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By Carlos Ortiz

The Huelva Flash Smelting Furnace was commissioned in September 1975. The Smelter and the Acid Plant were expanded in 1995 to their present capacity of 300,000 tpa new copper equivalent and one million tonnes of concentrate per year. During these years of operational experience, most of the initial practices have been reviewed, process control has drastically improved and main process equipment has been modernised. The fourth Flash Furnace campaign lasted 9 years (1995-2004) during which 8 million tonnes of concentrate were smelted. Increasing sulphur content in concentrates and new environmental requirements imply new challenges for smelters to keep production and operation costs down. This paper is an overview of the modifications and improvements carried out in the 2007 general shutdown in Smelter and Acid Plants. Al

Jan 1, 2008

By Francois Barthelat, Sam Goroshin, David Frost, Alexander Cappozi, Atefeh Nabavi

"In this study, a novel chromium–chromium sulfide cermet was produced by self-propagating high-temperature synthesis (SHS). Conventional techniques for manufacturing metal sulfides are complex, environmentally harmful, and not suitable for producing complex-shape articles. To overcome these disadvantages, a new method for the preparation of the metal-sulfur precursor charge is proposed, which can be described as reactive casting. The first cermet samples produced with the SHS process were found to be very porous, brittle, and have low mechanical strength. The possible sources for the generation of porosity were identified and analyzed and the process for manufacturing the cermet was modified. By improving the manufacturing process, the porosity inside the produced cermets was reduced from 70% to 12%.IntroductionMetal sulfide composites are in high demand in the chemical, metallurgical, and electrical industries because of their valuable characteristics such as hardness, semi-conductivity, electroluminescence, infrared transparency and catalytic properties. Current manufacturing methods for metal sulfides usually involve one of two different principal methods, including a complex multistage wet chemical process involving the precipitation of the corresponding salts from an aqueous solution with hydrogen sulfide, or hot sintering of the respective elemental reactant powders in a resistive furnace in a high-pressure inert or hydrogen-sulfide atmosphere [1, 2]. These conventional methods for synthesizing ceramic metal composites are complex, extremely time and energy consuming, environmentally harmful, and rarely able to manufacture articles with complex shapes. Therefore, in order to overcome these disadvantages, self-propagating high-temperature synthesis (SHS) was considered as an alternative method that offers significant improvements over the traditional cermet manufacturing methods [3]. SHS, which is a relatively new and attractive method for producing a wide range of advanced materials, is based on the self-sustaining feature of the highly exothermic reactions of the reactants. The SHS process results in high product purity, since the high temperatures generatedin the reaction cause any impurities to volatilize [4, 5]. SHS has low energy consumption and doesn’t require an external energy source and complex equipment, and it is self-contained [1, 5]. Since combustion synthesis has low power requirements, it is one of the few methods of materials synthesis that is feasible in outer space. Also, the process has a low cost and is capable of directly synthesizing articles with the desired shape, size and structure [5, 6]. The chemical reactions associated with SHS are typically completed in a few seconds leading to the formation of the condensed product. The high reaction rates and relatively rapid cooling in SHS reactions can avoid undesirable grain growth in products which often occurs with the conventional sintering method [3, 5, 7]. The traditional method for sample preparation in the SHS technique is to compact the reactant mixture powders in a steel die by a press to a typical density of about 80% of the theoretical maximum value, before igniting the mixture [8]. This method requires a large compression force to increase the green density and to minimize any pores in the green compact. To overcome these disadvantages, a new method for the preparation of the precursor charge in metal-sulfur by SHS is proposed which can be described as melt casting of a reactive mixture, or reactive casting in short."

Jan 1, 2012

By Zhang Yongzhu

Developments on bioleaching of low grade ores and refractory gold ores by T. Ferrooxidans in China are summarized. Effect of the ions on bacterial growth, bioelectrochemical reaction mechanism of sulfide minerals and bacterial reaction mechanism are also discussed.

Jan 1, 1992

By T. Shibasaki, S. Kamio, K. Kanamori

"Mitsubishi Process has been proven through fifteen years operation to be highly productive, cost efficient and easy to abate environmental requirements. However, in order the process to remain competitive from now on, it should also be adaptable to a variety of varying conditions. Various test works have been conducted from such a stand point of view and some of the new concepts have been implemented to the actual operation.The paper discusses the adaptability of the process to the change of concentrate grade with respect to copper and also impurities, acceptability of the secondary materials and the potential to increase unit capacity. IntroductionThe first commercial plant of Mitsubishi Process with 48,000 mt copper annual capacity started its operation at Naoshima Smelter of Mitsubishi Metal Corporation in 1974, and the second plant with 65,000 st annual capacity started in 1981, at Kidd Smelter, Timmins, Ontario, now Kidd Creek Division of Falconbridge Limited 2. These plants have increased their capacities to 90,000 mtpa respectively by adding oxygen and acid plant capacities while maintaining the original furnace design uncharged. Thereby both smelters have established more cost efficient operations. (3), (4)Mitsubishi Process applies so-called multi-furnace continuous system. Figure 1 shows conceptual flowsheet. Backgrounds that required and justified the development of such system are as follows:"

Jan 1, 1988

By Raj P. Singh

Two design-of-experiments studies were carried out to investigate the leaching of technical grade molybdenum tri-oxide (TGM) in the presence of hydrochloric acid and the mother liquor of ammonium di-molybdate crystallization used as an ammonia source. Results indicated that leaching of TGM in HCl is possible only when used at about 1N concentration. In high concentrations of HCl, technical grade MoO3 had very high solubility (7.5 to 40 g/L Mo). The most suitable conditions for HCl leaching of TGM were obtained at a slightly elevated temperature of 80°C. Using about 1N HCl at 80°C, potassium in the leached solids (TGM) decreased to about 110 ppm, a value typically obtained in TGM leached in HNO3 - NH4NO3media (3.5 - 4.0 moles /L HNO3 + 0.5 ? 1.0 moles/L NH4NO3). Mo losses under these conditions were 0.8-0.9 g/L Mo. The HCl-leach method, presented here-in, has a significant advantage in chemical cost and environmental benefits over HNO3 ? NH4NO3 purification method.

Jan 1, 2006

By Vadym Drozd, Yongzhou Sun, Shah Najiba, Jiuhua Chen, Andriy Durygin

"Phase transitions of the potential hydrogen storage compound, ammonia borane (NH3.BH3), was investigated using Raman spectroscopy and a diamond anvil cell at high pressures up to 9.5 GPa and low temperatures down to 90K. At room temperature, ammonia borane has three phase transitions in this pressure range. Upon cooling, four new phases were discovered through changes in characteristic Raman spectra. This result provides information about the stability of new bonding characteristics of this potential hydrogen storage material at low temperature and high pressure region.IntroductionDevelopment of hydrogen technology requires the safe, efficient and environmental friendly materials for hydrogen storage and hydrides have attracted much attention as hydrogen storage media. Among chemical hydrides, ammonia borane (BH3NH3) stands out due to its high gravimetric and volumetric hydrogen density ' "". Despite high hydrogen content, this compound is very stable. It releases hydrogen in several steps by thermal decomposition in the temperature range of 100°C to 500°C. Direct thermal decomposition also causes toxic borazine emission. Recent research interests on ammonia borane include destabilizing this compound to lower the dehydrogenation temperature with an enhanced hydrogen release rate using different techniques, e.g. the nanoscaffolds'', ionic liquids"" and acid'"" or transition metal catalysts' ""'. As a molecule of ammonia borane consists of protonic (NH) and hydritic (BH) hydrogens bonded by the polarized dative bond, thermal or catalyzed decomposition requires breaking of N-H and B-H bonding. Still now, the detailed information about the bonding characteristics of ammonia borane is not sufficient to understand details about its phases and structures. The development of methods to enhance hydrogen discharge rate from ammonia borane requires a detailed study about the structural and dynamical properties that control the stability and the intermolecular interactions of this material. This study is motivated to investigate the stability of the existing phases and also to explore the existence of any new phases at different temperatures and pressures which may have enhanced hydrogen release and uptake properties."

Jan 1, 2012

By O. E. Omotoso

This study is part of an ongoing investigation to understand the mechanism of stabilization/solidification of hazardous chromium wastes in ordinary Portland cement (OPC). Tricalcium silicate (C3S*),a major component of OPC is mixed with reagent grade Cr(lll) and Cr(VI) solutions, to simulate complex cementiCr waste systems. Scanning electron microscopy (SEM) and energy disperse spectrometry (EDS) were employed to provide microstructural and chemical information. Transmission electron microscopy (TEMlEDS), apart from complimenting the SEM, was used to probe the distribution of Cr in the hydration products of C3S and to provide crystallographic information. 29Si MAS NMR (magic angle spinning - nuclear magnetic resonance) Was used to characterize the influence of Cr on the hydrated silicate structure.

Jan 1, 1995

By Y. Y. Sheng

Plume flows created by gas injection into liquid metals have been studied extensively, however the dynamics of bubbles within the plume have not received adequate attention, particularly for large, irregular bubbles, characteristic of the processing of liquid metals. The present model uses a combined Eulerian-Lagrangian approach in which an estimated void fraction distribution is used to calculate the liquid flow field with a conventional Eulerian scheme. The trajectories of bubbles are then computed in a Lagrangian manner using the estimated flow field, and experimentally measured information on bubble drag coefficients', lateral migration due to lateral lift forces and interaction with turbulent eddies, and variation in bubble size due to break-up. Turbulence in the two-phase zone is modeled with a modified k-e model with extra source terms to account for the second phase which have been recently determined by the present authors. The computed void fraction and turbulent liquid flow field distributions are in good agreement with experimental measurements.

Jan 1, 1993

By Donald R. Sadoway

The viability of treating certain forms of hazardous waste by direct electrolysis in molten oxides is under investigation. Secondary residue or waste mud produced in the course of chromate chemical production is the focus of attention in this study. The goal is to reduce the water soluble hexavalent chromium either to insoluble trivalent chromium or to chromium metal. Electrolysis tests have been conducted in a high temperature cell containing chromate sludge dissolved in an electrolyte composed of Al2O3, SiO2, CaO, and MgO. Oxygen production on a carbon-free anode has been confirmed.

Jan 1, 1992

By J. D. Zhu, T. Ohmichi, H. Yasuda, S. Kashiwai, I. Ohnaka

"Since the casting process affects the properties of castings, its computer simulation has been greatly developed in the last decades. This paper presents our recent works, especially on mold filling simulation, because most casting defects such as porosities and inclusions that greatly affect the properties originate during mold filling. The first topic is the mold filling simulation with consideration of cavity pressure change during mold filling, including direct observation of flow phenomena with X-ray and pressure measurement. The second .one is the mold filling simulation in the lost foam process, in which gasification of polystyrene pattern and gas outflow through the coating and mold have been considered. The simulation can predict not only the mold filling sequences but also periodical vibration of the gas layer between the melt and pattern. The third one is the comparison of simulation of Al melt flow in a metallic runner and direct observation through a transparent mold, showing that the entrapped gas or inclusions is expelled ahead through the melt and its simulation needs very fine meshes. These examples show that the comparison of simulation and observation is very important to develop the numerical simulation further.IntroductionThe mechanical properties of castings are greatly affected by casting defects such as porosities and inclusions, and solidification structure. Although recently the structure simulation has greatly progressed [1-4 ], the application in plants is very limited, because the structure is mostly determined by chemical compositions and cooling rate, enabling us to estimate it from the structure of past similar castings without simulation.On the other hand, the casting defects often vary with each casting or time. Among the defects, porosities and inclusions are main causes to deteriorate the properties and mostly originate during mold filling. Therefore, a lot of efforts to simulate the mold filling and estimate those defects have been made in the last decades [l,5,6]. These efforts have been mostly to develop numerical techniques to solve the Navier-Stokes equation. However, the flow phenomena in molds have not been well understood, because the direct observation of the flow phenomena in mold is not easy. This means the accuracy of the simulation is still not clear."

Jan 1, 2000

By Lawrence L. Brown

As part of the Federal effort to help maintain an adequate supply of fertilizer materials, the Bureau of Mines conducted research to characterize complex low-grade Michigan phosphate materials and to devise methods for recovering fertilizer-grade phosphate concentrates. The rock is from middle Precambrian sedimentary formations in the Marquette Range located in the central part of the Upper Peninsula of Michigan. Occurrence of phosphate-bearing sediments in Precambrian rocks is rare. This deposit, containing 12 to 15 pct P2O5 is believed to be the richest Precambrian phosphate deposit in the United States. Petrographic examination showed that the conglomeritic rock contains crystalline apatite both in "black pebbles" and in quartz matrix. Attrition scrubbing and sizing tests showed that there is no tendency for phosphate to concentrate in any of the sized fractions. In beneficiation tests, which included grinding to minus 325 mesh followed by phosphate mineral flotation using a fatty acid-fuel oil collector, a phosphate concentrate was obtained that had a grade of 30 pet P2O5 and a P2O5 recovery of 72 pct. This concentrate should be suitable for fertilizer manufacture.

Jan 1, 1982

By Makoto Suzuki

After hot rolling, stainless steel strip is processed by the Hot Rolled Annealing and Pickling line (HAP) , where H2SO4 or mixed acid of HNO3 and HF is normally used. In the pickling bath, metal oxide accumulates in the form of sludge, which should be removed from the bath regularly. A new automatic continuous sludge disposal system has been introduced at Chiba Works of Kawasaki Steel Corporation to increase sludge removal efficiency and improve the working environment. The elements of the equipment are as follows. a. Ejectors in pickling bath: to carry the mixed acid into the circulation tank through the piping system. b. Sedimentation bath : to sediment sludge out of the bath. c. Skip conveyer : to convey a specified volume of sludge into a kneading for device for neutralizing. The sludge removal efficiency of this system is very high. and the volume of sludge accumulation in the pickling bath has substantially decreased.

Jan 1, 1996

By R. A. Masumura, C. S. Pande, D. Agassi

"Grain size has a different effects on the critical current density (Jc) of high and low transition temperature (Tc) superconductors. In high Tc superconductors, the critical current density Jc across grain boundaries depends sensitively on the misorientation 8. It was pointed out by Pande that this dependence is directly related to dislocation structure of the grain boundaries i.e., it is due to dislocation cores and stresses. These ideas are developed further in this paper leading to a relation between Jc and 8. The analytical result is compared with the experimental results on bicrystals and used to explain the difference in behavior between high and low Tc superconductors.IntroductionThe grain size distribution and its evolution with time and temperature is important in determining the properties of high and low transition temperature (T c) superconductors. The distribution is a convenient function to characterize the processing of a high Tc material during sintering. For example, it is known that the maximum density of ceramic materials is obtained when the grain growth is reduced but grain boundaries are still mobile. For practical superconductors, the processing parameters are selected to achieve optimum properties: highest possible T c and maximum critical current (Jc). In terms of an average grain size, the requirements for optimum T c and Jc are sometime in conflict. In A15 type superconductors and even in NbTi, larger Jc have been measured in smaller rather than larger grain sized material. Conversely, in a high Tc materials like YBa2Cu307, higher Jc have been found in larger grain sized or single crystal specimens.Extended defects such as grain boundaries in low T c superconductors can be effective pinning agents for magnetic flux lines, thereby increasing the transport critical current density of these materials [1]. On the other hand, the transport critical currents in polycrystals of high Tc superconductors such as YBa2Cu307 is found to be relatively small (much smaller than those in single crystals of the same material) [2]. It is now known that grain boundaries in high Tc polycrystals can in many cases form ""weak links"" reducing the critical current density across them. This phenomenon can be studied more precisely by experiments on bicrystals, where there is only one grain boundary. It is found that the critical current density is quite sensitive to the misorientation angle of the bicrystal [3,4]. Although the original experiments were conducted on YBa2Cu307, other Tc superconductors have been shown to give the same result [5]."

Jan 1, 1994

By Adam C. Powell

A new Cahn-Hilliard phase field model of transport-limited electrochemistry describes phase boundary motion due to oxidation and reduction reactions at metal-electrolyte interfaces. Benchmarks demonstrating the accuracy of the method include open circuit voltage and closed circuit current in metallothermic reduction, and linear stability theory in metal electrolysis, including a new stability criterion for reduction of liquid metal from liquid electrolyte. The model is applied here to understanding cathode interface stability in titanium electrolysis e.g. in the SOM process developed with Uday Pal, and to structure evolution in subhalide reduction of titanium dichloride by magnesium developed by Toru Okabe. Potential for application to new fuel cell and battery systems is also discussed.

Jan 1, 2006

By N. V. Gorelikova

A new type of zirconium mineralization has been recognized in the Devonian volcanic rocks from an orogenic depression in the Central Kazakhstan. The most characteristic features of this deposit are the fine-grained nature of the zirconium mineralization, an unusual texture of the zirconium ores, and a close association of zirconium with phosphorus in the ores. Zircon grains form fine globular aggregates with the features of hexagonal crystal habit. In addition to crystalline zircon, the ores contain metacolloidal zircon, similar to hydrozircon. The morphological and textural features of the zirconium ores suggest that the deposition of ore deposits took place at a low temperature from colloidal solutions. It is believed that this deposit should be considered to be a new type of zirconium mineralization that is related to low-temperature hydrothermal processes.

Jan 1, 1995

By K. E. Gonsalves, G. M. Chow

"Nanostructured powders (particle diameter of 1 - 100 nm) have uses in electronic, magnetic, structural, thermal applications as well as advanced processing of materials. Among many methods of making nanostructured powders, chemical routes offer many attractive features such as feasibility of cost-effective bulk quantity production, design of chemistry at the molecular scale, and chemical homogeneity of the powders. In this talk, two systems of chemically synthesized nanocomposite powders are presented, namely, granular magnetic materials of Fe-Cu and Co-Cu, and thermal-structural materials of AIN-BN. Synthesis and processing, characterization and properties of these materials are discussed.IntroductionNanostructured powders (particle diameter of 1 - 100 nm) are attractive materials because of many useful properties (e.g. catalytic, optical, magnetic etc.) and processing advantages (e.g. lower sintering temperature) [1]. There are many methods of making nanostructured powders, for example, physical and chemical vapor deposition, mechanical attrition, and solution chemistry [1, 2]. A common method of making composite powders involves the grinding, mixing and blending of constituents powders, but it has the limitation of inhomogeneous mixing. Chemical routes have many useful features. Using solution chemistry, precursors can be molecularly tailored and homogeneously mixed at the molecular level. The chemical approach may result in better properties of the final product. Compared to vapor-phase fabrication techniques, chemical routes are more cost-effective in producing large quantity of material. In addition, control of particle size, size distribution and stabilization of the nanoscale particles against agglomeration can be more effectively manipulated via solution chemistry.In this paper, we present an overview of some of our work in nanocomposite powders prepared by solution chemistry. Metallic systems of FeCu and Co-Cu, and ceramic system of AIN-BN are discussed. The powders were characterized using x-ray diffraction (XRD) , scanning electron microscopy (SEM), conventional and high resolution transmission electron microscopy (TEM, HRTEM), vibrating sample magnetometry (VSM), inductively coupled plasmaatomic emission spectroscopy (ICP-AES)."

Jan 1, 1994

By A. McLean, S. Dawson, N. D. G. Mountford

"IntroductionIn order to predict the accepted industrial practice for the year 2000, it may be helpful to first consider the rate of development of scientific knowledge. If the speed with which man can travel on commercial vehicles is taken as a criterion for determining the rate of progression, then it can be seen from Figure 1 that advancement in our present century is very rapid. Likewise, if computer technology is used as a criterion for the measurement of scientific advancement, it becomes evident that technological evolution can be highly exponential. These two examples are sufficient to demonstrate that engineers and managers cannot afford to regard scientific development as being linear with respect to time if they are to avoid underestimating the needs of society.Within this framework of overall development, the time required for individual ideas to progress from inception to regular application has decreased considerably. For example, X-rays first discovered by Roentgen in the 1890's and now used widely in medicine and engineering, required a developmental period of some eighty years. The motorcar evolved from early beginnings at the turn of the century to a position of great social impact in sixty years. Rectifier materials used in high frequency radar to the present explosion in communications, required forty years. As illustrated in Figure 2, the period is shortening rapidly.The use of sound waves appears to be following a similar path. There is now a considerable body of knowledge concerning their behaviour and exceptional advances have been made. In medicine and engineering the sonic approach to examination is well established, and acoustic testing forms the basis of several diagnostic and quality control applications. With respect to metals engineering, ultrasonic testing has contributed to the understanding of the relationship between the size and number of internal defects and the probability of premature failure. This has allowed the designer to incorporate appropriate safety factors in his designs; but more importantly, the realization of the deleterious effect of inclusions on the performance of the final product has resulted in a continuous pressure on the material suppliers to reduce the number of defects in their products.It is not only the designer who is demanding defect free material but also the fabricator, as material breakdown during manufacture can be prohibitively expensive. Examples of this can be found in both the aluminum and steel industries where ultra clean sheet is required to ensure that rejections are minimized during beverage can manufacture and other deep drawing operations."

Jan 1, 1988

By Nobuhiro Shinihara, Makio Naito, Keizo Uematsu, Tadashi Horta, Hiroya Abe, Masataro Okumiya

"A significant variation of strength was noted in silicon nitride ceramics made through the powder compaction processing with minor processing changes. The relevance of the fracture strength to the microstructure was examined in these ceramics. In the examination of microstructure, the ceramics were made into thinned specimens, and their internal structures were observed with an optical microscope in the transmission mode. This technique can distinguish a difference in microstructure associated with the minor processing changes. The strength of all ceramics examined in this experiment was qualitatively correlated with the -pore size distribution in the specimens. Clearly, the elimination of these detrimental defects will enhance the reliability of ceramics.IntroductionIn ceramics made through powder processing, a variation of properties is often encountered [l ,2]. This brings a major problem on producing reliable and cost-effective ceramics. The variation is often ascribed to the changes in the characteristics of defects. However, there is no clear evidence f\)r this explanation due to the lack of an adequate tool for identifying the defects determining the properties. Details of the origin of the variation have still been poorly understood.A new technique is very promising for clarifying the origin of the variation [3,4]. This has very high potential in detecting minor differences in structure for .engineering ceramics. With this technique, ceramics are made transparent with its thinning down to about 50 µ m and their internal structures are observed with various types of optical microscopes in the transmission mode. The characteristics of the defects determined through this approach were found to be directly related to the strength of the ceramics [4-6].The objective of this study is to clarify the ongm of fracture strength of silicon nitride ceramics. This material is representative of high performance ceramics, and the origin is of great practical interest. For this study, silicon nitride ceramics with minor changes in processing condition were prepared. Specific feature focused in this study is the difference of large pore structure determined with the new technique and its relevance to the strength of the silicon nitride ceramics."

Jan 1, 2000

By F. A. Steward

Copper is one of the trace minerals essential to life. It is added, usually in the form of copper sulfate, to virtually all formulated feedstuffs and to dietary supplements fed to animals on forage. Over the past five years, an improved inorganic copper source trademarked Micronutrients TBCC™, has been developed, tested and commercially introduced. TBCC is a crystalline form of basic copper chloride. Synthesis is accomplished in a continuous neutralization I crystallization process. In current commercial production, the primary sources of copper currently used as feedstocks are the etching solutions used to manufacture electronic printed wiring boards. These solutions have traditionally been managed as hazardous wastes, but their use to manufacture TBCC™ exempts them from regulation as wastes under the "Use/Reuse" provisions of RCRA. Research conducted over five years at multiple universities has shown that animals are healthier when fed this source of copper and that vitamin losses in feed are reduced by its use.

Jan 1, 2000

By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990