Search Documents

By Takamasa Ishigaki, Gervais Soucy, Mohamed Rahmane

"The induction plasma jets employed for the in-flight nitridation of molybdenum disilicide (MoSi2) powders were investigated in terms of their flow characteristics. The present study shows the effect of the operating parameters of the plasma torch, as used for this process, on the plasma jet properties. The enthalpy probe techniques, along with mass spectrometry, were employed for the measurement of the jet temperature, velocity and concentration fields. The measured values were compared to the results of a numerical simulation performed on the plasma flowing inside the torch-reactor system. The process operating conditions studied were the plasma plate power, chamber pressure and sheath gas composition. The optimal conditions for effecting the nitridation process using thermal plasma are obtained at moderate plasma plate power, at around atmospheric pressure and by using a mixture of argon and nitrogen as the plasma torch sheath gas.IntroductionMolybdenum disilicide (MoSi2) based composites are considered to be one of the most promising candidates for high temperature structural material applications [!], especially because of their high melting points, good oxidation resistance and relatively low cost. However, the wide application of these composite materials is still limited by some factors such as their brittleness at room temperature and lower strength at high temperature (> 1500 K). To overcome such limitations, a number of researchers [2-4] have earlier studied various kinds of reinforcements for MoSi2, e.g. oxides, silicides and nitrides. More recently, Fan and coworkers [5-9] have demonstrated the possibility of in-flight nitridation and carburization of MoSi2, using a thermal plasma process. This work has confirmed the plasma synthesis route as one of the most promising methods for creating an in-situ second phase structure. Properties of the plasma flow, such as its temperature, flow velocity and composition, are of crucial importance for the nitridation of MoSi2 powders during their flight in the plasma. Therefore, the optimization of such a process involving plasma· generated reactive species necessitates a thorough understanding of the plasma flow characteristics."

Jan 1, 2000

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

"Dowa Metals & Mining Co. Ltd. has developed and plant-practiced a unique scorodite synthesis technology (DMSP®) for arsenic immobilization by oxidizing Fe(ll) ions in the presence of As(V) ions. Dowa has improved the DMSP® technology and has developed the process extensively for other applications. This paper focuses on the applicability of the DMSP® for various cases of copper smelting, and introduces other technologies for fixing arsenic and recycling gallium from GaAs, simultaneously processing (fixing) arsenic and thallium, and fixing and recovering arsenic from dilute arsenic solutions. The DMSP® was found to be applicable not only for various processes in nonferrous smelting, but also for other applications with a high potential for reducing environmental problems.IntroductionDowa Metals & Mining Co. Ltd. developed a method for synthesizing scorodite at ambient pressure [1], The scorodite is precipitated by oxidizing Fe(II) ion in a high-concentration As(V) solution. The scorodite produced in this way does not readily release arsenic because of its high crystallinity. Dowa built a demonstration plant for this technology at the Kosaka Smelter and established the production of scorodite at 30 t As/month by treating intermediate products from copper smelting as the starting material. The DMSP® was demonstrated to be favorably applicable to copper smelting [2]. We are engaged in further increasing the amount of arsenic fixation by the use of this process. Further improvements in productivity, cost reduction and applicability in various processes have been devised. Dowa has been endeavoring to resolve other problems as well as to improve productivity. We have gained extensive knowledge on arsenic treatment in our endeavors, enabling us to solve problems and improve productivity. This paper introduces the investigations and developments related to DMSP®."

Jan 1, 2012

By Robert E. Moore

Renewed interest in olivine refractories has led to efforts to characterize them employing modern techniques of experimentation and data analysis. Initial studies have focused on determination of physical and thermophysical properties. Special equipment for the determination of thermal shock resistance and creep behavior have been constructed. Optimal compositions for maximizing various properties are being identified using appropriate statistical techniques. The overall goal is to develop response surfaces for each of a selected group of engineering design and use properties. Development of ?olivine Refractories? in the United States The term "olivine refractories" is used here because it does appear that domestic deposits of this rock will be the focus of renewed interest and "olivinell is the preferred term in this country. There are extensive deposits of high quality olivines extending through parts of Georgia. North Carolina and in the state of Washington. The eastern olivines are much more localized and extensively altered compared to the western materials. The Washington olivines exist as massive rock deposits in the Twin Sisters mountain area northeast of Seattle and their inaccessi-bility has slowed efforts to develop them. The North Carolina olivines have been used in steel plant applications since the 1930's. Geologists use the term "olivine" to describe assemblages of ortho-silicates. 2RO.SiO2, wherein the RO may be MgO. FeO. MnO. etc. When the RO consists essentlally of MgO and FeO. the material is called dunite and. as such, is synonymous with "refractory olivine." Refractory olivines utilizing North Carolina materials were developed for brick products by Birch and Harvey in this country around the mid-1930's. (I) Their work was completely independent of that of V. M. Goldschmidt and co-workers who used massive dunites located in Denmark. (2) These deposits are currently being mined by A/S Olivine of Denmark for the manufacture of a rather complete line of brick shapes for use in steel-plant. glassplant. and cement kiln applications. Birch and Goldschmidt

Jan 1, 1982

By Yuhua Pan

Generic mathematical models have been developed for simulating heat transfer in two types of slag resistance heating electric furnaces for sulphide smelting: i) six-electrode-in-line rectangular furnaces and ii) three-electrode circular furnaces. The models are based on three-dimensional steady-state heat transfer of conduction, convection and radiation. Solidification of liquid slag into solid slag by water-cooling units, for use as freeze lining of furnace walls, is also considered in the models. The developed models are capable of providing predictions with reasonable accuracy for electric furnaces on 1) temperatures in slag, matte, cooling water, freeze lining and other solid regions as well as temperatures at various fluid/solid interfaces, 2) freeze lining thickness, 3) furnace smelting rate and 4) furnace heat loss rate. These computer models are built into executable application programs that are very efficient, with execution time less than one second, and can be easily portable to most computing platforms. This paper describes, as an example, the modelling results on heat transfer in six-electrode furnaces. The major modelling results show that in six-electrode furnaces uniform electric power inputs to the electrodes likely lead to low temperature regions close to slag and matte tapping ends of the furnaces, and the power input and the formation of air gaps between freeze lining and cooling units have significant influences on the thickness of freeze lining maintained by the cooling units.

Jan 1, 2006

By Anjan Kumari, B. K. Soni, Manis Kumar Jha, A. Vidyadhar, Vinod Kumar

"In the present paper, recovery of valuable metals from the poly-cracked ash obtained by pyrolysis of discarded PCBs has been studied following physical beneficiation and a hydrometallurgical process alternate to smelting. The ash is subjected to comminution for the separation of metallic components from non-metallic fractions by scrubbing, tabling and froth flotation which enriched the metal in the concentrate -97% which was further screened to separate high and low metal concentrate. The finer fraction containing -12% metallic value was leached in acidic solution. Almost all (Cu, Pb, Fe, etc) were leached in 4M HN03 at 90°C in 75 min at a pulp density 100 g/L. The characterization of both ash and residues were made by XRD, EPMA, EDS, etc. to validate the experimental results. The metals from the leach liquor could be recovered/separated using solvent extraction techniques which can further be processed to get pure metal salts/ sheets.IntroductionPrinted circuit boards (PCBs) are an essential component of electrical and electronic equipments (EEEs) as it plays an important role during operation of these devices. The world market of PCBs has reached nearly $60 billion in 2012, with 1.7 percent real growth over 2011 [1]. The diverse technology-driven global market is expected to grow at an average annual rate of 5% by 2014 [2]. The waste EEEs are generated due to replacement of obsolete equipments with modem ones and thus their demand is also increasing rapidly [3]. The discarded e-wastes are being piled up as landfills which affect the environment and cause health threats to living organisms, if not disposed of properly. These e-wastes contain metals some of which are precious, few are hazardous and others as valuable."

Jan 1, 2014

By Marcel Sturzenegger

Though the extraction of copper is well established, generation of sulfur dioxide (S02) is still a troublesome issue. Conventional processes are further challenged by the increasing amount of impurities in the concentrates. Direct decomposition of the metal sulfides into the metal(s) and elemental sulfur under concentrated solar radiation offers a promising path to solve both problems. Thermogravimetric measurements under inert atmospheres have shown that synthetic chalcocite or chalcopyrite yield copper at temperatures as low as 1773 K. Even though optimum reaction temperatures might be somewhat higher, such temperatures are straightforwardly accessible in solar chemical reactors. The absence of oxygen will reduce the extent of slag forming reactions and thereby alter the evaporation characteristics of volatile impurities such as arsenic or antimony. Chemical equilibrium calculations for a chalcopyrite-enargite feed, e.g., have shown that under inert atmospheres arsenic compounds are completely evaporated at temperatures above 1000 K and an effective separation of arsenic from the matte is expected. An important step towards a solar production of copper is the design and testing of prototype solar chemical reactors for this reaction. Numerical modeling is a key tool supporting a rational design but it requires data of the high-temperature properties that prevail in these processes. Development of techniques for determining the essential quantities such as decomposition rates or radiative properties at temperatures up to 2000 K is therefore a main activity in our laboratory in order to control and optimize the process. Though developed in the frame of high-temperature solar technology, the experimental techniques are also suited to advance the understanding of conventional high-temperature processes. Keywords: Solar technology, Sulfur dioxide, Solar Radiation, Thermogravimetry, Chalcocite, Chalcopyrite, Numerical modeling.

Jan 1, 2003

By Alice Barreto Bevitori, Frederico Muylaert Margem, Noan Tonini SImonassi, Caroline Oliveyra, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The mechanical behavior and the fracture characteristics of composites with DGEB/TETA epoxy matrix reinforced with up to 30% in volume of continuous and aligned ramie fibers were evaluated by tensile tests. Specimens with selected thin fibers aligned along the tensile axis were room temperature tested to rupture. The fracture surface was analyzed by scanning electron microscopy. The results showed significant increase in both the ultimate tensile strength and the elastic modulus. The fracture analysis indicated the possible mechanism for the fiber/matrix interaction, which could be responsible for the composite performance.IntroductionSince the middle of last century, polymer composites have substitute many conventional monolithic materials in applications ranging from aerospace to sport [l]. The main advantages of these composites are the low density and flexible properties specially using fiber as reinforcement to suit the mechanical performance requirements [2]. These are usually high strength and stiffuess requirements that could be reached with synthetic fibers such as gloss, carbon and aramid fibers. Its most commonly used example is ""fiberglass"", i.e., a thermoset polymer matrix composite reinforced with glass fiber. Indeed, ""fiberglass"" has a specific strength of the order of 500 MPa.cm3/g, which is the double of the strongest steels like the maraging. This motivated, at earlier times, ""fiberglass"" to replace many conventional materials including wood and natural fiber composites. Today, ""fiberglass"" has a wide range of uses from aerospace systems and appliances to sport and leisure components. However, its fabrication as well as those of any synthetic fiber such as carbon and aramid composites, requires a relatively large amount of energy. Presently, a growing concern exists regarding the consequences to the environmental by gases like C02 associated with both the energy consumption and the processing of synthetic fibers and their composites. These gases are well known responsible for global warming [3]."

Jan 1, 2013

By J. Boltano

This paper discusses the study, design and implementation of the new gas handling system for the Caletones Smelter of Codelco-Chile. A discussion on design conditions for a future Sulphuric Acid Plant using Teniente Converter gases is also included. The old system which started to be modified in 1985 and relied on natural draft and used balloon flues, resulted in a limited gas handling capacity for operation under future process conditions. This system also caused excessive fugitive gases in the smelter working areas. The new system permits handling of process gases from the higher capacity Teniente Converters Installed in 1987-1989 improving the gas handling of the reverberatory furnaces and Peirce-Smith converters as well as the environmental conditions of the smelter. This system utilises improved converter gas hoods, evaporative cooling and electrostatic precipitators gas cleaning, and is based on natural draft.

Jan 1, 1992

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Dinesh Agrawal

Microwave energy has been in use for variety of applications for over 50 years. These applications include communication, food processing, wood drying, rubber vulcanization, medical therapy, polymers, etc. In the last two decades microwave heating has been also applied very effectively and efficiently to heat and sinter ceramic materials. Microwave heating is recognized for its various advantages, such as: time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved mechanical properties, better product performance, etc. The most recent application of microwaves has been in the field of metallic materials for sintering, brazing/joining and melting. Several common steel compositions, pure metals and refractory metals have been sintered in microwaves to nearly full density with improved mechanical properties. Many commercial powder-metal components of various alloy compositions including iron and steel, copper, aluminum, nickel, Mo, Co, Ti, W, Sn, etc., and their alloys have also been sintered in microwaves producing better properties than their conventional counterparts by using a 2.45 GHz multimode microwave system. This work has been further extended to join and braze bulk metal pieces, especially super alloy based turbine blades. Further, in a specially designed microwave cavity, even the bulk metals can be made to couple with the microwave field and melted. The implications of these findings are obvious in the field of powder metal technology.

Jan 1, 2006

By M Phil Schwarz

"A CFD model for the gas-side of an impinging jet iron bath reactor has been developed to assist in the interpretation and design of oxidizing gas-melt reaction rate experiments. Heat transfer and reaction at the surface have been included. A free surface model, which solves for the liquid motion within the bath as well as the gas motion above the bath, has also been developed. This model also predicts extent and shape of the dimple formed on the liquid surface by the impinging jet. Both models have been run for conditions typical of jet impingement experiments using CO2 , H2O and O2• The main conclusions are• Results from the model for gas-side mass transport are in good agreement with the empirical correlation of Belton and Belton (1980)• Experimentally determined rates of decarburization by CO2 should be corrected for mass transfer because the experiments are often carried out under mixed rate control, eg for gas flow rate 10 L/min when the sulphur concentration is lower than 0.045• If the rate constant for oxygen reaction is greater than about 5 mol/m2.s.atm, it cannot be determined using a gas flow rate of 10 L/min or lower because of mass transfer control.• A cavity of depth 4.5 mm is predicted for a gas flow rate of 10 L/min and this substantially changes the flow field (and hence reaction rate) compared with a simulation in which the surface is assumed to be flat."

Jan 1, 1999

By Robert H. Hsu

Palladium finely dispersed in a substrate of kieselguhr, Pd/k for short, has been successfully used for hydrogen storage, separation and pumping for a number of years at the Savannah River Site (SRS). Recently SRS has developed a new pd/k flow through bed (FTB) prototype for separating hydrogen from other gases and simultaneously storing the hydrogen on palladium. The FTB uses single-pass liquid nitrogen cooling during hydrogen absorption/separation/storage and electrical heating for desorption/unloading of hydrogen. Fourteen absorption-desorption or loading/unloading cycles using hydrogen have been conducted with the new FTB prototype. Test results show that all design performance objectives have been successfully achieved: recover 295% of hydrogen gas from feed gas, produce 99.9% hydrogen product gas and < 5% hydrogen in discharge gas. This paper will discuss characteristics of the palladium-coated kieselguhr or diatomaceous earth, design and operation of the FTB, and results of performance tests such as separation efficiency, hydrogen storage capacity and system heat transfer characteristics.

Jan 1, 2002

By Hong Yong Sohn

A thermodynamic and experimental investigation has been performed to develop a new process for converting sulfur dioxide to elemental sulfur by a cyclic process. The most promising new process is a cyclic reaction scheme involving calcium sulfide and calcium sulfate. In this process, the reaction between sulfur dioxide and calcium sulfide produces elemental sulfur vapor and solid calcium sulfate. The latter is reduced by a suitable reductant such as hydrogen to regenerate calcium sulfide. &apos;Experimental results showed that up to 60 % of calcium sulfide powder was converted to calcium sulfate in 10 min at 1153 K under a sulfur dioxide partial pressure of 25.8 kPa. More than 95 % of nickel-catalyzed calcium sulfate powder was converted to calcium sulfide in 20 min at 1123 K under a hydrogen partial pressure of 86.1 kPa, water vapor being the only gaseous product. Sulfur dioxide-containing streams from certain new sulfide smelting plants contain much higher partial pressures of SO2. The rate of the first reaction is expected to be accordingly higher than in the test conditions reported in this paper.

Jan 1, 2002

By D. Nozadze

A new method of isothermal electro-contact diffusion welding of layered composites under pressure is offered. The scheme is developed and laboratory installation is created on which preproduction models of the layered composite of steel and aluminum is produced. A new method of electro-contact hot deformation is proposed for realization of diffusion welding by pressure of stratified blanks providing high-temperature isothermal process. In this case a rolling process or composite pressing is meshed with simultaneous electric current transmission in deformation center. Considering that a resistance of transient layer far exceeds the resistances of composite components, the heat release takes place intensively just in this layer. As the surfaces are approached over a distance of inter-atomic forces, the energy of boundary atoms easily reaches the energy threshold of capture with a formation of qualitatively new metallic bond. Proposed method, providing isothermal process in deformation center, excludes a necessity of previous preparation and prevention of surfaces. In this case strength of layer connection may approximate or exceed strength limit of cladding layer.

Jan 1, 2006

By Ping Long, Bin Yang, Jian Wu, Xiumin Chen, Wenli Zhang

In this study, the analysis method of trace element in pure indium using glow discharge mass spectrometry (GD-MS) has been established by correcting the analysis result, which was obtained from non-standard quantitative method of GD-MS. The effect of instrument operating parameters, the resolution and isotopes and the pre-sputtering time on the determination results were investigated respectively. The optimized operating parameters of the instrument were obtained as follows: the discharge current was 37.5mA and discharge airflow was 475ml/min. Mass spectral interferences have been eliminated using selected resolution and isotope. The pre-sputtering time was 30 min. 4 trace elements in two pure samples were determined for 6 times. The RSD were less than 20%. The content of trace elements in indium samples was determined by GD-MS and Chemical Analysis Method of Indium which is tested by inductively coupled plasma atomic emission spectrometry, respectively. The results were consistent with each other.

Jan 1, 2016

By P. D. Nolan

Smelters operating under pollution control orders have become increasingly dependent upon the reliable operation of sulphuric acid plants and no factor affects the long term reliability of those plants more than efficient gas cleaning. The sources and characteristics of contaminants in smelter of fgases and the conventional approaches to removing these contaminants to accepted levels are discussed. New technology is described which offers advantages of lower capital cost, lower operating cost and reduced space requirements over the conventional approaches. This new technology has been developed by LAB s.a. and is licensed for metallurgical gas applications by Chemetics International Company.

Jan 1, 1983

The entrainment of copper matte in the slag during the slag skimming stage of a Peirce-Smith converter was studied with a dam break model. Experiments were carried out with a range of fluid pairs where the lighter fluid was allowed to overflow a weir and the amount of entrained heavier fluid measured. The resulting entrainment is measured as the ratio of the heavy to light fluid withdrawn. The fluids include oil-water, water- glycerol and salt solutions-water pairs to cover a wide range of densities and viscosities. It was found that the Richardson number, Ri, correlates the entrainment well. For the case of the liquid-liquid interface initially at the same height as the weir, the entrainment was found to vary with Ri-1/3. The transient flow was simulated with a volume of fluid (VOF) code written in-house and used a stairstep approach to represent flow obstacles. The code was validated against the experimental results with good agreement for the variation of the heights of the two fluid with time. The simulation showed that the prevailing mechanism for entrainment is due to a pressure differential created across the liquid in the converter during pouring resulting in the heavier liquid being rotated upwards and over the weir.

Jan 1, 1999

By Liang Li

Thermodynamic analysis and experiments were conducted in order to verify the feasibility of preparing crude titanium tetrachloride (TiCl4) via the carbochlorination of low-grade titanium slag in molten salt. Titanium slag, assaying 74.6 wt% TiO2 with high calcium and magnesium oxide impurities, was treated by an optimized carbochlorination process in NaCl molten salt. These impurities in the titanium slag were chloridized simultaneously, and chlorination products FeCl2, MnCl2, MgCl2, CaCl2 and CrCl3 were collected in the furnace slag. XRD and SEM/ EDS analysis of residue shown that SiO2 and Al2O3 in titanium slag were difficult to chlorinate completely. Theoretical calculations and industrial-scale experimental studies reveal the content of TiCl4 in the products was more than 98.8 wt% and thus proved the feasibility of utilizing low-grade titanium slag for TiCl4 preparation by molten salt chlorination technology.

By D. W. Collins

Several organic and inorganic substances are widely used to control deposit structure and morphology during the electroprocessing of copper. Methods for monitoring the levels of thiourea, glue and guar gum during electrorefining and electrowinning have been successfully developed under the trade names of Reatrol and CollaMat. Other instrumental methods have been developed for additives and decomposition products associated with the electroplating of copper and other metals. Generally, these methods have been found to be either insufficiently sensitive or lacking in the desired selectivity for some or all of the additives. These procedures have mostly employed DC techniques; i.e., cyclic voltammetry, Tafel analysis, etc. In this work, chronopotentiometry (CP) and AC voltammetry were used to examine the interaction of glue, guar gum, thiourea and chloride during the electroplating of copper onto a platinum electrode. In addition, the interactions between the additives have been explored. It was found that glue in pure electrolyte (H2S04 and CuS04 only) had no effect on the chronopotentiogram. Glue was only active if chloride ions were present. The addition of thiourea resulted in several different chronopotentiograms depending on the presence of either chloride or chloride and glue. Thiourea used in conjunction with glue and chloride showed a significant increase in the polarization during copper deposition when compared to the electrolyte containing only glue and chloride. The use of a modified channel electrode further increased the sensitivity of CP. The use of AC voltammetry was explored as a technique to monitor some of the additives. AC voltammograms have more spectral detail then their DC counterparts and it is possible to monitor some of the additives at very low concentrations with AC techniques.

Jan 1, 1999

By A. A. Trickett

In the treatment of gases from pyrometallurgical processes prior to acid manufacture, volatile components, sulphur trioxide and particulates ,are removed in wet gas cleantng systems. In the process a weak acid stream is generated, typically less than 10% H2S04, contaminated with volatiles such as arsenic, fluoride and chloride&apos;, plus metallic particulates. This effluent stream has, in the past, been disposed of in a variety of different ways. As a result of changing environmental legislation, smelters are having to review alternative solutions for treating this effluent stream. This paper&apos; will describe a process developed by Chemetics which treats this effluent stream, generating a small dry metal sulphate stream plus a clean acid stream which is suitable for recycling to the smelter acid plant.

Jan 1, 1992