Search Documents

By G. Van Weert, A. van Sandwijk, O. W. J. S. Rutten

"Cathodic and anodic reactions in an acidic nitrate medium were studied in reference to the production of electrolytic manganese dioxide from pyrolusite' (Mn02) ores by reductive leaching. Two USA ores were investigated. The reductant for the pyrolusite ore is produced cathodically in an electrolytic cell and can either be nitrous acid (HN02) or nitric oxide gas (NO). In this work emphasis was placed on the nitrous acid leach. In a high-temperature leach in a nitrous/nitric acid medium, manganese and silver are solubilized and iron is not. Anodic electrowinning of manganese dioxide from the acidic manganese nitrate electrolyte yields flaky y-Mn02, similar to that produced from sulfate and chloride electrolytes. Cathodic regeneration of nitrorts acid was studied in a membrane cell in 1.0 M nitric acid and 0.0 to 0.1 M nitrous acid on a' platinized titanium cathode. At cathode potentials ranging from +950 to +700 mV (SHE), cathodic reduction to nitrous acid takes place, at cathode potentials < +700 mV, cathodic reduction of nitrous acid to nitric oxide takes place. A conceptual process is presented and discussed.IntroductionManganiferous-silver oresLarge reserves of manganiferous-silver ores are present in the Southwestern United States and Latin America. These ores are generally refractory to hydrometallurgical methods of treatment, due to the insolubility of the higher oxides of manganese (Mn 4+) in all common lixiviants such as cyanide solutions, dilute sulfuric acid, nitric acid, ammonia, salt solution, thiosulfates, etc. The silver is either bound by the insoluble manganese, or is rendered inaccessible to cyanide leach solution by the surrounding manganese mineralization.Higher oxides of manganese will dissolve if they are first reduced pyrometallurgically to manganous oxide (Mn2+). This is a widely used pretreatment for manganese dioxide ores and subsequent dissolution in sulfuric acid is common. In order to avoid the pyrometallurgical pretreatment with its large energy requirements and gaseous emissions, fully hydrometallurgical processes have been proposed. These processes are based on the presence of a reductant in solution, in order to reduce the insoluble higher oxides of manganese to soluble lower oxides. Aqueous S02 has been proposed and tested on industrial scale by the U.S. Bureau of Mines. After washing, silver could be extracted by cyanidation. The neutralization of the pulp prior to cyanidation however causes problems in filtration and the reagent consumptions are high [1]. More recently, acidified thiourea and bacteria were proposed for the solubilization of both manganese and silver in a single leach step. High extractions were obtained, but drawbacks of these methods are high reagent consumption or slow kinetics [2,3]. For the options of manganese recovery from the leach filtrate, precipitation with persulfate or ammonium carbonate and ion exchange have been proposed. The proposed options for silver reclaim are precipitation with either zinc or Na2S and adsorption onto activated carbon."

Jan 1, 1997

By Hani Henein, J. Barry Wiskel

"The easy accessibility and power of the PC, as well as the education of our engineering students in the use of these tools, are compelling reasons for developing computer aided instructional (CAI) tools. There are a wide range of areas in the engineering curriculum where students must learn the steps and the process of applying judgement in problem solving. In the typical course instruction, · an instructor introduces theory to students; the application of the theory to solving problems is often demonstrated in the abstract. Students therefore spend a significant amount of time learning how to apply the theory to problem solving. Additional time and effort must then be spent to get students to the point of learning concepts and integrating this knowledge. A number of computer aided packages have therefore been developed for use in several courses in the materials science and engineering curriculum that encompass both calculational and instructional capabilities. This paper presents an overview of some of these packages which include the solution of a non-linear equation, the instruction of binary diffusion couples, an introduction of crystallography, an introduction to heat transfer and the solution of thermodynamic stability diagrams. The context in which these CAI Tutorials were developed and are being used will be discussed. The pitfalls in the development of these packages will also be discussed. The use of the tutorials has important implications on the expectations from an engineering education of both instructor and student.IntroductionTraditionally, it is quite routine to teach engineering students how to use a computer (the PC today for undergraduates) as a tool in performing engineering calculations or in simulating a process or a unit operation. This often takes the form of one course in computer programming, whether it is Fortran, Visual basic or a spreadsheet, and another course in numerical computation. However, the materials and electronic revolution have brought about considerable advances in computer power and speed, and accessibility. Today, the manipulation of digital images, movies, and speech are commonplace on a desktop PC.' Many mathematical models that were executed only on workstations can now be readily handled on a PC. Concurrently, more of our students own a PC even if their curriculum does not require them to purchase one. Today, virtually every university student has been introduced to the PC in either their elementary or high school education. Hence, the increased capabilities and accessibility of the PC and the familiarity of students with this tool make it compelling to explore its use as an educational tool for our engineering students. This is not a traditional role of a computer in our engineering curriculum."

Jan 1, 2000

By Corby G. Anderson

Hydrometallurgical technology for the pretreatment of refractory gold concentrates has been developed at Sunshine Mining and Refining Company. It employs a patented nitrous-sulfuric acid pressure leaching process which&apos; was proven industrially at the Sunshine refinery. Additionally, pretreatment for removal of antimony and some other impurities is done with alkaline sulfide leaching. This paper will discuss the successful application of these two technologies for pretreatment of a refractory gold concentrate prior to CIL gold recovery. A complex gold concentrate composed of pyrite, arsenopyrite and stibnite was tested. Results of antimony leaching in alkaline sulfide media will be discussed including some details of a novel and selective recovery method for gold leached by polysulfide or thiosulfate" Also, the factors important in and the results of the application of nitrogen species catalyzed pressure leaching to refractory gold concentrates will be detailed.

Jan 1, 1996

By Lionel Ryan

In 1996, the Dominican Republic operation of Falconbridge (Falcondo) developed a 5-year Process Control Plan in conjunction with the corporate Process Control group located in Sudbury, Ontario, Canada. This plan was further refined into an analysis of the areas of the highest potential economic return for the company with the reduction shaft furnace operation being the most promising. Historically, the reduction plant, which comprises 12 shaft furnaces, has been the bottleneck of ferronickel production. Since 1996 there has been a history of control development, and the current status is that all 12 furnaces are using advanced model-based multi- variable predictive control. The combination of advanced process control (APC), improved control system performance and improved process information management has resulted in an increased throughput of 6% per shaft furnace and a reduction in operating costs of 4.5 US cent/lb of Ni. This paper reviews some of the major milestones that have been achieved in this development Keywords: Advanced Process Control; Model Based Predictive Control; Connoisseur, Reduction Shatt Furnace; Nickel Laterite Ore; Ferronickel; MonitorMV

Jan 1, 2004

By Brian G. Thomas

Quality problems in continuous casting of steel can be identified as they occur by monitoring mold signals (level sensor, thermocouples in the mold walls, friction etc.) and taking appropriate action (such as slowing casting speed, changing taper, changing a clogged nozzle, or later visual inspection of the surface for possible downgrading. Surface depressions and groups of deep oscillation marks form at meniscus and reduce local heat transfer as they move down the mold at the casting speed. This slows shell growth, increases shell surface temperature, and causes characteristic dips in mold thermocouple signals. More importantly, they are also associated with longitudinal cracks. Characteristic thermocouple signatures have been identified for many defects, including sticker breakouts, transverse depressions and deep oscillation marks, narrow-face bleeds, transverse comer cracks, longitudinal cracks, mold level fluctuation defects, and other problems. With the help of computational models, these mold signals should be used to troubleshoot defects, and to take appropriate corrective action. Keywords: Continuous casting, defect detection, thermocouple signals, on-line control

Jan 1, 2003

By James C. Barker

Recent investigations of a 55-km long trend of intrusive complexes on southern Prince of Wales Island have identified significant resources of Nb, Y, REE. U, Zr, and a host of potential by-product metals. The northwesterly trend comprises multi-phased sodic alkaline and peralkaline diorite, monzonite, syenite, and riebeckite granite. There are at least three significant deposit types recognized, two of which, 1) pegmatite dikes/vein-dikes that zone laterally from the intrusions and 2) concentrically zoned pegmatites, contain most of the lithophile metals. A third, epigenetic replacement-type mineralization, contains much of the U resource. Other deposit types with minor or unknown resource potential include diatremes, carbonatite, and placers. This report summarizes the deposit evaluations, characterizes the mineralization, and estimates the resources. To date a total of 40.7 million tons of mineralized material is estimated as indicated or inferred. Most of the Y203 plus REO is at a grade exceeding 0.5% and half of the Nb20S exceeds 0.125%. Tonnage estimates would likely be substantially lncreased with additional exploration. Mineralogy is generally fine-grained and complex, and consists of more than a dozen principal REE-Y-Nb-U-Th-Zr phases, the sum of which may compose up to half of the rock. Approximately half of the REE-Y content comprises the heavy yttrium subgroup which is uncommon compared to deposits elsewhere. Although the Alaskan deposits are likely subeconomic at today&apos;s metal prices and consumption levels. recent technological advances suggest future demand may increase.

Jan 1, 1988

By Markus Reuter, Antoinette van Schaik

In this paper the link between process metallurgy, classical minerals processing, product centric recycling and urban/landfill mining is discussed. The depth that has to be achieved in urban mining and recycling must glean from the wealth of theoretical knowledge and insight that have been developed in the past in minerals and metallurgical processing. This background learns that recycling demands a product centric approach, which considers simultaneously the multi-material interactions in man-made complex ‘minerals’. Fast innovation in recycling and urban mining can be achieved by further evolving from this well developed basis, evolving the techniques and tools that have been developed over the years. This basis has already been used for many years to design, operate and control industrial plants for metal production. This has been the basis for Design for Recycling rules for End-of-Life products. Using, among others, the UNEP Metal Recycling report as a basis (authors are respectively Lead and Main authors of report), it is demonstrated that a common theoretical basis as developed in metallurgy and minerals processing can help much to level the playing field between primary processing, secondary processing, recycling, and urban/landfill mining and product design hence enhancing resource efficiency. Thus various scales of detail link product design with metallurgical process design and its fundamentals.

Jan 1, 2014

By L. G. Wiseman

The raw materials processed, highlights of technology used, and products produced at INCO&apos;s Copper Cliff Nickel Refinery in Ontario, Canada, are described in this paper. INCO&apos;s Bessemer matte separation process yields various nickel and copper products and intermediates. The latter presents the main supply of raw materials for the Refinery. Key features in the Refinery are Top Blown Rotary Converters and the INCO Pressure Carbonyl (IPC) process. Process improvements made since the commissioning of the Refinery in 1973 are also discussed. The Refinery produces a variety of nickel products, including nickel powders. Residue after carbonylation presents an important intermediate enriched in precious metals and cobalt that serves as feed to downstream operations for recovery of the residue&apos;s metal values. Also discussed are detection, measurement and control procedures which ensure safe operation.

Jan 1, 1988

By Jerry L. Smith

Industry on a whole has not been very receptive to government prodding to implement waste minimization programs. Waste minimization has the appearance of substantial benefits, however, there are underlying difficulties and suspicions that need to be addressed before industry will support pollution prevention initiatives. They can be summarized as follows: - Human behavior resists change, uncertainty, and unknowns. - New waste minimization techniques are difficult to find and research. - Calculating the true cost of present waste practices as well as new techniques being considered is difficult and time consuming. - Getting a consensus opinion of all the individuals affected on the course or technique to be employed in a pollution prevention program. New software products have addressed many of the problems associated with implementing pollution prevention programs: They contain research on a large number of pollution prevention techniques and case studies; they generally are accessed by EPA ID number, chemical name, or synonym; and some programs have the option to print a comprehensive written user-specific pollution prevention program.

Jan 1, 1994

By Robert Hanson, Mayur K. Patel

"Pneumatic conveying pipelines are used throughout a variety of industries, from food processing/packing to power generation plants, as an efficient means of transporting materials between storage and processing points. In general, different phases of pneumatic conveying exist when material is conveyed from point A to point B in a pipeline. This depends on the operating pressure and the material conveyed. Lean phase conveying exists when pipelines are operated at high airflow rates, relatively low pressures, inducing sufficient turbulence for particles to become entrained in the air stream. Thus, particles are conveyed along the pipelines at velocities in the range of IS-2Sm/s. Generally, the initial capital costs for lean phase system is low, however the running costs are high. The opposite is true for dense phase, high-pressure systems. In considering either conveying system, it is important that the rate of erosion of the pipeline be considered when designing such a system, since it is the rate of erosion that dictates the lifetime of components. In general, the high level of erosion occurs for lean phase flows, where high impact velocity contribute substantially to the rate of erosion as well as other processes such as particle breaking, if the particles are friable. This would lead to poor quality of material, not normally desirable. On a positive note, the process of erosion is used in other applications, which benefits from this process, e.g. abrasive guns.The failure, by puncture, of pneumatic conveyor bends in industry causes several major problems. Two of these are: (a) escape of the conveyed product causing health and dust hazard and (b) repairing and cleaning up after punctures necessitates shutting down conveyors, which will affect the operation ofthe plant, thus reducing profitability.The paper reports on modelling strategy used in the development of a modelling framework and the initial validation phases of the models incorporated within. The modelling framework encompasses Computational Fluid Dynamics (CFD) related engineering tools, based on Eulerian (gas) and Lagrangian (particle) approaches, to represent the two distinct conveyed phases, to represent the erosion process which is used to ascertain the lifetime of conveyor bends."

Jan 1, 2001

By Richard D. Hagni

Although the economically important uranium minerals are difficult to recognize under the ore microscope, they can be identified by a combination of qualitative and quantitative techniques. Useful quantitative techniques include indentation hardness, percent reflectance, spectral reflectance curves, and color coordinates. The latter two properties are especially distinctive for the primary urahlferous minerals uraninite, coffinite, brannerlte, and davidite. Together with the quantitative properties of indentation hardness and reflectance, the character and color of internal reflections are distinctive for many of the secondary uranium minerals. Ore microscopic techniques also provide an excellent means for determining the intergrowths of these minerals with other ore and gangue minerals. Such intergrowths are important to an understanding of the genesis of uranium deposits, and they may be important to uranium extractions.

Jan 1, 1981

By D. J. Senor

Closed chamber incineration (CCI) is a novel technique by which irradiated nuclear graphite may be destroyed without the risk of radioactive cation release into the environment. The process utilizes an enclosed combustion chamber coupled with molten carbonate fuel cells (MCFCs). The transport of cations is intrinsically suppressed by the MCFCs, such that only the combustion gases are conducted through for release to the environment. An example CCI design was developed which had as its goal the destruction of graphite fuel elements from the Fort St. Vrain reactor (FSVR). By employing CCI, the volume of high level waste from the FSVR will be reduced by approximately 87 percent. Additionally, the incineration process will convert the Sic coating on the FSVR fuel particles to SiO2, thus creating a form potentially suitable for direct incorporation in a vitrification process stream. The design is compact, efficient, and makes use of currently available technology.

Jan 1, 1994

By James P. Bennett

The U.S. Bureau of Mines, Tuscaloosa Research Center, is conducting a review of the usage of different types of refractories, the current industrial practices to recycle/dispose of spent refractories, and the concerns associated with these practices. This information will serve as the technical basis for initiating a research program to recycle or find alternate uses for spent refractory materials. Approximately 1.6 million metric tons of clay based and 1.2 million metric tons of non-clay based refractory materials were manufactured in the United States in 1992 alone, representing a value of almost 2 billion dollars. Landfill has been and remains the disposal means of choice. Issues such as environmental regulations, concerns over landfill disposal, future liability, and product stewardship programs have brought about increased emphasis for recycling or alternate material use. Information on refractory consumption and the issues associated with recycling or disposing of used materials will be discussed, including current recycling practices.

Jan 1, 1995

By Luben Savov

This paper presents recent research works on the removal of the tramp elements Cu, Sn, Zn and Pb from steel. The evaporation of Cu and Sn in iron-based melts treated at reduced pressure of the gas phase was studied in a vacuum induction melting furnace. The effect of chamber pressure, temperature and melt composition was investigated. Since the main source of contamination of steel with Sn and Zn is the recycling of tinplate and zinc coated steel, respectively, possibilities for the removal of meta1ic coatings in a scrap pre-treatment stage were studied, too. Tin was removed in the temperature range 400-5S0°C by treatment with reactive gases featuring high sulphur potential. Zinc can be removed by evaporation or by a combination of thermal and mechanical treatment. The paper discusses the thermodynamics of Pb in carbon-saturated iron melts, too.

Jan 1, 2001

By Denis Shishin

The pyrometallurgical production and recycling of non-ferrous metals involves the use of complex feed stocks, having awide range of chemical compositions from sources that include mineral sulphide concentrates, high value obsolete materials and process wastes. The commercial viabilities of these operations hinge on the ability to extract value from these materials. Increasingly, modern computer-based tools are used to describe and predict process outcomes, including mass and heat balances, the partitioning of elements and phase equilibria. At the heart of these predictive tools are thermodynamic databases that describe the fundamental chemical properties of a system and all the components present. A comprehensive research program has been established to develop an accurate, self-consistent thermodynamic database describing all gas-slag-matte-metal-speiss-solid phases in the system Cu2O-PbO-ZnO-Al2O3- CaO-MgO-FeO-Fe2O3-SiO2-S-(As-Bi-Sb-Sn-Ag-Au). The database can be used in conjunction with the FactSage computer platform. The accuracy of the database and its application to industrial practice is demonstrated.

By E. J. Peterson

Oil shale retorting induces mineral and chemical reactions to occur on the macroscopic and microscopic levels in the kerogen-bearing marlstone. The nature and extent of the reactions is dependent upon process variables such as maximum temperature, time at temperature, atmosphere, and raw shale composition. This report describes the investigation of the mineral, chemical, and trace element release properties of spent shales retrieved from an experimental in situ retort at Occidental Oil Shale, Inc. &apos;s Logan Wash site in Garfield County, Colorado. Correlation between mineralogy of the spent materials and the mobility of major, minor, and trace elements are indicated, and relationships with important process parameters are discussed. The progress .of carbonate decomposition reactions and silicat ion reactions is indicative of the processing conditions experienced by the shale materials and influences the mobility of major, minor, and trace elements when the solids are contacted by water. Shale minerals that are exposed to the extreme conditions reached in underground retorting form high temperature product phases including akermanite-gehlenite and diopside-augite solid solutions, kalsilite, monticellite, and forsterite. The persistence of relatively thermally stable phases, such as quartz, orthoclase, and albite provide insight into the extremes of processing conditions experienced by the spent shales. Leachate compositions suggest that several trace elements, including vanadium, boron, fluoride, and arsenic are not rendered immobile by the formation of the high-temperature silicate produce phase akermanite-gehlenite.

Jan 1, 1981

By James E. Hoffmann

Oxidative pressure leaching is gradually supplanting other techniques for the decopperizing of slimes. The reasons for this include: much more rapid reactions, more compact equipment, a reduced environmental burden, and perhaps most important, a much lower final copper concentration in the decopperized slimes. This paper will discuss the reactions occurring during decopperization, the acidity and temperatures encountered and the techniques employed for discharging non condensable gasses. A spreadsheet is provided which allows adjusting the operating conditions depending upon raw (undecopperized) slimes composition, solids concentration and lixiviant composition. A typical process equipment flowsheet is provided along with a process narrative.

Jan 1, 2000

By S. J. Macnaughton

The Olympic Dam deposit in South Australia contains 2% copper and 0.06% uranium, which are present as bomite, chalcocite, chalcopyrite, uraninite, coffinite and brannerite. The copper is principally recovered using flotation. The flotation tailings, which contain the bulk of the uranium, and typically 0.3% copper, are leached using sulfuric acid and an oxidant at atmospheric pressure. This paper describes the results from a detailed investigation of the leaching behaviour of this ore. The influence of acid strength, Fe3+ concentration, redox potential and temperature on the dissolution of uranium and copper minerals was studied. Experimental data were obtained from extensive batch leach tests. Mineralogical studies, including SEM analysis of individual mineral grains, were also carried out. The maximum extraction of uranium determined experimentally was in good agreement with that predicted from SEM determination of the proportion of refractory brannerite in the ore. The leaching rate of copper was found to be independent of acidity over the range 20 g L-&apos; to pH 2.0, but was strongly dependent on temperature and Fe3+ concentration. Uranium extraction showed a weak de endence on acidity, Arrhenius temperature dependence and a complex co-dependence on F>+ concentration and redox potential. A kinetic model has been developed, which predicts copper and uranium dissolution. This model will be incorporated into a more comprehensive model that can be used to predict leach performance and reagent consumption for specific ore samples.

Jan 1, 1999

By R. G. Henley

Mount Isa copper concentrate was combusted in a laminar-flow furnace. The conditions simulated those likely to be encountered in flames in flash smelters of the Outokumpu (air as oxidant) and INCO (oxygen as oxidant) types. The range of conditions studied was as follows: T 400-1400°C, 02 0-100%, SO2 0-95% for residence times up to 0.23 s. The distribution of sulfur, arsenic and lead between the particles and the gas phase was studied. Combustion was very rapid provided the concentrate was adequately dispersed, i.e., no agglomerates. The importance of the latter is discussed. It was possible to oxidize 80% of the sulfur present in the con¬centrate after only 0.1 s reaction time at 1000°C in an atmosphere contain¬ing 8.5% 02 and 12.5% SO2. Best volatilizations (90% of the As, 52% of the Pb) were obtained under localized conditions attained in an air-type flame. Average volatilizations were: air-type flame, As 50%, Pb 32%; oxygen-type flame, As 40%, Pb 30%. The substitution of oxygen for air reduced the arsenic volatilization. The products of combustion were mainly cuprospinel and cuprite; small inclusions of elemental copper were found in some of the particles. At high temperatures, there was a loss of copper due to vaporization of CU( g) CuO kg) (g)

Jan 1, 1983

By Asmo Vartiainen

Background of Direct-to-Blister Flash Smelting is discussed; especially slag chemistry relating to copper solubility, slag fluidity and impurity behavior. In December, 2000, Mini-pilot Flash Smelting test runs were carried out at Outokumpu Research Oy to produce blister copper from Chilean concentrate and white metal and from a mixture of them. Tested slag types were iron silicate slag, ferrous calcium silicate slag and calcium ferrite slag with different slag compositions and different concentrate/white metal ratios. The test runs were successful. The fluxing effect of copper oxide was clearly demonstrated and ferrous calcium silicate slags remained fluid on a very wide liquidus range. The distribution of arsenic between ferrous calcium silicate slag and blister copper is much higher than between iron silicate slag and blister copper. This successful test run with the new slag type offer new possibilities in Direct- to-Blister process design.

Jan 1, 2003