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By B. G. Belew

Recent operating improvements at the Phelps Dodge Chino Smelter, coupled with intensive capital expenditures since 1987, have resulted in a safer, higher quality, more productive smelter. This paper briefly reviews the flowsheet of the Chino Smelter with emphasis on recent capital expenditures. The main focus of the paper is to provide case studies of how operating functions have been improved. Case studies presented include: (1) safety, (2) anode quality control, (3) flash furnace cross-over build-up control, and (4) flash furnace temperature control. Most of these accomplishments have been achieved by providing specific measurable goals and subsequent feedback to operating crews.

Jan 1, 1993

By F. J. Tavera

The colloid flotation of lead carbonate precipitates in aqueous media is studied at a pH of 7. The flotation system consisted of five spargered flotation cells in a serial array. The flotation system was operated under controlled conditions of superficial air velocity, superficial liquid velocity, frother concentration, and collector concentration. The measured variables were gas hold-up, bubble size, superficial bubble surface flux, and lead recovery (reported to the concentrate). The experimental data show that it is possible to separate as much as 97% (w/w) lead from the aqueous media when the superficial gas velocity is 1 cm/s and the superficial liquid velocity is 0.19 cm/s.

Jan 1, 2006

By N. R. Green, N. J. Humphreys, D. McBride, T. N. Croft, M. Cross, D. M. Shevchenko

"Centrifugal casting offers a route to high quality products in difficult to cast high temperature low superheat alloys and thin section molds. Under centrifugal forces metal is forced into thin sections and can fill thicknesses of less than a millimeter. However, due to the high liquid metal velocities there is a high risk of surface turbulent flow and air entrainment within the liquid metal. The combination of interacting flow-thermal-solidification phenomena and associated defects is a challenging modeling task which the authors have previously described and validated. Capturing the metal-air interface, on what are inevitably complex three dimensional geometries, results in highly computationally expensive simulations and simulating a single cast can take weeks on a single processor. This contribution reports on modeling a complex centrifugal cast, gas entrainment, bubble transport and solidification, employing meshes of up to a million elements and investigates the scalability of the model on high performance clusters.Introduction The ultimate goal of any casting procedure is to produce a defect-free product. For difficult to cast alloys, such as Titanium, centrifugal casting has a number of advantage over conventional gravity methods [1]. In the casting of thin sections, such as turbine blades, the metal is forced into the thin sections under centrifugal forces. The centrifugal force can overcome the backpressure due to surface tension and the metal can fill mould sections with thicknesses substantially less than a millimeter. However, the materials used in these castings [2] tend to be highly reactive and requires low superheat. High liquid metal velocity gives rise to a high risk of free surface turbulent flow and of associated entrainment through free surface turbulence [3] and trapping of gas present in the flow [1]."

Jan 1, 2012

By Jong Hyeon Lee, Go-Gi Lee, Chang-Kyu Lee, Hong Youl Ryu, Sung-Koo Jo

This study deals with research on the reduction process of neodymium oxide by molten salt electrowinning. Neodymium fluoride and lithium fluoride electrolyte were used for feed stock of electrolyte and neodymium oxide was added as precursor. Cell current was confirmed that cell potential was applied as constant potential of 4.5V. Argon gas injection into the electrolyte was carried out to confirm convection effect on current efficiency. Applied current was gradually decreased without argon flow, but applied current was kept within a certain range with argon flow in electrolyte.

Jan 1, 2015

By Onuralp Yucel, Ahmet Turan, Murat Alkan, Hasan Ozer

SHS (Self-propagating High-temperature Synthesis) is one of the important methods to synthesize B4C powders. The process contains the reaction of boron oxide powders (B2O3) with magnesium reducing agent and carbon black carburizer. SHS products are leached in HCl media to purify synthesized B4C powders in the following step. In the present study, effects of various functional additives (KClO3, KHSO4, MgSO4.7H2O, NaCl, MgO and Na2SO4) in the SHS stage were carried out. Various proportions of the additives were mixed with the initial SHS charge mixtures. Two different molar ratios were employed in the initial SHS mixtures as 1:3:0.8 B2O3:Mg:C and 1:2.5:0.8 B2O3:Mg:C. After the SHS step, HCl leaching process was applied to the SHS products. Filter cakes were dried and characterized by using X-Ray Diffraction Spectroscopy, BET and chemical analysis techniques.

Jan 1, 2015

By Bingyi Bai, Wangjun Peng, Yanling Guo, Jieyu Zhang, Guoding Gao

The phase transformation of bayan obo ore with high concentration of iron and calcium was reduced at temperatures no more than 1000℃ were investigated in this study. The samples with insufficient carbon were treated at the temperature using a vertical furnace with a thermogravimetry (TG). The mineral phases and content were examined using Xray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) respectively. The complex phases of bayan obo ore transformed to some simple phases after treated with different content of carbon at the same temperature for 10 hours. The result of XRD、 XRF and TG showed that the reduction degree of Fe3O4 phase formation varied with the temperature and the carbon content of bayan obo ore.

Jan 1, 2015

A study of iron-removal from copper leachate by limestone precipitation followed by direct eltctrowinning of copper has been conducted. The influence of the process parameters: amount of precipitant, contact time, temperature, agitation intensity, solution acidity, and initial iron concentration on iron-removal was investigated. The effects of electrowinning time, cell voltage, solution acidity and temperature on electrowinning of copper were also investigated. The leachate contained 1.20 g/l cu2+ and 7.41 g/l total iron at pH 2.27. After contacting with 14 g/l precipitant for 2 hours, 97.5 % of the iron was attenuated and 98.4 % of the copper was recovered. With the following electrowinning conditions: 3 lead anodes, 3 stainless steel cathodes, 2.5 V, 39.41 A/m2 and 10.7 g/l H2S04, copper recovery-was 98.4 %. Purity of copper powder produced was greater than 99.0 %.

Jan 1, 1999

By Kazuki Morita

Dissolution mechanism and solubility of chlorine in the oxide melts, such as CaO-SiO2-Al2O3 (-Na2O), Na2O-SiO2-Al2O3 and CaO-SiO2-FeO systems, have been equilibrium technique was employed with controlled Po2 and PCl2, (Po2 = 10-6 -10 19 atm, PCl2 10-6 -10-13 atm at 1673-1748 K). The solubility of chlorine in the 40mass%CaO-40mass%SiO2- 20mass%Al2O3, slag was found to vary in proportion to Pb2/ w and pc/z/p' which proved that chlorine dissolved in the melts as C1 anion. Hence, the chloride capacity (CCI-), indicating the ability of molten oxide to absorb chlorine, has been defined as; The Ccl value was observed to increase with increasing slag basicity and temperature, and showed a reasonable relationship with that Of CS2-. Based on the result obtained in the present study, chlorine distribution during incineration with slags was predicted quantitatively.

Jan 1, 2003

By A. G. Raraz

Reactive metal electrorefining presents a number of problems that pose obstacles to commercial operation. Cerium has been chosen as the surrogate for certain reactive metals because of its thermodynamic and electrochemical characteristics. A comparative review of the properties for cerium and plutonium has been presented to justify the choice of cerium as the surrogate metal for studying electrorefining. This review has addressed the electrochemical, thermodynamic, and kinetic parameters of molten salt electrorefining of cerium metal to provide an insight to this extremely important process. The cell components and configuration, current efficiency of the process, purity of the cathodically deposited metal and the power requirement of the system are evaluated for a molten CaCl2-MgCl2 salt electrolyte using a molten, stirred impure anode. Crucible designs, salt electrolyte, cell temperature and electrode materials are also evaluated. Selection of the salt electrolyte and the cell temperature have been suggested from this study.

Jan 1, 1992

By Meyer Steinberg

"Some early experiences of a Cooper Union Chemical Engineer on the Manhattan project and his latest studies on CO2 Greenhouse Gas Mitigation Technologies are presented. Mitigating Global Greenhouse effect while maintaining a fossil fuel economy, requires improving the efficiency of conversion and utilization of fossil fuels, use of high hydrogen content fossil fuels, decarbonization of fossil fuels and sequestration of carbon and CO2 applied to all energy consuming sectors of the economy including electric power generation, materials production, transportation and industrial domestic heating. Decarbonization means removal of carbon as C or CO2 either before or after fossil fuel utilization and sequestration means long term disposal of C or CO2. The review will cover the principles of removal and recovery from power plant, stacks, the oceanographic and geological disposal of CO2 and the conversion of CO2 to gaseous and liquid transportation fuels. The global economic aspects of CO2 mitigation technologies are touched upon.IntroductionThis is an odyssey of a chemical engineer. My career started with the production of U235 at the Gaseous Diffusion Plant in Oak Ridge, Tennessee and the production of PU-239 metal at Los Alamos on the Manhattan Project. After 40 years at Brookhaven National Laboratory, I wound up performing studies on CO2 mitigation technologies. The following is a power point presentation on the subject of global warmingThe DOE is proposing to increase its sequestration development program in order to maintain the utilization of our vast resources in coal both for power and for transportation fuel production. Congress is considering steps to promote energy efficiency in attempts to solve not only the CO2 problem, but also the prime problem of energy supply. We will be promoting increases in energy efficiency as time goes on."

Jan 1, 2008

By Kouji Mimura, Masahito Uchikoshi, Minoru Isshiki

"HfO2 is expected to be a gate dielectric used in ULSI alternatives to S1O2. Although the materials used in ULSI are required to be significantly pure, commercial Hf contains > 2 mass% Zr. It is important to establish a process for removing Zr from Hf. In the present study, anion-exchange separation using a multi-column method was employed. The separation tests were carried out at variety of temperatures and flow rates. The decrease in the flow rate of the mobile phase made the elution curves of both Hf(IV) and Zr(IV) broaden contrary to the case of Co(II), Cu(II), or Fe(III). This is caused by the difference in adsorption rate on the anion exchange resin. In addition, more than one column was connected in series in order to enhance the separation. As a result, the content of Zr(IV) was successfully reduced to 1/100 of that relative to the raw material.IntroductionHafnium is one of the most important materials in modem society. The main applications of Hf metal are as a control rod in a nuclear reactors because of its large neutron-capture cross-section and as an additive to various alloys because of its corrosion resistance [1]. In addition to those applications, attention has been recently paid to HfCh as a high-x"" dielectric used in ultra large scale integration, ULSI, as well as ZrCh, AI2O3 and La2C>3, which are expected to be alternatives to conventional S1O2 thin films [2].The materials used in ULSI are required to have a high purity in order to avoid unexpected errors due to impurities. Furthermore, high purity Hf is indispensable for investigating the intrinsic properties of Hf metal. Thus, it is significant to establish the purification process for Hf from both the industrial and academic perspectives."

Jan 1, 2012

By Caisa Samuelsson, Sina Mostaghel, Theo Lehner

"Rönnskär smelter of Boliden Mineral AB, Sweden, is well known for recycling of base and precious metals. Slag from the electrical furnace is processed at the fuming plant to produce zinc clinker. The granulated slag is a by-product used as e.g. construction material. In this paper, influences of Al2O3 on mineralogy of the slag, which can affect its chemical and physical properties, are investigated. Different mixtures of Al2O3/fumed slag were prepared. Re-melting was carried out in a Thermo-Gravimetry (TG) furnace with an inert atmosphere. Scanning electron microscopy (SEM) and X-ray diffractometer (XRD) were then applied for the analyses. Investigations depict that addition of alumina to slag, results in an increase in the number of spinels and a transformation from iron rich to aluminum rich spinels. Anorthite (CaAl2Si2O8) will also be formed.IntroductionRönnskär smelter of Boliden Mineral AB is located in north of Sweden; the main products of this smelter are: Copper, Zinc clinker, Lead, Gold, and Silver, while sulphuric acid, liquid sulphuric dioxide, and Iron sand are some of the by-products. Reducing the energy consumption and decreasing the usage of finite natural resources are becoming more and more important for the Rönnskär smelter; this result in use of different recycling and scrap materials. Metal residues, from brass foundries, steel mills, and electronic scrap are recycled at Rönnskär smelter [1]. Most of the electronic scraps contain mixtures of various metals together with plastics and ceramics, which can affect the composition and properties of the slag considerably [2]. At the same time, treatment of slag and controlling its composition and properties are of much interest for Base Metals producers from different aspects. Composition of slag influences the physical properties such as: 1) Liquidus temperature [3-4] 2) Viscosity, which controls separation of valuable metals, especially copper by gravity separation [2] and also heat and mass transfer [5] 3) Electrical conductivity [6]."

Jan 1, 2008

By Sheng-hai Yang

The electrochemical synthesis was conducted in anhydrous ethanol solvent mixed with conductive reagent when tantalum plate was used as anode and stainless steel plate as cathode. The effects of different conductive reagents (such as NH4Br, (CH3)4NCl, (C4H9)4NCl), conductive reagent concentration and the space on the cell voltage and the current density were investigated. The current efficiency of electrosynthesis was more than 95%. The electrolyte, a mixed solution was then undergone air distillation and vacuum distillation to get the final product which was characterized by Fourier Transform Infrared(FTIR) spectroscopy, Raman spectra, 1H-Neclear Magnetic Resonance(1H-NMR) spectroscopy. Carbon and hydrogen contents in the product were determined by elemental analysis instrument. Results consistently show that the product was tantalum penta-ethoxide.

Jan 1, 2006

By M. D. Street

Lead and zinc production commenced in 1966 at Brunswick Smelting using the Imperial Smelting Process. In 1972 the blast furnace was modified to produce lead bullion only which was refined to corroding grade lead using conventional kettle refining techniques. Since 1972 consumption of lead concentrate and production of refined lead has doubled and this paper describes changes to operating and maintenance techniques which have contributed to this improvement. Reference is also made to improved environmental, health and hygiene practices at the smelter.

Jan 1, 1983

By Shun Fujieda, Shigeru Suzuki, Kozo Shinoda, Tetsuo Fujita

"Dowa's scorodite, synthesized by oxidation of Fe(II) ions in the presence of As(V) ions at atmospheric pressure, was characterized. The scorodite was well crystallized and had a very low solubility. To examine the conditions for stable storage of the scorodite for long periods, experiments with various synthesis and leaching conditions were done. The scorodite had a very low arsenic solubility in sea water. It was estimated in consecutive leaching tests that the arsenic concentration would eventually converge to zero. The prevention of arsenic leaching by adding goethite or ferrihydrite was limited in some cases. Very low toxicity was confirmed by toxicity tests. The investigation results suggest that disposal at a specifically designed well-controlled storage place is preferable for the scorodite whose toxicity had been made sufficiently low. Disposal to an isolated final disposal site with more stringent prevention for the outflow of toxic substances was thought another option.IntroductionArsenic is a considerable environmental concern. A system of technologies for the effective immobilization, storage and final disposal has been sought. Dowa Metals & Mining Co. Ltd. has developed a unique scorodite synthesis method (DMSP®) which works at ambient pressure [1]. The scorodite is precipitated by oxidizing Fe(II) ions in a high-concentration As(V) solution. The scorodite produced in this way does not readily release arsenic because of its high crystallinity. Final disposal is necessary because scorodite currently has no commercial value. A standard method for the final disposal of scorodite has not been established because its long-term stability under various conditions has not been fully examined."

Jan 1, 2012

By Roberto Parra

The operational control in a Flash Smelting Furnace is based on the mass and energy balance of the chemical and mineralogical composition of the concentrates. It is well known that many troubles in the dust formation and slag quality occur without a clear correlation to a specific process parameter such as the matte grade or heat balance. This paper outlines two new considerations that could both help improve the entire quality of the process: blend characterization and versatile slag composition control. Related to the blend control, laboratory scale study has shown that the magnetite and dust formation don't have a linear behavior with the weight proportion of the blend and some optimal blends of2 or 3 types of concentrates can be identified. Related to the control of stag composition, the quantification of the slag liquidus temperatures and viscosity could be an effective operational tool for both for ferrite and fayalite slag that can also directly help deciding the blending parameters. From these viewpoints the benefits of the combination of these two approaches for high temperature operation is discussed. Keywords: Optimization, Copper concentrates, Flash combustion, Blends, Slag composition

Jan 1, 2003

By Henrique Kahn

The Anitapolis alkaline massif in southern Brazil underlies a sub circular area of 6 km2. Bore-hole data show a concentric rock distribution, with mafic rocks in the central part and felsic rocks in the border zone. The rocks are covered by talus and weathered material, 30 m thick on average, and very inhomogeneous in composition. Phosphate mineralization associated mainly with two levels of the weathering mantle and with fresh rocks. A preliminary ore-type classification was based on distribution of apatite, feldspar, vermiculite, biotite-phiogopite, calcite, pyroxene, amphibole and analcime, determined by semiquantitative diffraction method. Technological tests performed on eluvial ore samples from three adits resulted in a subdivision of ore-types based on the difference in behavior due to mineral characteristics during mineral pr

Jan 1, 1991

Environmental and public concerns and the banned use of cyanide for the recovery of gold in some parts of the world have heightened the search for an alternative lixiviant to cyanide. Thiosulfate appears to be the most promising alternative to cyanide due to thiosulfate being non-toxic, relatively cheap compared to cyanide and generally gold recoveries are similar to those of cyanide. The most widely researched thiosulfate process is one where copper ions and ammonia are added to the solution. This paper reviews the leaching of gold in thiosulfate solutions and the contributions of the research at Monash University to the understanding of the gold oxidation reaction in thiosulfate solutions, the solution chemistry when copper ions, ammonia and oxygen are present, the influence of the changing solution chemistry on the gold leach kinetics, and the application of thiosulfate in the leaching of gold from ores. It is clearly shown that the gold oxidation rate is hindered in thiosulfate solutions. In the presence of copper ions the gold oxidation rate though is significantly enhanced and thus is why copper(II) is more effective than other oxidants in the thiosulfate leach system. The copper-ammonia-thiosulfate leach solution chemistry is shown to be very complex, especially in the presence of oxygen as the rate of thiosulfate oxidation increases and the majority of the copper ions are not maintained in the copper(II) oxidation state. The thiosulfate oxidation rate must also be maintained low as an intermediate thiosulfate oxidation product hinders gold leaching. In optimising the recovery of gold from ores with copper-ammonia-thiosulfate leach solutions it is important to evaluate and minimise any negative effect an ore may have on the leach solution chemistry and hence gold leaching.

Jan 1, 2003

By Tiffany Brown

In the thiosulfate gold leaching process, thiosulfate is used to complex gold following electrocatalytic oxidation of the native metal by Cu(II)-ammines. Unfortunately, Cu(II) complexes also catalyse the undesirable conversion of thiosulfate to polythionates. We have been seeking alternatives to ammonia, which fulfil the role of ammonia but minimize thiosulfate decomposition. One aspect of these studies has involved the determination of the rate of thiosulfate oxidation by the Cu(II) complexes from UV-Visible spectral changes. Various ligand classes, including pyridyls, polyamines, aminocarboxylates and picolinates, have been tested and the majority found to inhibit thiosulfate decomposition. Interesting variations in reactivity with the nature and denticity of the ligand and L/M ratio have been observed. In the case of open chain polyamine ligands with 2 to 5 nitrogen donors, the rate of thiosulfate oxidation was generally found to decrease with the denticity and the concentration of each ligand. Saturation of the Cu(II) coordination sphere appears to inhibit the oxidation of thiosulfate when excess thiosulfate is present. The Cu(II) complex of the branched polyamine ligand, tris(2-aminoethyl)amine (tren) exhibits this behaviour in excess thiosulfate. Interestingly, when the [Cu(tren)(OH2)]2+ complex is in excess oxidation of thiosulfate was observed. This unexpected finding prompted a spectrophotometric study of this reaction which has revealed that the oxidation of thiosulfate involves several processes, two of which involve the formation and decay of a tetrathionate radical.

Jan 1, 2003

By F. Leclerc, V. Rebeyrolle, M. Revil-Baudard, A. Jardy, M. Založnik, H. Combeau

"Since the quality of Vacuum Arc Remelted ingots is linked to their chemical homogeneity and metallurgical structure, a modeling study of the solidification during VAR has been undertaken. It is based on the solution of the coupled transient heat, momentum and solute transport equations during the remelting of a cylindrical ingot. Solidification mechanisms implemented in the model include a full coupling between energy and solute transport in the mushy zone, and accounting for nucleation and finite diffusion of solutes at the microscopic scale, in both solid and liquid phases. This modeling can be applied to actual multi-component alloys. In this paper, the macrosegregation in Zircaloy 4 ingots is investigated. To validate the model, one single melt of a homogeneous electrode has been specifically performed. The comparison between the predicted macrosegregation and the experimental results shows the importance of accounting for solutal convection to forecast properly the macrosegregation in remelted ingots.IntroductionVacuum Arc Remelting of zirconium alloy ingots is a key step in the manufacturing process of fuel assembly components in nuclear reactors. The control of the chemical homogeneity is indeed fundamental to ensure the quality and the in-reactor performance of the final products. Despite the use of electromagnetic stirring to homogenize the liquid melt composition, chemical heterogeneities develop in the mushy zone during the solidification stage. One of the main challenges for zirconium producers, as well as titanium producers, is to master the VAR process in order to control the macrosegregation in remelted ingots. Macrosegregation results from the association of microsegregation and transport phenomena. The latter are primarily due to the flow in the liquid and mushy parts. It is now well established [1-4] that the hydrodynamics of the melt pool in a VAR ingot depends on the combined action of the followings: thermal and solutal buoyancy, self-induced electromagnetic force and the periodic centrifugal force caused by the angular movement generated by the stirring. However, for zirconium alloy ingots, the effects of thermal and solutal buoyancy forces on macrosegregation through their influence on the flow in the mushy zone have not been clearly identified."

Jan 1, 2012