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By Itsuki Uehara, Hiroyuki T. Takeshita, Tetsuo Sakai, Nobuhiro Kuriyama, Hideaki Tanaka

"AB5 type hydrogen storage alloys (A: rare earths, B: transition metals) are extensively applied to a negative electrode of a nickel metal hydride (Ni-MH) rechargeable battery for portable electric equipments, electric vehicles, hybrid vehicles etc. Performance of a hydrogen storage alloy electrode is affected by various factors, microstructure and surface composition of the alloy and structure of the electrode as well as composition of the alloy. Control of those factors enables us to commercialize the Ni-MH battery in various field.IntroductionA Nickel-metal hydride (Ni-MH) battery has been extensively developed because of (1) good compatibility with a nickel cadmium (Ni-Cd) battery, (2) high energy density (1.5-2 times higher per unit volume than a Ni-Cd battery) and high dischargeability, and (3) low environmental pollution. The charge/ discharge reactions can be written as [l, 2,3]:(+) Ni(OH)2+OH- = NiOOH+H2O+e· (E=+0.490V NHE),(-) l/6LaNi5+H2O+e-· = 1/6LaNi5H6+OH- (E=-0.828V NHE),where E° is a standard potential of an electrode vs. normal hydrogen electrode (NHE). Because of the above advantages of a Ni-MH battery, the battery have been widely used as a power source of portable computers, cellular phones, electric vehicles (Toyota ""LAV4L EV"", Honda ""EV Plus"" etc.) etc. Some hybride vehicles (Toyota ""Prius"" and Honda ""INSIGHT"") and fuel cell vhehicles (Toyota ""FCEV"") are power-assisted by a high-power Ni-MH battery. In 1999, the production of Ni-MH batteries reached 870 million cells in Japan. Most of commercialized NiMH batteries are incorporated with rare-earth-based AB5-type hydrogen storage alloy as a negative_ electrode. The production of rare-earth-based alloy is estimated to be approximately 8000 tons.The battery performances of the Ni-MH battery, for example, capacity, durability (cycle life), dischargeability (kinetics) and selfdischarge, ate closely related to the metal hydride· (MH) electrode, especially, the hydrogen storage alloy in the electrode. Substitution of alloy components, heat treatment, and surface treatment in order to change surface and bulk structure of hydrogen storage alloys have been examined by us and many reseachers in order to improve the performances of MH electrodes. This paper is a review of our and their efforts to improve performances of MH electrodes."

Jan 1, 2000

By Takeshi Yoshikawa, Kazuki Morita, Kunitoshi Matsunaga

"In metallurgical grade silicon (MG-Si), most impurities mainly exist at the grain boundaries and distribute in silicon grains at extremely small contents. Grain boundary phases in MG-Si transform into liquid above the eutectic temperature, and migrate towards high temperature regions when heated under a temperature gradient. With the migration of all liquid phases in MG-Si to the surface, the impurity contents will be decreased less than their solubilities in principle.In the present work, the fundamental research was conducted to discuss the possibility for purification using the liquid phase migration technique. The purification limit was estimated by thermodynamic calculations, and metallic impurities were estimated to be effectively removed except for Fe and Al. The migration behavior of the liquid phase in the synthesized silicon substrate was investigated by unidirectional heating under infrared radiation at 1523-1548 K, and the proceeding of migration was confirmed. The migration velocity was 1.4--2.0xl0-7 mis, and found to be controlled by the liquid phase diffusion.IntroductionPhotovoltaic energy is one of promising energy resources in a sustainable society because of its inexhaustibility and cleanliness. Although the production and installation of solar cells have increased significantly during the last decade, the cost of solar cell installation is still high. To enable the widespread use of photovoltaics and for the photovoltaic electricity price to reach grid parity, a low-cost and abundant feedstock of solar grade silicon (SOG-Si) is essential. Recently, a modified Siemens process and a fluidized bed reactor process were developed to address the cost and energy issues associated with the conventional Siemens process. However, their cost reduction potential is limited because of the large energy consumption needed to convert silicon into gaseous compounds. Purification of silicon through metallurgical routes offers a promising way for producing SOG-Si from metallurgical grade silicon (MG-Si), because it enhances productivity and can also lower the process costs. Although several metallurgical processes such as directional solidification [l ], vacuum refining [2-4] and plasma oxidation [5-7], have been developed, processing times and refining efficiencies still have to be optimized."

Jan 1, 2013

By Jesus Gonzalez

Peirce-Smith converters (PSC) are long cylindrical chemical reactors where copper matte reacts with air. Traditionally, air is injected laterally through submerged tuyeres at different subsonic velocities. However, the accumulated experience in steelmaking, particularly in the basic oxygen furnace (BOF) process, shows that the gas bottom injection may improve the mixing efficiency of a liquid pool. The aim of bottom injection is to maximize the copper kinetic energy meanwhile avoiding excessive reactor splashing. When gas is injected from a single orifice at the bottom of a liquid pool, two main gas flow regimes can be identified, bubbling and jetting. In this work, a PSC with bottom air injection is studied by means of multiphase 3D CFD numerical simulations considering multiple air velocities. Special attention is paid to the bubbles and jet formation mechanism. The mixing efficiency is measured by calculating the turbulent kinetic energy of the copper matte.

Jan 1, 2008

By G. L. Watt

Fine sized titanium diboride (TiB2) powders have been synthesized in a thermal plasma reactor. Precursor for the synthesis were rutile, boron oxide, and methane. The effect of plasma gas type, precursor ratio, and input power on the synthesis was studied. The produced powders were characterized by X-ray diffraction and chemical analysis. The purified powders were CIP'd, HIP'd, sintered and characterized for porosity, hardness, and microstructure and the results compared with a commercially available TiB2 powder sample.

Jan 1, 1995

By Masatoshi Ogasawara

Saganoseki smelter & refinery operated two flash smelting furnaces, producing a combined 330,000 metric tons per year (hereinafter mtpy) of copper. In 1996, however, it successfully shifted to a single furnace operation while maintaining production at the same level. Since then, the production capacity has been further increased to the present 470,000 mtpy by technological improvements. Also, in order to reduce the converter load which represents a bottleneck in efforts to increase production, the matte grade was gradually increased and currently runs at 65 to 66% attaining the low copper content in the slag (hereinafter slag loss) of 0.7 to 0.8%. This paper introduces some improvements, recent operation results and thermodynamic analyses.

Jan 1, 2003

By Huayi Yin, Wang. Dihua, Wei Xiao, Xuhui Mao, Diyong Tang

"The world production of crude steel reached 1.55 billion tons in 2012,which generated ~2.5 billion tons of CO2. Electrochemical metallurgy especially through high temperature molten salt electrolysis with renewable electricity stands for a great opportunity for producing “green” metals. In recent years, electrolytic production of iron without emission of CO2 in different molten salt systems has been reported. A cost-affordable inert anode is the key to produce acceptable eco-friendly iron by the novel molten salt electrolysis processes. Based on the authors’ research, this paper will discuss iron production by molten salt electrolysis using a nickel alloy inert anode. On the other hand, the paper also covers a novel molten salt CO2 capture and electrochemical transformation (MSCC-ET) process, in which CO2 is effectively converted to value-added carbon and oxygen in a molten bath using a cost-affordable nonconsumable SnO2 anode.1. IntroductionEnergy and materials are cornerstones to support the development of human society. The traditional primary metal production, especially iron and steel, and electricity production are mainly based on the reactions between carbon (coal) and oxygen (represented by equations (1) and (2) respectively), which produce huge amount of CO2.MxOy + 0.5y C = x M + 0.5y CO2 (g) + Q1 ( 1 )C + O2 (g) = CO2 (g) + Q2 ( 2 )In 2012, the world production of crude steel reached 1.55 billion tons, of which 46.3 %, ~0.7165 billion tons were produced in China. Based on the average level of 1.7t CO2 emission per ton steel, more than 1 billion tons of CO2 generated from steel industry in China in the year. Besides the iron and steel industry, thermal power plant leads the CO2 emission in both USA and China. The total consumed electricity in China increased to 4959 billion kWh in 2012, ~70% of it was from coal fired power plant. The average CO2 emission for electricity production in the typical thermal power plant in China is around 0.78 kg kWh-1. It accounts for ~ 3.868 billion tons of CO2 emission from thermal power plant in 2012 in China."

Jan 1, 2014

By Shengli Wu, Jinming Zhu, Wei Huang, Xinliang Liu

The sinter of high basicity would interact with lump ores or acid pellets in the cohesive zone of blast furnace due to the difference of chemical composition and micro structures. The results of this work showed that the softening-melting properties of lump ores and acid pellet would be obviously improved by the high temperature interaction. However, the high temperature interaction index (INI) would be influenced by many factors, such as chemical composition, porosity, interaction interface and so on. The INI between sinter and porous limonite lump ore (L-2) was much higher than that of dense hematite lump ore (L-1) and acid pellet (P-1). In addition, though the softening and melting properties of L-2 were poorest in respective iron ores, the softening and melting properties of integrated burden B (consist of sinter and L-2) were not worse than other integrated burdens due to the strong high temperature interaction.

Jan 1, 2015

By R. A. Alock

The character, occurrence and genesis of the three types of nickel deposits, sulfide, laterite and deep-sea nodule are described, highlighting the differences in mineralogy and chemical composition that effect the extractive metallurgy of nickel and associated byproducts. World nickel production and current resources by deposit type and geographic location are also reviewed.

Jan 1, 1988

By Dietrich Gross

This paper describes an advanced oxy-fuel combustion technology for re-melting aluminum that significantly reduces energy consumption and emissions. This oxy-fuel combustion technology developed by Jupiter Oxygen is a patented process for combustion of fossil fuels with pure oxygen while excluding air, thereby creating an undiluted high flame temperature and increased efficiency for process heating in industrial furnaces. This unique process has led to improved heat transfer and longer residence time while maintaining the same process temperatures as with air combustion. The energy efficient combustion process allows aluminum companies to operate at a substantially lower cost due to a dramatic fuel savings of up to 70% for natural gas and waste oil (1). The results of more than 10 years of day-to-day experience utilizing the Jupiter Oxygen Corporation oxy-fuel combustion technology licensed to Jupiter Aluminum Corporation in the aluminum re-melting business are discussed.

Jan 1, 2008

By Antoine Allanore, Guillaume Lambotte, Bradley R. Nakanishi

Current industrial methods used for rare earth element (REE) extraction involve: 1) ore enrichment, 2) separation of rare earth oxides (REOs), 3) chlorination or hydrofluorination, and 4) individual electrowinning of REEs from a molten halide electrolyte. The complexity of REE extraction is inherited from their electronic configuration. Recently, molten oxide electrolysis (MOE) has been used to produce reactive metals directly from their oxides, e.g. titanium. As a single-step alternative to processes 3) and 4), or laboratory has investigated rare earth extraction by MOE. A key challenge is to find a molten electrolyte more stable than REOs. One possibility is to use binaries of REOs directly as a solvent. We have, therefore, developed two experimental approaches for studying molten REOs at temperatures exceeding 2200oC. The present work reports the most recent experimental results obtained with La2O3-Y2O3. Those promising results demonstrate potential for operating with molten REOs and refine the underlying materials challenge for electrodes to enable metal recovery.

Jan 1, 2015

By Xirneng Zhu

The electrochemical behavior of Pittsburgh and Illinois coal pyrite in basic and neutral borate/sulfate solutions was investigated. In the transpassive region, aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The formation of sulfur and polysulfides was identified by in-situ Raman spectroscopy. The growth kinetics of the reaction product film, resulting from transpassive oxidation of coal pyrites, were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The reaction rate was well correlated by a paralinear rate equation. The effects of electrode rotation speed, solution pH and temperature were examined. The kinetics were compared to those for mineral pyrite.

Jan 1, 1994

By Mathilde Guilpain

A wide variety of plants are able to extract nickel (Ni) from soils and accumulate this metal in their foliage. Hydrometallurgical processes have been developed to recover Ni in the form of metal or salts, starting from the plant A. murale. They include: (1) a combustion step, to obtain ash containing 15–20% Ni; (2) a leaching step; and (3) purification. That whole flowsheet has been thoroughly investigated, and the processes scaled up to the pilot scale. Another strategy is presented here, consisting of recovering Ni without burning the plant. Ni can be extracted from the dry plant by water leaching, but the leachate is a multi-element solution from which Ni has to be separated. Selective precipitation of Ni hydroxide is not possible since Ni is bound to organic ligands. In this work, the plant leachate is processed by adsorption on the chelating resin DOWEXTM M4195. The results showed that Ni was selectively retained whereas the other main cations were not. Nickel could be recovered at the elution step. This methodology needs to be further investigated but these initial results are very encouraging and open the possibility of Ni recovery by agromining.

By K. Adham

For use in many existing and emerging applications, the purification of natural graphite is required to achieve +99.9% carbon content with minimum metallic impurities. Currently, the hydrofluoric acid process is used, which carries certain environmental and workplace health and safety impacts. While thermal purification of graphite at temperatures over 2500 °C is a known alternative, such high-temperature furnaces are expensive to build and operate. Using chlorine at lower temperatures to purify graphite is also known and patented, but is currently limited to treating solid synthetic graphite shapes in small-scale batch furnaces. Chlorine treatment of natural flake graphite resources can be used commercially, if certain drawbacks are addressed through process improvements that can be helped with the use of fluidized bed reactor technology.

By Laurence Whitty-Léveillé

Proper handling of the radioactive fraction associated with the production of rare earth elements (REEs) in the mining industry is essential for a sustainable environment and human health. Actinides, such as uranium and thorium, have similar chemical properties to REEs, and are often co-dissolved in current hydrometallurgical processes. This causes radioactive contamination of the infrastructure through the extraction cycle. The present study optimizes, through experimental design, a sequential leaching procedure with Na2CO3/NaHCO3 and HCl for the rapid and selective dissolution of REEs and actinides. Optimization focuses on the main operating parameters (time, temperature, and concentration); different types of minerals, REE composites, and ores; on achieving maximal leaching yield; and on minimizing dissolution of the gangue metals (Fe, Si, and Ca). The final sequential procedure was rapid (1 h), effective, and led to the segregation of Th, U, and REEs with limited dissolution of the gangue metals.

By Jian Li, Guo Chen, Bingguo Liu, Hongying Xia, Jinhui Peng, Libo Zhang

"Decomposition of ammonium tetramolybdate to prepare Mo03 using silicon carbide crucible in microwave fields was investigated. The results were analyzed Using TG-DTG and X-ray diffraction. Meanwhile, the effects of heating rat, material thickness, socking time, socking temperature on the structure of preparing Mo03 were studied. TG-DTG curves show that the decomposition process of ammonium tetramolybdate is only one stage, in the temperature range 300-350°C, whose begin to decompose when temperature increases beyond 300°C. The molybdenum trioxide was prepared by thermal decomposition. The quality ofMo03 was not affected under the heating rat is 12°C/min. It was beneficial for decomposition ratio with the lower material thickness, longer soaking time, and higher soaking temperature. XRD curves showed that it is viable method for preparation of Mo03 by decomposition from ammonium tetramolybdate in microwave fields.IntroductionMolybdenum is widely used in national defense, aviation, industrial and agricultural production as rare refractory metal. Molybdenum trioxide is vital raw materials for the process of preparation of molybdenum. The traditional production technology of molybdenum oxide is that ammonium tetramolybdate is calcined in rotary kiln or 4-tube furnace [J,2J. But the longer production time, the higher production cost, the lower furnace thermal efficiency, and bigger the energy consumption, especially the powder is easy to leak, the working environment is poor by using rotary kiln [ 3 l _ The particle of molybdenum oxide is non-uniform by using 4-tube furnace because of the uneven temperature of every tube and the poor exhaust of boat bottom [4l _ However microwave heating is quick and uniformity, it is a meaningful research that the microwave is used in the process of calcining ammonium tetramolybdate."

Jan 1, 2013

By Dai Yongnian

The methods of treating zinc crust and its development in the last hundred years are compared and reviewed. There are better effects from normal pressure metallurgy turned into vacuum metallurgy. The traditional methods dezinc only. But we must consider that delead on further step. From lab tests to industrial scale experiment are researched. The first step-dezinc, second-delead, crude ,metal of, zinc, lead and silver are produced, The flowsheet of treating zinc crust are simplified, material consumption reduced, work condition improved, environment protect mended. This method is pointed out that its application can be expanded.

Jan 1, 1992

By Ximeng Zhu

In the transpassive region, about 0.4 to 0.8 V (SCE), aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The growth kinetics of the reaction product film, resulting from transpassive oxidation of pyrite were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The effect of electrode rotation speed, solution pH and temperature were examined. Potentiostatic measurements were well correlated by a paralinear rate equation, suggesting the formation of an intermediate passive film, associated with the simultaneous dissolution of the outer layer of the film. Activation energies of 66.17 kJ/mole (15.83 kcal/mole) and 38.67 kJ/mole (9.25 kcal/mole) were obtained for associated parabolic and linear rate constants respectively, at an applied potential of 0.6 V.

Jan 1, 1993

By Baozhong Ma, Yonglu Zhang, Yongqiang Yang, Chengyan Wang, Yongqiang Chen

During the past decades, slurry electrolysis (SE) has been implemented commercially for the processing of bismuthinite and complex Pb-Cu bearing gold concentrates. Recently, SE was proven effective for the treatment of As-rich antimonic gold concentrates. Laboratory test results suggest over 98% of the antimony was extracted, while the extraction of arsenic and gold was less than 0.5%, and that of iron was less than 6%. Moreover, the cathode antimony contained over 98% antimony and less than 0.3% arsenic. Considering the disadvantages of traditional 3 kA slurry electrolysis baths, such as smaller electrode area, reduced capacity, and greater electrode deterioration, the authors have developed an innovative 12 kA slurry electrolysis bath equipped with mesh and fence type titanium alloy electrodes. Furthermore, the technique was successfully used within a pilot scale plant yielding results similar to those observed in the laboratory. The technique yielded ametallic antimony ingot of 99.9% purity after arsenic removal via the addition of Na2CO3.

Jan 1, 2014

By Geoffrey A. Brooks, M Akbar Rhamdhani, Md Saiful Islam

A novel electrically-enhanced metal purification using slag has been developed. This was achieved by applying DC potential between liquid metal and slag phases. The concept was demonstrated through small-scale experiments at temperatures of 1500-1600oC for the removal of boron from Si-B melt using CaO-SiO2-16wt%Al2O3. Silicon (containing B) and slag were reacted in an alumina crucible in a resistance tube furnace. A circuit was produced by immersing graphite rods into the silicon bath and the slag layer. Electrical potential differences of up to 3.5 V were applied during the reactions. The reaction rates, the opencircuit voltages and short-circuit currents (in the case when the potential was applied) were then measured and determined for various slag to silicon ratio. It has been shown from this study that both the apparent rate and the boron partition ratio were increased by a factor of approximately 1.6.

Jan 1, 2014

By K. J. Murphy, A. R. Smith, A. P. Odorski

"The need for large quantities of oxygen for use in metallurgical processes was a major driving force in the commercialization of tonnage air separation plants. Oxygen, nitrogen and argon impact the quality, energy efficiency and environmental aspects of metals production. Cryogenic air separation processes have been used to supply most industrial requirements, however, newer technologies are available or under development to meet the needs of today's and tomorrow's metallurgical processes. This paper reviews the technical features and state of development of adsorption, chemical, cryogenic and membrane technologies. The technologies are compared in terms of plant size, oxygen purity and pressure, nitrogen and argon co-production, product use pattern and back-up requirements. Computer control systems are described that optimize operation over varying load patterns and ambient conditions; substantially lowering energy consumption. IntroductionOxygen production totalled 390 billion cubic feet in 1987. Although current production is lower than the peak of 455 billion cubic feet reached in 1979, oxygen remains the fifth leading chemical product manufactured in the u.s. (1) Metals manufacturing and fabrication accounts for sixty percent of the oxygen consumed in the u.s. Oxygen use in the steel industry consists of air enrichment for conversion of iron ore, purification of the iron in basic oxygen or other furnaces, and for cutting and welding the finished steel product. Nonferrous ores are smelted in oxygen enriched atmospheres to reduce energy consumption and increase capture of sulfur compounds to meet environmental requirements. In the future oxygen usage is expected to become even more important in metals production as energy costs increase, environmental standards become more stringent, and as new coal based processes become commercialized. Oxygen usage per ton of metal in the new direct reduction processes can be up to ten times higher than traditional steel making."

Jan 1, 1988