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By Daniel A. Norrgran

Grinding ball fragments discharging from SAG mills and ball mills causes extreme wear to downstream processing equipment. These ball fragments, recirculating in a milling circuit, will cause excessive wear to sumps, pumps, hydrocyclones, and interconnecting piping. A magnetic separation system to remove grinding ball fragments from the mill discharge has been developed and successfully applied in the milling circuit. This magnetic separation system - termed Trammel Magnet - was first applied at the Escondida copper concentrator in Chile. The Trommel Magnet consists of an arc of permanent magnets mounted at the discharge end' of the tommel screen. The magnetic arc attracts the ball fragments and removes them from the process stream. This retrofitted magnetic separation system removed 126 metric tons of ball fragments from the circulating load of a. single ball mill in the initial 24 hour period. The mill has since stabilized and the magnetic separator is currently removing 7 metric tons per day of ball fragments. The retrofit of the Trommel Magnet has: 1. Extended the pumpp life and the hydrocyclone life approximately 300 percent. 2. Provided a 5 percent increase in the throughput of the mills by removing grinding ball fragments that contribute very little to the grinding process. Variations of the Trommel Magnet have also been developed for removing grinding ball fragments directly from the mill discharge without the use of a trommel screen. In each case, permanent magnets are used to collect the ball fragments from the mill discharge stream prior to reporting to the sump. These other systems have been designed and fabricated for in-plant test work.

Jan 1, 1999

By Erik Olsson, Gunilla Hyllander, Stefan Schuster, Lena Sundqvist Ökvist, Maria Lundgren, Michael Hensmann, Olavi Antila

"Residual materials from the integrated steel plant itself or other sources often contain valuable compounds of e.g. C and Fe. Dust and sludge have to be agglomerated to be able to recycle to the blast furnace (BF) via top-charging. By injection of the materials, preparation methods in terms of e.g. drying and/or screening only, can be used. Alternative carbon materials (ACM) in terms of BF dust and sludge have been successfully injected up to levels of 60 kg/tHM in the LK.AB Experimental Blast Furnace (LKAB EBF®). Efficiency in recovery of valuable compounds as well as the behavior of undesired elements have been evaluated and are discussed.IntroductionTraditionally, recycling of steel in-plant fines is made via the sinter plant and blast furnace route. Steel plants operating with 100% pellet as ferrous burden and have no sinter plant. There are limited areas for land fill and costs are caused for preparation of landfills and deposit fees. Very fine paniculate dusts or sludges cause decreased productivity and increased coke rate in the sinter plant, and therefore other ways for recycling must be considered. Injecting them into the BF could be an economically and technically feasible alternative. Additionally, as the materials contain valuable compounds of e.g. C and Fe."

Jan 1, 2012

By M. Misra

The prediction and assessment of the reactivity of acid mine tailings has been a subject of numerous studies. The conventional approaches such as sulfur content, pH, net acid generating capacity and conductivity are used for assessing reactivity of the tailings. In this paper a new non-invasive Impedance Spectroscopy (IS) technique is used for the determination of reactivity and acid mine potential of tailings. This technique is also used to establish the long term stability and leaching propensity of the tailings agglomerated with alkaline binders.

Jan 1, 1994

By Petr Sulovsky, Jaroslava Ledererova, Miroslav Svoboda, Michaela Suchardova

"The thinning resources of natural raw materials necessitate an increased degree of waste material recycling. The building industry offers a range of technologies enabling incorporation of industrial wastes into building materials for construction purposes in an economically acceptable way. Our research is focused on finding the appropriate technologies for specific groups of industrial waste materials (IWM). The studied IWM involve coal combustion residues (CCR), desulphurization products, sludges, metallurgical slags, and various other wastes. Many of them contain increased amounts of toxic elements that can under certain conditions get released. In order to prevent this, each specific IWM requires finding the technology that best ensures the binding of toxic elements in the building matter are fixed for the long term.Introduction The sustainable development of mankind is more than ever viewed as a matter of resources. Many aspects of the switch from a throw-away to a recycling society concern one of the largest consumers of natural resources and producer of greenhouse gases, the building industry. One of the biggest tasks lying before the researchers in the field of building materials is to find substitute or alternative raw materials that would save the thinning reserves of natural resources. The most promising and natural way is to replace the traditional raw materials with rejected and unwanted products of industrial processes, classified as wastes. These of course are not produced with the primary intention of achieving some desired properties. The usage of industrial wastes therefore involves finding the optimal way of usage their existing positive (from the point of view of utilizations) properties and minimizing the impact of their undesired properties, i.e. from the perspective of the considered application."

Jan 1, 2008

By G. G. Barbante

Copper anode slimes are a valuable source of the precious metals, and selenium and tellurium. They are mineralogically complex and this has led to a great variety of process flowsheets for treating them. The traditional pyrometallurgical method utilises oxidation in a reverberatory furnace, but has numerous shortcomings. Recently deep-bath intensive smelting methods have been developed for use in the larger refineries. Despite these process advances, the thermodynamics of the reactions involved remains poorly understood. An initial description of the thermodynamics of slimes smelting is presented, but is severely limited by a lack of basic data. It is shown that slimes smelting is superficially similar to copper converting, but has many unique features. More basic thermodynamic data on selenium-based systems are needed before the process model presented can be further refined, and work in this direction has already commenced.

Jan 1, 1994

By T. T. Chen

Kidd Creek continuously-cast copper anodes are characterized by high levels of Se, Pb and Ag; the anode slimes constituents and their morphologies are controlled by both the anode composition and the casting process. Hollow Cu2Se spheroids and tube-like structures, enveloping Cu-Pb-As oxide and/or Cu2O, are present in the as-cast copper. During electrolysis, the selenides are liberated from the copper and accumulate in the slimes layer; the Cu2O and Cu-Pb-As oxide react rapidly with the electrolyte to form soluble species and PbSO4. Silver, which is present mostly as a solid solution in the anode copper, is also liberated during electrolysis and reacts with the Cu2Se to form (Cu,Ag)2Se. The ultimate composition of the selenides in the slimes layer depends mostly on the Ag and Se contents, but various other elements, including Au and Te, are also structurally incorporated. Although the selenides are the major Ag carrier, metallic silver also is present. A thin layer of Cu2O crystals sometimes forms at the copper surface, and may affect anode passivation. Copper sulphate is a common constituent and serves to agglomerate the slimes. Copper sulphate is present on both passivated and non-passivated anodes, but that observed on the passivated metal is present as a thick compact layer. Copper powder is associated with CuSO4.5H2O only on passivated surfaces.

Jan 1, 1987

By C. E. M. Meskers, U. Boin

"The increasing use of coated magnesium in consumer products results in creation of coated Mg scrap during product manufacture and after End-of-Life product treatment. Currently this material is generally not recycled, leaving a material resource unused. Closure of the magnesium cycle in a sustainable manner is necessary. In order to do so, the effect of coatings on the recycling process has to be quantified, predicted and minimized. For this purpose metrics have been developed, based on first principles supported by detailed understanding of the recycling process. The developed 3D metric enables quantitative assessment of the recyclability and links coating design, product design and recycling to each other in a visual manner. The parameters that form the metric can be measured and predicted, hence an engineering basis for Design for Sustainability of coated magnesium is provided.IntroductionEvery product progresses through the four phases of the product life cycle depicted by figure 1. In each phase residues are created. Their amount and composition is largely determined by the complex material combinations created/invented during product design in the manufacture phase. Compared to the ideal cycle the magnesium cycle is far from closed (fig. 2). Most noticeable is absence of the link between the EoL phase and raw materials production. A closed cycle only exists for class 1 scrap, which goes from the product manufacture phase directly to production from industrial material and returns to the manufacture phase as magnesium alloys. The four problematic streams are marked by ???. Coated semi-products are present in two of the four residues, namely in rejects and collected scrap. When these semi-products are recycled the amount and composition of the dross and salt slag residue is affected as well.During product design selection of the coating takes place, fixing the coating character¬istics and properties from this moment on for the rest of its life cycle. The choices made in the manufacturing phase are therefore critically linked to the recyclability of coated semi-products as well as the sustainability of the magnesium cycle as a whole. Sustainable closed life cycles, in which the quality of materials is preserved and residue creation and resource depletion are minimized, can be attained by selecting the appropriate alternative during product design. To realize this the effect of design choices on the life cycle and more specific the recycling process has to be known and quantified."

Jan 1, 2008

By Wang Yun-yan

In order to examine the adaptability and the kinetics of leaching different gold ores in alkaline thiourea system, six kinds of gold concentrate and/or calcine with different physical and chemical properties were chosen as objects. The leaching behaviors in alkaline thiourea system with high stability, acidic thiourea system and alkaline cyanide system were compared. Changes of phase, surface appearance, particle distribution and specific surface area of six kinds of gold ores before and after leaching were studied in virtue of modern analytic techniques, e.g., XRD, SEM, and so on. The results indicate that alkaline thiourea solution can be used to leach gold ore, for oxidized gold concentrate removed arsenic by microbe pretreatment(4#) the leaching rate of gold is up to 82.68%, such conclusion overthrows the parlance reported that pH value must be less than 1.78, or gold can not dissolve in thiourea solution. Chemical components and phase are related to gold leaching rate, different gold ores are fit for different leaching system, and alkaline thiourea solution is suitable for the pretreated oxidized gold ores with low content of sulfur and in which the main phase was SiO2, phase almost does not change after leaching basically. Generally speaking, when leaching in alkaline thiourea solution, surfaces of gold ores with glaze change greatly to ones with coarseness, distinct trace and holes of corrosion. Particle size decrease and specific surface area increase of gold ores after leaching in alkaline thiourea solution with high stability except gold concentrate of Zhongyuan gold smelter(5#).

Jan 1, 2006

By G. T. Lapidus, O. J. Solis-Marcial

"The oxidative dissolution of copper from refractory minerals, such as chalcopynte, represents a technological challenge that has occupied hydrometallurgists for more than half a century. Innumerable processes have been suggested, but the majority operates at high temperatures or employs corrosive media. The origin of this refractory nature is the formation of passivating phases of iron(III) or copper. One option is to add non-corrosive ligands that complex these metal ions, thereby facilitating their dissolution. In the present work, the effect of acetone in sulfuric acid solutions was studied. The initial experiments were on chalcopynte carbon paste electrodes using cyclic voltammetry, where greater reactivity was observed. Later, leaching tests with hydrogen peroxide, cupric sulfate and ozone and, as oxidants, were performed. High extractions were achieved in three hours at 50°C. The solid residues contained the iron in the form of Fe203 and FeOOH.IntroductionChalcopyrite is the most important mineral of polysulfide copper ores [1] and accounts for approximately 70% of the world's copper reserves [2]. Currently, the copper present in chalcopyrite is extracted mainly by pyrometallurgical processes, which generate environmental concerns because of the formation of SO2 gas and submicron particulates [3]. The development of a less aggressive hydrometallurgical process for the extraction of copper would constitute a possible solution to these problems. For that reason, studies of the dissolution behavior of chalcopyrite are of great technological importance [4], However, the proposed oxidative leaching routes for chalcopyrite, generally at high pressures and temperatures, have not been implemented on an industrial scale, because of the elevated costs required to equal the high copper extractions obtained in thermal processes. These extreme leaching conditions are required because of the refractory nature of chalcopyrite. Passivation has been used to explain this phenomenon, although researchers have disagreed on the composition of the layer, which is various have assumed to be sulfur, copper sulfides, and iron-bearing jarosites or hydroxides [5]. If the latter compounds are the cause, an alternative solution would be the use of polar organic solvents in the oxidative leach to decrease the formation of the passivating iron layer. In this work, the influence of acetone on the oxidative leaching of a chalcopyrite concentrate at room conditions is explored."

Jan 1, 2012

By Christian M. Sagedahl

The stringent environmental regulations for air pollution regarding emission control, along with the need of dry concentrates to feed autogenous smelting processes, are enhancing the development of cleaner technologies. Indirect drying of concentrates by a Kvaemer steam dryer is a technology with promising results, reducing dust entrainment to the exhaust gas stream and leading to smaller dust separation units. The Kvaemer dryers are designed for a very high availability, a high-energy efficiency, low amount and velocity of exhaust gases, no SO2, CO or CO, emissions combined with a wide range of satisfactory operating conditions and low total operational costs.

Jan 1, 1999

By Zhang Jianliang, Xu, Zuo, Runsheng, Haibin, Kexin, Jiao

Full oxygen blast furnace iron-making is one of the new technologies, which is most likely to realize large-scale application. In this paper, based on the technology of full oxygen blast furnace, the reduction behavior of pellets is studied systematically by using the analytic method of non-isothermal dynamics on the different atmosphere(CO,H2) and the dynamics model of gas-solid reduction reaction is constructed, which lay the foundation of reduction model establishment of full oxygen blast furnace burden. The result shows that the time of pellets which began to react is delayed with the increase of the content of H2. When the temperature is between 650 'C and 1050 'C, the content of H2 in the reduction atmosphere is larger, and the rate of the reduction pellets is larger. The reduction rate changes at 780 'C, and a certain amount of H2 in the reducing atmosphere will significantly improve the reduction reaction when the temperature is above 780 'C. Non-isothermal reduction behavior is controlled by interfacial chemical reaction and internal diffusion under high reduction potential. H2 ratio in reducing atmosphere increased from 0% to 100%. The reduction reaction of the apparent activation energy decreased from 49.03kJ-mor1 to 33.74kJ·mor1.

Jan 1, 2013

By Luciano B. Oliveira, Angela O. Costa, Sergio N. Monteiro, Luis Guilherme C. Marques

"Biofuels are gaining a relevant role in today’s world not only as a solution for the decreasing petroleum reserves but mainly as a positive contribution to the efforts in global warming mitigation. In Brazil, since 1975, the replacement of gasoline by ethanol started a so-called PROALCHOOOL program, which is now being complemented with the replacement of petroleum diesel by biodiesel. This biodiesel program was officially created in 2005 with mandatory goals, supported by legislation, of 2% addition in 2008 and 5% addition in 2013 into all commercialized regular diesel. In this work, a critical analysis of the Brazilian biodiesel program is presented. The technical aspects related to the different raw materials, including wastes, available for biodiesel conversion as well as the economical conditions associated with production costs and market logistic are discussed. The environmental benefits associated with the retention of greenhouse gases are also discussed.IntroductionToday the commonly accepted fact that the petroleum world reserves are probably passing through a maximum and start declining in terms of the total amount that can be extracted by existing technologies is motivating significant changes in our society. The continuous increase in the price of gasoline and other liquid fuels is an immediate worrisome and visible consequence. However, more than an economical problem, our civilization is already facing the effects of global warming, due to CO2 emission from burning fossil fuels, mainly from coal and petroleum. It is now realized that a large scale solution for these problems demands the prompt substitution of non-renewable fossil fuels by others that, in addition of being renewable, have a relatively lower contribution to the greenhouse gases."

Jan 1, 2008

By Youqi Fan

Complicated copper oxalate precursor powder was prepared using ammonium oxalate as precipitating agent in the Cu(II)-C2O42--NH3-NH4+-H2O system. The composition and morphology of the powder are characterized by chemical analysis, X-ray Diffraction (XRD), scanning electron microscope (SEM), infrared spectroscopy (IR). The effects of temperature, copper ion concentration, pH value are investigated. It?s indicated by the experimental results that precursor of copper oxalate is prepared below a critical pH value, whereas the precursor turns to be a complicated copper salt combined with NH3 while over the pH value. Probable chemical formula CuC2O4?x(NH3)?yH2O can be assumed which x and y are relation to experimental conditions. Technological parameters, such as temperature, initial copper concentration and solution pH value, have significant effects on particle size, morphology and dispersion of precursor powder. By controlling certain technological conditions, various morphologies of precursor, pie shape, spindle shape and rod shape can be synthesized.

Jan 1, 2009

By K. Suseelan Nair

Magnesium alloys containing rare earths are finding increasing applications in space programmes. A number of alloys have been developed and e good data base an the mechanical properties of these alloys is available. However details on metallurgical aspects are found to be sparse in, literature. This paper, at first, briefly reviews the available data on these alloys and subsequently presents the microstructural investigations conducted on quatenary fig-4.9% Zn-1% Rare earth-0.5% Zr cast alley, using optical metallic-graphy, electron probe micro-analysis and X-ray diffraction techniques.

Jan 1, 1989

By S. J. Macnaughton

The Olympic Dam deposit in South Australia contains 2% copper and 0.06% uranium, which are present as bomite, chalcocite, chalcopyrite, uraninite, coffinite and brannerite. The copper is principally recovered using flotation. The flotation tailings, which contain the bulk of the uranium, and typically 0.3% copper, are leached using sulfuric acid and an oxidant at atmospheric pressure. This paper describes the results from a detailed investigation of the leaching behaviour of this ore. The influence of acid strength, Fe3+ concentration, redox potential and temperature on the dissolution of uranium and copper minerals was studied. Experimental data were obtained from extensive batch leach tests. Mineralogical studies, including SEM analysis of individual mineral grains, were also carried out. The maximum extraction of uranium determined experimentally was in good agreement with that predicted from SEM determination of the proportion of refractory brannerite in the ore. The leaching rate of copper was found to be independent of acidity over the range 20 g L-' to pH 2.0, but was strongly dependent on temperature and Fe3+ concentration. Uranium extraction showed a weak de endence on acidity, Arrhenius temperature dependence and a complex co-dependence on F>+ concentration and redox potential. A kinetic model has been developed, which predicts copper and uranium dissolution. This model will be incorporated into a more comprehensive model that can be used to predict leach performance and reagent consumption for specific ore samples.

Jan 1, 1999

By Hector M. Henao

To provide thermodynamic data for converting nickel matte to liquid nickel at high temperature, an experimental study was conducted on the phase equilibrium between the Ni-S alloy and the FeOX-SiO2, FeOx-CaO, and CaO-A12O3 base slag in a magnesia crucible and the CaO-Al2O3-MgO slag in an alumina crucible. All experiments were carried out at 1773 K under controlled pso2 of 0.1 atm and po2 in a range between 5x10- and 10-5 atm by using CO-CO2-SO2 gas mixtures. The dissolution of nickel in the slag was found to be minimum for the CaO-Al203¬-MgO slag with a molar ratio of NCaO/NA1203=1.7. The solubility of nickel in this slag at p02 of 6x10 atm (just before the precipitation of solid NiO) was 4 mass%. This result suggests that a CaO-A12O3 base slag could be used in converting Ni-S melt to nickel while minimizing nickel losses to the slag.

Jan 1, 2002

By James C. Barker

Near Rainbow Mountain in the east-central Alaska Range an ultramafic complex forms a sill-like intrusion composed of dismembered bodies exposed along the south side of the Denali Fault and Broxson Gulch Thrust. The complex comprises dunite and peridotite with lesser gabbro, which together exhibit poorly defined, steeply-dipping compositional layering. The complex hosts four types of copper-nickel occurrences which have characteristic platinum-group elements (PGE), gold, and cobalt distributions. Three of the occurrence-types are considered to have formed as a result of primary mineral segregations which developed during intrusion of the complex. The fourth type of copper-nickel occurrence formed as a result of post-magmatic hydrothermal fluids at intrusive contacts. Scanning electron microscope examination indicates that PGE occur as micron-size telluride and arsenide minerals.

Jan 1, 1987

By Mohamad Omarei, S. M. Sadrameli

"The aim of this research work was to produce biodiesel (fatty acid methyl esters, FAME) from canola oil using KOH loaded on y-Al203 support as a heterogeneous catalyst. Different parameters such as effects of the molar ratio of methanol to oil, catalyst amount and reaction time on the yield were investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used for characterization of the catalysts. A biodiesel yield of 86.67% was obtained under catalyst preparation and transesterification conditions of calcinations temperature of 773 K, 4 h of reaction time at 338 K, and using 3.5 wt% catalysts and molar ratio of methanol/oil of 15:1. The leaching of potassium species in the spent catalyst was observed.1. IntroductionBiodiesel is an eco-friendly and alternative energy source for diesel engines that can be synthesized by transesterfication of vegetable oil or animal fat with alcohols [1 ]. There are four principal approaches to the synthesis of biodiesel involving the transesterification of the triglycerides of the plant oils and animal fats: base catalysis [2], acid catalysis [3-5], employing supercritical alcohol conditions [6] and enzyme catalysis [7]. The commonly used homogeneous catalysts are NaOH, KOH and their alkoxides. Homogeneous alkali-catalyzed transesterification is much faster than acidcatalyzed transesterfication [8]. However, a large amount of water is required to transfer the catalysts from the organic phase to a water phase after the reaction. Therefore, it is considerably more costly to separate the catalyst from the produced solution [9]. These disadvantages could be removed by use of a heterogeneous catalyst [10]. The use of heterogeneous catalysts eliminates the neutralization step, hence it results much easier to separate from liquid products. Also, they can be designed to give a higher activity and selectivity and to have longer catalyst lifetimes [11]. A large number of different heterogeneous catalysts have been synthesized for biodiesel production. For example, calcined Mg-Al hydrotalcites [12], zeolite and metal catalysts [13], metal oxides such as calcium oxide (CaO) [14], magnesium oxide (MgO) [15], zirconium oxide (Zr02) [16], and supported catalysts [17] have been investigated as heterogeneous catalysts. CaO and MgO are most frequently used heterogeneous catalysts for biodiesel production [18]. In this present work, we aimed at developing an efficient catalyst for transesterification of canola oil. We have prepared KOH/ Al203 by impregnation and applied to determine the optimum conditions for biodiesel production. Three different variables including reaction time , alcohol to oil molar ratio and catalyst loading with may influence the quality of the produced biodiesel were optimized. Moreover, SEM (scan electron microscope), XRD (X-ray diffraction) and XRF were used for characterization of the catalysts."

Jan 1, 2012

By Guillermo A. Vidal

With the introduction of monitoring technologies, process computers and Web services on Industrial Facilities the need for electrolytic processes automation has been set. Recently designed facilities have substantially improved plant layouts, automated cathode processing and copper harvesting. Despite these advancements only limited progress has been accomplished on the electric current distribution of the process. Lately a number of proposals focused on preventing short circuits and balancing cathode currents have emerged. Among these are the AZSA intercell, the Outokumpu double contact, and the Optibar InterCell Plus. Although these intercell bars are clearly superior to the conventional bar, little or conflicting data is available about their merits relative to each other. Consequently, selection of the best intercell bar for most applications is accompanied by uncertainty, which can lead to less than optimum results. A critical evaluation of the performance of the aforementioned bars on the basis of the application is provided, thereby giving the framework and guidelines for the selection of the best bar for each application.

Jan 1, 2003

By Wei Liu

A new process for extracting cadmium from the electric precipitated dust produced by ISP process was studied. A leaching rate of 89.1% of cadmium was attained by leaching the dust with NH3?H2O-(NH4)2SO4 system under the best leaching conditions: ratio of liquid to solid(l:s)=2.5, c(NH3):c(NH4+)=3:5, total concentration of ammonium and ammonia=8 mol?L-1, leaching time= 1.5h, temperature=35. The most troublesome impurity of lead could be deposited from the leached out solution automatically after put it static more than 15h when the total concentration of zinc and cadmium was up to 45gL-1 , and the final concentration of lead was 0.0047 gL-1, which meant 99% of it was removed. Metallic cadmium which contained cadmium more than 99% was prepared by electrowinning under the conditions: current density=750Am-2, total concentration of Cd2+ and Zn2+>25gL-1. The current efficiency was about 87% and the energy consumption for every ton of cadmium was about 548KWht-1. Main impurities of the metallic cadmium were copper and zinc and all of they could be got rid of in the following pyrometallurgical refining step.

Jan 1, 2006