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By Bruno Lebon, Koulis Pericleous, Georgi Djambazov, Mayur Patel

"High speed compressible jets are used in a number of steel-making applications. In the case of the BOF, a compressible oxygen jet reacts with a carbon-rich iron bath to reduce carbon levels and produce steel. The intensity of the process is governed by the speed of the jet and by the size and shape of the depression created in the metal and slag by the force of the jet, i.e. by the corresponding free surface. This is a difficult CFD problem, since there are compressible and incompressible regions in the flow domain, which need to be handled differently in a finite-volume (FV) pressure-correction scheme. Also, standard turbulence models do not account for compressibility, or the large difference in density between the cold oxygen jet and the hot reacting surroundings. Corrections are introduced to the k-E model to remedy this deficiency and the results are validated against experimental data. The compressible/incompressible boundary is handled through a transition region, based on Mach number.IntroductionThe deformation of a free surface by a compressible high speed jet is of paramount engineering interest, particularly for understanding the physical processes within a Basic Oxygen Furnace (BOF). In a BOF, a supersonic oxygen jet impinges on a molten iron surface, thereby creating a cavity. Oxygen penetrates the bath and removes carbon, resulting in low carbon steel [1].The challenges in modelling such a process lie in coupling a solution domain with distinct compressible and incompressible regions and in dealing with large density differences between the modelled gas and liquid. The modelling of compressibility within the jet is crucial, since the correct velocity profile in the jet is required to determine the cavity depth with accuracy."

Jan 1, 2012

By Keith M. Axler

This report addresses issues specific to the generation of hydrogen fluoride via reaction of calcium fluoride with sulfuric acid. This process has been established on a commercial scale and is under consideration for treatment of calcium fluoride residues from uranium processing. Magnesium fluoride slags are also available as a product of uranium processing. The technique of using sulfuric acid for the production of hydrogen fluoride from magnesium fluoride is also under consideration as a residue processing scheme. In the current study, thermodynamic modeling was used to investigate these chemical processing systems. The results presented herein reveal information relevant to the selection of processing temperatures and conditions. Details include predicted effects in system composition based on operating temperatures for both the calcium fluoride and the magnesium fluoride systems.

Jan 1, 1996

By Kexin Jiao, Huichang Song, Zhijia Zhang, Jianliang Zhang, Zhengjian Liu

A clear understanding of iron carburization reaction occurring between molten iron and carbonaceous materials is of great importance in blast furnace, and it is one of the hot spots that ironmaking workers pay close attention to. Although carburization rates between iron and coke have been studied, the factors directly controlling it have not been clearly identified. This study focused on the kinetics analysis of iron carburization reaction. Sulfur content was determined as having positive influence on graphite carburizing reaction rate in the range of 0.02% - 0.06%. The values of apparent activation energy calculated by the experiment are consistent with the existing literature, which in turn proved the reliability of the experimental data.

Jan 1, 2015

By Tianming Sun, Gabriella Tranell, Ragnhild E. Aune, Mark William Kennedy

Rare Earth Elements (REEs) are critical for the production of many advanced materials and products. Mining and primary production of REEs are generally associated with significant environmental impacts. By recovery of REEs from secondary sources, through recycling or as a byproduct, the adverse environmental impacts may be partly avoided. In the present study apatite concentrate originating from iron ore beneficiation done by LKAB in Kiruna, Sweden, is explored as a possible source for REEs. The composition and distribution of the REEs within the concentrates are studied using ICP-MS, XRD and SEM-EDS/EPMA, as well as the melting point and heat of fusion using DTA-TGA-MS. The behavior of the material during melting has also been studied through wetting and slag saturation experiments. The overall aim of the study is to evaluate the implications for future smelting experiments aimed at concentration and recovery of the REEs.

Jan 1, 2015

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

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

Jan 1, 1998

By D. Mukerjee, Ramen Datta, Sanak Mishra, R. Veeraraghavan, K. L. Rohira

"Recent efforts at Steel Authority of India Limited (SAIL) has led to the successful development of atmospheric and marine corrosion resistant high tensile Thermo Mechanically Treated (TMT) bars with minimum specified yield strength of 50 kg.mm-2. These rebars are increasingly being used for a wide range of end-applications, namely, concrete reinforcement structures, bridges, flyovers, dams etc. Welding is an important processing tool for each of the above applications. In view of the importance of welding, a comprehensive evaluation of the weldability properties has been carried for the two grades of steels using Submerged Metal Arc Welding (SMAW) process; the most popularly used technique of welding of reinforcement bars (re bars).Implant tests were conducted to assess the cold cracking susceptibility of the steels. The static fatigue limit (SFL) value, determined for the atmospheric corrosion resistant (Cu-TMT) rebars under no preheat and no rebalcing conditions was found to be 63.8 kg mm-2, which was significantly higher than the Minimum Specified Yield Strength (MSYS) (50 kg.mm-2). This indicates adequate resistance to hydrogen induced cracking (HIC). On the other hand, the SFL value obtained for the marine corrosion resistant rebars (Cu-Cr TMT) under no preheat, no rebaking conditions was found to be inconsistent. Repeat of the test with fully rebaked electrodes (350°C-2h) resulted in a high SFL value (60.3 kg mm-2)_The rigidity of the structure or restraint influences the susceptibility of the weld joint to cracking. The cracking tendency increases with restraint intensity (K) of an assembly. The critical restraint intensities determined for the two steels were found to be· in excess of 1680 kg/mm.mm, indicating good welding behaviour with the following welding conditions : for Cu-TMT rebars with no preheat and no rebaking and for Cu-Cr TMT rebars with no preheat and fully baked electrodes; that is under low hydrogen levels."

Jan 1, 1998

By Chunyang Guan, Jilai Xue, Zengjie Wang, Qiaochu Liu

Molten salts electrolysis method to prepare Al-RE alloys has attracted increasing attention recently. CaCl2 and Na3AlF6 were the most often used melts for this purpose. In this work, Al-Sc alloys prepared by electrolytic deposition process in both CaCl2 and Na3AlF6 melts were investigated, respectively. It was found that Sc distributes almost uniformly and Sc contents increase with increasing current intensity in both melts. Current efficiency was measured for comparison among various current densities applied. The alloy products were analyzed using XRD and SEM, where the formation behaviors of Al-Sc intermetallics were investigated in details. The experimental and theoretical results demonstrate that Al3Sc and Al0.968Sc0.032 are the major precipitates in the Al-Sc alloys prepared by molten electrolysis. The results are useful for selection and optimization of the molten salts compositions and the parameters of electrolysis operation.

Jan 1, 2015

By Young-Chul Kang

The Onsan Copper Smelter of LG-Nikko Copper Inc. is a unique plant, which has been operating two smelting processes since 1998. The operation of the first one was started in 1979 with a capacity of 80,000tpy of copper in concentrates utilizing Outokumpu flash-smelting technology. The other one was started in 1998 based on Mitsubishi continuous process with a capacity of 160,000 tpy of copper in concentrates. Through several expansion projects, the total smelting capacity of both processes is expected to reach 430,00Otpy of copper in concentrates towards the end of 2002. This article describes operation advantages of having two different processes at one plant and comparative operation results in terms of productivity, impurity distribution, energy consumption and environment issues and etc.

Jan 1, 2003

By Nicole de Jager, Michael J. Nicol

"In order to liberate gold from refractory gold ores and concentrates it is generally necessary to oxidise the surrounding sulphide minerals, typically pyrite and arsenopyrite. Traditional methods of oxidation include pressure leaching, roasting and bacterial oxidation. In recent years, bacterial and pressure oxidation have found increasing favour, although these methods are by no means completely satisfactory and each is subject to particular disadvantages.A novel process has been developed as an alternative to the traditional methods whereby electro-generated ferrate(VI) ions in alkaline solution are used to oxidise a pyrite concentrate. This process has been observed to proceed fairly rapidly and could prove to be a more economically viable process, as well as being more environmentally acceptable. As an added benefit, operating in an alkaline environment is advantageous for downstream cyanidation processes.Ferrate(VI) is a relatively unknown species, due mainly to its instability in acidic solutions. However, in alkaline solution it has been observed to be sufficiently stable for use as an oxidant when used under favourable conditions. Ferrate(VI) is most conveniently manufactured electrolytically via the dissolution of high-carbon anodes in strongly alkaline solutions. Some literature has been published on the electrolytic generation of ferrate(VI) and relatively high efficiencies have been observed by both the authors and other researchers.This study utilises both electrochemical techniques and leaching experiments to examine the kinetics of the oxidation of pyrite by ferrate(VI), which is produced electrolytically. Cyclic voltammetry, rotating disk voltammetry and potential step experiments have been used to investigate the kinetics and mechanism of the oxidation process."

Jan 1, 1997

By K. Nona C. Liddell

There is a significant amount of early work that has been largely forgotten that deals with the validity of the pseudo-steady approximation for liquid-solid reactions. Much of this was originally published in the chemical engineering literature but is highly relevant to hydrometallurgical processes. The purpose of this paper is to summarize some criteria that were been developed by various authors for determining the error associated with use of shrinking core models for liquid-solid systems.

Jan 1, 2002

By F. E. Wagner, L. J. Cabri, Y. G. Safonov, N. S. Bortnikov, A. D. Genkin, J. Friedl, G. N. Gamyanin

"A multidisciplinary investigation (including INAA, SIMS, EPMA, and Mossbauer Spectroscopy) was used to characterize gold in four of the largest Siberian mesothermal sulfide gold deposits. These are the Olympiada (""'750 metric tons gold) and Veduga (estimated at 75-100 metric tons gold) deposits in the Enisei Mountain Range and the Nezhdaninskoye (z500 metric tons gold) and Sentachan deposits in the Verchoyansk-Kolyma area. It was found that some of the mineralization is refractory in all four deposits, largely due to the occurrence of ""invisible"" gold in arsenopyrite as well as within pyrite, but with a lesser concentration. The gold concentration and its distribution varies considerably both within and between arsenopyrite grains, with implications for processing options such as heap leaching. The ore most likely to be amenable to heap leaching is the oxidized ore of the #4 orebody of the Olympiada deposit, but further quantitative mineralogical investigations are recommended for this orebody's sulfide ore and for the ores of the Nezhdaninskoye deposit. Following a full mineralogical characterization, it is possible that economic viability will depend on a combination of pre-concentration with or without pre-treatment, followed by heap leaching of some tailings products.Acknowledgements· The Russian authors performed this study under an ""Eco res"" Project which was financially supported by the Ministry of Science and New Technology of the Russian Federation. C.J. Stanley wishes to thank John Spratt and Terry Williams for help with EPMA. F.E. Wagner acknowledges the Deutsche Forschungsgemeinschaft for a grant supporting the Mossbauer studies. L.J. Cabri is grateful to the following: M. Beaulne, D. Carson and J.H.G. Laflamme for technical support, K.E. Haque for technical comments, and D.M. Hausen and W. Petruk for editorial suggestions."

Jan 1, 1997

By R. E. Brewer

Pilot scale flotation tests were conducted with a l?ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pet of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated. The tailings were first water leached at approximately 60? C, and the water-leached tailings, containing approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH' and sodium sulfide addition on gold flotation recovery and redox potentials were examined. Maximum gold flotation recovery, 36 pct, was achieved at pH 8,5 with a sodium sulfide addition of 0.18 Ib/st. Overall gold recovery by leaching and flotation was in the range of 70 to 80 pet.

Jan 1, 1989

By S. Suzuki, Y. Maeda, N. Wakamatsu

"A new pyrometallugical technology, named KLS process, has been developed by Dowa Mining at its Kosaka Smelter to smelt various kinds of lead raw materials.The process consists of clearly separated two reaction steps, smelting and reduction. For this purpose, respective stationary furnaces are installed which are connected by a slag launder.Dry raw materials, together with pulverized coal and oxygen-enriched air, are injected through a lance pipe into the molten slag in the first furnace. It is kept under a high oxygen potential to remove sulfur completely. Resultant PbO rich slag overflows to the second furnace where pulverized coal and insufficient air are also injected through a lance pipe to reduce PbO to lead bullion and to compensate for thermal deficit. The entire operation is carried out continuously. The process development started back in 1981. In late 1986, a pilot plant with a capacity of 3.5t/H was constructed.Already nearly 20,000 tons of raw materials, mostly lead sulfate mixtures have been smelted successfully.IntroductionFor a long time, main raw materials for lead smelting at Kosaka smelter have been such secondary incombustibles as lead sulfate and lead-barium sulfate. The former is leach residue of the copper smelter flue dust and the latter originates from Iijima zinc refinery. While the most of lead concentrates produced locally has been smelted by an ISF of Hachinohe smelter in which Dowa Mining has a share.The surplus lead concentrates were processed at Kosaka by a hydrometallurgical method to convert PbS to PbSO 4 as pretreatment, and followed by simultaneous smelting together with the above secondary materials (1). Approximate output has been 1,5000 /M of lead bullion and slightly more than 2,000t/M of refined lead by adding lead bullion returned back from Hachinohe smelter (2)."

Jan 1, 1988

By R. F. Hammen

Heavy metal contamination of water is a problem of immense national and international proportions. However, effective cleanup is complicated both by the toxicity and the low concentrations of metals in wastewater streams. Using high performance chelation chromatography, the solid phase extraction and purification of extremely dilute metals from water was highly effective. The process is based on selective displacement of metals from a chromatographic column containing a chelating resin. The resin is characterized by extremely efficient adsorption kinetics which allow rapid and complete removal of the metals.

Jan 1, 1993

By R. Stefaniuk, T. Le, J-Y Huôt, H. Henein

"One of the most important process variables in gas atomization is the gas to metal (G/M) mass ratio as it has a direct effect on the mean particle size of the atomized powder. If this ratio can be controlled during the atomization process, the powder produced would be more uniform and the d50 more predictable. Thus, atomization using a tundish or gravity feed from a crucible would be more stable. In gas atomization, the gas flow rate can be easily monitored; while it is very difficult to determine the molten metal flow rate. This research paper presents a new method of recording the molten metal height with time using a conducting metal height detector. The metal height recorded in real time during atomization was used to characterize using a model the friction losses in the metal delivery system. It is found that the integrity of the metal delivery tube and the cleanliness of the melt play a key role in the maintaining a stable metal feed.IntroductionIn the gas atomization process, molten metal is normally fed to the system either continuously using a tundish or in most cases a certain amount of metal is melted in a crucible and flows into the atomizing chamber under gravity. In the first case, the metal flow rate is believed to be constant during the atomization process despite the presence of slag or dross on the molten metal surface. In the second case, the amount of molten metal is depleted with time and the rate at which the metal flow decreases with time varies from test to test in a seemingly unpredictable fashion.' Furthermore, most atomization systems are confined units and the metal level in the crucible cannot be detected by a visualization method. In industry as well as in laboratories, the metal flow rate is normally calculated on either the mass of input material or the mass of total production divided by the duration of the test. This figure is not accurate enough and obviously cannot be used as a control parameter for the gas to metal ratio as it is only determined after the completion of an atomization run. The need exists for a metal flow rate measurement and control methodology; thereby the d50 of the powder produced may be estimated and controlled in real time. Clearly, the smaller the variation of the G/M ratio during the atomization process the more uniform the powder produced and hence the size of the particles can be predicted."

Jan 1, 1994

By Martin Brueggemann

In 1993, the El Paso Smelter began operation of the first commercial CONTOP copper smelting furnace. The CONTOP process was chosen for the plant modernization due to its low capital cost and the ease that it could be incorporated into a 100 year old existing smelter. After four years of operation, CONTOP has proved itself to be a reliable copper smelting technology. This paper will discuss a brief start-up history, current operation, and future modifications and improvements.

Jan 1, 1998

By Peter R. Sanford

Cyanides are present as a dilute constituent of streams from a variety of metallurgical and mineral-processing operations. In addition, a cyanide concentration in excess of approximately 100ppb is toxic to aquatic life, and consequently these operations require a waste-treatment process to reduce the already dilute cyanide species by several orders of magnitude. Furthermore, the waste streams may have flowrates in excess of a million gallons per day. The paper reports on research conducted with a laboratory?scale electrochemical porous (graphite felt) electrode (anode) flow-reactor, which was conducted in conjunction with a computer-aided simulation of a mathematical model describing the intrinsic rate-phenomena associate with the electrode processes. The laboratory-scale cell, of rectilinear geometry, was found to be capable of reducing a feed-stream anolyte (KCN-KOH and supporting electrolyte of a single salt ? K2SO4) with a cyanide concentration of 10ppm, to less than 100ppb, at current efficiencies in the neighborhood of 50%. The computer simulation of the cell performance based on the mathematical model (and constraints imposed for tractability) was found to provide only for qualitative agreement.

Jan 1, 1998

By B. Zilbergleyt

Current understanding of chemical equilibrium is based exclusively on the probabilistic considerations that are correct for isolated systems with only one chemical reaction to take place. For the systems with multiple chemical interactions, current paradigm of chemical thermodynamics promotes the idea of openness, artificially flavored with coefficients of thermodynamic activity. Recently introduced thermodynamics of chemical systems and the Method of Chemical Dynamics (MCD) offer explicit accounting for the multiple chemical interactions within the system. In the new theory, thermodynamic equilibrium of the j-subsystem obeys the logistic equation derived exclusively from the currently recognized concepts of thermodynamics. Having the only one new parameter -the subsystem's reduced chaotic temperature 'tj to describe external interactions, and reaction extent Ilj as independent variable, this equation covers the whole domain of the system's possible states from true thermodynamic equilibrium through the open equilibrium to bifurcations and chaos depending on the 'tj value. The MCD brings new opportunities to thermodynamic simulation of complex metallurgical and chemical systems, allowing for the analysis of their domains of states and the area limits, and for more accurate calculation of the equilibrium compositions. Its usage is exemplified in this paper by several applications. Keywords: chemical thermodynamics, open systems. complex systems, chemical dynamics.

Jan 1, 2003

By S. I. Sobol

Completeness of cobalt recovery from slag requires decomposition of maggemite and non - ferrous metal desorption with polymerized silicon-acid. Cobalt losses are reduced in leaching tai1s up to 200 g/t of iron.

Jan 1, 1993

By Guo Xian Jian

In this paper, the effects of matte grade, flux grain size, blast flowrate and blast O2 content on the process of silica flux melting in a copper converter were investigated. The results showed that the blast flowrate and the blast 02 content were not significant factors in the melting process. However, with an increase in grain size of flux and grade of matte, the amount of the flux molten decreased. The data on the melt rate of process correspond well with the mathematical model which simulates the chemical reactions occurring at the interface. The kinetic equations of melting are as follow:

Jan 1, 1996