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By Y. E. Brylyakov, M. A. Kostrova

"The apatite staffelite ores (ASO) of Kovdor deposit are dominated by fine-grained aggregates containing both phosphate minerals and silicates — vermiculite, smectites, zeolites. These minerals exhibit ion-exchange properties. In this connection, the magnitude of cation exchange, along with the content of P2O5 and CO2, is an important property of apatite staffelite ore, which largely determines the performance of concentration processes. In the examined ASO samples, the magnitude of cation exchange measured in terms of Ca2+ is 2546-4790 g/ton. The conducted laboratory studies of apatite staffelite ores with various mineral composition showed that adding calcined soda improves the recovery of P2O5 into the flotation concentrate. Full-scale tests were conducted at the apatite staffelite ore processing plant at Kovdor Mining and Concentration Operation and demonstrated the high performance of the proposed agent treatment. The test results showed that in the flotation of apatite staffelite ores, the optimum calcined soda feed rates range from 3,500 to 5,000 g/ton of the flotation feed. With close flotation feed and concentrate grade parameters, the P2O5 recovery gain is 17%. The effect of adding soda is associated with the desorption of the hardness cations from the minerals, precipitation in the pulp and, accordingly, improvement in the ionic composition of the liquid phase of the flotation feed due to a reduced content of calcium ions. Based on the test results, the proposed agent treatment with an elevated feed rate of calcined soda was implemented at Kovdor Mining and Concentration Operation in the flotation of apatite staffelite ore. The apatite staffelite ores (ASO) of Kovdor deposit are dominated by fine-grained aggregates containing both phosphate minerals and silicates — vermiculite, smectites, zeolites. These minerals exhibit ion-exchange properties. These minerals have certain properties requiring a more detailed examination for a better understanding of the flotation properties of apatite staffelite ores."

Jan 1, 2018

By L. Tavares

The significant capital and operating expenditure of size reduction operations have maintained comminution on the spotlight of mineral processing research during the last century and, more recently, the concerns about the impact of these operations on the sustainability of the minerals industry, will remain to do so in the 21st century. One of the most popular approaches that have been used to deal with these challenges is the application of simulation both to reduce the uncertainty in the design and improve the operation of size reduction operations. From the initially purely empirical approaches, including the energy size reduction ?laws? and the phenomenological approaches, of which the traditional population balance model is, arguably, the best example, comminution modeling now reached a point in which more fundamental and mechanistic models are sought. The paper analyzes some of the advances that now make multiscale modeling of comminution processes realizable. On the microscale, greater understanding of the phenomena involved in fracture and fragmentation of single particles under different stressing conditions now exists. Particle breakage testing methods are currently used in a routine basis by industry and good quantitative descriptions of different breakage mechanisms are now available, although research is still required to develop appropriate models for a couple of them. On the macroscale phenomena, the discrete element method (DEM) has been successfully used not only to provide insights but also quantitative information on the transfer of mechanical energy from the machine to the grinding media in mills and to particles in crushers, while smoothed particle hydrodynamics (SPH) and computational fluid dynamics (CFD) to describe fluid flow. The paper also analyzes the importance of modeling mesoscale phenomena in size reduction, which is the interaction of particles forming assemblies or beds of particles, demonstrating some of the areas requiring further attention. Examples of application of the multiscale modeling approach to the inadvertent comminution of ore lumps during handling, to the comminution in vertical impact crushers and tumbling mills are demonstrated. Keywords: comminution modeling, DEM, SPH, CFD, multiscale modeling approach

Sep 1, 2012

By Y. Nahmad- Molinari

We present a novel on line inductive sensor for the determination of the quality of the concentrates of iron ores. This device is coupled with a cheap USB Data Acquisition System that makes it versatile enough to simultaneously control up to seven fluxes at a very low cost (< $300 US dollars), and achieves a resolution better than 0.5 % on the determination of the magnetic iron content in the concentrate. A RLC circuit with its inductive element placed surrounding a sample of pure magnetite concentrate is tuned at its resonance frequency, by means of adjusting, the feeding voltage of a voltage-controlled oscillator (VCO) and several samples with mixtures of different contents of silica and magnetite are placed in order to get a calibration curve. After some signal conditioning, a National Instruments USB-DAQ NI-6008, acquires the amplitude of the signal via USB port on a PC using a Lab-View program designed for such purpose, in which the calibration curve is used for on-screen data presentation directly in percent of magnetite content. The implementation of this device for control purposes on line directly placed on the concentrators would allow better efficiency of the process and higher quality of the final concentrate by con-trolling; the rotation speed, the rising or dilution water fluxes or bypasses towards milling recirculation cycles.

Jan 1, 2014

By William Conger, Greg Schick

Grinding media consumption is a major cost variable in industrial mineral comminution circuits. Specifically, industrial SAG media consumption results from a combination of surface abrasion wear, media breakage, surface spalling and rejection size from the mill. Three main consumption rates; weight of media consumed per time, per kWh and per weight of ore ground are defined and compared. Recent industrial data has provided an opportunity to relate consumption in terms of weight of media consumed to weight of ore ground (g/tonne) and weight of media consumed per kWh of energy consumed (g/kWh) with SAG specific grinding energy consumed (kWh/tonne). Using relationships developed from this data it is possible to project SAG media consumption in future mineral comminution circuits.

Jan 1, 2014

By S. Mohanta

The air dense medium fluidized bed separator which has been developed for the dry beneficiation of coal is recognized as a low cost and high efficiency process. The success of this separator for beneficiating any specific coal, alone or in combination with other processing methods, mostly depends on the characteristics of run-of-mine coal. Therefore, a thorough knowledge of the mineralogical composition and washability characteristics of representative coal sample is highly essential for correctly and effectively assess the suitability of this process. Available literature conforms that although the characteristics of Indian non-coking coals are well known, the correlations between the particle compositions with its density are entirely lacking. In the present study the washability, proximate, ultimate and elemental analysis was conducted for four typical Indian high-ash non-coking coals and their elemental compositions were well correlated with the specific gravity of coal. The results obtained in this study provide some essential information to the coal-processing engineer for efficiently operate and control the process. Furthermore, the beneficiation potential of air dense medium fluidized bed was experimentally evaluated and compared with the results obtained from an operating wet beneficiation plant. Based on this comparative study the air dense medium fluidized bed is established to be a possible alternative to the conventional wet beneficiation method for beneficiating Indian coals with Ep values in the range of 0.03 to 0.06

Sep 1, 2012

By Vladimir Grujic, Milorad Grujic, Ivan Djurkovic, William Riggs

"In this paper, we have studied efficiency of different chemical structures of frothers on copper ore Majdanpek. The goal was to find out the best suitable chemical structure, which allows good bubble formation, size and interaction, forces on mineral surface. The particle size distribution was between 10 and 100 µm. Our research was oriented on three groups of frothers: alcohols, poly glycol ethers and poly glycols.We also used different collectors based on similar or less similar alcohol group in chemical structure as in frothers, expecting higher stability of air bubble in contact with copper minerals. Minimal potential energy was determinate in the hydrodynamic conditions for different particle sizes. It was founded that it is proportional to air bubble volume on 0.88° and contra proportional to the kinematics viscosity of pulp.Analyzing the results, we find out that poly glycols decreased surface tension the most. Also, it increased amount of coarser particles to the top of pulp. This group is less sensitive to pH value compared to the others too.From the class of frothers with higher efficiency in flotation process, we pointed OrePrep X-75 and X-133 as frothers with expressive frothing characteristic in the alkaline and low alkaline circuits. Special suitability of those frothers for floating copper minerals makes their hetero polar molecules with more than one hydrocarbon radicals connected to one polar group. However, those froters have no nether high or low solubility and are non-ionization. Those froters indicate some small collecting characteristics too. In dispersion systems, those two frothers make two types of bubbles: smaller di < 1.2 mm; V = 0.0008 cm3 and middle di < 16 mm; V = 2.2 cm3 (di – Bubble diameter, V – Bubble volume). Transportation speed of air bubbles it is possible to calculate based on equation: ?s = 27.5 * di 1.4 cm/s. Distribution of free surfaces for chalcopyrite is average 80% in the class –74µm +10µm and 20% in the class -10µm. If we get all class sizes, we find that recovery (R) depends from the time by equation:"

Jan 1, 2003

By Peter Ay, Bodo Müller, Jens Markowski, Manfred Kanthak, Florian Logsch

"Presently the global commodity situation for non ferrous-, precious- and rare metals is characterized by a strong increase in consumption and a simultaneous shortage of materials derived from primary sources. So the use of secondary raw materials gains is important due to economic and ecological reasons. Non Ferrous-, precious- and rare earth metals were detected in household waste (Municipal solid waste, MSW) for years. In MSW-treatments plants NF-metals are actually mostly separated from dried fractions. The separation of these metals is carried out with the aim of removing particles which disrupt further processing. A selective enrichment of individual non-ferrous metals has not been carried out previously. The separated fractions contain mixtures of Al, Cu, Zn, Pb, Sn, alloys, precious metals (e. g. Au, Ag, Pt) and rare metals (Ga, In, Nd etc.) along with considerable amounts of contaminations. The R&D project "NE-Rec" selectively processes the coarsely separated non-ferrous-metal-conglomerates increasing the concentration of targeted metals. Metals and metal mixtures are concentrated by sorting steps and the impurities are discharged from the process. Still contaminated precious metals are then subjected to a wet-chemical treatment. So metals can be specifically brought into solution or can be precipitated to separate unwanted components (inerts, polymers, foreign metals). Further the relevant metals will be concentrated by thermal-metallurgical processes. The technology, developed in the R&D project, enables identification, separation and processing of non-ferrous metals, precious metals and REM in household waste and transfers them into further processable individual fractions."

Jan 1, 2014

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 David Newton, Christian O’Keefe, Robert Maron, Jerin Russell, Paul Rothman, Dylan Cirulis

"The presence of unwanted coarse material in flotation feed streams negatively impacts both recovery and throughput of concentrator plants. The detection of this coarse material is a long-standing problem in mineral processing that has been poorly addressed by existing instrumentation systems. This problem has been overcome by the development of two new systems that detect in real-time the presence of coarse material in the overflow stream of individual hydrocyclones. They both use sensors mounted to the overflow pipe of the hydrocyclone and provide a robust and maintenance-free system measurement that enables corrective actions through operator intervention or automatic control strategies. One system is non-invasive and detects very coarse material 6mm or greater in size. The other system uses a wetted sensor and detects coarse material down to a lower size limit of approximately 100 um. Both systems have been commercially deployed. The systems will be described in detail. Validation data and typical plant data will be shown"

Jan 1, 2014

By Lei Zhang, Xianjun Lu1, Minjie Lian, Liyang Zheng

In order to investigate rheological behaviour of fine tailings backfill pastes, the fine iron ore tailings (size fraction of -0.074mm accounts for 70%) from Fuquan Mining Co., Ltd. of Sinosteel Corporation (Shandong, China) was investigated. The rheological parameters such as slump, viscosity and yield stress of the tailings pastes under different densities were measured in detail, and the effect of paste density on the rheological property and the relationships of different rheological parameters of the pastes were also discussed. According to the results, the rheological behaviour is in accordance with the pseudoplastic fluid in a wide range of paste densities (solid content, w/w) of 65% to 80% and the pastes turn to be Bingham fluids at higher shearing rates. Along with the increase of paste density, the slump drops gradually and the viscosity and shear stress increase gradually. However, the variation extent of the rheological parameters varies at different density ranges. According to the variation pattern of the rheological parameters at different paste densities, the flow ability of the pastes can be classified into three zones. The high fluidity zone was observed at the density range of 65%-69% where the rheological parameters vary slightly along with the paste density, the moderate fluidity zone was observed at the density range of 70%-76% where the rheological parameters vary significantly along with the paste density, and the low fluidity zone was observed at the density range of more than 76% where the rheological parameters vary sharply along with the paste density and the critical density for this sudden variation is about 76%. Furthermore, linear correlations of slump/viscosity and slump/yield stress were observed. It is possible to predict the viscosity and yield stress of the pastes based on the slump measurements.

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 Vincent C. Smith, Agit Singh, Daniel de V. van der Spuy, Bernard Muller

"Process control in the minerals industry is made difficult by factors such as the multivariable nature of the processes, noise, many disturbances, the changing nature of the processes, nonlinearities, process constraints, slow responses and large deadtimes. A good example of such a process is a milling circuit, where all these problems are experienced. Since model predictive control (MPC) effectively handles most of these difficulties, Mintek decided to develop, customise and test an MPC controller for milling control.Conventional MPC uses a dynamic model of the plant to calculate the future (predicted) plant outputs based on the movements of the manipulated variables in the past. The future moves of the manipulated variables can then be calculated using an optimisation algorithm that will minimise the difference between the setpoints and the predicted outputs. The least squares optimisation method is the quickest, but it does not cater for process constraints. Constraints can, however, be handled explicitly by using a quadratic programming optimisation method. This method ensures that the variables stay within the constraints at all times, but the calculation procedure is much more computationally intensive.• modifying MPC for the Minerals Processing IndustryIt was found that in order to obtain good, robust control using MPC in the minerals processing industry, the conventional MPC algorithm had to be adapted. The MPC controller was first tested on an extensive milling simulator, which was specifically developed for that purpose. Problem areas were identified and the MPC controller was specially adapted to accommodate for these difficulties. Some of the adaptations to the conventional MPC algorithm and special features added were as follows:Since milling plants contain many integrating processes (e.g. sumps), and integrating errors can cause offsets and poor control, it was essential that integrators be handled explicitly. This problem was solved by adapting the algorithm and also using an integrating error portion to compensate for integrating errors.Constraints on the inputs and outputs adversely affected the control. The controller using simple least squares optimisation was tuned with the constraints in place, while the maximum expected setpoint changes were made. This ensured that the process would be able to handle most setpoint changes up to these expected values without violating the constraints. A later improvement on this method was the incorporation of a quadratic programming algorithm to perform the optimisation. This method handles limits explicitly and was shown to perform better than the least squares methods (at the expense of a much higher computational cost)"

Jan 1, 2003

By H. Pearce, A. E. Lewis, A. Ochieng

"Hydrodynamics and mixing are fundamental to the operation of mineral process systems such as flotation cells and metal precipitation reactors. Hydrodynamic conditions influence phase mixing and mass transfer in a multiphase system, and these affect the overall performance of such a system. Detailed information on the effects of the hydrodynamics on the performance of agitated systems is still required for the design and optimal operation of hydrometallurgical systems, which are always multiphase. Computational fluid dynamics (CFD) techniques have been employed to study the hydrodynamics and mixing, most of which have focussed on the performance of axial and radial pumping impellers in agitated tanks. However, very little has been reported on the influence of a draft tube on the flow profile in such systems.CFD simulation of a stirred vessel centres on the way the impeller is modelled. Some of the most recent approaches to modelling an impeller are impeller boundary condition (IBC), snap shot, sliding grid (SG), multiple frame of reference (MFR) and inner outer (IO). The accuracy, with which these models predict experimental results and the corresponding computational demands, form the basis upon which the choice of an approach is made. Most of these approaches (IO, SG and MFR) address the key problem of the stirred tank modelling, namely, the simultaneous meshing of the rotating impellers and the stationary baffles. The MFR is computationally cheap and has been found to give predictions that compare well with experimental data.The CFD technique (code CFX4.4) has been employed in the present work to study the hydrodynamics in a mixing vessel stirred with either a Rushton turbine or a pitched blade impeller. The multiple frame of reference (MFR) approach has been used to model both impellers. A draft tube was used only in the Rushton turbine stirred vessel. The flow profiles for the impellers have been studied in three regions; below the impeller tip, at the middle of the tank, and near the liquid surface. The simulation results were compared with literature data obtained using a laser Doppler velocimetry in the three regions of the vessel, and it was found that the model predictions were better in the impeller region. There was a poor prediction of the experimental results in the region closer to the liquid surface; however, this was improved when the turbulence parameter (C2) in the k-e model was set to a higher value. The value of the impeller clearance at which the Rushton turbine generates an axial impeller type flow has been determined and it has been shown that, at this clearance, a draft tube can be used to enhance axial flow in a Rushton turbine stirred reactor."

Jan 1, 2003

By Pamela Castillo, Marcia Muñoz, Rodrigo Luca, Brian Townley, Fernando López

In the present study we discuss the value of multi-element geochemistry as a tool for semi-quantitative to quantitative bulk mineral characterization in geological and geo-metallurgical modeling of porphyry copper type deposits, with an emphasis on hydrothermal alteration associations, types and intensities. In mine production of porphyry copper deposits much effort is placed on ore grade and geological modeling, applied for predictive mineral processing behavior, from blasting, grinding, leaching or flotation, down to waste disposal and environmental management. High confidence geological models are commonly based on geological mapping of drill core and surface/ underground exposures, combined with discrete mineral characterization (e.g., petrography, QEMSCAN®, spectroscopy, etc.). Unfortunately these are expensive and applied to limited numbers of samples, thus lacking sufficient representation and not suitable for geo-statistical modeling. In addition, geological mapping always presents uncertainty, based mostly on qualitative estimates. The combination of information usually provides geological models that are hard to combine with geo-metallurgical data, much less with mineral processing predictive behavior models. The advent of multi-element geochemistry, at low cost, has allowed employment of such tools massively, yet little use is given to the data, usually focused on elements of economic interest (main ore and credits) and elements of negative impact to concentrates and/or process. Geochemistry reflects the mineral composition of rocks, thus allowing characterization of lithology, alteration types and intensities, and mineralization. As examples of such applications we present generic classification techniques which were developed on various porphyry copper deposits of northern Chile, these based on multi-element geochemistry, allowing for semi-quantitative to quantitative high resolution modeling of key aspects of lithology, hydrothermal alteration and mineralization, and which may be cross-referenced to metallurgical test samples and by that, to geo-metallurgical properties of rocks and modeling. In addition, as data is quantitative and continuous, modelling of gangue can benefit from geo-statistical modeling.

Jan 1, 2018

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 Ana C. C. Pacheco, Maurício L. Torem

"The aim of this work was the study of the effect of the type (Fe3+, Al3+ and Fe3+ and Al3+ mixture) and of the coprecipitant concentration on As5+ removal by ACF. Removal of As5+ using sodium dodecyl sulfate (SDS) as a collector was studied by Adsorbing Colloid Flotation (ACF) at laboratory scale. The morphology of the precipitate retained in the foam was analyzed by Scanning Electron Microscopy (SEM/EDS).In order to investigate the effect of the initial concentration of Fe3+ on As removal, sets of experiments were performed with a concentration of Fe3+ in the proper range of pH (5,0 – 6,0) previously observed in the coprecipitation tests. As removal improves significantly as the concentration of the coprecipitant agent increases from 60 mg.L-1 (77,4%) to 80 mg.L-1 (99,7%). This is probably due to the higher concentration of ferric hydroxide (Fe(OH)3) which provides a larger surface area available for adsorption of As. From the initial coprecipitant concentration of 80 mg.L-1, As removal has shown to be rather high (? 99,7%), with the maximum being (99,9%) by using a Fe3+ concentration of 160 mg.L-1. Therefore, for a maximum As removal, under these test conditions, the optimum concentration of Fe3+ is 160mg.L-1.This paper also shows the effect of the initial concentration of Al3+ on As removal at a suitable range of pH (7,0 – 8,0). A very significant increase on As removal was found to occur as the initial concentration of coprecipitant was increased from 60 mg.L-1 (35,7%) to 80 mg.L-1 (97,7%) and a decrease in As floatability (43,7% - 54,5%) was found to occur from that Al3+ concentration amount. Based upon those results, the optimum Al3+ concentration so as to remove As under these test conditions is 80 mg.L-1."

Jan 1, 2003

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 V. Avzian Belozersky reg 453524, Vasily V. Lodeischikov, Adolf F. Panchenko, Til E. Vidusov, Olga D. Khmelnitskaya, Vladimir E. Dementyev

"Presently, there is a number of gold deposits which cannot be developed using the conventional technologies with acceptable economic indices due to low gold content, high depth of ore occurence and other conditions. For such ores, an innovation technology of underground gold leaching in the place of their occurrence is of special interest. The technology excludes ore mining and hoisting to the surface. This enables the production cost of 1 g of gold to be considerably reduced in comparison with conventional methods of gold recovery.The Maminskoye deposit oxidized ores were chosen as the subject of underground leaching because they are ideally suited for this purpose due to their composition and hydrological parameters. The ore reserves within the underground leaching block are 90, 000 t with 0.7 g/t average gold grade.An experimental system for underground leaching with a throughput of 15 cubic m solutions per hour was developed. A combined filtration-and-infiltration system of the ore massif development by holedrillingwhere pregnant solutions are air-lifted was worked out.The underground leaching flowsheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution onto active carbon, carbon concentrate ashing and calcine melting to produce Dore metal."

Jan 1, 2003

By Sanggono Adisasmito

"The quality of the higher education in Indonesia is being improved by implementing a program financed by the World Bank under a project named QUE (Quality for Undergraduate Education). The investments are provided to selected study programs through a competitive selection process. The grant finances staff development, the purchase of equipments, textbooks, consumables, technical assistance, and incentives for outstanding faculties such as teaching grants, project grants, lecture note awards, and educational policy studies. These additional investments are provided to produce chemical engineering graduates that will compete beyond the national market.Chemical Engineering Department of Institut Teknologi Bandung in Indonesia has been selected to receive the QUE grant beginning the year 2000 and ending the year 2004. The department is actively involved in the mineral processing issues, particularly in the aspects of energy supply and the environmental protection. The activities are distributed in different laboratories and areas of expertise, such as: thermodynamics and utility systems, process equipment, chemical reaction and catalysis, microbiology and bioprocess engineering, process control, ceramics, as well as polymer and membrane technology. The main objectives of the QUE project are to improve the undergraduate program in the following aspects: Relevance, Academic atmosphere, Institutional management and commitment, Sustainability, as well as Efficiency and productivity, or abbreviated as RAISE. At the end of every fiscal year, the progress of the program is evaluated to measure the effectiveness of the project.The achievement of the QUE project objectives were assessed using performance indicators developed during the program design. There are six indicators to measure the performance of the individual program of study, such as: (1) Admission Test score, (2) average students' Grade Point Average (GPA), (3) average graduates' length of study, (4) graduates' waiting time before getting first job, (5) Test of English as Foreign Language (TOEFL) score, (6) Graduate Record Examination (GRE) score. Essentially, the RAISE evaluation criteria will be used to perform three main functions, such as (1) to measure the achievement through the six quantitative performance indicators, (2) to support the progress of evaluation and reporting throughout the implementation of the program, (3) to provide a universal framework for qualitative evaluation."

Jan 1, 2003

By K. A. Natarajan

"Interaction with microorganisms results in significant surface chemical changes on minerals. For example, chemolithotrophs such as Thiobacillus ferrooxidans and Thiobacillus thiooxidans significantly alter the surface chemistry of several sulfide minerals such as pyrite, chalcopyrite, sphalerite and galena. Heterotrophic bacteria such as Bacillus sp. could alter the electrokinetic properties of oxide minerals such as hematite, alumina, silica, kaolinite and calcite. Microbe-mineral interactions could thus be beneficially utilised in mineral beneficiation as different from bioleaching. Microbially induced mineral beneficiation unlike bioleaching deals with interfacial phenomena at mineral-solution-bacteria interfaces and surface chemical changes are brought about at very rapid rates amounting to a few minutes resulting in mineral separations in an aqueous medium.In this paper, the role of acidophilic chemolithotrophs such as Thiobacillus thiooxidans and neutrophilic heterotrophs such as Bacillus polymyxa in the beneficiation of sulfide and oxide minerals is illustrated. Mechanisms of bacterial attachment on various sulfide and oxide minerals are outlined with respect to the influence of bacterial interaction in bringing about mineral surface hydrophobicity or hydrophilicity. The role of bacterial cells as well as metabolic products such as bioproteins and exopolysaccharides in significantly altering the surface chemistry of sulfide minerals such as sphalerite and galena and oxides such as hematite, alumina, silica and calcite is discussed with probable mechanisms. Possibilities of generating mineralspecific bioreagents are outlined with respect to bacterial adaptation to mineral substrates."

Jan 1, 2003