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By S. B. Bortnikova

This paper presents the results of an investigation of the gold-silver oxidized ores at the Salair mine. West Siberia. High losses of precious metals during primary ore processing are the result of outdated technology that is not suited to treat the present ore compositions. The main mineralogical forms of gold and silver and their confinement to different grain size fractions have been determined. About 50% of gold in the slime fraction and 60% of the silver in the form of acanthite that are scattered from the secondary minerals are lost to the waste. The results of these investigations have provided the basis for the recommendation of a new technological process to upgrade the current practice of the gold extraction plant and for methods to reprocess the concentrates.

Jan 1, 1995

By Joseph C. Rota

The Carlin Trend is one of the most significant gold mining districts in North America. Located in northeastern Nevada, a total of over 17 million ounces of gold have been produced since 1965 at Newmont Gold Company's open-pit and underground operations. Oxidized portions of the sediment-hosted, disseminated gold deposits at Carlin generally consist of finely disseminated concentrations of sub-micron sized native gold particles hosted in Paleozoic siliciclastic or carbonate rock. Oxide ore is commonly amenable to dump leach or heap leach processing, yielding an average 50 to 70% recovery of total contained gold. Refractory unoxidized ore requires some form of pretreatment oxidation to ensure economic gold recovery. Geologic ore control is typically combined with standard assay and engineering techniques to maintain both grade and metallurgical control ofleach grade ores. Mine geologists provide a vital function through field observation and recording ofmineralogic data during daily, visual blasthole logging. Intricately mixed refractory materials must be separated from oxide ore to ensure highest possible gold recoveries. Geologic information is combined with assay data to create mine polygons in an engineering computer database. Mining selectivity is further enhanced by in-pit ore control geologists who are available to make production decisions based on direct mineralogic observations at active mine faces.

Jan 1, 1997

By Kazuki Morita

A new route to produce solar grade silicon (SOG-Si 6N) from metallurgical grade (MG-Si 98%) has been developed in Japan, which may satisfy the increasing demand for solar cells in the near future. Since some elements such as P and B have very large segregation coefficients, solidification refining is not effective for their removal and costly processes, such as electron beam vacuum melting and oxidation plasma refining, are required. According to our previous results which showed the effectiveness of leaching procedure with Ca addition for Fe and Ti removal, possibility of P and B removal by acid leaching was focused expecting that their affinities for Ca in molten silicon might be considerable. Hence, the effects of Ca addition on the thennodynamic properties of P and B in molten silicon alloys have been investigated for overall control and optimization of the SOG-Si production process in the present study. The interaction parameters between Ca and P, and Ca and B were determined by chemical equilibration techniques at 1723 K. Although the interaction parameter between Ca and B was slightly negative, that between Ca and P showed a large negative value. Also, the results for the leaching test with various amount of Ca addition revealed that the removal fractions of both elements, especially P, drastically increased with increase in the Ca content, which showed very good agreement with the prediction from the interaction parameters derived in the present work. The present results suggest that the preliminary leaching procedure can reduce the processing time and energy for SOG-Si refining. Keywords: Silicon, Solar Cell, Refining, Acid Leaching, Thennodynamics. Interaction, Phosphorus, Boron, Calcium

Jan 1, 2003

By Hiroyuki Sano

A closed recycling process for the low-grade scrap of Al-based composite materials was developed. In this process flux treatment with water-soluble halide is a key technique. In the present work, flux treatment conditions were discussed from the viewpoint of the separation and the recovery of the base material, reinforcement and flux. Optimum separation condition was obtained for the NaCl-KCI-KF flux treatment. The recovered aluminum alloy can be recycled for various usages. The recovered SiC particles cannot be reused as reinforcement because of the coexistence of the contamination, therefore it is necessary to eliminate these contaminates or to find another use. The recovered flux is reusable with supplemental addition of fluoride.

Jan 1, 2003

By L. Sh. Tsemekhman

The results of laboratory, large-scale laboratory and commercial scale investigations regarding the process of slag melts cleaning by oxidizing-reduction gas mixtures with a wide range of Po2 and the use of matte of various compositions as an extracting phase are presented. The copper, nickel and cobalt behavior during the cleaning process has been studied based on SEM and x-ray Microprobe of the quenched slag melts. The general cleaning mechanisms have been found. On the basis of the obtained data the most efficient cleaning methods have been proposed.

Jan 1, 2003

By P. Peczak

A Monte Carlo simulation technique has been used to study dynamic recrystallization in polycrystals. A continuum microstructure of the polycrystal is modeled employing a discrete lattice. The response of the material to hot deformation is simulated by adding stored energy and recrystallization nuclei continuously with time. The experimentally observed nonuniform character of deformation substructures is modeled by employing a phenomenological expression for inhomogeneous distribution of the stored energy. All simulations were performed on HP-Apollo 9000 Series 700 workstations. A program written in FORTRAN with use of PHIGS graphics library calls was used to interactively monitor the current state of the matrix and all relevant parameters: deformation stress, average grain size and effective nucleation rate. Visual analysis of the simulated microstructure allows a better understanding of the data developed by averaging over a number of very long Monte Carlo runs. Since the essential features of dynamic recrystallization are accurately reproduced by the model, it is used to discuss the role of the controlling mechanisms of the dynamic recrystallization in real polycrystal.

Jan 1, 1993

By H. Kohno

The Onahama No.3 tankhouse started commercial operation in early 1973, with the capacity of 8,500 metric tons per month. When the No.3 tankhouse was constructed, the starter sheet stripping section was rebuilt at the No.2 tankhouse and electrolyte purification section was expanded. The previous AIME paper in 1976 described the design principles of the No.3 tankhouse and its layout, This paper describes the starter sheet stripping machine in the No.2 tankhouse and the electrodes handling system in the No.3 tankhouse and all these equipments were developed for the operation of the No.3 tankhouse. A Hazelette continuous casting machine was also introduced in order to cast thin anodes with accurate shape. Owing to the adoption of thin anodes, gold, silver and copper inventory is reduced by 40%. Jumbo tanks and newly developed mechanical equipments were adopted and no work on cells during pulling up operation was achieved. Using thin anodes with accurate shape, inspection work was completely abolished while maintaining high current efficiency and high cathode quality. Labor cost was reduced by 70% and only six operaters can produce? 8,500 metric tons of cathodes per month. The same new electrolysis process is appreciated and has been used as a newly built independent tankhouse by Kidd Creek Mines Ltd., in Canada in 1981 with excellent results

Jan 1, 1987

By A. W. Worcester

The plant is designed to produce 60,000+ tons of refined lead per year from a nominal feed consisting of 110,000 tons of SLI and industrial batteries, and 10,000 tons of lead contained in drosses and scrap. The plant will also produce as by-products polypropylene chips and detergent grade sodium sulfate, using the Engitec Impianti CX Technology. The battery separation circuit will consist of a battery breaking hammermill and a vibrating screen with water sprays to separate the battery paste from the grid metal and other battery components. The battery components, consisting of ebonite, and separator materials, will be separated' from the grid metal and classified with the use of hydrodynamic water separators. The battery paste will be treated with sodium carbonate to produce a lead carbonate paste for smelting in a reverberatory furnace. The slag from the reverberatory furnace will be campaigned through a traditional primary blast furnace to produce hard lead. The sodium sulfate liquor from the lead carbonate filtration step will be crystallized to produce anhydrous sodium sulfate. The metallic grid metal will be treated through a small rotary smelter of the Engitec design to produce a hard antimonial lead. The plant's scheduled to be commissioned 12 months after receipt of all of the Federal and state permits. The plant will be integrated into the Buick Primary Lead Smelter, located in the center of Missouri's New Lead Belt, at Boss, Missouri. This will allow The Doe Run company to fully utilize all of its existing assets.

Jan 1, 1990

By J. L. Jambor

Sulfide-rich tailings accumulated in a 4l-hectare impoundment at the Waite Amulet minesite near Noranda, Quebec, have undergone partial oxidation and destruction of the principal sulfides (pyrite and pyrrhotite) in the vadose zone. Mineralogical studies and whole-rock chemical analyses of 18 samples from 3 boreholes along a cross-section of the tailings pile indicate that the principal chemical manifestations of the alteration are a pronounced depletion in sulfide-sulfur, and an enrichment in total Fe as Fe203' Other elements such as Al, Mn, Mg, Ca, Na, and K in the solids show erratic or inconsistent variations, but a trend to Si enrichment in the oxidation zone is clear. The trend is interpreted to be a relative enrichment whereby the proportion of the stable silicate minerals has increased as a consequence of the consumption of pyrite and pyrrhotite in the oxide zone.

Jan 1, 1989

By Chao Du, Xiaohui Ning, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

"TiCxOl-x solid solutions were synthesized by sintering a mixture of titanium carbide and titanium monoxide at 1600 °C. The corresponding structures and morphologies of the TiCxOl-x solid solutions were characterized by XRD and SEM. A series of tests has been performed on the electrochemical dissolution behavior of TiCxOl-x solid solutions in NaCl-KCl molten salt. The influences of synthesis time and electrokinetic parameters on the anodic dissolution behavior were also investigated. The results showed that TiCxOl-x solid solutions can dissolve as Tin+ into alkali chloride melt. Titanium ion species dissolved from TiCxOl-x solid solutions changes between Ti2+ and Ti3+ depending on the applied potential. The tail gas on the anode was monitored by a mass spectrometer. It was found the synthesis time significantly affects the components of the anodic gas.IntroductionTitanium and titanium alloys have been desired greatly because of their many uses. The critical factor that restricts the range of uses for Ti is its high cost of extraction. The primary titanium metal, sponge titanium, is still produced industrially worldwide by a process invented by Dr. Kroll in the 1940s[1] •Since the early 1970s, the research focus of the titanium industry has been directed towards developing a continuous process to produce high purity titanium at low cost. [2-10] Of the many alternative methods that have previously been investigated, the electrolytic process has been considered a promising method for titanium metallurgy [4-10]. Recently, several electrolysis and related methods such as the PFC-Cambridge process[11-15], calciothermic reduction[16-18], USTB [19,20] and MER[21] process were extensively investigated.The USTB process is a new approach where the pure titanium can be directly obtained by the electrolysis with an anode of titanium oxycarbide in molten salts[19, 20]. The titanium oxycarbide was produced by carbothermal reduction of titanium dioxide under vacuum at a temperature"

Jan 1, 2011

By R Bartlett

Process engineering-science originally developed for percolation leaching of ore in heaps is extended to the decontamination of unsaturated soil, either in situ or after excavation and emplacement as a soil heap on an impervious pad. Phenomena considered include: soil matrix porosity and permeability; percolating solution retention, capillarity and flow; washing sweep efficiency; optimum solution application rates during leaching; soil agglomeration to improve soil permeability and soluble contaminant transport by diffusion in soil agglomerates. Practical aspects briefly discussed include leach pad construction, solution distribution and recovery from the soil, and solution containment.

Jan 1, 1994

By Frank L. Marley

Mexican silver mining operations have existed prior to the sixteenth century. Recovery processes throughout the centuries were developed at the many mining localities and have progressed through smelting, the patio amalgamation process to cyanidation and flotation. A study of the present silver mining zones is reported in which the ores are evaluated in terms of the mineralogical constituents, their state in the matrix and the effects these are noted to impose upon the efficiency of recovery. Silver mineral identifications were by quantitative ore microscopic and scanning electron microscopic energy dispersive X-ray analysis.

Jan 1, 1982

By Dietmar Eifler, Marcus Klein, Hendrik Kramer

Conventional methods to characterize the fatigue behavior of metallic materials are very time and cost consuming. That is why the new short-time procedure PHYBALCHT was developed at the Institute of Materials Science and Engineering at the University of Kaiserslautern. This innovative method requires only a planar material surface to perform cyclic force-controlled hardness indentation tests. To characterize the cyclic elastic-plastic behavior of the test material the change of the force-indentation-depth-hysteresis is plotted versus the number of indentation cycles. In accordance to the plastic strain amplitude the indentation-depth width of the hysteresis loop is measured at half minimum force and is called plastic indentation-depth amplitude. Its change as a function of the number of cycles of indentation can be described by power-laws. One of these power-laws contains the hardening-exponentCHT eII, which correlates very well with the amount of cyclic hardening in conventional constant amplitude fatigue tests. To identify heat-treatment-parameters and SAE 52100 TRIP-alloys with high hardening rates as well as their damage tolerance the PHYBALCHT- and PHYBALLIT-method were used. One modified SAE 52100 TRIP-alloy was investigated in detail. The fatigue behavior and the cyclic hardening of the selected SAE 52100 TRIP-alloy was investigated and compared with conventional SAE 52100. Conventional stress-controlled fatigue tests were performed on a servo-hydraulic test system with a frequency of 5 Hz and a load ratio of R = -1. Different rates of cyclic hardening were identified. The size of the nonmetallic inclusions leading to crack initiation and the number of cycles to failure were used to evaluate differences in the damage tolerance capability.

Jan 1, 2015

By Thomas R. Wildeman

Experimental methods for studying vapors over solid minerals are reviewed and an especially developed method using atomic absorption is described. The method is used to study vapor pressures over Te. Ag, Au, Ag2Te, and AuTe2 from 250°C through 10S0oe. Vapor pressures observed and, concurrently. sintering properties are significantly altered by the form of the solid. The vapor pressures of the tellurium compounds reveal complex processes occurring on the surfaces of the solids. The data given also point out a method of recovering precious metals from their telluride minerals w

Jan 1, 1987

By Minh H. Pham

This paper presents a technique for imaging the extent of solidification of molten metal flowing in a cooled pipe based on the concept of eddy currents. A 3D mathematical model, which relates the geometry of solidification to the scattered field induced in a solenoid external to the pipe, is derived. The model is described by a set of integral equations which are solved numerically using the moments method. An iterative algorithm is developed to reconstruct the solidification distribution image. Experimental measurements have shown that the eddy current technique is sufficiently sensitive for practical purposes.

Jan 1, 2001

By M. Shevchenko

Integrated experimental and modelling research program on the phase equilibria and development of thermodynamic databases of the lead and copper metallurgical gas/ slag-matte-metal-solids systems (PbO-“Cu2O”-FeO-Fe2O3- ZnO-CaO-SiO2) is being undertaken to support improvements in the pyrometallurgical smelting and recycling processes. This is the first systematic investigation of phase equilibria of slag systems in equilibrium with Pb metal, providing information for systems in which copper coexists in slag with lead or zinc as major components. The experimental studies involve high-temperature equilibration of synthetic samples, rapid quenching, and measurement of the compositions of equilibrium phases using electron probe X-ray microanalysis (EPMA). FactSage-based thermodynamic database development is integrated with experimental research. Initial thermodynamic assessments are used to identify priority compositions and conditions for experiments, which are planned to provide specific data to assist thermodynamic optimisation. Significant improvement in the accuracy of the phase equilibria description is achieved. Continuous database improvement and extension to include new elements are targeted. Example of industrial application is given.

By Shengqin Zhang, Yousef Mohassab, Feng Chen, Hong Yong Sohn, Mohamed Elzohiery, Amr Abdelghany

The kinetics of hematite concentrate reduction by mixtures of hydrogen and CO of various compositions has been investigated as part of the development of a flash ironmaking process at the University of Utah. This process produces iron directly from iron oxides concentrates by the gas-solid flash reaction based on the partial oxidation of natural gas, resulting in a significant reduction in energy consumption and greenhouse gas emission. The reduction kinetics of hematite concentrate of an average particle size 21.3 μm by the above mentioned gases in the temperature range 1423 to 1623 K (1150 to 1350 ºC) was investigated. Hematite concentrate particles can be reduced to > 90% by any of these reductants in several seconds of residence time typically available in a flash reactor. The activation energy ranged from 214 kJ/mol for hydrogen to 231 kJ/mol for CO.

Jan 1, 2016

By A. C. Mollison

In November of 1983 a fire inside the autoclave caused the curtailment of operation of the Kidd Creek pressure leaching facility. Subsequent repairs and recommissioning of the autoclave in 1984 allowed Kidd Creek to increase its production of zinc as originally planned. This paper describes the operation of this process from 1984 to 1988 and details major mechanical work carried out on the vessel in 1.988:

Jan 1, 1990

By Wade L. Karlsen

"Revision surgery to replace joints in the human body requires materials that are strong, long-lasting, and biocompatible. Metallic implants made of cobalt-chromium-molybdenum alloys are already popular because of their proven corrosion and wear resistance properties, but there is an on-going effort to economically improve their performance. Alloying with inert nitrogen can enhance the mechanical properties of the alloy, enhance its corrosion resistance, and elevate the temperature at which the metallic implants can be thermally treated, without increasing the threat to the human body. The current work has produced a high-nitrogen Co-Cr-Mo alloy through HIP consolidation of metal powders that have undergone nitriding in a mechanically fluidized bed. The already fine microstructure of the powders combined with the increased nitrogen content resulted in significant property gains in the consolidated materials.IntroductionMetallic implants made of cobalt-chromium-molybdenum alloys are already popular because of their proven corrosion and wear resistance properties, but there is an ongoing effort to improve their performance. Research on a Stellite 21 cobalt-chromiummolybdenum alloy has shown that nitrogen alloying can be desirable from several standpoints [l]. Firstly, it has indicated that nitrogen can enhance the mechanical properties of the alloy, which could allow more demanding implant designs. The same work also demonstrated that nitrogen can elevate the temperature at which the metallic implants can be thermally treated, which is desirable in situations in which surface textures are to be sintered to the implant to enhance its fixation properties. Finally, that research work discovered that, not only does nitrogen not harm the corrosion resistance of the cobalt-chromium-molybdenum alloys, but it may in fact enhance it. Combining this with the fact that small amounts of nitrogen are not considered a threat to the human body, makes nitrogen alloying an attractive alternative for enhancing the properties of Co-Cr-Mo."

Jan 1, 2000

By R. Stefaniuk, T. Le, J-Y Huôt, H. Henein

"One of the most important process variables in gas atomization is the gas to metal (G/M) mass ratio as it has a direct effect on the mean particle size of the atomized powder. If this ratio can be controlled during the atomization process, the powder produced would be more uniform and the d50 more predictable. Thus, atomization using a tundish or gravity feed from a crucible would be more stable. In gas atomization, the gas flow rate can be easily monitored; while it is very difficult to determine the molten metal flow rate. This research paper presents a new method of recording the molten metal height with time using a conducting metal height detector. The metal height recorded in real time during atomization was used to characterize using a model the friction losses in the metal delivery system. It is found that the integrity of the metal delivery tube and the cleanliness of the melt play a key role in the maintaining a stable metal feed.IntroductionIn the gas atomization process, molten metal is normally fed to the system either continuously using a tundish or in most cases a certain amount of metal is melted in a crucible and flows into the atomizing chamber under gravity. In the first case, the metal flow rate is believed to be constant during the atomization process despite the presence of slag or dross on the molten metal surface. In the second case, the amount of molten metal is depleted with time and the rate at which the metal flow decreases with time varies from test to test in a seemingly unpredictable fashion.' Furthermore, most atomization systems are confined units and the metal level in the crucible cannot be detected by a visualization method. In industry as well as in laboratories, the metal flow rate is normally calculated on either the mass of input material or the mass of total production divided by the duration of the test. This figure is not accurate enough and obviously cannot be used as a control parameter for the gas to metal ratio as it is only determined after the completion of an atomization run. The need exists for a metal flow rate measurement and control methodology; thereby the d50 of the powder produced may be estimated and controlled in real time. Clearly, the smaller the variation of the G/M ratio during the atomization process the more uniform the powder produced and hence the size of the particles can be predicted."

Jan 1, 1994