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(304) Wesly, W., iMeZliand Textilber., 31, 62 (1950). (305) Westall, R. G., J . Sci. Food and Agr., 1, 191 (1950). (306) Wheaton, R., and Bauman, W , Division of Colloid Chemistry 117th Meeting AM. CXEM.Soc., Houston, Tex. (307) Whittaker, H., U. 8. Patent 2,500,727 (1950). (308) Wiklander, L., Kgl. Lanfbruks-Hogskol. Ann., 16, 670 (1949). (309) Wiklander, L., Soil Sci., 69, 261 (1950). (310) TVilliams, K. T., Potter, E. F., Revenue, A., and Scurzi, W., J . Assoc. Ofic.Agr. Chemasts, 32, 698 (1949). (311) Wirts, C., Rehfass, hl., Delsetone, B., and Wass, B., J. Clin. Inyesf.,29. 37 (1950). (312) Woodard, J. C., Snell, K. L., and Kicholls, R. S., U. S. Patent 2,492,173 (Dec. 27, 1949).
Vol. 43, No. 1 - - 7
14 (1950).
W. L., and Baumeister. T.. Trans. A m . SOC.Mech. Engr., 72, 491 (1950).
(316) (317) (318) (319) (320)
Yorston, F. H., P u l p h Paper Mag. Canada, 50, 108 (1949). Ibid., p. 111. Zarow, A., U. S.Patent 2,520,189 (Bug. 29, 1950). Zender, J., Ibid., 2,502,614 (April 4, 1950). Zhukov, I., and Brods Koyaya, N. T., Kolloid Zhur., 11,
332 (1949). (321) Zwart Voorspuij, A. J . , E'xpwirnentia, 5, 474 (1949). RECEIVDD October 14. 19.50
ATERIALS ANDLING
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ROBERT E. WRIGHT' MONSANTO CHEMICAL CO.,ST. LOUIS 4, MO.
I n 1950 a number OF new devices were introduced which gave the chemical industry new took for the more efficient handling of materials. In addition to new devices, most manufacturers introduced new models with increased work capacity, improved efficiency, or other design improvements. The trend toward the use of machinery to replace labor was so marked that writers onee again began to think about the effect of technological advances up3n employment.
HE annual review in past years has noted the increased attention being given to this field. During 1950 the developments in the materials handling field continued at an accelerated rate. A number of new devices of particular interest were introduced during the year
electric pump unit eliminates stuffing boxes, seals, couplings, and shaft wear, and the pump can be installed in any position ( 2 ) . A trash pump for liquids that would clog an ordinary impeller pump is also new. The impeller of this pump is bladeless (see Figure 1). I t is said that hard-boiled eggs can pass through the pump whole and even apples and oranges can be handled without bruising (8). Another pump has a new idea for automatic priming: a variable-capacity vane-type positive displacement pump mounted on the same shaft as the centrifugal impeller. When the piping system is filled with liquid, the priming pump shifts to a neutral position and stops pumping (IO). Another type of self-priming centrifugal pump, introduced during 1950, is said to have high efficiency during the pumping stage. There is no recirculation after priming is completed and no bulky priming reservoir is required. The pump is simple, yet it is said to have the priming ability of positive displacement pumps (11). A new pump is a v d a h l e for transmitting semisolids through a
COURTESY FAIRBANKS. MORSE d CO
Figure 1.
Bladeless Impeller for Trash Pump
LIQUID AND GAS HANDLING
PUMPS.Several new types of pumps became available during the year. One is a new centrifugal pump that is driven by a rotor-impeller hermetically sealed in the pump housing. This COURTESY FAIRBANKS. MORSE & CO.
Present address, Chemstrand Corp., 1617 Pennsylvania Blvd., Philadelphia 3, Pa. 1
Figure 2.
Two-Stage Packaged Compressor
January 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
109
pipe. It is said that any material which has a viscosity sufficient to permit flow through a pipe can be handled by this pump (27). A precisely calibrated pump has been developed for delivering 3 to 725 ml. per hour a t pressures up to 1000 pounds per sqdare inch. The liquid end construction is stainless steel and the packing is normally Teflon. Such a pump should find use in adding small quantities of chemicals or vitamins to a main product stream (3). Another interesting chemical feed pump will feed 3.38 gallons per hour against a pressure of 30,000 pounds per square inch (3). II
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COMPRESSORS. An entirely Figure 3. Mechanical Vibration Conveyer new design for electric'driven compressors has been developed which is notable for its simplicity and compactness (14). The for the return of the empty pallets. Another examiner compressor has only two main air connections, the intake and recommended approval of the petition of fifteen large midwestern the discharge, and the intercooler is built into the frame of the truckers for an average rate of one half of fourth class on return compressor. The air flow from the first stage through the inshipments of pallets, platforms, and skids @ I ) . These are notetercooler to the second stage is accomplished by air passages worthy developments because, if special rate schedules for return incorporated in the compressor frame. Advantages of the new shipments of pallets become general, the economics of palletized design are elimination of exterior piping, simplified installation, shipping is greatly improved. A Swedish manufacturer has developed a new method of pallet and reduced floor space requirements. Aside from the unique design. Nails fastening the deck boards are locked to the general design, the new compressor is said to have a number of important design refinements. The machine is basically a twostringers by a simple method which is remarkably effective. It is said that the force required to break the fastening is great enough stage, 80-to 125-pound-per-square-inch air compressor (Figure 2). A new oil ejector vacuum pumping unit, designated by the either to split the wood or t o exceed the yield point of the nail (20). manufacturer as KB-300 (6),has been introduced for pumping to atmospheric pressure large volumes of gas or air from the The Engineering Societies Library has published a comprehensive bibliography of 114 references covering all aspects of the subpressure range of 10 to 300 microns, The new unit is built to handle water vapor and corrosive materials; it is said to have ject of pallets, including design and construction of the different types, the handling of various materials on pallets, the savings high pumping speeds in the 50- to 500-micron pressure range, and below pressures of 200 microns to have more speed than ten large achieved in materials handling, and details of presentrday applicamechanical pumps (rated a t 100 cubic feet per minute) in parallel. tions in individual plants in a large number of industries One of the advantages claimed for this vacuum pump is the low (6). operating cost compared with other pumping methods. TRUCKS.Most manufacturers developed new and improved A small portable intensifier has been made available which can fork lift trucks, but there were no unique ideas announced in 1950. There is evidence of keen competition in this field, because produce UP to 23,000 pounds per square inch hydrostatic pressure from an air supply pressure of 90 pounds per square inch. The unit is compactly mounted on rubber tires and is equipped ready to work within a few minutes (4). This intensifier can be used in pressure testing of boilers and piping, and destruction tests in laboratories. SOLIDS HANDLING
The great limitation of palletized shipments has been the aost of freight on return shipments of the empty pallets. Recently, an Interstate Commerce Commission examiner recommended that the commission approve a proposal for a preferential freight rate
COURTESY G E N E R A L A M E R I C A N TRANSPORTATION CORP.
Figure
4.
Trans-Flo Car for Bulk Handling
INDUSTRIAL AND ENGINEERING CHEMISTRY
110
COURTESY HOFMAN LABORATORIES,
Figure 5.
INC.
Liquid Hydrogen Container
all manufacturers of fork lift trucks now have substantially the same attachments for the special handling of materials, the mechanical features are highly refined, and the fork trucks are taking on an amazing degree of similarity. A tiny bulldozer, weighing only 800 pounds, has been developed for small jobs and service in close quarters (16). It has a 5-hp., air-cooled motor, and can be equipped with a bucket lift, dozer blade, or snow blade assembly. The normal scoop capacity is 560 pounds of wet sand (4.5 cubic feet). CONVEYERS.Two manufacturers (16, 68) have announced new mechanical vibration conveyers which are said to operate at large power savings because of operation at positive resonance (natural frequency). The design of these conveyers isolates vibration within the machine itself, so that the supporting structures need only be designed to carry the dead weight of the equipment and its material load. It is said that abrasive wear on the decks is negligible, owing to hopping action of the material. Vibrating conveyers will convey hot, abrasive, or corrosive materials in granular, pulverized, or lump form, as well as boxes and packages. The trough can be enclosed to protect the material or prevent the escape of dust. One type uses spring bars (Figure 3); the other type uses coil springs. A n interesting new self-centering roller called the Lorig aligner has been announced. A load dropped in any position on a roller conveyer with Lorig aligners will gradually work itself to the center line of the conveyer as it rolls along. The load will stay centered without guide rails even around curves or with the conveyer a t a slight tilt. If used with a belt conveyer, the Lorig aligners will hold the belt in the center without the use of guiding devices, resulting in elimination of edge wear and fewer idlers (19, 22). Gerald Von Stroh, director of the Coal Mining Industries mining development program, indicates that the f i s t test of a stainless steel conveyer belt was successful (17). Although steel has been used in conveyer belts for some time, this is believed to be the first use of stainless steel. If the present development work on stainless steel conveyer belts is successful, such conveyers might find important application in the chemical industry. There is considerable interest in a proposed belt conveyer system to transport coal and iron ore approximately 130 miles from East Liverpool to Lorain, Ohio, with spurs to serve Youngstown and Cleveland. The estimated cost of this proposed conveyer is $210,000,000. The c*onveyerwould require 250,000 hp.
Vol. 43, No. 1
for operation a t full capacity of 52,000,000 tons per year (18, 69). BCLKHANDLING. Two new types of weatherproof truck trailers have been developed for bulk handling: one for granular and powdered materials and the other for handling pulverized materials. The latter design incorporates the -4ir-Slide aeration principle and hydraulic elevation of the trailer body for speedy disrharge of materials ( I d ) . A new railroad car has been designed for the sanitary and efficient bulk transportation of dry, granular, or powdered commodities such as flour, plastics, and chemicals (see Figure 4). The Trans-Flo car is essentially a covered hopper-type car, but it differs from the standard covered hopper car in that it is composed of two large compartments each having six sets of hoppertype bottoms, The compartments can be made of either stainless steel or high tensile low alloy steel (9). The Trans-Flo car is unloaded pneumatically in an operation that can be performed by one man in less than 4 hours. It should find application for commodities where sanitation, infestation, or high packaging costs are problems. Another approach to the bulk handling of materials is the recently developed Tote Bin, an aluminum container for handling about 4000 pounds of material. This cantainer is about thr size o f a conventional pallet and can be handled like a pallet load (31). Still another approach to bulk handling of materials is the Return-0-tainer. I n effect, this is a collapsible steel box which can be lined to be vapor- or moistureproof, if desired. The container can be emptied with a specially designed dumping device. When emptied, it folds down to about one-quarter size and it can then be returned and re-used ( 7 ) . During 1950, an increasing number of chemicals were moved by multicargo ocean-going tankers. Warren summarizes the current status of ocean shipping of chemicals (SO). MISCELLANEOUS MATERIALS HANDLING DEVICES
Much attention was given during 1950 to the use of polyethylene in various forms for packaging. As a result of the widespread use of polyethylene containers, a number of new machines have been developed for automatically making, filling, and sealing polyethylene bags. One manufacturer (1) has started a new method for shipping paper bags. The bags are built up on disposable, flat packed, paper boards t o give a unit load 48 X 48 inches. The bags are compressed in a specially designed press, and steel strapping is fastenrd while the bags are still under pressure. The pressurized packing is said to result in storage space savings of as much as 50%. The palletized unit load greatly reduces handling cost and time. A new bag packer has been developed for packing ground chemicals which have characteristics similar to flour. The unit consists of a screw-type feeder, an automatic scale, a packer, and a conveyer, all of which operate together automatically to permit one man to handle four 100-pound bags per minute. In spite of the high output, the manufacturer claims consistent weighing accuracy for 80% of the bags, with none of the remainder varying more than 2 to 4 ounces from the true weight (W6). Liquid hydrogen and liquid helium have been laboratory rarities because of lack of a good means for handling and storing. A patented new liquid hydrogen container is now available for this purpose (see Figure 5 ) . The container is made of three concentric copper spheres. The inner and outer spheres form a conventional vacuum flask with the facing interior surfaces polished to a mirrorlike fmish. Between them is placed a third sphere highly polished on both sides which acts as a radiation shield. This shield is attached to the inner sphere of a smaller side flask containing liquid nitrogen. By cooling the main container to the temperature of liquid nitrogen, the evaporation losses of liquid hydrogen or helium are reduced to a negligible minimum ( I S ) .
January 1951
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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
Filling machines are now available for free-flowing and nonfree-flowing products in which rapid and dustless filling is obtained by applying a controlled vacuum to the containers being filled. Large machines operating on this principle fill as many as 300 containers per minute with high accuracy, but small machines are also made for filling limited production items (24). During 1950, i t seems that all types of materials handling devices were improved, even the wheelbarrow. William Gemienhardt, a member of the staff of the New York University College of Engineering, has designed a new wheelbarrow with an ingenious wheel suspension which permits a loaded wheelbarrow to ride over a 4-inch curb with relative ease (25). Purdue University and the American Materials Handling Society sponsored the Second Annual Materials Handling Conference at Lafayette, Ind., in February 1950. This conference i s only one of many evidences of the increased attention being given to materials handling. In spite of increased use of new and better materials handling equipment, great improvements can still be made in the actual handling of materials. Perlman (93) says that only 3 hours of the average freight car’s day are spent in over-the-road movement, while 21 hours are spent in terminal detention. He sags that by adding 4 minutes per day to each car’s over-the-road movement, the nation’s car inventory could be increased by $100,000,000. This is only one of examples that could be cited to show the great potential field for better handling methods and equipment. LITERATURE CITED
( I ) Arkell & Smiths, Canajoherie, N. Y . , personal communication to
author. Atlantic Pump Corp., P.O. 6751, Philadelphia 32, Pa., unnumbered bulletin on Hermetik pump. 28, 3346 (1950). (3) CIiem. Eng. (4) CooperRessemer Corp,, Mt. Vernon, Ohio, bulletin on intensifier. (2)
111
(5) Distillation Products Industries, Division of Eastman Kodak Co., Rochester 3,N. Y., literature on KB-300 vacuum pump. (6) Engineering Societies Library, 29 West 39th St., New York 18, N. Y., “Bibliography on Pallets Used in Modern Materials Handling,” 1949. (7) Fab-Weld Corp., Pickwick and Richmond Sts., Philadelphia 34,Pa., unnumbered bulletin on Return-o-tainer. (8) Fairbanks, Morse & Co., 600 South Michigan Ave., Chicago 5, Ill., BUZZ. 5400 K-1. (9) General American Transportation Corp., 135 South LaSalle St., Chicago 90,Ill., literature and unnumbered bulletins on Trans-Flo car. Gilbert & Barker Mfg. Co., West Springfield, Mass., Bull. P-463. Goulds Pumps, Inc., Seneca Falls, N. Y., Bull. 636-1. Gramm Trailer Corp., Delphos, Ohio, bulletins on bottom hopper dump trailor and Air-Slide trailer. Hofman Laboratories, 216 Wright St., Newark 5, N. J., unnumbered bulletins on liquid helium container. Inpersoll-Rand Co., 11Broadway, New York 4, N. Y., Bull. 3150. Jeffrey Mfg. Co., 909 North Fourth St., Columbus 16, Ohio, unnumbered bulletin on mechanioal vibration conveyer. Mead Specialties Co., Inc., 4114 North Knox Ave., Chicago 41,Ill., literature on baby btdldoeer. Mech. Eng., 71, No. 10,848 (1949). Iba‘d., 72, No. 7, 583 (1950). Ibid., 72,No. 10, 821 (1950). Modern MuterTiuls Handling, 5, No. 9, 36 (1950). Ibid., No. 10, 16 (1950). Ibid., pp. 38, 39. Perlman, A. E., Mech. E n g . , 72, No. 8, 641 (1950). Pneumatic Scale Corp., Ltd., Quincy 71, Mass., unnumbered bulletin on Vacuflow fillers. Power Generution, 54, No. 6 (1950). Richardson Scale Co., Clifton, N. J., Bull. 3449. Roto-Flo Pump Corp., 2608 West Ruby Ave., Milwaukee 9, Wis., bulletins. Stephens Adamson Mfn. Co., Aurora, Ill., Bull. 849. Von Thaden, H., Mech; Eng., 72,No. 7, 549-51 (1950). Warren, R. F., Chem. Engr., 57, No. 1, 118-19 (1950). 42,79A (June 1950). Wright, R. E., IND.ENG.CHEM., RECEIVED October 16, 1950.
MIXING J. HENRY RUSHTON‘ ILLINOIS lNSTlTUTE OF T E C H N O L O G Y , C H I C A G O , ILL.
During the past year a large number of articles have appeared on agitation and mixing. There has been considerable activity along experimental lines, and important engineering performance data have been reported. Several articles give equipment performance data, both from the standpoint of power characteristics and process applications. Discussions have appeared which relate fundamental fluid mechanics theory to mixing. The most significant and valuable work available to date on mixing applied to fermentation (a gas-liquid-solid mixing operation) has been published. *
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H E previous annual review of developments in mixing AND was published in the January 1950 issue of INDUSTRIAL ENGINEERING CHEMISTRY (31) and it brought references u p to the date of October 1949. An annual survey of new equipment, as announced by equipment manufacturers, was published in Chemical Industries (8). A description of present theory and practice in mixing appears in “Technique of Organic Chemistry” (33). Special attention is directed to the proper use of mixers in organic chemical research. The new edition of “Chemical Engineers’ Handbook’’ (39) oontains a section on mixing. It includes most of the material of the previous editions to which have been added very brief summaries of some of the recent literature. A list of applications for various types of mixers has been published by Lyons (18). 1 Also director of research, Mixing Equipment Co., Rbchester. N. Y.
Morello and Poffcnberger (24) published an authoritative survey of commercial extraction equipment which includes performance characteristics of several in which mixers are used. A review of various methods reported in the literature for assessing the performance of mixers has been prepared by Black (4).
POWER CHARACTERISTICS OF MIXERS
Extensive data have been published by Rushton, Costich, and Everett (34) to establish basic mixing impeller characteristics. The fluid mechanical basis for power correlations is developed and shown to be an accurate basis for the correlation and interpretation of performance of the common types of mixing impellers, Data are correlated for impellers from 3 to 48 inches in diameter for tanks 8.5 to 96 inches in diameter, and for fluids with viscosities of from 1to 40,000 centipoises. From these data it is possible to predict power consumption for the majority of mixers in experimental and industrial use. The significance of power characeristics to proper use of impellers and tank fittings is pointed out. A technique is outlined whereby the operating characteristics of any impeller in any tank arrangement and fluid can be found by only a few experimental runs made a t significant conditions.
