WHICH CENTRIFUGALAND
WHEN? L. P. SNARPLES The Sharples Corporation,
Philadelphia, Penna.
( T u p ) PRE~URTITE SUPER- CENTRIFUGE^ FOR DEWAXING PETROLEUM On The oil is diluted and chilled to precipitate tlie wax, nnd the wax is separated from the oil soiulion in the Super-
Centdnge,
SUPEX-CENTRIFUGES I N A VEGETABLE OIL REFSXERY Caustic is mixed with the crude oil to neutralize it, and the oil and soap &ock are then separated in tho Super-Centii(h’ol/,oVz)
fage.
5RHAl’S you have a troublesome separation (liquidfrom-liquid or solids-from-liqnid) to make in your plant. What piece of cqnipinent is best fitted for the job? Should you use filtration, gravity settling, dist.illation, solvent ext.raction, or a vibrating screen? Or perhaps a centrifugal? After you have weeded out the filters, t.he gravity settlers, the stills, etc., you can then look over the field of centrifngals. Some advantageous features of a centrifugal are: (1) It is quick. From the tune the liquid enters the machine until it is separated and discharged, is generally a matter of 10 to 20 seconds. If theliquid is subject to spoilsge, spoilageis avoided. If it has been chemically trented immediately prior to centrifuging, the quick centrifugal separation generally lialts any further and undesirahle sidc reactions. (2) A centrifugal is
p’
continuous, lierice a bnlk of material in process can he avoided. Frequently the reduced investment in material in process more than pays for the centrifugal installation. A centrifugal fits perfectly as a step with ntlier contisinnus processes. (3) The centrifugal reqnires small space. Building overheads are decreased. (4) Amorphous materials may he handled. In contrast to a filter, the centrifugal has sio tendency to plug if gummy or gelatinous mat.eria1s are fed to it. ( 5 ) Liquid going tlirougir tlie centrifugal does not come into intimate contact with the contaminating solids already removed from previous material fed to it. It thus differs froin filtration. (6) The removed solids or sludges are highly cancentrated by the intensecentrifugal force. There is low loss of liquid with the removed solids. (7) Oils may be stripped from aqueous phases with remarkable conipletencss. 1072
SEPTEMBER, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
1073
Uses of Centrifugals Let us now oonsider the kinds of problems in industry that may be solved by the use of Centrifugals. In particular, let us explore to find which type of centrifugal fits each diflerent kind of prohlein. PROBLEM 1. Clarification or separation of a nonvolatile liquid which contains less than 0.5 per cent of insolubles. The simplest type of centrifugal having a high centrifugal force may be used--for instance, the standard model supercentrifuge shown in Figure 1. Its hourly capacity mill depend upon the difficulty of the separation; 1800 gallons per hour is attailled on an easy separation, 50 gallons on a very difficult one. The centrifugal force generated is 13,200 X gravity. The rotor or. bowl must be removed for clearrirrg when it hecornes filled with bowl cake. Centrifugals having rotors filled with disks to stratify the liquid may also he used for problems of this kind. The separation of acid slrrdge from petroleum oil is a problem that would fall into this category. I'nOBLEM 2 . Centrifugation of a volatile liquid which contains less than 0.5 per cent insoluhles. The same type ceutrifugd as for problem 1 may be used, but a totally enclosed model should he chosen-for instance, the Presurtite SuperCentrifuge shown in Figure 2. This may be operated under vacuum or pressure as the frame is of the autoclnvc type.
FIGURE
2.
TOTALLY ENClmsED CENTRIPUGE
It can be opernt,ed under modcrate pressure or vacuum nnd is suitable for use with volatile liquids.
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FIGURE 3. Ihw,. or R ~ T ~ J E ~ WHICH T O R AnmxxrIc.
