Centrifugation principles

Figure 9.12. Solid-bowl decanter centrifuge-principles of operation...

SpinPro includes two other functions that enhance its role as an expert advisor. This is in recognition that an expert provides more than expert advice. An ultracentrifugation expert serves in many roles a teacher of centrifugation principles, a describer of standard procedures, and a source of literature references. 

Hanni et al. (1976) described a continuous fluidized bed drier using the centrifugal principle. It consisted of a perforated horizontal cylinder rotating inside a plenum with hot air blown across the outside of the cylinder and perpendicular to the axis of rotation (Figure 1.20). Vanes placed in the air inlet allowed the incident angle of the air flow to be varied from 0° to 45° to the perpendicular. Particles were fluidized inside the Teflon-coated stainless steel cylinder which could be tilted by up to 6° in order to control particle residence time. The cylinder, of... 

Jordan Pulping Machine. It is used in preparing cotton for nitration. The machine operates on the centrifugal principle, by means of which the entering cotton is thrown from the large end of the beater to the small tapered end, and thence to a storage tank above the machine. 

Fig. 9. View of the deck of peptide synthesizer utilizing tilted centrifugation principle. (Photo by ML.)...

Centrifugal separators make use of the common principle that an object whirled about an axis at a constant radial distance from the point is acted on by a force. Use of centrifugal forces increases the force acting on the particles. Particles that do not settle readily in gravity settlers often can be separated from fluids by centrifugal force. 

H. Axelsson, Centrifugal Separations—Principles and Techniques, Alfa Laval Separation, Tumba, Sweden, presented at the Bioprocess Technology Program, University of Virginia, Charlottesville, Va., Oct. 17—25 1991. 

Manufacture. PVBs are manufactured by a variety of two-stage heterogeneous processes. In one of these an alcohol solution of poly(vinyl acetate) and an acid catalyst are heated to 60—80°C with strong agitation. As the poly(vinyl alcohol) forms, it precipitates from solution (77). Ethyl acetate, the principle by-product, is stripped off and sold. The precipitated poly(vinyl alcohol) is washed to remove by-products and excess acid. The poly(vinyl alcohol) is then suspended in a mixture of ethyl alcohol, butyraldehyde, and mineral acid at temperatures above 70°C. As the reaction approaches completion the reactants go into solution. When the reaction is complete, the catalyst is neutralized and the PVB is precipitated from solution with water, washed, centrifuged, and dried. Resin from this process has very low residual vinyl acetate and very low levels of gel from intermolecular acetalization. 

J. L. Modfied Minimum Principle for Stationay Flow in a Gas Centrifuge Re t. EP-3912-325-64U, Research Laboratories for the Engineering... 

FIG. 18-138 Principl es of centrifugal separation and filtration (a) sedimentation in rotating imperforate bowl (h) Bltration in rotating perforate basket. 

Boyce, M.P., Principles of Operation and Perfoimance Estimation of Centrifugal Compressors. Proceedings of the 22nd Turbomachinery Symposium. Dallas, Texas, September 1993, pp. 161-78. 

Elbow flow meters. The principle of centrifugal force at the bend is used to obtain the difference in pressure at the inside and outside of the elbow, which is then related to the discharge pressure. 

The principle of the solid bowl centrifuge is illustrated in Figure 4.19. It is essentially a device for enhancing the rate of sedimentation. The application of high G, however, creates stress in the machine and is equivalent to the application of pressure (cf. pressure filtration). There is therefore a balance to be struck between separating effect and stress. 

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