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By Han Ilhan

This paper discusses and describes aspects of a cost effective and safe tailings impoundment selection. In light of the current low metal prices and recent tailings embankment failures around the world, it is becoming extremely more important to develop tailings impoundment design that balance cost efficiency with safety. The paper will present critical design components associated with a tailings impoundment which need to be addressed during the planning phase. Procedures for identifying various tailings impoundment alternatives, and evaluation and selection of alternatives are presented.

Jan 1, 1999

By Laurentiu Nastac

"This paper describes the development and validation of a comprehensive multiscale modeling approach capable of predicting at the mesoscopic scale level the ingot solidification structure and solidification-related defects commonly occurring during the vacuum arc remelting (VAR) process. The approach consists of a coupling between a fully transient macroscopic code and a mesoscopic solidification structure code. The predictions from the multiscale model, including grain morphology and size, primary and secondary dendrite arm spacings, Laves and NbC phases, tendency for freckling and columnar-to-equiaxed transition, were validated against experimental measurements for a 20-inch diameter VAR alloy 718 ingots. The validated model was then used to investigate the effects of melting rate and ingot diameter on the solidification structure of VAR processed 718 ingots.IntroductionThe objective of this work was to develop a fully transient multiscale modeling approach to get an insight into the effect of processing parameters on the cast micro- and macro-structure during VAR processing. The developed model assists in achieving better control of the ingot solidification structure and to determine trends in the macrosegregation in these ingots. Another objective of this work was to analyze the transient effects of production rate and ingot size on the resultant ingot microstructures. This objective was met by first understanding the effects of the full range of processing parameters typically used in the VAR process. Processing parameters such as power input and heat extraction rate significantly influence the ingot liquid pool size and shape as well as the ingot structure, which in turn will greatly impacts the final ingot quality."

Jan 1, 2012

By Xiangru Chen, Qijie Zhai, Haicheng Li, Chao Yang, Zhang Wei

The Nb-rich phase generated by the addition of trace amounts of Nb(<0.1wt%) \ and the effects of different content of Nb on the morphology and distribution of graphite in ductile iron were studied in this paper. The results showed that when the content of niobium less than 0.1wt%, the two-dimensional morphology of Nb-rich phase existed in microalloyed ductile iron were mainly regular pattern such as square, triangle, polygon etc. Besides, Nb-rich phase in large size distributed in the matrix with a certain distance from graphite. With the increasing amount of niobium, the dispersion degree of graphite diameter, average diameter and roundness increased slightly, and the number of graphite decreased slightly.

Jan 1, 2015

By Seyed Mohammad Taghavi

In this report, the efficacy of different factors such as temperature of reaction, time of reaction and depth of bed are investigated in a process of recovery of zinc oxide from zinc ore concentration residues in a fluidized bed furnace. Under optimum conditions, there was more than 93.5% zinc oxide in products.

Jan 1, 2006

By James D. Navratil

Ferrites have been used to separate a wide range of substances such as dissolved metal species, particulate matter, and organic and biological materials; they have been used almost exclusively for metal waste treatment applications. The versatility of the ferrite waste treatment technique is evident in the wide variety of application methods. Furthermore, ferrites can be used to remove selected impurities in feed solutions containing metal products requiring purification. A brief overview of ferrite properties and recent applications for metal recovery and waste processing will be presented.

Jan 1, 1990

By O. C. Rojas

Improvements and modifications on lay out and process, from 1997 till 1998, are presented. Based on a Teniente Converter, started up 1993, a Strategic Development Plan was structured to increase the production efficiency and comply with the enviromental regulations, too. It considered the oxygen supplies to the Teniente Converter and Peirce Smith converters; reverberatory furnace shut down as a smelting unit; and the Teniente converter slag treatment through a combined process between a Slag Settler furnace and flotation. Also it included the off-gas handling and treatment.

Jan 1, 1999

The resist profile simulation is carried out using the combined data obtained. The nematic liquid crystal is clear only when a long range order exists, in the whole medium. using the Jones matrix method. Director can change from point to point and is, in general, a function of space. Details of the lens structure and of the devices fabrication and performance are described. Light from conventional light source or laser is passed through a polarizer and then incident on the specimen At the nematicisotropic, transition temperature, the medium becomes isotropic and looks clear and transparent. The transition can be approached by changing the impurity concentration or, indirectly, by tuning the temperature since the pinning strengths of the random and crystal potential have in general a different temperature dependence.

Jan 1, 2006

By Ken Baxter

The Sepon Copper Project is located in Laos and has a mineable reserve of approximately 16Mt of ore grading 5% copper with minor gold and silver values. The deposit is a clay-hosted secondary copper mineral suite, predominantly chalcocitic in nature with associated pyrite. The current project design is based on the production of 60,000t/a of LME Grade A cathode by an acid leaching process followed by solvent extraction and electrowinning. Significant metallurgical testwork was conducted as part of the Definitive Feasibility Study (DFS) with process challenges identified and overcome at each phase of testing. Flowsheet configuration is geared to autogenously generating sufficient acid and ferric iron to meet gangue acid consumption and to leach the copper. The ability to maintain acid and ferric levels in the process liquors is strongly influenced by the proportion of pyrite in the ore presented to the autoclave. This paper will outline flowsheet development from preliminary variability testing to pilot plant and DFS design. The Sepon process solution seeks a balance between operability and capital/operating costs, and provides insights into the basic mechanisms influencing flowsheet selection for these ore types.

Jan 1, 2003

By Gustavo A. Munoz

Activated carbons owe their adsorption capacities to their extensively developed pore network structure. As a result, these adsorbents generally exhibit high specific surface areas. Currently, granular activated carbons produced from coconut shells are traditionally used for gold recovery by adsorption from cyanide leaching solutions. Magnetic activated carbons (MACs) for gold recovery from cyanide solutions produced from sources other than coconut shells have been developed at the University of Utah by mixing a magnetic precursor with a carbon source, and treating the mixture under controlled conditions of temperature and gas phase composition. The pore size distribution of the activated carbons is dependent on the degree of activation, among other factors. The significance of the MAC pore size distribution on gold adsorption kinetics and gold adsorption capacity is presented.

Jan 1, 2003

By Roberto Parra

The wear and corrosion phenomena in the furnace lining of the ferrous and non ferrous pyrometallurgical processes are complex problems where chemical, interfacial and mechanical phenomena are presents. The characteristics of the processes determine the conditions to which these materials are submitted, where the thermal conditions reached during the operation is one of the most important parameter. Assuming that all the degradation phenomena are thermal activated, the rate of the different steps of the wear mechanism will depend on the thermal field in the lining. In view to apply the independent physicochemical knowledge of degradation mechanisms to the analysis and design of furnace lining the methodology of the Nodal Wear Model (NWM) was done. It combines the mathematical modelling of the heat transfer in the lining with the physicochemical control equation for the wear-corrosion phenomena. The NWM has been applied to different examples: theoretical analysis, laboratory scale test and industrial applications. We present in this paper the theoretical background of the model and two examples of applications: the sole of an electric furnace and the earth of a blast furnace.

Jan 1, 2006

By K. B. Dotson

A common international safety and health management system was developed. Analysis of selected major safety and health management systems from around the world was conducted. Functional elements of selected systems were grouped to identify common elements and key differences. Common elements were subjected to qualitative judgments of equivalency and then reconciled. With few exceptions, differing elements were revised to achieve cultural neutrality. The resulting 98 system elements were organized according to the NOSA numbering and title scheme. System summaries were produced in Spanish and English. A pre-implementation self-assessment evaluated conformance in three distinct cultures. The consensus 98 element system was internally named the BHP Copper Five Star Safety System Performance Management Guidelines. Development of a common system within an organization with international operations can enhance the ability of the staff function to share resources, programs and subsystem improvements and thereby increasingly protect workers. Common systems can increase the level of management support by demonstrating increased compatibility of the safety and health management function with traditional business objectives. Safety professionals, industrial and occupational hygienists, business managers and the safety and health of workers will benefit from further development and articulation of common systems for safety and health management.

Jan 1, 1999

By E. R. Vance, D. R. M. Brew

"Historically, Ordinary Portland cement has been the preferred medium to immobilise arsenic. However, arsenic in cement gives rise to calcium-arsenic phases and their known decomposition to calcium carbonate and arsenic trioxide via atmospheric carbonation raises serious questions about the long-term suitability of cement for arsenic immobilisation. Alternative matrices such as low-temperature ceramics (LTCs) potentially offer superior resistance towards carbonation owing to the absence of calcium. Consequently, the potential for arsenic immobilisation using LTCs has been investigated. Both AsIII and AsV have been incorporated and samples assessed according to a standard leaching protocol. AsIII persists in the porewater of alkali-bonded LTCs as sodium arsenite rendering them unsuitable for immobilisation. Thermal treatment of these LTCs to consolidate the microstructure and reduce open porosity resulted in sodium-rich cryptocrystalline matrices that leached arsenic and sodium readily. The omission of sodium in acid-bonded LTC formulations resulted in leach data that were close to the target value of 5 µg/ml in Toxicity Characterisation Leaching Protocol tests.IntroductionArsenic is a carcinogenic substance and its adverse effects of on humans, flora and fauna have been well documented [1-5]. As a consequence, many papers have been written on the prospective handling of arsenic-bearing waste. These can largely be divided into: (a) cleanup of arsenic-contaminated water using bacteria, precipitation, and/or UV irradiation to generate arsenic-rich sludges for subsequent immobilisation; (b) cleanup of arsenic-contaminated soil via chemical extraction for immobilisation of the As concentrate; and (c) immobilisation of industrial waste contaminated with As."

Jan 1, 2008

By B. Yalamanchili

Gerdau Ameristeel Beaumont presents its systematic approach for upgrade decisions that has developed over 30 years of ongoing capital projects for quality and cost improvements. This system serves to identify product needs, select process improvement strategies, justify them, and assist multi-department communications and decision-making. This is illustrated with Beaumont mills? last Stelmor upgrade and leads to a discussion of the need to consider Life Cycles of both products and technologies as we move to answer the challenges of the future.

Jan 1, 2006

By Issa S. AI-Kharusy

Oxidation/reduction (REDOX) alloy media, as used in wastewater treatment, is founded on the exchange of electrons. Because of this electron exchange, many contaminants are converted to harmless components which require no further treatment. Other types of contaminants are removed from the waste stream by electrochemically bonding to the alloy medium. This paper discusses the REDOX reactions, the role of the alloy medium in various treatment processes, and describes specific applications of REDOX alloy media for the removal and minimization of waste. The characteristics and handling of spent treatment media is also reviewed as a further consideration in waste minimization.

Jan 1, 1996

By P. Chris Pistorius

Calcium treatment of alumina inclusions, to convert the alumina to molten or partially molten calcium aluminates, is a well-established treatment for steel, to improve the castability of aluminium-killed steel. However, the role of magnesium in calcium-treated steel is not fully clear, nor is the origin of the several percent of magnesium oxide that is often present in calcium-treated inclusions. To study this, steel was sampled after calcium treatment at an industrial steel plant, and the inclusions identified by energy-dispersive X-ray microanalysis (EDX) on polished sections of the samples (analysing the samples in a scanning electron microscope). The predicted fraction liquid in the inclusion was estimated from the ternary alumina-magnesia-lime phase diagram. Inclusions with higher CaO contents generally had lower MgO contents, indicating that the calcium wire is not the origin of the magnesium in the inclusions; this was also confirmed by wet chemical analysis of the calcium wire. Instead, it appears that magnesium-alumina spinel inclusions form during extended ladle contact after aluminium killing and before calcium treatment. While such spinels have been stated to cause poor castability (clogging the submerged-entry nozzle), it is clear that calcium treatment successfully modifies the spinel inclusions to mixed alumina-lime-magnesia inclusions, where the magnesia content contributes substantially to liquefaction of the inclusions: for typical MgO contents of around 10%, the range of Ca:O ratios which yield liquid (or partially liquid) inclusions is extended substantially to lower Ca:O ratios.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By C. J. Boreiko

Traditional patterns of lead and zinc utilization are being evaluated in accordance with new paradigms that seek to ensure the long-term compatibility of global industrial activity with precepts of sustainable development and sustainable consumption. As a consequence, both industry sectors are experiencing intense scrutiny from the international community, and numerous regulatory options are being considered that may impact upon international industry practice. This paper reviews the growing expectations being placed upon industry, and highlights some of the common regulatory concerns being expressed regarding both metals despite their differing toxicological profiles.

Jan 1, 2000

By Gerson de Araújo Filho

This paper shows the use of tires as fuel to be employed into blast furnaces. The tires can substitute coal or even charcoal in the blast furnaces tuyeres. The injection into tuyeres, besides the contribution for energy generation, can also produce gas for iron oxide reduction. The tires, as powder to be injected into blast furnaces, contributes for an environmental use of this waste, which helps to obtain a high value product as well. So, the advantage of using such material is that it is waste and has lower cost for preparation. The obtained results showed that the tires have good combustibility. This one was obtained in a model that simulates the same conditions occurring in the blast furnaces tuyeres; these used raw materiais include tires and mixtures of tires with coal or even with charcoal.

Jan 1, 2006

By Bryn Harris

Much has been written over the past twenty years on the removal and chemical stabilization of arsenic from metallurgical process solutions. This paper reviews again the latest developments in this field, and concludes as before that the high-iron arsenical ferrihydrites, together with the high temperature arsenic minerals, scorodite and Type II, remain as the best and most viable vehicles for industrial control and disposal. However, a cautionary note is introduced, in that chemical environments cannot be considered in isolation, and that cogniscence has to be taken of microbiological activity in determining the disposal method. Data are also presented on a survey of industrial practice, which shows that arsenical ferrihydrite is by far the most widely-practiced and accepted method used worldwide. Finally, the disaster in Bangladesh is briefly discussed with reference to lessons that the metallurgical community might learn from this.

Jan 1, 2003

By K. Watling

Vibrational spectra of surface and solution compounds formed during cyclic voltammetry of a gold electrode in a deoxygenated 0.01 mol dm-3 NaCN solution have been examined using surface-enhanced Raman scattering (SERS) spectroscopy. The presence of cyanide at the electrode surface was indicated by Raman bands characteristic of the carbon-nitrogen stretch, CN.. Chemisorption of cyanide on the gold surface was evidenced by the presence of vibrational modes due to gold-carbon stretching, AuC, and gold-carbon-nitrogen bending, AuCN. Prior to the disappearance of the surface cyanide stretch band, a limiting value of the CN was obtained, the same as the value reported for adsorbed cyanide. Effects upon the voltammetry and vibrational modes of surface species due to additions of silver and lead to the gold-cyanide system have been observed.

Jan 1, 2003