INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1949
Hambelton (40) report on the explosion of the rotor of an airdriven centrifuge. LITERATURE CITED
(1) Aktieb, Brit. Patent 584,538(Nov. 1, 1944). (2) Ibid., 584,714 (Jan. 12, 1945). (3) Ambler, C. M.,Chem. Eng. Progress, 44,No.5, Trans. Am. Inst. Chem. Engrs., 405-10 (1948). (4) Andersson, G.,Sooker Handl., 2, 379-406 (1946). (5) Anon., U. S. Dept. Commerce, Office of Technical Services, P B 58,260. (6) Ibid., P B 81,287 (April 1947). (7) Ibid., PB 86,399. (8) Ibid., P B 86,400. (9) Ibid., P B 86,401. (10) Ibid., P B 86,402. (11) Ibid., P B 86,403. (12) Ibid., P B 86,404. (13) Ibid., P B 86,405. (14) Ibid., PB 88,153. (15) Ibid., P B 88,154. (16) Banderet, M., J.chim. phys., 44,52 (1947). (17) Behne, E.R., Intern. Sugar J.,49,261-3,295-7 (1947). (18) Broadbent, F., U. 9. Dept. Commerce, Office of Technical Services, P B 12,669 (October 1945). (19) Ibid., P B 22,184(February 1946). (20) Bromley, A., Brit. Patent 586,077 (Oct. 30, 1944). (21) Clayton, J. L., Intern. Sugar J.. 49,236-9 (1947). (22) Cobbing, J. H.W., U. 8. Dept. Commerce, Office of Technical Services, PB 25,647. (23) Corrigan, B., Am. Citg, 42, 98 (1947). (24) Ecker, P. G.,and Blum, J., Rev. Sci. Instruments, 19, 399-400 (1948). (25) Eckers, C . G., U. S. Patent 2,443,310(June 15, 1948).
21
(26) Froding, E., Tekn. Tidskr., 78,85-91 (1948). (27) Gee, E. A., and Cunningham, W. H., U. S. Bur. Mines, Rept. Inneat. 4191 (1948). (28) Hancock, A.,and Brown, T. F., J . Oil Colour Chem. Assoc., 30, 317-37 (1947). (29) Hartley, A. J., Brit. Patent 588,589 (March 1, 1945). (30) Hopworth, H.,et al., U. S. Dept. Commerce, Offioe of Technical Services, P B 28,951(December 1945.) (31) Huret, M.,Rev. cen. caoutchouc., 25,124-9 (1948) (32) Jullander, I., J. Polymer Sci., 2, 32945 (1947). (33) Lawrence, J., et al., U. S. Dept. Commerce, Office of Technical Services, PB 7944. (34) Loncin, Marcel, Rev. fermentations et inds. aliment., 2, 61-70 (1947). (35) Loumiet, J. P., Brit. Patent 592,154(May 23, 1944). (36) Pedersen, H.V.,A m . Citg, 43,86-7 (1948). (37) Rejtharek, A., Listy Cukrovar, 63,201-5 (1947). (38) Roberts, E., andstevens, G. E., U. S. Patent 2,347,157(April 18, 1944). (39) Rousselet, J. A. N., French Patent 860,206(Jan. 9, 1941). (40) Sanigar, E. B., and Hambelton, J. H., J . Franklin Inst., 244,23440 (1947) (41) Saunders, E., Ana?. Chem., 20,379-81 (1948). (42) Schmid, U.S.Dept. Commerce, Office of Technical Services. P B 6239. (43) Strezynski, G.T.,U. S. Patent 2,436,498(Feb. 24, 1948). (44) Sutcliffe, A. R.,U. S. Dept. Commerce, Office of Technical Services, P B 56,260. (45) Svedberg, T., Enhavour, 6, 89-95 (1947). (46) Taylor, R. L., Chom. Inds., 62,54-7 (1948). (47) Tecelemit, Ltd., Brit. Patent 584,292(Dec. 22, 1944). (48) Urie, R. W.,J. SOC.Chem. Ind., 66, 437-9 (1947). (49) Wilcox, A. C., University of Kansas, thesis,. 1947. RECEIVED October 20, 1948.
CRUSHING AND GRINDING mg
A
LINCOLN T. WORK,
METAL a THERMIT C O R P O R A T I O N , R A H W A Y , N. J.
NOTHER year since the last report (19)brings the steady encroachment of science and sound engineering into the complex art of crushing and grinding. To make it a science, the measurement of particle size must also progress-with regard to both improvement in methods and more extended use of present methods. The year brought a revised and enlarged edition of Dallavalle’s “Micromeritid’ (6). The revision is extensive. Five new chapters have been added, and all of them bear either direct scientific information or some practical views on the subject of this review. The behavior of particles under pressure has applications, in addition to powder metallurgy, in crushing and grinding. Some of the problems of storage and handling and the very action of many types of mills need an understanding of this. Diffusion of particles and dust clouds bears on particle size analysis and on classification equipment. Surface properties are important in measurement and in the final product of mill operations. The theory of sampling should contribute to an everpresent problem in this unit operation. In addition, the treatment of the theory of fine grinding gives an orderly analysis of friability, grindability, ball mill grinding, theory of crushing, particle size distribution of ground material, surface area and energy, and explosive shattering. Although some of these subjects are not yet practically applicable to crushing and grinding, all will give food for thought in tomorrow’s developments. Sieve measurement as a control in powder metallurgy is under study at the National Bureau of Standards ( 3 ) . I t has been noted that surrounding conditions such as humidity may have a significant bearing on the weights of retained solids. This adds
to the general knowledge of the subject and may lead to modification of test or a specification of acceptable conditions. Matheson (8) shows some modification in the Roller method of analysis for subsieve separations. Electron microscopy is further advanced in two papers. Watson (18)shows a number of errors that may creep into the use of this tool, and shows how simple precautions make it possible t o obtain reproducibility within about 5%. Hanson and Daniel (6) reduce measurement and representation to a mechanical function, having a scanning device for electron micrographs and a mechanical histogram computer. Walton (17) differs from Heywood and contends that there is significance in the statistical diameter of Feret. Jacobsen and Sullivan (7) show that sedimentation procedures are based on sound principles. Whether it be by sedimentation pan, cup, or specific gravity cylinder, results should be significant down to about 1 micron. They show a modified balance for such testing. A buoyancy factor is introduced to speed up testing, as it avoids the necessity for complete sedimentation. They advocate the use of the sedimentation centrifuge for fine sizes up to 1 or 2 microns and show ways to correlate data between the two methods. Their contributions to date are a substantial addition to sedimentation literature. Rossi (14), apparently beginning a series of papers, gives a calculation of the sedimentation curve, while Saunders (15) offers a nomograph for particle size measurement with the Sharples supercentrifuge. Schachman (16)presents a simple approximation to express the sedimentation constants in the Sharples supercentrifuge, derived from experiments on closely fractionated bentonite. Bardwell and Siverts (1)have made a critical study of the size
INDUSTRIAL AND ENGINEERING CHEMISTRY
22
of small dielectric particles by the Debye-Einstein equation. Turbidity ww measured with the Beckman spectrophotometer and refractive index with the Zeiss dipping type of instrument. They offer their contribution as a simplified technique to help extend the scope of work with this tool. Rose and French (13) present a thorough analysis of the extinction coefficient showing oscillations in the range of about 0 to 6 or 8 microns. They give consideration t o certain errors and raise a question on the accuracy of over-all turbidimetry. Mills (9) offers a simple device for permeability testing. He gives no data, but states some limitations and conditions. It is a liquid test, and emphasis is placed on the use of nonpolar fluid. Bugge and Kerlogue ( 2 ) have established a simple routine procedure for surface measurement by the low temperature sorption method. This is in a field of rapidly growing interest. Such methods have been especially valuable for porous particles, but there is now evidence of increased interest in the use of this general method for essentially nonsorptive fine powders. I n x-ray measurement, Muller (11) has pointed out that the arithmetic mean particle size is smaller than that determined by x-ray methods. CRUSHING AND GRINDING
Progress in this field tends to be slow and is largely limited to mechanical improvements. There has been considerable extension in the use of disintegration machinery, and a considerable a r t has developed, even though it has not fully become a science. The use of classification equipment to make cuts over a wide range of sizes has been extended, and the process of drying while grinding has also increased in scope. The jet mills, about which much has been said over the past few years, are finding a substantial place, particularly in the field of fine grinding where the relatively high energies per unit weight of material being disintegrated are still of a n economical order of magnitude. The Locomotive Development Committee is continuing experiments on the disintegration of coal by a nozzle and impact device, the coal to be fired directly in the combustion chamber of coal-fired gas turbine locomotives. Needless to say, the dust problem becomes an important one under such circumstances, with respect to both abrasion of equipment and the general admission of dust into the atmosphere (4). The ball mill is continuing t o find an expanding place and is now extensively used in the grinding of paints. Two references occur in this year’s literature in relation t o the study of ball wear in grinding problems. Norman and Loeb ( l a ) made a very thorough test in which they show that the use of marked balls can
Vol. 41, No. 1
give a quick evaluation of their general suitability. I n general, they find that ball wear is proportional to surface area. I n dealing with the forms of steel which may be used, they find that a matrix of martensite or low temperature bainite represents the best structure and with this structure, spheroidized carbides help to increase the wear. Any austenitic structure which is retained is satisfactory if it can be transformed to martensite through cold work, and the austenitic grain size is unimportant. I n general, high carbon is valuable, provided it does not remain in the form of grain boundary carbides. Sulfur, phosphorus, and the massive carbides of pearlite are detrimental, while alloys are generally favorable only if they favorably affect the martensitic structure, Mortsell (10) has also contributed to the subject, disputing tho Davis theory that wear is proportional to weight and again contending that it is proportional to surface. As he reviews other references to the subject, he concedes that there are some exceptions but that ball surface is an important factor in wear. He shows that wear on grinding balls first increases and then decreases with the time progress of grinding. I n a test on quartz, the ball wear increased with diminishing average grain size from 60 to 17 microns but as the quartz became finer still, ball wear rapidly diminished. He discussed briefly the effect of closed circuit grinding and classification on mill wear. The contributions which have been made within the past year to the a r t of particle size measurement and to the crushing and grinding problem are substantial although, as usual, progress toward the final goal of changing this art into a science is very slow. LITERATURE CITED
(1) Bardwell and Sivertz, Can. J . Research, 25, B, 255-65 (1947) (2) Bugge and Kerlogue, J. SOC.Chem. Ind., 66,377-81 (1947). (3) Ceramic Age, 51, 324,328 (June 1948). (4) Chem. Eng., 55, 103-5 (May 1948). (6) Dallavalle, J. M., “Micromeritics, the Technology of Fine Pavticles,” 2nd ed., New York, Pitman Publishing Corp., 1848. (6) Hanson and Daniel, J . Applied Phys., 18, 439-43 (1947). (7) Jacobsen and Sullivan, Anal. Chem., 19, 855-60 (1947). (8) Matheson, G.L.,Oil & Gas J.,46,307-8 (November 1947). (9) Mills, G. L.,Nature, 161, 313-4 (1948). (10) Mortsell, S., Eng. Min. J., 149,90-1 (May 1948). (11) Mllller, H.,Z . Naturforach, 2a, 473-4 (1947). (12) Norman and Loeb, Min. Tech., 12, T.P. 2319 (May 1948;(13) Rose and French, J. SOC.Chem. Znd., 67,283-88(1948). (14) Rossi, C.,Ann. chim. applicata, 37,216-29 (1947). (15) Saunders. E..A n a l . Chem.. 20. 379-81 (1948). (161 Schaehman, H.K.,J . P h i s . Colloid C h k , 52,103445 (1948). (17) Walton, W. H., Nature, 162, 329-30 (1948). (18) Watson, J. H. L., Anal. Chem., 20,576-84 (1948).
ENG.CHEM,,40,9 (1948). (19) Work, L.T.,IND.
RECEIVED October 29, 1948
CRYSTALLIZATIO E@$
S
C. S. GROVE, JR.,
AND
J. B. GRAY
SYRACUSE UNIVERSITY, SYRACUSE I O , N. Y.
OME of the facts and conclusions given in papers published during the past year on those phases of crystallization of interest t o chemical engineers are presented in this review. Supersaturation, phase equilibria, formation and growth of crystals, and the influence of surface phenomena on growth have been discussed by various investigators. Although fundamental studies of the crystallization process reported in the past year are relatively limited in number and scope, studies of applications, theories of formation, and growth of crystals have been continued. There have been numerous improvements in the techniques of producing crystalline substances in industry, particularly in
making large single crystals, in sugar manufacture, and in prclr duction of ammonium nitrate. Although many articles cover crystal constants, these papers have been considered, in general, outside the scope of this review. I n nearly all cases, papers are not included in which crystal formation in metals or melts has. been discussed. RATE AND THEORY
Determinations of rates of crystallization from a theoretical and fundamental approach have continued to lag behind techniques d
