Reports
I/EC
This month—reports on pressure packaging and model dust precipitators to M a r s ' moons and geological prospecting
Aerosol's Little Brother PressurePacking Grows Up Pressure-dispensed toothpaste is first on the market, but a number of food products are just a step a w a y from being on the shelves of your favorite supermarket I OOTHPASTE in a can ! This might be a "What will they think of next?" item. Truth of the matter is, it's only the beginning. Thinking caps of producers have their direction finders pointed to what next to put into cans—products that you're long used to seeing in glass bottles. These are special cans, or pressure containers, and the packaging is pressure packing. There is a basic difference between the familiar "aerosols" of the past few years and the types that are represented by the pressure packed dentifrice. The familiar insecticides, space sprays, shave creams, hair sets and paints, etc., employ low boiling organic propellants. When these propellants are used, the product as it emerges from the container includes substantial amounts of the propellant. In some cases this can result in an expanded foam, in other applications an extremely fine spray. With pressure packing, however, the propellant is gaseous and practically insoluble in the product in contrast to whipped cream where the gas used is selected for its solubility in the cream. Nitrogen is employed for the dentifrice and provides sufficient pressure to expel the product from the container without altering the physical or chemical properties of the product. The aerosol idea was first used in restaurants and drug stores for dispensing cream and toppings, and the patents were held by G. Frederick Smith. However, impact on the household market came with the 26 A
Dixie Reddi-Wip Corp.'s introduction of its aerosol whipped cream, Reddi-Wip, in 1949. I / E C published a report on the details of formulation and packaging of ReddiWip in the August 1949 issue. I/EC's earlier report also predicted that aerosol products would be a forerunner of pressurized foods such as waffle batter, toppings, and catsup, and medicinals and shaving cream. How prophetic it was is now showing with the coming of Colgate's pressure-packed toothpaste. Colgate
uses nitrogen to propel the toothpaste from the can. It is reported that production of pressure packed products differs from conventional aerosols primarily in the type of gassing equipment used. The only change needed on the regular squeeze-tube toothpaste is a slight modification to its viscosity. So far only Colgate is out with such a product, but Procter & Gamble and Lever Brothers are reported to be near the marketing stages with similar products.
ACTUATOR
HOLLOW NYLON VALVE STEM RUBBER GASKET
VALVE MOUNTING CUP
NYLON VALVE HOUSING
COMPRESSED GAS PROPELLANT
DENTIFRICE DIP TUBE (POLYETHYLENE)
D i a g r a m shows details o f the inside o f the pressure container f o r dispensing toothpaste. By pressing the actuator, the v a l v e stem is l o w e r e d into the nylon valve housing, causing the r u b b e r gasket to flex u p w a r d , exposing holes in the w a l l o f the v a l v e stem to the toothpaste. A steel spring (not shown) on the bottom of the valve stem pushes the stem up a n d closes the v a l v e , as soon as pressure on the actuator is released
INDUSTRIAL AND ENGINEERING CHEMISTRY
Information
Analysis Interpretation
The Future
Robert Hollister, American Can Co.'s assistant national sales manager in charge of pressure cans, thinks that pressure packing is leading to a whole new family of food products. Canco's research laboratories are busy working on reformulation of foods for pressure packing—for example, honey, fruit toppings, jams and jellies, cheese spreads, catsup.
Solar Furnace — Small Scale No fuel; no flame to blow out. While the world is focusing its attention on solar furnaces for power generation, John Garrett Thew of Westport, Conn., has focused the sun's rays by a 4.5inch paraboloid of polished aluminum, and has a practical cigarette lighter—a sort of benchscale furnace. Rough figures for your engineering curiosity: 2inch focal length, theoretical concentrating power 30,000 to 1, estimated 3000° C. temperature and 10-watt equivalent of sunlight gathered. We tried it: a light in 3 to 4 seconds in bright sunlight; Christmas-type spotlight (for gray days) took a little longer, infrared still longer—up to a minute. Meantime, we're just waiting for the beach season, where wet matches and wind are always problems.
Slim Designs Plastic models p a r e pounds of metal off electrostatic precipitators; point to lower costs S ÏSEARCH-COTTRELL has taken to three dimension views of electrostatic precipitator designs to save money for themselves and their customers. Through scaled transparent models, researchers can explain how smoke gets to the precipitator and whether or not it gets there the most efficient way. And, if it doesn't, can make changes until it does. As these models correlate directly with full scale precipitators, the results mean better designs and lower construction
I/EC
and operating costs for industrial gas cleaning systems, adds R-C. Important too, says R-C, these models can bring the precipitator industry out of the custom-designed class and into the standardized product class—not right now, but certainly at some future date. Today, precipitators are custom designed to fit into a given space. Others make component parts of the system such as flues and blowers, and these designs were also based on available space. Flues, for example, often ended up with short ducts and sharp turns which interfered with gas flow to the precipitator. Models exposed these deficiencies; showed how sharp turns increase turbulence and that baffles, flow splitters, and vanes have little effect on guiding gas flow to the precipitator—when looked at in 3-D. Hoppers, designed to trap dust in flues, really kicked the dust around more and contributed to pressure drop. Research-Cottrell points out that pressure drop costs from $40,000 to $80,000 an inch. Models can show how to design flues which reduce this pressure drop. Since flues proved so important to (Continued on page 28 A)
W h a t A b o u t the Containers?
So far, the tinplate can seems to have the edge on the market. But there are a couple of dark horses to watch. Du Pont is doing considerable work in the blow molding of nylon containers for pressure products. Aluminum containers may be available shortly. The plastic-coated glass bottle is another. Several major glass bottle suppliers are waiting only for the nod from food or pharmaceuticals producers. Rexall Drug Co. has already introduced an aerosol merthiolate preparation in a light red, plastic-coated glass bottle.
Dust s e p a r a t i o n patterns in exit flues o f m o d e l show areas o f low velocity and high turbulence. G a s is introduced into the exit flues f r o m the p r e c i p i t a t o r b y turning vanes. Precipitator p a r t o f model does not o p e r a t e and is included in models only f o r its effect on gas flow and pressure d r o p VOL. 50, NO. 4
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APRIL 1958
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I/EC
REPORTS
Electrostatic Precipitator C a p a c i t y Continues to Soar Year 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1960
Million Cu. Ft. Capacity 82.9 93.9 109.4 118.8 125.0 135.1 156.1 167.8 178.3 195.1 215.7 253.9 276.4 320 (est.)
precipitators, R-C has decided to branch out into flue designs. The long-range objective is to offer in dustry basic designs. Also planned, are smaller precipi tators—up to 2 5 % smaller than those made today. Reduced size is still a long-range idea, -but in the same thought is standardized pre cipitators. Precipitators would then cost less. Today's price ranges from 50 to 75 cents per c.f.m. of gas treated. This means that a unit which treats 1,000,000 c.f.m. would cost up to $750,000. As this price represents a custom job, the customer pays for design and engineering costs as well as custom fabrication and erection costs. Smaller units would also mean less plant space and lower power costs—the latter because pre cipitators can be made to treat gases at higher velocities, hence lower the costs per c.f.m. treated. And, smaller precipitators would mean less material costs. In the past, an overcapacity or safety factor was built into gas cleaning systems to account for uneven gas flow.
Now that R-C, through its models, has a way to control gas flow, this safety factor can be reduced. A precipitator is usually a unit that reacts 30,000 to 40,000 c.f.m. Smaller units would naturally broaden the market for R-C and possibly other precipitator manu facturers. Firms which could not consider them economical may now find units coming in a more attractive price range. Research-Cottrcll has integrated model studies into precipitator sales contracts. The firm will now design the flues which lead to a precipitator (or flues which go anywhere else). These studies, says the company, cost about 1 to 2 % that of the precip itator but lead to immediate cus tomer savings today through better precipitator operation—but still smaller costs tomorrow as the com pany's long-range ideas take shape, with models of course. W.S.F.
Mars' Moons First? Initial space flights may by pass moon because of its g r a v i tation; Martian satellites could be alternative target
N,
IEARLY a century ago Jules Verne wrote about a trip to the moon. Since then, science-fiction addicts have considered many fanciful ways to get there. But not all scientists agree that man will visit the moon first. Jan Schilt, head of Columbia University's Astronomy Department, believes that our moon will be bypassed by space pioneers. One of the moons of
Mars, he feels, may be the most practical destination for the initial round-trip space flight. It's true that the distance is much farther to a Martian moon than to our own—a minimum of 35,000,000 miles as against 234,000. But Schilt, director of the Rutherford Observa tory, says that the distances involved in interplanetary space travel may be of less practical concern than fight ing the moon's gravitation in landing and taking off again. A M o n t h to M a r s
A trip to the vicinity of Mars might take about 4 weeks, Schilt feels, given a great enough initial launching speed. Minimum orbital speed around the earth is 18,000 m.p.h. Between that velocity and 25,000 m.p.h., an object can orbit farther and farther out. Above that speed it can escape into interplane tary space. And the farther out the orbit is, the less the gravitational pull and the easier it is to accelerate. At 50,000 m.p.h., a ship could reach Mars in less than a month. Once in space at a desired speed, no further fuel would be needed to cruise. Schilt foresees sun-powered ionicthrust mechanisms for directional control as well as for supplemental acceleration. Details of an ionic rocket engine were given in a report in the August 195ό"(ρ. 15 A) I / E C . The tiny Martian moons, Deiinos and Phobus, are only 5 to 10 miles in diameter and possess negligible grav ity. Once in orbit around Mars, a spaceship could land or take off from one or the other moon at relatively little cost in fuel. For the return trip to earth, only enough power would be needed to accelerate from orbiting speed to cruising velocity. M o o n Landing Complicated
Man may be jumping off for Mars' moons from space stations which could look
like this
To land on and blast off again from the moon, more difficult problems would have to be solved. For one thing, Schilt says a greater counterthrust from the ship's rockets would be required for a lunar landing than for a landing on earth from space. Although gravitation is less there, the moon does not have any substantial atmosphere to slow down the falling vehicle. The necessary "braking" {Continued on page 32 A)
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INDUSTRIAL AND ENGINEERING CHEMISTRY
