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By Ana E. Bohé

Chlorination process is an attractive and efficient method for the metal recovery from complex materials. The process that is performed at high temperatures, allows converting all the metals contained in the material into their respective chlorides which are further separated in a selective way. Aluminum metal matrix composites with discontinuous ceramic reinforcement of short fibers, whiskers, and particles have been gaining wide acceptance as an important engineering material in automotive, aerospace, and electronic industries. Since the ceramic reinforcements are still quite expensive and contribute significantly to the final cost of composite materials, the feasibility of their recovery from the manufacturing scrap and further recycling is a factor of increasing economic interest. In the present work, a theoretical and experimental study is given for the recovery of Al2O3 and SiC particles and short fibers from three commercially available aluminum-matrix composites produced by molten metal mixing route. The process consists of transforming the constituents of metallic alloy matrices in gaseous chlorides that are dragged by the gaseous stream, while the ceramic reinforcement remains as a solid residue in the reaction bed.

Jan 1, 2006

By U. Meyer, A. Alonso, P. Banios

The sampling of cathodes has changed with the introduction of the ISA-process in copper refineries. A Jernkontoret joint working group of refineries and rod plants from both primary and recycled copper plants has been investigating whether the actual sampling of cathodes is representative for this type of cathodes. As a first stage, samples were sent to the members of the working group with the objective to find an easy basis for a comparison of the results of the next stages. All samples show the same tendency for nearly all elements. In some cases, there may exist differences in calibration and for some elements the detection limits are too high, especially when Optical Spectrometry is used. In the second stage, discs were compared with melted samples to answer the question whether the punching of discs is sufficient for the quality control of the cathode. The analyses of the discs represent fairly well the cathode quality. There are differences between cathodes from different crops. Three punches are sufficient to determine the cathode quality. Finally, samples from various lots of cathodes were compared with samples from the rod produced from these cathodes. The impurity content of the rod corresponds to the impurity content of the cathode.

Jan 1, 2000

By Florian Kongoli

The liquidus surface of multicomponent slags is an important parameter in various smelting and converting processes. It helps not only to optimize the slag, chemistry of current processes and their fluxing strategies, but also to determine the availability of new slags for more advanced technologies. In a series of our previous publications, the liquidus surface of some multicomponent iron oxide slags has been quantified at several constant oxygen potentials and the effect of the latter, ignored until that moment, was quantified along with the effect of some minor components. In this work, the liquidus surface of some iron oxide slags is quantified at constant CO2/CO ratios. This is a new convenient way for the quantitative description of the slag liquidus surface and the effect of several fluxes, especially in those processes such as slag solidification, where oxygen potential changes continuously. This type of diagram also describes more dynamically the effect of oxygen potential, clarifies the relation between CO2/CO ratio and oxygen potential in terms of the liquidus surface, which is not widely understood by metallurgist today, and reduces the gap between laboratory work and industrial experience.

Jan 1, 2002

By Jason M. Porter, Douglas L. Porter, David L. Olson, Travis W. Koenig, Van S. Blackwood, Brajendra Mishra, Robert D. Mariani

"Traditional alloy theory models have been applied relative to the three solid phases of uranium: alpha (orthorhombic), beta (tetragonal), and mainly gamma (body centered cubic)[l]. The Darken-Gurry and Miedema models, with modifications based on concepts of Waber, Gschneidner, and Brewer have been used to predict the behavior of four types of solutes: 1) Transition associated with alloying in and containment of the uranium fuel 2) Transuranic elements in the uranium 3) Rare earth fragmentation elements (lanthanides) 4) Transition metals and other fragmentation elements. Using these solute map criteria, elemental behavior have been predicted as highly soluble, marginally soluble, or immiscible (intermetallic phase formers) and have been used to compare solute effects during uranium phase transformations. The overlapping of these solute maps are convenient first approximation tools for predicting alloy behavior.IntroductionAn investigation is in progress to determine the role of various solute elements on size and shape of the 'Y phase field range for uranium to optimize the burning and material processing of nuclear fuel is in progress. Traditional alloy theory models based on correlations to elemental electronic and crystal properties are used to predict solubility and micro structural formation. The effectiveness of this model is based on microstructure property correlations. Darken and Gurry, and Miedema models, with modifications based on concepts of Waber, Gschneidner, and Brewer, models have been used to describe solute solubility with respect to uranium based the on correlation between elemental electronic structure and uranium phases. The alpha (orthorhombic), beta (tetragonal), and gamma (body centered cubic) phases have different solubilities for specific alloy additions as a function of temperature. Using the method of Waber, ellipse diagrams classified those solutes that should have broad solubility in the allotropes of uranium[2]. The predictive diagrams are made from four different correlations:"

Jan 1, 2012

By L. Petitnicolas

The experimental study of nitrogen absorption and its removal from a liquid Ni-20%Cr alloy at 1873 K has been undertaken, using an experimental, apparatus based on the Sieverts technique in order to determine the solubility of nitrogen in the alloy. as well as the kinetics of nitrogen transfer across the gas/melt interface. Experiments show that nitrogen solute equilibrium content can be calculated using the Sievens law. Measurements point out the nitrogen absorption reaction rate to be well described by first order kinetics, whereas experiments on nitrogen removal reveal that the rate is better expressed using a second order equation.

Jan 1, 1996

By Henrique Ventura Oliveira

Continuous casting is the most important process for solidification of steels. In this process, the fluid flow pattern in the tundish and in the mould have significant effect on the product quality. Problems associated to fluid flow in the tundish include surface turbulence, ?short-circuits?, formation of dead zones and vortexing. During grade changes, mixing in the tundish plays a significant role in determining the length of the intermixed slab. All these flow aspects can be studied by means of mathematical and physical models. In the last years, numerical simulation of fluid flow has become a very popular tool in the analysis of the performance of continuous casting tundishes. In setting-up these numerical simulations, special care should be taken in choosing the appropriate mesh distribution, the interpolation scheme, the adequate location of the inlet boundary and the turbulence model. In the present paper, turbulent fluid flow in different configurations of tundishes was simulated. Different turbulence models were used in the simulations. Residence time distribution (RTD) and mixing curves during grade changes were predicted and compared to results obtained in physical models. The performances of the different turbulence models were evaluated. For the tundishes that have been studied, the performances of the different turbulence models tested in the present work were similar. There is no evidence that any of the models provided sustained improvement when compared to the well-established standard k- model. All turbulence models tested presented limitations in simulating flows under low turbulent Reynolds numbers.

Jan 1, 2006

By Michael S. Moats, Daniel Kim, Shijie Wang

"The behavior and deportment of lead, arsenic, antimony and bismuth are critical in producing high quality cathode by copper electrorefining. A critical review of research related to these elements is presented along with a comparison to industrial data, where appropriate. These elements exist predominantly in the anode as complex oxides along die grain boundaries. Upon dissolution, Group 15 elements report both to the electrolyte and slimes while lead essentially enters the slimes. The deportment of the Group 15 elements appears to be influenced by several chemical interactions which are discussed. The effect of these elements on floating slimes and anode passivation is reviewed. Under normal electrorefining conditions, lead, antimony and bismuth are thought to enter the cathode through the encapsulation of slime particles. The literature indicates that arsenic enters the cathode predominately by electrolyte entrainment. Finally, areas for future research regarding these elements are presented.IntroductionControlling lead, arsenic, antimony and bismuth is critically important for the production of high quality cathode in copper electrorefining. The reasons for this are twofold. First, ASTM Grade 1 Cathode specifications [1] for these elements are low, as listed in Table 1. Second, they can affect the efficiency of the electrorefining process (e.g., through passivation, current efficiency, slime processing)."

Jan 1, 2012

By Selvin Yesilay, Munevver Caki, Canbora Bayraktar, Bekir Karasu, Rahmi Imrak

"In this study, the utilization capability of the solid wastes taken from a commercial roof tile and brick factory in Eskisehir of Turkiye has been investigated in the production of stoneware bodies which can be formed by slip casting. At the first stage, X-ray fluorescent (XRF) and X-ray difractometer (XRD) analyses of the wastes were performed. Depending upon the results, a body recipe with an optimum casting concentration was adjusted. The bodies obtained from prepared slips were fired at 1160 oC as glazed and unglazed forms. Then, they were undergone certain tests in order to determine their firing shrinkage values, water absorption levels and optical parameters. To establish what kind of phase formations occurred after firing as a result of waste incorporations into bodies XRD analysis was conducted. Additionally, effects of such a compositional modification on the microstructure of the bodies were examined by a scanning electron microscope (SEM). Consequently, it was concluded that fired roof tile and brick wastes could be evaluated in both glazed and unglazed stoneware bodies. Introduction Stoneware is the general name applied to many wares fired between 1150 and 1300 °C. It has a different and denser structure than those of ceramics produced at lower temperatures. Fired stoneware possesses a lower water absorption value. When matured at a high temperature, it gives a possibility for the use of feldspar as a main ingredient [1-2]. Colors of stoneware can be brown, red, white and most of the times beige. Firing usually takes place in oxidation atmosphere but also reduction can be rarely used. This naturally has an effect on the body colors [3]. Earth, which contains clay minerals, becomes plastic mud when mixed with water, has a capability to be easily shaped and can be hardened without cracking if fired at 900-1000 °C, is referred as one of the brick and tile raw materials [4]. Natural and aesthetic appearances of buildings obtained with brick and tile products, which make them preferable especially for construction sector, are of importance. Because clays being main raw material of that type of productions generally do not exist as pure materials in nature, their usability depends on their mineralogy and impurities they contain [5]."

Jan 1, 2008

By K. V. Sreenivas Rao

Solidification experiments have been conducted to study the effect of interface heat flux and air gap formation on cooling rate of the casting during solidification of Al-4.5wt%Cu alloy. The thermal history of the casting and mold during solidification is recorded using thermocouples connected to computer interfaced data logger. The measured temperatures in the mold are used as input to the IHCP (inverse heat conduction problem) algorithm for simulating multiple heat flux components at the boundary. It is observed that the filling effects induce spatial variation in the thermal field in the mold and casting regions and greatly influence the cooling rate of the casting. The study demonstrates the use of IHCP and in-situ measured thermal profile in analyzing the cooling rate and microstructure.

Jan 1, 2008

By Pan Gu, Zhen Zhang, Jiang Diao, Bing Xie, Hongyi Li

Viscosities of FeO-SiO2-V2O3-CaO-P2O5 slags have been measured at the temperature range of 1673 K to 1773 K (1400°C to 1500°C). This investigated system represents the major components of basic vanadium slag that is an important intermediate product of a novel vanadium extracting process, in which removal of phosphorus and extraction of vanadium can be achieved from the vanadium-containing hot metal simultaneously. It was found that higher CaO/SiO2 ratio resulted in lower viscosity in the composition range of interest. Also, the viscosities increase with the increasing P2O5 concentration. The varying viscosities can be attributed to the modification in complexity and polymerization of the slag network. The variation of apparent activation energies are in tune with the viscosity measurements. The results of this work revealed the effect of CaO/SiO2 and P2O5 on the viscous properties of FeO-SiO2- V2O3-CaO-P2O5 slags and therefore provide the theoretical foundation for the control of the coupling de-P and V-extraction process.

Jan 1, 2016

By Li Zhang

A novel green technology to recovery Titanium compounds from Ti-bearing blast furnace slag under the dynamic oxidation condition was developed and tested. Air was blown into the molten slag as oxygen resource through a lance during the dynamic oxidation process, in which six important results were found: (1) The TiC, (Ti2O3), Fe and (FeO) in the slag were oxidized; (2) The temperature of slag temperature rapidly increased; (3) The viscosity of slag decreased; (4) The coalescence, growth and drop of the metallic Fe droplets in the molten slag were carried out under an air agitation condition; (5) The dispersed Ti components were selectively enriched into the perovslite phase, and the perovskite phase could be selectively precipitate and grow. And also, the perovskite phase can be separated by the dressing method. The oxidation of molten slag gives off a large amount of heat, which helps chemical reactions proceed, improve the rate of chemical reactions, and promote the precipitation and growth of the perovskite phase. The features of the technique are clean, low cost and a great capacity to deal with a large quantity of slag. It was confirmed by experiments that the precipitation of the perovskite (CaTiO3) in molten slag is obviously affected by operation factors such as temperature, chemical composition, heat-treatment, additives and so on. The precipitating kinetics and mechanism of the perovskite phase from molten slag during the dynamic oxidation processes were also investigated.

Jan 1, 2006

By Barry T. Kilbourn

There is a continuous quest for better-performing materials, for example, to withstand higher temperatures, to resist more efficiently degradation or to be electrically conductive under extreme conditions. The oxides, and similar compounds, of the lanthanides and yttrium can, in some cases, help provide such behavior. Other advanced materials, such as hydrocarbon catalysts, optical ceramics or sensitive phosphors, may also require these oxides for some essential function. The role of the oxides in a wide variety of technologies, some novel and developing, will be reviewed and the underlying physico-chemical principles, the common threads, between several less well-known and apparently unrelated uses discussed.

Jan 1, 1989

By L. W. Beckstead

The use of acid ferric sulfate solution as a lixiviant for chalcopyrite concentrates has been of little interest from a practical standpoint due to the formation of a tenacious layer of elemental sulfur which severely impedes the reaction progress. CuFeS2 + 4Fe+3 ?Cu+2 + 5Fe+2 +2s° For example, an acid ferric sulfate leach of chalcopyrite concentrate results in only 12% copper extraction in a three hour leach at 93°C. Experimental results suggest that particle size is the only controllable variable which has a significant effect on the rate of acid ferric sulfate leaching at ambient pressure. Size reduction of the concentrate prior to leaching was exam¬ined using various methods of grinding. Of the grinding methods considered, attrition grinding was found to be the most effective. Leaching of an attritor-ground product (median particle size 0.5 microns) resulted in approximately 90% copper extraction in a three hour leach at 93°C. Energy measurements suggest that the costs associated with attrition mill¬ing are not unreasonable. Evidence indicates that "activation" or stored strain energy is not responsibile for the enhanced reaction kinetics of the finely ground concentrate, but rather the experimental results can be explained simply in terms of the increased surface area due to size reduction. Leaching reaction mech¬anisms operative in the acid ferric sulfate system are discussed and the application of ultra-fine grinding technology to other systems is considered.

Jan 1, 1976

By John E. Dutrizac, Tzong T. Chen

"Laboratory experiments were undertaken to ascertain the behaviour of various ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C and in the presence of 40 or 50 g/L of hematite seed. Copper, nickel and zinc are not significantly incorporated in hematite precipitates. Although the nickel contents increase to 0.22% as the Ni concentration increases to 60 g/L, the solid solution Ni contents are low relative to the bulk Ni contents. Thus, part of the Ni may be present as tiny particles of poorly soluble NiS04.H20. Increasing germanium concentrations to 2,000 mg/L result in products containing up to 0.59% Ge. The Ge occurs either in solid solution in the hematite or is adsorbed on the nanometer-size hematite crystallites. Increasing As(V) concentrations to 10 g/L increase the AsO4 contents of the products up to 16%. However, the products consist of hematite together with As04-containing Fe(SO4)(OH) and an unknown Fe-AsO4 species. All the hematite products contain - 1% SO4 which appears to be adsorbed on the nanometer-size hematite crystallites.IntroductionDissolved iron is a common impurity in most hydrometallurgical processing circuits and, generally, the iron must be eliminated prior to the subsequent recovery of the sought after metals. Simple neutralization of iron-rich solutions yields slurries which are difficult to thicken and filter. To address these concerns, the jarosite, goethite and hematite processes have been developed, and these technologies are able to reject the dissolved iron in a readily filterable form [1]. Despite its higher cost, the hematite process offers several potential advantages. Because hematite is an iron-rich, high-density compound, its formation would reduce the mass of residue and the size of a residue storage pond. Hematite is the thermodynamically stable form of iron under ambient conditions, and this stability would facilitate the impoundment of hematite precipitates. Furthermore, hematite has some market potential for cement manufacture and even for iron making [2]. In all the commercial hematite processes, the dissolved ferric ions are first reduced to the ferrous state. Subsequently, the pH of the solution is adjusted and the solution is then oxidized. The ferric ions gradually generated during solution oxidation hydrolyze and precipitate mostly as hematite, although commercial hematite products also contain trace or minor amounts of jarosite-type compounds. However, there are potential advantages in precipitating hematite directly from ferric ion solutions, as the reduction and subsequent oxidation of the iron are not required. Although the precipitation of hematite directly from relatively concentrated ferric sulphate solutions (up to 0.5 M Fe(SO4)is) was recently demonstrated [3], the behaviour of impurity species during hematite precipitation is largely unknown. To address this issue, systematic laboratory experiments were undertaken to ascertain the behaviour of a number of ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C, and the results are presented in this paper."

Jan 1, 2012

By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340'C by the two probe method using an ultra high resistance meter. The k value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it mouutuniocally increased from 10-5 to10-4 A' 1 cm-1 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the K value. The k value increased with the increase of Na proportion in the melt. For a 10mol% Na doped sulfur melt it was as high as max ~30 A 1cm -1 above 180 C under the irradiation of of ultrasconics.

Jan 1, 2003

By Pekka Hanniala

The falling real price level of copper metal and changes in the treatment and refining charges has been characteristic to the copper industry during the last few decades. Outokumpu's continuous development of the Flash Smelting Technology and increased productivity of the smelters based on these improvements may be one of the basic reasons that have influenced to these trends. From the early beginning of the Flash Smelting Technology, it has been characterized by low operation costs and low emissions, and the vision has been to develop the technology towards Direct Blister Flash Smelting. In Direct Blister Flash Smelting, both smelting and converting are carried out in one furnace making it possible to reduce the number of unit operation steps and thus lower both operation and investment costs. The merger of large copper production companies taken place during the last few years is a sign of a new age in copper production business. Now, the aim is to increase the productivity of copper production not just by utilizing the economy of scale but also by increasing integration and optimization of the whole production chain from mine to refinery. This also means increasing win- win based cooperation between companies. A Production Network concept based on the Flash Converting process enables existing smelters to decrease the operating costs and expand the smelting capacity with minimum investment and at the same time to decrease the emissions of the smelters. The new structure in ownership and partnership between copper production companies makes it easier to adopt the Production Network concept to both new and existing plants, where there exists a lot of built-in capacity. The paper presents Outokumpu's prediction on how the new options for the smelters will contribute to further changes in the structure of copper production. These visions are illustrated by giving examples on how the combination of matte production, Flash Converting, and Direct-to-Blister Flash Smelting could be adapted in existing and new smelters.

Jan 1, 2002

By X. K. Lan

The greater demand for high-quality large-diameter crystals has led to the robust idea of a free- flying solar-powered furnace satellite, whereby the buoyancy-driven convection effects are almost nonexistent, and diffusion-controlled crystal growth with minimal radial segregation is promoted. In the proposed solar furnace, a paraboloid of revolution imaging concentrator is used to focus the sun's radiation onto an-ampoule which holds the solid charge to be processed. The charge will start melting in the vicinity of the focal point, after which it is translated in order for the melt to resolidify as a single crystal. A ray-trace method has been developed to determine the incident concentrated solar heat flux on the ampoule surface for a perfectly-aligned configuration with an incoming columnated beam. A transient 2- dimensional conduction problem with phase change is formulated, which is solved using the commercial code FIDAP. Results highlighting the feasibility of growing GaAs, Ge and Si crystals with diameters of the order of 20 cm using the solar furnace satellite concept are presented. The transient temperature fields within various charge materials are quantified.

Jan 1, 1994

By Nan Wang

Based on the commercial computational fluid dynamics software, Fluent, a three dimensional finite-volume model has been established, and the fluid flow and heat transfer in the super-wide slab mold (cross section 3250mm×150mm) of Nanjing Iron and Steel Company has been simulated. The basic feature of flow and temperature field in a super-wide mold has been analyzed, and the effects of mold width, the submergence depth of SEN, outlet angle of SEN, casting speed, superheat and cooling rate on the flow and temperature field have been investigated. The results by comparing several simulated calculations for 3250mm×150mm slab show that a more proper fluid flow and temperature field in the super-wide mold can be obtained with 15°outlet angle, 120~150mm submergence depth of SEN and 1.2~1.4m/min casting speed. The results through numerical simulation provide a theoretical basis for optimizing the configuration design of SEN and choosing reasonable processing parameters for the continuous casting mold of super-wide slab.

Jan 1, 2009

By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340° C by the two probe method using an ultra high resistance meter. The II: value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it monotonically increased from 10-5 to 10-4 (omega) 1cm-4 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the II: value. The II: value increased with the increase of Na proportion in the melt. For a 10 mol% Na doped sulfur melt it was as high as max. ~30 (omega) 1cm-1 above 180°C under the irradiation of ultrasonics.

Jan 1, 2003

By Marie-Aline Van Ende, In-ho Jung

A thermodynamic database for the oxyfluoride system CaO-MgO-Al2O3-SiO2-Na2O-K2O-Li2OMnO- FeO-F has been developed based on the critical evaluation and optimization of all available experimental thermodynamic and phase diagram data. The developed database can be used for phase diagram and equilibrium solidification calculations for multicomponent systems and for understanding the solidification behavior of mold fluxes. Based on this thermodynamic database, a simple kinetic model was developed to simulate the interactions between the mold flux and molten steel using effective equilibrium reaction volumes combined with the thermodynamic database.

Jan 1, 2014