Gravity Separation Machines

Adsorptive solvent recovery with steam desorption and condensation units with gravity separator and a stripper have become a standard practice in modem production plants. The solvents-laden air (toluene, xylene) is collected from emission points, e.g., rotogravure printing machines, drying ducts by means of a blower and passed through the recovery plant. 

The separating effect, G, or power of centrifuge is the ratio of acceleration obtained in the machine terrestrial gravity, as illustrated in Figure 4.18. Noting that... 

For separation of colloidal particles and for breaking down emulsions, the ultra-centrifuge is used. This operates at speeds up to 30 rpm (1600 Hz) and produces a force of 100,000 times the force of gravity for a continuous liquid flow machine, and as high as 500,000 times for gas phase separation, although these machines are very small. The bowl is usually driven by means of a small air turbine. The ultra-centrifuge is often run either at low pressures or in an atmosphere of hydrogen in order to reduce frictional losses, and a fivefold increase in the maximum speed can be attained by this means. 

A machine used to separate particles of specified size ranges. Wet classifiers include settling tanks, centrifuges, hydrocyclones, and vibrating screens. Dry classifiers, also termed air classifiers , use gravity or centrifugal settling in gas streams. 

Separation with Air as an Adjunct.—Two devices for separating by the aid of air currents passed up through a bed or mass of material will illustrate the principles on which these machines operate. These machines should be described under the head of Concentration as they employ principles of separation which have received their greatest development in that art. But since in the solution of some problems for which they are advocated there are but slight differences of specific gravity in the parts to be separated it is thought best to treat of them here. 

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