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By Edgar Blanco

A thermodynamic and experimental investigation to develop a new process for converting molybdenite concentrate to molybdenum dioxide by a water-vapor oxidation process was carried out. In addition, the behavior of rhenium and selenium in molybdenum concentrate during the process was investigated. The kinetics of the reaction were determined by measuring the weight change of a sample with time in water vapor at temperatures between 700-1000°C. The results were analyzed by a Shrinking Unreacted Core model under chemical reaction control, which showed an activation energy value of 102 kJ/mol. To determine the behavior of rhenium and selenium, their concentrations in the molybdenum sulfide and the product molybdenum dioxide were measured by the use of ICP. While most rhenium remained with the molybdenum dioxide after the water vapor oxidation, almost all selenium volatilized. These results agree with thermodynamic analysis.

Jan 1, 2006

By Shadia J. Ikhmayies

"Cadmium sulfide (CdS) in the form of thin films is an interesting material because it has a large variety of applications ranging from photovoltaic to luminescent devices. N-type CdS is usually used as a window layer in the heterojunction CdS/CdTe thin film solar cells. A review of the photoluminescence (PL) spectra ofn-type CdS thin films prepared by different techniques was performed. The effects of different dopants and impurities and the effects of temperature and deposition parameters on the PL spectra were discussed. Annealing in different atmospheres causes the changes in material structure and phase change from cubic to hexagonal phase which can be detected through the variations in the PL spectra. CdCh heat treatment improves the cystallinity of the films and enhances the exciton peaks and the green band in the PL spectra.IntroductionThin CdS films deserve attention because their expected gap emission lies very close to the highest sensitivity of the human eye. Thus, one might assume that thin CdS films are an appealing host for photonic devices [ l]. They have been used in a lot of applications including electronic and optoelectronic devices [2]. Thin films ofn-type CdS are widely used as a window layer in heterojunction solar cells such as CdS/CdTe solar cells. Doped and undoped CdS thin films can be obtained by different techniques such as; spray pyrolysis (SP) [3], chemical bath deposition (CBD) [2, 4], pulsed laser deposition [5, 6, 7], laser ablation [l], thermal evaporation [8].Several experimental techniques have been used in order to study semiconductor defects. In particular, photoluminescence (PL) has been shown as a powerful and sensitive tool in examining the crystal quality of polycrystalline thin films. PL can be used in the detection of defects which are radiative active. These defects can also act as traps in the transport of carriers [9]. The photoluminescence (PL) of thin film CdS is strongly influenced by the unbalanced stoichiometry, which is typical for CdS and is in general evoked by a Cd surplus. With increasing Cd content, the emission spectra move far below the gap to the red spectral range. Besides stoichiometry problems, independent of the material deposited, the PL properties of thin films depend on surface features and the influence of the interface between the film material and the substrate [10]."

Jan 1, 2013

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002

By Toru Taniguchi

In the Mitsubishi smelting furnace, copper concentrate, silica sand and water granulated slag from the converting furnace are injected through the process lances, together with oxygen enriched air, into the melt. Because bath smelting is used, the rates of particles/melt and gas/melt reactions are high enough and therefore tine grinding of the solid materials is' not necessary. Among these reactions, the dissolution rate of silica sand is the slowest and limits the overall reactions in the smelting furnace. Information on the dissolution rate of silica sand plays an important role for design of a new furnace. Theoretical calculations of the dissolution rate .of silica particles have been reported elsewhere. The authors conducted cold model experiments and could verify the calculation. In this paper, the dependence of dissolution rates of particles on the gas blowing rate, particle size and solid penetration depth in the bath is discussed.

Jan 1, 2002

By Daniel Kim, Justin McAllister, Shijie Wang

"At the Kennecott Utah Copper Refinery, impurities in the electrolyte are being precipitated in the circulation system and form a hard scale in the piping. This scale must be removed periodically for proper electrolyte flow. Distinct layers of differing composition form as the operating conditions of the tank house change. Scale samples from the inlet and outlet pipes were analyzed to discover the nature of the precipitates. Each sample was sectioned and examined under optical microscopy and SEM. The composition of the scale was analyzed using ICP, XRD, and SEM/EDX mapping. The rate of deposition was determined by measuring the amount deposited on new pipes after elapsed time intervals. In order to determine how to minimize the formation of the scale, the mechanism was studied and the results are presented in this paper.IntroductionIn copper electrorefining, impure copper anodes are refined into pure copper cathodes. The impurities from the anodes are either insoluble and report to the slimes or soluble and dissolve concentrating in the electrolyte. These impurities are controlled by bleeding electrolyte from the system. Over time, the impurities combine to precipitate a hard scale on the surfaces contacted by the electrolyte. The scale causes problems with tank house circulation systems. In order for the refinery to operate properly, the scale must be removed periodically from the walls of the pipes. The first step to control the buildup of scale on the pipes is to understand the composition and the phases that are present in the scale."

Jan 1, 2012

By Mitsuru Tanahashi

Oxidation removal of boron from molten silicon by injecting oxygen and highly basic CaO-CaF2flux powder has been investigated with special attention to the dynamic behavior of the injected flux particles and gas bubbles. Since oxygen gas is injected into the melt, high oxygen partial pressure is maintained at the flux-O2-Si interface and the removal of boron proceeds under nonequilibrium conditions. By applying this process, boron concentration in metallurgical-grade silicon can be reduced to a single-ppm level. In this paper, the effects of the dynamic behavior of the flux particles injected into the silicon melt and the area of the reaction field (the flux-O2-Siinterface) formed in the vicinity of the flux-gas exit of the injection nozzle on the rate of the boron removal are discussed from the viewpoint of process dynamics. The experimental results clarified that the boron removal rate is affected by the kinetic energy of the flux particles which is determined by the injection conditions, such as the gas-flow rate of oxygen and the size of the flux particles. At higher oxygen gas-flow rates, the injected flux particles are expected to possess a significantly high kinetic energy such that they penetrate the O2-Si interface formed at the nozzle exit, which results in the formation of a new reaction field for boron removal. On the other hand, at lower gas-flow rates, the injected flux particles possess too low kinetic energy to penetrate the interface. In this case where the formation of the reaction field is limited, it is shown experimentally that the rate of the boron removal is constant, independently of the flux injection rate.

Jan 1, 2006

By R. Gampala

The consolidation of mom matrix composite monotapes occurs by the plastic (time independant) and creep deformation of monotape asperities. Past models of the process used seperate micromechanical analyses of the contact deformation by (rate independent) plasticity and power law creep (i.e steady state creep). These models are now used to simulate consolidation and to optimize/control consolidation process cycles so that the composite's microstructure is "steered" to, a user defined goal state. However, the models do not incorporate the sometimes dominant transient creep process and the instantaneous response of the plasticity mechanism causes finite discontinuities in the microstructure state vector field and therefore eliminates the possibility of using the powerful array of trajectory optimization schemes that all require continuous vector field for optimization and control. To overcome this problem, a inified creep/plasticity constitutive model that results in a continuous state vector field is used to rederive the contact deformation response during monotape consolidation. The contact blunting of a laterally constrained hemispherical asperity is first analyzed and its response represented by two coefficients; one relating the contact area to the blunting strain (C), the second, the mean contact pressure to the blunting rate (F).The C and F coefficients for this unified blunting problem are then obtained by finite element analysis, and detailed results presented for two composite matri-ces of topical interest (Ti-24A1-11Nb and Ti-6Al-4V).

Jan 1, 1996

By Osamu Takeda

A decomposition process for PCBs by using basic molten salts as a reaction field was investigated in order to establish a safe, simple and highly efficient decomposition process for polychlorobiphenyls (PCBs). PCB containing chlorine (e.g. 2, 2?, 4, 4?-tetrachlorobiphenyl) dissolved in n-nonane solution was supplied into basic molten salts (NaOH-Na2CO3 or KOH-K2CO3) maintained at 500-700 ?C together with the carrier gas (N2-21% O2) through an injection tube. The injected PCBs in a bubble are decomposed by the reaction with the molten salts and oxygen during rise in the molten salts. The decomposition efficiency of PCBs increased with increasing temperature and was achieved to be higher than 99.995% in a certain condition. From a series of systematic study, the effectiveness of the decomposition process for PCBs by using molten salts was demonstrated.

Jan 1, 2008

By Guo Xueyi

The electrochemical couple behavior of manganese dioxide with ferrous/ferric ions in acidic chloride medium was investigated, It was proven that the dissolution of Mn01 is due to the electrochemical couple reaction between MnO2/Mn2+ and Fe2+/lFe3+ in the solution, The driving force for the process originates from the rest potential difference of the two couples. The reduction of Mn02 is controlled by clectrochemical kinetics, whereas the conversion of F e2+ to Fe3+ is limited by diffusion, The factors such as the Mn2+, Fe2+, Fe3+, Cl concentration, pH of the solution and the temperature, have much influence on the kinetics of the couple process, This study will be useful to elucidate the mechanism for the leaching of manganese nodule from the deep ocean as well as manganese dioxide ores in land,

Jan 1, 2003

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from the University of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from the University of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from theUniversity of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from theUniversity of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from theUniversity of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

By A. J. Schindler, F-P Sawyer, T. Logan, M. L. Shutey-McCann, R. M. Perry

"Test work on biooxidation pretreatment of low-grade refractory gold ores has been ongoing at Newmont Gold Company since 1988, including laboratory testing and pilot biooxidation heaps (360 to 23,000 tonne). Metallurgical results of the biooxidation process utilizing Thiobacillus ferrooxidans (T. ferrooxiddans) have culminated in the design, construction, and operation of a biooxidation demonstration facility. The facility has processed 708,000 tonnes of refractory ore, using a batched process with separate pads for biooxidation and ammonium thiosulfate gold extraction. Siliceous sulfidic refractory (SSR) and carbonaceous sulfidic refractory (CSR) ores are treated separately during biooxidation pretreatment unit operation. Following biooxidation, the ores are neutralization with lime and placed on oxide leach pads or stacked on the ammonium thiosulfate leach pad. Gold is leached with either cyanide for SSR ores or ammonium thiosulfate for preg-robbing CSR ores.This paper will only address the biooxidation pretreatment process of the SSR and CSR ores.AcknowledgmentsThe authors appreciate the cooperation and approval of Newmont Gold Company Carlin Operations management for its support and permission to publish this paper. The paper draws on efforts and assistance of the following people and several others which are to many to list who participated over the past five years in bringing this project to its fruition: Dr. James A. Brierley, Chief Microbiologist, Newmont Metallurgical Services; Dr. Rong-Yu Wan, Metallurgical Manager, Newmont Metallurgical Services."

Jan 1, 1997

By Jinqian Zhao, Jiarong Li, Shizhong Liu

"Creep cavitation of in single crystal (SX) superalloy was investigated. The constant load creep tests, in single crystal superalloys DD6, were conducted at the conditions of 800°C/700MPa, 850°C/550MPa and 900°C/450MPa, respectively. It was found that there were square facets on the stress fracture surface, and microscopic cavities in the ruptured specimens in the vicinity of the fracture surface. Both the square facets on the fracture surface and microscopic cavities in the section of the ruptured specimens show the morphology of the same thing at the different views, namely creep cavities, which are take the form of flatten cuboid. In fact, creep cavities are the longitudinally tensiled creep cracks slowly growing during the stress tensiling. The factors of creep cracks nucleation and growth conditions include: (a) enough high temperature to activate diffusion (b) casting pores as nucleation origination (c) high strains and strain rates. Eventually, the instantaneous fracture mechanism of creep specimen is cleavage fracture.IntroductionFor the materials used in elevated temperature service, creep behavior has to be accounted for. It is well recognized that creep rupture in polycrystalline materials at high temperature occurs principally by the nucleation and growth of microscopic cavities at grain boundaries, followed by microscopic cavities linkage to form micro- and eventually macro-intergranular cracks[l,2]. Without the usual grain boundaries, SX superalloys have superior capabilities at high temperatures to polycrystalline superalloys, and have become an established feature of gas turbine technology where they are commonly employed in the manufacture of high performance blades[3]. A considerable amount of work has been done over the past tens of years, and many models for nucleation and growth of creep cavities have been proposed, however, those are mainly for polycrystalline materials.In order to improve creep resistance that single crystal superalloys, in which grain boundaries are removed, have been developed. Because there don't exist grain boundaries in SX superalloy, the mechanism of nucleation and growth of creep cavities must be different from that in polycrystalline materials.Understanding the formation and characteristics of creep cavitation is crucial to model the lives of single crystal superalloys.M. Marchionni and L.G. Zhao et al. found that there were square facets on the stress fracture surface [4,5]. Roger C. Reed pointed out creep cavities lie in the necked region[6]. In this paper, the effects on the formation of creep cavities are discussed, as well as the morphology of creep cavities and fracture mechanism of SX superalloys."

Jan 1, 2013

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 Wankun Wang, Shixing Wang, Jinhui Peng, Zebiao Zhang

"Germanium leaching from germanium dust and fume was carried out using sulphuric acid. Response surface methodology (RSM), based on a five level, four variable central composite design (CCD), was employed to obtain the best possible combination of liquid/solid ratio (Xi: 2-10), leaching time (X2: 1-5 h), sulphuric acid concentration (X3:3.15-15.75mol/L) and leaching temperature (X4:50-90 *C) for germanium leaching. The obtained experimental data were fit to a one-order polynomial equation using multiple regression analysis and also analyzed by analysis of variance (ANOVA). The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The optimum extraction conditions were: liquid/solid ratio of 10, leaching time of 1 h, sulphuric acid concentration of 15.75 mol/L, and leaching temperature of 87.8 'C. Under these conditions, the germanium leaching extent was 65.14%, which is in close agreement with the value predicted by the model. The samples were characterized before and after leaching using X-ray diffraction (XRD).IntroductionResponse surface methodology (RSM) is one of the relevant multivariate techniques which can deal with multivariant experimental design strategy, statistical modeling and process optimization [1-15]. It is used to examine the relationship between one or more response variables and a set of quantitative experimental variables or factors. This method is often employed after the vital controllable factors are identified. It is also used to find the factor settings that optimize the response. Designs of this type are usually chosen when a curvature in the response surface is suspected [6], The process optimization of the sulphuric acid leaching of germanium from germanium dust and fume has not been reported in the literature. Hence the present work intends to assess the effects of variables such as liquid/solid ratio, leaching time, sulphuric acid concentration and leaching temperature and to identify the optimum conditions using RSM. The characteristics of sample before and after leaching are assessed using the advanced analytical instruments such as X-ray diffraction (XRD)."

Jan 1, 2012

By Keuncheol Choi, Yonghack Lee

"The new lead smelter based on the QSL technology was started operation from May 1992 at Onsan Refinery of Korea Zinc Co., Ltd. The smelter is designed to treat not only various types of lead concentrate but also secondary materials coming from the zinc plant without special pretreatment.Shortly after the start-up of the operation, it has demonstrated that the smelter have a capability to treat wide range of raw materials. Continuous modifications and improvements of the plant are still under way to increase the feed rate and also the ratio of secondary materials to the feed.In this paper, the operating experience and results of QSL smelter, especially the injection of gases and coal to the melt, will be presented with major operation parameters and data.INTRODUCTIONThe QSL lead smelter based on new injection technology was commissioned at the Korea Zinc's Onsan plant from May of 1992. After starting the operation, the QSL lead smelter faced various kinds of mechanical and metallurgical troubles. However, these were gradually worked out by the continuous improvements and efforts.At present, the QSL lead smelter is operated stably at the total feed rate of 57 tonnes per hour with an increased amount of secondary materials."

Jan 1, 1996

By Chris T. Vild

"ABSTRACT NOT AVAILABLEPRESENTATION SUMMARYIntroductionToday, light gauge aluminum scrap is melted in sidewell furnaces using natural gas reverberatory burners. The scrap is introduced into the sidewell adjacent to the combustion chamber through a submerged archway. Super-heated metal is then pumped into the sidewell where it aids in melting the scrap. From the sidewell, the flow is returned to the combustion chamber through a second submerged archway at some lower temperature. Normally, the burners are set at a designed high fire level and the scrap is introduced at a rate to attempt to mat.ch the burner input. A thermocouple in the bath is programmed to throttle back the burners to low fire if a high temperature limit is exceeded.Jn many cases the thermal efficiencies of these furnaces can be very low. With inadequate circulation, air and natural gas furnaces run at a dismal 18% thermal efficiency. If a circulation system· is added, the efficiency can jump to 28%. For a $100 million lb/yr recycling facility, and natural gas prices reaching $4.50 per million Btu, fuel cost at 18% efficiency can reach $1 million per year. A 10% increase in thermal efficiency saves $350,000 a year in fuel costs.With an increase in thermal efficiency, furnace utilization also increases. A 10% increase in thermal efficiency would result in a 20 million Btu furnace producing 12,000 lb/hr up from 8,000 lb/hr or 35 million lb more produced per year. This is a 33% increase in output.Most current furnace development has focused on burner technology using oxy-fuel, regenerative burners, etc. However, thermal efficiency is also largely effected by the molten metal circulation rate and how well the scrap is mixed into the superheated metal. Therefore, the flow dynamics should be optimized first, before installing of more thermal power.Jn an effort to understand the effect of these variables, a series of computer models were made and the critical factors studied with the goal of demonstrating an increase in thermal efficiency and production. Large-scale graphical representations of these models will be presented."

Jan 1, 2000