EVAPORATION mg W. L. BADGER
AND
R. A. LINDSAY
THE DOW CHEMICAL CO., MIDLAND, MICH.
A g a i n the past year has revealed to us little advance in the theory of evaporation or the design
of evaporators. There has been increased use of the Rosenblad evaporator in the paper industry. This unit, ofcourse, has no economic significance but its use is primarily due to the continuing pressure on the part of governmental authorities regulating pollution. Scale continues
on the inside of the tube in determining the outside coefficient by to be a problem of major interest and there are several references to this problem in the current difference. The Dittus-Boelter equation was modified because of orifice literature. Again, over the past year we And that there are many patent references to evaporator design but in general these have only a limited field of interest and at best represent only minor plates which interfered with the water flow pattern. The fluids inmodifications ;nd no real contributions. volved in the investigation were Freon 12, methyl chloride, propane, and butane; the conditions of the investigation were comparARVEY and Foust (14) discuss two-phase unidimensional able to those encountered in commercial practice. Banerjee flow equations and their application to flow in evaporator and Roy (6) analyzed mathematically the flow patterns in tubes. A mathematical analysis is presented in which the a spray evaporator and constructed a diagram to show particle equations of state, the energy balance, momentum balance. and and gas flow in a typical evaporator. The analysis shows an equation of continuity are combined into a rather unwieldly that the particles do not come in contact with any surface equation which is solved by a method of isoclines. This gives a until they have become completely settled a t the bottom of relation between the maximum temperature attained in a longthe conical section. The hydrodynamics also indicate the prestubevertical evaporator and the vapor-head temperature. ence of a dead space a t the bottom. Penner (46) attempts to The difference, the elevation in boiling point due to the various analyze the kinetics of the evaporation of liquid taking into conloads that increase pressure in the tube, i s correlated except in sideration the theory of reaction kinetics and the theory of abthe instances where the exit velocity from the tube is approaching solute reaction rates. He concludes that the theory of absolute the sonic region. The authors tested the mathematical analysis and found it applicable to experimental data over a range of reaction rates may not be consistent with the evaporation phepressures, all less than atmospheric, when boiling water in a 20 nomenon. Dukler and Bergelin (16) report on the film thickness that occurs with concurrent liquid and gas flow relating this foot long by 1.25 inch diameter evaporator tube. Tolubinskii to the physical properties of the material and the energy loss. and Yampol'skil (57) report on experimental work using nonAt no flow on the vapor side, this equation reduces to give the condensable gases to promote boiling coefficients. This is a very interesting piece of work indicating what can be done by increasthickness of the film as a function of flow rate and physical proping the lift action of vapor formation in an evaporator tube. erties. The transition from viscous to turbulent flow occurs a t a Monroe et al. (38)have reviewed the work on heat transfer to Reynold8 number of 1080. The experimental technique used boiling liquids with special emphasis on the various types of here measured the film thickness to an accuracy of 0.001 inch. boiling that occur. They also included experimental work on An apparatus for semiautomatically carrying out evaporator the boiling of oxygen and nitrogen in tubes from atmospheric tests on low boiling liquids is discussed by Coles et al. (12). pressure to 2000 pounds per square inch gage. The heat transPerk (47) reveals that boiling system calculations on sugar fer coefficients obtained follow the general form for metastable evaporators can be performed directly rather than by trial and film boiling. As the temperature is increased a lower coefficient error, if computation is carried out in reverse sequence. The is secured and at low Reynolds numbers the coefficient is a funcauthor suggests starting with the quantity of last molasses, tion of the Reynolds number to the 0.8 power. At pressures then proceeding to the data of the last strike, and so on. The above the critical pressure the heat transfer coefficient increased method is illustrated with data from a commercial unit. Rhodes with pressure but decreased with the temperature difference. (49) discusses the heat transfer coefficient to a boiling liquid. Uchida et al. (59)report on heat transfer coefficients in climbing Data are presented for boiling of liquid nitrogen in the form of a film evaporators. The investigation covered tubes with diamplot of the temperature difference versus the rate of boiling. eters of 11.9, 18.6, and 25.5 millimeters with a length of 2.5 Bromley et al. (9) uses butyl alcohol to confirm that the Nusselt meters. Experiments were carried out both with water and equation for the condensate film coefficient is satisfactory if one mixtures of methyl alcohol and water. The liquid-vapor sepaassumes uniform temperature around the tube. This is also ration was performed in a cyclone and the rate of formation of confirmed mathematically. Hickman and Trevoy (86, 26) these was measured. Over-all coefficients of 1000 to 3000 kilohave conducted extensive work on the evaporation phenomenon gram calories per square meter per hour per ' C. were achieved, from liquids in a high vacuum. They point out that a t high and an equation is presented. vacuum conditions there are many factors to be considered and Boiling film coefficients outside horizontal tubes for several the so-called evaporation rate is not always as high as anticifluids which are used as refrigerants are presented for both plain pated. These low evaporation rates are generally attributed and thin tubes by Myers and Katz (41, 42). These data were to contamination of the liquid surface. The authors were able t o compared with field data that were available; a reasonably good describe a system wherein unity evaporation rate was observed in correlation is shown. The vaporizer had four horizontal tubes a specially designed falling stream tensimeter on kethylhexyl arranged in a vertical row so that the factors such as vapor phthalate and 2-ethylhexyl sebacate and glycerol. A device to blinding, higher head, and lower tubes could be properly evaluobserve the surface in a molecular pot still was developed and ated. The boiling-film coefficients on plain tubes were deterobservations are reported. An ethylhexyl phthalate surface is mined experimentally. On thin tubes it was necessary to use an entirely placid a t the start of evaporation, becomes active a t analytical analysis of the over-all coefficient. This was done by higher temperatures and lower pressures, but after some operation using R modified Dittus-Boelter type equation for the water film the area becomes divided into a hotter stagnant and a cooler
H
87
88
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
active area. The addition of 100 p.p.m. of silicone oil or 1% mineral oil emphasizes the difference between the placid and the active areas. The impurities act as a temporary skin preventing evaporation. This skin can be decanted and evaporation resumed. To measure the vapor emission from a local area a small anemometer was developed. The use of this instrument demonstrates that the vapor pressure a t the torpid area is smaller by factors from 2 to 1000. Further measurements were made on a surface pushed or pulled by a stirrer, and hysteresis was observed before purification of the material. Torpidity seems to be a general nonspecific phenomenon and can effectthe evaporation coefficient from 0 to unity. Hughes et aE. (28) discuss flash evaporation and report on a careful study of the vacuum flashing of hydrocarbon residues. This method of analysis can be applied to any flash evaporation such as the purification 3f fatty acids or the removal of glycerol from the by-product salt. The mechanical separation of vapor from the entrained liquid is a major feature in vacuum operations because of the high velocities normally used. Factors such as liquid atomization, drop separation, and flashing efficiency, and their relation to the design of the evaporator, transfer lines. an3 separator are discussed. The concepts are developed srmiquantitatively as a guide to further development work on these flashing operations.
OPERATIONS A literature survey on the use of the long tube vertical evaporator for sulfide waste liquor is presented by Dinsmore (14). He describes a forced circulation unit designed by Meisler and Jennese, its construction and operation. Also included are experimental procedures used in the evaporation of ammonia base sulfide waste liquor. The advantages claimed for the Meisler and Jenness unit are simplicity, steady operation, and no foaming except during warm up. The heat losses from the unit were negligible. When the unit was operated on water, the heat transfer coefficient increased with the temperature difference, but when the ammonia base sulfite waste liquor was fed, the heat transfer coefficient decreased with increasing temperature difference. Coefficients with water as high as 410 B.t.u. per hour per square foot per ' F. are reported, and coefficients from 164 to 296 are reported for the ammonia base sulfite liquor. The evaporator described achieves heat fluxes a$ much as 64% greater than have been reported by others for soda black liquor in the eame machine. Gillet (2.2)outlines grain establishment in sugar crystallization and decries the shock seeding method as nonconsistent and unreliable primarily because of the nonsugars present. He presents and recommends the substitution of an improved method of full seeding. A general review on evaporators and salt manufacture in India is presented by Godbole (25). Kameda and Tsuzuki (29) patented a method of vacuum concentrating waste caustic treated pulp liquor. The feed is treated with a mixture of a higher alcohol and paraffin. It is claimed that this forms a foam preventing layer. I t is possible to ignite the concentrate after vacuum concentration and to recover the caustic. M6scu (39) presents a comprehensive review on the principles of the production of salt by solar evaporation. He recommends a pennisular location and describes a typical layout. A &ea water composition is given in per cent of sodium chloride, magnesium chloride, magnesium sulfate, calcium sulfate and others, and a curve of 3.6" BB. sea water evaporated to 25 30 ', and 35 ' BB. is presented. At 25" BB. iron oxide, calcium carbonate, and calcium sulfate are precipitated. Sodium chloride starts to precipitate a t 25" and continues to 29". Equations are given for the calculation of the evaporation, depth of solution, and area required. The requirements for tank bottoms are given as impermeability, mechanical strength to permit recovery of product, mitable chemical composition to avoid contamination of the salt, and surface such as to promote crystallization. In this latter rase, concrete is inferior t o packed salt lagoon mud. The O,
Vol. 46, No. 1
author suggests that a layer of algae on the bottom of the tank bottom facilitates recovery of salt. A similar paper by Schrier ( 6 2 ) covers the operations of the Leslie Salt Co. on San Francisco Bay. This 6000-ton salt per day operation is the largest solar evaporation plant in the world currently utilizing 29,000 acres of brine ponds which may be increased t o 40,000 areas of brine ponds. The operation is described as the California process and requires the movement of 8800 gallons of water per ton of salt. As reported in a previous paper the gypsum is first precipitated to a concentration of 25' BB. Sodium chloride is precipitated between 26" and 29' and no magnesium chloride occurs until the concentration is equivalent to 30" BB. This unit is highly mechanized and is currently supplying almost 50% of the West Coast requirements for salt. Brunes (10) in an illustrated lecture covers 22 references about the recovery, evaporation, and burning of spent sulfite liquor in Sweden. For foam prevention in film evaporators Rosenblad (61) discloses that the feed should be introduced either through the space where the vapor from the evaporator is being passed to remove air or gas present, or by degasification of feed by indirect heating or by application of a vacuum. Storms ( 6 4 ) outlines concentrating, seeding, and crystallizing of sugar solutions. A satisfactory method of establishing concentrations by electrical resistance is presented. Chacravati et al. (11) identifies the role of clarifying agents in open pan boiling of sugar cane juice. An investigation was made with castor seed, peanut extract, and bhindi mucilage as clarifying agents. The castor seed and peanut extract removed most of the colloidal matter, also organic and nonprotein nitrogeneous constituents a t all stages of boiling, and were more efficient than the bhindi mucilage. The gur obtained was also of superior quality.
SCALE AND CORROSION Kelly (SO) discusses the reduction of scale and corrosion problems by the use of high vacuum evaporation techniques. He describes a falling-film evaporator operating a t about 10 millimeters absolute, presents its design, and covers the thermodynamic principles. The problem of corrosion and its relation to temperature is discussed; it is possible to reduce the corrosion rate of mild steel in the presence of a salt solution from 0.045 to 0,010 centimeter per year by reducing the temperature from 60' to 20" C. I n other words, the corrosion a t 20" C. is only about 25% of what would be present a t 60" C. The effect of velocity on corrosion is noted, and the statement is made that the tendency in present day evaporator design-particularly in the case of the forced-circulation unit-is to increase the liquid velocity in order to decrease the amount of heating surface that is required. In the falling-film evaporator heat transfer coefficients can be achieved with natural circulation that approach those that can be achieved with forced-circulation units. The common scale forming materials such as calcium sulfate have inverted solubility curves, and operation a t lower temperatures increases their solubility and thereby decreases the scale. Experimental work done on black liquor concentrating it from 10 to 50% solids indicated that the falling-film unit a t low pressure could operate as much as 60 hours without an appreciable decrease in capacity; whereas, conventional equipment indicated a significant decrease in capacity a t the end of 24 hours of operation. The author traces the possibilities of thermal recompression increasing the temperature difference available in multiple effect high vacuum evaporators and points out that in a triple effect evaporator with a heat pump an economy equivalent to nine effects can often be achieved, Therefore despite the greater area available due to the lower delta T's present the problem of corrosion and/or scale would certainly be easier to handle in three effects than it would be in nine, and the economy derived would more than offset the cost of corrosion or scale. Todt ( 6 8 ) describes an electrochemical method for measuring corrosion which he claims is of considerable value in iron evaporators.
la
4
January 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
The problem of scale in sugar evaporators is reviewed by Honig ( 2 7 ) who points out that the inorganic constituents of clarified
juice cause scale in evaporators and other heat transfer equipment. Chemicals can be added to modify scale, and the equipment can often be designed to mitigate its formation. The author discusses methods for calculating the heat transfer coefficient, the amount and nature of scale, the composition of scale, and the change in heat transfer coefficient caused by the scale. An analysis of scale removed from a unit operating on sugar grown in Cuba in 1952 is presented. Scale formation in spinning liquor evaporators in the viscous fiber industry is described by Kleinert et al. ( 3 2 ) . There are considerable plant data indicating that the scale formed is principally a mixed salt of sodium sulfate and calcium sulfate. Solubility data for this salt are given, and recommendations are made to prevent the formation of scale. According to Lepez (35) calcium sulfate deposits are much less likely to accumulate on butt welded construction than in riveted evaporator construction. Lewis (S6) describes superstat which creates an electric field of high intensity and changes the nature of scale forming materials to the point where the deposit on the heating surface can be loosened by fermenting molasses and removed without brushing. The use of the superstat reduces the cleaning time as much as 3070. Ulmer and Caro (60) traced the development of scale preventives for sugar evaporators, and provided analyses for raw beet juice, thin juice, evaporator sirup, and evaporator scale. However, this is not sufficient information to select the proper scale preventive. An apparatus is described which determines properly the correct scale preventive for any given material. Some of the scale preventives actually increase the rate of evaporation. No one treatment is satisfactory to prevent all scale at all locations a t all times; it is necessary to study each individual situation as it occurs t o assure the selection of the proper scale preventive. Walther ( 6 1 ) recommends inhibited hydrochloric acid plus an intensifier for the chemical cIeaning of black liquor evaporators. The coating of evaporators or crystallizers with chromium, paraffin, or bitumen is claimed by TT7erkspoor (62) to decrease the amount of crusting that occurs. Such coatings decrease the contact angle between the wall and the solution by a t least 25yob.
L A B O R A T O R Y TYPES Birch and Nathan (8) describe a laboratory climbing film evaporator which is easy to make; it requires only normally available standard laboratory equipment and very little glass blowing. The unit is constructed from a nine- or twelve-inch internal single coil condenser by modifying the cooling connection so that the lower end is connected to the feed reservoir and the upper end to a vapor separator. The unit is good for removal of large volumes of solvents and the evaporation of foaming liquids such as detergent solutions. A laboratory scale continuous flash evaporator is outlined by Dimick and Makower ( I S ) . The unit is suitable for removing volatile flavors, for determining thermal inactivation of enzymes, and for concentrating fruit juices. Numerof and Reinhardt ( 4 3 ) picture a laboratory evaporator in which special packing glands have been eliminated by using the plunger and housing of a syringe for the bearing. Matched staggered slots are cut in the plunger and housing permitting rotation by a stirrer and evacuation while evaporating. The authors claimed the unit worked exceedingly well. Wheat (63) describes a stainless steel pilot evaporator containing 26.2 square feet of area and a packed 4-inch distillation column. The unit has automatic control for complete continuous operation. Data are given for operation on fermented mash and the recovery of 2,3-butanediol solutions.
TYPES OF EQUIPMENT Anderson ( 3 ) reveals the structural details of a vapor recompremion evaporation using forced circulation for which he claims
89
extremely high operating efficiency, Escher Wyss (17) has patented a method of reducing the steam required in the evaporation of sugar solutions and reducing sugar losses. A system is developed containing five evaporators in which a constant vacuum and flow rate is maintained by automatically tapping the last effect and feeding a constant amount of sweet water. A special type crystallizing evaporator is outlined by Airaku (1). Bibby (7) describes an evaporator for separating, extracting, or purifying liquids, especially oils. Kestner ( 4 ) delineates an evaporator for the manufacture of diammonium phosphate which operates a t a pressure of 40 millimeters of mercury. The control of final crystallization in sugar manufacture is discussed by Bernadac (6). The writer covers the theory of desugaring mother liquor and the calculation of the amount of water to use. The calculations are applied to a commercial operation, and curves are derived to simplify the operation. The complete operations of the control lab are presented. Eckstrom (16) has patented a multiple-effectevaporator for electrolytic caustic which includes the removal of salt. Frenkel ( 2 1 )presents a compositeplate evaporator providing cyclic flow of the liquid by means of a combination of two (‘direct separation evaporator elements” which effect the evaporation as well as the separation of vapor and liquid in the same space. This operation is accomplished simultaneously in the upflow and in the downflow portions of the‘cycle, thus dispensing with the need for external liquidvapor separators. Other important advantages are claimed. This unit is further described by Frenkel ( 2 0 ) showing counterflow evaporation with evaporation and liquid vapor separation carried out in the same space. The composite plate evaporator can be built t o different capacities from the same structural elements, and it is easily dismantled. A complicated multipleeffect evaporator has been patented by Fischer (18). Data on heat transfer in a vertical tube evaporator with and without foaming is presented by Kirschbaum (31) in a comprehensive study of heat transfer. The evaporators and related equipment exhibited a t the 10th Exposition for Chemical Equipment, May 1952, in Frankfurt, Germany, are presented by Kraussold (33). Muller ( 4 0 ) claims improvements on a thinfilm evaporator. The operation of a Rosenblad-type evaporator in the concentration of ammonium base sulfide liquor from 9 to 30% concentration is discussed by Palmrose and Hall (45). In this pilot plant unit the authors achieved 0.888 pound of water evaporated per pound of steam and secured a concentrate that could be burned to give 5.3 pounds of steam per pound of solid with sulfur dioxide recovery. They report SO’% sulfur recovery from the spent liquor, about one half of which is normally lost in blow gases and waste liquor. Airaku ( 2 ) describes an apparatus for evaporation. The design of a first effect sugar evaporator for vapor bleeding is presented by Perk (48). In order that vapor bleeding can be executed properly the pressure of the vapor should be maintained constant a t or above the required minimum and the preheaters and vacuum pans that are going to use the bleed vapor should be provided with adequate means for condensate drainage and venting of noncondensable gases. Rosenblad (60) has patented an evaporator for foaming liquids such as d f a t e liquor. See (63)claims a new design for a submerged-combustion two-compartment evaporator for acids. Perforated baffles are located above the burners to distribute the combustion gases through the liquid and vaporize the water. The discharge ends of the two burners are opposed and dilute acid passes continuously from the first zone to the second zone where concentrated acid is removed. Such a system has many of the advantages of the normal multiple-effect evaporator inasmuch as it permits part of the water to be removed from a lower concentration of acid. This has further advantages in that the entrainment problem commonly associated with submerged combustion units is less because in the first zone the concentration of entrained acid is lower. Ohkawa (44) has obtained patent rights on a pressure-type evaporator. Tops@e(58) covers
90
INDUSTRIAL AND ENGINEERING CHEMISTRY
a rather unique type of evaporator in which liquid containing combustible substances is evaporated by circulating hot bodies through the apparatus. The hot material may be combustible, and heat can be obtained b y partially burning the circulated body while it is circulated. This unit may be operated under pressure, but heat exchangers should be provided to reduce heat losses. An excellent review of the types of evaporators, their advantages, and disadvantages is presented by Lindsey (37). This article is characterized by its excellent cutaway drawings presenting the design details of the important types of evaporators and major auxiliaries that are available in the United States. The basic problems of evaporation such as scale and liquid entrainment are explained, the applications for the various types of units are presented, and source information for different types as well as cost data are included. Some of the types specified are the turba film, Rosenblad switching, skin or falling film, and both mechanical and jet recompression types. The boiling-point-rise control and a viscosity instrument using an ultrasonic probe are also described. Young ( 6 4 ) outlines an automatic control system for a multipleeffect submerged-coil sugar evaporator. A central instrument assembly by Foxboro is described which handles automatic control of the liquid level in each effect, rate of evaporation, liquid density in each effect, and a method for adjusting the evaporation rate t o compensate for changes in juice supply. Automatic control for the operation of a vapor recompression unit is patented by Latham (34). Fondrk (19) reviews the use of multistage ejectors for high vacuum indicating the practical operating range is now as low as 50 microns. The paper discusses the operating characteristics, design calculations, method of selection, test methods, limitations, and utility of available instruments. Tallman (66) covers the cost of steam jet equipment.
LITERATURE CITED Airaku, H., Japan. Patent 4508-9 (Aug. 16, 1951). Ibid., 770 (March 4, 1952). Anderson, R., U.S. Patent 2,619,453 (Xov. 25, 1952). Appareils et Evaporateur Kcstner, French Patent 976,914 (March 23, 1951). Banerjee, S. K., and Roy, H. L., Trans. Indian Inst. Chwn. E ~ Q T s4,. , 97-115 (1950-51). Bernadac, B., I d s . agr. et aliment (Paris),69, 323-7 (1952). Bibby, J., and Sons Ltd., Ger. Patent 817,443 (Oct. 18, 1951). Birch, S. F., and Nathan, W. S., J . A p p l . Chem. (London), Suppl. Issue, No. 2, 5108-9 (1951). Bromley, L. A., Brodkey, R. S., and Fishman, N., IXD.ENG. CHEM.,44, 29624 (1952). Brunes, B., Fochbl. Papierfaby., 80, 864-70, 923-9 (1952). Chacravati, A. S., Prasad, K., and Khanna, K. L., J . Sei. I n d . Research (India),11B, 305-7 (1952). Coles, K. F., Wright, B., and Bamford, J., Chemistry &. Induat r y , 1952, pp. 875-7. Dimick, K. P., and Makower, B., Food Technol., 5, 517-20 (1951). Dinsmore, R. F., Paper Mill News, 76, No. 7, 14-20 (1953.1. Dukler, A. E., and Beigelin, 0. P., Ckem. Eng. Prop., 48, 55763 (1952).
Vol. 46, No. 1
(16) Eckstrom, A. W., U. S.Patent 2,631,926 (March 17, 1953). (17) Escher Wyss -4.-G., Swiss Patent 274,828 (July 16, 1951). (18) Fischer, E., Ger. Patent 809,311 (July 26, 1951). (19) Fondrk, V. V., Chem. Eng. Proyr., 49, 3-7 (1953). (20) Frenkel, M. S., Ent. and Boiler House Rev., 67, 252-9 (1952). (21) Ibid.,pp. 296-8. (22) Gillet, E. C., Congr. intern. i n d . u p . * 8th Cungr., Brxsaels, 1950, 112-27. (23) Godbole, N. N., Chem. Aye (India),Ser. 6 , 17-19 (1952). (24) Harvey, B. F., and Foust, A. S., Chem. Eng. Progr. Symposium Ser. 49, No. 5, 91-106 (1953). (25) Hickman, C. D., and Trevoy, D. J., C'hem. Eng. Progr., 49, 105-9 (1953). (26) Hickman, C. D., and Trevoy, D. J., VacuzLm, 2, 3-18 (1952). (27) Honig, P., Chem. Weekblad., 48, 301-5, 317-23 (1952). (28) Hughes, R. R., Evans, H. D., and Sternling, C. V., Chem. Eng. P ~ O Q T49, . , 78-87 (1953). (29) Kameda, K., and Tsuzuki, I%., Japan Pacent 5651 (Sept. 22, 1951). (30) Kelly, E. J., Clienz. Eng. Progr., 48, 589-93 (1952). (31) Kirschbaum, E., Chem.-Ing.-Tech., 24, 393400 (1952). (32) Kleinert, T., Pospischil, F., and Wurm, P., Ibid., 24, 401-2 (1952). (33) Kraussold, H., lbid., 24, 6 9 2 4 (1952). (34) Latham, Jr., A , , U. S.Patent 2,589,406 (March 18, 1952). (35) Lepez, P., Berg-u. hutenmiinn. Monatsh montan Hochschule Leoben, 97, 31-2 (1952). (36) Lewis, W. B., Proc. Qiteensland SOC.Sugar Technol., 19, 83-6 (1952). (37) Lindsey, E. E., Chem. Eng., 60, No. 4, 227-40 (1953). (38) blonroe, A. G., Bristow, H. 4.S.,and Newell, J. E., J . Appl. Chem. (London),613-24 (1952). (39) h16scu, C., Tknica g 6coizomiu (Bahia Blanca, A r g . R e p . ) , 1950, Nos. 4/5, pp. 39-5,5. (40) Muller, H. K., U. S. Patent 2,596,086 (May 6, 1952). (41) Myers, J. E., and Katz, D. L., Refrig. Eng., 60, 56-9 (1952). (42) Myers, J. E., and Kats, D. L., Chen. Eng. Progr. Symposium, Ser. 49, No. 5, 107-114 (1953). (43) Numerof, P., and Reinhardt, K., Anel. Ckem., 25, 364 (1953). (44) Ohkawa, T., Japan Patent 4507 (hug.16, 1951). (45) Palmrose, G. V., and Hall, J. R., Tappi, 35, 193-8 (1952). (46) Penner, S.S.,J . Phys. Chem., 56, 4 7 6 9 (1952). (47) Perk, C. G. M., S.African Sugar J., 36, 475-89 (1952). (48) Perk, C. 0. M., Ihid., 561 (1952). (49) Rhodes, Jr., J. E., Am. J . Phus., 21, 67-8 (1953). (50) Rosenblad, C. F., Ger. Patent 803,598 (April 5, 1951). (51) Rosenblad, C. F., U. S.Patent 2,589,733 (March 18, 1952). (52) Schrier, E., Chem. Eng., 59, No. 10, 138-41 (1952). (53) See, W. G., U. S . Patent 2,607,661 (Aug. 19, 1952). (54) Storms, J., Cong?. Intern. Ind. Agr., 8th Congr., Brussels, 1950, pp. 97-112. (55) Tallman, J. C., Chem. Eng., 60, KO.1, 17&9 (1953). (56) Todt, F., Werkstofe u . Koriosion, 3, 205-9 (1952). (57) Tolubinskil, V. I., and Yampol'skiY, N. G., Sukiaarnaya Prom., 25, NO. 12, 11-14 (1951). (58) TopsZe, H. F. A., Danish Patent 74,367 (June 30, 1952). (59) Uchida, S., Nishikawa, S., and Tadashi, S., Chem. Eng. (Japan), 15, 305-11 (1951). (60) Ulmer, R. C., and Caro, P. M., Sugar, 47, No. 5, 46-8 (1952). (61) Walther, H. H., Tappi, 33, No. 8 , 79-81.4 (1950). (62) Werkspoor, N. V., Dutch Patent 69,392 (Jan. 15, 1952). (63) Wheat, J. A., Can. J . Technol., 31, 42-56 (1953). (64) Young, W. S.,Sugai., 48, No. 3, 48-.50 (1953).
