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Ir/Ecl Unit Operations Review
Mixing by J. Henry Rushton, Purdue University, Lafayette, Ind.
A large amount of experimental work covered the entire field of fluid and solids mixing, with mechanics of twophase mixing operations receiving considerable attention
THIS
brings up to the date of September 1959 the series of mixing reviews, the latest of which covered a comparable period in 1958 (1959 Mixing Review). A book on mixing, authored by Sterbacek and Tausk (42),was published in Czechoslovakia. I t is a complete treatise on the subject, covering the theory of mixing of fluids, solids, and pastes, and is well up to date. References are given to a major portion of the literature on fluid and solids mixing. Equipment is described, as well as design techniques; the language is Czech.
liquid-liquid Contacting and Extraction In liquid-liquid mixing an important variable is interfacial area; Scott, Hayes, and Holland (39) studied the formation of drops and interfacial area produced by two-phase flow through a pipeline orifice. Average drop size formed in liquid-liquid mixing was measured and correlated with power consumption by Endo and Oyama (73). Yanishevski (47) studied the uniformity of dispersion of various immiscible liquid pairs in mixing tanks. Limiting velocities in countercurrent liquid-liquid extraction in a column with mixers was studied by Eguchi and others (77). They were able to correlate flooding velocities and phase inversions with dimensionless groups. Goldberger and Benenati (17) applied pulsation to liquid-liquid extraction in sieve columns and give data on changes in over-all mass transfer rates as a function of the pulsation. Kagan and others (79) reported results of work with extractors using mechanical mixers. Relations for scale-up of mixersettler equipment were given by Ryon and others (37) for solvent extraction of uranium compounds from sulfuric acid leach solutions. The design of a
mixer-settler for liquid-liquid contacting without the use of interstage pumps was described by Williams, Lowes, and Tanner ( 4 6 ) . A mixer and settler system operated by a n air stream to provide pumping and mixing of the liquid phases was described by Mathers and Winter (27). Performance data are given for one system. A box type mixersettler used for rare earth extractions was reported by Knapp and others (27).
Blending of liquids Data for blending of liquids in a large tank using a nozzle, an eductor, and a propeller were presented by van de Vusse (45). Relations between mixing time and operating variables were studied, and comparisons of performance are given for several different bases. Landau and Prochazka (24) studied the blending of salt water and water by means of marine-type propellers of three different sizes. Time for homogenizing is directly related to total flow and is independent of Reynolds number in turbulent conditions. Eck (70) described a rotating bucket wheel device for mixing of liquids.
Gas-liquid Contacting
A preprinted article by Calderbank on gas-liquid contacting reviewed last year has appeared in final form (6). Rates of oxygen transfer from air to water solutions as a function of mixing were reported by Endo (72). Different impellers were compared, and rates of mass transfer were correlated with power consumption. Karwat (20) determined the distribution of gas as a function of impeller type and power consumption. Gardner (76) discussed mass transfer as related to the motion of gas bubbles and liquid drops. Performance data on a new design gas-liquid “agitator absorber” were given
by Moore and Kate11 (37). A rotating impeller is used to spray a curtain of liquid through which gas must pass. Air requirements for mixing in Pachuca tanks has been determined by Lamont (23) as a function of depth, density, and other variables.
Dissolving and Solid-liquid Contacting Rate studies of the solution of phthalic and benzoic acid anhydrides and subsequent hydrolysis as a function of mixing was the subject of a study by Nagata, Yamaguchi, and Harada (33). They distinguished between three cases : diffusion controlling, reaction-rate controlling, and both mechanisms of equal effect. The experimental data are of basic interest. Rate of solution of solids as a function of particle size and power consumption was investigated by Oyama and Endo ( 3 4 ) . Kolar (22) presented data correlated with theory for the dissolving of solids in water as a function of mixing. Propellers and turbines were used, and change in conductivity of the solution was utilized to determine rate ofsolution. The effect of mixing on crystal purity during crystallization was studied by Steidl (47) also Matusevich (28). derived a nonlinear differential equation to describe the solution of solid crystals suspended in liquid by mixing. Data were presented by van de Vusse (43) at a symposium on scalingup. H e described the conditions encountered in reactors in which slurries are stirred.
Flow Patterns Flow patterns in mixing tanks were studied by Nagata and others (32) using Pitot tubes for quantitative measurements. Six different impeller forms were used with baffles at the lank wall. Results were compared with the same VOL. 52, NO. 6
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impellers without baffles, reported previously (1959 Mixing Review). Discharge flow and power distribution in the flow were compared. Motion of liquid in a mixing vessel was also studied by Melnikov (30). Fluorescent particles and ultraviolet light were used by Allen (2) to observe flow patterns in mixing liquids. Particles of various densities were used. Aiba ( 7 ) used a radioisotope of cobalt to study flow patterns in mixing tanks.
Continuous Flow Reactors Mixing in continuous flow reactors was discussed by Greenhalgh and others (78), and three basic “models” were defined whereby actual results can be related to theory and chemical reaction kinetics. Continuous flow systems were studied by mathematical models in a report by Cholette and Cloutier ( 8 ) . A design procedure is proposed for a flow system for partial mixing. A study of residence time in a continuous series of mixing zones was made by Buckler and Breitman ( 4 ) . Data are given and correlated with theory.
Basic Concepts An article by Pai (35) gives the mathematical relationships for the progress and expansion of a two-dimensional submerged fluid jet. As the flow from a turbine-type mixing impeller is closely related to the flow of a twodimensional jet, this study is of fundamental interest in mixing. Van de Vusse has derived mathematical equations describing the residence time and the distribution of residence times for particles settling in a turbulent mixing stream or tank ( 4 4 ) .
Axial and Pipeline Mixing Amplification and illustration of some previous publications on pipeline mixing (1959 Mixing Revielv) were given by Levenspiel (25). H e showed how contamination may be predicted between two fluids pumped successively through a pipe. Axial mixing in an extraction column has been analyzed theoretically by Sleicher ( d o ) , who proposed the use of four dimensionless groups to characterize the design and scale-up of extraction columns and certain reactors. Axial mixing in packed beds is the subject of a report by Epstein (74) in which he proposed a mathematical model based on a series of perfect mixing stages.
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11958). \ - - - - / .
(14) Epstein, N., Can. J . Chem. Eng. 26, No. 5, 210 (1958). (15) Foresti, R., Lin, T., IND.ENG.CHEM. 51, 860 (1959). (16) Gardner, F. H., Dechema Monograph 29. 291 119571. (17) ’Goldberger, W. M., Benenati, R. F., IND.ENG.CHEM.51, 641 (1959). (18) Greenhalgh, R. E., Johnson, R. L., Nott, H. D., Chem. Eng. Progr 5 5 , 44 f1959). - , (19) Kagan, S. Z., Aerov, M. E., others, Khim. Prom. 1958, p 432. (20) Karwat, H., Chem. Zngr. Tech. 31, 588 (1959). (21) Knapp? L., Schoenherr, R., others, IND. ENC. CHEM. 51. 639 11959). (22) Kolar, V., Colleckion Czechoslov. Chem. Communs. 24, 3309 (1959); Chem. iisty 52. 852 119581. (23) ’Lamont, A. G. W., Can. J . Chem. Eng. 36, No. 4, 153 (1958). (24) Landau, J., Prochazka, J., Collection Czechoslov. Chem. Communs. 24, 635 (1959). (25) Levenspiel, O., Petrol. Re$ner 37, 191 (March 1958). (26) Marsans, J. M., Ajnidad 35, 97 (1958). (27) Mathers, W. G., Winter, E. E., Can. J . Chem. Ene. 37. 99 11959). (28) Matusevich, -L. N., ‘ Z h u r . Priklad. Khim. 32,536 (1959). (29) McGhee, E., Oil Gas J . 57, No. 42,114 (1959). (30) Melnikov, V. I., Shornik Staiei 1954, No. 16, 105-20; Referat Zhur. Khim. Abstr. No. 31373 (1956). (31) Moore, I 9. S., Katell, S., Petrol. Rejner 37, 163 (1958). (32) Nagata, S., Yamamoto, K., others, Mem. Fac. Eng. Kyoto Uniu. 21, No. 3, 260 \ -
Mixing of Dry Solids Mixing of powdered solids in rotating drums and cones has been studied by Rose (36). An empirical relation is given for rate of mixing which is applicable to several types of mixers. Yano and others (48) examined the influence of the physical properties of solid powders on the degree and rate of mixing in different types of mixers. They give the optimum rate of rotation and volumetric charge as a function of size distribution and properties.
Viscous and Non-Newtonian liquids The power characteristics of different shapes and sizes of impellers for mixing non-Newtonian liquids was investigated by Calderbank and Moo-Young (7). Their work greatly extends the information on this subject. Another correlation of power required to rotate mixing impellers in the laminar flow conditions for pseudoplastic and Kewtonian liquids was given by Foresti and Lin ( 75). I n glass manufacture the molten glass is mixed during continuous flow through open channels. Viscous flow conditions prevail. Methods of mixing and evaluating the performance were described by Cooper (9).
(10) Eck, B., Chem. Zngr. Tech. 31, 260 (1939). (11) Eguchi, W., Nagata, S., others, Kagaku Kogaku 22,483 (1958). (12) Endo, K., Sci. Papers Inst. Phys. Chem. Research (Tokyo) 53, 216 (1959) (13) Endo, K., Oyama, Y., Zhid., 52, 131
Other Operations and Applications Heat transfer data have been obtained by Brooks and Su ( 3 ) for viscous and turbulent flow conditions in baffled and unbaffled kettles with mixers. Marsans (26) reviewed experimental techniques and equipment design for scale-up for miring equipment performance. Bungay (5) described a torsion-type dynamometer for use in measuring power in pilot plant mixing work. Mechanical details of mixer drives and shafts were described by Schwab and Linck (38). Mixers are used to suspend earth and other materials in water to form mud for deep oil well drilling. McGhee (29) reviewed the types of mixers and sizes required for these operations.
literature Cited (1) Aiba? S., A.I.Ch.E. Journal 4, 485 (1958). (21 Allen, M., Chem. Eng. 66, No. 9, 148 (1959). (3) Brooks, G., Su, G. J., Chem. Eng. Progr. 55, 54 (1959). (4) Buckler. E. J.. Breitman. L.. Can. J .
Chem (5) Bu (6 Engrs. 37, 173 (7) Calderhank. Ihid., 37,
(8) Cholett Chem. Eng. 37, 105 (9) Cooper, .4.R., J (1959).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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(33) Nagata, S., Yamaguchi, I., Harada, M.. Ibid.. 21. No. 3. 275 11959). a, Y . , Endo, K.‘, K a g a h Kogaku 876 (1959).
ai, S. I., J . Aeronaut. Sflace Sci. 26, Chem. Engrs. Chem. Ingr. (37) Ryon; A. D., Dailey, F. L., Lowrie, R. S., Chem. Eng. Progr. 5 5 , 70 (1959). (38) Schwah, A., Linck, E., Ckem. Zngr. Tech. 30, 701 (1958). (39) Scott, L. S., Hayes 111, W. B., Holland, C. D., A.I.Ch.E. Journal 4, 346 (1958). (40) Sle’icher,C. A., Jr., Zbid.,5, 145 (1959). (41) Steidl, H., Chem. listy 52, 852 (1958). (42) Sterbacek, Z., Tausk, P., “Michani
V. Chemickem Prumyslu,” Statni Nakla-
datelstvi Technicke Literatury, Prague,
1959. (43) Vusse, 3 . G. van de, “Proc. Joint
Symposium Scaling-Up Chem. Plant and Processes,” Inst. Chem. Engrs., London, 1957. (44) Vusse, J. G. van de, Chem. Eng. Sci. 10, 229 (1959). (45) Vusse, J. G., van de, Chem. Zngr. Tech. 31, 583 (1959). (46) Williams, J. A., Lowes, L., Tanner, M. C., Trans. Inst. Chem. Engrs (London) 36, 464 (1958). (47) Yanishevski, A. V., Zhur. Priklad Khzm. 38,1348 (1958). (48) Yano, T., Kanise, I., Kagaku Kogaku 22, 758 (1958).
