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By V. E. Vigdergauz

Possibilities of the analysis of potential energy of bubble-particle interaction on the basis of extended DLVO theory are discussed. Interaction energies of mineral silica, coal and pyrite particles with contact angles from 20 to 100 degrees and air bubbles in neutral and alkaline solutions are analyzed. It is shown that for hydrophilic silica, the formation of particle-bubble complexes (either in the area of primary or secondary potential minima) is impossible due to the high potential barriers (from 6000 to 140000 kT)and low values of the attraction force. There is shown that for coal and pyrite particles the energy of interaction vs. particle-bubble distance strongly depends on pH value. Improvement of floatability of minerals by the hydrophobization of their surface by collectors leads to the eliminating of potential barriers and the formation of the stable complexes of minerals and air bubbles in the area of primary potential minimum. In addition, due to hydrophobization of coal and pyrite changing pH has practically no influence on the energy of interaction. There are discussed results of the numerical calculations of normalized interaction forces in particle-bubble systems on the nanometer distances for pyrite, sphalerite, and chalcopyrite at contact angles up to 85° in comparison with the experimental data. The values of adhesion force for hydrophobized particles of coal and pyrite to air bubbles are about 10-5 N, that indicates stability of the formed flotation complexes. Examples of using the long-range and high-energy effect of hydrophobic interactions for improving minerals floatability are discussed. There are illustrated minerals wettability changes induced by the adsorption of thiol collector and hydrophobic polymer. Possibilities of flocculation and flotation of mineral slimes due the polymer-collector hydrophobic interactions are shown. Keywords: bubble-particle interaction, contact angle, extended DLVO theory, floatability

Sep 1, 2012

By Vinay Jain, Dharmendr Kumar, Beena Rai, Venugopal Tammishetti

"Selective dispersion-flocculation is considered to be an effective process for the beneficiation of ultrafine particles. This process is based on the preferential adsorption of a flocculant on the mineral particles to be flocculated, leaving rest of the mineral suspended. It has been successfully implemented at plant scales for the beneficiation of ultrafine particles of iron ores, for which conventional methods such as gravity separation, magnetic separation and flotation do not work efficiently. However, the key element responsible for the success of any selective flocculation process is the appropriate choice of the flocculant used for achieving the desired selectivity. At our lab, we are working on design and development of such selective reagents for mineral processing applications, including the beneficiation of iron ore slimes, using a combined molecular modeling and experimental approach. In this study we have employed density functional theory (DFT) to calculate the interaction energies and explain the interaction mechanisms of chitosan with the main minerals present in iron ore slimes, namely, hematite [a-Fe2O3], goethite [a-FeO(OH)], gibbsite [a-Al(OH)3] and kaolinite [Al2Si2O5(OH)4]. The magnitudes of the computed interaction energies follow the trend: Hematite > Goethite > Gibbsite ~ Kaolinite Al-OH terminated > Kaolinite Si-O terminated Analysis of the optimized geometries and electronic structures reveals that the O & N atoms of chitosan molecule form coordinate bonds with surface Fe-atoms of hematite while only weak hydrogen bonds are formed in the case of goethite, gibbsite and kaolinite surfaces thus explaining reasons behind the stronger interactions with the hematite surface. The theoretical findings were validated by performing selective flocculation experiments using chitosan as a flocculant. The selective flocculation experimental results show that a final concentrate of ~60% Fe can be obtained from a feed containing 53.13% Fe with Fe recovery of 74%. The mineral estimation in the obtained concentrate indicated that hematite and goethite are recovered in concentrate while gibbsite and kaolinite are rejected in the tails. These observations were consistent with our theoretical findings. Our work highlights the promising role molecular modeling techniques such as DFT can play in the design and development of selective reagents for beneficiation of alumina-rich iron ore slimes."

Jan 1, 2018

By Luís Marcelo Tavares, Daniel Francioli, Malcolm Powell, Mohsen Yahyaei

"Mathematical modeling of the comminution process requires understanding of all breakage mechanisms occurring in this mechanical environment. Modeling of high energy impact breakage is well established, however, modeling low energy breakage including incremental damage breakage, attrition and abrasion is still under development. Free fall incremental impact tests were carried out to investigate the surface fragmentation of a copper-gold ore. This process was achieved by dropping particles individually from a height of four meters onto a metallic plate. The impact specific energy was 0.01KWh/t. The setting of the metallic plate was changed to test the impact angles of 0°, 45°, and 60°. Tests were carried out using fresh angular rocks as well as smoothed particles. Changes to the plate angle and particle shape enabled the study of the influence of the tangential component of the impact energy along with particle shape on superficial breakage. By studying the fractional mass loss variation in each impact, two distinct stages of surface fragmentation were clearly determined: high fractional mass loss dominated in the first 10 impacts and was attributed to chipping, whereas low fractional mass loss occurred for the remainder of the impacts and was attributed to abrasion. Smoothed particles demonstrated higher resistantance to breakage and their surface fragmentation behavior indicated a closer relationship to abrasion, especially when lower impact angles were used."

Jan 1, 2014

By Xing Yang, Zhen Peng, Guangwen Zhang, Haifeng Wang, Yaqun He

"Triboelectric separation of ilmenite ore based on the tribocharge differences between ilmenite and gangue minerals was conducted in this study. Triboelectric characteristics of ilmenite and its associated minerals were studied using polyvinyl chloride (PVC), pentatricopeptide repeats (PPR), copper, polymethyl methacrylate (PMMA), stainless steel (SS), teflon and quartz glass (QG) tribochargers in lab triboelectric unit. Results demonstrated that the ilmenite particles tribocharged positively while gangue minerals tribocharged negatively using PVC as tribocharger. The particle size also has a significant effect on tribocharge, and the -0.125+0.074 mm is the optimal size fraction of triboelectric separation. Charge-mass ratios of minerals increase with the increases of tribocharging length, but the increasing rate gradually reduce. At 1.5 m tribocharging length, charge-mass ratios of ilmenite, quartz, feldspar and mica are up to 6.07 nC/g, -6.05 nC/g, -4.30 nC/g and -4.56 nC/g, respectively. Based on the triboelectric characteristics of each mineral, triboelectric separation of ilmenite was conducted, and the grade of ilmenite ore increased from 15.47% to 28.40%. INTRODUCTION As a transition metal titanium plays an irreplaceable role in medical, aerospace and materials due to its light weight, high strength and corrosion resistance. Pure titanium dioxide is an excellent white pigment and is widely applied in industries of paint and textile. Ilmenite is the main raw material for titanium industry. For the beneficiation of ilmenite, series methods have been proposed, such as the application of dry magnetic and wet gravity separations to separate the ilmenite from the zircon and rutile. Electrostatic separation is extensively used in the beneficiation of heavy mineral sands for the recovery of rutile, zircon and ilmenite while flotation is used to separate fine ilmenite (Mehdilo et al., 2014; Fan et al., 2014). Compared with flotation and gravity separation, electrostatic separation does not consume water, and native properties of materials will not be changed and energy consumption will be reduced (Wang et al., 2014). Thus, the wide application of electrostatic separation and other dry separation methods is a trend in separation and purification industry, especially in water-scarce areas."

Jan 1, 2018

By Tilak Raj Mankhand, Mudila Dhanunjaya Rao, Kamalesh K. Singh

"Zinc dust is used for the removal of primary impurities by cementation from the zinc sulphate electrolyte before electrowinning of zinc. However, the industrial zinc electrowinning plants has been reported that the zinc dust consumption is in large excess than the stoichiometric requirement. In the present investigation, morphology of the zinc dust has been altered by ball milling and utilized for the cementation of cadmium, which is one of the major impurity and compared the change in the rate of cementation with original zinc dust. Initially, 325 mesh size zinc dust was used for the optimization of the excess quantity of zinc dust to be used at a temperature of 50 °C. The chemical analysis of zinc dust before and after ball milling and morphology were studied by scanning electron microscopy (SEM), and the solution was characterized by Atomic Absorption Spectrophotometer. The rate of cementation increased with increase in ball milling time. The residual precipitate obtained after filtration was also characterized by X-ray diffraction analysis. Finally experiments were conducted to study the effect of temperature and kinetics of cadmium cementation using first order reaction kinetics. Based on the integral method, the calculated activation energy for the cadmium cementation with 4-hours ball milled zinc dust was found to be 3.39 KJ/mole. INTRODUCTION Primary production of zinc in the world is carried out by hydrometallurgical route. The primary impurities in the neutralized zinc sulphate solution that cause negative effect on electrowinning are copper, cadmium, cobalt, and nickel. Copper diminishes the current efficiency and cadmium contaminates the cathode zinc (Morgan, 1977) while electro winning. Nickel and cobalt lead to perforation in the zinc deposit and prevents the electro winning process (Abrasheva et al, 1984). Due to higher electro positivity of these metal impurities than zinc, they can co-deposit with cathode zinc at the time of electrolysis. In addition to that, some possible impurities (including cobalt) in the electrolysis may lower the hydrogen overvoltage, allowing deposition of hydrogen at cathode resulting in fall of current efficiency. The deposition of zinc on the cathode is possible only at higher hydrogen overvoltage which is practicable in the absence of such impurities (Raghavan et al., 1999). Cementation is one of the prominent purification technique, and in that less reactive metal can be replaced by highly reactive metal by allowing them into precipitation. Cementation of cadmium from zinc sulphate electrolyte is being done by the addition of zinc dust."

Jan 1, 2018

By Caitlin Rogers

The environmental and economic sustainability of froth flotation is dependent on effective management, which in turn improves the performance of a concentrator. In economic terms this means improved recovery of valuable minerals, in environmental terms this means effective management of acid generating tailings. Three indicators were selected to measure the performance of an integrated flotation system. The system consists of two stages of flotation; valuable mineral flotation followed by environmental desulfurisation by froth flotation. The suitable indicators were selected based on their fulfilment of four attributes. An attribute is a desired aspect of an indicator. The four attributes were: comprehensive, relevant, sensitive and quantitative. Two environmental indicators and one economic indicator were selected. They represent revenue generation from valuable minerals and environmental cost of management. The suitability of the selected indicators was shown using illustrative scenarios.

Jan 1, 2014

By M. H. Moys, M. M. Bwalya

The use of the Discrete Element Method (DEM) to simulate the interaction of particles in dynamic environments is growing rapidly. This technique is also being applied in the study of milling extensively. However, to date more focus has been on the validation of the model. In spite of the advantages of the detailed information that is available from the simulator, appropriate application of this information remains a daunting task. In this paper a technique that combines particle breakage probability data with the energy spectra generated from the DEM is discussed.

Jan 1, 2003

By P. Somasundaran

Treatment of mineral surfaces with appropriate surfactants plays an important role in mineral processing operations such as flotation, flocculation and dewatering. Recently biosurfactants, in particular, have received a considerable amount of attention because of their unique surface active properties and biodegradability. In this work we examined the performance of biosurfactants, sugar based alkyl glycosides and sophorolipid esters as reagents to control the hydrophobicity of minerals with selectivity of adsorption on mineral surfaces for flotation applications. It was discovered that n-dodecyl-ß-D-maltoside adsorbs on alumina, titania and hematite but, interestingly, not on silica. The hydrophobicity obtained is governed both by the surface coverage as well as the nanostructure of the adsorbed layer in terms of orientation of the adsorbed species. Surprisingly, even though the above surfactants are non-ionic, their adsorption was pH-dependent. We have correlated this pH dependence to the type of species on the mineral surface. Also it is shown that mixing of these surfactants with traditional ones can help reduce the carbon footprint due to synergy between the reagents and help selectivity due to antagonism. The experimental results were analyzed to get information on optimal pH and dosage conditions, for mineral surface modification. The study provides guidance for mineral treatments using biosurfactants and the potential use of these next generation reagents in mineral processing.

Jan 1, 2014

By B. K. Gorain

Mining of low grade deposits along with the necessity to design and operate flotation plants with high throughput presents unique metallurgical and environmental challenges that need to be addressed to reduce project risks, improve project economics and to sustain the profitability of operations over the life of a mine. Some of the key challenges include poor recovery of valuables and concentrate quality issues due to complex mineralogy, the need to use poor quality water such as brackish or sea water, reduce environmental impact from the process, integrate flotation with hydrometallurgy to maximize precious metals recovery, escalation of capital and operating costs, use of unproven technology and constant use of larger equipment, high ore variability, worldwide constraints on resource availability and an ever increasing need for reliable metallurgical input to financial models to evaluate economic viability of projects. The need to develop effective solutions to these problems in a short time frame is becoming a key to the success of any new project and for sustaining the profitability of a mining operation. An integrated multi-disciplinary approach to problem solving is crucial with the need for a more lateral thinking along with strategic partnerships and collaboration involving the right players. This paper presents some of the key findings based on experiences from a large number of challenging projects and operations focused on solving complex flotation problems Keywords: mineral processing, flotation, flotation problem solving, flotation optimization, plant design, innovation

Sep 1, 2012

By Klaus M. Hahn, Hermann Wotruba, Bernd G. Friedrich

"Due to an increasing demand for nickel and cobalt and the depletion of nickel sulphide deposits worldwide, the production of ferronickel from lateritic nickel ores becomes more significant. About 60 percent of nickel reserves are present in laterite deposits. Common production methods like acid leaching or smelting operations implicate high material and energy consumption. Physical processing methods are also not efficient, because of the fine microstructural intergrowth of the minerals carrying valuable elements such as nickel and cobalt. Due to the high energy consumption of metallurgical treatment of lateritic nickel ore (nickel grade: 0.8 - 3.0%, Co: 0.05 - 0.15%), the separation of waste material (about 75 - 85%) before the metallurgical treatment is desirable. Therefore, an alternative process has been developed, combining a pyro-metallurgical pre-treatment with selected mechanical processing methods. The developed process consisted of a selective pre-reduction and non-selective segregation of the contained metal phases in the first stage. By this, the properties of the metal carrying minerals were changed and could become subject to concentration by means of fine beneficiation processes afterwards. The parameters of the pre-reduction and segregation were varied and the pre-treated samples were examined concerning their efficiency of metalization grade and metal grain size. This paper describes the investigation of pre-treatment methods of a lateritic nickel ore. The pre-treatment and possible subsequent separation methods were examined with regard to the recovery of the valuable elements. Metalization grade was around 80% for both Ni and Co with metal phase grain sizes below 20 µm. Scanning electron microscopy revealed distribution of new metal phases not only on the reducing agent, but also on the “slag” material.INTRODUCTION Nickel laterites are characterized as strongly weathered regoliths with several zones containing reserves of nickel (Ni) and cobalt (Co). These laterites are formed on serpentinites and ultramafic rocks under climatic and/or tectonic conditions that have changed over time (Butt & Cluzel, 2013). The formation of Ni laterites is influenced by numerous geological and environmental factors. In general, there are three ore types named according to the dominant Ni hosting minerals: oxides, hydrous magnesia (Mg) silicates and clay silicates (Butt & Cluzel, 2013). The most Ni laterite deposits contain two of these ore types, usually an oxide zone and an either clay or Mg silicate zone. Distribution of these principal deposit types, their average Ni-bearing phases and mean Ni grade are shown in Table 1. A schematic profile of the different deposits based on the development on serpentized ultramafic rocks is given in Figure 1 (Butt & Cluzel, 2013)."

Jan 1, 2018

By Mingfei He, Yude Gao

"The leaching kinetics was studied during leaching of indium-bearing zinc oxide to recover indium. The effects of temperature, sulfuric acidity, particle size, stirring rate on dissolution rate of indium were investigated. Results showed that the leaching process was controlled by chemical reaction at the condition of low sulfuric acid concentration. While the acidity increased to 1.8 mol/L, the leaching process was transformed into an internal diffusion controlling model . The corresponding value of reaction orders under low acidity and high acidity were 1.194, 0.156, respectively. Further calculation results indicated that the leaching reaction activation energy was only 10.97kJ/mol under the condition of high acid. The leaching rate constant was inversely proportional to the square of particle size, while the effect of stirring rate on leaching process was insignificant. The leaching process can be enhanced by increasing the temperature and acid concentration, as well as the decrease of particle size. And a final kinetics eqution was proposed. KEYWORDS Indium, extration, leaching kinetics, zinc oxide INTRODUCTION Indium[1,2] plays an important role in many aspects of living and industrial production owning to its special physical and chemical properties. The reserve of indium is rare on the earth, and most of indium is distributed in some other minerals[3]. Some researchers [4,5] have proposed that indium mainly substitutes for the lattice of other minerals by isomorphous. Therefore, the extraction of indium should take into account of the production technologies of those minerals to comprehensively recover the valuable metals."

Jan 1, 2018

By Richard K. Komarek, Antonios Zavaliangos, Roman T. Dec

Roller presses are widely utilized in mineral industry for fine milling and compaction. Recently used models are providing only limited information about the material behavior in the roll bite. This paper introduces a 2-dimensional finite element model for analyzing those two basic processes. A pressure-dependent plasticity model with linear elasticity was used as a constitutive model for the particular material. Coulomb friction law was used to describe phenomena on the material/roller surface interface. Two basic roller geometries are considered: smooth (used for milling and compaction) and with cavities, commonly used for briquetting. Comparison of the results obtained from the model with experiment indicates that they are following the general trends of experimental values recorded with laboratory roller presses. It is shown, that the model is suitable to analyze material behavior through all stages of the rolling process: feeding zone, nip region, neutral plane and release section. It can predict pressure, shear stress, slip of the material over the roller surface, material velocity field, failure of the compact during release and the course of other important process variables. This allows the process engineer to gain an improved understanding, leading to a better process and equipment design and control.

Jan 1, 2003

By X. L. Song

A large amount of tailings in concentrators bring a series of problems to the environment and society. It is significant to reclaim the huge tailings and reuse them in industries in order to utilize mineral resources adequately. Primarily Lead-Zinc tailings with a certain quality of clay and feldspar were used to produce ceramic tiles by sintering method under specific technical conditions. By testing the properties of the ceramic tiles, it was shown that the amount of Lead-Zinc tailing used in the tiles was 60%~70%, and the mechanics properties were good. The optimum proportion parameters were Lead-Zinc tailing 60%, clay 35%, feldspar 5%, and the maximum flexural strength of tiles was up to 38.2MPa when it was sintered at 1090? for 30min. Its flexural strength, water absorption and thermal shock resistance reached the State Standard of GB/T4100.4. The product is suitable to be used in pavements and paths of parks.

Jan 1, 2014

By H. Kasaini

Batch wise adsorption tests for platinum (Pt) on the surface of activated carbon pellets (Norit RO 0.8 BET surface area 1100 mg/g) were carried out in mixed chloride solution. The purpose of this study was to assess and compare the adsorption performance of amine-treated activated carbons (AACs) and native activated carbons (NACs) in terms of adsorption capacity and selectivity. The effect of pH and temperature on adsorption capacity and selectivity was established. The amine- treated ACs were prepared by anchoring the amino groups (butyl amines) on the surface of AC pellets in aqueous media and the UV-Vis was used to determine the amount of amine sequestered from solution by ACs. The dosage of butyl amine on the surface of ACs averaged 0.15 g/g, carbon. The adsorption mechanism was described by the ionization and complexation model whereby interaction between the protonated AAC surface and the anionic chlorocomplex ions (PtCl5 [H2O]-, PtCl62-) proceeded by either electrostatic attraction or/and by covalent bonding [(NH3)2PtCl6 or (CH2COO)2PtCl6]. By comparison, the adsorption capacities of Pt on amine-treated ACs and native ACs were 53.8 mg/g and 33.03 mg/g, respectively which highlight the benefits of anchoring functional molecules on ACs. The selectivity of AACs was influenced by solution pH. Pt adsorbed selectively on the surface of amine-treated ACs at pH<1.5. The highest separation factor that was recoded pertained to Pt and Fe species (ßPt/Fe = 90) then followed by Pt and Ni species (ßPt/Ni = 30) or Pt and Cu species (ßPt/Cu = 15). The lowest separation factor was recorded for Pt and Cr ions (ßPt/N= 5). Adsorption kinetics of Pt on amine-treated AC surfaces, according to the first and second order reactions, were investigated and results showed that rates were in the order 10= 5). -4 min-1 and 102 g?min/mg, respectively. The pseudo 1st order kinetics predicted the adsorption capacity of 51.81 mg/g which was almost similar to the experimental value (53.8 mg/g) while the second order rate equation predicted Pt adsorption capacity of 40.1 mg/g. Both The Langmuir and Toth isotherm fitted the Pt adsorption at pH < 1.0. The Freundlich isotherm tended to underestimate the adsorption capacity of AACs.

Jan 1, 2014

By V. Ross

"The Upper Group 2 (UG2) reef in the Bushveld Complex in South Africa hosts an estimated 40% of the world’s Platinum Group Metal (PGM) resources. The processing of this ore via flotation poses two particular challenges: limiting the levels of chromite in the concentrate to reduce downstream smelting problems, and enhancing the recovery of ultrafine (typically -10 micron), liberated PGMs. Conventional ways of suppressing the entrained chromite, such as froth washing, is not effective in PGM operations, which are dominated by mechanical cells. The recovery of fine particles is hampered by low collision efficiencies with air bubbles, as well as oxidised surface layers especially in tailings operations. This paper documents the results of laboratory tests on a run-of-mine PGM UG2 ore, investigating the application of a pneumo-mechanical column (PMC) and its effect on PGM flotation and its selectivity with regard to chromite. A key feature of the device is the stage-wise release of aerated slurry from an agitated downcomer, thus creating conditions where the superficial velocity profiles of air and slurry change axially within the separation zone. This aids segregation of the silicates and chromite-rich fractions in the separation zone, concentrating the latter towards the bottom of the column and minimising its entrainment into the concentrate. Comparison of the performance of the PMC to that of mechanical laboratory cells under equivalent operating conditions showed improved PGM flotation kinetics and recovery. This was accompanied by a decrease in gangue recovery compared to the mechanical cells by more than 40%, thus doubling the final rougher concentrate grade from 50 to 100 g/t. Significantly, whilst the overall Cr2O3 recovery was reduced by more than 60%, the selectivity (PGM recovery vs Cr2O3 grade in the concentrate) was doubled.INTRODUCTIONThe Bushveld complex in the northern part of South Africa hosts the world’s largest reserves of Platinum Group Metals (PGMs), representing approximately 40% of the total PGE. It is characterised by three main PGM bearing reefs, namely Merensky, Upper Group 2 (UG2) and the Platreef. The Merensky and Platreef are dominated by silicates in the form of pyroxenites, and carry economically recoverable amounts of copper and nickel, in the form of chalcopyrite and pentlandite. The UG2 on the other hand is a chromitite ore with chromite as (ideally, FeO.Cr2O3) the most abundant gangue, often constituting more than 70% by mass with a PGM grade of around 4.5 g/t. Other key gangue minerals are pyroxene, feldspar and talc. The PGEs occur in a wide variety of minerals, with platinum and palladium sulphides typically accounting for about half of the total. Base metal sulphides such as chalcopyrite, pentlandite and pyrrhotite occur in only very minor amounts, accounting mostly for less than 0.1% by mass."

Jan 1, 2018

By P. T. L. Koh

The effect of particle shape on the flotation process has been investigated in laboratory experiments with monosized spherical ballotini and roughly ground ballotini. The particles were treated by partial methylation with trimethylchlorosilane to achieve varying degrees of hydrophobicity. In flotation, the process of film thinning and liquid drainage is critical in the formation of a stable bubble-particle attachment and this is affected by the particle shape and surface hydrophobicity. The rate of attachment affects the overall flotation rate. Flotation tests with different particle sizes at various degrees of partial methylation have been performed in a modified Denver cell. Predictions from a computational fluid dynamic model of the cell which incorporates fundamental aspects of bubble-particle attachment are compared against flotation test results. Contact angles of the particles have also been measured using the capillary rise technique to indicate surface hydrophobicity.

Jan 1, 2014

By K. Hori

In this study, the determination of optimal conditions for jig separation has been investigated with a TACUB jig separator. The TACUB jig, from which a Batac jig originated, is a useful gravity separator that is effective to separate crushed solid wastes as well as coarse ores. A mixture of crushed polyethylene (specific gravity 1.3) and polyvinyl chloride (specific gravity 1.5) was separated by a batch TACUB jig by varying the frequency (wavelength) and the amplitude (pulse stroke length). It was found that the sample particle layer in the separation chamber was fluidized without turbulence by the rising water pulse resulting in the separation. However, a too strong water pulse reduced the efficiency of the separation of the particles. The results indicate that the specific velocity of the rising water is necessary to fluidize the particle layer without turbulence to separate the particles. The expansion ratios of the thickness of the particle layer in rising flows were measured in a cylindrical column. The pressure losses by the particle layer were calculated from the expansion ratios and the velocity of the rising flows by Ergun?s equation. The curve of the pressure loss vs. the velocity of rising flow showed a maximum point corresponded to the point of fluidization. The velocity of a rising flow on the point of fluidization provided the optimal separation condition.

Jan 1, 2014

By Juan B. Yianatos

"After almost 100 years, since the first commercial application began in Australia, flotation has shown an extraordinary growth and nearly 2 billion tons of ore per year are presently treated by flotation processes. During this time flotation has promoted a wide scope of research activities ranging from fundamental chemistry and hydrodynamic studies to studies of industrial operations. In general, fundamental studies have been mainly related to ideal situations. In recent years, however, large efforts have been focusing on achieving a better insight into the actual sub-processes provided by the development of new and more sophisticated instrumentation. Since the massive incorporation of flotation columns, around 15 years ago, a renewed interest in flotation fundamental studies, process modelling and new cell designs have been observed worldwide. The key role of the froth has been recognized as an independent and sometimes rate limiting process step. Thus, separation of pulp and froth process stages seems the most appropriate in terms of process modelling, diagnostic, design and scale-up purposes.In relation to flotation equipment development, until the middle of the 1970?s, only the sub-aeration mechanical cells were dominant. Since the 1980?s, the use of pneumatic cells and forced air mechanical cells has emerged strongly. Also, in the last decade, flotation equipment has shown a dramatic increase in size, reaching values of 200m3 in unitary mechanical cells and more than 300m3 in columns. The general feeling, however, is that, despite the great advance observed in terms of process knowledge, the mechanisms and principles of industrial flotation cells design and scale-up are still not fully understood.Advances in process instrumentation and control now in use allow for more efficient operations, both in metallurgical performance and savings in operating costs.INTRODUCTIONFlotation is a widely used process within the minerals processing industry, as well as being used for water treatment and de-inking of recycled paper. Froth flotation started in Australia at the beginning of the 20th century and since then flotation technology has made significant advances. Flotation was firstly applied to sulfide ores. The largest tonnages treated by flotation are copper and copper/molybdenum ores, handling about 50% of the total ore processed. Also significant are phosphate, iron ore and coal treatments. At present, Chile is the foremost copper producer in the world with around 35% of the world?s production. Figure 1(a) shows the evolution of copper production in Chile over the last decade. The total amount of fine copper produced in year 2001 was 4.7 million tons, from which 3.2 million tons was processed by flotation while 1.5 million tons went through LIX-SX-EW processes, which also showed significant development during the same period (Anon, 2001). The total flotation treatment of copper ores in Chile is about 325 million tons per year (Anon, 2002), so the world treatment of copper ore by flotation can be estimated at about 1 billion tons per year. Consequently a total of nearly 2 billion tons of ore per year is presently processed worldwide by flotation (Fuerstenau, 2001). In order to handle the higher tonnage of low-grade ore, a worldwide trend towards the development and use of larger flotation machines began in the 1960?s. Figure 1(b) shows that the trend became extremely marked from the beginning of the 1990?s, which is consistent with the strong increase in copper production during the same period."

Jan 1, 2003

Mineral processing is an energy and water intensive activity. Mill comminution equipment usually has high energy requirements which necessitate extensive cooling to remove heat. Cooling requirements are typically 10% to 20% of the comminution energy. If there is an adequate supply of suitable water, open water-based cooling systems are the simplest, cheapest and most energy efficient cooling method available. This paper describes a method to determine the water demand for open water-based cooling systems at a plant and to determine whether the mine has sufficient water to meet that demand.

Jan 1, 2014

By David I. Verrelli, Peter T. L. Koh

"Recent experimental measurements of induction time made by direct observation with the ‘Milli-Timer’ indicated that angular particles were able to attach much more rapidly than spherical particles. There was around a tenfold difference in the respective induction periods for particle-bubble attachment. For industrial application, a more holistic comparison is needed, with the induction period for attachment being just one input. Over the years, CSIRO has developed a CFD-flotation model that incorporates both rigorous hydrodynamics, to simulate real industrial cell geometries, and a detailed model of the embedded flotation process, in which the induction period is an important parameter. We conducted transient modelling of batch flotation. First, spherical particles were modelled, as a ‘baseline’, for different particle sizes and levels of hydrophobicity. In the second set of results, the induction period was decreased by a factor of up to ten, simulating flotation of angular particles. Flotation recovery was found to depend upon induction period in a complex manner. For highly hydrophobic or fine particles, the induction period for spheres was already so low that recovery was limited by other factors (e.g. bubble-particle collision frequency). Further decreases in induction period, as for angular particles, did not have a significant effect on recovery in these cases. By contrast, when weakly hydrophobic or coarse particles were modelled, the recovery was predicted to be greatly enhanced for angular particles, in comparison to spheres. For these particles the induction period was limiting recovery, so that the flotation rate constant could be improved directly by reducing the induction period. This is consistent with batch flotation experiments using Ballotini reported earlier. Therefore, when dealing with weakly hydrophobic particles or relatively large particles that are to be floated, an enhancement can be expected for more angular particle shapes. In such cases, judicious specification of the grinding circuit may improve the overall efficiency."

Jan 1, 2014