Search Documents

By Yoshihiko Maeda

It is said that the 21 st century will be an era of the remedy of the global environment. In order to reserve natural resources for the future and to avoid the dispersion of heavy metals after usage and to avoid pollution problems, it is extremely important to recycle heavy metals as much as possible by reasonable recovery procedures. The nonferrous metal industry is expected to play a important role in the recycling of heavy metals that are originally their products. From the depressed metal price experienced in Japan in 1980th due to the sudden change in current exchange rate between US dollar and Japanese yen, one of major nonferrous metal company, Dowa Mining, has diversified its business area not only to the so-called down stream, but also to the environmental business including metal recycling, industrial waste treatment and soil remediation by utilizing technologies and facilities once used or still used for mining and smelting of copper, zinc, lead and precious metals. In this paper some of these applications will be presented.

Jan 1, 2003

By P. Myllykoski, J. Nylander, A. S. Korhonen, J. Larkiola

The coefficient of friction and the deformation resistance have been determined from the measured rolling parameters by applying the Bland-Ford-Ellis rolling force model and the artificial neural network model (ANN). The dependence of friction on the parameters such as reduction, rolling speed, front and back tensions, contact pressure and deformation resistance have been studied by the ANN model. Measured data of over 10 000 coils have been used in the training stage. Various dependencies have been examined and the results show that the friction coefficient does not depend much on the rolling speed. The reduction and deformation resistance seem to have the strongest effect on the friction coefficient. A friction model based on neural computing has been included into the existing rolling force model.

Jan 1, 1994

By Scott R. Giese, Lucas Dix

"Recently, there is a growing trend in the aluminum foundry industry to develop· improved melting and casting processes to produce lightweight, high-strength, and thin-wall castings for the aerospace and transportation industry. One casting method that has demonstrated industrial potential for producing clean, thinwall castings is vacuum-assisted, counter gravity casting. This process has the benefit of expeditiously and quiescently filling the casting cavity with a dramatic reduction of furnace related and reoxidation inclusions. Additionally, lower casting temperatures can be utilized because the application of vacuum during filling overcomes the resistive internal cavity pressure resulting in a finer, as-cast microstructure. The paper explores and discusses the processing and design conditions in improving the mechanical properties of A206 casting alloy using the vacuum assisted, counter gravity casting process.IntroductionThe process of metal casting has been, over the centuries, the chief production technique for components used in everyday life. However, the casting process has certain inherent problems that can adversely effect the properties of a finished product. These problems are directly attributable to the gravity pouring technique used to transfer molten metal to the mold and to fill the mold cavity.A recent study for the American Metalcasting Consortium demonstrated reoxidation products created during the casting process are five times more likely to cause product rejects than entrapped molding aggregates, melt slag, or furnace lining materials1. Formation of nonmetallic and intennetallic compounds are more prevalent in aluminum and titanium alloys because of their reactiveness to furnace lining materials and their high affinity for oxygen. The incorporation of undesirable compounds can be attributed to four areas of the casting operation. The sources are charge materials, melting technique, pouring methodology, and casting cavity filling. Aluminum foundry men have addressed the first three areas by selecting high quality melt stock, non-stirring melting equipment, and the use of porous ceramic filters. Unfortunately, little consideration is given to the last, but yet tl.1e most important part of the casting operation, the actual fill mg of the casting cavity.The generation of inclusion defects during the casting process can be described by two methods. As the liquid metal flows in the gating network and casting cavity, abrupt changes in flow d1rect10n cause the metal to become agitated. This mechanism liquid metal splashing, is generated by instability of the advancing liquid metal interface from turbulence effects as schematically illustrated in figure 1a2 . The surface oxide film bursts under high velocity conditions, folds over, and becomes dispersed and incorporated in the bulk liquid. Additionally, fragmented liquid droplets ejected from the disturbed interface oxidize and become dispersed in the metal stream."

Jan 1, 2000

By Shigeatsu Nakazawa

Activities of Bi and In in the Bi-In liquid alloy were measured over the whole range of composition at the temperatures from 850K to 1050K. An alloy was vacuum-sealed in a quartz cell and heated at the temperature of interest. The absorption for 307nm radiation from Bi lamp was measured for Bi atom vapor in the cell. By heating a pure metal as a standard and measuring the absorbance as a function of the temperature, an analytical curve for Bi atom vapor was constructed and used for conversion of the absorbance to the vapor density. Bi activity was determined as the ratio of the Bi atom vapor density over the alloy to that over a pure metal. The same procedure was applied to the In 304nm radiation from In lamp and In activity was determined independently of Bi. Results showed that the liquid Bi-In system behaves like a regular solution.

Jan 1, 2003

By Edwin de Jesús Deveaux

After 32 years of operations beneficiating lateritic nickel ore in a fully integrated pyrometallurgical complex, Falconbridge Dominicana (FALCONDO), situated at Bonao and La Vega Provinces, Dominican Republic, has become profitable with one of the lowest nickel grade content processing plants in the world, and literally without any by-product (granulated slag, will be utilized in the future as a post-processing subproduct). To December 2002, mineral reserves were 64.1 million tonnes containing laterite grading as low as 1.15 % Ni when full dilution is applied. At a cut-off grade of 1.20% Ni, the reserves will provide 15-20 years of production. The mineralized thickness over the seven active deposits averages 6 m. Development of very selective and unique mining practices, together with improvements in the process plant, are key to achieving the production goal (30 kt Ni/yr) and to meet the quality standards for the ferronickel produced. Keywords: Laterites, grade control, mining methods, environment

Jan 1, 2004

By S. Stoyanov, M. Cross

"Silicon components containing transistor circuitry are at the heart of electronic products such as computers, mobile phones, etc. These components are connected to printed circuit boards (PCB's) using solder material that acts as the conductor for both electricity and heat. During the lifetime of a product it will undergo many thermal cycles where the chip becomes hot during product operation and then cools when the product is switched off. At the product design stage engineers undertake thermo-mechanical simulations to predict the thermal stress in the solder joints due to this thermal cycle and to ensure that the stress magnitude will not result in early fatigue-type failure. The design engineer's aim is to identify component parameters which ensure that the solder will survive beyond a certain number of thermal cycles.The aim of integrating computational mechanics and optimization tools together is to speed up dramatically the design process. From viewpoint of a design engineer in the electronics manufacturing sector, these tools can be used to quickly estimate key design parameters (i.e. material properties, product dimensions, etc) that will guarantee the required product performance. In this paper a modeling approach coupling computational mechanics techniques with numerical optimization is presented and demonstrated. The integrated modeling framework is obtained by coupling the multi-physics framework - PHYSICA - with the design optimisation tool- VisuaLDOC. Thermo-mechanical simulations are presented that predict the creep strains in solder material. Different numerical optimization procedures: Direct and Response Surface based optimization plus Design of Experiments, are tested as a part of this modeling framework."

Jan 1, 2001

By Florian Kongoli

New operating conditions and process parameters are often necessary in today's industrial practice of non-ferrous smelting and converting in order to accommodate various new chemical compositions of mineral charges and environmental requirements or to conceive new and more efficient industrial technologies. An important parameter in non-ferrous smelting and converting is the liquidus surface of multicomponent slags. This surface is affected by multiple factors such as temperature, gaseous potentials, the content of each component in the slag, etc., and cannot be quantified by the existing ternary liquidus diagrams. In this work a new type of representation of the liquidus surface of multi component systems has been presented by means of a thermodynamic model. This representation waives the need of the multidimensional representation of multi component systems and yields practical two-dimensional diagrams, which can be easily used in the industrial practice.

Jan 1, 2000

By Ray D. Peterson

The hydrothermal enrichment of chalcopyrite by CuSO, occurs in the absence of oxidizing or reducing reagants. Kinetics of the enrichment process were determined under autoclave conditions in the temperature range of 398°K (125°C) to 473°K (200°C). Covellite (CuS) formed first, followed by digenite (Cu,,,S), with rejection of iron to the solution. The kinetics have been explained by a model which includes diffusion during the first stage formation of covellite followed by surface reaction rate control when digenite be. The effects of particle size, temperature, pH, and cupric and ferrous ion concentrations on the leaching kinetics were examined. Additions of ferrous ion to solution markedly increased the rate of reaction.

Jan 1, 1994

By Yasushi Sawada

An experimental investigation was carried out to study the rates of reduction of iron oxides dissolved in liquid Ca0-SO2-A203 slags by Fe-C droplets at temperatures ranging from 1325 OC to 1550 OC. The %FeO in the slag was varied from 5.5 to 18. Flash X-ray images were employed to observe the behavior of Fe-C droplets in the slags during the reactions and for determining the slag-gas-metal interfacial area. Effect of P205 in the slag and sulfur in the droplet was also investigated. The reduction rates were determined by measuring the volume of CO evolved as a function of time and the estimated slag-gas- metal interfacial area. The reduction rates have increased with increasing %FeO in the slag and the slag temperature. The experimentally established relationship between the reduction rates and FeO (wt%) in slag is given by

Jan 1, 1992

By Teixeira

An experimental investigation on the kinetics of oxidation of As(III) with H202 in synthetic effluent solutions followed by precipitation of Fe/As (V) compounds was carried out. The variables investigated were: As concentration (200 -3000 mg/l) , oxidation pH (2.0 -11.0), oxidation temperature (25 -800C) , H202 stoichiometric excess (50% -100%), precipitation pH (5.0 -7.0), precipitation agent (Fe2+ -Fe3+). Fixed conditions were, Fe/As molar ratio (6:1) and stirring speed (560 rpm). The results were empirically modelled. The precipitates obtained were amorphous. The precipitates were checked upon their environmental stability according to the United States Environmental Protection Agency (U.S.E.P.A.) Toxicity Test, and were considered to be adequate for deposition in impermeable waste dumps. The combined Fe/H202 detoxification process, in selected conditions, was able to reduce the As contents of effluents containing 1600 mg/l As to 0.1 mg/l, in about 2 1/2 hours of total processing time.

Jan 1, 1990

By Charles H. Rawlins

Reported is work done on processing of steel mill effluents in the areas of dewatering and separation. Much of the waste from these operations is in the form of sludges from scrubbers, in which the primary constituent is iron oxide. Recycling of the sludge&apos;s magnetic fraction has become economically attractive in order to reduce the overall volume placed in landfills. The objective of this research is to determine the effectiveness of combining magnetic and cyclonic forces, to recover iron oxide particles from waste water stream, while decreasing the volume to be disposed. Three different size hydrocyclones, operating within the field of a quadripole magnet, were tested using varying feed pulp densities of magnetite, magnetite/dolomite, blast furnace (BF), and basic oxygen furnace (BOF) slurries. In the first three cases, the percentage of magnetics recovered increased to greater than 95%. The limiting operational factors are; high pulp density for small cyclones, which can cause flow blockage within the magnet field, and extremely fine particle sizes (<2 microns), which cannot be recovered. The results indicate this technique can remove virtually all the magnetic particles from some steel effluents to a 40-50% weight percent solids pulp, on an in line continuous basis.

Jan 1, 1994

By Mostafa O. El-Bealy

"To estimate the interdendritic cracking tendency in casting processes, a new model for interdendritic cracking criteria has been proposed. The model combines a concept of the alloying element effect on the interdendritic strain generation and therefore on the susceptibility of interdendritic cracking phenomena. A susceptibility of interdendritic cracking is modeled by using El-Bealy's interdendritic cracking susceptibility function ""BJCSF' and the opening displacement between the dendrites ""EIA "". These concepts are modeled based on the previous experimental observations and ElBealy' approach. The model is implemented numerically for a one-dimensional model problem with some similarities to the casting of steel. The variation of some key parameters that are known to influence the frequency and severity of the interdendritic cracking is then studied.I. INTRODUCTIONInterdendritic cracking ""hot tearing"" commonly encountered in both ferrous and nonferrous castings (1,2]. It is generally believed that interdendritic cracks start to nucleate and develop in the interdendritic strain region within the mushy zone [l-5]. The interdendritic strain region is then definitely coherent, but continuous films of liquid still exit (4,5]. This distinguishes interdendritic cracks from cold cracks forming during the casting process after complete solidification (6,7].Much effort has been put into the understanding of the interdendritic cracking phenomena, and several theories have been proposed. Fellini [8] stated that interdendritic crack ""hot tear"" will result if the material is subjected to too high of accumulated strain within so called vulnerable part of the solidification interval. Kinosita et. al. [9] and Campbell (10] also emphasized the role of tensile stresses in the forming of interdendritic cracks. Most interdendritic cracks criteria simply consider the size of solidification interval, stating that solidification range is associated with a lager interdendritic cracking susceptibility than a short range. Clyne and Davies (11] formulated a more refined such criteria based upon the time spent in different regimes of the solidification interval. They defined a vulnerable region in which thin continuous films of interdendritic liquid exist, and the permeability is low. When thermal strains are induced in this region, the film is not able to sustain the stresses, and an interdendritic crack will form."

Jan 1, 2001

By Yoichi Takeda

Copper solubility in Si02-CaO-FeOx slag equilibrated with copper matte in 10% S02 atmosphere at 1573K was estimated. Essential parameters are activity coefficients of copper oxide and sulfide, oxygen and sulfur potentials and activity of copper in the slag-matte system. A large number of experiments provide proper parameters to calculate copper solubility in slag. A classical thermodynamic model postulating CUOO.5 and CuSo.; molecules assists in estimating copper solubility in slag. Additions of Si02 and CaO reduce copper solubility almost in any condition. Copper loss, that is function copper solubility and slag volume, in the silica saturated Si02-FeOx binary slag is minimally equilibrated with less than 66% copper matte while copper loss in the 50% FeOx-SiOrCaO ternary slag saturated with 2CaOSi02 is minimally equilibrated with over 66% copper matte. This slag composition has potential for continuous copper converting, direct copper production or high-grade matte production.

Jan 1, 2003

By Shu Yamaguchi

The behavior of halide impurities in pyrometallurgical processes such as Wealtz kiln and MF process has been discussed based on the thermochemical data and the reported data of PbO activity in PbCl2-PbO melts. The role of PbCl(g) has been estimated to be significant in the chloridization evaporation reaction. From reported data on the PbO activity in PbC12-PbO melts, activity of PbCl2 has been calculated by the numerical integration of Gibbs-Duhem equation, and the stability domains and the composition of the liquid phase as well as the vapor pressure of PbCl2 have been estimated as functions of log P2HCI/PH2O and temperature. From the discussion of the path during cooling process on the log P2 HCI . PH2O vs. temperature diagram, the authors proposed a possible dechioridization process that utilize water vapor as a dechloridizer for the direct precipitation of PbO from gas phase.

Jan 1, 2003

By Francois Reizine

Infrared sensors will include scanning detectors and positioning sensors. The focus will be on 1, 2, and 4-color wavelength pyrometer systems which allow the accurate measurement of emissivity and, consequently, of the true temperature even in the presence of scale, slag, and fumes. Such sensors are being used in blast furnaces, BOF&apos;s, and galvanizing lines. Laser sensors will be presented using different principles of physics, mainly time-of-flight, pulsed infrared lasers for level measurement and dimensional measurement; triangulation lasers for width and thickness measurements; and laser Doppler velocimeters for velocity and length measurements, including mass flow, elongation, and tension control, cut-to-length applications. These sensors and systems are based on state-of-the-art technical developments to improve productivity and quality and reduce maintenance and downtime.

Jan 1, 2001

By A. Vahed

The Goro Nickel Project is situated in the Southern Province of New Caledonia. Inco Limited and Goro Nickel S.A. have developed a process that features the use of pyrohydrolysis to produce nickel oxide. The process treats a blend of laterites by Pressure Acid Leaching followed by solvent extraction of nickel and cobalt using Cyanex 301®. Purified nickel chloride solution is converted to high purity NiO product and 6M hydrochloric acid, which is recycled back to the SX circuit. In co-operation with Andritz AG, spray roaster and fluid-bed pyrohydrolysis technologies were examined for this purpose. Tests were conducted at the Andritz AG pilot plant in Vienna, Austria, and at Goro in larger scale installations. The latter served to establish process engineering design parameters for scale-up. Several process variables were investigated in both technologies and the off-gas characteristics were established. Fluid-bed pyrohydrolysis was selected for the Goro commercial plant, primarily because it produced a granular nickel oxide. The main focus of this paper is to outline the results obtained in pilot plant studies of liquid fueled fluid bed pyrohydrolysis for the Goro Project. Keywords: lnco Goro Nickel, Fluid Bed Pyrohydrolysis, Pilot Plant Tests

Jan 1, 2004

By Stober, Frank Allan

The paper describes the development of components in an lntegrated Furnace Control system for shielded-arc smelting focusing on operation and crucible integrity enhancement. The paper reviews the mechanisms of power, feed and energy input and losses into the shielded-arc smelting process and describes the furnace control system module development and integration to tailor the process. The ultimate success of a furnace control system application is transfer of knowledge, training, and operational support during furnace start-up and ramp-up phases and a model for how this has been achieved is discussed. The control modules of a shielded-arc laterite smelting furnace are described in detail including measured results and screen captures from application in a laterite smelting furnace. This paper focuses on developments in Integrated Furnace Controls tailored to shielded-arc laterite smelting but development of common furnace control modules for improved crucible and tapping operation integrity applied to other furnace processes, including immersed-arc smelting, is also covered. Keywords: IFC, Power, Feed, Supervisory, Control

Jan 1, 2004

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transfonnation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling.

Jan 1, 2003

By M. J. Collins

Direct pressure leaching of zinc sulphide concentrates was started? commercially in October 1980. Continuing research and development studies at Sherritt and feasibility studies for a number of clients have defined various pressure leach configurations for integrattons with existing roast- 1 each operations and for grass roots plants. Existing and potential applications of zinc pressure leaching are discussed.

Jan 1, 1990

By J. A. Gonzalez-Dominguez

During the electrorefining of lead by the Betts process, ionic concentration gradients become established within the slimes layer. These gradients contribute to precipitation of secondary products and to gradients in electrode potential applied to slimes filaments, and thereby affect the dissolution of noble impurities. This paper describes the experimental results obtained when a typical lead anode was dissolved under galvanostatic conditions with concurrent interruption of current at preset slimes thicknesses. Reference electrodes were incorporated within the lead anode to follow the potential gradients across the slimes electrolyte. Samples of the slimes electrolyte were withdrawn in-situ and their compositional changes were related to transport processes across the slimes layer. Upon current interruption the anodic overpotential decays, first abruptly (as the uncompensated ohmic drop disappears), and then slowly (due to the presence of a back E.M.F. created by ionic concentration gradients that decay slowly). Current interruption measurements showed that: (A) concentration gradients exist across the slimes layer, (B) inner solution potentials within the slimes layer can be larger than those measured from reference electrodes located in the bulk electrolyte, (C) secondary products can shift the inner solution potential to negative values that reverse upon re-dissolution and (D) ionic diffusion is seen upon current interruption but it is complex and difficult to model due to the presence of processes that can support the passage of internal currents. SEM and X-ray diffraction analysis of the slimes filaments indicated that secondary reactions leading to the formation of Si02 and PbF2 take place (mainly at the anodelslimes interface). The onset of these reactions and their relationship to the Pb-F-Si-H20 Eh-pH diagram are linked to the industrial operation of the Betts process.

Jan 1, 1994