Search Documents

By C. Gomez, J. Finch, R. Dalhke, J. Torrealba-Vargas

The velocity of gas passing through a flotation cell can be estimated by collecting bubbles by natural buoyancy in a closed tube and measuring the rate of pressure increase. The governing equation is derived and verified. Single- and two-tube gas velocity sensors are described. The latter design permits a correction for bulk density and level change during signal collection.

Jan 1, 2003

By S. A. Bogidaev, M. Yu. Tiunov

"The paper describes the results of the flotation tests with complex rare metal ores from deposits in the Trans-Baikal Territory. Correlations between the quality of produced wolframite, hubnerite and mica concentrates with or without the presence of various alkaline modifiers are determined. Commonly, rare metal ores contain minerals of comparable value to main elements recovered in processing plants using gravitational methods. The paper describes the results of flotation recovery of valuable minerals – main and associated – from gravity tailings of deposits in the Trans-Baikal Territory. It was found that gravity tailings from the first deposit contained fine-grained wolframite, mica (muscovite, lepidolite etc.), feldspar; hubnerite, scheelite, beryl, fluorite, rubidium-containing muscovite from the second deposit, correspondingly. This paper presents the results of the stage flotation tests with the production of tungsten (wolframite, hubnerite), fluorite and mica concentrates from gravity tailings. Figure 1 demonstrates the flowsheet of tungsten ore minerals and mica stage flotation from gravity tailings of the first deposit.Wolframite can be floated using oleic acid with the presence of soda ash, a complexing collector (IM-50), under slightly alkaline conditions in combination with a nonpolar collector [1, 2, 3, 4]. The study included wolframite flotation using the combination of two alkaline modifiers. Flotation of wolframite was performed after pulp desliming, using tall oil saponified with soda ash. The recovery of wolframite in the concentrate of rougher flotation reached 80-85%; the concentrate contained up to 1% of tungsten oxide that can be upgraded to a saleable product using gravitational methods. This procedure was tested during flotation of wolframite, tantalite-columbite and pyrochlore, and provided high performance regardless of a season, at pulp temperatures of 8-10°C, though fattyacid collectors are significantly inefficient at such low temperatures due to low solubility, dispersion and increased collector consumption, consequently. The introduction of two alkaline modifiers in pulp appears to improve these characteristics.The first stage of the tests was focused on increase of iron-bearing tungsten ore minerals recovery from gravity tailings and stabilization of the cold pulp flotation process."

Jan 1, 2018

By Bert Huls

Already starting, new drivers will dictate how future mineral processing plants will be designed and operated. These drivers include requirements in water and energy conservation because of rising costs, larger demand for mineral and metal products as the result of a rising population, and the increasing demand from the population in general to have influence over what type of operations will be developed where. Mineral operating facilities will require processing of lower grades. To do this economically, design engineers will be influenced to introduce newer concepts, or return to older processing concepts once deemed not desirable. Our understanding of the fundamentals must be improved, and this may come from better measurement techniques and more process piloting, and will go in hand with a reduction of waste generated during the process, improved separation of minerals or product size. Process engineers will also be required to not just design according to the established 3D methodology for efficient plant installation. Already in other industries the design concept encompasses the entire range from source to product. Not only that, the design will be affected by public influence that must be illustrated prior to project execution. On the one hand, the added dimension in design may slow a project; on the other hand it may result in a blessing, and in a higher responsibility for engineering.

Jan 1, 2014

By Gábor Mucsi, József Faitli, Imre Gombköto, Sanjay Kumar, Zoltán Molnár, Balázs Ráczkevi, Ádám Rácz

"Generally, fly ash particles are very fine (< 100 ?m), mainly spherical and glassy materials form an outer shell on it. This paper deals with the laboratory investigation of ground fly ash based geopolymer. This material can be applied in many fields, mainly in the construction industry, e.g. non-structural elements, concrete, pavements and products, containment and immobilization of toxic, hazardous and radioactive wastes, advanced structural tooling and refractory ceramics, and fire resistant composites used in buildings, etc. The preparation of fly ash using high energy density milling is presented. Systematic experimental series were carried out in order to optimize the preparation process. The particle size distribution (LPSA) and structure of fly ash (FTIR) and the uniaxial compressive strength ,the permeability and structure of geopolymer product, furthermore the rheology of geopolymer paste were investigated. The product properties were studied as a function of the fly ash fineness. As a result of the investigation the relationship between the grinding circumstances, the ground material properties and the geopolymer characteristics was identified. It was found that the above mentioned physical properties of the geopolymer strongly depend on the grinding process."

Jan 1, 2014

By J. Bouchard, Ali Vazirizadeh, R. del Villar

"The amount of water reporting to the concentrate correlates well with the solid entrainment. It is well known that the frother and collector dosage as well as the froth depth and gas rate influence the amount of water reporting to the concentrate. This is also true for gas dispersion properties such as gas holdup and bubble surface area flux. On the other hand, a positive bias rate, required to reduce hydraulic entrainment, also affects water recovery and thus the particle recovered by entrainment (depending on the their size). Up until now, the effect of the gas rate on the water recovery has been studied, but no comprehensive investigation on the gas holdup, bubble size and bubble surface area flux has yet been reported. This research precisely aims at addressing this issue. The experimental work was carried out under a constant gas flow rate to eliminate the gas volume effect, while other gas dispersion properties have been varied by modifying the frother concentration and the shearing water introduced to the frit-and-sleeve sparger. A constant froth depth and no wash water were used, in order to be able to evaluate the exclusive correlation between the water recovery and the bubble surface area flux and/or the bubble size. It is worth mentioning, that the particle size of the hydrophobic particles did not show a significant effect on the amount of water going to the concentrate. Not surprisingly, experimental results demonstrate that water recovery increases with the bubble surface area flux and with the gas hold-up."

Jan 1, 2014

By John Nell, Paul den Hoed

Carbochlorination tests were conducted with matched particle-size fractions of rutile, ilmenite and high-titania slag in a small bubbling fluidized-bed reactor. The effects of temperature, the type and proportion of solid reductant in the charge, and the fraction of Cl2 in the fluidizing gas were investigated. Tests confirm the need for solid carbon in the bed if chlorination is to run at high rates. With solid carbon in the bed, CO supplied with the fluidizing gas does not increase significantly the degree of chlorination after 75 minutes. Ilmenite is chlorinated more quickly than titania slag, which in turn is chlorinated more quickly than rutile. Rates of chlorination at 1100°C and 1000°C are much the same and significantly higher than at 900°C. Chlorination is associated with significant increases in particle porosity (even for rutile), which is brought about by the rapid initial chlorination of FeO and MnO (in ilmenite and slag) and (it is argued) by the chlorination of Ti2O3 which forms at high-energy surface sites. A reaction mechanism is presented; where possible, its validity is demonstrated by the support of empirical observations.

Jan 1, 2003

By E. V. Bratygin, S. P. Elnikova

"In the article carrying out technique of experiments for estimation of power efficiency of process of crushing in cone crushers «in a layer». The conformity of the granulometric characteristics of the crushed products obtained as a result of the tests, the theoretical equations for the size characteristics, and the choice of the optimal equation for the prediction of the granulometric characteristics of the final products obtained by crushing ""in a layer"". Optimization of granulometric composition of power of crushers working ""in a layer"" is carried out with the purpose of reduction of the electric power consumption at reception of a product of required quality. As a result of the experiments, dependencies are obtained, the relevance and applicability of the crushing process ""in the layer"" for obtaining crushed stone of improved quality is proved. INTRODUCTION A number of equations have been proposed for calculating the breakage energy. These include equations by Kirpichev and Kick, Rittinger and Bond (Bogdanov, Olevsky, 1982). Another equation for calculating the specific breakage work in breakage by impact and in stratum was proposed by Devyatkin (Boiko, 2003). In these equations, the breakage energy is proportional to the particle size raised to some power. In the equation proposed by Devyatkin, the ore piece thickness or the feed average diameter is used. The relationship between energy and breakage can be expressed as an equation (Lynch, 1981; Tikhonov, no. 3, 2008) where k is a coefficient characterizing the energy parameter depending on the strength of the feed, l is size in microns. The Rittinger formula is obtained for n = 2, the Kirpichev-Kick formula for n = 1, the Bond formula for n = 1.5. For n = 3 or higher, the equation describes fine and ultrafine grinding. R. Hookey proposed a formula (Lynch, 1981, Tikhonov, no. 3, 2008), where the size exponent n is substituted by a size function In all of the above equations, a single value of the feed and product size is used; for example, in the Bond equation, size is defined as the particle size of the 20% oversize (P80 and F80). However, a single size value can represent multiple distributions, making that the Bond method inappropriate for determining the size (Lynch, 1981). Describing an equation for estimating the grinding energy will allow to design the electric drive and ore preparation circuit for the given breakage method."

Jan 1, 2018

By V. E. Vigdergauz

The work presented shows results of electrochemical study of pyrite hydrophobicity evaluated by air bubble induction time (IT) measurements. On the basis of measured IT?s an average thickness of the thin liquid film prior to its rupture has been evaluated, which confirms long-range character of the interactions between air bubbles and hydrophobic surfaces. Obtained data are discussed in the frame of recent studies of structures of solid-liquid interface based on molecular dynamics simulations and results of surface force measurements.

Jan 1, 2014

By Lev O. Filippov, Inna V. Filippova

"Flotation of metal-organic precipitate in column is sensible to the hydrodynamic conditions determined by the diameter and the dispersion of rising bubbles. Thus, the dissipation energy in the system resulting of ratio between superficial fluid velocities (gas and feed) in the column is the main parameter for precipitate flotation in pilot or industrial scales. The suggested limiting factor is the aggregate stability under the turbulence created by the rising bubbles. The stability of precipitate is related to the structural organisation of aggregates, which determines the size distribution of particles during precipitation and flotation stages.Structural evolution of Mo precipitate and the destruction phenomenon were described by using of the various fractal dimensions. The fractal studies allow the detection of a structural scaled organisation of the precipitate flocs. The fractal dimension of the particle mass distribution Dm=1.94+/-0.15 suggests, for the floc structure, a cluster-cluster aggregation process either with restructuring or breakage phases.The destruction process, which occurs for the lowest values of the dissipation energy E (0.02 . 0.05 W/kg) was characterised by a fractal dimension Dg of size distribution. Besides, the destruction of floc produces very fine particles, and thus induces the difficulties of bubble-particle collision during the precipitate flotation in column."

Jan 1, 2003

By Kazimierz Trybalski

"Simulation methods have a big potential in the studies and analyses of complex technological processes and schemes. The simulation method used jointly with flow diagrams and related transmittance models allows describing and analysing dynamic characteristics.The paper presents results of simulation analysis of dynamic characteristics of ore dressing system, called closed circuit mill-classifier-mill. Such systems are widely used in ore processing plants. The system was analysed as a typical system with material feedback, to establish its dynamic characteristics.Flow diagram conforming to the technological scheme is presented in a figure. Transmittances shown in the scheme are defined as follows:GMP - transmittance of rod mill,GP, KZ, GW, KZ - transmittances of overflow and underflow streams of spiral classifier, respectively,GMK - transmittance of ball mill,GT - transmittance of underflow stream from classifier to ball mill,GU, MP, GU, MK - fraction transmittance of outflow streams of rod and ball mill, respectively, summed up at classifier input.Taking into account, in base of carried out analysis the transmittance forms of individual system elements. The calculations are based on numeral forms of transmittances of individual blocks, defined through industrial experimentation.Step input function to rod mill was assumed to be a step of mass ore flow rate to the mill. Responses are defined as product densities.This figure demonstrates the way of input signal transmission by consecutive elements of the system and shape of these elements' responses. It can be noticed that step signal undergoes gradual change from the stream of the first order to those of higher and higher orders as a distance from process leading edge increases. Simultaneously, the impulse signal is subject to systematic smoothing and decay. From the technological point of view, the most important is response stream in point 5 (on the above figure) that characterises classifier overflow, which is a final product of this system."

Jan 1, 2003

By Remmerswaal, U. Boin, M. B. G. Castro

"To design sustainable products that can be recycled with high resource efficiency, low environmental impact and economic feasibility, the choice of materials and materials combinations, made in the design stage, is fundamental. The products we design, manufacture and use now will be the resources of the future. Designers are able to select materials for a product according to the many functional requirements they must fulfil. But they have a limited knowledge of the recycling processes and its requirements regarding quality of the secondary material streams. Resource Engineers have to manage the processing of these streams, that are becoming more complex with the increasing variety of materials and decreasing size of components. After mechanical separation of the materials streams resulting from shredding of EOL (endof- life) products, there is always a degree of contamination, from two possible causes:Incomplete liberation: the bonds between different materials combined in a component are not completely destroyed by shredding, resulting in some particles containing two or more materials attached;Separation efficiency: the mechanical separation processes are not able to separate perfectly the many material particles; there are always a number of foreign particles in the recovered streams.Sometimes, those contaminants cannot be removed by the industrial metallurgic recycling processes, and a more serious problem occurs when the contamination levels compromise the recycling of the material stream by lowering its quality (i.e. the properties of the recycled material will be lower due to the contamination). As a consequence, the material must be diluted in virgin raw material and/or used in a less demanding application (downgrading), causing resource depletion and increased energy use, waste production and recycling costs. In order to make the best choice of materials combinations for a product, a systematic approach is necessary, that can close the gap between the knowledge areas of Product Design and Recycling Technology."

Jan 1, 2003

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. Hydrodynamic conditions influence phase mixing and mass transfer in a multiphase system, and these affect the overall performance of such a system. Detailed information on the effects of the hydrodynamics on the performance of agitated systems is still required for the design and optimal operation of hydrometallurgical systems, which are always multiphase. Computational fluid dynamics (CFD) techniques have been employed to study the hydrodynamics and mixing, most of which have focussed on the performance of axial and radial pumping impellers in agitated tanks. However, very little has been reported on the influence of a draft tube on the flow profile in such systems.CFD simulation of a stirred vessel centres on the way the impeller is modelled. Some of the most recent approaches to modelling an impeller are impeller boundary condition (IBC), snap shot, sliding grid (SG), multiple frame of reference (MFR) and inner outer (IO). The accuracy, with which these models predict experimental results and the corresponding computational demands, form the basis upon which the choice of an approach is made. Most of these approaches (IO, SG and MFR) address the key problem of the stirred tank modelling, namely, the simultaneous meshing of the rotating impellers and the stationary baffles. The MFR is computationally cheap and has been found to give predictions that compare well with experimental data.The CFD technique (code CFX4.4) 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 impellers 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 Megan Becker, Cyril O’Connor, Jenny Wiese, Gaynor Yorath

The effect of particle shape on true flotation has been widely reported. The present paper presents results obtained in investigating the effect of particle shape on the entrainment of particles during the flotation process. Different hydrophilic minerals with particles of varying aspect ratios were used and their shape determined using rheological tests and QEMSCAN. Their entrainment properties showed a close relationship to their shape with the recovery due to entrainment increasing as the aspect ratio of the particles increased. The effect of surface charge, by changing pH, and size of particles showed that the effect of shape was sustained at different pHs and particle sizes. Proposals are made to explain these observations in terms of the known relationships between drag coefficients and terminal velocities and shape. Since it has been previously reported that different milling procedures can affect particle shape, these results indicate that it is possible that such different procedures may result in increased entrainment of hydrophilic minerals.

Jan 1, 2014

By D. Saramak

Investigations over the application of hybrid comminution circuits with the High-Pressure Grinding Rolls (HPGR), on the main comminution stage on the basis of the lime and cement industry, were presented in the paper. Two crushing circuits were investigated, the first HPGR-based and the other one, with conventional jaw crusher. The results presented in the article confirm that hybrid comminution circuits with the application of HPGR are innovative ones, and they assure achieving the technological and economic competitiveness in the mineral raw materials processing industry. They are much more favorable in terms of the final product fineness and capacity but insignificantly less effective about the unit energy consumption. Technological performance of conventional crushing circuit and HPGR-based one were also compared in lab scale. The circuit with HPGR application gives finer products both on crushing and grinding stages. The average particle size reduction obtained in HPGR-based circuit is as much as twice greater, comparing to the conventional crushing devices. Keywords: comminution, HPGR technology

Sep 1, 2012

Gold thiosulfate complex is difference with gold cyanide complex, which is easily adsorbed on activated carbon while gold thiosulfate complex cannot be satisfactorily recovered by activated car-bon. However, Gold thiosulfate could be recovered by activated carbon if cyanide is added into the thiosulfate solution. To avoid the cyanide solution, this paper will review several possible processes to recover the gold from thiosuldate solution: such as the cementation with metals, ion exchange resin and solvent extraction. The gold cementation with the powders of zinc, copper, iron and aluminium will be discussed. The advantage and disadvantage of each are compared. The consumption of thiosulfate and copper and feasibility of solution recycling will be discussed. The gold recovery by some ion exchange resins will be suggested. The processing conditions, its applications and the resin elution methods will be presented. The gold recovery by using solvent ex-traction will be reviewed. The processing conditions of solvent extraction process are discussed and compared.

Jan 1, 2014

By T. Sun, J. Kou, C. Sun, D. Gong

"HPGRs (high pressure grinding rollers) have demonstrated higher energy efficiency than conventional comminution equipment due to their application of particle-bed breakage mechanism. In the past decades, a large number of studies have been conducted to understand the characteristics of particle-bed breakage, however, few of them concerned the difference between single-particle and particle-bed breakage in compression comminution. This comparison is able to demonstrate possible advantages of particle-bed against single-particle in a breakage event due to the isolation of the effect of force loading mechanism. The present study investigated progeny fragment size and energy efficiency of these two breakage methods at variable energy inputs and particle sizes. The results show that at low energy inputs of around 0.25 kWh/t, the numbers of fines resulting from the two breakage methods are very similar. However, at higher energy inputs of around 1.0 or 2.0 kWh/t, particle-bed breakage generated significantly more fines. From the perspective of newly generated surface energy, particle-bed breakage is obviously more energy efficient than single-particle breakage at energy inputs between 1.0 and 2.0 kWh/t. It was also found that HPGRs demonstrate high energy utilization rate in generating new surface energy within their typical range of specific energy input. INTRODUCTION Rock comminution is an important and energy-intensive process in mining operations. Nowadays, decreasing head grade and mineral liberation size of ore deposits greatly increase the energy cost of comminution process. HPGRs have been successfully applied in the mining industry to improve the energy performance of comminution circuits. Typically, 10 to 30% of energy saving can be achieved due to the application of HPGR (Wang et al., 2013; Casteel, 2005; Günter et al., 1996)."

Jan 1, 2018

By Masoud Askari, Ahmad Rafizadeh, Shahamat Rostami, Mohammad Qaredaqi

Gole - Gohar Iron ore mines located in Sirjan, Southeast of Iran, have more than 1 billion Iron ore deposit and this area comprises 45 % of Iran Iron reservoirs. The aim of Wet tailing processing line is recovering Hematite ore from wet tailing of Gole - Gohar iron ore processing plant. The Investigations of Hematite recovery plant showed that the recovery of Iron ore to concentrate in Wet Tailing Processing (WTP) line is very lower than that has been predicted, sampling, and designing of the process parameters are not accurate and designed magnetic field intensity is not reasonable for the recovery of Iron in form of Hematite in this line feed. Applying of MIMS in WTP separator and changes in circuit caused in overwhelming increase of Fe recovery, from 11 to 40%. Although recovery of WTP line was improved, but low recovery of this processing line and high content of Hematite ore in WTP tailing, made applying Wet High Intensity Magnetic separators unavoidable. Two kinds of WHIMS have tested for processing of WTP line tailing. Results showed that traditional Jones separator with grooved plate matrix, is more suitable to achieve a better quality of concentrate compared to Slon® separator.

Jan 1, 2014

By A. V. Bogdanovich

Until recently, in consideration of fundamentals of gravity concentration theory, all computations have been based on determination of particles? fall velocity in an unrestricted medium (hydraulic size). Meanwhile, gravity separation processes are realized under conditions of particles? restricted fall, when important and sometimes decisive role is played by interacting forces of particles, dependent on their varying size, density and shape, i.e., segregation forces. We have developed devices and methods for measuring segregation velocities of fine particles of various size, density and shape during their loosening in air or aqueous medium. Besides, to exclude influence of medium upward flows, loosening was provided by superposition of vertical harmonic oscillations on measuring cell. It was established, that maximum segregation velocities are observed at certain optimal acceleration values and amplitudes of oscillations; excessive loosening leads to mixing and worsening of segregation. Velocity of some particles segregation through others depends on particles? size, density and shape, as well as nature of medium (air, water). Absolute segregation velocities of particles in air medium may reach 1~2 mm/s, in aqueous medium such velocities are by an order smaller. Analysis of rare-metal sands material gravity concentration results showed, that owing to segregation process during gravity separation, fine-size isometric particles of heavy minerals are recovered into gravity concentrates more actively, than larger ones, but more elongated in shape. It is convenient and simple to estimate mineral grains? shape by extent of their oblongness, described as ratio of particle minimal dimension to maximum. Besides, mineral mixtures gravity separation results are directly related to extent of oblongness of heavy particles, recovered in gravity separation process, and also to root-mean-square coefficient of their shape variation. The performed research showed that particles segregation in gravity concentration process plays not a lesser role, than hydrodynamics parameters, and demands further theoretical inquiry and experimental studies.

Jan 1, 2014

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 Yi-jun Cao, Jin-cai Ran, Guo-sheng Li, Jiong-tian Liu, Li-jun Deng, Shu-lei Li

A fly ash sample from a power station in Guangdong province has been characterized by size separation, X-ray diffraction, contact angle measurements and X-ray Fluorescence. The ash sample had a loss-on-ignition (LOI) (%) of 15.54% and a large proportion of the unburned carbon was distributed in the +74 µm and -20 µm fractions. Contact angle measurements suggested that the removal of unburned carbon from the fly ash using flotation would present some challenges. The effects of various operating variables on the removal rate of unburned carbon (RUC) (%) and (LOI) (%) were determined using a cyclonic-static micro bubble flotation column (FCSMC). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil (frother) dosage was 600 g/t, pulp density was 20%, superficial gas velocity was 1.4 cm/s and circulating pressure was 0.20Mpa. Column flotation tests indicated that the FCSMC method a viable and effective separation process for removing the unburned carbon from the fly ash. Under the optimized conditions, a clean ash with 2.13% LOI and 94.21% RUC was obtained.

Jan 1, 2014