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During the course of an investigation into the fundamental chemistry of the cyanide process, it became evident that the usual method of determining protective alkalinity was not completely satisfactory. T.he routine method for the determination of protective alkali by first removing free cyanide by the addition of silver nitrate, followed by titration of alkali with dilute acid using. phenolphthalein as indicator, can be shown to give correct results only when the alkali is a strong base. For other sUbstances, the alkali so determined is not the protective alkali. In view of the complications associated with the presence of zinc in cyanide solutions the discussion will be restricted in the first place to solutions free from zinc. Until the chemistry of simple cyanide solutions is placed on a quantitative basis it will be difficult to elucidate the behaviour of complex mill solutions.By the use of physico-chemical theory, it is possible to treat certain aspects of 'the chemistry of cyanide solutions in a manner which not only illustrates the important variables involved, but which also shows the need for care in interpretIng results obtained by conventional methods.In the following, comparatively simple systems are discussed; the principles established should be of use in interpreting the behaviour of more complex solutions. The methods described are not intended for routine work, but may be regarded as supplementary to the usual analysis carried out for the control of plant solutions, or as alternatives to be used when the latter do not appear to be satisfactory.

Jan 1, 1948

By David R. Sadedin

The highly negative Gibbs free energies of hydrogen atom reactions suggest that refractory oxides such as titanium dioxide should be easily reduced by hydrogen atoms. These reactions appear to be most favourable at low temperatures; oxides should be reducible even at room temperature. Since hydrogen atoms are produced in plasmas containing hydrogen a number of investigators have used hydrogen plasmas of various sorts to test these possibilities for reducing refractory oxides, in particular TiO2. None of these attempts has succeeded, a small degree of reduction being achieved in only a thin layer near the surface. A deeper consideration shows that several factors complicate the reactions expected on the basis of the negative Gibbs free energy. One factor is that the back reaction by water molecules produces molecular hydrogen, not hydrogen atoms, and the metal atoms that have been reduced may be immediately re-oxidised. In plasmas there are complications due to diffusion, thermal and charge boundary layers and charged particle reactions. Interpreting the results of hydrogen atom reactions is difficult. Hydrogen is not detectable by electron dispersive spectroscopy and amorphous products are not determinable by x-ray diffraction. Another consideration is economics. The cost of producing hydrogen atoms has a large bearing on the metals for which hydrogen atom reduction may be competitive. In this paper these factors are discussed, some necessary basic studies are highlighted and the general principles of a laboratory reactor are given, together with the results of tests using ZnFe2O4, ZnO and TiO2 as test oxides.

Jan 1, 2006

By H. R. Masoumi

This paper presents a numerical model for the prediction of free field vibrations due to vibratory and impact driving. As the focus is on the response in the far field, where deformations are relatively small, a linear elastic constitutive behavior is assumed for the soil. The free field vibrations are calculated by means of a coupled FE-BE model using a subdomain formulation, proposed by Aubry and Clouteau (1992). The model is validated by means of the results of Kaynia and Kausel (1991) for the impedance of a single pile. First, the case of vibratory pile driving is considered, where the contributions of different types of waves are investigated for several penetration depths. The results show that in the near field, the response of the soil is dominated by a vertically polarized shear wave, whereas in the far field, Rayleigh waves dominate the ground vibration and body waves have been importantly attenuated. Second, the case of impact pile driving is considered. A linear wave equation model is used to estimate the impact force during the driving process. Furthermore, it is investigated how the soil stratification influences the ground vibration considering the case of a soft layer on a stiffer half space. The results show that when the penetration depth is smaller than the layer thickness, the layered medium has a small influence. However, when the penetration depth is larger than the layer thickness, these effects become more significant. Finally, the computed ground vibrations are compared with experimental data reported in the literature.

Jan 1, 2006

By Arkady Senchenko, Yuri G. Seredkin, Alexander Aksenov

"This paper describes the development of efficient technology for the treatment of complex ores containing gold and copper as major valuable components, where silver is present as well. Copper is mostly represented by oxidized minerals in these ores; however, copper sulfides are also present. Gold is present in its free form and in associations with oxidized and sulfide minerals; silver usually accompanies gold. Complex composition of the ore requires complex solutions for their treatment. The results of searching for the techniques to recover valuable components are described in this paper. Gravity methods allow for free gold recovery, flotation methods allow one to recover major part of copper and precious metals in associations; and in the result of leaching process additional amount of copper, gold and silver is reported to solution. Combining all these methods help achieving high levels of valuable components recovery. When implementing a combined technological flowsheet about 80 % of copper goes to concentrates from gravity and flotation of sulfide and oxidized copper minerals; and sulfuric acid leaching allows increasing total copper recovery up to 90 % and higher. Major part of precious metals (up to 90 % of gold and 80 % of silver) is recovered to these concentrates, and after hydrometallurgical treatment it is possible to increase gold recovery up to 96 %, silver recovery - up to 90 %. The suggested technology helps solving the problem of precious metals recovery from complex gold-copper ores, and allows treatment of the ore with different proportion of sulfide and oxidized minerals, and at different valuable components grade."

Jan 1, 2014

By Edmund Leaver

IT is generally recognized that the .addition of limited small amounts of various lead salts may aid the extracting power of the mill cyanide solution in the dissolution of silver from ores and in some cases may aid in the treatment of gold ores. Excess soluble lead compounds retard the dissolution of precious metals by the usual mill cyanide solution. Another phase of cyanidation is the use of the zinc-lead couple as an aid to better precipitation of gold and silver from solution containing a low percentage of cyanide. The chemistry of the use of lead salts in cyanidation has been dis-cussed by Clennell;1 the addition of lead salts in various cyanide mills is recorded by von Bernewitz;2 and the reasons for the use of lead salts in cyanidation have been explained by Clevenger.3 This paper deals with the adaptation of cyanidation to a different condition, in which the presence of lead minerals in a gold ore that is refractory to direct cyanidation complicates the treatment. If free gold is roasted in the presence of sulfur and lead salts, or if pyritic gold ores containing even a small percentage of lead minerals are roasted to free the gold from the pyrite, lead compounds coat the gold particles enough to make them almost insoluble in the usual mill cyanide solution contain-ing lime for protective alkalinity. Also, the lead compounds remaining in the calcine are slightly soluble in the mill solutions and such dissolved lead may retard the dissolution of the gold by the removal of oxygen or

Jan 1, 1933

By J. W. Rutter, K. T. Aust

Observations are presented of the formation of annealing twins during the growth of a recrystallized grain into a striated, melt-grown crystal of high-purity lead. The formation of an annealing twin resulted in replacement of the original migrating boundary by a large-angle grain boundary of the caincidence-site type or by a near-twin boundary. The results support the Fullman-Fisher theory of annealing twins and demonstrate the usefulness of the coincidence-site model. FULLMAN and Fisher1 have advanced the following theory to account for the formation of annealing twins during grain growth. Whenever a grain A grows into a matrix of grains S1 and S2, a twin A' of grain A may form, as shown in Fig. 1, if the following energetic condition is satisfied: where "E" and "a" refer to the specific interfacial free energy and the area, respectively, of the boundaries indicated by the subscripts. In effect, the twinned grain will persist when the energy of the boundary between the twin(A') and the matrix grain (S, or S,) is less than that of the boundary between the original growing grain (A) and the matrix grain by an amount which exceeds the energy of the coherent twin boundary between A and A'. Experimental observations on the changes in grain boundary free energy accompanying the formation of twins1 are in agreement with the theory outlined in Eq.[l]. Direct observations of the formation of annealing twins at moving grain corners1"3 and the depend-

Jan 1, 1961

By Clifford Wilson

SCREENED pipe is designed with the view of restraining the fine, free-running sands of the production zone from entering oil wells. Its successful use is dependent on a number of factors. The nature and effects of some of these factors can be determined through experiment and observation, but some of the elements that have a distinct bearing on the use of screened pipe can be evaluated only by estimate. The important subsurface conditions which affect the use of screened pipe are: 1. Depth of production zone. 2. Extent of production zone. 3. Reservoir pressure. 4. Character and relative quantity of oil and gas. 5. Character of sediments a. Consolidation of beds. b. Variation in beds. c. Grain-size gradation of sands. d. Free-running characteristics of sand from different levels. Aside from the use. of mechanical equipment and tools, the measures to be taken in the installation of screened pipe involve: 1. Size of liner. 2. Length of liner. 3. Design and mesh of screen. 4. Portion of liner to be screened. 5. Manner of setting liner. 6. Preparation of or washing of the well before or during the setting of the screen. 7. Manner of bringing in the well. 8. Manner of flowing the well. Values applicable to the actual subsurface conditions that exist at any well can only be approximated. The accuracy of the estimate will be measured by the amount and quality of the evidence at hand and the personal factor of ability to interpret the evidence fairly, whether

Jan 1, 1932

By J. Tikka, E. Bäcklund, N. -O. Lindfors

Tornados are the most violent weather events in the world, and we have all seen the forces and phenomena created by tornados in nature. Airgrinder AB has been working with a material treatment technology, which most easily could be described as an artificial tornado. The process consists principally of one air fan providing a high-velocity airstream that enters a mechanical cyclone. When the gas enters the cyclone, an outer vortex is created. This outer vortex rotates next to the cyclone wall, and at the bottom of the cyclone funnel the gas stream is turned and an inner vortex is created. The control of the air flow is tuned by a special device on top of the cyclone. The gas outlet is at the top of the cyclone and the material outlet at the bottom. The material is fed through a feeding device into the air stream channel prior to the inlet into the cyclone. The process is basically an improved grinding and dehydrating system, which is very efficient and environmentally friendly and can even be employed with very sticky materials. Also due to its rotating comminution, the material particles become rounded during grinding, hence more free flowing and easier to handle. MEFOS has already tested more than 30 different applications in the pilot equipment. The materials tested range from metallurgical slags containing 2?3% moisture to sludges with up to70% moisture. This technology has a potentially strong impact on mineral beneficiation, including the drying of sticky fine-grained materials, improved and selective gas scrubbing and the manufacture of free flowing powders.

Jan 1, 2007

By J. E. Johnson

The subject of blast-furnace slag is one which has had much consideration, particularly from the scientific standpoint, and several years ago technical literature contained many learned discussions on the oxygen-ratio of the acids and the bases, all on the assumption that acids and bases must be present in a ratio depending on molecular weight and chemical valency. Much work has also been don.e, sometimes in conjunction with the former, on the total heat and the temperature of initial fusion or softening of various slags. A wider knowledge of the blast-furnace now enables us to say that for practical purposes this work has been of almost no value. It is now generally admitted that on,the physical side the important point of a given slag is neither its total heat of fusion nor its softening-point, but its free-running temperature, since this is the critical temperature of the furnace. This temperature bears no definite relation to the softening-temperature, as determined by Seger cones, for instance, because some slags melt relatively like ice, with a very short viscous-range, while others melt relatively like tar, with a very long viscous-range. In one the difference between the softening- and the free-running temperature may be very small, as little as 100° F., while in another this difference may easily be 200' or 300°. The importance of this difference is so great in practice as to destroy completely the value of exhaustive investigations, even such as those of 0. Boudouard, published a few years ago.'

Jan 1, 1913

By Clifford S. Wilson

ScReened pipe is designed with the view of restraining the fine, free-running sands of the production zone from entering oil wells. Its successful use is dependent on a number of factors. The nature and effects of some of these factors can be determined through experiment and observation, but some of the elements that have a distinct bearing on the use of screened pipe can be evaluated only by estimate. The important subsurface conditions which affect the use of screened pipe are: 1. Depth of production zone. 2. Extent of production zone. 3. Reservoir pressure. 4. Character and relative quantity of oil and gas. 5. Character of sediments: a. Cossolidation of beds. b. Variation in beds. c. Grain-size gradation of sands. d. Free-running characteristics of sand from different levels. Aside from the use of mechanical equipment and tools, the measures to be taken in the installation of screened pipe involve: 1. Size of liner. 2. Length of liner. 3. Design and mesh of screen. 4. Portion of liner to be screened. 5. Manner of setting liner. 6. Preparation of or washing of the well before or during the setting of the screen. 7. Manner of bringing in the well. 8. Manner of flowing the well. Values applicable to the actual subsurface conditions that exist at any well can only be approximated. The accuracy of the estimate will be measured by the amount and quality of the evidence at hand and the personal factor of ability to interpret the evidence fairly, whether

Jan 1, 1933

By M. M. Papic, J. C. Whitehead

"A sample of Hat Creek coal has been extracted using supercritical aromatic solvents in a laboratory-scale extraction unit. Extract yields in the range 21 to 27 per cent of dry-ash-free coal were obtained.These yields are significantly lower than yields available from high-volatile bituminous coal and some lignites. Thus in a combined extraction/hydrocracking scheme for the production of liquid fuels from Hat Creek coal the char product would exceed that required to supply the energy and hydrogen requirements of the process. Excess char could be used for the production of power or gas for sale.IntroductionThe Supercritical Gas Extraction (SGE) process developed by the U.K. National Coal Board operates in two stages: an extraction stage in which a coal extract is separated from mineral matter and undissolved coal and a subsequent hydrogenation stage.The SGE process is based on the ability of a compressed supercritical fluid to dissolve relatively high molecular weight substrates. It is operated under conditions where a hydrogenrich portion of the coal is selectively extracted in a short residence time extraction stage leaving a hydrogen-deficient char. The process schematic shown in Figure I illustrates that the extract produced is separated from the solvent and passed to a conventional hydroprocessing stage while the char product is utilized in the production of heat, power and hydrogen for the process. An extract yield in the order of 50 per cent dry-ash- free coal represents a ""balanced"" case for such a process in which there is just sufficient char for the provision of these commodities."

Jan 1, 1985

By D. Reddish

The combination of free standing steel supports, such as arches, and rock bolts (mixed support) has Frequently been in used in UK coal mine roadways when it is considered that the strata and/or environmental conditions would not be suitable for rock bolts solely. However, how such mixed support systems operate is not fully understood. Due to the differences in the support method provided by rock bolts and free standing steel, the total support generated is not simply a case of adding the contribution to the support of the roadway given by the two systems. This paper describes a numerical investigation into mixed support systems when used in coal mine roadways. A series of 2D and 3D geomechanical models are described and the method of modelling the rock bolts and steel supports in coal mine tunnels is discussed. The numerical models described include rock boltd only roadways, steel supported roadways and mixed supported roadways in a variety of geological and in-situ stress conditions. Conclusions are formed that allow an insight into mechanisms of strata reinforcement provided by the support systems modelled. Further to this, a review of the numerical modelling of pre-tensioned rock bolted systems is described identifying the contribution to support efficiency given by the adoption of tensioning in full column resin anchors. The results obtained highlight that the effectiveness of the pre-tensioned load is dependant on the rock mass quality and in- situ stress level at the site where it is to be used.

Jan 1, 2004

By Ronald R. Bauer

Wollastonite is a little known industrial mineral of the silicate group. The largest and purest known deposit in the free world is being mined and beneficiated in Millsboro, New York by NYCO, A Division of Processed Minerals Incorporated. The associated garnet and diopside are separated from the wollastonite using dry high intensity magnetic separators. Beneficiated wollastonite is used extensively as an additive and filler in the ceramic, paint, refractory, and wallboard industries. Wollastonite acts as a functional filler due to its unique chemistry and physical acicularity.

Jan 1, 1982

By Tim Robinson, Georges Houlachi, Michael Moats, Marco Ginatta, Michael Free, David Creber, Neale Neelameggham, George Holywell

"Electrolytic processing is used commercially to recover and/or refine metals such as aluminum, copper, magnesium, nickel, and zinc. There are also new and exciting opportunities to utilize electrometallurgy in the production of titanium, lead, and other metals. This paper reviews some of the main technologies that are used to produce and refine metals as well as some of the recent advances and future directions the electrometallurgy industry may implement to meet the challenges faced now as well as those that are likely to be faced in the future.IntroductionElectrolytic processing is used commercially to recover and/or refine metals that include large scale production for metals such as aluminum, copper, magnesium, nickel, and zinc as well as small scale production for metals such as gold and silver. There are also new and exciting opportunities to utilize electrometallurgy in the production of titanium, lead, and other metals. This paper will focus only on electrometallurgical processing of metals with relatively large production markets."

Jan 1, 2012

By Benjamin H. Clark

"For over 50 years, Derrick Corporation has been renowned for its innovative and durable fine screening equipment and screen surface technology. Derrick’s latest innovation, the patented Stack Sizer, offers mineral processors both high tonnage capacity and high separation efficiency on an extremely small footprint.The Stack Sizer is suitable for separations from 6.3 mm down to 75 microns (200 mesh). The Stack Sizer, coupled with Derrick’s patented urethane screen surface technology, offers an extremely economical alternative to hydraulic classifiers, hydrocyclones, and less efficient low volume wet screening systems. Stack Sizers have been used in feed preparation for flotation, spirals, and a variety of jigs. Mineral processors wishing to reduce grinding circuit circulating loads and generation of slimes due to over grinding, thereby enhancing the efficiency of flotation and gravity circuits, now have another technology at their disposal to perform this critical sizing and grade control function.Over 200 Stack Sizers have been installed in numerous mineral processing applications worldwide attesting to the rapid acceptance of this technology. Stack Sizers are currently screening ferrous and non-ferrous metal ores, mineral sands, silica sand, kaolin clay, feldspar, garnet, phosphate, aluminum dross, potash, coal, tantalum, spodumene, niobium, and other rare earth mineral ores.INTRODUCTIONDerrick engineers have long understood and demonstrated the importance of screen width in coupling both high capacity and high separation efficiency for fine wet sizing applications. As opposed to fine dry sizing, where the length of the screening machine is critical for high separation efficiency, introducing slurry feed to screens in a thin and even layer at minimal velocities across wider screen surfaces allows for high capacities and efficiencies, with maximum screen cloth life. This is due primarily to the combination of free liquid and high frequency vibration of the Derrick motors, which allow fine undersize material to pass through the screen apertures. Lacking either of these factors would be extremely detrimental to the screening process. Without the high frequency vibration of the motor, the screen is essentially a low efficiency sieve bend. Without the free liquid to carry fines through the screen openings, the screen is for all intents and purposes a glorified conveyor or dewatering unit, as little or no sizing takes place once the screen is devoid of free liquid. For optimal screening results, Derrick recommends feeding slurry to a screen at approximately 20% solids by volume. Figure 1 shows the Stack Sizer design concept. Note that a single feed point is used to evenly distribute the flow to the five separate feed points."

Jan 1, 2007

By Jessie L. Bonner, W. Stephen Blomberg, Mark Leidig, Heather Hooper

Understanding the effects of the bench on ground motion can improve the design of cast blasts and achieve improved blast efficiency while remaining below vibration requirements. A new dataset recorded in September 2003 from a coal mine in Arizona has allowed us to examine the excitation of short-period Rayleigh-type surface waves from four simultaneously-detonated explosions in and below a topographic bench of a mine. The explosions were recorded on a network of over 150 seismic sensors, providing an extensive understanding of the ground motion radiation patterns from these explosions. We detonated two separate explosions (~3 tons and ~1.5 tons ANFO) in the deepest pit of the mine, thus the explosions were shot to solid rock. Within 25 meters of these two explosions, we detonated two additional explosions of similar explosive yields in a bench, thus these explosions were shot to the free face. Radiation patterns and spectral ratios from the explosions show increased amplitudes (by a factor of 1.5 to 2) at azimuths behind the bench relative to the amplitudes in front of the bench. We compared these findings to seismic observations from two ~1.5 million pound cast blasts at the same mine and found similar radiation patterns. Modeling of these blasts shows that the variations in ground motion are caused by the topographic bench as a result of 1) horizontal spalling of the rock falling into the pit and 2) non- linear scattering near the free- face. We also note that shooting to a buffer (previously blasted rock) causes the azimuthal variations to be significantly reduced.

Jan 1, 2005

Safety is the No. 1 concern of any drill contractor or mine operator. Everyone in the industry knows a safe site helps stabilize operational costs and enables higher productivity. When it comes to exploration drilling, research has proven a majority of injuries are caused by the mishandling of coring rods. A driller helper will typically handle up to 50 rods per shift or up to 15,000 rods per year. With an annual 340 t (750,000 lb) in rods managed by hand, the risk of serious injury is extremely high. Because of this, the top request from the exploration industry is diamond rod handling. The Boart Longyear 4200 surface exploration drill, slated for release in 2009, will give the industry a hand-free, operationally safe rig.. Developed through the collaboration of its global drilling services and products divisions and targeted at the 1,200-m (3,900-ft) NQ market, the upcoming Boart Longyear 4200 surface exploration drill features the safest and most flexible rod management sys-tem in its class. The rig includes the industry?s first, truly hands-free rod handling system. This increases operator safety on the jobsite. In addition to the rod handler, the rig also features many new innovations that boost productivity and rig efficiency while minimizing the risk of downtime due to component failure or operator error. Boart Longyear has also included an intelligent PC-based operating system designed to allow complete drilling control as well as diagnostics reporting for the rig.

Jan 1, 2009

By W. A. Ahrens, J. H. McNamara, J. G. Franek

"An economical, pollution-free process has been developed for the hydrometallurgical extraction of copper from sulphide ores. The extracted copper, in the form of cuprous chloride (CuC/), is converted by reduction to copper metal. The metal is melted and fire -refined into wire bars which meet the standards of electrolytic tough pitch (ETP) copper wirebars. IntroductionThe successful development of the Cyprus Copper Process has been an evolutionary series of events covering a time span of some nine years. The original process, based on an electrolytic membrane cell principle , was abandoned in 1975 because of technical, economic and pollution problems. During the past four years, the pilot plant has been reconstructed based on a new flowsheet and operated successfully in several campaigns, some for as long as four months. The pilot-plant hydro section operates at a 225-lblhr copper rate. In October 1977, a feasibility study was completed by Jacobs Engineering, Pasadena, California. The study showed favourable economic and technical feasibility. Jacob's studies in 1978-79 revealed favourable comparative economics with other known pyrohydro processes and favourable economies of scale.The Cyprus Copper Process converts copper concentrates of varying composition into copper metal, which has been proven to be equivalent in every way to electrolytic tough pitch copper, suitable for electrical applications. This is accomplished at capital and operating costs which are estimated to be lower than those associated with any other known currently applicable technology. Also, the total energy requirement is equal to or less than any other known process and the process is essentially pollution free."

Jan 1, 1980

By None None

Use this month wisely — go online and take advantage of your new member benefit. As an SME member, you can read and download for free all of the full-text papers of the Mining, Metallurgy & Exploration (MME) journal, including the 22 papers in the launch Special Issue on Mineral and Metallurgical Processing in Honor of Professor Emeritus Douglas W. Fuerstenau as well as the archived articles of Minerals & Metallurgical Processing (MMP), all the way back to Vol. 1, No. 1. Just follow the instructions on this page.

HIGH-GRADE manganese ore, from which manganese is obtained commercially, is not found in large quantities in any major steel-producing nation in the free world. The U. S. is a "have not" nation with respect to deposits of directly mineable high-grade manganese ore. Known resources of 48 pct Mn or better grade ore amount to less than 200,000 tons. In 1950 the U. S. steel industry consumed 1.8 million short tons of metallurgical grade manganese ore that contained about 800,000 tons of manganese. About 16 pct of the manganese content was lost in processing, so that about 650,000 tons, or 13 pounds per ton of steel actually entered into steel production. Under present practices use expands directly with steel output, and by 1975 the demand in both the U. S. and the rest of the free world is expected to be roughly 60 pet greater than in 1950. In peacetime about 80 pet of manganese consumption goes into steel production; high-manganese steel, dry cells, and chemicals account for the remainder. The manganese supply problem centers around high-grade ore for ferromanganese production. Use of ores containing less than 35 pet Mn sharply increase the costs of making ferromanganese. Use of ferro-manganese of grade below 70 pet in turn requires changes in steelmaking that increase steel cost. Under normal conditions the present small domestic production cannot be expected to increase. Major resources in the U. S. consist of 12 low-grade deposits. The cost of mining and treating these ores to extract a product as good as that yielded by imported ores is at least twice and in some cases more than four times the 1951 price of foreign ores delivered to the U. S. However, as long as trade relations and overseas shipping are not interrupted, deposits in India, Africa, and Brazil can meet steadily increasing demand at approximately present costs. Cost considerations indicate that the U. S. should continue to rely upon overseas sources for its peace-time supply, and that this situation is satisfactory. But, this does not take into account the question of how the U. S. will be able to meet its needs in war. Position of the Rest of the Free World In 1950, free world steel producers outside the United States, with a steel output of 70 million ingot tons, consumed about 1.3 million tons of metallurgical-grade ore. Their manganese ore demand, expected to increase directly with steel production, will by 1975 be about 2.3 million tons. Russia possesses over half the known manganese ore reserves of the world and is producing twice the tonnage of any other country. It supplied more than a third of the U. S. manganese requirements up to 1938 and again in 1948, but by 1950 Soviet manganese exports to the free world had virtually ceased. The free world's supply of manganese now comes mainly from India and Africa. Somewhat over 10 pet of U. S. imports came from Brazil and Cuba. Security Considerations In the event of war the U. S. might be substantially cut off from 90 pet of present sources. Reduction in manganese specifications might cut consumption by over 10 pet without seriously affecting steel quality. By elimination of losses in the production of ferromanganese savings as high as 10 pet might be possible. But, wartime manganese requirements cannot be met through conservation alone. To meet possible future emergencies the U. S. should continue its comprehensive security program for manganese, including stockpiling and research on the economic use of low-grade ore, domestic ores, the recovery of manganese from slag and the reduction of manganese requirements in steel production. If this work, including additional pilot plant operation is pursued vigorously, it should be possible in an emergency to get an adequate supply of manganese from domestic sources. The national stockpile then can be looked upon as a source of supply during the period of at least 2 years required to reach full-scale production from low-grade resources. Ferromanganese Smelting In comparison with smelting of pig iron, ferro-manganese smelting is a very wasteful process. Under present ferromanganese blast-furnace smelting practice, about 8 pet of the manganese in the furnace charge is lost to the slag, and roughly the same amount is lost to the stack gases; the total loss approaches 15 pct. Present practice is a compromise between excessive slag loss and excessive stack loss. In fact, it may be seriously questioned whether conventional blast furnace design is suitable for manganese smelting. U. S. Resources The known manganese deposits of the U. S. contain a total of 3500 million long tons of raw material and 75 million long tons of metallic manganese. More than 98 pct of this contained metal is in 12 large low-grade deposits of which the most important are those at Chamberlain, S. Dak; Cuyuna, Minn.; Aroostook County, Maine; and Artillery Peak, Ariz. Reserves of high-grade ore (48 pct Mn) amount to less than 200,000 tons. About 20 million tons of ore average over 15 pct Mn, and when grade is decreased to 10 pct Mn reserves amount to about 100 million long tons. If cut-off grade is decreased to 5 pet Mn, resources amount to 800 million long tons. Many of these low-grade ores may be beneficiated by flotation or other concentration methods. Pyrometallurgical Methods For smelting ferromanganese, it is essential to have an ore containing at least 50 pct manganese, with an Mn:Fe ratio of about 8:1. Direct smelting of 20 pct Mn concentrates is not promising. The only method that offers any promise involves two-step smelting.

Jan 1, 1952