TUBULAR-BOWL CENTRIFUGES

Disc stack centrifuge Scroil decanter centrifuge Single and multi- bowl basket centrifuges Tubular bowl centrifuge... 

Disc stack centrifuges, tubular bowl centrifuges, filtration centrifuges Alfa Laval company also has Thermal and Plow divisions Other company connections... 

The hquid-handling capacity of the tubular-bowl centrifuge varies with use. The low end shown in Table 18-11 corresponds to stripping small bac teria from a culture medium. The high end corresponds to puri ng transformer oil and restoring its dielectric value. The sohds-handling capacity of this centrifuge is limited to 4.5 kg (10 lb) or less. Typically, the feed stream solids should be less than 1 percent in practice. 

High-speed, vertical axis, tubular bowl centrifuges are used for the separation of immiscible liquids, such as water and oil, and for the separation of fine solids. The bowl is driven at speeds of around 15,000 rpm (250 Hz) and the centrifugal force generated exceeds 130,000 N. 

Tubular bowl Good dewatering, high centrifugal force, easy to clean, bowl easy to remove Limited solids capacity, solids recovery laborious, discontinuous operation... 

Figure 4.14. Separation of cell lysates containing pharmaceutical products, employing large-capacity centrifuges that are configured with tubular bowl (A), multi-chamber bowl (B), disc stack bowl (C), or decanter (scroll) bowl (D).

In those cases where the particles are small and/or the viscosity of the fluid is high, filtration is not very effective. In such cases, centrifugation is the most common and effective method for separating microorganisms, cells, and precipitates from the fermentation broth. Two major types of centrifuge - the tubular-bowl and the disk-stack - are used for continuous, large-scale operation. 

Figure 9.3 Two major types of centrifuges, (a) Tubular-bowl centrifuge (b) disk-stack centrifuge.

Using a tubular-bowl centrifuge rotating at 3600 rpm, determine the terminal velocity of Escherichia coli in a saline solution (density pp = 1.0 gcm ) at a radial distance 10 cm from the axis. 

In order to separate the particles in a suspension, the maximum allowable flow rate through the tubular-bowl centrifuge, as shown schematically in Figure 9.3a, can be estimated as follows [1]. A suspension is fed to the bottom of the bowl at a volumetric flow rate of Q (m" s" ) and the clarified liquid is removed from the top. The sedimentation velocity of particles in the radial direction (v = dr/di ) can be given by Equations 9.7 and 9.8 with the use of the terminal velocity under gravitational force v (m s" ) and the gravitational acceleration (m s" ) ... 

Using a tubular-bowl centrifuge, calculate the sedimentation velocity of a 70S ribosome (from E. coli, diameter 0.02 pm) in water at 20 °C. The rotational speed and distance from the center are 30 000 rpm and 10 cm, respectively. 

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