Centrifugal filtration scale

Based upon the results of the factorial study, the manufacturing-scale centrifuge filtration time (6000 X scale) was reduced 73% from the simultaneous addition process developed in Option 2 above. 

However, scale-up synthesis of polymer-grafted nanoparticles was hardly achieved, because complicated reaction processes, such as centrifugation, filtration, and solvent extraction, are required for the synthesis and isolation of polymer-grafted nanoparticles, and a lot of waste solvent is generated. 

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. 

It is known that the specific resistance for centrifuge cake, especially for compressible cake, is greater than that of the pressure or vacuum filter. Therefore, the specific resistance has to be measured from centrifuge tests for different cake thicknesses so as to scale up accurately for centrifuge performance. It cannot be extrapolated from pressure and vacuum filtration data. For cake thickness that is much smaller compared to the basket radius, Eq. (18-116 7) can be approximated by... 

More detailea descriptions of small-scale sedimentation and filtration tests are presented in other parts of this section. Interpretation of the results and their conversion into preliminary estimates of such quantities as thickener size, centrifuge capacity, filter area, sludge density, cake diyness, and wash requirements also are discussed. Both the tests and the data treatment must be in experienced hands if error is to be avoided. 

Regardless of the machine device, centrifuges are typically maintenance-intensive. Filters can be cheaper in terms of capital and maintenance and should be considered first unless centrifugal equipment already exists. Small facilities (<1000 liters) use filtration, since centrifugation scale-down is constrained by equipment availability. Comparative economics of the two classes of operations are discussed by Datar and Rosen (loc. cit.). 

Two methods are commonly used, these are centrifugation and filtration. Both methods are used on a large scale and are economically feasible. 

In fine chemicals manufacture, batch filtration prevails. This operation is the subject of R D in various steps of process development. The aim of R D on filtration is (1) to establish an effective procedure of filtration and washing providing a filter cake and/or filtrate of desired quality, and (2) to select the most appropriate filter or centrifuge for full-scale operation and determine its productivity. The productivity is defined as ... 

After dissociation of the 70 S ribosome into its two subunits followed by zonal centrifugation for the separation and isolation of the 30 S and 50 S subunits on a preparative scale, the ribosomal proteins were extracted by acetic acid and then separated by cellulose ion exchange chromatography and by gel filtration on Sephadex in the presence of 6 M urea. In this way all the 53 individual ribosomal proteins have been isolated (Wittmann, 1974). Proteins prepared in this manner have been used for physical studies (Brimacombe et al., 1978 Wittmann, 1982) as well as for immunological investigations (Stoffler et al., 1980 Lake,... 

Optimal fermentation parameters have been well established and air-lift, stirred tank, and hollow fibre systems have all been used. At commercial scale, fermentation volumes in excess of 1000 litres can be used, which can yield 100 g or more of final product. While hybridoma growth is straightforward, production levels of antibody can be quite low compared with ascites-based production systems. Typically, fermentation yields antibody concentrations of 0.1-0.5 mg/ml. Removal of cells from the antibody-containing media is achieved by centrifugation or filtration. An ultrafiltration step is then normally undertaken in order to concentrate the filtrate by up to 20-fold. 

When appropriate, biocatalysts on an industrial scale are applied as in tact whole cells or as cell lysates. If biocatalyst purification is not required on the basis of productivity, specificity or product quality demands, it is usually omitted. In those cases, cells are harvested by filtration or centrifugation and used directly or a lysate is prepared and the biocatalyst is used without further purification ( crude lysate ). 

Because of the above considerations, it is preferred to use filtration as a clarification step for small scales (less than 2000 L of culture harvest), whereas centrifugation might be the choice for larger scales of operation. 

In those cases where the particles are small and/or the viscosity of the fluid is high, filtration is not very effective. In such cases, centrifugation is the most common and effective method for separating microorganisms, cells, and precipitates from the fermentation broth. Two major types of centrifuge - the tubular-bowl and the disk-stack - are used for continuous, large-scale operation. 

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