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By Wang Xu, Tao Dongping, Zhang Jie, Tao Youjun

Based on the principle of fly ash triboelectrification, the mineral electrical index and testing method are introduced. The electric differences of various mineral components of fly ash are discussed in view of the results of chemical and mineral composition analysis of the fly ash sample acquired from the Xin-wen power plant. The dielectric constant and charge-mass ratio of carbon and ash in the fly ash are determined. The data were then used along with the rotary triboelectrostatic separator (RTS) testing results to investigate the charging characteristic of fly ash particles in different sizes. The results show that the dielectric constant of fly ash with different particle size decreased with the decrease in particle size, which led to a poor electrical conductivity. Thus particle size has an important effect on conductivity. The charges of carbon and ash particles increased with decreasing particle size. The charge-mass ratio of carbon and ash particles of the same size increased with decreasing particle size. This indicates that finer particle size is more favorable for triboelectrification separation from the charging efficiency point of view. The rotary triboelectrostatic fly ash separation tests show that the best decarbonization performance was achieved with particles in the size range of 0.038-0.074mm with which the decarbonization rate and efficiency index reached 38.93% and 120.83% spectively.

Jan 1, 2014

By B. Q. Xiao

The nitrate content is an important factor for environmental water samples and flour. In a 0.35 mol/L H2SO4-2NO solution, has a strong catalyzing function on the decolourization of Gallocya-nine (GC) oxidated by NaBrO3. Based on this, a novel method was developed to measure the NO and -3NO concentrations in water and flour. The flow injection technology was introduced into the analysis system. A single-valve dual- cingulums to inject which the Copperized-Cadmium slice and the reduction zone are isolated. The optimum solution for this method contains 1.48×10-4 mol/L GC, 0.06 mol /L NaBrO3 and 0.2 mol /L of NH4-2NOCl. Two empirical equations were proposed to calculate the and -3NO concentrations based on the measured signals. It can be used to measure -2NO of from 0.001 mg / L to 2.0 mg/L and -3NO of from 0.002 mg / L to 2.5 mg/L. The measurement frequency can be up to 20 samples / h. The relative standard deviation for eleven samples is less than 5%.

Jan 1, 2014

By Reza M. Rahman, Seher Ata, Graeme J. Jameson

"This paper presents the results of a through investigation into the froth recovery measurements in a controlled plant environment using a device that allows direct collection of dropback particles from the froth phase. Test work was performed at the Northparkes concentrator (NSW, Australia), using a feed taken from the head of the cleaner scavenger bank. The feed slurry had a relatively higher copper grade varying from 5.2% to 6.8%. Experiments were performed to investigate the effect of important flotation parameters such as air flowrate on the froth recovery. The size of the particles in the relevant streams was also analysed to acquire in-depth knowledge about the froth dropback mechanism. The results suggested that the froth recovery could be as low as 70%, although it was relatively easy to achieve the values in the range 75% to 85% by the correct choice of operating variables. It was found that the air flowrate has a positive impact on both collection (pulp) and froth zone recoveries. However, the effect was more prominent in the froth zone. It appeared that the froth recovery is a strong function of particle size."

Jan 1, 2014

By P. Raghavan1

Reverse froth flotation experiments were carried out in the laboratory using two different types of kaolins for the separation and removal of coloring titanoferrous impurities from cryo-filtered clay after subjecting to high shear pre-treatment. This high shear pre-treatment consists of high shear agitation of a high solids clay slurry with the dispersant (high shear dispersion, HSD) followed by high shear agitation with the collector (high shear conditioning, HSC). After this pretreatment, the slurry is diluted and reverse flotation is carried out. One sample is from, Gujarat, India (Mamuara clay, ?MC?) while the 2nd sample is from Amberg, Germany (AKW clay, ?AC?). While MC consisted of 89% particles below 2µm and analyzed 1.06% of TiO2 and 0.29% Fe2O3 and measured a brightness of 83.4 %ISO, the corresponding values for AC are 67% below 2µm, 0.3% of TiO2? 0.49% Fe2O3 and 83.4 %ISO. The flotation performance is found to be greatly influenced by the conditions of high shear treatment. Important variables are HSD intensity (rpm), HSD time, HSC intensity (rpm), HSC time, HSD/HSC time ratio, ?HSD+HSC? total time etc. Higher shear intensities favor both the impurity liberation and collection. For both clays, it could be shown that impurity removal increases as total pretreatment time (?HSD +HSC? total time) increases up to a certain limit. For MC, the HSD time was only half or less than that of HSC time, while for AC, HSD time is at least twice (or more) than HSC time which is just an opposite manifestation. This is believed to be due to the striking differences between these two clays. Most importantly, the shear frequency is found more influential than the shear rate for the overall flotation performance for both clays. Interestingly, at high shear frequencies, i.e., when a stirrer with more number of teeth on the rotor is used, the ?HSD+HSC? total time is greatly reduced. Again, increased shear frequency helps to reduce flotation time and significantly improves flotation performance. At optimum conditions, product titania reduced to 0.35% for MC whereas the same reduced to 0.13% for AC. The product of flotation of MC measured 85%ISO brightness while that of AC measured84.6%ISO thus enhancing the value of the final product. It could also be established that the high shear pre-treatment shows better flotation performance than that due to collector dosage. Keywords: high shear dispersion, high shear conditioning, titanoferrous impurities, shear rate, shear frequency, brightness, clay recovery, Mamuara clay, AKW clay

Sep 1, 2012

By H. Z. Kuyumcu

Coking of coal blends using high volatile coals with poor coking abilities to produce a high quality coke for blast furnace application can be achieved by compacting the coal blend prior to the carbonization process. Here densification up to a relative material density of 80 %, i.e. a compact density around 1100 kg/m3, has proven to be advantageous. Coal is compacted by stamping, if the so-called stamp charging process applied. Compacting of the coal by pressing is practised in case of the cokemaking with so-called heat-recovery ovens. Stamped and pressed coal cakes require over the cake volume uniform high density and mechanical stability. Besides the aspects of the coal selection, the efficiency of the process is mainly determined by the operating parameters compacting time and compacting energy for coal cake making. At the Department for Mechanical Process Engineering & Solids Processing of the Technical University Berlin the two sub-processes of densification and strengthening during stamping and during pressing are theoretically and experimentally investigated using specially developed lab-scale compacting test units and a strength test device. Describing cake density in terms of coal properties for a given coal and measured compacting energy input then leads to a compacting equation with the so-called Stampability as the integral model parameter for the stamping process. For the pressing process the cake density can be calculated with the measured compacting pressure and the Compressibility factor, respectively. Investigations were carried out to provide evidence of a significant influence of coal type, coal surface moisture, coal granulometric and mechanical properties on the densification process. The overall objective of the work is to establish a comprehensive mathematical model on the compacting behavior of large coal bulk quantities and the optimization of the compacting processes by stamping and by pressing. Keywords: coal compacting, agglomeration, stamping, pressing, cokemaking

Sep 1, 2012

By David De Klerk, Maximilian Richter, Thirunavukkarasu Pathmathas, Indresan Govender

We consider the average power dissipation distribution for dense granular flows of an idealised mono-sized charge (5 mm glass beads) in a 300 mm diameter tumbling mill operated in the cascading-to-cataracting Froude regime. By combining the inherent frictional nature of particles within a dense flow regime and noting that tumbling mills are typically characterised by collisional and turbulent stresses, we derive the power dissipation distribution for athermal boundary conditions. The input data to the model (velocity, solids concentration, pressure and flow depth) are obtained directly from non-invasive measurement using a nuclear imaging technique: Positron Emission Particle tracking (PEPT). The power dissipation due shear stresses is shown to be the dominant mode of dissipation in the tumbling mill with up to two orders of magnitude difference between pressure induced dissipation and shear.

Jan 1, 2014

By Wei Zhang, Jinhong Zhang

"In froth flotation, the adsorption of collector on mineral surface is critical for a successful flotation process. In present work, an atomic force microscopy (AFM) has been applied to study the adsorption of potassium amyl xanthate (PAX) on copper sulfides, i.e., chalcopyrite, chalcocite and bornite. The in-situ collected AFM images show that PAX adsorbs on chalcopyrite mainly in the form of oily dixanthogen; while it strongly adsorbs on chalcocite and bornite in the form of insoluble metal xanthate, which binds strongly with the mineral surface. The information obtained from the AFM study shed lights on the collectivity and therefore the selection of specific collector for different copper sulfide minerals in industrial practice.INTRODUCTIONFroth flotation, which treats the highest throughput in mining industry and produces the maximum economic outcome of any surface chemistry process, has been widely applied for the concentration of copper sulfide minerals, i.e., chalcopyrite, chalcocite and bornite. In flotation, collectors are added into the pulp (mixture of water and fine-grained minerals) to selectively adsorb onto the target mineral and render its surface with high hydrophobicity, which is generally beneficial for a strong mineral-bubble attachment and thus a high flotation recovery. Therefore, the adsorption of collector on mineral surface is vital for a successful flotation process and it has been studied by applying various surface analysis techniques, such as IR (Infrared Spectroscopy), CV (Cyclic Voltammetry) and XPS (X-ray Photoelectron Spectroscopy). (Poling, 1963; Allison et al., 1972; Mielczarski et al., 1984; Leppinen et al., 1989; Kartio et al., 1996) These studies have revealed a lot of information, such as the reaction, product and mechanism, of the adsorption of chemicals on mineral surface. It is also of great interest to directly get the image of adsorbed collectors on mineral surface changing with pulp chemistry, such as pH, redox potential, ionic strength and chemical’s dosage."

Jan 1, 2018

By E. Scheepers

Within a phosphorus producing submerged arc furnace it was found that the continuous fluctuation of the furnace between a flowrate-driven state (high throughput) and a thermodynamic-driven state (low throughput) caused both techniques to have similar overall, predictive abilities and resulted in a linear, ARX-type, adaptive prediction model as the model of choice. Secondly, this pre-diction model was developed, tested and then shown to have a reasonable, 8-hour-ahead predictive accuracy (R2, coefficient of determination) of 30% (±6%) on future Pslag values. This inherent relationship exists because, at the precise moment of a Pslag prediction, the furnace already contains the metallurgical memory (input variables to the linear model) needed to ensure that some predictive possibilities will always exists - all as a result of the long residence times in the furnace. Residence time, however, is not a directly adjustable variable but rather a fully dependent variable and a function of an array of interconnected and interactive variables. In fact, this applies to virtually all input variables, reemphasising the importance of innate metallurgical memory. Thirdly, predictive control possibilities were explored by simulating the set-points of two fully independent variables used by operators to control the process: the ratio of fixed carbon-to-P2O5 and the ratio of silica gravel-to-pellets. This linear, predictive control model showed only a slight improvement with an 8-hour-ahead predictive accuracy of 35% (±7%). This highlights how ineffective current adjustments are in optimally steering the process and how difficult even incremental improvements in feed-forward and predictive control can be. Finally, it is shown that fundamental design-, sampling- and process restrictions currently associated with the process will always limit the predictive and especially control accuracy or meaningfulness of any dynamic model. These restrictions include the size of the furnace resulting in long residence times, 8-hours sampling intervals, an extremely complex and interactive process and a 16% spatial analyses variation on the Pslag values ? the very value that the model is to predict. The point is made that, given the current status quo, even the perfect dynamic prediction model can not improve on an 8-hour-ahead prediction of 30% (±6%). This barrier can only be pierced with e.g. tidier and more frequent sampling regimes and other upfront capital investments, a decision that becomes a cost accounting exercise and that can only be taken by the management structure. An investment demanding ever-increasing attention is CFD software and it?s potential to shed more light on the complex interactions within the furnace.

Jan 1, 2014

By S. H. Lau

Rapid 3D characterization of multiphase mineral particles in a variety of mineral processing applications is described, including: mineral liberation analysis, grain size, mineral exposure analysis, particle damage, and pore network structure for fluid flow simulation in heap leaching. While micro X-ray computed tomography systems (microCTs) have been used for many years, industrial adoption is limited due to a variety of reasons, including insufficient resolution, the general lack of imaging contrast to differentiate different mineral phases within a multiphase mineral particle and the lack of automated 3D mineral processing software. For example, resolution with industrial CTs and desktop microCT is of the order of tens of microns to a few microns at best, depending on specimen size and CT configuration. We describe a novel lab-based X-ray microscope, XRM, which overcomes these resolution and contrast limitations, notably as the industry is going towards finer grains and more complex ore bodies. Using lens-based optics and detectors (similar to its XRM counterpart in synchrotron beam lines), resolution of the lab based system is in the submicron range with contrast better than conventional microCTs. Hence, visualization, differentiation and segmentation of most mineral phases of interest to the industry are now feasible. Coupling these high resolution and high contrast tomography images with a suite of customized 3D segmentation algorithms and analysis software, applications in mineral liberation analysis for process control, particle damage assessment and other mineral processing applications can be achieved. This non invasive 3D technique which requires relatively little sample preparation is currently being considered for coal, industrial minerals, and base/precious metal ores, complementing existing microscopy techniques such as QEMSCAN and MLA for a variety of applications

Sep 1, 2012

The Sydvaranger magnetite mine was shut down in 1996 due to low iron ore prices. It was reopened in 2009. The flowsheet has remained more or less as in the old plant, based upon two grinding steps followed by magnetic separation. The Sydvaranger magnetite is free of harmful elements and should therefore be sold on the high quality market. This requires a concentrate containing less than 2 % SiO2. In the old plant, this grade was achieved by amine flotation. Amine was preferred as collector because it could be used in process water from the sea. The use of amine has been restricted by the Norwegian pollution authorities during the time the mine was shut down. Test work to replace cationic with anionic flotation is therefore done. Research on activation of quartz with Ca or Mg ions prior to anionic flotation was shown by basic research in the period from 1960 to 1980 to be effective under simplified laboratory conditions. This old research has now been followed up from a practical/empirical point of view. The basic work was mainly done on quartz and iron minerals only. In this case, an actual feed containing a number of minerals common in iron ores is used, in order to demonstrate that a commercial process is possible. Calcium activation is shown to work excellently but requires too high pH to be environmentally and economically attractive. Magnesium activation is a more difficult process, because the maximum concentration of MgOH+, which was shown to be the activator, is about 100 times lower than the alternative CaOH+. Flotation success depends partly upon the ore, some amphibole minerals are more difficult to float than pure quartz. Ordinary batch flotation test work is time consuming. A South African microflotation test cell has shown promise, because work can be focused upon flotation of the more critical coarser fractions of the Sydvaranger ore. Keywords: iron ore concentration, anionic flotation, mineral activation, microflotation, Sydvaranger

Sep 1, 2012

By J. J. Cai

The status of fossil fuel and secondary resource in metallurgy industry in China were reviewed, and conversion efficiency of fossil fuel, utilization technologies of secondary energy were studied. Fossil fuel, accounting for over 90% of energy structure in metallurgy industry, took in the highest flight in China, and a great deal of which was converted to secondary energy through the equipment of blast furnace and coke oven. These secondary energy which were mostly made of blast furnace gas(BFG), coke oven gas(COG) and Lindz Donawitz gas(LDG) occupied about 30% of total secondary energy. The way enhancing fossil fuel conversion efficiency, secondary resource recovery and the secondary energy such as BFG, COG, LDG utilization promoted to save fossil fuel was discussed in this paper. And efficient use of lower caloric value fuel was studied, such as preheating combustion air and fuel, generating electricity power etc. and regeneration purposes of high-caloric fuel was also researched, for producing hydrogen, methanol or direct reduction iron etc. The using model of secondary energy at iron and steel works was presented as fuel and chemical materials. The results suggest that utilization of these energy efficiently and reasonably could help to energy saving and environment protecting.

Jan 1, 2014

By T. Onnela

Metso Mining and Construction Technology is one of the world leading suppliers of equipment and knowhow for aggregate and mining industry. The processing capacity, ease of use, and reliability are featuring Metso?s state-of-the-art cone crushers. Crushing is a complicated process affected by numerous parameters. The optimized crusher kinematics is one of the key factors for high performance. To fine tune the crusher kinematics and crushing chambers one needs to know how different parameters affect. The main cone crusher parameters are head angle and diameter, gyration point, shaft speed, eccentricity, stroke length, and inclination and design of crushing cavity. Selecting the correct combination of these parameters is a multi task optimization challenge. In practical life there are more factors to achieve satisfactory performance, like crushing chamber wear and profile management keeping the performance constant over the whole wear life, control of crusher frame loads, ability to handle disturbances in feed material etc. The extensive research work has lead to a solution that enables the highest possible material density in the crushing chamber. This design provides maximum reduction of processed material and thus increased share of 0/10 mm product. High density in the cavity offers further benefits, such as high throughput capacity, less material contact with wear parts and even load on crusher frame and bearings. The challenge that an equipment supplier involved with high density crushing is how to design a robust cone crusher, which is able to cope with the high crushing forces due to high resistance from the crushed material against the gyration movement. Metso has launched a new series of cone crushers HP3, HP4 and HP5 that are all able to work in high density crushing applications The test results and evidence from over 300 installations clearly prove the effectiveness and importance of high density crushing. Keywords: cone crusher, crushing chamber, crusher kinematics

Sep 1, 2012

By S. Schade-Dannewitz

In terms of a sustainable waste management, high recycling rates and purities of the different collected waste components are very important. Especially the recycling of used packaging materials with valuable components like plastics, ferrous and non-ferrous metals and liquid cartons (light weight packaging) requires a complex technology. In plants to recycle those light weight packaging materials films cause problems and often manual sorting is necessary to remove them. The Nordhausen University of Applied Sciences together with the company Schulz & Berger from Altenburg tries to replace manual sorting with fully automated technologies. The objective is a technology that can enable a high recovery of recyclable film and satisfy the maximum purity requirements for the film fraction. For that purpose, a new machine called Low-pressure Separator was developed. The test materials used consist of separately collected recyclables from the yellow recycling bins or bags in Germany?s Dual System (Duales System Deutschland ? DSD), the recyclable waste collection system. First tests show that high purities of the film-fraction, for example the required 92% or higher, can be realized. Next to the film-purity, furthermore the mass yield and the recyclable yield are discussed because they play an important role to evaluate the efficiency of the recycling process. Further activities to improve and establish the developed technology are mentioned.

Sep 1, 2012

By I. Silin, H. Wotruba, J. Huben, A. Ognyanova

"With increasing shortage of raw materials, the beneficiation of ultra-fine ores will play a larger role in the near future. Many established process technologies do not yield satisfactory separation results for ultra-fine materials. Without selectivity, high-grade concentrates cannot be produced. The material at hand is a taconite which had to be ground to d(90) = 25 µm to guarantee liberation of the iron oxides. The comminution was done by High Pressure Grinding Roll (HPGR) and resulted in smooth surfaces and clear grain boundaries. This is an indication of selective grinding and mineral liberation. Further processing steps included selective desliming, magnetic separation as well as reverse flotation. INTRODUCTION During the last centuries, the processing of iron ores became increasingly important. The coarse-grained, so-called lump ores that are ready for direct usage in blast furnaces without further processing are becoming gradually less abundant. The processing of ultra-fine-grained ores, which in addition require a complex ore beneficiation due to the composition of the material, will progressively gain relevance with increasing resource shortages in the future (Arvidson, 2013). The term “ultra-fine” does not hold a precise definition in mineral processing. In this paper, “ultra-fine-grained” ores are defined by the required grind size for full liberation smaller than 20 µm. Many established mineral processing technologies do not yield satisfactory separation results for ultra-fine materials. Thus, they are limited in their application to produce high-grade concentrates suitable for sintering and pelletizing for direct reduction processes. The production of a high-grade iron concentrate (over 68% Fe) with low silica content (under 2.5% SiO2) is possible from both magnetite and hematite containing ore. In addition to the mineral processing technologies (magnetic and gravity separation, flotation), technologies for the liberation of fine-grained iron ores need to be developed and improved. In contrast to the conventional wet grinding circuit by means of tumbling mills, several future trends in dry and wet grinding and regrinding are already in use. These include technologies such as vibration mills (Palla®Mill), stirred media mills (Vertimill®), vertical roller mills (Loesche) and high-pressure grinding rolls (HPGR) (Jankovic, 2015). This study preliminary investigated the mineral processing of a low-grade, ultra-fine-grained, complex iron ore in a laboratory scale after dry grinding by HPGR to 90% < 25 µm without consideration of the grinding, milling, energy and classification cost."

Jan 1, 2018

By Auhin Kumar Maparu

Metal oxide nano-particles are used as additives in various industrial applications such as pigments in paints, additives in adhesives, plastics, cosmetics, functional coatings, personal care and health care products, for antibacterial applications and more recently in heat transfer applications. In most of these applications, usually dry nano-particle powders are added to the formulations. However, often it becomes difficult to achieve a uniform and stable dispersion of nano-particles in the given formulation. Thus, a scalable and commercially viable process for in-situ production of stable nano-particles suspensions in the desired medium will certainly be more beneficial. Ultra-fine grinding in high energy mills (planetary mill, stirred media mill) has been used to produce fine particles (sub-micron size). However, in order to obtain nano-particles (particle size <100 nm), the choice of appropriate dispersant and solvent is crucial, since freshly generated nano-particles tend to agglomerate due to their high surface reactivity. We have employed molecular modeling (MM) based selection methodology to arrive at the most suitable solvent?dispersant combination for preparation of the given metal oxide nano-particles. Molecular modeling techniques are employed to compute the interaction energy of a given dispersant with surface of the metal oxide particles in the presence of the dispersion medium. The interaction energy helps identify a dispersant that has strong affinity for the metal oxide surfaces allowing for strong dispersant adsorption and hence a more stable dispersion. For example, in case of aqueous nano-titania suspensions, poly-carboxylic acids like citric acid provide better dispersion than mono-carboxylic acids like lauric acid, mysristic acid, and oleic acid. While in non-aqueous medium like ethanol, p-hydroxybenzoic acid and glycerol trioleate perform better. The suspension is produced in-situ by ultra-fine grinding of the metal oxide powder in the presence of the selected dispersant and dispersion medium in a planetary ball mill. By careful selection of various process parameters such as percent loading of powder, jar filling, grinding media to powder ratio, time and amount of dispersant addition, both aqueous and non-aqueous suspensions of metal oxide nano-particles with average particle size less than 100 nm are produced. The aqueous suspensions of alumina and titania produced in presence of citric acid dispersant exhibit median particle size of 83 and 62 nm, respectively. These suspensions have been found to be stable for nearly 3 years. The nano-particles thus produced are used in the preparation of nano-fluids?advance heat transfer liquids, which show enhanced heat transfer capabilities and unaltered stability and performance even after several heating-cooling cycles. The nano-particles are also utilized for making efficient photo catalysts, which are found to be highly effective under sunlight. Keywords: stability, nano-fluid, milling, grinding, thermal conductivity, nanocoolant, photocatalyst

Sep 1, 2012

By V. E. Dementyev

This paper presents a brief overview of some IRGIREDMET advances in gold hydrometallurgy. Original impulse-percolation technology and equipment for intensive cyanidation of gravity concentrates have been developed and introduced into industrial practice by IRGIREDMET since 1980s (RF Patents N1593250). The process is based on leaching using special hydrodynamic and reagent conditions providing high dissolution rate for coarse gold particles. Gold and silver are precipitated from pregnant solution by cementation or electrowinning. There was also proposed an im-proved cementation method using zinc in a contact with electrically conductive material. The units including closed water recirculation, tails detoxification and semi-dry tails IRGIREDMET is well experienced in gold adsorption technology using ion exchange resins and activated carbons. The comparison of CIL and RIL processes were done for a number of gold mines, for example for Sukhoi Log gold deposit. The properties of prospective foreign and domestic ad-sorbents including strong-base, bi-functional and weak-base resins as well as activated carbons were studied. The Institute has developed some adsorption/elution technologies and equipment, such as a two stage RIP adsorption technology for gold/silver ores, an improved technology for gold elution from loaded resin and carbon, electrowinning cells for gold recovery from RIP and CIP eluates etc. Large scale ?Resin In Pulp? tests using weak-base resin were finalized and process design criteria were developed. Gold plant design is on progress at the moment. Improved technology for carbonaceous (preg-robbing) gold ores was developed. It was tested for some gold deposits including Sukhoi Log. It allows to overcome preg-robbing activities of ores treated and to improve dramatically performance of cyanidation and adsorption circuits. The studies on refractory gold ore treatment including bio-oxidation, pressure oxidation, roasting and ultra-fine grinding were conducted. Heap leach technology was tested and introduced by Irgiredmet for a number of Russian mines. Zinc cementation, activated carbon and ion-exchange resin adsorption were used for gold recovery from pregnant heap leach solutions. The options including combined technology ?Heap leach/ RIL or CIP? for clay ores were also developed and tested. The plant using developed technology is at construction stage now. The study on In-Situ gold leaching was conducted. The comparison of different gold lixiviants for this purpose was carried out. Gold recovery from pregnant leach solution by activated carbon and anionite including gold elution from loaded adsorbents etc. was also studied. In 2000 the In-Situ leaching technology was commissioned at Maminskoye gold deposit (Ural). The technologies for treatment of complex ores and by-products were proposed. For example, the technology of gold, silver, copper and zinc recovery from calcines after sulphuric acid production was developed.

Jan 1, 2014

By F. Ngoroma

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is, to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers, that would provide more independent control of bubble size and froth stability. This study demonstrates, through the use of batch flotation tests, how blending low molecular weight alcohols with commercially available frothers impact the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.

Sep 1, 2012

By Xiaoxu Sun, Jianchao Yao, Jiancheng He, Shijie Lu, Hongxi Zhou

"The ball mill performance relies on impact grinding, but it has disadvantage of the lower efficiency when the ore is finer; while tower mill relies on friction shear affection with high energy efficiency, which is considered to be one of the most potential fine grinding equipment all over the world. Generated by the agitator device, the internal media movement is complex because of comprehensive interaction of screw mechanism, cylinder structure and adjacent media, which is the key factor of grinding process. But the kinematics parameter ,such as speed, acceleration, stress and so on, of media motion cannot be obtained through traditional laboratory test method, which restricts deeply research on finer grinding mechanism seriously. In order to solve this problem, characteristics of media motion in tower mill is studied via the discrete element method. Coefficient of restitution, coefficient of static friction and coefficient of rolling friction are the key parameters affecting the media movement, which were calibrated by stacking angle test firstly. A 3kW tower mill is established as the model for simulation. At last one appropriate simulation strategy is selected to increase simulation accuracy. The characteristic of media motion is obtained based on the computer simulation analysis: macroscopically, the media in tower mill is a dynamic equilibrium state generally accompanied by spiral up and down movement all the time. And it has been found that the maximum lifting height is proportional to the rotation speed of agitator shaft. The velocity of media at the edge of screw stirrer is biggest, while the velocity of media near the cylinder wall is smaller, so the grinding performance between the two ring areas is the best. The rotational speed of agitator shaft and media filling ratio are the two most important operating parameters in tower mill. The impact curve of two main operating parameters on the grinding intensity and energy efficiency are obtained. All these can provide theoretical basis and technical support for operating parameters setting of industrial tower mill."

Jan 1, 2018

By T. Wallmach, S. B. Blancher, A. Delaporte, P. Goncalves

"Fe-Ti oxides concentrates produced from heavy mineral sand deposits are widely used for the production of titanium dioxide pigments that are critical components of white paint, plastics and paper. According to mining industry, the Fe-Ti concentrates mostly consists of three phases: ilmenite, leucoxene and rutile. However, a few mineralogical studies have shown that the variety of Fe-Ti oxides found in sand deposits is far more complex, mostly due to alteration processes. The aim of this contribution is to characterize in detail by means of Qemscan analyses the mineralogy of the three main concentrates (ilmenite, leucoxene and rutile) produced by the Grande Côte Operation (GCO) mineralurgical plant in Senegal. The ultimate goal is to characterize the different products and textures formed during the natural ilmenite alteration processes, to localize the phases carrying the main impurities (Cr and P), and finally to determine the physical properties of each mineral component to improve metal recoveries. Along alteration processes, Ti content increase. Ilmenite (FeTiO3) is progressively transformed into pseudorutile (Fe2Ti3O9) particles which could also be altered and transformed into hydroxylian pseudorutile [FeTi6O12(OH)3.3H2O] or complex blends of anatase microcrystals (TiO2). These transformations are accompanied by significant changes in particle textures. Microporosity and fractures appear and the impurity content also increases. Anatase rich microcrystal assemblages, so far described as Leucoxene, could be identified to consist of grains with higher porosities, water contents and higher intrapore impurities. These particles are the main carriers of chromium and phosphorus. The observed mineral transition textures have a significant impact on the ore dressing processes. During these transformations, the physical properties of these phases change, the magnetic susceptibility as well as densities decreases, due to the increase in porosity. The separation of particles, especially those with high porosity will help improving the GCO mineralurgical plant performance and to reduce the impurity contents in finals products."

Jan 1, 2018

By Patricio Berrios, David Barriga, Peter Amelunxen, Gerson Sandoval, Roger Amelunxen

Laboratory test equipment and methods have undergone relatively little change since their introduction in the 1950’s. The Denver sub-A cell is still by far the most commonly used laboratory batch cell, but bottom-driven and instrumented cells are beginning to appear. Test procedures have also changed little over the past 60 years, and most engineers continue to rely on empirical models for predicted plant scale performance from laboratory scale tests. This approach is problematic, because changes in the froth phase characteristics in the lab hamper the reliability and reproducibility of the empirical extrapolation to plant scale. In a previous work, the authors reported on the impact of froth recovery at the laboratory cell, showing that variability in the froth recovery can lead to significant error in the modeled kinetic rate constant unless it is properly accounted for in the scale-up model. In this work, we review the role of hydraulic entrainment in the lab cell, and how variability in particle specific gravity, shape factor, and froth residence time can impact the entrainment recovery.

Jan 1, 2014