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By C. Pichler, A. Ressler, D. Gregurek, A. Spanring

In order to improve the refractory lining life at one of the RHI key customer test procedures were developed within a two years collaboration project. In the first year of cooperation detailed refractory corrosion work in the rotary kiln with Ca-ferritic slag was performed. The main results of the second year of cooperation, reported in this article, involve a detailed testing work with nickel matte and pre-selected refractory brands which was performed in TBRC. A first part of this work was a complete chemical and mineralogical characterization as well as FactSage calculations carried out on provided matte samples. According to these results testing in the TBRC was realized at different process temperatures with several magnesia-chromite bricks. Based on the mineralogical investigation a high chemothermal load caused by sulfidic matte resulted in a deep reaching infiltration of the brick microstructure and partly corrosion of main brick components.

Jan 1, 2015

By Terry Gerritsen

Electrode control systems regulate power by physically positioning electrodes. Due to the size and weight of the electrodes, this is a slow process where power fluctuations of less than a few seconds are not fully corrected. Nickel laterite AC furnaces operating in high voltage, shielded arc mode typically incur frequent power variations of approximately +I- 20% around the power set point. To provide enhanced power control, Hatch has recently supplied, at commercial scale, a thyristor-switched reactance system called an SPLC. The SPLC incorporates predictive control software to operate furnaces at the maximum transformer rating by reducing the large power swings experienced without the SPLC. The resulting higher average power enables higher production, without increasing transformer or power plant capacity. A 60 MW production version of the SPLC has been commissioned on Falconbridge Dominicans's laterite nickel furnace, yielding excellent results with a 3 to I reduction in power fluctuations. Keywords: SPLC, AC Power Supply, Electric Furnace

Jan 1, 2004

By S. Eckert, G. Gerbeth, K. Timmel, B. Willers, T. Wondrak, N. Shevchenko, M. Röder

The quality of the produced steel in the continuous casting process is significantly governed by the melt flow in the mold. However, direct flow measurements in liquid metals are still rather scarce. In order to investigate these flow phenomena, three experimental facilities operating with low melting liquid metals were installed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The melt flow in the models is measured by the Ultrasonic Doppler Velocimetry (UDV) or the Contactless Inductive Flow Tomography (CIFT), multi-phase flows can be visualized by X-ray imaging. The obtained measurement results are primarily used for validation of numerical models. In this paper we will investigate the fluid flow in the mold and the behavior of the surface of the liquid metal using flow measurements by UDV and surface profile measurement by a laser scanner, respectively. Strong fluctuations and deviations of the free surface were observed in case of a static magnetic field

Jan 1, 2016

By Kuniaki Murase, Tetsuji Hirato, Yasuhiro Awakura

"Electrodeposition of CdTe was studied using aqueous ammonia-alkaline electrolytic baths in which Cd11-and Te1V-ions are dissolving as Cd11(NH3)/+ and Te1vol-ions, respectively. Ca-thodic polarization curves of the baths suggest the presence of strong interaction between the Cd11-and Te1V-ions; electrodeposition of tellurium is inhibited by the presence of Cd(NH3)/+ ions. The interaction makes it possible to electrodeposit CdTe films with stoichiometric composition. Polycrystalline CdTe thin film of about 1 µm thickness was electrodeposited at 343 K from ammonia-alkaline solutions (pH= 10.7) containing TeO32-(<20 mmol dm-3) and Cd(NH3)/+ ( < 60 mmol dm-3) ions. Increasing Cd(NH3)/42+/TeO32- mole ratio or decreasing total concentration of ammonia/ammonium-ion gave flat and smooth crystalline CdTe deposits at constant cathode potential-0.70 to -0.30 V vs SHE at 343 K.IntroductionCadmium telluride (CdTe) is well-known as a compound semiconductor whose band gap, i.e. 1.44 eV, is suitable for solar energy conversion with a photovoltaic cell. Various methods, such as CVD (chemical vapor deposition) and electrodeposition, of preparing CdTe thin films for solar cells have been investigated.Acidic sulfate solutions with a pH of 1-2 are usually employed for CdTe processing by electrodeposition.1-3) The electrodeposition of compound semiconductors is usually achieved (i) at a higher cathode potential than the redox potential of less-noble species, can in this case, and (ii) under the condition of diffusion-limiting current of a more noble species, Te1Y.4) There-fore, a suitable CdII/TeIV concentration ratio in the acidic electrolytic baths, resulting in the deposition of stoichiometric CdTe, is determined by the diffusion-limiting current density of TeIV- reduction, i.e. the concentration of HTeIVO2+ · Since the solubility ofTe1v species HTeIVO2+ in the acidic solutions is quite low, the rate at which CdTe is deposited from the acidic solutions is extremely slow."

Jan 1, 1998

By F. H. Froes, O. N. Senkov, N. Srisukhumbowornchai

"Mechanical alloying (MA) and thermohydrogen processing (THP) approaches were used to synthesize amorphous or nanocrystalline powders of the titanium-aluminide-based alloys and composites. Fully dense samples with nanocrystalline and bimodal structures were produced from these powders by hot isostatic pressing. The stability of the microstructures during continuous heating at high temperatures was studied. Characterization techniques including X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, and differential thermal analysis were used in this work.IntroductionAs performance demands increase, so do the demands for enhanced mechanical property combinations at reduced overall weight; and reduced weight can most efficiently be realized by the use of low-density metals with high specific strength, such as titanium alloys and titanium-aluminum intermetallics [l]. The TiAl-based alloys are attractive for high temperature applications, however, they exhibit poor ambient temperature ductility and fracture toughness [2-4]. Incremental improvements can be obtained using ingot metallurgy processing [1,2] but more substantial developments require ""far from equilibrium"" (FFE) synthesis [5-8] which allows development of novel constitutional and microstructural effects, leading to enhanced physical and mechanical properties. Improved ductility of titanium aluminide intermetallics can be achieved by disordering, grain refinement and deoxidation of the matrix, while good elevated temperature properties are achieved due to a dispersion of fine, thermodynamically stable, second phase particles.The approaches for producing nanocrystalline and amorphous TiAl-based alloys and composites used in this work included FFE powder metallurgy techniques such as rapid solidification, mechanical alloying and thermohydrogen processing. The rapid solidification (RS) technique allows extension of solubility limits, production of novel phases, and much more refined microstructures (down to nanostructure or even amorphous range) than is possible using the ingot metallurgy technique [9]. Mechanical alloying (MA) is a process in which heavy working of powder particles results in intimate alloying by repeated deformation, fracturing and welding. This process can produce greater departure from FFE than RS, leading to greater refinement effects; and additionally allows production of a dispersion of second phase particles [10]. Thermohydrogen processing involves hydrogen as a temporary alloying element in titanium to facilitate processes, refine microstructure, and improve final mechanical properties [11]; it was used in the present work to improve MA process. The combination of these three processes was expected to control the final microstructure even better than either process used alone."

Jan 1, 1998

By Jose F. Hevia

This study is part of a broader project on the hydrothermal conversion of copper concentrates to metallic copper by solid state reactions in which the copper remains localized in the solid phases. The kinetics of the solid/solid hydrothermal hydrogen reduction of tenorite (CuO) and cuprite (Cu,O) to metallic copper are presented. After an induction period, the process is governed initially by a nucleation step followed by rapid solid state reduction. Nucleation promoter agents decrease the induction period and control the particle morphology. Separate nucleation and reduction rate processes have been identified. Following nucleation, reduction follows a shrinking core process.

Jan 1, 1994

By Jacques Magnaudet, Julie Cranga, Didier Huin, Pascal Gardin

"With the aim of controlling steel grade in steelmaking reactors, IRSID and IMFT are developing a numerical description of the evolution of bubbles in the vicinity of a liquid steel/ slag interface. The objective is to identify the main parameters affecting the hydrodynamics of the various phases. The goals of the present paper are:• To describe the numerical technique developed to predict the multi phase flow including bubbles, liquid metal and slag layer.• To analyze the influence of the absolute pressure on the bursting of bubbles in a RH degasser. Validation is given by comparison with results available in the literature. The major point concerns the distinct behaviors observed whether the pressure is low or high.• To study the influence of the properties of the slag layer (thickness, viscosity and interfacial tension) on the entrainment of liquid metal in the wake of the bubble and on the nature of the projections from the bath surface.IntroductionMost of secondary steelmaking processes use gas stirring for homogenization, removal of nonmetallic inclusions or decarburization under reduced pressure. The bursting of gas bubbles at the metal or slag layer surface produces a beneficial ejection of metal droplets in the low pressure atmosphere, provided that there is no violent projection, which may have detrimental effects on the process.Our objective is to develop a numerical tool to study the phenomena occurring in the vicinity of the bath surface, in particular bubble bursting under reduced pressure and entrainment of metal in the slag layer. In this paper we report the first conclusions of our study. In the first section we describe the numerical model used to describe the three-phase flow and the expansion of the gas bubbles under the effect of the ferrostatic pressure. The second section is devoted to the study of pressure effects on bubble rise and bursting. The third section reports some computational results about the rise of a gas bubble through the interface between the two liquids."

Jan 1, 2001

By Bernd-Arno Behrens, Klaus-Georg Kosch

"In times of increasing energy costs automotive lightweight construction is gaining in importance. This paper deals with the production of hybrid steel-aluminum compounds by forging. The compound forging process is a promising method to successfully manufacture functional parts by applying resource-saving process steps. Nevertheless, challenges resulting from different material properties must be solved.The heating of hybrid material work pieces made of steel and aluminum is a great challenge. Steel is forged at a temperature of at least TSt =900 °C, while aluminum should not exceed a temperature of TA1= 500 °C. For achieving the required temperature gradient extensive experimental investigations have been carried out. Intermetallic phases form during the manufacturing process and can influence the bonding and the global part quality. In addition, methods for the characterization of the joining zone between the materials steel and aluminum are analyzed and the factors influencing the formation of intermetallic phases are determined experimentally.IntroductionIn times of increasing energy costs and stricter conditions relating to environmental protection, automotive lightweight construction is gaining in importance. The production of hybrid compounds by forging is a promising method to manufacture functional parts by applying resource-saving process steps. In compound forging a hybrid raw part consisting of a solid core, which is enclosed by a hollow casing, is joint in the forming process. This results in a graded material structure in the part in which the mechanical properties can be specifically adapted to the requirements. Compound forging is the form joining and/or firmly bonded joining of at least two different materials while plastic shape forming occurs (Figure 1)."

Jan 1, 2012

By Srinath Viswanathan, Adrian Sabau

"In general, the occurrence of microporosity during metal casting is due to the combined effects of solidification shrinkage and gas precipitation. The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies on microporosity, it is considered that the porosity formation does not influence the fluid flow in the mushy zone. In this study, a computational methodology is presented for the numerical simulation of interdendritic fluid flow and microporosity evolution. The solution algorithm presented includes a fully coupled, implicit treatment of microporosity and local pressure in the mushy zone. The effects of microporosity evolution due to the local pressure drop in the mushy zone, and pore expansion in casting regions where liquid feeding alone cannot compensate for the solidification shrinkage are also considered. It is shown that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops. By its growth, microporosity partially compensates for the solidification shrinkage, reducing the feeding demand. A reduced feeding demand requires less fluid flow to compensate for solidification shrinkage, and results in smaller pressure drops in the mushy zone. Therefore, in order to accurately describe casting defects, comprehensive models of fluid flow, heat transfer, and solidification must include the effect of microporosity as well.IntroductionIn the terminology commonly used by foundrymen, porosity is usually considered to be either ""hydrogen"" or ""shrinkage"" porosity. Hydrogen porosity is the term given to porosity that is generally rounded, isolated, and well distributed. Porosity that is interconnected or clustered, and of an irregular shape corresponding to the shape of the interdendritic region, is usually termed shrinkage. In general, the occurrence of microporosity in aluminum alloys is due to the combined effects of solidification shrinkage and gas precipitation [1]. Continuum models [1, 2- 7] have been used to predict the level of porosity in castings. A number of other studies have also attempted to understand the phenomena of porosity formation and pore growth [8-10] and pore morphology [11].The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies [4, 9, 10], it is considered that the porosity formation does not influence the fluid flow in the mushy zone. Kubo and Pehlke [3] presented a methodology for the prediction of microporosity distribution in shaped castings by considering the effects of both the hydrogen precipitation during solidification and the pressure drop in the mushy zone. In their approach, the local pressure and porosity were computed in an uncoupled manner based on a ""flux of interdendritic liquid"" criterion, i.e., either pressure or porosity was first computed using the other variable at the previous time step. Their approach has been used with little change in numerous studies [6, 12, 13]. Recently, Kuznetsov and Vafai [14] presented a fully coupled, one-dimensional model for the computation of pressure and porosity. They showed that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops and an over-prediction of final porosity. They also showed that the influence of porosity formation on the pressure is larger at lower pressures in the mushy zone."

Jan 1, 2001

By Roberto Parra

The classic criteria of the preparation of the charge for the smelting of copper concentrates in a flash furnace considers the mass and energy balance from the chemical and mineralogy composition of the concentrates. The operation parameters fixed with this method don&apos;t assure the stability of the operation and the critical problems of the slag quality and dust formation occurs very often. This paper presents the results of a laboratory test that allows the predicition of the behavior of concentrates blends in the view of the minimization of the dust formation and the magnetite control in the slag. The combustion of different copper concentrates and blends were done in a drop tube furnace. The results show that the magnetite and dust formation don&apos;t have a linear behavior with the weight proportion of the blend and some optimal blends of 2 or 3 types of concentrates can be identified. From the reasonable hypothesis that the qualitative behavior of blends in the drop tube represents the real behavior in the burner, the preparation of the charge with this approach could help to solve those operational problems.

Jan 1, 2003

By S. C. Grund

In secondary copper smelting as it is performed at Hüttenwerke Kayser plant in Lünen, tin-and lead-containing flue dusts are produced as intermediate products. These flue dusts are further processed in a hearth furnace. Followed by certain refining operations a saleable tin-lead-alloy is produced. Even though the hearth furnace technology has been in use for this purpose for a long time still its performance undergoes changes in search for optimum processing conditions regarding to the increasing complexity of the raw materials and tightening economical and ecological boundaries. The use of modern statistical tools for the calculation of accurate mass balances is demonstrated for the tin-lead hearth furnace. These reliable mass balances are the basis for any further modelling of the process with the aim of optimization. Incorporating metallurgical knowledge and experience as well as different mathematical modelling techniques, further studies are planned in which the recoveries of valuable and minor elements and their dependency from various process parameters are examined. The aim of this modelling is to optimize the recoveries of the valuable elements, to minimize the energy consumption and the processing costs and thus to keep the process competitive in a harsher economical and ecological surrounding. The modelling principles are transferable to other metallurgical operations and are especially suited for ill-defined pyrometallurgical processes.

Jan 1, 1999

By R. Lanza, M. Hytros, N. Saka, I. Jureidini, J. H. Chun, D. Kim

"A novel method for delineating the solidification front in metal casting has been developed using the attenuation phenomenon of electromagnetic radiation (y-rays or x-rays) and computed tomography (CT). The densities of the liquid and solid phases that exist during metal casting may differ anywhere from 4 to 12 % depending on the metal. As in the medical imaging field, CT provides an excellent means of mapping this density variation in a solidifying casting into two-or three-dimensional images.In an effort to develop an industrial-scale sensor, laboratory-scale experiments have been conducted using a cobalt-60 (Co60) radioisotope and a sodium-iodide (Nal) scintillation detector. The CT image reconstruction was performed on a crucible containing pure tin in a two-phase state. Although the spatial resolution and data acquisition speed were not optimum, the CT images clearly differentiate the liquid and solid phases of the tin in the crucible. To maximize resolution and minimize data acquisition time, a linear accelerator (linac)-based CT sensor is being developed and tested for application in the continuous casting of steel and aluminum alloys.IntroductionIn all casting processes, the quality of a finished product and its production rate depend upon the shape and movement of the solidification front. From a quality perspective, it is well documented that solidification kinetics (heat and mass transfer, fluid flow, microstructure evolution) greatly influence the final properties of castings [l,2,3]. Product shortcomings, such as surface defects, cracks, macro-and microsegregation, and inclusions are directly controlled by the solidification process. By understanding the role the solidification front plays in the casting process, product quality may be dramatically increased through the reduction of defects."

Jan 1, 1997

By H. Dijkman

The PAQUES Bio Systems&apos; core technology, marketed under the name THIOPAQ®, consists of various high-rate biological processes for metal-sulfur-water systems, complemented with common solid/liquid and gas separation steps. Sulfur species are converted to sulfide, which is a valuable component as it can be used for metals reduction and precipitation. Selective recovery of valuable metals can be employed, leading to revenue from metal values. In this paper, biotechnological systems for the treatment of metal sulfate solutions and dilute SO, gases are described. These installations can be designed to either produce predominantly aqueous (NaHS) or gaseous (H2S) sulfide. The emphasis here is on hydrogen sulfide gas. The main case history discussed is the demonstration plant that ran on hydrogen gas at Kennecott Utah Copper. Three years of operating experience clearly show that sulfate reduction with hydrogen gas is a viable option. Furthermore, the selective recovery of copper from leach water with the hydrogen sulfide produced was shown to be very effective.

Jan 1, 1999

By Varuzan Kevorkijan

A new method for faster production of functionally graded metal-ceramic laminates is based on reactive pressureless counterflow infiltration/penetration of a ceramic substrate with two different metallic infiltrants. The porous or dense ceramic preform is pressurelessly infiltrated or penetrated from one side by the first metallic infiltrant to the desired cross section of the preform, producing the top layer made up of the solidified infiltrant and the underlayer consisting of reactive infiltrated preform. The partly infiltrated perform is then completely infiltrated starting from the other side by the second metallic infiltrant, in this way fabricating the internal layer, consisting of the ceramic perform infiltrated with the second infiltrant and the bottom layer formed by the solidified second infiltrant. Systems already investigated include carbide, nitride and boride ceramic performs infiltrated with aluminum and magnesium alloys.

Jan 1, 2003

By J. van Driel

NOx is a growing concern for acid plant operators due to recent legislation reducing the allowable stack limits, as well as continually more stringent requirements for product acid quality. NOx also causes a major problem during maintenance as NOx rich acid residues fume following exposure to moisture in the air. Until recently, the solution for NOx related issues was to treat the symptom, rather than the cause. NOx in product acid was treated using chemicals and the NOx in the plant stack was generally left untreated. As part of an environmentally driven change in concentrates, Budel Zink installed the first gas phase NOx destruction process to be incorporated into a commercial scale acid plant. Nitrogen oxides contained in the process gas are reduced selectively with ammonia over a catalyst to form nitrogen and water. As a result, the NOx reduction is in agreement with the permit requirements.

Jan 1, 2002

By M. Cavallini, G. Cannavale, P. P. Milella, A. Pescetelli, C. Lupi

Ni-Cd sealed and vented cells have been widely used in the last few years. The environmental hazard related to the heavy metals contained in Ni-Cd batteries is well known. Therefore, a number of scientific studies and commercial processes have been implemented in order to recycle them. Since spent batteries are a heterogeneous and complex material, any kind of recovery process needs some preliminary treatments. The proposed process described in this paper has been tested in laboratory and further developed in a pilot plant. It consists of a combination of mechanical and hydrometallurgical treatment steps, and is able to treat all type of Ni-Cd batteries. In particular, the mechanical treatments have to be done separately on vented and sealed cells, while the hydrometallurgical step is performed on a mixture of the two products obtained from mechanical steps. A fully automated dismantling line would allow the separate recovery of the plastic or metallic casing, terminals, KOH electrolyte, and electrodes to be further processed· for Ni and Cd recovery. The electrodes coming from dismantling line and sealed batteries are submitted separately to an original crushing and elutriation treatment to separate metallic and active paste in the first case and metallic, plastic and active paste in the second case. The hydrometallurgical treatment is carried out on active paste bearing product to produce Ni, Cd, and Fe comn1ercial salts through acidic leaching followed by a multi-step solvent extraction operation to obtain pure solutions.

Jan 1, 2000

Studies of electric pulse (EP) disintegration were conducted on ores of disseminated precious minerals, &apos;on platinum-bearing chromitites of the Konder Complex, Russia, on diamond-bearing impactites of the Popigai meteoritic crater, Russia, and on and diamond-bearing metamorphic rocks of Northern Kazakhstan. It was shown that EP disintegration ~s a technology that achieves ideal liberation of disseminated minerals, and is a new efficient method to study accessory minerals.

Jan 1, 1991

By Ilie Butnariu

Steel manufacture in VOD procedure needs a very attentive correlation and pursuit of the technological stages ,on the background of keeping the influence factors within best performances zones. For a better co-ordination of the main stages specific to this process ,this work presents a detailed study of the optimization possibilities for each stages ,beginning with the furnace charging ,going on with the pre-aftinage and aftinage stages in the electrical furnace and then with the refinement stages in the VOD installation. One has intended the effective emphasis of the main influence factors with global implications on the process and especially on the purity and quality of the stainless steel ,Among the main novelties proposed by this work , we can emphasize the following: - a computer assisted charging method ,with the possibility of using a large scale of wastage, also respecting the density proportions of the components of the charges; - the advanced recuperation of the elements of the charge by reducing the combustion of the valuable elements ; - the optimization of the oxygen blast conditions and of the aftinage stage ,by establishing some calculations concerning critical carbon content , that requires the oxidation to be continued very carefully; - the simulation of the thermic and chemical parameters by modeling the alloying process of the stainless steel in the case of some large amounts of additions.

Jan 1, 1994

By Benoit DeBecker

Laboratory-scale experiments have shown that chromium metal could be recovered from chromate wastes by modifying slightly the chromium electrowinning flow-sheet. After reduction by sulhr dioxide and precipitation of chromic hydroxide, the solid residue is dissolved in the chrome alum solution and the metallic impurities are removed by cementation on manganese. The presence of dissolved manganese in the electrolyte does not affect the cathodic deposition of chromium and it eliminates the anodic production of Cr(V1).

Jan 1, 1994

By Joseph C. Rota

The Carlin Trend is one of the most significant gold mining districts in North America. Located in northeastern Nevada, a total of over 17 million ounces of gold have been produced since 1965 at Newmont Gold Company's open-pit and underground operations. Oxidized portions of the sediment-hosted, disseminated gold deposits at Carlin generally consist of finely disseminated concentrations of sub-micron sized native gold particles hosted in Paleozoic siliciclastic or carbonate rock. Oxide ore is commonly amenable to dump leach or heap leach processing, yielding an average 50 to 70% recovery of total contained gold. Refractory unoxidized ore requires some form of pretreatment oxidation to ensure economic gold recovery. Geologic ore control is typically combined with standard assay and engineering techniques to maintain both grade and metallurgical control ofleach grade ores. Mine geologists provide a vital function through field observation and recording ofmineralogic data during daily, visual blasthole logging. Intricately mixed refractory materials must be separated from oxide ore to ensure highest possible gold recoveries. Geologic information is combined with assay data to create mine polygons in an engineering computer database. Mining selectivity is further enhanced by in-pit ore control geologists who are available to make production decisions based on direct mineralogic observations at active mine faces.

Jan 1, 1997