Separation in the Field of Centrifugal Forces

The second term in the right-hand part of (8.156) characterizes the increase of sedimentation rate due to inclination of the channel. The smaller is the slope and cross-sectional dimension of the channel b, the greater is this increase. 

The separation of the particles from carrying medium has important practical applications in petroleum and gas industry. Before delivery of oil and natural gas into the oil and gas main pipelines, it is necessary first to separate water from oil and mechanical admixtures, as well as gas condensate and water from gas. These processes are performed in special devices - the settling tanks, separators, and multiphase dividers, in which separation of phases occurs under action of gravitational, centrifugal and other forces. The methods used in modeling separation processes of hydrocarbon systems are described in work [45]. 

In the previous section, the method of gravitational sedimentation has been considered as applied to separation of relatively large particles from the liquid. A pe- 

The centrifugation method is widely used in biology for separation of macromolecules in physiological solutions and is known as ultra-centrifugation. Frequently, instead of particles (e.g., macromolecules) density p, the specific volume of macromolecules is used. Then instead of the velocity U, we can introduce parameter 

In principle, the concentration distributions of macromolecules or colloidal particles over r are about the same, as are distributions over height in a container at gravitational sedimentation. 

---

Differences in mobilities of ions, molecules, or particles in an electric field can be exploited to perform useful separations. Primary emphasis is placed on electrophoresis and dielec trophoresis. Analogous separation processes involving magnetic and centrifugal force fields are widely apphed in the process industiy (see Secs. 18 and 19). 

An Improved disc centrifuge photosedimentometer (DCP) was developed for use in the determination of the particle size and size distribution of latices, pigments and other particulates. Separation is based on Stokes Law for the sedimentation of particles in a centrifugal force field and does not rely on the use of particle size calibrants or standards. The DCP Instrument provides accurate stable particle size analyses over a wide range of conditions while at the same time is rugged enough for heavy use in both a research and quality control environment. A stand-alone data collection, analysis and management system was developed both for routine quality control operation and for research use of the instrument. 

Centrifugal separation depends on differences in the behaviour of particles in a gravitational field. In principle, the Earth s gravitational field influences the movement of particles, but for particles on a molecular scale, this force is not sufficient to cause... 

A particle, whether it is a macromolecule, a precipitate or a cell organelle, is subjected to a centrifugal force when it is rotated at a high speed, the latter being commonly expressed in terms of revolutions per minute. The particles are normally present in a specified liquid medium held in tubes or bottles, which are loacted in the rotor of a centrifuge. The rotor is positioned centrally on the drive shaft of the centrifuge. Particles which differ in density, shape or size can be separated since they sediment at different rates in the centrifugal field. 

---