26
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
on centrifugal selection can serve as a foundation for intelligent selection and cost estimation. Hebb and Smith (12) present cross-sectional vieas of several of the more common types of ccentrifugals and also sizes of certain units. Vilbrandt (55) has increased his treatment of rentrifugals in the new edition of his text. A series of photographs is used to illustrate a description of a iiew centrifuge capable of exerting forces of 260,000 times gravity (2). Smith (QY)in a recent article has described the new applicaLions of equipment, and listed the equipment announced during the past 2 years. The operation of a self-discharging centrifugal has been described (37). Centrifugals have been employed for the removal of tannery waste sludge from spent vegetable tanning liquors (21). Difficulties in the separation of high viscosity sugar solutions from sugar crystals have been reported by Hruska (13). The removal of quick settling sludges resulting from the dry-lime treatment of waste pickle liquors has been achieved with centrituges (16). Wastes from whisky distilling sources have been concentrated by centrifugation and evaporation (24). Ambler ( 1 ) has described the use of centrifugals in the separation of oils in steel plants. Centrifuges have been used for the clarification of heer a r d wort (56). RECENT PATENTS
A number of patents have been issued recently. I n the reviewer’s opinion it is essentially impossible to evaluate the significance of such patents unless the complete patent picture is known. Consequently they are merely tabulated by title. Centrifugal amalgamator ( 9 ) Centrifuge bowl with discharge valves for separating sludge trom liquids (10) Centrifugal filter for separating crystalline sugar from mother liquor ( 6 ) Centrifugal separator of coal fines from heavy iinliurities ( 11 ) Centrifugal separator for separating solids from liquid and discharging them upwardly by force of acquired velocity (26) Centrifuge for separctting whey from cheese constituents (31) Clarifying mash (52) Continuous-discharge centrifugal ore concentratoi (6) Uewaxing oils ( 1 7 ) Drying green fodder (20)
Vol. 42, No. 1
LITERATURE CITED
(1) Ambler, C. M., I r o n Steel Engr., 26, No. 6,108-16 (1949). (2) Anon., Product Eng., 20, No. 2 , 9 2 4 (1949). (3) Bie, G. J. vander, Mededeel. Nederland. I n d . Inst. Rubberonrlrrzoek Buitenaorg, No. 48,1-12 (1948) (4) Cecil, R., and Ogston, A. G., Biochem. J.,43,692-8 (1948). (5) Chisholm, G. G., Can. Patent 454,703 (Feb. 22, 1949). 1 Delius, H. A., U. S.Patent 2,464,440 (March 15,1949). Eckhardt, H., Chem. Eng., 54, No. 5,121-3 (1947). Gofman, J. W.. Lindmen. F. T.. an3 Elliot. H.. J. Bbl. @hem. 179, 973-9 (1949). Hamilton, T., U. S. Patent 2,472,475 (June 7, 1949). Hanno, T. V., Ibid., 2,467,742 (April 19,1949). Harrineton, J., Ibid., $,454,798 (Nov. 30, 1948). Hebb, M. H., and Smith, F. H., in “Encyclopedia of Chernioal Technology,” Vol. 3, pp. 601-21, New York, Intermiewe Publishers, 1949. Hruska, J., L i s t y Cukrogar. 64, 233-7 (1948). Klassen, C. W., and Troemper, A. P.,Proc. 3rd Ind. Wabte Conf., Purdue Univ., Eng. Bull. Extension Ser. 64, 153 64 (1947). Le Page, G. A., and Schiieider, W. C., J . Biol. Chem., 176, 1b24 7 (1948). Lewis, C. J., I r o n A g e , 163, No. 3,48-53 (1949). Lindgren, H. O., U. S. Patent 2,439,434 (April 13, 1948). Loukomsky, S.A., and O’Brien, 8. J., Am. Soe. Testing Matrraa h , Proc., 46, 1437-50 (1947). Nash, C. W., Can. Pharm. J.,8 2 , 2 5 1 4 (1949). Nieuwenhuyzen, J. L. von, Dutch Patent 63,290 (May 16,1949), Reuning, H. T., Sewage Works Eng., 20, 133 (1949). Robison, II. E., and Martin, S. W., J . Phys. & Colloid p h m 52, 854-81 (1948). Ibid., 53, 860-86 (1949). Sehachman, H. K., Ibid., 52, 1034-45 (1948). Sharples, L. P., U. 8. Patent 2,446,559 (Aug. 10, 1948)” Smith, J . C., Chem. Inds., 65,357 -64 (1949) Ibid., pp. 519-20. Smith, J. C., IND.ENC.@HEM., 39,474-9 (1947). Snellman, 0..and Erdos. T.. Biochem. et Biophw. . . Acta, 2. 6.W-9 (1948). Snellman, O., and Tenow, M., Ibid., 2, 384-8 (1948). Strezynski, G. J., U. S.Patent 2,4611,129 (Feb. 8, 1949). Strohmaier, A. J., and Lovell, C. L., Ihid., 2,461,938 (Feb. 16,. 1949). Vilbrandt, F. C., “Chemieal Engineering Plant Design,” gp. 388 40, Now York, McGraw-Hill Book Co., 1949. Wales, M., J . Phys. &: Colloid Chem., 52, 235-48 (1948). Wales. M.. Williams. J. W.. Thomoson. J. 0.. and Ewart. K. I3 . Ibid., 52, 983-8 (1948). Windisch, F., Brauuelt, 1947, 233-7. Zambrovski, V. A., Sakharnaya Prom., 22, No. 12. 22-5 [1048). ~
a
C O N S U L T I N G E N G I N E E R , M A P L E W O O D , N. 1.
HE postwar period, up to the present, has emphasized diversity in the application of crushing and grinding equipment in oontrast to the development of new devices. Modification of current types of machines to meet new conditions and to incorporate new knoxledge continued through the year. Although the drastic departures embodied in the conical ball mill, ball ring mills, and jet mills are developments of earlier years, it is to be expected that new major changes will appear in the near future (8). It has been reiterated in previous reviews (68) that the tools of measurement of fineness quality are an essential to marked progress in this field. The past year has shown considerable advances in the application of present, tools and more reliable data are being made available today on the performance of these grinding machines. Much still remains t o be done in that regard, chiefly the elimination of unreliable or meaningless data.
During the past year, “Industrial Rheology and Rheologica Structures” (28), by the late Henry Green, was published; the final touches on this work were done by Ruth Weltman who had cooperated closeJy with him for more than 10 years. Although this work deals with solid-fluid systems and particularly with viscosity functions, part I11 comprising chapters 12 through 16 deals with the particle as a basis of the rheological structure. Little is given 11s to methods with the exception of the microscope and the electron microscope. The philosophy of the writer that a true knowledge of the particle is essential to a full understanding of the subject is equally applicable in the fields of crushing and grinding. Sedimentation methods (26, 3 6 ) still tend to hold the spotlight because they yield distribution data with a minimum of effort. Commercial equipment in this field includes the Fisher-Dotts ail-
January 1950
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INDUSTRIAL AND ENGINEERING CHEMISTRY
27
and have reported results on a number of solids including quartz, fluorite, glass, calcite, labradorite, and others. Crushing is accomplished by the dropping ball method and surface areas are measured by permeability. Their work also includes studies of surface measurements by a modification of the Emmett-Brunauer method and correlations with energy input. Surface and permeability measurement add to the fundamental knowledge, although it does not depart from the general conclusions on earlier work. With respect to mills for both grinding and classification, developments are in progress on an air classifier for fine sizes by Sturtevant Mill Company, and on a crushing and attrition mill for coal grinding. At the meeting of the American Institute of Mining and Metallurgical Engineers ( 1 ) a paper by Weston (67) was entitled, “Technical Appreciation of the Aerofall Mill.” This mill appears to be widely adaptable for large size material with reduction to very fine sizes or to intermediate sizes. For the fine sizes, air sweeping and size classification are employed. Chemical Industries (17, 90) has sections on grinding and on classification with definite indications as to mill types and manufacturers. There is a tendency toward the production of portable mills and toward production of smaller mills for a wide variety of applications either in custom grinding or in laboratory sample grinding. Announcements (10-14,28) exemplify some of the trends of the year. The proper size balls for ball mills is still a subject of considerable discussion (44). A paper by Nordquist and Moeller (43)discusses the various diameter grinding balls in producti,on mills. It now seems fairly well established that the wear rate per u n a of surface area is constant for a given material being ground independent of the ball sizing. Myers of the Tennessee Copper Company (41) presented a progress report on grinding a t his company. By increasing mill diameter, use of slower speed, and other mechanical improvements they have made substantial savings in power. Thib also involves a reduction in size of ball from 2 to 1inch and greater efficiency. Bond (6) presented a paper on classifier circulating load and efficiency. The subject of grinding has received considerable attention in the American Institute of Mining and Metallurgical Engineers and the committee on comminiition under Bond has initiated activities within the year on a three-point program: dFvelopment of standardized laboratory procedure for measuring grindability ; collection and analysis of grinding data from grinding plants; and study of the theory of crushing and grinding. Classification as an adjunct to size reduction involves a number of devices which are finding new applications or are being improved. Technical improvements in centrifuges (63) to adapt them to new uses are extending their ground of coverage. The Dorr Company announced the Type H classifier (26)which has, improved head motion and rake path, and Allis-Chalmers announced an improved electromagnetic vibrating screen (18). In dust collection. there has been a growing interest in the selfcleaning collector developed by Hersey (31) and licensed to a number of manufacturing organizations. Work is actively progressing on the use of ultrasonics for the agglomeration of dusts in air in order to make them more readily filterable. I n the application of principles of this unit operation reference has already been made to paints and to fluidization. Work has carried forward in the clay (99,46), limestone (61),and talc fields toward the uniform production of fine particle size. In powdered GRINDING coal (as>,the classification of fine powders is a subject of interest. There was considerable laboratory and plant study aimed t o deMetal powders (9, 94), agricultural dusts (3, 3 U ) , mineral fillers velop a more complete understanding of the mechanism and per( 7 ) , and photographic materials (39) are also under extensive formance of mills. Prediction of product screen analyses (36), study. distribution curves in the breaking of solids (27), and the use of LITERATURE CITED sieve analyses in rating grinding efficiencies (38)are indication of (1) Am. Inst. Mining Met. Engrs., meeting, Columbus, Ohio (September 1949). these developments. The paint industry has taken increasing (2) Armour Research Foundation, Symposium on Particle Size, cognizance of grinding, and a number of the paint production Chicago, Ill. (June 1949). clubs are.working on this subject; publication from the Baltimore (3) Birchfield, H. P., Gullstrom, D. K., and McNew, G. L.. Anal. club is noted (46). Siret and his students a t the University of Chent., 20, 1168 (1948). (4) Blake, P. D., J . SOC.Chent. Ind.,68,138 (1949). Minnesota (37) have brought some of their work t o completion
paratus (19) which needs a period of further testing ‘and evaluation before its place is established. Two other types appear t o be moving forward steadily-namely, the hydrometer method (66) and the photoelectric sedimentation method (6). In view of the slowness of standard sedimentation methods in the general area of 1micron, more work is being done on centrifugal sedimentation (47‘)for this fine size range. Nomographs (64)are definitely popular for the resolution of sedimentation data. In the field of wave-length measurement, work on light scattering and aerosols (69) has been reported along with particle size determination by soft x-ray scattering (69). This is supplemental to the consistent progress being made with light scattering as the recording instrument in sedimentation studies (6). Sorption methods have been subjected to continuing study, and there are other papers which indicate that the work of Langmuir and of Emmett and Brunauer is being supplemented (29, 33). The application of such adsorption technique is a t this time especially important for its application to catalytic materials. The symposium on fluidization (32) has brought together a series of papers in which there is always hidden in the background some relation between the surface available for catalytic action and the general external size characteristics of catalysts for physical handling (34,48, 60). In the field of catalysis the determination of pore size has been important, and a recent paper by Drake (96) shows how the merctry displacement method can be utilized for diameters below 200 A., which was the previous lower limit, down to 35 A. In the method of Emmett and Brunauer every effort has been made to attain a single layer on the surface without reaction. In consequence, high vacuum and low temperature with an inert gas were essential. It will be recalled in earlier years that Emmett stressed the fact that active gases would, in some cases, carry out reactions with some materials. There is a tendency to revert into this area with a thought that more readily lique stances than nitrogen would furnish v some relation to pore diameter and ea be an important variation in studiee of grinding because the faces are not so great as those commonly measured in the Brunauer-Emmett method and more condensable materials may yield better data. Within the past year there has been some activity in connection with the sieve method; the need is reiterated for proper pretreatment in wet sieve analysis to ensure clean-cut separations (42),and there has been further emphasis on machines (21,4U). The permeability method appears to be falling into its place as a control method which can be quickly employed but which should be checked adequately by the use of other methods (23, 66). Following the thoughts of Green (98) that the language of particle size must have a tangible meaning and be specific, papers comparing methods for surface area and other particle size measurement are particularly welcome ( 4 ) . Continuance of activity over the next several years, on the scale shown recently, should bring particle size measurement into a more generally useful and understandable form and eliminate many of the inaccuracies which exist in data heretofore offered. The symposium on particle size ( 2 )contributed further toward the interrelation of methods.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY Bond, F. C., presented before the Am. Inst. Mining Met. Engrs., Columbus, Ohio (September 1949). Bransom, 9. IC., and Dunning, W. J., Zbid., 68,80(1949). Bremner, J. G., and Colpitts, J. E., Trans. Inst. Rubber I n d . . 24, 35 (1948).
Brown, C. O., IXD. END.CHERI., 40,No. l I , 7 9 A (1948). Burden, H., and Barker, A., J . Inst. Metals, 75,51(1948). Chem. Eng. News, 27,246 (1949), Ibid.,p. 714. Ibid., p. 1240. Zbid., p. 1478. Zbid., p. 1552. Zbid., p. 1828. Zbid., p. 3077. Chem. Znds., 63,405,407,414 (1948). Zbid., 64,260 (1949). Ibid., p. 808. Zbid., 65,628,529 (1949). Chem. Proc. Preuiew, 12,No. 6,91 (1949). Coughanoor, L. W., and Norton, F. H., J . Ant. Cerum. Sac., 32, 129 (1949). Deryagin, B., Fridlyand, R., and Krylova, V., Dokludy. Akad. Nauk. S.S.S.R., 61,653 (1948). Deslisle, L., J . Metuls, 1,228 (1949). Drake, C., IND. ENQ.CLIEM., 41,780 (1949). Enoksson, B., Nature, 161,924 (1948). Epstein, B.,IXD. ENG.CEIEM., 40, 2289 (1948) Green, Henry, "Industrial Rheology and Rheological Structures,'' New York, John Wiley & Sons, 1949. Greg& S. J.,and Jacobs, J., Trans. F u r r h y Soc., 44,674 (1948). Gdlstrom, D.K.,and McNew, G. L., Anal. Chsm., 20, 1174 (1948). Hersey, J. C.,.patents pending. IND. ENQ.CHEW,41, 1099-1250 (1949). Keenan, A.G.,J . Chenz. Education, 25,666 (1948). Kiselev, A.V., and Mikos. N. M.. J . Phus. Chem. (U.S.S.R.),22. 1048 (1 948). I
JR., AND
1
(35) Klovere, E. J., E n y . Min. J., 150, No.6,80 (1949). (36) Kunkel, W.B.,J . Applied Phys., 19,1066 (1948). (37) Kwong, J. N. S., et al., Chem. Eng. Progress, 45,608 (1948). (38) Legsdin, A, and Sohenck, F. Id., Eng. Min. J., 150, No. 4, 88 (1949). (39) Loveland, R. P., etaZ., J. F'runkZinIn,ut.,'246,459 (1948) (40) Martsell, S.,Acta PoZGech., No. 30 (1949). (41) Myers, J., presented beforc -the Am. Inst. iWining Met. Engru., Columbus, Ohio (September 1949). (42) Nijhawan, S. D.,and Olmstead, L. B., Soil Sci. 9oc. Am., Proc 12,60 (1947) (Pub. 1948). (43) Nordquist and Moeller, presented before the Am. Inst. Minirlg iMet. Engrs., Columbus, Ohio (September 1949). (44)Olevskit, V. A.,Garnyl Zhur., 122,No.1,30(1948). (45) Paint, Oil, Chem. Review,111, 66 (1948). (46) Putnam, H. M.,Verre silicates ind., 13,98 (1948). (47) Robison, H. E.,and Martin, 9. W., J. Ph,ys. & Colloid Chcm., 53 860 (1949). (48) Ross, S.,J . Am. C h m . Soc., 70,3830 (1948). (49) Schmidt, L. D., McGee, J. P.,McSlone, M. C., (.%em. err^ Progress, 44,737 (1948). (50) Schofield, R,. K., and Talihuddin, O., Dkcusilions Flzraclau-Soc.. 3,51 (1948). (51) Siesholta, €1. W., and Cohan, I-,,IT., IND.ENQ.CKEM.,41, 300 (1949). (52) Sinclair, D., and LaMcr, V. K., Chem. Revs., 44,245 (1949). (53) Smith, JulianC., C/hm.In&., 65,357(1949). (64) Tanner, C. B.,and Jackson, N.1., Sod2 Sci. Soe. Am., Proc., 12. 80 (1947) (Pub. 1948). (55) Totterman, H., Finska Kemistsumjmdeta, Medd., 55,34 (1946), (56) Tovarev, V. V., Ginsburg, Y. N., Massil'on, T,K., Tsammt 13, No.7, 12 (1947). (57) Weaton, D., A.I.M.E. meeting. (58) Work, L. T.,IND. ENQ.CHSM.,41, 21 (1949). (59) Yudowitoh, K.L.,J . Appl,ied Phys., 20, 174,(1949)R E S E I V ~ Nnvernhei. D 8. 1940.
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C. S. GROVE,
Vd. 42, No.
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1. B. GRAY
SYRACUSE UNIVERSITY. SYRACUSE, N. Y.
1 growth, describing ne!? aorlr which bears on the cluesof the reality of the Toliner layer, utilizing data obtained 117 interferometric methods Dislocations in crystal grovi th have been discussed by Burton, C'abrern, and Frank ('7). They claim that the discrepancj l ~ e tneen obaerved and theoletical values ran he reconciled by rccog nizing that the crystals that grow '3re not perfect. Real crystals voutain dislocations and in low suppisaturations do not grcm Miihout the presence of disloeationfi. Gay (17) has shown by a study of dendritic cnystal growth of the monohydrate of polashiurn hydroxide that the ratio of growth rateq, perpendicular t c RATE AND THEQRY the crystal faces, is not changed. A dendrite is therefore not Studies on rates of crystal growth and on theoretical factor+ different from normally gromn crystals, but only the edges grop controlling crystallization have not progressed to s u c c ~ s ~ f n l whereas the faces do not. Bragg (8) has described rcsaarrh 3 1 conclusions as rapidly as new techniques and skills in this field x-ray method8 of determining crystal structure and the structuit have developed. Wells ( 4 8 ) has contributed an interesting and configuration of atoms within a moleculc. informative review, containing 142 references, on crystal growth Some correlation of crystal phenomena may be obtained froru This review covers various topics under the following headings: the work of Finch, Wilman, and Yang (14), who state thtii cathodic crystal growth is influenced primarily by: ( a ) the ra k Theoretical, including relations between internal structure and of arrival of the metal ions; ( b ) their mobility on the cathod? face development surface before becoming part of a growing crystal; ( c ) the atoniii Studies of the growth of single crystals arrangement in the substrate surface on which the ions are ad Effect of impurities on crystal habit Oriented overgrowths sorbed and discharged; ( d ) the concentration of the electrostatic Perfection of internal structure and of crystal faces field near the projecting parts of the more or less rough cathode Miscellaneous topics, including supersaturation and nucleus surface; and ( e ) the presence or absence of other ions, molecules, formation and technique of growing single crystals or colloidal substances which can be adsorbed or codeposited on the rathode. Thomson (49)has published a critical review on the kinetics NTEHEGT in the btudg irid ( l e i eiogiiirnt of c.rystallizatiori processes has increased during the past year. This may bP due in part to the publicity glwn in technical and popular journals on the growth and use of large migle crystals. Theie are other developments and studies, howevri , Jqbich have been desciibed recently in the techn 1 and scientific literature Some of the more important papers 011 ciystalli7ation are ieviewed herewith under the following topics: Rate and Theory, ?hase Equilibria; Industrial Crystallization; and Lar gc Smgli~ Crystals
liori
