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By Mário César Mantovani

The steel for gas turbine compressor discs (26NiCrMoV14.5) requires some mechanical properties like strength, impact, toughness, fatigue, and creep resistance in order to be used in such application. To achieve the properties required for the gas turbine compressor discs, the material should have very low contents of sulfur, phosphorus, antimony, tin and arsenic. The level of cleanliness should also be very high and this is possible by achieving low oxygen content keeping the deoxidation elements like silicon, manganese and even the aluminum in very low percentages. The main problem in refining such steel is to adjust a sufficiently low oxygen content to have a good desulfurization and at same time a good cleanliness without using silicon, manganese or aluminum as deoxidizers. Combination of initial selection material, steelmaking process control, forging sequence and heat treatment cycles can provide uniform mechanical properties throughout the gas turbine compressor discs. Villares Metals SA as a big player on special steels with complex process has been developing this kind of material for several years. The objective of this work is to show the process technology evolution involved in the production of this kind of steel under the discussed preconditions.

Aug 17, 2017

By Duk-Won Park

The excavation of a longwall panel causes a continuous stress redistribution in the surrounding strata for every face advancement. The understanding of the behavior of rock to high level of stresses is instrumental to the structural design of underground mines. In order to achieve a realistic analysis of the behavior of strata, the three-dimensional finite element method is frequently used. Also the model developed for the analysis has to be designed large enough to represent the influenced strata in the study area and a sufficient number of elements has to be used to provide detailed information on the stresses and displacements. Due to the size of the model and its numerical solution the CRAY X-MP/24 supercomputer has been used for this study. The mine site selected for the analysis is a coal mine located in the Black Warrior Basin in Alabama. The mine has two longwall sections at a depth of 2,000 feet with various dimensions of chain pillars, including yield pillars. Various research programs at this mine have been carried out by Park et. al. ( 1984 ). Therefore data were already available on the geology, and physical properties of rock and coal. In addition a rock testing program has been carried out to obtain rock mass classification parameters. The progressive failure technique has been utilized to simulate stress redistributions. The failure criterion after Hoek and Brown ( 1980 ) which is based on rock mass behavior was used for the iterative technique. Simulated stress redistributions are therefore very realistic. In order to automate the process involved in the application of progressive failure technique, a computer program has been developed. The combination of a large scale three-dimensional finite element model and the automation of progressive failure simulation provided a tool that can generate a large amount of information related to the behavior of rock and coal as a response to a longwall mining operation.

Jan 1, 1989

By R. Houot, C. Leschevin, G. Gillet

In mineral processing, conventional magnetic separators are equipped with traditional magnetic circuits (magnetic iron yoke with copper coils or iron-clad solenoid) that develop magnetic fields of less than 2 T'. For minerals of low magnetic susceptibility, use of these circuits has many disadvantages. Only a separator with a superconducting magnet can contribute to solving the problems and produce a high magnetic field. This paper presents and describes a magnetic separator having a superconducting magnet with integrated closed circuit for helium liquefaction. The system generator and maintenance are simplified by extensive automation realized by a versatile program- mable autocontrol unit. A comparative study if the results on concentration and purification of different raw materials with the new and with conventional separators is described.

Jan 1, 1987

By F. S. Knoll

Magnetic separation employing superconducting technology is now accepted within the Kaolin processing industry, proving the value of this technology and its ability to operate reliably even at the most remote site. Developments in superconducting magnet engineering, including cryogen free operation, combined with experience in mineral processing enables new forms of Wet and Dry superconducting magnetic separation to be developed. Applying the high magnetic force advantages at 5 T else available from such magnets to other materials is now a reality. High magnetic force mineral separating system developments are reviewed allowing the mineral processor to take advantage of a technology that is no longer confined to the laboratory.

Jan 1, 1997

By M. Rieber

The potential for the wide-spread commercialization of superconductivity, the disappearance of all resistance to a direct current (D.C.) electric flow, began in 1986-87 with the development by Bednorz and Muller at IBM's Zurich Laboratory of an yttrium -barium -copper oxide conductor which attained zero resistance at 90t:. Although the status of superconductivity is still pre-bench scale, it is useful to forecast its probable effects on the copper industry. I t should not be forgotten that at their inception, the impacts of transistors, semi-conductors, thin films and fiber optics on the electric/electronics sector of this industry, were largely underestimated. Superconductors are not metals, but a class of ceramics. They represent an efficiency increase of one or more orders of magnitude. If their development is to be a boon to the copper industry, rather than a reduction of metal demand through miniaturization or material substitution, vastly expanded copper containing electrical uses must be in prospect. In this paper the projected uses of high temperature superconductivity are examined, followed by the remaining problems to be overcome. Assuming success, a time horizon for maturation is estimated. The penalties for the non-recognition of new markets and material substitution are shown on the basis of past forecasts. Finally, the application of successful superconductivity to the copper industry over the forecast period is estimated.

Jan 1, 1990

By Anja Pfennig, Axel Kranzmann, Sabrina Schulze

The CCS technique involves the compression of emission gasses in deep geological layers. To guarantee the safety of the site, C02-corrosion of the injection pipe steels has to be given special attention when engineering CCS-sites. To get to know the corrosion behaviour samples of the heat treated steel 1.7225 42CrMo4, used for casing, and the stainless injectionpipe steel 1.4034 X46Cr13 were kept at T=60 °C and ambient pressure as well as p=lOO bar for 700 h - 8000 h in a C02-saturated synthetic aquifer environment similar to possible geological on-shore CCS-sites in the northern German Basin. The isothermal corrosion behaviour obtained by mass gain of the steels in the gas phase, the liquid phase and the intermediate phase gives surface corrosion rates around 0.1 to 0.8 mm/year at ambient pressure and much lower about 0.02 to 0.2 mm/year at 100 bar where the C02 is in its supercritical state. Severe pit corrosion with pit heights around 4.5 mm are only located on the 42CrMo4 steel. Main phase of the continuous complicated multi-layered carbonate/oxide structure is siderite F eC03 in both types of steel.

Jan 1, 2013

Today’s world relies upon advanced green technologies that are made of critical elements with unique properties. Examples include rare earth elements (REEs) that are critical in the manufacturing of wind turbines and electric/hybrid vehicle batteries, key components of a greener future that face supply uncertainty and near zero recycling. To tackle their supply challenges, activities have begun for urban mining from waste electrical and electronic equipment (WEEE) that contain considerable amount of REEs, but their current level of recycling is less than 1%. Current recycling practices use either pyrometallurgy, which is energy intensive, or hydrometallurgy that utilizes large volumes of acids and solvents and generates large volumes of hazardous waste. In this study, we developed a novel and sustainable process to recycle REEs from WEEE, NiMH batteries in particular. The developed process relies on supercritical fluid extraction (SCFE) utilizing CO2 as the solvent, which is abundant, safe, cost effective, and inert. The effect of seven operating parameters, namely temperature, pressure, residence time, sample to chelating agent ratio, agitation rate, complex formulation, and methanol addition on REE extraction efficiency was investigated, and optimum operating conditions were determined. This work is the first to utilize a very efficient and safe process that runs at low temperature to extract metals from postconsumer products with minimum hazardous waste generation, while offering about 90% leaching efficiency for REEs. We expect our process to find widespread applicability in urban mining of REEs using green chemistry.

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 W. Swisterski, G. Romaniszyn, S. A. Lukasiewicz

The present paper analyzes the motion of a particle of material in a horizontaly rotating tumbling mill. The sliding of the particle under action of dynamic and friction forces and its free flight fall are analyzed. It was found that mechanism of free-fall occurs at supercritical rotations of the mill.

Jan 1, 1991

By D. C. Seidel, W. K. Tolley

Supercritical water alters the structure of common sulfide minerals by partially removing sulfur from the mineral structure. This discovery has been applied to the treatment of pyritic gold ores to improve precious metal recovery without generating or utilizing environmentally sensitive products such as S02, chlorine, or cyanide. Pretreating pyrite concentrates in supercritical water under mildly oxidizing conditions provided by certain metal oxides or oxygen improved gold leaching using thiourea. The pretreatment differs from chlorination or roast pretreatments in that elemental sulfur rather than sulfuric acid is the major product. A pyritic ore containing 58 g/mt Au was pretreated with oxygenated supercritical water at 24 MPa and 400°C, then leached with 20 g/L thiourea. With pretreatment, gold recovery was 90%; by contrast, gold recovery was below 10% without pretreatment.

Jan 1, 1990

By William P. Blake

Postscript to the paper read by Prof. William P. Blake at the Lake Superior meeting, September, 1904. POSTSCRIPT.*-Since the publication of my paper upon the blackening of the surface of rocks in desert regions, I have noted that similar views of the origin of superficial discoloration in the case of certain rocks from the Salt Lake basin of Utah have been expressed by Prof. George P. Merrill. In the pamphlet, he described the brown-coated weathered boulders from Tooele county, reaching the conclusion that the discoloration was due to the solution of the manganese and iron compounds 'in the interior of the boulder, while they were in the water, and the gradual bringing of this material to the surface through capillarity and its oxidation when exposed.

Mar 1, 1905

By Donald M. Ulbrich

Any of you who served in the military remember the admoniton to "get the lead out," In the military environment, where cost wasn't always a factor, "get the lead out" was more often a call for activity of any sort than activity of a particularly productive nature. As a result, when the top sergeant yelled "get the lead out," lots of people started moving.. . usually to get out of his way. Now there's a new cry, ..one that comes not only from the military but from an entire nation threatened with dependence on foreign sources for its energy needs. That cry ...get the coal out, Like the earlier order, it's a call to activity. A signal that the coal reserves of the United States must be tapped so that Project Independence can succeed by 1985, But it's more than a mere call to activity; it's also a call to achieve productivity. ,a call to produce coal both efficiently and acceptably. And that leads us to the key questions of where the coal is going to come from to meet that 1985 goal, and how can it best be mined. Where will the coal come from? There's no doubt much of it must come from surface mining in the West. How can this coal be mined? There are several options available but there is an excellent case to be made for using mining shovels and haul trucks due to their versatility in stripping, loading and reclamation, We'll explore this approach in this talk today.

Jan 1, 1976

By R Riquelme

The El Salvador porphyry Cu deposit (26¦ 15Æ Lat S, ~2700 masl) and associated exotic mineralisation is situated at the back-scarp of the late middle Miocene Atacama pediplain in the western Precordillera. New, together with published 40Ar-39Ar data from El Salvador combined with morphologic analysis reveal that the palaeospring plumbing system related to exotic mineralisation at the Damiana exotic Cu deposit and the local geomorphology has not changed fundamentally between the late Eocene and late Miocene. Stable H/D isotope data on supergene alunite from El Salvador indicate an overall increase in dD values (VSMOW) from -74ë at 35.82 ¦ 0.95 Ma to -23ë at ~11 Ma. The transition from strongly to moderately negative deuterium values occurred between ~16 and ~13.5 Ma. Supergene alunite from the El Hueso (3950 masl) sedimentary rock-hosted epithermal deposit ca 35 km SE from El Salvador was dated at 8.19 ¦ 0.01 Ma and yielded a dD value of -25ë. We interpret the increasing deuterium excess as the result of strong evaporation and recycling of meteoric water after ~15 Ma and as indicative for a change in precipitation patterns and climate desiccation. In contrast, the strongly negative dD value for late Eocene supergene alunite points to a more humid climate and an elevation similar to the present. The late Miocene supergene activity at El Hueso is probably related to an uplift of the Precordillera to elevations sufficient for capture of orographically controlled precipitation. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By P A. Williams, P Leverett

Many of the worldÆs stibnite deposits are found in orogenic zones and are mesothermal or epithermal in origin. They commonly occur near contacts between intrusives and metasediments. However, the spatial extent of anomalous Sb levels around such deposits is not well documented. This project has aimed to gain a better understanding of the mineralogy and geochemistry of Sb by deriving solubility and thermochemical data for some of the most common secondary Sb minerals. This has then been applied in field exploration for Sb ore deposits. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

Supergene enrichment of ilmenite occurs through a complex series of reactions with initial oxidation and hydration followed by leaching and dehydration. Lateritization appears to be associated with the early phase of the supergene process and if ilmenite grains are encased in iron oxides no further alteration proceeds.

Jan 1, 1986

The Khanong supergene-enriched copper resource, (~23 Mt at 3.0 per cent Cu), is one of several resources recently discovered in the intrusive-centred, sediment-hosted Au-Cu Sepon mineral field located in southern Lao PDR. The unusual style of hypogene mineralisation and unique set of conditions have resulted in the development and preservation of a supergene-enriched profile in this subtropical climate. Hypogene sulphide-rich mineralisation replaced calcareous cataclastite (fault rock) developed in the flat-lying, extensional, Khanong Fault. Spatially, the hypogene mineralisation was immediately out board of the skarn û hornfels Cu-Bi front and in board of sediment hosted Au-(As-Sb) mineralisation in a zoned intrusive-centred hydrothermal system. In situ supergene enrichment of the sulphide protore has resulted in a high-grade chalcocite-clay zone (~10.3 Mt at 4.6 per cent Cu) overlain by leached limonite-clay. A very high-grade in situ to exotic limonite-clay Cu-oxide-mineral zone is locally developed above impermeable dolomite at the base of chalcocite-clay zone. Exotic Cu-Mn-wad mineralisation developed for up to 1 km down the hydraulic gradient from the chalcocite-clay zone. Unique supergene enrichment conditions have resulted in the high-grade Khanong Cu resource in a subtropical weathering environment. The base of the currently active supergene profile coincides with the base of a flat-lying, pyrite-rich fault rock, dipping parallel to the hill slope, maximising Cu enrichment. Meteoric water has been channelled along subvertical faults and narrow horizontal subsurface zones. Low permeability of the fault host rock and footwall rocks has controlled the low volume and slow movement of groundwater required for supergene enrichment. Erosion has been slowed by the resistive ironstone and limonite-clay layer at surface, which assists in preserving the gentle slope over the chalcocite-clay zone.

Jan 1, 1999

By F R. M Pires, R M. Carvalho

Supergene processes in banded iron formation (BIF) result in important dissolution, material transport and simultaneous disorder of the residual bands. The rock physical properties such as density, porosity and rheology change during the weathering attack. The itabirite, Paleoproterozoic metamorphic BIF from Quadrilßtero Ferrffero (QF) û Brazil, shows several weathered facies. Strong linking between topographic surface, rock density and iron grade occurs within the weathered zones. This linking is due to partial dissolution of silica and carbonate from itabirite and gravitational rotation and break of the remaining blades, generating kink-like slump structures. The original itabirite density, 3.7 t/m3, decrease at the first leaching steps, until 2.7 t/m3, and increase at the end of the leaching process until 3.6 t/m3. Iron grade increases from 38 per cent to 68 per cent and depressions (sinkhole), subsequently filled by Cenozoic basinal sediments, are developed over the enrichment zones. The formation of important supergene iron ore deposits of QF is intimately related to such a process. Several iron deposits at QF, such as Pico do Itabirito, Fßbrica Nova, Casa de Pedra, Tamanduß, -gua Claras, Cappo Xavier, etc., reveal the aspects related to the proposed evolution, implying that the formational process of the soft iron ores had a regional character. Granular medium model helped in the understanding of the development of the structure and the formation of the deposits. A numerical model has been developed in order to simulate a leaching system in a two-dimensional matrix, composed of two types of materials: leachable and unleachable. Equal volume proportion and vertical banding were considered. Drilling data was used as multipoint attractors to remove leachable matrix nodes.

Jan 1, 2002

By C. M. Clapperton, K. E. Darke, A. J. Boyce, C. M. Rice, S. D. Redwood

"Abstract - The Kori Kollo gold deposit is hosted by a c.15 Ma sericitized dacite stock in the La Joya district on the Bolivian Altiplano. The mineralization is of the Bolivian polymetallic vein (BPV) type, with a significant amount of the gold reserves contained in the oxide cap. Field and microscopic studies, K-Ar dating, ??34S values of pyrite, alunite and jarosite, and ??18O values of alunite and jarosite demonstrate that some of this gold is supergene. Two types of supergene gold are present: minute gold grains, 1 to 10 microns across, of high fineness and associated with jarosite and iron oxy-hydroxides; and ‘invisible’ gold, which is probably sorbed onto minerals such as jarosite and iron oxy-hydroxides.Pyrite ??34S values fall in the limited range -3.5 ± 0.6‰, consistent with a magmatic origin. Sulfate ??34S values are homogeneous and overlap closely with those of pyrite (-1.2 ± 2.1‰), which supports petrographic evidence that sulfates replaced pyrite. By contrast, sulfate ??18O values are inhomogeneous with a large range (alunite +2 to 26‰, jarosite -5 to +18‰). These data are interpreted as reflecting kinetically controlled reactions involving various proportions of atmospheric oxygen and local meteoric water. This is typical of supergene alteration and is due to the seasonally dry climate of the Altiplano.The oxide-zone mineralogy is dominated by sulfates and iron oxy-hydroxide minerals with some phosphates and halides, which indicates that the groundwaters were acidic, oxidizing and relatively saline. Under these conditions the most likely complexes responsible for gold mobilization are halides.Geological data and K-Ar ages indicate that oxidation of the BPV deposits began at least around 11 Ma and possibly up to 15 Ma ago, and that supergene alteration lasted until around 4 Ma. During this period, erosion was minimal. Although supergene processes have been active on the Bolivian Altiplano since the Middle Miocene, in contrast to Northern Chile, enrichment of gold has not occurred."

Jan 1, 1997

By C. M. Clapperton, K. E. Darke, A. J. Boyce, C. M. Rice, S. D. Redwood

"The Kori Kollo gold deposit is hosted by a c.15 Ma sericitized dacite stock in the LaJoya district on the Bolivian Altiplano. The mineralization is of the Bolivian polymetallic vein(BPV) type, with a signi?cant amount of the gold reserves contained in the oxide cap.Field and microscopic studies, K-Ar dating, ??34S values of pyrite, alunite and jarosite, and ??18O values of alunite and jarosite demonstrate that some of this gold is supergene. Two types of supergene gold are present: minute gold grains, 1 to 10 microns across, of high fineness and associated with jarosite and iron oxy-hydroxides; and ‘invisible’ gold, which is probably sorbed onto minerals such as jarosite and iron oxy-hydroxides.Pyrite ??34S values fall in the limited range -3.5 ± 0.6‰, consistent with a magmatic origin. Sulfate ??34S values are homogeneous and overlap closely with those of pyrite (-1.2 ± 2.1‰), which supports petrographic evidence that sulfates replaced pyrite. By contrast, sulfate ??18O values are inhomogeneous with a large range (alunite +2 to 26‰, jarosite -5 to +18‰). These data are interpreted as reflecting kinetically controlled reactions involving various proportions of atmospheric oxygen and local meteoric water. This is typical of supergene alteration and is due to the seasonally dry climate of the Altiplano.The oxide-zone mineralogy is dominated by sulfates and iron oxy-hydroxide minerals with some phosphates and halides, which indicates that the groundwaters were acidic, oxidizing and relatively saline. Under these conditions the most likely complexes responsible for gold mobilization are halides.Geological data and K-Ar ages indicate that oxidation of the BPV deposits began at least around 11 Ma and possibly up to 15 Ma ago, and that supergene alteration lasted until around 4 Ma. During this period, erosion was minimal. Although supergene processes have been active on the Bolivian Altiplano since the Middle Miocene, in contrast to Northern Chile, enrichment of gold has not occurred."

Jan 1, 1997

Confirmation of significant mineable reserves of high grade silver ore at Elura Mine has led to the development of a high cost, high recovery mining system. At the contact of oxidised and sulphide ores lies a supergene zone of enrichment which has provided a contrast, not formerly imagined, to Elura's primary development and stoping operations. Because of the soft nature of the ore, intense ground support practice has been combined with a panel cut and fill continuous mining system to extract a reserve of small, but most valuable Proportions.

Jan 1, 1988