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By Bradford C. Wesstrom, Omar Araujo

"Impurities from an electrolytic refinery are typically extracted from the electrolyte utilizing conventional electrowinning cells. These cells are arranged in series with cascading solution flow and are commonly referred to as liberator cells. The Freeport McMoRan Copper & Gold El Paso Refinery has optimized the removal of arsenic in cascading liberator cells by utilizing two separate feed solutions. The primary feed solution is recycled liberator electrolyte and the secondary feed solution is ""neat"" tank house electrolyte. The secondary feed solution is added based on the voltage response across the individual cells utilizing independent variable frequency drive (VFD) pumps. When the voltage across a cell changes, a signal is sent to the VFD pump to maintain a cell voltage of 1.98 volts. By maintaining this voltage the copper content in each cell exits at 2-4 grams per liter. This safely optimizes the arsenic removal as copper arsenides on the liberator cathodes.IntroductionDuring the electrolytic refining of copper, impurities from the copper anode report both to the bottom of the electrolytic refining cell as slimes and to the electrolyte. The impurities which enter the electrolyte are arsenic, antimony, bismuth and nickel. The impurities that report to the electrolyte during the electrolysis process gradually increase. As these impurities increase, they are incorporated into the refined copper cathode. There are many processes that have been used to remove these impurities from refinery electrolytes. Some of them are listed as follows: solvent extraction, ion exchange, hydrogen sulfide reduction, bioreactor, adsorption onto a low - solubility metal-oxide hydrate, adsorption onto activated carbon and EMEW cells. The conventional process used by the copper refining industry for controlling the level of impurities in electrolyte involves multistage electrolytic cascading liberator cells. In these cascading liberator cells copper, arsenic, antimony and bismuth are removed as various mixed deposits from the electrolyte. Removal of these impurities is achieved through an increase in voltage resulting from the depletion of copper in the electrolyte through electrowinning. With this higher voltage, the Group Vb elements, arsenic, antimony and bismuth are deposited on the copper cathode and report as slimes to the bottom of the cells. Nickel is removed in a subsequent process."

Jan 1, 2012

By Maria Margarida Lima, Maria Lucelinda Cunha, Dora Algarvio

"The main goal of the present work is the quality improvement of the recycled aggregates produced by a construction and demolition waste (C&DW) recycling facility located in Montemor-o-Novo, Portugal. The recycling process was developed on a pilot plant scale with 50 t/h of capacity. Process operations are the hammer mill comminution, magnetic separation and screening.In order to improve the knowledge on the C&DW, a characterization procedure was implemented by hand-sorting, magnetic and density separation on representative samples. On the other hand, to improve the quality of the produced aggregates, the bar screen size fractions were analysed, according to the Portuguese Standard (NP EN 933-1 2000).Wood was identified as the critical contaminant, representing 17% by weight of the total contaminants. Sieving results showed that about 97%, 76%, 56%, 98% and 57% were on the correct size range, which lower results are probably due to the type of screens and/or the material characteristics of the recycled aggregates.IntroductionThe construction and demolition waste problemConstruction and demolition waste (C&DW) is generated by the construction activity, resulting from both, buildings or other structures construction and old structures demolition. As a reference, it can be told that C&DW comprises about 40 to 50% of rubbish (concrete, asphalt, bricks, blocks and dirt), 20 to 30% of wood and related products and 20 to 30% of miscellaneous wastes [1]. In Portugal, C&DW is classified in the LER (Portuguese nick name for the European Waste List), Chapter 17, and includes a diversity of wastes, like concrete, bricks, ceramics, bricks, wood, glass, plaster, copper, zinc, lead, iron, steel, as well as insulation and roofing materials. C&DW stream has several characteristics which make it particularly difficult to deal with and are summarized in the following five items.(1) Lack of information on quantities generated: In Portugal, the C&DW sector has been neglected over the past years, which meant that there are not consistent information concerning the quantities and composition of these wastes yet. Several estimates, based in different assumptions, indicate different results, which may vary from 219 Mt to 10 931 Mt [2]."

Jan 1, 2008

By Wankun Wang, Shixing Wang, Jinhui Peng, Zebiao Zhang

"Germanium leaching from germanium dust and fume was carried out using sulphuric acid. Response surface methodology (RSM), based on a five level, four variable central composite design (CCD), was employed to obtain the best possible combination of liquid/solid ratio (Xi: 2-10), leaching time (X2: 1-5 h), sulphuric acid concentration (X3:3.15-15.75mol/L) and leaching temperature (X4:50-90 *C) for germanium leaching. The obtained experimental data were fit to a one-order polynomial equation using multiple regression analysis and also analyzed by analysis of variance (ANOVA). The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The optimum extraction conditions were: liquid/solid ratio of 10, leaching time of 1 h, sulphuric acid concentration of 15.75 mol/L, and leaching temperature of 87.8 'C. Under these conditions, the germanium leaching extent was 65.14%, which is in close agreement with the value predicted by the model. The samples were characterized before and after leaching using X-ray diffraction (XRD).IntroductionResponse surface methodology (RSM) is one of the relevant multivariate techniques which can deal with multivariant experimental design strategy, statistical modeling and process optimization [1-15]. It is used to examine the relationship between one or more response variables and a set of quantitative experimental variables or factors. This method is often employed after the vital controllable factors are identified. It is also used to find the factor settings that optimize the response. Designs of this type are usually chosen when a curvature in the response surface is suspected [6], The process optimization of the sulphuric acid leaching of germanium from germanium dust and fume has not been reported in the literature. Hence the present work intends to assess the effects of variables such as liquid/solid ratio, leaching time, sulphuric acid concentration and leaching temperature and to identify the optimum conditions using RSM. The characteristics of sample before and after leaching are assessed using the advanced analytical instruments such as X-ray diffraction (XRD)."

Jan 1, 2012

By Linli Wu, Guangchun Yao

"The influence of deformation on the properties of short-carbon-fiber reinforced 2024 alloy matrix composites was investigated in this study. It was found that the distribution of carbon fibers changed from the random state before deformation to the ordered state that carbon fibers arranged along the direction of rolling and extruding after deformation. Under the temperature range in control, the increase of rolling and extruding temperature would benefit to improve strength and elongation of composites, but was not conductive to improve the hardness of composites. With the increment of total deformation, all the strength and the hardness of composites became greater, nevertheless the elongation decreased. After being rolled and extruded, the strength and the hardness of composites were all bigger than those of composites before being rolled and extruded; moreover, the strength of extruded 2024 alloy matrix composites was higher than that of rolled 2024 alloy matrix composites under the same heat treatment conditions.IntroductionCarbon fibers have been reckoned as very important reinforcements due to the high specific strength, specific modulus, high thermal and electric conductivity, low expansion coefficient and good self-lubricant properties [1-4]. Light metal composites reinforced with carbon fibers, such as carbon fibers in an aluminum matrix, are widely used and studied. Some studies have concentrated on the interfacial characteristic of CF/Al composites in order to search for the way of improving the bonding between carbon fibers and the matrix alloy [5-8], and on the influence of the carbon fiber percent composition in the composites [9-11]. Some researchers began to take interest in the deforming characteristic and failure behavior of carbon fiber reinforced metal matrix composites [12-16]. However, the same with other metal materials, most of CF/AI composites were prepared by some single processes, such as powder metallurgy, extrusion casting and vacuum press infiltration, which caused that the composites products could not be manufactured directly. In order to cover the shortage of the mentioned above processes and get composites products with perfect mechanical properties and dimensional accuracy, the composites should be reworked by rolling, extruding or forging process. Compared with research about manufacturing process, the correlative investigation on the reworking of CF/Al composites was much less evidently, which restricted the application and the further development of CF/Al composites."

Jan 1, 2012

By Jie Li, Liangxing Jiang, Yexiang Liu, Junfeng Gui, Bo Hong, Xiaocong Zhong, Yanqing Lai, Xiaoying Yu

"Pb-based alloys with Pr and Ag were prepared in vacuum electromagnetic induction furnace. The tensile strength, corrosion rate and anodic potential in sulfate solution were measured, and the experimental data were analyzed according to the metallographic phases of alloys, the micromorphology and composition of their oxide films. The results show that, with the addition of Pr, the ultimate tensile strength and corrosion rate of pure lead were increased, and the anodic potential decreased. The extra addition of Ag can improve the properties of alloy further. Comparing with Pb-Ag0.8 alloy which is widely used in zinc electrowinning industry, the ultimate tensile strength of Pb-Ag0.6-Pr2.0 alloy was increased by 31.75%, the anodic potential under 50mA/cm2 was decreased by 30m V.IntroductionIn zinc electrowinning industry, the Pb-Ag (0.5-1.0 wt.%, 0.8wt.% normally) anode is widely used as an insoluble anode['l. It can meet the basic requirements, but still has several problems such as high oxygen evolution over-potential (about 860mV), unsatisfactory corrosion resistance, lead contamination of the cathode product and high consumption of Ag etc.In order to reduce the energy consumption, enhance the corrosion resistance, improve the product quality and reduce the consumption of Ag (or even dispense with it), much research has been done, mainly focusing on Pb-based alloy anodes and Ti-based coated anodes. Detailed investigations have already been carried out on binary alloys (Pb-Ca and Pb-Co), ternary alloys (Pb-Ag-Ca, Pb-Ag-Ti, Pb-Ag-Sn, Pb-Sr-Sn, and Pb-Ca-Sn) and quaternary alloys (Pb-Ca-Sr-Ag, Pb-Ca-Ce-Ag, and Pb-Ag-Sn-Co)[Z-4l, Although these anodes can effectively reduce the consumption of Ag, only the Pb-Co and Pb-Ag-Sn-Co anodes perform well with regard to reducing the anodic potential. However, their complicated manufacturing conditions restrict further commercial use.Besides its application in nonferrous metal electro-winning industry, Pb-based alloy is also used as grid alloy for lead-acid battery, serving as active materials supporter and current collector. In order to enhance the corrosion resistance and deep-cycling performance, reduce the impedance of the corrosion film, the addition of appropriate rare earth elements into anodic grid alloys has become a research focus. Studies proved that RE can enhance the mechanical strength of grids, inhibit the formation of anodic Pb(II) film on the surface of grids and then reduce the impedance of the film[ 10-12l."

Jan 1, 2013

By Erich Hovestädt, Hans-Jürgen Odenthal, Christian Wuppermann, Herbert Pfeifer, Antje Rückert

"During the argon oxygen decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall nozzles and a top-lance. Due to the large amount of the injected processing gas, low frequency oscillations of the vessel can be observed. It is suspected that these oscillations can influence the converter's structure. The exchange of forces between fluid and the surrounding vessel is the focus of this study. An oscillation model was developed and tested, one objective being to limit the computational effort which is necessary for fully coupled and time resolved CFD and FEM simulations. Experimental results obtained from water-model studies as well as from on-sight measurements are available and were used in order to validate the numerical results. The authors' intention is a contribution towards a more in depth understanding of the factors influencing vessel vibration during the AOD process.IntroductionDuring the last four decades the AOD process has been established as a reliable and efficient refining process in stainless steel making. The injection of process gases (O2, N2, Ar) through sidewall nozzles shows advantages in mixing effectiveness compared to other injection geometries e.g. bottom blowing [1]. Stainless steel grades contain usually more than 10% chromium. With decreasing carbon content during the decarburization periods the tendency of chromium oxidation increases according to the varying chemical equilibrium which depends on the partial pressure of carbon-monoxide (CO) in the gas phase. That's why oxygen is gradually replaced by inert gases, usually argon or nitrogen, in order to lower the CO partial pressure and thus to minimize chromium oxidation. Despite the high injection velocity of approximately Ma = 1, the kinetic energy of the gas jets is consumed within a short distance from the nozzle exits due to the large density ratio between gas and melt of approximately 1:8000. With increasing distance to the nozzle exit, the initial horizontal velocity of the gas jet decreases and due to buoyancy force motion of the detached bubbles turns into a vertical direction. Subsequently a gas plume develops with its typical conical shape described by various authors [1-4]. Due to the drag force between gas bubbles and melt also the liquid phase is forced into a vertical motion. Near the free surface and the wall regions the melt flow is deflected in different directions. Subsequently, the typical flow pattern in the AOD vessel arises, as sketched in Figure 1 and described in literature [5-9]."

Jan 1, 2012

By Byung-Young Choi

Nitrogenated carbon films were deposited on the high-frequency induction hardened steels by ion beam assisted deposition. X-ray photoeleetron. spectroscopy and scanning electron microscopy were used to analyze the chemical content and the morphology of the coated steels. Rolling contact fatigue tests were performed using Polymet RCF-1 machine with a constant supply of lubricant. It was found that CNx films adherent to the steels substrates were formed by ion beam assisted deposition. It was also found in the rolling contact fatigued specimens that non-propagating crack was initiated in the white etching area indicating the maximum shear stressed, region, leading to surface failure.

Jan 1, 2000

By Robert S. Sokolowski

The future of Materials Processing in Space (MPS) in the Space Station Era is being assured today by a strong coordinated science program which looks to solve these problems, the answers to which serve to underpin the technical foundation upon which future metallurgical and materials processes will be built. The critical link between the product and process development activities that accompany this science endeavor is the "nuts and bolts" hardware that will ultimately operate in the space environment. Ground-based facilities including drop facilities and aircraft provide excellent product development and process concept study tools. Shuttle flights with Spacelab and commercially developed space facilities represent the evolutionary path to Space Station processing facilities. Today the most promising areas of MPS are crystal growth, containerless, and quasicontainerless processing. The unique features of these processes will be highlighted. Finally a more visionary perspective of MPS will be presented that incorporates the limits of today's knowledge with the economic "necessity" of tomorrow.

Jan 1, 1988

By Keizo Uematsu, Satoshi Tanaka, Zenji Kato, Nozomu Uchida

"A novel technique is developed and applied to evaluate the binder segregated at the· surface of granule. Compressive strength of each granule was measured directly with a micro-compressive instrument. The relation between compressive characteristics and the amount of binder was discussed quantitatively.IntroductionCharacterization of granules is essential in the production of ceramics, since they govern the structure of green compact and thus the structures and properties of ceramics. However, there is no research to clarify the relation between the strength of granules and structure of granules, especially of binder segregation at granule surface. We develop a novel technique to determine the binder concentration in the granules by the iodine method. In this study, we measure yield strength of granules directly and discuss the relevance between compressive characteristics and the concentration of binder.ExperimentalGranules were prepared by spray-drying of aqueous slurry of commercial alumina (AL160-SG1. Showa Denko, Tokyo, Japan) and PVA (PVA 105 Kurare, Japan). PVA. concentration in granules was 1.1, 1.5 and 2.3 wt%. The inlet and outer air temperatures were 200 and 95 °C , respectively. Iodine-potassium iodide solution was prepared by dissolving iodine (0.15mol) and potassium iodide (0.15mol) in diluted water (50ml). A saturated boric acid solution was prepared by mixing boric acid powder with a diluted water."

Jan 1, 2000

By V. B. Telles, D. C. R. Espinosa, J. A. S. Tenório

"The purpose of this work was to study the reutilization of the steelmaking dust, derived from steel production in the electric arc furnace (EAF), in iron ore sintering process aiming zinc elimination. In each sintering process were collected sintered samples, these materials were analyzed by chemical analysis using atomic absorption spectrophotometry in order to determine the zinc content. Samples of not sintered mixtures were also characterized by chemical analysis aiming to determine the initial amounts of zinc, i.e. in order to check the zinc amounts present in the mixture before the sintering process. The comparation among the zinc contents of samples sintered and not sintered allowed to determine the elimination of zinc during the experiments. Results showed that the zinc elimination in the process is proportional to the ratio reducer/waste. The zinc removal was lower when the reducer/waste ratio was decreased.IntroductionThe electric arc furnace dust (EAFD) is a residue generated in the steelmaking process using electric arc furnace. Aproximately 30% of all steel produced (in the year 2009) was obtained through electric arc furance (EAF). In the United States of America the percentage of this process in the total crude steel production was about 62% in 2009, while in 2000 this percentage was only 47% [1].The iron ore sintering is a process that reuses wastes generated in metallurgical industries. However, the materials used must be physical and chemical characteristics compatible with the blast furnaces.The quantity of zinc, cadmium, chrome and other metals present in the EAFD depends on the quality of the scrap used to feed the EAF and the type of steel that it is been made [2,3]. The reuse of EAFD waste is interesting to steelmaking processes because of its iron content. However the presence of zinc inside a blast furnace is undesirable since the zinc oxide can be deposited on the blast furnace walls and in the drivers of gas output, interrupting the flow. Another part of the zinc oxide can form deposits on the refractory lining of the blast furnace [4,5]."

Jan 1, 2012

By Kimura. E.

Continuous estimation of phosphorus content of molten copper is required to produce phosphorus deoxidized copper in a continuous casting operation. The phosphorus content of molten copper was related to its electric resistivity, which was measured by the four-probed technique with a specially-shaped cell. In a laboratory scale, the linear relationship between the above factors was confirmed in the temperature range of 1083OC through 1200°C. The phosphorus concentration range measured was from 40 to 500 ppm. The phosphorus content was monitored successfully by measuring the electric resistivity of the molten copper in the distributor of a continuous caster in an industrial scale.

Jan 1, 1992

By J. M. Toguri

The viscosity of the molten FeO-Fe2O3-Si0z system in the composition range of interest to copper smelting has been investigated using a rotating cylinder technique. The silica content of the slag was varied from 20 to 35 wt percent while the oxygen pressure of the system was varied from 10-7 10-11 atm. The temperature range investigated was from 1200 to 1350°C. It was found that the viscosity of the slag generally decreased with increasing temperature and increasing oxygen pressure. As the silica content was increased, the viscosity was found to increase.

Jan 1, 1976

By R. L. Miller

An industrial wastewater, including plating wastes, is treated with sodium sulfide and ferrous sulfate to form a sulfide-oxide precipitate containing chromium and other toxic metals. Hydrocarbons, in the water, coat the sulfide-oxide particles, impeding metal recovery. Froth flotation, without reagent addition, was found to recover 93.9% of the solids from the sludge with simultaneous rejection of 89% of the water. Methyl isobutyl carbinol (MIBC) improved recovery and potassium amyl xanthate improved both recovery and grade. The process design has wastewater feed (without MIBC) to the rougher circuit. The rougher concentrate is conditioned with MIBC and fed to a cleaner circuit to achieve a high grade concentrate. About 95% of the water is recirculated to the waste treatment plant.

Jan 1, 1992