I&EC REPORTS & COMMENTS Producing high vacuums through adsorption Eliminating the pilot plant stage Choosing productive areas for industrial research
CRYOSORPTIVE PUMP Space technolopy enters the civilian market The nation's space program contributes much technology which can be adapted for civilian use. An example is cryosorptive pumping, a method which combines Molecular Sieves and cryogenics to produce ultrahigh vacuums. These pumps solve a vexing problem for space simulation chambers. Noncondensable gases such as hydrogen and helium could not be removed by other pumping methods, therefore space simulators were not duplicating conditions beyond 300 miles above earth. Such conditions, expected in the Apollo "Moonshot" program, were not a problem in earlier space efforts. Pressures of less than 10-18 torr are anticipated. This method has been successful in space simulators, and will have wide use in civilian technology. Possible applications include vacuum metallurgy, vacuum tube systems, high energy accelerators and chemical processing under vacuum. Here, removal of the noncondensable gases achieves the extremely clean high vacuum desired for these processes. Union Carbide's Linde Division developed the process under an Air Force contract at Arnold Air Development Center, Tullahoma, Tenn. The system successfully achieved the desired torr (lo-" mm. of Hg absolute pressure). Best previous result of cryopumping was 10-'0 torr. Here is how cryosorptive pumping works. Pumpdown is initiated using a liquid nitrogen-refrigerated cryosorption rough pump. Heating of the chamber is started as soon as it has been evacuated to the 10-
micron range. Heating activates the cryosorption panel and continues concurrently with rough pumping for 10 to 12 hours. Rough pumping of air achieves a vacuum range of 1 micron to 10 microns. The valve to the auxiliary helium refrigerated cryosorption rough pump is opened and rough pumping is completed to lo-' torr. The chamber walls are cooled to ambient temperature as soon as heating is completed. Liquid nitrogen and liquid helium cool the cryopanels from 80' K. to 20' K. The cryosorptive vacuum pump contains liquid helium-cooled Molecular Sieves (Linde 13X) bonded directly to the helium reservoir. The sieve absorbs helium and hydrogen vapors to maintain a temperature of 4.2' K. with the aid of attached internal A hdium-coolcdpnecl ns to lo-" 11
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copper fins. A seven-liter stainless steel vessel acts as a helium reservoir. Plate and disk baffles refrigerated by cold helium vapors provide thermal radiation and act as a cryopump for removing easily condensed nitrogen and oxygen. Removal of these gases, at the baffles, leaves a higher panel capacity for cryosorption of the lower boiling gases. Only periodic topping-off with liquid helium is required. The vacuum casing cooled by liquid nitrogen intercepts room temperature radiation and cryopumps water vapor. The upper surfaces of the plate and disk baWe are painted with a highly emissive coating to increase the baffle's efficiency as a radiation shield. Stainless steel thermo resistance and copper thermal conductors, lo-
molecular sicvcs absorbs helium and hydrogen unpors to achicua
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I&EC R E P O R T S
cated along the helium fill and vent lines minimize the fill and steadystate liquid helium losses. The upper opening of the pump is connected to the vacuum system with a 6 in. shear seal flange with copper gasket. Although no clear market picture is evident, Linde’s sales division is presently taking orders for these pumping systems on a special-order basis. As to the future, Linde plans to continue marketing standard items for the system. 30 decision to license the manufacture of these units has yet been announced.
DROPPING THE PILOT Is the pilot j l a n t becoming obsolete? Eliminating the intermediate steps in process scale-up from bench to plant becomes more an economic necessity and less a n academic ideal. Examples of the successful elimination of piloting are few, and fewer still are those with the textbook success of the Goodyear-Scientific Design isoprene process. I n describing the results of their design, begun in 1961, J. J. Garmon, W. E, Morrow, and V. J. Anhorn of Goodyear contend that the scale-up problem isn’t as formidable as it may seem. There is always risk involved, but added to their rapidly increasing pool of experience with large scale-up factors, today’s chemists and engineers have available improved bench-scale equipment for laboratory studies, rapid and accurate analytical equipment, high speed computers for modeling, and better statistical methods for minimizing human bias in experiments at the bench. The principal object in designing the Goodyear plant was to obtain polymerization grade isoprene from the dimerization, isomerization, and pyrolysis of propylene. Scale-up factors ranged from 1000 for the more active catalysts in the isomer14
INDUSTRIAL AND ENGINEERING C H E M I S T R Y
izer to 20,000 for the critical pyrolysis furnace. The success of the design is best seen in the exact agreement between the product analyses for the benchscale dimerizer and the plant reactor ; the over-all agreement was nearly as good. The greatest problems encountered in the design were obtaining sufficiently precise data on the properties of the materials and development of the model for the computer. As demonstrated for the National Meeting of the A.1.Ch.E. in Boston, these problems were ultimately solved.
CHOICE OF RESEARCH PROJECTS The most dzficult task in objectiz)e research is to determine the direction From the U.K.’s Gas Council comes a discussion of the place of basic research in an industrial organization, and of the kind of projects which should be undertaken there. In a report presented before the meeting of the Institution of Gas Engineers held last November, J. A. Gray described che application of such planning in the Gas Council Basic Research Group. He divided basic research into fundamental, pure, or academic research on the one hand, and basic applied, objective or speculative research on the other hand. Using Dr. Gray’s definitions, both types are carried out to increase the knowledge of the nature of the material world. The pure variety follows a line of investigation selected to satisfy the intellectual curiosity of the individual worker. Objective basic research is defined as “an exploratory search for knowledge that can be used technologically, and the criterion that projects must satisfy is that of relevance to the industry.” Dr. Gray points out that the universities are ideally suited to conducting (Continued on page 16)
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Any particular uses i n mind?
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Pump in 3 1 6 S t a i n l e s s Ampco’s modern design lengthens pump-life and steps up efficiency several ways:
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Interface velocity is reduced losses by hydraulic friction, shock, a n d turbulence are practically nil. Velocity, corrosion and abrasion are held to a minimum. Pressure break-down areas are restricted to parts that axe inexpen-
sive a n d convenient to replace. Casing and shaft are protected new-pump characteristics are maintained longer. I n addition to stainless steel, Ampco Centrifugal Pumps are available in Ampco aluminum bronze and Illium “G.” Elastomer-lined pumps are also available. Representatives i n principal industrial areas. Write for Bulletin P-3c. Do it today.
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P.48
Don’t overlook EFFICIENCY
,
. .it’s a yardstick o f performancef
A M P C O METAL, INC. Dept. 149-A, Milwaukee, W i s . 53210
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I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
pure basic research, in fact, industry often sponsors pure research within the universities. He notes, Iiowever, that in the British universities there is a conspicuous lack of research of the kind directed to new chemical processes. These institutions therefore make little contribution to large areas of cheniistry. This lack represents the gap bethveen science and technology, and it is the basic research group in industry that is particularly suited to bridge this gap. If this is the aini of objective basic research, the task is a most dificult one. The research workers must be familiar with both the underlying science and the industrial technology. The most promising areas of ivork are those which are relatively neglected, the problems are complex, the techniques difficult. Yet Dr. Gray feels that the greatest difficulty is the evaluation of lines of investigation, and the choice of a program most likely to lead to technologically significant recovery. This program must be chosen by the scientists themselves, because only those with adequate background and training can evaluate the trends in science, and hazard a guess as to what may be possible in the future. The scientists must then accept full responsibility for the projects they chose to study, within guide lines set by management. Dr. Gray recognizes the role of chance in scientific discovery, but disposes of the argument that chance has been the major factor in scientific breakthrough. He points out that several ”chance” discoveries resulted from systematic investigation of research areas which meet his major criteria : relevance to the industry, and little prior investigation. Once begun, such studies can hardly fail to lead to the “chance” breakthroughit remains only for the scientist to recognize his opportunity. And it should be remembered that chance continues to operate even in the most promising areas.
