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By Patrik Fredriksson

Thermodynamic data concerning FeO-containing slags is of importance in ladle refining of steel. With a view to generate a set of reliable and self-consistent thermodynamic data for these slags, experimental determination of the activities of FeO in binary and ternary slags was carried out using the gas equilibration method involving CO-C02-Ar gas mixtures at steelmaking temperatures. The slag samples in Pt crucibles were quenched after the equilibration and subjected to chemical analysis. The thermodynamic activities of "FeO" in the slags were calculated from the experimental data. The results are incorporated into a thermodynamic description of silicate melts in the present laboratory. The model is based on a Temkin-Lumsden approach and is able to compute the thermodynamics of higher order systems from the lower order ones.

Jan 1, 2003

By Cristián Araya L.

A dynamic agglomeration, heap leaching, solvent extraction and electrowinning software, called NICO, has been developed in order to either design or simulate copper ore recovery plants. NICO contains a library of routines, each representing a unit operation or piece of equipment, which are assembled like a meccano to match almost any wet plant configuration. Routines include agglomeration or curing either in drums or belts, belt conveyors, heap stacking and reclaiming, heap leaching of oxide, sulfide or mixed copper ores, heap irrigation, drainage, ponds, mixer-settlers, filters, columns, coalescers, tanks, electrowinning cells, pumps, and all connections and related piping. All models are semi- phenomenological, i.e., they include all physical-chemical, mass, thermal, transport equations, which are required to represent as closely as possible the equipment or unit operation. However, operating experience has been incorporated into the model in order to make it simpler, faster and reliable. This experience has been tested in several plants in Chile since 1992. Site meteorological data is simulated also; in this way the model is responsive to weather conditions (temperature, solar radiation, ambient humidity, atmospheric pressure, wind velocity, etc). NICO has been used recently for design and optimization studies in copper plants in Chile like Radomiro Tomic, Collahuasi and Zaldivar. A user-friendly interface allows fast and comprehensive simulations. The entire plant is shown in a single graphic screen, so the user can see all the relevant information, and soft-keys are provided in order to change parameters on-line and watch their effect in final copper production in cathodes. Model also calculates and reports operating parameters, as well as estimated investments and operating costs.

Jan 1, 1999

By A. Schönecker, P. Y. Pichon, B. Kraaijveld, Y. Meteleva-Fischer

"Ribbon-growth-on-substrate is a casting method, which offers a possibility to control heat flow, nucleation and subsequent crystal growth at the liquid-substrate interface. This technology allows for low-cost and high throughput shaping of silicon sheets with controlled crystal grain size and orientation for use in solar cells. In this work, sheets of silicon- metal silicide composite materials were produced and their microstructure was studied. It was shown that depending on the relevant phase diagram and casting conditions, a micro/nano-sized eutectic structure of the casted sheet can be formed. Such composite materials possess properties promising for various applications in energy generation, storage and conservation. The advantages, potential and challenges of the ribbon-growth-on-substrate technique for production of composite sheet materials as well as novel areas of application for such materials are discussed.IntroductionThe Ribbon Growth on Substrates (RGS) process is well known in the solar industry as a process to produce multicrystalline silicon wafers. An industrial size pilot production line for continuous casting of silicon wafer was developed by RGS Development B.V. in the Netherlands (Figure 1). A comprehensive review of this technology and properties of the produced silicon wafers were reported by Schönecker et al [1]. The principle of the RGS process is explained in Figure 2. The relatively cold substrate extracts the crystallization heat from the liquid silicon in the casting frame. This results in the growth of a silicon ribbon (Vc) in contact with the substrate. When the substrate (Vp) is transported from the casting zone into the cooling section, the crystal growth stops, the wafer can be removed and the substrate can be re-used. Last few years large work was done on the industrialization and market development of RGS wafers for the solar industry. Part of this work was discussed by Schönecker et al [2]. Although there is still a good perspective on the middle and long term solar market for the RGS wafers, the current market situation was found to be unfavorable for new entrants."

Jan 1, 2014

By Cleusa Cristina Bueno Martha de Souza

Nowadays in Brazil the final disposal for spent batteries include sanitary and industrial landfill for hazardous waste from domestic waste and industrial waste respectively. The problems of environmental impact caused by spent batteries had been discussed of several years, considering the fact of metals contents, like Cd, Hg, Pb and Zn. Some techniques are been proposed for recycling this type of waste in order to protect the environment while bringing also economic advantages of recovering metals. The reclamation of metals from secondary raw materials had been employed and further applications of this flexible technology are planned to the future. The processing of metals solutions involving hydrometallurgical techniques is an efficient method for recovering metals, since it provides completely recovery of metals with low energy requirements. This paper discusses the spent alkalline batteries characterization and leaching stage experiments results with sulphuric acid as leachant. After batteries dismantling by mineral processing techniques, the black powder sample produced was submitted to diffraction X-ray characterization and atomic absorption spectrophotometry in order to verify all the substances presented. Some experiments were carried on to develop a hydrometallurgical process for initial metal recovery aiming to get Zn into a soluble form on aqueous solution in order to propose the next stages of purification and recovering Zn, as electroplated deposition. The sulphuric acid was chosen not only for being cheaper than other leachants but also for improving the extraction of soluble Zn as ZnS04 form at diluted acid concentration. Batch laboratory experiments leaching procedure were conducted to determine appropriate leaching conditions from the viewpoint of maximize zinc extraction. In these tests an amount of dry powder batteries was added to different acid concentrations and solid/liquid ratio and after leaching and filtration the aqueous solutions were submitted to atomic absorption spectrophotometry analysis to verify the Zn content.

Jan 1, 2000

By D. W. Lawler

Prior to the manufacture of sulphuric acid in metallurgical plants, the SO2 rich gas from the smelter, roaster, or furnace must be cleaned to removed particulates, volatile contaminants, SO3, and water. Cleaning is accomplished by contacting the. gas with cooled weak acid. The system is designed so that all the contaminants, originally in the gas are captured in the weak acid, which then becomes an effluent from the plant. Historically, the entire weak acid effluent stream has been treated for disposal, with no attempt to recycle or recover any part if it. This is becoming increasingly environmentally unacceptable, and operators must consider better methods of treatment and recovery. In this paper, Kvaerner Chemetics discuss a number of options that allow the contaminants to 'be separated from the acid' value. This will result in an acid byproduct that can be sold or used elsewhere, and will minimize the volume of hazardous byproducts that must be discharged.

Jan 1, 1998

By David G. Dixon

Although the kinetics of leaching processes are of paramount importance in the design and analysis of nearly all hydrometallurgical flowsheets, these concepts remain poorly understood and, as a result, are only rarely applied to mass and heat balance models. In this second of two papers, we demonstrate how simple yet powerful models of leaching kinetics and other rate processes may be added to mass and heat balance models, and apply these concepts using a spreadsheet model of a simplified pyrite autoclaving flowsheet. In particular, we focus on the interpretation and scale-up of batch leaching data, and on simple means for modeling other phenomena commonly associated with leaching, such as reagent depletion, gas-liquid mixing, and the precipitation of oxides and basic salts.

Jan 1, 2002

By Jim Sundal

Primary steel manufacturers using electric arc furnaces generate one of the largest hazardous waste streams nationwide. The waste stream, known as electric arc furnace dust, is a listed hazardous waste with the designation K061. Oregon Steel Mills, Inc., (OSM) of Portland, Oregon, has implemented a process known as Glassificationn, which uses KO61 as an ingredient in an onsite recycling process. Because OSM was able to demonstrate that the Glassificationm recycling process beneficially uses all toxic constituents in the electric arc furnace dust and that the recycling process produces marketable products, the process is not subject to Resource Conservation and Recovery Act (RCRA) permit requirements. The marketable products manufactured using Glassificationn include roofing granules, ceramic glazes and colorants, abrasive blasting media and, more recently, synthetic slag fluidizers. The purpose of this paper is to identify the regulatory issues for recycling hazardous waste and demonstrate that OSM glass frit is effective as a slag fluidizer in primary steel manufacturing.

Jan 1, 1994

By O. Norman Lotter

The formulation and use of mixed collector suites in sulphide flotation can be traced back as far as 1957 with the work of Glembottskii and his co-workers in Moscow. The subject was reviewed by Lotter and Bradshaw in 2010, and proposed a synergy between ideally-selected different reagent types to deliver improved performance, in particular the in situ catalysis of a xanthate to dixanthogen by a dithiocarbamate. Correctly formulated for a particular application, an optimally arranged mixed collector suite delivers the following improvements to the flotation process: • An increase in the flotation kinetics • Improvement in coarse, or middling, particle recovery • Reduction in total dosage requirement • Best results are found from testing the ratios of the collectors. This is of critical importance. In all an optimally formulated mixed collector system usually delivers an increase in paymetals recovery of 1–4% absolute, with a gain in concentrate grade in the range 10–20% relative. In recent years, the addition of semi-conductor theory and associated electrochemistry has contributed significantly to this toolbox by way of identifying optimum domains of Eh and pH for the flotation of individual minerals. In the case of mixtures of minerals, this is where the mixed collector system delivers significant value by way of presenting a mixed set of collector radicals and dimers in a common Eh and pH domain for overall performance. This calls on a fundamental understanding of organic chemistry, mineralogy, semiconductor theory, and electrochemistry. Whereas the selection of grinding media type effectively influences the Eh, the pH can be easily controlled by pH modifiers. The theory of this system, and some industrial case studies, are discussed.

By Walter Curlook

An atmospheric acid leaching process for leaching nickel and cobalt from highly-serpentinized saprolitic fractions of nickel laterite deposits has been developed and patented [I]. The process involves leaching the highly-serpentinized saprolitic portion of the nickel laterite ore profile in strong sulphuric acid solutions at atmospheric pressure and temperatures between 80°C and 100°C, essentially autogenously, to extract over 85% of its contained nickel content and a large proportion of its cobalt content after leaching times of about one hour. The amount of sulphuric acid used in the leaching process is between 80% and 100% by weight of the finely ground highly-serpentinized saprolite ore on a dry weight basis. The metal values are recovered as intermediate products. Key words: Atmospheric Leaching; Nickel Oxide Ores; Laterites

Jan 1, 2004

By Zheng-qi Guo, De-qing Zhu, Feng Zhang, Jian Pan

Iron mainly exists as the magnetite and fayalite, while copper is primarily dispersed in the form of fine matte particles in the copper slag, which is difficult to recover by conventional separation techniques. In this paper, the feasibility of an integrated technological route to improve beneficiation of copper and iron components from copper slag through the modification of molten slag was investigated, and the results shows that: the copper grade of rougher copper concentrate was increased from 6.43 to 11.04%, iron recovery from magnetic separation was increased significantly from 32.40 to 63.36%, and other evaluation indexes were changed slightly, in comparison with unmodified copper slag. Meanwhile, the grains of the target minerals in the modified slag grew considerably to a mean size >50 lm after slow cooling. Ultimately, the beneficiation efficiency of copper and iron was improved because of the ease with which the target minerals were liberated.

Mar 1, 2017

By KNona C. Liddell

Goethite is an important naturally occurring sorbent for divalent heavy metals and has often been used as a model compound in studies of adsorption on oxide mineral surfaces. Surface complexation modeling, surface spectroscopy, and electrochemical techniques have all been applied to goethite adsorption. Modeling studies have shown that usually several different sets of fitted parameters are equally successful in representing surface charging and adsorption data. Surface spectroscopic data are proving valuable in determining the nature of the surface sites, and refined models now incorporate structural information on interatomic distances and coordination numbers. Multisite surface complexation models can give very good fits to surface charging and adsorption data, but further improvements are needed to better represent surface reactions involving exchange of protons and divalent cations. Recent experimental and modeling studies on adsorption of divalent transition metals on goethite are described and the present status of the field is assessed.

Jan 1, 1999

By A. S. Usmani

The flow associated with the pouring of molten metal into moulds has been modelled on the basis of certain simplifying assumptions. A finite element based Navier-Stokes equation solver has been used to analyse the flow. The velocities obtained from the Navier-Stokes equation solver are used to advect a pseudo-concentration function for modelling the fluid front. A simple problem with a known analytical solution is solved first to test the model. Subsequently, several more examples with varied geometrical configurations are modelled, including one with curved flow boundaries.

Jan 1, 1992

By Andres Vikdahl

The Rönnsktär smelter has recently undergone a series of technical and operational changes. This changes are caused by our own will to remain and gain in competivety and to adapt to the ever changing surroundings. To be able to remain competitive in surrounding with high wage costs, high inflation and high environmental standards thorough cost management is needed. The Swedish economic policy in the beginning of the 80'ies consisted amongst other things of two devaluations. The exchange rate of the Swedish Krona was reduced with approximatively 25 %. This boosted the profits of our export industry, some even believed we entered the land of milk and honey ... And working in this promised land where everything turns into profit it is very difficult to be careful and restrictive with your spendings. Apart from some healthy and fruitful investments we allowed ourselves yearly steady increases in salary for ever reduced number of worked hours and we of course employed more people. Inflation rates went up and so did property prices. In 1986 finally reality catched up on us. Reality in the form of too high costs started to hit Swedish export industry 5-6 years after the big devaluations. Furthermore the high inflation rate also hit the domestic industry a couple of years later. Together with other important factors Sweden faced a severe home-made recession in the beginning of the 90'ies. With this background we now report and analyse our smelter's performance and operating results, shown in fig 1 The main constrictions on smelting and refining at Rönnsktär are today: * Income restrictions by governmental production level Limit * Throughput resmctions by governmental emission limit * High capital costs in the aftermath of Swedish high inflation in the recent decade * Low work force turnover Below we will illustrate how we tackled with these issues along the following lines: * People * Quality * Technology

Jan 1, 1993

By Y. Kumagai, F. A. Souza

"Electroless plating process has been used in many fields such as automobile and electronic industries. Solutions used in these processes must be disposed or treated. Commonly, in these solutions metal ions, organic materials and others chemicals are in very high concentration. It is very difficult to keep the environmental regulations for disposal of these materials, and the cost of the plating process becomes higher.The objective of this study was to investigate the recovery of components of those baths in order to decrease the cost of the plating process as well as to meet the environmental regulation.In this study the recovery metal ions, sulfate ions, phosphite ions and organic compounds were investigated. Organic compounds used in electroless plating solutions are the organic acids. In this work the solvent extraction of the most used organic acids included citric, lactic, succinic, tartaric and malic was studied. The solvent phase considered in these studies was ethyl acetate.About 95% of the metal ion was recovered by chemical plating onto mica powder. The hypophosphite remained is oxidized to phosphite and with the sulfate ion, both are recovered as calcium salts by selective precipitation in pH 7 and 2 respectively. Organic acids were recovered by solvent extraction using ethyl acetate as solvent phase and the best results were for lactic acid and succinic acid.Along with this study, was developed the analytical parameters to perform wastewater analysis by using Ion Chromatography, High Performance Liquid Chromatography (HPLC), Fourrier Transform Infrared Spectroscopy (FTIR). Ion chromatography was used to perform analysis of sulfate and phosphite ions in liquid matrix, HPLC was used to perform analysis of organic acids in liquid matrix and FTIR was used for characterization of the solids obtained in the recovery processes."

Jan 1, 1997

By Autumn Fjeld

The filling and solidification of an industrial scale composite casting has been simulated to investigate the re-melting of the outer shell material during casting. Production of a composite requires a two-step casting process which includes centrifugal casting of a hard outer shell material and subsequent conventional ingot casting of a tough core material into the shell-mold assembly. During casting of the core, a thin layer of the shell material re-melts and mixes with the core material producing a bonding layer of intermediate composition. The present numerical model employs the volume of fluid method and an enthalpy-porosity technique to couple the filling of the core material and re-melting of the shell material. The interface between the two materials is tracked and can be used as a guide to examine the extent of melting and, to some degree, mixing of the two fluids and species diffusion.

Jan 1, 2008

By Robert R. Beebe

On the night of August 1'9-20, 1995, seepage was seen at the toe of the Omai tailings dam in Guyana. The mill was immediately shut down, and within two hours the flow, then mostly water, was diverted into an inactive mining pit nearby. At about the same time a second more serious break occurred at a point where water and solids could flow directly into the Omai River. By the time Ii coffer dam could be completed in the early morning of August 24, some 4.2 million cubic meters of tailings water and solids had escaped from the dam, of which nearly2.9 million cubic meters had reached the Omai River. This paper outlines some initial Process considerations and operational decisions which might have contributed to the dam's failure, describes how the Government of Guyana and the operator, Omai Gold Mines Limited, cooperated in dealing with immediate problems and shows how the Government set about investigating the accident. In particular, the paper details the work of a Process Review Committee comprising Guyanese and foreign experts convened to assess the gold processing and effluent management systems at Omai, and to recommend actions where appropriate.

Jan 1, 1998

By Flavio Begazo, William A. Enrico

"Southern Peru Copper Corporation's Ilo Refinery, the largest in Peru, began operations in 1975 with a production capacity of 165,000 stpy. Southern Peru bought the Refinery from the state owned Minero Peru SA on June 1, 1994.The Refinery processes blister from Southern Peru's I/o Smelter. Blister copper is processed in an anode plant equipped with two 365 st tilting reverberatory furnaces, a 26 mold casting wheel and an anode press machine. Copper is electrorefined in a tank house equipped with 768 commercial cells, 44 stripper cells, and 40 liberator cells, utilizing two electrolyte circuits and a 21,000 Ampere rectifier.During 1989 through 1994 a program for improving productivity was carried out by increasing the number of cells and increasing current density to the total rectifier capacity. As a result, a capacity 215,000 stpy of refined copper, 2 million tr. oz silver and 6,000 tr. oz gold per year was achieved. In 1994 Southern Peru announced plans to increase capacity to 250,000 stpy of cathode with a US$ 18 million investment and a US$ 2 million investment in environmental improvement projects, as part of the purchase agreement with the Peruvian government.This paper outlines the scope of the SPCC lio Refinery modernization and environmental program. It describes the implementation of the Electrolytic Plant expansion based on instaliation of polymer concrete cells, a new rectifier, a new selenium roaster and a Precious Metal Plant upgrades."

Jan 1, 1997

By Mark Jolly

"Instead of using the traditional batch casting process, the CRIMSON [1] (Constrained Rapid Induction Melting Single Shot Up-Casting) method employs a high-powered furnace to melt just enough metal to fill a single mould in a closed crucible. The crucible is transferred to a station for computer-controlled counter gravity filling of the mould for optimum filling and solidification. The CRIMSON method therefore holds the liquid aluminium for a minimum of time drastically reducing the energy losses attributed to holding the metal at temperature. With the rapid melting times achieved, of the order of minutes, there isn’t a long time at temperature for hydrogen to be absorbed or for thick layers of oxide to form. The metal is never allowed to fall under gravity and therefore any oxide formed is not entrained within the liquid. Thus higher quality castings are produced leading to a reduction in scrap rate and reduced overall energy losses.IntroductionEngineers at the University of Birmingham, England, with local company, NTec, have invented a new casting process that will reduce the energy costs of light-metal foundries. The technology, entitled CRIMSON, means that foundries need only heat the quantity of metal required to fill a single mould rather than large batches that use unnecessary energy and create waste. The complete concept of CRIMSON requires a change of philosophy in the approach to casting and requires the user to think holistically in order to reap the full benefits from the process. This paper will discuss the various aspects of energy wastage within the foundry sector and discusses the processes whereby the energy can be reduced. Primarily the author focuses on the aluminium sector but CRIMSON can be applied to many of the non-ferrous “light” alloys. Ferrous materials and non-ferrous “heavy” alloys can also benefit from some of the ideas but not necessarily directly from the application of CRIMSON."

Jan 1, 2010

By Fathi Habashi

"Davy, Faraday, and Bunsen laid the foundation of electrometallurgy which had a· great impact on other areas of metallurgy. Electrometallurgy is presently dominated by the production of aluminum, the electrorefining of copper, and the electrowinning of zinc. It has also been successful in the electrowinning of copper from solutions obtained by leaching-solvent extraction. Electrowinning processes, however, are capital intensive. Improvement of the present technology should be intensely investigated especially when it is expected that such processes will increase greatly as a result of a shift from certain pyrometallurgical processes to pressure hydro metallurgy.INTRODUCTIONPyrometallurgy was used for thousands of years to produce copper and iron from their oxide ores!). Today it is still the only route to produce iron and steel and it is certain that it will remain so for many decades to come because pyrometallurgy is most suitable for the treatment of high grade oxide ores. Even when high grade iron ores are exhausted, it is possible to beneficiate the low-grade ores and produce pellets suitable for reduction in the blast furnace, which is a very efficient reactor, being a heat exchanger as well. Hydrometallurgy on the other hand can be traced to the time of alchemists in the Middle Ages when they were seeking to transmute base metals into gold, and thus were able to prepare many acids and bases which are the essential leaching agents."

Jan 1, 1997

By N. Krishna

The utilization of Electrochemical Impedance Spectroscopy (EIS) in conjunction with Atomic Force Microscopy (AFM) is a powerful surface characterization technique to study the role of sulfur formation during acidic oxidation of chalcopyrite. It has been established that the chalcopyrite dissolution kinetics is controlled by the formation of passive sulfur layer during leaching. The objective of the study was to characterize the intermediate sulfur layer formation at different oxidation conditions in acidic solution. The chalcopyrite samples were subjected to anodic oxidation and the oxidation process was analyzed using impedance spectroscopy. The sulfur growth on the chalcopyrite surface during oxidation was further analyzed using Atomic Force Microscope for sulfur roughness and grain size, peak height and sulfur growth.

Jan 1, 1999