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By Raymond M. Coveney

Bedded sulfide ores in Cambrian Chinese black shales typically contains at least 2% Ni, 4.5% Mo, 1% As and 0.2% Se. Thin laminae and replaced on colites from the ore contain intimate mixtures of fine-grained Ni-rich sulfides and jordisite complicating ore treatment. The ores contain abundant jordisite, vaesite, nickelian pyrite, and barite and lesser amounts of sphalerite, gersdorffite, millerite, tennantite, fluorite, chalcopyrite, and HgSe (probably tiemannite). At present only ores that are sufficiently rich (>4.5% Mo) for direct roasting are mined and treated to produce, ammonium molybdate. The ores contain Pt, Pd, and Au in amounts totaling up to -2.5 ppm, but these are not recovered.

Jan 1, 1993

By Kuo En Chang

Many rare earth - transition metal (RE-TM) compounds absorb/desorb hydrogen reversibly at room temperature and atmospheric pressure. For LaNi5 which is used as a battery material, the electrochemical nature of this process is well known. In the case of Nd-Fe-B which has found wide application as a powerful permanent magnet, the absorption of hydrogen has both significant advantages and disadvantages. However, a fundamental understanding of the hydrogenation process at ambient temperatures and its effect on subsequent corrosion behavior is currently lacking. This paper reports the results of the hydrogenation of NdFeB two alloys, (NdDy)15Fe78.3A10.7B6 and (NdDy)15Fe67Co5V4A12B7, which are compared with that of LaNi5. Results show that hydrogenation can be accomplished by either electrochemical methods or immersion in dilute sulfuric acid. For the latter method, the change in lattice parameter indicates that the level of hydrogen absorbed by the NdFeB particles corresponds fairly closely to an overall composition of Nd2Fe14BH2.7. Cyclic electrochemical charge/discharge experiments show that the maximum hydrogen discharge capacities of the NdFeB, NdFeB-Co-V, and LaNi5 are 40, 60, and 210 mA?h?g-1, respectively. Anodic potentiodynamic polarization measurements and calculated values of icon reveal that absorbed hydrogen in NdFeB-Co-V and the NdFeB may lead to significant increases in corrosion rates.

Jan 1, 1995

By Niloy K. Nath

Two layer sintering by charging green sinter mix with normal coke rate in the upper layer and reduced coke rate in the lower layer, can substantially reduce the coke rate and also improve the sinter quality by producing more uniform thermal profile through out the bed height. The two-layer sintering process have been analyzed by numerical simulation of the process by a detailed CFD based model, considering all the important phenomena like gas-solid reaction, melting and solidification, flow through porous bed, heat and mass transfer etc. Optimization techniques like genetic algorithm, differential evolution is then applied to evaluate the optimum coke rate in the two layers of the bed to produce the ideal thermal profile and melting fraction in the sinter bed for optimum sinter quality. Through this optimization method both high quality sinter with minimum return fines can be achieved along with reduced coke rate. Application of a genetic algorithm for this type of process optimization has several advantages over the traditional optimization techniques since it can identify global optimum condition and perform multi-objective optimization much easily for complex industrial process like iron ore sintering. Keywords: Two-layer Sintering, Iron Ore Sinter Quality, Ergun's Equation, Gas-solid reaction, Melting Fraction, Multi Objective Optimization, Pareto Set, Genetic Algorithm

Jan 1, 2003

By T. Johnson, B. Q. Li

"Electromagnetic stirring has found a wide application in metals processing for the benefit of obtaining refined solidification microstructures. This paper presents an experimental study on the melt flow and turbulent behavior in an electromagnetically stirred Woods metal pool. The experimental setup consists of metal bath unit equipped with temperature control to allow both cooling and heating, velocity probe positioning unit and data and signal acquisition and processing unit. The whole measuring system is under the control of an IBM personal computer. Velocity measurements are made using the incorporated magnet probes, which are calibrated using a turntable. The measured results showing the effect of the coil positions, coil arrangements and the applied currents on the melt flow are presented. Both mean flow and turbulence quantities are discussed.1. IntroductionElectromagnetic stirring is widely practiced in the metals industry for melt mixing and for casting microstructure refinement. Industrial examples are taken from induction furnaces where the electromagnetic forces are applied to generate desired melt mixing and also various types of electromagnetic stirrers used in various stages of steel and/or aluminum casting processes to produce fine grain solidification microstructure or to eliminate undesired defects such as TCG (twinned-columnar-grain) structure. For ultrahigh purity aluminum or high strength aluminum alloys containing zirconium or lithium, grain refinement can be difficult with the conventional technique, and electromagnetic stirring provides a particularly powerful means to obtain the refined solidification microstructure [1]. A fundamental understanding of the melt flow and the turbulence characteristics in these magnetically-driven flow systems is of significant engineering importance to both process design and product quality improvement.There exists extensive literature on the magnetically-driven melt flows in material processing systems. Nakanish. et al. [2] were perhaps among the early investigators to mathematically and physically model the magnetically-driven flow phenomena in molten metal systems. Subsequent theoretical and experimental work by Tarapore and Evans [3, 4], Szekely and Chang [5], Hunt and Moore [6] and Szekely and El-Kaddah [7] has contributed very significantly to our understanding of magnetically-driven flow in inductively stirred melts. They have developed mathematical models for the electromagnetic field and turbulent flow in induction furnace and validated the models by either laboratory experiments or direct measurements in the industrial-scale induction furnaces."

Jan 1, 1998

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 Kuniaki Murase, Tetsuji Hirato, Yasuhiro Awakura

"Electrodeposition of CdTe was studied using aqueous ammonia-alkaline electrolytic baths in which Cd11-and Te1V-ions are dissolving as Cd11(NH3)/+ and Te1vol-ions, respectively. Ca-thodic polarization curves of the baths suggest the presence of strong interaction between the Cd11-and Te1V-ions; electrodeposition of tellurium is inhibited by the presence of Cd(NH3)/+ ions. The interaction makes it possible to electrodeposit CdTe films with stoichiometric composition. Polycrystalline CdTe thin film of about 1 µm thickness was electrodeposited at 343 K from ammonia-alkaline solutions (pH= 10.7) containing TeO32-(<20 mmol dm-3) and Cd(NH3)/+ ( < 60 mmol dm-3) ions. Increasing Cd(NH3)/42+/TeO32- mole ratio or decreasing total concentration of ammonia/ammonium-ion gave flat and smooth crystalline CdTe deposits at constant cathode potential-0.70 to -0.30 V vs SHE at 343 K.IntroductionCadmium telluride (CdTe) is well-known as a compound semiconductor whose band gap, i.e. 1.44 eV, is suitable for solar energy conversion with a photovoltaic cell. Various methods, such as CVD (chemical vapor deposition) and electrodeposition, of preparing CdTe thin films for solar cells have been investigated.Acidic sulfate solutions with a pH of 1-2 are usually employed for CdTe processing by electrodeposition.1-3) The electrodeposition of compound semiconductors is usually achieved (i) at a higher cathode potential than the redox potential of less-noble species, can in this case, and (ii) under the condition of diffusion-limiting current of a more noble species, Te1Y.4) There-fore, a suitable CdII/TeIV concentration ratio in the acidic electrolytic baths, resulting in the deposition of stoichiometric CdTe, is determined by the diffusion-limiting current density of TeIV- reduction, i.e. the concentration of HTeIVO2+ · Since the solubility ofTe1v species HTeIVO2+ in the acidic solutions is quite low, the rate at which CdTe is deposited from the acidic solutions is extremely slow."

Jan 1, 1998

By Jinjing Dua, Jun Zhua, Kuiren Liub, Bin Wang, Xiaolei Wua

V-Ti-Fe as hydrogen storage alloy was prepared by reducing metal oxides with a metallothermic reduction method. The deoxidation process of the V-Ti-Fe alloy was performed by electro-deoxidation and vacuum induction melting method, respectively. The results showed that the content of oxygen impurity can be controlled at about 0.2wt% after electrolyzing for 240min. Both the maximum values of hydrogen absorption capacity and the effective hydrogen desorption capacity are 2.65wt% and 1.01wt%, respectively. The deoxidization effect of vacuum induction melting process is more remarkable, with Ce as the reducing agent. It is found that Ce addition is beneficial for reducing the componential segregation, promoting the hydrogen absorption activation of V-Ti-Fe alloy. When m(Ce)/m(alloy) is up to 5%, the oxygen content has been reduced to 0.05wt% and the maximum hydrogen absorption capacity and the effective hydrogen desorption capacity are up to 3.36wt% and 1.85wt%, respectively.

Jan 1, 2015

By Yuzhe Zhang, Xiaodi Huang, Xinli Wang, Bowen Li, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Likun Li

With the development of the world, the waste tires have been a serious environmental problem. There are about 2 billion waste tires produced all over the world every year and about 500 million waste tires are produced in the United States. Most of the waste tires are land filled, which waste a lot of space. It takes hundreds of years to resolve the macromolecules of waste tire into the standard which does not pollute the environment. Microwave irradiation is a thermal processing way for waste tires decomposition. In this study, the relative dielectric loss factor of the tire at various temperatures was determined to understand the behavior of tires under microwave heating.

Jan 1, 2016

By P. E. Nolan

The disproportionation of carbon monoxide is an important aspect of reduction processes, in the production of carbon filaments for composites, and in the removal of CO from CO,. It can also be a hindrance, causing carbon fouling of equipment and metal dusting. The reaction is thermodynamically favored at lower temperatures, but it occurs slowly. Catalysis of the reaction by transition metals has been examined. A materials science approach to the selection of a catalyst material and of optimum operating conditions is being taken in the present work. Of particular interest is characterization of a catalyst that can be repeatedly regenerated to prevent deactivation in long term use. Experimental data on a less studied catalyst, ruthenium, are reported.

Jan 1, 1992

By M. M. Swan

A stratiform gold occurrence of Precambrian age located 20 miles southeast of Prescott, Arizona, within the Agua Fria Mining District, displays chemical, mineralogical, structural and lithological patterns indicative of a distal, exhalative volcanogenic environment. Metavolcanic and metasedimentary rocks of the Proterozoic Yavapai Series (1775-1820 m.y.) host the mineralization and are&apos;characterized by greenschist grade metamorphism, steeply-plunging penetrative folds and steeply-dipping schistosity. Mineralization is confined to a 100m thick stratigraphic section that is comprised of a series of thin auriferous massive sulfide beds and intercalated schist .containing disseminated sulfides. The mineralization extends more than 4km along strike. Coincident with, and largely confined to the mineralized strata, are anomalous amounts of As, Sb, Cu, Pb, Zn and Ag and associated silicification, sericitization and carbonatization. This exhalative mineralized system is interpreted to have been deposited in a paleo topographic low on the distal flank of a submarine rhyolite dome and to represent the final episode of a Precambrian volcanic cycle.

Jan 1, 1981

By Kang-In Rhee

Nonferrous metal recycling not only provides energy saving and environmental benefits but also is a significant factor in the supply of various types of metals used in our society. Recycling plays an important role in establishing the sustainability of materials. The total amount of recycled nonferrous metals by weight accounts for less than 5% but their value is larger than 50% compared to ferrous metal recycling which consists of about half of the total metal recycling in weight. This paper describes trends and typical achievements in nonferrous metal recycling and overviews the present and future of nonferrous metal recycling technology and business in Korea.

Jan 1, 2006

By Rubén J. Sánchez Rodriguez, Carlos M. Fontes Vieira, Carlos E. Gomes Ribeiro

Ornamental compound stone are produced by industry for decades, however, few published studies describe these materials. Brazil has many deposits of stone wastes and a big potential to produce these materials. This work aims to evaluate the chemical resistance of ornamental compound stones produced with marble waste and unsaturated polyester. An adaptation of Annex H of ABNT NBR 13818:97 standard, with reagents commonly used in household products, was used. The results were compared with those obtained for natural stone used in composite production.

Jan 1, 2015

By Du Sichen, S. Seetharaman, J. A. Bustnes

"The present study deals with the kinetic studies of reduction of some selected transition metal tungstates with hydrogen. The measurements were carried out by the isothermal thermogravimetric method. Shallow powder beds were employed in order to avoid the effects due to transport phenomena affecting the reaction rate. In this way, the chemical reaction rates could be selectively studied. The experiments were carried out in the temperature range 873 - 1173 K. From the experimental data, the activation energies were evaluated and were found to be around 88 kJ / mol in the case of both iron as well as cobalt tungstates indicating the similarities in W-O bonds in both cases. The activation energies obtained are discussed in the light of the position of the transition metal in the periodic table as well as the thermodynamic stabilities of the various tungstates.IntroductionThe tungsten containing hard metals, characterized by high density, belong to a class of two-phase metal matrix composites. While these types of materials have traditionally found their applications within the defence industry as armour-piercing projectiles, counterbalance in helicopters and military aircrafts, outer casings of hand-grenades, etc., commercial applications for this class of alloys also exist, including radiation shields, penetrators for the oil industry, turbines for turbo-jet engines and a wide range of sports related parts. A possible route to the production of these alloys is to reduce the tungstates such as FeW04, Co W04 and NiW04 using a reductant like hydrogen or carbon monoxide. In order to have a better understanding of the processes involved in the production, it is important to have a knowledge of the reduction kinetics for these tungstates. According to the knowledge of the present authors, while the reduction ofNiW04 by hydrogen gas has been investigated earlier in the present laboratorypl no systematic reduction study has been carried out previously for the tungstates of iron, cobalt."

Jan 1, 1996

By Luciano E. Ramírez, Jesús L. Valenzuela, José R. Parga

"An innovative process for removing copper cyanide complexes including silver and zinc from cyanidation circuits has been developed. The technology was based on the inducing the nucleated precipitation of copper and silver in a tube serpentine reactor, using sodium sulfide as the precipitate and sulfuric acid as pH control. The results showed that pH had a great effect on copper cyanide removal efficiency and the optimum pH was about 3 to 3.5. At this pH value copper cyanide removal efficiency could be achieved above 97 and 99 % ,when influent copper concentration ions were 650 and 900 ppm respectively. In this process (sulphidizaton-acidification-recycle-thickening), the cyanide associated with the copper cyanide complexes is released as HCN gas under weakly acidic conditions, allowing it to be recycled back to the cyanidation process as free cyanide. This system was successfully commercial applied at Minera William in Mexico.IntroductionThe recovery of gold and silver from minerals and concentrates with cyanide is an important hydrometallurgical process, which has been studied for more than 124 years. Patented by MacArthur in 1888 [1], the process relies on the fact that gold dissolves in aerated cyanide solutions to produce the gold cyanide complex. The stoichiometry by wich this reaction occurs is known as the Elsner equation as shown here. Silver is accomplished in the same fashion."

Jan 1, 2012

By Masami Taguchi

"It is found that lead monoxide, PbO, has an ionic conductivity, and the all solid-state electrochemical cell using this oxide as an electrolyte has attracted the attention of battery researchers. In this study, thin film PbO2/PbO/Pb solid cells were produced on glass substrates and their discharge properties were investigated. The acti.ve material for the positive electrode, PbO2, was obtained by reactive sputtering of a Pb target in oxygen plasma. The PbO electrolyte and the active material for the negative electrode, Pb, were vacuum evaporated from /3 -PbO powder and a Pb block, respectively. The open-circuit voltage of the cell agreed with the theoretical value based on the thermodynamic data, and the close-circuit voltage was improved by the addition of a univalent impurity such as sodium or potassium to the PbO electrolyte. The connection of the cells in series and in parallel produced a higher electromotive force and a larger capacity. Also, the charge-discharge cycling test revealed that the cell could be charged and function as a storage battery.IntroductionGenerally, the ionic conductivity of a solid-state electrolyte is lower than that of a liquid electrolyte near room temperature. This has been a serious obstacle to using such electrolytes in an electrochemical cell. However, some solid-state electrolytes, which can preferentially pass a specified ion and have high ionic conductivity, have been found. Lead monoxide, PbO, which is an oxygen ion conductor, is such an example (1)(2). If a solid-state electrolyte is adopted for use in an electrochemical cell the problem associated with a liquid electrolyte such as leakage can be alleviated. The cell structure also can be simplified, because the electrolyte plays the role of separator to prevent the active materials from mixing. Thus, physical vapor deposition technology may make it possible to develop a very thin film cell, which consists of only solid phases (3)(4). In this study, the thin film PbO2/PbO/Pb solid cell with a thickness· of only a few micrometers, in which all the constituents were systematically deposited on a glass substrate by reactive sputtering and vacuum evaporation, has been produced and the charge-discharge properties were investigated. An attempt was made to improve the discharge properties by doping impurities such as Na2CO3 and Sb2O3 into the PbO electrolyte. Moreover, the connection of the cells in series and in parallel to get a higher electromotive force and a larger capacity, and the charge-discharge cycling test to determine its use as a storage battery were carried out."

Jan 1, 2000

By Young-Sool Jin, Heung Nam Han, Hong Joon Kim, Jae Kon Lee

A mathematical model was developed considering non-symmetric cooling' and stress distribution in both thickness and width direction of strip on a run-out table of hot strip mill. In order to solve a transient heat transfer equation including the heat evolved from phase transformation, a finite element method coupled with thermodynamic and kinetic analyses was applied. The heat capacity of each phase and heat evolution due to phase transformation were obtained from the thermodynamic analysis of the Fe-C-Mn-Si system based on a sub lattice model. The phase transformation kinetics of the steels was derived by using an inverse additivity technique with continuous cooling experiments. Heat transfer coefficients of strips on the run-out table were, by applying an inverse method, determined from the actual mill data under various cooling conditions. As for the stress analysis, the density change of strip due to cooling and phase transformation, and the transformation superplasticity were considered. A 90nstitutive equation for the transformation superplasticity, which is related to the phase transformation kinetics and the internal stress due to the density change of strip, was applied. A finite element method was adopted to calculate the deformation behaviour of strip on a run-out table of hot strip mill. Using the models, the temperature-phase-deformation history and distribution of a strip on the run-outtable was calculated.

Jan 1, 2001

In accordance with the new concept described in the paper presented at the TMS annual meeting in 1989, 1 a new zinc cellhouse was constructed and successfully operated. The new concept was proposed in order to reduce energy requirements and to mechanize the electrode handling in the cellhouse. Major modifications involved the use of an electrode unit consistfog of assembled anodes and cathodes with frame bodies between each cathode and anode. The space between a cathode and an anode could be halved by this unit structure. In this paper actual operation data are summarized and discussed in comparison with the calculated figures.

Jan 1, 1990

By Yasuo Kudo, Wu, Hayato Sato, Hiroshi Nakazawa, Shouming

"In order to recover copper from a waste nickel condenser powder, bioleaching experiments were carried out using Thiobacillus ferrooxidans in a shaking flask. The content of nickel and copper in the waste nickel condenser powder in this study were 8.0% and 3.5%. X ray analysis showed the peak of barium titanate. In the preliminary study using metal nickel and copper powders , the dissolutions of nickel and especially copper were accelerated with the addition of ferric iron in the bioleaching of nickel and copper powders while not in the absence of ferric iron. Ferric iron oxidizes both metals, and Thiobacillusferrooxidans oxidizes ferrous iron resulting from the oxidation of metals, whereby the dissolutions of metals proceeds. The dissolution rates of nickel and copper increased with increase in the concentration of ferric iron in the bioleaching of the waste nickel condenser powder.1. IntroductionNickel condensers rejected from manufacturing plants are crushed and landfilled. Waste nickel condensers contain nickel and copper and could be considered as nickel and copper ores. Since the capacity of landfills is diminishing, it is required to recycle metals of waste nickel condensers in order to reduce the amount of wastes landfilled. Conventionally, metals in the waste were recovered by dry metallurgy after the incineration.Nickel has been refined by solvent extraction - electrowinning method (SX-EW method). Recently the amount of copper refined by SX-EW method has increased (Takahashi, et al. 1994). This method is cleaner and consumes less energy than conventional methods. Nickel dissolved well in acid solutions, but copper is not. If copper is leached efficiently from a waste nickel condenser powder, SX-EW method will be applied to recover copper from them"

Jan 1, 2000

By Akira Kaneda, Nozomu Hasegawa

"In the Mitsubishi Continuous Copper Smelting and Converting Process, slag/matte mixture overflowed from the smelting furnace is separated continuously in an electric furnace (slag cleaning furnace, CL-furnace). In order to improve the separation efficiency of slag and matte and to minimize power consumption, the design and the operating conditions of the CL-fumace should be optimized. In the previous study, the authors developed a mathematical model for simulating phenomena in the CL-furnace. The model consisted of 3 modules, electric field analysis, heat and fluid flow analysis and the particle tracking method. In this study, the model was partially modified: k -E. model was adopted, and the effects of various conditions, such as furnace shape (including accretion) and scale, electrodes configuration, immersion depth of electrodes, and thickness of slag layer, were evaluated. And the optimum design and operating conditions were discussed.IntroductionUnder the recent environmental restriction, advantageous features of the Mitsubishi process have attracted much attention. The process uses 3 furnaces connected by launders. Mixture of matte and slag formed in a smelting furnace flows continuously to a slag cleaning furnace (CL-furnace), where the matte is separated from the slag. The matte is continuously siphoned out to a converting furnace and converted to blister copper. The slag overflowed from the CL-furnace is discarded. Because the slag contains about 0.6 % copper, improving slag/matte separation efficiency and decreasing copper loss make a great profit. Moreover the process requires a large amount of electric energy, so reduction of electric power consumption brings in enormous benefit.The objective of this study is to optimize the design and the operating conditions of the process, especially the CL-furnace. This will be achieved by developing the mathematical model and clarifying relations between the design or the operating conditions and various phenomena in the furnace. Fig. 1 shows an outline of the CL-furnace. The mixture entering through an inlet is separated to slag layer and matte layer . In order to maintain the temperature of the melt at a predetermined level, 6 electrodes are immersed into the lag and Joule's heat is generated by 3-phase alternating current flowing."

Jan 1, 2000

By Hiroshi Hashimoto

For the application of sodium carbonate slag treatment to product high purity copper on an industrial scale, the counter-flow batch process that reduces the amount of utilized slag is proposed from the viewpoint of the post-treatment of slag. Based on the distribution ratios of several impurities between the slag and molten copper determined previously, the effectiveness of this process is discussed using a mathematical model and confirmed experimentally. According to the model, the slag consumption to remove Sb to a required level in case of the counter-flow batch process with 3 reactors is calculated to be around 30 % of that in the case of an ordinary batch process, where pure sodium carbonate is used as a slag at every stage.

Jan 1, 2003