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By R. W. Lawrence

A method by which it is possible at an oxidation potential below 680 mV SHE to achieve quantitative conversion of sulphide sulphur to elemental sulphur instead of sulphate in a biological leach of chalcopyrite and bornite has been investigated. The process chemistry, biological phenomena and process flowsheet options are discussed. Several copper concentrates have been evaluated and have been found to be amenable to th process. Results to study the progression of chalcopyrite decomposition during the leach are presented and mineralogical factors affecting the requirement for silver addition are discussed. A chloride addition method for improving silver recovery is described. The results of a small scale continuous leach test have demonstrated that continuous operation can be carried out with high copper extraction and stoichiometric conversion of sulphide sulphur to elemental sulphur.

Jan 1, 1985

By Jian Ye

Recycling of aluminum scrap, such as Used Beverage Container (UBC) scrap is steadily increasing. In secondary remelting of such scrap, it is a common practice to use protective molten salt cover. An appropriate salt protects metal from oxidation, promotes coalescence of the suspended metal droplets, and separates clean metal from the oxide contamination. The molten salt also reacts with metal. This causes metal loss and change of resulting metal composition. In this paper, role of molten salt fluxes in melting of UBC scrap is discussed, and selection criteria for molten salt are provided.

Jan 1, 1995

By H. Bernier

The Noranda Inc., CCR Division, copper refinery located in Montreal-East, Québec, Canada, has expanded over the years to reach a capacity of 410,000 metric tons of cathode production per year. The expansion process resulted in nine, parallel, 200 m. long bays each equipped with its overhead cranes and manually operated washing machines. Anode scrap washing and piling was done manually. The mechanization of the tank house involved the elimination of 18 cells at one end of each of the bays in order to install transfer conveyors where anode scrap and cathode loads are deposited by the bay cranes. The cathode loads are brought by new transverse cranes to new machines where cathodes are washed, piled in predetermined bundle weights, check weighed, strapped then shipped in trucks or railroad cars. Suspension bars are automatically removed, stacked in magazines and sent back to the starting sheet machines. Anode scrap loads are brought to machines located near the anode furnaces where they are washed and piled in bundles for easy charging. The mechanization has eliminated numerous hazardous jobs and has realized a reduction of 0.2 man-hours/ton. After these modifications, the refinery production capacity now stands at 370,000 metric tons per year.

Jan 1, 1987

By Jörg Wallner

In order to limit SO2 emissions, the Montanwerke Brixlegg AG has installed a desulphurisation plant with the primary aim of reducing the peak emissions from the copper converter that are of particular ecological concern. The author discusses the process requirements, the desulphurisation process selected and the results achieved.

Jan 1, 1996

By Takeo Fujino, Nobuaki Sato, Yarong Wang, Kohta Yamada

"Ternary mixed sulfides of some transition metals MTS3 (M=Ba, ·Pb, T=Ti, Zr) were synthesized by a relatively low temperature process using sulfur melt. The mixture of starting materials, such as, metals and/or binary sulfides and a large excess of sulfur was reacted in a vacuum-sealed Pyrex or quartz ampoule at 350- 600 °C for one to three weeks. After the reaction, the remaining sulfur was completely removed by a process composed of filtration of sulfur melt and followed dissolution in CS2• The binary sulfides impurities coexisted in the products were removed by rinsing the products in water and acetone. By using the above method, BaTiS3, PbTiS3 and BaZrS3 'Were obtained in pure form. The effect of addition of halides on the yields of these ternary sulfides were also discussed.IntroductionThere have been a vast number of studies on the preparation and physical and /or chemical properties of mixed metal oxides. As is well known, some of such compounds exhibit excellent materials properties, causing them for use in mechanical, electronic, magnetic and chemical devices. Not a few mixed metal sulfides show similar physico-chemical properties to those of the corresponding mixed metal oxides. However, the study of the mixed sulfide crystals is rather sparse mainly due to difficulties in preparing these compounds. In various methods which have been adopted for preparing mixed sulfides, the simplest method would be the solid-solid reaction of the component binary sulfides or elements. However, there are always diffusional constraints with regard to the reactions in solid phases causing it necessary to heat the reactants at sufficiently high temperatures, viz. 800-1200°C. On the other hand, some mixed sulfides are unstable at high temperatures or to change their materials properties due to sulfur nonstoichiometry and structural modification depending on temperature, i.e., synthesis of such compounds needs to be made at lower temperatures. Processing in alkali halide melts is hopeful to overcome the above problems but to obtain the halide melts the temperatures above ~ 600 °C is needed. Low temperature reaction has been carried out for the preparation of Hg1.24TiS4, which was formed by the ·combination of TiS2 and molten Hg metal at 320°C[l]. Reaction of WS2 with LiBH4 melt at 350°C yielded LixWS2[2]. These sophisticated methods, however, can be applied only to the vary special cases."

Jan 1, 2000

By Peng Bing

Stainless steelmaking dust is classified as a hazardous waste due to higher than acceptable heavy metal leachabilities such as zinc, lead, cadmium and chromium. In addition to being an environmental hazard, the flue dust is also an economical concern to stainless steelmakers as it contains large amounts of valuable alloying elements, especially for iron, chromium and nickel. A new technology of direct recycling of stainless steelmaking dust has been developed to recover the metals from the dust. But it was found that zinc was accumulated in the dust collection system in practical run of direct recycling. This study focuses on the effect of the operating parameters such as temperature, dust feed rate and the ratio of CO to dust on the reduction of zinc oxides present in the dust. The mathematical model for the reduction process was setup based on the experimental research. According to the mathematical model, the temperature has obvious effect on the reduction of zinc. It is benefit to the process of zinc reduction to increase the temperature. But the temperature will not be the main factor for the reduction process after 1228C. It will promote zinc reduction to decrease the dust feed rate and control the ratio of dust to CO. It was also found from the experiments that ZnFe2O4 in the dust could be decomposed at high temperature. Decomposing ZnFe2O4 in the dust increases the recovery of zinc from the dust distinctly.

Jan 1, 2006

By K. Narayan Prabhu, W. D. Griffiths

"Heat transfer during the unidirectional solidification of a cast iron alloy against cast iron chills was investigated using an inverse modelling approach. Chills of thickness 100 mm and 10 mm were used, to simulate gravity die cruiting conditions and the use of chills in sand moulds. In both cases transient heat transfer, measured by the interfacial heat flux and heat transfer coeffieient; declined from initially high values in the first few seconds of solidification, to values about an order of magnitude lower which persisted for the remainder of the experiments. In the case of the thin chill it became saturated with heat until it was no longer in a position to extract further heat from ·the casting. These results were interpreted by studying the resistance to heat transfer from the casting offered by the ·casting-chill interface and the chill itself for example, the thermal resistance of the casting-chill interface can be influenced by the deformation of their respective surfaces and their subsequent relationship.IntroductionDie casting cast iron offers several advantages such as energy savings, higher mould yield, and better surface quality over the sand casting process1 • The process is· environmentally' friendly because of the elimination of the sand. However the design and construction of metallic moulds is expensive and a faulty die design may result in a defective casting: A simulation based process design of die castings would enable die designers and solidification modellings to try better designs of dies on the computer and arrive at a cost effective solution more quickly. This has numerous benefits for the die caster, as he would be able to produce sound castings with very short lead times.The success of a solidification model to predict accurately the thermal history and the location of hot, spots inside a solidifying casting depends to a large extent on the heat transfer data prescribed at the metal/mould interface. Many measurements of the heat transfer coeffident (or the heat flux) between a solidifying aluminum alloy and a chill have shown that the heat transfer coefficient is a function of most of the variables of the casting process2 - 8. However heat transfer studies during the solidification of ferrous alloys are rather limited. The high temperatures involved suggest that the contribution due to radiation heat transfer cannot be neglected."

Jan 1, 2000

By Buket Tunçer, Mehmet Buğdaycı, Onuralp Yücel

ZrB2 and TiB2 are one of the most significant metal borides. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, TiO2, B2O3 were used as starting material and Mg used as a reductant to produce ZrB2-TiB2 powders via SHS. Therefore, it was aimed to determine production parameters, leaching conditions and comprehensive examination of final product features. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques

Jan 1, 2015

By Xue Ping

Sm2Fe17 alloy is an important precursor for the preparation of Sm2Fe17Nx magnet, which possesses a higher Curie temperature, larger anisotropy field, better resistance to oxidation and thermal stability. In this paper, the wet chemical co-precipitation was developed for synthesis of the Sm-Fe alloy oxide precursor. Based on the principles of simultaneous equilibrium and mass balance, a series of thermodynamic equilibrium equations of Sm(III)-Fe(II)-NH3-C2O4 2--H2O system at ambient temperature were deduced theoretically and the thermodynamic diagrams of lg[M2+]T (M=Sm, Fe) versus pH at different solution compositions were drawn. Then, the experiments were done to address the various effects on the wet chemical process, including solution pH value, reactant concentration, reaction temperature and aging time, etc. It is found that by precise control of the process, the Sm-Fe alloy oxide precursor was synthesized with fine crystallization and special size &size distribution.

Jan 1, 2008

By B. C. F1intoff, R. G. Bradburn, E. Groiss

"The concentrator at Brenda Mines Ltd. treats a copper - molybdenum porphyry ore with current head grades of 0.185% Cu and 0.036% Mo. The consistently low head grades provided the driving force to explore methods of improving plant productivity. Computer based process control was recognized as one means of addressing this objective. Over the period from 1974 to 1982 a control system evolved which now extends to every area of the mill. Control strategies are built on elements of classical, modern and rudimentary expert control. In addition, the control system has often served as a catalyst for other technological developments. The economic returns associated with the system are very significant and it has played an important role in the mine's survival in times of poor metal markets. This paper presents an overview of the computer control system at Brenda.PreambleOne can scarcely avoid picking up a trade magazine or newspaper today without seeing some reference to technology and its potential impact on North American business. _A recurring theme is the need to apply technology to raise our standard of plant automation in the manufacturing and process industries. The general thesis of these articles has been concisely captured in the mutually exclusive set:AUTOMATE or EMIGRATE or EVAPORATEProcess control is one form of automation that has been successfully exploited by various sectors of these industries. In minerals and metal processing the wide scale adoption of process control technology has, until recently, been largely limited to a few companies - most of whom have a history in the area dating back to the early 1970’s. However, there is definitely an increased and much broader interest in process control as a technology which can improve performance, productivity and profit.The economic hardships that were visited on the mining industry in the early 1980's are not easily forgotten. It is the authors' conviction that the mining industry must move to implement proven technology, in particular process control, in order to be well postured for the next (inevitable) down cycle.In pursuing the technical and trade literature, one can discover a number of example of the successful utilization of process control systems in mining and related applications. In the text which follows, the authors describe the process control efforts undertaken in the Brenda Mines Ltd. concentrator."

Jan 1, 1989

By N. El-Kaddah, J. W. McKelliget

"A mathematical model for the analysis and design of hybrid plasma reactors for advanced materials synthesis is presented. The model is based upon a solution of the electromagnetic vector potential equation and is capable of predicting the two-dimensional velocity, temperature, and electromagnetic fields as well as the reaction kinetics inside the reactor for any axi-symmetric coil configuration. The model is used as a computer aided design tool for the design of hybrid plasma reactors consisting of a conventional DC torch augmented by an RF induction coil and it is demonstrated that the hybrid system possesses superior characteristics for materials synthesis over conventional DC or RF systems. The coupling between the RF and DC components is found to affect both the temperature field and the flow field and to have a significant effect on the reaction kinetics and on materials recovery. The model is used to study the thermal decomposition of silicon tetrachloride as a function of reactor design and operating parameters and it is demonstrated that through a CAD approach it is possible to significantly improve the operation of materials synthesis systems.IntroductionIn recent years there has been growing interest in the use of the inductively coupled plasma for chemical synthesis as a way of meeting the increasing demand for high quality, high performance materials for use in critical applications/l/. Although the basic feasibility of this approach has been demonstrated in the laboratory/2,3/ there still exists a number of operational problems that adversely affect system performance for some applications. In particular, the recirculation and back flow effects that arise from the electromagnetic forces in the plasma can result in the repulsion of the reactants from the hot plasma core and their subsequent deposition on the walls of the reactor. Another operational problem arises from the fact that the energy dissipated in the plasma has to compensate for the heat losses to the environment by conduction, convection, and radiation in order to maintain the ionization of the plasma and, hence, the stability of the plasma may be affected by the presence of the reactants and their products."

Jan 1, 1988

By Dhanesh Chandra

Long term stability studies were conducted on four variants of LaNi5; 10,000 hydriding/dehydriding cycles were used to evaluate their suitability for a metal hydride cooling system. Thermodynamic and structural studies were conducted to determine changes in these materials during cycling test period. The hydrogen sorption properties of LaNi5.2, and Lao 9Gd0.1Ni5 and LaNi4.75In0.27 were seriously degraded during the tests but the LaNi4.8Sn0.22 hydride was virtually unaffected. Hydride isotherms were measured at the beginning and at intervals through out the test period to observe the nature and extent of damage degradation in the sorption properties. X-ray diffraction studies of the alloys (LaNi5.2, LaO.9Gd0.1Ni5 LaNi4 8Sn0.22) and their respective hydride, before and after test, provided insight with regards to the observed changes in the hydride properties. Electron microscopic studies were also conducted to evaluate the changes in particle sizes.

Jan 1, 1989

By N. A. Vatolin, L. I. Leontjev, S. V. Shavrin

The ever growing interest to the complex iron ores may be attributed to possible production of the naturally alloyed metals and the efficient recovery of the associated elements. However, the conventional technique for complex ore processing is complicated and in some cases even impossible. A pyrometallurgical benefiation of such ores without melted slag formation has been advanced. A version of the technique assumes pellet production with metal coagulated within a slag shell on grinding the pellets, the metal phase is mechanically separated from the slag shell. The technique has been run up with ferro chromo nickel, high-titanium, high-magnesia, alumina phosphorus ores and concentrates. Another version of the pyrometallurgical benefication without melted slag formation in a rotary kiln has been developed from the schemes for processing red mud of alumina manufacture and high-titanium concentrates. Means have been put up to improve schemes available for lex iron ore processing with primary emphasis on material pretreatment before blast furnace and steelmaking processes. Vanadium-bearing titanomagnetite conentrate oxidized pellets possess low strength at reduction. The technique suggested for pelletizing in the controlled atmosphere improves the afore said pellet metallurgical properties. Prodution of metallized pellets in a conveyor roasting machine holds considerable promise for blast furnace and steelmaking processes. In processing the high-sulphur iron ores still another technique is proposed to roast the fluxed pellets with 95% and more desulphuration.

Jan 1, 1988

By Darryl Lovato, Ramiro Pereyra, Daniel S. Schwartz

"During an annual inventory of nuclear material, a plated steel container which contained plutonium oxide failed. The container had been packaged for temporary storage but had been overlooked and remained in storage for more than 23 years. Although it was determined that the failure occurred through the slip-top rim, a metallurgical evaluation was requested to help to determine the integrity of the container.Optical metallography and scanning electron microscopy were used to analyze the character and degree of corrosion in the container. The depth of corrosion, measured at approximately 10 µm, did not pose a threat to the integrity of the container. However, the corrosion morphology and chemistry did suggest that a galvanic cell had developed between the tin and steel from the condensation of water. The morphology also suggests that the attack of the steel took place over a series of cycles due to changes of the environment.IntroductionMetallographic analysis was requested as part of the investigation into the mechanism of the failure of a slip-top container (#38621) containing plutonium oxide (PuO2) powder. The container had leaked during a special nuclear material (SNM) annual inventory causing contamination and closure of the vault. A photograph of the container and interior container is shown on the right in Figure 1. An initial investigation established that the source of contamination was the consequence of the failure of multiple layers of containment. Initially by the deterioration of the interior plastic bottle and polyvinyl chloride (PVC) bagout bag, and finally through the lid and steel container interface at a location where tape had not adhered properly [1]. Although the source of the breach was established, it was determined that metallographic analysis was important to establish the extent of deterioration of the steel container."

Jan 1, 2008

By Julie M. Melluish

The metallurgical response of the Point Leamington deposit has been studied. Two series of bench tests were conducted and various ore samples and flotation products were examined using image analysis techniques. The majority of sphalerite and chalcopyrite grains in this texturally complex ore were found to be smaller than 10 micrometres. Copper recoveries were low with losses mainly as fine inclusions in pyrite. Sphalerite recoveries were somewhat better due to a generally coarser habit. Gold and silver recoveries were also low and only solid solution silver was identified in the ore. The deposit shows poor economic prospects unless additional tonnage of high grade zinc ore can be delineated.

Jan 1, 1989

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By James C. Sever

Two green field magnesium reduction plants are under consideration using dolomite as the raw material. The Calix calciner was independently selected for both plants. The unique design of this calciner is detailed and the advantages defined for the specific application. The low carbon foot print of this unit combined with the ability to capture food grade carbon dioxide makes this an environmentally proactive approach to carboniferous ore calcination.

Jan 1, 2015

By V. Vergara

Four copper composites were obtained by mechanical alloying, using as dispersed phases of four carbide powders; they were: boron carbide, chromium carbide, silicon carbide and zirconium carbide. The purpose of this work was to study some characteristics of these compounds and their feasibility for use as materials for electrical equipment. Raw materials used were copper powder finer than 150 mesh, and 2-4 vol % of powder carbides finer than 325 mesh. The alloying process was carried out using both a Spex 800-D mill with tungsten jars and balls and a hardened stainless steel jar and balls, the purpose of which was to measure the degree of contamination induced by the milling media. The changes in particle size, morphology and microstructure of copper alloys were studied with SEM and TEM for each alloyed powder. The degree of saturation of copper by the carbides was measured by X-ray diffraction. Sound samples were obtained by hot isostatic pressing at 1073°K. The best characteristics were obtained for the compound copper-chromium carbide, based on their hardness, tensile strength and electrical conductivity values. The other alloys failed due to their excessive brittleness after hot pressing.

Jan 1, 1999

By Dave Tahija

"Many investigations are being performed with the goal of removing carbon dioxide from the atmosphere and permanently storing it in geologically stable settings. At the same time, carbon dioxide in the form of dissolved carbonate is steadily accumulating in the world's oceans. Both carbon dioxide sequestration and oceanic accumulation are constrained by the aqueous thermodynamics of the carbonate system. These constraints are illustrated using the STABCAL computer model to generate potential-pH and aqueous distribution diagrams of seawater in contact with various pressures of carbon dioxide gas. STABCAL diagrams and titration simulations are also used to model some potentially useful cation-carbonate sequestrationsystems.IntroductionAtmospheric carbon dioxide concentrations have risen dramatically in the past couple of centuries and are rising still, primarily as a result of human activities, especially the burning of fossil fuels. Increased atmospheric carbon dioxide concentrations have been implicated as a main cause of global warming but have other effects as well.Rising levels of atmospheric carbon dioxide result in increased concentrations of dissolved carbonate complexes in water, including the oceans. These dissolved carbonates interact with other dissolved substances, altering overall seawater chemistry, most noticeably causing lowered pH levels.Some of these chemical changes are observed directly, for instance the general drop in oceanic pH, [1], while others can be inferred and predicted using thermodynamic modeling. The chemistry of dissolved carbonate in seawater is not especially intricate, as such chemical systems go, but neither is it simple enough to be worked out on the back of an envelope. Interactions between the several simple carbonate species and all the major dissolved cations in seawater should be considered, as well as the effects of competing anions, especially chloride and sulphate, since they are much more abundant than carbonate in seawater."

Jan 1, 2011

By Alysson Tadeu Pereira Almeida

Steels with low concentrations of nitrogen, hydrogen and carbon have been in large demand lately. The RH process is a secondary refining process that can simultaneously attain significant levels of removal of these interstitial elements from liquid steel. In the RH process, the melt circulation rate plays a very important role in determining the productivity of the equipment, since it affects the decarburization rate. In the present work, a physical model of a RH degasser in a 1:5 scale of an industrial reactor has been built and used in the study of the circulation rate and of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. The experimental results indicated that the kinetics of decarburization can be described by a first order equation. Based on the results, it was possible to determine the contributions of the decarburization in the upleg snorkel and in the vacuum vessel.

Jan 1, 2006