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By Gabriel Plascencia

Copper was oxidized in the temperature range from 300 to 1000 GC under different pressures of oxygen. In the range from 300 to 500°C, copper oxidizes following the logarithmic rate law; while in the range from 600 to 1000°C oxidation follows the parabolic rate law. Transition from logarithmic to parabolic growth occurs at about 525°C. X-ray diffraction was performed on oxide scales to account for the CuO/Cu2O ratio at different temperatures. Activation energies found in this work are in good agreement with reported values.

Jan 1, 2003

By Lu Lin, Yanping Bao, Xiang Li, Linzhu Wang, Xiaobai Yan

The results showed the microinclusions were mainly Al2O3 and sulfide inclusions from tapping to the beginning of LF refining. Al2O3 inclusions were modificated into calcium aluminates after calcium treatment. Lots of spherical calcium aluminates composite inclusions containing MgO, TiO2 and MnS were found after soft blowing and during tundish metallurgy and left in the slab which caused the defects of beam plates. Pure Al2O3 inclusions were observed again after soft blowing 8min. Average sulfur content in inclusions decreased because of the high desulfurization ability of refining slag. Average Ca/Al ratio value in inclusions increased during LF refinging because of the reduction of CaO in slag by carbon and it increased obviously during the process of soft blowing 8min because of the dissolusion of calcium wire.

Jan 1, 2015

By Alan M. Russell

In recent years, several rare earth intermetallic compounds with the B2-type structure have been reported to exhibit high tensile ductility and high KIC fracture toughness at room temperature. These materials retain considerable ductility even at 77K. These are noteworthy findings because most intermetallics possess poor room temperature ductility and low fracture toughness unless one or more special contrivances are applied (e.g., doping with small additions of interstitial elements, offstoichiometric compositions, testing in ultra-dry atmospheres, etc.). This paper summarizes recent findings on rare earth B2 intermetallics. These include the determination of the active slip systems; the strain rate sensitivities; yield strength maxima at elevated temperatures; the search for possible twinning and stress-induced phase transformations; ab initio calculations of their defect energies and the anisotropy of dislocation line tension. Potential applications of these materials and the possibilities that this study may suggest strategies for increasing ductility in other intermetallic compounds are discussed.

Jan 1, 2008

During electrowinning of nickel chloride, hydrochloric acid was regenerated instead of chlorine in a two membrane cell, by segregating the chloride catholyte with an anion exchange membrane, and the sulphate anolyte with a cation exchange membrane from the middle electrolyte (ampholyte) compartment. Successful operation of such a cell depends on controlling chloride leakage through the cation exchange membrane to the anolyte. Small amounts of chlorine gas could be detected in the oxygen evolved at the anode. In this paper, the chloride. leakage as a function of various types of cation exchange membrane and different composition of the anolyte is reported and discussed. Ag+ was added to the anolyte to eliminate chloride leakage to the anode. The cell voltage, electrode potential and voltage drop over the membrane as a function of current density has also been investigated.

Jan 1, 1996

By Georgios Kolliopoulos

Water is a critical commodity of our generation and a key compound for the chemical and mining industries. Sustainable industrial development is directly associated with the ability to recover clean water from contaminated sources. Forward Osmosis (FO) is a low-energy footprint membrane process allowing the recovery of clean water from high salinity effluent streams. In FO, water is recovered spontaneously into a concentrated draw solution (CDS). Energy is required to separate the recovered water from the resulting dilute draw solution (DDS). In the current work, the fundamentals of the FO process and the most important aspects affecting its performance are discussed. An energy comparison of FO and conventional water recovery technologies is presented. Finally, the opportunities FO presents in the field of hydrometallurgy are analyzed.

By Saad Elias Kaskah

"The Box-Behnken Design (BBD) is used to model the sacrificial Cathodic Protection System (SCPS) to find the factors effectiveness behaviour. For protection potential assessment the BBD receives (resistivity of environment, sacrificial anode alloy, distance between anode and cathode and surface area for the structure to be protected) as input and gives the protection potential as output. By applying BBD with their analysis tools we get many results. The important results which are the factors individual effectiveness on the sacrificial cathodic protection (SCP) process are the resistivity which has the greatest effect on the potential protection (rank=l) followed by sacrificial anode alloy type (rank=2), surface area for structure protected required (rank=3) and distance between anode and cathode (rank=4). The interaction of sacrificial anode alloy and cathode area {X2X4 ) has significant effect on CP process with the limits which are used in this work while the other factors interaction (X1X2, X1X3, X1X4,X2X3, X3X4 ) has insignificant effect on the limits which used in this work.IntroductionFor carbon steel in seawater the normal corrosion potential E '°""_is in the range -550 to -600 mV vs. Ag/AgCI [1]. The most effective method to overcome the corrosion is cathodic protection {CP) which represents a control method in the steel wall corrosion. Cathodic protection has been used in several areas including marine and underground structures, storage tanks, and pipelines [2]. Sacrificial anodes system generates protective current which depends upon the inherent potential difference between the anodes and the structure to be protected. If the structure is made of iron or steel, any metal that is more active in the electromotive force series can theoretically be used as anode material [3]. There are many factors influencing on cathodic protection like resistivity (NaCl content), chemical composition of sacrificial anode alloy, distance between anode and cathode, surface area of cathode, temperature, humidity, velocity of solution, dust, impurities, bacteria and etc .. The present work studied four factors: NaCl content, resistivity), chemical composition of sacrificial anode alloy, distance between anode and cathode, surface area of cathode) with different three levels of values for each one. Then this work will find the optimum value from the factors levels that tacked to investigated there influencing on sacrificial cathodic protection system."

Jan 1, 2013

By R. Padilla

Enargite (Cu3AsS4) occurs normally associated with copper sulfides, mainly chalcopyrite. When the enargite content in chalcopyrite concentrates is high, direct smelting of the concentrate presents problems related to environmental pollution and contamination of the final metallic copper. Leaching processes are viable alternatives to treat copper concentrates with high content of enargite. Consequently, in this paper, the pressure leaching of enargite in sulfuric acid-oxygen system is discussed. The leaching rate was studied in the range 160 to 220 °C and partial pressures of oxygen of 74 to 200 psi. The enargite dissolution increased substantially with temperature increase. Complete dissolution of enargite was obtained at 220°C, and 100 psi of oxygen pressure in 90 min. The shrinking core model controlled by surface reaction was used to analyze the kinetics of enargite dissolution. Activation energy of 70 kJ/mol was obtained for the temperature range 160 to 220 oC.

Jan 1, 2008

By Muhamad Firdaus

There is a growing interest in Magnetoelectric (ME) materials in view of both fundamental understanding and novel desirable applications. The application potential for multiferroic materials with the possibility of reversing the magnetization by applying an electric field (or vice versa) is quite promising especially in data storage application. The rare earth ortho-ferrites (REFeO3), such as NdFeO3, have been studied extensively in recent study in the context of discovery of magneto-electric (ME)/multiferroic nature materials. In this paper a potential high temperature recovery of rare earth elements in the form of REFeO3 from waste permanent magnets using direct oxidation in air was investigated. It was found that REFeO3 (NdFeO3) phase can be separated from the other oxide phases by thermal treatment of NdFeB magnet waste at 1100 °C in air atmosphere. The REFeO3 also found to have different physical characteristic (density) from the other layers and can be separated physically. This paper will include a proposed flowsheet to recover Nd as NdFeO3 through powder separation. The technique can be beneficial and favourable for RE recycling and recovery from waste permanent magnets.

By Toshihide Takenaka, Takashi Matsui, Nao Murakami, Masahiro Kawakami

"Electrowinning of Ti have been investigated in a LiF-NaF-KF melt including K2TiF6 at 773-923K by applying electrochemical oxidation ofH2 gas as an anodic reaction. The cathodic behavior of titanium and the anodic behavior of H2 gas were studied by voltammetry in detail to clarify the electrolytic condition for the process. The electrowinning of Ti was carried out by potentiostatic _electrolysis. Steady electrolysis was achieved under the suitable electrolytic condition without breaking out the anode effect. Titanium metal was electrodeposited on a Ti cathode though the deposits were usually powdery. It is concluded that this process is potential if the morphology of the deposit can be improved.IntroductionTitanium has such good properties as high specific strength and high corrosion resistance. However, the availability of Ti has been limited because the price of Ti is much higher than those of other common metals, such as Fe and Al. The production process of Ti ingot from its ore is rather intricate so that the production cost is high. If the simpler process is developed, the production cost should be retrenched. Titanium metal is usually produced by the Kroll process, which consists of the electrowinning of Mg metal in molten salt and the chemical reduction of TiCl.i by Mg metal. The Kroll process is very elabrate, but not simple. Because the chemical reduction ofTiCl4 by Mg metal is highly exothermic, a considerable amount of energy is wasted.Titanium metal can be electrowon in molten salt bath in principle. A simpler and more effective process than the Kroll process may be realized by the direct electrowinning so that the electrowinning of Ti metal has been studied widely[ 1]. Some researchs progressed to a pilot plant stages [2], but the electrowinning of Ti has not been industrialized yet."

Jan 1, 2000

By J. Jakumelt

The coupled simulation of mold filling and solidification for an investment casting process presents difficult. This is due to the complexity of the carious physical process and the geometry, To achieve this task in a precise way, the CFD program FLUENT and the casting simulation tool CASTS were closely coupled. Any physical quantity, such as velocities or temperatures, can be exchanged via files after each time step of the simulation. The communication and operating sequence of the programs is controlled by PERL-scripts. This enables the expertise of FLU ENT for flow simulation and the strength of CASTS, for casting simulation to be combined. The coupled simulation was successful applied to an aerospace investment casting. Several physical models were tested for correct treatment of the casting filters, the porosity of the mold and the viscosity of the liquid metal. The results demonstrate that even complex investment casting geometries can be investigated using CASTS-FLUENT.

Jan 1, 2003

By Ho Jung Heo

The proper control of slag composition is a dominant factor affecting yield of iron as well as dephosphorization efficiency in an electric arc furnace (EAF) operation. Moreover, thermophysical properties of slags such as viscosity are strongly affected by the changes in slag composition. Slag foaming, which is also a function of viscosity, is directly connected with the yield of iron and thus optimum slag chemistry are highly required in view of thermodynamics and physical properties. Therefore, we analyzed the slag composition in commercial melt shop (70 ton EAF) with the aim of higher yield of iron as well as higher dephosphorization during EAF process.

By R. T. Seaman

Pressure oxidative treatment of whole ores and/or mineral concentrates is used to leach or liberate metals of value for downstream recovery. Silver, when present, is often lost in processing, precipitating as a cyanide-insoluble jarosite in the residue. Depending on pressure oxidation conditions, the degree of silver loss to jarosite can vary dramatically. Batch bench-scale testwork is often performed to define that loss, and then assess the implications in continuous operations. This paper focusses specifically on the impact of CESL pressure oxidation conditions on silver recovery, and discusses limitations of batch bench-scale testing as well as means of overcoming these limitations to better predict silver recovery in the scale up from bench-scale to continuous operations. Since silver is only partially soluble in both sulphate and chloride media, it will gradually leach and deport to a jarosite as oxidation progresses. When a silver-insoluble anion, for example iodide, is dosed prior to oxidation, there is a marked improvement in silver recovery from batchgenerated residue; however, that benefit is not consistently seen in continuous operations. The difference has been attributed to the dynamic solution conditions in the batch test, specifically the first few moments of oxidation. Using these principles, a predictive correlation has been established between initial leach concentrations of iron and acid and ultimate silver recovery with iodide addition.

By Timothy W. Ellis

"This paper presents the basic theory of operation, physical chemistry and phase equilibria which allow the development of liquid-liquid extraction circuits based on metallic solvents. The incorporation of reduction and reduction/diffusion processes into the process scheme is discussed and a detailed description of several liquid-liquid extraction schemes are developed. A synopsis of experimental results obtained using this method to separate rare earth and other metal based materials will be given.IntroductionConcerns over the effects of waste materials in the environment has been one of the significant social hallmarks of the late 20th century. Essentially every industrialized country has had to incorporate the cost of waste material into the equation of production. Legislative initiatives have led to the passing of very tough laws, by historical standards, which govern the environmental impact of materials processing.Liquid-Liquid extraction is a very common unit operation normally using aqueous and/or organic based solvents. Early work at the Ames Laboratory focused on the use of this technique for the reprocessing of spent fuel from liquid metal breeder reactors by the use of metallic solvents. Recently, we have revisited this area as a means to recycle/reprocess several emerging rare earth based materials, although this method has a much wider range of application. The reinvestigation of this technology is particularly timely as hydrometallurgical based processes are coming under increasing scrutiny in the U.S.A. by the Environmental Protection Agency (EPA). Although technology currently exists to remove contaminants from aqueous based waste streams, often the application of such methods is expensive. With proper design and judicious selection of reagents liquid metal extraction can achieve a high recovery along with a benign waste stream.This process has several possible advantages over other technologies. First is the elimination of aqueous solvents. Therefore, problems associated with disposal or reprocessing of the aqueous carrier are eliminated. Second, with proper system design, very high separation coefficients can be obtained thus limiting the number of stages required. Third, metals are extracted from metals with a metallic product, thereby eliminating the need to re-reduce metal for oxides or other compounds which are the common output for aqueous based extraction procedures."

Jan 1, 1996

By Massoud Hassanabadi

Filtration using Ceramic Foam Filters (CFFs) is a method widely used to separate inclusions from molten aluminium. In the present work, the specific permeability and form drag coefficients of nominal 50 mm thick commercial Al2O3- based CFFs, of grades 30, 50, 65 and 80, have been calculated from pressure drop experiments using high (60–500 mm s−1) and low (0.2–10 mm s−1) water velocities. Moreover, 2D axial symmetric Computational Fluid Dynamic (CFD) models have been developed, using COMSOL Multiphysics® to validate the experimental results. The empirically obtained values were defined as global parameters used to model the pressure, as well as the velocity fields in the water pipes and in the CFFs. The modelled pressure drop over the filter thickness for the high water velocity experiments showed < ± 1% deviation from the corresponding experimental results for all CFF grades. Moreover, the developed model also showed good agreement with the experimental results obtained from the low water velocity experiments, where the deviation of the pressure drop for the CFF samples of grade 30, 50 and 65 were ≤ ± 4.6% and for CFF samples of grade 80 ≤ ± 13.4%.

By Manfred K. Walther

"Tests were conducted on instrumented plates cast in the Abex Experimental Foundry to compare recorded solidification histories with results computed for corresponding models simulated with the C.A.S.T. program. The first plate was cast of low alloy steel and the second of carbon steel with a graphite chill at one end. Both were cast in molds of bonded silica sand. Temperature histories were recorded in the castings, molds and chill. Exceptionally good agreement was achieved between computed and experimental data. Other investigators will find the results useful as a benchmark against which they can compare the results of their own calculations.IntroductionSince the early 1970's our foundry engineers have used both two- and three-dimensional versions of the G.A.S.T. program to gain knowledge of the solidification process [1,2,3]. Study of the computed data gave insight as to how the rigging and risering of specific castings might be changed or adjusted to improve quality and yield. New schemes based on such analyses were then recommended for implementation on the foundry floor. The degree of success of the new practice was subsequently evaluated after the part had been poured, shaken out and examined. Similar conditions were noted in the sectioned castings whenever porosity and voids had been predicted by the computations. Appropriate modifications, when found successful in the model, were applied to the process. This led to a reduction, if not complete elimination, of the defects. Such results gave credence to the use of these programs as an aid in the production of better castings.Earlier investigations on simple shapes revealed excellent correlation between output derived with the G.A.S.T. program and exact solutions. Results also compared favorably with data calculated using other codes as reported in the literature [4] and summarized in the Appendix. However, since the computer program had not been verified by direct experiment, it was decided to run instrumented tests to check the theoretical predictions with actual measurements."

Jan 1, 1986

By Andreas Siegmund

During the decade of the nineties the conventional method of primary lead smelting (sinter machine/blast furnace) was successfully challenged by the introduction of novel direct and continuous smelting processes. In combination with a significant shift in market structure, as well as more stringent government regulations these modem technological innovations like the QSL, Kivcet, and Isa/Ausmelt processes became more than major competitors. They have proven to be economically and environmentally viable. The intensification of the metallurgical reaction by applying oxygen enriched or pure oxygen bath or flash smelting principles resulted in cost savings and a higher flexibility with respect to raw materials and additives usage. By synchronizing individual auxiliary plant sections with the smelting process a virtually waste-free production and low-emission mode of operation with nearly optimum energy exploitation is achieved. The primary lead industry will gradually substitute the sinter -blast furnace operation with novel high-energy efficient technologies in the new millennium.

Jan 1, 2003

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces, They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-OB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderúrgica de Tubarão, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By A. Andreas Hejja

Flow of slag and settling of matte in slag resistance electric furnaces are discussed in conjunction with furnace geometries, stirring action of the electrodes, buoyancy and electromagnetic effects. The rectangular electric furnace was regarded as a channel reactor and the mode of slag flow as a channel flow. The flow is affected both by buoyancy and electromagnetic forces, however the effect of electromagnetic forces is minimal. The flow velocity is made up of two components; (i) that developed by the action of the electrodes, and (ii) the bulk flow velocity determined by the smelting rate and the volume of the reactor. Slag samples were taken from various depths of the molten bath and were analyzed microscopically to determine the size and distribution of matte particles, The action of the electrodes was described by a simple mathematical formula indicating a balanced settling rate in the area of electrode action.

Jan 1, 1996

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 Yuri Gelfgat

"This paper presents some results of the investigation of the steady magnetic field influence on hydrodynamics and heat/mass transfer in processes of semiconductor single crystal growth (Si, Ge, InSn). The investigation employed mathematical and physical simulation techniques of relevant processes and full-scale experiments on growth facilities. A number of additional MHD phenomena have been found generated in the melt due to the rearrangement of flow pattern, the formation of specific convective cells, and the origin of MHD boundary and shift layer.IntroductionMagnetohydrodynamic (MHD) means of creating forces by contact-free methods in liquid conducting media have been widely used in the production of volume semiconducting single crystals. The goal of this method is to control convective transfer processes in the melt volume and on the crystallization front [1-3]. This is due to the sufficiently high conductivity of semiconductor melts (s = 104 /106 O1m-1 ) and an obvious relationship between the hydrodynamics in the melt and at interfaces and the conditions of formation of single crystals and their quality [ 1].All types of MHD effects rest upon the generation of volume electromagnetic forces in the melt by various means as well as on the possibility to direct them arbitrary in space and to adjust easily their absolute values. Fig. l presents different means how to implement MHD phenomena during single crystal growth. It should be emphasized that in all the modifications given in Fig. l additional energy introduced into the melt cannot influence directly the crystallization process since it is incomparable to the energy of molecular forces. Both the influence and efficiency of MHD means are determined solely by the change of motion, heat and mass transfer characteristics."

Jan 1, 1998