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By J. Wiese, K. Corin, Z. Song

"Relating flotation performance to the electrochemical characteristics of a pulp is complex both in fundamental research and in practice. In the case of thiol collectors, different Eh values in the flotation system can result in the formation of the dimer or the metal thiolate which may or may not enhance the hydrophobicity of the mineral. Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, are usually manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system. A variation in pulp potential may also be achieved by the addition of potential modifiers such as sodium hydrosulphide (NaHS), sodium hypochlorite (NaClO) or hydrogen peroxide (H2O2). There exists anecdotal evidence which suggests that the addition of small amounts of H2O2 to the flotation process can improve sulphide mineral recovery. The objective of the present study was to investigate the effect of the addition of the potential modifier, H2O2, on sulphide mineral recoveries and grades in the flotation of sulphide minerals from two copper bearing ores from China and compare the results to those obtained for a PGM bearing ore South Africa. Batch flotation tests were conducted using the three different ores at the natural pH of the different systems, in the presence of a xanthate collector and the absence and presence of H2O2 as a potential modifier. The results indicate that the addition of carefully controlled low concentrations of H2O2 resulted in improvements in flotation performance. INTRODUCTIONElectrochemical potential as a control parameter in the flotation of sulphide minerals has been widely studied (Allison et al., 1972; Gardner and Woods, 1979; Ross and Van Deventer, 1985; Chander, 2003; Woods, 2003; Javadi, 2013). There is concensus that in order to be recovered during flotation, sulphide minerals require a suitable redox environment. During the flotation process thiol collectors and sulphide minerals are involved in electrochemical reactions which result in the formation of hydrophobic species at the mineral surface (Finkelstein and Goold, 1972; Rand and Woods, 1984). Sulphide minerals act as semiconductors and electrons are transferred during the interaction of the mineral with collector. The resultant potential difference and its magnitude are responsible for the transfer of electrons and the rate of the reaction (Bard and Faulkner, 2001; Fuerstenau et al., 2007). Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, may be manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system (Heyes and Trahar, 1979). The use of potential modifiers viz. reducing or oxidizing agents which include H2O2, NaClO, and NaHS, is an alternative method by which to control the potential of the pulp in a flotation system which may or may not promote the flotation of desired minerals (Rao, 2004). The oxidizing agent, H2O2, undergoes a cathodic reaction which can result in the enhanced flotation of valuable minerals. The potential of the system is increased which results in a shift in the mixed potential of a mineral. The magnitude of the over-potential influences the rate of the oxidation process and thus the flotation response of sulphide minerals (Kocabag and Guler, 2008). Equation 1 shows the proposed oxidation of xanthate by H2O2 (Lipkina and Streltysn, 1970)."

Jan 1, 2018

By M. Saghaeian, R. Hejazi, M. Farahani, M. Dehghani, A. Tohry

"Wet tailing dams of iron ore processing plants typically contain a significant amount of valuable minerals. In more recent years, due to the increase in iron’s prices and technological innovations, as well as the low energy consumption which required for processing of materials from tailings, dams can consider as potential valuable deposits. However, the production of iron concentrate from tailings is usually complicated where the high moisture content of the material, the high clay content and the presence of chemicals of processing such as flocculants, acids and flotation reagents, all make materials highly sticky which can be easily swollen. In the present paper, the optimization of operational parameters to recover ultrafine hematite iron ore from the wet tailings dams of the Chador-malu iron ore mine was investigated. The optimization of operational parameters, showed that with modification of the washing unit components for slurry making, the challenge of constraints from feeding the plant could be overcome. To decrease the magnetite content in the tail stream of the medium intensity magnetic separation (MIMS) and subsequently increase the efficiency, the orifice of the cleaner tail flow exit pipe was changed from 7 inches to 3 inch and yoke angle changed from 14 to 8 degrees. These changes increased mass yield by 3% and decreased the magnetite content in the final tailings to 1.2%. By recirculating the cleaner SLons of final tailings within the circuit, the solid percentage of the feed to rougher SLons decreased to around 15%, and as a result the matrices were not overloaded that easily, and mass yield increased to about 13% from 7%. All the above mentioned optimizations were achieved without significantly affecting the concentrate Fe grade."

Jan 1, 2018

Calaverite is a gold telluride found in the Kalgoorlie region, Fiji, Cripple Creek Colorado and numerous other locations. It is known that a high pH is necessary for calaverite cyanidation, with the leach rate increasing substantially above pH 12 due to the hydroxide ion concentration. In most circumstances lime is used to achieve high pH, however lime saturates at approximately pH 12, limiting the maximum pH obtainable in a critical region for calaverite leaching. Plant observations, laboratory experiments and thermodynamic modelling show that the maxi-mum hydroxide ion concentration that can be achieved with lime (CaO) is strongly dependent on common ions. The presence of calcium, as commonly found in saline waters, substantially diminishes the maximum pH that can be obtained with lime. Conversely the presence of sulfate ions, as generated through oxidation of sulfides, substantially increases the maximum pH that can be achieved with lime. Sulfide oxidation during cyanide leaching of complex ores may generate acid and sulfate ions, making overdosing with lime at the front of the circuit, or staged addition down the leach train, important to maintaining the maximum hydroxide concentration.

Jan 1, 2014

By C. V. G. K. Murty

Sillimanite, chemically named Aluminum silicate, 3Al2O3SiO2 is one of the three forms of alumino silicate polymorphs and commonly encountered in aluminous metamorphic, plutonic, and volcanic rocks and their weathering products. Most of the sillimanite deposits are granular and are of high grade available in coastal areas as associated mineral along with Titanium bearing minerals namely ilmenite, rutile etc. Sillimanite is one of the widely accepted raw materials for the manufacture of high alumina refractories (55-60 % alumina) or bricks. Sillimanite based refractory bricks are used for the lining of Blast furnaces, Arc furnaces, Soaking pits, Reheating furnaces of iron and steel, rotary kilns for cement manufacturing and general kilns for lime production. Considering the vast potential of unexploited sillimanite reserves in India, M/s Trimex Sands Pvt. Ltd., (TSPL)has set up a Mineral Sand Processing plant in 2010 at Andhra Pradesh with a capacity to produce about 50,000 tons of sillimanite per annum besides the production of various heavy minerals such as ilmenite, rutile, zircon and garnet. Traditionally in India, sillimanite is upgraded by froth flotation technique using Oleic acid as a collector cum frother, sodium silicate as depressant and soda ash as pH regulator. At TSPL, Conventional mechanical float cells are installed to float sillimanite. In addition to the usual problems associated with conventional cells, poor flow ability of the sillimanite concentrate is experienced in dry circuit due to the presence of sodium oleate. Fine garnet in the sillimanite concentrate contributes to high iron content in the final product, making sillimanite separation a nightmare for operators (lower recoveries coupled with inferior grades). Various efforts were made to improve the performance of the circuit such as introduction of additional frother like MIBC, optimizing the operating parameters such as pulp density, collector dosage, depressant dosage, air flow rate, pH etc., use of collector aids, stage wise addition of reagents etc. The challenges faced to produce a sillimanite product with stringent quality norms and the efforts made to improve the grade and recovery are described in this paper. Keywords: sillimanite, froth flotation, conventional mechanical cell

Sep 1, 2012

By B. McFadzean, J. Taguta

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a valuable and reliable means of determining solid surface properties such as wettability, it has seldom been applied in mineral processing research. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. The enthalpies of immersion were then related to the first-order flotation rate constant as determined by the microflotation technique. The same measurements were also made on sulphide minerals whose surfaces were modified to different degrees of hydrophobicity using different percentage coverages of amyl xanthate collector. The enthalpy of immersion technique was capable of distinguishing and ranking minerals according to their wettability. All mineral types and collector-treated minerals conformed to the same relationship that was found between the enthalpy of immersion and the flotation rate constant. This conformed, empirically, to a power law equation. As the enthalpy of immersion decreased, there were large increases in flotation response for very small changes in hydrophobicity. In addition, a critical enthalpy of immersion (CEI) was found, above which no flotation could occur. The scatter in the data points could be corrected for by adjusting the rate constant using the density of the minerals to produce a robust relationship between the rate constant and enthalpy of immersion. These results have shown that the enthalpy of immersion is able to indicate both the natural mineral hydrophobicity and the extent to which collectors can render a mineral hydrophobic. This technique has considerable potential to be used as a sensitive and accurate measure of mineral surface wettability in order to predict flotation performance.

Jan 1, 2018

By D. Moradkhani

Copper metal has important role in the basic industrials, as if it did not exist, modern human life would not develop! Copper leaching, as the first step, is important step in copper production processes. In this research, efficient factors on the leaching have been investigated. For this reason, four efficient factors on leaching namely pH, liquid to solid ratio (L/S), temperature and time, as independent variables, were optimized using response surface (RSM) with D-optimal. A quadratic equation was used to create response and contours. According to the results from analysis of variance (ANOVA), the value of determination coefficient (R2=96.77%) indicates that the model was good fit. Optimum experiment condition also was found: pH of 1, L/S of 8.24, temperature of 26.06 ? and time of 43.64 min. At this condition, the maximum recovery of copper was equaled to 92/38 in which good desirability achieved.

Sep 1, 2012

By V. K. Kuppusamy, M. Holuszko

"Lamps and lighting products are the most commonly used electrical products around the globe. With the improvement in lamp technologies, lighting products have grown complex and hence require an improved recycling process. The LED lamps consist of various valuable metals such as iron, copper, aluminum, chromium, silver, and gold, as well as non-metals such as glass, plastics, and fibers. In addition, there are also traces of hazardous substances such as lead, arsenic, and mercury. A major step in the recovery process is size reduction, and researchers have suggested that up to 40% of the total valuable material is lost during the shredding and grinding processes. SELFRAG is a high voltage selective fragmentation comminution technology that uses high voltage pulses in a water medium to efficiently separate the metals at a coarser size without generating many fine particles. It has been proposed that during the fragmentation process of electronic waste (e-waste), the metals can be separated without fine grinding. This research considers the applicability of high voltage pulse fragmentation for LED lamps. Eight different types of LED lamps were processed through the SELFRAG unit at varying pulses to study metal liberation. The product obtained was characterized for metal liberation, metal grades, and liberation analysis. The specific energy consumption for this size reduction process was also monitored. INTRODUCTION Lamps and bulbs are the most commonly used electrical products in homes, offices, industrial operations, and streets. According to Energy Star research (2006), an average US household has more than 40 sockets for light bulbs and consumes approximately 2100kWh every year for lighting. The development in lamp technology has pushed the boundary for newer products. The LED lamps have been taking over the market from the incandescent bulbs and compact fluorescent lamps (CFL). According to the US Department of Energy (2012) and myLEDlight.com (2007), LED lamps have several benefits over other lamps. LEDs produce light hemi-spherically, which increases their efficiency in directional light emission. It has higher breakage resistance from vibration or transportation. LED lamps use up to 90% less power than incandescent bulbs thus making them highly energy efficient; They have a longer lifespan, lasting 10 times longer than a CFL and 133 times longer than the traditional incandescent bulb. Because of all the benefits, Smallwood (2014) suggested that the market of LED lamps will grow to $12.2 billion by 2018."

Jan 1, 2018

By Z. M. Dai

Microorganisms in AMD (Acid Mine Drainage) were enriched in 9K culture medium. The enrichment was applied to leach copper pyrite after the microbial community structure and metabolism was stable. Before and after bioleaching, the microbial DNA was extracted and applied to RFLP (restricted fragment length polymorphism) analysis to demonstrate the relationship between the leaching efficiency and the change of microbial community. Atomic absorption spectrometry results showed that when concentration of the pulp was 10% and pH were 1.5, 2.0 and 2.5, the leaching rate were 56%, 57% and 34% on the 18th day respectively. These results indicated that the rise of pH resulted in the decrease of leaching rate. In lower pH condition, the growth of microbe was faster: when pH was 1.5, the microbial cell number reached to 1.4×107cells/mL on the 9th day; while pH was 2.5, the microbial cell number decreased to 4×106cells/mL. The analysis of microbial community structure showed that Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans were dominant species before bioleaching (account for 43% and 32% respectively). And after bioleaching, these two species were still dominant when the initial bioleaching pH were1.5 and 2.0. While the initial bioleaching pH was 2.5, the proportion of these two species decreased. These results demonstrated that the initial bioleaching pH would affect the microbial community structure in bioleaching system at room temperature, and this affect could lead to different copper pyrites bioleaching efficiency.

Jan 1, 2014

By Y. G. Seredkin, A. A. Vasiliev, A. Y. Senchenko, A. V. Aksenov

"The valuable materials resulting from the processing of gold-bearing ores are often refractory to direct gold recovery through cyanidation. There are multiple methods for chemical liberation of gold prior to cyanidation such as pressure and biological oxidation as well as atmospheric oxidation which is typically used in combination with physical activation of material by ultrafine grinding such as the Albion ProcessTM. This paper will examine the data from process testworks carried out to estimate the efficiency of the Albion Process™ for the oxidation of materials with a wide composition range prior to cyanidation. The data will be compared to that obtained by direct cyanidation of the feed (without oxidation) and from the testing of pressure oxidation on the feed prior to cyanidation. Albion Process™ tests were conducted in Institute TOMS with participation of Glencore Technology Pty Ltd (Australia). Refractory concentrates obtained from the ores of several Russian and CIS deposits were used as feed for the testing. These concentrates were also subjected to a material composition study and testing using conventional recovery methods. The resulted test data make it possible to perform an integrated assessment of process properties for materials with different compositions, compare performance of various process flowsheets for the materials under study, and conclude on efficiency of Albion Process™ application for gold recovery from refractory materials different in their composition.INTRODUCTION It is often the case that gold ore concentrates are refractory to gold recovery by direct cyanidation. This refractory nature is as a rule attributable to fine gold dissemination in minerals, most often in pyrite and other sulphides, as well as to the increased amount of components impeding cyanide leaching of gold due to cyanide consumption and reducing process conditions. The refractoriness of the concentrates results in low gold recovery values when conventional cyanidation technology is used. In this context, various additional processes are applied to breakdown such refractory sulphide concentrates, i.e. mechanical breakdown (fine and ultrafine grinding), chemical breakdown (atmospheric oxidation, e.g. Leachox, acid-oxygen oxidation, pressure oxidation – POX, bacterial oxidation – BIOX), and thermochemical breakdown (various roasting methods). Such breakdown processes allow for increase in recovery of finely disseminated gold during the downstream cyanidation, however, their application is cost-intensive and does not always ensure economic benefit."

Jan 1, 2018

By S. N. Titkov

Flotation of halite?new, recently begun to be developed method of processing water-soluble minerals. In the paper the results of studies of the new directions of the application of halite flotation are represented. Studies on the flotation separation of halite and sylvite in the salt solutions of different composition, showed the possibility of the halite flotation realization not only in the carnallite brine (content of salts: MgCl2 25.5% ~ 26.0 %, chlorides of potassium and sodium 5.5% ~ 6.0%), but in the sylvinite brine, which contains 10.5% ~ 10.8% KCl and 20.5% ~ 21% NaCl. On the basis obtained results are carried out experiences on the halite flotation from samples of the converted products of sylvinite ores by flotation method and by the method of the electrostatic separation. It is shown that in all cases it is possible to accomplish effective and selective recovery of halite. The halite recovery into the foam product of flotation makes 80% ~ 90% with an increase in the content of KCl in the cell product of flotation in comparison with a composition of flotation feed: - from the product after the electrostatic separation of ore ? from 76% KCl to 95% ~ 97% KCl; - from the small fraction of ore (- 0.25 + 0 mm) ? from 30% KCl to 60% ~ 64% KCl; - from middlings (intermediate products) of sylvite flotation from 16% ~ 31% KCl to 45% ~ 80% KCl. An increase in the molecular weight of alkylmorpholines increases the selectivity of the flotation separation of halite and sylvite. Halite recovery from small size fraction of ore or/and middling of sylvite flotation with the sub-sequent joint filtration halite product and tails of sylvite flotation allows to reduce considerably expenses for manufacture potash chloride from Pilot-industrial tests for the first time confirmed the possibility of the effective halite flotation in the saturated solutions of chlorides of potassium and sodium (sylvinite brine).

Jan 1, 2014

By V. Grujic, M. Grujic, D. Salatic

"Two areas are involved in the research work of the comminution process (crushing and grinding). The first one involves the changes of the size class distribution values that are definded by the differential equations in the function of the ore property and working conditions. The second area involves the comminution of the different levels in order to optimize the working parameters and to decrease the operational costs in the grinding process.We have studied, in detail, the possibility of functioning the crusher at the maximal loading, over 4500 kN, ball mills with diameters larger than 5.0 m and semiautogenous mills with diameters larger than 10.0 m.Using the computers, we have achieved the maximal loading range of the crusher, over Fc ? 4500 kN in the crushing process. In the grinding process, using the adequate differential equations in the automation process, we have established the correlation between the pulp mass capacity in the mill, pulp dencity, ore fineness in the pulp and recirculating ore charge.With the appopriate text, equations and graphs, this paper shows the results of our several years research work in the laboratory and in the ore comminution plant of Majdanpek Copper Mine."

Jan 1, 2003

By Axel Pankewitz, Andrew Smith, Mathias Stender, Christian Behrens

"Particle size measurement is one of the most important factors in obtaining peak performance of the mineral processing plant in order to ensure efficient milling and flotation circuit operation. Off-line particle distribution analysis technologies only allow an infrequent check of the ore slurry size and hence do not allow for timely process monitoring or intervention. Most existing on-line particle size analysers suffer from a variety of disabilities such as poor statistics, non-representative sampling or mechanically complex setup. This paper will describe an Ultrasonic Extinction based method which overcomes many limitations of existing online analysers and has proven its performance for mineral applications over many years. Installation examples will be given. Since new technologies usually raise e questions about comparability and agreement to common particle size analytical methods e.g. sieving or laser diffraction analysis, extensive studies were performed comparing these different technologies to quantify the quality of results as well as its mathematical robustness."

Jan 1, 2014

By F. Burat

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

Sep 1, 2012

By R. ?. Shishmarjov, Yu. ?. Davidenko, S. V. Bukhalov, ?. S. Baksheev, M. S. Shkirya, N. ?. Aikasheva, D. V. Bogdanovich, ?. Yu. Faustova

"The goal of prospecting operations in the Republic of Altay was to locate gold-sulfide-quartz mineralization. For this purpose we applied the technology of electromagnetic sounding and induced polarization (EMS-IP). These operations resulted in localizing promising sites with presence of sulfidization. The EMS-IP method proved to be highly efficient amongst other prospecting methods targeted at recognizing zones of sulfide mineralization making up 91%, considering that in more than half cases the ore intervals were the case. In the Yakutian diamondiferous province the EMS-IP technology was approbated during three field seasons to accomplish the assignments on searching for kimberlite bodies under conditions of various geological types. As a result, the reference objects were distinguished, and geoelectric parameters of kimberlite pipes of explosion were defined.INTRODUCTION In the time span 2015-2016 in Gorny Altay the EMS-IP technology was approbated in the Novokuznetsk area. The on-land areal geophysical survey was performed by EMS-IP method applied to identify, outline and locate promising sites with Au-Ag-bearing polymetallic mineralization within surveyed areas. Compared to the hosting rocks, the sulfides contained in polymetallic mineralization are typified by low specific electrical resistivity (SER) and high polarization. The areal survey conducted via EMS-IP method provided spatial characteristics of searched object. From July 2016 to August 2017 our expedition group carried out serial test works and laboratory investigations intending to define performance capabilities of EMS-IP technology in searching for kimberlite bodies under conditions of diverse geological types. The prerequisites for serial work were operations accomplished at the «Listvenichny» site lying 35 km away from Mirny town in the Sakha Republic (Yakutia), where the EMS-IP technology was probed for locating position and measuring geoelectric parameters of tuff pipe «Buardakhsky». After successful completion of operations it was decided to evaluate geoelectric parameters of kimberlite pipes of explosion."

Jan 1, 2018

By X. Xu

This paper presents the research on comprehensive recovery of copper, gold, silver and iron from tailings from high-intensity magnetic separation in Tonglushan Mine. By comparison of experimental results of three flowsheets?regrinding of tailings-conventional sulphidizing flotation, water heating enhanced sulphidizing flotation and acid leaching-sulphidizing precipitation flotation, it is concluded that regrinding of tailings-conventional sulphidizing flotation flowsheet has the best economical and technical performance and practicability. Regrinding and using the mixture of sodium hydroxamate and sodium xanthate are two of the notable technical characteristics of this best flowsheet. The system for comprehensive recovery of tailings has been put into production. It not only can recover the valuable minerals from tailings in Tonglushan Mine, but also can reduce the environmental pollution, resulting great economic and social benefit.

Jan 1, 2014

By C. Igathinathane

Coal is the most widely used fossil fuel in the world, providing more than 25% of world?s electrical power. Since, the behavior of coal particles in crushing and grinding circuits, concentration operations, and solid-liquid separations is strongly dependent on size, a reliable and accurate measurement of particle size and particle size distribution (PSD) is a vital aspect in coal cleaning. This paper presents a method for the characterization of ground coal particles using image analysis. We utilized a machine vision (MV) approach that used a document scanner as the imaging device and a user-coded ImageJ plug-in that processed the image and automated the PSD analysis and output results in textual and graphical forms. This approach used a sum of volumes (SVolume) as weighting factor for particle length as the primary dimension of analysis and was successfully applied to ground coal. The plug-in was further improved for computational performance in this study. Mechanical sieving (MS) was also used to compare the MV results. MV results showed that the PSD of ground coal followed a uni-modal normal distribution, and the log-normal plot against particle size exhibited a linear trend for most of the range. MS results, however, had three linear segments, when the width-based sieving results were transformed to lengths by applying the shape factor (width/length), but a definite deviation between the PSD plots was observed. This study demonstrates successful application of the MV SVolume approach for PSD analysis of ground coal, which can be extended to similar particulate minerals and products. Keywords: dimension, fiji, image j, image analysis, coal, particle size, plug-in

Sep 1, 2012

By A. A. Remes

High precision on-line particle size distribution measurement of mineral slurries has recently be-come available. It provides new tools for the development of monitoring and optimization methods for mineral grinding and separation circuits. The paper presents the development work at the Kemi chromite concentrator plant of Outokumpu Tornio Works in Northern Finland. The Kemi concentrator processes annually 1.2 Mt of chromium ore. The products are upgraded lumpy ore and metallurgical grade concentrate. The concentrate is produced using gravity separation methods, preceded by a rod mill - ball mill grinding stage. The separation process performance is strongly dependent on the particle size distribution of the grinding product at the Kemi plant. Particle size distribution has a significant effect on the concentrate grade and recovery. Currently a new laser diffraction based on-line particle size analyser is used for monitoring the grinding product. The analyser system allows the measurement of the whole cumulative particle size distribution simultaneously. It provides a wealth of new measurement information for process control. A monitoring and optimization scheme for grinding and gravity separation based on the particle size information is presented. The goal is to minimize the production of fine slime, and subsequently to improve the concentrate quality and minimize chromite recovery losses. Data-based recursively identified linear PLS process models are developed for optimization purposes. The preliminary results of the monitoring system operation in on-line use are presented.

Jan 1, 2014

By M. Gonzalez Fernandez

"If the final goal of metallurgy is the extraction of metals from a given ore, everyone knows that this achievement relies on many separation steps involving much more than a biphasic material made of metal and gangue. Nevertheless, still today, most of the design and follow-up of industrial processes only consider metal grades; in best case metal grades per size class. Working with such heterogeneous material, made of several minerals, with different grain size and texture, implies to consider finer ore models to be able to predict the behavior of material and the subsequent operation performances. Analytical tools are now available to provide such relevant and accurate data which are applied in geometallurgy. To achieve a true geometallurgical approach for process design, but also for optimization, accurate process simulation absolutely needs to combine these fine ore models with the corresponding unit operation models. Based on generic, but configurable, criteria of description and a hierarchical approach, the material modelling tool embedded in the USIM PAC process simulator provides the necessary flexibility to describe any type of ore with almost no limit in the level of details and associated physical properties that can be met in the mining industry. The simulation engine and the mathematical models of unit operations are designed to manage such a diversity of material modelling. The paper present various ore models and some of their applications in flowsheet simulation. It proves the interest of this detailed and advanced approach to accurately predict plant performances. INTRODUCTION Process simulation used for process design and optimization requires accurate unit operation modeling. During the last decades, main efforts of the different teams developing software simulators have been dedicated to those models for comminution and physical separations such as flotation or gravity concentration (Kojovic et al., 2012, Soni and Yoon, 2014). In most case, the ore is modelled with a size distribution and metal or mineral grades. A water phase is considered for wet processes. The association of unit operations and such material models generally allows, after some parameters adjustment, to achieve good agreement between experimental and simulated data. The use of the obtained simulator to test alternative configuration of circuits or settings of equipment devices can be accurate enough as far as the ore processed is close to the ore used for simulator adjustment. However, when the ore gets very different grades, coming from different mineral proportions or grain sizes, the simulation results can be of poor accuracy. Because any physical separations such as gravity, magnetic or flotation, do not sort metal and gangue but particles, made of minerals, containing metals, the only way to be accurate enough for allowing extrapolations, is to model particles. The phase model tools embedded in the USIM PAC process simulator gives this possibility. However, as such level of details are not always available for analyses, the tool has been designed with a high level of flexibility, to adapt the model to the available data. In this paper, the principles of this conceptual modelling tool are presented, and some application cases illustrate the material model flexibility and its interest."

Jan 1, 2018

By Gerke Gilian, Pretz Thomas, Pehlken Alexandra

"The evaluation of health hazards within the treatment of mineral and waste materials is gaining more and more importance in industrial countries. The need to control occupational health and safety has been recognised, and regulations which describe general protective measurements for personnel provide a tool to protect their health. It is the aim of the paper to give an outlook for practical approaches to risk assessment and to present measures for exposure reduction in accordance with the state of the art in Germany.Both the treatment of minerals and of waste materials are described in relation to the risk assessment. The method of evaluating health hazards in the two industries is similar and therefore both examples are presented next to each other.The example presented in the paper is the German “Biostoffverordnung” (the regulation for biological materials) which is important for the waste treatment industry. All kinds of waste treatment facilities (like composting facilities, waste dumps, sorting facilities for packaging materials) are obliged to carry out an assessment of health hazards for a variety of working areas and working places. The possible safety requirements deriving from this regulation are presented and discussed under the aspect of biological hazards."

Jan 1, 2003

By H. H. Li

Reverse flotation is usually used for hematite/silica or bauxite/clay flotation separation in which the silica or clay is floated and rejected. Some properties of these silicate minerals such as particle size and surface characteristics have significant effect on their flotation behaviours. Firstly, the silicate mineral particles (especially clay minerals) generally have fine particle size (< 5 microns) in their natural states or due to overgrinding and they display poor flotation kinetics, consequently having low flotation recovery. Secondly, the wettability difference on different particle basal planes influences the affinity for adsorptions of different types of chemicals such as collectors or macro-molecule. Common polyacrylamide (PAM) flocculants can be used to minimize the exposure of the most hydrophilic planes of clay particles via hydrogen bonding but they can not efficiently enhance the overall particle surface floatability due to the hydrophilic properties of this type of macromolecules. A novel method to improve both flotation kinetics and surface wettability of silicate minerals has been developed and studied. That is to use a temperature-sensitive polymer, poly (N-isopropyl acrylamide) (PNIPAM), as a process aid in the flotation of silicate minerals. Unlike PAM polymers, PNIPAM can induce a hydrophilic/hydrophobic transition on the particle surface when the temperature is changed to be lower or higher than its critical solution temperature (CST). At a lower temperature, the PNIPAM adsorbs on the particle surface via hydrogen bond similar to PAM. It induces strong hydrophobic aggregation when the temperature is increased above the CST. Thus, both floc size and mineral floatability are greatly increased. The flotation results show very good flotation performance and the addition of conventional flotation collector was no more required because the increased particle surface hydrophobicity induced by PNIPAM. Contact angle measurements explained the role of PNIPAM in manipulating particle surface hydrophilic/hydrophobic transition.

Jan 1, 2014