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By N. T. Beukes, W. Banda

Recovery of Co from slag is a recent advancement in the extractive metallurgy of nonferrous metals. In this study a DC arc technology at laboratory scale has been applied to investigate the selective recovery of Co from slag, under three different flux types with an emphasis on influencing the activity of FeOx, SiO2 and CoO in the slag. It is known that reduction of slag by carbon is only up to a certain level after which, the recovery will depend on the chemistry of the slag, hence the need to modify the slag chemistry. Two power settings were employed to induce higher temperatures and aggressive agitation. The results were interpreted by comparing how much Co and Fe was in the slag and alloy. TiO2 reduced the amount of Fe in the product alloy compared to when CaO and CaF2 were used. The change in power did not seem to have had a major effect on the recovery although the amount of material lost to flue dust was more at a higher power rate.

Jan 1, 2003

By Sarthak Kaushik

Zeta potential measurements show that the isoelectric point of crandallite, in aqueous solution of 10-2 N sodium chloride is at about pH 5.5. Measurements of turbidity confirm the point of zero charge or crandallite. Calcium ions specifically adsorbed on the surface and thus changed the zeta potential and turbidity. From the measured data, it is confirmed that starch acts as a flocculent for crandallite. Oleic acid, which is a collector used in phosphate ore processing is weakly adsorbed on the surface of crandallite. This results in hydrophobic coagulation of particles resulting in a lower turbidity.

Sep 1, 2012

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

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

Jan 1, 2018

By 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 G. Weingrill, H. Flachberger, J. Neubacher

The so called Bublon®-process is an innovative process for the controlled expansion of volcanic glasses such as Perlite and for thermal treatment of other minerals. In this manner, functional light fillers with astonishingly altered physical properties can be manufactured. In contrast to conventional Perlite expanding processes no fossil fuels are burned in order to achieve the expansion. Instead, the feed material is heated electrically mainly by radiation based on heat transfer from heating elements. The main advantage is the better controllability of the production process. Therefore, the heating elements are segmented along the flow of the particles, hence in direction of the ongoing expansion. Overheating of the particles, which ultimately leads to the destruction of the particle surfaces and consequently decreasing the quality of the expansion product, can be reduced significantly. Due to flow characteristics and settling behaviors of fines the lower particle size limit of the feed in this process is restricted to not less than 100 µm. Otherwise process instabilities are to be expected. Manufacturing industry demands light and fine hollow microspheres. Therefore, a proven cooperation between Montanuniversität Leoben and Bublon GmbH was formed to develop a new process called ‘Bublite’. This issue was addressed by changing the conveying principle into a pneumatically conveying system transporting particles from the bottom to the top of the kiln by the means of a drag flow. This approach makes it possible to handle the difficult flow patterns in the kiln and to control the retention time of the particles in the heat transfer zone. As a result, it is now possible to expand very fine Perlite particles into a high quality functional lightweight filler with a glazed-closed surface. The dependence of the polymer industry on importing this kind of fillers from overseas can be reduced by producing it close to sites of demand. Also the Perlite mining and processing companies benefit from this technology because the mine lifespan and the output of the processing plant can be increased.

Jan 1, 2018

By Olli Haavisto, Heikki Häkkänen, Tommi Kauppinen, Navid Khajehzadeh

Raman analysis is a well-established method for finding the abundant minerals in an ore sample. In this study, Raman spectroscopy is tested as a method for rapid and contactless on-line mineral analysis. Rapidness might enable on-site analysis of rock drillcore, which in turn would lead to more cost-efficient solutions in mineral exploration. This paper discusses the use of Raman analysis to identify minerals and to measure their concentration. The sample set under study consists of rock drillcore collected from Agnico-Eagle Kittilä Mine, Finland. Selected parts of the sample set are measured by Raman spectroscopy and the minerals are identified using reference spectra from a public source. Moreover, the direct measurement of concentration of different minerals with the help of Non-negative least squares (NNLS) optimisation algorithm is considered. The optimisation algorithm was constructed to form a linear combination of reference spectra which best represent the measured spectrum, or an average of measured spectra, from an ore sample. The results show that NNLS can identify abundant minerals in a given sample. Also through this method of analysis the results of a traditional point-count method can be expanded: It was observed that, due to grain size, multiple minerals consistently appear in the spectra measured over an area, which means that point-count method is not a proper way to interpret the spectra. This can be seen as a new result, as formerly the discussion has attended to other methods.

Jan 1, 2014

By S. Banisi, E. Arghavani, M. Pourkani, M. J. Rajabi, Gh. A. Mohamadian, H. Bidshahri, Gh. A. Parsapour

The Sarcheshmeh copper complex flotation circuit of plant No.1 consists of two identical north and south sections where each includes four rougher (each bank consists of 14 cells), two cleaners (each bank consists of 8 cells), two recleaners (each bank consists of 2 cells), and two scavenger banks (each bank consists of 10 cells). The reduction of feed grade along with a change in the mineralogical composition is the main reason of current lower concentrate grade (24%) compared with the design concentrate grade (32%). Because of a lower feed grade, the amount of rougher concentrate has decreased which in turn has significantly reduced the feed rate to the cleaner, recleaner, and scavenger banks. This has increased the mean residence time of the material in the cleaner section resulting in a lower final concentrate grade. A laboratory study showed that the final concentrate grade can be increased by 2-4% if one cleaner stage is added to the flotation circuit. In this research, based on the laboratory results, one cleaning stage was added to the current flotation circuit. In order to make this modification instrumentally possible in the plant, the final concentrate was gravity transported to the Mo-Cu thickeners. This released 2 pumps and associated tanks which made addition of one cleaning stage practicable. Finally, a part of the cleaner and scavenger cells were used as the third cleaning stage. This decreased the residence time in the cleaner and scavenger banks. After implementation of one cleaning stage in the south section of the plant, the performance of the circuit compared with the identical north section. It was found that at the same recovery, the concentrate grade of the south section increased by 2.5%. The promising results led to the implementation of adding one cleaning stage in all sections of the flotation circuit.

Jan 1, 2018

By Graeme Heyes, Warren J. Bruckard, Michael A. Somerville

"Over the past few years CSIRO Minerals has been conducting research aimed at developing a continuous copper converting process to replace the traditional two-stage batch process that is currently used to produce blister copper. Sirosmelt type reactors and calcium-ferrite (lime-based) slags have been used rather than the conventional iron silicate slags. The research work has now been extended to focus on the development of a single-stage continuous copper making process (so-called direct copper converting) in which copper concentrates are converted to low-sulfur blister copper in a single step, that is the smelting and converting steps occur in one continuous stage.One feature of the direct copper converting process is that copper losses to the slag phase can be high, meaning the slag produced needs to be treated to recover the copper value. The feasibility of the whole copper making process will most likely depend on the efficiency and cost effectiveness of the copper recovery stage. Flotation has been identified as the most economical option to recover the copper from direct copper converting slags where it has been estimated that a copper recovery from the slag of above 90% is required to make the overall single stage copper making process economically feasible.A limited series of laboratory batch flotation tests was conducted on a suite of calcium-ferrite-based slags made in laboratory smelting trials. Copper sulfide concentrates from MIM were used as feed-stocks. The objectives of this work were to develop a robust flotation process to maximise the copper recovery and iron rejection from slags made in the process, and to establish operating conditions for future continuous flotation pilot plant trials.The slags treated included a reduced low copper slag, an oxidised high copper slag composite, and a very reduced low copper self-pulverising slag. The copper content of the slags varied from 2.9% to 14% Cu and the CaO/Fe ratio varied between 0.30 and 0.54. In general, the higher the copper content the more oxidised the slag. The copper was present as metallic copper, oxide copper and copper-calcium ferrite phases with the phase mix related to smelting conditions. The slags were crushed, ground, wet-screened at 355 or 210 µm to remove coarse metallic particles of copper, and floated at natural pH (about pH 11) using reagents and conditions appropriate for the selective recovery of the copper phases. Reagent additions were typically 200 g/t KEX and 500 g/t Na2S.9H2O and the grind size was generally a P80 of about 40 µm."

Jan 1, 2003

By Christopher M. Rule, Martyn P. Hay

"A methodology was developed in the mid-1980’s to predict plant performance from standard laboratory flotation tests. The methodology incorporates a flotation simulation program “SUPASIM” which translates flotation performance from bench-scale tests to full-scale plant. The technique is based on a simple, empirical kinetics model, and is tailored for use by the practical metallurgist. Kelsall’s unmodified equation incorporating two rate terms describing slow and fast floating components is used as the basis of the method. The flotation behaviour of an ore is described by a set of numbers, which can be compared in the evaluation of ore types, mineralogy and operating conditions. In so doing a precise relationship is developed between metallurgical performance in terms of grade and recovery and flotation kinetics.To date the performance of more than 20 flotation plants has been predicted, encompassing copper, lead, zinc, nickel, phosphate, pyrite, graphite, cassiterite, platinum and various slags. In three cases, plants have treated more than one type of ore. The method has successfully been used to predict and design four flotation plants using data generated from bench-scale laboratory flotation testwork. All have since been commissioned, and have performed as predicted. In the last year alone it has been used to drive flowsheet development for at least seven new plants in South Africa and the Americas. It is also being used to assist in the optimisation of existing operating plants."

Jan 1, 2003

By Komar Kawatra, Joseph Halt

"Bentonite clay has been the traditional binder for iron ore pellets. However, bentonite increases pellets’ silica contents and is expensive. Researchers have proposed lowering bentonite doses by mixing it with other common binders. These mixtures may only be successful if the fundamental bonding mechanisms are understood. For example, what happens when bentonite (physical bonding) is mixed with fly-ash (chemical bonding)? What happens when bentonite is mixed with cornstarch (physical bonding)? In this paper, experiments are described where bentonite was mixed with various ratios of cornstarch and fly-ash, and pellets were agglomerated using 0.66 % w/w binder. Ca(OH)2 and CaCl2 were added as activator and accelerator, respectively, to the bentonite-fly ash mixture. Curves of pellet dry strength vs. bentonite-starch ratio were linear, suggesting the physical-physical bonding mechanisms were compatible - acceptable strengths (> 22 N) were produced at all bentonite-to-starch ratios. This was contrary to bentonite-fly ash mixtures, which displayed dry strength curves with a noticeable minimum due to competing binding mechanisms. Bentonite alone and fly ash alone produced acceptable strengths (> 22 N), but their mixtures resulted in weak pellets. Due to the positive results using cornstarch (CS) binders, the effects of CS solubility in water were investigated using two CS with high and low solubility (60 and 7.5 %). CS was premixed with bentonite at various ratios (0, 20, 40, 60, 80, 100 %). Pellets were agglomerated using 0.66 % w/w binder. The dry strength of pellets ranged from 50-300 N using the high solubility CS mixtures, and from 50-85 N using the low solubility CS mixtures. Fired strengths exceeded 2200 N/pellet at all bentonite-cornstarch ratios. This research showed that cornstarch solubility is an important factor in determining its effectiveness as a binder for iron ore concentrates, but significant work is still necessary before it can be used as a bentonite replacement."

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

"This research aims at improving the beneficiation of coals and minerals in fine and ultrafine size fractions. A widely used method for upgrading fine and ultrafine particles is froth flotation, which is generally classified into mechanical flotation and column flotation. The present work is focussed on column flotation. A flotation column equipped with a conventional bubble diffuser/sparger was used with oscillatory air supply generated using a fast-switching solenoid valve. The flotation tests were carried out for coal particles and mineral particles, respectively, and a comparison in flotation performance was made between oscillatory air supply and steady air supply. It was found that use of oscillatory air supply with a proper valve switching frequency and on/off time ratio to replace steady air supply could lead to increased recovery of coals or minerals by more than 14 percentage points and substantial reagent cost savings. The improved flotation performance was attributed to enhanced gas dispersion and flow conditions. This research offers a simple new approach to improving the beneficiation of fine coals and minerals with using flotation columns.INTRODUCTIONFroth flotation has been widely used for the separation and concentration of fine coals and minerals by exploiting the difference in their affinity to air bubbles in aqueous medium. Froth flotation is an effective method for beneficiation of coal and mineral particles in a certain size range. It remains difficult to upgrade ultrafine mineral particles. One of the reasons for the ineffective flotation of fine particles is the low probability of bubble-particle collision in the collection zone (i.e., the pulp zone). According to Reay and Ratcliff (1973) and Yoon and Luttrell (1989), the probability of collision is significantly affected by bubble size and particle size, and the collection zone recovery can be increased by decreasing the bubble size."

Jan 1, 2018

By P. K. Fedotov

Annually at least 5% percent of world power consumption is involved in the process of ore dressing while ore processing technology. Such rate of energy consumption demonstrates the importance of a given process study in the human life-sustaining activity. Examining of interparticle destruction being under external stress pressure in ore responses this problem solution at the greatest degree. The technology of destruction in the roll press is of great interest. The use of the given equipment allows to save a significant amount of energy by means of the built-in ore destruction mechanism. Examination of stress-strain fields which determine the level of interparticle destruction between the rolls in the ore layer enables to specify both level of ore destruction and power consumption. The mathematical computer modeling for the deformable environment use based on the finite-element method (FEM) allows to carry out the given research. We use FEM solution for elastic contact problem for the most complete study of power consumption employed in ore and interparticle destruction. This problem solution allows also to examine energy consumption expenses spent for ore crushing in the roll press. Also we have identified the mechanism of ore in a layer of the particles under pressure roller press. It is established that high level of performance and reduction of energy consumption in interparticle destruction of ore in the layer due to the appearance of the gradient of normal stresses in contact of particles of mineral raw materials. The algorithm has been developed determining crushing product particle size distribution of fractured particles in the layer, using the Bond’s theory of crushing. The use of our FEM model reduces the time of equipment selection for new plant and at the design stage to reduce the risks of errors in the choice of roller presses.

Jan 1, 2018

By Markus Dammers, Christopher Robben, Hermann Wotruba, Christian Schropp

"In most underground mining processes the entire extracted ore is transported from underground workings to surface processing plants for separation of valuable minerals and gangue material. Most of the transported material consists of barren rock with negligible metal content, especially for low grade deposits, such as in the copper or gold metal ore mining. Increasing mining depths result in higher costs for transportation and hoisting. Therefore, rejecting waste rock as soon as possible from the material stream gains importance. The concept of resource to product integration in the form of earliest waste rejection in combination with subsequent backfilling follows the philosophy of ‚leaving waste underground?. Implementing mineral processing underground can lead to less required mass movement to surface, hence reducing transportation and hoisting costs. At the same time, rejected waste can be used as backfill to increase extraction rates by reducing pillar volumes. In the mill, a stable high grade feed leads to decreased specific operating and investment costs as well as increased productivity and recovery. These effects as a whole have a large potential to reduce cut-off grades so that resources can be turned into reserves. Within the I²Mine (Innovative Technologies and Concepts for the Intelligent Deep Mine of the Future) project of the European FP7, investigations are carried out by the Unit of Mineral Processing of RWTH Aachen University, the Institute of Mining Engineering I and TOMRA Sorting Solutions | Mining. One aim of the cooperation is to develop new concepts for a comprehensive integration of near-to-face processing in combination with backfill into the overall underground mining process. Effects on up-, down- and side-streams are investigated to prove the potential of resource to product integration in comparison to common underground mining systems and processing methods."

Jan 1, 2014

By Glaser. C., J. Balz, F. Logsch, R. Heiduschke, M. Leiker, P. Ay

The treatment of iron-hydroxide-containing water from ground water and surface water is achieved by a combination of the process steps of flocculation and subsequent mechanical dewatering. The aim is to create solid pellet structures by extending the structure forming flocculation process with a build-up pelletizing process which can be transferred directly into a drying unit. A Taylor-Couette-reactor (diameter of the inner cylinder – 40 mm, gap width – 5 mm) was used for these experimental studies. To produce the necessary flow profile the inner cylinder was rotated at a speed of 230 rpm. The iron hydroxide-containing suspension (dry matter content: 2 mass %) was added simultaneously with the addition of a cationic high-molecular flocculant in various flocculant dosages and residence times of 5 to 15 min. The pellets were examined for parameters such as geometric dimensions, dry substance content and dewatering behaviour. As the results show, there is a direct relationship between the residence time and the geometric dimensions of the pellets. After a residence time of 5 min, round pellets with an average diameter of 6 mm were formed. With an increase in the residence time up to 15 min, a compaction of the pellets could be observed, which resulted in an increase in the dry substance content of 8.0 to 11.2 mass % on average. After completion of the pelletizing process, the pellets were mechanically dewatered by filtration. By applying this innovative wet pelletizing of iron-hydroxide containing suspensions in a Taylor-Couette-reactor, it is possible to carry out the process of flocculation combined with the pellet formation with simultaneous pellet compaction in a single process step. The resulting pellet structures are distinguished from conventional floc structures by an improved water discharge capacity. After classification the pellets can be marked directly as easy-to-handle bulk material, suitable as feedstock in percolation columns for the purification of contaminated fluid streams

Jan 1, 2018

By Peter J. Coghill, Michael J. Millen, Brian D. Sowerby, Kirby D. Cunningham

"CSIRO Minerals has developed an integrated particle size analysis system for deployment in the grinding circuits of minerals processing plants. The system includes a slurry sampling station, a de-aeration tank and an ultrasonic particle size analyser (UltraPS). The UltraPS analyser is based on ultrasonic attenuation and velocity spectrometry combined with gamma-ray transmission. The technology is applicable to the measurement of 0.1 to 1000 µm diameter particles directly in highly concentrated slurries without dilution. The analyser incorporates a gamma-ray transmission gauge utilising an ultra-low activity radioisotope source that is exempt from International Atomic Energy Agency (IAEA) and Australian licensing regulations.The UltraPS analyser consists of a submersible probe and an electronics package. The probe can be immersed directly in a minerals processing plant stream if the aeration level in the stream is low. For applications where a de-aerated slurry stream is not available, CSIRO has developed an integrated system that includes a sampling station, a de-aeration tank as well as the UltraPS analyser itself. A schematic drawing of the continuous flow gravity fed system is shown in the figure. A commercial sampling system is used to supply slurry at a rate of 2.5m3/hr to the deaeration tank. The aim of the de-aeration tank is to remove air in the slurry to a level where meaningful particle size measurements can be performed. The tank volume is about 0.2m3, thus giving the slurry flowing through the tank a mean residence time in the tank of approximately five minutes. Tests at a number of concentrators have shown that five minutes is sufficient time for slurry to de-aerate to a level where ultrasonic measurements can be made. The tank incorporates an ultrasonic level detection sensor and flow to the deaeration tank is adjusted based on the level of slurry within the tank. The UltraPS probe is mounted through a flanged section of duct, which is bolted to the bottom of the de-aeration tank."

Jan 1, 2003

By N. Naude, W. P. Roux

"Traditionally minerals processing equipment, such as jigs, are studied by characterising the feed and products from these processes. With this approach important details on the mechanisms of a process can be overlooked since assumptions have to be made on the internal operations of the equipment. Positron Emission Particle Tracking (PEPT) is a non-invasive technique that can be used to track a particle’s movement inside a closed vessel. PEPT makes it possible to observe the inner workings of a process, providing new information that was unattainable only a few years ago. Jigging has long been considered as one of the most difficult mineral processing techniques to model, due to the complexity of the mechanisms contributing to the separation of minerals during the jigging process. In this investigation PEPT was used to study the particle flow inside a laboratory batch jig. The aim was to determine if the particle trajectories could provide new insight into the jigging and its mechanisms. Three dimensional particle trajectories were observed with spatial and temporal resolution high enough to see details of the individual pulses during jigging. It was found that the pulse height is very dependent on the position in the jig bed. The vertical component from the trajectories showed the rate at which particles move through the jig bed (stratification rate) and it was seen that the density of a particle affects the stratification rate more that the particle’s size and that the shape in the range that was tested had little to no influence. Other phenomena such as a circular flow pattern was observed inside the jig and it was found that smaller lower density particles are affected by this circular flow pattern which tend to disperse these particles throughout the jig bed. Visualising the flow inside a jig by means of PEPT has shown to be instrumental in the deeper understanding of the process."

Jan 1, 2018

By S. Martins

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

Jan 1, 2014

By M. Pelser, Lorenzen L.

"The presence of calcium and magnesium in the hydrometallurgical processing of base metals, results in a number of process difficulties. These problems range from the contamination of the final product (where the final product is a precipitate) to high energy consumptions and large bleed streams during electrowinning. Calcium poses an additional problem in sulphate solutions owing to the low solubility of its sulphate salts. This can easily lead to a process stream that is supersaturated with calcium sulphate, resulting in unwanted solids formation within the process equipment.A review of literature has proven that there is no conventional method for the control of calcium and or magnesium, although a number of potential processes have been identified. The technologies investigated included precipitation, ion exchange and solvent extraction, for which at least one method was found under each. To make the reader aware of these processes a short description was provided of each within the text.Of these processes, fluoride precipitation was selected for experimental investigation based on the low solubility of calcium and magnesium compared to the base metals. This process involves the addition of a soluble fluoride to precipitate CaF2 and MgF2. The experiments were designed to investigate the equilibrium of the system at varying parameters of which the level of fluoride addition, the ratio of calcium to magnesium, and the identity of the soluble fluoride was reported. In all of the instances the process showed high selectivity towards calcium and magnesium over the base metals. The experiments proofed the process to have a higher affinity towards the removal of magnesium at compositions where the molar ratio of calcium to magnesium was higher than 1:3. It is often the case that the calcium to magnesium ratio is in the region of 1: 10. From this it follows that the fluoride addition has to be stoichiometric or greater for calcium and magnesium combined, if the calcium is to be precipitated. This was demonstrated as well. On the identity of the soluble fluoride hydrogen fluoride was compared to ammonium fluoride, of which the latter was found to be preferred."

Jan 1, 2003

By F. L. Mentg

The utilization of acid leaching tailings was studied. It is obvious that the Fe in acid leaching tailings can be leached into solutions as Fe2+. In this paper, the influence of conditions, including the concentration of ferrous sulfate, pH, temperature and velocity of air flow was investigated. The optimum conditions for preparing seed crystal are as follows: the concentration of ferrous sulfate is 20 g/L; pH is 9.5~10; reaction temperature is 10~20?; velocity of air flow is 0.4m3/h. The optimum conditions for preparing iron oxide red are as follows: the concentration of ferrous sulfate is 5 g/L; reaction temperature is 80~85?; velocity of air flow is 0.13m3/h. At last, the product of iron oxide red could be prepared by ammonia method.

Jan 1, 2014