TECHNOLOGY
Chemistry's High Stake in Sonics Sonic processing, measurement and controi are two big Fields of future application Pulsation is practical for increasing extraction efficiencies with packed columns CINCINNATI.—The use of sonics as a tool is by no means second nature to the chemist and chemical engineer, but the chemical technologist of the future will b e referring more and more often to work of an acoustical nature. This theme ran through the annual Christmas Symposium of the ACS Division of Industrial and Engineering Chemistry, recently. It probably didn't surprise many of the members of the Acoustical Society of America, who participated with the ACS in this discussion of pulsatory and vibrational phenomena, but it is safe to say that a good many ACS members present were overwhelmed, both by the field of pulsatory and vibrational phenomena itself and by some of the possibilities of its application in chemical fields. A man who sees both sides of the coin—a chemist who represented the Acoustical Society—reviewed the overall picture and listed several aspects of sonic processing as promising the most immediate future in application to chemical subject. Ernest Yeager, Western Reserve University, said that application of sonics should be very useful in the formation of suspensions and in coagulation effects, in degassing, crystallization, grinding and cutting applications, and many other effects. Ultrasonic degreasing and soldering equipment is available commercially, he said, and it may b e possible to use ultrasonics for thermal bonding. The ratio of separation of deuterium and hydrogen in heavy water production is considerably improved b y use of ultrasonics. Sonochemistry (such as food processing), Yeager said, is still in its very early stages, and efficiencies and yields are poor. More and more, he predicted, interest will be shown in determining fast reaction rates, and this can b e done by the study of relaxation effects through absorption measurements. Later in the meeting Yeager, with D. O. Myatt, Atlantic Research Corp., and chairman of the symposium, led a panel discussion participated in by Oscar Mattiat, Clevite Brush Corp., E. A. Heidemann, of Michigan State's physics department, Wilfred Roth, Rich and Roth Laboratories, and Adelbert Tischler, Rocket division, NACA L a b oratories. Yeager points out that the 316
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study of shock waves in metals, mentioned earlier by Thomas C. Poulter, Stanford Research Institute, might b e an extremely good tool for the study of the solid state at extremely high pressures (Poulter gave pressures as high as 500,000 atmospheres ), a n d indicated also t h a t there appears to b e some r e lation between r u p t u r e in metals and cavitation in liquids.
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North American's unit for determining dynamic response of pressure pickups Looking over t h e field of using sonics measurement and control, Roth divides it into three areas: where the material under test is t h e source of vibrations, where the properties of the material effect vibrations from external means, and w h e r e the material affects operation of t h e equipment producing the vibrations. Under t h e first class he includes detection of fractures in opaque plastics a n d t h e technique of producing a sound spectrum, for detecting fractures. T h e second includes use of t h e reflectoscope to detect flaws and t h e testing of effect of additives b y absorption methods. For the third, w h i c h is an application using low intensity sound, he describes t h e instrument known as t h e Ultra-Viscoson, an ultrasonic probe of Bendix Aviation, which is used to measure automatically the viscosity of liquids. Typical industrial uses of this instrument are for quality control in oxidation of asphalt a t t h e oxidation point (500° F.) and i n color control of printing inks. The lowest limit of quantity at which the instrument can b e used, Roth said, is a few drops, and the maximum operating t e m p e r a t u r e of the p r o b e is normally a b o u t 650° F . T h e probe works in m e r c u r y a n d molten solders, h e said, a n d might b e used w i t h liquid
metals if t h e operating temperature can be increased. Types of transducers for processing applications, according to Mattiat, include ultrasonic sirens for smoke precipitation, the liquid Pohlman whistle for emulsifying liquids u p to a sevengallon per minute flow, a n d a new transducer for depolymerizing liquid high polymers. Comhustion-driven oscillation problems in combustion systems can b e identified as coupling of an oscillating mechanical system with the combustion reaction, say Tischler. Among t h e many interesting answers to questions posed to the panel by members of the audience were two which indicated that t h e use of ultrasonics still seems to fall short of successful coagulating in crude oil desalting, a n d that ultrasonics has not yet been successful in breaking foam because of t h e difficulty of getting ultrasonic energy into air. Eliminating Inaccuracies. Many physical a n d chemical processes requiring pressure oscillation measurements take place at elevated temperatures and pressures. Pickups m a d e to stand extreme conditions cannot be calibrated by conventional methods. R. B. Lawhead of North American Aviation, says that experiments show it is probably safe to assume that the dynamic sensitivity of a pickup will be accurate to within 20% of that determined from a static calibration, u p to frequencies of 3500 cycles per second. In equipment used by North American for determining dynamic response of pressure pickups, the pickup to be tested is placed in a small cylindrical chamber excited acoustically with a loudspeaker. Both are flush with the end walls of the chamber, placing them Robert Lemlich of the University of Cincinnati says that the coefficient of heat transfer is not altered when direction of vibration is changed. To demonstrate a lit cigarette is held under a wire in horizontal vibration. The smoke curls up and around the vibrating path with none appearing to pass through the path
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TECHNOLOGY at positions of maximum pressure variation. By doing t h e same with a standard calibrated microphone and comparing the results, a dynamic frequency response-calibration curve can be obtained. Effect of Vibration on Heat Transfer. Natural convection from electrically heated wires subjected to transverse vibration in air has been studied at t h e University of Cincinnati to determine the effects of vibration on heat transfer. According to Robert Lemlich, vibrations can materially increase the coefficient of h e a t transfer, and with other variables held constant in turn, the coefficient of heat transfer increases with amplitude and with frequency, decreases with diameter, a n d shows no change when direction of vibration is changed. To explain this latter observation, h e proposes the concept of a "stretched" film surrounding the entire path of vibration, instead of being carried back a n d forth b y the wire. A lit cigarette is held under a wire in horizontal vibration. The smoke curls u p a n d around the vibrating path, with none appearing to pass through the p a t h , supporting the concept of a streched film. Lemlich also shows that the effect of the vibrational variables may be correlated in terms of a vibrational Reynolds number defined as twice the product of amplitude, frequency, linear dimension, a n d density, divided b y viscosity. Pulsed Columns for Extraction. Some very interesting conclusions have been drawn as a result of work done at Cornell on application of pulsation to liquid-liquid extraction. Both packed and sieve plate columns were used, employing two types of pulsators, and electric motor driven copper bellows, and a proportioning p u m p with valves removed and inlet line sealed. For packed columns, R. V. Von Berg says that application of pulsation is practical for increasing efficiency, and can reduce the column height required as much as three times. Best operating conditions are with both frequency and amplitude of pulse varied, but greater efficiency can be obtained with the proper low amplitude at high frequencies than is possible at low frequencies. Changes in feed rates h a v e less effect o n efficiency when pulsation is used than with the usual packed column operation. The only negative factor introduced with pulsation is a slight ( 5 to 10%) reduction in maximum throughput. F o r sieve plate columns, average plate efficiencies as high as 70% can b e obtained when t h e columns are pulsed. High throughput rates compared to packed column capacity m a y b e used with high efficiency. Smaller perforaVOLUME
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tions give greater efficiency b u t seem prone to corrosion and clogging problems as well as reduced capacity. Discussing the power requirements for pulse columns, A. C. Jealous of Oak Ridge National Laboratory developed an equation for the theoretical total power that must be applied by t h e puiser to a liquid-liquid system in a sieve plate column and said that performance of a 24-inch column, 50 feet long, fitted this equation, with t h e maximum power requirement being less than five horsepower. Why Chemical Reactions with Sound Irradiation? Trying to answer this question, Virginia Griffings, Catholic University, starts with the experimental fact that no observable chemical reactions take place under such conditions unless there is a permanent gas dissolved in the solution and t h e sound intensity is high enough to make t h e liquid cavitate. As a result of her experiments, Griffings feels there is conclusive proof t h a t chemical effects directly produced by ultrasonics are thermal gas phase reactions—they take place inside the gas bubbles. However, she says, it is impossible to completely rule out the possibility that t h e mech-
anism may be gaseous discharge inside the bubble rather than temperature. At present she is re-examining data and has initiated new experiments to try to settle this question. Other Applications of Sonic Energy. Sonic energy is becoming more and more applied in the fluidization of granular solids, but the designer often finds his solid does not have the characteristics which allow free flow. Fine granular materials ( such as encountered in the increasing application of fluidized beds to ore reduction) are often in this category. Low-frequency (50 to 500 cycles per second ) sonic energy, above 110 decibels in intensity, after absorption in beds about one foot deep was found by R. D . Morse of DuPont to markedly improve fluidization of nonfluent, fine-grain powders. It does not improve fluidization of coarse, freeflowing granular materials. Transverse vibration will also aid in promoting the flow of small-particle, nonfluent materials, but poor mechanical coupling between the walls and the particles, with consequent damping of the vibration in the intermediate layers of material, may limit its effectiveness.
Profits D o w n , Research Stays High fibers,
Low profits fail to stymie textile r e s e a r c h ; n e w finishes, processes, products stimulate industry
N E W YORK.-Although 1954 was generally unsatisfactory profit-wise for t h e textile industry, the never-ending need for something new, something cheaper, or something better continued to encourage research activity. Shrinking profits bring hope that research may b e t h e panacea, declares J. B. Goldberg, consultant, to the American Association for Textile Technology. Acrylic fibers showed a great deal of pilot plant activity last year, says Goldberg. American Cyanamid's "X-51" was replaced by "X-54", while Tennessee Eastman was said to b e conducting limited mill trials on a continuous filament version of their experimental acrylic fiber. Eastman was also reported to be evaluating a new polyester fiber, identified as "S-50". A triacetate fiber developed by Celanese was announced in October; is "probably entitled to be called the first new baby of 1954", declares Goldberg. Features of low moisture regain, quick drying, good wrinkle resistance, pleat and crease retention, dimensional stability, ready dyeability with good color fastness, high ironing temperature, coupled with comparatively low price 2 4,
1955
of 55 cents per pound encourage a number of mills to evaluate this newest addition to the ever-increasing family of man-made fibers. Three new manufacturers of nylon " 6 " caprolactam fiber and yarn were in limited production by the end of the year, says Goldberg. Also, under construction is a comparatively small plant for the manufacture of 10 denier nylon filament yarn from regenerated waste. Unconfirmed rumors mentioned two additional nylon-like fibers. "Efylon," derived from waste materials in Germany, was» said to be superior to nylon, and Russion "Nitrilon" claimed to be at least equivalent to nylon but more like natural silk, offering greater heat and light stability. Further developments on cyanoethylated cotton await results of large-scale evaluations now being carried out. Practical applications and costs were studied with pilot plant production. Construction changes in the Barotor dyeing machine eliminate sliding bars, permit three hour dyeing cycles without use of a carrier. And a new hydrocarbon product removes the itch from wool, eliminating allergies. 319
