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By Junji Shibata

In a present process to treat the tungsten carbide tool waste, the wastes are roasted in air and then an alkali leaching is carried out in an autoclave. An environmentally friendly process is required to recover rare metals (Co and W) from the wastes. The effect of mechano-chemical (MC) treatment on leaching of rare metals was investigated in this study. The solvent extraction and crystallization-stripping methods were applied to separate and recover tungsten and cobalt in the leached solutions. The MC treatment for the rare metal leaching is effective to dissolve rare metals from the wastes due to the change in crystalline structure of WC and oxidation of WC with KMnO4. Cobalt ions are extracted with D2EHPA by a cation exchange reaction. Tungsten in the leachate can be extracted by TOA (tri-octyl amine) as an extractant, because tungsten species exist as a form of anionic species in acidic solution. The rare metals in organic phase are recovered as insoluble salts such as oxalates and ammonium salts in the crystallization-stripping process. Keywords:unheated oxidation, solvent extraction, crystallization-stripping, recycling

Sep 1, 2012

By G. Pahomova

"It developed an alternative to traditional flotation enrichment refractory of complex lead-zinc ores to obtain conditional lead and zinc products. The scheme involves the use of the processing method of gravitational enrichment of the primary cycle and the combined gravity-flotation-hydrometallurgical in finishing. The method has a high level of comprehensive utilization of mineral raw materials in relation to the elements that are extracted in the process of enrichment in lead concentrate, and the increase in recoverable value of processed ores. INTRODUCTION The primary source of lead are complex sulphide lead-zinc ore, lead ore actually rarer. The value of lead and zinc ores (except lead and zinc) is determined by the presence in them of a wide range of associated components: silver, contained mainly in galena; gold; bismuth in the form of its own minerals, but is associated with galena; cadmium contained mainly in the sphalerite; indium, thallium and gallium contained in sphalerite and galena; selenium and tellurium are present as impurities in the sulfide, tellurium is also found in the form of its own minerals. Of note harmful impurities antimony, which is often associated with lead sulphosalts and arsenic, having a substantially own minerals. By quality (content of lead, or the total content of lead and zinc) lead-zinc ores are divided into rich, ordinary and poor; by oxidation - to sulfide (with a lead oxides content less than 15% and zinc oxide content less than 10%), mixed and oxidized (50% oxide); the latter have a subordinate importance as a source of zinc and lead. Traditionally, the most contrasting technological properties of sulfide ores of nonferrous metals considered flotation properties, which determines the priority in the selection of flotation technology of their enrichment. Other methods of enrichment - gravity (jigging and enrichment in heavy suspensions), radiometric sorting (separation) are used as preliminary operations whose main purpose is to increase the content of lead and zinc in the ore sent to flotation, as well as the removing of part of empty rock in dumping tails prior to flotation. Effective implementation of these methods is possible at large size emphasizing in the ore of lead and zinc minerals, which is typical of the rich ores and which so far mainly worked. At the same time, non-ferrous metal ores (polymetallic, lead-zinc, copper-zinc, etc.) have a sufficiently high contrast to gravitational properties since ore minerals have a higher density compared with a rock minerals. But the gravity of the practice of non-ferrous ores enrichment is not widely used, despite its high degree of environmental safety and lower cost expensive."

Jan 1, 2018

By S. Serranti

The recycling of end-of-life concrete into new concrete is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The possibility to realize a larger re-use of silica aggregates from old concrete, strongly contributes to reduce environmental impact (reduced exploitation of natural resources, reduction of CO2 emissions, airborne dust production, etc.).To reach this goal, innovative processing techniques, as well as innovative sensing units and architectures have to be developed. In this perspective an analytical approach, based on hyperspectral sensing techniques, is proposed, discussed and critically evaluated in order to perform an automatic quality control assessment, finalized to maintain a high standard of concrete demolition waste, from the earliest stage of recycling to the further processing stages, according to the detected in-situ demolition waste characteristics. The paper deals with the analysis and the evaluation of the problems related to the integration of this approach with state-of-the-art demolition and building processes and procedures. Keywords: end-of-life concrete, recycling, hyperspectral imaging, NIR spectroscopy, quality control

Sep 1, 2012

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

Cationic flotation using alkylamines and their derivatives as collectors, and characterized by high selectivity of mineral particle separation, is finding ever growing industrial application. In recent years the industrial application has been initiated of new cationic collectors - alkylmorpholines. Efficiency of cationic surfactants operation as collectors is dependent upon their colloid and sorption properties and the availability of silicate .carbonate rock-forming mineral impurities in the ore, which sorb the cationic collector. Investigations have been carried out on the influence of frothers and organic depressors with various compositions upon physical-chemical and flotation properties of alkylamines and alkylmorpholines. On the basis of these investigations requirements for organic depressor were developed and new flotation reagents were proposed (V-1 frother and KS-MF depressor). The use of new reagents enables one to decrease considerably the consumption of expensive cationic collectors and to enhance the floatability of coarse mineral particles. Data of new reagents industrial application is presented. The reagents developed can be used for flotation processing of other ores.

Jan 1, 2003

By A. M. Muhamedilova, S. M. Narbekova, L. V. Semushkina, D. K. Turysbekov, N. K. Tussupbayev

The research and development of new, more selective collectors in order to improve flotation efficiency represent one of the main priorities in the development of innovative technologies pertaining to flotation separation of various substances and minerals. The use of collectors’ mixtures is considered as the universal instrument for ensuring necessary proportion of chemically and physically sorbed collecting reagents in every individual case. Currently hard-dressed, refractory ores and man-made raw materials, which are characterized by low content of valuable components, fine dissemination of mineral assemblages and similar technological properties of constituent minerals, are widely involved in the recycling processes. The possibility of processing tailings, which are left after flotation beneficiation, has been considered in the case study of tailings of the Zhezkazgan beneficiation plant and the Tishinsk copper ore deposit with utilization of the modified multifunctional flotation reagents. Modified poly-functional collector is the mixture of composite Aerofloat, TC-1000 and butyl xanthate. Reactants ratio is 1:1:3. The advantage of the suggested flotation reagents is that they are composed of two polar groups and have a long hydrocarbon radical. This structure, being in the water during flotation process, plays a dual role: first, as a collector adsorbing on the mineral surface it produces metal complexes with polar groups in the form of bridges; second, apolar radicals flocculate valuable slimed components, thereby intensifying flotation process. It has been shown that flotation of Zhezkazgan tailings with utilization of the lesser modified reagent amount compared to butyl xanthate has enabled to produce crude copper concentrate with 13.0 % copper grade and 80.22 %recovery. Compared to the baseline technology, copper content of crude concentrate has been increased by 5.1 % and the recovery by 31.4 %. It is shown that tailings flotation of the Tishinsky field by applying modified collector allows for increase of the of useful components extraction in a collective concentrate with: copper 9.63 %, lead for 8.41%, zinc 9.2 %, iron 2.73 %, gold 3.57 %.

Jan 1, 2018

By A. Kogelbauer, A. Stadtschnitzer, A. Boehm, F. Schillab

"The paper covers the design and implementation of an industrial dense medium cyclone plant for carbonaceous iron ore, the proving of efficiency as well as the development of a predictive model for plant control. The VA Erzberg GmbH mines about 12 Mio.t of carbonaceous rock ore at the “Steirische Erzberg”. Due to increased demand of the Austrian steel plants, the production of ore concentrate was raised by 30 % up to 3.0 Mio t/a during the last 5 years. One of the projects to realize the increase in capacity at improved concentrate quality was the implementation of a dense medium cyclone plant for the fine size fraction – 8 +1 mm replacing the former dry permanent magnetic drum separators. By physical separation the siderite variety “spateisenstein” (42% Fe) of a density of 3,8 g/cm³ is separated from ankerite (10 – 17% Fe), the second iron bearing carbonate with a density of 3,2 g/cm³, dolomite, calcite and silicate bearing schists. The feasibility of the process was proven by the test results obtained from a test rig, that was constructed and operated in close cooperation between the Chair of Mineral Processing, Montanuniversitaet Leoben and VA Erzberg GmbH. The density separation surpassed the efficiency of magnetic separation clearly shown by •- values. The plant performance tests (capacity 120 t/h) verify the cut densities defined by Tromp T50 -values and the assigned efficiency found in the pilot tests at varied settings of media density, pressure drop, cone angle and apex diameter. The test rig as well as the final process will be presented. In order to create a tool to predict the performance of the DMS in the centrifugal field at various settings for varying feed composition the experimental results from size and density testing are analyzed in a modified way to obtain physically justified, smooth approximations for the performance curves. Models developed on coal washing plants are checked for their validity at increased densities."

Jan 1, 2018

By Vladimir F. Skorokhodov, Nikolay N. Melnikov, Svetlana P. Mesyats

"Among the problems of the civilization development, a problem of interaction between man and natural environment can be highlighted. In the twentieth century the human transforming activity had got scales of geological processes and defined the contradiction between the goal to increase the quality of human life and possibilities of the natural environment. Last twenty-five years after the World Summit on the Environment (1992) indicate that the development of civilization is still based on receiving super profits from the natural resources exploitation. This statement is confirmed by economy globalization rates, growing contradictions between consumption and production, depletion and degradation natural environment. A new technological order is formed at the time of growing world population, technological capacities, organizational complexity, from one side, and global scales of geo-resources consumption, on the other side. Sciences, determining the further civilization development, should take on the task to change the social worldview, since the preservation of human population consists in remediating and maintenance of biosphere functions as a regulator of ecological balance. The new worldview in the geo-resources exploitation is based on the Ecological strategy of mining development, which consists in reducing mining-induced loading on natural environment while increasing efficient mineral production and processing, and providing for a comprehensive solution of tasks on mineral deposit development. One of strategic trend of mining development is to increase complexity and completeness of useful component extraction from ore and mining deposits while reducing wastes and decreasing their stockpiled volumes. The implementation of the ecological strategy has shown that the future is determined by reduction of the environmental impact while improving the efficiency of mineral mining and processing.INTRODUCTION The global nature of environmental problems caused by the scale of consumption of natural resources, huge amounts of waste, and intensive man-made impact on the environment requires a revision of the strategy for the natural resources development. Many existing technologies are ineffective in achieving the ultimate goal. Direct output in the raw materials - the end product technological chain rarely exceeds 10%, which implies a huge amount of work to move the soil. In addition, the feature of scientific and technological progress at the present stage is the growth of power-to-weight ratio."

Jan 1, 2018

By F. Karakas

Water based paint formulations consist of some industrial minerals with quantities varying from 20 to 50 %. Quality of paint is directly related to these minerals used as pigment or filler in the production. Titanium dioxide is the most important and expensive pigment in paint formulations. Other minerals such as calcite and calcined kaolin are used as filler and mainly as a substitute for TiO2. Consequently, particle-particle interactions including adsorption, coating and size distribution of pigment mixture directly affects the paint quality. In the present paper, a new type of pigment mixture for possible use in architectural water based paints was developed through grinding. The effect of different types of grinding methods on physical properties of TiO2 and calcite mixture and the quality of paint produced by these mixtures have been revealed. Three different types of mills; conventional ball mill, vibratory ball mill and high-speed attritor were used for grinding of TiO2 and calcite. Viscosity, zeta potential and particle size distributions were used to characterize the pigment mixtures obtained upon grinding. The quality of paint was evaluated by standards based on both wet and dry paints such as viscosity, density, opacity and gloss. The paint produced with the pigment mixtures prepared in vibratory ball mill and high speed attritor showed improvement in physical properties particularly in the distribution and dispersion of mineral particles. Keywords: grinding, pigment, paint, TiO2, calcite

Sep 1, 2012

By Y. J. Ferdosi

This paper presents the outcomes of the preliminary investigation focused on the potential usage of Electrochemical Impedance Spectroscopy (EIS) in minerals processing. Currently, Electrochemical Impedance Spectroscopy has been successfully employed in the characterization of multilayer structures formed as molecules adsorb on flat surfaces and is commonly used in bio-related research. Few studies have explored the application of EIS in minerals processing, particularly for mineral particles and flotation systems. In the first series of tests, the impedance response was investigated as a function of particle size, shape and hydrophobicity using model quartz particles. The particle size fractions and the shape were found to contribute to the impedance response. The more hydrophobic quartz particles resulted in a higher impedance values. Further tests involved pure sulfide minerals including chalcocite, bornite, chalcopyrite and pyrite. The AC impedance measurements were conducted as a function of collector (sodium ethyl xanthate) dosage. The AC Impedance data was modeled using the combination of reference circuits. It has been shown that adsorption of collector onto sulfide minerals surfaces results in a higher magnitude of impedance. Increasing the collector dosage resulted in an increase in AC impedance for chalcopyrite, while a decrease was observed for chalcocite. Significant variations in impedance were exhibited by bornite and pyrite with a gradual increase in collector dosage.

Sep 1, 2012

By B. Csoke

To improve the efficiency of the crushing/screening plant of Bazalt-Középko Kobányák Ltd. (Hungary), the implementation of computer aided quality control is planned. In the current phase, the R & D work aims at the solution of high-priority tasks: 1) Developing the process models, validation of the models by means of industrial measurements. 2) Developing the algorithm for the process control of the crushing/sizing plant. 3) Developing the suitable computer program. To develop the mathematical models of crushing (breakage and probability functions) and to determine the model parameters, the experimental industrial trials were carried out on hydrocone crushers of types Svedala H 4800 EF and H 4800 F, changing the gap size and crushing relatively narrow grain size fractions. Additionally, the parameters of the separation function for the screens operating in the system were determined. It was established that the crushing probability depends on the grain size of the feed (Y) and the gap size (s), so the breakage probability S, for each cone crusher, can be well characterised by the function formed using the ratio of these two parameters: SfYsf==. The distribution of the broken grains can be described reliably using the relative grain size distribution function B(? = x/Y) (usually Schuhmann-Gaudin- or Rosin-Rammler-shaped function). For the screens, the probability function ()2()111/NTx = xd ???---???? is suitable for cha-racterising the separation (where x? grain size, ?-open-area ratio, d ? rectangular screen aperture size, N ? number of appearance of the particle on a screen surface). Using these functions, the comminution circuits were described by means of vector/matrix equations. The calculations and measurements verified the reliability of the developed models and algorithms.

Jan 1, 2014

By Sirish L. Shah

It is now common to have archival history of thousands of sensors sampled every second over long time. Yet we frequently have process engineers complain:??.We are drowning in data but starving for information??. How can these rich data sets be put to use? This paper addresses the issue of information and knowledge extraction from data with emphasis on process and performance monitoring including fault detection and isolation. Most of the major plant, factory, process, equipment and tool disruptions are avoidable, and yet preventable fault detection and diagnosis strategies are not the norm in most industries. It is not uncommon to see simple and preventable faults disrupt the operation of an entire integrated manufacturing facility. For example, faults such as malfunctioning sensors or actuators, inoperative alarm systems, poor controller tuning or configuration can render the most sophisticated control systems useless. Such disruptions can cost in the excess of $1 million per day and on the average they rob the plant of 7% of its annual capacity. Over the last decade the fields of multivariate statistics and data visualization and analysis methods have merged to develop powerful sensing and condition-based monitoring systems for predictive fault detection and diagnosis.These methods rely on the notion of sensor fusion whereby data from many sensors or units are combined with process information, such as physical connectivity of process units, to give a holistic picture of health of an integrated plant. Such methods are at a stage where these strategies are being implemented for off-line and on-line deployment. This article attempts to outline the field of sensor fusion - the application of signal processing methods, in the temporal as well as spectral domains, on a multitude and NOT singular sensor signals to detect incipient process abnormality before a catastrophic breakdown is likely to occur Keywords: Process analytics, process and performance monitoring, multivariate statistical analysis, sensor-fusion

Sep 1, 2012

By Rainer M. Lotzien, Michael J. G. Battersby, Jan Kleefeld, Julian V. Brown, Rainer M. Imhof

"The standard method of separation using flotation is compromised in terms of kinetics and efficiency, because of the generally slow separating differentials of fine bubbles and fine particle suspensions. A new flotation system has been developed that addresses these issues and imparts other benefits. The new technology is based on established pneumatic flotation designs called Imhoflot which use intensive in-line pre-aeration to aerate the flotation pulp prior to its introduction to the separating cell. Consequently the cell is designed only for the separation of the phases and not for bubble-particle contact. In the new system this separation is speeded up dramatically by the introduction of centrifugal motivation in the separating vessel, without the use of internal moving parts. The design focuses on providing increased differential forces on buoyant mineralised bubbles and hydrophilic fines. The observed result of these differential forces is the improvement of concentrate qualities by the reduction of the amount of misplaced material found in the froth. The commercial benefit to industry is much reduced residence time, less than 30 seconds, which offers considerable cost savings in equipment and infrastructure.Prototypes of 0.65m, 1.7m and 2.2m cell diameter size have been constructed for hydrodynamic and industrial scale tests to assess the previously established computational methods for scale up of the process. The 1.7m cell has been installed and operated for cleaning of potash concentrates in Germany, at throughputs of 150 m3/hr, with extremely encouraging results. A 2.2m cell has been installed and operated in plant trials for superfine coal in South Africa. Results are presented that illustrate the effects of differential separations by comparison with conventional pneumatic and mechanical flotation techniques. Predictions of performance are provided in the contexts of the applications tested."

Jan 1, 2003

By F. Burat

The present research covers the results of experiments carried out with high frequency vibration screen on dewatering of coal fines. In the tests, the addition of surface active reagents was studied employing a high frequency vibrating screen. To increase the efficiency of mechanical dewatering processes, ultrasonic treatment was applied along with surfactants and optimum dewatering conditions were obtained. The moisture content of the feed material was from 82.5% to 41% by the optimization of operation parameters including the angle of the screen, vibration frequency, feed rate and screen opening size. Optimum parameters obtained in dewatering processes carried out with the vibrating screen were kept constant and the effects of surface active reagents and ultrasonic treatment on dewatering were investigated. Finally, the moisture level of the material was further reduced from 41.0% to 37.66%.

Sep 1, 2012

By L. Ya Agapova

Emissions from pyrometallurgical processing of copper concentrates are usually subjected to wet scrubbing. The washing sulphuric acid so produced contains up to 0.2 g/L of rhenium, which is recovered by solvent extraction in the form of crude ammonia permeate (NH4ReO4). The mother liquor, obtained from the sulfuric acid wash, contains up to 35 g/L of rhenium and significant amounts of impurities. Crude rhenium salt is commonly processed by double recrystallization to produce marketable salt. A ton of high grade NH4ReO4 can be produced using 3.0-3.5 m3 of mother liquor. We propose an efficient technology of mother liquor pre-treatment aimed at removal of water-soluble organics with subsequent electrodialysis. Electrodialysis of mother liquor in a multichamber electrodialyzer resulted in the production of pure rhenium acid, from which a marketable NH4ReO4 is precipitated using ammonia solution. Multiple steps of recycling consisting of dissolution of NH4ReO4 salt, rhenium acid production from NH4ReO4 salt by electrodialysis and precipitation of NH4ReO4 from rhenium acid made it possible to upgrade the purity of obtained rhenium compounds by 1-2 orders of magnitude. A rhenium metal powder of 99.997% purity was produced by high-temperature reduction of high-purity NH4ReO4 with gaseous hydrogen. Rhenium metal powder of high purity can be produced from sulfate solutions of NH4ReO4 by non-platinum anode-based membrane electrolysis processes also. Keywords: rhenium, mother liquors, membranes, electrodialysis, rhenium acid, ammonia perrhenate, reduction, powder, electrolysis

Sep 1, 2012

By I. Gombköto

In the EU-region, the automatically operated approximately 200 (rotating hammer) shredder plants processing large technical equipment (end-of-life vehicles, large household appliances) annually produces 8-9 million tons of non-metallic grinded by-product, which ends in landfills, without recovery. Although this by-product is organic material, still contains large amount of metal components worth recycling. These operations, such as shredding and processing end of life vehicles or mixed metal components are a growing market and it is become more potential if EU directive 2002/96/EC will become obligatory for new member and candidate countries and they have to apply EU regulations. Eddy current separators (ECS) are one of the most important units of separation of non-ferrous metals from insulators in waste recycling. The product of ECS processing of shredded ELV?s is usually a mixture of Al, Cu, Brass and stainless steel. This mixture has relatively low price on the market, while purified metal products are required by smelters for which shredder operators are able to get even higher price. Our aim at University of Miskolc was to find solution producing pure metal products using dry separation processes. Authors are presenting a possible solution, using ECS. Institute of Raw Material Preparation and Environmental Processing possesses an ECS, equipped with 305 mm wide belt, and a concentric magnetic rotor. The subject of our work was to investigate the behaviour of model particles with different shape, conductivity (aluminium and brass), orientation and size in order to separate Al and Brass. We used model particles with similar shapes of shredder plant originated ones. The magnetic flux and magnetic frequency was constant and derived by the design of the rotor. During our research work, belt speed and rotor speed of ECS were varied. The particle distance and trajectory caused by throwing was determined and the results are reported in this paper.

Sep 1, 2012

By M. A. C. Goes

Over the last twenty years CETEM has been involved in the preparation and certification of reference material from ores, concentrates and related materials for use in analytical laboratories associated with mining, metallurgy and earth sciences. CETEM provides reference materials from mineral samples, not available from the existing sources, to meet the needs of the mining and mineral industry. CBPA-1 and CBPA-2 respectively are samples of copper sulphide ore and flotation concentrate, both originated from Sossego Mine, located in Pará State, Brazil. The batch characterization was carried out by a collaborative measurement program with participation of 20 industrial, commercial and government laboratories from South America, North America, Europe, Asia and Africa. The certificates and report were issued in December 2007 (http://www.cetem.gov.br/ mrc/ing). The objective of this paper was to describe the procedures for material preparation and the collaborative approach involving a collaborative interlaboratory measurement program to certify CBPA-1 and CBPA-2.

Jan 1, 2014

By Morin D. H., Battaglia-Brunet F., D'Hugues P.

"In the mineral-processing field, bioleaching of metal sulphide concentrates is currently operated in very large mechanically agitated tanks. Such bioreactors have considerable requirements in terms of power consumption for mixing, aeration and heat transfer. The use of slurry bubble column, where the particles are suspended by gas motion as well as by liquid upward flow, could be an alternative to achieve bioleaching in more economical conditions. In order to compare these two techniques, a unit of stirred reactors in cascade and a bubble column were comparatively operated at laboratory scale in the bioleaching of a pyrite concentrate. For both pieces of equipment, experiments were performed not only in batch mode but also in continuous conditions.Bubble column performances were significantly affected by unpredictable technical difficulties met to maintain continuous feeding in the bubble column and by a significant settling of the heavy solid particles. Nonetheless, theoretical kinetic data, extrapolated from results in batch conditions, could be compared to those obtained in continuous tests, in bubble column and in mechanically agitated reactors. These kinetic data were used to evaluate the influence of reactor design and configuration choice on bioleaching performances."

Jan 1, 2003

By M. Saghaeian, R. Hejazi, L. Hosseini, M. Zare

Difference between plant feed specifications in practice and design feed is a problem that most of processing plants face during operating and commissioning. This topic has led to inappropriate operating and necessitates repeating the basic tests on new feed. Gol-E-Gohar fourth concentrate line with a capacity of 2 MTPY, located in Kerman province, is the first iron concentrate plant in Iran in which High Pressure Grinding Roll (HPGR) technology has been applied. Plant&apos;s feed consists of 30% AG mills pebbles of lines 1-3 and 70% run of mine crushed ore whose Fe=51%, Fe/FeO=2.5, S=1.7% and work index=15 kWh/t. Desired concentrate has Fe>68% and S<0.7%. After the plant construction and operation commencement, providing design feed was not possible due to the crushing unit`s not being complete, therefore the plant was fed by AG mills pebbles. For predicting optimal conditions of the plant and investigating the possibility of improving the current concentrate specifications, sampling from the new feed and laboratory and pilot tests was performed again. Studies showed that new feed has Fe=41%, Fe/FeO=3.5, work index=17 kWh/t. Results of laboratory tests with Davis tube device and pilot tests run using magnetic separators with simulating the plant`s circuit showed that with current feed, achievable recovery in industrial scale would be 75.52% which compared to plant&apos;s recovery in studied period (75.94%) shows that plant operated in optimal conditions. To improve the current concentrate specifications (Fe=66%, S=1.03%, Ferec=75.94%) and for achieving desired concentrate, samples were reground to four fractions with k100= 300, 212, 100, 45 and Davis tube tests were performed on each of the samples separately. Results showed that the fraction whose k100=212 µm or k80=200 µm has respective Fe and S grades of 68.27% and 0.681% which are consistent with the desired concentrate.

Jan 1, 2014

By Jochen Petersen, Steven Bradshaw, Guven Akdogan, Ngoie Mpinga, James Mwase, Jacques Eksteen, Cornelius Snyders

"The platinum group metals (PGMs) and associated minerals are particularly refractory to most traditional direct leach processes. However, the remoteness of many new ore deposits, socio-political risks, the scarcity of skilled labor and constraints on the availability of water and electrical power makes it increasingly more difficult to implement the conventional mill-float-smelt-refine process routes to extract and refine PGMs in remote areas. This paper discusses a process to extract PGM’s from low grade ore and concentrate using a sequential stage heap leach process entailing heap bioleaching and high temperature cyanide leaching, and evaluates the feasibility of implementing a carbon-in-pulp process to recover the PGMs from the pregnant leach solution. The heap bioleaching extracts the base metals in an acidic sulfate medium using a mixed culture of thermophiles. After heap bioleaching the heap is reclaimed, rinsed, agglomerated and restacked for high temperature cyanide leaching where the cyanide liquor is directly heated via solar energy in panels. Palladium, gold and platinum are recovered during the cyanide leaching stage. The pregnant leach solution was evaluated for potential carbon-in-pulp adsorption and subsequent elution similar to gold processing. The kinetics of adsorption and elution compared well with gold adsorption and elution."

Jan 1, 2014

By F. Henríquez

Traditionally, the implementation of an automated control for a ball mill has been a challenging one. First, it must be capable of processing a variable SAG mill feed while at the same time avoiding to become a process bottle neck. Second thing is, it must deliver an adequate quality product (P80) to the process downstream. Then the ball mill itself and its associated classification equipment has problems of its own: it must maintain adequate control of cyclone?s pressure, density and pump-box level with often, less manipulated variables than needed, namely, variable pump speed and the opening/closing of cyclones. Thus, it becomes a non-linear multi-variable type of process with often too multiple and contradictory control objectives to satisfy simultaneously. On top of that, to extend cyclones availability and yet, maintaining their performance, is must both for process and maintenance purposes. Trying to solve the puzzle, Minera Los Pelambres implemented a novel and successful combination of MPC (Multivariable Predictive Control) and advanced control in two of its newest ball mills, reducing considerably process variability while maintaining high throughput and keeping the process well within constraints limits. Because of their differences in processing capacity, size and topology, two different stabilizing-control strategies were developed, tested and tuned. Hence, for both control approaches their implementation process, main results, areas of applicability, limitations and their key performance indicators are discussed further. This paper also discusses the need of such advance control technologies in the mining industry, including the impact of these technologies on best practices for their implementation, operation and long term sustainability

Sep 1, 2012