Atmospheric Pollution
September 1951
Research, based on the conclusion that atmospheric pollution problems in Allegheny County, Pa., must be attacked from the industrial point of view, is -well under way by r
B' , HE second annual report of the -™- Allegheny County, Pa., Bureau of Smoke Control appeared on July 1, 1951. Thomas C. Wurts, director, points out that the work of the bureau covers the entire county of Allegheny except that portion included within the corporate limits of the city of Pittsburgh. This area comprises approximately 700 square miles and embraces 128 separate municipalities. With the exception of Los Angeles County, Calif., its area is at least ten times greater than any other over which control of air pollution is exercised. The steel industry within the jurisdiction of the bureau has an ingot capacity of approximately
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problem of cleaning up the atmosphere of Allegheny County must be attacked from the industrial rather than the domestic point of view. The seven-man staff of the bureau is supplemented by the Smoke Control Advisory Committee which embraces subcommittees on fuels, railroads, and steel. In consultation with the fuel advisory subcommittee, the bureau has drawn up specifications for both hand-fired and stoker-fired fuel, which is readily obtainable in the area. The fuel specifications were published in a bulletin, issued in May 1951, which was given wide circulation. The retail coal marketers report that this bulletin has had an effect on the type of
the 14,000,000 tons annually, production coming from 132 openhearth furnaces, 29 blast furnaces, and more than 1000 heating and reheating furnaces. Some 1675 by-product coke ovens serve the steel industry. The annual consumption of igure 1. Mine Waste File Opened to Extinguish Fire coal is in excess of 50,000,000 tons, Between 1,300,000 fuels that are now being used in the and 1,500,000 tons per year are Allegheny County area. used domestically, somewhat less The steel subcommittee has enthan 3 % of the total. Three gaged in research on the effluents from ferromanganese furnaces, or four years ago there were open-hearths, Bessemer converters, only a few Diesel locomotives operand blast furnaces. On May 1, ating in the county and a, Diesel 1950, a fellowship for studying air tow-boat was a rarity. Today appollution problems was established proximately 525 Diesel locomotives at the Industrial Hygiene Foundaare in operation in the county and tion, Mellon Institute, by the Iron 60 Diesel tow-boats operate on the and Steel Institute. The director rivers. Wurts concludes that the September 1951
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anticipates that this work will enable the steel to industry rematerially duce its present atmospheric pollution. The U. S. Steel Co. recently has completed a study of a pilot plant installation for control of ferromanganese effluent and has made an appropriation for full scale installation for two furnaces to be operated on ferromanganese at the Duquesne Works. A method has been devised for measurement of the particulate matter from open-hearth furnace stacks and a very extensive series of tests has been run on the quantitative and qualitative analysis of stack emissions. At present, plans are under way to transfer the pilot plant used in these studies of ferromanganese emissions to open-hearth operations. The National Tube Co. and Jones & Laughlin Steel Corp. are investigating control of emissions from Bessemer converters. Quantitative and qualitative analyses of emissions have been made, but the major problem is that of hooding the converter and maintaining safe operating conditions for the 25 Bessemer converters in the county. The Pittsburgh Coke and Chemical Co. is studying control of the emissions of air pollution resulting from blast furnace slips. A comparatively inexpensive means has been employed in one furnace which has reduced slips to between 4 and 8 per month, where 50 or 60 slips were the normal occurrence before. Pilot plant tests on open-hearth effluent have included ultrasonic precipitators and cyclone and other mechanical types of scrubbers, but to
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enactment of the Allegheny County ordinance and in compliance with it, the Western Pennsylvania Coal Operators Association, on January 1, 1949, established a fellowship at Mellon Institute for the purpose of studying the control of gob-piies and of means of laying down mine wastes so that they would not fire spontaneously. There are between 20 and 25 such burning piles throughout the county and hundreds of other piles which Wurts believes may fire at any time. There are numerous records of piles, which have been dormant for 20 years, suddenly igniting. The School of Mineral Industries at Pennsylvania State College is also studying this problem and the Western Pennsylvania and Central Pennsylvania Coal Operators Association has a mine waste committee that is coordinating these activities. The research on gobfires at Mellon Institute and the School of Mineral Industries, is incorporated in an appendix to the Allegheny County annual report. Returns from a questionnaire sent to coal mining companies throughout the United States constitutes a significant portion of this appendix. The return questionnaires from companies in Pennsylvania reporting on 383 piles showed that 4 1 % were burning and 22% had burned out. Only 37% were not burning at the present time. The questionnaires from out of the state, reporting on 419 gob-piles, showed that 26% were burning, 18% had burned out, and 56% were not burning. The most effective means of controlling such fires, within economic limits, appears to be storage in thin layers followed by packing, either by trucks passing over the material or by compacting it with a bulldozer.
these have not been satisfactory. In it.s report to the director, the .subcommittee states that an appreciable percentage of the (Just is so fine in particle size as to indicate that mechanical dust collectors may give only moderately high removal efficiency. It is concluded that because the total emission of small particle size is small and as such fine particles do not fall to the ground until their dilution is very great, the idea of using mechanical type dust collectors is persuasive. The committee's observations ou the open-hearth emissions are not in accord with results of openhearth tests reported in this column in March 1951. Mean particle size of the emission in that instance was 0.5 micron with no particles larger than 3 microns. There are many, including the writer, who believe that aside from the nuisance consideration the larger particles of such emissions are not the crux of the dust problem. Although much submicron dust is carried away by the wind, a considerable portion of it finds its way into heating systems and is deposited on relatively cool walls, draperies, and furniture. There is no conclusive evidence to prove or disprove that such particles constitute a health hazard, but generally only those particles smaller than 5 microns enter the respiratory tract. Submicron material scatters light and when present in significant quantities it forms an effective "smoke" screen. As Allegheny County continues to make progress in other phases of control of atmospheric pollution one wonders whether the effective control of dust of this nature will not follow as a matter of course. It is rather certain that mechanical collectors will not be effective on such dusts.
Correspondence coneerning this column will be forwarded promptly if addressed to the author, % Editor, INDUSTRIAL AND ENGINEERING C H E M -
ISTRY, ll.iô—10th St., N. W„ Washington 6, D. C.
Throughout Allegheny County and the Appalachian coal mining area generally, mine waste (gob) fires (Figure 1) are receiving considerable attention. Anticipating the
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