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By Nils Eivind Kamfjord, Roar Jensen, Ingeborg Solheim

"SINTEF has carried out several pilot scale silicon process experiments in the past, but always with an open off gas system. In order to test the possibilities in running a semi closed furnace operation, a new off gas hood has been designed and tested. The off gas hood is designed to collect all off gases to gain insight into the phase compositions in the off gas and at the same time have the opportunity to monitor and maintain the charging/stoking of the furnace. The furnace hood has regulation and control of the air inlet into the combustion zone in two different heights. The off gas temperature and composition was continuously monitored and analyzed during the experiment. In order to expand the knowledge on NOx- formation in silicon metal production, such information is vital.IntroductionBecause of the negative environmental impact, the attention towards all kinds of NOX emissions increases in Norway. The authorities’ demand towards better surveillance and control of emissions increases as well.Earlier and new industrial measurements in FeSi- and Si-metal furnaces reveal quite high NOX-emission. The measurements also show that the NOX formation (mainly as thermal NOX) is distinct connected to the formation of dust (SiO?SiO2) in the combustion chamber above the furnace surface, when the temperature is high and the access to N2/O2 is good. This means that stoking, charging and temperature straight above the furnace surface is important factors for the NOX formation."

Jan 1, 2012

By J. Antonio Barrera-Godinez, S. E. James, J. Sun

The solvent extraction separation of iron from a zinc sulfate medium using DEHPA was investigated. After loading, the ferric ions were reduced in the organic phase using metallic zinc. The ferrous ions produced could be easily stripped into a sulfate solution with pH values in the range of 1.4 to 2.0. The small, laboratory scale pilot system used in this study allowed for continuous cycling of the organic and strip aqueous solutions. It was possible to establish and evaluate a series of steady state conditions under selected operating paiameters. The effects of processing parameters such as solution chemistry, flow rates, zinc metal loading and pH on iron recovery and efficiency were also evaluated. Under proper conditions, it was possible to remove about 5 g/L iron from the organic phase in one stage and to produce a concentrated iron sulfate strip solution containing ferrous ion concentrations in the range of 90 to 130 g/L. Preliminary feasibility tests were also made on electrowinning metallic iron from the strip solutions and crystallizing ferrous sulfate as a means of making a marketable iron product.

Jan 1, 2000

By M. Drozd

Multi-use pad operators require an efficient and economic method to destroy cyanide in their process residues so new material can be stored on the pad and leached. Operators of the dedicated or single-use pads require an effective cyanide destruction method for pad closure. Cyanide destruction can be accomplished by utilizing oxidants such as hydrogen peroxide or calcium hypochlorite, or by utilizing ferrous sulfate which sequesters the cyanide in strong acid dissociable complex. Ferrous sulfate can be the preferred method of cyanide destruction because it is a less costly chemical, reaction rates are almost immediate and unlike oxidants, it can penetrate the total depth of a pile without being destroyed by side reactions. Literature indicates that the (Fe(CN)6)-4 com~lex is produced slowly but it appears that complexes such as Fe(CN)4(H20)2-or Fe(CN)4(OH)2)-4, are formed quickly and should have no U.V. sensitifity, unlike (Fe(CN)6)-4. Stoichiometry of the testwork indicates that Fe«CN)4(OH)2)-4 complex may be the species formed. The usage of ferrous sulfate has the advantage of being able to bring ~ level down that divalent metal ions such as Cu++, Cd++, Hg++, Pb++ and Zn will form insoluble complexes and precipitate from solutions does not destroy weak acid dissolvable complexes and can leave a heavy metal problem behind after cyanide destruction.

Jan 1, 1990

By Guy Deschênes

In spite of the wide use of lead compounds to enhance cyanidation of free milling sulphide-bearing gold ores, an industrial control method was only implemented four years ago. This study presents the results of the investigation that led to the development of the on-line control technology. Two free milling sulphide-bearing gold ores and high purity minerals were used to develop and test the concept. The first ore contains 2.8 g/t Au, 6.2% pyrrhotite, 2.1% pyrite 0.6 % arsenopyrite, 0.1% chalcopyrite and 0.1% organic carbon. The second ore contains 10.4 g/t Au, 3.2% pyrite, 0.8% pyrrhotite and 0.38% chalcopyrite. The first ore showed a much higher oxidation rate in the pre-leach than the second one and consumed seven times more cyanide. A relation between the formation of thiosulphate and thiocyanate and the additions of lead nitrate were quantified. The ?reducing power?, a titration with permanganate, predominantly determines the concentration of thiosulphate and thiocyanate in cyanide solution. The relation between the reducing power and the addition of lead nitrate at various concentrations of pyrrhotite and chalcopyrite in the ores was established, providing a monitor/control strategy for lead nitrate addition.

Jan 1, 2006

By Akira Yazawa

The composition of ferrous calcium silicate slag is located on the tie line between FeOx and calcium silicates in ternary FeOx-SiO2-CaO system. This slag has never been used as copper smelting slag because of high sulfidic copper solubility. However, when the dissolved copper in slag is just oxidic, as in direct white metal production or in converting process, this slag is quite attractive and can be regarded as the third copper smelting slag after fayalite and calcium ferrite slags. Based on the authors' studies on phase separation thermodynamics and laboratory experiments, it was clarified that the oxidic copper loss in this ferrous calcium silicate slag become the minimum not only %Cu in slag but also the total copper loss when the amount of slag is taken into account. It has been proven that calcium ferrite slag is suitable for continuous converting where the dissolved copper is oxidic, but there exist some drawbacks such as limited solubility of silica, low lead removability and too high fluidity. To overcome these difficulties accompanying traditional slags, ferrous calcium silicate slag is the hopeful alternative. In view of the general trends of modem copper smelting processes, the interesting features of this new slag system are discussed.

Jan 1, 1999

By Mohamed Ahmed, A. Kawy

"Smelting of scrap copper and residual anodes and cathodes carried out in a reverberatory type furnace. In this, deoxidation process is carried out by wood, which acts as a resource of reduction gases such carbon monoxide, hydrogen and methane. Use of wood causes the formation of soot pollutants and efficiency of oxygen removal from copper is low leading to added costs in removing contaminants. This expensive problem was solved by using of reformed natural gas as a source of reduction gases (CO+ H2).IntroductionThree reverberatory furnaces were used for smelting of scrap copper and residual anodes and cathodes. Each furnace had a 7tpd capacity and was operated at 1183 °C.In this furnace, Step1-compressed air supplied by tubes from the side of the furnace to remove sulfur from copper matte by oxidation .The copper is also oxidized to copper oxide .[1]Step 2- copper from matte is deoxidized by a reductant. Typically deoxidation process is carried out using wood as a resource of carbon monoxide, hydrogen and methane which are the reduction gases. Use of wood causes the following:1- Forms soot pollutants2- Oxygen removal efficiency from copper is low; more contamination in copper matte increased energy in deoxidation3-the process is highly expensive.In the recent trends, this problem has been solved by using reformed natural gas as a source of reduction gases (CO+ H) .This results in 1-Reduced pollution during smelting.2- High efficiency in the removal of oxygen from copper to produce oxygen free copper. The surface of copper produced from this method is smooth which helps in forming and machining.3- Low cost and natural gas is more readily available in Egypt than wood."

Jan 1, 2010

By Roberto Parreiras Tavares, Frederico da Costa Fernandes, Guilherme Antonio Defendi, Vangleik Ferreira da Cruz, Júlio César de Sousa Pena

"Near-net-shape casting is an important area of research in the iron and steel industry today. Among the near-net-shape casting processes, the single-belt caster seems to be the most promising, since it is the only one that can achieve levels of productivity similar to those obtained with conventional continuous casting machines. One of the most important aspects in the single-belt casting is the feeding system used to deliver liquid metal over the belt. This system determines the velocity distribution and the levels of turbulence of the liquid metal and affects the quality of the strips. In the present work, a metal delivery system having a simple geometry was proposed. Using the CFD code CFX 5.6, a mathematical model to simulate three-dimensional turbulent fluid flow and heat transfer in that system has been developed. This model was used to analyze different configurations of the metal delivery system and the free surface shape of the fluid was also determined. A physical model of the feeding system was built and used to validate the predictions of the mathematical model. The fluid flow calculations have been validated by dye injection experiments and laser doppler anemometry. Measurements of the free surface levels have also been performed. These experiments provided supporting evidence for the predictions of the mathematical model.IntroductionTo maintain its competitiveness in the present market, the metallurgical sector, particularly the steelmaking companies, are developing new techniques of production. Some of these new processes are focussed on the strip casting technologies. Among these technologies, the SingleBelt process is considered the most interesting option, reducing the number of rolling steps and, consequently, the final cost of the product, especially the part associated to the energy consumption (fuel and/or electric energy). This process can also reach levels of productivity that can not be matched by other strip casting methods(1). One of the most important aspects concerning these new processes is related to the liquid metal delivery system. This system can have a significant effect on the final quality of the strips, since it determines the velocity distribution and the levels of turbulence of the liquid metal."

Jan 1, 2004

By Alain Jardy, Thibaut Quatravaux, Denis Ablitzer

"A numerical model of the Vacuum Arc Remelting process has been developed and applied to simulate remelting of various metallic materials, such as specialty steels, titanium and zirconium alloys. In practice, electromagnetic stirring is sometimes used, resulting in a complex 3D molten metal flow. After having validated the numerical model for different remelting conditions, we can use it to study the effect of applying a constant or alternated magnetic field on the thermohydrodynamic behaviour of the melt pool. The intensity of flow turbulence, computed with a classical k-E model, is shown to depend strongly on the nature of electromagnetic stirring.IntroductionThe principle of the Vacuum Arc Remelting (VAR) process, illustrated in figure I, consists in melting a consumable metallic electrode of the required grade under a high vacuum, in order to obtain a sound ingot of good structural quality.During remelting, an electric arc is maintained between the tip of the electrode and the top of the secondary ingot, in order to ensure melting of the electrode. The metal droplets fall through the arc plasma and progressively buid up the ingot, which solidifies in contact with the walls of a water-cooled copper crucible. The secondary ingot formed in this way contains three distinct zones, corresponding to the liquid pool, fully solidified metal and intermediate mushy zone. In order to stabilize the arc, it can be confined with the aid of a magnetic field created by an external induction coil. This field can also be used to stir the liquid metal, the rotation induced being in the orthoradial direction. By reversing periodically the coil current, stirring can be alternated."

Jan 1, 2004

Roasting treatments were investigated to remove arsenic from a nickel concentrate. The main arsenic minerals and their proportions in the concentrate were niccolite (NiAs)-50%, gersdorffite (NiAsS)-40% and arsenopyrite (FeAsS)-10%. Thermal analysis showed that gersdorffite and niccolite began decomposing when heated above 640 and 830°C respectively. The maximum roasting temperature was limited by agglomeration of the concentrate above 900°C. A small vibrated bed reactor was used to investigate the effects of temperature and gas flowrate, the latter to sweep away evolved arsenic. At 900°C, 24% of the original arsenic remained in the concentrate. SEM examination of the calcine showed that the residual arsenic was associated with the calcium in the gangue minerals. Additions of sulphur (either as elemental sulphur or from pyrite) facilitated the decomposition of the arsenic-containing minerals, decreased reaction with calcium in the gangue and produced calcine containing 4-6% of the original arsenic. Treatment with chlorine during roasting was effective in reducing the arsenic content to similar levels. Generation of chlorine in the bed by sulphation of CaC12 also produced encouraging results. Arsenic, Nickel Concentrate, Roasting, Chlorine, Sulphur, Gersdorffite, Niccolite

Jan 1, 2005

By Alex Luyima, Jaan Kers, Lifeng Zhang

"The pyrolysis of PWBs was investigated by a TG-DTA-MS furnace at 300–1173 K. The kinetics and the control of emitted gas during the pyrolysis of PWBs with and without chemical additives were studied. Moreover, the possibility of controlling the amount of toxic exhaust gases like HBr, C6H6, Br2, Cl2, HCl gas and recovering beneficial gaseous fuels like CH4 and H2 from pyrolysis process is discussed. The MS data for each PWB sample were examined as a function of temperature and particular m/z values could be associated with the mass loss steps in the TG data. The degradation of the organic material was characterized by m/z = 2, 16, 18, 28, 36, 44, 71, 78, 81, and 160. Fe2O3 was the best inhibitor of toxic HBr and C6H6 when compared to Al2O3, CaO Y-zeolite and ZSM-5. Moreover, it had no significant effect on the valuable H2 and CH4 gas evolution. This selective inhibition of toxic gases while maintaining the valuable ones make Fe2O3 the best candidate among the investigated additives in controlling gas emissions from PWB pyrolysis process.IntroductionThe electronic and electric industry is one of the world’s largest and fastest growing manufacturing sectors. As a consequence of this growth, electrical and electronic waste (e-waste), such as computers, washing machines, printers, mobile phones, television sets, stereos, radios, etc., is generated in large quantities around the world. Printed wiring boards (PWBs) are a common component of many electronic and electric systems.[1]. The rapid development and expansion of the electronics industry over the past several decades have led to a dramatic increase in the production of PWBs and a corresponding increase in the amount of waste generated from both production and disposal. The environmental impacts of the treatment and recycling of PWBs waste have become a major concern [1-2]. PWBs are particularly problematic to recycle because of the heterogeneous mix of organic material, metals, and glass fiber [1]."

Jan 1, 2012

By Luiz A. Teixeira

This paper reports the results of kinetic studies involving the precipitation of arsenic from aqueous solutions as FeAs041 Fe(OH)3' using FeS04 as source of Fe ions, and Air or H202 as oxidizing agents. Both systems lead to an efficient removal of arsenic. The differences in oxidants performances are in the precipitation reaction rate -much faster using hydrogen peroxide. Mechanisms of reactions were suggested based on the following main steps:

Jan 1, 1996

By Qian Li, Li-chen Hou, Yong-bin Yang, Tao Jiang, Jian-jun Hu, Bing Xu

Extraction of gold from refractory gold concentrates usually requires an oxidation step to remove arsenides、sulphides and carbonaceous matter. In this investigation, the gold concentrates were two-stage roasted under different atmospheres and temperatures. Results indicated that at the first stage, under neutral atmosphere, the removal rate of arsenic increases as the temperature rises. Under the oxidizing atmosphere, with the increase of temperature, arsenic content in the residued calcine increases, in addition, the volatilization of arsenic is also affected by the oxidation of carbon that generated CO, which is advantageous to the decomposition of arsenate decomposition. At the second stage of roasting, it is the higher temperature and stronger oxidizing atmosphere, the faster sulfur and carbon oxidated rate is, but at the same time, the calcine appears the phenomenon of consolidation because of the phase of silicate compounds generate.

Jan 1, 2015

By Kelly J. Driscoll

Impure zinc (98.5%) was electrorefined to high purity zinc (99.995%) using a fused salt electrolyte of molar composition 1: 1 : 1 :2 ZnCI2:KCl:NaCl:LiCl with a current efficiency of about 90% at 723 K. A recessed channel electrorefining cell was developed which achieved excellent mixing of both the metal and the electrolyte and by ensuring a very small anode to cathode spacing the voltage drop across the cell was 0.16 V and at a current density of 7kA m-2. The physical characteristics of the cell were observed using a low temperature model which showed the formation of droplets and rivulets which provided mixing. The application of this approach to the refining of other non-ferrous metals is discussed.

Jan 1, 1992

By A. J. van der Zeeuw

The use of SME 529 in the extraction of copper from acidic liquors and of copper and nickel from ammoniacal solutions, is illustrated with results of laboratory and bench scale mixer/settler experiments. Special features of SME 529 are its high loading capacity and the ability to keep the complexes dissolved in the organic phase up to quite high concentrations.

Jan 1, 1976

By A. Navarra

Within conventional copper and nickel-copper sulfide smelters, ladles of molten matte are fed into converters. These converters blast oxygen-enriched air into the matte, thereby eliminating iron and sulfur. The converting reactions are exothermic and, indeed, the converter heat balance is often a limiting consideration on the smelter throughput. If a portion of the matte were fed in solidified (granulated) form, this would support higher oxygen enrichment, and lower volumes of converter offgas, allowing higher throughput. This approach is not applied in conventional smelters, partly because of the copious amounts of water that must be evaporated in typical granulators, as in the Kennecott-Outotec process. The current paper recalls a waterless matte granulator that had been pioneered in the 1990’s, and is applicable to conventional smelters. A mathematical formulation is presented that can be used in the context of simulation-based optimization, to estimate the size and impact of waterless matte granulation.

By Sang Han Son

The vapor pressures of FeCI2 and ZnC12 in the FeCl2-ZnCl2 system were measured by the transpiration method at 873K and 917K. The vapor pressure data were interpreted to indicate the formation of complex ions in the FeCl2-ZnCl2 melts. It is presumed that the complex molecule FeZnCl4 as well as FeCI2 and ZnCI2 exists in the vapors in equilibrium with molten FeCl2-ZnCl2 mixtures. The activities in the FeCl2-ZnCI2 system are shown a negative deviation from Raoult's law. These results suggest the formation of complex ions such as ZnCl42- in molten FeCI2-ZnCI2 mixtures.

Jan 1, 2003

By M. Misra

The removal of lead and other heavy metals present in an active US Army small arms firing range soil was evaluated in a pilot scale test program at Ft. Polk, Louisiana. Two different acid based extraction processes in conjunction with conventional physical separation methods were used. Physical separation processes consisting of screening and gravity operations removed most of the coarse lead particulates and slugs. Hydrochloric acid leaching followed by precipitation of lead as hydroxide recycled clean soil containing less than 500 mg/L. total lead and less than 5 mg/L TCLP lead. Lead extraction efficiency with hydrochloric acid was 96 percent. The results of lead removal by physical separation in conjunction with acetic acid leaching were not consistent over the whole test period and the total soil processed.

Jan 1, 1998

By Youngkook Lee

The precipitation kinetics of NbC in ferrite matrix of the Nb microalloyed steel was investigated experimentally and numerically. The mole fractions of NbC precipitates formed at different isothermal temperatures were measured as a function of holding time by electrical resistivity test and were compared with both a mathematical model based on time-dependent nucleation and growth rates and the hardness. There is a good match among the calculated and measured precipitation kinetics of NbC and the hardness. The isothermal precipitation-temperature-time diagram of NbC in ferrite matrix of the Nb microalloyed steel was newly generated. Keywords: Precipitation, Carbide, Ferrite, Nucleation, Growth, etc

Jan 1, 2003

By W. G. Davenport

Chapter 10 showed that any given smelting task, e.g. production of 65% Cu matte, 1500 K, from CuFeS2, can be done with many different combinations of: blast%02 hydrocarbon fuel blast temperature. This chapter repeats the Chapter 10 calculations but reports the results in terms of the mass industrial oxygen mass hydrocarbon fuel blast preheat energy combinations that will produce 65% Cu matte, 1500 K, from CuFeS2 concentrate. It also determines the energy inputs equivalent to these combinations.

Jan 1, 2001

By John Wallace, Chib Iheagwara

"Refinements in sensor design have produced low-cost rugged elements to act as loop coupled with stable detection hardware for eddy current measurement in difficult environments. This has allowed direct dimension gauging of nonferrous and ferrous products above the curie point for absolute dimensions and electrical conductivities independently. The software was developed for the analysis of electrical conductivity profiles in CZ silicon crystal growth, then refined for monitoring bar properties and tube properties. Since in most metal working operations, speeds at the minimum of a few hundred feet per minute are encountered the design of the gauge was optimized for a rapid measurement. Independently extracting electrical conductivity provides data in some metal systems for determining the temperature of the monitored product.IntroductionThe primary reason for the use of eddy currents in gauging is that in hostile environments of metal working techniques such as laser gauging and ultrasonics are not always robust enough for in process measurements. Our goal is to use the technique of eddy current measurement as a quantitative control element in various hot and cold processing operations. Inspection in the early stages of metal and semiconductor processing is usually too costly to introduce in a well developed process and these tools are usually only employed in process development. Until recently there has been no efficient general analysis to allow real time measurements in the cylindrical and the probe geometry that could separate dimensional changes from material property changes both which effect the eddy current response. The basis for these measurements is that forward electromagnetic problem for conductors can be solved exactly for the test geometry which allows an inverse analysis to be made by relaxing the dimensions and conductivity to values which reproduce the measured response[!]. This transformation is based on analysis developed in Robert Siegfried' s thesis and was explored both by modeling and by physical measurement. This analysis was extended over the last few years to allow a more compact data set to be used to exact physical properties. The main result was that the technique would work on high ·quality physical data on as little as three test frequencies with the penalty being that the analysis is computational intensive. The main result of this work was that a quantitative inverse analysis of eddy current response would allow a general instrument to be used for a variety of measurements rather than being tailored for a specific measurement on a specific material test geometry. The development of these instruments has progressed over the last ten years for monitoring real time solidification, crystal growth[2] and hot seamless tube forming where the use of standards in traditional eddy current is limiting. The specific instrument design was dictated by the requirements of the algorithm for both frequency selection and levels of systematic noise that could be tolerated. Because the data is need for real time information this dictated that the system be a parallel multifrequency eddy current instrument feeding the same sensor. The sensor have to be simple and robust and usually a single loop or several loop of heat resistant wire or tube. This presentation is about using inversion of multifrequency eddy current data in real time to produce dimensional and property data on cylindrical conductors and planar conductors in real time. The object of the measurements is to produce dimensional outputs on measurements of conducting material without having to establish a detailed standard for each material or size tested. The dimensional measurements using eddy currents is complicated by material variations in conductivity due to temperature and composition. Those variations that are not geometric are often not of critical interest and complicate the measurement. The dimensional changes are often of more importance"

Jan 1, 1997