Search Documents

By R. Boom, Y. V. Meteleva-Fischer, B. Kraaijveld, H. Kuntzel

"Segregation of impurities during refining of metallurgical grade silicon (MG-Si) is an option to produce solar grade silicon (SG-Si). Directional solidification is a last step in production of SG-Si effective for removal of metallic impurities. The possibility is investigated to use metallic impurities originally present in MG-Si for removing boron and phosphorus. MG-Si has been treated using two methods: 1) alloying with calcium and 2) refining with Na2O-CaO-SiO2 slag, both by controlled cooling. The microstructure of silicon and the impurities distribution have been studied before and after the treatments. Using EPMA phosphorus and boron have been detected in 1-2 wt% concentration range in several intermetallic compounds in grain boundaries after both treatments. This observation points to a different possible mechanism of silicon refining from boron and phosphorus. Controlled cooling improves migration of phosphorus and boron to the silicide phases in grain boundaries, which can be removed by acid leaching treatment.2. IntroductionStandards for silicon solar cells and growing demand on “green” energy require economical and efficient route to the production of solar grade silicon. Refining of cheap metallurgical grade silicon is one of the promising options, where application of existing metallurgical approaches can result in cost-efficient production on industrial scale. Focus in refining is on impurities, which are most difficult to remove: B, P, Al, Ti, due to their large segregation coefficient in silicon and low vapour pressure [1]. Moreover, more environmentally friendly technology in comparison to the traditional Siemens process [2] will be in accordance with societal needs. Based on properties of common impurities in metallurgical grade silicon, alloying refining and slag refining are suggested as competitive techniques having potential effect on removal of impurities harmful for conversion of solar energy [3, 4]. Alloying with Ca followed by acid leaching was found to be effective for removal of Fe and Ti from silicon [5] and to enhance also removal of boron [6] and phosphorus [7, 8]. In the work of Inoue et al. [8] drastically increasing removal of phosphorus from silicon has been observed with an increase of Ca content and a thermodynamics-based explanation was provided. Since phosphorus has been found to condense in the secondary precipitate mainly composed of CaSi2, it can be removed together with iron and titanium by consecutive acid leaching treatment. Slag refining is one of the metallurgical methods proposed to be effective for refining of metallurgical grade silicon from boron [9, 10]. Slags with additions of the following oxides to silica have shown positive effect on removal of boron: CaO [11-13], Na2O [11,14]. Mechanism of slag refining from boron is based on oxidation of boron followed by its incorporation in the slag network [9,11]; the same mechanism is suggested for refining from phosphorus taking into account that oxides of boron and phosphorus are known as network-formers [15]."

Jan 1, 2012

By John W. Ahlrichs

Microscope, electron microprobe and x-ray diffraction have been used to provide quantitative evaluation of products from the mill, smelter, refinery and other metallurgical processes. Phase compositions and their quantities are necessary for an adequate understanding of the various products obtained throughout an operation and in laboratory testing. By careful evaluation, important information can be gained in improving recoveries and increasing grades at various stages of processing. Four case histories are discussed in this paper. Quantitative microscopic counting techniques are applied to mill products to determine degrees of locking and liberation of the economic minerals. Rapid, but accurate evaluation aids the metallurgist to develop or improve the grinding and flotation circuits. In the smelter, the identification and quantification of the phases are important for predicting reaction mechanisms and kinetic trends. Mineralogic techniques have been applied to conventional smelter products, and to those obtained in laboratory tests for newly developed innovations to smelting. Small, but important, values of gold occurrences in ore are difficult to determine. Evaluation of gold usually requires special separations into various mineral concentrates, followed by assays and mineralogic determinations of the products. Numerous occurrences of solid solution constituents can be treated as by-products, but often they are deleterious to metallurgical treatment. Most solid solution problems can be unraveled by the mineralogist's tools.

Jan 1, 1981

By Ruiling DU, Jiazhi Zhang, Yong Zhao, Keng Wu

Reaction kinetics of metallurgical physical chemistry which was successfully applied in metallurgy (as ferrous metallurgy, non-ferrous metallurgy) became an important theoretical foundation for subject system of traditional metallurgy. Not only the research methods were very perfect, but also the independent structures and systems of it had been formed. One of the important tasks of metallurgical reaction engineering was the simulation of metallurgical process. And then, the mechanism of reaction process and the conversion time points of different control links should be obtained accurately. Therefore, the research methods and results of reaction kinetics in metallurgical physical chemistry were not very suitable for metallurgical reaction engineering. In order to provide the definite conditions of transmission, reaction kinetics parameters and the conversion time points of different control links for solving the transmission and reaction equations in metallurgical reaction engineering, a new method for researching kinetics mechanisms in metallurgical reaction engineering was proposed ,which was named stepwise attempt method. Then the comparison of results between the two methods and the further development of stepwise attempt method were discussed in this paper. As a new research method for reaction kinetics in metallurgical reaction engineering, stepwise attempt method could not only satisfy the development of metallurgical reaction engineering, but also provide necessary guarantees for establishing its independent subject system.

Jan 1, 2015

By Hidefusa Takahara, Koichi Miyake, Dierk Raabe

"Mechanical properties of copper wires were examined. The copper wires containing 5-10 mass % chromium and 1-3 mass % silver were produced through heavily cold deformation. It was expected that the copper wire was easily fractured during cold deformation because of the existence of brittle chromium phase in the alloy. In fact, the copper wire was fractured due to large work hardening, when the true strain [n] exceeded 5. However, the copper wire annealed at 1273K for 6 ks ·in the middle of deformation process could be smoothly drawn to 11=8. After precipitation treatment for silver phase at 473k for 1.8 ks, the wire was able to further drawn to n=8.4. The final deformed wire showed tensile strength higher than 1200MPa.IntroductionDownsizing of electronic devices has led to the demand of finer and higher strength materials for cables. Conventional copper alloys have about 800MPa in ultimate tensile strength. These strength are mainly obtained by precipitation hardening. Nowadays, a process for higher strength wire has been developed, where dual phase copper alloy is used. When it is drawn heavily, the' second phase is elongated along drawing direction and the wire gets high strength due to fiber reinforcement (1). That alloy is so called in-situ formed fiber reinforced ·alloy. Cu-Ag(2), Cu-Nb(3) and Cu-Cr(4) systems are well known as such alloys. It is also well known that chromium is brittle material except single crystal and high purity of chromium. However, Mihara et al. C5l have achieved 1 GPa in ultimate tensile strength in the Cu-Cr-Zr and Cu-Cr-Ti alloys by appropriate thermo-mechanical processing.In this study, the Cu-Cr-Ag systems were investigated: The alloys contained 10 or 5% chromium and 3 or 1 % silver. It was demonstrated that silver precipitated in copper matrix contributed on further hardening."

Jan 1, 2000

Proposed by outstanding electrochemist and electrometallurgist Prof. Raphael Agladze (191 1- 1989), process of copper and manganese co-electrowinning was enhanced to the pre- electrowinning stages: low,temperature co-leaching of copper and manganese containing materials, and to high-temperature co-roasting of the same materials with consecutive leaching. The report presents results of experimental investigations of the processes mentioned above, as well as results of thermodynamic investigations of co-roasting processes, and co- leaching processes computer modeling.

Jan 1, 1997

By Ben Bowman

For certain ferroalloy furnaces, such as ferrochrome or ferromanganese, there is still doubt about the mechanisms operating under the electrode tips. In this paper a model is built that does not call upon an arc. The medium is best described as an electrically conducting slurry, a mixture of liquids, solids and gas. There are two sources of propulsion, the Lorentz force within the conducting part and buoyancy generated by CO bubbles, creating two opposed poloidal circulation loops, downward below the electrode axis and upward further out.

Jan 1, 2014

By Zhonglin Ye, Yifeng Shi

"This paper has outlined forms of Au & Ag losses in copper smelting process and methods for increasing Au & Ag recovery, analyzed factors influencing Au & Ag recovery in copper converting process, presented Au & Ag behavior in copper electrorefining process, and reviewed effect of current density/electrolyte circulation rate during electrolysis and surface finish of cathode on Au & Ag losses. Measures and research direction for decreasing Au & Ag losses in electrolysis have also been introduced. Based on Au & Ag behavior in copper electrorefining process and previous studies by others, new approach for increasing Au & Ag recovery in copper smelter has been discussed. And brief comparison has made between continued multiplication method and equilibrium method application in the case of calculation of Au & Ag recovery in copper smelter.IntroductionAs gold and silver are the major by-products from copper smelting process, efficient Au & Ag recovery has become one of the key approaches for copper producers to increase economic efficiency. With similar physicochemical properties, Cu, Au and Ag belong to the first subgroup of elements in the same periodic table. Au and Ag will be enriched into Cu phase firstly when both matte-slag phase and copper-matte phase appear in copper smelting process. However, great changes have taken place in Au & Ag proportions into individual phase due to changes of physicochemical conditions in each smelting process. Metallurgists at home and abroad have carried out a great deal of pilot plant tests and laboratory tests in order to increase Au & Ag the former Soviet Union with regard to Au & Ag losses in copper smelting process in the 1970s and 1980s, and he proposed solutions to increase Au & Ag recovery in copper metallurgical plants. As more than 20 years passed, Jingchun Lu's paper, Discussion on Increasing Au & Ag Recovery in Copper Smelting System, remains as a literature of the most comprehensive study. Based on Jingchun Lu's literature, the authors of this paper discussed new approaches to increase Au & Ag recovery in copper metallurgical plants with combination of many researches done by other researchers for over 20 years."

Jan 1, 2013

By John L. H. Patterson

Handheld XRF has become the favorite way of measuring the content and identity of alloys in the field. This is because of the very portable nature of the instrumentation and its simple operation. However, these analyzers have been unable to determine the concentration of the light elements like Mg and Si due to the very low energy of the x-rays produced by these elements. In the past accessories such as vacuum and He flush have given some analyzers the ability to determine these light elements with modest detection limits. The introduction of the Silicon Drift Detector (SDD) into this class of instrumentation has added a new level of analysis capability to portable XRF instrumentation. X-ray fluorescence is achieved by exciting a sample with a beam of x-rays, which in recent portable equipment are generated by a small tube. This results in the emission of characteristic x-rays from the sample under test. By measuring the energy of each x-ray it is possible to determine what element generated it. By counting the number of x-rays at each energy it is possible to determine the concentration of each element. The detection limit for each element is dependent upon the number of x-rays which reach the detector. As the number of x-rays increases the detection limit will improve. One of the major factors in an x-ray reaching the detector is the energy of the x-ray. As the energy of an x-ray increases the probability of that x-ray reaching the detector increases. The energy of an x-ray is inversely proportional to the atomic number (AN) of the element generating the x-ray. For example, an iron x-ray (AN=26) is 6.40 keV while an aluminum x-ray (AN=13) is 1.49 keV. As the energy decreases, the detection of the x-ray becomes less and less probable because the x-ray may be absorbed by the windows which are part of the instrument and detector or the air in the path between the sample and detector. In SiPIN based portable XRF analyzers, the lowest element which is detected with acceptable detection limits is normally considered to be Ti (AN=22). The detection limits for 60 second measurements on typical SiPIN XRF analyzer are given in Table I. Thus, portable analyzers have not been useful for measurement of aluminum and titanium alloys as major components of these alloys are Mg (AN=12), Al (AN=13) and Si (AN=14).

Jan 1, 2009

By Willem P. C. Duyvesteyn

A novel hydrometallurgical process for Escondida copper concentrates has been developed by The Minerals Laboratory of BHP. The Escondida Process consists of concentrate leaching, solution purification, electrowinning and residue flotation. Part of the copper will be sold as high grade concentrate and part as high purity SX-EW copper. Contrary to previous efforts for the development of a hydrometallurgical process for copper concentrates, this patented process does not advocate the total dissolution of copper. It only aims for the copper that is readily soluble in a mildly oxidizing environment with an ammoniacal or acidic lixiviant. Both lixiviants were studied, but ammonia was preferred because of fast kinetics at ambient temperatures and pressures. By controlling the oxidation potential, the formation of sulfate ions and, consequently, of an ammonium sulfate byproduct, is precluded. These mild leaching conditions also prevent the dissolution of unwanted impurities and result in the production of ultra-high purity electrowon copper. Solution purification is carried out by solvent extraction with LIX-54. The very high loading capacity of this organic results in a compact SX circuit, consisting of two loading, one scrubbing, and one stripping stage. As the organic is selective for simple copper ions, the copper amine complex is broken down and free ammonia is regenerated and recycled for leaching. High purity copper cathodes are produced in a conventional sulfuric acid based electrowinning system. One scrubbing step is needed to separate the ammoniacal circuit from the acid circuit. Limiting copper dissolution to less than 50% also provides an opportunity to produce high grade concentrates by residue flotation. Copper recoveries in excess of 98% with precious metal values reporting to the final concentrate can readily be obtained. Complete breakdown of the copper mineral- pyrite middlings results in a final concentrate grade that can be even higher than the original feed material. The Escondida Process also provides an opportunity to accept lower grade copper concentrates producing improved copper recoveries in the mill and yet high quality concentrates for marketing. The Paul E. Queoeau International

Jan 1, 1993

By Zhao Hengxian

We studied the phase diagram of Na3AlFe-ZrO system, reduction of ZrO2 by aluminium and electrochemical behaviours of ZrO2 in the system. The results show that Na3ALF6-ZrO2 system is a simle eutectic one, that the velocity of reduction of ZrO2 in the system is rapid al 960'C and that the Zr content in the alloy abtained can reach as high as 2.5wt%. Potential scanning shows that there exist new current peaks on the potential scanning plats except for the cuurent peaks corresponding to the oxidation of aluminium. The method of making Al-Zr alloy in our paper has advantages over the traditional method of mixing metals.

Jan 1, 1992

By Onuralp Yiicel, Ozlem Okur, Murat Alkan

"In this study, Co-Cr-Mo alloys were produced using a mixture of Co304, Cr203 and Mo03 powders with Al powders by a Self-propagating high temperature synthesis process. SHS is a process of material synthesis that has revealed a number of reactants combinations capable of much higher energy release than conventional explosives. Al203 is added to the mixture to decrease the adiabatic temperature of the system. The thermodynamic simulations and the calculations of adiabatic temperature were examined with FactSage 6.2. In the SHS experiments, different Co304/ Cr203/Mo03 ratios were examined, and their effects on the metal recovery and alloy compositions were carried out. The samples were characterized by using chemical analysis, XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis (SHS) has significant advantages compared to the high technology furnace applications, such as very short processing time, simple operation, low energy requirement and low cost [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. This work aims to establish a scientific and engineering background in the production of some cast Co-Cr-Mo master alloys via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys."

Jan 1, 2013

By G. C. Yao

Branch and needle-shaped intermctallic compounds of iron, silicon and aluminum normally exist in the molten aluminum. If a suitable amount of manganese metal is added into molten aluminum, the shape of the intermallie compound particlcs may become lumpish and spherical. According to the difference in electric and magnetic properties of these impurity particles and molten aluminum, these impurity intermctallie compound particles can be separated by applying an alternating magnetic field. In this experiment the alternating magnetic field was formed by a "C" type loop with AC (50Hz) current. The inner vacuum of the fireclay refractory separator is 25>< 15" 130mm3 with a lateral baffle inside. The separator was put into the interspace of the "C" type loop. It was found that the longer the separation time, the larger the amount transferred of impurities. The amount of transferred impurities increases with the increase of separation time and intensity of magnetic field. The addition of manganese metal enhanees signifieantly the efficiency of impurity separation.

Jan 1, 2003

By José R. de Tenorio

The aim of the present work was to investigate the reduction process of MnO~FeO-Si02 slags by carbon-saturated liquid iron. The effect of the initial Mn content in the bath was explored. The initial Mn content was in the range of 0 up to 40 wt. %. The MnO content in the slag was kept constant at 40 wt. %. Tests were performed in laboratory apparatus. Samples of slags and bath were taken. In the first 5 minutes, it was observed a very strong reduction of FeO. This first step promoted a MnO-Si02 enrichment of the slag and a formation of CO bubbles, which increases the slag level. The increase ofMn content decreases the MnO reduction rate.

Jan 1, 1996

By Tailoka F.

Various metallurgical residues from iron and steel making processes have been treated by chlorination in excess air with hydrogen chloride gas generated from the combustion of scrap polyvinyl chloride (PVC). The residues include dust from both the electric arc and blast &maces, hydrocyclone overflow, zinc - lead blast furnace slags and dust rich in zinc and copper from copper refining. Chlorination is achieved either directly by mixing the residues with scrap PVC or indirectly in a two furnace system. In the latter, scrap PVC is combusted between 523 and 573 K in a horizontal furnace and the resulting gases are then reacted with metallurgical residues in a vertical furnace at 1166 to 1329 K. Gas chromatography, thermogravimetric measurements, XRD and AAS have been utilised to study the reactions. The recovery of non ferrous metals is as high as 80 to 90 % and only a negligible amount of iron is carried over. The optimum temperature for combustion is between 518 and 573 K. Above 600 K, the evolution of HCI is so fast that sufficient chlorination is not achieved. Analysis showed that no dioxins were present in the gases, the residues or the chlorides.

Jan 1, 1997

By K. J. Cathro

A hydrometallurgical process is described for the recovery of copper from chalcopyrite concentrates. The process is based on a cupric chloride leach, the concentrate having first been "activated" by heating it with sulphur at a temperature near 400°C. This activation process converts most of the iron of the chalcopyrite to pyrite, which is insoluble in the cupric chloride leachant. The copper is converted to the mineral idaite, which dissolves readily in hot cupric chloride: at 106°C, 98% of the copper is extracted in a three-stage countercurrent leach, the leaching tirqe being 1 hour per stage. The sulphur of the chalcopyrite appears as elemental sulphur, which is recycled for the activation of further concentrate, the final leach residue consisting of pyrite, plus the gangue present in the original concentrate. The copper extracted can be recovered by electrowinning, using a diaphragm cell. Current efficiency (one-electron basis) is about 70% but the cell voltage is only about 1 V, so that power consumption is three times lower than for the conventional sulphate electrowinning process. The leachant is simultaneously regenerated in the anode compartment. The behaviour of minor elements in the concentrate has also been studied.

Jan 1, 1976

By Wenjun Duan, Zongliang Zuo, Qingbo Yu, Qin Qin, Junxiang Liu

Moving bed has been widely used in the field of heat and mass transfer and reaction between solid particles and gas. In order to enhance the heat exchange coefficient, there will be tube banks inserted in the moving bed. In the process of drying ammoniates particles or heat recovery from high-temperature particles with moving bed, the particles flow behavior around the tube banks is significant. In this paper, the particles flow behavior around the tube banks is investigated, and all the results can provide guidance for the design and operation of a moving bed.

Jan 1, 2016

By Robert D. Pehlke

"Current continuous casting processes are going through a rapid evolution of advances and new developments. At the same time, intense efforts are being directed to the development of radical new technologies such as continuous casting of thin slabs and strip steel.Traditionally, the casting processes for steel have been anticipated by the development and implementation of processes in the non-ferrous industry. This trend is reviewed and what it may portend for steel is described.IntroductionThe continuous casting of steel has been a widely adopted process in the production of steel. The concepts for this processing go back into the early and mid 1800's; however, commerical development was delayed for a variety of reasons until the mid twentieth century.Beginning in the early 1960's, adoption of continuous casting was initiated and continues at this point in time to be accelerated. In Japan, more than 90% of the steel produced is continuously cast (1). More than 50% of the steel produced in the United States is continuously cast and this fraction continues to rise (2). Numerous examples can be cited of installations costing well over $200,000,000 which have provided a payoff in less than a year and a half. As this process has continued to be applied and its technology to increase, computer control systems have been installed. In particular, in the larger plants producing slabs, sophisticated computer systems involving the integration and networking of mini-computers, micro-computers, and mainframe including back-up systems at all levels are being utilized. Pehlke (3), and Harabuchi and Pehlke (4) have described the structure of these systems."

Jan 1, 1988

By G. C. Yao

Iron and silicon impurities can form needle and branch shape intermetallie compounds in molten aluminum when there is no manganese. It is difficult to separate them from molten aluminum by electromagnetic separation. The Fe-Si-AI and Fe-AI intcrmetallic compounds were transformed into Mn-Fe-Si-AI and Mn-Fe-AI compounds by the addition of manganesc into molten aluminum, In molten aluminum the morphology of these intermetallic compound particles is lumpish and spherical. Migration resistance of these impurity particles is small, which is beneficial to separation. FeSiMnAl4 and FeMnAl6 arc paramagnetic. These impurity particles can be moved by magnetic force and can be separated from the molten aluminum.

Jan 1, 2003

By James R. Myers

A source of clean gas containing sulfur dioxide and sufficient oxygen for convers.ion to sulfur trioxide ?is essential to the production of sulfuric acid. S02 containing gases obtained from roasting sulfide ores are heavily contaminated with inorganic dust and volatile impurities. If not removed, these contaminants will reduce product acid quality, foul the catalyst beds and mist eliminators, and accelerate equipment corrosion. This paper reviews conventional gas cleaning systems for metallurgical acid plants, followed by a discussion of modern systems utilizing DynaWave Scrubber technology. This technology is based on a unique approach to? gas scrubbing that can concurrently accomplish several gas cleaning/processing tasks scrubbing liquid is injected into the gas stream to create. a "Froth Zone". This is a region of extreme turbulence, with a very high rate of liquid .surface renewal. It efficiently removes both particulate matter and gas contaminants, and is also a cost effective quenching device for gases as hot as 1250º C. Smelter

Jan 1, 1992

By Allan MacRae

Freeport-McMoRan Inc. operates an ISASMELTTM furnace for the smelting of copper concentrate at the Miami Smelter in Claypool, Arizona. In May 2017, the furnace was restarted after incorporating newly designed copper cooling elements from just above the tap hole to the underside of the roof. The objective of the improved cooling design was to extend campaign life by eliminating existing failure mechanisms with the wall refractory. In addition to upgraded bathline coolers and complete coverage of the gas offtake transition, or ‘kettle’, with plate coolers, a novel arrangement of coolers was installed in the remaining freeboard area. The shell required significant cutting and re-stiffening, as well as extensive modification of the cooling water piping. Based on performance observed to date, it is expected that smelter throughput will be increased due to extended ISASMELTTM refractory campaign life.