Search Documents

By Takahiko Okura

Japanese non-ferrous industry introduced large-scale smelting plants along seashores for overseas concentrates with increasing demand of metals around 1970s. Although serious environmental pollution became obvious, with economic growth, the industry got rid of pollution by installing new processes and improving operation technologies. At present, over 99.8% of sulfur input to smelters is fixed as stable compounds. Through those decades Japan had steep rises of oil prices, sudden change of exchange rate, and inadequate treating charges, we were faced to consider the closure of smelters. The industry has survived by increasing productivity, saving energy and reducing manpower. Furthermore the industry made great effort to recycle valued metals from scraps and wastes for the resources-recycling society. Academic research also contributes to support these individual technologies. Thus the industry has fostered world-acclaimed technologies in terms of efficiency and energy conservation. This paper presents technology development and environmentally-benign sulfide smelting processes.

By N. Can

Kinetics and mechanism of the chemical interactions between Si3N4 and TiC were investigated by isothermally reacting samples under nitrogen and argon atmospheres at temperatures between 1600°C and 1700°C? The initial composition of the powder compact contained 20, 30 and 40 volume per cent TiC? Kinetic analysis were performed by measuring mass losses and composition of the titanium carbonitride (TiC1-xNx) at predetermined time intervals? It was found that in the Si3N4-TiC system the degree and rate of the reactions increased with increasing temperature and content of TiC in both nitrogen and argon atmospheres? Si3N4 in the presence of TiC was stable in nitrogen atmosphere and the reactions were confined to Si3N4/TiC and TiC/N2 interfaces? At both interfaces interchange reaction occurs by simultaneous diffusion of nitrogen towards the centre of the particle and desoprtion of carbon in the opposite direction resulting in formation of titanium carbonitrides with various compositions? Reaction products under nitrogen atmosphere were B-SiC, TiCl1-xNx and N2? The maximum "x" value in TiC1-xNx was found to be 0?67 under nitrogen atmosphere? Si3N4 was found to be unstable in argon atmosphere in the presence of TiC and dissociated into liquid silicon and nitrogen gas within approximately four hours of reaction time, depending on temperature? The reaction mechanism in the initial stages of the interaction between Si3N4 and TiC under argon atmosphere proceeds similar to reactions under nitrogen atmosphere? However, considerable amount of Si3N4 dissociates within the first half hour? Liquid silicon aggressively attack both TiC1-xNx and unreacted or partially reacted TiC particles through cracks and pores and diffuses into interier part of the particle forming liquid solutions? After this stage, reactions under argon atmosphere proceeded according to Si-Ti-C ternary system?

Jan 1, 1999

By Z. Yang

The flotation behavior of the. green algae Chlorella vulgaris and a wild Chlamydomonas spp. was studied in the presence of Zn(II) using dodecylammonium chloride as collector. At about pH 6. both organisms readily float as amine concentration approaches lx10-3 kmol/m3. In addition, electrokinetic measurements were made on the organisms as a function of pH in both the presence and absence of Zn(II). It was found that the Zn(II) has a considerably greater effect on the zeta potential of C. vulgaris than on Chlamydomonas. Zn(II) adsorption studies also indicated that C. vulgaris is able to accumulate more Zn from solution than the Chlamydomonas.

Jan 1, 1991

By Takashi Ikeda, Masafumi Maeda

"Demand for solar cells is increasing linearly throughout the world. Last year production totaled 3000 tons worldwide. The market size of solar silicon is expected to increase further because of international ""political"" demand to reduce carbonaceous emission from energy consumed. Most elemental silicon is produced by the carbon reduction of Silica in an electric arc furnace. Purity of silicon at this stage is 90-99%. Major impurities are Fe, Ti, Ca· and Al, and minor ones are P, B and carbon. The oxidizing metallurgical process is no longer effective to remove transitfon metals because those are less noble to silicon. Nonmetallic impurities such as phosphorus and boron must be reduced to 0.001ppm for semiconductor use. The most common process for high purity silicon is the Siemens C process, which is basically distillation of hydro-chlorinated silicon followed by CVD of SiHCl3. The cost of such silicon is expensive to allow its popular use in solar cells. Currently scrap silicon -of semiconductors is used for this; however, the supply-of that scrap is limited to just a portion of semiconductor production.In this paper world demand for silicon will be reviewed and some of the processes proposed summarized.IntroductionSilicon is element 14 in atomic number and has an atomic weight of 28.0855. Little elemental silicon is found in the earth, and it is mostly found as oxides or silicate. The Clark number of silicon is very large and the second in its number. If we were discussing the volatility of silicon element on the globe, we would never worry about it. However, it is very difficult to obtain pure elemental silicon because a high purity silicon compound is very rare. In most cases these are silica (silicon oxide SiO2). As shown in Table 1, there are many grades of silica ore classified mainly by their content of iron and alumina."

Jan 1, 2000

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011

By Jeong-Soo, Joon Soo Kim, Rajesh Kumar, Sohn, Jin-Young Lee

"Liquid-liquid extraction (LLE) studies of tetravalent platinum from acidic chloride solutions have been carried out with Alamine 336 as an extractant diluted in kerosene. The title metal shows the inverse behavior at higher acid concentrations. Plot of log D vs. log [Acid], mol.L-1 gave a straight line with a negative slope of 0.8±0.03 indicating the exchange of one mole of hydrogen ions for every mole of platinum(IV) extracted into the organic phase. Extraction of platinum(IV) increases with increase of extractant concentration. The plot of log D vs. log [Extractant], mol.L-1 is linear with slope 1±0.3, indicating the association of one mole of extractant with the extracted metal species. The plot between metal distributions to aqueous to organic phases is 1.3±0.01; it indicates monomeric species was formed in organic phase. Stripping of metal from the loaded organic (LO) with mineral acids such as hydrochloric, sulphuric, nitric acids and bases like ammonia, hydrogen peroxide and sodium hydroxide are studied. The results indicated that hydrochloric acid and sodium hydroxide are the better stripping agents when compared with other acids and bases. Increase of temperature decreases the percentage extraction of metal indicating the process is endothermic. Regeneration and recycling capacity of Alamine 336 and extraction behavior of associated elements such as aluminium(III), magnesium(II), cobalt(II), iron(III) and nickel(II) were studied.IntroductionThe demand for platinum group metals (PGM’s) has risen in the last five years expected to keep in rising. Right now, the demand is already beyond the supply. The primary use of PGM’s today is in the automotive industry. Catalytic converters used in the PGM’s process to reduce greenhouse gases. Because of the current demand to reduce the green house effect the expected need for platinum is here stay. Country’s now advancing in the use of car production also are phasing increasing the needs for this metal. Chemical processing also use it, too. These industries account for more than 50% of all platinum production. Jewelry is other primary use of this precious metal whose value is much greater than gold. Other uses include computer data storage, scientific developments, fuel cell technology and in the glass manufacturing processes."

Jan 1, 2008

By James D. Navratil

Advances in hydrometallurgy require the introduction of new separation and purification processes, but they can be complex, costly and energy intensive. Chromatographic processes have low energy requirements and possess very high separation efficiencies. However, they have not yet made the great industrial impact that might be expected from their benefits. The large-scale and difficult separation of rare earths would greatly benefit from an improved continuous chromatographic operational device. Truly continuous, multicomponent chromatographic separations may be achieved by means of the continuous annular chromatograph. Work has been Initiated at The University of New South Wales involving the improvement and development of such equipment for the separation and purification of rare earths.

Jan 1, 1990

By K. Morsi, S. K. Kassegne, K. S. Moon, A. Numula

"Current Activated Tip-based Sintering (CATS) is a new process for the powder-based manufacturing of macro, micro and possibly nano-scale features and shapes. CATS enables the selective sintering of powders by localizing current activation conditions through an electrically conducting small tip (either in the stationary or moving mode). This paper presents preliminary experimental results on the CATS of reactive mixtures of Ni/Al powder to form nickel aluminide intermetallics. Preliminary investigations on the effect of current on the reaction characteristics are discussed.IntroductionSpark Plasma Sintering (SPS) has been the subject of intense research over the past decade [1,2, 3,4,5,6]. The process boasts remarkable advantages which include ultra fast heating rates (hence by-passing low temperature non-densifying sintering mechanisms), considerably lower sintering temperatures and shorter sintering times than achieved in conventional sintering. The process is however limited to the generation of simple geometries on the macro-scale. Recently three of the authors conducted work on a novel process ""Current-activated tip-based sintering (CATS)"" [7], where electric current is passed through a conducting tip that is placed or allowed to travel over a powder bed/compact to locally sinter powders. lD, 2D and 3D micro-scale sintered shapes can be generated with the possibility of 3D rapid prototyping on the macro/micro or nano-scale. Although CA TS of single phase powders has been conducted, the CATS of reactive powders has not yet been investigated.The Ni-Al phase diagram contains five intermetallic compounds, AhNi, AhNh, AlNi, AhNi5 and NhAl. Out of these intermetallics, NiAl and NhAl have received the vast majority of scientific and industrial interest [8]. NhAl can be formed by reaction synthesis, where nickel and aluminum reactant powders are heated to a reaction ignition temperature at which the reactant powders are converted to the intended intermetallic product. The reaction is exothermic which gives rise to considerable compact self heating, thus instantaneously raising the compact temperature by several hundred degrees which facilitates sintering [8]. Applying and electric current locally would not only provide for a rapid local reactive sintering, but would generate a number of intriguing scientific investigations. For example, of interest would be, how would the reaction propagation and microstructural/phase evolution be affected by the temporal and spatial temperature and current distributions."

Jan 1, 2011

By T. T. Chen

Raw anode slimes consisting primarily of PbSO4, AgCuSe, Cu3Se2, Cu2-x Se, Cu2O, CuSO4.5H2O, Sn arsenate and Sb-Bi-As oxide are batch-leached with electrolyte-O2 to dissolve Cu. During this process, Cu2O and CuSO4.5H2O are solubilized and the Cu in the selenides is leached with the formation of Ag2Se and Se. A small amount of Cu remains in the Ag2Se, Sn arsenate and Sb-Bi-As oxide. The decopperized slimes are repulped in Na2CO3 solution to convert most of the PbSO4 to NaPb2(CO3)2(OH). The Sn arsenate and Sb-Bi-As oxide partly react, but the Ag2Se is not significantly affected by the Na2CO3 solution. The NaPb2(CO3)2(OH) intermediate phase is dissolved in acetic acid to leave a final product consisting of Ag2Se, Se, Sn arsenate and Sb-Bi-As oxide, together with small amounts of PbSO4, NaPb2(CO3)2(OH) and various gangue constituents.

Jan 1, 1993

By Gerald M. Rich

Magma Copper Company, a subsidiary of Newmont Mining Corporation, has initiated many changes in the continuous casting of 5/16 inch diameter copper rod since startup of the San Manuel rod plant in early 1972. With rod production at forty percent over design capacity, many production records have been established including a record cast of 761 tons of salable rod in a twenty-four hour period. The most challenging and rewarding introduction was the continued utilization of an alloyed copper casting wheel in lieu of the conventional steel wheel. With proper cooling and careful control of the mold release agents. as much as 58.000 tons of copper were cast on a single copper wheel. Other advantages are: 1) Fifteen percent increase in available casting time 2) Reject rod from steel inclusions was reduced by nearly one-hundred percent 3) Wheel cost was decreased by ninety-one percent 4) Natural gas consumption dropped approximately fifteen percent 5) Large increase in refractory component life 6) Reduction of manhours/ton. Many other modifications have contributed to excellent rod quality and high operating efficiency. A two-piece launder was replaced with a single castable launder which reduced oxygen pickup and provided better slag removal. Modifications to the bar preparation unit, pickling system, and coiler resulted in considerably higher milling efficiency.

Jan 1, 1976

By C. A. Summers

The U.S. Bureau of Mines applied process mineralogy to investigate a lead and zinc deposit located near Story Creek, Colville Mining District, Alaska. Mineralization is hosted by the Kayak Shale in veins, veinlets, and breccia. Sphalerite and galena, with supergene anglesite, occur in symmetrical quartz veins and between breccia clasts. The study sample analyzed 2.11 percent Pb, 5.37 percent Zn, 0.014 percent Cu, and 1.2 oz/ton Ag. Analyses of crushed products showed that 33 percent of the sample weight, and more than 50 percent of the Pb and 65 percent of the Zn, are in the minus 850 um fraction. Liberated grains of sphalerite and galena were found in crushed products finer than 300 um. Beneficiation tests indicate the material is amenable to processing by traditional gravity and flotation techniques.

Jan 1, 1991

By Jeffrey W. Braithwaite

The laboratory characterization of the oxidation of chalcopyrite under conditions of deep solution mining is presented in this paper. A salient feature of this system is the pH buffering effect resulting from simultaneous acid producing and acid consuming oxidation reactions. The solution chemistry and related sulfur partitioning of the oxidation reactions are detailed. The contribution of temperature, acid concentration, oxygen pressure, particle size, and solution additions to the kinetics of copper extraction are presented. A mixed kinetic model was used to describe the kinetics of oxidation.

Jan 1, 1976

By Frank L. Marley

Mexican silver mining operations have existed prior to the sixteenth century. Recovery processes throughout the centuries were developed at the many mining localities and have progressed through smelting, the patio amalgamation process to cyanidation and flotation. A study of the present silver mining zones is reported in which the ores are evaluated in terms of the mineralogical constituents, their state in the matrix and the effects these are noted to impose upon the efficiency of recovery. Silver mineral identifications were by quantitative ore microscopic and scanning electron microscopic energy dispersive X-ray analysis.

Jan 1, 1982

By Debbie Marshall

Nickel and cobalt in lateritic ores can be extracted by either a hydrometallurgical or a pyrometallurgical route. The high-iron limonitic fraction of a deposit is best processed' hydrometallurgically while the magnesium-rich transitional and saprolitic fractions are more suited for pyrometallurgical processing. During hydrometallurgical processing, it may be attractive, for economic reasons, to blend the limonitic component with transitional and saprolitic ores, which contain higher nickel levels. However, blending increases the concentration of magnesium in the feed, leading to increased acid demands. The decision on how much ore to process then becomes an economic one. Ore samples with different magnesium contents were prepared for the leach test program by blending limonitic and transitional ores. The ore samples were slurried in seawater and tested in the Falconbridge Hydrometallurgical Pilot Plant. As expected, acid consumption increased with increasing magnesium content of the ore. For target extractions of 95% nickel and 92% cobalt, the required residual free acid concentration increased from 30 g/L at 1.7% magnesium to 50 g/L at 2.7% magnesium. When the magnesium content was raised to 3.8% and 4.6% in subsequent pilot plant testing, the final free acid requirements did not increase beyond what was observed at 2.7% magnesium. Thus, the cut-off ore composition to maximize nickel units and minimize acid requirements is between 1.7- 2.7% magnesium. Keywords: high pressure acid leaching, laterites, magnesium

Jan 1, 2004

By Ian Buterbaugh, Calvin Lo, Tomoko Sano, Brendan Koch, James Catalano, Timothy Walter

In this research, two grades of alumina, one at nominally 85% composition and the other at 99.5% were characterized. Microstructural and phase characterization was conducted using Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-ray Diffraction, and micro-computed X-ray tomography. It was determined that the Knoop hardness values were influenced by the porosity in the 85% composition. Quasi-static compressive tests and high strain rate compression experiments were conducted to determine the influence of the microstructure to the compressive properties. It was observed that the overall compressive strengths increased with strain rate. Although the Knoop hardness values were much lower in the 85% alumina due to the porosity, the compressive strength at both quasi-static and dynamic strain rates were not significantl lower than those of the 99.5% composition.

Mar 1, 2018

By Joseph Bloch

The hydriding of bulk metals and alloys is a gas-solid reaction in which a hydride product layer is initially nucleated adjacent to the gas-solid interface and continues to grow until a complete transformation of the parent (a) phase into the hydride phase. The combination of measurements of the overall hydriding kinetics of samples having defined shapes and dimensions, together with examinations of partially hydrided samples, enables the presentation of the reaction rate in terms of an appropriate reaction model. A common and important type of topochemical development of the hydride in bulk metals and alloys involves a hydride layer formed on the metallic surface. The continuity of the layer can affect the reaction rate. The rate of hydrogen absorption in a sample, in the presence of a hydride layer, is usually analyzed using a model combining several sequential steps in which the hydrogen is transferred from the gas phase into the reaction site. Coupling the flux equations across the layer under proper steady state conditions, results in a complex rate equation in which the steady state rate of hydrogen absorption (proportional to the hydride layer velocity) is expressed in terms of the pressure, temperature, the rate constants of the sequential steps and the critical concentrations of hydrogen in the hydride. Generally, the rate constants of the individual microscopic processes are comparable in magnitude, so that the overall rate is not controlled by any of the specific sequential steps. However, there are two limit cases related to the first stage, the adsorption, for which the general rate equation is much simpler, namely, the fast and the slow adsorption approximations. Using this limit cases, equations are derived for the steady state hydriding rate of a given system. These equations provide means to anticipate the pressure dependence of the steady state absorption rate under low pressures, close to Peq and under very high pressures. At the low pressure regime both the fast and slow absorption cases yield linear pressure dependence. For the very high pressure range, it is found that the rate become independent of the applied pressure. The rate is given then by a combination of the individual rate constants of the system and the critical hydrogen concentrations. The model is shown to apply in several real cases, such as ZrCo, LaNi5 and titanium.

Jan 1, 2002

By Tapio Ahokainen, Asmo Vartiainen

"Outotec's portfolio contains a wide variety of smelting solutions for non-ferrous metals. Some of these include flash smelting for primary copper and nickel, flash converting for copper, Ausmelt technology for primary and secondary copper, nickel, tin, lead, and zinc residues and waste, Kaldo technology for secondary copper, lead, and precious metals recovery. Outotec also offers slag cleaning technologies and much more.Company provides complete process solutions tailored to each customer's individual needs. Decades of experience have resulted in extensive metallurgical know-how that ensures the most profitable process choice and optimal performance. Outotec's life cycle technology partnership with their customers spans from the early stages of process solution design through the supply and commissioning of the entire process chain. They include integrated process control and holistic service and support concepts. Continuous research and development ensures that the customer is provided with the latest advancements in process and equipment solutions.IntroductionOutotec develops and provides technology solutions for the sustainable use of the Earth's natural resources. Solutions are ranging from various processes and special equipment needed for metallurgical extraction and mineral processing of ores to the production of refined metals and minerals. The processes include not only the grinding and physical separation of ores but also the smelting and leaching of base metals and precious metals. The company provides engineering services for whole projects as well as life cycle services on the equipment and products that they supply."

Jan 1, 2012

By George A. Calboreanu

In order to overcome drilling and tapping of high hardness wear resistent material in slurry pumps, most of time mild steel inserts are mounted in the mold and after pouring they become an integrated part of the casting. This process is limiting the size and design possibilities of slurry pumps and efforts were made to drill and tap the hard iron itself. The paper will present practical results obtained in drilling and tapping Cr-Mo wear resistent material with hardness in excess of 700 HBN. The life time of the slurry pump parts used in hazardous waste fuel transportation with high slurry velocity and 15% solid loading some of it being quartz, increased 2.5 to 6 times.

Jan 1, 1996

By Christoph Sagadin

Corrosion mechanisms between high melting synthetic ferronickel slags and refractory were investigated. The used slags were prepared by mixing and melting of specific oxides. Substrates of the applied refractory material and specimens of FeNi slags were heated in a hot stage microscope up to 1650 °C. The experiments were performed under a defined gas atmosphere of 60% CO and 40% CO2. A further examination of the formed phases between slag and refractory occurred by scanning electron microscope. The investigations indicate that the slag penetrates between magnesia grains and partly dissolves magnesia. Spot analyses show that iron diffuses into the magnesia grains, which transform to magnesiawustite, meanwhile SiO2 forms different types of olivine like forsterite and monticellite. Thermodynamic calculations confirm the formation of these phases. The combination of practical lab scale experiments and thermodynamic calculations should finally contribute to an improvement of the refractory lifetime and performance.

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