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By P. M. Tait, N. A. Warner

"The refining of thermally produced zinc is currently performed using a highly energy intensive and arguably outmoded process, distilling zinc under atmospheric pressure at temperatures of 900°C to 1000°C. In order to produce refined zinc more profitably and with less environmental impact a new process has been proposed. This process is generic to all thermal zinc smelters and aims to match the purity of zinc from current technology (99.99%-99.999%). The objective is to perform all separation processes using only the heat contained in the smelter product stream. Vacuum conditions are extensively used lowering operating temperatures and enhancing separations. As part of this process zinc is distilled under vacuum from high concentration obtaining a refined product with respect to lead content. A mathematical model has been developed from fundamental principles to describe this stage, the distillation of zinc across a temperature difference between two circulating zinc streams in open channels under vacuum. Heat for the distillation is supplied by the liquid phase, necessitating a large recycle to maintain high operating temperatures, and keep zinc concentrations high. In determining this model and the operating conditions required, relationships between temperature, pressure and composition are considered.IntroductionCurrent technology (the Refluxer) used to refine thermally produced zinc is both expensive and highly inefficient. At present 80% of the worlds zinc is produced via the electrolytic process reflecting the poorer performance of the thermal route, the zinc-lead blast furnace and Refluxer. A new process is proposed to overcome the drawbacks of current processes. These drawbacks are both economic and environmental. The Refluxer requires 6.6 GJ of energy to refine one tonne of SHG zinc 1, other disadvantages of the Refluxer stem from high operating temperature, around 900°C, and liquid zinc being highly corrosive towards ferrous metals. The Refluxer is constructed from silicon carbide sections which join together by means of flat machined faces making liquid metal leaks inevitable. The Refluxer columns are very sensitive to thermal cycling, thermal shock and mechanical vibration, which easily lead to structural failure. To avoid thermal stress on the columns the feed rate and feed temperature need to be kept constant which means the feed baths to the columns must be able to accept solid and liquid feed as the Refluxer has to operate when the smelter is shut down."

Jan 1, 1998

By Cynthia K. Belt

Improved energy efficiency has grown in importance within industry as energy costs have escalated. The analysis of trends and changes to a process is critical in making the best business decision in energy management. Frequently, energy use per day (Kilowatt-Hour or British Thermal Units) is used to track energy efficiency. Sometimes, the somewhat more complex method of energy per processed weight (Kilowatt-Hour per Metric Ton or BTU per Pound) is used to make this evaluation. Yet both methods ignore the effects due to throughput and weather. In this paper, different thermal processes and systems will be evaluated using statistical methods to highlight alternative methods to evaluate energy efficiency. Examples and potential problems will be discussed for both a single process and a collection of processes within a plant or corporation.

Jan 1, 2008

By T. Gunawansa, T. L. Alford, Zhao Zhao, A. R. Lanz, N. David Theodore

Many sustainability issues arise during the manufacturing processes that are currently used for solar cells. Solar energy is a renewable energy source that is independent of the earth’s resources, and it is therefore important for the development of more sustainable technologies. Microwave annealing (MW) has been proposed as a technically feasible fabrication scheme for large area silicon solar cells. Apart from that, microwave annealing has been demonstrated to be a promising alternative for repairing damage and electrically activating dopants in ion-implanted semiconductors for integrated circuit manufacturing. A microwave oven is cheaper than conventional furnace systems. In addition, microwave heating is much more efficient than conventional furnace heating, as heating is directly produced inside the material. This minimizes the loss of energy due to heating of the ambient. There is a need for more efficient processing techniques. In this study, microwave annealing is used as an alternative to the current postimplantation processing. Arsenic-doped silicon was microwave annealed (with an aluminacoated silicon carbide susceptor) to activate dopant atoms and to repair damage that was caused by ion implantation. Sheet resistance and Hall effect measurements were used to assess the extent of dopant activation. Rutherford backscattering spectrometry (RBS) with ion channeling was conducted to determine the extent of recrystallization. The dopant activation and recrystallization resulting from microwave annealing is compared with that resulting from conventional rapid thermal annealing (RTA) with the same heating profile. The results show that when compared to RTA, susceptor-assisted microwave annealing results in better dopant activation for shorter anneal times under the same heating conditions.

Jan 1, 2015

By Celaletdin Ergun, Ibrahim Erden, Gurbuz Gunes, Thomas J. Webste, Huinan Liu, Abdurrahman Bahadll

"B, Ti, Ag, AI and Cu substituted hydroxyl apatites were synthesized via precipitation method. Then the samples were air-sintered at 1300°C for 2 hrs and characterized with XRD, SEM, FTIR, and cell adhesion behaviors.IntroductionSynthetic hydroxylapatite (HA, Ca10(P04)6(0H)2) has a similar composition and structure to biological apatite. Therefore, it has been safely and extensively used as an implant material for bone substitute. However, synthetic HA has been used for a various applications including medical or non-medical applications, such as matrices for drug release control, bone cements, tooth paste additive, blood purification agent, monolithic implants or coatings on metallic implants, packing media for column chromatography, gas sensors, catalysis and host materials for lasers and luminescent materials, etc. [1-9].The major factors affecting the performance of HA on these applications are crystal morphology, density, porosity, pore size and distribution, chemical composition, and surface structure. As provided by the high flexibility of the apatite structure a great variety of cationic and anionic species can be substituted into HA structure which is specifically considered as an effective method to modify the properties of HA [10,11]."

Jan 1, 2012

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen temary system, which is of fundamental importance for discussing the recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, Sb015 and Sb203 in the PbO-SbOu and PbO-Sb203 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen ternary system, which is of fundamental importance for discussing the' recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, SbO1.5 and Sb2O3) in the PbO-SbO1.5 and PbO-Sb2O3 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By Ch. -A. Gandin, M. Rappaz

"The grain selection mechanism which occurs during the growth of columnar dendritic structures is routinely used in the investment casting industry to produce directionally solidified (DS) and single crystal turbine blades. However, the evolution of the grain density with increasing distance from the chill has rarely been correlated with the evolution of the grain texture. This contribution presents a three-dimensional (3-D) stochastic modeling approach which permits the computation of grain maps, pole figures and grain density evolutions in DS superalloys. These predictions are compared with measurements resulting from an automatic indexing technique of Electron Back-Scattered diffraction Patterns. This 3-D stochastic model, which applies to uniform temperature situations, has to be extended to the dendritic growth in a thermal gradient. As a preliminary step, a 2-D Cellular Automaton (CA) has been coupled recently to Finite Element (FE) heat flow computations in order to predict the grain structures in complex shape investment cast part. The application of this CAFE model to the investment casting of a turbine blade is presented. Considering these results, the extension of the CAFE algorithm to three dimensions is discussed.INTRODUCTIONThe selection of columnar grains during the directional solidification of alloys plays a key role during the investment casting of directionally solidified (DS) and single crystal (SC) components for aerospace applications [I]. This selection mechanism, leading to a competition of the dendritic network propagation at grain boundaries, has been the subject of many investigations. In particular, the study of Walton and Chalmers [2] is remarkable since it provides a link between the evolutions of the density and of the texture of columnar grains with increasing distance from the mold wall. Since this original work of Walton and Chalmers, two new tools have become available, which enable one to revisit the problem of grain selection in much greater depth. The first one is a fully automatic indexing technique of Electron Back-Scattered diffraction Patterns (EBSPs) [3-6] which directly gives the crystallographic orientation of the solid at any location of the specimen. Pole figures, orientation distributions, misorientations between grains can be visualized very easily with this technique. This information can be directly compared with the results of a second tool: a three-dimensional (3-D) stochastic model (SM) describing the nucleation and growth of grains in a uniform temperature field [6-9]. In order to extend this model to non-uniform temperature situations, a preliminary 2-D model has been developed [10]. It is based on a Cellular Automaton (CA) algorithm coupled with Finite Element (FE) heat flow computations. Since the details of both the automatic indexing technique of EBSPs and the simulation tools have already been published [3-10], only a brief summary is given here."

Jan 1, 1994

By M. Giralico

Optimized mixer settler designs will now handle flows of over 25,000 GPM. The size and expense of the equipment hamper experimental settler optimization efforts. Computational Fluid Dynamics (CFD) is a timely and predictable tool for settler design development. In the past, CFD has been used to evaluate only the flow field in pumped and auxiliary tanks. A similar numerical analysis is used to evaluate settler flow and phase separation. Phase separation is analyzed using multiple species for the aqueous and organic phase. Experimental validation shows good agreement between the computational and experimental solutions in both flow field and phase separation. The computational model is used to show performance differences between various choices of settler geometry, liquid depth, with variable flow rates. Understanding the differences allows the development of optimized settler designs. System improvements are predicted to lower entrainment levels further and/or allow new smaller footprint designs. This paper focuses on the major design components of the settler and how future technological advances will lead to further improvements in their design. LIGHTNIN?s new designs will handle tomorrow?s production requirements, while maximizing profits.

Jan 1, 2003

By Masayuki Kudoh, Kiyotaka Matsuura

"Molten aluminum and nickel cast onto a steel block exothermically react and produce molten nickel monoaluminide, NiAI, which is simultaneously joined to the steel. The heat of the exothermic reaction is transferred to the steel block, and steel near the surface of the block is melted. The depth of the melted steel increases with both the initial temperature of the steel block and the thickness of the produced NiAI. Iron from the melted steel dissolves in the molten NiAI, and an intermetallic compound of NiAI-Fe pseudo-binary system is produced. During solidification of the intermetallic compound, it is strongly joined to the steel. The Ni.Al-Fe intermetallic compound has an excellent resistance to oxidation and corrosion.IntroductionAn intermetallic compound of nickel monoaluminide, NiAl, offers many advantages over conventional superalloys, such as higher melting temperature, lower density, greater specific modulus and higher thermal conductivity [1]. NiAl also exhibits excellent high-temperature oxidation resistance when doped with zirconium or hafnium, and excellent high-temperature corrosion resistance when doped with chromium or yttrium, that are superior to existing high temperature alloys or coating materials [1-4]. On the other hand, NiAI is significantly brittle at temperatures below 600 K [5-7], which is the most sigriificant disadvantage of NiAI. A possible way to overcome the disadvantage and to utilize NiAl as an environmental-resisting high-temperature structural material may be joining of NiAl to a ductile material."

Jan 1, 2000

By John L. Hostetler

GALFAN, the Zn-5% Al-mischmetal hot-dip galvanizing alloy is coated onto steel sheet, wire, and tube using high-speed continuous galvanizing lines. Factors critical to producing high quality GALFAN are reviewed, The relationship between minimum mischmetal content in the GALFAN alloy and furnace dewpoint will be described. The relationship between peak annealing temperature and furnace dewpoint will also be shown. Typical suategies for operating multi-purpose hot-dip galvanizing lines including GALFAN will be described. A recent development has allowed preparation of steel smp for GALFAN coating using aqueous fluxes rather than high temperature annealing. This allows production of GALFAN-coated smp without over-ageing of the steel, and allows high steel strengths and hardnesses to be obtained. The principles of this process will be described.

Jan 1, 1992

By R. H. Rubisov

Sulphuric acid pressure leaching of nickeliferous laterites has attracted considerable attention from the nickel industry during the past five years. The process is especially advantageous for limonitic laterites that mostly contain goethite, because iron precipitates releasing acid and thus rendering low acid consumption. It is also applicable to mixtures of limonites and saprolites, although at higher acid consumption due to magnesium. Effective process design requires the solubility of metals that precipitate during the process to be known. In the present work, determination of metal solubilities is based on a simple speciation program that assumes the presence of only one dominant complex for each metal. The thermodynamic data for the precipitation reactions are extracted from high-temperature experiments with monometallic systems published previously. The validity of the approach is then tested against mixed bimetallic systems, and finally applied to calculate the solubility of aluminium, iron and magnesium in laterite leaching effluents "at temperature". In both cases of limonitic feed and limoniticfsaprolitic blends, the prediction closely follows metal solubilities measured experimentally at temperatures from 230 to 270°C and at terminal he acidities ranging from 10 to 75 g/L.

Jan 1, 1999

By K. Olsen

As aluminum alloy usage in automobiles grows, there are increasing demands on recycling processes and facilities to deal with mixed alloy automotive aluminum scrap. These processes and facilities strive to produce near virgin aluminum stock, which can be relatively costly and difficult. One alternative is to use physical processing methods to upgrade the scrap properties instead of chemically refining the scrap. The Impulse Atomization Process (LAP, patent pending) is a new process for making metallic and ceramic powders. It can produce fine homogeneous microstructures in scrap aluminum alloys due to high undercooling and rapid solidification. The particles have a very narrow size distribution and are in a convenient form for consolidation. This paper compares and contrasts the microstructural features of Impulse Atomized. and quenched Impulse Atomized powders,' for both AL6061 and a scrap aluminum alloy composition.

Jan 1, 1995

By Sacha Neven

Submerged lance technologies combine high intensity processing characterized by rapid mixing and reaction rates using a simple reactor design. The Isasmelt technology uses a central submerged lance to inject oxygen-enriched air and fuel into a bath thus creating large gas bubbles and intensive turbulence and splash. The lance is equipped with swirlers to increase gas velocity and heat transfer. This enables the formation of a frozen slag layer on the lance which protects it from the aggressive environment. Water models as well as high temperature reactors were used to validate the Davidson-Schiiler model on bubbling. Frequencies and pressure amplitudes were measured in a wide range of gas flow rates: from m3/sec using a water model to more than 30 m3/sec in an industrial process. Agreement with the model was satisfactory. The experiments however also clearly showed that cross-flow and bubble wake induce slightly higher frequencies. No influence of the use of swirlers on the bubbling frequency was observed in the water models.

Jan 1, 2002

By Elders. Wilfred A.

Petrological and geochemical methods, the utility of which has long been established in the mining industry, are proving useful and cost-effective in elucidating the thermal evolution of active geothermal fields. In return, they yield insights into sulfide-silicate equilibria, mass and energy transfer in convecting hydrothermal systems, and the genesis of hydrothermal ore bodies. Within the Plio-Pleistocene sediments of the delta of the Colorado River, in the Salton Trough, several active geothermal systems are known. Temperatures vary from 100-365°C, at less than 2 km depth, and salinities vary from 3,000 to 280,000 ppm, total dissolved solids. The hydrothermal alteration causes marked induration of the sediments, producing greenschist facies metamorphic minerals, including hydrothermal ore minerals. Subsurface authigenic minerals show strong correlation with increasing temperature. A typical sequence in sandstones is (below 150°=C) montmoril-lonite-kaolinite, (above 180°C) chlorite + illite, (above 225°C) calc-alumino-silicates, (above 325°C) biotite. There is a transition from porosity-dominated\to fracture-dominated permeability in the hottest and deepest geothermal reservoirs. This regular series of minerals provides a practical tool during exploration drilling. From drill cuttings, we can make predictions on reservoir temperatures, useful in making decisions on well completion. Other types of geothermometry we have employed include light stable isotopes, fluid inclusions and vitrinite reflectance measurements. A combination of these techniques not only improves our temperature predictions, but together with fission tack annealing studies, permits us to model the dynamics of temperature change and fluid flow in these geothermal reservoirs.

Jan 1, 1981

By Reimers. Jan H.

Practically all the world's lead is produced by sintering and blast furnace smelting, or the Imperial Smelting Process which is a variant of the blast furnace process. Increased coke and labour costs and strict lead emission limits have, however, made blast furnace smelting undesirable in most countries. A change-over to other lead smelting processes providing better working conditions and lower emissions is, therefore,. expected to occur once economic conditions improve and the necessary capital expenditures can be justified. The need for new lead smelting processes has long been evident and a number of new processes have been proposed 'and advanced to various stages of development. One of the new processes is already proven on commercial scale, while several others are still being tested on pilot plant scale.

Jan 1, 1983

By A. Slotwinski, R. E. Barry, M. M. Menon, P. T. Spampinato

"A coherent FM laser radar based sensor for remote metrology of plasma facing material surfaces in a fusion reactor is described. The sensor is capable of 3-D mapping of surfaces, based on a series of precise range measurements from large distances (up to 20 m). Other features include the ability to operate under adverse environmental conditions involving very high gamma radiation (3xI04 Gy/hr), ultra-high-vacuum (<I0-5 Pa), and high temperature (200°C). The paper describes the basic principles of the sensor, together with experimental results obtained with the sensor. The ability of the sensor for remote rendering of ""visual quality"" images without the need for any external illumination is also illustrated.IntroductionMeasurement of the features of large area surfaces (-1500 m2) to sub-millimeter accuracy, from relatively large distances (20 m), is necessary in the case of the International Thermonuclear Experimental Reactor (ITER -a 1500 MW fusion reactor that is currently in the design phase). Furthermore, the measurements may have to be performed after the reactor is temporarily shut down. During such shut-downs, the ITER in-vessel environment will be highly radioactive due to neutron activation of the reactor wall (gamma radiation field of 3xl04 Gy/hr), the vessel will be maintained under ultra-clean vacuum conditions (<10-5 Pa), and the plasma facing surfaces will be maintained at elevated temperature (200°C). Therefore, the precision measurements must be conducted remotely, and because of the large dimensions of the fusion reactor and the limited number of access ports, the measurements must be done from large distances. The reactor vessel is a large toroid. Fig. 1 shows the cross section of the toroidal vacuum vessel, and the location of the metrology probe. Because of the very large surface area involved, fast scanning capability is also needed to reduce the reactor down-time."

Jan 1, 1997

By T. Manlyama

The Tamano Smelter of Hibi Kyodo Smelting CO., Ltd. went into operation in 1972. The Flash Smelting Furnace that was originally adapted was equipped with electrodes that were attached to the settler substitute of the slag cleaning furnace. Later the development of our own original coke combustion technology was promoted and a new Tamano Type Flash Smelting Furnace (T-FSF), without electrodes, was put into operation in 1988, T he technology of coke combustion and combustion the burner have continued to improve. As a result the copper losses in the Wag have been reduced as well as a stable operation has been achieved, Furthermore; this has been accomplished while increasing the concentration feed and the matte grade. The current objective is to continue to strive for high matte grade operation and to raise production efficiency while paying attention to the important subject of copper losses in the slag. In this report, the data related to the copper loss in the slag reduction are presented along with the influence of the thickness, settling time and coke. The recent operation conditions of the T-FSF are also presented.

Jan 1, 2003

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified.

Jan 1, 2006

By G. Sterzik, W. A. Jankola, T. L. Salway, D. J. McKay

At Trail, British Columbia, Cominco's zinc leaching and solution purification processes include direct pressure leaching of zinc concentrates, leaching of fume from the lead smelter, leaching of calcine and electrolyte purification. These processes have been adapted to match the unique characteristics of Cominco's integrated zinc and lead operations. Recent modifications include changes to the purification process and iron-residue handling circuits. In 1997, a new five-compartment autoclave, complete with ancillary equipment, was installed in the pressure leaching plant. This paper discusses these changes, the current flowsheet and further improvements.

Jan 1, 2000

Pyrometallurgical reactors constitute a key processing component in the total primary and secondary resource cycle, being involved both in primary smelting, converting and extraction, as well as the reprocessing of scrap, from aluminum cans to end-of-life automobiles. To effectively control the overall resource cycle, one needs to take a systems modeling approach of the whole cycle, seeking to also understand the dynamic process behavior of the individual components of the cycle, and then especially the part that contributes most to the chemical conversion, namely the pyrometallurgical reactor. This paper highlights the role of pyrometallurgical thermodynamics, in the whole resource cycle and specifically places equilibrium thermochemistry in the context of process dynamics where large variable inventories are recycled or maintained within the system. This paper will therefore review the semi-empirical dynamic modeling tools, which are used to model complex systems with the specific goal of developing dynamic predictive models, which also include slag-alloy chemistry, towards controlling the recycling in a feed forward manner. To illustrate the primary processing side, high carbon ferrochrome will be presented as a brief case study. It also will show how the distributed nature of the chemistry of melts in the case of primary extraction, and secondary materials such as recycled end-of-Iife vehicles, have a significant impact on the process outcomes and model predictions. It is therefore argued that the fundamental thermodynamics and kinetics in metallurgical reactors playa final crucial role in modeling the closed material cycle, but only when it is used in conjunction with process systems theory based on reconciled data for parameter estimation and model calibration.

Jan 1, 2003