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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 Ryokichi Shimpo, Akio Fuwa

"In order to elucidate the present status of process-control technology, survey study has been made on the present process control schemes of representative copper smelting and converting processes in Japan. Conceptual control flow diagrams have been deduced and shown on respective functional reactors, i.e. drying, smelting, converting and fire-refining units, where the objective OUTPUT items are correlated to the INPUT variables through respective CAUSE-AND-EFFECT RELATIONSHIPSFuture view has been also discussed on several feasible and desirable improvement and refinement ~n measurements and control system for better copper smelting and converting operations.INTRODUCTIONIn other to seek for the better and efficient operation in copper smelting and converting process, survey study has been first conducted on the present process-control schemes of respective functional unit processes, i.e. drying, smelting, converting and refining unit processes, of representative copper production processes in Japan. Conceptual process flow chart of control scheme has been then deduced where output items are correlated to input items through the respective cause-and-effect relationships.After this survey study, future view has been discussed on the feasible and desirable improvement and refinement in the measurement and control system in these processes. Emphasis has been placed on the better and precise measurements of temperature, oxygen partial pressures in respective furnaces and end-point in converting and refining unit operations."

Jan 1, 1989

By Nobuhiro Oguma, Yuji Mizuta, Hideya Sato, Shigehiko Iwahori

"Recyclable materials containing copper and precious metals have been treated at the Mitsubishi Process in Naoshima. In 2003, a new incinerating and melting plant (pre-treatment plant) for waste materials, such as shredder residue of automobile and scrapped appliance, was constructed. All of produced slag/metal mixture is treated at the Mitsubishi Process, and which results in the significant increase of recyclable materials treatment. The combination of two processes has realized a highly efficient and environmentally friendly system for recycling valuable metals in the waste which used to be sent to a landfill. Naoshima continues to make efforts to achieve the highly efficient operations of the two processes, and plans to increase the treatment of recyclable materials further. This paper summarizes the recent operations and the various improvements implemented in the pre-treatment plant.IntroductionRecyclable materials containing valuable metals such as copper and precious metals have been treated at the Mitsubishi Continuous Copper Smelting and Converting Process (Mitsubishi Process) since the start-up in 1991. In the early stages, recyclable materials consisting mainly of metal scrap were charged into the process and the treatment had been increased steadily. In order to promote the recycling business, treatment of various kinds of materials including printed circuit boards was started. However, the treatment hit the ceiling due to a limitation of furnace boiler capacity, since they contained large amounts of combustible materials. In addition, severe corrosion of boiler tubes was caused by halogen contained in recyclable materials."

Jan 1, 2012

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

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 Dinesh Goyal

Industrial fly ash from (electro static precipitator) was mixed with soil at different levels on v/v basis for raising of pulpwood tree species. In field trials conducted on degraded soils increase in the plant growth of Eucalyptus tereticornis, Acacia auriculiformis and Casuarina equisetifolia by 10 %, was observed during the initial six months after plantation at 18-24% (v/v) fly ash concentration which was at par with chemical fertilizer treatment. Level of As, Se and Mo in flyash was 6.2, 3.6 and 4.0 ppm respectively. The radioactivity analyses 40K, soil and 28 fly ash showed that the activity levels of gamma emitting radionuclides K, Ra, Ac were within the permissible limits and mixing of fly ash with soil at tested concentration would have no deleterious effects. Available Co, Cr, Ni and Cd in rhizospheric soils were below detection limit. Fly ash at 10-20 % level (v/v) was also found to be a good potting mix material in forestry nurseries in terms of improving biomass production by 20 %, when tested in nursery seedlings of Eucalyptus tereticornis. Nursery addition of fly ash in soil decreased soil dehydrogenase activity and the soil bacterial population was negatively affected. These results indicate that use of fly ash in forestry sector involving nursery and plantations as a soil amendment agent upto 10-20 % v/v is a gainful utilisation of fly ash.

Jan 1, 2002

By M. S. Moats

Galvanic stripping, in conjunction with solvent extraction, has been proposed as a technical option to the challenging problem of iron removal in certain hydrometallurgical processes. The galvanic stripping process is based on the ability of a solid metal to directly reduce ferric ion to the ferrous state in an organic media. Stripping the iron into the aqueous phase is then easily accomplished. Previous work has shown the reaction kinetics and efficiency are affected by such operating parameters as water and oxygen contents, temperature, time and metal reductant. In this study, the optimum operating range for some of these variables was determined. Both zinc and iron metal were used in the separate stripping of iron from D2EHP A. Reasons for the differences in the extent of the reaction obtained using the various conditions are discussed.

Jan 1, 1996

By F. H. A. Abdalla

A process is described for the recovery of valuable nonferrous metals from steelmaking dust by suiphatizing roasting using ammonium sulphate. Maximum recoveries of soluble metal sulphates achieved at optimum conditions were> 99.0 %. Selective metal separation of the soluble sulphates in the leached liquors were performed either by controlling the roasting temperature or by adjustment the pH values of the leached liquor ranging from 3.6-6.2. Either pure zinc oxide orland tin oxide could be obtained at optimum conditions, and the products were evaluated chemically and by X-ray analyses. The residues rich in iron oxide can be removed and recycled. The mechanism of sulphatizing roasting process was considered. A general flow-sheet for the overall process of treatment the steel making dust to recover its valuable nonferrous metals was suggested, which ca be applied for other nonferrous bearing materials.

Jan 1, 1996

By Courtney Young, Jerome Downey

"The various technologies developed for treating spent potlining (SPL) from primary aluminum smelters have been reviewed on several occasions. The technologies generally involve physical, chemical, and thermal processes, either individually or in combination, with the primary objective of total recycle, waste minimization, or complete disposal. In general, those technologies geared for recycling involve separations and are therefore subject to recovery inefficiencies that are attributed to several factors. However, the inefficiencies could be reduced or possibly eliminated if the pots were designed for recyclability. This concept is applied to SPLASH, a recently developed SPL management technology.IntroductionAluminum is produced by molten salt electrolysis via the Hall-Héroult process. The process is conducted in an electrolytic “pot,” which is comprised of a steel frame first lined with insulating refractory brick, and then conductive graphite blocks, which serves as the carbon cathode [1, 2]. These materials are collectively referred to as “potlining.” Anodes comprised of petroleum coke/pitch are suspended above the pot and extend down into the molten cryolite (Na3AlF6) electrolyte. The electrolyte temperature is maintained at approximately 980 °C by resistance heating as low voltage (4-5 volts) and high current (50,000-300,000 amps) are applied across the two electrodes.High purity alumina is added to the cryolite bath, where it dissolves and becomes amenable to aluminum reduction at the cathode:"

Jan 1, 2008

By L. Filip

The roast-leach-electrowinning (RLE) process for zinc was modified to treat two typical complex concentrates containing zinc, lead, copper, gold and silver. Laboratory testwork results indicated that the optimum roasting temperature ranged from 700 to 800°C, in order to produce acceptable residual sulfur levels. The calcined concentrate was subjected to a three-stage leach sequence. The resulting leach solution was purified by hematitic precipitation and directed to the recovery of copper and zinc by solvent extraction and electrolysis. Alkaline smelting and subsequent electrolytic purification recovered the lead and precious metals from the leach residue. A flowsheet was developed based on the laboratory testwork results, and demonstrated in a large-scale pilot plant. The recoveries produced during the pilot plant operation ranged from 90 to 92% for zinc and copper, 85% for lead and 90% for gold and silver, respectively.

Jan 1, 1999

By K. Potluri, S. Akella, S. Bhansali

"This paper presents the design and angular strength analysis of microneedles for use as a transdermal interface for drug delivery, fluid analysis and sampling etc. Microneedles of different dimensions were designed and fabricated using various materials viz. Si02, OxideNitride- Oxide (O-N-0). The design, modeling and analysis was done using the Finite Element Analysis (FEA) software ANSYS™ 6.1. Angular strength analysis of the microneedles was done using angular loading in ANSYS™, with the corresponding inaterial property settings. Using the force-displacement settings, forces of magnitudes in the range of 10 mN - 25 mN were applied on the microneedles at loading angles ranging from 30° to 90° was applied on needles. Square and circular shaped microneedles were modeled and the displacements and stresses generated were studied to characterize the angular strength of the microneedles. The buckling and force-displacement analyses show that O-N-O microneedles are more strong and robust as compared to needles of other materials. The analysis shows that while circular microneedles have uniform stress distribution, square microneedles have low stresses concentrated along the edges.INTRODUCTIONIn modem clinical and biomedical applications, drug delivery is done either by oral administration or by hypodermic injection. Hypodermic injection of drugs using needles is often painful. Hence, transdermal drug delivery techniques are increasingly being sought out as an alternative. In transdermal drug delivery the needles puncture the Stratum comeurn - the outermost layer of the human skin. The advantage of transdermal drug delivery (or transdermal measurement) technique, is that it reduces pain and tissue trauma."

Jan 1, 2004

By J. F. White

An experimental study was undertaken to evaluate the feasibility of a selective chloridizing roasting pre?treatment process for the elimination of impurities from zinc feed?stocks prior to recovering zinc by conventional unit operations. In this investigation, a number of chemistries that might serve as a basis for such a pre? treatment process were examined. A variety of chloridizing agents were admixed with EAF dust to promote the selective removal of lead and cadmium by the formation of volatile metal chlorides, he results of the experimentation firmly establish that selective chloridizing roasting is a technically feasible means of eliminating lead and cadmium from EAF dust. Excellent extraction efficiencies were accomplished with a number of chloride additives; as high as 98 percent lead extraction and 88 percent cadmium extraction were attained with minimal zinc losses, Continuous pilot?scale tests reinforced the trends established by laboratory?scale experimentation, Attempts of chlorine elimination using pyrohydrolysis were less successful. The extent of chlorine elimination was found to be highly dependent upon EAF dust sample type and treatment temperature.

Jan 1, 1996

A study was undertaken to remove the Se from waste solutions using a raw form of the biomass called Iota Chips derived from the seaweed, Eucheuma spinosum. Removal of Se from solutions was investigated as a function of time, pH, conc. of Se in solution (0.1 to 100 ppm) and lota Chips to liquid ratios of 10-2 to 10-5. For solutions containing initial conc. of 0.1 ppm Se, with the addition of Iota Chips at a solid to liquid ratio of 10-3, the Se conc. decreased to 0.03 ppm in about 3 hours. Iota Chips absorption capacity to the Se and its application to the treatment of the metallurgical processing effluents are discussed.

Jan 1, 1992

By Xinlei Jia, Wenming Guo, Yanling Zhang

A large amount of stainless steel dust rich in Fe, Cr, and Ni has been being generated in China. Smelting treatment is accepted as a practical method for the recovery/reutilization of these second resources, during which Fe, Cr, and Ni is reduced into one metal phase and then separated from the residue slag. Based on the typical compositions of stainless steel dust, the residual slag can be termed as CaO-SiO2-MgO-Al2O3 system. In this paper, the activity coefficients of Cr in Fe-Cr-Ni-C (-Si/Al) melt and the properties of CaO-SiO2-MgO-Al2O3- 1%CrO system thermodynamically approached. Then, in laboratory experiments, the recovery ratios of Cr and its distribution behaviors between Fe-Cr-Ni-C melt and CaO-SiO2-MgO-Al2O3 slag system were examined.

Jan 1, 2015

By Bora Derin, Sertac Yazici, M. Seref Sonmez

"In this study, the recycling conditions of waste liquor obtained after the production of tungsten boride powder from calcium tungstate by self-propagating high temperature synthesis (SHS) and the following hydrochloric acid leaching were investigated in detail. Environmentally unfriendly and extremely acidic (pH~ -0.3) liquor consisting of calcium, magnesium, and boron ions was treated with 1 M sodium carbonate solution to precipitate magnesium carbonate and calcium carbonate phases. The obtained amorphous precipitates were heated up to the temperature of 400°C for re-crystallization. As a result, MgO, CaC03 and CaMg(C03)z phases were obtained, while sodium, boron, chlorine ions were remain in the solution. The present study is still in progress.IntroductionSelf-propagating high temperature synthesis (SHS) is one of the techniques used in the production of a variety of advanced ceramics, inter-metallic, organic and inorganic compounds, oxygen free single crystals, and polymers [ 1, 2]. The reaction becomes selfsustaining and propagates in the reactant mixture, after initiation in SHS process. SHS products may contain the mixture of several unwanted compounds and elements. Therefore following acidic leaching process may be needed to purify the target product. In the previous study, calcium tungstate (Ca W04), magnesium (Mg) and boric acid (B20 3) mixture were reacted to produce tungsten boride powder by SHS process according to the Reaction 1. Then, magnesium and calcium containing byproducts (i.e. MgO, Mg3B206 and Ca3B206) found in the SHS product were leached out by using concentrated hydrochloric acid (HCl) solution to obtain pure tungsten boride powder [3].Ca W04 + 0.5B203 + 4.5Mg = WB + 4.5Mg0 + Cao (1)After the leaching, filtrate solution consisting of different amounts of magnesium, calcium, and boron requires additional treatment for the environmentally acceptable disposal.Several works were carried out about magnesium precipitation conditions and kinetics from brines. Rabadzhieva et al. investigated the precipitation of Mg(OH)z from brines by using NaOH as well as caustic soda [ 4]. Turek ve Gnot investigated the precipitation efficiency of Mg(OH)z for the temperature range between 10-40°C, while the reaction was kinetically experimented by Alamdiri et al [5, 6]. Homogeneous precipitation of nesquehonite (MgC03.3H20) by the reaction of MgCli with (NH4)2C03 in supersaturated solutions and factors that influence the precipitation of MgC03.3H20, such as reaction temperature, initial concentration, stirring speed, titration speed, equilibration time, have been studied by Wang et al [7]. The precipitation of Mg(OH)z by calcium hydroxide from aqueous solutions was studied by Baird et al. [8]. Stratful et al. focused on conditions influencing the precipitation of magnesium ammonium phosphate from wastewaters [9]. 1031"

Jan 1, 2011

By Gus Van Weert

Hydrometallurgical oxidation of sulphides is capital and energy intensive, with autoclave and bio-technology competing for lowest overall cost status. The use of surface aerators instead of stirred tank reactors could provide lower costs for bio-oxidation of concentrates. With this in mind, the Delft Inclined Plate reactor was designed with inclined plates above a settler shaped reactor to continuously return slurry from the lowest point in the settler to the surface of the liquid. The multiplate superstructure overcomes the scale-up restriction of the standard circular surface aeration patterns. DIP aerator energy and volume requirements for oxygen transfer from air will be presented in terms of kg O2/kWh and kg O2/m3/h transferred as a function of wt % sand in the slurry and compared to stirred tank performance. Scale up from the 4 m3 pilot unit will be discussed.

Jan 1, 1996

By Onuralp Yiicel, Ozlem Okur, Murat Alkan

"In this study, Co-Cr-Mo alloys were produced using a mixture of Co304, Cr203 and Mo03 powders with Al powders by a Self-propagating high temperature synthesis process. SHS is a process of material synthesis that has revealed a number of reactants combinations capable of much higher energy release than conventional explosives. Al203 is added to the mixture to decrease the adiabatic temperature of the system. The thermodynamic simulations and the calculations of adiabatic temperature were examined with FactSage 6.2. In the SHS experiments, different Co304/ Cr203/Mo03 ratios were examined, and their effects on the metal recovery and alloy compositions were carried out. The samples were characterized by using chemical analysis, XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis (SHS) has significant advantages compared to the high technology furnace applications, such as very short processing time, simple operation, low energy requirement and low cost [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. This work aims to establish a scientific and engineering background in the production of some cast Co-Cr-Mo master alloys via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys."

Jan 1, 2013

By N. Choi

The distribution behavior of selenium and tellurium in nickel sulfide smelting was investigated in the temperature range of 1250-1300 °C under an inert gas atmosphere and various oxygen partial pressures. The distribution coefficients of selenium and tellurium between nickel-copper-iron matte and silica-saturated iron silicate slag were detennined in terms of matte and slag compositions, temperature, and oxygen partial pressure. The effect of slag additives such as CaO, MgO, and Ah03 on the distribution coefficients of those elements was also investigated. It was observed that the distribution coefficients of selenium and tellurium increased with increasing matte grade and temperature. The solubility of selenium and tellurium in the slag decreased with increasing the partial pressure of oxygen within the range investigated in this study. The distribution coefficients of selenium and tellurium increased with the amount of CaO and MgO. Tellurium distribution coefficients also increased by the addition of Ah03. Meanwhile, the addition of Alz03 decreased the distribution coefficients of selenium at high matte grade.

Jan 1, 1996

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By H. Y. Sohn, Joshua E. Ramos, Moo Eob Choi

"A new technology for ironmaking based on direct gaseous reduction of iron ore concentrate is under development. This technology would drastically lower CO2 emission and reduce energy consumption by nearly 38% of the blast furnace requirements. Experiments were performed using iron oxide concentrate at 1150oC in a bench-scale facility, which was the highest temperature that could be reached in the facility. The reduction extent was determined at residence times of 3.5 - 5.5 seconds in which the reduction extent approached 43% with 0% excess H2 and 95% with 860% excess H2. Separate kinetics measurements showed that the rate is much faster at 1200 - 1400 oC. Experiments were also carried out using syngas (mixtures of H2 + CO). About 90% reduction in 3.5 seconds with 860% excess hydrogen contained in the syngas demonstrated sufficiently fast reduction for a suspension process and the feasibility of usingsyngas instead of pure hydrogen.IntroductionDespite the improvements in the modern blast furnace (BF) process, it suffers from many drawbacks. The process requires the feed in the form of sinters or pellets and high-grade coking coal. Thus, BF iron production is projected to decrease gradually [1]. The main factors for this are the environmental regulations [2] and the high capital investment cost.A large number of new ironmaking technologies have been developed or are under development [3]. Most of these processes, however, are not sufficiently intensive to replace the blast furnace because they cannot be operated at high temperatures due to the sticking and fusion of particles. Therefore, a new technology is under development for producing iron directly from fine concentrates by a gas-solid suspension technology, which would reduce energy consumption by about 38% of the amount required by the blast furnace and drastically lower environmental pollution, especially CO2 emission, from the steel industry."

Jan 1, 2009