Document 107a8NoRkmqp03dLoNX36b2QK

--TT Steel Mills Fight Their Pollution Problems BLAST FURNACES, Important producer* of pig iron, eon cause air pollution Industry ano local enforcement agencies today recog nise the full import of air** and stream-pollution problems. Aa a result, the emphasis on clean-up U shifting from the power field with it* relatively high performance level, Power, April, p 73, to the manufecturing and process industries. Studies and experiments these industries ere carrying out point tha way to many advances of vital interest to power services engineers. Take the steel industry as an example. In one year its fuel requirements run over a billion gallons of fuel oil, several hundred billion cubic feet of natural gas, 17 million tons of coal for power boilers, 94 million tons of coal for coke to blast furnaces. `The problems of air-pollulion control facing this industry have been iremendoui.1 Out in the Allegheny County area of Pennsylvania a Smoke Control Ordinance, passed June 1, 1949, provided for a research program to be undertaken by the steel industry on its individual difficulties. So the Jones & Laughlin Steel Corp, Pittsburgh Coke & Chemical Co, U.S. Steel Co combined in a Joint research program committee. That committee reflected a very practical outlook by o mem bership made up of operations, research and technology people. Their over-all assignment was to determine practical methods (or controlling emissions caused by blast-furnace slips, open-hearth furnaces, bessemer converters. This com mittee has done a lot. Some of its findings are being put Into operation. In fact, beginning on the facing pdge a case history report tells how one company has tackled a single phase of these special problems with considerable success. But first let's look at the available reports on the steel industry** pollution-control progress.1*1 Open Hoarths. Most of the reported work on open-hearth problems occurred on oil-fired furnaces. Dust loadings, they found, varied widely from almost sero to peak loads as high as 2 gr per cu ft. These loadings stretched over the si* major periods of open-hearth operation--the melt down, hotmetal addition, ore boil, lime boil, working heat and empty . furnace--with the peoks developing at hot-metal addition, ore-* boil, lime-boil periods, and when working with oxygen. Particle site broke down into about 50% by weight running smaller than 5 microns (one micron =* I/25,400-in. dia), and only a few percent 20 microna or above. Many particles run less than one micron. The chemical analysts showed an iron oxide content of about 90%. Incidentally one point of par* ticular interest was a complete lack of correlation between color of open-hearth discharge ond its dust loading, so the Ringelmsnn Chart mode no sense here at all. lUpenewi tVUk Atr Ptlluti** Abatement in Ike InAnttry, C A Dttwp. Research Associate U.S. Smt Co, before the Air Pollatiea Prcrteiioo Aun, CtevcttnO, Ohio, June IHJ. *Op*n Heeefk Duet CewirW, bj 8 Vsfde. Ofice of Chief- Rr*ir*r, C M Dreher. General Technics! Dept, Jooci k Lau*hlio Steel Corp- before Air PoJIatien Prevention Assn, CiivtUnd, Obi* font 1983. 94 ENOINCEBINO AND MANAGEMENT SECTION POWtf render the stack virtually clear means a 95 to 98% rijeo in the Fnlsslon. (Ed. note: Up In the range ^jey's power plant collectors. Power, April, p 73). But 7.5 gr per cu ft It forms aa a result of vaporization and con densation. High-energy wel washers will clean this type fume. But ijeost irtaiaUing and operating the available dust-col- maintenance costs run high since the collected ferromanganese devices* to give this dust-removal performance is so has very definite cementing properties. Over end above this S^ur** |0 be prohibitive for practical purposes. consideration was' the fact that a rather elaborate water- Out in ^n*e*e4 County, where, to our knowledge, you'll s d (he only open-hearth gas-cleaning installation now being *Ld in the country, you run into a different set of conditions. treating plant would have to go in (see the eoie history fol lowing). Sonic coagulators for agglomerating the fume had been 1-^ dust loadings average 0.0 gr per cu ft, all the metal tkjrie enter* the furnace as scrap, as agelnat blast-furnace supplies in `he Pittsburgh area, and the fume contains studied in a preliminary fashion by others. Their findings indicated a required gas-retention time in the sound chamber of over three seconds at a sound-pressure intensity of shove ujec amounts of zinc and relatively Uttle iron oxide. How shout gas-fired open hearths? The American Steel ed Wire Co at Donora, Pa. uses natural gas and reports dust 160 decibels. Converted to economic terms, sonic agglomera tion at its present state of development lacked definite appeal. What U.S. Steel elected to install was a dry electroitatle biding* down around 0.02 to 0.07 gr per cu ft against a 0.43 ptr cu ft average with oil. The dual looding ranges from 01 to 0.4 gr per cu ft on an average when natural and coke- oven gases are employed. But while the loading drops, the particle-site distribution 'u tougher. About 90% by weight run smaller than 5 precipitator that handles a specialty conditioned gas. They set up a pilot plant to study the various steps involved, and as a result of these studies a plant ho* been designed and is under construction to clean 135,000 cfm of ferromanganese blast-furnace gas. The major operating considerations were (I) a spray microns. Stack gas seems particularly dirty with this site tower for conditioning the gas, (2) en electrostatic precipi distribution and makes color comparisons completely un tator, (3) a special briquetting process involving a pyro- realistic as far a* total dust-loading judgment goes. phoring kiln. - -. Blast Furnaces. Cleaning blast-furnace gas has long been The dirty gas, to be treated, first enters s spray cooler ot Id established art. Today, more than 7,000,000 efm are being an average temperature of 700 F. This cooler operates without cleaned in the bloat furnaees in this country. Results have any wsier effluent to cool and humidify the gas with a 350-F been excellent. Power. Sept 1951, p 96. The quantity of gas jerobbed and the waste waters involved, though, have led to still another problem, that of atream pollution. One solution we present just below. exit-gas temperature. It is absolutely essential that all spray water be evaporated in this unit. Any bottom drip causes the fume to form a hard-setting cement. Incidentally, somewhere around 10% of the solids in the gas leave this tower as a dry Over and above the well-understood problems of cleaning material. ps from those furnaces that:produce basic pig iron are the From here, the gas passes through s 98%-efficient plate- relatively fewer, but more stubborn, ferromanganese blast type electrostatic precipitator, and then to power boilers for fofasces whose difficulties prompted special treatment. The gas-cleaning equipment differs sharply because tha gas loading is so different. Whot's.more, there nre.two types of duly os o fuel. The visible effect of gas cleaning from the pilot unit on the boiler stack waa impressive indeed. No discernible fume was emitted at all, while other boilers handling an un dust coming off a ferromanganese blast furnace. One, com-' treated gas did give off a noticeable fume. Stack-effluent prising about 20% of the dust present, consists of particles loadings measured only 0.05 gr per cu ft. The cleaned gas of about 20 microns that seem to develop when the coke and burned with a short, bright blue flame. ferromanganese burden disintegrate. A conventional dust But now bow about the basic blast-Iumace-gas furnaces? catcher can remove this fraction. But the other 80% is a Since they produced in 1952 some <51,530,000 tons of pig iron different story. It is a typical fume with particle sizes ranging ogainst the 630,000 or so tons from the fcrromsngoneie fur Iron 0.10 to 1.0 micron and dust loading, averaging about naces, (heir handling seems most important. f , i ***'' .Here's How the J & L Steel'Corp Makes Its Blast-Furnace Gas Yield Rich Iron Ore By W A WALTON, Apporotn Dept, Droro Carp Out of tho blast-furnace gas dis'barged in the process of making 62,000,000 tons of pig iron by the basic `bethod, some 3,000,000 tons of iron ore *ere recovered last year. Collection and removal of all forms of dust from blast furnace gas has long been carried out. But only of recent years with the heavy pressure of stream-pollution laws has Quell attempt been made to recapture `be important iron ore in this dust, Jones & Laughlin Steel Corp recently completed e modern blast-furnace fluedust-recovery plant for its Aliqolppa Works, Aliquippa, Po. The last word in dust collection, the system not only pro vides complete recovery of high ironcontent dust, but also conforms to the Pennsylvania State Department of Health*# Clean Streams Program. The plant handles a flow of 16,000 gpm of washer water containing about 100 gr per gat of flue dust with on iron content of about 45% (dry basis). The flue dust is removed from tha water in special thickeners in a slurry form con sisting of about 50% solids. Overflow from theta thickeners, with more than 95% of the aolids removed, discharges to the Ohio River. The thickened slurry is pumped to o filler house, and then fed to one of two disk-type filters. Here it is filtered and the final cake, pro- bOVlMBfl 1953 ENGINEERING AND MANAGEMENT SECTION 95