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By Aubrey Mainza, Malcolm S. Powell

"A hydrocyclone with two vortex finders, named the three-product cyclone (3PC), has been successfully tested in the Platinum industry for dealing with the dense Chromite found in UG2 ores. This dense component preferentially reports to the cyclone underflow, resulting in an over-ground fine Chromite component in the final product. The dense media effect caused by a high concentration of this in the cyclone feed produces a coarsening of the cyclone overflow, which results in loss of recovery through over-size silica in the PGM carrying component material in the float feed. The fine barren particles of Chromite that report to the overflow are recovered through entrainment in the flotation process, resulting in detrimental contamination of the slag produced from the concentrate.Data from many industrial scale tests of the 3PC have shown that three distinct products are obtained when the inner vortex finder length (LIVF) is extended to the region either above (normal classification) or below (reverse classification) the transition zone (a region were the inner and outer overflow streams are identical). Due to wear problems arising from extending the IVF deep into the cone of the cyclone, it is advantageous to use the shorter IVF. Only the normal classification results are reported here, but similar outcomes (to opposite overflow streams) were obtained for the reverse classification. The results showed notable differences in the percentage split of the plus 100µm material in the product streams, confirming that three distinct products are discharged from the 3PC. About 12% of the plus 100µm material in the feed reports to the middlings stream, 1% reports to the final product, and the remainder to the cyclone underflow.Results of silica and chrome splits to the three distinct products namely, the inner overflow (INO), the outer overflow (OUO) and the underflow (U/F) are given in Table 1. These show that the 3PC can be used to recover coarse silica through screening the middlings product - which has a high silica content. When the vortex finder ratios (ratio’s of cross-sectional areas) are carefully selected, the split of plus 100µm silica to the middlings product ranged from 2.9 to 9.6%. Large amounts of oversize silica and chrome report to cyclone underflow, explaining their high percentages in the underflow stream."

Jan 1, 2003

Separation performance of a Floatex Density Separator (FDS) has been studied both experimentally and theoretically. Experimental results reveal that at a lower bed pressure the FDS acts like a classifier. Higher bed pressure is required to attain the concentration effect as proper development of suspension density occurs under these conditions. It is seen that the size or density alone is not able to describe the partition fully. The terminal settling velocity, which includes both the size as well as the density of the particle can be a useful descriptor of separation in a FDS. While a narrowly distributed feed offers better performance of a FDS, a wide size distribution of feed results in large scatter in the terminal settling velocity distribution and renders the separation difficult. The closely sized feed enhances the density effect in concentration. A higher teeter water flow rate also helps in carrying larger-lighter particles to the overflow by increasing the cut off terminal settling velocity as it increases the net upward force. A detailed description of separation performance in a Floatex Density Separator has also been established from theoretical considerations. Separation performance of the separator is described using a simple slip velocity model. The model has been validated com-paring the predicted FDS performance results with those experimentally measured under widely different operating conditions.

Jan 1, 2014

By Z. Cheng, Y. Han

"For non-sulphide minerals such as oxidized minerals, fluoride minerals, and oxysalt minerals, there are generality in the molecular structure of their floating collectors, and similarity in crystal structure of the minerals. In the paper, adsorbing mechanism of these collectors on the surface of these mineral particles in different pH pulp was investigated by means of Pauling's rules & valence bond theory, Valence-shell electron pair repulsion theory (VSEPR) theory, Crystal and ligand field theory, and quantum chemistry simulation by DMol3 and CASTEP modules of Material Studio software. Besides, the role and status of hydrogen bond in the floating adsorption mechanism were studied emphatically, and the confirmation and characterization of hydrogen bond were explored also based on the test results. What is more, the conclusion “the effect of hydrogen bond can not be overlooked in adsorbing mechanism of flotation collectors on the minerals” and a new viewpoint of multi-polarity collaboration and hydrogen bond coupling were summarized eventually based on analysis of the measurements. Finally, a novel collector 2-Amino-3-Methyl Heptyloxy-Propylamine (AMHP) was developed based on the new viewpoint of molecular structure design, and its collecting performance was exhibited.INTRODUCTIONWhen it comes to the recovery of flotation, it is necessary for researchers to investigate the flotation mechanism of collectors. In traditional theory, when collectors were used to collect minerals, the attractions between collectors and minerals were divided into chemical, electrostatic and physical attractions (Wills, B.A., 2006). Especially, because of the reaction between sulphide minerals and sulphydryl collectors is complex and various mechanism has been proposed (Yoon and Basilio, 1993), when collectors were used to collect non-sulfide minerals, it can be classified into oxyhydryl anionic collectors and cationic collectors. In traditional theory, the adsorption of oxyhydryl anionic collectors were due to water-repulsion, and the adsorption of cationic collectors were due to electrostatic attraction between the polar head of the collector and the charged electrical double layer on the mineral surface (Wills, B.A., 2006)."

Jan 1, 2018

By A. P. Wang

Porous carbon adsorbents derived from inorganic materials templates such as zeolite and mesoporous silicate attracted considerable attention in the last decade and got great progress in re-cent years. However, so far almost all of templates used in the process were artificial porous materials; the porous carbons prepared by this method are very costly, which restricts the synthesis and application of templated porous carbons. In order to reduce the cost of templated porous carbons, natural inorganic porous minerals have been taken into consideration, which maybe possible and promising templates to prepare carbon adsorbents. In this work, we describe template process using tubular halloysite, rich mesoporous zeolite and low bulk density diatomite, as exemplars of the categories of inorganic porous templates which we have studied and discussed the effects of different templating structure on the resultant carbons. Two main carbon precursors, sucrose and furfuryl alcohol, were used respectively. The morphology of minerals and corresponding templated carbons were characterized using electron microscopy. The pore structures of minerals and templated carbons were characterised with nitrogen adsorption. The results showed that the morphology and pore structure of porous carbons are in good pertinence to those of corresponding templates. The morphology and pore structure of templated carbons could reflect those of corresponding templates at nanometer level. The templated carbons with high specific surface areas and rich mesopores can be prepared by using these three kinds of natural porous minerals as templates. The higher the surface area and pore volume of the minerals, the higher those of the corresponding carbons. The template carbons from halloysite possessed higher pore volume and mesoporosities. Based on the large mounts of experiment results, a model for the mechanism of resultant nanopores formation has been proposed. The nanopores of templated carbons are mainly composed of three kinds of pores: templated pores formed by removing mineral, hereditary pores formed by inheriting the pores of templates and nanopores formed during carbonization. These three kinds of pores have a close relationship with corresponding template.

Jan 1, 2014

By Xinyang Xu, Chen Zhang, Lixia Li, Zhitao Yuan

"Density functional theory was employed to clarify the mechanisms of the activation of a quartz surface and its collection by the flotation method at the molecular level. The calculation results indicated that hydrogen bonds on the quartz surface (1 0 1) existed in pairs while in contact with water. The simulation was carried out to investigate the different effects of Ca2+ and Ca(OH)+ on a quartz surface with hydrogen bonds, and the results suggested that Ca(OH)+ most likely adsorbed onto and activated the quartz surface. Mulliken population analysis of the external oxygen atom of the quartz surface, calcium atom of Ca(OH)+, and the oxygen atom of oleate showed that there were electron transfer and the formation of a chemical bond between Ca1-O1 and Ca1-O3, which were indicative of strong interactions between the three atoms. In addition, the –OH of the Ca(OH)+ contributed to the activation, which suggested that the Ca(OH)+ group acted as a bridge between the surfaces of oleate and quartz.INTRODUCTIONFlotation is an effective separation method in mineral processing that takes advantage of the physicochemical differences between minerals and gangue, and the properties of the mineral surfaces play a key role in this process (Liu et al. 2016, Qin et al. 2017). In the reverse flotation process of iron ore, gangues are captured by cationic or anionic collectors and floated with air-bubbles as tailings, and the pre-depressed iron oxide minerals are left at the bottom as concentrates (Lima et al. 2013, Yianatos et al. 2015, Zhu et al. 2015). Quartz (SiO2) is one of the major gangues of hematite ores and cannot be easily removed. It is a naturally hydrophilic mineral, in which silicon is the cation in its crystal structure and has very limited solubility. Therefore, quartz must be activated, usually by metal ions, for its effective rejection as a float-product by reverse flotation (AIME. et al. 1976)."

Jan 1, 2018

The value creation with kaolin clays depends on removing the colored impurities which manifests in to higher brightnessone of the most sought after properties on applications such as paper coating, paint and others. The processes for removing impurities include magnetic separation, froth flotation and selective flocculation. While the flotation and selective flocculation processes exploit the physico-chemical differences between the surface properties, the magnetic separation uses the bulk magnetic susceptibility differences between the diamagnetic clay and ferro- and para-magnetic nature of the impurities. The major advantage with magnetic separation remains high yield and no or low reagent usage. However, the magnetic separation technology suffers from low separation efficacy when finer colored impurities (<1 µm) are encountered in the feed. Use of stronger magnetic intensities during magnetic separation showed limited success; nonetheless the adverse effect due to finer size range remains a dominant effect even at 5 Tesla magnetic field. Furthermore, the presence of diamagnetic colored impurities irrespective of their sizes can not be removed. Cytec Industries has recently developed a ?bolt-on? chemical enhancement technology for magnetic separation that essentially embraces the best product performance attributes of flotation and selective flocculation while keeping the chemical usage to a minimum level and using the readily available magnetic separation equipment. The paper will outline the technology and illustrate optimization work at pilot plant magnet on a wide variety of crude accommodating the process needs and plant limitations. The major advantages of chemical enhancement technology to magnetic separation include: 1) simple extension to existing magnetic separation technology, 2) ability to produce comparable product in quality with cost effectiveness compared to flotation and selective flocculation, 3) removal of impurity minerals over wide size range, 4) removing non-magnetic impurities, 5) providing robust process with high process yield and 6) operation-friendly nature. Furthermore, chemical enhancement technology for magnetic separation has also emerged as a platform for re-moving impurities at low levels in other mineral systems as well.

Jan 1, 2014

By Charlene Gokhale

Geopolymerisation has emerged during the last few years as an industrial and ecological approach to construction and waste management. By utilizing waste materials and their reactive properties, it is now possible to create geopolymers systems that not only mechanically durable enough to be used as construction materials but are also potential stable immobilisation systems for toxic waste. Previous studies by Van Jaarsveld et al. (1997) and Van Jaarsveld et al. (1998) have reported on the numerous applications of geopolymers in the immobilisation of toxic metals. Research into the possible utilisation of geopolymers as an encapsulation media for organic waste has however been rare. This paper therefore provides an insight into the possible utilisation of geopolymers as a binder for hazardous organic materials.

Jan 1, 2003

By J. Menuge, G. Barker

"Liberation (QEM-SCAN) and surface chemical (time of flight secondary ion mass spectrometry -ToF-SIMS) analyses have been undertaken on plant Pb circuit flotation samples with the aim of defining the factors resulting in sub-optimal recovery. Lead flotation circuit feed, cleaner concentrate and tails samples were examined on a size-by-size basis using QEM-SCAN. Sulfide minerals accounted for approximately one third of the flotation feed with pyrite making up 16 wt.%, followed by sphalerite (13 wt.%) and galena (3 wt.%). Non-sulfide gangue minerals comprised calcium carbonates calcite (26 wt.%), dolomite (14 wt.%) with quartz, feldspars and barite all contributing > 5 wt.%. QEM-SCAN analysis indicated that liberation was not the primary cause of the poor flotation response. Principal component analysis was applied to the ToF-SIMS data derived from five samples (as for QEM-SCAN plus rougher concentrate and tails) to enable identification of correlated surface chemical components. Although a significant range of correlations were observed we focus here on those that show a discernible pattern throughout the float circuit. It was found that for the flotation feed the surface of galena were largely obscured but where Pb was observed there was a strong correlation to surface Fe. For the rougher and cleaner concentrates the galena surfaces were relatively clean with no correlation to Fe for the rougher concentrate and minor correlation in the cleaner concentrate. However, in the rougher and cleaner tails the clear correlation of galena with Fe was again apparent. These results suggest, in combination with prior studies of pyrite morphology, that the principal factor effecting grade is the rapid oxidation of the framboidal pyrite resulting in the contamination of the galena surface with a high loading of hydrophilic oxidised Fe species, thus depressing flotation."

Jan 1, 2014

By l. Bokányi

The Tóth adsorption isotherm-model was derived and has been widely used for the inhomogeneous solid surfaces. The three-parameter isotherm incorporates the effect of the interaction between the adsorbed substances as well. All classic isotherms can be clearly derived from this one. Bio sorption is the sequestering of dissolved components, i.e. metals from aqueous environment by living or dead biomass. The mechanism of the bio sorption is rather complex and predominantly refers to the affinity of the chemical functional groups: acetoamido groups of chitin, structural polysaccharides, amino and phosphate groups in nucleic acids, amino, amido sulfhydryl and carboxyl groups in proteins, hydroxyls in polysaccharides, sulphates, etc. towards the soluted substances, i.e. heavy metal ions. The physisorption, as well as the micro precipitation also play a role in the bio sorption mechanism. The description of such a complex process can be done by a model reflecting this complexity. According to our experimental results obtained using algae and immobilised algae for the sorption of heavy metal cations, the most appropriate model for such a description is the Tóth-isotherm, the parameters of which can be interpreted. Flotation process is also a very complex one, the overall result of which depends on the partial results of many micro processes and parameters. The particle interaction which very often takes place in the flotation systems makes the phenomenon even more complex. The flotation kinetic model with particle interaction was already introduced by author in 1994 and further developed in 2000. In this paper based on the experimental results obtained with metallic particles in case of recycling flotation the applicability of the Tóth-equation as an alternative flotation kinetic model for the systems with particle interaction is proved. The applicability of Tóth-model in mineral processing demonstrates again its universal character and the great talent of the late József Tóth, great Hungarian chemist. Keywords : Toth isotherm, biosorption, Langmuir, Freundlich

Sep 1, 2012

With shortage of sulfide nickel ores, laterite ore was paid more attention by scientists. Because its grade is commonly lower than sulfide nickel ores, laterite ore can not be utilized effectively be-coming the bottleneck of study. Leaching laterite ores from Yuanjing, Yunnan province, organic ac-ids show better selective than sulfide acid in nickel and cobalt recovery. Organic acid has low de-pendent on pH, keeping leaching capability even higher than 3. On the other side, when pH up to 2, sulfide acid can not leach laterite ores any more. After four kinds of organic acid leaching laterite ores, besides citrate, malate and succinate have good leaching and effectively selective capability. Especially, succinate has the best selective leaching capability of nickel and cobalt in four kinds of organic acids for latter anion purification and separation. Isolated from waste water with sugar, Aspergillus niger (zs1) has great capability to produce organic acids and vigorous growth. Laterite ores have been respectively processed by direct-leaching and indirect-leaching. Indirect-leaching gives a better result than direct-leaching. Extraction of nick-el by indirect-leaching reaches 44.3%, far more than that of direct-leaching. Moreover extraction of nickel at pulp density of 5% is higher than that at pulp density of 10%, reaching 63% in 11 days and extraction of cobalt also is 48.1% in the same period. Compared with nickel and cobalt, iron gives low extraction in solution, containing organic acids produced by Aspergillus niger .

Jan 1, 2014

By H. Pearce, A. E. Lewis, A. Ochieng

Hydrodynamics and mixing are fundamental to the operation of mineral process systems such as flotation cells and metal precipitation reactors. The computational fluid dynamics (CFD) technique has been employed in the present work to study the hydrodynamics in a mixing vessel stirred with either a Rushton turbine or a pitched blade impeller. The multiple frame of reference (MFR) approach has been used to model both impellers. A draft tube was used only in the Rushton turbine stirred vessel. The flow profiles for the pitched blade impeller have been studied in three regions; below the impeller tip, at the middle of the tank, and near the liquid surface. The simulation results were compared with literature data obtained using a laser Doppler velocimetry in the three regions of the vessel, and it was found that the model predictions were better in the impeller region. There was a poor prediction of the experimental results in the region closer to the liquid surface; however, this was improved when the turbulence parameter (C2) in the k-e model was set to a higher value. The value of the impeller clearance at which the Rushton turbine generates an axial impeller type flow has been determined and it has been shown that, at this clearance, a draft tube can be used to enhance axial flow in a Rushton turbine stirred reactor.

Jan 1, 2003

By Cheng Gan, Gui Xiahui, Li Shulei, Cao Yijun, Liu Jiongtian, Wu Lun

Flotation rate constant is an essential parameter in the flotation process. The fine coal sample utilized in this investigation is anthracite from the Shenhuo mine in eastern China. Fine coal flotation rate tests were conducted to compare the flotation rate constant at constant power input with that at gradually increasing power input. Results indicate that the flotation rate constant decreases with the flotation process and increases as the flotation energy is increased. In addition, the flotation rate constant is close to the maximum value. The increasing trend of the flotation rate constant gradually slows down as the flotation energy input increases.

Jan 1, 2014

By J. Ma

Vanadium ore is widely distributed in black rock series (Fan, Zhang and Ye, 2004) in many provinces of China, which accounts for 87% (Zuo, Peng and Dugang, 2001) of vanadium reserves in China. In Cambrian black rock series in south Qinling Mountain, there are large or medium-sized sedimentary deposits such as Zhongcun vanadium deposit, Yinhua vanadium deposit, Qianjiaping vanadium deposit, Xiajiadian gold-vanadium deposit and Lengshuigou vanadium deposit. The vanadium is distributed in other minerals mainly in the form of isomorphic replacement. These types of ore are characterized by no independent vanadium mineral, low grade and vast reserves. Now in China the vanadium extraction technology is backward with low utilization rate of resources. The difficulties of vanadium extraction from black rock series are that the enrichment by means of mechanical beneficiation is difficult; the cost of direct chemical extraction is high and the emission of waste gas from pyrogenic process does not conform to environmental protection standard. Therefore the study of vanadium occurrence, the improvement & optimization of vanadium extraction technology and the realization of pollution-free and low-cost extraction of vanadium from black rock series are of great and realistic importance for environment-friendly exploitation & utilization of vanadium resource in China. The study is based on carbon content in ore of Cambrian black rock series in south Qinling Mountain. Two kinds of ore are selected. Vanadium ore with low carbon content (TC<1%) is taken as Sample 1 while vanadium ore with high carbon content (TC>10%) as Sample 2. Based on analysis of ore?s lithologic features and vanadium?s occurrence, a vanadium extraction technological process characterized by selective grinding, low cost and no pollution is proposed.

Jan 1, 2014

By P. Fawell, C. Castillo, C. Ihle

"The need to reduce fresh water consumption has pushed many Chilean mining companies to utilize seawater obtained from distant locations. At the same time, increasing amounts of fine particles in copper tailings raise new operational challenges, in particular, the thickening and transport of tailings featuring significant fine fractions, which are predominantly clays. In the present paper, we study the role of salinity – using seawater and NaCl – on the flocculation efficiency of copper sulphide tailings to which kaolinite was added. To mimic the water recovery stage in thickeners, flocculation has been induced in jar tests and the corresponding aggregate size distribution has been estimated from chord length distribution data obtained using a focused beam reflectance measurement (FBRM) probe, at various mean turbulence intensities. Results show that for constant flocculant dosing, a measurable influence of the salt on the resulting aggregation exists. For each case, resulting optimal turbulence levels are also reported, a particularly interesting feature when comparing flocculation efficiency of the coarse and fine fraction. INTRODUCTION The concentration of copper minerals through comminution and flotation is intensive in the use of fresh water. The need to reduce the consumption of fresh water and the environmental standards associated with increasingly demanding mining operations have driven improvements in the techniques of recovering water from tailings. The challenges are even greater when required to treat minerals with high clay contents. In Chile, kaolinite is one of the most important clays to consider due to its abundance in the tailings from many operations. The most common and highest throughput unit operation in the mining industry for the recovery of water from tailings is gravity thickening, with sedimentation of fine particles assisted by flocculation. Flocculation is the process of forming aggregates by contacting the suspended particles with a flocculant. The flocculant is typically a water-soluble synthetic long-chain polymer, where copolymers of acrylamide and sodium acrylate are the most common types used in the Chilean mining industry. The aggregation mechanism includes the following key steps: (1) flocculant distribution through the suspended particles, (2) flocculant adsorption onto particle surfaces, and (3) collisions between particles leading to polymer bridging to form aggregates, but concurrently (4) breakage of aggregates becomes a factor under prolonged shear (Gregory, 1988)."

Jan 1, 2018

By Naoki Hiroyoshi, Hajime Miki, Tsuyoshi Hirajima, Masami Tsunekawa

Acidic solutions for chalcopyrite leaching contain cupric, ferrous and ferric ions, and the oxidizing power of the solutions is indicated by a redox potential, determined by the concentration ratio of ferric to ferrous ions. This paper reviews our previous studies on the redox potential dependence of chalcopyrite leaching in sulfuric acid solutions. Leaching and anodic-polarization experiments showed that coexistence of cupric and ferrous ions activate anodic dissolution of chalcopyrite, causing faster copper extraction at the potentials below a certain value (critical potential). The analysis of the AC impedance spectra for chalcopyrite electrode indicated that a high-resistance passive layer grows on the chalcopyrite surface without cupric and/or ferrous ions, and that coexistence of these ions causes a formation of another product layer and inhibits the passive layer growth at low potentials. These results are explained by a reaction model assuming the formation of intermediate Cu2S due to chalcopyrite reduction and the subsequent oxidation of the Cu2S. The critical potential corresponds to the redox potential of the Cu2S formation and the predicted values matched with the experimental results. Catalytic effect of silver ions on chalcopyrite leaching was also discussed based on experimental results and the above model.

Jan 1, 2003

By Y. S. Song

Flotation separation of galena, sphalerite with pyrrhotite in ethanoic acid + sodium acetate sys-tem was studied in this paper. The flotation tests show that galena and sphalerite can float but pyr-rhotite can hardly float in the pH range of 3.6 to 5.6 in ethanoic acid + sodium acetate system. The flotation tests also show that galena can be separated efficiently from pyrrhotite and sphalerite can be separated on the whole from pyrrhotite, but the separation efficiency of the former is much better than the latter. The flotation results have been investigated by ultraviolet spectrum and XPS analysis, and explained by theory of hard and soft acid and base (HSAB), hydrogen bond and galvanic coupling.

Jan 1, 2014

By P. Radziszewski

In comminution research, ore breakage and wear are usually studied independently of one another. Much of this is due to the fact that wear is usually a slow process compared to ore kage. However, the abrasion wheel test used to determine the abrasive wear contribution to total steel media wear provides the opportunity to study not only abrasive wear and friction but also ore breakage. In this paper, we will explore the use of the abrasion wheel wear test device to study abrasive wear, friction and ore breakage using standard Ottawa foundry sand. We will look into the feasibility of applying the work index as well as t10methodologies to this test set-up. We will also look at how the work index results evolve with abrasive wear and friction. We will then discuss the merits of pursuing the use of this abrasion wheel test for not only wear characterization but also breakage characterization.

Jan 1, 2014

By Joseph Kelly, Christopher Kelsey

This revolutionary super-fine crusher has the unique capacity to generate fine and ultra-fine products from single stage reductions of coarse or fine mineral feeds. The crusher consists of a rotating compression chamber and an internal gyrating mandrel. The axis of rotation of the shell is displaced relative to the axis of the vertically mounted mandrel. The inner surface of the compression chamber is machined as double cone frustums at an angle equal to the displacement angle. Crusher feed is accelerated into a compacted particle bed, which lines the inside of the compression chamber. The depth of the compacted bed progressively increases until the mandrel is engaged. The mandrel is then free to rotate with the compression chamber. Continued feeding increases power draw and triggers the counter rotating mandrel gyration drive. The gyrating mandrel delivers multiple compressions at high pressure to the rotating particle bed. High concentrations of energy are harnessed within a small active volume over short retention times. The combination of extraordinarily high power intensity and extreme compressive force results in primary compressive fracture and induced secondary tensile failure. The axially displaced rotation of the compression chamber effectively distributes the breakage forces throughout the particle bed. This paper covers open circuit, pilot trials on magnetite, perlite, garnet, marble and a copper/pyrite concentrate. Particular emphasis is placed on the extraordinary results achieved with trials on zircon and highly refractory fly ash. The extreme duties were deliberately chosen to demonstrate the crusher’s application scope and potential to impact capital operating and maintenance costs as the technology matures. Super-fine crushing, once considered impracticable has the potential to offer compelling options for the generation of ultra-fine products.

Jan 1, 2014

By A. K. Majumder

In an effort to test the extent to which fundamental fluid mechanics can provide a prediction of particle separation, a study on a simple parallel-sided sluice has been carried out using glass bead and ilmenite mixtures at various particle concentrations and flow rates. Great care was taken to devise a flow splitter at the end of the sluice that permitted accurate measurement of the fluid flow profile and collection of slurry samples, allowing evaluation of the particle species concentration profiles. The actual particle separation taking place was compared to predictions made by first describing the fluid flow by a modified ?law of the wall? model. The hydrostatic pressure variation in the flow was taken into account and the eddy viscosity was calculated from a mixing length expression incorporating Van Driest?s damping function. Using an average density and viscosity provides an explicit expression for the velocity gradient that can be numerically integrated for the flow profile. The particle concentration distributions were then modelled with Hunt?s sediment transport model assuming the particle eddy diffusion coefficient to be the same as that for the water. Hindered settling velocities of the particles were calculated using Brauer and Thiele?s formula, which takes the particle size and density distributions and solids volumetric concentration into account. The resulting predictions of particle separation are shown to be a strong function of the settling velocities of the particles used. Keywords: flowing film concentrators, fluid velocity

Sep 1, 2012

By John Starkey

"The development of the Minnovex SAG Power Index (SPI) Test in Canada has created a new and accurate way to measure ore hardness in a SAG environment. Coupled with the standard Bond Ball Mill Work Index Test it is now possible to determine from these two relatively inexpensive laboratory tests, the amount of energy required to grind an ore from the primary crushed size to the desired liberation size. By testing multiple samples to discover where the hard and soft ore zones are located, the representative hardness distribution for the ore body can be determined and grinding equipment selected that is capable to meet production targets for all mining areas of the deposit.In the last century, it was deemed prudent to select up to 50-tonne samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5-tonne sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50-tonne sample is no longer required for SAG design because it is better to measure the representative hardness distribution of the ore body than the hardness of a “chosen” representative sample. This is demonstrated to be true by the fact that the lower horizons of an ore zone cannot initially be accessed to recover 150mm pieces, and the bulk samples taken, rarely represent the desired design hardness of the ore. Median hardness will not yield a good result in most cases and a clear understanding of the location and extent of the hardest zones is imperative to achieve a truly successful grinding circuit design.This paper discusses two plants (Kubaka and Agnico Eagle) that have been designed using SPI and Bond with no pilot plant test backup. Both have been very successful in that they can grind design tonnage on the hardest ores in the mine. This guarantees that the mine’s profitability is protected in any mining sequence. It also allows the extra power to be converted to higher throughput on softer ores if additional cash flow is needed. The advantages from the owner’s point of view are dramatic. This procedure will be attractive as well when considering the costs for test work, and the samples for testing. Existing diamond drill core is normally used and this allows the inclusion of data from the deepest regions of the mine. In addition, it is also clear that the decision to use a crusher can now be made at the design stage of a project based on measured parameters and the estimated capital costs of alternative designs."

Jan 1, 2003