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By D. P. Cook, Jr. Jones, J. W. Evans

"It is well understood that the flow of liquid metal in the mold region of the caster can have a notable effect on the overall solidification behavior in aluminum casting. Previously our group has characterized the flow in this region in a water model, using particle imaging velocimetry. The flow is significantly effected by the specifics of the metal delivery system, i.e. size, geometry, used during the cast. Recently, a time-averaged 3D numerical model of the nozzle, combo bag and sump region has been developed and its validity has been tested against experimental data. Cases were run for different sized combo bags as well as bags that have been blocked. The results show satisfactory agreement between the physical and mathematical models.IntroductionFluid flow in the head of an electromagnetic (EM) and direct chill (DC) ingots has been shown to effect many important operational parameters in casting such as superheat removal, macrosegregation, and hot cracking. In most cases, the momentum from the nozzle is diverted through a delivery system, termed a bag, before entering the mold region. The specific geometries of the bags vary widely from operator to operator suggesting that there is still some question as to the optimum design. Several studies [1-4] have been carried out to understand the influence of the bag design on the solidification behavior in aluminum casters. However, few studies have included numerical prediction with experimental verification. Unfortunately, many simulations performed today still do not accurately account for flow in such devices.Recently, a significant amount of research into the flow resulting from the metal delivery systems has been performed [5-8]. The thrust of this research has been characterizing the flow patterns by a measurement technique called particle imaging velocimetry. The data suggest that the method of delivering the liquid metal into the mold region has a significant effect on the nature of the flow. With a detailed set of quantitative data from a water model, a numerical model can be built and tested to ensure a proper description of the flow field. The computational model used in these simulations is designed to represent a laboratory scale model of a caster in which ""combo"" bags were simulated. Such bags are mostly of a densely woven glass fiber material with low permeability to aluminum. ""Windows"", of a more open weave, permit aluminum to flow from the bag, see Fig. I. Two different sized combo bags were modeled, each subject to two different outflow window configurations. Furthermore, experimental measurements [9] were used to validate the model results."

Jan 1, 1999

By Gerardo Muñoz

All along this century CODELCO's smelters have been operating on conventional technology, which Codelco has streamlined by using oxygen, developing oxy-fuel burners for reverberatory furnaces and introducing oxygen smelting of concentrates in converters (Teniente Converters). Chuquicamata began capturing sulfur from its first Teniente Converter in 1985. Since then, it has implemented a program allowing to gradually increase such capture. In 1994 a Frame Law on the Environment was enacted in Chile. By virtue thereof and of CODELCO's corporate environmental policy, an investment program aimed at capturing more than 95% of gaseous pollutants in all its smelters in a term not exceeding twelve years was established. The above entails a substantial improvement of the operational management as regards fugitive gases capture and treatment. This paper describes the way CODELCO is to deal with this challenge with a view to fully complying with environmental regulations and obtaining the required environmental certifications of its operations.

Jan 1, 1996

By E. S. Geskin

New material processing tools should be developed and reduced to the practice in order to meet the challenges facing the contemporary material production industry, One of such potentially important tools is supersonic liquid projectiles. It was shown that at the speed of 1500-1750 m/s the water projectile are able to demolish reinforced concrete plates, forge, to pierce and weld metals, to destroy with no explosion non dischargeable mines, etc. These projectiles are generated by simple, low cost launchers run. It is obvious that these projectiles can be applied to the ore mining and comminution. Thermodynamic considerations show feasibility of the use of these projectiles also for smelting, refining and forming. The presented paper discusses the results of the experimental study of supersonic liquid projectiles as well their potential metallurgical applications.

Jan 1, 2006

By D. E. Woolley

The rate of reduction of iron oxide from calcia-silica-alumina slag by carbon in liquid iron has been measured over the temperature range 1400-1600°C by monitoring the rate of carbon monoxide (CO) evolution. Slags containing ferric iron have been used in order to study the reduction of both ferric and ferrous cations. Results show that ferric iron is reduced before ferrous iron, so that the ferrous iron concentration increases initially. It is also shown that the rate constant, k, decreases at low reaction rates, or, equivalently, at low concentrations. The authors conclude that the reaction occurs in two periods. During the first period, ferric iron is reduced to ferrous iron. During the second period, ferrous iron is reduced to metallic iron, and the rate-limiting step during the second period is the mass transfer of ferrous cations in the slag phase to the slag-metal interface.

Jan 1, 1998

By Shunsuke Yagi

A surface alloying technique was investigated using alternating pulsed electrolysis in an aqueous solution containing a single metal component for the formation of an Fe-Cr layer on an iron substrate. In the process, the iron substrate was dissolved during each anodic polarization of the pulsed electrolysis, providing iron ions in the vicinity of the substrate, while the Fe-Cr alloy was electrodeposited during subsequent cathodic polarizations. A bright, flat, and crack-free Fe-Cr layer with a composition gradient was obtained using a solution containing a trivalent chromium component and a complex forming agent together with some supporting or buffering salts.

Jan 1, 2006

By J. Sjöblom

New copper and nickel processes, flash converting and DON, direct high-grade nickel matte smelting, have been developed in order to replace the conventional and not so environmentally friendly PS-converting process. With a laboratory scale laminar-flow furnace the combustion reactions of sulfidic feed particles can be investigated under simulated flash smelting conditions. In the present study, finely ground and screened feed fractions of a copper matte and a nickel matte were flash oxidized in a laminar-flow furnace. The experiments were carried out using 20, 21 vol% and 75 vol% O2 in nitrogen, at temperatures 1100 and 1300 °C and reaction zone length of 7.5-16 cm. The samples were quenched in a water film after a specified reaction time. The matte particle reactions were stopped after short residence time intervals in order to obtain a better understanding of the reaction mechanisms. Chemical analysis was used to determine oxidation degree, and optical and scanning electron microscope combined with energy dispersive analysis was used for characterization of the reacted particles. On the basis of the experimental results the reactivity of the mattes is discussed and possible reaction and dust formation mechanisms are considered.

Jan 1, 1999

By Andre Thess, Oleg Zikanov

"Direct numerical simulation methods are applied to study the influence of a constant magnetic field on turbulent flows of liquid metals. The flow is assumed to be homogeneous and the problem is reduced to the classical case of the turbulent flow in a 3D box with periodic boundary conditions. The main subject of the study is the anisotropy developing in a liquid metal flow affected by constant magnetic field.To investigate the long-time evolution of initially isotropic flow the large-scale forcing is applied to maintain the flow energy at a statistically steady level. It is found that the flow evolution depend strongly on the magnetic interaction parameter (Stuart number). In the case of small Stuart number, the flow remains three-dimensional, turbulent, an approximately isotropic. At large Stuart number (strong magnetic field) the turbulence is suppressed rapidly and the flow becomes two-dimensional and laminar. Very interesting is the intermittent flow evolution at moderate Stuart number. Long periods of almost two-dimensional, laminar behavior are interrupted by strong turbulent three-dimensional bursts.The influence of a constant magnetic field on scalar transport properties of liquid metal turbulence is investigated using the simplified formulation of homogeneous flow driven by an imposed mean temperature gradient. Such a flow consists primarily of two turbulent antiparallel jets providing an effective mechanism for heat transfer. It is shown that the magnetic field parallel to the mean temperature gradient stabilizes the jets and, thus, enhances heat transfer considerably."

Jan 1, 1999

By Robert W. Bartlett, Keith A. Prisbrey

"Natural biooxidation of shallow, refractory ore heaps, relying on gaseous oxygen diffusion from the heap surface is attractive because of its simplicity and potential low cost, especially without using a lined pad, which is possible if percolation of leachate through the heap is avoided. In this case, the excess oxidation enthalpy must be removed by water evaporation from within the wet ore heap, and the rising water vapor flux within it will impede the downward oxygen flux. An analysis of this process shows that for typical values of pyrite grades and limited temperature increases in the ore heap, the oxidation rate and penetration into the heap is reduced to values between about 30 percent and 50 percent of those obtained when leachate percolation occurs and water evaporation is not a significant mechanism of heat removal.IntroductionHeap biooxidation of refractory gold ores, needed as a pretreatment step to liberate the gold for subsequent extraction by leaching, requires large amounts of oxygen for the normal amounts of sulfide minerals that are typically present, one to two percent pyrite and/or arsenopyrite.The importance and potential limitations of oxygen transport into commercial ore heaps, which are much larger than encountered with column tests of ore and with pilot heaps, has been recognized111 • Commercial ore heaps using radial stacking conveyors are typically about nine meters high and may be 100 meters or more in lateral dimension. Three oxygen transport mechanisms have been identified and analyzed: ( 1) natural convection, which arises from an increase in buoyancy caused by the temperature rise and gas composition changes associated with the exothermic oxidation of the sulfide minerals within the ore heap, (2) forced air ventilation, using low pressure fans and air distribution pipes within the heap, and (3) diffusion of oxygen in the gas-filled void spaces within the ore heap driven by the oxygen concentration gradient from the surface of the heap to the mineral oxidation loci within it."

Jan 1, 1997

By Fernando Guevara

Many smelting and slag-cleaning furnaces operate with cooling systems designed to freeze a slag layer over the refractory to protect it. The fluid flow and heat transfer conditions associated with the freeze layer and mushy zones are poorly understood. These phenomena were simulated with a small-scale room temperature, 2-dimensional model, using an aqueous solution of calcium chloride to simulate the slag. Reasonable similarity with conditions encountered with copper and nickel smelting systems was achieved (Pr 50 and Ra 108, in the laminar-turbulent transition). Measurements of the freeze layer development and velocities were made with the Particle Image Velocimetry (PIV) technique. Direct Numerical Simulations (DNS) were also made of the unsteady fluid flow and heat transfer problem. It was found that the solidification process is well described using an improved model for high molecular viscosity in the mushy zone. Solid front growth, isothermal profiles, velocity profiles and heat transfer through the walls showed good agreement between the PIV and DNS results. Experimental and numerical velocity profiles close to the freeze layer show a parabolic behaviour in the vertical velocity profile which is completely different from the calculation of heat transfer using a sharp interface model. The reason for this is attributed to the effects of the mushy zone with a high viscosity and high shear stresses acting on that area.

Jan 1, 2006

By Matthew Jeffrey

Leaching, cementation, electroplating and flotation are all electrochemical phenomenon. They are also key processes in the hydrometallurgical treatment of metals. Unfortunately electrochemical methods tend to be under-utilized when studying these processes and one possible reason for this is the confusion surrounding the large number of electrochemical techniques available. In this paper four former PhD students of Professor Ian Ritchie present an insight into how one electrochemical technique can be used to compliment rate/kinetic studies. The paper details how to perform the experiments, interpret data, and recognize complications with the results. Examples where this approach has been highly successful are presented, and include: cementation of zinc by aluminium, cementation of copper by nickel, cyanide leaching of gold and the cementation of gold thiourea by mild steel. The examples illustrate that this universal approach adopted by Ian Ritchie provides the key to understanding the mechanism of many hydrometallurgical reactions.

Jan 1, 2003

By Dean G. Heitt

"The Rain and SMZ mines from 1987 to 1994 produced a total of22.0 t of gold from a pre-mine reserve of 14.24 Mt of ore grading 2.13 g/t Au.Gold at Rain is hosted within the basal portion of the Mississippian Webb Formation. ·Mineralization is closely tied to the Rain Fault which is interpreted to be the main feeder for the deposit. Multiple collapse and hydrothermal breccia events provided permeability for the mineralizing fluids in the otherwise unreactive siltstones. Major alteration events include: decalcification and dolomitization of the Devils Gate Limestone; and silicification, baritization, argillization and oxidation of the Webb Fm. Six ore types based on XRD and visual rock chip Jogging have been identified: siliceous ore containing >40% quartz and <30% barite; siliceous-baritic ore containing mostly silica but >30% barite; baritic ore containing >40% barite; argillaceous ore containing >40% total clays (including alunite); calcareous ore containing mostly calcite and dolomite; and carbonaceous ore which has significant pyrite and organic carbon. Metallurgical testing of the oxide leach grade ores found that recoveries, on -1.3 cm crushed material, were greater than 70%. Results also found that Rain ore has strong grind dependency due to silica encapsulation.The Rain leach pad was commissioned in 1988, and to date 9.3·Mt at an average grade of0.65 g/t Au have been placed. Life to date recovery, through December 1995, is approximately 51 %, for a total of3.87 t of gold produced. Two major factors have contributed to the low leach recoveries at Rain when compared with the metallurgical testing: 1) More argillaceous ore than expected was placed on the pad especially late in the mine life and 2) approximately 50% of the tons placed were run-of-mine with no agglomeration."

Jan 1, 1997

By Norihiko Fukatsu

In order to use effectively the previously reported new sensing system for hydrogen and oxygen potentials in molten copper, the criteria of the potentials for getting sound castings have been determined in the laboratory experiment. The copper melt equilibrated with a given hydrogen and an oxygen potential was rapidly quenched in the crucible. The relations between the holding potentials and the gas porosity in the solidified sample were investigated by measuring the density of the sample and microscopic observations. It was found that the defects of the gas porosity became the maximum at the potentials where the dissolved amount of hydrogen and oxygen was in the mole ratio 2: I. The samples having the density more than 99% of the theoretical value were obtained in the higher oxygen and lower hydrogen potential region or in the lower oxygen and higher hydrogen potential region. The criteria thus determined were examined by comparing with the measured potentials in the practical easting machine. In tough-pitch copper casting, the problem due to gas porosity was found to be serious when the hydrogen potential increased. In the oxygen-free copper casting, the evolution of hydrogen was found not avoided. The gas porosity in the casting, however, was found eliminated when the oxygen potential was kept at a low value.

Jan 1, 2003

By Y. Ikeda

Typical electric appliances were dismantled into component pieces to study the recyclability of these discarded goods. Types and weight ratios of these component materials were investigated and characterized. The results showed that if they are dismantled properly, these goods could be classified into several groups of similar materials and/or structures, namely those consisting of single materials, metal-plastic combinations, metal-metal combinations and complex combinations of many different materials. By separating each combination into recyclable materials and isolating hazardous materials, it was found that the final waste for disposal could be reduced and the recycling efficiency could be improved markedly as compared to the conventional shredding method. The metal-metal combinations account for 60% by weight of the total metal contents in electric appliances, and therefore, it becomes important to segregate these metals. For the complex combinations, a process consisting of pyrolytic decomposition of plastic contaminants followed by smelting of the residue is proposed. It is anticipated that nearly zero-emission recycling of electric appliances will be achieved by applying this treatment process.

Jan 1, 1995

By Kenneth G. Thomas

This paper reviews the alkaline and acid gold autoclaving experiences gained at Barrick Gold Corporation. Alkaline autoclaving was operational at Barrick Mercur, Utah, U.S.A., on carbonaceous/sulphide refractory ore for eight years commencing in 1988. Acid autoclaves have been operational at Barrick Goldstrike, Nevada, U.S.A., on sulphide refractory ore since 1990 and now process 17,500 stpd of ore through six large autoclaves. Information is presented on operating costs, materials of construction, reagent requirements and flow sheet developments that reduced capital and operating costs.

Jan 1, 2000

By Noboru Masuko, Sachiko Ono

"The structure and composition of anodic films formed on aluminum in a borate solution have been investigated by using TEM and SIMS with respect to the effect of current density and electrolyte temperature. The film is composed of a boron-containing outer layer and a boron-free inner layer with disc-like crystals present at the interface. The thickness of the film formed at constant current density up to an identical voltage, decreases with increasing current density. The thickness increases remarkably with elevated temperature. The transport number of Al3+ estimated from the thickness ratio .of the cuter to the inner layers is 0.4 when the film is formed at the current density of 20 Am-2 at 60°C. It increases slightly with increasing current density and decreases significantly with increasing temperature. Content of boron in the outer layer increases 1.5 times when current density .increases 10 times. These changes in film structure and composition with electrolysis conditions must have a significant role in the determination of electric properties of anodic alumina films as a capacitor material.IntroductionThe growth of anodic alumina film in ·a neutral electrolyte proceeds at both film/electrolyte and film/substrate interfaces giving a duplex structure. The oxide layer formed at the former interface includes electrolyte anions while a-pure alumina layer is formed at the latter interface. The thickness ratios of each layer respectively represent transport numbers of Al3+ and 0 2 - (1). The film thickness and the incorporated anion content as well as transport numbers of both ions must affect the dielectric properties of the film as a capacitor material. However, the correlation between film structure and electrolytic conditions is not fully understood (2). For the further clarification of anodic film growth mechanism, more detailed characterization of anodic films in relation to electrolytic conditions is advantageous. In the present paper, therefore, the effect of current density and electrolyte temperature on the microstructure and composition of anodic barrier films formed in a neutral borate solution was studied. The films were characterized by direct observation using transmission electron microscopy (TEM) and depth profiles of constituent elements obtained by secondary ion mass spectroscopy (SIMS)."

Jan 1, 2000

By Jorge Alberto Soares Tenório, Amilton Barbosa Botelho Jr, Denise Crocce Romano Espinosa, Mónica M. Jiménez Correa

Wastewater from nickel lateritic process still has valuable metals that could be recovered. Using an ion exchange to recovery these metals, the iron becomes a problem due to the fact that it precipitate at pH 2. The aim of this research was to make iron soluble by reducing Fe+3 to Fe+2. A synthetic solution was prepared with sulfate ferric. The reducing agent sodium dithionite was used and the potential was varied (initial potential: 700, 600, 500, 450 e 400 mV) using as a reference the Pourbaix diagram for iron created by HydroMedusa software. The pH was ranged between 0.5 and 2.5, the reducing agent’s concentration was 0.5 M and the reaction time ranged between 30 and 120 min at room temperature. The ferric iron and total iron concentration were verified using a spectrophotometer with 5-sulfosalicylic acid (SSA) to determine Fe(III) and ammonia to determine Fe(II) and Fe(III) in 500 and 425 nm, respectively. The results indicated that total reduction was at 400 mV in any pH between 0.5 and 2, but less than 40% in pH 2.5 at this potential value.

Mar 1, 2017

By John A. Mavrogenes

The Texaco gasification system developed at the Monte Bello pilot plant efficiently bums petroleum-coke thereby producing syn-gas and electricity. This system produces more electricity than conventional burners, yet the only by-products are pharmaceutical grade sulfur and V -rich slag. Vanadium is known to exist in multiple valence states in compounds which possess a wide range of melting points and physical properties. Consequently, it becomes important to carefully regulate oxygen fugacity throughout the system in order to control vanadium valence state. Vanadium phase equilibria is presently poorly understood, in large part because of the multiple oxidation states of vanadium (-I, 0, +2, +3, +4, and +5) and the difficulty of unequivocally identifying the valence state(s) in many compounds. The operation of these gasifiers at approximately 1400°C is well above the melting point of V20S but considerably below the melting temperature of V02 and V 203. If J02 can be regulated to keep the burner within the V 205 field, slag material would more likely remain molten and more easily flow out of the bottom of the burner. In pure V oxides. the oxidation state is readily determined by microprobe analysis. where V20S (V+5) is 56% V, V02 (V+4) is 61.4% V, and V203 (V+3) is 68% V. However, V valence in multi-element phases (especially phases containing other elements of variable valence) cannot be resolved by microprobe analysis alone. Petroleum-coke gasification slags collected from within the gasifier under different oxidation conditions were studied by electron microprobe analysis (EMPA). X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman spectrometry in conjunction with microprobe analysis was found to resolve the valence of vanadium in the phases of these slags. Raman spectra collected from homogeneous single phase V-oxide standards in vacuum at low temperatures (-150°C) yielded peaks characteristic to each valence state. Gasifier slag samples are, however, much more complicated. Oxidized samples contain: fine grained (Ca. Mg, Fe. V) oxide matrix of variable composition, (Fe. V, Ni) spinel. (Fe, AI, V, Ni, Mg) spinel, V205laths, AI-Si glass blebs and Ni sulfides. Reduced samples contain: crystalline Ca-siIicate matrix, subhedral to euhedral (V, Fe, Mg, AI) spinel, subhedral V02, Fe and Fe-Ni sulfides, Fe-Ni alloys, and complex Ca-oxide matrix. The different spinel assemblages, the characteristic V-oxides and the distinctly different character of the matrices makes the oxidized and reduced slags readily discernible.

Jan 1, 1995

By C. J. Newman

Production levels at the Kidd Creek copper operation increased during the 1980&apos;s by expansion of both the smelter and refinery and by major modifications to equipment which was causing bottlenecks. As a result, there was a significant reduction in the unit cost, some manpower reductions and hence a significant increase in productivity. In the last two or three years, there have been no major expansion projects leading to unit cost reductions and yet these have still been attained. This has been achieved by the development and implementation of various techniques designed to maximize the inherent potential of the operators and maintenance employees. This paper will initially describe the operation but will then place emphasis on employee involvement through such methods as idea awards, incentive schemes, loss control and continuous improvement programs. Organizational changes are discussed, particularly with reference to changes from the traditional operator role to one which encompasses maintenance skills and to cross-training of maintenance employees into multi-discipline fields. The effect of these changes are discussed by a review of the salient plant parameters of safety, production levels, cost and quality.

Jan 1, 1993

By Jinxia Nie, Yunnen Chen, Dachao Zhang

"Rare earth resources are strategic and non-renewable resources. But disordered exploitation on rare earth metals leads to resources waste, environmental pollution and ecosystem destroyed. In this paper, soil collected from garden was cultured in thermostated incubator. Adding exogenous rare earth to the soil and the effects of recombination action of rare earth lanthanum, cerium and yttrium on soil enzymatic activities were studied. The results showed that single metal La and Ce can increase urease activity, but Y inhibits its. Coexist La/Y or La/Ce in soil inhibit the urease activity, coexist Y /Ce or coexist three metals promote its. Single metal La, Y and Ce can promote catalase activity, and that of coexist three metals. Pairwise coexist La, Y, Ce in soil inhibit catalase activity. With certain concentration of rare earth recombination action, urease activity in soil has been very significant direct proportion to ionic impulse, but catalase activity been insignificant inverse proportion to its.1. IntroductionThe increase of rare earth element content due to anthropogenic inputs frequently takes place in agro-industrial areas, leading to soil pollution episodes that may cause serious environmental problems because of their potential toxicity to microorganisms, plants, animals and human beings [ 1]. China is abundant in lanthanides resources. Rare earth metals are used in many frontier technologies such as photic devices, magnetic materials, and fine ceramics, and the amount of the rare earth metals used in these industries has been increasing. In addition to their use in industry, rare earth metals are more widely applied to cropland as microelement fertilizers due to their ability to promote growth and productivity of some crops [2]. As a result, more and more rare earth metals are moving into the ecosystems. While a permanent contamination of soils results in populations of micro-organisms with high resistance to rare earth metals, a short-term burden of contaminants at high concentrations could exert inhibitory effects on microbial carbon [3]. They accumulate in soils, bioaccumulate in crops, and enter the food chain, causing a potential problem of rare earth metals environmental pollution in China [4]. This contamination may also severely influence organisms and soil activities [5]."

Jan 1, 2011

By Markus A. Reuter

In this paper various hybrid modelling architectures are proposed for the modelling and metallurgical control of pyrometallurgical reactors. Discussed are architectures in which data reconciliation is combined by thermochemical, neural net and dynamic modelling to improve the models. At the same time the data reconciliation models can act as soft-sensors for estimating unmeasurable data. Cases that are discussed are (i) the modelling of a submerged arc furnace for the production of thermal phosphorous, (ii) the processing of Sn-Pb-Zn flue dust (originating from secondary copper) in a hearth furnace, (iii) modelling of a steel converter, and (iv) dynamic modelling of a flash smelter.

Jan 1, 2001