Search Documents

By G. Fazel Jahromi

Enargite, known as one of the major arsenic containing copper minerals, with approximately 19% arsenic, introduces challenges to typical processing options. In most hydrometallurgical processing methods, arsenic remediation occurs after the copper recovery in an autoclave or in a stepwise neutralization process. In this study, the in situ precipitation of scorodite was investigated during an atmospheric leaching process in the presence of carbon-based catalysts and chloride media. The effective parameters of initial ferric addition, temperature, catalyst addition, and oxygen sparging rate were studied and the ferric behaviour was monitored during the scorodite precipitation. The most influential parameters on efficient scorodite precipitation are found to be: initial ferric addition, catalyst to concentrate ratio, and temperature. A 99% scorodite precipitation yield was achieved in this process.

By X. J. Wu

Effects of various factors such as diaphragm materials, composition of electrolytes and current density on copper electrowinning from cupric chloride solutions was investigated. It is found that the crux of this process is to prevent the dissolution of copper by cupric ion and the formation of suspended CuCl precipitate. A process with high difference of copper concentrations between the feed solution and the spent electrolyte was selected. With this process, in which the feed solution contains 90 g/dm3 [Cu"], 3M NaC1, and 10mg/dm3 bone glue, and the spent electrolytes contains 10 g/dm3 [Cul, a very smooth and dense copper cathode can be produced with current efficiency above 93% and energy requirement less than 1.7 kwh/kg Cu at 25°C with N2 sparging. If a slightly higher energy requirement is permitted, smooth and dense copper cathodes can be produced at the current density up to 800 A/m2 with the identical solutions.

Jan 1, 1991

By Kenneth P. Michalek, James E. Kelly, Jonathan A. Dantzig

"Many investigations have been reported regarding the simulation of continuous casting with emphasis on in-mold heat transfer. These analyses have been limited, however, because they require either estimation or measurement of the characteristic heat transfer between the ingot and the mold. In this paper, a self-consistent model 'is presented for calculating the heat transfer between a solidifying continuous casting and the mold, in the context of the continuous casting of steel. Using both thermal and stress analyses, the air gap formed during continuous casting is calculated and used to compute the heat transfer coefficients. Iteration between the thermal and stress analyses is used to determine a self-consistent solution. IntroductionThe continuous casting process for steel is illustrated schematically in Fig. 1. Molten steel is tapped into a tundish from which it flows at a controlled rate into the continuous casting mold. The initial shell of the casting forms in the mold by transfer of heat from the metal through the mold wall to the cooling water. The remainder of the casting is solidified by application of water sprays, and/or radiation cooling below the mold.Heat transfer in the mold portion of the process is important because it controls the formation of various defects which are deleterious to subsequent processing. Examples of defects formed in this region are surface irregularities, such as cold folding and oscillation marks, and more serious defects, such as longitudinal or transverse cracks. A more catastrophic problem which may occur is a breakout, in which the shell ruptures and molten steel is discharged in an uncontrolled way."

Jan 1, 1986

By Yuan Zeping

The distributions of impurities in the copper melt, the slag and the gas phase in copper flash smelting process were under study in the Guixi smelter, particularly during operating conditions of high oxygen enrichment with production of high grade matte. Several methods for the removal of impurities such as As, Sb and Bi in the copper smelting process were developed and implemented at the Guixi smelter. This paper described the effects of high oxygen enrichment, elevated matte grade, high temperature and high production rate on the distribution of impurities, methods adopted at the smelter for the removal of impurities, and the associated benefits in the utilization of these removal techniques which include the mathematical model for material blending, high thermal intensity operation at the flash furnace, extended converter blowing, and injection of slag modifiers consisting of Na2CO3 and CaO powder mixture to the converters and anode furnaces.

Jan 1, 1999

By Zviad Kovziridze

Structure of celsian ceramics in BaO-Al2O3-SiO2system is studied with electron microscope in the entire temperature region of baking interval. The process of the pores filling and the full consolidation of material growth at comparatively high temperatures of baking intervals are described.

Jan 1, 2006

By D. D. L. Chung

"In-situ network composites are composites in which the filler network is formed during composite fabrication, in contrast to ex-situ networks which are formed prior to composite fabrication. A homogeneous in-situ network composite has the entire network at the same composition; a heterogeneous in-situ network composite has different parts of the network at different compositions. The homogeneous network composite is made either by the Method of Molten Filler Flow or the Method of Dissolution and Deposition; a heterogeneous network composite is made by the Method of Liquid-Phase Networking. Examples include polymermatrix and metal-matrix composites.IntroductionNetwork composites refer to composites containing a continuous three-dimensional network as the filler. These composites are attractive in their lack of delamination failure, which is usually characterised by two-dimensional composites. The filler and matrix in a network composite can be considered two interpenetrating networks. The mechanical interlocking of the networks adds to the cohesion of the composite. In cases where the filer is much better than the matrix in a certain property, the network nature of the filler makes the filler highly effective in improving that property in the composite in all directions. The property desired in the composite may be high strength, high modulus, low coefficient of thermal expansion, high thermal conductivity, or low electrical resistivity."

Jan 1, 1994

By W. K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating improved technology for mineral flotation. A variable often neglected in flotation control is redox potential. The use of redox control is illustrated by the separation of molybdenite from chalcopyrite. Laboratory testing showed that redox potential had a greater effect on product quality than collector addition. A significant need in froth flotation is greater reliability of the sensors used in measuring and controlling redox potential in mineral slurries. The USBM has developed an automated method for removing scale and reconditioning gold redox-sensing electrodes. Fouled electrodes are anodically polarized to 1.2 V versus the AglAgCI reference potential to remove scale. The electrodes then are conditioned by a brief potentiodynamic treatment to re-establish electrochemical equilibrium. In laboratory tests, this technique removed calcarious deposits from gold electrodes and reconditioned them for useful service in approximately 10 min. In plant practice, this technique would obviate the need for plant operators to manually polish electrodes, and also should result in greater reliability in redox measurements. Inexpensive, automated equipment to condition electrodes in a plant setting is described.

Jan 1, 1995

By Levent Özmen

Colemanite is a mineral containing varying amount of boron that is found in abundance in Turkey. It has a good possibility to be used as a flux in iron and steel industry. In this study a review of the use of colemanite, as a flux agent in steel production has been carried out and various related aspects such as its influence in metal-slag reactions, solubility of lime and magnesia in the slag are discussed along its performance in several points of views including its technical and environmental usage characteristics. Positive and negative factors of using this material as a flux are also underlined.

Jan 1, 2006

By J. E. Allen

The trend in refractory technology for the copper and nickel industries has been to higher quality raw materials and improved processing technology. These changes have been dictated by the changes in pyrometallurgical processes in these industries. For example the introduction of flash smelting, reaction type smelting and auxiliary slag cleaning furnaces havedemanded better refractories materials. Extensive field applications and improved laboratory testing procedures have helped make this transition possible. Changes in refractory technology, primarily in basic refractories, are followed from the late fifties to the present and into the future.

Jan 1, 1994

By Takashi Ikeda, Masafumi Maeda

"Demand for solar cells is increasing linearly throughout the world. Last year production totaled 3000 tons worldwide. The market size of solar silicon is expected to increase further because of international ""political"" demand to reduce carbonaceous emission from energy consumed. Most elemental silicon is produced by the carbon reduction of Silica in an electric arc furnace. Purity of silicon at this stage is 90-99%. Major impurities are Fe, Ti, Ca· and Al, and minor ones are P, B and carbon. The oxidizing metallurgical process is no longer effective to remove transitfon metals because those are less noble to silicon. Nonmetallic impurities such as phosphorus and boron must be reduced to 0.001ppm for semiconductor use. The most common process for high purity silicon is the Siemens C process, which is basically distillation of hydro-chlorinated silicon followed by CVD of SiHCl3. The cost of such silicon is expensive to allow its popular use in solar cells. Currently scrap silicon -of semiconductors is used for this; however, the supply-of that scrap is limited to just a portion of semiconductor production.In this paper world demand for silicon will be reviewed and some of the processes proposed summarized.IntroductionSilicon is element 14 in atomic number and has an atomic weight of 28.0855. Little elemental silicon is found in the earth, and it is mostly found as oxides or silicate. The Clark number of silicon is very large and the second in its number. If we were discussing the volatility of silicon element on the globe, we would never worry about it. However, it is very difficult to obtain pure elemental silicon because a high purity silicon compound is very rare. In most cases these are silica (silicon oxide SiO2). As shown in Table 1, there are many grades of silica ore classified mainly by their content of iron and alumina."

Jan 1, 2000

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. Ahokainen, J. Pitkälä, J. L. Xia, A. Jokilaakso, J. Vaamo

"The aim of the present paper is to use the two CFD codes to model the two phase flow in a water model ladle with central gas injection. The codes examined are CFX and Phoenics. An Eulerian two phase model is used and predictions are compared against the experimental data available. The results show that the codes can reasonably well predict the gas-liquid plume in the ladle, and predictions are generally in a good agreement with experimental data. However, differences do exist in predicting the gas volume fraction and velocity profiles. The results should be interpreted most carefully and cautiously, because they are very sensitive to the boundary conditions and dependent on the models for the physical phenomena involved. IntroductionSubmerged gas injection has widely been used in the metallurgical industry for more than a century. At the present, the use of gas is most effective in steelmaking industry where the advantages of the gas injection have already been long well understood. Effective mixing, large contact area between reactants, easy modifications and flexibility of the processes are the most important advantages. Disadvantages include refractory wear, blocking in the tuyeres, and splashing. These disadvantages can be reduced and advantages further improved by studying the flow phenomenon in process vessels. However, it is difficult to study flow in a real vessel because of the high temperatures and physical and mathematical modelling is therefore increasingly used in the process development work."

Jan 1, 1999

By M. Furuta

Tamano Smelter of Hibi Kyodo Smelting Co., Ltd. has been operating without a slag cleaning furnace (SCF) since its start-up in 1972. It has used its own developed coke combustion technology, the Tamano-Type Flash Smelting Furnace (T-FSF). The coke combustion technology that is the core of the process, along with the installation of a computer guided system and the improvement of the concentrate burner combustion in the T-FSF have all contributed to having acceptable copper loss levels in the slag without using a SCF. However, recently, because a high concentrate charge rate has been used in order to achieve a high matte grade in the T-FSF, a short settling time has been experienced and copper losses in the slag have become difficult to maintain at a lower level. Furthermore it is estimated that copper losses will further increase after the completion of the next expansion because with the aim of having a higher matte grade operation at 67% less coke will be charged and the reduction effect of the settler will be smaller. Therefore, in order to maintain the copper losses in the slag within proper levels the installation of SCF was decided. This paper, describes the operation before the introduction of SCF along with some theoretical considerations of slag chemistry.

Jan 1, 2006

By T. Maruyama

The Tamano Smelter of Hibi Kyodo Smelting CO. ,Ltd. went into operation in 1972. The Flash Smelting Furnace that was originally adapted was equipped with electrodes that were attached to the settler substitute of the slag cleaning furnace. Later the development of our own original coke combustion technology was promoted and a new Tamano Type Flash Smelting Furnace (T-FSF), without electrodes, was put into operation in 1988. The technology of coke combustion and combustion the burner have continued to improve. As a result the copper losses in the slag have been reduced as well as a stable operation has been achieved. Furthermore, this has been accomplished while increasing the concentration feed and the matte grade The current objective is to continue to strive for high matte grade operation and to raise production efficiency while paying attention to the important subject of copper losses in the slag. In this report, the data related to the copper loss in the slag reduction are presented along with the influence of the thickness, settling time and coke. The recent operation conditions of the T- FSF are also presented.

Jan 1, 2003

By D. G. C. Robertson

Counter-current staged reactors offer several advantages over batch reactors for mass transfer between two phases. Several metallurgical reactor designs have utilized the counter-current principle, e.g. the WORCA and QSL processes. But before the principle can be widely adopted, it will be necessary to overcome several significant problems. These include the need to minimize longitudinal mixing in a single reactor or to use several separate staged reactors and to carry out different reactions in sequence, e.g. phosphorus oxidation and sulfur reduction. Theoretical and experimental approaches to these problems will be discussed in the paper.

Jan 1, 1988

By Leszek Blacha

Since several years aog there is noted an increasing importance of the metallurgical vacuum technologies. This refers mainly to the extra furnace steel treatment processes, melting of steel and special alloys in the induction and arc vacuum furnaces, as well as refining processes of nonferrous metals. In the presented work, there is discussed a phenomenon of evaporation of volatile components of metal bath under reduced pressure with description of kinetics of this process. In this article are presented are the evaluation of the mass transfer coefficients in the melt and gaseous phase. Based on results of our own research on removal rate of impurities from liquid copper (bismuth, lead) in vacuum refining process, it is determined the thickness of hypothetical boundary layer in the gas phase. This allowed to formulate a general kinetic equation defining the evaporation rate of gaseous components from metal bath. The values of mass transfer coefficients determined from this equation were compared with experimental results by other authors working on the evaporation effect of melt components of metal alloys.

Jan 1, 2006

By Bemd. E. Langner

At Norddeutsche AfFmerie the CollaMat is an important instrument for controlling the activity of glue in copper electrolyte. Thanks to on-line measuring of the glue activity appropriate action can to taken in the event of sudden changes, such as an intemption in the glue supply, as well as long-term trends, such as continuously decreasing glue activity over days or weeks. Laboratory tests on the dependence of glue degradation on temperature have shown that relatively small increases in temperature of only 3OC cause the half change value of the glue degradation to reduce by 25 %. It is a similar picture with the sulphuric acid concentration in electrolyte. An increase in the acid concentration from 160 g/l to 200 g/l can - depending on the temperature - likewise result in a decrease in the half change value of up to 25 %.

Jan 1, 1995

By R. M. Lamya

A considerable part of gold encapsulated in some refractory sulphides can be dissolved during sulphide matrix decomposition in non-complexing aqueous media. This has been concluded from laboratory results of gold extraction from pyritic and arsenopyritic concentrate containing 172.8ppm Au, into 10% hydrochloric, sulphuric and nitric acids. The degree of sulphides decomposition in the non-oxidative acids limits the gold extraction from this specific concentrate to about 10%. In the case of nitric acid, the gold dissolution follows the rapid decomposition of sulphides, reaching 32 to 42% of extraction at almost total decomposition of the sulphidic minerals. Accumulation of gold in this acidic and non-complexing solution to several ppm was not affected by the soluble products of the sulphides decomposition. An attempt to explain this gold behaviour is undertaken and some practical implications are discussed. In the investigated concentrate the "soluble gold" is mostly associated with arsenopyrite. This is consistent with the latest findings of other authors that gold disseminated in arsenopyrite can occur as cation Au3+. In a comparative test the gold extraction into highly concentrated chloride solution, in the same oxidative conditions, amounted to 92.34%.

Jan 1, 1995

By Robert Kozicki, Eric Graham, George Wrightson

"IntroductionThe manufacture of Ferro Chromium involves the smelting of various ores and fluxes to produce the metallic product.Slag is inherent in the process. It has a much lower density than the metallic FeCr. Some chrome may be trapped in the slag as either FeCr or Cr203.Previous methods to estimate the slag in the FeCr have revolved around separating the slag and metallic portions by exploiting the differences in density. The downside with that procedure is that material will often contain pieces that are adhered FeCr and slag. The Metallic FeCr may also be completely encapsulated in the slag.An alternative and more precise method involves calculating the slag content based on chemical analysis of Mg and Al. The Mg and Al will be at relatively low levels (less than 0.1 % ) in the Metallic FeCr pieces and considerably higher in the slag (3% or greater). The overall sample will have a proportional amount and is calculated using simultaneous equations with the assumption there is only one kind of slag and one kind ofFeCr present. ""Pure"" slag and ""pure"" FeCr are needed in order to determine the Mg and Al in each. The detemlination of the Mg and Al in the overall sample would then be used to calculate the amount of slag.When the particle size is small, it is difficult to sample and get ""pure"" pieces of the slag and FeCr of sufficient quantity to perform a proper analysis. Often, historic data is used but that is dependent on the source of the FeCr and the materials used in its production. Mg and Al levels in slag can vary between 3% and 20% in different FeCr slags depending on their origin."

Jan 1, 2013

By T. Alboussiere, O. Paireau

"We have designed an experiment to simulate natural convection in a direct-chill aluminium ingot. In this experiment we induce natural convection within a hemisphere filled with liquid-metal (mercury). The device consists of a copper hemispherical bowl closed by a copper plate. The top is maintained at superheat temperature while the boundary is cooled. While the temperature measurements were found using thermocouples, the velocities were obtained using an original technical procedure that relies on MHD properties. By applying a steady local magnetic field, we measure the velocity. The distribution of temperature and velocity can be separated into a thermally stratified core bounded by thermal wall jets. These wall jets greatly influence the degree of macrosegregation in ingots.1. Natural Convection in Aluminium CastingIt is well known that the quality of the final product in aluminium casting depends on the movements within the liquid metal such as forced or thermogravitational convection. Strong buoyancy-driven flows are known to occur in the liquid metal pool of an aluminium ingot caster. These flows have a significant influence on the metallurgical structure of the ingot through the redistribution of heat, fragmented dendrites and segregated material within the pool. Macrosegregation mechanisms depend on favourable temperature and flow distributions in the sump, and these factors will determine the pattern and degree of macrosegregation. Moreover, for many years, the importance of thermally-driven natural convection in casting has been underlined (Cole & Bolling, 1965). In this way, a precise determination of the velocity and temperature fields is required in order to improve understanding of the macrosegregation mechanisms. That is precisely the aim of this paper, which provides experimental data of the flow and the temperature distributions in a natural convection experiment. We intend, with this laboratory experiment, to determine accurately the velocity field, particularly within the thermal boundary layer where the effects of the flows may have an important role in the transport of crystals."

Jan 1, 1999