Liquid Extraction an
II/EC] Unit Operations Review by Robert C. Treybal, Departmeru of Chemical Engineering, New York Uniuerdy, New York 53, N. Y.
b The year's progress is characterized by considerable attention to fundamental problems: extraction from single drops, motion of drops immersed in another liquid, and formation of dispersions in mixing vessels b Mixer-settlers and pulsed columns have received more extensive treatment than other types of equipment b As measured by number of publications, activity is greatest in application of extraction t o metal separations b The number of new extractor designs
patented has decreased
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literature of liquid extraction continues to accumulate a t an accelerating rate, and this has required a change in the nature of this review. Previous summaries of this series have included substantial treatments of process applications. For reasons of economy of space this is no longer possible, and the present review is confined to the unit operations aspects of the subject with only a very brief indication of the significant process applications.
Reviews and Compilations
Reviews covered specialized areas such as chemical aspects ( Z A ) and Craigtype distribution in pharmacy ( 4 4 ) . A revised edition of a book on laboratory practice has appeared (7A), and there is a new volume in a series devoted to industrial solvents (514). A complete bibliography of solubility diagrams for ternary and quaternary liquid systems has also been issued (3.1).
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Theoretical
Work
Recommended procedures for computing important characteristics of fractional extraction, including equilibria, material baIances, and number of stages have been gathered in one place (7B). Methods of analyzing batch extraction processes have been summarized (4B) in some detail, while for continuous processes the relative inutility of raffinate reflux has been pointed out ( 9 8 ) . One report (8B) has integrated the equations relating the extent of extraction, the number of transfer units, and the extent of longitudinal backmixing as measured by extract and raffinate Peclet numbers, computed the results by machine, and presented them in the form of a table. The results are useful particularly in scale-up computations hut, of course, presuppose knowledge of the eddy diffusivities for backmixing to compute the Peclet numbers. The results cover a wider range of the variables, but are much the same as contained in another study (6B), which
INDUSTRIAL AND ENGINEERING CHEMISTRY
additionally provides computations for the internal concentration profile. The importance of the backmixing phenomenon cannot be over-emphasized, as rate coefficients computed from experimental data without accounting for backmixing cannot be used for scale-up or for useful correlations of the data. This reviewer earnestly pleads that writers in this field describe familiar physical quantities with familiar language and mathematical symbols, which will lead to much more rapid use of their work. Another investigation (ZB) in this area appeared, but this reviewer has not yet been able to study the original paper. For laboratory multistage separations, a new mathematical treatment making use of the linear algebra led to exact formulas for the distribution of substances to be separated a t each instant and at each stage ( 7 8 ) . A special table of results for the Watanabe-Morikawa separation scheme is given. A threephase counterpart to the Craig twophase distribution scheme has been de-
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an vised (519); mathematics of the operation are presented. The scheme is evidently a powerful analytical tool. In simple experiments in an agitated vessel. so designed that variations in the interfacial tension were not of importance. the direction of extraction of fatty and aromatic acids bei-ween aqueous and organic phases was found to have a profound influence on the rate (3R). The phenomenon was attributed to solvation at the interface. Drops In a continuation of work reviewed here last year, over-all coefficients were determined (7C) for extraction of acetic, propionic. and butyric acids from drops formed from a \vide xariety of solvents into water. The rates for benzene drops were unusually high, and this was ascribed to the presence of trace impurities. For other systems, Higbie's coefficients together with the principle of additivitv of both film resistances approximate the observed results. The rate of solution of benzene drops saturated Irith diethylene glycol into that solvent was measured ( I C ) . The rate increased with temperature. For systems of low interfacial tension, there is considerable internal circulation within drops. Rates of transfer were measured with such drops (2C), and the values obtained may well represent the maximum rates obtainable from drops moving freely in a continuous liquid. Two new methods of determining the size of drops formed in perforated-plate extractors (7C) include use of an electromechanical counting device and a n oscillograph representation of the dropforming process. Studies were continued (8C) of the ultimate velocity of liquid drops in liquid media; data were gathered for systems of low interfacial tension and high continuous-phase viscosity. When the continuous-phase viscosity is low, low interfacial tension systems are handled well by the available correlations. For high Newtonian viscosities, the ordinary drag coefficients for rigid spheres seem best. For non-h'ewtonian continuous-phase liquids, the drop shapes are quite different (6C, 8C). The best method developed to deal with drop velocities in such liquids involves assigning the non-Newtonian liquid a viscosity of a Sewtonian liquid through which a drop of the same size, density difference, and interfacial tension moves a t the same velocity (6C). The rigid-sphere drag coefficient then applies reasonably well. I n other words, a single experimental measurement with the nonNewtonian system should permit computation of the remainder of the velocitydrop diameter relationship.
'Terminal velocities for liquid drops falling in water were measured (5C). For all 31 systems, the velocity seems to have passed through a maximum M-ith increasing drop diameter. I n addition to correlations of the peak velocity and maximum drop size, there is one for the relationship among the drag coefficient, Reynolds number, and system properties. The last was developed in a logarithmic plot which contains the same important physical-property dimensionless group as a prominent feature of both abscissa and ordinate. I n such cases one cannot judge the utility of the correlation without a direct comparison of the computed and observed terminal velocities, this was not provided. The end effects and influence of internal circulation on mass-transfer rates within a falling drop have been measured (3C). By means of a number of graphical techniques, the diffusional resistances within the drops were isolated from the end effects. The effective diffusivity was found to approximate the semitheoretical value of 2.25 times the molecular diffusivity for drops in which circulation occurred during fall, while it was as large as 29.6 times if oscillation occurred. These generally confirm previous measurements for circulating drops. Equipment
Mixer-Settlers. One of the most complete studies available of mixeroperations was provided ( 4 4 0 ) for the extraction of uranium from sulfuric acid leach liquor by di(2-ethylhexyl) phosphoric acid with tributyl phosphate in kerosine. Data were gathered from mixers with diameters of 6 to 36 inches operated both in batch and continuous fashion, and the influence of agitator power, turbine to tank diameter ratio, contact time, and type of dispersion on extraction rates were reported. Settlers were also studied. Space does not permit a complete summary of the work, but a few of the more important conclusions were: geometrically similar mixers provide equal rate coefficients a t equal power input per unit volume, the flow capacity of settlers to handle the dispersion can be measured in terms of the thickness of a band of unsettled dispersion a t the interface, which grows as flooding is approached, and the flow rate per unit cross-section of settler is a basis for scale-up for settlers. A few of the minor conclusions, which are probably specific for the system studied, are a t variance with the previously recorded experiences of others, and these will have to be reconciled when more data become available. A very complete description of the shrouded mixer-impeller device in its
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application to extraction of uranium was provided (2SD). I n this device the mixing impeller, as well as the mixing and settling spaces, are all in the same vessel. A draft tube leads the mixture to the impeller, which is surrounded by a hood ring. The large-scale vessels are 20 feet in diameter and are fitted with 18-inch impellers operated at relatively slow speed to minimize the formation of unsettlable emulsions. In the uranium-recovery plant of U. S. Phosphoric Products a t Tampa, Fla., which operates on wet-process phosphoric acid containing 0.01 to 0.02% uranium, the extractant is capryl pyrophosphate in kerosine ( 5 0 ) . Conventional turbine-agitated mixers are used, followed by interstage centrifuges to separate the difficultly settled dispersion, in a four-stage plant. Uranium is removed from the extract by precipitation as green salt, UF,, rather than by the more conventional stripping. Several new mixer-settler designs have been described. The air-operated mixer-settler is being given serious consideration for the processing of spent fuel from nuclear reactors (320). This is a box-type device which uses an air-lift principle for mixing the contacted liquids in the mixer and gravity flow from stage to stage. A model capable of handling 100 tons of uranium per year has been tested and found comparable in volumetric efficiency with the pulsed packed column and pump-mix mirtersettler. I t has no moving parts, shows high stage efficiency, at least for systems easv to extract, and warrants further attention. A mixing vessel for extraction, fitted with a cooled packing gland at the entrance of the agitator shaft, is especially useful for flammable solvents ( 2 0 ) . A multistage mixer-settler (32D)features agitation accomplished by bubbling a gas through the mixer. Several bench-scale designs are also of interest. These may serve for research and development and even for production plants dealing with small flows. An all-polyethylene box-type mixersettler uses drinking cups for the mixer vessels (26.0). A 56-stage model is used to process rare earth nitrates and has been used for tantalum-niobium separations. Another design (520) utilizes the basic principle of the familiar Craig device but differs in that both liquids pass through continuously. hfore than 100 pounds of zirconium-free hafnium have been produced with it. Another device ( 5 7 0 ) is somewhat similar. Small batch extractors for use with radioactive materials were described (270). One of the important factors in mixersettler design is knowledge of the interVOL. 52. NO. 3
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facial surface produced in the mixer. I n this country, this has been studied by a light-scattering technique in the past several years, and a similar technique is now used in the Soviet Union ( 5 3 0 ) . T h e speed of the impeller producing uniformity of liquid-liquid dispersions was measured ( 3 5 0 ) and correlated with the various fluid properties and vessel dimensions for a mixer made from a 300mm. round-bottomed flask. A similar technique, together with a sedimentation method, led others ( 2 3 0 ) to a relationship between the surface produced, the fluid properties, and the vessel characteristics, which is much simpler than those heretofore proposed by others. Still another Soviet work ( 3 6 0 ) revealed the presence of dual emulsions when the dispersed phase viscosity was large in comparison with that of the continuous phase. This led to still a different correlation. Theoretical relationships between the average drop size and the principal velocity of the agitated liquid were developed ( 7 0 0 ) . Settling of the dispersion is equally important. T h e various factors influencing settling and coalescence and the devices currently in use to deal with the problem have been reviewed ( 7 0 0 ) . I n the extraction of uranium leach liquors, where solvent losses caused by incomplete settling are an important factor in evaluating process costs, the entrainment losses were effectively monitored in the region of 33 p.p.m. by introducing carbon-14labeled decane into the kerosine ( 2 7 0 ) . Settling and emulsion dificulties in the uranium extraction are intensified if unclarified slurries, rather than clear leach liquors. are extracted. Omission of the clarification is economical, however. Solvent entrainment increases with increased slurry density up to about 50% solids in the slurry ( 9 ) . Part of the entrained solvent can be recovered by dilution with water, and entrainment can be reduced by addition of hydrophilic agents (organic sulfonates) before contacting with the solvent. A fundamental study utilized simple synthetic slurries ( 5 0 0 ) . Settling was enhanced by increased temperature u p to a t least 40' C. and by decreased pH. Electrostatic coalescence speeds u p the settling in a new process for desulfurizing naphthas ( 3 7 0 ) . T h e use of low viscosity hexane (rather than kerosine) to carry tributyl phosphate in the extraction of uranium leach slurries has improved many phases of the extraction operation ( 6 0 ) . A mixer-settler plant uses centrifugal pumps as mixers and avoids emulsions with the slurry by recycling settled extract back to the pump to keep the organic-to-aqueous ratio high. Spray Towers. In the Soviet Union, the extraction of vanillin, guaicol, and
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phenylethyl alcohol between water and several organic solvents was studied in glass spray towers of a variety of sizes ( 7 5 0 ) . End effects were marked, but an empirical correlation of the over-all mass-transfer coefficients was nevertheless produced in terms of familiar dimensionless numbers. In another study (250), acetic acid or uranyl nitrate was extracted in 1-inch diameter columns with the organic phase dispersed. in either one or a series of columns each fed with fresh solvent. T h e extraction rates were better than when the interface was maintained at the center of the column, with both phases dispersed. A report from India ( 7 7 0 ) deals with the extraction of uranyl butyrate in a laboratory spray column. Heat transfer, rather than extraction, between mercury drops and water was studied in a spray column ( 3 8 0 ) . T h e column efficiency decreased markedly with increased length, which is indicative of strong end effects. The unusual flow pattern developed by the continuous phase which was observed undoubtedly contributes to the limited usefulness of spray columns. as has been noted in many extraction studies. For example, a substantial portion of the water by-passed the mercury drops, and, in addition, there was evidence that the water surrounding the drops traveled downward with them (a form of backmixing). Packed Columns. Peclet numbers for longitudinal backmixing have been measured for dispersed and continuous phases in towers packed with spheres or rings ( 2 2 0 ) . Kerosine, mineral oil, and water comprised the systems. If the dispersed phase does not wet the packing, the Peclet number decreases with increased flow rate of the continuous phase and with decreased rate of the dispersed phase. If the dispersed phase wets the packing, the numbers decrease with increased flow of either phase. I t was concluded that if backmixing in the dispersed phase is a limiting factor in the column performance, then the continuous phase should wet the packing. I t has been demonstrated that iron may be successfully separated from aluminum as the salicylhydroxamic acid chelate by extraction into butanol in a packed column ( 3 7 0 ) . Rotating-Disk Columns. Phenol and gas oil were used as double solvents to fractionate a mixture of aromatic hydrocarbons and gasoline in a tower 4.16 cm. in diameter ( 4 8 0 ) . At superficial solvent rates corresponding to 1.6 to 4.8 feet per hour and at speeds of 200 to 300 r.p.m., the stage efficiencies were 4 to 6%. The Texas Power and Light Co. is using an extractor 3 feet in diameter and 16 feet tall with 24 stages to fractionate
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Texas lignite tar a t the rate of 1000 gallons per stream day, with aqueous methylalcohol and hexane as the double solvents, Pulsed Columns. Individual-phase mass-transfer resistances were studied by using the partially miscible, twocomponent system isobutyl alcoholwater and determining the degree of mutual saturation ( 7 7 0 ) . An elaborate discussion of the observed results, based on the film theory, accompanies this report. The major influences upon the mass-transfer resistances are film rupture and reformation, together with the interfacial area of the dispersed phase droplets. The last predominates, and enlargement of this area is the principal effect of pulsation. The improvement of extraction rates when pulsation is used has been demonstrated by several studies. I n one of these (780), a 2.7-inch diameter tower was fitted with a single conventional perforated plate, with a downspout for the continuous phase. In the extraction of benzoic acid between water and toluene, moderate pulsation resulted in little improvement in the rates, but when the pulsed volume exceeded the light liquid feed rate, the number of transfer units in the tower could be more than tripled. The advantage of this construction over the customary pulsed sieve plates without downspouts is that the tower cannot be flooded by inadequate pulsation. In a 1.5-inch tower with sieve plates at 1.97inch spacing and without downspouts, the same system gave comparable heights of transfer units as in the above research, when pulsed ( 4 0 ) . The extraction of phenol from gas works waste waters with butyl acetate as solvent in a pulsed sieve-plate column was also studied ( 2 4 0 ) . Economy in construction owing to lower tower heights when pulsation is used is emphasized. Another study ( 7 0 ) involved the easily extracted system acetic acid-methyl isobutyl ketone-water in a 2.3-inch diameter sieve-plate pulsed column. The mass-transfer coefficients reported are corrected for longitudinal backmixing, and the backmixing diffusivities are also given. Both are correlated as functions of flow rate, pulse amplitude, and frequency. A useful summary of existing data from pulsed perforated-plate columns has been compiled ( 4 7 0 ) . Some 665 experimental flooding points have been correlated using the customary exponential functions of dimensionless groups, with the constants worked out on an IBM-650 digital computer. T h e resulting relation, in equation and nomograph form, represents the data to within 19.6y0. Over-all HTU's for 285 data points representing extraction from the
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an dispersed phase to an aqueous continuous phase were similarly correlated and represented to within 20%. T h e major transfer resistance was assumed to reside in the dispersed phase. A second study ( 3 0 0 ) offers new data on backmixing in such columns, taken with several systems in a 2-inch diameter tower using steadv-state and delta-injection techniques. Continuous-phase eddy diffusivities for longitudinal backmixing are correlated to within 1770 with a n experimental function of dimensionless groups, for aqueous phase continuous. Backmixing was more serious than in packed columns, and increased with increased hole diameter and plate spacing and decreased plate thickness. A number of closely spaced plates with small holes inserted above the feed plate decreased the backmixing markedly. Pulsed packed columns were also studied in some detail. I n one of the studies ( 3 4 0 ) , uranyl nitrate was extracted from water into tributyl phosphate-kerosine, and the extract was stripped with aqueous ammonium sulfate. For the system acetic acidbenzene-water ( 4 7 0 ) using 0.25-inch rings, the H T U passed through a welldefined minimum as the product of pulse amplitude and frequency was increased and was much less sensitive to flow rate ratios than the unpulsed tower. Other workers ( 4 6 0 ) compared the relative efficiencies of pulsed packed, sieve-tray, and spray towers with their unpulsed counterparts in the extraction of acetic acid between benzene and water. The characteristics of the packed and sieve-plate columns were found to be essentially the same. A new design ( 7 9 0 ) of pulsed column has been suggested for systems showing a reversal in the sign of density difference with increased solute concentration. I t had been suggested previously that either the liquids in the perforated-plate column could be pulsed, as is usually done, or the plates themselves could be vibrated. A column using the latter arrangement was briefly described by Isaac and DeWitte ( 2 0 0 ) ; 3000 cycles per minute at l/zs-inch amplitude are typical. Few experimental data were offered, but more are promised. Centrifugal Extractors. Applications of the well-known Podbielniak machine in water washing of refined oils ( 3 9 0 ) and in extraction of uranium ( 3 0 ) were described. I n the latter case, the Texas-Zinc Minerals Corp. at Mexican Hat, Utah, extracts 500 gallons per minute of sulfuric acid leach liquor with an amine solvent which does not require that the iron present be reduced prior to extraction. A second “Pod” is used for stripping the extract with ammonium nitrate solution. Molybdenum concen-
trations in the extract are kept at workable levels by continuously stripping a small bleed stream with soda-ash solution. A new centrifugal extractor design has been described ( 2 9 0 ) . Other Equipment. I n Japan, a compartmented, agitated, countercurrent column has been studied for some time. The compartments are formed by horizontal plates with two relatively small openings for passage of the liquids. Each compartment contains a paddletype agitator, all mounted on a single vertical shaft and located off-center. In the latest report ( 8 0 ) , flooding and hold-up data are given for three columns of diameters ranging from 2.7 to 11.8 inches and a variety of liquid systems. Two flow regions were recognized. The first of these was limited by the common flooding phenomena, the second by an inversion of the dispersion. Both limits were separately correlated in terms of the usual dimensionless groups. In the Soviet Union, a column consisting of alternate agitated mixing sections and sections packed with Raschig rings was studied ( 7 4 0 ) . Extraction rates increased with increased dispersed phase flow rate, agitator speed, height of packed section, and with decreased interfacial tension, kinematic viscosities, and column diameter. Another column (760) contains injectors at each end for obtaining dispersions, and improved extraction rates are claimed. Still another ( 4 9 0 ) consists of a series of chambers, with provision for pumping the liquids from chamber to chamber. A variant of the perforated-plate extractor was offered; each stage consists of two perforated plates, one above the other, separated by a small distance ( 4 0 0 ) . This permits more ready control of slowly breaking dispersions. Another extractor ( 7 2 0 ) uses serrated weirs to cause dispersion of one of the liquids, and a United States patent has been issued for Scheibel’s well-known extractor (450). TWOstudies ( 4 2 0 , 4 3 0 ) of pipeline flow characteristics of two-liquid-phase mixtures will be of use in sizing interextractor pipe lines. The use of air lifts to transfer liquids from one extraction tower to another when a series of towers are concatenated was discussed ( 7 3 0 ) . T h e system proposed is simply controlled, and offers the advantages of lack of moving parts and simplicity, especially useful where corrosive liquids or liquids containing suspended solids are handled. For volatile solvents, evaporation losses into the pumping air would habe to be dealt with.
Highlights of Industrial Applications
Petroleum Processes. T h e great bulk of the literature is in the form of
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patents where, as usual, new solvents and new flowsheets for old ones are suggested for refining lubricants, desulfurizing naphthas, and separation of aromatic hydrocarbons. A fine description of experienct-s with the Vnisol process for mercaptan extraction in Great Britain is available ( I E ) ; it includes a description of the mixer-settlers. A novel process for recovery of oil from bituminous sands is noteworthy ( 72E) : a water slurry of the pulp is extracted with liquid propane in a disk-and-doughnut baffle tower. By-product Coke-Oven Processes. There is considerable interest, particularly in Europe, in the use of butyl acetate as a solvent for removing phmol from waste waters of various sorts. New data for the extraction of phenols from tars into urea solutions (77E)are most interesting. Evidently the presence of paraffins, which are known to form urea complexes, not only does not interfere but actually improves the extraction of phenols. Detailed operating data are also given for extraction of phenols from tar diluted with ligroine with methylalcohol in a packed column (74E). T h e steel industry in the United States has adapted the petroleum refiner’s techniques to make aromatic hyclrocarbons of high purity from coke-oven light oil. Both United States Steel Corp. and Jones and Laughlin are using a Udex extraction to produce low-paraffin aromatics, preceded by a desulfurization step. Their plants are both on stream. Pharmaceutical Processes. Most of the literature is in the form of patents. Many represent applications in the manufacture of antibiotics. Metal Separations. As measured by sheer numbers of publications, this area represents, as it has in the past several years, the field of greatest activity in liquid extraction. Most of these des1 with separations of interest in the atomic energy business, including winning and recovery of uranium and thorium, reprocessing of spent fuels, rare earth separations, and the like. There is increased activity (in writing, at least) in Australia, Canada, and the U.S.S.R. Many publications resulted from the Second (1958) Geneva Suclear Conference, and a brief review of these has been provided (76E). Several excellent books and symposia have been published (among them ZE, #E), and these provide most helpful summaries and collections. T h e most interesting activity appears to be in the recovery of uranium from phosphate solutions resultin5 from wet-process phosphoric acid manufacture, extraction of unfiltered slurries of uranium leach liquors, aad fused salts as solvents for spent fuel reprocessing. VOL. 52, NO. 3
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Miscellaneous Processes. There are many. Some of the most interesting include the extraction of food-grade phosphoric acid from acid-treated phosphate rock solutions with butyl alcohol (7E), the production of synthetic glycerol ( 5 E ) , production of coffee concentrate (75E), and applications in the autoxidation process for manufacture of hydrogen peroxide (6E, 8E-IOE, 73E, 77E). An unusual process for manufacture of salts involves an interchange of ions between a n organic solvent and a n aqueous solution (3E). literature Cited
(1958). -\ -
Reviews ( lA4)Alders, L., “Liquid-Liquid Extrac-
tion: Theory and Laboratory Practice,” 2nd ed., Elsevier, The Netherlands, 1959. (2A) Gel’perin, N. I., Liakumovich, A. G., Khim. Nauka i Prom. 3,725 (1958). (3A) Himmelblau, D. M., Brady, B. L., McKetta, J . J., Jr., “Survey of Solubility Diagrams for Ternary and Quaternary Liquid Systems,” University of Texas, Austin, 1959. (4A) Macek, K., &skoslov. farm. 7, 528 (1958). (5A) Mellan, I., “Source Book of Industrial Solvents,” Vol. 111, Reinhold, New York, 1959. Theoretical Work (1B) Borsch-Supan, W., Z. Naturforsch. 14b, 56 (1959). (2B) Eguchi, W., Nagata, S., Mem. Fac. Eng. Kyoto Univ. 21, 70 (1959). (3B) Goncharenko, G. K., Gotlinskaya, A. P., Khim. Nauka i Prom. 3, 515 (1958). (4B) Jeffreys, G. V., Brit. Chem. Eng. 3, 594, 660 (1958). (5B) Meltzer, H. L., J . Biol. Chem. 233, 1327 (1958). (6B) Miyauchi, T., McMullen, A. K., Vermeulen, T., U. S. Atomic Energy Comm. UCRL-3911 (1957); Suppl. (1958). (7B) Scheibel, E. G., Petrol. Refiner 38, 227 (1959). (8B) Sleicher, C. A.. A.Z.CI2.E. Journal 5 , ‘ 145 (1959): (9B) Wehner, J. F., Zbid., 5, 406 (1959). Drops (1C) Fujinawa, K., Nakaike, Y . , Kagaku Kogaku 22, 540 (1958). (2C) Garner, F. H., Foord, A,, Tayeban, M., J . Appl. CXem. (London) 9, 315 (1959). (3C) Johnson, A. J., Hamlielec, A., others, Can. J . Chem. Eng. 36, 221 (1958). (4C) Konnecke, H. G., Leutert, M., Z. physik. Chem. 211, 101 (1959). (5C) Krishna, P. M., Venkaleswarlu, D., Narashimhamurty, G. S. R., J. Chem. Eng. Data 4, 336, 340 (1959). (6C) Mhatre, M. V., Kintner, R. C., IND.ENG.CHEM.51, 865 (1959) (7C) Planovskii, A. N., Bulatov, S. N. Nauk Doklady Vysshei Shkoly, Khim. i Khim. Tekhnol. 1958, 804. (8C) Warshay, M., Bogusz, E., Johnson, M., Kintner, R. C . , Can. J . Chem. Eng. 37, 29 (1959). Equipment (1D) Atkinson, E., Freshwater Brit. Chem. Eng. 3, 554 (1958).
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(2D) Ballard, A. E., Brigham, H. R. (to U. S . Atomic Energy Comm.), U. S. Patent 2,858,196 (Oct. 28, 1958). (3D) Chem. Eng. 66, 98 (March 23, 19593. (4D) Choff6, B., Gladel, Y . L., Rev. insl. franG. pdtrole et Ann. combustibles liquides 14, 108 (1959). (5D) Cronan, C. S., Chem. Eng. 6 6 , 66 (May 4, 1959). (6D) Ibid., p. 28, (Nov. 2, 1959). (7D) Eguchi, W., Nagata, S., Kagahu Kogaku 2 3 , 1 4 6 (1959). (8D) Eguchi, W., Nagata, S., others, Ibid., 22, 483 (1958). (9D) Ellis, D. A , , Long, R. S., Bryne, J. B., Proc. UN Intern. Conf. Peaceful Uses At. Energy, 2nd Geneva 1958 3, 499. (10D) Endo, K., Oyama, Y . , Sci. Papers Phys. Chem. Research (Tokyo) 52, 131
D. C . ,
1D) Eugenio, M. R., U. S. Atomic Energy Comm. ANL-5874 (1958). 2D) Farmer, M. H. (to Esso Research and Engineering Co.), U. S. Patent 2,861,027 (Nov. 18, 1958). 3D) Fowler, A. H., Jasny, G. R., Chem. Eng. Progr. 55, No. 1, 64 (1959). 4D) Gel’perin, N. I., Kravchenko, I. I., Khim. Mashinostroenie 1959, No. 1, 28. 5D) Gel’perin, N. I., Krokhin, N. G.. Kiseleva, E. IT., Zhur. Priklad. Khim. 31, 1026 (1958). (16D) Gel’perin, N. I., Liakumovich, A. G.. ListoDadov. M. V.. Sauk Dokladb Vysshe’; Shko’ly, K k m . i Khim. Tekhnoi. 1958, No. 1, 193. (17D) Ghosal, S. R., Dutt, D. K., Chem. @ Eng. Data Sei. 3, 258 (1958). (18D) Goldberger, W. M., Benenati, R. F.: IND.ENG.CHEM.51, 641 (1959). (19D) Hicks, T. E., Lehman, H. R., Rubin, B. (to U. S. Atomic Energy Comm.), U. S. Patent 2,852,349 (Sept. 26, 1958). (20D) Isaac, N., DeWitte, R. L., A.Z.Ch.E. Journal 4,498 (1958). (21D) Jackson, J., U. K. .4tomic Energy Authority, Ind. Group C/M 365 (1959). (22D) Jacques, G. L., Cotter, J. E., Vermeulen. T.. U. S . Atomic Energy -. Comm. UCRL-8658 (1959). (23D) Kafarov, V. V., Babanov, B. M., Zhur. Priklad Khim. 32, 789 (1959). (24D) Kagan, S. Z., Makarov, G. N., Vostrikova, V. N., Gazovaya Prom. 1958, No. 9, 16. (25D) Karpacheva, S. M., Khorkhorma, L. P., Medvedev, S. F., Atomnaya Energ. 2, 558 (1957); Engl. transl. So& J . Atomic Energy 2, 685 (1957). (26D) Knapp, L., Schoenken, R., others, IND.ENG.CHEM.51, 639 (1959). (27D) La Pointe, C. M., Can. Dept. Mines and Tech. Surveys, Mines Branch, Research Dept. R-25 (1958). (28D) Lash, L. D., Mining Eng. 10, No. 11, 1161 (1958). (29D) Madany, G. H., S . D. Jarvis Co., Decatur, Ill., Bull. (1959). (30D) Mar, B. W., Babb, A. L., IND. ENG.CHEM.51, 1011 (1959). (31D) Mathai, K. J., Lahiri, C. R., Bhaduri, A. S., Trans. Indian Znst. Chem. Engrs. 9 , Pt. 2 , 14 (1956-57). (32D) Mathers, W. G., Winter, E. E., Can. J . Chem. Eng. 37, 99 (1959). (33D) Myers, H. S., U. S. Patent 2,851,396 ‘ (Sept. 9, 1958). (34D) Oyami, Y . , Yamaguchi, K., Kagaku Kogaku 2 2 , 6 6 8 (1958). (35D) Pavlushenko, I. S.,Yanishevskii, A. V.. Zhur. Priklad. Khim. 31, 1348 (1958): (36D) Zbid., 32, 1495 (1959). (37D) Phillips, R. J., Napier, H. G., Petrol. ReJSner 38, No. 2, 151 (1959).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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