Centrifugal separators cyclones

Cyclones are the principal type of gas-solids separator employing centrifugal force, and are widely used. They are basically simple constructions can be made from a wide range of materials and can be designed for high temperature and pressure operation. 

Cyclones are suitable for separating particles above about 5 /im diameter smaller particles, down to about 0.5 gm, can be separated where agglomeration occurs. 

Api = solid-fluid density difference in standard conditions = 2000 kg/m3, 

Ap2 = density difference, proposed design, p,i = test fluid viscosity (air at 1 atm, 20°C) 

An alternative method of using the scaling factor, that does not require redrawing the performance curve, is used in Example 10.4. The cyclone should be designed to give an inlet velocity of between 9 and 27 m/s (30 to 90 ft/s) the optimum inlet velocity has been found to be 15 m/s (50 ft/s). 

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Centrifugal separators (cyclones) are most widely used to retain the powdered catalyst in the regenerator and reactor, but electrostatic precipitators (Cottrell) are also used, especially in older plants. The sizes of particles handled by various entrainment separators are approximately as follows ... 

Other Centrifugal Collectors. Cyclones and modified centrifugal collectors are often used to remove entrained Hquids from a gas stream. Cyclones for this purpose have been described (167—169). The rotary stream dust separator (170,171), a newer dry centrifugal collector with improved collection efficiency on particles down to 1—2 pm, is considered more expensive and hence has been found less attractive than cyclones unless improved collection in the 2—10-pm particle range is a necessity. A number of inertial centrifugal force devices as well as some others termed dynamic collectors have been described in the Hterature (170). 

Centrifugal Separation Centrifugal force can be utilized to enhance particle collection to several hundredfold that of gravity. The design of cyclone separators for dust removal is treated in detail in Sec. 17 under Gas-Solids Separations, and typical cyclone designs are shown in Fig. 17-43. Dimension ratios for one family of cyclones are given in Fig. 17-36. Cyclones, if carefully designed, can be more efficient on hquids than on solids since liquids coalesce on capture and are easy to drain from the unit. However, some precautions not needed for solid cyclones are necessary to prevent reentrainment. 

Cyclone is a centrifugal separator which collects and removes particulates from gases. 

Venturi and orifice scrubbers are simple forms of wet scrubbers. The turbulence created by the venturi or orifice is used to atomise water sprays and promote contact between the liquid droplets and dust particles. The agglomerated particles of dust and liquid are then collected in a centrifugal separator, usually a cyclone. 

Adopting 60-mm [2.4-in.] cyclones, which operate at lower spin speeds for the same flow rate, resulted in smaller centrifugal separation forces. This probably results in a less dense central core, which requires a higher reject ratio to allow complete oil removal. Additionally, the TLP crude exhibits a high tendency to foam, which, when combined with the flash gas that exists preferentially in the reject stream, creates a foamy gassy mixture. This in effect reduces the Vortoil capacity because the flow rate needs to be limited to reduce Ato ensure that sufficient driving force exists. 

CENTRIFUGAL SEPARATION. Theoretical as well as experimental studies have been made on the separation of powder in a cyclone by Nishihara, Kori, and Yoshi-zumi (1G). The inner distributions of velocity are measured, and a method of calculating the separable size of powder is presented. 

The next step in the process is removal of remaining soluble and insoluble protein. Starch slurry discharging from the primary centrifugal separator must be diluted with process water to a slurry density of 10-12° Baume (18-21% dry solids). The starch may then be further purified in a second centrifugal separator to a final insoluble protein level of <0.38% dry basis (preferably 0.27-0.32% dry basis). However, since solubles content of the slurry must next be reduced by filtration of centrifugal decantation, the second step currently preferred is to utilize 8 to 14 stages of liquid cyclones which simultaneously remove residual gluten and wash the starch.207-209... 

The cyclone or centrifugal separator is a device utilizing radial acceleration for separating partides suspended in a gas stream. It con-... 

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