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INDUSTRIAL AND ENGINEERING CHEMISTRY
Literature Cited Harte, C. R., Jr., and Baker, E. M., IND. ENG. CHEM.,25, 1128-32 (1933).
Harte, C. R.. Jr.. Baker, E. M., and Purcell, H. H., Ibid., 25, 528-31 (1933).
Hatta, S., J. SOC.Chem. I n d . J a p a n , 37, Suppl. Binding, 275-7 (1934).
Hatta, S., Tech. Repts. Tohoku I m p . Univ., 10,613-29 (1932). Ibid., 10, 630-62 (1932). Hatta, S., and Baba, A., Ibid., 11, 365-82 (1934). Hatta, S., and Katori, M., J. SOC.Chem. I n d . , J a p a n , 37, Suppl. Binding, 280-2 (1934). Hitchcock, L. B., IND.ENG.CHEM.,26, 1158-67 (1934). Hitchcock, L. B., Trans. Am. Inst. Chem. Eagrs., 31, 347-64 (1935). Hitchcock, L. B., and Cadot, H. M., IND.ENG. CHEM.,27, 728-32 (1935). Hitchcock, L. B., and Mcllhenny, J. S., Ibid., 27, 461-6 (1935). Howe, H. E., Ibid., 20, 1091-4 (1928). Kiehl, S. J., and Loucks, R. D., Trans. Electrochem. SOC.,67 (preprint) (1935).
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Killeffer, D. H., private communication. Lewis, G. N., and Randall, M., “Thermodynamics and the Free Energy of Chemical Substances,” New York, McGraw-Hill Book Go., 1923. McInnes, D. A,, and Belcher, D., J . Am. Chem. SOC., 55, 263046 (1933).
Menzel, H., 2. physik. Chem., 100, 276-315 (1922). Payne, J. W.. and Dodge, B. F., IND. ENG. C K ~ M 24. . , 630-7 (1932).
Riou, P., and Cartier, P., Compt. rend., 184, 325-6 (1927). Sieverts, A,, and Fritzsche, A., 2. anorg. allgem. Chem., 133, 1-16 (1924).
Ibid., 133, 17-25 (1924). Walker, A. C., Bray, U. B., and Johnston, J., J. Am. C h m . Soc., 49, 1235-56 (1927). Whitman, W. G., and Davis, G. H. B., IND. ENG. CHEM.,16,
264-6 (1924). (24) Williamson, R. V., and Mathews, J. H., Ibid., 16, 1157-61 (1924). RECEIVED January 18, 1937. This paper is based on a dissertation presented by Charles S. Comstock in June, 1935, to the faculty of the Graduate School of Yale University, in candidacy for the degree of doctor of philosophy
Bubble-Cap Column as a LiquidLiquid Contact Apparatus The operation of a small three-plate bubble column was studied in which the
M. C. ROGERS A N D E. W. THIELE Standard Oil Company (Indiana), Whiting, Ind.
interior could be observed when used to extract a heavy motor oil with dichloroethyl ether. The observed plate efficiency was quite low, not over 33 per cent at most. This is attributed to lack of agitation in this type of column.
continuous thread. No droplets were formed, and it was quite certain that the mixing with the solvent was poor. In order to improve the cap, a little “gable,” 0.25 inch wide, was soldered over each notch so that the liquid would be discharged away frpm the cap. This worked quite satisfactorily, and droplets were easily formed.
T
HE study of liquid-liquid extraction processes which has been made in recent years has brought into prominence the analogy between these processes and distillation. At present the apparatus used for the countercurrent extraction of liqujds with liquids usually consists either of a packed column or of a series of mixers and settlers; each combination of a mixer and a settler is the analog of a single bubble tray in distillation. Since the bubble tray is standard and efficient equipment in distillation, it is natural to think of adopting this type of apparatus to the extraction process. The work described here was undertaken with this idea in mind.
)PLATE GL
,TOP OF C A P PERFORATED
Apparatus The apparatus used is illustrated in Figure 1: It is essentially a small, rectangular, three-plate bubble column made of wood, with one rectangular cap per plate; the column is cut in two lengthwise, and the long side of the column is made of glass. By means of steel clamps, the plate-glass side is ’ held tight against rubber gaskets coated with shellac. The half-caps are made of galvanized sheet iron and are fastened t o the back wall. Three types are shown in Figure 2; in any one experiment all three caps were of the same design. The three types studied were V-notch, punched, and slotted. The V-notch type (Figure 2 A ) was first used with simple Vnotches cut into the metal. In operation, however, it was found that the liquid issuing from the top of the V-slots of this cap simply flowed up the metal of the cap and left at the top as a
EXTRACT O U T
u II
FIQWRE 1. LABORATORY BUBBLE-CAP EXTRACTION TOWR
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The second type of cap (Figure 2B) resembles a screen plate. This worked quite well also as a droplet roducer. Only one of the slotted caps (Figure 28) was tried, and it behaved in the same manner as the original V-notch cap. It was abandoned and no further consideration was given t o it.
Materials The materials used for the experimental work were Chlorex (dichloroethyl ether) and an untreated lubricating distillate from a Texas crude oil. Chlorex is a commercially available solvent with a specific gravity of 1.22. The lubricating distillate was an S. A. E. 50 grade, wax-free oil of 117 and 2582 seconds Saybolt Universal viscosity a t 210" and 100" F., respectively, and 0.9415 specific gravity a t 60' F. It was chosen primarily because it was readily available and was as viscous a stock as might be extracted; since it was waxfree, the temperature limitations were not important.
Behavior of the Column All runs were made a t temperatures of 80" to 85" F. The liquids were pumped to the column from small tanks by a Hills-McCanna proportioning pump. The oil feed rate was essentially constant a t approximately 23 gallons per hour for all runs. The Chlorex rate was adjusted to give the desired ratio of solvent to oil and varied from approximately 20 to 40 gallons per hour. As has been pointed out, cap construction in which the light liquid issued from an opening in a vertical wall was obviously inefficient, s i n c e t h e liquid clung to the wall. Where the light liquid rose directly into the heavy liquid, good distribution of drops was observed. T h e d r o p s were rather large. There appeared to be little V-NOTCH W I T H EAVES entrainment; a c c o r d A ingly, after the first run the overflow dam was extended so that it came close to the bottom of the next tray. This arrangement, which is the one illustrated in Figure 1, gives more s p a c e f o r liquid-liquid contact and PUNCHEDs PLATE less for disengaging of emulsion. This alteration caused no difficulties. I n the column as originally operated the oil phase played the part of the vapor phase in an ordinary column. Since the oil phase is more viscous than the solvent phase, it was thought R E C T A N G U L A R NOTCH that better results might C be accomplished if the FIQTJRE 2. THREE TYPES OF HALF-CAPS parts played by the two liauids could be interchanged. Accordingly, in one run the column was inverted. The column operated just as before. There was some improvement in the appearance of the liquid flowing through the bubble caps, but it was obviously not much better than
FIQTJRE 3. COMPARISON OF SINQLH-STAGE CONTACTOR WITH BUBBLE-CAP COLUMN when the caps were operated in the conventional way, and no data were taken.
Results The property chosen to define the degree of extraction was the oil viscosity index (1). If the three trays together are equal to one theoretical tray, the same viscosity index should be obtained a t the same temperature and solvent to oil ratio as on a simple batch extraction. Accordingly, a series of batch extractions was made a t 80" to 85" F. and various solvent ratios, and the results are plotted on Figure 3. On the same plot the results of the various runs on the bubble column are given. The equipment on the various runs was as follows: 1 2, 3 4
Original V-notch caps without gables; low overflow dam
V-notch cap with gables Punched holes in horizontal skirt of
cap
The plate efficiency is quite low, less than 33 per cent in every case. In view of the fact that the first part of the extraction occurs with a high driving force, the efficiency is probably considerably less than this, but it has. not seemed worth while to make elaborate calculations. The low efficiency no doubt arises from the fact that, whereas the phases are relatively viscous, the agitation is much more gentle than in the case of distillation, and the time allowed for contact is relatively short. This is due, in turn, to the relatively low efflux velocity of the liquid from under the caps. Reference to the equation for this velocity developed by the authors (9)shows that the velocities to be expected, because of the much greater density of the vapor phase and the small difference in density of the phases, are only a few per cent of the velocities in the case of distillation. Entirely different cap dimensions would be required to secure good agitation, and the resulting column would probably be rather impractical. It 'appears, therefore, that the packed column is more advantageous in extraction than the bubble type column.
Literature Cited (1) Dean and Davis, Chem. & Met. Eng., 36, 618 (1929).
( 2 ) Rogers and Thiele, IND.ENG.CHEM.,26, 524-8 (1934). RECEIVED January 11, 1937.
