Separator, centrifugal sedimentation

The processing operations for fluid or manufactured milk products include cooling, centrifugal sediment removal and cream (a mixture of fat and milk semm) separation, standardization, homogenization, pasteurization or sterilization, and packaging, handling, and storing. 

Centrifugation. Centrifugal devices include clarifiers for removal of sediment and extraneous particulates, and separators for removal of fat (cream) from milk (see SEPARATION, CENTRIFUGAL). 

Factors Influencing Centrifugal Sedimentation. The sedimentation velocity of a particle is defined by equations I and 2. Each of the terms therein effects separation. 

Particle Size Distribution. Almost every feed slurry is a mixture of fine and coarse particles. Performance depends on the frequency of distribution of particle size ia the feed. Figure 5 shows that whereas all of the coarse particles having a diameter greater than some are separated, fewer of the very fine particles are, at any given feed rate. The size distribution frequency of particles ia feed and centrate for a fine and coarse feed are quite different. More coarse particles separate out than fine ones. Classification of soHds by size is often done by centrifugal sedimentation. 

Sedimentation Equipment. Centrifugal sedimentation equipment is usually characterized by limiting flow rates and theoretical settling capabihties. Feed rates in industrial appHcations may be dictated by Hquid handling capacities, separating capacities, or physical characteristics of the soHds. Sedimentation equipment performance is illustrated in Figure 8 on the basis of nominal clarified effluent flow rates and the appHcable values. The... 

These operations may sometimes be better kno Ti as mist entrainment, decantation, dust collection, filtration, centrifugation, sedimentation, screening, classification, scrubbing, etc. They often involve handling relatively large quantities of one phase in order to collect or separate the other. Therefore the size of the equipment may become very large. For the sake of space and cost it is important that the equipment be specified and rated to Operate as efficiently as possible [9]. This subject will be limited here to the removal or separation of liquid or solid particles from a vapor or gas carrier stream (1. and 3. above) or separation of solid particles from a liquid (item 4j. Reference [56] is a helpful review. 

Centrifugal potting, 16 18 Centrifugal pumps, 19 513 affinity laws related to, 21 63 costs associated with, 21 87 efficiency of, 21 60 nonmetallic, 21 76 suction specific speed of, 21 63 Centrifugal sedimentation, 18 142, 143-144 Centrifugal separation(s), 5 505-551 ... 

The starch fraction was washed initially with 0.02% NaOH, the extract being added to the protein solution (Figure 2). The starch was then slurried in distilled water, separated by sedimentation, and dried at 30°C. The combined protein extracts were adjusted to pH 4.5 with IN HC1 and the whey separated from the curd by centrifugation in the basket centrifuge (1100 x g). The protein curd was washed twice with water adjusted to pH 4.5, then resuspended at pH 7.0 using IN NaOH. The proteinate was freeze-dried. 

Figure 8.5. Schematic diagram of separation by centrifugal sedimentation.

In centrifugal separation, the sedimentation rate of a particle is increased many thousands of times compared with gravitational forces, to enable efficient separation of particles with relatively small differences in density or size. 

Yeast separation and concentration. Extraction of ethanol from biomass requires several separation steps, traditionally by centrifuging, sedimentation and cake filtration. First, after the fermentation, the yeast is removed from the fermentation broth and may be recycled. Additionally, after ethanol is stripped from the fermentation broth by steam followed by the removal of solid fractions, the remaining material called the thin stillage can be clarified for reuse upstream as the process water. 

Sedimentation Techniques. Other techniques that effect a physical separation include gravitational or centrifugal sedimentation, in which particles or emulsion droplets are separated on the basis of size and density. The separation that occurs can be quantified by monitoring X-ray or light absorbance as a function of position. Stokes law then can be used to determine the particle size distribution from the absorbance data as a function of the sedimentation time (73, 74). 

In centrifugal sedimentation, the separation is due to the difference in the density of two or more phases. This is the more important process, where both solid-liquid mixtures and liquid-liquid mixtures can be completely separated. If, however, the separation is incomplete, there is a gradient in the size of the dispersed phase within the centrifuge due to the faster radial velocity of the larger particles. Operated in this way, the centrifuge becomes a classifier. 

Because the centrifugation forces are relatively weak for small molecules, sedimentation FFF is most applicable for molecules with molecular weights exceeding 10 . Such systems as polymers, biological macromolecules, natural and industrial colloids, emulsions, and subcelluar particles appear to be amenable to separation by sedimentation FFF. 

PRINCIPLES OF CENTRIFUGAL SEDIMENTATION. In a sedimenting centrifuge a particle of given size is removed from the liquid if sufficient time is available for the particle to reach the wall of the separator bowl. If it is assumed that the particle is at all times moving radially at its terminal velocity, the diameter of the smallest particle that should just be removed can be calculated. 

Centrifuge An apparatus in which an applied centrifugal force is used to achieve a phase separation by sedimentation or creaming. For cen-... 

Precipitation is a process in which dissolved compounds are separated from the reaction medium in the form of low soluble compounds in their solid states, which can then be separated by sedimentation, filtration, centrifugation, flotation, etc. Precipitation is carried out either by a chemical change of dissolved substance, or by a change of the reaction medium. As precipitants, mostly acid, base or salt solutions are used. 

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