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By SIMON TIMBILLAH

The chalcopyrite-molybdenite (Cu-Mo) flotation industry is increasingly turning to organic depressants as suitable replacements for inorganic reagents, such as NaHS, due to environmental and safety concerns as well as high consumption rates of the inorganic reagents. This presents an opportunity for improvements or design and synthesis of alternative reagents. Disodium carboxymethyl trithiocarbonate (Orfom® D8) depressant is an organic depressant with a carboxylate group on one end and a trithiocarbonate group at the other end. Fundamental results are shown regarding the interaction of the Orfom® D8 depressant in the bulk flotation of a Cu-Mo concentrate from an operating North American mine. Cyclic Voltammetry on pure copper and Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) measurements on pure chalcopyrite with Orfom® D8 depressant treatment are also reported. Through such characterization techniques a potential adsorption mechanism of Orfom® D8 on the mineral surface was identified and its depressant characteristics in the Cu-Mo flotation systems explained.

By P. N. Anyalebechi

The effects of a cross-hatched grooved mold surface topography, casting speed, and superheat on the morphology of solidifying shells of aluminum alloy 3003 have been characterized by a series of immersion tests. The cross-hatched grooves were 0.232 mm deep with wavelength or spacing between 1 mm and 15 mm. The shells solidified at casting speed of less than 10 mm/s on the 1 mm spaced cross-hatched grooved mold surface were fairly uniform with little or no localized variations in thickness. However, the propensity for non-uniform shell growth morphology was exacerbated by an increase in casting speed, melt superheat, and the wavelength of the cross-hatched grooves. This is provisionally attributed to their effects on interfacial heat transfer and wetting of the mold surface by the molten metal.

Jan 1, 2008

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By Goran Vukovic

The use of gas purging plugs in the copper industry is a widely used practice. They provide substantial improvements especially in anode refining furnaces, where savings in process time and energy are obtained as well as refractory wear and buildups inside the furnace are minimized. The newly developed system, enables purging plugs to be implemented in both stationary and tilting furnaces, is in operation in vessels on three continents. An additional advantage in these furnaces above all other benefits is the significantly improved melting rate. This innovative and patented gas purging system consists of a purging plug cooling device and a slidable, cooled piping system. It provides compensation for any thermal expansion in the furnace lining and minimizes the risk of undesirable copper infiltration. User experiences and results of this widely used system are reported in this paper.

Jan 1, 2014

By H. J. Garcia

Biodegradation of cyanide by microorganisms isolated from solids previously exposed to cyanide has been investigated. Initial sodium cyanide concentration was 300 ppm at pH 10.5. The kinetics of biodegradation were found to be first order with respect to cyanide concentration, and the overall reaction rate constant is k = 0.102 day-1. The activation energy and the frequency factor were determined to be { A }Ea = 5.45 Kcal/mol and A = 1.28 x 10-2 sec-1, respectively. Based on these values, thermodynamic properties of an intermediate activated complex were assessed. All tests resulted in cyanide concentrations less than 0.1 ppm in about 35 days at 250C, whereas at 350C the time of biodegradation to reach this cyanide level was 30 days. Kinetic data were also established to relate biodegradation to amount of inoculum. The maximum theoretically-attainable rate, Vm , and the optimum amount of inoculum, K , were determined to be 4.8 x 10-4 M NaCN/day and 7.5 % of amount of inoculum. With respect to the mechanism of biodegradation, cyanide was shown to decompose to carbonate, bicarbonate and ammonia. Titrimetric analyses revealed concentrations of 5.6 x 10-3, 4.8 x 10-3 M, and 70.2 ppm for carbonate, bicarbonate and ammonia, respectively. The average cell population was determined to be 3.75 x 108 cells/mL.

Jan 1, 1994

By Masatoshi Ogasawara

Saganoseki smelter & refinery operated two flash smelting furnaces, producing a combined 330,000 metric tons per year (hereinafter mtpy) of copper. In 1996, however, it successfully shifted to a single furnace operation while maintaining production at the same level. Since then, the production capacity has been further increased to the present 470,000 mtpy by technological improvements. Also, in order to reduce the converter load which represents a bottleneck in efforts to increase production, the matte grade was gradually increased and currently runs at 65 to 66% attaining the low copper content in the slag (hereinafter slag loss) of 0.7 to 0.8%. This paper introduces some improvements, recent operation results and thermodynamic analyses.

Jan 1, 2003

By Gus Van Weert

This paper describes the results of autoclave testwork where ferric nitrate was hydrolysed in the presence of certain cations and anions and the resulting hematite analyzed for foreign constituents. For the cations Zn++, Ni++, Cu++, and AI+++, selectivity factors of over 107 were found. Magnesium gave 3.106. These factors are calculated as Me/Fe in solution over Me/Fe in the hematite; Me representing the metal in ion added. As-a result of the testwork at Delft University of Technology, BUDELCO (the Netherlands electrolytic zinc producer) ran a series of ferric nitrate hydrolysis tests in the presence of 10 additional trace elements. Impurity levels were prejudiced on Me2 EPHA extraction of iron from their zinc circuit, followed by HNO3 stripping. Good selectivity against base metals was confirmed, but trace elements forming anions (As. Sb) and sulphate were incorporated in the hematite. These BUDELCO results are also presented.

Jan 1, 1995

By Mansoor Barati

The present paper is based on a term project for final year undergraduate students, requiring them to evaluate a process for producing silicon from rice husk. The traditional method for production of silicon involves carbothermal reduction of quartz in electric arc furnaces at temperatures exceeding 2000 °C. The technology consumes a considerable amount of electrical energy as well as fossil fuels, resulting in significant CO2 emissions. A flowsheet for production of silicon metal from rice husk is laid out in this paper. The technology will consist of combustors, which will generate steam using the rice husk biomass, power generator, and electric furnace for reduction of the rice husk. Materials and energy balance calculations presented here indicate that such process can be operated independent of external electricity.

Jan 1, 2014

By E. Açma

In this study, the production of Cu, Co, and magnetic iron oxide from the ancient copper, slags, located in Küre-Turkey, is investigated. In the process under development, fayalitic slags containing 1% Cu, 0.43% Co are reduced in a D.C. arc furnace with coke or graphite additions. A metallic alloy, consisting of 3.8% Cu, 3.3% Co, 2.1% S, and the rest being Ice, is produced by granulation of the liquid metal. About 85% recoveries of Cu and C:o are achieved by hot sulfuric acid leaching of these granules followed by H2S precipitation. The, production of magnetic iron oxide is possible from the discarded leach solution, loaded v:ith FeS04, by using a method with geothite precipitation, dehydration, controlled reduction, and re-oxidation steps. The magnetic oxides produced have 20 m2Jg surface area, 1:8.3 aspect ratio, and the coercivity of 330-380 Oersted.

Jan 1, 1993

By Kenji Matsuzaki

A mathematical simulation model of the Imperial Smelting Furnace operation has been developed for purpose of improving the furnace operation. The model consists of top, shaft and bottom regions, Analysis in the shaft region is based on differential heat and materials balances taking account of reaction kinetics and heat transfer rates, and those in the top and the bottom regions are based on heat and materials balances under a steady-state condition, Longitudinal distributions of process variables such as temperatures of gas, sinter and coke, gas composition and fractional conversion under a practical operating condition were calculated, With this model, the furnace performance under various operating conditions also can be shown reasonably predicted,

Jan 1, 2003

By Malsuzaki. Kenji

A mathematical simulation model of the Imperial Smelting Furnace operation has been developed for purpose of improving the furnace operation. The model consists of top, shaft and bottom regions. Analysis in the shaft region is based on differential heat and materials balances taking account of reaction kinetics and heat transfer rates, and those in the top and the bottom regions are based on heat and materials balances under a steady-state condition. Longitudinal distributions of process variables such as temperatures of gas, sinter and coke, gas composition and fractional conversion under a practical operating condition were calculated. With this model, the furnace performance under various operating conditions also can be shown reasonably predicted.

Jan 1, 2003

By Takuya Shinagawa

After vitrification of the residues from a municipal solid waste incinerator, the vitrified products can be used as a construction material, and the dust can be used as raw materials for the non- ferrous industry. The NKK electric-resistance furnace is operated under a reducing atmosphere, and heavy metals such as zinc and lead in the ash vaporize to form dust. Also, dust from the NKK electric-resistance ash melting furnace is composed of water insoluble zinc and lead components and water soluble NaCl and KCI. This is why, The concentration of zinc and lead in the dust after washing is sufficiently high for the dust to be used as a raw material for the zinc and lead industry. NKK developed a heavy metal recovery process in which zinc and lead in the dust are reclaimed as a raw material for smelting by making the best use of the characteristics of the dust.

Jan 1, 2002

By Stavros A. Argyropoulos, Michael Trovant, Norman J. Goudie

"Two studies were carried out to estimate the thermal resistance of various interfaces using experimental and computational techniques. Three types of interfaces were examined. The first study investigated metal-mold interfaces, and the second study focused on metal-metal and metal-oxide interfaces.For the metal-mold interface, the air gap size was measured and subsequently correlated with the interface thermal resistance. The procedural details are outlined for the development of a correlation which predicts thermal resistance as a function of air gap size.Investigation of the metal-metal and metal-oxide interfaces employed data from a series of experiments as input into a model, which solved the inverse heat conduction problem in terms of a resistance estimate. These experiments, involved dipping a cold cylindrical metal into a liquid metal or liquid oxide, respectively. Under these conditions, a shell freezes around the cylindrical addition and a thermal resistance develops during the time period which shell exists . The Heat Transfer Coefficient (HTC) at the addition shell interface differs significantly among the various types of metals and oxides used. In the case of an oxide shell, the (HTC) is about an order of magnitude lower than the (HTC) of the metal shell.INTRODUCTIONIn many metals processing operations there is a need to estimate the thermal resistance at metal-metal, metal-oxide, metal-mold interfaces. This need was further intensified with the recent proliferation of mathematical models, which predict various transport phenomena events. There are many factors which can influence the magnitude of the interfacial thermal resistance. Some of the factors, among others, are as follows: contact temperature, metal thermal conductivity, apparent contact pressure, surface roughness, interstitial gas conductivity, and interstitial gas pressure.In this paper, two studies are reported on the estimation of thermal resistance. The first involves, the development of heat transfer coefficient-air gap relationships at the metal-mold interfaces. The second includes, estimations of thermal resistance at the addition-shell interface. The former case is encountered in the metals solidification and the latter during the melting and/or dissolution of additions to liquid metals or slags."

Jan 1, 1999

By Moelans. N.

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NilNiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at I 100 and 1200 °C and pO2values between 10-3 and 10-12 bar were obtained. The measurements were evaluated with thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By N. Moelans

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NiINiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at 1100 and 1200°C and pO2 values between 10-3 and 10.12 bar were obtained. The measurements were evaluated with? thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By Evgueni Jak

Pyrometallurgy is an important sector of modern industrial society actively participating in solving current environmental, economic, materials scarcity and other challenges. Recent advances in analytical methods, experimental techniques, thermodynamic, phase equilibria and process modelling tools provide new opportunities to increase the productivity of pyrometallurgical reactors, the treatment of complex feeds and metal recoveries. Fundamental theoretical models can now be used to make a significant next step towards the development and implementation of computerised models describing real industrial processes—Virtual Reactors, and computer-aided smart-decision-making systems that may be called Pyro-GPS by analogy to GPS; these developments can facilitate knowledge-based improvement and optimisation strategies. The implementation of these improvements require ongoing collaboration between researchers, industry and government.

By Debbie Marshall

Process water is an important consideration in the development of a nickel laterite project. Depending on the location of the ore body, sufficient fresh water may not be available and it may be necessary to use seawater (or saline groundwater) for ore preparation. This introduces various species, which have major effects on materials of construction and leaching chemistry. This paper summarizes batch testwork completed at the Falconbridge Technology Center. The leaching behaviour of eleven different laterite ore samples were compared using seawater and fresh water. For brevity, six of the eleven samples are reported here-the other five samples showed similar results. Each ore type was leached under identical conditions in both freshwater and seawater and the leaching chemistry compared. The batch test results were confirmed in a continuous pilot plant, and leach kinetics for the two systems were compared. Keywords: high pressure acid leaching, laterites

Jan 1, 2004

By Gui-fang ZHANG, Zhe SHI, Lei GAO

Secondary V-recycling slag, an industrial waste containing high gallium is being dumped continuously, which causes the loss of gallium. Thus, the alkali fusion process was employed to recover gallium from this slag. The effects factors on extraction of gallium such as roasting temperature, roasting time, alkali fusion agent concentration and CaO concentration were investigated in the paper. The experimental results indicated that excessive roasting temperature and roasting time is unfavorable to the recovery rate of gallium. The appropriate roasting temperature and duration are 1000 and 2 hours, respectively; The appropriate proportioning of Na2CO3: NaOH is 2:1 when the concentration of alkali fusion agent weighs 0.4 times the mass of the slag; In order to remove SiO2 from the leaching liquor, CaO should be used as an additive in the roasting process. The appropriate concentration of CaO should weigh 0.2 times the mass of the slag. Employing these optimal alkali fusion conditions in the roasting process, gallium recovery is above 90%

Jan 1, 2015

By Kandipati Sreenivasarao

A promising method for removing heavy metal ions from dilute effluents is ion- or precipitate- flotation, in which a suitable collector is added to form hydrophobic metal-collector complexes or compounds that can be collected as foams. We have successfully removed Cu(II), Cd(II), and Pb(ll) from dilute solutions using sodium dodecylsulfate and ethanol as collector and frother respectively. However the process would not be economically viable unless the collector could be recycled, and the heavy metals recovered in a concentrated, preferably marketable, form from the foams. We investigated four different methods to decompose heavy metal-dodecylsulfate complexes, namely precipitation of hydroxides, precipitation of sulfides, chemical stripping, and electrolysis. We compare the performance of these methods. In each case the observed behavior is related to known thermodynamic data, and potential applications are discussed.

Jan 1, 1995

By Michael D. Odekirk

The U.S. Bureau of Mines investigated solvent extraction methods for recovering scandium from water leach filtrates of sulfated tantalum tailings. These complex solutions typically contained 20 or more metals in significant quantities. Two commercially available organics, DEHPA and PC-88A, were identified as effective scandium extractants. The two organics were tested in continuous solvent extraction circuits to compare loading and stripping kinetics, recyclability, and general processibility. Results showed that 95 pct of the scandium, greater than 80 pct of the zirconium, and only small amounts of other solubilized metals were extracted. Scandium was stripped directly as a 3.6 pct Sc precipitate when a 3n NaOH liquor was used as the stripping agent. This precipitate was subsequently upgraded to 94 pct ScE3 via a selective HE leach.

Jan 1, 1993