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By A. Siegmund, R. D. Prengaman

Lead anodes used in zinc electrowinning generally contain 0.5 - 1.0 % silver to reduce the rate of corrosion over the service life. For good quality zinc, the cathodes must contain less than 10 ppm lead. In order to reduce the lead contamination of the cathode, the lead anode must become coated with a protective layer of Pb02/Mn02. The formation of this layer may take as long as 30 - 60 days, during which time zinc production is substantially reduced and the cathodes are contaminated with lead. To improve the mechanical properties of Pb-Ag-anodes alloying elements such as calcium, strontium, barium and others are added. The production of cast lead-silver or lead-silver-calcium anodes often results in the formation of numerous holes, voids or laps in the anode surface that can initiate localized internal corrosion. Based on the experience as the major supplier of rolled anodes for copper electrowinning, RSR Technologies has developed an improved anode for zinc electrowinning. The anode consists of a rolled Pb- Ag-Ca-alloy with a controlled surface grain structure. It forms an adherent protective oxide coating within 2 - 3 days when placed in an electrowinning cell. The preferred calcium and silver contents of the alloy are 0.03 - 0.08 % and 0.3 - 0.4%, respectively. Rolling sheets significantly reduces the presence of internal porosity or laps. The lack of defects results in long anode life. The rolling also produces a uniform grain structure to which the corrosion product readily adheres, thus significantly reducing the conditioning period.

Jan 1, 2000

By Julien Favre, Akihiko Chiba, Damien Fabregue, Yuichiro Koizumi, Eric Maire

"The mechanical behavior of Co-20Cr-15W-10Ni alloy is studied by compression tests at high temperature. Microstructures after deformation are evaluated using SEM-EBSD. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T>1100°C, <0.1s-1), and at high strain rate (~10s-1). Dynamic recrystallization is discontinuous and occurs by grain boundaries nucleation, leading to a necklace structure. The nucleation mechanism is most likely to be bulging of grain boundaries. However, recrystallization occurs also by rotation of annealing twins which can bulge as well. The modeling of mechanical behavior gives a fair quantification of flow softening due to dynamic recrystallization, indicating the progress of dynamic recrystallization with deformation.IntroductionCobalt-chromium alloys are used in biomedical applications for the elaboration of implants due to their outstanding mechanical properties and their high resistance to corrosion. For stent application a large ductile behavior is required in addition to the high mechanical strength. Indeed stents have to undergo a deformation until e˜40% during their expansion [1]. Conventional Co-Cr-Mo (CCM) alloys exhibit limited ductility (maximal deformation about e˜30%) [2]. Co-Cr-W-Ni (L-605) alloy is a better candidate for stent elaboration since its fracture strain can exceed 40% (comparable to nickel superalloys (Figure 1), while it keeps high mechanical strength. In spite of the presence of nickel element in this alloy, biocompatibility is sufficient for vascular implants, therefore L-605 alloy is extensively used for heart valves and stent elaboration [3]."

Jan 1, 2012

Pyrometallmurgical reactors constitute a key processing component in the total primary and secondary resource cycle, being involved both in primary smelting, converting and extraction, as well as the reprocessing of scrap, from aluminum cans to end-of-life automobiles. To effectively control the overall resource cycle, one needs to take a systems modeling approach of the whole cycle, seeking to also understand the dynamic process behavior of the individual components of the cycle, and then especially the part that contributes most to the chemical conversion, namely the pyrometallurgical reactor. This paper highlights the role of pyrometallurgical thermodynamics, in the whole resource cycle and specifically places equilibrium thermochemistry in the context of process dynamics where large variable inventories are recycled or maintained within the system. This paper will therefore review the semi-empirical dynamic modeling tools, which are used to model complex systems with the specific goal of developing dynamic predictive models, which also include slag-alloy chemistry, towards controlling the recycling in a feed forward manner. To illustrate the primary processing side, high carbon ferrochrome will be presented as a brief case study. It also will show how the distributed nature of the chemistry of melts in the case of primary extraction, and secondary materials such as recycled end-of-life vehicles, have a significant impact on the process outcomes and model predictions. It is therefore argued that the fundamental thermodynamics and kinetics in metallurgical reactors playa final crucial role in modeling the closed material cycle, but only when it is used in conjunction with process systems theory based on reconciled data for parameter estimation and model calibration.

Jan 1, 2003

By Maria Salazar-Villalpando, Todd H. Gardner

"Efficient utilization of CO2 can help to decrease global warming. Methane reforming using carbon dioxide has been of interest for many years, but recently that interest has experienced a rapid increase for both environmental and commercial reasons. The use of CO2 provides a source of clean oxygen, which eliminates the need for costly oxygen separation plants. The product of dry reforming is useful syn-gas, which can be used to generate electrical power in a SOFC or in the production of synthetic fuels (hydrocarbons and alcohols). Hexaaluminate catalysts prepared at NETL may represent a product that can be utilized for the conversion of CO2 to syn-gas. In this work, transition metals dispersed in barium hexaaluminate have shown to be promising new catalysts for dry methane reforming. In this investigation, a series of BaNixAl12-yO19-d catalysts with varying Ni content were prepared by co-precipitation followed by calcination at 1400°C. CO2 reduction by dry methane reforming was carried out to determine catalyst performance as a function of temperature and carbon formation was also quantified after the reforming tests. Results of catalysts characterization, dispersion and surface area, were correlated to catalytic performance.IntroductionEfficient utilization of CO2 can help to decrease global warming. Methane reforming using carbon dioxide has been of interest for many years, but recently that interest has experienced a rapid increase for both environmental and commercial reasons. The use of CO2 provides a source of clean oxygen, which eliminates the need for costly oxygen separation plants. The product of dry reforming is useful syn-gas, which can be used to generate electrical power in a SOFC or in the production of synthetic fuels (hydrocarbons and alcohols). The dry reforming reaction has been known for a long time. Recent publications have reported studies over several catalysts. For example, the CO2 reforming of CH4 over mesoporous nanocrystalline zirconium powders (ZrO2–3%M2Ox; M: Ce, La and K) at 700ºC have shown methane conversion up to 60% (1). Similarly, the effect of Ni content (1–12 wt%) on the surface and catalytic behavior of bimetallic PtNi catalysts supported on ZSM-5 for reforming of methane with CO2 has been studied and report shows a maximum conversion of 16% and catalyst deactivation was observed during the first hour of time on stream (2). In another report, (3) Ni/a-Al2O3 catalyst was tested for syn-gas generation at 750ºC. The maximum methane conversion was 25%."

Jan 1, 2008

By Yutaka Shiraishi

Two methods were developed to measure the viscosity of the slag from the glassy to the liquid states in an ascending temperature process. The first method employs rotating parallel plates within which is placed a solid cylindrical sample in line with a sphere. The second method uses a tube which is pushed into a sample held in a rotating crucible. Both methods were tested using standard glasses, including boron trioxide and NBS standard glass #711. The main difference between these two methods is in sample preparation. Comparative measurements between two methods were performed using a sodium boro-disilicate glass containing 5%mol of alumina. The results showed good agreement in the mid-range of glassy viscosities, 105 to 107 Pa.s. In the liquid state, there were no significant differences between the two methods.

Jan 1, 2003

By John M. Rapkoch

In the continuing search for copper matte converting methods, commercially available and feasible choices remain Peirce-Smith Converters, Hoboken Converters, Mitsubishi Converting, Ausmelt converting, and Outokumpu/Kennecott Solid Matte Oxygen Converting (?Flash Converting?). While each alternative improves on Peirce-Smith Converters? limited fugitive gas capturing capability, the Peirce-Smith Converter is relatively easy and economic to operate and has an unmatched ability to accept valuable but difficult-to-handle material such as scrap anodes and purchased scrap copper. Recent experience with designing, building, and starting up an ISASMELT facility, applied in primary smelting of copper concentrates, has led the authors to speculate on how suitable the ISASMELT process would be for copper converting, given its low fugitive gas release and its ability to accept a variety of feed types. This paper reviews the potential metallurgical challenges posed by converting copper matte in an ISASMELT vessel and considers possible engineering and design challenges posed by the inclusion of this technology into a new or refurbished copper smelter.

Jan 1, 2006

By Zhang Yongzhu

The metallogeneticy and mineralogy of three types of Chinese refractory gold deposits (Au-As; Au-As-MeS; Au-As-C) which are somewhat different from those abroad are discussed. The modes of occurrence, the distribution of grain size, and the morphological features of gold in minerals and their influences on gold recovery by direct cyanidation are also discussed. According to the mineralogy of gold and minerals, bacterial leaching, pressure leaching and roasting technology are suitable for the pretreatment of arsenopyrite-Au, pyrite-Au and carbonaceous-clay-Au refractory gold ores prior to cyanidation, respectively. The most important sulfide pyrite bearing much gold is difficult to be oxidized, its crystalline structure, conduct-types , and minor elements in different mineralizing stages are also discussed. The pyrite aggregates in different deposits are very complicated and much different. Gold grade of arsenopyrite is much higher than that of pyrite for some deposits which have a high correlation coefficient of Au vs As.

Jan 1, 1992

By R. W. Lee

The first prototype plant using the Imperial Smelting Process commenced operation in 1950. It is timely therefore to review the developments that have occurred with the process over the past half-century. A major advantage claimed initially for the process was its ability simultaneously to recover zinc and lead from bulk concentrates. This has remained a fundamental advantage, but it has been extended by the increasing treatment of secondary materials containing zinc and lead. This has been facilitated by the development of hot briquetting and tuyere injection. These techniques and their impact on the technology of the operation will be described. The other major advantage claimed for the process was its potential to achieve new levels of productivity in the pyrometallurgical smelting of zinc. This has been realised with operating furnaces producing up to 400 t/d of zinc. The technical developments that have enabled this scale of operation will be reviewed.

Jan 1, 2000

By M. Zamalloa

Slag foaming is an important phenomenon in many metallurgical processes. It creates large surface areas for multi-phase reactions to take place. In other applications, it protects electrodes and improves the energy efficiency by reducing radiation from hot surfaces. However, it may also be a source of serious disturbances. To control and optimize the use of slag foams, an extensive knowledge of the factors controlling the foam formation and stability is required. Slag foaming experiments were carried out using synthetic FeO-CaO-Si02 slags at temperatures ranging from 1200 to 1350 "C. A data acquisition system was used to continuously measure the foam height, gas flow rate, bubble frequency and temperature. The experimental results show that the gas injection rate has a strong effect on the behaviour of slag foams. At high flow rates and rapid bubbling, unstable foams with short decay times were created. The addition of P20, favours the foam formation and stability by lowering the surface tension of the slag. The average foam life increases with decreasing basicity (CaO/Si02). It is proposed that this is attributed to the increase of the surface viscosity due to surface adsorption of a thin film of silica, retarding the drainage of the liquid films.

Jan 1, 1992

By Hideki Yarnarnoto

The simultaneous removal for NH4+ and PO43- in aqueous solution was carried out by using Ca type zeolite synthesized from coal fly ash. The effect of pH on the cation exchange capacity and adsorption properties of the obtained zeolite, the simultaneous removal of NH4&apos; and ~04&apos;. in various solutions and the mechanism of simultaneous removal were investigated respectivel? ,The Ca type zeolite used in this study can simultaneously remove NH4+ and PO43- In aqueous solution without releasing counter ion, and this method gives great advantage over the other ordinary removal methods.

Jan 1, 2002

By Tracey Brommer, Britt Elin Gihleengen, Elsa Olivetti, Randolph Kirchain

"Increased demand resulting from the economic and environmental advantages of recycling secondary materials has constrained secondary material supply. As a result of constrained supply, the conventional strategy to maximize recycled content in an individual aluminum alloy must be expanded to maximizing total recycled content in a given production period. This work compares the performance over a two week period of an actual remelter for two strategies; a sequential charge-by-charge optimization framework and an integrated approach that explicitly incorporates the production schedule. Optimizing across the entire two week production is found to increase recycled content and minimize primary and alloying material additions. It is expected that as the scrap material market continues to be constrained by high demand, longer term batch planning strategies that can optimize material allocation will deliver improved performance.IntroductionIntensifying economic and environmental pressure to incorporate secondary aluminum into products is pushing remelters to explore additional strategies and tools to increase recycled content. Aluminum remelters are exploring alternative sources of secondary materials because of constrained secondary material supply and relatively high primary and secondary material cost [1]. Computational models, such as blending models are a tool that could help industrial remelters mitigate supply and cost challenges and thereby increase recycled content. In particular, computational tools can help manage the incorporation of new raw materials of variable quality. Blending models find many industrial applications and have been explored for over sixty years originating with the classic nut-mix problem dating back to 1950’s [2]. Blending models optimize the raw material input to make a desired product subject to a series of constraints such as product specifications and material availability. Deterministic and linear blending model formulations are presently implemented in some industrial aluminum remelters [3]. The primary reluctance of aluminum remelters against computational model implementation is the incapability of their blending models to reflect the intricacy of industrial remelting conditions [4]. For example, to reduce calculation time, industrial aluminum blending models usually optimize a batch plan for a single alloy and are not formulated to optimize several products simultaneously. Since such a model does not include knowledge of subsequent charges in the optimized batch plan, the resulting batch plans tend to deplete the “cleanest” secondary materials leaving the more uncertain and compositionally challenging materials for later charges. As a result, a remelter may override the calculated batch plan or leave certain scrap materials out of the material input to conserve these materials for alternative products scheduled for later production. This work explores an alternative aluminum charge planning tool that can optimize across an extended production schedule and compares it to a heuristic sequential optimization strategy reflecting an industrial remelter."

Jan 1, 2012

By Akira Nishikawa

During the twentieth century the copper smelting industry achieved dramatic expansion corresponding to the vast growth of global economy. This was largely due to innovations in pyro-metallurgical processes, such as autogenous smelting and continuous smelting and converting technologies. However, as copper production capacity increased, its impact on the environment also could not be ignored, and thus with increasing global environmental awareness, many smelting operations either had to renew or rebuild their facilities. In addition to these changes, in places like Japan and Europe, with scarce primary resources, the treatment and recovery of metals from a variety of items such as car shredder dust, used electrical appliances and electronic devices, on top of scraps traditionally treated, is having a profound effect on the reduction of waste and the preservation of primary resources. Thus compared to the days when copper smelting focused on the environmental control in order to break with "Smoke Stack Industry", copper smelting today is making an important contribution to the sustainable development of human society.

Jan 1, 2003

By Wenliang Cao, Jidong Li, Mingjie Zhang, Yiyong Wang

In CaC12-CaF 2 System, we studied the electrode process and discharge mechanism of preparation of Al-Ca alloys by fused salt electrolysis with CaO as raw material. The change of back electromotive force after adding CaO was measured by continuous pulse oscillograph method and the discharge process mechanism was also investigated by cyclic voltammetry. The finial results indicate that back electromotive force decreases by 0.6V after CaO of 1 % is added and there was a peak of oxidation current ahead of the potential at which the negative chlorine ions precipitated. According to thermodynamic calculation, it was determined that current peak was caused by the CO2 produced by 0 2 - ionic discharge due to CaO addition.

Jan 1, 2014

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001

By Nils Lippmann, Ulrich Weber, Siegfried Schmauder, Jr. Mishnaevsky

"A computational approach to the optimization of fracture resistance of multiphase materials (here - high speed steels) by varying their microstructure is presented. The main points of the optimization of steels are as follows: (1) development and verification of the model: numerical simulation of crack initiation and growth in real microstructures of steels, (2) computational experiment: simulation of crack growth in different idealized quasi-real microstructures and (3) the comparison of fracture resistances of different microstructures and the development of recommendations to the improvement of the fracture toughness of steels. Numerical simulations of crack growth in real microstructures of steels and different idealized carbide distributions are carried out. On the basis of the simulations, recommendations for the improvement of high speed steel microstructures are given. It is shown that the fracture resistance of the steels is much higher for the fine than for the coarse version of the same type of microstructures.IntroductionThe purpose of this work is to develop an approach to the optimal design of multiphase materials on the basis of numerical simulation of their behaviour under mechanical loading. We suggest here the following strategy:1. Collecting input data for the simulations: taking a micrograph of a microstructure, and determining mechanical properties and failure conditions of the material constituents [1, 2],2. Simulation techniques and assumptions are tested for a real microstructure of the material: crack growth in a real microstructure is simulated and then compared with the experimental data,3. Computational experiments: different microstructures of materials are tested in the numerical model under the same loading conditions. The calculated service properties of the different microstructures are compared, and recommendations are developed. As differentiated from the ""real"" experimental techniques, the computational experiment is much cheaper and not labor- and time-consuming."

Jan 1, 2001

By E. C. L. Cardoso

Hydrocarbon polymers, as PP, made from cheap petrochemical feedstock are important in many branches of industry. However, they have an undesirable influence on the environment and cause problems due to waste deposition and utilization. Polymeric materials composites account for an estimated from 20 to 30% of total volume of solid waste disposed. Thus, there is a tendency to substitute such polymers by those ones that undergo biodegradable processes. Polypropylene (PP) is a commodity, with high melting point, high chemical resistance, low density, with a balance between physical and mechanical properties and easy processing at low cost. Nevertheless, PP shows limitations for some special applications in automotive industry and civil construction. In order to minimize this deficiency, related to rheological behavior of polymer melt, especially referring to viscosity in processing temperature, a 50% mixture with HMSPP (High melt Strength Polypropylene) was used. PP/HMSPP was blended with 10, 15, 30 and 50% of natural (sugarcane bagasse) and synthetic polymers (PHB and PLA) aiming to partially biodegradable materials. The admixtures were subjected to gamma-irradiation at 50, 100, 150 and 200 kGy and then further assessed by mechanical tests in order to evaluate their degradability.

Jan 1, 2015

By Brent W. Madsen

The acid-ferric sulfate leaching of low-grade sulfide copper mine waste provides more than 10 percent of the U.S. supply of new copper, but recoveries and leaching rates are very low. In Federal Bureau of Mines research to improve the leaching process, experiments on 5- to 10-ton lots of mine-run ore were more revealing than bench-scale tests on fine ore. This report discusses the results obtained by leaching run-of-mine and minus 6-inch plus 112-inch samples of low-grade chalcocite-bearing mine waste. The samples were leached for 461 days and 61.6 and 37.7 percent of the copper was extracted from the minus 6-inch plus -112-inch and run-of- mine samples, respectively. A mixed kinetics model was applied successfully to the leaching of the sample with the fines removed where bulk solution transport was not rate controlling. The model, when applied to the run-of- mine ore, gave somewhat higher predicted copper extractions than experimentally determined. Subsequently, oxygen was introduced into the run-of- mine ore, leaching continued for an additional 312 days, and an additional 53.0 percent of the copper was extracted. Before the leaching experiment was dismantled and the residue sampled, the ore was treated with sulfur dioxide and its permeability was improved markedly. The results of each of these procedures are interpreted in relation to the attendant condition of the test.

Jan 1, 1976

By James E. Hoffmann

This paper briefly reviews the conventional technologies employed for the treatment of copper refinery electrolyte bleed. The strength and weaknesses of conventional practice will be reviewed and a number of process options to address the weaknesses of present process technology will be described and evaluated. The effect of process selection upon energy consumption and the environmental aspects of process effluent control will be discussed.

Jan 1, 1997

By Min Zhu, Yu Ji, An-chao Ren

"After being welded in the weld plant, the 100-meter heavy rails with the specification of 60kg/m are found broken during the straightening process in four planes. Failure analysis is made using the optical microscope and SEM with the result showing that the broken rail contains the imperfection of protrusion which exists at the edge of rail foot, about 1 00mm away from the rail end. When the protrusion is peeled off by deseamer from rail surface, cold scratch is generated which causes the rail to be broken during the subsequent straightening process. By adjusting the roll diameter differences between top and bottom roll of universal finishing mill and the height of pass line, it is possible to maintain the rails flat when leaving the mill. This prevents the upsweep and downsweep phenomena and, thus, the imperfection of protrusion can be eliminated. IntroductionThe development of rail transit worldwide has entered into a new era since the 1960s. The hi-tech rail transit system has gradually gained recognition over the world. In particular, the emergence of new-type passenger trains represented by TGV of France, ICE of Germany and Shinkansen of Japan and heavy haul trains as well, has revealed the charming way and more prosperous future of the modern and hi-tech rail transit system to the people all over the world. It should be pointed out that rail transit system is still the most effective solution to traffic jams among urban cities and in the central cities during the 21 '1 century, especially high-speed railway and subway which take overwhelming advantages over air transport, marine transport and road transport in terms of high speed, high efficiency, safety, comfort, environment protection and high flow. With the trend of increasing speed and heavier load of trains, higher product quality of rails is demanded. The rails for passenger dedicated lines require high cleanness, high accuracy in size, high flatness, high surface quality and large size (100-meter fixed length). The rail quality has direct influence on the operating performance of rail and railway traffic safety. The 100-meter heavy rails with the specification of 60kg/m are broken subject to the straightening process in four planes after being welded in the weld plant. This paper analyzes the reason for rails being broken and provides the theoretical proof for determining the rolling process."

Jan 1, 2013

By David G. Dixon

From its first implementation for the recovery of gold from low-grade ores by cyanidation in the early 1970s, heap leaching has developed into a key hydrometallurgical technology, in conjunction with solvent extraction and electrowinning, for the recovery of base metals, including most notably copper from both oxides and secondary sulphides, and more recently, nickel and zinc. And, given recent advances in bioleaching with thermophilic microbes, the successful application of heap leaching technology to low-grade primary copper ores seems only a matter of time. However, with each new development, it becomes increasingly apparent that the successful application of heap leaching technology will ultimately depend on our having an ever more complete understanding of the fundamental processes underlying it. Much work has been done toward the development of this understanding, on many different fronts. In this paper, a critical overview of heap leach modeling work to date is presented in terms of the most important phenomena which occur during heap leaching, and potential directions for future work are discussed.

Jan 1, 2003