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By K. Fagerlund

Methods for simulation of settler reactions, matte-slag separation and matte settling in copper flash smelting have been examined. The reaction, separation and settling phenomena of slightly oxidized chalcopyrite samples and cuprous sulfide-magnetite mixtures in fayalite type slags were examined at about 1300°C under inert atmosphere. Two methods based on introduction of molten samples of oxidized chalcopyrite concentrates or synthetic matte-magnetite mixtures onto the surface of molten iron silicate slag were tested. In the first method the samples were water quenched and polished specimens were studied and analysed using light optical microscope, scanning electron microscope, energy dispersive spectrometer. In the second method processes taking place after the introduction of samples onto the slag are followed "in situ" using X-ray transmission image monitoring. Great differences were observed in separation and settling behaviour of low and high grade copper mattes produced as a results of interaction of initial samples and slag.

Jan 1, 1997

By K. Ohmori, K. Takeya, S. Yoshizawa, A. Kawamoto, T. Ishikawa

"High performance Sm2Fe17N3 magnet powder is developed nitriding Sm2Fe17 alloy that 'is made using a reduction and diffusion method. Typical remanence, coercivity and maximum energy product of the fine powder are 1.40 T, 1.13 T and 323 kJ/m3, respectively. Decreasing samarium content, oxygen content and the amount of a-Fe are found to be the important factors to realize high-energy product.High performance injection molded Sm2Fe17N3 anisotropic magnet is also developed using the powder and an original binder system developed in order to mold at low temperature. Typical remanence, coercivity and maximum energy product obtained are 0.77 T, 0.78 T and 103 kJ/m3, respectively in the density of 4.77 Mg/m3The temperature coefficient of remanence is -0.07 %/K and that of coercivity is -0.54.%/K. The initial irreversible flux loss of the magnet that has a permeance of two is -5 % at 100 °C and the irreversible .flux loss of it is -4.4 % exposing it at 80 °C for 1000h.IntroductionSm2Fe17N3 alloy powder is expected to be very useful for a bonded magnet. The reasons are as follows. The magnetization is as large as the Nd2Fe14B alloy. Curie temperature is even higher than the alloy. The uni-axial anisotropy is comparatively higher than the alloy. Consequently it is possible to obtain high coercivity after just milling the powder and therefore possible to obtain high-energy product in a bonded magnet as it is realized in the SmCo5 bonded magnet. On the other hand, sintering is difficult because it will be decomposed into samarium nitride and a-Fe when heating it up to 500°C:"

Jan 1, 2000

By Gang Qi

The solubility of nitrogen in pure molybdenum was measured over the temperature range 2173 to 2473 K and up to one atmosphere (101 kPa) of nitrogen gas pressure. Both thermochemical and kinetic aspects of this phenomenon were considered in this study. The solution of nitrogen in molybdenum may be expressed by the reaction 1/2N2(g) = {N} (Mo,s), for which the standard Gibbs energy is given by the expression {A}G° = 78,500 + 27.36T Joules/g atom N. The formation of molybdenum nitrides, specifically Mo2N, was considered. Attention was also focused on the mechanism of nitrogen solution in molybdenum. Estimates of the diffusivity of nitrogen atoms in solid molybdenum were derived from the kinetic data.

Jan 1, 1991

By Jason H. Nadler, Jason A. Kulpe, Stephanie J. Lin

"A numerical method has been developed to predict the microstructural characteristics of reticulated metal foam. The porosity of this foam is derived from sacrificial template particles of known particle size distribution, which are incorporated with other precursor components. In this approach, a porous structure is numerically generated starting with Powell's sphere packing algorithm. The resulting stochastic structure has characteristics similar to those of corresponding metal foam. Deterministic inter-sphere connections are calculated to more accurately model the pore morphology that evolves during thermochemical synthesis. Estimations of pore morphology and specific surface area of the simulated material are compared to lab-synthesized materials composed of equivalent constituent compositions. In addition, the effect of template particle size, inter-sphere connections, and the geometric constraints on pore morphology and permeability are investigated to refine microstructural evolution and design.IntroductionReticulated foams, characterized by their interconnected pore network, can be obtained by incorporating spherical sacrificial template particles into precursor materials followed by template removal processes. The resulting structure is composed of contiguous spherical pores whose morphologies reflect those of the original templates. Based on some of the unique features of this synthesis approach, a methodology is introduced in this work whereby these foams are digitally constructed using experimental data from the template particle sizes and precursor formulation. Digitally constructed porous structures can then be compared to their laboratory synthesized counterparts through the quantification of structural features such as porosity and surface area per unit volume, which in tum are used to inform the foam's fluid transport propertiesThe spherical template particle packing algorithm developed here is adopted from Powell's work [1], which also includes approaches to obtain percolation and density in random packings [2]. Gervois gives a mathematical development for the stereological sectioning of packed hard spheres [3]. Stereological sectioning facilitates determination of relevant three dimensional morphological properties from two-dimensional data [4]. Studies on the sphere distribution size and the related particle packing density and coordination number results are studied in [5, 6]. Lastly, Kato describes a sintered neck structure, which is used with these packings [7]. This neck structure, as a model of the particle shape following heat treatment, is implemented here in a similar manner. A strong difference between the available literature and the methodology here is that spheres are packed to ultimately represent porous space, not rigid solid space."

Jan 1, 2011

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (M-f'), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By Kathryn C. Sole

A novel solvent-extraction process for the refining of gold was recently commercialised, with the commissioning in May 1997 of a 24 t a-' refinery at Harmony Gold Mine in Virginia, South Africa. The MinataurTM Process (Mintek Alternative Technology for Au Refining) uses solvent-extraction technology to produce gold of 99.99% purity from the cathode sludge arising from a conventional carbon-in-pulp / electrowinning circuit. Implementation of this process introduces significant cost benefits compared with the conventional dore smelting / toll-refining route previously followed. This paper outlines the process, presents selected operating results obtained during the first few months of operation, and provides some details of the associated techno-economic advantages.

Jan 1, 1998

By W. K. Collins

Engineered Scavenger Compounds (ESCs), developed by the U.S. Bureau of Mines, are a novel class of compounds that can selectively recover a desired element from a solid or molten alloy. Lithium titanate (Li2Ti3O7 or L'20-3T'02) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (Al-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both are metastable, the hexagonal phase that forms during the scavenging of Li from Al-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electrodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li2Ti3O7 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1993

By Kimio Itagaki, Makoto Ohtsuka, Kouki Chiba, Minoru Matsumoto

"The properties of Ni-Mn-Ga films such as chemical composition, crystal structure, microstructure and transformation temperature were investigated with respect to sputtering conditions in the present study. The Ni-Mn-Ga films were deposited on a polyvinyl alcohol substrate with a radio-frequency magnetron sputtering apparatus using the NisoMn2sGa2s and Nis2Mn:«1Ga24 targets. After separating from the substrates, the films were annealed at the temperature between 873 and 1273 K for 3.6 ks. The chemical composition of the films depended on the radiofrequency generating power, however, there was no dependence on the heat treatment temperature. Each deposited film had a columnar grain structure. After heat treatment, the width of columnar grains widened and then became indistinct with increasing heat treatment temperature. The Heusler type cubic crystal structure of the fi4n with heat treatment at 1073 K changed to the tetragonal one through the martensitic structural transformation during cooling. The martensitic structural transformation temperature increased with increasing nickel content of films, while the Curie temperature decreased. The film obtained at 200 W using the Nis2Mn24Ga24 target after heat treatment at 1073 K showed one-way shape memory effect through the reverse martensitic structural transformation during heating.IntroductionThe ternary intermetallic compound NiiMnGa has a Heusler-type crystal structure and is an intelligent material, which has a shape memory effect and a ferromagnetic property. The martensitic structural transformation occurs within the ferromagnetic temperature region. The cubic crystal structure of L21 at high temperature changes to a tetragonal one through the martehsitic structural transformation during cooling. The films of this compound can be applied for an actuator of micro-machines."

Jan 1, 2000

By W. Kasprzak

Modern light metals processing technologies are very complex and involve a diverse set of variables that must be quantitatively evaluated. The most effective way to design new casting processes that deliver specified metallurgical and mechanical properties is to develop a method of simulating the "real-time" process within a test sample of sufficient size. The results can then be analyzed and the required optimizations can be performed. This paper presents a novel method of simulating the industrial casting processes in a laboratory environment using an experimental apparatus based on the principle of high frequency induction heating. The applicability and accuracy of the proposed analytical method is demonstrated, for example, by simulation of the solidification and heat treatment of a test sample composed of two dissimilar materials. The simulation can be used to develop a stress model for an engine block made from an aluminum based alloy with iron cylinder liner inserts.

Jan 1, 2002

By Norihiro Murayama

Syntheses of zeolitic materials were carried out from coal fly ash by alkali hydrothermal treatment as part of the reuse and recycle technologies of coal ash, For the obtained zeolites, the cation exchange capacity and acid resistance, which are very important in the practical use of cation exchanger in aqueous solution, are investigated during this stufY, The cation exchange amounts of the NaP, CaP and K-CHA zeolites are measured for various cations such as K+, Na +, NH4+ Ca2+, Mg2+, Pb2+, Cd2+ and so on. The change in crystallization degree are researched as a function of pH. The simultaneous removal ability of NH4+ and PO43- in solution is examined for an example of the water purification with CaP zeolite. From these results, the characteristic and its mechanism of cation exchange are clarified for the various zeolitic materials obtained from coal fly ash.

Jan 1, 2003

By den Bulck A. Van

In Europe, 50% of the copper originates from recycling. High-Cu containing scraps are regularly rich in impurities like Fe, Ni, Sn and Pb. Many high-Cu containing scraps are fed directly into anode-furnace casting installations or furnaces with limited refining capability. The impurities levels of the anodes produced in these processes should however remain acceptable for further electro-refining. The distribution of Sn between copper and slag has been investigated for conditions relevant to copper converting. Unlike previous studies, this work focuses on the behavior of Sn relevant to fire refining conditions, which are essential for anode refineries.In this study, liquid Cu–1Sn and CuOx–FeOy–SiO2 slag, with CaO additions, were equilibrated at 1300 °C in vacuum sealed SiO2 ampoules. After metal–slag equilibration, the samples were quenched in water. The composition of the slag and Cu metal was investigated with Electron Probe X-ray Microanalysis. The distribution coefficients of Sn between slag and Cu metal were determined as a function of slag composition.

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (Mf'), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By W. D. Riley

Engineered Scavenger Compounds (ESCs), developed by the U. S. Bureau of Mines I are a novel class of compounds that can selectively recover a desired element from 'a solid or molten alloy. Lithium titanate (Li2Tip7 or Li20' 3TiO.) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (AI-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both of the structures are metastable, the hexagonal phase that forms during the scavenging of Li from AI-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electtodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li.Til07 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1991

By Signe Kjelstrup, Leiv Kolbeinsen, Marit Takla, Odne Burheim

"This paper presents a Seebeck-type solid state thermoelectric power generator unit, designed to investigate the possible recovery of radiant waste heat at a silicon plant in Norway where roughly 703 of the total input energy leaves the process as waste heat. The unit is 0.5 m x 0.5 m and is built of 36 commercially available thermoelectric devices based on bismuth telluride p - and n - type semiconductors. Thermoelectric devices directly convert fractions of a heat flux into an electric current (and vice versa) and may therefore be convenient for recovery of waste heat when the heat source is discontinuously available. The purpose of the thermoelectric unit is to give a proof of principle of direct thermoelectric energy conversion on a large scale. We present the initial test results for the generator. At an average temperature difference between the heat reservoir and the heat sink of 98°C, we measured an open ciruit potential of 23.44 ± 0.06 V and the matched load power output was 39.4 W. At a temperature difference of 220°C, we predict the generator open circuit potential to be 40.8 V, which corresponds to an efficient Seebeck coefficient of 242 µV /K, and matched load power output to be 120 W.IntroductionThe world's power demand increases, driven by population growth and increase in living standards and simultaneously global warming is recognized as one of our most serious environmental problems. According to the International Energy Agency[l], the industrial sector accounted for approximately one third of the total global power consumption in 2005. Increasing the energy efficiency of industrial processes thus represents a benign and substantial route for addressing environmental concerns and energy security.In accordance with the second law of thermodynamics, all real processes are associated with lost work which is energy being dissipated as heat to the surroundings[2]. Improving the energy efficiency of industrial processes is about finding the process path associated with a minimum of lost work. The more evenly the losses are distributed, the smaller are the losses [3, 4]. In addition, exploiting the unavoidable waste heat will contribute to improve the energy efficiency. The waste heat may be utilized for heating purposes and/or it can be upgraded to work for instance via some sort of heat engine."

Jan 1, 2012

By Takahiko Okura

Most non-ferrous raw materials are associated with sulphur. To extract the metals, the sulphur is recovered typically as sulphuric acid or liquid SOz, On the other hand, natural gas may contain over 20% of hydrogen sulphide (HzS) and a huge quantity of elemental sulphur is produced through oil and gas refining processes in the world. A large fraction of the sulphur mined from natural sources is eventually returned to the earth as fertilizers, by-products of desulphurisation and neutralisation processes, or as fugitives to the atmosphere. However, the supply and demand for sulphur are in imbalance. Such situation urges to develop a new smelting process without sulphuric acid production. This paper briefly reviews the global sulphur balance and the technologies for recovering elemental sulphur. The core of this paper is a proposal to convert SO2 gas to elemental sulphur by using organic materials. Some results of thermodynamic calculations and experiments are presented.

Jan 1, 2003

By H. Y. Sohn, M. Y. Mohassab-Ahmed

"As part of research to develop a novel flash ironmaking process using reduction of iron ore concentrate by natural gas or hydrogen, sulfur and phosphorus distribution ratios between MgOsaturated slag and iron were determined in the temperature range 1550-1650°C under three different gas atmospheres: H2/H2O, H2/H2O/CO/CO2, and CO/CO2. The distribution coefficients of sulfur (Ls) were 4.0, 2.0, and 0.8, respectively, under these atmospheres. The distribution coefficients of phosphorus (Lp) were, respectively, 8, 17, and 20 under these atmospheres. In the flash process over -25 wt% P and S volatilize during ore concentrate downward flight in the reactor shaft in addition to avoiding coke. Therefore, iron produced by the flash ironmaking process would have much lower sulfur contents than the typical hot metal produced by the BF.IntroductionGiven the issues related to large carbon dioxide emissions and energy consumption in the existing ironmaking technologies, a novel flash ironmaking technology was conceived by Sohn [1-3] at the University of Utah. This technology is the first ironmaking process that will convert iron ore concentrate directly to metallic iron in-flight. This process will produce iron directly from concentrate without requiring pelletization or sintering and avoid the need for coke. In addition, this process concept takes full advantage of the fine particle size of concentrate with a large surface area, which permits rapid reduction by a gas. In this novel ironmaking process, potential reductants and fuels are H2, natural gas, and coal gas. Therefore, an iron-slag bath is expected to be at equilibrium with gas atmospheres of mainly H2/H2O or CO/CO2/H2/H2O, respectively, corresponding to the use of H2 or natural gas/coal gas. Since the effects of an H2O- containing atmosphere on slag properties have not been studied before, it is critical for the development of the novel flash process to determine these effects. In H2-H2O-CO-CO2 gas mixtures under ironmaking conditions, H20 was found to have the most pronounced effect on the slag chemistry [ 4, 5]. In addition, it was found in this laboratory that water in the gas atmosphere affected the distribution of Mn between slag and molten iron [6]. Most previous work used CO/CO2 gas mixture to control oxygen partial pressure (p02) [7, 8]. Others used only inert atmospheres [9], although Kor and Richardson [10] used a mixture of C02/H2 to control p02. For phosphorus, previous research focused on Ar [11], Ar-CO mixture [12], CO [13], CO/CO2 [14] or N2/CO [15]. Therefore, it was necessary to investigate the effect of water vapor content in H2-H2O-CO-CO2 mixtures on the equilibrium distribution of sulfur and phosphorus between CaO-MgOsatSiO2-Al2O3-FeO- MnO (0.2-0.8 wt%)-P2O5 (0.1-0.9 wt%) slag and molten iron as part of the development of the novel flash ironmaking technology."

Jan 1, 2014

By Steven R. Pittman, Colin McCullough, Peter Galuska

"Traditionally Continuous Fiber Aluminum Matrix Composites have been fabricated using high strength fibers and high strength matrices, often commercial alloys, with the goal of producing high strength composites. However the specific role of the choice of matrix alloy on composite properties has not been well established. One way to control composite tensile strength is to use coatings to introduce a low strength interface between fiber and matrix which tends to reduce the importance of the matrix selection, but unfortunately renders the transverse strength unacceptably low. Thus using a system with strong bonding between fiber and matrix is desirable, such as an alumina fiber / aluminum alloy matrix system. In this case the transverse strength is a strong function of the matrix strength. However the longitudinal strength then depends largely on the characteristics of the matrix. The important role of the matrix is discussed using examples of alumina fibers in various aluminum alloy matrices. The key attributes are matrix constituent phases, alloy chemistry, alloy reactivity with the fiber, and matrix strength. From the understanding developed in these systems a set of design rules may be established for selecting an optimum matrix. IntroductionAluminum matrix composites (AMC's) reinforced with continuous fibers offer very attractive property gains over AI alloys, such as strength, stiffness, and fatigue resistance. These gains are magnified when specific mechanical properties are compared which make them attractive candidates for replacing steel, nickel, titanium and aluminum alloy parts in weight critical applications (1). Many systems have been tried in the past; B/AI, C/AI, SiC/AI, Si-Ti-C-O/AI and AI203/AI. Technically B/AI was a very good system but was expensive in regard to both fiber cost and fabrication and SiC/AI and C/AI systems are still plagued with reactivity problems. The Si-Ti-C-O/AI appears to be a good strength system but with lower stiffness. Until recently, the AI203/AI was a low strength system, in part due to a lack of a high strength fiber. Recently 3M introduced a high strength AI203 fiber - Nextel™ 610, which leads to high strength composites (1,2) and may also be both low cost and also compatible with less expensive casting approaches for fabrication."

Jan 1, 1996

By Adrian C. Deneys, David G. C. Robertson

"Fluid flow phenomena on the surface of a molten slag have been documented using video photography in a laboratory scale D.C. arc furnace. The flow on the surface of the slag appeared to be electromagnetically influenced. This was confirmed by varying the position of the anode, which changed the direction of flow on the surface of the slag. Temperature measurements in the bath also confirmed the change in the directional nature of the fluid flow induced by the arc.During some periods, solids were fed into the arc attachment zone (AAZ) down the center of the hollow graphite electrode. Significant movement of the arc around the basal annular surface of the hollow electrode takes place. The point of attachment of an arc on a hollow electrode was more variable than an arc attached to a solid graphite electrode. Video images showed that the solids were rapidly incorporated into the bulk of the slag. Temperature measurements confirmed the existence of a superheated slag layer at the slag-gas interface, which allowed the solids to be rapidly incorporated into the melt.This work has been conducted to study fluid flow, temperatures, and solid behavior during feeding, in the arc attachment zone of a D.C. arc furnace. The work also has relevance to optimizing furnace design for pyrometallurgical slag cleaning processes."

Jan 1, 1999

By A. E. Isaacson

Bureau of Mines researchers developed and tested equipment to measure corrosion rates on a commercial-scale mill as an aid in predicting the effect of corrosion on minerals and how this effect relates to downstream processing. Bench-scale experiments were designed for duplicating ore grinding conditions closely enough that realistic rate determinations can be made in laboratory tests. Rates measured in a laboratory system compared favorably with those measured in the field. Cast steel was found to have corrosion rates in a copper mill and laboratory test cell of 22 and 21 mpy, respectively. Corrosion was found to account for less than 5% of the total grinding media wear in the operations studied.

Jan 1, 1987

By C. Mattich, A. L. Beyzavi

The Waelz Plant at Taiwan Steel Union Co. Ltd. (TSU) was erected within nine months from September 1, 1998 to May 15, 1999. The nominal capacity of the plant is 50,000 tonnes per year of electric are furnace dust (EAFD). The plant, consisting of material handling, a waelz kiln, a waste gas cleaning system, waelz oxide leaching and waste water treatment, was commissioned within three months from July 1, 1999 until October 12, 1999. The specific problem of the plant is the high chlorine content in the EAFD pellets which is up to 6 %. Lurgi Metallurgie GmbH, Frankfurt, Germany was responsible for the engineering erection and commissioning of the plant.

Jan 1, 2000