Search Documents

By Tetsuya Uda, Sakae Shirayama

"With the aim of producing nickel (Ni) metal directly from acidic aqueous solution containing cobalt (Co) and other impurities, selective reduction of Ni was examined. As a preliminary experiment, sodium hypophosphite monohydrate (NaH2PO2·H2O) was selected as a reductant, and reacted with aqueous solution containing 0.1 mol L-1 nickel sulfate (NiSO4·6H2O) and 0 ~ 0.05 mol L-1 cobalt sulfate (CoSO4·7H2O) for 3 hours at 90 °C. As a result, it was revealed that Ni was selectively reduced and separated from Co in the acidic region (pH= 4.8). In this study, differences of reduction behavior between Ni and Co were investigated, and the feasibility of Ni I Co separation by the selective reduction of Ni was discussed.IntroductionEfficient Ni condensation and separation from Co are essential in nickel hydrometallurgical processes. Currently, the hydrometallurgical production of Ni from oxide ore is mainly carried out by acid leaching at elevated temperature, followed by the removal of impurities using neutralization, and condensation of Ni and Co into intermediate products such as hydroxides and sulfides. Then, the intermediate product is dissolved in acid aqueous solutions, and Ni I Co separation is conducted by solvent extraction. Finally, Ni and Co are recovered by electro-winning. This complicated process consumes large amounts of alkali, hydrogen sulfide (H2S), and organic solution in a multiple-staged process'. To reduce the consumption of these chemicals, it is important to recover Ni more efficiently from acidic aqueous solution containing impurities."

Jan 1, 2014

By Jr. Loper, M. H. Kim, H. H. Jo, C. S. Kang, T. S. Song

"An investigation has been conducted to describe the effect of grain refiner (e.g.,Ti) or modifier (e.g., Sr) on the microstructure of an Al-11.3wt%Si alloy produced by the Ohno horizontal continuous casting process using a heated mold so as to obtain directional solidification at high cooling rate of 300 to 2000°C/s. Experimental results demonstrated that the directionality of the primary a grain was promoted by the addition of0.2 to 0.4%Ti or by the addition of0.02%Sr, whereas the addition of0.6%Ti suppressed this directionality. Feathery a grains were promoted by the addition of 0.2%Ti, while these feathery a grains were suppressed when over 0.4%Ti (grain refinement) or when 0.02%Sr was added. The addition of Ti also resulted in increased coarsening of the eutectic Si in these Al-1 l.3wt%Si alloys.IntroductionThe mechanical properties of conventionally cast Al-Si alloys can be enhanced through judicious control of the casting parameters, by the addition of grain refiners (e.g., Ti) and by the addition of eutectic modifiers (e.g., Sr).[1-3] The Ohno continuous casting process[4-5] uses a heated mold (maintained at a temperature above the alloy liquidus temperature) to produce a casting with a mirror surface free of shrinkage defects. The process is especially suitable for the production of high quality and non-deformable rods of small diameter. This study was conducted at investigate the effects of Ti and Sr on the microstructure of Al-1 l .3wt%Si rods cast by the 01).no process."

Jan 1, 1998

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

By Esa J. Peuraniemi

Copper smelting to form blister in one single step has been possible for a long time even from low grade concentrates. In spite of obvious benefits, it has been economically viable only with few special raw materials having high enough Cu/Fe and Cu/S ratio. Outokumpu Blister Flash Smelting is currently applied at three operations, and three others will be commissioned in the near future. With typical chalcopyrite concentrates two main obstacles have prevented wider adaptation of direct blister processing: slag formation and heat generation. Oxygen potential in the reaction shaft must be high in order to produce blister with targeted sulfur content below 1%. When large amount of iron is oxidized, as well as sulfur, copper is inevitably also oxidized into slag. High copper amount in substantial tonnages of slag lead on to costly down stream recovery operations to obtain discardable slag. Almost complete oxidation of sulfur and iron releases a high amount of heat which traditionally has been solved by lowering oxygen enrichment of the blast leading on to oversized off-gas line and acid plant. One challenge in direct blister smelting relates to the attack of aggressive high-copper containing slag against furnace refractory lining. In continuously operated Outokumpu Direct Blister Flash Smelting this is taken care of by preventing vigorous melt movement in the settler. Stable bath conditions and stationary slag against refractory lining enable the formation of a protective autogenous layer between aggressive slag and vulnerable refractory. These direct blister smelting challenges are addressed from equipment and process development point of view. New solutions to overcome the obstacles are presented and discussed.

Jan 1, 2006

By Xi-Shan Li, Qian Li, Yong-bin Yang, Li-na Cui, Tao Jiang, Jie Ge

"With regard to control environment pollution in the roasting pretreatment of sulfur & arsenic-bearing gold concentrate, roasting of double-layered pellet was proposed. In the paper, the characteristics of double-layered pellet roasting were studied. Removal and solidification rates of sulfur and arsenic were investigated as primary factors. The result indicated that the removal and solidification rates of arsenic reached up to 95.91 % and 98.95% while the sulfur was 97.19% and 97.90% respectively on the premise of adopting slaked lime as solidified agent at temperature of 6000, the package proportion of 2.14 and roasting time of 3h. However, pyrite and arsenopyrite were transformed to hematite and magnetite and product of solidification mainly consisted of calcium sulfate, calcium arsenate and calcium sulfite within optimum roasting parameters.IntroductionUtilization of refractory gold resources has been gradually concentrated on with the depletion of the gold resources which are easy to deal with in the world [1]. Sulfur and arsenic-bearing gold ore is a typical refractory gold one, in which ultrafme gold is encapsulated in the structure of metal sulfide minerals [2,3], so it gives poor recovery through direct cyanide leaching. These refractory ores need pretreatment before the process of cyanide leaching to undermine lattice structure of pyrite and arsenopyrite containing gold [4] so that the gold could touch with cyanide solution [5]. Among various methods of pretreatment, conventional roasting method is most effective, but this process generates gases such as S02 and As203 harmful to environment. Therefore solidification roasting was proposed to solve this problem occurring in the conventional roasting at the end of last century."

Jan 1, 2013

By Guozhu Ye, Eric’ Burstrom

"Despite of numerous solutions for recovery of zinc from EAF dust have been suggested and tested in laboratory scale over the last three decades, Waelz kiln process is still the most dominating process for treatment of EAF dust. Few of the proposed alternative methods have gone beyond the laboratory tests. This paper will give you insights to some of the concepts that have been pilot tested at MEFOS. The innovative aspects of these concepts will be shown and the major results will be highlighted. These include the following concepts: - Production of a crude zinc oxide product with low halide content for zinc electrowinning using a DC furnace with hollow electrode- Production of a bypass filter dust containing more than 50%ZnO by injection of EAF dust to the electric arc furnace during refining combined with a bypass filter system- Elimination of zinc ferrite by CaO treatment for electrowinning with EZINEX process - Selective reduction of iron oxide in zinc ferrite for simultaneous recovery of ZnO andmetallic ironIntroductionRecovery of zinc from EAF dust is dominated by the Waelz process since EAF dust has been classified as hazardous waste by EPA in the early 1980´s. A large number of alternative processes have been suggested and tested without commercial success due to two major reasons [1]:- High content of chlorine and fluorine for the pyrometallurgical alternatives- High content of ZnOFe2O3 for the hydrometallurgical processesMany innovative concepts for treatment of EAF dust for zinc recovery have been pilot tested at MEFOS in the past 20 years. This paper will review some of the concepts focusing on the two problems mentioned above."

Jan 1, 2008

By Biao Zhou, Qian Li, Kuo-Chih Chou, Yi-Long Liang, Jie-Yu Zhang, Qun Luo

"In this work, the phase transformational behaviors and microstructural characteristics of 60Si2CrVAT spring steel were systematically investigated as a function of applied cooling rates in the range of 0.l-10°C/s. A quenching deformation dilatometer was used to austenize and quench. The dilatometric curves between length changes and temperature of samples suggest three characteristic stages could be identified as different ranges of cooling rates, which meets well with metallographic examination and the measured hardness results. As the cooling rate increases, the structure transformed from pearlite, granular bainite to finally martensite. The F + P and B zones are completely overlapping in continuous cooling transformation (CCI) curve, which indicates that this steel is difficult to become single bainite and shows good hardenability.IntroductionThe 60Si2CrVAT, a high-carbon low ally super-high strength steel developed from the ?OCT 60C2XFA and 60Si2MnA, is often used for coil spring of heavy vehicles and high-speed railway by hot deformation or cold deformation [1-3]. The addition of Si improves relaxation resistance significantly, through the refinement of tempered carbides as the result of the retardation of E -carbide conversion to cementite during tempering. Due to its deleterious effects on decarburization and toughness, the maxinJum content of Si has limited to 1.5 or 2.0% [4-5]. Additionally, V and Cr can improve sag resistance due to the precipitation of fine carbonitrides during hot rolling [6-7]. To best of our knowledge, the strengthening by precipitation of alloy carbides of Cr and V often referred to secondary hardening [8]."

Jan 1, 2013

By Kang Wan, Lei Tang, Jianchao Li, Jieyu Zhang, Minqi Sheng, Jifang Xu

"The viscous flow phenomenon in slag close to the liquidus temperature was considered. A simple approach that liquidus temperatures of melt could be derived from viscosity data was employed. The potential of this method for estimating the liquidus temperatures of pure water and binary alloy was demonstrated. The liquidus temperatures of the CaO-Alz03 based slags obtained from the second derivative method depends upon the number of viscosity values available at different temperature intervals. The results indicated that plots start deviating from the straight-line behavior at temperature as expect, and the second derivatives show the break points at a certain temperature, which is the liquidus temperature. Comparisons among the present observations as well as the characteristic temperature of the selected slags, which measured by the hemisphere method and DSC, indicated that it is possible to get a reasonable idea of estimate the liquidus temperatures from activation energies for viscous flow.IntroductionThe liquidus temperature of slag, which has a significant effect on the kinetics of chemical reactions and the slag-metal separation, is extremely important for metallurgical operations. Experimental measurements of the liquidus temperatures of slags are difficult, since slags invariable supercool. In addition, behavior of a single constituent in a multi-component slag is different in different circumstances due to its interaction with other constituents. Hence, it is essential to study the liquidus temperature of each particular slag resulting from a special process. Usually, the compositions of the slags aimed to the single liquid region of the phase diagram. However, the phase diagram of many slag systems, which back often to the 1950's, involves considerable uncertainties. Many liquidus temperatures are given as dotted lines in Slag Atlas [1]. Disagreements between the phase diagram and the reality have been found [2]."

Jan 1, 2013

By Roderick 1. L. Guthrie, Mei Li

"A mathematical model was developed to study the role of orifice shape in the detection of inclusions in LiMCA (Liquid Metal .cleanliness Analyzer) system. The fluid flow field within the ESZ was obtained by solving the Navier-Stokes equations. The trajectories of entrained particles were calculated using the equations for motion of particles. A numerical study of the effect of orifice shape on signal shape generated by inclusions passing through orifice showed that the signals in a parabolic orifice are gaussian in shape, while those in a cylindrical orifice are trapezoidal in shape. This signal shape difference needs to be taken into account when performing particle discrimination. Orifice shape influences also pass-through fraction of inclusions. Finally, a study of the orifice shape on critical conditioning currents suggested that as the polynominal coefficient of the parabolic orifice increases, the critical conditioning current, which is also the maximum operating current, decreases dramatically. These critical conditioning currents also increase as the fluid flow velocity within the ESZ increases. IntroductionThe presence of non-metallic inclusions in metals often leads to impaired mechanical properties such as a reduction in fatigue strength, and to processing problems such as tear-offs in deep drawing and increased breakage rates in wire drawing operations. Similarly, inclusions cause a variety of surface defects in rolled or extruded products.Prior to the development of the LiMCA system (1) at McGill University in the early 1980's, it was not possible to measure inclusions, in situ, in liquid metals. Compared with other techniques, such as sedimentation, filtration and metallography, which require considerable amounts of labor and time, the LiMCA method has the advantage of providing not only information on the volume concentration of inclusions, but also on the size distribution of inclusions immediately and quantitatively."

Jan 1, 2001

By S. Saptharishi

Selenium, which is a 6A group element of the periodic table, constitutes about 7x10-5 % of the earth?s crust. Even though selenium is a dispersed element with respect to its commercial exploitation, it is capable of forming number of minerals and nearly forty selenium minerals have been identified, out of which the copper ores are the richest sources of selenium. Electronics industries and glass industries are the major consumers of selenium, while pharma grade selenium used as micronutrient for humans and animals. Various methods have been developed to recover selenium as a by-product from copper anode slime during copper refining. Selenium being amphoteric in nature, it is soluble in both acid and alkali. While acid roast process is widely used, considerable work has been carried out in Russia for recovering selenium through alkali route. This paper enlightens the process developed at Central Research and Development Laboratory, for recovering selenium from decopperised slime through alkali pressure leaching. The decopperised slime is pressure leached with alkali under oxidizing conditions by which almost all the selenium present is converted to alkali selenate, which is easily separable from the rest of the decopperised slime. The solution so obtained is neutralized, during which, most of the impurities are precipitated out. Then selenium is precipitated in its elemental form upon purging sulphur-di-oxide under warm acidic medium. The purity of the selenium obtained by this process is higher than that of the selenium from acid roast process. Moreover selenium can be crystallized as sodium selenate and it can be marketed. The acidic content of the effluent is recovered and it is recycled back to the process. The sodium content of the effluent is converted into high purity sodium sulphate, which is marketable. The hazardous waste containing arsenic is precipitated as its sulphide and can be disposed off as landfill.

Jan 1, 2006

By F. Ríos

Fundamental research, at laboratory scale, on the biomass adsorption capacity of a liquid mining effluent has been done. The biomass used corresponds to a Chilean seaweed called Gracilaria chilensis. The waste water effluent corresponds to clear water coming from thickeners of a Chilean copper mining operation. The biomass was dried, washed, treated with an acid solution, and then reduced in size. A characterization of Zeta potential was made, finding negative values in a wide pH range with a ZPC equal to 2.5 1. Adsorption tests were made- in an agitated system containing an artificial solution of CuS04 at a controlled temperature of 25 degrees Celsius; also, the effect of pH over the copper adsorbed was studied. Maximal adsorption of copper was found at pH equal to 6, and the Langmuir model indicated values for saturation of 52.08 mg/g and for standard free energy of about -21 KJ/mol. Kinetic adsorption was very high and fitted very well with a second order model equation, finding that 90 per cent of the adsorption occurred during the initial 10 minutes. After stoichiometric when 1 mol of copper is adsorbed, 2 mol hydrogen are released, showing that the main mechanism to remove heavy metals is the ionic exchange, and the seaweed ensures total discharge of copper adsorbed when the pH value is about 1. Experiments done with real waste water from thickeners lead us to conclude that optimal results for copper and molybdenum adsorption are at pH around 3.25 and the remaining treated water may be partially discharged into the water currents, thus showing that Gracilaria chilensis can be used to remove heavy metals easily from liquid effluents in the copper mining industry.

Jan 1, 1999

By Wayne Bell, Shivanand A. Borkar, Anish Upadhyaya, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"A refractory ore body located in Michigan’s Upper Peninsula contains high concentrations of nickel and copper chiefly occurring in the minerals pyrrhotite, chalcopyrite, and pentlandite. Refractory ore bodies are difficult to treat by conventional mineral processing methods so microwave pre-treatment of the ore is employed to increase metallic-particle/host rock liberation by making use the differential thermal expansion properties of the mineral phases that absorb microwave energy. The Curie temperature measurement of metallic-bearing particles is in agreement with the known value for pyrrhotite occurring at 325°C. A nickel-rich iron sulfide mineral is found to be in occurrence and also appears to be magnetic under BSE imaging. It is shown the ore particles heat rapidly when exposed to microwave radiation for short durations of time mainly due to the high concentration of ferromagnetic mineral phases. Rapid heating causes thermal expansion of constituent mineral phases that produce cracks within ore particles. SEM imaging shows fracture occurring along grain boundaries and throughout host rock matrix. Ball milling experiments show an increased grindability of the ore resulting in a decrease in work index values.IntroductionCrushing and grinding operations consume 50-70% amount of energy used in mineral processing operations [1]. All these processes involve high energy impact of surfaces to develop compressive stresses that produce cracks to initiate breakage of particles. Microwave pre-treatment of certain types of ore might provide an energy savings to these type grinding processes by taking advantage of the tensional forces produced by selectively heating microwave absorbing type mineral phases. The heating of ore particles produces cracking by thermal expansion of the constituent mineral phases. Conventional heating has been investigated and shown to positively aid in grinding processes but determined energy inefficient to be used commercially."

Jan 1, 2011

By L. Becze, S. J. Hock, G. P. Demopoulos

"Regeneration of HCl from chloride solutions is commercially practiced by high temperature (800-900 °C) pyrohydrolysis associated with high energy consumption and capital cost. As an alternative to pyrohydrolysis a novel low temperature ( <200 °C) non-autoclave hydrolytic process has been studied in this research work, which comprises two steps. In the first step, ferrous chloride is oxidized by oxygen at 1;150 °C, followed by hydrolytic decomposition of ferric chloride to coarse hematite particles and superazeotropic hydrochloric acid (8-9M) operated at approximately 180 °C. This paper provides a summary of the laboratory results related to both oxidation and hydrolysis and presents a newly designed conceptual process flowsheet.IntroductionRecovery of base, noble and rare metals from ores and secondary materials (slags, dusts, residues) by chloride-based hydrometallurgical processes holds a lot of promise if a low cost HCl process becomes available. This is particularly so due to the high activity of HCl or more accurately activity of hydrogen ion [1] in concentrated chloride media and the formation of chlorocomplexes allowing for effective leaching under atmospheric leaching conditions and simultaneous ease of metal separation. However, during leaching significant amount of iron, which is associated with most of ores and secondary materials, goes into the solution. Hence, the obtained leach solution has to be treated to convert iron chlorides into easily filterable iron oxide and simultaneously produce concentrated hydrochloric acid. Apparently the critical operation of these processes is the regeneration of the lixiviant (HCl). Currently in the industry, its regeneration is accomplished by high capital and intensive pyrohydrolysis which operates at 700- 900 °C. Aimed at lowering the operational cost of pyrohydrolysis a process called PORI [2] was developed and tested in pilot plant scale in the 1970s for the purpose of treatment of pickle liquors without, however, resulting in industrial application."

Jan 1, 2011

By Paul O. Malan

"The Tusc gold deposit is located along the Carlin Trend approximately 13 kilometers north of Carlin, Nevada and 2.5 kilometers northwest of the Gold Quarry mine. Tusc is one of several structurally controlled oxide gold deposits located along the Good Hope fault within the Maggie Creek subdistrict. Mining commenced in 1994 with an oxide reserve of780,000 troy ounces of gold at an average grade of 1.34 g/t Au. The Good Hope fault forms the southwestern edge of the Schroeder Mountain uplift (also known as the Carlin Window) and juxtaposes carbonate rocks of the Siluro-Devonian Roberts Mountains Formation against siliceous mudstone, siltstone, and silty limestone of the Devonian Rodeo Creek unit. Submicroscopic gold mineralization is disseminated in the Good Hope fault system and in fractured hanging wall carbonate rocks. Wallrock alteration includes silicification, deca!cification, sericitization, and late alunite replacement and veins. All Tusc ore is transported 2.5 kilometers to Gold Quarry for processing. Leach-grade ore (0.2 - 1.7 g/t gold) is placed on the oxide leach pads, and mill-grade ore(> 1.7 g/t gold) is processed through the CIL oxide mill. IntroductionThe Tusc gold deposit is located in Eureka County, Nevada, U.S. A, approximately 13 kilometers north of the town of Carlin and 2.5 kilometers northwest of the Gold Quarry mine (Fig. 1 ). Tusc is one of several open-pit, oxide, gold deposits within the Maggie Creek subdistrict of the Carlin Trend. Tusc is a structurally controlled gold deposit located along the Good Hope fault. Submicroscopic gold mineralization is disseminated in the brecciated and silicified Good Hope fault zone and along intersecting northeast and northwest striking structures."

Jan 1, 1997

By James C. Sever

"With the advent of high energy costs and increasing concern for the environment leading to the incorporation the C02 life cycle as a criteria for the material used in a finished product, it is beneficial to analyze the plant and the process used in producing a raw material in order to identify practical, economic energy recovery opportunities. To this end a study was made of the proposed Nevada Clean Magnesium, Inc. Tami-Mosi reduction facility. Each source of waste heat is listed together with the assessment for potential co generation or direct recovery. The overall impact on energy requirement and C02 generation is provided.IntroductionHistorically metal reduction plants, large consumers of energy, do not recover waste heat. This occurred for many reasons:• Energy costs were low and the capital for a co-generation system could not be justified;• Waste heat sources contained entrained solids or liquids which would inhibit efficient energy recovery;• The exit temperature for the heat source was too low for efficient use by aaqueous Rankine cycle system.The business environment has now changed adding impetus to the recovery of energy previously discarded. Power costs have greatly increased. Global warming and the impact of carbon dioxide on the environment has become an issue which could impact the permitting of a plant. Technology improvements especially the development of a scaling environment waste heat boiler [l] and the development of the organic cycle Rankine cycle recovery system enable up to 70% energy recovery from ""low grade"" heat sources [2].With the inception of Nevada Clean Magnesium, Inc. 's (formerly Molycor Gold Corporation, Inc.)Northern Nevada Tami-Mosi project [3], an opportunity was presented to incorporate energy optimization from the initial design phase."

Jan 1, 2013

By Yuri Gelfgat

"This paper presents some results of the investigation of the steady magnetic field influence on hydrodynamics and heat/mass transfer in processes of semiconductor single crystal growth (Si, Ge, InSn). The investigation employed mathematical and physical simulation techniques of relevant processes and full-scale experiments on growth facilities. A number of additional MHD phenomena have been found generated in the melt due to the rearrangement of flow pattern, the formation of specific convective cells, and the origin of MHD boundary and shift layer.IntroductionMagnetohydrodynamic (MHD) means of creating forces by contact-free methods in liquid conducting media have been widely used in the production of volume semiconducting single crystals. The goal of this method is to control convective transfer processes in the melt volume and on the crystallization front [1-3]. This is due to the sufficiently high conductivity of semiconductor melts (s = 104 /106 O1m-1 ) and an obvious relationship between the hydrodynamics in the melt and at interfaces and the conditions of formation of single crystals and their quality [ 1].All types of MHD effects rest upon the generation of volume electromagnetic forces in the melt by various means as well as on the possibility to direct them arbitrary in space and to adjust easily their absolute values. Fig. l presents different means how to implement MHD phenomena during single crystal growth. It should be emphasized that in all the modifications given in Fig. l additional energy introduced into the melt cannot influence directly the crystallization process since it is incomparable to the energy of molecular forces. Both the influence and efficiency of MHD means are determined solely by the change of motion, heat and mass transfer characteristics."

Jan 1, 1998

By Mari Naess, Jan Erik Olsen, Gabriella Tranell

"Fume, also known as dust, is produced during metal refining. Exposure to fume is damaging to the health of plant operators. A mathematical model has been developed to study the different factors governing the fuming mechanism. It is shown that natural convection is the main driving force of the phenomenon, and that the fuming rate is highly sensitive to the area of the exposed metal surface. A new feature introduced in the modeling concept is the ability to include a gas flux of unconsumed process gas flowing up through the metal surface. This reduces the fuming rate, and should normally not be neglected.IntroductionFormation of fume from the ladle in which metal is refined into its final specifications is an environmental issue of importance for the working environment in the production plant. In layman-term fume is often known as dust. It is formed when metal reacts with oxygen. As an example of a fuming process, we will focus on ladle refining of silicon. Note that many of the principles and conclusions will apply to other metal refining processes. For silicon production, silica fume (S1O2) is produced when silicon metal (Si) reacts with oxygen (O2).Silicon is produced in a submerged arc furnace. The metal is tapped from the furnace into a ladle for refining. The refining is conducted by injecting a mixture of air and pure oxygen at the bottom of the ladle. The oxygen reacts with the metal and the impurities, and the amount of impurities is reduced according to product specification. At the ladle surface, metal also reacts with oxygen present in the air surrounding the ladle. This reaction produces silica fume as illustrated in Figure 1."

Jan 1, 2012

By Kunio Nakahara, Kashiwagim Junichi, Takao Hayashi

"There are many problems for electronic devices and parts which were caused electrostatic damage by static electricity. It is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating. Mitsui Mining & Smelting Co., Ltd. developed metal oxide type electroconductive pigment PASSTRAN (trade mark) Type-IV which is barium sulfate coated with SnOz(Sb) thin electroconductive layer. This paper shows about pigment characteristics and film condition of antistatic transparency paint which contained PASS TRAN.L.IntroductionRecently rapid development of electronics technology diffused electronic devices and products to Office, Factory, Laboratory and our life. But the other side, there are many problems for electronics parts which were caused electrostatic damage under static electricity. Demand of antistatic materials were become lager by this situation.There is close relationship between surface resistivity of material and static electricity. If the surface resistivity of object is enough low (under 109 Q /Sq), static electricity is dissipated quickly. So it is necessary for prevention of electrostatic charge to decrease surface resistivity of material using electroconductive coating.1) There are many type of electroconductive materials, for example, carbon black, metal powder, electroconductive polymer and so on. Especially, carbon black is used for general purpose by reason of its low cost, but it has big problem of black color. It can not get any color without black, and it caused contamination of carbon.In recent years, metal oxide electroconductive pigment (ECP) was developed and used for special purpose which demands transparent coating or easy dispersion to make ECP paint or endurance under hard environment and so on. Mitsui Mining & Smelting Co., Ltd. developed electroconductive pigment PASSTRAN Type-IV which is BaS04 coated with electro-conductive Tin oxide layer."

Jan 1, 1998

By Rauno Peippo

Horizontal Waste Heat Boiler (WHB), today&apos;s proven and dominating technology for copper smelter gas cooling, has been utilized by the industry for over half a century. During this time development has taken place in geometry, flow characteristics, cleaning technology and design details. This development has been driven by improved understanding of the specific process requirements, gained both by wide experience and by utilizing new emerging design tools, like computer flow modeling. It had to wait till mid 90&apos;s to unite effective and proven Spring Hammer cleaning technology and the process benefits gained by gas guiding vanes or baffle wall in the copper smelter WHB design. The new design has demonstrated improvement in gas cooling efficiency and the process conditions down stream in form of less dust sticking problems in the boiler and precipitators. Reduced weak acid production has also been reported as a result of the design. The theoretical aspects, computer flow modeling results and actual benefits measured in old smelting line modernization are discussed. Experience £tom modernization projects such as Phelps Dodge, Atlantic Copper, Mexicana de Cobre, and Nippon Mining, Saganoseki, are discussed. In mechanical design there has been development resulting improved gas tightness with less corrosion and better control of dust sulfation. An essential improvement is the integration of the boiler hopper and dust removing conveyor. Having no steel plate casings in the hopper and conveyor section but using of boiler tube membrane instead eliminates thermal expansion differences. The dust conveyor will be effectively cooled against hot dust lumps falling down while the acid dew point corrosion is prevented in the cooler sections of the hopper. Conceptual features are presented of a new generation Copper Flash Smelter WHB presently under construction at Boliden Mineral, Skelleftehamn, Sweden, where the latest development and innovations are adopted.

Jan 1, 1999

By Yeliz Demiraya, Onuralp Yucelb

"Production of strontium metal from its oxide was studied under the pressure of 1-5 mbar by methalothermic process. SrO with 99 % purity was used in the experiments. Effects of Al powder addition (100, 200, 300 % of stoichiometric ratio) and time were investigated on recovering of metallic strontium. Effects of BaO addition (100 %, 200 %, 300 %) was also investigated. The final residues were examined for their chemical composition. XRD, AAS and Flame Photometer were used for chemical analysis. More than 96 % of strontium metal recovery can be obtained.IntroductionStrontium is an element which is used in many advanced technology applications. Barium strontium titanat, strontium bismuth titanat, and strontium bismuth tantalat thin films are promising materials in ferroelectric and Schottky-based microelectronics technologies, especially for memory applications. Physical vapor deposition (PVD) techniques as magnetron sputtering, thermal evaporation and molecular beam epitaxy (MBE) are the most widely used methods for growth of these thin films [1-3]. In these techniques high-purity of Sr metal is used as evaporation sources and sputtering targets. Furthermore, metallic strontium is used as a ""getter"" in electron tubes, and as an alloying elements in aluminum alloys [4].The most used Sr compound is SrCO3 and widespread process used in production of SrCO3 is the hydrometallurgical carbonation of celestite. Although there are considerable amount of Selestite reserves, SrCO3 and strontinum metal are not being produced in Turkey, yet [5].Concentrated celestite (SrSO4) is conversed to SrCO3 in carbonate media. Black ash and direct conversion processes are currently used methods. There are many satisfactory studies about hydrometallurgical carbonation of celestite and decomposition of SrCO3 [6, 7]. Since strontium metal is produced from it’s oxide (SrO), SrCO3 needs to be decomposed to SrO."

Jan 1, 2011