Equipment and OesCgn ~~
Disengaging velocity may be increased when foam is decreased by antifoaming agents or other means by David E. Pierce OAM
may be desirable in certain
F beverages and detergents, but it is
often a disadvantageous factor in chemical plant operations. This limitation was pointed out in our column of February 1953, in which it was emphasized that the rate a t which liquids may be boiled (disengaging velocity) is often controlled by foaming. That the problem described in the article was not unusual has been shown by the number of letters received during the past few months, all agreeing that the writers had encountered similar difficulties and were interested in ways of solving the problem. Drive
Hot O i l
Inlet
Figure 1.
Process Kettle b e f o r e Alteration
In “The Case of the Reluctant Water,” the desired increase in hourly evaporatioii rate was achieved by pumping the boiling liquid into a flash drum. Flowing tangentially into the cylindrical drum, the liquid was broken into a thin sheet and presumably into a large number of drops which gave a large increase in disengaging area. The desired result could ha7.e been accomplished also by using an evaporator of large diameter November 1953
relative to the depth of liquid. Often, it is necessary to provide a large amount of headroom above the liquid so that the foam may break and fall back into the liquid. One interesting problem of this sort arose in the case of a nonaqueous material treated with an aqueous solution to effect changes in the properties of the compound. Removal of the water required long heating, with the upper three fourths of the kettle filled with foam a5 near to the sight glass in the cover as could be tolerated without having the batch go out through the vapor vent. The jacketed aluminum kettle, heated by circulating hot oil, is shown in Figure 1. To meet production requirements, a battery of these kettles was used, each one being much larger than would have been required by the liquid contents, thus providing the necessary headroom for the long foaming period. Because the high temperature used in the operation caused softening of the aluminum with subsequent distortion and failure, it was decided that nickel might be used for the material of construction of the vessel instead of aluminum. The new kettle, duplicating the dimensions of the existing units, was finally fabricated and put in service. To the surprise of all concerned, there was no foaming problem with, the new vessel! The foam formed, of course, but rose only a few inches above the liquid. The operator could look down through the sight glass and see the foam, far down in the vessel, rolling over from the sides near the top of the jacket and breaking very easily. The next step, naturally, was to increase the size of the batch. Unfortunately, after ZL relatively small increase in the number of pounds being processed, the foaming conditions reappeared. The familiar filling of the entire kettle with foam took place, and the time of operation was about the same as with the aluminum kettles. Analysis of the batches made in the
new kettle showed that a very small amount of nickel had been dissolved in the material being processed. Although nickel salts had never been publicized as foam breakers, it was reasoned that, since the only difference between the new and the old kettles was in the metal, this could be the answer. Accordingly, the laboratory made a series of small batches to which various nickel compounds were added. There was no evidence of lese foam in these batches than in those that were used for controls. Drive -
Figure 2.
Kettle with High Jacket
Although the chemical theory had drawn a blank, i t seemed evident that the effect on foam must be due to the difference in the two metals. One obvious difference was in their coefficients of heat conductivity. Tabulated values for the two metals at 212’ F. were 119 B.t.u. per hour per foot of thickness per ’F. temperature difference for aluminum and 34 for nickel. Although the values would be somewhat different a t the high temperatures being used, the ratio would still be very large in favor of aluminum as a conductor. The question was, “How could the difference in
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Equipment and Design the thermal conductivity produce the sharp decrease in foaming level?” Because the obseived effect took place a t a level inside the nickel kettle corresponding to the top of the jacket surioundiiig the bottom section of the vessel, it seemed possible that theie ivas a short section of the wall all around the kettle that was heated close t o the temperature of the hot oil circulating through the jacket. Because of the relatively low conductivity of the thin nickel wall above this aiea the heat could not be conducted a n a y as fast as it was in the aluminum kettle with its thicker malls and much greater conductivity. That is, there could be a hot zone that caused the foam t o burst upon contact. The fact that the foam-breaking ceased when the batch was increased to a level higher than the jacket appeared to confirm this hypothesis. As a check on the use of a nariow band of heated metal for breaking foam, electric strip heaters, curved to the outer mall, were applied t o the outside of a nickel semiworks kettle. It was found that batches of the product could be iiiade in the small kettle without trouble and that the heated band did break the foam. Although it seemed probable that the best way to apply the heat for breaking foam would be to weld a sinall jacket around the wall of the laige kettle near the top, other methods vere tried. One of these methods wap to me an electrically heated grid fastened below the kettle cover. A thermo:ouple in the grid provided an indication of its temperature. As long as ’oam unmixed with drops of liquid IT as *king, the grid functioned fairly well. However, a small amount of spray would drop the temperatureto 100” C. 3ecause of the high latent heat of the hops of water. Then the effectiieless disappeared. Another may of ipplying heat near the top of the rapor space was by means of a steam :oil fastened around the inside wall If the kettle near the corer. This, too, ,T-asonly moderately helpful because it sas not hot enough. Still another nethod that was tried with little ,uccess was a steani sparger to diiect iteam around the wtvall of the kettle iear the top. Finally, one kettle after another TI as dismantled and a small “high jacket” was welded on the outer shell, as shown in Figure 2 . Khen hot oil wak
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 11
How to
Insulate Your Towers against rising maintenance costs
One simple step can help you hold tower insulation replacement costs within bounds.
Use Monele hexagon netting. Monel tie wire.
. . Monel bands . . .
Monel successfully resists corrosive attack b y moisIt prolongs t h e ture a n d acid or alkaline fumes life of insulation in d a m p a n d humid areas, coastal locations, a n d t h e corrosive atmospheres of industrial locations.
...
You get other advantages, too. Although Monel is stronger a n d tougher than structural steel, it is pliable a n d easy to handle. You can bend a n d twist thin Monel wires to snug fits. You can stretch a n d crimp
Monel bands tightly without snapping them.
Y o u can see, then, how Monel is almost certain t o bring you important economies over t h e years. Monel-secured tower insulation goes on easily.. stays tight.. .lasts long.. .saves frequent erection of expensive scaffolding.
.
For your next tower - or tower repair job - insure permanence a n d future savings b y using Monel hexagon netting, a n d Monel bands a n d tie wire. Consult your Distributor of Inco Nickel Alloys for t h e latest information on their availability. R e m e m ber, too - it always helps t o anticipate your requirements well in advance. T h e International Nickel Company, Inc., 67 Wall Street, New York 5, N. Y.
lnco Nickel Alloys A Monel.. November 1953
.YOUR PARTNER IN PROGRESS
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Equipment and Design circulated through these jackets, the foam could be controlled and the batch size increased very substantially above the original quantity. This was true, even in the aluminum kettles, although the effect was not as pronounced as in those made of metal of lon-er conductivity. Various other methods of breaking foam have seen used throughout the chemical industry since the development described in this month's column. One of the most interesting is the use of a relatively small amount of a chemical which changes the surface characteristics of the foam. We shall he glad t o know what our readers have to report in this field and hope to summarize their experiences in some future column. One correspondent has given thiee instances in which the use of a commercial antifoaming agent reduced the foaming to such an extent that the rate of evaporation was no longer controlled by the foam but by the late a t which heat could be supplied. I n one case, in which an aqueous solution of a sulfonated organic compound was being concentrated fiom 10 to 40%, the average normal rate of evaporation \vas 8 pounds of water per 3quare foot of disengaging surface pel hour. Addition of a very small miount of the antifoaming agent permitted the rate to be increased to 25 pounds per square foot per hour. The other two cases involved the ,team distillation of organic liquids. In one of these, the rate had been 8 to 16 pounds of the organic material per ,quare foot per hour. This rate v-as ncreased to 26 pounds by the use of he agent. The other steam distillaion showed a change from 26.5 to 53 3ounds per square foot per houi. These cases show that foam has taken in a new look in recent years. 2orrespondence concrrmng this column will br orirarded promptly If addressed to the author, 5 Editor, INDUSTRIAL AUD ENQIXEERING :HEMISTRY,llZ5-16th S t , N W., Washington I , D. c.
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I N D U S T R I A L A N D E N G I N E E R I N G CHEh
STRY
Vol. 45, No. 1 1
x
Crown Cork & Seal Company Inc., originators and x
world‘s largest makers of crown corks, have used Glycerine for nearly 40 years. Glycerine helps to keep the binder in the cork
discs supple, assuring a de-
Xvo properties make Glycerine a natural for use in Crown Cork & Seal’s composition cork discs. Glycerine helps keep the discs resilient, so that they provide a tight, longlasting seal. W h a t is equally important, Glycerine is non-toxic. It is accepted by medical associations and government agencies as sale lor use i n contact with foods. Indeed, U. S. F! Glycerine is a n important ingi-edient i n many conlections, flavoring agents, and other food products. Versatile Glycerine can serve as a sweetener, solvent, or blending agent. Its high viscosity imparts smoothness to mixtures, prevents graining. A handy 16-page booklet, “IYhy Glycerine for Foods?” reviews Glycerine’s unique range ok properties and applications. For your copy, write Glycerine Producers’ Association, 295 Madison .lvenue, New York 17, N. X
pendable seal and troublefree bottling.
November 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Modern Safeguards-Brink's
for Money, Bailey for Process Materials
Are Your Process Materials Guarded As Well? HERE'S H O W TO PREVENT SPOILAGE AND WASTE
T"
avoid waste of valuable process materials and finished products, process rates and conditions must be accurately measured and controlled. That's where Bailey Meters, Analyzers and Controllers can help you t o improve the efficiency of your plant. Take flow for instance. Bailey Meter Company offers a complete line of flow measuring and controlling equipment for applications ranging all the way from high pressure steam to low pressure gas. We measure
flow in pipes, open channels, d i i c . ~ s ,fiirnaces, slnrlters, kilns, ovens, dryers.
When you call Bailey Meter Company, you get the help of years of experience as well as rerorntnendations from a wide selection of measuring and controlling devices. Your local Bailey Engineer is as near as your Lelephone. H e has the experience and the equipment necessary to set u p a n rffecLive guard for. \.our process materials. P 26
AREA TYPE FLOW METER Transmitter goes into 1, 2 or 4 inch pipe line like a valve and transmits flow measurements electrically to recorder in remote location. Measures oil and other clear liquids under static pressures up to 600 psi. Minimum range 0 to 1200 Ib. per
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C L E V E L A N D
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
10,
O H I O
Vol. 45, No. 11
