degree of dryness in this system is determined by the amount of water necessary in the cake to carry out sufficient chloride for an 8.5 to 9 percent chloride concentration in the filtrate. A centrifugal filter was used in the pilot plant to remove excess liquor from the cake collected in the material balance run (Run 10) prior to analysis and disposal. The filter operated well, reducing the wet cake to about 30 percent moisture. 

Whole-broth clarification Rotary vacuum drum filtration Centrifugation Crossflow MF, UF Maintains high throughput Does not require filter aids... 

Centrifugation is one of the most widely employed types of filtration, notable for operational speed (assuming the solid packs well on the filter cloth, or sintered metal bowl, and the porosity of the solid cake is maintained to allow thorough washing) and for producing a relatively dry cake—it is not uncommon for a centrifuged filter cake to be dried out to a solvent content of approximately 20%. Sometimes... 

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