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By S. Martins

The aim of this work is to compare three different results of charge motion in a modified 5ft diameter lab mill and to identify differences and similarities in these results. The lab mill is modified from tumbling a ball charge to tumbling a charge of disks. This modification replicates 2D motion. This 2D condition is measured using an instrumented disk (iDisk) and analysed using a video imaging system. The iDisk is equipped with a 3D accelerometer array and rotation rate sensors. With the help of a video system, some measured quantities are also determined externally. The results of these three predictions or measurements are presented. A discussion is included.

Jan 1, 2014

By Barda K. Mishra, Surya P. Mehrotra

"INTRODUCTIONIn a jig, which is primarily a coarse mineral concentration device, the bed of mineral particles is pulsated with a stream of water resulting in the particles of different specific gravities. It operates in a cyclic manner – the jig cycle consists of four stages, namely, inlet, expansion, exhaust and compression. In the inlet stage the bed lifts up en masse. Near the end of the lift stroke the particles at the bottom of the bed start falling resulting in the loosing of the bed which, in turn, causes its expansion or dilation. During the third and fourth stages the particle resettle through the fluid, and the bed collapses back to its original volume. The pulsation and suction are repeated to bring about stratification with respect to specific gravity across the bed height. Various parameters affecting the stratification process include amplitude and frequency of pulsation, bed thickness, rate of hutch water flow, and feed characteristics. This paper first presents a review of various jigging theories and then describes a new approach to mathematical modeling of jigging employing the discrete element method.JIG MODEL BASED ON DISCRETE ELEMENT METHOD (DEM) APPROACHThe jig models based on DEM essentially involve tracking the position of each particle incrementally, applying Newton’s law of motion and a force displacement law at the contact. The model presented here is based on a three dimensional mathematical description of solid-solid and fluid-solid interactions. In this model, the force balance on a particle is extended to account for the effect of continuously varying fluid on the particle. The total force on each particle is made up of a known external body force, fluid particle interaction force and particle-particle and/or particle-wall interaction force. The fluid-particle interactive force is primarily made of drag and buoyancy. Di Felice’s correlation is used to evaluate the drag force. Solid-solid interaction is described by treating particles as discrete elements that are indestructible but interact with each other and any other elements present, such as walls, when they make physical contacts. A pair of spring and dashpot represents a contact The contact forces are computed from the amount and the rate of overlap of the particles at the contact. The motion of the particle is due to movement of the fluid, which transmits its energy through the particle-particle contacts. A computer program incorporating both the contact and the fluid model has been developed. It takes the operating parameters such as amplitude and frequency of the pulsating fluid, pertinent data concerning particle properties and the geometry of the jig bed as inputs."

Jan 1, 2003

By P. Prakash

A dual-drive planetary mill, which has a rotating shaft that sweeps a circle of diameter 750 mm, has been designed. The planetary mill is powered by a 5 hp motor to rotate the main shaft and a 3 hp motor to rotate the jars. The charge dynamics inside the horizontal-axis planetary ball mill was established using three-dimensional DEM simulations. The simulation results provided data to determine the impact energy distribution and the effect of process parameters such as mill speed and filling. It has been observed that the mean impact energy per unit time increases with rotation-to-revolution ratio, whereas the average number of inter-particle impacts per unit time decreases. The mill was also used to synthesize a variety of powders. Here three case studies of reaction milling are briefly presented: (i) cementite and silicon carbide, (ii) oxide dispersed strengthened (ODS) steel, and (iii) magnetite from blue dust. In each case, the powder was produced by mixing and then milling the corresponding pure components. The phase evolution, particle size distribution, and morphology of particles during milling were studied for various samples collected at different milling times using laser size analyzer, SEM, TEM, and Mössbauerspectroscopy. The results established a convenient way to produce powders of high technological and commercial value.

Sep 1, 2012

By K. A. Natarajan

Involvement of various indigenous microorganisms in extracellular and intracellular iron oxide formation is a convincing index for iron ore biogenesis. Biomineralization of various iron oxides such as hematite, magnetite, goethite and limonite with the participation of aerobic and anaerobic microorganisms is well established. Various aerobic and anaerobic bacteria such as Gallionella, Leptothrix, Acidithiobacillus, Thermoplasmales, Pseudomonas, Bacillus spp and Shewanella putrefaciens, which are implicated in the formation of higher and lower oxides of iron have been isolated from different iron ore deposits. Diversity of microbial life in iron ore deposits can be put to beneficial use such as selective removal of undesirable constituents such as silica, alumina, clays, phosphorous and calcite and also to bring about environmental detoxification. Role of microorganisms such as Paenibacillus polymyxa, Bacillus subtilis, Yeasts and a sulfate reducing anaerobe in the biobeneficiation of hematite is illustrated. Surface chemical changes brought about by bacteria - iron ore mineral interactions are discussed with respect to hydrophobcity, adsorption isotherms, zeta potential data and bioreagents generation. Bacterial adaptation to minerals such as hematite, quartz, alumina, calcite, apatite and clays results in secretion of mineral ? specific biosurfactants such as proteins and polysaccharides. Such bioreagents can be used as selective collectors, dispersants and flocculants in iron ore beneficiation. Research results are highlighted to demonstrate silica, alumina, phosphate, calcite and clay removal from hematite. Environmental friendliness of such biobeneficiation processes is demonstrated with respect to biodegradation of toxic amine collectors, utility of ?in situ? organisms in enhancing settlement of fines in tailing dams and water harvesting. Keywords: bio-mineralization, bio-beneficiation, bio-remediation, Gallionella, Leptothrix

Sep 1, 2012

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 C. Y. Sun

Flotation of chalcopyrite and unactivated malachite with xanthates (ethylxanthate, butylxanthate, octylxanthate and dodecylxanthate) is studied in this paper. Minerals interacted with xanthates are detected by FTIR, and simulated by molecular mechanics. It shows that chalcopyrite can be floated with 4 kinds of xanthates, and unactivated malachite can?t be floated with ethylxanthate but can be floated directly with later 3 kinds of xanthates while characteristic absorption peaks of those four kinds of xanthates are all detected by FTIR on chalcopyrite and malachite surface. After simulating the interaction between xanthate and mineral, it shows that H2O and OH-can interact with chalcopyrite and malachite, and their interaction energy may be so called energy bulwark which must be overcome by collector when collector interacts on minerals; the two sulfur atoms in xanthate group interact with copper and neighbor iron atoms on chalcopyrite. It also shows that molecular mechanics results with logP of collectors can interpret the mechanism of xanthate-mineral on atom scale.

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 Alejandro Rubio-Lopetegui, Gonzalo Montes-Atenas

The occurrence of Enargite (Cu3AsS4) in hydrometallurgical plants bears a number of challenges. One question lies on how Copper and Arsenic can be selectively extracted from the solid surface structure when immersed in aqueous solution. The leaching of Enargite in ambient conditions has been extensively studied; nevertheless, challenges regarding the process kinetics and surface structures enabling the extraction process remain ill-understood. Prior knowledge indicates that different conditions of pH, Eh, temperature, speciation of the aqueous phase or variations of these parameters defines the overall rate at which metals and other elements will be transferred to the solution. One aspect that the research studies have seldom addressed involves studying the main features of the surface structures formed during the leaching process at the outmost surface atomic layer. Such structures will mediate between the solid bulk and the solution to undertake subsequent stages of leaching process. The aim of this research work is to critically analyze the state of the art of Enargite electrochemistry from the mediator formation-dissolution mechanisms standpoint occurring at the mineral-solution interface. The most probable mediator species reported in the literature were found to be: Arsenolite and Sulfur (acidic media), Covellite (acidic and alkaline media) and Tenorite (alkaline media). As a result of this analysis, it was observed that the surface speciation was not in full agreement with the previous knowledge suggested to explain Enargite leaching reactions and, therefore, modified Eh-pH diagrams are presented. The acquired insights on the surface structures rising from the Enargite-aqueous solution interactions is further revised to provide new experimental protocols towards selectively separating Copper and Arsenic through hydrometallurgical paths.

Jan 1, 2014

By J. Broadhurst

"A number of metal supplying industries have in recent years seen the compilation of life cycle inventories (LCIs) and life cycle assessments (LCAs). The activity has largely been driven by the interest of ultimate metal users, such as the automotive industry, in the interest of designing more sustainable products. Often, the compilation of such inventories has been little more than an auditing exercise. However, the process of conducting an LCA can have more value, guiding designers and operators to points within the technology train where significant emissions and impacts originate. The LCA product can thus be used to inform on-site environmental management, and, where process data is used to construct dynamic operational models, to support strategic decision making in the realm of project planning and technology selection. LCA thus serves as a valuable tool to support the industry’s drive to support the sustainable development of the societies in which it operates.This paper reviews and compares the priorities of environmental and closure planning in the design phase, with environmental management and auditing during operation, and with green procurement of minerals and metals products. It shows how life cycle assessments of various complexities can be used to reconcile these various objectives, ensuring that the latter, critical to business success, can be addressed from the outset in a new project. The paper then reviews a case study of the use of LCA in the base & precious metals industry, where the complexity of the operation disallowed the simpler auditing process so that a detailed process understanding had to be built up in order to compile a meaningful life cycle inventory."

Jan 1, 2003

By G. P. Wong

"The Inco Matte Separation process was the first commercial application using mineral processing techniques to separate nickel from copper from a slow-cooled matte in Sudbury since 1945. In Inco Sudbury operations, bulk sulphide concentrate containing chalcopyrite, pentlandite, pyrrhotite and some gangue minerals is flash smelted and converted to Bessemer matte. During the controlled slow-cooling of the Bessemer matte, discrete mineral grains of new mineral phases are formed: copper sulfide precipitates as chalcocite (Cu2S), nickel sulfide as heazlewoodite (Ni3S2) and a Cu-Ni-Fe alloy is also formed. Flotation is employed to separate Cc from Hz under high lime conditions (pH>12) with diphenyl guanidine (DPG) as both collector and frother.A simplified matte separation flowsheet is as follows. After grinding, the Cu-Ni-Fe alloy is removed by magnetic separation. All precious metals are recovered in the metallic alloy. Following the rougher flotation, a Cu concentrate is produced after cleaner and re-cleaner flotation in mechanical and column cells. Two Ni concentrates are produced: a high-grade Ni product containing less than 0.8% Cu from the scavenger column tails and a low-grade Ni product containing 5% Cu from the middlings circuit tails. A stream containing the inseparable Cc and Hz from the middlings circuit is generated and recycled back to the smelter. The quantity of this stream is typically about 3% of total feed and can be as high as 5%, greatly decreasing the overall matte separation efficiency. The large mass of the recycle stream is a direct result of poor Cc/Hz separation selectivity in the middlings circuit. The middlings circuit, consisting of a thickener, a regrind mill and two columns, processes two streams: cleaner tailings and scavenger concentrates. The thickener contributes significantly to oxidation due to the long residence time of the pulp in this unit."

Jan 1, 2003

By David I. Verrelli, Peter T. L. Koh

"Recent experimental measurements of induction time made by direct observation with the ‘Milli-Timer’ indicated that angular particles were able to attach much more rapidly than spherical particles. There was around a tenfold difference in the respective induction periods for particle-bubble attachment. For industrial application, a more holistic comparison is needed, with the induction period for attachment being just one input. Over the years, CSIRO has developed a CFD-flotation model that incorporates both rigorous hydrodynamics, to simulate real industrial cell geometries, and a detailed model of the embedded flotation process, in which the induction period is an important parameter. We conducted transient modelling of batch flotation. First, spherical particles were modelled, as a ‘baseline’, for different particle sizes and levels of hydrophobicity. In the second set of results, the induction period was decreased by a factor of up to ten, simulating flotation of angular particles. Flotation recovery was found to depend upon induction period in a complex manner. For highly hydrophobic or fine particles, the induction period for spheres was already so low that recovery was limited by other factors (e.g. bubble-particle collision frequency). Further decreases in induction period, as for angular particles, did not have a significant effect on recovery in these cases. By contrast, when weakly hydrophobic or coarse particles were modelled, the recovery was predicted to be greatly enhanced for angular particles, in comparison to spheres. For these particles the induction period was limiting recovery, so that the flotation rate constant could be improved directly by reducing the induction period. This is consistent with batch flotation experiments using Ballotini reported earlier. Therefore, when dealing with weakly hydrophobic particles or relatively large particles that are to be floated, an enhancement can be expected for more angular particle shapes. In such cases, judicious specification of the grinding circuit may improve the overall efficiency."

Jan 1, 2014

By Markus A. Reuter, Albert Scholte, Ewoud V. Verhoef, Gerard P. J. Dijkema

"A dynamic, interactive map has been developed of the life cycle of a number of metals, from mining through to minerals processing, metal production, product manufacturing, recovery and waste management. Whilst the existing metal process network and waste management infrastructure provide substantial scope for (product) design, these also limit change because of the strong path dependency of industry and infrastructure development. The metal production network is complex, as it consists of an interconnected and integrated system that incorporates multiple production routes for a spectrum of metals. More often than not, the production or recovery of a single metal is related to or dependent on the generation or recovery of another. The effects of these other metals is of great importance. In order to realize the potential economic importance of impurities, research and development have integrated the processes of copper production with those of lead and zinc, and connected the processes to those of among others silver, bismuth, tin and platinum group metals (PGMs), for example. The recovery of these elements from the interconnected circuits is extremely complex, as most of the elements must be circulated between two or more circuits before they are concentrated enough to make their extraction possible, and their recovery as a compound profitable.From such a system’s perspective, it can easily be seen that a complication for solid waste management has arisen through the development of products (consumer goods) that bring together metals that are not linked in natural resources. As a consequence, many of these materials are not compatible with any process in the metals production network that was developed for the processing of primary, natural resources, optimized for the processing not only of the primary metal but also for all mineralogically associated minor valuable and harmful elements. The formation of large or complex residue streams or undesired harmful emissions then inhibits processing and recovery of said products at their end-of-life. Another complication is that any change to the system (in metal production, SWM or product design) affects the system configuration. Due to the changing demands for metals as a result from the changing products made from the metals for example, the relationships between the processes in the interconnected metal production systems change. This affects both the demand for old scrap (required amount and grade) from waste management, and the environmental profile of the metals. Preferably, therefore, product designers, waste processors and metal producers must cooperate to realize optimal metal recovery in processing discarded consumer products."

Jan 1, 2003

By Vladimir E. Vigdergauz

"Bubble-mineral complexes could be formatted by an attaching of hydrophobic particles to the surface of air bubbles or by an evolution of bubbles from solution onto hydrophobic surfaces. Measurements of contact angles, detachment forces (DF), induction times (IT), evolution pressures (EP) and flotation recoveries (FR) for the studying of minerals wettability at various pH and electrochemical potentials were used. An analysis of the obtained IT results show that a process of bubble attachment to a mineral surface is a rather slow one and it will scarcely be enough for bubble-mineral complex formation under the conditions of real flotation.The ranges of adhesion potentials obtained by DF measurements, Figure 1, correlate with the data of floatability-potential for pyrite. The ranges of adhesion potentials obtained by DF measurements for galena (-1 ÷0.2V) and chalcocite (-0.5÷1.2V) correlate with the potential ranges of floatability for galena (<0.2V) and chalcocite (>-0.4V). An increase of the DF and the cathodic limit of the adhesion potential with increasing length of the hydrocarbon chain were observed. EP-pH curves for sulfides are a mirror-like to the DF-pH curves, Figure 2. Structure of solid-liquid and liquid-gas borders has a determinative importance for formation of bubble-mineral complexes and subsequently flotation results. Under vacuum on the mineral surface there are produced micro bubbles and preferably they will be appeared on the hydrophobic sites. Water structure breaks near a hydrophobic surface facilitate water mass destruction and formation of gaseous phase embryos under decompression in the impeller zone. It simultaneously reduces a probability of produced micro bubbles dissolution as a result of pressure increasing owing to constant fluctuation of liquid densities into impeller zone. Comparison of Taggart’s evaluation of the suction behind blades of the impeller of an agitation-froth machine and ABEP data on galena, Figure, shows that gas evolution will be observed in the range of 1300-2700 revolutions of impeller per minute for hydrophobic and hydrophilic surfaces successively."

Jan 1, 2003

By Milind Sabne, Pradip, P Kapur, Beena Rai

"The efficiency of an industrial flotation circuit depends on (a) the selectivity and the kinetics of the reagent combination selected for the separation (b) the hydrodynamic conditions prevailing in the flotation cell (essentially equipment design parameters) affecting both the pulp and froth phase (c) the operating parameters such as feed rate, pulp density, pH, temperature etc. including the mineralogy, particle size distribution and relative proportion of liberated and composite particles of constituent minerals in the feed to flotation circuit and (d) the circuit configuration itself. We have developed a molecular modelling based reagent design and selection framework to assist mineral engineers to arrive at the preferred reagent combination based on a rigorous, scientific and quantitative comparison of various options available for this purpose. Similarly we have also utilized a general circuit design methodology proposed by Kapur and Mehrotra in 1974. The advances thus made in modelling both the reagent chemistry as well as circuit design, along with the availability of sophisticated, automated tools for characterization of ores (liberation as well as mineralogical composition of the different flotation streams) provides a scientifically rigorous, quantitative, robust framework for design and optimization of complex flotation circuits. We illustrate in this paper the power and the utility of our rigorous optimization based approach to designing industrial flotation circuits for the beneficiation of a multi-component feed with the help of few case studies from our own work. With the proposed methodology, higher levels of process efficiencies can be achieved in the industrial flotation plants, in particular those processing complex, multi-component feeds requiring multiple stages of flotation separation. We are currently developing an IT platform consisting of computer-aided decision support tools for arriving at the preferred flotation circuit and the appropriate reagent chemistry for a given ore deposit and/or a given plant."

Jan 1, 2014

By Bronwynne K. Williams

"In deriving flotation kinetic models, the froth phase was, until recently, either ignored or treated entirely empirically. The behaviour of the froth is now known to be usually important and sometimes dominant in determining flotation performance. Hence numerous methods have been developed for sampling the flotation froths and models incorporating the effects of the froth behaviour have been derived.Such models will assist in determining more accurate estimations of the kinetic parameters utilised in the designing of industrial scale plants thus reducing the incurred costs of over designing. In particular, improved models for batch tests may lead to more effective use of batch testwork for prediction of continuous plant behaviour. A more detailed model is thus proposed which allows for a more realistic approach to the flow distribution in the froth phase.PROPOSED MODELThe batch flotation process is split into two stages in time, namely before the froth begins to overflow and after. The assumptions made, and hence the calculations, are different for each stage.The air enters the slurry at t=0 and generates froth. The superficial velocity of the air through the cell is given by go. It is assumed that the rate of froth breakage (gb) is constant during the first stage. The froth rises with a uniform net velocity throughout the cell and no mixing is assumed to occur.After the froth begins to overflow, the velocity distribution of the gas is modeled by segmenting the froth phase as shown in Figure 1. A model for bubble breakage rate or measurements of froth velocity allows one to obtain the volumetric rate of concentrate froth production. The entrained water and associated particles and a drop-back mechanism are also allowed for in the model."

Jan 1, 2003

By M. Evertsson, E. Hulthén

"In aggregate production and mining the operators are responsible for controlling and monitoring the process to maintain high plant throughput and safe operation. Operators have to make different decisions to control the process due to changed demand on the operation from both management and conditions of the process. The quality of the response and the time it takes for an operator to respond to altered demand relies on what information is available and the experience of the operator. In this work a dynamic simulation platform has been developed to be used for operator training. Models for representing production units and process control for plant simulations have been developed and implemented in MATLAB/SIMULINK to simulate time-dependent plant behavior. Stochastic and scheduled events are included using the discrete events simulation toolbox SimEvents. The human-machine interface was developed using the human-machine interface software ICONICS. The operators’ cognitive process, in interpreting the plants semantic, has been studied by observations and with informal interviews with operators. This was done to get information about the daily operation and the problems that occur in the process. By interacting with operators that experience different physical interactions with the process; more qualitative e-learning software for supporting operator training in a dynamic operator environment could be developed. The quality of the operator training environment was evaluated with a usability study that was performed with operators and others within the production."

Jan 1, 2014

By J. D. Miller, C. L. Lin

In general, x-ray computed tomographic (CT) techniques are able to provide 3D images of the internal structure of opaque materials in a nondestructive manner. The unique cone beam geometry allows acquisition of all 2D projections with only one rotation of the sample thus providing for fast data acquisition and better x-ray utilization, as a complete 2-D detector array receives the cone-shaped flux of rays. Thus, an isotropic 3D volume can be reconstructed without the mechanical translation and the stacking of sequential slices as is the case for more conventional CT scanners. In this regard, a state-of-theart, custom designed x-ray microtomography facility to provide very detailed 3D spatial analysis of multiphase particles has been installed and is in operation at the University of Utah. The reconstructed 3D tomographic volume allows for an adjustable spatial resolution from 5 to 20 microns for sample dimensions from 10 to 40 mm in diameter, respectively. For example, a packed bed of coal particles is shown below in which different crystalline froms of pyrite are distinguished in 3D.

Jan 1, 2003

"The thiosulfate leaching process developed by Barrick to treat sulfidic high preg-robbing gold ores uses calcium thiosulfate as the leaching reagent for ores pre-treated by pressure oxidation, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a means of reagent recovery. A large portion of the research that led to the development of the technology was based on previous studies completed by different groups over the years, mainly focused on the ammonium thiosulfate system. Operational limitations in the use of the ammonia-containing recycled water in the pressure oxidation circuit were some of the main drivers for the change from ammonium to calcium thiosulfate for the development of the industrial scale process. One of the main aspects for successful gold extraction and recovery in the thiosulfate system is the pseudo-equilibrium reactions that drive distribution of the different gold species (in solids, solution and on resin) in the system. Previous studies have been focused on the thiosulfate reactions and equilibrium constants for the oxysulfur ions (thiosulfate, trithionate, tetrathionate). However, the literature around the effects of the different metal-oxysulfur complexes (Cu and Hg complexes) that form when the ore is in contact with the leaching reagents, and the related effects on stability of the gold complex is limited. The main changes in the gold complex chemistry and stability in the calcium thiosulfate system as compared to the ammonium and sodium equivalents, as well as related effects on gold recoveries, were investigated in the presence of different types of double refractory ores. INTRODUCTION Barrick has developed a thiosulfate leaching process to treat double refractory gold ores, by combining the use of acidic and alkaline autoclave pre-treatment with thiosulfate resin-in-leach (RIL). The process currently in operation at the Goldstrike mine (the TCM process), uses calcium thiosulfate as the leaching reagent, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a mean of reagent recycle. The main feed to the process plant is highly preg-robbing sulfidic ore from Goldstrike’s open pit. Prior to feeding the pressure oxidation circuit, the ore is processed through the crushing and grinding circuits and treated in preparation for acid or alkaline autoclave processing (POX)."

Jan 1, 2018

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 Igor P. Solozhenkin, Peter M. Solozhenkin, Sanda Krausz

"In this work, authors will show the efficiency of computer technology and chemical programs at studying collectors for flotation of minerals of elements of platinum group (EPG). Clusters various minerals EPG (flotation reagents) are created, named us clusters minerals (reagents) as their structure corresponds to the chemical formula, and the distance between separate atoms corresponds to the known tabulated data. By molecular modeling are investigated clusters sperrylite PtAs2, stumpfilyte PtSb, sadberryte PdSb, sobolevskite PdBi, palladoarsenyte Pd2As, paolovyte Pd2Sn, rustenburgyte (Pt3Sn, Pt6Sn2) and their computer parameters (absolute rigidity, electronegativity, transfer factors of carry, charges of the atoms) are determined. Tellurides of palladium (IV, II) merenskyite PdTl2 and kotulskyte PdTe and platinum clusters are investigated: PtFe4, Pt3Fe, PtFe (Pt2Fe2), Pt2Fe (Cu) Ni. The technique of attachment of the collector (composites) to cluster atoms EPG is offered. For the first time, it is established that at linkage of flotation collectors on monodentate, bidentate and bridged to circuits with atoms clusters the minerals containing atoms As, Sb, Bi, Pb, Sn, reaction of connection with change of a degree of oxidation of these atoms and occurrence of a proton operates. It is executed virtual skirling organic compounds connections by the developed criteria from accessible libraries of a database. The principle of an estimation of interaction energy for flotation reagents with mineral clusters is offered. It is developed the prognosis of collector activity evaluation (P?AE) and his values for candidates in collectors for flotation of minerals EPG are calculated. For flotation of ores containing Pt and Pd minerals, a number of reagents, including compounds on basis P (III), for innovational technology of Pt, Pd mineral flotation are recommended. Key words: flotation, minerals, flotation reagents on the basis of phosphorus (III), molecular modelling, chemical programs, program ????? , electronic energy."

Jan 1, 2014