Sedimenting separators

Of the contents of this section, 7B (Sedimenting Separators), 7C (Centrifuges) and 7D (Cyclones and Hydrocyclones) are solely concerned with sedimentation, 7E (Coalescers), 7G (Mist Eliminators) and 7H (Electrostatic Precipitators) are largely so, but 7E (Wet and Dry Scrubbers) is as much concerned with filtration as well. 

The figure shows a continuous gravity settier in which the liquid/solid mixture enters at one end and flows steadily towards the other. On their way the solids settle to the bottom and a clear, particle-free liquid runs off from the outlet at the far end. 

A refinement of the gravity settler in Fig.1 is to place a baffle at the input end and inclined plates in the tank. This increases separation efficiency at the solid particles start from a better setting position and have a shorter distance to travel before reaching their point of settling. 

These solids can be removed continuously by a screw conveyor fitted in the rotating vessel. It is this principle that is used in decanter centrifuges. 

By rotating the vessel and its inserts, the effect of centrifugal force added to that of the inclined plates and the shorter sedimenting distance results in a very efficient separation. 

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The water and sediment contents of crude oils is measured according to the standard methods NF M 07-020, ASTM D 96 and D 1796, which determine the volume of water and sediments separated from the crude by centrifuging in the presence of a solvent (toluene) and of a demulsifylng agent Table 8.13 gives the bottom sediment and water content of a few crude oils. 

This technique has been applied to the determination of chlorinated insecticides, carbamate insecticides and substituted urea type herbicides in soil and chloroaliphatic hydrocarbons in non-saline sediments. Separation is usually achieved on thin layers of silica gel or alumina. 

JC Giddings. Generation of variance theoretical plates, resolution and peak capacity in electrophoresis and sedimentations. Separ Sci 4 181-189, 1969. 

Henzler H, Kauling J, Schmitt F, Beckers E, Boedeker B, Von Hugo H, Konstantinov K, Naveh D (2003), Continuous high cell density fermentation unit for cultivating suspended animal or plant cell lines uses sedimentation separator of specific surface area, Patent W02003020919-A2. 

The optimal concentrations were determined at which iron and silica sediments separate rapidly from a mixed sol as it coagulates, forming banded jaspilite-like layers. In these experiments, differential deposition of iron... 

Spherical glass material, solid and hollow glass microspheres in ranges of particle size 1-515 pm to be used as standards in scientific studies on sedimentation, separation, insulation, reflection and... 

Turning our attention to the sedimentation equilibrium, vye encounter similar difficulties. In principle it should be possible to derive the distribution of molecular weights in a mixture, from the concentration gradients in the sedimentation equilibrium. In practice, however, this is nos achievable. Even in polydisperse mixturet of compact particles a complete analysis along these lines is often impracticable. The more so with loosely built structures, where the molecules are too interlinked to sedimentate separately. The attainment of the equilibrium distribution, if at all possible, would require many weeks, or else such great dilution would have to be made use of, that experimental work would become practically impossible. This does not mean that all experiments in this field are illusory. However, some of the contradictions which still exist in the physical chemistry of long-chain molecules are doubtless due to difficulties encountered in experiments on their sedimentation (compare the examples in section 10 of this chapter). For an explanation of some of these contradictions see p. 103. 

FFF technology is applicable to the characterization and separation of particulate species and macromolecules. Separations in FFF take place in an open flow channel over which a field is applied perpendicular to the flow. Among the various FFF subtechniques, depending on the kind of the applied external fields, sedimentation FFF (SdFFF) is the most versatile and accurate, as it is based on simple physical phenomena that can be accurately described mathematically. SdFFF, which uses a centrifugal gravitational force field, is a flow-modified equilibrium sedimentation-separation method. Solute layers that are poorly resolved under static equilibiium sedimentation become well separated as they are eluted by the laminar flow profile in the SdFFF channel. In normal SdFFF, where the colloidal particles under study do not interact with the channel wall, the potential energy of a spherical particle, (p(x), is related to the particle radius, a, to the density... 

Distillation Sedimentation Separation by membranes Cyclones separation Sieving... 

This essentially practical text nevertheless covers the underlying theory of centrifugal sedimentation separations in some detail, which further extends its usefulness to the research or design engineer looking for new ideas. 

This is clearly a word to be used with care in any filtration and sedimentation context. It is used in this Handbook only in the general sense when unmodified, so that the term separator means any form of physical separation equipment. The term only has a specific meaning when preceded by a modifier magnetic separator , lamella separator , or, as is mainly the case in this section, gravity separator or sedimenting separator . 

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