Search Documents

By A. Saramak

"The paper focuses on problems of atmospheric pollution by the dusts, produced during the course of crushing and grinding processes, and the main objective of investigative programme is an assessment of emission of particulate pollutants for following crushing devices operated in plant scale: impactors, cone and jaw crushers. All crushers operate in aggregate production plants in Poland. In the first stage of investigations there were determined dust emission levels and supporting characteristics for all crushers under investigation. Then there were introduced indices that allow for comparative analysis in terms of dust emission, for devices with different energy consumptions and comminution ratio. It appeared that crushers with high the overall dust emission do not always achieved unfavorable dust emission per comminution ratio or energy consumption. The introduced indices proved their usefulness, because they helped to carry out a comparative analysis among crushers, operating under different technological conditions. It is also easier to assess environmental impact of individual crushing devices, under analysis. Results of investigations also show that environmental impact of different types of crushers is diverse and it is difficult to compare dust emissions of various types of crushers without taking into account technological aspects (like throughput, comminution ratio, energy consumption, and others) of their operations.INTRODUCTION Mineral processing of raw material is a complex process, involving in general operations of size reductions and separation. Depending on the type of specific raw material, the technological circuit may include operations of comminution and size classification. This is a typical circuit for aggregate production. In ore treatment industry the process in much more complicated and include also a metallurgical treatment of ore concentrate – the final product from processing plant stage.In general, regardless the type of raw material, operations of size reduction are present in each technological circuit of mineral processing. Operations of crushing and grinding are an integral part of processing technology, because they play a crucial role in effective treatment of mineral raw materials (Gawenda 2013). Their duty is to liberate the useful minerals from the gangue in ore treatment industry, or to produce the material with the required particle size in case of aggregate processing. Crushing and grinding operations are of a high negative impact on environment and humans. They consume great amounts of energy, what indirectly contributes to higher emission of carbon dioxide CO2. Apart from energy, crushing and grinding device consume significant amount of steel and other metals and alloys due to high wear of working parts and grinding media. This is also of negative environmental impact due to emissions of additional amounts of CO2 in production of steel and other metals required as spare parts for comminution devices."

Jan 1, 2018

By Kilian Neubert, Hermann Wotruba, Henning Knapp

Sensor-based sorting has been integrated into more and more applications in mineral processing over the past decades. Various sensor types, such as line scan cameras, near infrared sensors and X-ray transmission sensors, allow the separation of a vast variety of raw materials. Sensor-based sorting has several economic benefits which can make the difference between an uneconomic operation and a profitable mine. Sensor-based sorters can be applied to fulfill various sorting tasks, such as waste rejection, product quality improvement and ore type diversion, and have a significant impact on the layout of the processing plant. Therefore, it is important to include sensor-based sorting into the planning of a processing plant at an early stage. To evaluate the applicability of sensor-based sorting for any specific ore type, it is currently necessary to provide several hundred kilograms of material for subsequent bulk tests. In exploration, ore samples are usually rare and only available in form of drill cores. The acquisition of drill cores is time-consuming and expensive especially for deposits in great depth. Hence, it is unfavorable to spoil valuable drill cores for bulk tests. This paper describes a methodology to evaluate the applicability of sensor-based sorting based on drill core analysis. That methodology offers the possibility to calculate the achievable performances of different sensor types for various grain sizes without comminution of drill cores. The general methodology is shown on basis of an exemplary test work on drill cores from a currently conducted exploration.

Jan 1, 2014

By E. V. Manlapig, M. C. Harris

"The complexity of the flotation process has made the identification of an appropriate model structure for the predictive simulation of flotation circuits far from obvious. Work performed under the auspices of the AMIRA P9 flotation program has indicated that the metallurgical performance achieved from a flotation cell arises from the interaction of two essentially independent property classes, namely the cell operating conditions and the properties of the cell feed stream. These observations have led to the development of a model structure that associates a constant set of flotation parameters to the streams of the circuit, which are transformed into a flotation response depending on the operating conditions within the flotation cell.A variety of alternative model structures exist within the literature which do not make this distinction between cell and stream flotation properties, and many of these models are in widespread use for flotation optimisation and design studies, both in industry and academia.In this paper, circuit survey and laboratory batch flotation data collected from an industrial flotation circuit are analysed. The data demonstrate that streams in an industrial flotation circuit exhibit varying particle floatability – concentrate streams typically float faster than tailing streams (Figure 1(a)). This floatability, however, is generally conserved around the various units within the flotation process (i.e. the effective floatability of the combined feed and product streams of a unit is equivalent (Figure 1(b)))."

Jan 1, 2003

By Hermann Wotruba, Günther Petzold, Fabian Riedel

"Increased mechanisation in underground stoping operations results in higher waste percentages in the run of mine. A new method of reducing waste is optical sorting. Optical sorters have low maintenance costs and can be installed underground. Rejected waste can be backfilled directly without having to be hoisted, therefore increasing the shaft capacity for a more valuable product.Pre-Concentration by Optical SortingA series of tests with an optical sorter at the laboratories of the Mineral Processing Department of the RWTH Aachen have shown that it is technically possible to sort almost any kind of ROM which has even slight differences in colour (Platinum Reef, Gold Reef, Kimberlites, Industrial Minerals, Aggregates, Coal, etc.).By employing optical sorters prior to conventional sorting plants, it is possible to reduce the amount of waste to be processed. Figure one shows test results of ore which is quite similar in colour to the waste (grey). With increasing waste in the feed, the recovery decreases according to the graph. In figure two, the colour ratio parameter of the sorter was changed with a similar waste percentage in the feed. With increasing loss of ore, a cleaner product can be achieved. Before designing a sorting plant, throughput tests are carried out. Throughputs vary depending on the size range. Sorters have a limit of about 250mm top size. In this upper size range, throughputs of 150t/h can be achieved."

Jan 1, 2003

By Heribert F. Broicher, Arne Volland

"The analysis of laser-induced fluorescence (LIF) combines remote sensing techniques with laser spectroscopy. Over variable distances different rock types are identified or changes in the quality of one rock type are recognised. LIF Analysers operate non-destructive, non-contact, on-line and in real-time. Installed over conveyors or over driveways the analysers ""look"" at the moving bulk solids 20 times per second and provide in real-time information for downstream sorting, blending or optimisation of processing. LIF Analysers recognise rock types (hardness information or dilution control), degrees of alteration, degrees of oxidation and –semi-quantitative- content of certain minerals in an ore. Only under favourable conditions quantitative assay information can be obtained, as e.g. the phosphorus content of Kiruna type iron ore.The main application of LIF Analysers is seen in big open pit operations, where the muck is trucked to an in-pit crusher and the crushed rock conveyed out of the pit to its respective destination: e.g. the primary high grade ore to the mill, the low grade or oxidised ore to the leach pads and the internal waste to the dumps.In underground mining and especially in block caving operations dilution control is of utmost importance. Here a LIF Analyser mounted on the back of a pick-up truck can be moved from drawpoint to drawpoint and quickly assess the degree of dilution.Closer to the mill the stockpile management based on LIF analysis will lead to stockpiles sorted according to rock type (hardness), degrees of alteration and oxidation. In case of direct feeding rom ore to the mill the knowledge of the type and quality of all the material between the in-pit crusher and the mill facilitates optimisation of e.g. reagent dosage."

Jan 1, 2003

By Braulio Fernández, Gonzalo Montes-Atenas

The mechanisms taking place during the leaching of chalcopyrite when it is in contact with other sulphide minerals, particularly pyrite, is still a matter not fully solved. The GalvanoxTM process has been suggested as a technical solution to extract copper from chalcopyrite at commercial level inhibiting passivation phenomena widely reported in the field of hydrometallurgy. Although there are some rules of thumb to implement the process in fully flooded stirred conditions such as the optimum pyrite/chalcopyrite mass ratio should range between 2 and 4, among others; not many research studies have been focused on studying the effect of the surface contact area between chalcopyrite and pyrite to reach best copper extraction conditions. The aim of this research work is to determine the effect of the mass and surface area ratio between the minerals and the surface area of each of the mineral species effectively exposed to the leaching solution. Different particle size distributions of pure pyrite and chalcopyrite were contacted in a small column and subjected to leach tests using sulphuric acid in concentrations close those used in industrial leaching processes. The mass and surface area ratios which optimize the extraction of copper were obtained. It was found the best leaching conditions were attained when reducing the particle size distribution of pyrite regardless the particle size distribution of chalcopyrite. Further analysis concerning the impact of this conclusions on large scale operations is presented and discussed.

Jan 1, 2014

By P. A. Harvey

Previous studies have reported that inorganic electrolytes can enhance floatability of coal. The research has shown that the enhancement, if any, is highly dependent on changes in solution pH, type of electrolyte, and electrolyte concentration. The reasons for this are still not clear. In this study the floatability of coal particles in mono and divalent salt solutions was investigated. The zeta potential and hydrophobicity of the coal was measured experimentally, and a modified Hallimond tube was used to determine the floatability of coal particles by single bubbles, where the collision efficiency was equal to unity. The experimental information was used in conjunction with the Hogg-Healy-Fuerstenau equation to quantify the electrical double layer interaction. It was found that for low electrolyte concentration (less than 0.1 M) solutions the flotation recovery of coal particles was less than that for distilled water, and decreased with increase in concentration. Conversely, at electrolyte concentrations above 0.1 M, flotation recovery increased with increasing concentration (Figure 1). Both of these results are consistent with previous observations, but are inconsistent with expectations when considering the possible influence of electrical double layer interaction. Modelling of the system indicates that the electrical double layer is compressed with increasing electrolyte concentration, resulting in an increase in flotation recovery due to a diminishing of the (electrical double layer) repulsion between the bubble and the coal particles. Moreover, for electrolyte concentrations above about 0.1 M the electrical double layer is completely depressed and would have little further influence, if any, on the flotation process. Therefore, the electrical double layer interaction is not the principal determining factor for the flotation of coal in electrolyte solutions.

Jan 1, 2003

By Fernando Concha

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

Jan 1, 2014

By E. V. Manlapig

"Some researchers postulate that the floatability of a particle in the streams of an industrial flotation circuit is a function of only its size and liberation properties. They do not discount the importance of reagent or surface contamination on particle floatability but assume that the reagent coverage or surface contamination of the particle surfaces is essentially uniform for particles of similar size and mineralogical properties when subjected to a particular chemical regime.In this paper, samples collected from laboratory batch flotation tests performed on different streams of Cominco Teck’s Red Dog lead cleaning circuit have been characterised with respect to their size, mineral association and mineral surface exposure. An analysis of this data set indicates that the flotation rate of a particle in an industrial flotation environment is a strong function of its size and also of the mineral composition of its surface (Figure 1). It is a function not only of the proportion of the most floatable mineral on its surface but of the floatability of the other minerals on its surface as well.Nodal analysis is a technique developed by the authors that can be used to determine if the ore floatability of a particle class is changing within an industrial flotation circuit. This technique is used within the paper to show that the floatability of all the different types of particle classes studied within the Red Dog circuit did not change significantly during the lead cleaning stage. However, it was also concluded that particles with the same size and mineral composition did not all float with the same rate in the individual streams of the flotation circuit, but with a distribution of rates. It is suspected that the particles within a size mineralogical class in this study have varying degrees of surface oxidation and that this results in varying particle flotation rates. Thus basing particle floatability on size and mineralogical effects, alone, in a flotation model is not always valid."

Jan 1, 2003

By Herman D. Mendoza

"The removal of finely dispersed mercury from the effluent of small-scale gold mining operations and the eventual recycling of the recovered mercury was investigated. The conventional method of amalgamation, or “ball milling”, involves the mixing of a substantial amount of mercury with ore to recover free gold during the grinding stage. During grinding, a portion of the mercury is transformed into minute droplets, which readily float and disperse in the effluent. A kilo of gold ore containing 20-30 g Au/t, when ground with 3 g of mercury, yields 0.005 to 0.050 mg/l of mercury in the effluent, exceeding the concentration of 0.002 mg/l allowed by law for surface water.A rapid recovery/ recycling process was introduced using the surface-chemical properties of finely dispersed mercury in aqueous suspension. It was observed that fine droplets of mercury in an aqueous environment readily attached onto a collector having positive surface potentials for pH 3 to 10. An example of a suitable collector is alumina (Al2O3), which has an iso-electric point of pH 9.8. When an effluent, coming from a settling procedure after an amalgamation-grinding stage, was passed through a column-bed packed with alumina fiber, removal and subsequent collection of finely dispersed mercury occurred under acidic conditions, pH 3-6. Recovery was around 99.5%, yielding an acceptable quality of water safe for disposal into the aquatic environment. The collected droplets of mercury, which are left in the column-bed of alumina fiber, were subsequently treated with a cleansing solution at alkaline conditions pH 10 -12. At these conditions, both mercury and alumina fiber carry negative surface potentials, which results in the eventual detachment of attached mercury from the alumina collector. The effective recovery of attached mercury from the alumina collector by the detachment procedure is only 30-35%. The collected mercury from the cleansing stage can be collected, cleaned and can be used for subsequent amalgamation processes. The attachment and detachment behaviour of finely dispersed mercury onto and from the microscopic collector alumina is shown in Figure 1. The result of attachment and detachment were analyzed using existing interaction energy theories like the Darguin-Landau- Verwey- Overbeek (DLVO) Theory."

Jan 1, 2003

By S. S. Indi, D. Santhiya, S. Subramanian, K. A. Natarajan

"With the gradual depletion of the high-grade ores and finer dissemination of values in the leaner samples, it has become imperative to develop innovative approaches to process such complex ores. The beneficiation of complex sulphide ores containing copper, lead and zinc minerals, remains one of the most important challenges in base metals metallurgy. The advent of biotechnology in mineral processing has opened up immense possibilities to exploit such difficult-to-treat ores. Bioprocessing techniques thus hold promise as potential substitutes for the conventional technologies in vogue. Several types of autotrophic and heterotrophic bacteria, fungi, algae and yeasts are implicated in mineral beneficiation processes. Adopting a bioprocessing route to mineral beneficiation has attractive benefits, such as lower cost and energy requirements, environmental acceptability and operational flexibility.The interaction of sphalerite- and galena-adapted Bacillus polymyxa (B. polymyxa) cells with sphalerite and galena has been investigated through adsorption, electrokinetic and flotation studies. The amount of sphalerite-adapted cells adsorbed onto sphalerite and galena is found to decrease with increase in pH. On the other hand, the adsorption density of galena-adapted cells onto galena shows a feeble maximum around pH 8, and the amount adsorbed is marginally higher in the pH range of 8 – 11.5. In the case of sphalerite the amount adsorbed is higher in the pH range of 5 to 7. The adsorption density of both the adapted cells is higher for galena vis-à-vis sphalerite. Electrokinetic studies indicate significant surface chemical changes on the chosen sulphide minerals and the bacterial cells, consequent to microbemineral interactions. Selective flotation tests on a synthetic mixture of galena and sphalerite confirm that sphalerite could be preferentially floated from galena, using galena-adapted cells, but not with the sphalerite-adapted cells. The cells adapted to galena assay a higher polysaccharide content and are more hydrophilic, while the sphalerite-adapted cells have a higher protein content and possess greater hydrophobicity. Transmission electron microscopic studies have provided evidence in support of the differences between the cell surface characteristics of sphalerite- and galenaadapted cells (Figure 1). Possible mechanisms of interaction between the minerals and the bacterial cells are discussed."

Jan 1, 2003

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 K. W. Stöckelhuber, A. Wenger, H. J. Schulze

"An important elementary step of the flotation process is the forming, drainage and rupture of a thin intervening liquid film between bubble and mineral particle.After the encounter of the bubble with the solid surface a wetting film is formed. The initial thinning of this film is driven by the capillary pressure inside the bubble. When the film has reached a certain thickness rupture can take place. There are two possible mechanisms describing this process:(a) Gas nucleation, caused by nano bubbles inside the film.(b) Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive forces (electrostatic, van der Waals).Metastable wetting films on negatively charged, hydrophobic glass surfaces (gaseous phase methylated), or on hydrophilic, positively charged glass surfaces (with Al3+ ions), have been analysed by means of the kinetics of film thinning according to the Reynolds law. These experiments demonstrate that both mechanisms can be responsible for the rupture of a thin wetting film."

Jan 1, 2003

By Katsunori Okaya, Toshio Inoue

"Movement of mill charge in the centrifugal mill is essentially dissimilar from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. This dissimilarity is the reason for the substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Bradley et al. (1983) developed a math model regarding the mill charge as a lump. This model is presented in a simple equation with which motion of the mill charge can be predicted in terms of the parameters describing the specification and the operation of the centrifugal mill. This equation can be used to explain the power draft of the mill as well as the stability of mill operation. More recently, on the other hand, a numerical simulation technology called discrete element method (DEM) has become a vital vehicle for estimating the motion of the grinding media in the mill. The authors developed a mill simulator called ‘Mill Solver’. Mill Solver is designed to simulate various types of mills including centrifugal and vibration mills. The principle of this simulator is to calculate individual kinetic events of interaction of balls in the mill in a minute time interval, hence the mill performance can be constructed for estimation."

Jan 1, 2003

By Rajamani R. K.

The design of tumbling mills has progressed from the Bond work index concept of the 1950s to the population balance concept of the 1980s and then made a quantum leap forward with the discrete element method in the 1990s. The failure of a SAG mill at the Grasberg mine site set in motion the inquiry into the role of shell lifter geometry on the profile of the charge motion within the mill. Quickly, it became evident that this could only be accomplished by tracking individual motion of ore particles and grinding balls and not by study of en masse motion of the charge that had been established previously. The discrete element method (DEM) which was prevalent in the civil engineering literature at that time proved suitable to tackle this simulation problem. In 1991, the two dimensional simulation of laboratory scale mills was validated with the DEM. Later this simulation method evolved into ?MillSoft?? a simulation software package for the design of lifters in ball and SAG mills. MillSoft?simulations proved that cataracting charge motion is not conducive to the life of lifters. The old rule of thumb that the number of shell lifter rows should equal twice the diameter of mill in feet was shattered by simulation results. Instead, the number of rows equal to the diameter of the mill in feet, providing that the lead angle of lifter is around 25 degrees, was established as being more optimal. This bold design change was first implemented and tested by Mark Sherman at Alumbrera Mines in Argentina. Two 36-ft SAG mills responded extremely positively to the design change. This success was immediately repeated at Collahuasi, Pelambres and other mines in South America. The design change has so far exceeded expectation that there is not a single SAG mill around the world today that does not employ a relief angle on its shell lifter. The DEM method has advanced in the hands of the author, mining companies and universities, notably in Australia and South Africa. Today, three-dimensional simulation of charge profile and slurry transport is a standard in the design of mills. There is strong pursuit of a virtual comminution machine with DEM in Australia. In South Africa, an experimental method known as positron emission tracking is emerging as a method for tracking particles in grinding mills. The computational burden of computing with millions of particles in three-dimensional simulations has been eased to less than a day with a technique known as GPU computing. Keywords: DEM method, GPU computing, SAG mill, tumbling mill simulation, discrete element method

Sep 1, 2012

By K. Ananth Krishnan

Today we see a paradigm shift in political, environmental, and economic trends, which are challenging the mining industries. It is very clear that these issues are reaching unparalleled scale and complexity. Cost efficiency and corporate social responsibility are the two primary drivers for the mining industry today. The current challenges facing the industry include: ? Due to deterioration of quality of ores, the scale of operations has become humongous which necessitates high degree of automation and remote operations ? Scarcity of skilled manpower and the necessity to minimize employment of humans at unsafe locations ? Automation of routine activities, improving the efficiency of operations and reducing the cost of production ? Land, water and energy have become scarce in most of the resource rich regions In the current macroeconomic conditions, it is obvious that the industry is under tremendous pressure and it is imperative that the industry embraces sustainability, enhanced energy efficiency, and improved resource allocation. Closely related sectors like energy and utilities have set an example by acknowledging the need to alter their business practices to meet the essentials of sustainability, adoption of new operating models, policy and regulation structures. There is a need to continuously optimize the operations across the entire process value chain as well as across geographies in order to meet the market demand while dealing with supply chain constraints. The goals of optimization could be enhancement in productivity, reduction of production costs, carbon footprint, etc. The gamut of operations is vast, starting from exploration to mining, mineral processing, smelting, refining, casting, rolling (deformation processing), heat treatment, and finally manufacturing of industrial products / components. Advances in information and communication technologies (ICT) in combination with modeling and optimization tools have made it possible to address these issues in a quantitative manner based on real life data. Manufacturing industry, for example, has successfully leveraged these technologies (ERP, PLM, MES, APC, etc.) to enhance productivity and quality. In this presentation, I would like to illustrate the benefits that could be derived by implementing ICT-leveraged solutions available today for the mining industries. I will focus on the following recent technological developments in the context of their applications in the mining and minerals industries: Mobility technologies: The industry is looking for strategically sustainable solutions that fit the working profile of mining engineers and which provide up-to-date information in real time. Mobile applications for iPhones and iPads are gaining popularity, which is helping mining engineers to work on-line as well as off-line. Mobility technologies have made it possible to provide data anywhere and anytime in a form you prescribe. This enables proactive responses to changing dynamics of the marketplace. For example, a plant engineer can access information about any critical process equipment, monitor its performance and do the needful as and when needed. Similarly, scheduling of operations can be optimized based on the market demand and on the availability of raw materials, labor, and status of equipment.

Sep 1, 2012

By V. G. Prikhodko, G. I. Sukhinin, I. V. Yarygin, A. V. Fedoseev, S. A. Novopashin

"The first experiments on the vacuum drying of spherical clay sample are presented and the theoretical model of the process is considered. The model is based on the solution of the heat and the moisture transfer equations with the effective thermal conductivity and water diffusion coefficients for wet porous clay-like medium. The time and radial dependence of the temperature and the moisture were calculated for different initial conditions. The results obtained for the time dependence of the moisture content are in good agreement with the experimental results obtained in the initial period, when all the moisture in the sample did not freeze to form an ice crust. INTRODUCTION Capillary-porous materials very often occur in nature and in industry. A porous medium is a solid matrix with voids, or pores, which are continuously connected. These pores are usually filled with fluids or moisture, water vapor and air that can pass through the medium because the voids are interconnected. The void fraction in the solid matrix is referred to as the porosity. Porosity or void fraction is a measure of the void (i.e. ""empty"") spaces in a material, and is a fraction of the volume of voids over the total volume. The moisture content in porous media determines the properties of the porous body, its mechanical and thermo-physical properties, such as density, plasticity, viscoelasticity, swelling, cracking, and so on. Complex processes of heat and mass transfer occur in porous bodies when they are heated or cooled, during drying or freezing (Luikov,1966). The course of these processes depends essentially on the physical-chemical composition of the solid matrix of the porous body, on its fractal dimension, porosity and morphology. The clay and clay minerals are the most important porous materials in the history of the mankind (Mukherjee, 2013). Clay is a very fine grained, unconsolidated rock matter, which is plastic when wet, but becomes hard and stony when heated. It has its origin in natural processes, mostly complex weathering, transported and deposited by sedimentation within geological periods. Clay is composed of silica {SiO2), Alumina (Al2O3) and water (H2O) plus appreciable concentrations of oxides of iron, alkali and alkaline earth, and contains groups of crystalline substances such as quartz, feldspar, and mica. Building materials, bricks, and tiles, pottery, porcelain and faience are made from clay. Clay is used in the food and medical industry, and, not least, in the mining industry as a carrier containing aluminum, silicon and other valuable elements, as well as metals (copper, gold) as constituents, contained in the pores in the form of micro- and nano-particles or grains."

Jan 1, 2018

By Claudio Bisso, Javier Vargas, Charles Lozano

"This paper summarizes the activities performed to predict SAG milling throughput at Minera Esperanza. Having highly reliable geometallurgical models aided by the new computer tools and specific metallurgical testing to rely on has become a major issue in recent times due to their impact on the business. Minera Esperanza’s SAG throughput model was constructed by characterizing the ore feed and operational parameters of the plant. Producing a robust model required satisfying number of requirements for the parameters used for both the ore and the plant as follow: 1) geologic and geometallurgical characterization parameters; and 2) parameters of a plant running at the rated production under optimum operating conditions. Obtaining these parameters required increasing the quantity of samples and metallurgical testing through drilling campaigns, mapping the drill holes and putting samples through various comminution tests while sampling all operational flows at the plant to obtain the metallurgical information for the operational parameters. The information was entered on the JKSimMet software to enable a throughput model to be developed to output SAG mill throughput predictions that are very close to actual throughput figures, i.e., accurate within a range of 2% on a monthly basis."

Jan 1, 2014

By Khoi Nguyen, Luke Keeney

"Hardness" is an important yet diverse material physical property and is a key parameter in the mining industry in fields such as comminution, geotechnical and blast modelling. Several laboratory and field based measurement techniques exist to measure hardness (e.g. Point Load Testing, Vickers, Brinell, A*b, BMWi, UCS), all are designed for specific applications. Current tests are generally destructive and require specific sample preparation procedures which results in high cost tests that are not conducted in adequate quantities to map hardness across an ore body. The EQUOtip rebound hardness tester is a device that has been developed for application in ore body hardness domaining within the AMIRA P843 GeMIII Research Project. The rebound hardness test is non-destructive and suitable for application on half and whole diamond drill core. Data acquisition protocols and a data processing software application (EQProcess) have been developed to facilitate routine collection of comparative hardness information. This paper outlines the data acquisition and processing methodology and provides application examples of defining relative hardness domains in different geological deposit styles.

Jan 1, 2014

By I. H. Mukhametshin, E. N. Baranova, I. B. Fadina, E. A. Ashirbaeva

The purpose of the research is the development of a complex of solutions for the maximum extraction of non-ferrous and precious metals from persistent mineral raw materials by heap bioleaching from spent heap leaching (HL) stacks. Methodical recommendations for assessing the suitability of primary and technogenic refractory mineral raw materials for heap bioleaching are developed. Active associations of microorganisms have been created for the conversion from various types of ores to the solution of S, Fe, As, Sb, Cu, Zn, Mn, Ni, Mg, P and other elements, as well as methodologies for their storage, immobilization and preparation of bioreagents in industrial conditions. On a pilot scale, tests were carried out on samples weighing 15-17 thousand tons of refractory gold-sulphide ores (more than 50% of gold is associated with sphalerite), gold-quartz ores with colloidal gold (74% associated with quartz and pyrite) and gold-silver ores with elevated copper and zinc content (1.5 and 3,5%, respectively), as well as man-caused material lying for 4-5 years of spent quarry material of oxidized gold-silver ores. In the pilot-industrial tests of heap bioleaching of gold-sulfide ores, gold recovery of 84-85% and silver was achieved to 89-90%, the possibility of obtaining high-yield solutions of copper and zinc, suitable for hydrometallurgical processing, from gold-silver ores, and the possibility of obtaining waste with a dump content of valuable components, suitable for deep disposal in the construction industry. When comparing two technologies for processing refractory ores after biooxidation under HL conditions, when 1000 tons of ore processed by the bioreagent were re-milled from a size of 40 mm to 0.1 mm and cyanated under the conditions of the factory process, the same results were obtained for gold recovery (85%) and silver (90%), as with the heap version. The copyrights of the development are protected by a patent.

Jan 1, 2018