PROCESS METALLURGY Where chemical techniques have unlimited opportunities for development or those chemical technologists seeking a challenge, F p r ocess metallurgy is a promising field. It is an area where rearrangements such as price changes, population expansion, or depletion of natural reserves can cause economic disorder as well as weaknesses in our national defense. The problem is aggravated further by increasing demand for higher purity metals in astounding quantities which can perform in fantastically severe environments. More efficient recovery methods will be needed, as well as methods for exploiting lower grade deposits. The iron industry is a case in point-new methods of ore beneficiation are needed. This is the situation: When it was predicted as early as 1943, that the high grade iron ore reserves in Minnesota would be exhausted within 10 years, explorations for new deposits throughout the world were begun. Also, processes for using low grades ores were sought. Both routes were successful: Blast furnace production from high grade ore? has increased to the point where former shippinq grade ores are considered inferior and thus need beneficiation. These new ventures required high capital expenditure, and many large steel companies went into the mining and pellet-making business. For independent mining companies to compete with the new high grade reserves, they must beneficiate a larger percentage of their ores. Open pit operations have not been greatly affected, but many higher cost underground operations in the Lake Superior district have been abandoned, and unless more efficient concentration techniques are developed, per18
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
haps entirely new processes, more mines will have to close down. T h e thesis that new techniques, so urgently needed for iron ore beneficiation, can be found in chemical processing, is not without precedent. High purity manganese is an example. Manganese was not introduced in pure form until a process based on chemical technology was developed. Commercial production was begun in the late thirties at about 1000 pounds per day, using low grade ores-high grade deposits are not found in the United States. For 1962, estimated volume approaches 100 tons per day. Economic considerations, despite years of commercial production based on low grade American ores, dictate employment of lower cost, high grade foreign ores. However, in times of emergency, United States ores, available in large volumes, can be used but production costs will be higher. T h e U. S. Bureau of Mines pioneered the project, and in 1930 issued a report on leaching manganese ore with sulfur dioxide. I n 1936, the Bureau said in essence : Manganese has been electrolyzed on a laboratory scale from both fused salts and aqueous solutions. Aqueous solutions are cheaper if satisfactory deposition can be obtained in the presence of hydrogen. Several factors affect current efficiency and purity and texture of the deposit. More importantly, rapid deterioration of the electrolyte limits total deposition, increases impurities, and complicates interpretation of results. A year or so later the Bureau built a pilot plant designed for 15 pounds per day. Ore containing 31.170
a new frontier
. r
!
manganese was heated to 600' to 700' C. for 30 to 60 minutes in a strongly reducing atmcsphere and cooled to 100" C. before exposing to air. Manganese metal, 99.5 to 99.8% was obtained along with'hydrated manganese dioxide as an anode oxidation product which had to be retreated as ore. On the basis of this experience, a 24-cell unit for - producing 1 ton per day was built at Knoxville, Tenn., by the Electromanganese Corp., now a part of Foote Mineral Co. However, the transition was too abrupt' difficulties developed with anodes, cathodes, solution lines, impurities, salt deposition, and diaphragms. T h e plant had to be redesignedand rebuilt. In the new plant, oxidation of manganese at the anode was made negligible by developing new anodes and cathodes and methods of surface preparation. Flowsheets were intensified and purification processes were made quantitatively reliable: recoveries were increased from 40 to 90%, and current efficiencies from 50 to 68%. In putting the process on a commercial basis, numerous problems were encountered such as control of magnesium in the electrolyte, cell cooling, and evaporation of electrolyte to make. space for the leach-residue wash waters. All manganese ores,especially domestic deposits, carry magnesium which, because electrolytic solutions are generally saturated, will eventually crystallize out, usually in inaccessible spots such as in pipe lines or pumps. Any appreciable drop in temperature can have disastrous results. At Knoxville, these three problems were solved by
A STAFF FEATURE
direct evaporation of solution. A large quantity of cell anolyte is circulated over cooling towers; this reduces volume by evaporation and holds cell temperature to about 35' to 40° C. Most importantly, a complex sulfate of Mg, Ca, NHa, and Mn is crystallized out which can be used as a fertilizer for citrus fruits. Subsequent to this exploratory period, production volumes have increased phenomenally, but changes in the process have been few and small. At present there are two producers-The Electromanganese Division of Foote Mineral Co. at Knoxville, Tenn., operating for economic reasons on high grade imported ores, and The Union Carbide Metals Co. employing slag at Marietta, Ohio. However, American Potash and Chemical Co. have announced intentions to build a new plant. What is the status of high punty manganese and what are its chances for growth? Unquestionably, demand will increase for use in steels and other steels having low
A CRITICAL PROBLEM The need i s urgent for new processes of making high grade iron concentrates from nonmagnetic ores.
Al-
ready, because such processes are lacking, the greater parl of the Mesabi Range has been declared a distress area.
Perhaps chemical technology can furnish the
answe-s
it solved the problem of high purity
manganese production. VOL 5 4
NO. I O O C T O B E R 1 9 6 2
19
carbon specifications. Large quantities are consumed in making cast aluminum engines for automobiles. A decrease in price would increase demand, but already plants are operating at near capacity. Iron Ore Beneficiation as It I s Today
The bulk of ores processed by the steel industry can be classified into four groups-merchantable, wash, intermediate, and taconites. Merchantable ores are high grade materials which are shipped without beneficiation, except for crushing, screening, drying, and sintering. Wash ores, lower in grade, are classified according to size and scrubbed (7A, 2OA). However intermediate ores do not respond to simple sizing and scrubbing because of a higher gangue content in the coarse particles. Processes such as heavy media, jigging, flowing-film concentration, or flotation are used, all of which depend on particle size needed for liberating the iron from gangue. As liberation size decreases, complexity of the process increases ( 7 A , 24A). Processes under Development. As ores decrease in iron values and liberation size, chemical processes may become more important. T h e Krupp-Renn processes (26A), used in Germany and Japan, is a pvro process based on reduction with coal of iron minerals in a rotary kiln. Gangue materials are then separated as slag at temperatures below the melting point of iron. The iron minerals are reduced to sponge iron, a part of which is reoxidized to form a low melting slag with the gangue which rises to the surface and prevents further oxidation of the iron. Carbon within the particle then reduces the iron in the slag to sponge iron again, and the product is a nodule of iron coated with gangue slag. The mass is then crushed and iron is recovered with magnetic separators. Over-all iron recovery is above SOY0. However, the process requires close control and maintenance of Lhe kiln refractory is a severe problem. Samples of domestic nonmagnetic ore have been shipped to the Krupp Steel Works in Germany for tests. The Strategic-Udy (22A) process produces metallic iron or steel as a final product. It uses a kiln in conjunction with an electric furnace, but makes the irongangue separation by smelting above the melting temperatures of iron. LOWcost electricity and ores containing 40 to iron are essential. The R-T\: process ( 4 A ) uses a special kiln with temperatures and atmosphere controlled by air inlets spaced along its length. Sponge iron is produced below the melting point of iron, coal is the reductant, and the final product is metallic iron. However, neither the iron or gangue is melted-rather they are separated by crushing and magnetic separation. Therefore, the process depends on liberation size and mineral composition, whereas the Krupp-Renn and the Strategic-Udy processes do not. However, the iron product does not pick up as much phosphorus and sulfui from the carbon fuel as it does in the higher temperature processes. MAGNETIC ROASTING. Magnetic separation is low cost and capable of handling large tonnages. Several roasting techniques have been considered, all based on ex20
INDUSTRIAL AND ENGINEERING CHEMISTRY
posing the iron minerals to a reducing gas at temperatures ranging from 800 to 1400 F. The reductant is usually carbon monoxide and/or hydrogen in equilibrium with carbon dioxide and/or water. Reduction stops at magnetic and does not proceed to nonmagnetic wustite. The process is attractive because of the high iron recovery obtained, almost without regard to mineralogical composition of the ore. However, because of high heat requirements, it is considered uneconomic. The furnace for magnetic roasting must heat the ore, dispose of volatile products, expose the ore tu the reducing agent, recover the heat from the reduced ore and exit gases, and discharge the ore as a stable magnetic product. Furnaces that have met these requirements in varying degree are the rotary kiln (TOA), shaft kiln (5A, T U ) , fluidized bed reactor ( 1 4 4 , 76A), and the horizontal traveling grate (25A). Magnetic roasting makes the ore very friable and may decrease liberation grinding cost by as much as 507‘. The ore should be handled in as coarse a form as possible; however this advantage varies with the type of ore. Dense material must be finely ground to give a reasonable reduction and retention time, and roasting a friable, highly weathered ore would not give an appreciable saving in grinding cost. The rotary kiln is the only furnace that will handle an unsized feed with any degree of efficiency. Dusting is a problem but can be minimized by using low velocities and longer retention periods. Fines must be agglomerated for either the shaft or traveling grate ; otherw~isethe beds will become impermeable. Fluidized beds must have a feed of less than IO-mesh. The chemical reaction in magnetic roasting is exothermic and theoretically requires only enough fuel to provide the reducing atmosphere and remove moisture. However, a furnace that approaches this ideal has not been built. If the fuel requirements could be halved (from 800,000 to 400,000 B.t.u. per ton) magnetic roasting might be economical. One approach is 10 use a large volume of gases of low heat content to produce efficient heat transfer during conversion. Another is to size the ore and use several types of furnaces for various particle sizes. A combination of these two methods is proposed for Russian quartzite ores.
AUTHORS T h i s staf feature
was prepared with the he& of C. L. Sollenberger and C. L . Stevenson, Research Division, Allis-Chalmers Manufacturing Co., Milwaukee, Wis.; F. M . Stephens, Jr., Director of Research Planning, Chemical Engineering Department, and John E . Hanway, J r . , Acting Division Chief, Extractioe Metallurgy Division, both of’ Battelle Memorial Institute, Columbus, Ohio; and C. L. Mantell, Consulting Engineer, Nex York, iV.Y . Material for the paragraphs (pages 24 and 25)on heat transfer in steel production, improving blast furnace operation, and plutonium production was derived from articles to be published in the January issue of IBEC’s quarterly, (‘Process Design and Development.” Material on fluidized reduction of iron ores was taken f r o m a report by A . P. Kerschbaum, Armco Steel Corb.
I n Europe, high intensity magnetic separators ( 7 7A) are being used for concentrating the feebly ferro-magnetic hematites. Although considered here, no commercial applications are reported. Electrostatic separators ( 1 A ) are also being considered because separation does not depend on magnetic properties. Rather it depends on surface charges of different intensities on the minerals. Both processes depend on liberation before separation. FLOTATION RESEARCH.Two basic flotation methods have been investigated-flotation of the iron and of the gangue ( 2 4 ) . Flotation of iron is being done commercially (23A), but the process seems applicable only to clean ores-those low in slimes and iron silicates. Gangue flotation has not been used commercially, but it offers the best possibility for making high grade concentrates. A continuous cationic flotation technique for removing siliceous material is being investigated (79A), where the middling particles (part iron and part gangue) do not enter the concentrate but are rejected with the gangue. To improve selectivity of flotation reagents, new combinations are being tested constantly. Temperature of pulps has received attention and one commercial plant is using a hot iron mineral float to make a final concentrate. Selective flocculation of the fine iron minerals is promising ( 3 A ) with selective reducing agents in an
WHAT OTHER
aqueous medium. Ultraflotation or “piggyback” flotation is effective for floating clay slimes and may be applicable to iron mineral slimes. Chemical Processes. Because of unfavorable economics, chemical processes have not become commercial. However, they may become so as beneficiation increases in complexity. Iron ores may contain nickel, cobalt, copper, vanadium, titanium, sulfur, chromium, selenium, arsenic, aluminum, manganese, and cerium. In some instances, these minerals may be more valuable than the iron, and the first chemical process may produce iron concentrates only as a by-product. Basically, two chemical methods have been considered-dissolution of either the iron or gangue. Because quartz and other silicates are nearly always present in ore concentrates, leaching with reagents selective toward these minerals may be effective. Some varieties of silica respond to caustic leaching (73A). For dissolution of the iron minerals, a sulfuric acid leach has been proposed ( 9 A ) which converts the iron to sulfate. Insoluble fractions are filtered off and iron is recovered by evaporation and crystallization as ferrous sulfate which is then calcined to the oxide. Impurities are removed by extraction. The resulting high purity oxide is then reduced directly to metallic iron. A pilot plant, built near Aurora, Minn., operated for a few months, but costs were too high for commercialization.
EXPERTS THINK
I&EC editors queried other process metallurgists, experts in iron, steel, copper, lead, zinc, and less common metals. The following paragraphs are a composite o f their opinions. Our need for metals can no longer be supplied through simple treatment o f high grade ores. Instead, lower grade deposits must be exploited and, t o d o this, new complex processes must be developed, which are scientifically based. This means that metallurgical processing science i s rapidly merging with chemistry and chemical engineering. The accompanying article describes only a few o f the processes being developed t o maintain supplies o f r a w materials. Already, in the picture as it appears today, chemical technologists have important areas o f operation. Chemists, often in cooperation with chemical engineers, have the primary role of developing quantitative analytical techniques for r a w materials, alloys, and intermediate products. They derive basic data for process operations, ranging from mineral deposits through t o the product of prespecifled composition. Chemical engineers, sometimes jointly with chemists and metallurgists, evaluate existing o r new processes from the economic and technical standpoint. Sometimes this involves the entire process-Le., basic theoretical studies in areas such as heat transfer, thermodynamics, and kinetics, as well as evaluation o f experimental, pilot plant, and production data. Where a change in processing operations is involved, chemists and chemical engineers have important roles.
In some areas, the distinction between chemical and metallurgical technologists is rapidly disappearing. For example, in hydrometallurgical plants for extracting copper, lead, and zinc, the titles metallurgist, chemist, and metallurgical o r chemical engineer are practically synonymous. In pyrometallurgical plants, a casual observer may discern a distinction more readily than those working in the field, because there are few steps which d o not involve chemical reactions between liquids and gases. Such reactions can be understood only by the physical chemist. In the simple procedure o f melting copper cathodes to make refined copper shapes, equilibria must be understood, between liquid and solid copper and gas-forming elements, oxygen, sulfur, hydrogen, and carbon. The same is true for equilibria between these elements and the numerous metallic impurities. Here, the analytical chemist operates with concentrations ranging from 0.1 t o 10 p.p.m. In refined copper today, few impurities exceed 10 p.p.m. Although important in the basic production of copper, lead, and zinc, chemists and chemical engineers are even more essential in making and handling by-products. N e a r l y all o f these metals produced today come from sulfide ores, and to eliminate the sulfur, sulfuric acid o r sulfur dioxide is produced on a large scale. This i s clearly a chemical engineering problem. In short, separation of impurities involves a bewildering interplay o f chemical reactions which can be dealt with successfully only by the combined efforts o f chemists and mathematicians. VOL. 5 4
NO. 1 0
OCTOBER 1 9 6 2
21
Selective reduction and agglomeration of iron slime minerals ( 3 A ) by adding reducing agents has heen proposed, with subsequent recovery by flotation or magnetic separation. This or other chemical processes may be effective for concentrating the intermediate grade nonmagnetic ores. A process applicable to all types of ores and not dependent on liberation size or mineral composition is desirable-e.g., pyro-metallurgical processes involving direct reduction and subsequent beneficiation such as the Krupp-Kenn and R-N processes. Another possibility is that chemical processes such as leaching or reduction may some da)7 supplant all other iron ore beneficiation processes. The need is great, and there is an opportunity for chemists and chemical engineers to make an outstanding contribution. Volatilization in Nonferrous Process Metallurgy
Volatilization is important in extractive metallurgy processing of mercury, antimony, arsenic, cadmium, magnesium, molybdenum, zinc, and tin. Also, it is the basis of many chloride metallurgical processes which have been proposed, and is an integral part of processing newer refractory metals such as titanium, zirconium, and niobium. In some cases volatilization is involved only in intermediate stzps: nevertheless, it is a critical and useful unit operation. Because of inadequacy in equipment, many volatilization tcchniques in metallurgy have not been particularly successful, especially where temperature-dependent selectivity among volatile materials is needed. Equipment such as rotary kilns, retorts, or shaft furnaces does not provide proper or flexible atmosphere control, or the efficient heat transfer necessary. Perhaps more importantly, such equipment cannot maintain temperatures within the required limits. However, to a great extent, these disadvantages have been overcome by fluidizedsolids techniques which have become prominent, particularly in oxidation roasting of ores and concentrates. reduction of metallic compounds, and the dryinq of many materials. I n fluidized-bed processing, a solid material having a particle size of about 4-mesh maximum to subsieve sizes is suspended dynamically in a vertically rising stream of gas having a superficial velocity somewhat greater than the terminal velocity of free fall of the particles. Thus, the solid material, kept in a continuous and energetic state of mixing and agitation in a well defined zone, is not entrained in the exit gases. The small amount that is entrained can be removed with various types of separation equipment. The fluidized zone resembles an ebullient liquid and, in fact, obeys many of the laws of hydraulics. The apparent density depends on bed material and conditions of operation, but for common metallic ores it usually ranges from 60 to 100 pounds per cubic foot. Gas-solid contact and heat transfer within the fluidized bed are very efficient. Stagnant layers of gas are not formed around the particles to inhibit heat transfer. Because the fluidized bed is made up of relatively fine 22
INDUSTRIAL AND ENGINEERING C H E M I S T R Y
particles having a large ratio of surface area to mass, the high heat transfer coefficients permit large amounts of thermal energy to be exchanged with a system having a lower mass or total volume requirement. Thus, the technique is uniquely applicable for both volatilization and condensation. Experiments with Volatilization. ARSENICFROM COBALTCONCENTRATES. Leaching methods for recovering cobalt from sulfide minerals depend on conversion of the cobalt mineral to a soluble form, usually by roasting under oxidizing conditions. In the presence of arsenic, however, complex compounds of arsenic and cobalt are formed, which are insoluble in the usual leaching media and which decrease recovery. Experiments were conducted with a fluidized-bed reactor tube, Type 304 stainless steel, 41/2 inches in inside diameter, 24 inches long, and with a Ijz-inch feed tube and a 1-inch discharge tube. The discharge port was 12 inches above the bottom of the reactor which was heated by a resistance furnace. Bed and furnace temperatures were measured w-ith Chromel-Alumel thermocouples and a continuous temperature recorder. About 5 pounds of bed material was used. Feed material, introduced by a screw feeder, could he varied from about '/z to 2 pounds per hour. The fluidizing medium, usually a mixture of nitrogen and carbon monoxide, was metered through a rotameter, passed through a pulsator which interrupted the flow approximately 600 times per minute, and then fed to the rcactor. Exhaust gases were passed through an electrical precipitator. The cobalt concentrate contained 12.27' of cobalt and 35y0 of arsenic which seemed to be in the form of sulfarsenides andlor arsenide, Other constituents in per cent were: S, 23.3; Fe, 11.2; Ni, 3.8; Cu, 1.6, and others, 23.3. The removal step is presumably a sulfide volatilization as As2S2 (boiling point, 565" C.) or As2 S3 (boiling point, 707" C , ) . Efficient volatilization required a sulfurto-arsenic ratio of a t least 1, and therefore additional sulfur as pyrite (FeS2) was added. Apparently, the reaction mechanism involves distillation of the labile sulfur atom of pyrite and conversion of the original arsenic compounds to their lower boiling point sulfides. Unless the treatment was performed in an inert or nonoxidizing atmosphere, oxidation occurred and an insoluble and refractory arsenic-cobalt complex was formed. A small amount of hydrogen or carbon monoxide, less than 5'%, was added to the nitrogen fluidizing gas to remove traces of oxygen. Excess sulfur is necessary, and u p to a ratio of 1.5 to 1, it progressively facilitates arsenic removal. About 1.1 to 1 seems adequate. This ratio is important but it seems less sensitive than temperature or retention time. Between 700' and 900" C . , arsenic volatilization increased from 20 to about 907'. Calcines containing about '/2y0of arsenic were produced which corresponds to an arsenic elimination of about 9570. Above 900' C. operation was impossible because the bed material tended to fuse and defluidize. Optimum
Table 1.
Materials Adaptable to Separation by Volatilization.
increased the degree of volatilization. About 90% of the germanium could be volatilized within 4 hours at o x - SulEleEleox- Sul1000" C. Such atmospheres probably prevent the ment Halide ide Jide ment Halide ide jide formation of nonvolatile germanium oxides or tend to reduce the original GeSz to the more volatile G e S . Also, Sb x Ni X As x x Nb X the hydrogen cancels the effect of water vapor. Thus, Be X P X if enough hydrogen or other reducing gas is added, such B X Si X X as carbon monoxide, combustion gases may be used for C X x Ag X heating. Further studies in a bench-scale fluidizedCe x S X bed reactor confirmed these results on volatilization. Cr X Ta X The zinc sulfide concentrate was essentially unchanged Ga X Sn X X by the volatilization treatment and could be used in Ge x Ti X conventional zinc-recovery processes. Hf X w X NIOBIUM. I n the extractive metallurgy of niobium, Pb X x v X volatilization is only one step. I n one method, the raw Hg x Zn x x x material is chlorinated and the niobium pentachloride Mo x x Zr X is separated from the gangue by volatilization. Although it is difficult to differentiate between effects a Flutdazed-solads techntques can be upeful for amfroving the processes. caused by chlorination and those caused by volatilization, the system was studied because it represents in principle, an important application of volatilization. temperature was 875' C. Retention times approxiA tube furnace was charged with a ZOO-mesh conmated those expected in commercial operation-i.e., centrate, containing about 5% niobium, which was about 4 hours. mixed with carbon and contained in porcelain boats. All heat must be supplied externally. The most Chlorine, gaseous carbon tetrachloride, or a mixture of logical method is through sensible heat of the fluidizing chlorine with other gases were introduced. The volatile gases and ideally, by using hot combustion gases. Such products were collected in a surface condenser cooled gases contain carbon dioxide which might deter arsenic with a dry ice-acetone mixture. The products collected removal, but nitrogen containing up to ZOyo of carbon on the surface condenser were weighed, hydrolyzed by dioxide with a trace of carbon monoxide was used withboiling with dilute acid, calcined, and reweighed. Also out deleterious effects. Thus, gaseous products of the residue remaining in the boat was weighed, and both combustion are usable provided free oxygen is excluded. products were weighed. A residual arsenic level of 470 permits acceptable At temperatures above 550" C., substantially all of cobalt recoveries from the calcines. This method apthe niobium was volatilized at retention times of about plied to a commercial furnace should result in calcines 1 hour. The condensates amounted to about 60% by containing less than 1yoor arsenic. weight of the original concentrate and contained about Sulfide sulfur content, about 25y0 in the low-arsenic ZOYo niobium tetrachloride, Z5y0 ferric chloride, 10% calcine, was substantially unchanged. Thus, autogtitanium tetrachloride, 25y0 silicon tetrachloride, and enous reaction in the subsequent oxidation treatment 20% of miscellaneous chlorides such as aluminum and for cobalt recovery can be maintained. The original manganese. Although recovery results were excellent, complex system of minerals was converted into a relait was obvious that the volatile products would have to tively simple mineralogical phase. The new phase be separated into individual components before the formed at the expense of the original ore minerals by process is feasible. Theoretical considerations and removal of arsenic and by crystalline rearrangement. limited experimental work indicate that this separation GERMANIUM FROM ZINC SULFIDECONCENTRATES. can be accomplished with fluidized-bed condensation. Many zinc sulfide concentrates contain appreciable Potential Uses of Volatilization. Volatilization techamounts of germanium which, if recovered, would be of niques offer several advantages in extractive metallurgy considerable value. A zinc flotation concentrate conand fluidized-solids technology : a flexible and efficient taining less than O.05y0 germanium with zinc and sulfur means for providing the necessary environment, good content of about 60 and 32y0, respectively, was used. gas solids contact, close control of treatment atmosphere, Volatilization experiments were performed in a tube uniform temperatures, and rapid heat transfer necessary furnace and static charges of the concentrate were heated for successful volatilization techniques. Many potential in Alundum boats to temperatures of 759" to 1000" C. uses involve processes which combine both volatilization As temperature increased, recovery rose from about 55 and condensation. If fractional separation of the volato 95%. Nature of the atmosphere was critical. With tile products is desirable, stagewise condensation in purified nitrogen, 75 to 80% of the germanium could be fluidized-solids equipment is advantageous. volatilized at 1000" C. within four hours. Traces of Other Areas Where Chemical Techniques May Be Applicable oxygen decreased recovery markedly-e,g., 3% of water vapor reduced volatilization to less than 20%. Heat Transfer in Steel Production. Material and On the other hand, traces of hydrogen in the nitrogen energy balances, concepts of unit operations, and VOL. 5 4 NO. 1 0 O C T O B E R 1 9 6 2
23
principles of heat transfer are being used increasingly. The steel industry furnishes an outstanding examplethe quality of steel is strongly influenced by temperature of the molten metal as it is poured into ingot molds. Also, if the mass cools excessively before pouring, production losses are caused by the metal freezing to the ladle. Temperatures from 2600’ to 3200’ F. must be carefully controlled, and heat losses during transfer of the metal from furnaces to molds must be known. Reduction of Iron Ores. Direct reduction of iron ore has received considerable attention, and many studies have been made tn determine the reaction mechanism. Several techniques under consideration are patterned after those already established in the chemical industry. Use of the fluidized bed is an example, and application of methods used by chemical I t
I,
engineers to correlate drying data may be productive in analyzing test results. Improving Blast Furnace Operation. During the last two or three years, the practice of injecting hydrocarbons into blast furnaces has been growing rapidly throughout the world. Several publications have given results obtained with natural gas and coke-oven gas, and data for Bunker C fuel oil are becoming available. However, data vary widely. Furnace operations seem to be important, but more work needs to be done. Plutonium Production. High purity plutonium metal has been produced in large quantities by bomb reduction techniques, but the process is difficult and time consuming. Electrorefining offers a simpler route, and processes are being developed which are also adaptable to processing of plutonium metal scrap.
”””I‘,
An inlagrated qsfm such m this fw extracting niobium WaJd h o c scocrof camrnnciol mimtagcs: ra@Z reaction and wlotiliration mu, &imt cadmation, and high Puriry producfs which arc easy to hnndle
7
I
Residue
Carrier gas Scrubber
Vent TiCli
REFERENCES h n Ore CDnceneation (1A) Barthdemy, R. D., Eng. Mining J . 159,87 (Decemher 1958). J. B., “FIotation of Iron Ores,” 8th Ann. Mining (2A) Cl-er, Symposium, January 1615,1947, Cox, R. P., U. S.Patent2,952,532
(3A) (4A) (5A) (6A) (7A)
(Scpt. 13, 1960).
Cronan, C. S.,C h . Eng. (May 5, 1958), p. 52. DeVaney, F. D., Trrmr. AIME 193,1219 (1952). E d . , 196, 1121 (1953). b a n , H. R., Radban, V. S., J. Minrr, Mefds, Fuclr (July 1960). (SA) Eridraon, S . E., plat. ATME 10,612 (1951). (9A) Firth,C. V., U. S. Patent 2,413,492 (Dee. 31, 1946). (1OA) Hain-, D. J., ‘‘Magnetizing Roarting,” Electmhcm. Soe. Ann. Meeting, Chicago,M a y 2-5,1960. (11A) Huhl, J. B., Eng. Mi* J. 160,89 (November 1959). (12A) Kirkland, T.G., Sollenberger, C. L., Platner, J. L., Edens, W. W.,, Blast Furnace Coke Oven and Raw Mat. Conf., AIME,
Philadelphia, April 1961. (13A) Llmdquiat, R. V., Mining Eng. 5,413 (April 1953). (14A) Makborin, K. E., Bugaenko, B. P., Mcfdlwgy, p. 1219 (Octoba 1960). (15A) Pe-n, P., SMlingr Mining Reo. 51, No. 9, 1 (March 3, 1962). (16A) Ricatley, R. J., Blarf Furnace and Sfeel Plan8 46, 30S6 . @ m h 1958). (17A) Ro+ L. A,, “Imn Ore Beneficiation,” p. 27, 102, Minerals Publishing Co.,Lake Blulf, 111. (18A) W i n g s Mining Rru. 48, No. 50 (March 12,1960). 24
INDUSTRIAL A N D ENGINEERING CHEMISTRY
t AlCii
Chlbrine
, Sicla
(19A) Zbid., 51, No. 6 (Feh. 10, 1962). (2OA) Sollenberger, C. L., “Current World Iron Ore Beneficiation Mcthoda,” A.1.Ch.E. Ann. Meeting, NewYork, N. Y.,Deecmher 6, 1961. (21A) Stowaaaer, W. F., Tram. ATME 202 4735 (1955). (22A) Udy, M. J., Blackbum “Strategic-Udy Direct Iron Reduction Roe-s,” Keppers &., Inc., Pittsburgh, Pa. (23A) Urich, D. M., Mining World 23, No. 12, p. 30. (24A) University of Minnesota Institute of Technology, “Iron Ore Beneficiation,” p. 27, October 1, 1949. (25A) Wade, H. H., Schulz, N. F., Trrmr. ATME 217, 479-83 (1960). (26A) Wucrker, W. E., Mining Eng. (January 1951), p. 25. Nonferrous Processes
(1B) Bahina, I. V., T m f n y e M d d . 31.70-7 (July 1958). (2B) Caldwell, H. S., others, U. S. Bur. Mines Rcpt. Invest. 5703, h c m h c r 1960. (3B) Coffer, L. W., C h . Eng. 65 (Z), 107-22 (1958). (4B) Dancy, W. B., U. S. Patent 2,804,373 (Aug. 27, 1957). (5B) Handbook of Nonferrous Metallurgy (2nd ed.), Vol. 2, pp. 54651, McGraw-Hill, New York, 1945. (6B) Kenworthy, H., others, U. S. Bur. Mines, Rcpt. Invest. 5190, January 1956. (7B) Kershncr, K. K., Caehran, A. A,, U. S. Bur. Mines, Rcpt. Invest. 5298, January 1957. (8B) Nord, M., C h . Eng. 58 (9), 15746 (1951). (9B) Sehlechtcn, A. W., Eng. Mzning J. 155 (ll), 81-3 (1954). (10B) Sieger, J. S., Fink, C. G., Tbid., (10) p. 10-13.
r
