Search Documents

By L. A. Kazanbayev

The Chelyabinsk Electrolytic Zinc Plant (CEZP) was commissioned in 1935. Over the elapsed years the Plant capacity has been increased from 10 thousand tons of zinc (1935) to 150 thousand tons of zinc (2005). The paper describes the Plant main achievements in production updating for the last 10 years.

Jan 1, 2006

By KNona C. Liddell

The time and spatial dependence of component and species concentrations during in situ uraninite leaching have been modeled using a reactive transport model based on partial equilibrium between reactive minerals and the solution. The flow field is represented by mixing cells in series. The effects of the H2O2, (NH4)2CO3, and NH4HCO3 component concentrations have been simulated, and results are presented for a one-dimensional flow field.

Jan 1, 1995

By C. P. Broadbent

Due to growing .public awareness of environmental issues and greater sensitivity towards waste management, many countries around the world are implementing more stringent legislation governing the storage and disposal of hazardous wastes containing heavy metals such as As, Sb, Pb, Cd or Hg. These wastes can no longer be dumped without providing clear guarantees that the material concerned is environmentally safe and will not leach toxic elements to the surroundings. In the Netherlands the current dumping charge for chemical waste (i.e. worst category) is $280/t, and for industrial waste this cost reduces to $75/t. If the material can be reused there may be a small positive credit for selling it, for example discard slag as an aggregate to the construction industry. A number of (pyre)-metallurgical operations, mostly associated with the extraction of metals from sulphidic ores, produce arsenic residues in the form of As2O3 containing flue dusts and speises. If the flue dust is of high purity it can be sold, though many traditional uses are being substituted by other materials. In many cases upgrading the quality of the arsenical dusts is not possible for either technical or economic reasons. Traditional practice is to dissolve these dusts in acid prior to precipitation as ferric arsenate, which is at present classified by many countries as industrial waste and can be dumped. Recent work, however, has cast doubt on the stability of arsenates for disposal and alternative disposal routes have been investigated. Tests have shown that up to 10% (dm) As can be incorporated into "glassy" silicate slags with very low levels of arsenic leaching in the cooled product. Calcium arsenate was added to a range of synthetic and industrial slags from the system SiO2-FexOy-CaO-A12O3-AsmOn, under mildly oxidising conditions and quenched subsequently in water. It would appear that this represents an environmentally acceptable method for the disposal of many arsenical residues and there is some optimism that this method will be equally applicable to the disposal of other toxic metal residues.

Jan 1, 1994

By Lauri Pajunen

DSA-anodes are widely used in metal electrowinning. In zinc electrowinning the electrolyte solution contains manganese ions, and the deposition of manganese dioxide happens on the anode. This manganese dioxide layer cannot be removed without losing the active coating of the DSA-anode. The same problem can be found with hybrid anodes. In hybrid anodes mixed metal oxide coated titanium mesh is attached to a lead base material. In this study, the effect of dissolved manganese on anode behaviour is studied with three different anodes. These anodes are lead anode with 0.6% silver, hybrid anode and DSA-mesh. Methods of study include polarization, galvanostatic and potential mapping experiments.

Jan 1, 2003

By K. Osseo-Asare

Aqueous stability diagrams (25°C) are presented for the systems M-H2O and M-Oxalate-H2O where M=Sm, Nd, Co, and Fe. With the aid of these diagrams (i.e., Eh-pH and log[Metal]- log[Oxalate]), the solution-chemical constraints on metal dissolution and precipitation are identified. By comparing the corresponding stability diagrams, conceptual flowsheets are developed for metal recovery from Sm-Co and Nd-Fe-B magnet scrap.

Jan 1, 1997

By T. Lezhava

For the purification of quarry waters from copper and their further utilization a three-sectional electrochemical reactor is constructed providing the extraction of 90-95% copper as a self-loosing powder from the quarry water running as a steady flow. Four variations of the integrated processing of quarry water are developed and their relative technical and economical parameters are calculated. The detailed technological scheme is given for the variant that is the most profitable for Georgia.

Jan 1, 2006

By R. Cheng

The kinetics of the solvent extraction of ythium from HCl solution with mono-2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (HEHEHP) have been studied using a rotating diffusion cell (RDC). The effects of rotation speed, pH, ymium and extractant concentrations and temperature on the rate of extraction were examined. The rate of extraction of ythium appears to be controlled by an interfacial reaction of metal ion and extractant. The concentration of the latter is determined mainly by diffusion through the membrane. The contributions of the rates of diffusion in the diffusion layer, diffusion in the membrane and chemical reaction at the interface to the overall rate have been calculated on the basis of a kinetic model.

Jan 1, 1992

By Randy Martin

"Greenstone Resources Ltd. constructed and operates the Santa Rosa open pit, heap-leach gold mine in Veraguas, Panama. The project was commissioned in 1995 at a designed capacity of 1.8 million tons per year. The ore exhibits a long leach up to three years, and requires three stage crushing to minus 3/8 inch to achieve on average a 74% gold recovery. The crushing plant is required to handle high volumes of clay and the circuit includes a Barmac Crusher. Panama receives over 3 meters of rain annually and Greenstone is using innovative means to control the project's water balance. Greenstone has developed a successful approach to operating a low grade (1.5 gm Au/T) deposit under difficult operation conditions.ABSTRACT ONLY"

Jan 1, 1997

By P. J. Moor

Britannia Refined Metals Ltd. was built in 1931 to refine the lead bullion produced at the Mt. Isa mine in Queensland, Australia. Several periods of expansion and development have taken place over the intervening years, leading to major increases in the refining capacity for both lead and silver. A plant for treating recycled lead-acid batteries was added in 1976. This was redeveloped in the early 1990's to utilise Isasmelt technology for the smelting operations. Most recently the No. 2 refinery kettle floor was extended to enable it to process lead bullion produced from two Imperial Smelting Furnaces (ISF), at Britannia Zinc Ltd. in Avonmouth, England and at MIM Hüttenwerke in Duisburg, Germany. This expansion included the provision of a plant for the hygienic handling of drosses and skims. This paper briefly describes the present primary refining operations and gives an update on the most recent developments in the process metallurgy and operating practices that have taken place.

Jan 1, 2000

By Larry Southwick

In the early 1940's, the Caron ammonia ? ammonia carbonate leach process was used to produce nickel from Mayari ores at the Nicaro plant in Oriente Province, Cuba. While plant operation was generally successful, it was not broadly economical and was shut down. The plant was later restarted in the 1950's and a number of investigations initiated to resolve the more serious operational and performance issues. Processing steps studied included iron reduction (chemistry ? nickel and iron, reductant, equipment), ore variability (homogeneity and consistency of mineral concentrations, serpentine vs. laterite), leach solution strength, nickel recovery (temperature ? reduction and leaching, reoxidation) and a variety of other topics. These studies and their findings will be discussed. Caron himself obtained good results on these ores in the laboratory. They could not be duplicated in the field, the reasons for which will be reviewed. (Note: the ore looked like garden dirt; charcoal made from palm trees was one of the reductants attempted; and ammonia was the leach solution. Mixing the three, so to speak, was to yield nickel.)

Jan 1, 2006

By Felipe P. D. Lopes, Jr. dos Santos, Sergio N. Monteiro, Frederico M. Margem

"Continuous and aligned fiber composites provide the highest possible reinforcement for a polymeric matrix. In particular, the impact resistance is significantly increased in comparison with a low energy absorbed brittle polymer. For this reason, investigations have been carried out with both synthetic and natural fibers as a way to improve the toughness of polymeric composites. Among the natural fibers, ramie was not yet been studied for its reinforcement effect to make tougher polyester composites. Thus, the present work assesses the impact toughness of polyester composites incorporated with different amounts of ramie waste fibers.IntroductionIn most engineering and other technological areas, the use of materials associated with low energy processing conditions is gaining attention for the possible environmental benefits. This offered an incentive towards the substitution of natural renewable and biodegradable materials for the traditional energy intensive synthetic materials [1]. Natural fibers from both origins: animal, such as silk and wool, and vegetable, such as cotton and jute, are typical examples of those environmentally friendly materials. Low cost and highly reduced processing machinery wear are important advantages of the natural fibers over the most common synthetic ones such as glass fiber and nylon. For these reasons, polymeric composites reinforced with natural lignocellulosic fibers have nowadays been the subject of investigation [2,3].The mechanical strength is one important property of lignocellulosic composites to access the possibility of uses like structural materials for building parts such as doors and panels, as well as furniture. In this case, mechanically strong fibers like sisal, jute, curaua and ramie [4-7] are most convenient. Moreover, the relatively low fiber/matrix interfacial shear stress in these composites is associated with higher impact energy. In fact, a greater energy has to be expended for the rupture of a weak interface. The many cracks that are formed by impact tend to branch during the fiber pullout from the matrix [8]. A larger number of cracks correspond to a greater fracture surface and consequently higher toughness."

Jan 1, 2008

By Anders Salwén

In 1975 T. Nishizawa and A. Chiba reported on observed deviations from the ferrite-austenite local equilibrium in several diffusion couples based on the Fe-Cr system. In order to try to verify these results the austenite-to-ferrite transfonnation in a Fe-20 %Cr-Invalid Code [Fe-]-%Cr diffusion couple held at 1100 for 100 hours has been simulated. The simulation model is based on the postulated principle of maximum dissipation rate of Gibbs energy during transformation, which allows non-equilibrium interface conditions. Keynotes: Computer Simulation, Austenite-to-Ferrite Transfonnation, Diffusion Couple

Jan 1, 2003

By I. Sofia Fernandez del Rio

This paper describes a process for the treatment of the dusts generated during the operation of blast and reverberatory furnaces in the lead smelter, to remove zinc, cadmium, arsenic and halides from the circuit. The process consists of a Pefloles' developed leaching/purification stage and a solvent extraction process developed by Lurgi. The plant capacity is 5,000 tonnes Zn/year. The feed to solvent extraction contains 8 g/1 Zn. Impurities such as copper, iron, arsenic and cadmium are removed by conventional cementation processes. The cadmium product is 99.99 % pure. The solvent extraction process consists of two extraction stages, one washing stage and two stripping stages. D2EHPA is used as the extraction agent and 25% ammonia as the neutralizer. The rich-zinc solution is sent to the electrolytic zinc plant for zinc recovery. The raffinate produced, which is a mixture of ammonium sulfate and chloride, is used for agricultural applications.

Jan 1, 2000

By Roberto Giovanardi, Isabella Lancellotti, Luisa Barbieri, Ercole Soragni, Fernanda Andreola

"Recovery of precious metals (PMs) is a present topic, as they are used almost in every electronicelectric device. Gold is the second PM in order of consumption (following silver) and it is almost ubiquitary in electronics where it mainly finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. Given this, discontinued electronic and, with a minor role, electric devices may represent a primary source of PMs as gold mines or jewelery wastes.At present the recovery of gold from such waste is generally accomplished by two strategies: by oxidative thermal treatment followed by metallurgical or chemical processes or by cyanide chemical etching; both techniques do not represent the optimum as the first one deserves a great amount of energy and non-combustible pollutant slag and fumes are produced, while the second procedure comports the use of a highly pollutant agent as cyanide.The aim of this work is the characterization of different electronics scraps to evaluate the gold concentration, and the selective recovery of this metal using enviromentally-friendly techniques. In particular, a new process was developed in order to overcome such environmental and efficiency issues. The process reaches the goal of detach the gold film from the substrate by selective leaching of the supporting metal.IntroductionThe treatment of waste from electrical and electronic equipments is a current topic as their role in modern life is increasing. The disposal of such waste represents both an environmental and an economical concern due to the vast amount of both precious and non precious metals.The use of precious metals (PM) in this field is of primary importance given PM’s unique properties, which give to each of them a specific and irreplaceable role. Silver is the most used, with a demand of over 5000 tonnes per year, mainly for switches and contacts in electric appliances. Gold is the second PM in order of consumption (over 250 tonnes per year and 8% of the total demand) and it is almost ubiquitous in electronics where it finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. It is also used as solder in integrated circuits (in alloy with tin) or for wide coatings where it ensures protection against corrosion. Palladium, platinum, rhodium and iridium follow in order of consumption [1- 3]."

Jan 1, 2008

By Gerardo R. Alvear

The ability to efficiently remove impurities contained in concentrates is a key point to consider when selecting copper smelting technology for new plants or modernisation projects. Volatilisation of impurities such As and Sb should occur as early as possible in the process, and preferably in the smelting furnace, so that they do not impact on downstream unit operations. The ISASMELTTM process has been demonstrated to remove impurities efficiently, through high levels of volatilisation. This behaviour is promoted by attributes of the process such as the strong bath agitation, and the flexible nature of the process design, allowing the operator to choose the optimal matte grade for impurity partitioning, and the positive effect of the moisture content in the feed. This paper presents the distribution of minor elements in the copper ISASMELTTM furnace. Distribution impurities of As, Sb, Pb, Zn and Co observed in the ISASMELTTM furnace at Mount Isa Smelter are reported. Then, based on plant results and thermodynamic considerations, the potential application of ISASMELTTM technology for processing complex concentrates is discussed.

Jan 1, 2006

By Toshitaka Ota, Hisao Suzuki, Minoru Takahashi

"Perovskite-type lead zinc niobate (PZN) exhibits excellent electrical properties such as high dielectric constant, high electrostrictive coefficient and superior piezoelectricity. Therefore, PZN ceramics are very promising for high performance electronic devices. However, perovskite phase PZN is not stable under the ambient atmosphere. Accordingly, it is very difficult to prepare single-phase perovskite PZN ceramics. In this study, A-site cation of lead was partially substituted for barium to stabilize the perovskite phase of the PZN (Ba-doped PZN) powder. In addition, molecular design of an alkoxide precursor was controlled for a low-temperature processing. As a result, molecular design to suppress the lead-volatilization during calcination was preferred for a low-temperature processing. Processing temperature for a single-phase perovskite was depended on the amount of barium dopant. Doping of20 mole% of barium resulted in the single phase perovskite at 900 °C. The temperature for the single phase perovskite of Ba-doped PZN powder, which depended upon the amount of Ba-doping, was lower than that of the powder prepared by the atmosphere controlled conventional powder processing at least by 150 °C.IntroductionFerroelectric thin films and powders with perovskite structure are of renewed interest for micro-electronic applications, including ferroelectric random access memory (FRAM), dynamic random access memory (DRAM), and thin-layer capacitors integrated onto a silicon wafer [1-3]. In addition, recent advancement in micro-machine requires a high performance micro-actuator [4]. A perovskite type relaxor of Pb(Zn113 Nb213)03 is one of the promising materials for a high performance capacitor and microactuator because of their high permittivity and electrostrictive coefficient [5]. Therefore, this paper focuses on the low temperature processing of Ba-doped PZN powders.Chemical solution deposition (CSD) from molecular-designed alkoxide precursor solution is one of the most promising techniques for processing high-performance powders and thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature [6]. However, chemical solution deposition of perovskite type PZN powders and ceramics are very difficult because of the formation of stable pyrochlore phases. Therefore in the past, PZN powders and single crystal have been prepared by the hydrothermal method or flux method as well as the partial substitution method of a A-site cation [7-10]. In this study, a suitable molecular design for a preparation of perovskite type Ba-doped PZN powders with a chemical solution deposition process is investigated as well as the effect of A-site cation substitution. Chemical solution deposition from molecular-designed alkoxide precursor solution is expected to decrease the amount of a A-site substitution and/or a crystallization temperature for a single phase perovskite. This paper describes ""the relation between molecular-design and processing temperatures for a single-phase perovskite of Ba-doped PZN powders in comparison with the conventional oxides mixing method."

Jan 1, 2000

By Camila Martini Matos, Maria das Graças da Silva Valenzuela, Francisco Rolando Valenzuela Diaz, Lucy Gomes de Sant' Anna, Orley de Oliveira Magalhães, Flavio M. S. Carvalho, Isaac Jamil Sayeg

"Kaolin clays are widely used in various industry segments. Its main properties are fine granulometry, chemical inertness and whiteness. In general, kaolins are not easily organophiilized as a result of its 1: 1 structure. The aim of this paper is to describe the modification of a Brazilian kaolin sample, in order to obtain an organophilic kaolin of high performance. The clay as received was identified by X-ray diffraction and characterized by optical microscopy, cation exchange capacity and swelling tests for observation of their performance in water and organic solvents. Then, the sample was treated with a 10% sodium carbonate solution and with ammonium quaternary, washed several times with distilled water, dried at 60°C, and characterized by XRD and swelling assays. Our results show that the clay was organophiilized and its ability to swell in organic solvents has increased.IntroductionThe kaolin clay, also known as ""china clay"" is chemically a hydrated aluminum silicate characterized as a very fine powder and lamellar structure (1:1), being constituted mainly by kaolinite [l]. Kaolin is a mineral extremely used as raw material. Its properties such as color, softness, small particle size and chemical inertness make it a suitable material for several industrial applications. The desired properties of kaolin varies widely for each application, beginning with its largest use in the paper industry until minor uses in the sectors of cosmetics and pharmaceutics. These two last applications require purified kaolin with defined functionality [2]. To find improvements in the functionality of kaolin for specific applications is important for many industrial uses. Sometimes the way to find these improvements might be modification of the kaolin clay by treatment with a chemical substance as ammonium quaternary, causing surface modifications [3,4]. In this work is described the modification of a Brazilian kaolin sample by treatment with cetyl trimethylammonium chloride (CTAC). The properties of the modified kaolin are being assessed by characterization and essays to understand its functionality and industrial application."

Jan 1, 2013

Four slag types covering the range of Fe-Ca-Si-O compositions and two iron blast furnace slags were melted at 1300 °C and doped with 1% of arsenic, antimony, cadmium, zinc and chromium. The melts were either slow cooled or quenched and the solidified slags were leached according to TCLP procedures. The morphology of the solidified slags was characterised using XRD, optical and electron microprobe techniques. Theoretical considerations showed that the capacity of the molten slag to hold the above toxic elements depended upon slag basicity and this was confirmed in practice. The experiments showed that the leaching of the toxic elements was a function of surface area and the phases present, both of which were affected by the mode of cooling. Iron silicate slags produced in nonferrous smelting operations and blast furnace slag from ferrous smelting operations both show promise of being suitable media for immobilising low levels of toxic elements and complying with current regulatory requirements.

Jan 1, 1994

By David E. Jones

In any manufacturing process, the generation of secondary, associated or waste products along with the primary product is inevitable. Today there is great emphasis on the concept of waste minimisation. As part of that overall strategy, the search .for markets for these materials formally regarded as wastes, can mean the development of whole new industries. This paper examines some of the work necessary to develop recycling and markets for associated products with particular reference to iron and steelmaking slags.

Jan 1, 1994

By Jianhui Wu, Jing Zhan, Chuanfu Zhang, Zhijian Wang, Chu-ping Xia

"A novel technology about interactive roast of complex bismuth sulfide ore with low grade and Pyrolusite was put forward using the low-grade bismuth sulfide ore and pyrolusite as raw materials. The predominance diagram of Bi-Mn-S-O system was drawn by thermodynamic calculations. Stable coexistence area ofBizO3 and MnSO4 and its control condition was obtained. The interactive roast conditions including roasting temperature, roasting time, the ratio of n(MnO2)/n(S), ventilation rate and so on are investigated systematically. The results show that the sulfur-retained ratio reaches about 98%, in which formation rate of MnSO4 was 94.04%, most of the residual sulfur in the ore exist in the form of BhsO32(SO4)10 in the roasting products The optimum roasting conditions were as follows: roasting temperature of 650°C, roasting time of2h, 1.4 for n(MnO2)/n(S) and 140L/h for ventilation rate.IntroductionBismuth is a ""green"" rare metal with the characteristics of safe, nontoxic and low melting point[l].The use of bismuth and its oxides is extending from traditional fields such as pigment, fusible alloy, bismuth class of drugs and metallurgical additives to the high-tech fields such as semiconductor, high-temperature superconducting materials and nuclear power and so on. Bismuth is one of the precious advantageous resources in China which owns the most abundant bismuth resources in the world. Bismuth metallurgical process is divided into the pyrometallurgy and hydrometallurgy [2-4]. Hydrometallurgy for bismuth is mainly used for the processing oflow-grade complex bismuth ore, whose key steps are oxidative leaching process of the bismuth sulfide ore by strong oxidants(FeCb, Clz, HNO2 etc) in hydrochloric acid system. Therefore, the corrosion of strong oxidants, high demand for equipments and poor operating environment are its inherent disadvantages. Pyrometallurgy for bismuth is mainly used for the processing of high-grade bismuth raw materials or concentrate, which is the main method for bismuth metallurgy at present."

Jan 1, 2013