Chemical Engineers M e e t in Boston
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Top to bottom. D . P. Morgan of W P B ; J. H . Rushton, University of Virginia; J. C. Elgin, Princeton; and M . C. Moisted, University of Pennsylvania 560
OSTON, convention city for the third time to the American Institute of Chemical Engineers, was host to more than 500 institute members at the 34th semiannual meeting held May 11 to 13. K e y events were the presentation of the Walker Award to E . C. Williams and an all-day Symposium on Heat Transfer held jointly with the American Society of Mechanical Engineers. Dr. Williams, directpr of research of General Mills, is the recipient of the seventh William H. Walker Award. I t was granted to him for his work on the production of synthetic glycerol and reported by him in the 1939 Transactions of the institute. Dr. Williams at the banquet Wednesday evening accepted the medal on behalf of his co-workers a t the Shell Development Corp. where the work was done when he was director of research of that company. James G. Vail, former vice president of the institute and vice president and chemical director of the Philadelphia Quartz Co., made the presentation. Other speakers at the banquet, at which Gustavus J. Esselen, Boston consultant, was toastmaster, were Kenneth E . Bell, chairman of the Boston section and technical director of the A. C. Lawrence Leather Co.; Sidney D . Kirkpatrick, president of the American Institute of Chemical Engineers and editor of Chemical & Metallurgical Engineering; Stephen E . Simpson, professor of chemistry at the Massachusetts Institute of Technology; and James W. Parker, vice president of the Detroit Edison Co. and president of the American Society of Mechanical Engineers. The joint Symposium on Heat Transfer was held on Wednesday with W. H. McAdams, professor of chemical engineering of Massachusetts Institute of Technology, presiding. Nine papers were presented during the day and abstracts appear below. At the business meeting on Monday the A. McLaren White award to the winner of the institute's National Student Chemical Engineering Contest was presented to Charles C. Neas, a senior at the University of Illinois. Second and third prizes, respectively, went to Gilbert R. Shockley, Missouri School of Mines and Metallurgy, and Karl H. Rothe, Cooper Union Institute of Technology. Honorable mentions went to Harold R. Frisbie, Oregon State College, Robert E. Deatz, Kansas State College, and Herbert Kress, Pratt Institute. T h e contest problem this year was prepared by a committee from the technical staff of Monsanto Chemical Co. and was under guidance of the committee chairman, B . E. Thomas. T h e Monday afternoon meeting was devoted to a closed discussion on War Problems of the Chemical Industry and C H E M I C A L
Top to bottom. S. L. Tyler, secretary of the A . I. Ch. E./ H . S. Lukens, of the University of Pennsylvania; J . R. M i n e v i t c h , E. B. Badger & Sons; and E. W . Comings, University of Illinois A N D
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Left to right.
J. R. Huffman, N e w York University; J. L. Bennett, Hercules Powder Co.; James G . V a i l , Philadelphia Quartz Co.
Walter G. Whitman of the WPB presided. The discussion was, at the request of the institute, considered confidential and no report can be made of the information presented. The technical sessions were opened with an address by W. M. Rand, vice president of the Merrimac Division of the Monsanto Chemical Co., whose general subject was "New England Serves Again". Mr. Rand traced the rise of chemical industry in the New England area up to the present time, stating that:
Tower Packings", by M. C. Molstad, A. R. Thompson, J. F. McKinney of the University of Pennsylvania and R. G. Abbey, of the General Refractories Co.
Abstracts of Scientific Papers A. H. Maude, chemical engineer of the Hooker Electrochemical Co., Niagara Falls, N. Y., opened the technical sessions with a paper on "Anhydrous Hydrogen Chloride Gas". The history of the com-
Although some of the roots of the chemical industry were firmly set in the sparse soil of New England, the main stem, the foliage, and the fruits have developed elsewhere. But this does not mean abandonment of New England by the chemical industry. There are some materials which may be found useful—some kaolins, some excellent sands, forests of spruce and hard wood. The contributions of New England to the war effort are not insignificant. It is truly an important part of the arsenal of democracy. In its borders are two large shipyards and many smaller ones turning out battleships, destroyers, cargo ships, mine layers, and smaller craft so badly needed today; two arsenals, two large Army training camps, and an important air base. In addition, its countryside is dotted with hundreds of war plants, ranging from a huge aircraft plant t o hundreds of small machine shops. The Nation looks to New England to supply destroyers rather than smokeless powder, airplane engines rather than toluene, the Garand rifle rather than magnesium, uniform cloth rather than aluminum, machine tools rather than tanks. The technical papers were presented as previously reported in the program and brief abstracts are here included with the exception of three papers, all of which appeared in the April 25 Transactions of the institute. They are "Chemical Engineering Aspects of Centrifugal Fan Design", by Carl V. Herrmann, of E. I. du Pont de Nemours & Co., Inc; "Compressed Air for Ammonia Oxidation", by Donald G. Morrow, Hercules Powder Co.; and "Performance of Drip-Point Grid V O L U M E
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Above. G . J. Esselen, consultant of Boston. Below. G . G . Brown, University of Michisan
M A Y
2 5,
1942
mercial production of hydrogen chloride was traced, and the technical problems in plant construction and equipment design were given. The method described most fully by Maude is the synthetic production of hydrogen chloride by burning of chlorine and hydrogen. Materials of construction depend upon the physical conditions. Early plants utilized silica and brick construction but today metals are used, provided certain precautions are taken such as correct metal temperature to prevent hydrogen chloride corrosion and dew formation. Thus iron may be used safely at 3 0 ° C. and copper a t 5° C. above the dew point. If the gas is cooled to a temperature below the dew point, however, nonmetailic surfaces, such as glass, stoneware, impregnated graphite, and silica are necessary, though tantalum may also be used. Ignition of the gases is yet a problem, the best solution today being a retractable air-hydrogen blow torch. Alternate methods of HC1 production were also given. The principal commercial method of concentrating hydrogen chloride is absorption in water to form a concentrated solution and subsequent distillation and condensation of water from the vapors and drying of the hydrogen chloride gas by sulfuric acid. An alternative method consists in absorbing the hydrogen chloride with a metallic salt in a manner analogous to the addition of water of crystallization by some anhydrous salts. The compound when saturated with hydrogen chloride gas is heated to remove the pure hydrogen chloride from the nonvolatile salt and the latter re-used to repeat the cycle. Among the salts considered are lead and copper sulfates which are thought to form PbS0 4 .2HCl and CuS0 4 .2HCl, respectively. At 83° C , 1.5 moles of hydrogen chloride are removed from the copper salt, but 0.75 mole of hydrogen chloride is still retained at 100° C. In the case of the lead compound 1.5 moles of hydrogen chloride are removed at 32 ° C. but the balance is not removed even at 100° C. 661
Moisture must be absent in such an ab sorption process, and this system is said to work satisfactorily with gases contain ing 50 per cent hydrogen chloride or more. All the gas cannot be absorbed, however, and from 1 to 5 per cent may pass through to water scrubbers. Through the use of carriers for the absorbing salt, equipment now exists which can extract from the gas stream 14 pounds of hydrogen chloride per cubic foot. J. G. McGiffin, Standard Oil Co. of Ohio, gave considerable data pertaining to the performance of a commercial crude naphtha stabilizer. His investigation cov ered six different engineering performance tests run on a stabilizer, 42 inches in diam eter, 61 feet high, and a total of 30 trays spaced at 18 inches except that the 3 bot tom trays were 3 feet apart. Each tray had 18 bell caps, 4 7 / 1 6 inches outside di ameter, and the feed to the tower entered on tray 16. Four runs were made attempting to cut between isopentane and normal pentane and two tests were made to cut normal butane and isopentane. Operation was such as to produce nearly flooding condi tions in the tower. For the particular tower and problem involved, McGiffin concluded that fractionation suffers from flooding, and downcomer liquid velocities in the lower portion of the tower become excessive when the rates are 1.5 feet per second when reboiler weight vaporization to bottoms ratio is above 3 / 1 , or 1 foot per second when reboiler-bottoms ratio is above 1.5/1. He also found that frac tionation is satisfactory when downcomer liquid velocities, in lower portion of tower, are maintained below 0.9 foot per second when reboiler-bottoms ratio is at a mini mum of 1.4/1. Fractionating suffers somewhat when actual vapor velocities exceed the critical velocity as calculated by formula VQ = 4.04
V
TS MPwhereT
=
vapor temperature R°; S = liquid specific gravity at temperature Τ; Μ = vapor molecular weight ; Ρ = operating pressure in pounds per square inch absolute. A summary of experimental and devel opment work conducted during the last five years to bring a grain distillery up to date from the engineering standpoint was given by A. Herman, Ε. Μ. Stallings, and H . F. Willkie, of Joseph E . Seagram & Sons, Inc., Louisville, Ky. In grinding experiments, a subject of great controversy in the distilling indus try, it was claimed that no difference was found between corn ground in roller mills or in hammer mills. This refutes the former belief that roller mills produce flat particles and hammer mills irregular shaped particles. Experiments indicated that roller mills required one third to one half less horsepower per bushel than ham mer mills to produce similar fineness, but maintenance on the roller mill was double 662
the cost for the hammer mill. T h e cook ing process, formerly requiring 2 to 3 hours, is now accomplished on a continuous basis taking only 30 seconds. The slurry of
W. M . Rand of Monsanto's M err i mac Division water and grain, about 25 per cent by weight of grain, is preheated to 165° C. and then passed through a steam mixing jet into a holding vessel. During its pas sage it is cooked as thoroughly as in the old operation. Flow charts of the new low-temperature system for distillation of fermented mash were given. The particu lar advantage of this new system is the production of spirits that are more neu tral. The lower the temperature in dis tillation, the more neutral, relatively, are the spirits obtained. Stillage is recovered by screening to re move solids, and the liquid from the screen ing is evaporated in a five body, quadruple effect evaporator. Through experimenta tion, forced circulation, long tube evapora tors were found to have the best qualities for the problem of evaporating the highly viscous stillage. Three effects, however, have natural circulation, while the last two effects are forced circulation as they evapo rate the most viscous material. " Vitamin assays showed that the sirup concentrated in the evaporators was high in riboflavin and other members of the Β complex. Cattle feed of recovered solids and sirup is made by mixing these two products and drying in drum dryers. "Pumps in the Chemical Industry" was the subject discussed by W. W . Mellen and A. P. Smith, of the E . I. d u Pont de Nemours & Co., Inc., plant at Penns Grove, N . J. Classified into three groups by the authors, centrifugal, positive dis placement, and lift types, pump selection is based on five factors—corrosive action, C H E M I C A L
erosive action, head and specific gravity, temperature, and viscosity. In selecting pumps for corrosive services the authors made the following observa tions: for pumping hydrochloric acid, centrifugal pumps of durochlor are used extensively up to 30 per cent acid and from 30° to 40° C. High chrome nickel iron alloys are used for sulfuric acid of 72 t o 98 per cent con centration, whereas acid of 100 per cent and over can be handled by cast steel. For lower concentrations hard lead or high silicon iron may be used. No satisfactory practice exists for hydro fluoric acid. For acid above 60 per cent a small inexpensive cast iron gear t y p e pump with direct motor drive, having a capacity of 20 gallons per minute, is used. Pumps are replaced frequently and no re pairs attempted since cost of the unit is low. Carbon may prove to be a good ma terial for this acid in the lower concentra tions. Mixtures of nitric acid and sulfuric acid of varying compositions are pumped with horizontal externally mounted pumps, t h e materials of construction being high chrome nickel alloy. Dowtherm and diphenyl at tempera tures up t o 200° C. are pumped with a centrifugal internal bearing type pump, of Ni-resist casings, carbon steel rotors, bronze bushings, and Nitraloy shaft, sleeves. For pumping lead a t 450° C. a special pump was designed having enlarged steel shafts of precision finished steel and high tensile strength. The pump column w a s fabricated from steel pipe having welded steel stiffening ribs, bearing surfaces were Stellited, and discharge lines were 18-8steel. It was found that a system of regular inspection and maintenance repair by a crew of trained pump specialists played an important part in minimizing breakdown. For an increase in production of 100 per cent, the increase in pump maintenancecosts in locations where pump inspections, were not provided was four times as great as in comparable locations where pump i n spections were systematic. The fundamental factors influencing t h e performance of rotary dryers was the con tribution of C. O. Miller, Case School of Applied Science, B. A. Smith, Bartlett and Snow Co., and W. H . Schuette, D o w Chemical Co. Direct heat rotary dryers were investigated for heat transfer rela tionships representative of a system re moving surface moisture from nonhygroscopic materials. D a t a were collected on the effects of temperature difference, air velocity, number of flights, flight size, and retention time. The rate of heat transfer (for similar operating conditions) was found t o be di rectly proportional to the temperature dif ference. Increased air velocity results in A N D
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NEWS;
a more efficient removal of moisture, since too low a velocity leads to the air becom ing saturated before traveling the length of the dryer. The effect of the number of flights was expressed as a slope of 0.69. This appeared as a power for the number of flights in the final equation indicating an increase of heat transfer rate for in creased nights. The heat transfer was independent of the retention time. After comparing the experimental results with several large-scale installations the authors obtained the following expression for pre dicting capacity for rate of heat transfer in a rotary dryer. Q/Θ = 0.85 £,/>«/··«·
