Hard Ore Counters Hard Times Iron range and steel industry alike look to lowgrade domestic taconite ores as their future life's blood
u1
- P I N THE,
IRON RA.NGE C O U n t r y
of
Minnesota, the word "taconite" is heard with mounting frequency. To mine owners and t o their research and development men, this word calls u p a picture of some 30 years of deliberate, often frustrating work o n a tough problem—one that has only recently begun to yield to the combined efforts of many minds and hands. To the area's mine workers and "businessmen, on the other hand, it's a word with a mild glow for the present a n d a promise of greater effulgence in days to come. For at a tLrne when sharply lowered demands for iron ore h a v e resulted, at least temponLrily, I n serious dislocations in the iron range economy, development of taconite properties and construction of -taconite processing plants in the area htave combined to bolster a sagging martcet for labor, and provide new promise for t h e future. Taconite LS (or taconites are, since there are sereral types of taconite) the extremely hard rock that makes up some 9 5 % b y voliarne of the famous Mesabi Range's vast iron-bearing deposits. Interspersed throughout the low-grade taconites (£-5-30% iron content) are relatively small pockets of high-grade (over 50% iron) '^direct shipping" ores; the latter have for many years supplied u p to 85% of all iron ore fed to the nation's hungry blast furnaces. Until the greatly accelerated depletion of high-grade ores occasioned by, and sustained since, World War II, there had been b u t little incentive for taconite development. On the one hand, its low iron content precluded direct use in the blast furnace; on t h e other, its extreme hardness defied all attempts to evolve simple, economical mining and beneiloiation methods. (Old miners say there is nothing tougher than taconte—except old miners.) As long as knouvn reserves of direct shipping ore loomed large, and the steel industry couild count on development of new higlL-grade ore bodies virtually as fast as the old ones were consumed, there was a general disinclination to do battle with the intractable taconites. In recent years, however, cries of alarm—altho-ugh often exaggeratedhave been lieard with increasing frequency as f t has become increasingly clear that Minnesota's high-grade ores definitely are not an inexhaustible resource. It i s already certain that rates of shipping such ores will be declining in the next few years. While continuing to prospect for direct-shipping ore deposits both a t home and abroad, 3342
therefore, the steel industry has turned with a will, and almost with a single mind, to conquest of the taconites it once regarded as useless. Former Tax Laws Discouraged Development of N e w O r e Bodies
For many years, Minnesota's tax laws discouraged development of new ore bodies, or the expenditure of funds on taconite beneficiation. Owners are taxed on the amount of known ore in
must be said that its leaders h a v e by no means been oblivious of taconite's potential. As early as 1916, an experimental plant rated at 100 tons per day was in business in Duluth, developing processes and apparatus for group known as the "Mesabi Syndicate/' led by D . C. Jackling of Utah C o p p e r fame. In 1919, the newly incorporated Mesabi Iron Co. took over the assets and processes of the syndicate a n d proceeded to build at nearby Babbitt, Minn., a plant, town, and other auxiliaries. Completed in 1922, t h e p l a n t operated for two years; it concentrated a total of 516,021 tons of crude ore, and shipped 156,370 tons of sinter analyzing 62% iron. T h e plant was simply 3 0 years a h e a d
Electric shovels and trucks are busy removing rock at Erie Mining's taconite site at Aurora, Minn. Initial pit is two miles from processing plant; ore will be hauled by mine railroad and unloaded into primary crushers. A 73-mile railroad is under construction from Aurora to Two Islands, where "Taconite Harbor" is under development the ground, and few were eager to prospect for new deposits before they were actually needed—or to develop processes that would bring taconite under the classification of usable ore. As a result of recent tax revisions, particularly the 1941 "Taconite Tax Law," a small assessment is now placed on taconite land holdings in the Lake Superior district, with the major tax applied to the iron concentrates at the time of actual shipping from the district. Should the budding new taconite industry ever be forced to pay as straight iron mining has, or should its legislative support ever be reversed, it would doubtless fall by the wayside. The change has given important encouragement to steel companies to develop taconite beneficiation processes. In the steel industry's defense, it
of its time. Unable to compete with direct shipping ores, t h e n both plentiful and cheap, it closed down in June 1924, and never reopened. (Nearly 20 years later, the property w a s acquired by Reserve Mining Co., n o w one of the major forces in taconite development. T h e old plant was put in standby condition, and obsolete e q u i p m e n t was removed and sold. In 1 9 5 2 , Reserve began operating at Babbitt a 300,000-ton-a-year plant to help organize for its much larger installation now under construction at Silver Bay.) For the past 20 years, and particularly since the war, interest a n d activity in taconite processing h a v e been decidedly on the u p g r a d e ; today it can b e said with little danger of dispute that for taconite " t h e time has come." Besides Reserve Mining, which is now
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owned half-and-half by Armco Steel and Republic Steel, two other giants are busy on taconite problems at trie experimental, semicommercial, arid commercial levels. Erie Mining C o . , owned by Bethlehem Steel ( 4 5 % ) , Youngstown Sheet and T u b e ( 3 5 % ) , Interlake Iron ( 1 0 % ) , and Steel C o m pany of C a n a d a ( 1 0 % ) , is booming along toward commercial operation on the grand scale, while Oliver I r o n Mining Division of U. S. Steel is busily gathering data at the experimental a n d semicommercial levels. W h a t ' s H a p p e n i n g Today? Construction a t Top Speed
A few miles north and east of Aurora, Minn., in t h e great Mesabi area, E r i e is putting together the largest initial
quirements of the plant for more than 50 years. T h e initial pit wall be about two miles from the processing plant; taconite ore ( 2 9 - 3 0 % iron) will be hauled to the plant by a mine railroad, a n d unloaded directly into primary crushers. A 73-mile, single track, standard gage railroad is under construction between Aurora and Two Islands, Lake Superior, where "Taconite Harbor" is u n d e r development to handle the transfer of finished taconite pellets to Great Lakes ore boats. Taconite Harbor will also be the unloading point for inbound cargos of coal a n d oil for use in the processing plant a n d in the large generating plant for electric power. Developed through more t h a n 20 years of experimental work in taconite
Erie Mining's preliminary taconite plant was constructed in 1948. It has a rated capacity of 200,000 tons per year. This preliminary plant has been important in testing methods and equipment, such as these rod and ball mills, to be used in Erie's large plant. The new plant, when completed, will have a capacity of 7.5 million tons a year ore concentrating plant ever built. Over a thousand m e n are carving there, from virgin wilderness, a townsite to accommodate several thousand homes, a trailer campsite for temporary housing of hundreds of families, access roads, and sites for auxiliary buildings to supplement the m a m m o t h processing plant already u n d e r construction. Tremendous trucks with a capacity of 24 cubic yards each, and with special beds preheated b y Diesel exhaust (to prevent freezing of loads in winter), a r e at work around the clock and around the calendar, removing dirt and rock from construction areas, and hauling away the overburden being stripped from taconite deposits in preparation for open-pit mining. Erie has u n d e r its control on the Mesabi range enough raw materials to meet maximum reVOLUME
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processing, the Erie method (like Reserve's) is based on magnetic separation of iron-bearing particles from the ore gangue. Super-hard taconite rock will b e blasted loose at the mine; large pieces will b e reduced by a series of crushers and grinders to a fine p o w d e r ( 1 0 0 % through 100 mesh; 6 0 - 8 0 % through 325 m e s h ) . Iron particles will b e separated magnetically, and rolled in a d a m p state into small balls. Heated to 2300° F. in a vertical furnace, the balls lose moisture and are "fused" into hard pellets suitable for charging to the blast furnace. Scheduled to cost over $300 million, and likely to h a v e an eventual capacity of u p to 10.5 million tons of taconite pellets a year if needed, the Erie development is by a fair margin t h e largest u n d e r way. It is not, however, the
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only one, nor will it b e t h e first in operation. Its i m m e d i a t e predecessor, a 200,000-ton-per-year pilot p l a n t built at Aurora in 1948 as a p r o v i n g ground for equipment and m e t h o d s , w a s t h e first to produce pellets i n large quanti ties—and on a sustained basis—from Lake Superior taconite; the first full cargo of pellets was s h i p p e d d o w n t h e great Lakes from this pilot plant in 1948. By t h e end of 1 9 5 3 , m o r e than $15 million had been spent o n this entire project, and t h e experimental plant had turned out over 375,000 tons of pellets. T h e pellets, incidentally, have been used successfully in blast furnaces by all the companies t h a t are co-owners of Erie. Reserve Pushes Construction of 3 . 7 5 M i l l i o n Ton Per Y e a r P l a n t
First taconite plant s c h e d u l e d to begin shipment o n the millions-of-tonsper-year scale is that of Reserve Mining, which mines taconite from property leased from Mesabi Iron. Already turning out 300,000 t o n s of pellets a year (rated capacity) at its Babbitt plant, Reserve is p u s h i n g construction of its m u c h larger E. W . Davis works at Silver Bay (near Beaver B a y ) , about 55 miles northeast of D u l u t h o n Lake Superior. Concentrating a n d pelletizing plants for the first 2.5 million-ton section at the Davis W o r k s (named for E. W . Davis of the University of Minnesota, for m a n y years director of the University's Mines E x p e r i m e n t a l Station, and a pioneer in t a c o n i t e processing development) a r e scheduled to start operation about t h e m i d d l e of next year, and will be in full production from rune to 12 m o n t h s thereafter. Mining a n d preliminary crushing will be handled at Babbitt; taconite will then be shipped by 47-mile company railroad to the Silver Bay plant for final processing. R a t e d capacity of t h e Davis Works is to be 3 . 7 5 million tons a year of pellets with 32% iron content. Capacity can b e further increased to 10 million tons a year as d e m a n d warrants. Board Chairman Charles R. Hook of Armco, which shares o w n e r s h i p of R e serve with Republic Steel, reported this spring that good results are being o b tained in blast furnace runs with t a c o nite pellets, first commercial shipments of which were received by Armco last year. While Reserve expects to begin shipping taconite concentrates from Silver Bay in 1955, Erie expects t h a t it will be 1957 at the earliest before first major production issues from the 7.5-millionton installation now u n d e r construction for the Aurora commercial plant. T o t a l production from all p l a n t s i n Minnesota, after expenditures aggregating about a half-billion dollars, is expected 3343
to run around 12 million tons per year by 1958, and rise to perhaps 2 3 million tons by 1963. (Humboldt Mining Co., owned by Cleveland-Cliffs Iron Co. a n d F o r d Motor Co., is constructing in Michigan facilities that will eventually p r o d u c e u p w a r d of 600,000 tons of "shipping ore" from lean ore each year. This is not taconite, however, but jasper, a nonmagnetic cousin. Beneficiation involves froth flotation instead of m a g netic separation.) W h a t ' s Coming? Estimates G o as High as 6 0 Million Tons a Y e a r
A 1953 study Federal Reserve by 1972, output could go as high
b y the Minneapolis Bank indicated t h a t of taconite pellets as 60 million tons a
over-all taconite utilization problem. For, while development of magnetic separation processes for taconite beneficiation has added h u n d r e d s of millions of tons to usable iron ore reserves, there are h u g e quantities of nonmagnetic taconites, jasper, and other ores that do not lend themselves to this treatment in its simplest form. Taconites containing iron in nonmagnetic form thus have presented a special— a n d tough—recovery problem. At the 1953 Buffalo meeting of the American Institute of Mining and Metallurgical Engineers, a reductionoxidation process for concentrating such ores was outlined b y technologists Stephens, Langston, and Richardson of Battelle Memorial Institute. Based on conversion of the nonmagnetic ores to
Significant contribution to taconite progress has been development of new "jet piercing" method of preparing blast holes in ore deposits. Even the hardest known drill bits, in churn drills previously employed, made but little progress in the extremely hard rock. Drilling one foot through taconite, in fact, often required u p to an hour, with as many as four drill bit changes in the bargain. Jet piercing machine, a highly specialized flame thrower, has brought dramatic changes. Its 4500° F. flame jet, resulting from combustion of light petroleum oil (usually kerosine) intimately mixed with oxygen, pierces its way through taconite at average rate of 18 feet per hour. Intense heat of flame causes thin surface layer to expand and break away; jet action whisks spalled rock aside, exposing fresh surface to attack. Water quench and pressurized steam embrittle the rock and help blow rock chips up out of the hole, six to nine inches in diameter. "Drilled" to 40-foot depth, holes are filled with high explosives which blast out "benches" 35 feet high year. At that rate, taconite would undoubtedly h a v e replaced high-grade r a w ore as the leading iron source. Actually, although it has n o t b e e n heavily publicized, even m u c h of t h e "soft" ore now being used is concentrated at the mines prior to shipment. Beneficiation of such ores is easier t h a n processing taconites, because of the latter's hardness. F o r the p a s t several years, about a third of all ores shipped from the region have been upgraded— from iron contents as low as 3 5 % t o the usual over-50% characteristic of directshipping ores. I n 1952, about 80 million tons of high-grade ore, a third of which had received some u p g r a d i n g , was shipped from the Lake Superior ranges, in contrast to less t h a n a half million tons of up-graded taconite. By 1972, says MFB.B, the corresponding figures might be 60 million for taconite a n d 3 5 million for high-grade ore. Vast though t h e y are, current taconite projects are merely a start on t h e 3344
magnetic form b y heating, followed then by magnetic separation, t h e Battelle-developed process promises again to extend potential iron reserves tremendously. By cutting down initial h e a t requirements and b y recovering a n d reusing much of t h a t heat, the Battelle m e t h o d appears to have solved t h e principal problem of prohibitive heating costs. Hydrogen a n d / o r carb o n monoxide were found most suitable as reducing agents; pilot plant studies indicate that the process is applicable to a variety of ores, including mixtures of hematite, magnetite, a n d siderite. Competition w i t h High G r a d e Ores?
Most steel company spokesman are as yet unwilling to go out on a limb with definitive predictions for taconite's future in competition with directshipping ores. They w a n t to see first h o w the processing plants function in full-scale operation, and how closely they have estimated processing costs.
Naturally, these costs will for a time exceed costs of mining easily-accessible, high-grade ores, b u t as t h e latter diminish and as taconite processing efficiency improves, the margin will narrow. Already taconite has shown promise of p a y i n g part of its own way; in blast furnace tests with the pellets, iron oirtput has been higher because of t h e pellets' higher ( 6 0 - 6 5 % iron) concentration, while demand on coke and limestone remained normal. T h e Battelle process for nonmagnetic taconite could g o even further to improve the competitive outlook for taconite; at t h e experimental level, high (92—96*^0) recovery of iron in magnetic form is coupled with improved grindabiiity of t h e processed ore. Savings in grinding costs thus might more t h a n offset trie cost of the extra conversion step and improve the over-all economics of taconite use. Actually, its high requirement for labor is one of taconite's drawbacks in economic competition. Three to four tons of taconite must b e mined for each toxi of p r o d u c t shipped, and processing requires additional labor—as well as large amounts of power, fuel, and wa-ter. Despite extra costs, u p g r a d e d taconite is expected to b e competitive with imported high grade ores u n d e r some circumstances and is rapidly shouldering its 'way, u n d e r its own power, into the big time. How soon it m a y surpass domestic direct-shipping ores in tonnage depends in large measure on the rate at w h i c h new reserves of such ores are developed. While Mesabi reserves are currently estimated a t approximately a billion tons (a 10- to 12-year supply at c u r r e n t rates of consumption), i t must be remembered t h a t since rriining operations began late in the 19th century, two tons of new reserves have been developed for every three tons of ore removed. Current estimates of Mesabi reserves do not differ very greatly, in fact, from the 1920 estimate of 1.3 billion tons— although some 1.3 billion tons h a v e actually been shipped since then. B e tfaat a s it may, it is obvious that new high grade ores cannot forever b e discovered i n t h e United States at the rate of two tons for every three tons of ore shipped. Hence, taconite seems destined to dominate the domestic scene some day. Eventually, it will domina-te the entire iron ore picture if— and as long as—it can compete economically with the rich deposits currently "being opened u p in Labrador, Liberia, Venezuela, and other foreign lands (C&EN, Aug. 9, p a g e 3 1 1 4 ) . Costs will determine its ability to compete, and there's a large amount of money riding on the gamble that taconite will hold its own.
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