Rtmospheric Pollution Pilot plant studies at U. S. Steel have provided design data for a plant which will remove and dispose of fumes from their ferromanganese blast furnace
T
HE Defense Production Administration is urging the active collect‘on of scrap iron and steel throughout the country to aid the defense program. Admittedly the best source of such scrap is the automobile salvage yards of the naton. The American Iron and Steel Institute est’mates that there are a p proximately 6,000,000junked cars in these graveyards and that there are 25,000 such depositories. A juaked auto yields an average of 1 ton of high grade steel scrap. Bethlehem Steel Corp. has developed a portable crane which employs a %ton “drop” to flatten the vehicles into a foot thick package for easy transportation. The flattened cars are transported ten to a cargo on a trailer truck. Prior to flattening the nonferrous materials-wood, rubber, plastics, paint, and upholstering-are burned out of the bodies. Burning is necessary to remove sulfur and other objectionable substances that would build up in the fur-
naces if the combustible material were charged with the scrap. These combustible materials are not easily burned after flattening but before the bodies are cut up for charging to the furnaces. Burning off the bodies has encountered opposition in many air pollution conscious cities because of the smoke, fumes, and odors that are generated. Incinerators are not now available for burning out the combustibles, and it is doubtful whether the ceiling price of $40 per ton for such scrap would permit their construction even if time and construction materials were available. This is one of those situations which calls for cooperation between the scrap industry and the public. Some alleviation of smoke and odors has been obtained by manual removal of rubber and plastics before the body is set on fire. Burning single vehicles instead of setting them on fire in great piles also has been effective in holding the nuisance within bounds. A proper
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* (I)
I micron Figure 1.
November 1951
Eleoti+onMicrophotograph of Unburned Fume
regard for weather conditions would be of further help. Burning in fog or in early morning when ground inversions are common should be avoided. Clear weather and gentle air movement is the best time for such operations consistent with local fire regulations.
New York smo@ I n the forenoon of September 12, coincident with the Section 1, air and stream pollution meetings of the XIIth International Congress of Pure and Applied Chemistry, New York City put on a demonstration of air pollution that Los Angelinos in attendance considered equal to their particular brand of smog. Indeed there was considerable discussion in the local press as to whether this was a true “smog” or only smoke and fly ash mixed with a good Atlantic fog. Regardless of the semantics the visibility was reduced to four or five blocks, and there was appreciable eye irritation. On this particular day temperature inversion was prevalent over a considerable part of the region, and complaints of irritating air pollution came from several places in the greater New York area. Just now New York is going through one of those domestic Donnybrooks that is too often characteristic of air pollution work. It is understandable under the circumstances that the most obvious sources of air pollution receive credit for the trouble and that enforcement officials and the public exert pressure for abatement of the suspected contaminants. Reduction of smoke and fly ash is a commendable objective which if attained will bring appreciable improvement, but will the results measure up to expectations? Many who are familiar with such problems suspect that Manhattan’s air pollution is not entirely of its own making. This would not be the first time that smog has ignored political boundaries. A survey by qualified technicians to (Continued on page 136 A )
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Atmospheric Pollutlon determine the quantity and kind of objectionable contaminants in the air in the greater New York area at this time would be helpful to everyone concerned. Such a base of reference is assurance against disappointments later 011.
G a s cleaning ia the
eteel Indnetrw Bishop (1, 8) of United States Steel Co., Pittsburgh, Pa., and his associates recently have published two papers on air pollution abatement in the steel industry. The first emphasizes the progress that has been made in studying the open hearth, Bessemer, and blast furnace problems and the second reports the work undertaken by the United States Steel Go. in developing a practical method for removing and disposing of fumes from the ferromanganese blast furnace. The first step in the cleaning of ferronianganese blast furnace gas was to define precisely the problem in terms of fume loadings, fume composition, gas flow, gas composition, and temperature, and t o obtain several hundred pounds of the fume for use in developing a disposal process. The manganese content of the fume collected vayies from 15 to 25% (Table I) and the alkali content from 8 to 15%. The high alkali content presents a problem in the recovery of the manganese for use because of possible damage to the wfractory lining of the furnace. I.
TABLE SOME C H E M l C A L AND PHYSICAL PROPERTIES OF FERROMANGANESE FUME
Per Cent hlanganese 15-25 Iron 0 3-0.5 Tota! alkali (as .”;azoand KzO) 8-15 SiOt 9-19 .4180a 3-1 1 cao 8-15 hlgO 4-6 Total s (as SO,) 5-7 Carbon 1-2 Ayyaient density 12 (lh./cu. ft.) Particle size (aveiage) 0 . 3 (Micron)
The particle size range (Figure 1) was 0.1 to 1.0 micron, the average being approximately 0.3 micron; such fine material presents a problem in handling the fume and treatment after collection. High energy wet washers, a sonic corigihtor, and an electrical precipitator were considered for cleaning the blast furnace gas. Wet washers were not used because of the reported high maintenance cost due to the cementing prop(Continued 011. page 138 A ) erties of 136 A
Atmospheric Pollution the fume and the necessity of large wale water treating facilities. Some preliminary testing was done with the sonic coagulator ( 8 ) but it was concluded that, in its present state of development, it is not attractive. After redesigning the gas conditioning equipment, previously used with an electrostatic precipitator on ferromsnganese fume, this equipment waa used. A plate-type precipitator was installed in the pilot plant with a guaranteed 98% removal of fume. The precipitatoi performed as guaranteed at normal throughput. At 20% overload in gas flow, its collection efficiency dropped to 91%. At normal flew but with no gas conditioning, the cleaning efficiency was reduced to 83%. The fume wm found to be pyrophoric. If heated to 350’ F. and exposed to air, it oxidized with considerable liberation of heat. The manganese oxides were further oxidized and the carbonates decomposed. A process was developed for briquetting the fume for storage in the open. It was found that half the alkalies could be leached from the burned dust prior to brIquetting, but the manganese content of the product is still too low to encouragd ts use except under Emergency conditions. No fume discharge was vis ble from the stack on which the pilot plant WLS installed. While the loading of the :leaned gas entering one boiler was about 0.12 grain per standard cubic foot, the stack effluent loadings were only %bout 0.05 grain per standard cubic foot because of the dilution of the gaa lvith air used for combustion. In the pilot work, which is described z t length in the original paper, emphasie s given to the operation of the spray ;ower, precipitation, and pyrophoring riln, but all parts of the plant were operLted R sufficient length of time to provide .lata for the design of a plant to clean 135,000 standard cubic feet of ferronanganese blast funrace gas per minute.
Ctteraturs eCted .1) Bishop, C. A,, “Air Pollution Abatement in the Steel Industry,” Yearbook, American Iron and Steel Institute (1950). 2) Bishop, C. A., Brisse, A. H., Thornpaon,
R. G., Liebel, C. R., and Swaney, W. A., “Cleaning Ferromanganeae Blast Furnace Gas,” Ibid. (1961). 3) Brisse, A. H., 2nd. Healing (November 1950). Zorrespondenoe oonoerning this oolumn will he orwarded promptly if addresred to the author, 6 Editor, INDUSTRIAL A N D E N Q I N ~ E I I N G C,EEXSTRY, 1155-16th St., N.W., Washington 6, D. C.
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