Search Documents

By Florian Kongoli

While calcium ferrite slags have been successfully used in continuous copper converting for the last 30 years, ferrous calcium silicate slag was proposed about 8 years ago as an additional alternative for copper smelting. Although both slags are normal extensions of each other their phase relations have not been completely clarified. In this paper the liquidus relations of both slags have been quantified at various areas that cover both of them. The existing experimental data have been first reviewed and discussed in relation to the solidification procedure. An original physical model is then used to predict various diagrams of the liquidus surface of both slags. It is shown that the ternary liquidus diagrams normally used for FeOx-SiO2-CaO system are not suitable for industrial slags. The new model diagrams of Fe/CaO versus SiO2 and Fe/SiO2 versus CaO as well as Fe/CaO versus Temperature and Fe/SiO2 versus temperature are proven to be much more convenient for ferrite and ferrous calcium silicate slags. Based on these diagrams the effect of SiO2 and CaO on the melting temperature is quantified. The effect of Cu2O is also quantified through the model. Some Fe/CaO versus Cu2O and Fe/SiO2versus CaO at various copper contents are predicted and the results show good agreement with the experimental data. It is also shown that in the presence of liquid copper, Cu2O is dissolved in the slag depending on the oxidation degree of the system and might lower the liquidus temperature. Some discussions are also presented taking into account plant observations and important conclusions are drawn for copper smelting and converting

Jan 1, 2006

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and' presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995

By Henrique Hesse, Rosana de Cassia de Souza Schneider, Wolmar Alípio Severo Filho, Ezequiel Bavaresco, Rodrigo Klamt, Luciano Roni Silva Lara, Luciano Dornelles

Alkyd resins are used in surface treatment. They are product of the glycerolysis followed by polymerization. In the present work it was studied methods of alkyd resin production from crude glycerol compared with resin produced with pure glycerol. This glycerol corresponds to 10% of the final products in the biodiesel production. The crude glycerol was partially purified with neutralization, flotation and adsorption. The experiments were accomplished with temperature control, inert atmosphere and with several quantities of the substrate. For the products characterization physic-chemistry methods, infrared spectroscopy and hydrogen nuclear magnetic resonance were used. According to the observed results, the resins obtained with crude glycerol have presented similar properties of the classic alkyd resin produced with pure glycerol. The exploitation of the crude glycerol reduces the stages and costs of the process.

Jan 1, 2008

By Corale L. Brierley

Bioheap leaching, commercially applied for secondary copper ores and agglomerates, is rapidly gaining popularity. Bioleaching of chalcopyrite concentrates is imminent. Copper bioheap leaching encompasses the bioleaching of acidified and agglomerated coarse, secondary copper ore, stacked on permanent or on/off pads. The stacked ore is irrigated with raffinate containing bacteria. LME-grade cathode copper is produced by SX/EW. Low capital and operating costs, rapid start-up, environmental benefits, operational simplicity and a good performance record make bioheap leaching an attractive technology. This paper looks at the state-of-the-art of copper bioheap leaching and chalcopyrite concentrate leaching, the risks, the benefits, costs, bioheap performance and the future prospects of copper bioleaching.

Jan 1, 1999

By Gustavo A. Munoz

Activated carbons owe their adsorption capacities to their extensively developed pore network structure. As a result, these adsorbents generally exhibit high specific surface areas. Currently, granular activated carbons produced from coconut shells are traditionally used for gold recovery by adsorption from cyanide leaching solutions. Magnetic activated carbons (MACs) for gold recovery from cyanide solutions produced from sources other than coconut shells have been developed at the University of Utah by mixing a magnetic precursor with a carbon source, and treating the mixture under controlled conditions of temperature and gas phase composition. The pore size distribution of the activated carbons is dependent on the degree of activation, among other factors. The significance of the MAC pore size distribution on gold adsorption kinetics and gold adsorption capacity is presented.

Jan 1, 2003

By Jean Frenay

Bacterial leaching tests have been carried out on Portugese pyritic ores containing zinc, copper, lead and silver as valuable elements. Both indigenous and isolated strains of Thiobacillus ferrooxidans were used. During the tests the factors pH, Eh and dissolved oxygen were measured and related to the leaching activity of the bacteria. Different means to estimate or determine the real bacteria concentration were examined. The influence of nutrient media and particle size has been evaluated. The role of galvanic couples was studied by electrical linking of mineralogical samples of pyrite, sphalerite and chalcopyrite. Leach residues were examined by optical microscopy to follow the mineralogical alterations during the leaching. The results show a rather good leaching of the sphalerite. However, the dissolution of copper from chalcopyrite is much more difficult, 50 % recovery never being obtained.

Jan 1, 1985

By José C. Escobedo B.

A kinetic study of nitrogen dissolution in a. electromagnetically stirred Co-Cr-Mo alloy bath was made. The experiments were carried out at 1693, 1723 and 1743K of temperature, with a nitrogen pressure of 0.67 atm. The mass transfer coefficients were obtained, finding that their values increase as temperature grows. The true kinetic constants were calculated. It was found that at 1693K of temperature, the kinetics of the nitrogen dissolution process is controlled by a mixed mechanism involving both transport processes and chemical reaction, while at 1723 and 1743K of temperature, the kinetics is controlled only by transport processes mechanisms.

Jan 1, 1995

By Y. Mori, K. Kawanaka

The permeability changes during the sintering of the feed for the Imperial Smelting Process (ISP) were investigated using an experimental sintering pot, as well as with a mathematical model. The results obtained were as follows. The blowing resistance in the sintering bed changes as the sintering reaction proceeds. It increases at the beginning of the reaction when the temperature of the bed is still low. Then it decreases as the reaction continues, accompanied by an increase of the bed temperature. The increase of the blowing resistance in the bed during the sintering process mainly occurred in the drying zone, and was comparatively small in the reaction and cooling zones. Based on Erugen's equation, the change of the permeability during sintering is explained by the decrease of the apparent fractional void volume in the drying zone of the bed.

Jan 1, 2000

By Francis Vanbellen

In Union Minière's Hoboken smelter and refinery for complex non-ferrous materials, the treatment of recycling products, containing precious metals, occupies a dominant place. For all feed materials, the first step, prior to their treatment, is to classify them in order toselect an accurate and economical procedure for sampling as well as to dispatch them to the optimal process scheme. More than 150 different procedures for sampling are commonly used. The most important ones are briefly discussed in the paper. Precious metals bearing recycling materials vary widely with respect to their physical aspect, their chemical composition and the value of their precious metal content. All these parameters are taken into consideration to select the most appropriate process among the multiple possibilities of Union Minière's flexible integrated flow-sheet. Different stages of the operations as well as the main flow-sheets are described.

Jan 1, 1995

By T. A. Edison

A distinct hydrocarbon maturation anomaly coincides with the Gold Acres open pit, Nevada (Figure 1). Both atomic hydrogen to carbon (H-C) ratios and reflectance measurements of contained organic matter indicate significantly higher maturity in samples collected within the confines of the open pit than in samples from the surrounding region (not shown in Figure 1).

Jan 1, 1987

By C. J. Lewis

This presentation concerns calcium oxide-better known as high calcium quick lime High calcium quicklime is produced by calcining high calcium limestone, mostly in the many rotary kilns located throughout the United States and Canada. This paper presents suggestions on the handling of lime based on field experience. The subjects covered are chemical analyses, transporta¬tion, lime storage, lime slaking to form a water slurry of calcium hydroxide solids, slurry transportation, slurry viscosity, and scaling of lime slurries. It is hoped that the comments on the foregoing areas will be of use to those designing or operating lime systems.

Jan 1, 1992

By Yoshihiko Maeda

It is said that the 21st century will be an era of the remedy of the global environment. In order to reserve natural resources for the future and to avoid the dispersion of heavy metals after usage and to avoid pollution problems, it is extremely important to recycle heavy metals as much as possible by reasonable recovery procedures. The nonferrous metal industry is expected to play a important role in the recycling of heavy metals that are originally their products. From the depressed metal price experienced in Japan in 1980'h due to the sudden change in current exchange rate between US dollar and Japanese yen, one of major nonferrous metal company, Dowa Mining, has diversified its business area not only to the so-called down stream, but also to the environmental business including metal recycling, industrial waste treatment and soil remediation by utilizing technologis and facilities once used or still used for mining and smelting of copper, zinc, lead and precious metals. In this paper some of these applications will be presented.

Jan 1, 2003

By Magdalena Regel-Rosocka

Extraction of zinc(II) from hydrochloric acid solutions is discussed. The literature on the extraction of zinc(II) in the presence of iron(III) and iron(II) with various basic and solvating reagents has been reviewed. It was found that tributyl phosphate (TBP) is the best compromise, and permits both effective extraction of zinc(II) and its stripping with water. The process was confirmed in a continuous laboratory mixer-settler circuit.

Jan 1, 2003

By G. A. Irons, G. S. Hanumanth

A three-dimensional mathematical model for the electric furnace of Cominco's Kivcet process was developed to compute the electric field intensity, power dissipation, temperature and velocity distributions in the furnace. A number of simulations of the electric furnace operation were carried out for various electrode immersion depths and electrode currents. The results showed that the current penetrated the bullion layer, generating high current densities in a layer approximately 0.3 m thick located in the slag/bullion interface region. An increase in the electrode immersion depth increased the furnace power as well as slag temperatures, and generated more vigorous bubble stirring and thermal homogeneity in the slag. For a given applied current, the computed power was in reasonable accord with the measured power input. The calculated temperatures were in rough agreement with the tapping temperatures of slag and bullion.

Jan 1, 2000

By C. R. Bennett

The first phase in the design, development and implementation of a comprehensive computational model of a copper stockpile leach process is presented. The model accounts for transport phenomena through the stockpile, reaction kinetics for the important mineral species, oxygen and bacterial effects on the leach reactions, plus heat, energy and acid balances for the overall leach process. The paper describes the formulation of the leach process model and its implementation in PHYSICA+, a computational fluid dynamic (CFD) software environment. The model draws on a number of phenomena to represent the competing physical and chemical features active in the process model. The phenomena are essentially represented by a three-phase (solid-liquid-gas) multi-component transport system; novel algorithms and procedures are required to solve the model equations, including a methodology for dealing with multiple chemical species with different reaction rates in ore represented by multiple particle size fractions. Some initial validation results and application simulations are shown to illustrate the potential of the model.

Jan 1, 2003

By Y. F. Jia

Arsenic constitutes a major contaminant for the hydrometallurgical industry. Its removal and immobilization from process effluents typically involves lime neutralization and co-precipitation with ferric iron (Fe (III)/As(V)>3). Alternatively, precipitation of scorodite (FeAsO4?2H2O (cr)) may be applied to arsenic fixation. The mechanism of arsenic fixation in the former process has been suggested to be surface adsorption. Unequivocal characterization of these products is difficult because of their amorphous nature hence a variety of methods need to be applied including the particularly powerful method, extended x-ray absorption fine structure (EXAFS) spectroscopy. In this study, we have investigated the preparation of arsenate-adsorbed ferrihydrite with the purpose to compare its structure to that of Fe(III)-As(V) co-precipitates and scorodite (both amorphous and crystalline). Furthermore the solubilities of these Fe(III)-As(V) solids are measured as a function of pH. Their structures are elucidated and correlated to their solubilities and thereby the application of these findings to the practice of arsenic removal and disposal is assessed.

Jan 1, 2003

By John M. Boyle

The use of high vacuum mercury retort recovery as a safe and effective means of removing mercury from mercury hazardous waste solids rendering them non-hazardous and recovering mercury suitable for recycling.

Jan 1, 1995

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified.

Jan 1, 2006

By A. H. -J. Siegmund

Since the last survey of lead smelters in 1987, the lead industry has experienced many changes. Technological innovations, in combination with a dramatic shift in the market structure as well as more stringent government regulations, caused major upheavals in many different areas. Therefore, a new survey was performed to review the progress in the technology of lead recovery over the least decade. The newly conducted survey reflects all current phases of the world's primary lead production, from charge preparation to refined metal shipment. It was prepared by sending questionnaires to individual companies, and the detailed statistical data of this survey are presented. In considering the data developed from the survey, it should be recognized that the primary lead industry is at a crossroad where novel technologies will gradually substitute the sinter machine - blast furnace operation in the new millennium.

Jan 1, 2000

By Robert D. Boiler, Bill Wilkie

"There is a wide choice of different types of woven filter media for hundreds of different filtration applications. Factors such as type of fiber, synthetic polymers used, weave style, fabric finishes and fabrication techniques all play an important part in selecting the best choice for a specific type of filter and process application. The purpose of this paper is to offer some basic knowledge of these factors and how they can impact the performance of a filter, the life of the media and the overall cost of operation through case studies of actual plant filtration applications.IntroductionThe use of woven filter cloth in liquid/solid separation applications is generally well known. Woven filter cloth, by the nature of the weaving process, offers unique consistency and repeatability when compared to some other filter media such as needled felts, papers, sintered structures and knitted cloth. This unique consistency and repeatability is particularly applicable to woven filter cloth produced using monofilament fibers. These fibers are consistent in shape and form the basis for a woven cloth with predictable pore size and throughput characteristics. Woven filter cloth can be used in most wet filtration applications. Typical examples are the separation of chemical and pharmaceutical solids from process liquors, waste stream solids capture, liquid foods clarification, mining separations, and polymer filtration.EnvironmentOne of the first considerations is the environmental demand of the given process. Though it is tempting to look immediately at the particles in a filtration process, it is often better to consider some of the more basic needs of the system. There are numerous materials available, both synthetic and wire cloth. Each has its own unique set of properties."

Jan 1, 2012