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By A. V. Tarasov

There are still a number of copper smelters in the world using the roasting and smelting process flow diagram for treating sulphide raw materials. The technical, economic and environmental performance indicators of such operations are inferior to the respective indicators of advanced processes. First of all with respect to copper and sulphur recovery: 95% and 75% as compared with 98% and over 90%, respectively. Based on the studies of the single-stage smelting process to produce white metal and blister copper conducted during recent years an analysis of the feasibility of roastingsmelting technology improvement was carried out in the Gintsvetmet Institute to substantially increase the copper and sulphur recoveries. On the basis of this analysis, it was proposed to modernize the technology and equipment within the framework of the existing process flow-sheet. The proposed modernization implies an increase in the roasting temperature; higher desulphurization degree in the process of roasting; a number of modifications in the roaster design depending on the particular conditions of a given operation; addition of lime flux to the feed charge to roasting; and transition to combined calcium-silicate smelting slags. The metallurgical and energy computations made have indicated that the proposed modifications of the technology will improve the copper and sulphur recovery up to 98% and 90%, respectively. The required capital investments have been estimated using as an example a particular copper smelter, the payback period determined taking into consideration additional output, fuel saving and a reduction in fines for sulphur emissions. For comparison, the capital cost of a smelter modernization is given for change-over to basically new autogenous Ausmelt, Outokumpu and V anyukov smelting technologies.

Jan 1, 2007

By D. M. Bastidas

The reduction of copper sulfide and copper oxides originated during artificial tarnishing of copper was studied using potentiodynamic potential/current density experiments. Six copper surface treatments were considered: mechanical polishing; indoor exposure for 7 days; chemical etching in 1.6 M nitric acid; chemical etching and heating at 160°C; and chemical etching and dipping in a 9x10-4 M or 0.9 M potassium sulfide (1(25) solution at 70°C. Cuprite (Cu20) and chalcocite (Cu2S) were the main compounds formed. A linear relationship with the square root of the scan rate (v) was obtained by plotting the potentiodynamic potential/current density for the tarnish dissolution processes. A relationship between potential and current density cathodic peaks was not obtained, according to Müller's model, showing a proportionality factor with the dimensions of a resistance.

Jan 1, 2007

By M. Sanchez

In the last decades, the Chilean copper mining and metallurgical industry have had to modify their technological processes to meet the environmental regulations implemented by the Chilean government, and also to support the pressure of the public opinion. Thus, air quality standards for sulfur dioxide and particulate matter (primary and secondary), plans for reducing emission of arsenic by the Chilean copper smelters, effluents discharge limits, among others regulations were applied by the environmental agency. Additionally, agreements on cleaner production were carried out by mining sector and government. Now, a draft law on mine closure, and another on environmental mining wastes (abandoned mines) are being discussed by the authorities and the mining sector. In the context, production and environmental impacts in different ways to produce copper in the Chilean mining industry are reviewed and regulatory tendencies as well as abatement technologies today used are exposed and discussed in this presentation. Pyro, hydro and electrometallurgical processes employed and their current effluent and contaminants are presented showing various alternatives of treatment in the copper industry. An update of regulations established in Chile vis a vis copper production, with an especial attention to mine closure are also presented.

Jan 1, 2007

By C. G. Anderson

With demand and prices for copper and gold at near record high levels, coupled with a lack of readily treated orebodies, the emergence of environmentally sound hydrometallurgical treatment of enargite concentrates has become a priority. This paper will outline the application the industrially proven technologies of low pressure and temperature NSC (Nitrogen Species Catalyzed) pressure leaching and ASL (Alkaline Sulfide Leaching) for the recovery of copper and gold from enargite. Copper can be recovered as cathode metal or as a clean concentrate suitable for smelting. Gold is recovered by smelting, conventional cyanidation or alkaline sulfide hydrometallurgy. Coupled with this is the effective precipitation and stabilization of arsenic as scorodite and ferrihydrite.

Jan 1, 2007

By I. S. Laitinen

Outokumpu Technology has recently introduced new technology in both copper electrorefining and electrowinning. This technology includes, among other things, a new permanent cathode (Outokumpu Permanent Cathode) and new busbar technology (Outokumpu Double Contact System). The new technology has already been tested in commercial scale cells. To get a better understanding of the busbar system a multiphysical simulation model of the electrowinning and electrorefining cells was developed. A mathematical model of electrical conduction and heat transfer in a copper electrolysis cell was developed from partial differential equations. The model was expanded to a cell group including seven electrolysis cells connected electrically in series. The model was solved numerically using the finite element method (FEM). Using the model, different intercell busbar systems were simulated. Typical electrical disturbances, like loose contacts between cathodes and the main busbar and short circuits between electrodes, were included in the simulation. The results of the simulation runs with conclusions are presented in this paper.

Jan 1, 2007

By Louis J. Cabri, Donald Hoy

"Samples with contrasting gold mineralization were studied quantitatively prior to metallurgical tests. The AD samples are coarser-grained and characterized by abundant Sb minerals (jamesonite, berthierite, stibnite). The finer-grained MW sample has abundant pyrite and pyrrhotite, with arsenopyrite and galena next in abundance. A large number of gold mineral particles were determined by SEM investigation of hydroseparation concentrates, ranging from 150 to 597 per sample. The grain-size distribution of the gold minerals shows evidence of bimodal grain-size distributions (volume %), with the coarse fraction being most significant in sample MW-1 (maximum ECD=308µm). The coarsest gold minerals in the AD samples range from 139µm to 281µm ECD.The deportment of gold minerals is as electrum, aurostibite, native gold, and a possible new mineral (AuNiSb4). Gold also occurs in nisbite. The gold minerals are dominated by electrum in three samples and aurostibite is next in abundance. The major gold minerals are probably representative of three stages of gold mineralization. The first stage is represented by electrum, which is partly to completely replaced by Sb-rich mineralization forming aurostibite, and the last stage is native gold, often occurring as rims on one or the other earlier gold mineral. The gold minerals are strongly associated with sulphides in the AD samples (55 to 60 vol.%). At the grind used for the hydroseparation the liberated gold mineral quantity (volume %) is also significant, ranging from 65% for sample MW-1 to 30 to 37% for the AD samples.INTRODUCTIONThe Clarence Stream deposit is located 70 km south-southwest of Fredericton and 25 km northnorthwest of St. George, south-western New Brunswick, near the international boundary with Maine (Fig. 1)."

Jan 1, 2007

Roasting of molybdenite concentrate is an important stage in the production of commercial molybdenum trioxide. The oxidation kinetic and mechanism of molybdenum sulfide concentrates from two plants were investigated at temperatures from 444 °C to 640°C. The rate of reaction was determined for thin layer samples in a muffle furnace at controlled temperatures, oxygen excess and removal of sulfur dioxide. For both concentrates the rate of reaction is fairly slow at temperatures below 500°C and remains fairly constant from 540 to 600 °C. It was observed that the concentrate from the first plant presents a tendency for sintering or glazing at temperatures above 620°C, whereas the same phenomena was observed at 20 or 30 °C higher temperature for the second concentrate. A kinetic model of two reactions, involving the formation of Mo02 as intermediate oxide for the production of Mo03 is proposed and activation energies of 23.0 and 20.8 kJ/mol for the first and second reaction were calculated for temperatures between 520 °C to 600 °C. These low values of activation energies indicate that the overall rate of oxidation is controlled by mass transfer, particularly in a porous layer of oxides. Therefore, the renewal of the surface by mixing and motion of the concentrate layer is of great importance. Sublimation of Mo03 becomes significant for temperatures above 650 °C.

Jan 1, 2007

By I. Dimitrov, S. R. McCutcheon

"Industrial-grade limestone is found in both the Lower Silurian La Vieille Formation and Upper Silurian LaPlante Formation of the Chaleurs Group in northern New Brunswick. Currently, between 150 000 and 200 000 tonnes of limestone are produced per year from the proximal facies of the LaPlante Formation at the Sormany quarry of Elmtree Resources Ltd., located west of Bathurst.The proximal facies of the LaPlante Formation was deposited on the margins of tectonically uplifted Ordovician terranes. This facies comprises stromatoporoidal-algal bindstone intercalated with wackestone, packstone, and floatstone in variable proportions. The distal facies comprises calcareous shale and minor limestone deposited deeper offshore.Folding and faulting related to Middle Devonian Acadian tectonism have caused an increase in the apparent thickness of the limestone sequences, especially adjacent to the regional Rocky Brook-Millstream fault. Structural and stratigraphic observations indicate that some of the limestone bodies in the area have been tectonically displaced from their site of deposition.A variety of prospecting techniques was used to locate new limestone resources, including geological mapping, airborne and ground electromagnetic surveys, and satellite remote sensing. Clastic rock units above and below the LaPlante Formation have distinctive properties that help to trace the intervening limestone along strike. Because of water-saturated glacial cover, thick vegetation, and the small size of targets, airborne geophysical methods did not prove effective in delineating limestone beds, but aeromagnetic surveys helped map the underlying clastic unit. The remote-sensing data and especially high-resolution digital elevation models helped in identification of karst topography related to limestone."

Jan 1, 2007

By I. V. Kojo

Continuous development of technologies has been self-explanatory for Outokumpu Technology's engineers for decades. The aim in the development has always been the improvement of profitability of the copper production but also the sustainability of the processing i.e. high copper recovery, low external fossil based energy utilization, high emission captures and of course low operation and investment costs. Outokumpu Technology's long-term view of the development is a change towards continuous processes and elimination of number of unit operations in smelting i.e. elimination of possible sources of emissions. Outokumpu blister smelting processes i.e. Outokumpu Direct-to-Blister Flash Smelting and Kennecott-Outokumpu Flash Converting have shown excellent operational results during the years of operation and it is expected that soon more than 10 % of the world primary copper is produced by these technologies. The paper will give some background of this development trend.

Jan 1, 2007

By N. Dahata

Earlier research has indicated that an addition of titanium master alloy to aluminum alloys, results in improved fillability, grain refinement and finer pores. B206 alloy differs from other alloys used in automotive industry, with lower titanium level. This paper examines the effect of alloy chemistry (copper and titanium levels) and grain refinement (A1-5`)oTi- 1%B grain refiner) on grain size, microstructure and microporosity in B206 aluminum alloy. In this study, characterization of grain size, microstructure and microporosity was carried out using light optical microscopy (LOM) and scanning electron microscopy (SEM). Results have shown that the addition of 0.05 wt % titanium resulted in grain refinement of B206 alloy. With an increase in titanium to 0.25 wt further grain refinement, much reduced pore size and uniform distribution of pores resulted. These results suggest that B206 with proper addition of titanium has a promise as an alloy for automotive casting.

Jan 1, 2007

By C. Cortés

Flotation is a highly interactive process where a change or disturbance in any part of the circuit results in different final grades and recoveries. This high variability of the circuit metallurgical performance complicates the diagnosis of the scavenger stage at the end of the line, as copper losses in the final tailings are erratic and not totally a consequence of problems in the scavenger section. The assessment of the scavenger performance requires a more elaborated procedure than that used for others stages of the circuit. This communication describes the application of an approach that combines results of laboratory flotation tests with those of surveys performed at the plant. The approach is based on running surveys in one of the circuit lines to collect samples for determining grade vs. recovery curves for total mass and size-by-size fractions. Full mineralogical and liberation analyses are also considered on some samples of the feed and tailings streams selected to have a range of feed grades. A separate sample of the feed is used to run laboratory flotation tests to determine optimum flotation time. Two additional pieces of information are the effect of operating variables on recovery, determined through a test program based on design of experiment techniques, and operational data on every cell in the line gathered by visual observation. The application of this approach to one of the scavenger lines at Los Colorados concentrator (Minera Escondida, BHP Billiton) is demonstrated.

Jan 1, 2007

Arsenic bearing minerals such as enargite (Cu3AsS4) and tennantite (Cu12As4S13), which may associate with major copper minerals such as chalcopyrite (CuFeS2), chalcocite (Cu2S) and bomite (Cu2FeS4), usually report to the copper concentrate in conventional flotation due to their similar flotation properties. Arsenic in a copper concentrate causes environmental problems and also problems in the subsequent pyrometallurgical process. Voltammetric studies were carried out to investigate the oxidation characteristics of enargite, tennantite, chalcopyrite, chalcocite and bomite. Contact angle measurements and micro-flotation tests were conducted to examine the flotation characteristics of enargite and chalcopyrite under controlled pulp potentials. Selective flotation of enargite from chalcopyrite under varied pulp potentials was conducted to investigate the feasibility of arsenic removal from a copper concentrate. The test results indicate that the non-arsenic bearing copper minerals ( chalcopyrite, chalcocite and bornite) were easier to oxidise than arsenic bearing minerals ( enargite and tennantite) in an alkaline solution. Enargite floated well at a potential as high as +0.45 V vs. SCE while chalcopyrite was completely depressed at a potential higher than +0.43 V vs. SCE. Selective flotation revealed that enargite can be successfully removed from chalcopyrite through controlling the pulp potential at +0.30 ~ +0.50 V vs. SCE.

Jan 1, 2007

By H. Salamanca

HighService has developed different equipment using wireless technology and machine vision systems that were specially designed to allow 1) the online determination of the SAG mills liner's service life, 2) the automatic detection of a missing dipper tooth in mineral extraction shovels, 3) the reduction of accident risk potential in the mineral transportation within the mine, and 4) the reduction of collision risk potential between shovels and wheel dozers during mineral extraction. For the development of all these systems at HighService, extensive research has been done in radio frequency and image processing fields. The integration of both technologies with the expert knowledge of the company on the typical harsh environment conditions of the mining industry has led to the development of heavy duty equipment that tolerate the extreme mechanical requirements of SAG mills and electrical mining shovels.

Jan 1, 2007

By R. Abel

During the last eight years, the Ventanas electrolytic refinery has been improving its results by applying a series of new operational practices, such as the reduction of electrode spacing from 115 mm to 105 mm., raising the current density to 305 A/m2, modification in the operators shifts to about 70% of the workers, reducing the pulling cycles by two hours, and the erection of a new anode preparation machine. These improvements allowed an increase in the refinery capacity from 323,000 to 382,000 metric tons of electrolytic copper per year. In the same period it has obtained certification under the ISO 9001:2000 and ISO 14001:2004 standards. All of these developments have been achieved using conventional technology with copper starting sheets. The continuous improvement that is covered in this paper has allowed Ventanas to optimize its production, costs, and operational results. For the next years, it is planned to follow the same tendency, bringing the productivity of the plant to higher levels.

Jan 1, 2007

By H. Perez, A. Lavoie, V. Prévost, P. Létourneau, P. Lind

The Home smelter is a custom copper smelter located in Rouyn-Noranda, Quebec. In 2005, the smelter produced 145,000 t of copper containing 807,000 oz of gold, 20,388,000 oz of silver in addition to 515,000 t of sulphuric acid. Recently, a flexible flow sheet has been developed incorporating the intermittent use of the Noranda Continuous Converter allowing for the increasing or decreasing of production based on market conditions, while attaining 90% or greater sulphur fixation regardless of operating mode. For 2006, the smelter is operating in full production mode and production is expected to be approximately 185,000 tm of copper. Mechanical modifications, process changes, metallurgical concepts, minor element treatments, and operational techniques that have allowed the smelter to develop this flexibility are presented. Current efforts to increase the productivity of the converter aisle and anode furnaces as well as improvements being made to address fugitive emissions are also discussed.

Jan 1, 2007

By L. V. Volkov

The equilibrium of the CuO-Cu20-Cu+-Cu2+ system with various chloride ion concentrations in solution in the presence or absence of an oxidant was investigated. It is shown, that, regardless of the presence or absence of chloride ions or oxidant (oxygen) in the system, the process can be divided into three stages, which are characterized by differing rates and mechanisms of metallic copper cementation and cuprite precipitation and, hence, lead to differing rates of the dissolution of nickel into solution. The effect of the concentrations of chloride ion and oxidant on the phases in the process residues is also discussed. The addition of an oxidant increases the amount of cuprite (Cu20) in the leach residue. With increasing chloride ion concentrations, the rate of copper cementation increases, even without an oxidant in solution. The results of these laboratory experiments and the mechanisms developed are consistent with analysis of samples of industrial cement copper obtained from the Severonickel Combine.

Jan 1, 2007

By Claude Bazin, Patricia Obiang

"The slurry density (pulp percentage of solids) and the size of the grinding media are often used for the optimization of an operating ball mill. In many cases a change of ball size is made at the slurry density used with the original ball size. But is the optimum slurry density changing with grinding media size? Laboratory grinding tests were conducted to answer that question and results indicate that more than likely there is no need to adjust mill slurry density when adjusting the size of a grinding media in a ball mill. Full scale behaviour could be different because slurry density affects the slurry transportation through the mill and the classifier operation.INTRODUCTIONOre preparation begins with a fragmentation step that liberates valuable minerals or exposes mineral surface to the environment. The size reduction step of a mineral processing operation is energy demanding and the optimisation of this process should always be an objective for the plant metallurgists. Various approaches could be considered for improving the operation of a grinding circuit. For a close grinding circuit an adequate tuning of the classifiers operation may lead to substantial savings (McIvor, 1988). Once a grinding mill is in operation, few variables remain to be considered for process optimization. The ball charge is usually maintained to achieve a target power drawn by the grinding mill motor. The rotation speed is seldom considered (McIvor, 1983; Bazin and Lavoie, 2000) as a change of mill speed usually implies a costly pinion change. If the liner and lifter configuration is critical for SAG and AG mills (Latchireddi et al., 2005), few discussions are available for ball mills (Fuerstenau and Abouzeid, 1985; McIvor, 1983). The mill feed size distribution can also be adjusted but this implies changing the upstream processes, which transposes the optimization process to another level. Modification to grinding media shape is a possible avenue (Cooper et al., 1994), but it remains that slurry density and grinding media size are probably the most frequently considered variables for the optimization of a ball mill."

Jan 1, 2007

By A. Rahimi

Refractory castables based on alumina-silicate aggregates are commonly used in casting wheel components and launders. In this research the recycling process of waste magnesia chrome bricks for production of refractory castable lining for launders and casting wheel ladles at Iranian Sarcheshmeh copper complex (I.S.C.C.) is discussed. The smelting plant of ISCC consumes 4,000 tons refractory materials and produces 2,000 tons waste refractories annually. In order to reduce the environmental pollutions and gain the economical advantages, the recycling of waste refractories proved to be a solution [1]. In ISCC, 800 tons alumina or alumina-silicate refractory castables are used for linings of anode furnace ladles and launders annually [2]. In the present work, the spent bricks from reverberatory, converter and anode furnaces were analyzed in term of microstructural changes from hot zone to the cold end to evaluate the changes in texture and chemical composition. Different formulations based on recycled magnesia chrome aggregates and various particle size distribution and cement content were tested. Economic recycled magnesia chrome refractory mixture was prepared after crushing and sizing the non-deteriorated regions of wasted bricks. After evaluation of physical and mechanical properties of samples, one ton of refractory castable was prepared and successfully installed in the casting wheel ladles.

Jan 1, 2007

By J. Standen T.

The main purpose of this publication is to present relevant advances in processes and technologies of importance for consideration in the design of new refineries and the modernization of existing refinery facilities. Operation at current densities of between 300 A/m2 and 350 A/m2 is already part of the criteria customarily implemented on recent projects. This is due in part to the development of permanent cathode technology. In recent years, this technology has also been integrated with process control and automatic electrode handling and preparation machines. The combined implementation of these technologies has the advantage of enabling the process to be monitored, thus assuring traceability and allowing greater knowledge of the process to accrue.

Jan 1, 2007

By G. Bartolacci

In a COREM-McGill collaborative research and development project, gas dispersion parameters and froth properties were manipulated in a copper flotation plant to study interactions between the collection and the cleaning zones. In this paper, specific work on developing some relationships between operating conditions and froth stability in several different types of flotation cells is reported. Froth stability, measured by image analysis, was related to the following process conditions for specific flotation machines in an industrial case study: Gas flow rate, collector dosage, pH, frother type and dosage. Across the range examined, froth stability was improved through an increase in gas flow rate and/or frother dosage. Metallurgical results (grade and recovery) showed that both gold and copper were dependent on froth stability. Results indicated that flotation conditions could be optimized by monitoring froth stability.

Jan 1, 2007