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By R. Hurman Eric

The dew-point technique of activity measurements take advantage of the volatility of a component in solution. The pressure of the volatile component over a sample is determined from observations of the temperature at which condensation of the vapor occurs. The method is applicable best when the vapor pressure of the components would differ by about two to three orders of magnitude. Experimentally, this is a closed system involving the use of evacuated and sealed transparent quartz sample probes. Furthermore reliable vapor pressure data of the volatile component is essential along with a specialized high temperature furnace capable of giving reproducible results. In this context, the vertical Dew-Point Furnace (DPF) was designed and built after elaborate trails until enough proficiency was gained for reproducible results. Over the years the DPF was modified and improved. The DPF developed was versatile and could easily be used for activity measurements in the isopiestic mode (another method of measuring activities of a volatile component in a solution). The necessary ancillary systems; namely evacuation-flushing-evacuation followed by sealing of quartz sample probes under vacuum were also perfected over the years. As and when necessary the dew-point technique was supplemented by classical equilibration-quenching method employed on the sealed quartz sample probes to reveal necessary phase equilibrium information. The following were studied utilizing the above technique: (i) Activities in CU2S-PbS and FeS-PbS binaries and CU2S-FeS- PbS ternary at 1200°C; (ii) Activities in Cu2S-SnS and FeS-SnS binaries and Cu2S-FeS-SnS ternary at I200°C; (iii) Phase equilibria and thermodynamic in Cu-Pb-S, Fe-Pb-S, Fe-Sn-S, Cu-Sn-S and Ag-Sn-S systems. Most recently the following systems have been tackled: (i) Phase equilibria and thermodynamics in the Ag-Pb-S and Sn-Pb-S systems; and (ii) Activities in Ag2S-FeS-CuzS-PbS quaternary at 1200°C.

Jan 1, 2003

By J. Howarth

Two electrochemical processing methodologies have been used to electrogenerate bromine-laden solutions for gold-leaching purposes. In the first process, a laboratory-scale cell in which the anode and cathode compartments were separated by a cation-exchange membrane was employed. The bromine produced by electrolysis of a 4% bromide solution was used to leach gold from a low-grade ore. The pregnant leach solution was then returned to the cell to recommence the cycle. High current efficiencies (90-93%) were maintained over six cycles. In the second process, an undivided hypochlorite generating cell (Chloropac"') was used to generate bromine from a simulated leach solution. Electrolyses were performed on a pilot-scale (100-150 gallons) with solutions containing different levels of bromide ion. The current efficiencies were also high (80-90%) and unaffected by the bromide concentration (over the range 2.5-5%) provided the electrolysis was run to low conversion « 15%). The Chloropac module was capable of delivering 0.6 kg bromine per hour at a power cost of $0.09 per kg. Using these figures, a detailed economic assessment for a 1000 metric tonnes (MT) per day gold ore processing plant was made. Electrolytic regeneration of bromine in a gold leach/recovery circuit dramatically improves the process economics over cyanidation.

Jan 1, 1991

By James W. Evans, Dong Xu, Jr. Jones

A physical (water) model based on particle image velocimetry (PIV) has been constructed at UC Berkeley. The PIV technique enables the use of water modeling to quantitatively characterize the fluid flow behavior in the mold during the continuous casting of steel, in a whole field sense, i.e., section by section. A method to obtain e\e time-averagevelocity (TA V) vector maps was developed by averaging 40 instant aneous vectc -r plots revealing the time average features of the flow. Another benefit of TAV vector maps is the ability to compare with present mathematical models, which are mostly based on the time-average technique. Bifurcated submerged entry nozzles (SEN) with ports inclined at various angles to the horizontal were used in the modeling to study their effects on the flow inside the caster. Argon was also introduced into the model to simulate the influence of argon injection on the metal delivery from the tundish into the caster. The bubble sizes and distribution (in specific sections) of argon were characterized, at the same time, by the imaging system of the PIV. This will allow for validation of current mathematical models that were developed to simulate argon injection in casters. Comparison with results calculated by the commercial finite element package FIDAP is also presented.

Jan 1, 1998

By Toshiyuki Kozuka

CdTe metal composite semi-conducting material has high potential in good performance of energy conversion efficiency for solar cell and there is much room for improvement of the performance by developing a process of making a thin CdTe film. In this paper, the imposition of intense magnetic field on CdTe electro-depositing surface is proposed, which is one of the possibilities for improving the energy conversion efficiency. In the experiment, cryogen-free super-conducting magnet up to 5T was used and CdTe film was deposited electrically in -o.nv vs. SHE The electrolyte was Cd and Te ammonia alkali solution with controlled temperature in the acrylic cell of 70mm diameter. Electro-deposition behavior of CdTe has affected by the imposition of the intense magnetic field due to microscopic convection in the vicinity of the depositing surface. Electro-deposited surface of CdTe becomes smooth due to microscopic convection around the surface, and the crystallization behavior is also affected, where crystallization temperature and the grain size is changed by the imposition of intense magnetic field.

Jan 1, 2003

By Adam Powell

A Cahn-Hilliard phase field model is formulated to describe transport-limited electrochemical reactions coupled with fluid flow in a metal reduction cell. When the reaction is limited by mass transfer of metal ions from the electrolyte to the cathode, the metal-electrolyte interface at the cathode exhibits a Mullins-Sekerka instability, leading to the growth of dendrite-like "streamers" of liquid metal into the electrolyte, which in turn significantly enhance the apparent mass transfer coefficient there. Model results for iron reduction from ferrous oxide in slag show formation of these streamers. Although the double-layer is not included in this model, the related phenomenon of electrocapillarity can be represented by a gradient penalty term which includes the electric potential gradient, such that interfacial energy is a function of the electric field normal to the interface.

Jan 1, 2003

By Joachim Ulrich

The spreading and splashing behaviour of single tin, lead, copper, aluminium and steel droplets impacting on a solid surface were experimentally examined. The droplet impact was observed using a high speed video imaging technique. The onset of splashing and the mass of the secondary droplets of impacting tin and lead droplets was quantified by the weight difference of the droplets before melting and the splat after the impact. The spread factor and the mass of the secondary droplets in dependence of the impact velocity is shown for different droplet materials, initial droplet diameters, target temperatures in ambient air and inert gas atmosphere. An empirical found correlation predicting the transition from spreading to splashing is presented by means of dimensionless numbers.

Jan 1, 1999

By H. Y. Sohn, S. PalDey

"Fine particles of nickel aluminides and Ni4Mo were synthesized by reducing mixtures of, respectively, A1Cl3 + NiC12 and NiC12 + MoC12 vapors with hydrogen. Though thermodynamically favorable, the coreduction of NiC12 and A1Cl3 by H2 to form Ni3Al did not readily happen experimentally. The addition of a small amount of aluminum vapor was needed to initiate the coreduction reaction. The product particles as observed by TEM were very fine but usually agglomerated. The electron diffraction pattern of particles identified NiAl and NiA13 along with Ni3Al and metallic Ni. The content of Ni3Al was maximized at 52 mol% at 1050°C under the partial pressures ofH2, A1Cl3, and NiC12 at 57, 1.4, and 0.5 kPa, respectively. When a mixture of NiC12 + MoC15 was reduced by hydrogen, Ni4Mo particles with some Ni or Mo particles were obtained, the maximum content of Ni4Mo obtained being 93 mol % . The particle size was in the range of 100 to 200 nm. An Ni4Mo coating of 700 nm thickness on an Ni substrate was also prepared.IntroductionThe search for new high-temperature structural materials has stimulated much research on intermetallic compounds. Nickel aluminides have low densities, relatively high melting points, and good high-temperature strength properties. They show an increase, rather than a decrease, in yield strength with increasing temperature (1). Ni4Mo is also of interest as a high-temperature structural material. The major shortcomings of these intermetallics are their inherent brittleness at room temperature when they are in polycrystalline form. For much the same reason, the conventional casting of intermetallics is difficult. Ingot metallurgy and powder metallurgy are two other processing techniques. The first technique is quite energy consuming. In powder metallurgy, the powders of metals and alloys are consolidated in near net shape and then subjected to secondary processing. It would, therefore, be advantageous if intermetallic compounds can be produced in fine powder form from inexpensive raw materials, using less energy."

Jan 1, 1998

By Jesús Contreras

Since the commencement of its activities in Huelva in 1970, Atlantic Copper has maintained a course of action that has been more demanding than the successive environmental legislations current at different times. As its primary objective it has sought compatibility between the protection of the environment and both its industrial activity and the social and economic development of the area in which its Metallurgical Complex is located. For this reason, since the seventies it has maintained a continuous programme of investments which have allowed it to attain its present environmental situation. As a consequence of the Environmental Policy of Atlantic Copper, in April 1998 it obtained certification for its Integrated System of Environmental Management (SIGMA) according to international standard IS0-14001, and under European Community Regulation 1836/93 (replaced by the 76112001) for the Eco-Management and Eco-Audit System (EMAS). The SIGMA formalises the environmental management practices of Atlantic Copper and engages it to have available a system that can be fully audited. Atlantic Copper was the first European Company in the non-ferrous metallurgical sector to obtain both the UNE-EN-ISO 14001 certification and the EMAS registration. The present paper reviews the actions by Atlantic Copper in environmental matters that have allowed it to achieve its present position. It also describes the coming stages of improvement planned and the modifications to be carried out in the near future, in particular the criteria for the selection of technologies on the basis of the concept of BAT (Best Available Techniques) introduced by the European Union, and always guided by the final objective of converting Atlantic Copper into a reference within the sector, comparable to the best designed and operated installations in the world.

Jan 1, 2003

By R. H. Hanewald

The INMETCO process has been modified so as to recover nickel. chromium and Iron from a wide variety of metal containing waste-streams. This now includes the recovery of metals from spent acid solutions such as chromic acid etching I1quids. nJcke1 and chromium plating solutions; stainless and superalloy pickling solutions. etc. In addition. hazardous electric furnace stainless steel and. superalloy baghouse bags can be processed so as to recover the valuable metall1cs. A detailed review of the above new recovery techniques w1ll be discussed as well as the current operating methods used at INMETCO.

Jan 1, 1992

By Gaifeng Xue, Xiaohong Xu, Meng Liu, Yijie Song, Guotao Xu, Jixiong Liu

BN (Boron Nitride) based composites were prepared with hot-pressing by using h-BN as main material in ceramic preparation process. The relative density, bending strength, vickers’ hardness, thermal shock resistance, thermal expansion coefficient, thermal conductivity, phase composition and microstructure were tested and analyzed by using modern testing technology. The results indicate that the best formula is B, the relative density is 97%, the bending strength is 260 MPa, the hardness is HV5 343kg/mm2, the thermal expansion coefficient is 2.8×10-6℃-1, the thermal conductivity is 22 W/(m.K) and have no crack after thermal shock for 20 times by water cool. XRD analysis indicates that the main phase compositions are h-BN, β-Si3N4 and sialon. SEM studies show that the grains wrapped up by solid solution.

Jan 1, 2015

By G. Glinski, K. A. Pericleous

"Recent advances in new computational modelling techniques such as Lattice-Boltzmann and Dissipative Particle methods offer the prospect of simulating complex fluids such as colloidal and dense suspensions in industrial processes. They are referred to as mesoscopic methods since they lie between molecular dynamics at a microscopic atomistic scale «lO-9m) and traditional macroscopic CFD methods (> 1O-2m). The models behave like a 'coarse-grained' gas consisting of fictitious interacting particles, which are much larger than the real molecules of the actual fluid they represent. Inter-particle forces are set so that the collisions collectively mimic the phenomenological transport properties and flow of the underlying fluid at a macroscopic scale.Much of the developmental work to date has focused on laying theoretical foundations based on thermodynamic and kinetic theory. Successful applications include predictions of macroscopic transport properties of complex fluids and flows in porous media and filters. With the constant increase in computational power, these mesoscopic methods are now sufficiently developed to determine their suitability to simulate complex fluid flows in real industrial processes. This work describes the application of meso scopic methods to the stencil printing of solder pastes in the assembly of electronic components. The aim of this work is to assess the ability of these methods to study the transport mechanisms of individual solder particles suspended in the flux solvent as they enter and fill the micro-apertures of a stencil. This paper demonstrates the coupling of such mesoscopic methods to continuum CFD methods to predict the flow of dense suspensions (i.e. solder paste) in industrial processes."

Jan 1, 2001

By G. C. Yao

Iron and silicon impurities can form needle and branch shape intermetallie compounds in molten aluminum when there is no manganese. It is difficult to separate them from molten aluminum by electromagnetic separation. The Fe-Si-AI and Fe-Al intermetallic compounds were transformed into Mn-Fe-Si-Al and Mn-Fe-Al compounds by the addition of manganese into molten aluminum. In molten aluminum the morphology of these intermetallic compound particles is lumpish and spherical. Migration resistance of these impurity particles is small, which is beneficial to separation. FeSiMnA4 and FeMnAI6 are paramagnetic. These impurity particles can be moved by magnetic force and can be separated from the molten aluminum.

Jan 1, 2003

By Xu Zhang, Xuewei Lv, Guibao Qiu

Slag foaming phenomenon is of vital importance to the mass and energy transfer in metallurgical processes. A considerable extensively studies carried out via out-gas in the past cannot simulate well the foaming phenomenon formed in the blast furnace where high TiO2 iron ore is used. A gas reaction was designed in the water-glycerol system to simulate the inner-gas system. This study investigated the influences of solution viscosity, particle concentration and particle size on foaming caused by endogenetic gas. The results show that the foaming height decreases with the increase of solution viscosity, which means reduced foaming ability, more difficult foaming elimination process and prolonged time for natural defoaming. With increasing the solid particle content, the foam height presents a trend which increases firstly and then decreases. Under a certain solid particle content, foaming height decreases with the increase of solid particle size, indicating a weak foaming ability.

Jan 1, 2015

By Tetsuya Uda, Sakae Shirayama

"With the aim of producing nickel (Ni) metal directly from acidic aqueous solution containing cobalt (Co) and other impurities, selective reduction of Ni was examined. As a preliminary experiment, sodium hypophosphite monohydrate (NaH2PO2·H2O) was selected as a reductant, and reacted with aqueous solution containing 0.1 mol L-1 nickel sulfate (NiSO4·6H2O) and 0 ~ 0.05 mol L-1 cobalt sulfate (CoSO4·7H2O) for 3 hours at 90 °C. As a result, it was revealed that Ni was selectively reduced and separated from Co in the acidic region (pH= 4.8). In this study, differences of reduction behavior between Ni and Co were investigated, and the feasibility of Ni I Co separation by the selective reduction of Ni was discussed.IntroductionEfficient Ni condensation and separation from Co are essential in nickel hydrometallurgical processes. Currently, the hydrometallurgical production of Ni from oxide ore is mainly carried out by acid leaching at elevated temperature, followed by the removal of impurities using neutralization, and condensation of Ni and Co into intermediate products such as hydroxides and sulfides. Then, the intermediate product is dissolved in acid aqueous solutions, and Ni I Co separation is conducted by solvent extraction. Finally, Ni and Co are recovered by electro-winning. This complicated process consumes large amounts of alkali, hydrogen sulfide (H2S), and organic solution in a multiple-staged process'. To reduce the consumption of these chemicals, it is important to recover Ni more efficiently from acidic aqueous solution containing impurities."

Jan 1, 2014

By K. Sarveswara Rao

The present paper firstly describes some recent trends from literature on energy management via process intensification to arrive at sustainable technologies for aqueous processing of minerals, metals and materials. Secondly, the energy saving measures practiced in leaching, solid-solution separation, solution purification, metal and material winning and environmental aspects have been discussed. The emerging importance of interdisciplinary nature of hydrometallurgy for practical applications is also highlighted. With the above background, the present paper describes an overview of energy conservation and autoclave processes with a special reference to hydrometallurgical research activities of our Laboratory.

Jan 1, 2008

By M. M. Kim

As-electrogalvanized coatings of pure Zn, Zn-11% Fe, and Zn-18% Fe coatings were characterized in terms of initial crystal structure and surface morphology. Samples were then subjected to heat treatments simulating the paint bake cycle of automobile manufacturers. Surface morphology changes were correlated with the process variables, and crystallo.graphic changes were interpreted by mapping heat treatment routes on the Fe-Zn phase diagram. The morphology of pure zinc electrogalvanized coatings with heat treatment from platelets to smeared platelets. The zn-11% Fe coating changes with heat treatment from tetrahedral nodules to a mixture of round and tetrahedral nodules, with the Zn-:18% Fe coating always having round nodules. Regarding crystal structure, a critical transformation time can be defined at any selected temperature, below which the crystal structure does not change. This temperature is related to iron content.

Jan 1, 1990

By Dhanesh Chandra

Long term stability studies were conducted on four variants of LaNi5; 10,000 hydriding/dehydriding cycles were used to evaluate their suitability for a metal hydride cooling system. Thermodynamic and structural studies were conducted to determine changes in these materials during cycling test period. The hydrogen sorption properties of LaNi5.2, and Lao 9Gd0.1Ni5 and LaNi4.75In0.27 were seriously degraded during the tests but the LaNi4.8Sn0.22 hydride was virtually unaffected. Hydride isotherms were measured at the beginning and at intervals through out the test period to observe the nature and extent of damage degradation in the sorption properties. X-ray diffraction studies of the alloys (LaNi5.2, LaO.9Gd0.1Ni5 LaNi4 8Sn0.22) and their respective hydride, before and after test, provided insight with regards to the observed changes in the hydride properties. Electron microscopic studies were also conducted to evaluate the changes in particle sizes.

Jan 1, 1989

By Alexander V. Suvorin, Vladyslav M. Sokolov

"The traditional technologies for production of the coprecipitated and deposited catalysts are analyzed from the standpoint of diversion of application of the feedstock and increase of efficiency for its usage. The options for return of the metals of spent catalysts to the catalysts production are described. The novel environmentally friendly and cost efficient approach for reutilization of the spent catalysts is realized in practice. It anticipates application along with spent catalysts of the waste generated in the catalytic productions. Reutilization of the Ni-containing catalysts is referred as an illustration. Introduction The recent development of large catalytic manufacturing for organic and inorganic synthesis, and petroleum refinery as well as for applied environmental catalysis has brought about increase and diversification of catalysts production. The generation of spent catalysts has been increased correspondently. The feedstock for production of catalysts is mostly metals in a form of nitrates, carbonates, hydroxides, hydroxydcarbonates. Sometimes salts of organic acids, of ammoniates, of chlorides and of sulphates occur. All these materials are scarce and expensive. So their repeated use by reutilization of spent catalysts is very actual issue. The traditional recycling the Fe-, Cr-, Ni-, Cu- or Zn-containing spent catalysts are carried out by pyrometallurgical reclamation of pure metals or alloys. They can not be used directly in production of catalysts [1, 2]. The hydrometallurgical approach is used for recycling spent catalysts with PGM, W, Mo, Co, Ni or Cu. It provides production of salts of these metals in a form of sulphates, chlorides, carbonates, hydroxydcarbonates and sometimes nitrates or ammoniates. Only a limited number of these salts can be used directly in production of catalysts. Material losses during catalysts production The basic feedstock for manufacturing coprecipitated and deposited catalysts that may be produced from the spent catalysts is aqueous solutions of metals nitrates. Their production is based on application of nitric acid as a dissolvent. About half of it is lost with the flue gases in a form of nitrates vapor and nitrogen oxides (II, IV). The last compound is generated by reaction:"

Jan 1, 2008

By Varadajan Seshadri

Kambara Reactor (KR) consists of a ladle where pig iron is stirred by an impeller during addition of a flux powder. The objective is to improve agitation leading to dispersion, of the flux powder, in the molten pig iron in order to improve desulfurization of the liquid melt by improving solid liquid interaction. The life of the impeller is limited as it is subjected to abrasion at high temperatures. The shape and design of the impeller also has an effect on the performance of this reactor. A 1:7 scale cold model of a KR unit of the Companhia Siderurgica de Tuberao ,one of the integrated steel plants in Brazil was constructed in order to evaluate the mixing and mass transfer conditions. Mixing efficiency was investigated by tracer additions and subsequent measurement of conductivity. Mass transfer in the reactor was assessed through iodine transfer between water and kerosene and employing a macroscopic model. Mixing depends on impeller shape and depth of immersion The role of dispersion is highlighted by faster kinetics when impeller velocity is increased. The results enable assessment of design aspects of the impeller on the process.

Jan 1, 2006

By C. J. Beyke

The U.S. Bureau of Mines has developed a process for the selective recovery of Pb metal from a mixed Pb-Zn concentrate. The concentrate was leached in recycled H2SiF6 at atmospheric pressure and 95° C with a redox potential of 570 mV (Eh). Eighty-five pct of the Pb was selectively leached from the concentrate while 87 pct of the Zn remained in the residue. Pressure leaching of the concentrate was slightly less successful, with 78 pct of the Pb leaching from the concentrate and 80 pct of the Zn remaining in the residue. Pure Pb metal was successfully electrowon from a purified PbSiF6-H2SiF6 solution with 96 pct current efficiency and 0.69-kW.h/kg energy consumption.

Jan 1, 1991