Centrifugal example

The reproducibility of curves P< = f(n) is usually good (Figure 3) for the same polymer and for two polymers prepared under the same conditions (where Pi = weight of fraction i, n = cc of methanol for 25 cc of initial solution). Differences in curves may be related to accidental factors such as temperature increase and variation of rotation speed during centrifuging. Examples of precipitation are given in Tables I, II, and III. 

Centrifuge considered. The centrifuge example whose separation performance is to be evaluated has the dimensions of the centrifuge tested by the Standard Oil Development Company in 1944 and described by Beams et al. [B3] ... 

May [M6] has calculated the effect of varying the circulation rate N on the separative capacity of this centrifuge example operated at peripheral speeds of 400, 500, and 700 m/s, at a feed rate of 0.03171 g UFg/s, using the parameters of Table 14.14, with results shown in Fig. 

Antibiotics. Solvent extraction is an important step in the recovery of many antibiotics (qv) such as penicillin [1406-05-9] streptomycin [57-92-17, novobiocin [303-81-1J, bacitracin [1405-87-4] erythromycin, and the cephalosporins. A good example is in the manufacture of penicillin (242) by a batchwise fermentation. Amyl acetate [628-63-7] or -butyl acetate [123-86-4] is used as the extraction solvent for the filtered fermentation broth. The penicillin is first extracted into the solvent from the broth at pH 2.0 to 2.5 and the extract treated with a buffet solution (pH 6) to obtain a penicillin-rich solution. Then the pH is again lowered and the penicillin is re-extracted into the solvent to yield a pure concentrated solution. Because penicillin degrades rapidly at low pH, it is necessary to perform the initial extraction as rapidly as possible for this reason centrifugal extractors are generally used. 

Example 3. A centrifugal pump moving a corrosive Hquid is known to have a time-to-failure that is well approximated by a normal distribution with a mean of 1400 h and a standard deviation of 120 h. A particular pump has been in operation for 1080 h. In order to plan maintenance activities the chances of the pump surviving the next 48 h must be deterrnined. 

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). 

Clear-Hquor advance reduces the quantity of Hquor that must be processed by soHd—Hquid separation equipment (for example, a filter or a centrifuge). The reduction in Hquor flow through the separation equipment may allow use of smaller equipment for a fixed production rate or increased production through fixed equipment. 

Reversible Processes. Distillation is an example of a theoretically reversible separation process. In fractional distillation, heat is introduced at the bottom stiUpot to produce the column upflow in the form of vapor which is then condensed and turned back down as Hquid reflux or column downflow. This system is fed at some intermediate point, and product and waste are withdrawn at the ends. Except for losses through the column wall, etc, the heat energy spent at the bottom vaporizer can be recovered at the top condenser, but at a lower temperature. Ideally, the energy input of such a process is dependent only on the properties of feed, product, and waste. Among the diffusion separation methods discussed herein, the centrifuge process (pressure diffusion) constitutes a theoretically reversible separation process. 

It should be noted that the separation factor for the centrifuge process is a function of the difference in the mol wts of the components being separated rather than, as is the case in gaseous diffusion, a function of their ratio. The gas centrifuge process would therefore be expected to be relatively more suitable for the separation of heavy molecules. As an example of the equiUbrium separation factor of a gas centrifuge, consider the Zippe centrifuge, operating at 60°C with a peripheral velocity of 350 m/s. From equation 68, OC is calculated to be 1.0686 for uranium isotopes in the form of UF. ... 

Example 2 Vibration Consider an electric motor rotating at 1800 rpm driving an 8-vane centrifugal pump rotating at 600 rpm. For this 3 1 speed reduction, assume a gear box having two gears of 100 and 300 tooth. Since 60 Hz is 1 rpm,... 

Type of dryer tions, extracts, milk, blood, waste liquors, rubber latex, etc. gents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. trifuged sobds, starch, etc. dry. Examples centrifuged precipitates, pigments, clay, cement. ores, potato strips, synthetic rubber. objects, rayon skeins, lumber. sheets. her sheets. 

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