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By Goren Lindkvist

Elkem has a small industrial scale. Muti-Purpose furnace at the MEFOS Metallurgical Research Facility in Lulea, Sweden. The furnace is 2 meters in diameter with installed power of 4.8 MVA, equipped with oil coiled freeze lining, gas tight electrode seals and feed chutes and a slag flow control for continuous tapping. During tests in June, 1991, the furnace was continuously operated on a high silica slag at loads from 1.5 to 4,0 MW. The slag was then charges to a low silica, high iron and lime composition. Steel plant dust was added, smelted and reduced. The slag was made more ceramic by adding alumobrick and alumina. Data from the start-up and initial operating phase of the, Elkem EAF dust plant at Laclede Steel will also reviewed.

Jan 1, 1992

By J. Van Boven

The Hoboken plant has continued the program, started in 1973, for monitoring the impact of processes on the environment. Progressive improve¬ments including new installations and equipment have been commissioned resulting in reduced emissions of lead in air. The Hoboken Smelter now fully complies with regulation and observes a yearly mean value of less than 2 micrograms Pb per cubic meter of air in the vicinity of the plant. In addition a new central water-treatment installation permits the discharge of waste water to the River Schelde in accordance with present day regulations. Mention is made of methods used to measure the emissions and immissions at the plant. Results of modifications and new installations recently commissioned are discussed.

Jan 1, 1983

By A. J. Maselli, E. C. Cemak

Hartford Steel Technologies (HST) has a pyrometallurgical and hydrometaliurgical process capable of reclaiming valuable metals from a hazardous waste· stream such as EAF Dust. The HST Process effectively addresses the growing environmental concerns surrounding the increasing production of EAF Dust without producing any hazardous waste material as byproducts. Currently EAF Dust production levels are exceeding the 1,000,000 metric tons per year mark. The HST Process is designed to separate iron, zinc, lead, cadmium, copper, and silver metals using a two-phased process. The Pyrometallurgical side of the Process utilizes a Rotary Hearth Furnace to separate the iron metal from the remaining metals. These remaining metals are further separated, using a Hydrometallurgical Process, in a series of digestion tanks. The individual metals are then collected in saleable form.

Jan 1, 2000

By Metehan Erdogan, Furkan Özdemir, Ishak Karakaya, Mustafa Elmadaglı

Tungsten is mainly produced by H2 reduction of WO3 which makes its production difficult and costly. A promising method was recently reported for direct electrochemical production of tungsten from CaWO4 (scheelite) which is estimated as the seventy percent of the all tungsten reserves of the world. This paper investigates the application of pulse current in the electrochemical reduction of CaWO4 pellets attached to a current collector. The electrolyte was composed of calcium chloride and sodium chloride salts at eutectic composition (48 pct mol NaCl at 873 K). The reduced samples were cleaned with dilute hydrochloric acid solutions and characterized by X-ray diffraction and scanning electron microscopy. Examination of the results revealed that metallic tungsten was obtained by pulse current reduction.

Jan 1, 2016

By M. Pineau, G. A. Monteith, M. Laliberte, G. Houlachi

Conventional physico-chemical treatment methods, either hydroxide or sulfide precipitation, can hardly achieve a high removal of selenium from the liquid effluents which can be generated in some metallurgical operations. In weak acid solutions, selenium exists mainly as anionic species (selenite Se03-2 and selenate SeCV2) which, therefore, cannot precipitate as metal hydroxide or metal sulfide compounds. At the same time, neither selenite nor selenate form stable precipitates with the common cations (Ca, Mg, Fe, etc.) that are typically used in water treatment. At Noranda Inc., CEZinc Division in Valleyfield, Canada, the introduction of new discharge requirements for effluent toxicity initiated a R&D program which resulted in the full-scale implementation of a new treatment method for selenium removal. The goal of this paper is to present this new method which is now being patented by CEZinc. The process chemistry will be presented along with pilot-scale developments and full-scale operational results.

Jan 1, 2000

By T. T. Natarajan, Nagy EI-Kaddah

"Numerical simulation of electromagnetic confinement systems generally requires large CPU time due to the strong coupling between the electromagnetic and the free boundary problems. The present paper examines the accuracy and the computational efficiency of the most common numerical schemes used in modeling such systems. Levitation melting was taken as a test case. In this study, a comparison was made between the finite element and surface integral methods for electromagnetic field calculations. The computational efficiency of Lagrange and the modified Hestenes methods for solving the free boundary problem were investigated. The convergence of the Lagrange method was found to be much faster than the modified Hestenes method. It was also found that finite element method not only gives accurate solutions, but faster convergence to the final equilibrium shape than the surface integral method. The applications and the limitations of these techniques in modeling electromagnetic confinement systems will be discussed.IntroductionIn recent years there has been a growing interest in the use of electromagnetic forces for confinement of molten metals as a means to eliminate molten metal contamination during melting and to improve surface quality of cast products. Continuous casting of metal without contact of a mold is now a reality, and is being commercially applied for casting of aluminum slabs /1/, and copper rods /2/. New applications of electromagnetic confinement in melting and casting include containerless melting (Magnetic Suspension Melting) /3/, edge containment in twin roll casting, and meniscus shape control in continuous casting of steel /4/.Modeling of confinement systems involves the determination of the electromagnetic field and the equilibrium shape. These two problems are strongly coupled due to the dependence of the field on the shape of the melt. While significant advances have been made in computational electromagnetics /5/, the application of developed computational techniques to electromagnetic confinement problems is not a simple task. The principal difficulty in using these methods is that the solution domain is not known a priori. due to coupling between the electromagnetic field and the free boundary problems. These two problems have to be solved simultaneously, leading to an iterative solution procedure. As a result, numerical simulation of electromagnetic confinement systems are computationally intensive with computational time at least an order of magnitude larger than the fixed domain problems."

Jan 1, 1994

By Viktor. P. Popov, Oleksandr. V. Derev'yanko, Oleksandr. I. Raychenko

"This paper is devoted to scrutiny problem of obtaining electro-contacts by electro-discharge sintering technology. A new unconventional method of electro contacts production (on Aggraphite base) can yield essential optimization resource.Review of three electro-technological methods of processing contacts materials is presented:- using graphite powder cladded by Ag;- mixture of graphite powder(which is a non-cladded powder) with Ag powder and addition of Fe powder particles;- method of infiltration of melted Ag into graphite piece without deformation and rupture of object.This technological approach can give the possibility to increase of compression strength of electro-contacts materials up to 340 MPa and more under conditions of additional reinforcing components (for example, by Fe).IntroductionThe electric current can be an active ""participator"" of the powder metallurgy technology [l]. At the passage of electric current through powders or some powder mixtures the phenomena including phase transformations arise. Here such effects, which are observed in the Ag-graphite and Ag-Fe-graphite powder mixtures and in the pair Ag-porous graphite, are described.The Ag-graphite composition materials (CM) are used, for example, as electric contacts [2, 3]. Since a material being produced is destined for the contacts it is necessary to take into account the following aspects: commutating current, its character and voltage, active or reactive character of working load, geometrical dimensions of contacts, quantity and frequency of switching on and switching off, pressure on contacts, distance between contacts, method of arc control, surrounding medium, its content, pressure and temperature. Thus, these and, maybe, choice of some other circumstances influence design, materials and production technology of contacts. The range of problems concerned dictates such steps as alloying of contact materials, optimization of structure, selection of kind of graphite, its connection with metal [4-10]. It is expedient to recall the main procedures of the first stage of the conventional technology: dosage of the initial graphite powder and binder-phenolic resin plastic varnish (for example, Bakelite), mixing, densification, thermal treatment, crushing, grinding, sieving, drying, dosage of grained graphite, dosage of the initial silver powder, obtaining of the silver salt solution, settling of salt, filtration, washing, drying of the cladded graphite powder, thermal treatment, obtaining of the graphite powder of particles cladded by silver. The second stage of the convectional technology starts by obtaining of the cladded graphite powder and finishes by annealing of the pressed blanks (Fig. 1)."

Jan 1, 2004

By Kezhuan Gu

Data on the kinetics and thermodynamics of dephosphorization are analyzed in terms of the dynamic partition ratio, determined by a combination of slag thermodynamic properties and the balance of oxygen supply and consumption. A recently developed phosphate capacity correlation is combined with data on kinetics to quantify the most significant parameters in controlling the interfacial oxygen potential. The role of slag composition, entrained gas fraction and temperature are discussed in addition to metal carbon and sulfur content. It is demonstrated that the mass transport of oxygen in the slag is enhanced by factors increasing conductivity and inhibited by entrained gas. The mass transfer of phosphorus in the metal is described considering surface renewal induced by CO bubbles.

By S. J. Gerdemann

The U.S. Bureau of Mines is studying the kinetics of wet oxidation of sphalerite concen- trate (ZnS) as a possible process for a gravity-pressurized reactor (GPR). At tempera- tures in excess of 200' C, a sphalerite water slurry will react with 0, to form zinc sul- fate (ZnSO,). However, the pressure required to keep the water from boiling at these temperatures has kept this reaction from becoming a viable continuous process. The GPR can easily obtain the high pressures required for this reaction. The reaction rate is complicated by the solubility of 0, in water and the further oxidation of ZnSO, to insoluble zinc oxysulfate (Zn4(OH),S04.4H20). The effects of pressure, temperature, and particle size on the rate of reaction were investigated. Reaction rate was found to be limited by the amount of oxygen in solution. However, at 250" C and 1500 psia, over 90 pct of the zinc was solubilized in less than an hour. The conditions for maxi- mizing the Zn++ in solution, while minimizing oxysulfate formation, are discussed.

Jan 1, 1993

By Niels Verbaan, Ralph Fitch, Charlotte Forstner, David Dreisinger

A process has been developed to extract gold, silver, indium, gallium, lead, copper, zinc, and other metals from a large resource using an oxidizing acid chloride heap leaching technology. The ore is crushed and/or ground to improve reactivity and then contacted with a solution containing NaCl-HCl-NaOCl. The value metals are leached into solution as chloro-complexes. The leachate is treated in a series of separation and recovery processes to produce separate saleable or disposable products. The paper will provide a summary of process development and application to a silver-indium ore from Bolivia. The possible application of the process to other ore types will be presented for discussion.

Jan 1, 2015

By Xiaoming Huaa

The effect of the anodic polarization on the composition and morphology of the surface layer formed on chalcopyrite during ammonia–ammonium chloride leaching was investigated. The anodic polarization on the chalcopyrite electrode was used for oxidation and dissolution of chalcopyrite, and the resulting oxidized layers were characterized by XPS, SEM and optical microscopy. The results show that oxide layers exist on the chalcopyrite surface with or without any anodic polarization in the leaching solution at ambient atmosphere. However, the composition and morphology of the layers are strongly depended on the extent of polarization. The distribution of FeOOH and Fe2O3 within the oxidized layer was inhomogeneous for the sample at the open circuit potential (OCP). The composition and morphology of the oxidized layers which were formed at anodic potentials lower than 0.3 V versus SCE were similar to those of the chalcopyrite at the OCP. At anodic potentials above 0.4 V, the oxidized layers contained many cracks, and they were fragile and exfoliated. Furthermore, the sulfide had been oxidized to sulfur species with higher oxidation states. The oxidation of the chalcopyrite seemed to undergo a cyclically oxidative process that suggested growth and spallation of oxidation layers on chalcopyrite in a layer-by-layer sequence.

By A. W. Bryson, S. P. Fox, S. A. Godorr

"This work is an extension of a previous investigation on the development of surface roughness during electrodeposition of copper. A comprehensive model based on diffusion and migration in a force field together with surface diffusion and sticking probabilities is used to generate profiles which are compared to those produced experimentally. The roughness is characterized by using the technique of fractal geometry which is shown to describe both qualitatively and 9uantitatively the development of surface morphology during electrodeposition.The work is extended to the deposition of copper in the presence of various concentrations of thiourea. The development of roughness is observed experimentally on the edge of a thin copper disc mounted between two glass plates. This enables photographs to be taken at various stages during growth. The surface outline is digitized using an image analyzer which enables the fractal dimension to be determined as growth proceeds. As expected, the presence of thiourea at low concentrations produces a fractal dimension which is closer to unity (i.e. the surface becomes smoother).IntroductionThe development of surface morphology during electrodeposition has far-reaching implications for copper plating in the electrowinning and electrorefining processes. Short circuits as the cathode surface grows unevenly require operator intervention in a dangerous environment and imply processing delays, and the inclusion of electrolyte in small gaps in the plated cathode have implications in downstream processing of the cathode. Higher current densities are obviously desirable, as they result in greater production rates, but as shown by Ettel et. al.(l), Harvey et. al.(2), Cook (3), and Harvey et. al.(4), it is not possible to operate near the projected economically optimum conditions because the electrodeposition of copper from sulphate and acid solutions is a mass transfer controlled process. It has been shown (Ettel et. al.(l), Harvey et. al.(2)) that the closer a system operates to mass transfer limiting conditions, the poorer the resulting cathode quality. One solution is to use agitation techniques to increase the limiting current density. Another is to add surface active additives to the electrolyte which has been shown by Ettel et. al.(l), Harveyet. al.(2) and Afifi et. a1.(5) to allow higher rates of production without decreasing cathode quality. The second proposed solution is of interest in this work, since there is very little knowledge of the conditions under which these additives operate effectively, and little fundamental understanding of the mechanism by which they operate. The current work seeks to contribute to this field by correlating a simulation model with experimental results to describe the development of surface morphology in the electrodeposition process."

Jan 1, 1997

By Juan Ruiz-Ornelas, Yousef Mohassab, Ricardo Morales-Estrella, Hong Yong Sohn, Noemi Ortiz-Lara

The effect of mechanical activation on the reduction kinetics of magnetite concentrate by hydrogen was studied. The magnetite concentrate was milled for 8 h using a planetary mill. After the milling process, the average particle size was reduced from 14 to 4.4 m resulting in a lattice microstrain of 0.30. Thermogravimetric experiments were conducted to focus on the chemical reaction as the rate controlling factor by eliminating external mass transfer effects and using a thin layer of particles to remove interstitial diffusion resistance. The onset temperature of reduction was decreased due to the mechanical activation, and the degree of conversion was decreased by sintering of particles which was confirmed by SEM analyses. In view of the results, a reaction rate expression is discussed from which the activation energy is calculated.

Jan 1, 2016

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Xingbin Li

A direct hydrometallurgical process of extraction molybdenum and nickel from molybdenum-nickel ore by pressure water leaching without reagent was studied. The extraction of Mo and Ni from molybdenum-nickel ore by oxygen pressure leaching, which exploit the characteristic of molybdenum-nickel minerals contain high concentration amorphous sulfide which has highly active, and make the most of easily oxide to sulfuric acid and sulfate at low temperature and excess oxygen presence of the amorphous sulfide. Under oxygen pressure conditions, considerable molybdenum and almost all the nickel were extracted into solution in the leaching process. The results show that with the leaching time for 3~4h, temperature at 150o C, liquid-to-solid ratio of 2mL/g, mineral granularity of 0.074mm, oxygen partial pressure of 0.4~0.5MPa without other reagent, molybdenum leaching percentage can be over 80% and nickel leaching percentage can be more than 97%. Furthermore, about 80% sulfur in the Mo-Ni ore has been transformed into sulfuric acid.

Jan 1, 2014

By K.H. Song, H.T. Son, H.S. Kim, W.Y. Kim

In order to evaluate the grain refining and mechanical properties due to severe plastic deformation (SPD), this wrok was carried out. Convential rolling (CR) and cross roll rolling (CRR) as a SPD method were introduced, and NI-20Cr alloy as an experimental material was chosen. The materials were cold rolledto 90% in thickness reduction ans subsequently annealed at 700oC for 30 min to obtain the fully recrystallized microstructure. For annealed materials after cold rolling, electron back-scattered diffraction (EBSD) analysis was carried out to investigate the grain boundary characteristic distributions (GBCDs). CRR process was more effective to develope the grain refinement relative to CR process, as a result, grain size was refined from 70 um in initial material to 4.2 um (CR) and 2.4 um (CRR), respectively. These grain refinements directly affect the mechanical properties improvement, in which microhardness and yield and tensile strengths were significantly increased than those of initial meterial.

Jan 1, 2012

By I. H. Bonekamp

Norddeutsche Affinerie has operated an Outokurnpu type flash smelter for more than 25 years. In recent years, the concentrate smelting capacity was increased to 750,000 tpy, double of the initial design capacity. Maintaining this high performance level requires very good metallurgical process control. It is not enough to base this control on thermodynamics and kinetics since the furnace is highly dynamic. Understanding these dynamics and being able to quantify them can have significant financial benefits. A mass and energy balance model was developed and is discussed based on measured data. At this time the model is based on the major elements copper, iron, sulfur and silica. With it is possible to quantify the differences of the various material streams such as matte, slag, flue dust, matte carry-over to settling furnace, etc. Comparing the reconciled energy balance model with the fundamental thermodynamic model makes it possible to quantify the dynamics. These dynamics are related to input parameters using methods such as statistics and neural nets. In the future this database will be used to improve the understanding of the dynamic process as well as the dynamic process control.

Jan 1, 1999

By B. M. Fisher

A process for making electrolytic copper of high quality from copper flotation concentrates is described. The concentrates are first slurried and then subjected to a high-temperature, high-pressure, oxidation-leaching operation under controlled conditions. The resulting slurry from the oxidation-leaching operation is cooled or flashed to atmospheric pressure and then subjected to a solids-liquid separation. The separated liquor, containing the recovered copper values, is cooled and then fed to an electrolytic deposition operation where metallic copper cathodes of high purity are produced. The spent electrolyte is then subjected to a sulfide treatment to precipitate the residual amounts of copper not deposited in the electrolytic cells. The precipitated copper sulfide is recovered and recycled in the form of a slurry to the initial stages of the process.

Jan 1, 1976

By Jiling Wang, Xuefeng Liu, Haojian Duan, Lifeng Zhang, Ying Ren, Wen Yang

"In order to study the influence of MgO-C refractory on steel cleanliness and inclusions during steelmaking process, and to understand the reaction mechanism deeply, laboratory deoxidation and equilibrium experiments were respectively performed in MgO crucibles at 1873K. In the former experiment, after Al addition, steel samples were taken at different holding time. In the latter experiment, different slag components and different contents of carbon and aluminum in steel were considered respectively. The inclusion characteristics of each experiment were analyzed. The results showed that with the increasing of holding time after deoxidation by Al, MgO existed in the small inclusions firstly, and then in the large ones such as the clusters. The MgO content in the inclusions increased with the increasing of holding time, indicating that the MgO in crucible could be individually reduced by the aluminum in the molten steel. The reaction could occur within nine minutes.IntroductionNon-metallic inclusions would have positive or negative effect on steel quality depend on the quantity, size and composition of inclusions. Large inclusions are always detrimental. From the point of view of inclusion property, plastic inclusions are required by steel cord, while hard inclusions are preferred by pipeline steel. One of the most important ways to increase the steel quality is reducing the inclusion size and controlling the inclusion composition in steel. Nowadays, MgO based refractory is used as ladle glaze material with more and more frequency, which results in different inclusion characteristics in molten steel, for example, the inevitable generation of MgO contained inclusions during ladle treatment of steel. In other words, the inclusions in this type ladle will influence on the steel cleanliness and the product property. Thus, keeping an eye on the inclusion formation behavior in the steel with MgO-C ladle glaze is important for the steel industry. There have been a few studies in this regard. Li et al[l] studied the reactions between MgO-C refractory, molten slag and metal using a high temperature X-ray radiographic apparatus. They found that the local corrosion was regarded as due to the cyclic dissolution of MgO and graphite in the refractory into slag and metal phase. The gas bubbles formed according to the reaction of (FeO)+C(s)=Fe(l)+CO(g) greatly influenced the corrosion. On an industrial scale, Du[2] found that ladle glaze is a major source of inclusions in the ladle. An experimental study has been performed by Lehmann in order to estimate the importance of the reaction between a MgO-based tundish refractory and an Al-killed steel[3]."

Jan 1, 2014

By T. Nakamura

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of TiO2 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the TiO2 film in H2S or CS2 gas at 1273 K for I hour, the surface atomic structure was changed. Furthermore, the Tirri02 film was successfully prepared by the subsequent ablation of Ti and Ti02 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By A. F. Sidorov

A method of improving mineral recoveries from ores by modifying the physical and chemical properties of minerals using radioisotope radiation was tested. It was observed that irradiation modifies mineral cell sizes, changes the crystal structure of some minerals, reduces the sulfur content 1 to 1.5 % in sulfides, changes the zeta potential, alters the surface properties of mineral grains I and produces other changes. Preliminary tests indicate that accelerated electron treatment of ores in connection with mineral processing has a potential for improving mineral recoveries by flotation and by magnetic separations.

Jan 1, 1989