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By Chuanyao Sun, Yang Yu, Zhen Guo Song, Wei. Ming’An

"Carbonate minerals are very important mineral source of extracting metal, radioactive element and rare earth elements. Furthermore,some carbonate minerals, such as calcite and dolomite, are common and important components of sediments and sedimentary rocks. Many flotation processes involve the separation of valuable minerals with carbonate minerals. So it is of great significance to the flotation theory and industrial practice to investigate the flotation behaviors of carbonate minerals. As regulators, metal ions play a major role in minerals flotation. The study of influence law of metal ions on minerals flotation is helpful to eliminate or utilize the effect of metal ions. In this study, calcite and smithsonite laboratory scale flotation, surface analysis and zeta potential determination in the presence of Fe(II) ion were performed to investigate the effect of Fe(II) on carbonate flotation. The results show that Fe(?) depresses the flotation of calcite and smithsonite. The depression effect of Fe species on calcite and calamine flotation can be improved with the increase of Fe(?) concentration. The zeta potential measurements and surface analysis show the existence of iron hydroxide products on mineral surface, which may be link to carbonate site instead of exchanging with calcium on the mineral surface. Fe species on the mineral surface inhibit the interaction between the reagents and calcite/smithsonite through the formation of surface precipitation coating on the calcite/smithsonite surface when the Fe(?) concentration is higher."

Jan 1, 2014

By Masakazu Niinae, Tasuma Suzuki, Mai Moribe, Yohhei Okabe

Bench-scale electrokinetic experiments were performed to elucidate the electrokinetic remediation mechanisms of arsenate from artificially contaminated kaolinite. The electrokinetic experiments in which a constant voltage was applied demonstrated that high soil pH favored arsenate remediation with respect to both the remediation time and electricity consumption. It was also demonstrated that applying a pulse voltage (1 hour ON, 1 hour OFF) significantly improved the electricity consumption efficiency when the soil pH was maintained at the initial value during the experiments; this trend was not observed when the soil pH was gradually increased from the cathode side. These electrokinetic experimental results indicate that the remediation rate-limiting step varied with soil pH. When the soil pH was maintained at the initial value of 7.2 during the experiments, arsenate desorption was the remediation rate-limiting step rather than the migration of dissolved arsenate toward the anode. Conversely, when the cathode pH was not controlled and the soil pH was correspondingly increased gradually from the cathode side, the migration of hydroxyl and desorbed arsenate ions toward the anode played a more important role in the control of the overall remediation efficiency.

Jan 1, 2014

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 Lokesh K. Thakur, Peter Radziszewski

"For the cases tested (11 mills with 15 operating conditions), the Bond abrasion test steel media wear rate prediction gives an overall error of 73% and a standard deviation of 192.5%. However, total steel media wear in a given mill (ball or SAG) grinding process is a product of three recognised wear mechanisms -- impact, abrasion, and corrosion. A total media wear model can be defined on the assumption that the effect of each wear mechanism can be independently determined which allows for a total media wear model to be defined as the summation of the wear result of each mechanism (eqn. 1). It is assumed that impact and abrasive media wear is a function of the energy dissipated in impact and abrasion as estimated by a DEM charge motion simulation. Corrosive media wear is assumed to be a function of the media surface area present in a mill.The 3 initial tests developed (steel abrasion wheel, corrosion batch mill, impact chamber) coupled with the impact and abrasion energy spectra from a DEM charge motion simulation produced total steel wear rate results for the same cases as the Bond abrasion test giving an overall error of 0% and a standard deviation of 66.1%. However, if one were to consider the general observation that wear is proportional to energy and maintain the assumption that corrosion is proportional to media surface area then one would realize that the total media wear eqn. (1) can be reduced to eqn. (2). As this is a linear equation and one has, for the same mill, media wear and operating data for three different operating cases, one obtains three equations with three unknowns. This defines a simple matrix manipulation to determine the constants k1, k2 and k3. From the previous data set, we had 6 identical mills grinding the same ore but having different worn liner profiles and charge volume which provided the opportunity to average out the ki values over 20 combinations of 3 cases. With the determined ki values, it was possible to determine a second estimate of the contributions of impact, abrasion and corrosion to total media wear giving an overall error of 0% and a standard deviation of 56%."

Jan 1, 2003

By Williams Calderon, César Arredondo, Gonzalo Montes-Atenas

The quality of final concentrate in froth flotation circuits is largely dictated by the correct implementation of the froth washing operation in flotation cleaning stages, which are commonly installed in column flotation cells. In flotation plants, this aspect has been largely overlooked and the froth washing is restricted to the use of perforated piping through which process water flows producing a similar effect to that observed in "fountains": jet created with low energy crosses the froth phase washing out entrained particles as well as particles weakly attached to bubbles. The aim of this research study is to assess the efficiency of traditional froth washing systems theoretically and experimentally. A theoretical model was implemented using Fluent® software where a jet of variable speed was introduced in a continuous soft matter phase with physical properties similar to those observed in a froth phase in wet and dry conditions. In addition, a simple experimental protocol was designed to validate the model. It was found that the water process jet-like flow influences the behavior of 2 to 3 times the equivalent volume in the froth phase. Such influence zone is dramatically reduced as the froth phase becomes drier. These results were confirmed by the experimental findings indicating that a better froth washing technologies must be assessed and implemented. Some aspects of the ideal froth washing system are derived and discussed in details.

Jan 1, 2014

By Katarina Theander, Robert J. Pugh

In the flotation process, control of the stability of the froth is extremely critical. In the case where the froth is too stable then mechanical entrainment of particles can occur but in the opposite case, where the froth is too unstable and difficult to skimm-off, then a reduction in recovery can result. In minerals and deinking flotation, commercial fatty acids are used and may act as both both collectors and frothers. However, frequently the fatty acids are mixed with nonionic ethoxylated surfactants to give more effective froth control and increase the flotation performance. It is of interest to note from the surface chemistry literature, that such mixtures may cause synergistic effects in surface activity which may explain changes in bubble size, foaming and carry over of particles. In the present study, we have carried out foaming and drainage experiment with oleic acid and model nonionic surfactants; hexa(ethylene glycol) mono-dodecyl ether, C12E6 and tetra (ethylene glycol) mono-dodecyl ether, C12E4 both in separate and mixed systems. Frothing was carried out in a column, equipped with a series of conductivity electrodes which enabled the water content of the froth to be measured along the length of the column, during various stages of the drainage process. The variation in water content of the froth enabled the process to be characterised by distinct three stages; (a) an entrainment state where the water transfer from the bulk phase to the froth was dominant (b) a steady state when entrainment and drainage are balanced and no water is transferred to or from the froth and (c) the drainage step when drainage predominates and the volume of the bulk phase increases. We also carried out surface tension measurements on the oleic acid/ nonionic systems and related the results to the frothing and drainage performance. From the surface tension data, the adsorption interaction parameter of the mixed systems at the air/solution interface could be calculated and was found to depend on the oleate/ nonionic surfactant ratio. This value was related to the frothing performance and the results indicated a positive interaction parameter for the mixed surfactant systems which could explained the synergistic effects in frothing performance.

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 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

By David Deglon, Martin Harris, Mehdi Safari

This paper investigates the effect of energy input on the flotation of galena in a novel oscillating grid flotation cell (OGC). Oscillating grids generate near ideal hydrodynamic environments, characterised by turbulence which is relatively homogeneous and isotropic. Previous work was limited to quartz (-100 µm). Galena (-150 µm) was floated in the OGC at power intensities from 0.5 to 3 W/kg using 0.13, 0.58 and 0.82 mm mean bubble sizes (d10) and at three collector dosages. Results show that the effect of power intensity on flotation kinetics is strongly dependent on both particle and bubble size. For fine particles (-19 µm), increasing energy input increases the flotation rate at a low collector dosage but leads to an optimum at both the moderate and high collector dosages. For intermediate particles (+19-38 µm), increasing energy input has no effect on the flotation rate at the low collector dosage but leads to an optimum at both moderate and high collector dosages. For coarse particles (+38-150 µm), increasing energy input has no effect on the flotation rate at the low collector dosage and leads to a general decrease at both moderate and high collector dosages. Optimum conditions for fine particles are using small bubbles at a moderate collector dosage and an energy input of around 2 W/kg. Optimum conditions for moderate particles are using small bubbles at a high collector dosage and energy inputs of around 1.0 W/kg. Coarse particles do not benefit from agitation.

Jan 1, 2014

By Ming’an Wei, Chuanyao Sun, Yangge Zhu, Fayu He, Yanbo Shang, Xingrong Zhang

In order to discuss the separation mechanism of copper-molybdenum ore, surface electronic structures of chalcopyrite and molybdenite were studied in the paper, by using First Principles method of quantum chemistry. So, the separation mechanism of thioglycolic acid (TGA) with chalcopyrite and molybdenite was revealed better. The results showed that differences of the electronic structure of chalcopyrite and molybdenite could directly affect their interactions with TGA, such as band structure, density of states, Mulliken populations, and so on. And the frontier orbitals of chalcopyrite and molybdenite were also calculated by Dmol3 after the optimization by CASTEP, from which the interaction energies between minerals and TGA were obtained and compared. So, the essence of flotation separation of copper and molybdenum were well revealed.

Jan 1, 2014

By F. S. Hoseinian, K. Filho, D. Deglon, T. Souza, M. Safari

"This paper investigates the reverse flotation of hematite in three laboratory flotation cells with very different contacting environments. The main objectives are to investigate the recovery of coarse quartz by flotation and fine hematite by entrainment. The laboratory flotation cells used were the mechanical, oscillating grid and pneumatic cells. The effect of froth height and solid concentration were investigated in the mechanical and pneumatic cells. The effect of impeller speed and energy input were investigated in the mechanical and oscillating grid cells. Froth height results show that coarse quartz particle recovery decreases almost linearly with increasing froth height due to increased detachment of coarse quartz particles in the froth. Fine hematite particle recovery also decreases almost linearly with increasing froth height due to decreased water recovery and associated entrainment. Agitation/energy input results show that coarse quartz particle recovery increases with increasing impeller speed to an optimum, after which this decreases dramatically. The increase is due to improved gas dispersion, generation of smaller bubbles and increased bubble-particle collision and attachment. The decrease is due to significantly increased bubble-particle detachment at higher impeller speeds. The recovery of coarse quartz particles in the OGC is higher than that in the mechanical cell with an optimum at a much lower energy input. Solids concentration results show that both mass recovery and water recovery increase with increasing solid concentrations. The pneumatic cell achieves higher mass recoveries and lower water recoveries than those in the mechanical cell at equivalent solids concentrations and operating conditions. INTRODUCTIONFlotation is a selective process for separating different minerals from each other. The flotation separation efficiency depends on the recoveries of the mineral species by both true flotation and entrainment (Neethling and Cilliers 2009; Wang et al. 2015). Both chemical variables and hydrodynamic conditions within the flotation cell affect the recovery and selectivity of the flotation process. Cationic reverse flotation of hematite is a common method for selective separation of quartz from iron ores to produce pellet feed. The presence of coarse quartz particles in the tailings and fine hematite particles in the concentrate are two major challenges in the reverse flotation of hematite (Vieira and Peres 2007)."

Jan 1, 2018

By Ashok M. Raichur, S. P. Vijayalakshmi

"Recent advances in technology and the growing environmental concern have laid emphasis on the usage of fine clean coal. Coal fines are also generated in large amounts during various coal processing operations and are difficult to be treated, handled and disposed. Since most of the operations use water as the carrying medium, the fines so generated contain lot of moisture. Conventional technique for processing coal fines includes flocculation by a polymeric reagent followed by moisture removal using a rotary drum or a pressure plate filter, which produce a product with more than 30% moisture. Polymeric flocculants though required in small amounts, need high shear mixing for good performance and operate only in a narrow pH range. Moreover they increase the viscosity of the solution by many folds. Hence it becomes imperative to emulate newer methods for efficient fine coal processing. One such method is the novel use of microorganisms in coal processing.The present investigation deals with the utilization of two gram-positive microorganisms, Mycobacterium phlei and Bacillus subtilis, as bio flocculants and dewatering aids in fine coal processing. Preliminary characterization done on J-coal and M.phlei showed that they are negatively charged over most of the pH range. B.subtilis was found to possess positive charge below pH 4.7. The adhesion studies proved the high potential of microorganisms for adsorption to surfaces. Adhesion tests were conducted at various experimental conditions by varying parameters like pH and ionic strength of the suspension. Results obtained showed that adhesion is always higher in the presence of an electrolyte like KNO3 and most of the adhesion takes place in 15 minutes. With change in pH the amount of B.subtilis adhering on to J-coal remained almost constant and for M.phlei it decreased at higher pH values. Increase in ionic strength did not increase the adhesion of bacteria. Flocculation experiments confirmed the ability of the bacteria to act as bio flocculants. It was seen that about 98% of the coal settled in about 2 minutes on the addition of bacteria along with the addition of the electrolyte. The electrolyte was found to be indispensable for efficient flocculation of the coal suspension and for the attainment of a clear supernatant after flocculation. Also the optical micrographs revealed the formation of large, tight flocs when the electrolyte is present along with the bacteria. Further, flocculation tests were done in the pH range of 2-10 and the flocculation efficiency was found to be independent of pH."

Jan 1, 2003

By Janusz S. Laskowski

"Frothers offered by different manufacturers are marketed with some information on their chemical and physical properties (e.g. density, viscosity, color, water-solubility, safety/toxicity, etc.). But frothers are used in flotation to generate fine bubbles and to stabilize the forth, and this information is only provided in a very qualitative description of the visual appearance of bubbles and froths. The terms “powerful” and “selective”, which have been commonly used to characterize frothers, have intuitive rather than scientific meaning.This paper introduces the DFI (Dynamic Foamability Index) plotted vs. CCC (Critical Coalescence Concentration) diagrams to classify flotation frothers (Fig. 1). The frothers characterized by low CCC and high DFI values have properties of strong flotation frothers, while those with high CCC and low DFI values are more selective. The proposed frother classification system, based on simple CCC and DFI measurements, provides, for the first time, a solid ground-work for characterization of the flotation frothers."

Jan 1, 2003

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 Wieslaw Wszolek, Kazimierz Trybalski, Ryszard Tadeusiewicz

"The present work is an attempt of neural networks application to the description of complex technological processes of useful minerals enrichment. Neural networks are among the most convenient tools that have been added recently to the professional toolbox of modelling specialists, and they are particularly useful in realisation of multiple practical tasks, characterised by great complexity and relatively low amount of available a priori knowledge about the nature of the modelled processes. They are successfully applied in a wide variety of problems related to data processing and analysis, their prediction, classification or process control. The object of the study was the technological site for copper ore enrichment by floatation, being a part of technological line in the Ore Enrichment Plant ZG „Polkowice”, KGHM „Polska Miedz” S.A.The main floatation is described by parameters measured by the supervision and control system, which can be grouped with respect to the functions performed for the object:a) input function: aFG - copper contents in the feed material for the main floatation [% Cu]b) control: LFG I - level in the first section of the floatation unit [%], LFG II - level in the second section of the flotation unit [%], LFG III - level in the third section of the floatation unit [%], LFG IV - level in the fourth section of the floatation machine [%]. These quantities compose the five elements long input vector.c) output function: ? - copper contents in the waste from main flotation (final waste) [% Cu]The measurement data, containing the above-mentioned parameters, have been collected during the normal operation of the plant. The data contain momentary values of the parameters, registered every 10 minutes, covering the period of 196 hours of the plant’s operation (1176 measurements for each quantity).For construction of the model used in the study classical multi-layer perceptron-type neural network has been used, with one hidden neuron layer, trained by the error back propagation method."

Jan 1, 2003

By Andrei Kolesnikov

"The results of CFD modelling of complex heat transfer and fluid flow in DC electric arc furnace are presented. The model includes energy and momentum conservation equations for gas phase (freeboard), liquid phase (molten bath) and solid phase (walls and graphite electrode). Simulation revealed the temperature distribution in all elements of the furnace. The influence of the arc and melt resistance on the temperature distribution is discussed.Computational Fluid Dynamics (CFD) becomes a powerful tool for better understanding of the heta and mass transfer processes in industrial equipment. In current work commercial CFD software STAR-CD was used to analyse complex heat transfer in DC EAF, including forced and natural convection, conduction and radiation. The finite volume solver using body-fitted grid was used. The grids are non-staggered hexahedral grids and all variables are evaluated at cell centers. Steady-state calculations were performed with PISO algorithm. For the convective terms in equations the hybrid differencing scheme was used. An upwind differencing scheme was used for other terms. Conjugative heat transfer was taken into account in heat transfer calculations on gas-liquid and gas-solid interfaces. Radiation from the arc and inner surfaces of the furnace was calculated by a “discrete beam” approach. Source term in energy conservation equation was used to represent heat release in the zone occupied by the DC electric arc. The volume of this zone was calculated from semi-empirical equations. The Joule heat and heat due to chemical reaction in the melt were calculated through the source term expression in the energy balance equations for the slag and metal in the molten bath. The gas acceleration in the electric arc zone and stirring of the slag due to gas bubbles motion were accounted for by momentum source terms in the momentum conservation equations.All simulations were carried out using axisymmetric two-dimensional grid. The grid resolution was 20 cm per cell in most part of the furnace, except the arc region, where resolution was 5 mm per cell."

Jan 1, 2003

By M. Özer, G. Önal, F. Arslan

"The use of ultrasonic in industrial processes has increased during the last few years. Ultrasonic vibrations are used in sieving, grinding, ore washing, cleaning, and flotation in mineral industry. There are also some attempts for the utilization of ultrasonic treatment in separation and removal of fine particles from gases and liquids. In Kalemaden A.S. (Turkey) four different types of clay mixtures (1. A mixture of clays from Balikesir-Düvertepe and Istanbul-Sile, 2. A mixture of clays from Ukrania and Balikesir-Düvertepe, 3. Sögüt-Kadikelimesi, 4. A mixture of clays from Sögüt and Istanbul-Sile) and kaolin from Balikesir-Düvertepe (Turkey) are concentrated before their use in ceramic production. Dewatering is the important step in those types of concentration plants. Sedimentation of concentrated clay has always been difficult and taken long times due to their nature and having small particle sizes. Flocculants can be used to enhance the sedimentation, but they are not preferred by the ceramic industry since they affect the quality of ceramic products. For this purpose, ultrasonic treatment is used in the sedimentation of clays mentioned above for solving the problems encountered related to the ceramic industry and promising results were obtained.Kaolin sample, subjected to this experimental study, from Balikesir-Düvertepe region of Turkey was brought from the plant as a pulp in containers and throughly mixed with a stirrer before sedimentation experiments. A two liter graduated cylinder and an ultrasonic bath (with 25 kHz frequency and 0.5 KW power) were utilized in the tests. Superfloc A-120 (1% concentration) was used as a flocculant. The settling distance was reported against the settling time during the experiments. Initial and final pulp densities were also determined. The effects of several parameters such as pulp density, flocculant addition, and ultrasonic treatment on the sedimentation of kaolin were investigated and the results are represented in terms of settling distance versus settling time."

Jan 1, 2003

By Nicolás Caussade

"The IMPC 2014 slogan "Optimizing Water and Energy Usage for Sustainable Mining" refers to the ever decreasing availability of fresh water and energy, which has turned out to be a crucial aspect in assuring the competitiveness of the mining sector in Chile and the Andes region in general. The concern for sustainability and the supply of water and energy is nowadays part of the top priorities of mining countries and communities. This is also the case for Antofagasta Minerals. Several years ago its mining group implemented an energy policy based on intelligent, strategic and sustainable management, in order to successfully face the challenges imposed by the market. It is called an intelligent policy because it intends to provide energy through a diversified range of sources, which includes the development of in-house alternatives. It is also a policy focused on efficient energy consumption and one that is strategic. Because it is in line with the characteristics of the mining activity, it is developed for the long term. Finally, what makes the policy sustainable is that it gives priority to energy usage from renewable resources and as such, the required capacities have been developed to generate innovative solutions that respond to the restrictions that characterize the industry today."

Jan 1, 2014

By G. S. Hansford, G. E. Searby

"Ferrous iron oxidation kinetics was measured in continuous culture at temperatures between 65 and 75ºC, using thermophilic microbes suitable for high temperature bioleaching. The resulting specific oxidation rates were modelled as a function of the ferric/ferrous iron ratio. The results were compared to those obtained by conventional mesophilic microbes.Microbially mediated ferrous iron oxidation is a vital sub-process in the mesophilic bioleaching of sulfide minerals and is expected to be of similar importance at elevated temperatures using thermophilicmicrobes.A thermophilic archaeal culture used in chalcopyrite bioleaching was successfully grown in continuous culture on ferrous sulfate, indicating the capability of the microbes to sustain growth for long periods on the energy provided by the conversion of ferrous iron to ferric iron, the primary leaching agent in sulfide mineral bioleaching.Steady state data was obtained at residence times of between 70 and 10 hours, with washout occurring at residence times between 11 and 9 hours, corresponding to a maximum growth rate (µmax) of between 0.09 and 0.11 hr-1. The reactions were followed by measurements of the solution redox potential, soluble iron concentrations, and offgas analysis of the oxygen and carbon dioxide utilisation rates."

Jan 1, 2003

By K. H. Luo, J. Y. Liu

An experimental study on interparticle breakage of three iron ores was carried out by compressive stressing of particle-bed in a piston-die device. The feeds to the particle-bed stressing were five narrow size fractions in the size range of 0.2~3.2 mm respectively and a wide size fraction of 0/4.0 mm. The pressures applied were in the range between 30 and 360 MPa. The results show that the energy absorption of the particle bed increases linearly with the pressure; the increase of the product fineness with the pressure declines as the pressure goes up; and the product size distributions resulting from interparticle breakage of different narrow size fractions have no self-similarity. Using data obtained from the piston-die compressive stressing test, the suitability of a previously-developed material-characterization model for interparticle breakage was verified for these ores. It is shown that the particle-bed compression test conducted with piston-die device in lab-scale may provide a cost-effective way of studying and modelling size-reduction of ore materials by interparticle breakage.

Jan 1, 2014