January 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
Strzynski (87) has arranged outlets for discharging solids through nozzles tangentially t o the bowl in such a manner that they jet backward relative to the direction of rotation. This results in a reduction in the power which is required to drive the unit. Sharples (88) has devised a scheme for separating solids from liquids in a perforate basket, conducting the solids away and evaporating the liquid with the solids by a stream of gas. Schutte and Mack (18) have a method for separating B light solid from a heavy liquid and continuously discharging the solid. Schutte (17) and McCurdy (18) have also obtained patents on centrifugal separators. Process Patents. The drowning of nitrocellulose with water and the separation of the waste nitration acid and the wash water are described by Peanon and Askcraft (14). An apparatus equipped to remove the gases from solid-liquid mixtures in order to hasten the settling of the solid particles in a centrifuge has been devised by Flowers (8). Kopplin (10) has patented a method of washing sugar in a centrifugal by wing intermittent spraying. There is a switch mechanism for achieving the intermittent action. A method for separating blast furnace slag from water has been patented by Bartholomew (8). Continuous soap manufacture employing centrifugal equipment has been patented by Sender (19, BO). Sender has also patented a device (81) for discharging a viscous effluent from a. centrifuge. Smely (84) has mtented a centrifugal apparatus adopted for sugar processing. It is known that fundamental investigations of the behavior of centrifugal equipment are under way in universities and in industry. It is hoped that the results of such studies will be made available in the near future.
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LITERATURE CITED (1) Andersson, G., Socker Handl., 2, 379-406 (1946). (2) Bartholomew, T., U. S. Patent 2,422,464 (June 17, 1947). (3) Benedict, M., Chem. Eng. Progrees, Trans. Am. I d . C h . Engrs., 43, 41-60 (1947). (4) Boruff, C. S., IND.ENQ. CHBM.,39, 602-7 (1947). (5) Corrigon, B., Iron Age, 159, 66-62 (1947). (6) Dickey, G. D.. and Bryden, C. L., “Theory and Practice of Filtration,” New York, Reinhold Pub. Corp., 1946. (7) Eckhardt, H., Chem. Eng., 54, 121-3 (1947). (8) Flowers, A. E., U.S. Patent 2,417,747 (Mar. 18, 1947). (9) Gernigon, E., Chimie & industrie, 54, 382-8 (1945). (IO) Kopplin, F. W., U. 8. Patent 2,418,776 (Apr. 8, 1947). (11) Lyons, 8. C., and Johnson, A. L., Am. Inst. Mining Met. Engrs., Mining Technol., 11, No. 4; Tech. Pub. 2195 (1947). (12) McCurdy, H., U. S. Patent 2,425,110 (Aug. 5, 1947). (13) Memo Centrifugal Co., “Recovery of Barite from Rotary Drilling Mud by Centrifugal Separation,” San Franafsco, Calif. (14) Pearson, J. D., and Askcraft, D. C., Brit. Patent 578,691 (July 9, 1946). (15) Perry, J. H., “Chemical Engineers’ Handbook,” New York, McGraw-Hill Book Co., 1941. (16) Riegel, E. R., “Chemical Machinery,” New York, Reinhold Pub. Corp., 1944. (17) Schutte, A. H., U.S. Patent 2,398,967 (Apr. 23, 1946). (18) Schutte, A. H., and Mack, A. W., Ibid., 2,394,015 (Feb. 6, 1946). (19) Sender, L., Ibad., 2,411,468 (Nov. 19, 1946). (20) I W . , 2,411,469 (Nov. 19, 1946). (21) I W . , 2,412,099 (Dec. 3, 1946). (22) Sharplea, L. P., IbM., 2,409,713 (Oct. 22, 1946). (23) Smart, G. S.,Intern. Sugar J., 48, 293-6 (1946). (24) Smely, V., U. 8.Patent 2,416,073 (Feb. 18, 1947). (25) Smith, J. C., C h .Id.,61, 417-18 (1947). (26) Smith, J. C., IND. ENQ. CHEM.,39, 474-9 (1947). (27) Strzynski, G. J., U. S. Patent 2,410,313 (Oct. 29, 1946). .(28) Terhune, C. F., Canadian Patent 435,913 (July 23, 1946). (29) Tholl, J. F., U. 5. Patent 2,396,622 (Mar. 12, 1946).
RECEIVED November 8, 1947.
CRUSHING AND GRINDIN6 LINCOLN T. WORK, METAL a THERMIT CORPORATION, RAHWAY, N. J,
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HE report presented last year (98) referred to the relatively slow progress which takes place in this old unit operation. . The importance of the growing knowledge of measurement was also stressed, since, particularly in the subsieve range, this gives information needed for exact analysis of the operation. Progress during the past year is not great, but it is substantial. Methods of Measurement. Several survey papers have been published. McCabe (13) presented a classification of methods, giving a brief and illuminating discussion of each type. He showed the increasing importance of the electron microscope and of the x-ray scattering by fine grains. Vernon (86) discussed various sedimentation, centrifuging, and microscopic methods in a brief paper of somewhat lesser scope. The Road and Building Materials Group of the Society of Chemical Industry and the Institution of Chemical Engineers held a joint meeting on February 4, 1947, a t which was presented a symposium on particle sire measuremenbs. Heywood (8) presented a paper on scope of analysis and standardization, giving limits of application and a somewhat detailed description of various methods. Davies (8)presented an extensive study of the sedimentation of small suspended particles, showing a treatment for spheres, flat particles, and clouds. He discussed the effecta of Brownian movement and diffusion, and the problem of accurate sampling from air streams. Gregg (6)discussed adsorption and
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heat of wetting methods for measuring surface erea. He observed that adsorption of gases yields better than relative values. Although there are problems in adsorption from liquids and in heat of wetting measurements, there are also elements of promise. Lea and Nurse (11)dincussed permeability methods indicating the practicability of the method in spite of some difficulties in securing absolute values. Skinner and Boas-Traube (81) discussed light extinction methods, including the effects of particle concentration and of length of light path on light extinction. Walton (87) showed the application of electron microscopy, recognizing that present instrumentation is reaching its limit of resolution and that improved performance in present instruments will be made. These papers are a11quantitative in their approach, and a wealth of data is contained in them. A second session gave the industrial applications. This included papers by Stairmand (93) on practical aspects, Newman (18) on paint pigments, Schofield and Russell (19) on soils, Smith (2%) on the radio industry, and Whipp and Bernhardt (88) on bitumen emulsions. Other work on spec& aspects of measurement is briefly cited. Johnson and La Mer (10)discussed light scattering by sulfur sols. DeVore and Pfund (S), working with pigment materials in various media, presented some interesting data on the spectral transmission of Alma of dielectric powders having uniform particle size.
10
INDUSTRIAL AND ENGINEERING CHEMISTRY
Guinier (7) made size determinations of submicroscopic particles by x-rays using a variety of materials. Steinherz (94) presented a study of shape as it may be determined from comparisons of settling velocity, count of particles, and measurement of projected images. Gooden and Updike ( 5 )offered standard powders of spherical and rod shapes as a basis for calibration. The experiences of some industrial organizations in developing and applying methods of test have become available in pamphlets published by the companies. Such information will be useful in the ultimate standardization of methods. Metals Disintegrating Company of Elizabeth, N. J., has added to its folder (14) a section on the permeability test with an analysis of its application and limitations. The Eagle-Picher Research Laboratories of Joplin, Mo., has published, as its first in a series of papers on research technique and technology, a paper by Musgrave and Harner on turbidimetric particle size analysis (15). This papor includes a brief survey of other methods and a detailed treatment, including operating instructions, for their optical methods. Grinding Mills. In the field of mill equipment, Wuensch (SO) has announced a classifying ball mill which is of the centrifugal bowl type. The bottom and side faces are so constructed and the mill speed is sufficiently high that balls and feed cling to the walls, while the grinding motions take place further in the bowl, so that mill wear is reduced. Feed and overflow are arranged so as to give internal classification with attendant savings in power, and with substantially higher grinding rates to given sieve mesh products than are obtainable with conventional milling. However, surface measurements are lacking, and no comparison of efficiency of milling can be derived from the data offered. Schurecht (10)studied the effect of deairing treatments in the manufacture of porcelain balls on the wearing qualities in ball mill operation, and found best results when the clay was deaired in the extruder, pressed, and again deaired. Timmermans (25) gave a brief report on wear of ball sizes, with respect to characteristics of balls tested, fineness of feed, and ratio of ball sizes. Metallurgical character associated with hardness-martensite and decarburization-produced substantial differences in wear. Large balls wore more with coarse feed. Myers, Michaelson, and Bond (16)presented extensive plant and laboratory data on rod milling. Within limitations of the data, their paper gives a concise and comprehensive analysis of performance of these mills based on sound data, as to particle size among other variables. Johnson (9) reported on the crushing practice at Braden Copper Company. The relation of bins, feeders, and crushers was shown diagrammatically, and reference was made to an electric interlocking system to eliminate choke-ups. Myers and Tower (17) presented a symposium on milling devices and practices. In this there is little reference to grinding mills, but the accessory equipment connected with such type of operations is definitely of interest. Cantributors to this symposium included expert representatives in many of the mining and smelting companies primarily with nonferrous ores. Classification. In the field of classification Foley ( 4 ) stressed terminal velocity rather than calculated diameter as a better expression of the dust-particle characteristics. Lyons and Johnson
Vol. 40, No. 1
(11)showed applications of continuous centrifuging in fine particle size classification. Grindability. Bond ( 1 ) has again contributed to the literature of grindability with eleven pages of compactly tabulated data on a great variety of materials with respect to standard ball mill and standard rod mill grindabilities. He has also given an extensive table of impact crushing tests with occasional values of compressive strength. Such accumulation of data should go far toward estimating performance for design. Although the published contributions and the disclosed new devices during 1947 are relatively limited, the character of the work which has been done is more quantitative. It is now based on engineering data and, where necessary, treated by statistical methods. LITERATURE CITED
Bond, F. C., Mining Technol., 11, T.P. 2180 (Apr. 1947). Davies, C. N., Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 12-26 (Feb. 1947). DeVore and Pfund, J . Optical Soc. Am., 37, 826-32 (Oct. 1947).
Foley, R. B., Trans. Am. SOC.Mech. Engrs., 69, 101-8 (Feb. 1947).
Gooden and Updike, IND.ENQ.CHEM.,ANAL.ED., 18,p. 802, 1946.
Gregg, 5.J., Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 27-33 (Feb. 1947). Guinier, A., Bur. of Mines, Znf. Circ. 7391 (Dec. 1946). Heywood, H., Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 1-11 (Feb. 1947). Johnson, E. R.,Mining Technol., 11, T.P. 2150 (Feb. 1947). Johnson and La Mer, J . Ant. Chem. SOC.,69, 1184-92 (May 1947).
Lea and Nurse, Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 34-43 (Feb. 1947). Lyons and Johnson, Mining Technol., 11, T.P. 2195 (Apr. 1947). McCabe, R. P.. Ceramic Age, 50, 155-7, 190 (Feb. 1947). Metals Disintegrating Co., “Particle Sire Analysis of Metal Powders,” 1947. Musmave and Harner. Research Technique and Technology No. 1,Eagle-Picher Lead Company (1947). Myers, Michaelson, and Bond, Mining Technol., 11, T.P. 2175 (Apr. 1947). Myers and Tower, Zbid., 11, T.P. 2162 (Mar. 1947). Newman, A. C. C., Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 69-74 (Feb. 1947). Schofield and Russell, Zbid., p. 75. Schurecbt, H. G., J . Am. Ceramic SOC.,Ceram. Abstracts, 48,99 (June 1947). Skinner and Boas-Traube, Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 44-50 (Feb. 1947). Smith, M. L.,Zbid., pp. 77-84. Stairmand, C. J., Ibid., pp. 58-68. Steinherr, A. R.,J. SOC.Chem. Z d , (London), 65, 314-20 (Oct. 1946).
Timmermans, 0. E. B., Eng. Minino J . , 148,78 (May 1947). Vernon, A. A., J . Chem. Educatwn, 23, 448-60 (Sept. 1947). Walton, W.H., Inst. Chem. Engrs.-Soc. Chem. Ind. Symposium on Particle Size Analysis, 51-7 (Feb. 1947). Whipp and Barnhardt, Zbid., pp. 85-9. Work, L. T., IND.ENG.CHEM..39,11 (1947). Wuensch, C. E.,Mining Congr. J . , 33,22-5,49(Sept. 1947). RECEIVED November 25, 1947.
