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By William Petrul

Image analysis studies were performed on mill products from laboratory flotation tests of the Zn-Pb ore from the Faro deposit in Yukon, Canada, to determine mineral liberations at specific grinds and to predict recoveries at optimum flotation conditions. The minimum and optimum grinds for liberating sphalerite and galena were predicted from size analysis data for the minerals in large ore pieces, and determined by image analysis studies of the mill products. The determined optimum grinds are about 2 Tyler mesh sizes larger than predicted because sane of the fine grained sphalerite and galena occurs in interstices between coarser grained pyrite and is liberated when the pyrite grains are broken apart. Materials balance calculations were performed on the analyzed values for the liberated and unliberated sphalerite and galenaa to determine their distributions in the mill products. The laboratory flotation tests recovered 74% of the sphalerite and 83% of the galena in Zn and Pb concentrates respectively. The mineral evaluation study indicates that the optimum recovery for sphalerite and galena are 85 and 83% respectively. The company is currently recovering 80% 'of the sphalerite and 82% of the galena.

Jan 1, 1989

By M. Brian Maple

A rich variety of phenomena are produced by superconducting-magnetic interactions in rare earth and actinide compounds. These phenomena, and the materials in. which they have been observed, are described in this talk, with an emphasis on the new high superconducting transition temperature (Tc) copper oxides. The Materials The-materials in which these phenomena occur can' be divided into two classes. In the first group, there are two distinct interpenetrating systems of electrons, a set of localized 4f or 5f electrons and a set of itinerant electrons. The localized f electrons carry magnetic moments and interact with the spins and momenta of the the itinerant electrons, which are involved in the superconductivity, via exchange and electromagnetic interactions; respectively. This category includes materials containing rare earth (R) and actinide elements with partially-filled f electron shells which have been inroduced as substitutional impurities [e.g., La1-xCexA12, Th1-xUx] or form a sublattice in compounds [e.g., RRh4B4, RMo6S8, RMo6Se8, the high Tc. superconductors RBa2Cu3O7-d(d - 0.05)]. Materials of the second type are characterized by a single band of electrons that is responsible for both superconductivity and magnetic order. This group includes heavy electron rare earth and actinide compounds [e.g., CeCu2Si2, UBe13, UPt3, URu2Si2], and the high Tc copper oxide superconductors such as the hole-doped systems Lag- MxCuO4 (M = Ca, Sr, Ba, Na) and RBa2Cu3O7-d(0 =d= 1) and the electron-dope system Ln2-xMxCuO4-y (Ln = Pr, Nd, Sm, Eu; M = Ce, Th; x = 0.15; y - 0.02).

Jan 1, 1992

By K. W. Cathrine Solem

Filtration of liquid aluminium is widely used in the industry for the removal of inclusions, and Ceramic Foam Filters (CFFs) are often the filtration media of choice. It is known that PH3 (phosphine) can be released from used phosphate bonded CFFs when in contact with water. Additionally, there is a need of an improved understanding of the thermal stability and the chemical reactivity of these types of filters, as there is limited information available in the public domain. In the present preliminary study, three CFFs, i.e. Substrate 1–3, with varying AlPO4 (aluminium phosphate) content were studied under controlled conditions. Samples of the substrates, as produced and in contact with 5N pure aluminium, were heat-treated in a vacuum induction furnace at 850 °C and 1300 °C, as well as thermally studied at 850 °C using a Differential Scanning Colorimeter connected to a Thermogravimetric Analyser (DSC-TG). All tests were performed under an inert atmosphere of argon (Ar). Mass changes of ∼0.001 % were registered for the pure substrates, and 0.003-0.10 % when in contact with aluminium. In the latter case, diffusion of P (phosphorous) from the bulk of the substrate to the interface was established to have taken place. A colour change, from white to orange/brown, was also observed at the interface, which is a clear sign that a chemical reaction has taken place. As a result, the thermal stability of the substrates can be questioned under present conditions.

By D. McConchie

Management of caustic red mud wastes at the QAL bauxite refinery uses an innovative approach . involving neutralising the red mud with seawater; solids settle in a Red Mud Dam and residual water (pH = 8.6) is discharged to a tidal inlet. A survey of 18 trace elements in sediment, water, mangroves and molluscs, and an ecological survey of benthic fauna in the inlet, and at near-pristine control sites, revealed no significant trends that were linked to the discharge, except for the concentration of Al which was slightly elevated within 100m of the outfall. Trace element concentrations in water samples were close to, or below, world average seawater values and oysters collected near the outfall were acceptable for human consumption. The impact of discharges is minimised by a high tidal range, >60% flushing of the inlet in each tidal cycle, and the very high trace element binding capacity of sediment in the dam (> 100meq/ 100g dry mud).

Jan 1, 1996

By Dao Su, Ganghua Fu, Xuling Chen, Yufeng Guo, Min Gan, Tao Jiang, Xiaohui Fan

"The sinter quantity and quality of limonite in the magnetite and hematite sintering models were studied and compared. For the sintering of magnetite, the results showed that the increase of limonite improved the permeability of sinter mixture, increased the sinter quantity and quality. The sinter strength and productivity were decreased when the proportion of limonite exceeded 50%. The appropriate proportion of limonite was 40%-50%. For the sintering of hematite, the sinter quantity and quality were first maintained at the same level thereafter declined, more obviously when the proportion of limonite exceeded 40%. The amount of calcium ferrite increased whose shape changed from acicular to leaflike and block gradually with the proportion of limonite increased from 0% to 80%.IntroductionWith the fierce competition of domestic and overseas iron markets in the twenty-first century, cheap ores such as limonite are used to be sintering raw materials to cut the costs of sinter and pig iron for steel making, and boosts the competitiveness of steel companies [1, 2]. In addition, as the reserve volume of hematite of high grade is reducing year by year, the usage amount of limonite in sintering are expanding in major domestic and international sintering plant [3, 4]. Sintering can be divided into two types, majoring in concentrates and fine ores, according to the different types of raw materials. The sintering characteristics of limonite in the two types above have been studied and compared in this paper, which makes a significant sense for the research of limonite sintering properties and guidance of ore proportioning in sintering plants."

Jan 1, 2012

By Alicia Esther Ares, Carlos Enrique Schvezov, Alejandra Silvina Roman, Claudia Marcela Méndez

In this paper the structure of aluminum based alloys and their corrosion behavior by using different electrochemical techniques as characterization methods are considered. Currently, it becomes imperative to know the role of the Al2Cu against the susceptibility to corrosion of these alloys. The present work aims to studying the electrochemical behavior of aluminum base alloys with the following compositions: Al-1wt.%Cu, Al-4.5wt.%Cu and Al-15wt.%Cu (with different grain structures), in 1M NaCl solutions, at room temperature. Cyclic potentiodynamic polarization tests were performed and were found that the alloys with more than 1wt.%Cu in the matrix have an unstable behavior and without tendency to reach passivity. The equivalent circuits derived from electrochemical impedance spectroscopy technique (EIS) generally showed two capacitive contributions. The susceptibility to corrosion becomes a complex function, not only of copper concentration and structure, but also with interdendritic spacings and distribution of phases in the alloys.

Jan 1, 2015

By Jonkion M. Font

An expression for the distribution ratio of arsenic between slag and copper matte or liquid copper was developed by both, an extension of the Reddy-Blander model for deriving a priori the arsenic capacity, and by a relationship between the arsenic capacity and the arsenic distribution ratio. In this study, the a priori arsenic capacities in the FeO-SiO2, CaO-SiO2, MgO-SiO2, FeO-CaO-SiO2, FeO-FeO1.5-CuOo.5-MgO-SiO2, FeO-FeO1.5-CuO0.5-CaO-MgO and FeO-FeO1.5-CuO0.5-CaO-MgO-SiO2 slags were calculated at 1573 K. The a priori arsenic distribution ratio between the FeO-FeO1.5-CuO0.5-CaO-MgO-SiO2 slag and copper matte (L s/m as), and between the FeO-FeO1.5-SiO2 or FeO-FeO1.5-CuO0.5-CaO-MgO slag and liquid copper (L s/Cu as) were calculated. The model calculated data are found to be in good agreement with the reported experimental data. The availability of reliable thermodynamic data for slag components and impurities in the slag-matte-metal system is essential for the accurate prediction of impurity capacities and distribution ratio data. The arsenic distribution ratio model developed here, can be extended for prediction in multi-component slags and mattes or liquid metal, and thereby may lead to the development of new slag systems for the efficient removal of arsenic in the copper smelting, converting and refining processes.

Jan 1, 2003

By Richard D. Hagni

Polished sections of pyrometallurgical intermediate products from a simulated commercial flash furnace were examined by reflected light microscopy, scanning electron microscopy-energy dispersive spectrometry and electron backscatter analysis, and microprobe analysis for phase and textural relationships. The smelter feed is a copper concentrate from a porphyry copper deposit. The concentrate consists primarily of chalcopyrite, bornite and pyrite with smaller amounts of covellite, chalcocite, molybdenite, magnetite, galena, and sphalerite. The flash furnace reactions for pyrite and chalcopyrite can be observed by reflected light microscopy. Reacted angular particles of pyrite exhibit successive rims of fibrous pyrrhotite and hematite or magnetite. Reacted angular chalcopyrite particles show successive rims of bornite, digenite, and chalcocite. Spherical particles, formed by the complete melting of former pyrite particles, consist of variable amounts of granular pyrrhotite with magnetite rims and minor hematite. Spherical particles, formed by the complete melting of former chalcopyrite particles, exhibit exsolution intergrowths with varying proportions of intermediate solid solution, bornite, digenite, and chalcocite and have rims of hematite, magnetite, and copper-iron spinel. Sphalerite and molybdenite do not show evident mineralogical reactions.

Jan 1, 1987

By Graham J. C. Carpenter, Marc Charest, Jason Lo

"The method of producing magnesium-based composites with silicon carbide (SiC) particulates embedded in the matrix of magnesium AZ9I D alloy by the squeeze-casting technique are described. This method involves the fabrication of a SiC particulate preform and the subsequent squeezing of molten magnesium into the preform. In this study, alumina, aluminum phosphate and a proprietary binder were used for the fabrication of SiC particulate preforms. The procedures employed in the fabrication of SiC! AZ9ID composites are presented, together with the results of characterization of the composites using optical and transmission electron microscopy. Special attention is given to the reaction products in the bulk alloy and at the interfaces between SiC particles and the AZ9ID matrix alloy.1. IntroductionInterfacial, microstructural and metallurgical characteristics play an important role in determining the mechanical properties of a composite. In theory, reinforcing magnesium with SiC particulates should provide an improvement in strength and modulus of the composite over the unreinforced counterpart. However, many factors resulting from the fabrication process can cause degradation rather than improvements to the mechanical properties. In particular, the interfacial characteristics are known to critically influence the properties of composites [1]. Before evaluating the mechanical properties of a composite, it is always useful to examine the microstructure, which is closely related to the mechanical behavior. This helps to reduce the labor-intensive steps of sample preparation for mechanical property evaluation, which can be particularly difficult as a result of the high hardness of composite materials, as well as providing a wealth of information on the microstructural and interfacial characteristics, particularly the reaction products caused by processing. This information is also pertinent in understanding the factors governing the mechanical properties of the composites.There are many factors which determine the nature of the interfacial characteristics of a SiClMg composites. Qualitative estimations of the interfacial bonding have been performed based on thermodynamics, electronic and electrostatic concepts. In addition, the kinetic conditions during the fabrication play an important role. From an interfacial energy standpoint, the driving force for the formation of a metal/ceramic interface is the decrease in free energy that occurs when intimate contact is established between metal and ceramic surfaces. The simple representation of the energy change per unit area of interface formed (~G) is given by Dupre equation [2]:"

Jan 1, 1996

By G. G. Krishna Murthy

Interactions of wustite and hematite pellets with Fe-C melts were investigated experimentally by examining the effect of pellet size and bath temperature on the reduction rates of the pellets. Experiments were carried out in the temperature range 1473-1923 K. A flash X-ray equipment was used to obtain images of the melt surface during its reaction with an oxide pellet. The reduction rates were calculated using experimentally estimated time for complete reaction of a pellet, tR. The value of tR was determined employing gas mass flow rate, or pressure rise in the sealed furnace, versus time traces. The value of tR was the same for both wustite and hematite pellets of equal weight at or above 1723 K and it decreased with increasing melt temperature. But the reduction rate was substantially lower at temperatures below 1651 K, the melting point of wustite. The rates were defined as the rate of moles of oxygen removed from the pellet per unit area of bath free surface and it was found that the bath surface area affects the reduction rates. It was established that the overall reaction followed nth-order rate kinetics with the values of n falling between 0.3 and 0.4 for temperatures above the melting point of wustite. The apparent activation energy determined using the apparent rate constants obtained from the experimental data was 76.2 + 27.7 kJ/mol-O.

Jan 1, 1992

By Qingyu Deng, Shiwei Ma, Guibao Qiu, Hua Wang

"The flow behavior of the blast furnace slag bearing titanium, like viscosity, play an importance role during the iron-making process with the vanadium-titanium magnetite, which is a very special minerals in Panzhihua, China. The dependency of the viscosity on the chemical composition like TiO2, Al2O3, MgO, binary basicity (CaO/SiO2), temperature, reaction time were studied. The experiments showed that the viscosity decreased with the increase of TiO2, MgO content and binary basicity, and it increased with the increase of Al2O3 content and temperature. The viscosity showed a slight decrease within 60mins’ reaction with graphite crucible, however, it increased rapidly afterwards with the formation of Ti(C, N).IntroductionThe ordinary iron ore has been an essential part of raw materials for vanadium-titanium magnetite smelting in Panzhihua to avoid a series of problems, such as slag thickening, adhesive bond of slag and hot metal, etc. The ratio of vanadium-titanium magnetite has been decreased gradually since 1970s, and has down to about 65% now. However, with the substantial appreciation of price of imported ordinary iron ore, Panzhihua Iron and Steel Group aims to increase the ratio of vanadium-titanium magnetite and decrease the dependence on ordinary iron ore in order to lower the cost of smelting process."

Jan 1, 2012

By Lauri E. K. Holappa

Ferrochrome, as the central constituent in stainless steels is one of the most rapidly growing primary metallic products. In this contribution results of a comprehensive study on the reduction process of chromite ore to FeCr are presented including thermodynamic examination, experimental work on kinetics and mechanisms in solid state, and smelting reduction conditions as well as kinetic modelling of solid state reduction.

Jan 1, 1999

By Toshihiro Kuzuya

A hydro metallurgical process has been developed for the recovery of metal values such as Co, Ni and rare earths from the electrode materials of spent nickel metal-hydride(Ni-MH) secondary battery. MmNis_xCo. (Mm : Misch metal) intermetallic compound could be separated from the electrode materials mixture by sedimentation. A typical chemical composition of MmN5-xCox was approximately, in mass%, 56.0%Ni, 13.4%Ce, 10.6%La and 7.9%Co. The time dependency of leaching intermetallic compound with sulfuric acid solution was examined with processing factors such as sulfuric acid concentration, temperature and agitation intensity, The leaching of rare earth metals proceeded very rapidly, reaching completion in less than 1.8ks. On the other hand, the slow leaching of nickel was observed. The percent of nickel leached at 328K could only reach about 70%.

Jan 1, 2003

By Jaroslav Horskoý, Miroslav Raudenský, Bogdan Filipic, Božidar Sader

This paper describes main elements and practical use of the computational system for automated setting of optimized casting conditions in the continuous casting of steel. The system consists of the heat transfer model of the process, empirical metallurgical criteria, and optimization algorithm. The physical model of the, strand temperature distribution relies on the classical Bennon-Incropera mixture continuum formulation for the convective-diffusive heat transport. Fluid flow effects are considered through enhanced thermal conductivity of the liquid phase. The model is solved by the operator-splitting Crank-Nicolson finite volume version of the Voller-Swaminathan scheme. The solution procedure is coupled with the IDS solidification analysis package. Boundary conditions for the strand cooling rely on combination of the generic and plant-specific mold, spray, and roll heat transfer coefficients ' by coping the effects of the casting speed, casting temperature, casting powder, mold oscillation mode, steel grade, water or air-mist spray type, running water, trapped water on the rolls, and radiation. The caster safety and productivity and the quality of the strand are related to nine empirical metallurgical criteria. The criteria ensure the caster safety and economy as well limit the internal, longitudinal, and transversal surface cracking possibility. The problem of finding optimum casting parameter values is stated as a minimization problem based on the analytical form of the cooling criteria evaluated from the steady-state temperature distribution of the strand. To solve the optimization problem, a genetic algorithm is employed. The algorithm explores process parameters settings heuristically by applying the principles of biological evolution. It starts with a random set of solutions and iteratively improves them through selection and variation. Solutions are evaluated by running the heat transfer model of the process and extracting the values of the empirical metallurgical criteria.

Jan 1, 2000

Although anion exchange resins are widely used for gold recovery in Russia and the former CIS, accounting for almost 50 percent of gold recovery in that part of the world, the technology has not been adopted in the West, apart from one small operation in South Africa. This situation is likely to change as the gold industry heads into the twenty first century. With gold prices having declined steadily through the 1990's, mining companies are under great pressure to reduce costs and improve gold recovery. Most studies on the use of resins for gold recovery from cyanide solution or pulp have shown that this technology has the ability to achieve both these goals. Resins can also be used to recover and recycle free and complexed cyanide in gold plant tailings, which has the potential to significantly lower operating costs, and latest developments in this area of technology are discussed. Finally, recent studies on thiosulphate leaching of gold have'shown that this process is very well suited to the treatment of carbonaceous, preg-robbing ores from the Carlin trend (Nevada, USA), and elsewhere in the world, because the gold thiosulphate complex does not load on to carbon. Whilst this obviously benefits the leaching process, it means CIP and CIL are ineffective in this situation, and the use of ion-exchange resins for gold recovery from thiosulphate leach solution are discussed.

Jan 1, 1998

By John R. Goode

The fist part of this paper comprises a general discussion on refractory gold ores and their mineralogy. Processing methods now in use are reviewed and test procedures for the important methods are discussed. Factors determining the selection of a process are outlined. The paper includes a survey of production plants using pressure oxidation, roasting and biological oxidation to process refractory ore. The status of processes under development is briefly reviewed.

Jan 1, 1993

By M. J. Adam

The U.S. Bureau of Mines is investigating the partitioning of selected complex minerals into simple phases using sulfidation reactions. Successful partitioning of complex mineralogy to simple phases may afford an opportunity to improve selective extraction of mineral constituents of economic value. The research has shown that complex minerals, such as chalcopyrite (CuFeS2) and pentlandite [(Fe,Ni)9Se]' may be partitioned to the simpler phases covellite (CuS) plus pyrite (FeS2) and vaesite (NiS2) plus pyrite (FeS2), respectively. Demonstrations of these reactions were verified through long-react ion-time (24 h or more) experiments, but basic rate investigations and modeling were not included in the previous research. This report describes research aimed at determining the rate at which the complex mineral CuFeS2 converts to the simple sulfides CuS plus FeS2. Small samples of CuFeS2 were blended with elemental S prior to thermal treating under an He atmosphere for time periods up to 4 h. Products from each treatment period were characterized using metallography, chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results of the investigation revealed a rapid conversion of CuFeS2 to CuS plus FeS2 early in thermal treatment periods. As the reaction occurred, a CuS rimming of particles was observed which separated the reacting species (CuFeS2 and S) and caused a considerable decrease in transformation rate.

Jan 1, 1991

By H. Cui

Rapid technological development has caused an increase in the demand for rare earths. Ancylite, a strontium rare earth carbonate, is a potentially significant source of rare earths. In this research paper, essential aspects of the magnetic separation and flotation processes for Bear Lodge ore are presented. A flowsheet is proposed based on an optimization of the variables and flotation simulation. The economic feasibility of the proposed processing operation is analyzed.

By Christopher B. Vierrether

Reflected light microscopy, scanning electron microscopy, and electron microprobe analysis have been used to determine the mineralogy, phase percentages, grain sizes, textures, and partitioning of cobalt and nickel in two cobalt-nickel rich mattes. These mattes were prepared by submerged bath smelting from a flotation cobalt-nickel concentrate containing 4.8% cobalt and 5.1% nickel. The concentrate was derived from lead-zinc-copper ores of the Viburnum Trend, southeast Missouri. Eleven discrete phases have been distinguished in the matte samples, three of which contain significant cobalt and nickel. The phases are cobaltpentlandite ((Co,Ni,Fe)9S8), cobalt-bearing marmatite ((Co,Fe,Zn)S), shandite (Ni3Pb2S2), bornite (Cu5FeS4), galena (PbS), magnetite (Fe3O4), pyrrhotite ((Co,Ni,Cu,Fe)1_xS), chalcocite (Cu2S), CuPbS phase, metallic copper, and metallic silver. Cobaltpentlandite and cobalt-bearing marmatite- occur in coarse grains (50 µm) that would separate readily during grinding, but shandite contains small (5 - 10um), abundant inclusions of pyrrhotite and bornite.. Some mineralogical variations between the two matte samples were due to differing degrees of oxidation during smelting,

Jan 1, 1988

By E. V. Verhoef

The proposed EU directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment promotes the substitution of lead in consumer electronics to reduce emissions from lead in the end of life phase. In this paper, the consequences of substituting lead in solders is assessed using the Eco-lndicator-99 method for the examples. The base metal production system is considered as an interconnected network modeled dynamically in Simulink 4 and Matlab 6 (Mathworks Inc 2000), where the recovery and production of metal components of the assessed product partially overlap. This approach requires global modeling of metal production processes and mass balances and resulting allocation choices. It also reveals the susceptibility of LeA scores to different choices in the modeling and data availability and uncertainty. Besides the comparison between lead-free and lead-containing solders, other side effects are revealed. Lead is carrier material for the recycling and production of many co-elements in the interconnected production and recovery system. Substitution may have adverse effects such as temporary shortages of other connected metals that are often not considered in normal LeA assessments, thus leading to erroneous results. The suggested approach provides directions for including these external effects and for further assessment of the environmental effects of substituting lead. This paper shows that in order to assess the environmental aspects of metallurgy, dynamic modeling of the total system is required based on the fundamental thermodynamics in each metallurgical reactor, the basis of this dynamic model. With this the true environmental impact of metallurgy can be explained. In the case of lead free solder, it is shown that the mining of substitutes has a very much larger impact.

Jan 1, 2003