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By M. Ghiani, R. Peretti, S. di Giovanni, G. Zonnedda, A. Serci

"An interesting occurrence of gold bearing ores of economic interest has recently been discovered in the Serrenti- Furtei district, central-southern Sardinia (Italy). The upper part of the orebodies are leaner and fairly porous, and are undergoing intense oxidation processes. In the lower parts sulphide ores predominate, chiefly enargite-luzonite and pyrite and these have a more compact structure. The passage from the oxidized to the sulphide zones, is rather irregular and difficult to delineate. The gold, generally occurring in its native form, is found in small grains. Mineral reserves in the area concerned were originally estimated to total 2.77 Mt: 0.63 Mt of oxide minerals with average gold content of 2.75 g/t and 2.14 Mt of sulphide ores with average gold grade of 3.18 g/t.Recovery of the valuable metals is a complex problem.The effectiveness of a variety of gold extraction techniques has been evaluated conducting tests on batches of ore representative of the different orebody depths obtained from core samples.The techniques investigated were: heap and vat leaching; flotation and flotation followed by leaching of the flotation tailings. The findings indicate that:• the gold contained in the ores in the upper oxidized zones of the deposit can be efficiently recovered by direct cyanidation via heap or vat leaching;• the sulphide ores in the deeper portions, that are not amenable to direct cyanidation but contain enargite concentrations of potential economic interest can be processed by means of flotation to produce a gold/copper bulk concentrate;• beneficiation of the difficult-to-treat minerals contained in the transition zone requires some knowledge of their intrinsic properties. A distinction should be made between the ores containing minor amounts of enargite which appear to be amenable to vat leaching and those with relatively higher enargite content which are processed using bulk flotation of the gold and copper minerals followed by vat leaching of the resultant tailings."

Jan 1, 2003

By Sonia Helle, Ursula E. D. Kelm

"From a metallurgical point of view, acid leaching of oxide zone copper ore is considered in the first place in terms of ore grade, whole rock mineralogy, rock granulometry, crushed aggregate size distribution, porosity, permeability and corresponding fluid flow characteristics. Despite exhaustive physicochemical and general mineralogical characterization, drops in copper recovery occur and are often attributed to and “unquantified mineralogical misbehaviour” of the gangue phases. This study establishes an experimental link to monitor and quantify the chemical interaction of chrysocolla, malachite and atacamite with reactive gangue phases.Laboratory-scale sulphuric acid (15%) leaching in small columns is carried out using a synthetic rock composed of 57% quartz, 1% ore phase, and 42% reactive gangue. Gangue phases were selected to represent mineralogy found in argillic, advanced argillic, and propylitic alteration zones. Exotic copper ores of Codelco Norte (in particular Mina Sur) served as model for the modal distribution of mineral phases. Natural reactive gangue phases (<200 Tyler mesh) were chosen as pure as possible: Saz-1 and Swy-1 montmorillonites, KGa-1B and KGa-2 kaolinites (all Clay Mineral Society, USA, Source Clays) Nau-2 nontronite, Imt-1 illite (both Clay Mineral Society Special Clays) and Chilean mordenite, laumontite and bentonite. Ore phases are: mineraloid chrysocolla from Radomiro Tomic (Codelco Norte), reagent grade malachite and a purpose synthesized atacamite-paratacamite mixture. Complete chemical, physicochemical and mineralogical characterizations were carried out for ore and gangue phases.The following observations hold for samples with and without mineralization: Smectite-rich gangue increased up to 75% in volume. Once wet, air-filled vesicles formed due to the rapid sealing effect of overlying smectite in the column. No volume change occurred for illite, mordenite and kaolinite gangues. For kaolinite mixtures acid puddles formed on top of the column during initial leaching due to the delamination and barrier formation of this phyllosilicate. Fluid recovery was <60% for expandable phases and reached up to 80% for non-expandable mixtures. These observations confirm the very low extractions obtained in ore with a combined smectite – kaolinite gangue for Mina Sur. The most important mineralogical changes observed in the solid residues are: reduction of basal smectite phase reflections (XRD), and slight loss of illite intensities. This is also reflected in the major element composition of the residues, which demonstrate a loss of Mg, Mn, Ca, Na, K followed by Fe, Al and Si; with their proportions depending on the starting materials. Furthermore, alunogen and meta-alunogen formed, with related phases coquimbite (illite) and godichite (nontronite) also depending on gangue mineral chemistry. For laumontite samples, meta-alunogen and alunogen precipitated from the leachate."

Jan 1, 2003

By Zoran M. Stevic, Mirjana M. Rajcic-Vujasinovic, Zvonimir D. Stankovic

"Covellite is one of the most important copper sulfide minerals. Its behavior during the anodic polarization, as well as its rest potential in various solutions are of importance for flotation processes and also define the mechanism of electrochemical extraction of copper from sulfide minerals.Measurements of the rest potential have been performed in water solutions in presence of different cations and anions. The existence of the Nernst type dependence of the rest potential on the activity of some of the investigated ions was established. The biggest influence on the rest potential of covellite exhibits the change of activities of the ions forming the crystal lattice of investigated mineral, i.e. Cu(II) and S(II). The dependence of the rest potential of covellite on logarithm of Cu(II) activity has a shape of a strait line with a positive slope of 60 mV, while when concentration of S(II) anions increases ten times, the rest potential of covellite decreases about 120 mV. The first dependence was established in acid medium, while the second was registered in alkali one.Different electrochemical techniques have been used for the investigation of the behavior of covellite during anodic polarization. In the basis of all these measurements is a three electrode system consisted of: 1) working electrode made of the sample of natural covellite from the Bor mine (Eastern Serbia, Yugoslavia); 2) reference electrode (saturated calomel electrode) and 3) counter electrode (flat platinum). Electrolyte solutions used in these investigations are of the same kind as those used in the rest potential measurements. Sulfate and chloride solutions, as well as the mixed sulfate/chloride solutions, are the most perspective from the application point of view.Cyclic voltammetry has been the first used method that confirmed the formation of passive layer on the electrode surface during anodic polarization. Elementary data about the reaction mechanism have been obtained too. More detailed data needed for more precise conclusions about the mechanism and rate of the anodic process on covellite have been obtained by galvanostatic method. It was established that the essential difference exists between the reaction mechanism in sulfate and chloride solutions. Also, the difference is exhibited in the nature of reaction product directly connected with the passivation of the electrode surface. Chronopotentiometric investigations have been performed in sulfate, nitrate, chloride perchlorate and mixed sulfate/chloride solutions applying different current densities. The shape of obtained curves indicate if there was a surface passivation and how intensive it was."

Jan 1, 2003

By A. Collings, A. Farmer

"Power ultrasound may be used in the processing of mineral suspensions to clean the particle surfaces of oxidation products and fine coatings, mainly through the large, but very localised forces, produced by cavitation, which is the formation and sudden collapse of bubbles in a fluid. Cavitation occurs preferentially at solid surfaces in a liquid: at container walls, inserted objects or suspended particles. When the cavitational bubbles collapse near a solid they do so by forming a very high energy jet directed from the point on the bubble furthest from, and directed towards, the surface of the solid, in effect micro jet blasting.This paper highlights some of the major mineral processes where ultrasonics is beneficial namely: Surface cleaning of detrital mineral particles, where container quality glass sand was upgraded to tableware quality and up to 20% improvements in the sharpness of high tension separation of mineral sands was achieved"

Jan 1, 2003

By Ronald Díaz

"Cerro Corona is a porphyry ore with different geometallurgical units and alterations produced by an extensive family of geological failures that have determined a special type of mineralization. With the increasing depth of the mine, it is estimated that the host rock will be less altered. Consequently, the ore will have a higher resistance to breakage accompanied by associated problems such as lower throughput. In light of this reality, various projects have been carried out with the objective to optimize mineral processing of ore with low clay content and high hardness, including reducing the blasting grid, increasing the load factor, using adequate mixtures of hard ore, reducing crusher settings, installing air guns in the transfer chutes, increasing ball charge, and changes in the lifter design, wear control in the hydrocyclones, syntonization of control logics, supervisor control of the SAG mil, characterization of feed ore, etc. However the most important factor was the teamwork between mine and plant personnel, aiming at common objectives for the company. These projects started in 2011, including characterization of mineralogical domains, breakage and blasting characteristics, and also a revision of the actual operating conditions in the crushing and grinding circuit. The development of different designs of the SAG mill lifters and the unloading grates, a 16% ball charge increase, improvements in the blasting process, reduction of the primary crusher setting, weight reduction on the feed lid, and variation of operational parameters, all allowed the company to achieve its objectives of maintaining impact control and steel recharge within the expected operational parameters. The achieved throughput is above design capacity, sustainable, and not without new challenges for maintaining and optimizing this production level."

Jan 1, 2014

By Marlize Barkhuizen, Chris Aldrich

"Owing to environmental constraints, safety considerations and competitive pressures, the development of model-based process control and other automated systems have experienced considerable growth in the last few decades. Reliable process models are usually critical to the successful implementation of these systems. In complex processes, these models are often constructed from process data, as modelling from first principles may not be feasible or cost-effective.Even so, modelling or identification of nonlinear systems from historic plant data can be a daunting task and in the process industries the problem is complicated by the presence of noise from various sources, nonstationarity of the data, intermittence, such as observed in particulate flows, etc. Traditional methods, such as frequency analysis and linear modelling do not handle these systems well. Similar problems arise with the application of nonlinear theory developed over the last few decades, where much of the analysis depends on embedding of the data in a phase or pseudophase space, since these methods were not originally designed to deal with noisy systems.With singular spectrum analysis, the data are embedded in a high-dimensional reconstruction, followed by the introduction of a new coordinate system, where the origin is moved to the centroid of the reconstructed system states and the axes are represented by the dominant principal components of the states (points)."

Jan 1, 2003

By Anatoly F. Usov, Vyacheslav A. Tsukerman

"The Russian scientists have developed a new energy saving method for an efficient destruction of the sturdy and hard materials (rocks, ores, frozen soils, concrete blocks ets.) - the Electric Pulse Discharge method of materials destruction (EPD). The detailed researches of a broad circle of problems connected to development EPD-disintegration of materials of a various nature and area of use are executed. The electrical and power characteristics of process, physical fundamentals of selectivity of a breakdown and destruction are investigated, the means of electric pulse splitting and refinements of materials are developed, the technological efficiency of disintegration of industrial minerals estimated.One of the most important characteristics of the EPD-disintegration of ores is the high selectivity of destruction, which provides a large ratio of useful minerals' grains opening, and at the same time, it destroy them less. This ensures in the subsequent stages of beneficiation of ores considerable increase of the extraction and improving the quality of concentrates.The technological tests of various industrial minerals have shown a possibility the EPD-disintegration, as a process that provides the best efficiency of disclosure of useful minerals in all types of ores. Technological and economic efficiency of the method of ore beneficiation is the highest for difficult beneficiated ores with rather low extraction by existing methods. The increase of extraction in this case can reach several percents. As a rule, at a EPD-disintegration the disclosure of mineral grains happens in earlier stages of material comminution than at a mechanical comminution, and with less damage of products. This promotes a simplifying the process of ore preparation and for reducing the power consumption."

Jan 1, 2003

By Slobodan B. Vujic

"Some twenty years ago, during construction of flotation in the “Veliki Krivelj” copper and non-metallic mine Bor, a computer supported system for remote controle of technological process was installed. Nowadays, the major part of equipment of this system is worn-out and technically old-fashioned. Having this in mind a decision was made to design a new computer supported information-management system for Flotation. The paper presents a concept and features of project solutions.For the requirements of remote monitoring and management of technological process in Flotation of “Veliki Krivelj”, Copper and non-metallic minerals mine in Bor, Yugoslavia (hereinafter: CNM Bor), a measuring-regulation equipment was implemented and a computer control system, adjusted for that time, built some twenty years ago. The major part of this equipment is today worn out and technically out of date.Having estimated that production and business activities could hardly be more efficient, operative and successful on one hand, and available mineral and other resources rationally exploited, the CNM Bor made a decision in 1999 to improve information-management function of Flotation. The idea was that the set task be realized through development and introduction into practice up-to-date integrated and computer-supported production-business information-management system. The first logic step in completion of this task refers to engineering-creative determination of information management system (hereinafter: IMS), namely to project elaboration.When considering the real system from technical, technological, organization, monitoring-management, logistic and business aspects, the Project on IMS of Flotation, should provide a rational, modern and, for the real system conditions, complete solution. The Project solutions should be based on the most recent knowledge from computer and measuring-regulation technics as well as from CIM concept (Computer Integrated Manufacturing)."

Jan 1, 2003

By Dingwu Feng, Jannie S. J. van Deventer

"The effect of ultrasonication on reactions at solid/liquid interfaces was investigated by using an ultrasonic probe in two slurry systems, i.e. cyanidation of a refractory sulphide ore and geopolymerisation of metakaolinite. The surfactant dithiophosphate was used to render the gold bearing sulphide particles hydrophobic, in an attempt to induce the formation of cavitation bubbles directly at the desired surfaces. Oxygen was injected into the cyanidation system to improve the attachment of oxygen bubbles to the hydrophobic sulphide surfaces. Geopolymerisation occurs in highly alkaline solution with waste aluminosilicate oxides and silicates as the reactants. The process of geopolymerisation is believed to involve dissolution of Al-Si oxides from solid particles, diffusion of dissolved Al-Si complex from the solid surface into the gel phase, condensation of gel phase and hardening of the gel phase. It has never been investigated how ultrasonication affects the above steps in synthesising geopolymers, despite a number of papers dealing with sonochemical synthesis of materials. The introduction of power ultrasound into such slurry systems is expected to result in advanced geopolymer materials.In the cyanidation of the pyrite concentrate, the kinetics of gold extraction were significantly enhanced in the presence of ultrasound, due to the prevention of passivation and the enhanced dissolution of sulphides. Cyanide consumption was significantly reduced with ultrasonication, owing to the oxidation of soluble sulphides to sulphate, minimising the cyanide consumption by sulphides. With oxygen injection, ultrasound significantly enhanced the leaching of gold from the pyrite concentrate, as oxygen could enhance the formation of the oxidation radicals by ultrasonic cavitation. In the presence of dithiophosphate, ultrasound further improved gold leaching in the oxygen-aerated system. Dithiophosphate could selectively adsorb at gold host sulphide surfaces, and make the surfaces hydrophobic. As a result, the ultrasonication effectiveness could be enhanced through forming cavitation bubbles directly at the interfaces."

Jan 1, 2003

By Ashton M. Swartbooi, Robert van Hille, Alison E. Lewis

"Nickel production by precipitation using hydrogen reduction generates an ammonium sulphate solution containing approximately 2g/L of nickel, and 1g/L of cobalt as an impurity of the process. Sulphide precipitation is an effective method for heavy metal removal, especially when compared to hydroxide processes: metals can be removed from solution at relatively low pH levels, small quantities of sludge are formed, and due to the high reactivity of sulphides the reactor retention time is reduced. However, the low solubility of sulphide species can lead to spontaneous nucleation of fines (due to higher supersaturation levels which are difficult to separate from solution, leading to reduced process efficiency. Using a fluidised bed reactor, fines formation can be minimised as the pellets provide a large surface area and promote heterogeneous nucleation.A synthetic nickel-cobalt ammonium sulphate solution was reacted with two forms of sulphide reagent: (a) a liquid sulphide solution and (b) gaseous hydrogen sulphide. A range of factors (including pH, reagent concentrations, metal to sulphide molar ratio, flow rates and recirculation rates) influencing the efficiency of the precipitation reaction have been studied. The efficiency of the precipitation reaction was measured using both metal recovery and fines formation as indicators.Figure 1 shows the effect of decreasing the metal:sulphide ratio (at constant SS = 2.725e+17), on the metal removal for liquid sulphide. By decreasing the metal:sulphide ratio, up to 99% removal of both nickel and cobalt could be achieved.These results also indicate that the precipitates that formed were polysulphides, since no sulphide was present in solution after the experiment. This would also indicate that a lower metal:sulphide ratio would be more favourable. However, decreasing this ratio (at constant metal concentrations) would lead to an increase in the fines concentration, because of increased supersaturation levels induced by the higher sulphide concentrations. To decrease the supersaturation, dilute solutions of either reagent would be employed."

Jan 1, 2003

By Xin Tan, Changgen Li

"The floatabiliby of chelate CF-collector for zinc and lead oxide minerals was described. It found that CF-collector possesses a strong collection power for zinc and lead oxide minerals as well as excellent selectivity for the gangue minerals. A new technology of zinc and lead oxide flotation with CF reagent as a collector, lead nitrite as a activator and water glass as modifier was presented. The mechanism of interaction between reagents and minerals was discussed by means of adsorption, zeta potential, nephelometric titration, XPS and infrared spectra was investigated.CF-collector, newly developed by Beijing General Research Institute of Mining and Metallurgy (BGRIMM), is a kind of chelate collector for the flotation of oxide minerals. CF-collector mainly consists of N-nitroso-N-phenylhydroxylamine ammonium salt. The CF-collector was used for the selective flotation of scheelite in the Chinese plants.In this paper, the effects of the dosages of activator Pb(NO3)2 and depressants (sodium hexametaphosphate, polyphosphate, water glass and salified water glass) on the floatabilities of several minerals (cerussite, smithsonite, calcite, dolomite, limonite and quartz) as well as their mixtures were investigated in the presence of the CF-collector. The results show that the CF-collector is the excellent collector for selective flotation of cerussite and smithsonite. Pb(NO3)2 can selectively activate the oxides of lead and zinc resulting in a decrease of the CF-collector dosage. The sodium hexametaphosphate plus the salified water glass are the effective depressants for gangue minerals. Based on the above facts, the “CF process”, namely, used CF reagent as a collector, Pb (NO3) 2 as a activator, and sodium hexametaphosphate plus salified water glass as depressant, has been used for the flotation separation of the lead oxide mixtures or zinc oxide mixtures without disliking and heating. For the feed lead assaying 19.07%, the lead concentrate assaying 49.81% Pb at the recovery 80.69% was obtained after one step flotation. For the feed zinc assaying 12.85%, a zinc concentrate of assaying 29.56% Zn at recovery 83.87% was obtained."

Jan 1, 2003

By Aubrey Mainza, Malcolm S. Powell

"A hydrocyclone with two vortex finders, named the three-product cyclone (3PC), has been successfully tested in the Platinum industry for dealing with the dense Chromite found in UG2 ores. This dense component preferentially reports to the cyclone underflow, resulting in an over-ground fine Chromite component in the final product. The dense media effect caused by a high concentration of this in the cyclone feed produces a coarsening of the cyclone overflow, which results in loss of recovery through over-size silica in the PGM carrying component material in the float feed. The fine barren particles of Chromite that report to the overflow are recovered through entrainment in the flotation process, resulting in detrimental contamination of the slag produced from the concentrate.Data from many industrial scale tests of the 3PC have shown that three distinct products are obtained when the inner vortex finder length (LIVF) is extended to the region either above (normal classification) or below (reverse classification) the transition zone (a region were the inner and outer overflow streams are identical). Due to wear problems arising from extending the IVF deep into the cone of the cyclone, it is advantageous to use the shorter IVF. Only the normal classification results are reported here, but similar outcomes (to opposite overflow streams) were obtained for the reverse classification. The results showed notable differences in the percentage split of the plus 100µm material in the product streams, confirming that three distinct products are discharged from the 3PC. About 12% of the plus 100µm material in the feed reports to the middlings stream, 1% reports to the final product, and the remainder to the cyclone underflow.Results of silica and chrome splits to the three distinct products namely, the inner overflow (INO), the outer overflow (OUO) and the underflow (U/F) are given in Table 1. These show that the 3PC can be used to recover coarse silica through screening the middlings product - which has a high silica content. When the vortex finder ratios (ratio’s of cross-sectional areas) are carefully selected, the split of plus 100µm silica to the middlings product ranged from 2.9 to 9.6%. Large amounts of oversize silica and chrome report to cyclone underflow, explaining their high percentages in the underflow stream."

Jan 1, 2003

By Fernando Concha

"Thickening development and innovation in the 20th Century occurred in two decades periods. From 1900 to 1920, Dorr invented the continuous thickener and the first method of thickener design was proposed by Coe & Clevenger. From 1920 to 1940, the operating variables of continuous thickening were discovered by Comings at the University of Illinois. From 1940 to 1960, the first theory of sedimentation was proposed by Kynch and several authors, Talmage and Fitch, Ysioka and Hasset used this theory to develop new thickener design methods. From 1960 to 1980 Shannon and Tory demonstrated that this theory applied exactly for the sedimentation for small rigid spheres in water and Scott showed that it is not valid for flocculated suspensions. From 1970 to 1990 the phenomenological theory of thickening was developed based on the theory of mixtures. Papers by Kos, Bascur, Thacker and Lavelle, Concha and Bascur, Concha and Barrientos, Auzeris, Buscal and White, Landman, White and Buscal show the application of this theory to thickening and Adorjan presented the first thickener design method based on this theory. In 1980s the mathematical analysis and solutions of Kynch’s model for batch and continuous thickeners was obtained by Bustos. The new Century brought solution to the phenomenological thickening model which was applied to thickener design, simulation and control. The method of thickener parameter determination was improved by designing new laboratory and on-line instruments and advanced control strategies was designed and validated in plants. Structural thickener design produced improved feedwells and feed dilution mechanism, stronger raking mechanism and different thickener shapes according to new ambient requirements, such as high rate thickener and paste thickeners that increase the water recovery. New challenges include better flocculation and advanced control strategies."

Jan 1, 2014

By Claudia Ríos Figueroa, Gonzalo Montes-Atenas

"Among the many variables mentioned in the literature that may influence the froth flotation performance, particle size is perhaps one of the most renowned. Empirical knowledge has indicated that recovery of fine particles will inevitably drop below certain particle size threshold. Several processing alternatives have been suggested to improve the recovery of fine particles. Some of these initiatives have been reached the status of patents and other intellectual property related documents; however, there is still a disconnection between the scientific knowledge available and the industrial operations practicalities implemented to address this matter. In fact, in general terms, none of these ideas or processes concepts have become a final solution to this problem. At first glance, economical reasons may be argued as the main cause hindering the development of these and other ideas, but it would be an oversimplification as technical issues behind them are still themes to be discussed and sorted out. This study aims to review technical aspects behind scientific ideas and processes concepts suggested to solve the problem of low beneficiation of fine particles in froth flotation. The analysis was performed using the theory of inventive problem solving (TRIZ) which allows identifying technical gaps these initiatives have not considered or overlooked. Statistically the scientific databases indicates that reports on fine particles froth flotation only represented less than 50% of all reports involving fine particles processing. Most of the solutions derived from classic contradictions derived from bubbles and particles hydrodynamics only (reducing the bubble size or increasing the turbulence would increase the rate of bubble-particle aggregates formation but may reduce the recovery). This contradiction encompasses a small range of contradictions possible to be accounted and to be resolved. The method is expected to provide insights towards designing definitive solutions for the industry in this field."

Jan 1, 2014

By O. A. Punishko, G. G. Mineev, Zabaikalsky Ore-Dressing Plant, M. V. Malova, O. V. Belousova, S. A. Bogidaev

"In order to intensify benefication processes (flotation and magnetic separation) for rebellious tantalitecolumbite ores electrochemical machining of pulp (ECM) is suggested instead of costly mechanic-chemical activation and magnetizing roasting. Any change in the surface mineral-semiconductor potential under the action of electrochemical treatment results in the change in the isoelectrical state of the surface and the adsorption property of the mineral with respect to ionogenic reagents-collectors. In this case conditions are created for regulating the ion composition, reduction-oxidation potential and pH of the liquid phase of the pulp without any extra introduction of expensive and often ecologically harmful chemical substances.Ores containing tantalum and niobium are characterized by complex chemical composition, determining their physical properties (conductivity, dielectric penetration, magnetization value, etc.) and their electric susceptibility.The authors investigations show that the pulp electrochemical treatment leads to the increasing magnetic susceptibility of the paramagnetic minerals. The main chemical elements forming the columbite-tantalite minerals except tantalum and niobium are iron and manganese. They determine the rare-metal minerals paramagnets properties. The electrochemical treatment changes the relation of the oxidized and reduced forms of these elements having. The method of cathode pulp treatment before flotation is successfully tested industrially.In the field of noble metals metallurgy new technological proposals are reduced to the following. As is know, the production of noble metals from unusual raw materials demands the elaboration of principally new technologies new technologies in so far as the methods for gold and silver extraction from ores are as a rule low elective and at the existing level of engineering are economically not expedient.The analysis of the main trends in the field of non-standard raw material treatment shows that the perspective ones are the geo- and biotechnological processes (underground leaching and leaching in heaps - UL and HL and microbiological methods of metal extraction)."

Jan 1, 2003

By M. Brennan, A. Majumder

"The mineral processing research community has devoted enormous efforts to the modelling of mineral separators over the last 50 years. While many efforts have been made to use only fundamental physics as a basis for the models, fluid flow patterns in separators are not simple while the motion of particle swarms through fluids is extremely complex.Sluices are the simplest forms of the flowing film concentrators and have been used in the mineral industry since at least the 15th century (Agricola, 1556). Flowing film concentrators, in general, still have widespread applications in the mineral industry and their designs vary according to the specific need.Particle separation in a sluice appears deceptively simple, but the separation mechanism has proven complex and difficult to quantify. Separation in the sluice takes place in a flowing film a few millimetres thick. The particles are suspended by turbulent eddies and motion relative to the fluid takes place in socalled hindered settling mode. The difficulty arises because the presence of the particles influences the flow pattern and when the particles are fully transported by the flow, the flowing slurry may not have the same viscosity as water and does not have the same density. For this reason a universal theory which can explain the behaviour of a suspension in a sluice or any other gravity equipment has still not been developed. Few attempts have been made to analyse the mechanisms involved in the concentrating processes of pinched sluices and Reichert cones.Fluid flow behaviour and slurry transportation characteristics in open channels have, however, been active research topics in the disciplines of fluid mechanics, chemical engineering and civil engineering for many years. As a result, an extensive literature is available, which has led to the development of the model described in this paper.In an effort to test the extent to which fundamental fluid mechanics can provide a prediction of particle separation, a study on a simple parallel-sided sluice has been carried out using glass beads at various particle concentrations and flow rates, and the actual particle separation taking place compared to predictions from modelling.The modelling strategy was divided into two parts; the first was to predict the horizontal slurry flow velocity profile and the second to predict the solid particle concentration over the depth of the flow at different flow conditions. The predictions were then validated with measured data sets. This can easily be done if the slurry flow is split at different fractional flow depths so that the mass flow of solids over different flow heights is measured accurately over a fixed period. Mass flow splits can then be calculated by integrating the product of the predicted slurry velocity profile and the predicted solids concentration profiles from the base of the sluice bed to the slurry free surface."

Jan 1, 2003

By Gideon Chitombo

"Mining is a "continuous" process of dependent breakage and materials handling stages, from the initial breakage of the in-situ rock, extraction from the pit or underground, and finally to the surface stockpile and downstream processing. Over time, underground and in-pit mining activities diverged into two separate disciplines, each using a variety of in-situ breakage techniques and surface activities, with processing techniques dependent on mineralogy or grades. This artificial separation of underground and open pit activities was exacerbated when the two became increasingly managed as separate cost centres rather than as an integrated unit. Mass mining essentially began in 1903 when metallurgist Daniel Jackling initiated the world’s first open pit, mining system at the Bingham Canyon porphyry copper deposit in Utah. The term mass mining has since been construed to mean large open pits and cave mining methods, including their variants. These methods are largely non-selective, involving the mass extraction of a deposit irrespective of the uneven distribution of grade and mineralogy. The advantages of mass mining have historically applied mostly to low grade, large scale deposits. With the depletion of mineral reserves closer to the surface, however, new deposits are deeper, lower grade and mixed with more impurities. These and other factors make extraction more difficult and costly. Mass mining is moving rapidly into a new and less certain environment where revolutionary changes are required to effectively deal with future challenges which are technical, economic and environmental (licence to operate). This keynote address presents current initiatives being considered for the next generation of both underground and surface mass mining systems in order to significantly reduce lead times and mining costs (CAPEX and OPEX), substantially increase productivity and meet license to operate requirements. The address is designed to solicit discussion on how better integration of mining and processing can become a platform for these next generation of mass mining systems and can also help the industry deal with the future challenges."

Jan 1, 2014

By Tomás Vargas

Treatment of copper sulphides minerals via leaching-solvent extraction-electrowining (lix-sx-ew) have been for years the process scheme proposed from hydrometallurgy as an alternative to the conventional flotation-smelting route. Many different hydrometallurgical technologies of this type have been proposed, investigated and tested over the years, but until today none of them has come close to endanger the predominance of the flotation-smelting route in the copper industry. However, bioleaching introduced an important breakthrough in this context as this technology enabled the alternative hydrometallurgical treatment of secondary copper sulfide ores and low grade ores by applying heap bioleaching processes. Extension of its application to primary copper ores have been limited until now by the nature of chalcopyrite which is very refractory to leaching. However, important improvements are expected by using of improved designs that enable to operate at high temperature ranges where copper is leached faster under the catalytic action of thermophile microorganisms. The present work analyzes future scenarios for the application of this technology either in heaps or in-situ, which can become very attractive as copper can be produced reducing drastically the energy consumption associated to the mining, crushing and grinding stages.

Jan 1, 2014

By N. Panteleeva, E. Konoplev, I. Michailova, S. Titkov, T. Gurkova, T. Chumakova, Sylvinit Co.

"INTRODUCTIONFlotation of mineral particles by cationic surfactants – namely alkyl amines and their derivatives – is finding ever growing application in processing of various ores and in quality refinement of the benefication end products, iron concentrates for example. In the recent years application of cationic collectors - alkylmorpholines - enabled the development of new highly efficient procedure of water-soluble mineral processing, being also the one with low energy consumption. This procedure is a reverse flotation of carnallite from bay salts of salt-pans and from carnallite ores.The efficiency of cationic SAS influence depends upon colloid-chemical state of the collector in flotation liquid phase, especially if the latter comprises mineral salts. Availability of clayey impurities or slime particles of iron oxide in cation flotation feed, which actively sorb the cationic collector, deteriorate considerably the cation flotation performances. In Halurgy Institute the investigations of cation flotation under potash and carnallite ore processing have been carried out, and new reagent modes, enhancing cationic surfactants sorption at mineral particles, have been developed. Application of new reagents enables one to decrease considerably the consumption of expensive cationic collectors and to enhance the floatability of coarse mineral particles."

Jan 1, 2003

By G. S. Hansford, G. E. Searby

"Ferrous iron oxidation kinetics was measured in continuous culture at temperatures between 65 and 75ºC, using thermophilic microbes suitable for high temperature bioleaching. The resulting specific oxidation rates were modelled as a function of the ferric/ferrous iron ratio. The results were compared to those obtained by conventional mesophilic microbes.Microbially mediated ferrous iron oxidation is a vital sub-process in the mesophilic bioleaching of sulfide minerals and is expected to be of similar importance at elevated temperatures using thermophilicmicrobes.A thermophilic archaeal culture used in chalcopyrite bioleaching was successfully grown in continuous culture on ferrous sulfate, indicating the capability of the microbes to sustain growth for long periods on the energy provided by the conversion of ferrous iron to ferric iron, the primary leaching agent in sulfide mineral bioleaching.Steady state data was obtained at residence times of between 70 and 10 hours, with washout occurring at residence times between 11 and 9 hours, corresponding to a maximum growth rate (µmax) of between 0.09 and 0.11 hr-1. The reactions were followed by measurements of the solution redox potential, soluble iron concentrations, and offgas analysis of the oxygen and carbon dioxide utilisation rates."

Jan 1, 2003