UNIT O P E R A T I O N S
Size Reduction
AT
THE beginning of the period covered by this report the Chemical Engineering Achievement Award honored contributors to the Extractive Metallurgy of the Atomic Age Metals. I n these processes, involving size reduction and related fluidization steps, new impetus has been given to basic principles and practical applications in the area covered by size reduction. T h e period closes with the Division of Industrial and Engineering Chemistry, American Chemical Society, Symposium on Non-Kewtonian Flow. This is an important but inadequately known or used aspect of both grinding and classification, for both liquid and gaseous media. Between times, the American Society for Testing Materials held a Symposium on Methods of Particle Size Measurement. which ranged over an extensive group of methods now being employed. T h e American Institute of Chemical Engineers reviewed size reduction equipment and also dry classification. These are typical of current activity in other technical literature from both here and abroad.
the type of sieves used here was considering proposing a standard for the world based on the tenth root of 2 and multiples of it. Such a series would depart greatly from the Rittinger or Bureau of Standards series? which is standard here and throughout the greater part of the world employing sieves. A conciliatory effort was made to find a common ground, but the degree of success was inadequate. The matter is still open; but it is unreasonable to consider drastic change from a standard of several decades in use here and throughout much of the world. As a by-product. a tightening of tolerances in our standard has appeared to be both desirable and feasible. Such a change has been adopted as tentative in ASTM and will be processed toward an American standard when a proper interval of time has elasped. The electron microscope is finding an ever-increasing value in particle size studies. Its main limitation is in handling relatively coarse materials. The microfluoroscope. using x-rays. is being
Equipment
Size Evaluation There has been an extension of methods to include new techniques for measurement, and considerable experiA mental comparison of methods. tendency toward automation and toward simpler operation is evident. Sieves have had more than their usual share of attention. Techniques of cleaning while in use, with air or lvith sonic vibrations, tend to make unnecessary the wet operations so commonly needed for accuracy. However, the dispersion problem is not automatically resolved with improved sieving technique. Those working hvith petroleum catalysts have taken special interest in the finer sizes. The improvement in electrodeposited sieve cloth and in its use is showing results. One of the outstanding papers in the .4STRI symposium was illuminating. The international situation on sieve standards became acute. A committee of the International Standards Organization representing largely those countries not heavilv involved with investment in
have been employed. T h e subject of packing volumes and flobv is of general interest as well as specific to milling operations. A nomograph for settling velocity is helpful. A recording sedimentation balance is reported with perhaps some improvement over earlier ones. The ultracentrifuge is still a useful tool. A technique for centrifugal separations by density. employing dense media, has been carefully studied. The Coulter counter reported last year has been used to develop more experience and achieve greater usefulness. With its rapid electronic counting of projected areas. i t should become a valuable tool. A continuous flo\v device for gas adsorption was reported. The sample is held in a container at liquid nitrogen temperature while a stream of nitrogen and helium controlled as to ratio is passed through the container. \\'hen adsorption is complete, the nitrogen is recovered by warming and its amount is measured. This obviates the use of vacuum and should offer a simpler technique for those who cannot justify maintaining current equipment oi' the t y x
There has been a striking interest in crushing equipment for cans and for paper boxes to make convenient handling of these scraps and for the disintegration of wastes for disposd or for recovery treatment. This would be a specialized treatment, adapting linoivn principles to specific needs. More basically,
Courtesy Du Pont Co. and Chicago Boiler Co.
Sand grinder for paint
developed; and it may find a place in evaluating fine material. Sedimentation methods are still very popular. There was considerable interest in sedimentation volumes as well as in size measurement. Radiometric techniques
LINCOLN T. WORK received his A.B., Ch.E., and Ph.D. degrees from Columbia University where he taught chemical engineering for 20 years. After 10 years as director of research a t Metal & Thermit Corp., in 1949 Work resigned to engage in private consulting work. He was chairman of the Division of Industrial and Engineering Chemistry of the ACS for 1950.
VOL. 51, NO. 3, PART If
MARCH 1959
395
UNIT OPERATIONS Significant Applications (7) Size measurement Comparative tes Sieves Microscopy Adsorption Sedimentation Techniques for aerosols Grinding Theory Ball and tumbling mills
Courtesy Research-Cottrell
Cyclo-trell dust collector
there is a continuing interest in the fundamentals of grinding. Figures from many years back are cited to show that there is room for improvement in the utilization of energy in ball mill grinding. Perhaps the vibratory ball mill will find a way to retrieve some of that lost power. This has been put together into a compact package setup, which is said to be economical in energy requirements. I n large scale field operation, one of the copper companies is spending over a quarter million dollars to re-evaluate the comparison of ball and rod mills for their purposes. T h e year has been strikingly marked with advances in the technique of “sand grinding” developed by Du Pont. I t is a variant of the ball mill, which is specifically adapted to the dispersion of pigments in vehicles. No large amount of grinding energy is required, but there is need for many points of contact and for much rubbing in thin films. I n practice roughly mixed feed enters at the bottom of a vertical cylindrical tank in which there is a slow-speed stirrer and a grinding charge of 20- to 30-mesh Ottawa sand. T h e sand is rounded and has no sharp corners to wear off and enter the paste. As stirring proceeds, the sand becomes the grinding medium and disperses the pigment mechanically. Finished product is taken off through screens a t the top, retaining the sand free paste as product. I t is important that conditions be carefully controlled to have a proper sandcharge volume relation. Such mills are compact and simple, and are said to have high capacity. There is a growing place for impact or hammer mills in the chemical process
396
industries. T h e choice of wear-resistant materials and of operating conditions makes these mills simple, effective, and economical. Jet mills are also being pushed for fine grinding. In that field, there is another mill system of the opposed j e t type reported. T h e importance of good classification and recirculation of over-size in both the impact and jet types is an important factor in success they may achieve as fine grinders.
Classiflcation a n d Collection T h e usual attention has been devoted to screen separation, but there seems to be new interest in devices which are effective in the finer mesh. Study is being given to the several needs-the kind of vibration for maximum capacity, freedom from cloggage, and advance use of coarse scalping as with cyclones. There is continuing interest in dry classification and in particular the clearing of h e s from collected solids with an auxiliary air stream. Devices of a compact nature for insertion in dust lines are of growing interest. T h e double eddy has been a problem in cyclones, and still js. O n e equipment producer has a scalping device above the inlet to remove the coarse material which cannot cross the vortex and which often floods into the outlet to the detriment of the product. Another feeds the classifier from the top, using vanes to create the vortex and taking the inward moving fines out with a vortex adapter while the coarse particles hug the side and fall into the cone for removal. A study was reported on the performance of miniature hydrocyclones.
INDUSTRIAL AND ENOINEERING CHEMISTRY
Sand grinding Jet mills Classification and dust collection Cyclones Dust collection Filters Applications of Fuels and coking Clay and ceramics Cement Abrasives Catalysts Phosphors Explosives and propellants Fertilizers Metals Bio1ogica 1s Spray drying Paint Dusts and air pollution
(lOA, 18A, 79A, 27d, 28A)
(5B, 7B)
(8C,l l C , 75C)
(le,SC,
76C)
(6C) (140,330, 4 8 0 ) ( 5 0 , 180, 2 1 0 ) (80) ( 170) (300, 470) (280) (730,200) (20)
(770,220,250, 310. 430. 4 5 0 ) (160,’ 190, 320, 340, 350, 4 6 0 )
( 4 D , S D , IOD, 75D)
T h e Clarkson slurry valve is offering interesting performance qualities in the control of discharge from regular size hydrocyclones. Scrubbers, filters, and air cleaners still hold an active place in technical development: largely because of their protection against air pollution. There was a thorough study of power and efficiency of dust scrubbers, leading to the conclusion that energy input is needed to get results. A high temperature dust filter has also been announced, using a glass cloth filter medium.
Bibliography
Books and General References (1) Bikerman, J. J., “Surface Chemistry. Theorv and Applications,” 2nd ed., Academic Press, New York, 1958. (2) Chamot, E. M., Mason, C. W., “Handbook of Chemical Microscopy,” vol. I, 3rd ed., J. Wiley, New York, 1958. (3) Chemical Engineering Catalog, Reinhold, New York, 1958. (4) Chem. Week 83, I1 (September 1958), Buyers’ Guide. (5) Eirich, F. R., “Rheology,” vol. 11, Academic Press, New York, 1958. (6) Rose, H. E., Sullivans, R. M. E., “Ball,
A packaged vibrating ball mill, grinding paint by rounded grains of sand, and equipment for better separations and recoveries are current marks of progress Tube, and Rod Xlills," Chemical Publishing Co., New York, 1958. (7) Work, L . T., IND.ENG.CHEK 50,4815 (1958). Properties a n d Measurement of Particulates
(1.4) Allen, hi.,Chem. Eng. 65, No. 19? 176 (1958). (2.A) Ibid., No. 25, 182-3 (1958). (3A) Am. SOC. Testing Materials, Bdl. 231, 21 (July 1958'1. (4.4) Am. SOC.Testing hlaterials, Tentative Spec. E l l - 5 8 T (1958). (5'4) Anal. Chem. 30, 73'4 (June 1958;. (6A) Cartwright, J., LYheatley, K., Sing, K. S. W., J . Bppl. Chem. 8, 259-64 (.April 1958). (74) Chem. Eng. AVezes36, 56-7 (Sept. 22, 1 9 5 8 i..
(6B) Can. M i n . .tJet. Buli. 51, 495-504 (August 1958). (7B) Charles, R. J., M i n i n g Eng. 10, Trans., 481-4 (1958). (8B) Chem. E n g . 64, Yo. 12, 190 (19573. (9B) Ibid., 65, No. 6, 179 (1958). (10B) Ibid., No. 18, p. 55. (11B) Ibid., No. 19, p. 204. (12B) Zbid., No. 21, p. 234. (13B) Ibid., No. 23, p. 66. (14B) Ibid., No. 24>p. 150. (l5B) Ibid., h-0, 25, pp. 94-6. (16B) Chem. E n g . ,Yws 35, 61 (Nov. 25, 19571.
( l i B j Ibzd., 36, 123 (Sept. 22, 1'9581. (18B) Chem. E n g . Progr. 54, 134-5 (19581. (19B) Chern. 3 Ind. ( L o n d o n ) . S o . 46, 1506-7 (1958). (20B) Compressed A i r .\lag. 63, 22 (Xlarch 1958). (21B) Drug and Cosmetic Ind. 82,213 (Februarv 1958). (22B) Frefi;nann, V. F., Rock Products 61, 151-2 (1958). (23B) ISD. ENG.CHEM.50, 104.4 (Xlarch 1958). (24B) Mech. Eng. 80, 80 (August 1958,. (25B) Nagel, T., Eng. hJinzng J . 159, S o . 4, 110-1 (1958). (26B) Utley, H. F., P E /and Quarr? 51, 92 -3 (July 1958).
(8.4) Clayton, J. C., Rullie, J. E.. ChemistAnalyst.47, 62-4 (1958). (9.4) Connor, P., Hardwick? \V. H., Laundv, B. J., J . Apbl. Chpm. 8, 716-23 (November 19583. (10'4) Dimmick, R. L., others. A..\J.d. Arch. Ind. Health 18, 23-9 (July 1958'. i l l A ) Dintenfass. L.. Chem. & Ind. (Lon' doni, N o . 4, 98199 iJan. 25. 1958). (12.4) Dintenfass, L., J . Appl. Chem. 8, 34951 (June 1958). (13.4) Erlander, S. R., French. D., J . .hi. Chem. SOC.80, 4413-20 (1958). Classification a n d Collection (14.4) Friedman. G. hf.. J . Geol. 66, 394. 416 (July 1958). (1C) Archer. I$'. E., Chem. Eng. 65, No. 25, (15.V Hazel: J. F., Fiorito, L., J . Elerfro188-92 (1958). chem. SOL.105, 57-8 (January 1958;. (2C) Chem. Eng. 65, No. 10, 84 (1958 . (16.1) Hermans, J. J., Ryke, A . M., J. Col(3C) Ibzd., No. 20, pp. 177-8. loid Sci. 13, 508-9 (19583. (4C) Chem. E n g . x'ezis 36, 53 (Oct. 13. (17.4) IND.ENG.C H m . 50, 24A-5.4 (June 1958). 1958). (5C) Ibzd., 36, 69 (Kov. 10, 1958 . (18.4) Jacobs, hf. B., others, Am. J . Pub. (6C) 1h.D. Ew. CHE!vf. 50, ic'o. 2, 124.4 Htalth 47, 1430-3 (19571. 11958'1. (19.41 Katz, hf., Sanderson, H. P.! Fergu(7C) Ibid., No. 6, p. 114.4. son. hl. B.? Anal. Chem. 30, 1172-80 (8C) Ibid., Xo. 8,p. 11O.i. (1958). (9c3 Ind. Equip. Al-ezcs 26, 74 (February 120.4) Lester. R. H.. Bull. Am. Ceram. SOC. 1958). (1OC) Zion and Steel Eng. 35, 143 (hfay 1958). (11C) Matschke, D. E., Dahlstrom: D. A,, Chem. Eng. Progr. 54, No. 12, 60-4 (1958 I . Ana/. Chem..30, 1387-90-119 (12C) O'Mara, R., Flodin, C. R., C ' h p m . (23.43 Pattee, H. H., Jr., Science 128, 977E n g . 65, No. 9, 139-42 (1958). 81 (19583. (13C) Rock Products 61, 101 (April 1958). (24.41 Phelps, G. W.,Maguire, S. G., Jr., (14C) Ibid., 61, 78-9 (August 19581. J . ,4m. Ceram. SOC. 40, 399-409 (19571. (15C) Sanders, D. S., .Mining Congr. J . 44, (25'4) Rhoden, ht., Chem. Eng. 65, No. 5, 55-8 (March 1958). 160 (1958). 116C) Semrau. K. T.. hlarvnowski. C. Ll'.. (264) Rochow, T. G., Botts, XI. C., A n a l . ' Lunde, K. E., Lapple, C. E., I ~ DESG: . Chem.. 30, 640-56 (19583. CHELi. 50, 1615 (1958i. (27.4) Smith, F. T.? J . Chem. Ph>s. 28, 746-7 (1958'1. (28.41 Thomas, J. IV., Chem. Eng. 6 5 , No. 3. 148 119581. Applications (29k) Thompson, J. K,! A n a l . Chem. 29, 1847-50 (19571. (1D) ,411en; hl., Chem. Eng. 6 5 , KO. 8. 168 (30'41 Vistelius, A . B.? J . Geol. 66, 224-6 11958). (19 58~ 1 . (2D) r\rmiger, IV. H., Fried, hf.. J . .Igr. Food Chem. 6, 5351-43 (1958). (3D) Bartok, W., ILlason, S. G., J . Colloid. Sci. 13, 293-307 (1958). Grinding (4D Blackmore, S. S., Jnd. Tlhstes 3, S o . 3, '3-8 (1958). (IB) Bond, F. C., Bull. Am. G r a m . Soc. 37, (5D) Bowers, D. J., Snvder, XI. J., Bull. 361-3 (1958). Am. Ceram. Soc. 37, No. 5, 220-1 ( 1 9 5 8 1 . (2B) Bond, F. C., ;IJining E n g . 9, Trans., 16D) Calvert. S.. Miller. R. H.. ISD. EYG. 1372-6 1,1957). CHEM.50, i793-8 (1958). (3B) Ibid., 10, Trans., 592-5 (1958). (7D) Checkel, R . L., .Modern Plasttcs 36, (4B) Bosse, D. G., Ofic.Dig., ,Vat/. Paint. 125-6 (October 1958). Varnish, Lacquer Assoc. 30, 250-76 (3farch (8D) Chem. E n g . 65, No. 8,60-2 (19581. 19581. Chem. E n g . .lrews 36, 106 (Oct. 20, (9D) (5B) Brown, J. H., Illining Eng. 10, Trans., 19581. 490-6 (19581. 1 1
\ - ' - -
(l0D) Ibid., 36, 7 (Dec. 1, 19581. (11D3 Coffer, I,. \$'., Chem. Eng. 65, No. 2, 107-22 (1958). (12Dj Crosby, E. J., liarshall, \V. R., Jr., Chem. E n g . Progr. 54, h-o. 7, 56-63 (1958). (13D) Dolan, J. E., J '4ppl. Chem. 8, 471-7 (.4ugust 1958). (14D) Dunlop, D. D., Griffin, L. I., Jr., Moser, J. F.: Jr.: (?hem. Eng. Progr. 54, No. 9, 39-43 (1958). (l5D) Faith, W.L., Jvd. T f h s t e s 3, S o . 3, 79 (1958). (16D) Fenburr, H. I>., Ofic. Dig. Paint, Varnish,Lacquer Assor. 30, Xo. 406, 1280-4 (1958). (17D) Gormly, \V. hi., Buli. .4m. Curam. SOC. 37, NO. 2, 77-80 (19581. (18D) Gould, R. E., others. Ceram. Ind. 71, 124-31 (September 1958). (19D) Graff-Baker. C . . J . &b/. Chem. 8, 590-7 (1958). (20Dl Green, L., Jr.?J e t Piopitision 28, 15964 jhlarch 1958). (21D) Gruver, \V-. E., Foundrj 8 6 , 94-6 (July 1958). (22D) Harrington, C . D.: Ruehle, '4. E., Chem. Eng. Progr. 54, KO. 3 , 65-70 (1958). (23D) Harris, hl. R., Sing, S. rV., J . AppI. Chem. 8, 586-9 (1958). (24D) Hester, A . S., Johannsen, A., Danz, I\'., IND.ENG.CHEM.50, 1500-6 (1958). (25D) Iron Age 182, 103-11 (Sept. 18, 1958 . _ _ I. (26D) Iwasyk, J. hf., Thodos, G., ChPm. E n g . Progr. 54, S o . 4, 69-'5 (19581. (27D) Johnson, P. €I., Kelsey, R . H., 139, 227--31 Rubber I170rld 138. 8'7-82: (September Sovember 1958 1. ' (28D) Lehmann, W., J. E/?chochem. SOC. 105, No. 10, 585-8 (1958). (29D) Leighton. I$:. B., Soap and C h o n . Specialties 34, 79-81 (August 1958). (30D) hlalanchuk, hf., Stuart, E. B., IND. E K G . CHEM. 50, 1207-10 (1958'). (31D) Metal Powder Assoc.~ 130 \Vest 42nd St., New York 36, N. Y., Procerdings 13th Annual Meeting, 1358. (32D) hlitton, P. K., \Vhite, L. S., Ofic Dig. Paint, Varnish: Lacquer Assoc. 30, NO. 406, 1259-76 (1958). (33Di hlolstedt, B. V., Moser, J. F., J r . , IND.ENG.CHEX.50, 21-3 (19581. (34D) OBc. Digest P a i n f , Lhrnish, Lacgufr Assoc. 30, S O .397, 156-82 (1958). (35D) Ibid., No. 402, pp. 729-35. (36D) Orr, C., Jr., others, J . ColloidSci. 13, 472--82 11958). (37D) Patterson, R . C.: Combustion 30, 4757 (July 19581. (38D) Pfeifer, V. F . ? Vojnovich, C., Maister, H . G., Heger, E. N., Bogart, LV, hl.. ISD. ENG. CHEM.50. 627-32 (1958). (39D) Phillips. .\. B., others. J . Agr. Food Chem. 6, 449-53 ( 1 9 % ) . (40D) Preuss, L. E., .I. Sci. Instr. 35, 307 1AuPust 1958 1. (4lD)'-Ramser, J. H.: Hill. P. B., IND. ESG. CHEM. 50, 117--24 (19583. 142D) Roos. C. LV.. Chem. Erie. 65. No. 1. ' 168 (i95si. (43D) Shafer, \V. 5 1 , Harr, C. R., J . Electrochem. Soc. 105, No. 7, 413-7 (1958:. (44D) Somers, J. C.: .\fech. Eng. 79, 1022-4 119571. 145Dl Steel 143. 114-15 (Seut. 8. 1958). I
,
, I
Y
I
(January 1958). (48D) Yeager, \'. B , Potie? Eng. 62, 61-4 (July 1958).
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