Centrifugation Tubular centrifuges

The Imperforate Bowl Centrifuge. In an imperforate bowl centrifuge the dow of the continuous Hquid phase is nominally axial, except for areas immediately adjacent to the feed inlet and efduent oudet. Tubular soHd-bowl basket and imperforate bowl conveyor-discharge centrifuges satisfy this definition. 

Rotors are made of titanium or aluminum and may be cylindrical or bowl-shaped (see Fig. 12). Larger bowls reach 100,000 G smaller units reach 250,000 G. The tubular rotors permit feed rates up to 60 L/h at 150,000 G or 120 L/h in a larger unit at 90,000 G. Such centrifuges may be used to separate relatively large quantities of vkal material from larger quantities of cellular and subceUular matter, as, for example, in the production of vaccines (see Vaccine technology). 

The laboratory tubular centrifuge is similar to the industrial model. It operates with a motor or turbine drive at speeds to 50,000 rpm, generating 65,000 G at the latter speed in the 4.5 cm diameter bowl. The nominal capacity range is 30—2400 cm /min. This centrifuge is uniquely capable of separating far finer particles than any other production centrifugation equipment except the botde centrifuge. It is widely used in the production of flu vims. 

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. 

Experience in using the Z concept has demonstrated that the calculated Z factor should be modified by an efficiency factor to account for some of the aforementioned effects which are absent in the theoiy and, as such, this factor depends on the type of centrifuge. It is nearly 100 percent for simple spin-tube bottle centrifuge, 80 percent for tubular centrifuge, and less than 55 percent for di centrifuges. The... 

Purchase Price Typical purchase prices, including drive motors, of tubular and disk sedimenting centrifuges are given in Table 18-16. The price will vary upward with the use of more exotic materials of construc tion, the need for explosion-proof elec trical gear, the type of enclosure required for vapor containment, and the degree of portability, and this holds for all types of centrifuges. 

TABLE 18-16 Typical Purchase Prices/ Including Drive Motors/ of Tubular and Disk Sedimenting CentrifugeS/ 1996... 

FIG. 23-25 Typ es of industrial gas/Hqiiid reactors, (a) Tray tower, (h) Packed, counter current, (c) Packed, parallel current, (d) Falling liquid film, (e) Spray tower, if) Bubble tower, (g) Venturi mixer, h) Static in line mixer, ( ) Tubular flow, (j) Stirred tank, (A,) Centrifugal pump, (/) Two-phase flow in horizontal tubes. 

Separation Rates in Tubular-and Solid-Bowl Centrifuges To evaluate the radial velocity of a particle moving toward a centrifuge wall, the expression for particle settling in a gravitational field is applied ... 

By virtue of its chemical and thermal resistances, borosilicate glass has superior resistance to thermal stresses and shocks, and is used in the manufacture of a variety of items for process plants. Examples are pipe up to 60 cm in diameter and 300 cm long with wall tliicknesses of 2-10 mm, pipe fittings, valves, distillation column sections, spherical and cylindrical vessels up 400-liter capacity, centrifugal pumps with capacities up to 20,000 liters/hr, tubular heat exchangers with heat transfer areas up to 8 m, maximum working pressure up to 275 kN/m, and heat transfer coefficients of 270 kcal/hz/m C [48,49]. 

Centrifugal casting Process in which tubular products are fabricated through the application of resin and glass strand reinforcement to the inside of a mold that is rotated and heated. The process polymerizes the resin system. 

The centrifugal separator used in conjunction with the tubular nitrator is described in two patents (Refs 53 64)... 

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. 

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