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By M. Urda-Kiel

Stainless steel is increasingly used as a cathode starting sheet. It was shown earlier that even when depositing copper on copper, a substrate-influenced zone appears in the deposit structure, followed by a transition zone and finally by the electrolysis-influenced structure. On copper, the substrate-influenced zone has a thickness of twenty micrometers and on titanium, eventually more than fifty micrometers. Initial nucleation and growth have a considerable influence. In this paper, copper was deposited in a channel cell on four different 304 stainless steel substrates: mechanically polished and anodized, respectively, at 0, +400 and +800 mV/SHE in 1M H2SO4 at 20°C. Copper was deposited under electrowinning conditions after solvent extraction (SX) (40 g/l Cu++, 180 gh/l, H2SO4, 20 or 60°C). The results showed that, although Auger surface analyses of the substrates were only slightly different one from another including the oxide thickness, nucleation and initial stages of growth were very sensitive to the surface treatment of the substrate. Potential step and current step methods gave similar results : progressive nucleation followed by 3D diffusion controlled growth. The highest nucleation frequency was observed on stainless steel anodized at 0 mV/SHE, under various electrolysis conditions. The potential influence of these findings on industrial practice is discussed.

Jan 1, 1999

By Burkhard Seeger et al.

The oxidation of copper sulfides can be highly accelerated in the presence of nitrous gases (NOx) as reaction catalysts. Sulfur and sulfate are simultaneously produced in this highly exothermic reaction. This process, carried out in sulfuric acid medium, is performed at an approximately normal pressure and at a temperature of around 110 °C, in a closed container, adding either oxygen or air. The oxidation is automatically controlled through a computer. The process covers the following steps: Catalytic oxidation, filtration and crystallisation of the hot concentrated liquid, electrowinning, mother liquor treatment through jarosite formation, recovery of dissolved copper and zinc and regeneration of industrial water, and non-soluble residue treatment with extraction of sulfur and recovery of silver and gold. No combustibles are needed. No air is contaminated, and no waste water is produced. Solid residues are in a stable, non-toxic and non-corrosive state of equilibrium. Risk of accident is low. Investment costs are small compared to those of the comparable pyrometallurgical process, and production costs are competitive.

Jan 1, 1999

By Bart Blanpain, Tom Peter Jones, Muxing Guo, Liugang Chen, Huayue Shi

Fayalite based slag is formed during the smelting process of secondary copper resources. It was found that with the presence of high ZnO, the slag became viscous, causing a slag tapping problem. In the present paper, the phase relations of the slag system ZnO-“FeO”-SiO2-Al2O3- CaO (ZnO = 0-12 wt%, Al2O3% = 0-15 wt%, CaO = 0-1.5 wt%, with iron saturation) at 1150 °C is studied by using quenching technique followed by phase identification and compositional analysis of equilibrated samples. The dependence of FeO and Al2O3 solubility in the liquid slag on the chemical composition of slag is characterized. Based on the experimental data, the solid fraction of the slag, which may considerably, influences the slag viscosity, at the tapping temperature can be reasonably estimated and, therefore an appropriate modification of the slag composition can be made.

Jan 1, 2016

By A. L. Davies

The MTDATA computer software package consists of a rigorous implementation of an algorithm for calculating chemical phase equilibria by the technique of Gibbs free energy minimization and a database of the thermochemical properties of common materials, such as slags, mattes, metals, gases and aqueous solutions. We have used MTDATA to contribute to our understanding of the chemical reactions occurring in several specific unit operations of the Kennecott Utah Copper Garfield Smelter. The following two examples illustrate the range of environments to which the method is applicable. Calculation of the liquidus phase relations of the FSF fayalite and FCF calcium ferrite slags helped in the early diagnosis of several operating problems. Calculation of the deportment of fluorine between the FSF offgas and the FSG scrubber liquor helped in the identification of operating conditions under which significant hydrogen fluoride concentrations could be introduced to the contact section of the acid plant. Without the painstaking assessment of solution phase properties undertaken over many years, these calculations would not be possible.

Jan 1, 1999

By G. St-Amant, V. Cloutier, E. Ghali, S. Jin, G. Houlachi

During the casting of lead-silver anodes, variations in cooling rates result in the formation of an uneven microstructure. The slowly cooled areas (SCA) have a coarser microstructure than that of the remaining part (called "the general zone"). The effect of anode microstructure on the electrochemical behavior was investigated using galvanostatic, potentiodynamic and electrochemical impedance techniques. The results show that the resistances for the two steps of the oxygen evolution reaction on the slowly cooled areas of Pb- Ag anodes are higher than that on the general zone. The double layer capacitance for the first step of the oxygen evolution reaction (OER) and the pseudocapacitance of the second step of OER on SCA are smaller than those on the general zone. The potentiodynamic results show that the amount of lead dioxide formed on the SCA is greater than that of the general zone of the anode. The potential decay curves after 30 minutes of galvanostatic polarization at 45 mA/cm2 show that the corrosion potential of the SCA is 200 mV lower than that of the general zone. This can lead to perforation because of the formation of a galvanic cell with a small anode and a large cathode.

Jan 1, 2000

By M. Frades, C. Frías, G. Díaz, A. B. Mejías

"In recent years, zinc recovery from flue dusts and other industrial wastes has been increased, offering to the market a large tonnage of secondary zinc oxides, which can not be processed directly to render high quality zinc because of the hazardous impurities and halogens content.The ZINCEXTM Technology has been commercially applied for more than thirty years and represents the most suitable solution to deal with secondary or crude zinc oxides due to its flexibility, simplicity, and cost-efficiency, allowing production of SHG electrolytic zinc and pure zinc sulfate salts thanks to the flexibility and selectivity of the zinc solvent extraction unit regarding to get rid of impurities.A dual plant able to produce electrolytic zinc and crystallized zinc sulfate has been engineered to provide a flexible and profitable solution to zinc market. A description of the study and the relevant achievements is presented in this paper.IntroductionZinc is a valuable commodity in the marketplace and can be recycled again and again and still maintain its physical and chemical properties. Zinc recycling offers both environmental and economic benefits such as reducing volumes of material that end up in landfills, saving energy by reducing the need for mining and smelting, and relieving environmental impact on the land and water, and conserving zinc ore [1].The supply of zinc able to be re-processed will be increasing from year to year according to secondary materials enter the recycling stream, and as a result, more recycled zinc will become available in the market. Thus, some existing zinc refineries are implementing an annexed treatment line to process secondary oxides in conjunction with primary zinc concentrates [2].The galvanized steel scrap is normally recycled in electric arc furnaces or in basic oxygen furnaces, which generates a large tonnage of zinc-bearing flue dusts (EAFD). Around one million ton EAFD is yearly produced at the USA and the EU, respectively. The flue dusts are treated commercially by pyrometallurgical ways such as waelz kilns, electrothermic furnaces, etc, to yield secondary zinc oxides that can not be processed directly to render high quality zinc because of the hazardous impurities and halogens content [3]."

Jan 1, 2008

By Laurence G. Dyer, David G. Dixon, John Rumball, Maziar Eghbalnia, Edouard Asselin

"Linear scan voltarnmetry was used to determine the reactions that occur during the cyanidation of petzite (Ag3AuTe2). Gold oxidation in petzite requires more oxidising conditions than are required for pure gold, it also does not achieve the same current (related to reaction rate). Tellurium oxidation occurs at a similar potential in water and cyanide, but as a component of petzite is impeded somewhat in water, likely due to the stability of the precious metals. Pre-treatment of petzite to oxidise tellurium in the absence of cyanide prior to gold recovery appears to be at least moderately successful.IntroductionWhile gold occurs most prevalently in its native form, many other gold bearing phases appear throughout natural systems [I]. Tellurides are a common group of such minerals, many of which also contain silver, often existing in association with native gold deposits. The six major gold-bearing tellurides are calaverite (AuTe2), sylvanite [(Au, Ag)2Te4], montbrayite [(AuSb)zTe3], krennerite [(Au1-x, Ag,)Te2], petzite (Ag3AuTe2) and muthmannite (AuAgTe2) [2]. While several other phases exist they are much more complex (i .e. buckhornite), which dilutes and confuses the influence of each specific component. Studies of gold tellurides have predominantly focussed on calaverite as it is the simplest and most common phase, however petzite, commonly found in Australia and North America, is the focus of this investigation.Gold processing via cyanidation has been operated for more than a century and is a highly effective hydrometallurgical treatment of native gold deposits. However, some gold alloys such as tellurides have proven to be somewhat less responsive under the same conditions. Several groups have shown that gold/silver tellurides are amenable to cyanidation, but are significantly more refractory than native gold [3]. Pre-oxidation steps have been tested to remove constituents that would consume cyanide such as sulfides. Such species are also linked to the precipitation of oxidised telluriwn, forming a passive layer, further inhibiting gold recovery [2]. It is uncertain to the definite reasons underpinning the refractory nature of precious metal tellurides in conventional cyanidation."

Jan 1, 2012

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 P. M. Pincheira Brown

The widely accepted inverse relationship between copper prices ail stocks, has been commonly used by analysts to explain the behavior of the copper market and to forecast film copper pries. However, empirical data have not shown such a clear relationship between copper prices and stacks. Existing evidence only indicates a weak tong-nut relationship that vanishes in some periods. In this paper a simple comprehensive model is provided which explains both parallel and opposite direction movements between prices and stocks. Former are explained mainly by stocks demand expansions-contractions while the latter are in essence due to increases in the supply curve. Furthermore, econometric estimations are provided, thus giving a powerful tool to forecast and explain price developments of the copper market.

Jan 1, 1999

By E. M. Alcântara

This paper describes some aspects about the relationship between copper electrorefining addition reagents and the hydrogen in the cathode. The conditions of electrorefining were studied by factorial design methods. The advantages of this technique are reduction in the number of tests, well organized experiments; improvement in productivity and reliability of results. The dosage of the two main addition agents, glue and thiourea, were varied simultaneously and compared with the hydrogen content in the cathode. The influence of these factors, as well their interactions were analyzed by statistical methods denominated ANOVA (Analysis of Variance). The increase of thiourea quantities, within of levels studied, influenced significantly at 95% confidence in the hydrogen content in copper cathode.

Jan 1, 1999

By Claire A. Chanenchuk

Catalytic Extraction Processing (CEP), a technology commercialized by Molten Metal Technology, Inc., a US.-based company, can convert industrial, household, and government wastes into commercial resources. CEP is an innovative elemental recycling technology that uses a molten metal bath to completely dissociate hazardous or toxic components of a feed and convert them to valuable products. The catalytic action of the molten metal bath converts the feed to its elemental constituents and the reducing atmosphere prevents the formation of any dangerous byproducts (NOx, SOx, dioxins, furans, etc.). Selective reactant addition allows engineering of valuable products from otherwise unexploited resources. Synthesis gas is generated from hydrocarbon feeds, ferro-alloys from metallic wastes, and ceramics from select inorganic species. Commercial-scale processing of multiple wastes and waste surrogates has been carried out at a destruction and removal efficiency exceeding 99.9999 wt.%, validating theoretical predictions. Unlike conventional hazardous waste treatment technologies, CEP offers resource recovery, minimal byproduct generation, and the potential for closed-loop recycling.

Jan 1, 1994

By V. Bredykhin

The efficiency of scrap processing depends firstly on reliability of information about its chemical composition. The paper presents the results of the investigation and development regarding solid copper alloy scrap in the range of lump size 40÷300 mm. Nowadays the sorting of lump scrap is done by two methods: 1. Sorting according to metals and alloys is done at places of scrap generation, and further till metallurgical processing each lot has its "certificate"; 2. Hand sorting of scrap is done according to the marks on solid items in special shops using proximate analyzers or manually by experienced workers. This sorting process is labor - consuming low efficient and involves mistakes. The informational method is a promising trend in the copper scrap sorting. The method is direct, i.e. as a result of sorting the chemical composition of each scrap lump or main elements is determined, and assured data of qualitative and quantitative composition are received.

Jan 1, 2006

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 Z. S. Wronski

In rapidly solidified Fe-Nd-B permanent magnet alloys, the content and distribution of Nd-rich intermetallic and Fe-phases determine coercivity Hc and remanence Br. Consequently, microstructure plays a crucial role in deter- mining the (BH) max-product of permanent magnets fabricated from these alloys. A study has been initiated to investigate changes in microstructure and the effects on magnetic properties as the material is processed from arc-melted ingot to melt-spun flakes and finally to a product consolidated by hot-forming. Anisotropic magnetization behaviour has been observed in rapidly solidified flakes after low-temperature annealing.

Jan 1, 1989

By O. C. Rojas

Improvements and modifications on lay out and process, from 1997 till 1998, are presented. Based on a Teniente Converter, started up 1993, a Strategic Development Plan was structured to increase the production efficiency and comply with the enviromental regulations, too. It considered the oxygen supplies to the Teniente Converter and Peirce Smith converters; reverberatory furnace shut down as a smelting unit; and the Teniente converter slag treatment through a combined process between a Slag Settler furnace and flotation. Also it included the off-gas handling and treatment.

Jan 1, 1999

By P. A. Olubambi

The effect of ore mineralogy on the bioleaching of metals from complex sulphides was studied by investigating the bioleaching of zinc and copper from a bulk complex sulphide ore from Ishiagu, Nigeria, using mixed cultures of Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum in mechanically stirred reactors at varying particle sizes. Mineral phases within the varied particle sizes of -53, 53, 75 and 106µm were identified using X-Ray Diffraction (XRD), while the elemental distribution within the varied particles sizes was determined by X-Ray Fluorescence (XRF) and Optical Emission Spectrometry using Inductively Coupled Plasma- Optical Emission Spectrometer (ICP-OES). Bulk ore and the leached residues were examined by X-Ray Diffraction. The highest bioleaching recoveries were obtained at particle size of 75µm, while particle size of 106µm gave the least recoveries. Lower recoveries at particle sizes of 53 and -53µm were as a result of their higher silica and siderite content which affects pH, iron mobility and oxidation.

Jan 1, 2006

By Yuan Zeping

The Guixi smelter is the first Outokumpu flash smelter in China .It was commissioned on December 31, 1985. Originally, the smelter was designed to produce 90,000 tonnes of copper annually. After the implementation of oxygen enrichment and other modifications, the smelter will reach its anticipated annual capacity of 200,000 tonnes of copper in December 1999. This paper describes the performance of the smelter, the first phase modification project and the second phase expansion project which have made Guixi one of the best copper smelters in the word through the use of existing and innovative technologies.

Jan 1, 1999

By P. Barrios

Over a period of one year, an in-depth investigation was carried out in a conventional copper refinery to understand the behaviour of silver in copper electrolysis. The increase in silver content in the cathodes increases almost linearly with the duration of electrolysis, and the silver content of the electrolyte between the electrodes shows similar behaviour. The silver content of the cathode deposited daily depends directly on the silver concentration of the electrolyte and this, in turn, is strongly influenced by its internal temperature. The average temperature between the electrodes rises from the first to the second and to the third crop, because of the increase in the distance between the electrodes and the heat generated by the passage of the current. The mechanism of dissolution of silver from the anode, and its passage to the cathode, are discussed. Following the change to the Isa system, it was proved that the results and conclusions are analogous. Based on these results, a reduction of more than 20% in silver losses in the cathodes was achieved.

Jan 1, 1999

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 Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006