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By Imre Gombköto, Zoltán Pap, Ákos Debreczeni, Sándor Nagy

Eddy current separators have become generally used in waste recycling industry during the last decade. There are many papers dealing with separation processes on eddy current separators, and also many article describes particle trajectory and different particle features affecting particle trajectory. These data are used in modeling as well. Within the frame of R&D project called ‚Fundamental research into the exploitation of the economic development potentials of critical raw materials in international co-operation - CriticEl?, authors are aimed for using Eddy Current Separator (ECS) as a mechanical separation step of high value critical elements recovery of selected WEEE’s like display panels, PCB’s. ECS, equipped with 305 mm wide belt, and a concentric magnetic rotor is used for experiments targeted development of methodology for determining separability of different particles on ECS. The subject of our work was to investigate the behavior of model particles with different shape, conductivity (aluminum and copper), orientation and size in order to separate Al and Cu according to the results of many experiments were carried out in this field. However it looks like that throwing distance of one particle is only possible to describe by a certain distribution for even the same particle within the frame of the same conditions. Sample mean and standard deviation are depending on some of the particle feature and acting forces. The paper is going to draft the first results on the relationship between distribution of throwing distance and particle properties.

Jan 1, 2014

By E. P. Olberg, A. Yu. Chikin, S. V. Petrov, M. P. Belykh, N. L. Belkova

"Bacteria that grow in autochtonous communities of gold heap leaching (HL) wastes are adapted to high concentrations of contaminants and environmental conditions. An example of a mine in the Sakha (Yakutia) Republic showed that the bacterial factor had a significant influence on cyanide breakdown and copper and nickel removal in the conditions of HL ore pile zoning compared to chemical oxidation. The diversity of bacterial communities growing in natural and simulated conditions of a HL ore pile was determined for the purpose of the study. The identified bacterial communities included genus Achromobacter and Serratia, which were found to be adapted to a wide range of temperature and can be considered as potential microorganisms for detoxification of gold HL wastes. INTRODUCTION Technologies and systems of passive treatment are of a special interest in relation to solving environmental problems of gold HL wastes detoxification, when neutralization time is not considered as a limitation (Alvarez et al. 2005). Passive treatment methods are based on reagentless spontaneous breakdown of cyanide caused by natural factors, including activity of autochthonous bacterial communities. Implementation of a reagentless biodetoxification technology for mature HL operations provides reduction of environmental impact on industrial site locations and substantial economic benefits compared to conventional chemical processes of neutralization that prevail in the Russian Federation territory. Passive treatment of cyanide-containing wastes was investigated by M. Botz, T. Mudder, S.V. Petrov, L. Simovic, A. Smith, C.A. Young etc. However, the bacterial factor (autochtonous bacterial communities) role in this process is practically unexplored. Thus, the aims of the study included the investigation of a bacterial factor influence on passive treatment of gold HL wastes and the identification of functional groups of bacteria involved in passive treatment."

Jan 1, 2018

According to the Darcy?s law, filtration rate should increase with increasing pressure drop (?P) across a filter cake. In centrifugal filtration, ?P is created by the free water present on the surface of a filter cake. Thus, ?P can become negative when the free water disappears from the cake surface, which makes it difficult to achieve low cake moistures. In the present work, we have developed methods of overcoming this problem by either increasing the air pressure inside or applying vacuum outside a centrifuge. Laboratory dewatering tests conducted using these provisions showed that the moistures of various minerals and coal fines can be reduced to the level that can obviate the need for thermal drying. The new concept has been successfully tested both at pilot- and full-scale, which lead to commercial deployment through Decanter Machine, Inc., under the trade name Centribaric® centrifuge. Keywords: dewatering, hyperbaric centrifuge, pressure drop, Darcy?s law, Centribaric® centrifuge

Sep 1, 2012

By L. Tong

Stirred milling of laterites offers possibilities for improving liberation and selective size reduction of soft nickel-bearing minerals in laterites. Batch grinding tests were performed in a Netzsch LME4 stirred mill on a siliceous goethitic (SG) nickel laterite sample (-2000 µm particle size) to evaluate the effect of operating conditions such as stirrer speed, grinding time, pH, solid content, water salinity and charge volume. The target was to produce a -38 µm fraction in the milling product with high nickel recovery and grade. Addition of dispersant (sodium hexametaphosphate) was also optimized with respect to the rheology of the slurry. In terms of stress intensity, the optimum grinding conditions for selective size reduction were: 1000 rpm, 50 per cent charge volume. At higher stress intensity (2000 rpm), Ni recovery in the -38 µm product was higher, but Ni grade was low, due to the breakage of the harder siliceous particles. Decreasing the yield stress by modifying slurry pH or adding dispersant improved the rheological properties of the pulp, but had no great influence on Ni upgrade in the fine product. Modifying water salinity by adding 2 M NaCl had also little effect. The breakage of the +38 µm particles in the feed determined Ni upgrade greatly. Ni grade in the -38 µm product decreased with grinding time, suggesting that the Ni-bearing minerals break first, while the harder siliceous minerals have a lower breakage rate. The breakage rates with respect to sample mass for Ni, Mg and Si indicate that: Mg > Ni > Mass > Si. The optimum grinding time for the highest Ni upgrade was 0.25 min. The Ni grade increased from 0.88 per cent to 1.35 per cent (upgrade 54 per cent), with 24 per cent Ni recovery. Keywords: fine grinding, stirred media mill, nickel laterite, slurry rheology

Sep 1, 2012

Beneficiation and dephosphorization of refractory oolitic hematite ore are investigated in this paper. It is shown that single magnetic separation, gravity separation or flotation is unable to recover iron effectively from the ore due to the complex mineralogy. The joint separation by spiral chute-shaking table shows a prospect for the treatment of the ore. An iron concentrate with 58.67% iron grade and 51.93% recovery is obtained by the joint separation of spiral chute and shaking table under the fineness of ?0.074mm 90% and dispersant dosage of 2kg/t for a sample ore of 37.51% Fe and 0.88% P. However, P content in the concentrate is still up to 0.52%. Dephosphorization from the concentrate is hence carried out. The final iron concentrate assaying 59.26% Fe and 0.056% P is obtained when the concentrate obtained by joint separation is leached by sulfuric acid of 1% (mass fraction) with solid percentage 10% at room temperature for 10min.

Jan 1, 2014

By E. V. Konoplev

Russia is one of the largest manufacturers of potash fertilizers in the world. Processing of potash ores basically is carried out by a flotation way. Potash ores of the Verhnekamsky potash deposit contain sylvite (KCl), halite (NaCl) and water insoluble impurity (up to 8 %), presented silicate- carbonate minerals, easily slimed by ore crushing in rod mills. Ore of some deposit sites, developed by ?Uralkali? Co, contains a significant amount of a carnal-lite (KCl.MgCl2.6H2O). Work practice of flotation potash plants has shown, that increase of car-nallite content in ore leads to increase magnesium ion content in a circulated plant brine (saturated salt solution of potassium and sodium chlorides-sylvite brine) and to deterioration of indicators of ore processing. In the Paper we present results of researches of floatability of various size sylvite and influences silicate-carbonate slimes on sylvite flotation in brines with the various magnesium chloride content. It is established, that with increase magnesium chloride content in the brine mainly decreases the flotation of coarse sylvite and amplifies adverse effect of silicate-carbonate slimes on sylvite flotation. In this connection deterioration of potash ore flotation is caused not only decrease sylvite floatability but also strengthening adverse action of water insoluble impurity on potash flotation. It is shown that the application of frothing agents, which render the stronger dispersive action on the colloidal-micellar structures of amine in the salt solution increases the absorption of collector on the sylvite and improves the flotation of sylvite into magnesium the containing salt solutions. The application of an organic depressor to the greatest degree of decreasing the absorption amine on the slimes and to the smallest degree possessing anionic properties proves to be most effective with the flotation carnallite of the containing potassium ores. It is offered the application the frother on a basis of glycol ethers and organic depressor on a basis of urea-formaldehyde resin. Results of industrial tests developed reagent modes for flotation treatment of ores with the raised carnallite content (to 6 %) on ?Uralkali? Co plant have shown that their application has allowed to receive equivalent indicators potash flotations at change of magnesium chloride content in the brine from 0.7 % up to 2.4 % .

Jan 1, 2014

By D. Moradkhani

Copper metal has important role in the basic industrials, as if it did not exist, modern human life would not develop! Copper leaching, as the first step, is important step in copper production processes. In this research, efficient factors on the leaching have been investigated. For this reason, four efficient factors on leaching namely pH, liquid to solid ratio (L/S), temperature and time, as independent variables, were optimized using response surface (RSM) with D-optimal. A quadratic equation was used to create response and contours. According to the results from analysis of variance (ANOVA), the value of determination coefficient (R2=96.77%) indicates that the model was good fit. Optimum experiment condition also was found: pH of 1, L/S of 8.24, temperature of 26.06 ? and time of 43.64 min. At this condition, the maximum recovery of copper was equaled to 92/38 in which good desirability achieved.

Sep 1, 2012

By I. V. Shadrunova

Annually it is formed more than 95 Mt of clinkers in iron and steel industry of Russia, including 79 Mt of clinkers in blast-furnace, steelmaking, foundry and ferroalloy productions. Complex development of clinkers will provide not only extraction of valuable components, but also preservation of ecosystems. Processing of solid slags is realized, as a rule, in a cold condition by mechanical methods only including stage-by-stage crushing of slag on devices, working on principles of compression and shift (jaw and roll crushers). However it doesn?t provide the complete extraction of metals from clinkers. The intensification of decomposition, in our opinion, can be provided under the use of the devices working on a principle of free kick. At such influence on a material, its destruction occurs on micro cracks, sides of cohesion that is there is a selective destruction of the components possessing various resistances to impact. Decomposition of a piece on the basis of free kick about a material or metal is realized in centrifugal-shock crushers and mills of research-and-production association ?Ural Center?. The share of the joints sharply lowering the efficiency of enrichment thus is minimal. The efficiency of application is proved by morph-metrical measurements with the help of system of image analysis ?SIAMS-600? and physical-mechanical tests of clinkers and their components (impact strength, micro hardness). The experience of application the devices of centrifugal-shock crushing for processing clinkers in blast-furnace, martin and converter productions of Open Society MMC, clinkers of rough-edged copper melt of Joint-Stock Company "Karabashmed" and aluminium clinkers of Joint-Stock Company « Samara plant of aluminium alloys » has allowed to confirm the efficiency of application these devices for selective decomposition of metallurgical clinkers and the opportunity of using clinkers as resource of ferrous and nonferrous metallurgy.

Jan 1, 2014

By Ela Mielczarski, Jerzy A. Mielczarski

"The adsorption of xanthate takes place at a different potential on each major sulfide mineral, hence, as it was demonstrated in the past, each mineral component can be selectively separated from ore under well controlled potential conditions. In real flotation this concept never works out for two reasons: the potential of single mineral particle results from complex surface reactions controlled by solution chemistry, and there is a galvanic interaction between different mineral particles present in the flotation pulp.In this study the formation of amyl xanthate hydrophobic products on pyrite, galena and chalcopyrite has been spectroscopically investigated in the presence of combinations of these minerals. The type of the adsorbed species and their amount were determined directly on mineral surfaces by infrared external reflection technique. Galvanic contact between grains of two different minerals has tremendous consequence on the adsorption of collector on both minerals. The detected changes are dramatic, from no adsorption to a coverage formation of a few monolayers. The results obtained indicate clearly that the observations and conclusions about the collector adsorption, hence also the surface hydrophobization, made for a single mineral system does not describe the real situation in a multi-component mineral system such as flotation pulp."

Jan 1, 2003

By G. M. Wolfaardt, B. C. Qi

"From a lifecycle point of view, biologically digested sludge is a valuable product that should be reused if possible. Sludge may be applied to agricultural land for further sludge treatment and improvement of the characteristics of the soil. The characteristics of sludge that affect its applicability for soil conditioning include moisture content, pathogens, nutrients and metals. In this paper, the use of solid anaerobic digestion sludge of the lignocellulosic residues to condition soil was investigated in regards to nutrient composition, water content/retention capacity, hygienic quality (contamination of pathogenic bacteria) and heavy metal adsorbing/releasing characteristics of the sludge.It was found that the digested sludge had approximately 44.5% free and immobilized water and 46.9% bound water. The water-holding capacity of the sludge was high. This was a merit to apply the sludge to agriculture in dry areas. Anaerobic digestion under thermophilic conditions showed a promising disinfecting effect to the sludge, in contrast to the landfill digestion. The anaerobic digestion sludge could be considered as a humus-rich hygienic product that improves soil fertility and water holding capacity, nourishes plants and immobilizes heavy metals in the environment"

Jan 1, 2003

By K. Yoo

Cuprous oxide is one of the oldest antifouling agents and also acts as red pigment in these paints. In printed circuit board manufacturing industries, waste etchant contains a substantial amount of copper ion. In the present study, a process was suggested for recovering cuprous oxides from the waste etchant and optimum conditions were investigated to recover the cuprous oxides. The process consists of two steps: in first step, Cu powder is added into wastewater solution, and cupric ions re-duce into cuprous ions (Cu+Cu2+?2Cu+), where cuprous ions precipitate as cuprous chloride; In second step, cuprous oxide is synthesized by adding NaOH into cuprous chloride solution (2CuCl+2NaOH?Cu2O+NaCl+H2O). Optimum conditions were investigated to recover cuprous oxide in the processes. When copper powder was added into wastewater with copper ions, Cu concentration decreased from 15.6% to 2.6% and ORP decreased from 620 mV to -59.9 mV. This result shows that cupric ions reduced into cuprous ions. XRD data indicated that the precipitate was cuprous chloride powder. Using the cuprous chloride recovered and NaOH solution, cuprous oxide was synthesized. To investigate the optimum condition, various NaOH solutions were added into water with CuCl, and then pH, ORP, Cu concentration, Cu contents in precipitates were analysed. XRD data showed that main component of precipitates was cuprous oxide.

Jan 1, 2014

By L. G. Wang

The stability of foams and froth plays an important role in flotation, in which small amounts of relatively weak non-ionic surfactants (frothers) are used to produce air bubbles and foams. In the present work, factors affecting the stability of the foams produced in the presence of common frothers, such as n-pentanol, n-octanol, methyl isobutyl carbinol (MIBC), and polypropylene glycol (PPG), have been studied. We used the thin film pressure balance (TFPB) technique of Schelud-ko-Exerowa type to measure the equilibrium film thicknesses. The results were used to determine the contributions from the various surface forces to the disjoining pressures in the thin lamellae (foam) films formed between air bubbles. In addition, we used a model developed by Wang and Yoon (Colloids and Surfaces A: Physicochem. Eng. Aspects, 2006) to calculate the elasticities of the lamellae films at the critical thicknesses at which films rupture. The surface forces and elasticity da-ta were then compared with the foam stabilities in the presence of the various flotation frothers. It was found that foam stabilities are controlled by both film elasticity and surface forces, the relative contributions of which change with frother type and concentration. In general, surface forces play a more important role at relatively low frother concentrations, while elasticity plays a more important role at higher concentrations. At the frother additions usually employed in the mining industry, MIBC relies on surface forces while PPG-400 relies on film elasticity in producing stable foams. The former is capable of dampening the hydrophobic force, which is a major attractive force destabilizing lamellae films, while the latter is capable of reducing surface tensions at low concentrations.

Jan 1, 2014

By ?. S. Yusupov, V. P. Isupov, N. Z. Lyakhov, A. G. Vladimirov, S. A. Kondratiev

"Considering the shortage of lithium reserves, the desirability has been shown of studying the possibility of processing into spodumene concentrates the concentration tailings and low-grade ore reserves at Transbaikalian Mining and Processing Project (ZabGOK). The mineral and chemical composition and the particle size distribution of the mineral feed, separability and recoverability of spodumene have been studied, forming the basis for the development of a concentration process and flowsheet for the studied mineral resource. Prospects have been established for impact ore grinding in a disintegrator, the efficiency of mechanochemical processes has been shown in the separation of quartz and feldspar and the recovery of lithium from concentrates.INTRODUCTION Lithium is widely used in various industries - nuclear power engineering, defense technology, power generation, ceramics, special-purpose glass and other technologies. The increasing demand for lithium and its compounds (lithium carbonate and hydroxide) for use in the manufacture of high-tech products (lithium-based materials for chemical sources of electric power and electrochemical energy) explains the need for establishing a sustainable raw material base (Mohr et al. 2012; Moores, 2007). The main sources of lithium are spodumene pegmatites (Vladimirov et al. 2012; Garret, 2004), brines (salars), and hydromineral materials (Garret, 2004; Zeng and Liu, 2009; Kotsupalo and Ryabtsev, 2008). However, in view of the absence in Russia of extractable hydromineral resources of lithium, the practical significance of spodumene ores remains decisive. Russia controls some of the world’s largest reserves of rare-metal pegmatites holding over 8 million tons of Li2O: approximately 7 million tons on the Kola peninsula and 1 million tons in the Sayan mountains. The main lithium mineral in pegmatites is spodumene LiAlSi2O6 containing 8.1% Li2O. It can be efficiently recovered by gravitational concentration and flotation. However, most of the deposits are located in remote areas and none is currently developed. In this connection, special research is focused on technogenic raw materials, which are increasingly seen as a solution to the resource base problem (Chanturia, 2008, Kurkov and Kotova, 2007)."

Jan 1, 2018

By Zhu Yangge, Hu Xiaoxing, Feng Qiming, Zhang Guofan, Zhang Xingrong

"During the flotation process of ilmenite and titanaugite with fatty acid as collector, unavoidable ions such as Ca2+, Mg2+, Al3+, Fe3+ and Fe2+ demonstrate considerable influence on the floatability of the minerals. In this study, flotation test, zeta potential test, and solution chemistry calculation were adopted to investigate the mechanism of how these metal ions affect the floatability of ilmenite and titanaugite in different pH conditions. The results show that in weak acidic solution, Ca2+ and Mg2+ mainly freely exist in the solution with little adsorption on mineral surface, and their reaction ability with oleate ions is weaker than active site on ilmenite surface (Fe), thus they show negligible effect on the flotation of ilmenite; Al3+ shows similar reaction ability with oleate ion compared to Fe3+, which lead to competitive reaction with collector, so the flotation of ilmenite is depressed. While Fe3+ can adsorb on surface of titanaugite in the form of Fe(OH)3, and it shows stronger reaction ability with oleate ion compared with active site on titanaugite surface (Ca and Mg), which proves an activation effect on titanaugite flotation. In alkaline solution, all these five kinds of ions can adsorb on titanaugite surface, and the floatability of titanaugite will be activation. Based on the above analysis, it can be deduced that in the flotation system using fatty acid as collector, the adsorption of metal ions on mineral surfaces and the stronger reaction ability with collector than active site on mineral surfaces, are the two prerequisites for metal ions show activation effect on mineral flotation.INTRODUCTIONIn flotation pulp, the existence of metal ions is often inevitable. There are two sources for these metal ions: the first part is generated in grinding and flotation process due to the oxidation, reduction, corrosion or dissolution of minerals or grinding medium; the second part is from the flotation water or the addition because of the technology need. The metal ions in the pulp have a considerable influence on mineral flotation. Earlier researches are focus on the activation effect of mineral floatation by metal ions to obtain a higher flotation efficiency, many effective activators were found, such as Cu2+ activated sphalerite, Pb2+ activation wolframite, and Ca2+ activation quartz flotation, these metal ions have become the commonly used activators in industrial production. And many studies attempted to explain the mechanism of how metal ions affect the floatability of minerals. James (James et al, 1972) suggests that metal hydroxide precipitation is the main component leads to activation effect, while the study of Fuerstenau (Fuerstenau, 1976) showed that the metal ion hydroxyl complexes played significant role. In recent years, the reuse of mineral processing wastewater has attracted more attention (Rao et al, 1989; Liu et al, 2013; Wang et al, 2014), as a main component in flotation wastewater, the influence of “unavoidable ions” on flotation process still need in-depth study."

Jan 1, 2018

By Carmina Quintanar, Mario Palominos

"The mining industry is currently facing significant challenges to identify and adopt sustainable collector chemistry that effectively recover value minerals in difficult-to-process low-grade resources. These are typically characterized by complex mineralogy and the presence of significant amounts of penalty gangue sulfide minerals, especially pyrit which is a challenge to separate from value minerals at many major mine operations. Three chemical strategies for dealing with gangue sulfides and penalty elements are: a) selective flotation of value minerals while rejecting penalty minerals in the whole circuit, b) rejecting penalty minerals in an appropriate part of the circuit using selective depressants, c) using a combination of selective collectors and depressants in appropriate parts of the circuit. This paper will evaluate different strategies for dealing with those penalty elements and propose the most efficient alternative. New products and application technologies have been developed in the past 25 years by Cytec for implementing these strategies as dictated by the particular needs of a given plant. However, in recognition of the growing interest in meeting the sustainability challenges, Cytec Research and Development have been focused in the development of greener products (collectors, modifiers and frothers) and processes using FLOTATION MATRIX 100TM approach used to develop the optimal collector system for each specific ore. An overview of these new developments is given in this paper using case studies of application of selective collectors and polymeric modifiers including the newer, greener chemistries."

Jan 1, 2014

By Yuhua Wang, Haitao Zheng, Guangli Zhu, Yuehao Zhao, Fushun Yu, Dongfang Lu

"Spodumene, feldspar and quartz possess similar surface properties, which make the difficult to separate spodumene from other silicate minerals by flotation. The differences of crystal structure, surface property and floatability of three minerals were studied by various technical means. The results show that Li-O and Al-O bonds in spodumene structure are not strong and easy to be broken. However, Al-O and Si-O bonds in feldspar and Si-O bond in quartz are very strong and not easy to be broken. High contents of Al and Li on spodumene surface were found by XPS measurements, which is benefit for the adsorption of anionic collector. The surface energies of main cleavage planes of spodumene (110), feldspar (001) and quartz (001) are 1.88 J/m2, 2.97J/m2 and 2.68J/m2, respectively. Hence, the exposed surfaces of feldspar and quartz are not saturated and easy to adsorb OH- ions from solution and cause the lower IEP than spodumene. The contact angles of three minerals in water are lower than 16º, suggesting that the hydrophilicity of three minerals is high, and the order of hydrophilicity is quartz > feldspar >spodumene. Correspondingly, contact angles and flotation recoveries of spodumene are bigger than that of feldspar and quartz in presence of a combined anionic and cationic collector named YOA.INTRODUCTION Flotation technology plays most important role for the recovery of spodumene from pegmatite ore. Generally, spodumene with fresh surface is easy to be floated using soap and oleic acid as collector, and the best flotation pH range is 4.0 to 9.0. However, the flotability of spodumene will become worse when its surface was polluted by slime which produced by the weathering of spodumene and other silicates (Dresler et al. 1998; Moon and Fuerstenau 2003; Menéndez et al. 2004; Yu et al. 2015). In addition, the species of Ca2+, Fe3+, Mg2+ and other metal ions in pulp can not only activate the flotation of spodumene, but also the activation of gangue minerals, and then the flotation selectivity of spodumene from gangue minerals became wores (Wang and Yu 2007; Yu et al. 2014). In order to eliminate the negative effects of slime and metal ions on the flotation of spoddumene, the desliming and long time scrubbing with the addition of NaOH and Na2CO3 were adopted. Usually, NaOH shows the activation for spodumene flotation, and the recovery of spodumene increases with the increase of NaOH dosage. Na2CO3 can eliminate the non selective activation of Ca2+, Fe3+, Mg2+ ions in the pulp, and the concentrate grade of spodumene increases with the increase of Na2CO3 dosage. Anionic collectors such as chelants, hydroxamic acid, oxidized paraffin soap, naphthenic acid and oleic acid were widely used for the flotation of spodumene (Dresler et al. 1998; Moon and Fuerstenau 2003; Menéndez et al. 2004; Yu et al. 2015)."

Jan 1, 2018

By Carlos Rabanal, Levi Guzmán

"The concern regarding grinding media consumption rates is as old as the invention of the tumbling mill. Over the years many materials and grinding media shapes have been tested. Through all this, steel grinding balls have proved to be the most effective media for comminution in tumbling mills. There have been several approaches to be able to the wear of the ball charge in any given mill, all of them based on limited empirical evidence. The mining industry still utilizes the Bond Abrasion test that was developed in the 1960´s. As shown later in this publication, this approach shows error greater than 60%. More recently, in 2007, Radziszewski from Mc Gill University has proposed a different total grinding media wear model; this model is based on decoupling the effects of the abrasion, corrosion and impact wear mechanisms. Also in 2007, Benavente, at the time with Moly-Cop Peru, presented an empirical model relating both ore properties and operational conditions that would affect the wear performance of the grinding media. For the database referred in this article, Benavente’s model shows an average error of ± 12% which represents a higher degree of improvement in comparison with previous approaches. The current paper presents recent research conducted by Moly-Cop Peru to further improve the capability of the empirical model originally developed by Benavente to estimate grinding media wear rates. The work performed included extensive determinations of the Bond Abrasion Index for different types of ores, collected at industrial grinding applications where the corresponding operational information was made available. The results of the research enabled us to build a more robust and confident model for estimating the grinding media wear rate. The average error of this new model is in the order of ± 9% which is a significant improvement over the models previously described."

Jan 1, 2014

By Ali Dehghani Ahmad Abady

In Sarcheshmeh Copper Complex, a molybdenite floatation concentrate was produced by selective removal of copper impurities with 7 stages of cleaner floatation banks, that contains around 1% copper and 54.5% molybdenum. Mineralogical studies, physical and chemical characterizations showed that the sample contained 91% molybdenite (MoS2), 2.6% chalcopyrite (CuFeS2), 0.2%Covellite (CuS), 1.6% pyrite (FeS2) and 4.6% other nonmetallic impurities. In the present study, the removal of the copper sulfide was investigated by ferric chloride leaching for achieving a molybdenite concentrate with copper content less than 0.3%. Therefore, the application of response surface methodology (RSM) for modeling and optimization of the influence of three control parameters including ferric chloride (FeCl3) dosage, reaction temperature and reaction time, each varying in five levels, were considered, and the mathematical model for prediction of %Cu removal from molybdenite concentrate was derived. This study showed that RSM could effectively be applied for the modeling of ferric chloride leaching, and finding an economical optimum condition to achieve maximum de-coppering efficiency while consuming minimum leaching reagents. The optimum dissolution conditions to maximize Cu extraction were 200 kg/t for ferric chloride dosage, 120 min for reaction time and 80 °C for reaction temperature with a prediction of 83.20% Cu dissolution. Keywords: molybdenite concentrate, ferric chloride, leaching, response surface methodology (RSM)

Sep 1, 2012

By Z. Pokrajcic

The traditional comminution circuit is a major consumer of energy ? both as electrical energy and through consumption of media and wear resistant liners. Up to 40% of electrical energy con-sumed at a mine site is attributed to comminution however only a few percent of this energy is used in the generation of new surfaces from size reduction. This paper describes the evaluation of modifications using simulation models based on two operating comminution circuits. The aim of these modifications is to decrease both the amount of electrical energy consumed in the size reduction process, known as direct energy, as well as to decrease the consumption of grinding consumables such as steel grinding media and mill liners, designated as indirect energy. The approach is two-fold: ??Employ, where possible, autogenous grinding techniques to eliminate the need for grinding media and reduce mill liner wear. ??Optimise the use of the grinding energy distribution in the comminution circuit by using more energy efficient grinding devices to target typically problematic features of a comminution circuit such as critical size material from the primary mill and overgrinding in the secondary mill. The investigations show that significant total energy savings, as high as 50% in some cases, can be achieved by employing the techniques described while maintaining circuit throughput and product size. Investigations also show potential benefits in downstream flotation processes as the product size distribution generated from the eco-efficient circuit is generally ?narrower? in shape for improved flotation performance and containing less material in the coarse fraction for overall better liberation.

Jan 1, 2014

By Hossein Zarei, Masoud Kashani, Mehdi Safari

The feed of flotation unit in Angouran mine, as a part of Iranian Lead and Zinc National Corporation, contains about 34.26% zinc (about 12% Zn sulphide) and 10.14% lead (about 2% Pb sulphide). The grade of Pb and Zn in the final concentrate (rougher+scavenger), under optimal conditions (200 g/ton PEX, 500 g/ton zinc sulfate, 30 g/ton MIBC and pH = 7.5), was 63.18% and 13.01%, respectively, and the total Pb (sulphide-oxide) recovery was about 19% which included 95% Pb sulphide. The grade of Pb and Zn in rougher concentrate step was about 71.86% and 5.97%, respectively, when PEX (Potassium Ethyl Xanthate) was used as collector. While in the presence of PAX (Potassium Amyl Xanthate), the grade of Pb and Zn in rougher concentrate step was 66.8% and 10%, respectively. Tailing of the galena flotation (with 8.48% Pb grade and 34.92% Zn grade under the optimal conditions) was used as a feed for sphalerite and oxide section flotation.

Jan 1, 2014