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By B. McFadzean, J. Taguta

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a valuable and reliable means of determining solid surface properties such as wettability, it has seldom been applied in mineral processing research. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. The enthalpies of immersion were then related to the first-order flotation rate constant as determined by the microflotation technique. The same measurements were also made on sulphide minerals whose surfaces were modified to different degrees of hydrophobicity using different percentage coverages of amyl xanthate collector. The enthalpy of immersion technique was capable of distinguishing and ranking minerals according to their wettability. All mineral types and collector-treated minerals conformed to the same relationship that was found between the enthalpy of immersion and the flotation rate constant. This conformed, empirically, to a power law equation. As the enthalpy of immersion decreased, there were large increases in flotation response for very small changes in hydrophobicity. In addition, a critical enthalpy of immersion (CEI) was found, above which no flotation could occur. The scatter in the data points could be corrected for by adjusting the rate constant using the density of the minerals to produce a robust relationship between the rate constant and enthalpy of immersion. These results have shown that the enthalpy of immersion is able to indicate both the natural mineral hydrophobicity and the extent to which collectors can render a mineral hydrophobic. This technique has considerable potential to be used as a sensitive and accurate measure of mineral surface wettability in order to predict flotation performance.

Jan 1, 2018

By D. J. Zhao

The reduction and nitridation of preoxidized ilmenite pellets were investigated with the prospect of creating grain refiners containing titanium oxides and titanium nitride dispersoids. All the reduction and nitridation reactions were conducted in a furnace with a thermogravimetric analysis system under a H2-N2 gas mixture of 5 L/min. The ilmenite pellets were reduced at 1100°C for 4 hours under 80%H2-20%N2 gas mixture, and then respectively nitrided at 700°C, 800°C, 900°C and 1000°C for 12 hours under 10%H2-90%N2 gas mixture. The products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), and analyzed by Energy Dispersive Spectrometers (EDS) and Electron Probe Mapping Analysis (EPMA). Iron oxides were reduced into metallic iron, and oxides of titanium were found, but titanium nitride particles were not identified in the products under the prevailing conditions.

Jan 1, 2014

By K. W. Stöckelhuber, A. Wenger, H. J. Schulze

"An important elementary step of the flotation process is the forming, drainage and rupture of a thin intervening liquid film between bubble and mineral particle.After the encounter of the bubble with the solid surface a wetting film is formed. The initial thinning of this film is driven by the capillary pressure inside the bubble. When the film has reached a certain thickness rupture can take place.There are two possible mechanisms describing this process:-, Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive forces (electrostatic, van der Waals). -, Nucleation inside the film.Metastable wetting films on negatively charged, hydrophobic glass surfaces (gaseous phase methylated), or on hydrophilic, positively charged glass surfaces (with Al3+ ions), have been analysed by means of the kinetics of film thinning according to the Reynolds law. These experiments demonstrate that both mechanisms can be responsible for the rupture of a thin wetting film. In the case of hydrophobic surfaces the nucleation mechanism is preferred; in the case of opposite charged silica surface the capillary waves mechanism due to an attractive electrostatic double layer force between silica and air bubble takes place.Hereby the existence of a long range hydrophobic force. on a hydrophobic surface can be excluded. The apparent interaction can be explained by the presence of gas nuclei formed on heterogeneous surface sites. The results provide deeper insight into the mechanisms of wetting film stability, adhesion process in flotation and droplet coalescence."

Jan 1, 2003

By Gülay Bulut, Ferihan Göktepe

Pyrite is the most abundant and widespread sulphide mineral and its flotation has been investigated by many researchers. It is well known that, pyrite is floatable under acidic conditions and recovery drops with increase in alkalinity due to changes in solubility of iron hydroxides on the pyrite surface. Most of the works also revealed out that pyrite displays variable behaviour in flotation circuits. This behaviour mainly related with origin and mineralogical composition of ore, liberation size, electrochemical behavior of minerals constituting ore, the trace and minor element content of the mineral, texture, application variables belonging to flotation circuits. In this study, copper activation effect was examined on different origin of pyrites. The experiments were performed with five high grade samples of pyrite from the different mining districts of Turkey. The pyrite samples were different from each other with respect to either their physical or chemical properties; they were different physical appearances and contained different associated minerals. In the micro-flotation tests, 1x10-4 mole/L copper sulphate and 1x10-4 potassium ethyl xanthate were used as flotation reagents. First of all pyrite samples were floated using only xanthate at different pH. Results showed that best floatation results obtained at acidic pH range for all pyrite samples. When copper ions were used to activate, all pyrite samples floated at neutral and basic pH values, too but depending on the samples, recovery and pH ranges were slightly changed.

Jan 1, 2014

By J. Vilcáez

The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as the activity of the microbe used. We studied copper extraction yields obtained from chalcopyrite with three thermophiles, Acidianus brierleyi, Sulfolobus metallicus, and Metallosphaera sedula, under various pH and temperature conditions and with different initial amounts of ferric iron. The results indicated that the capacity of each thermophile strain to leach iron as Fe3+ differed, which affected the influence of pH, temperature, ORP, and microbial activity level on the yield of copper. Microbial activity can cause ORP to be close to the critical value (450 mV) at which copper extraction at 65 °C can be higher than that at 80°C. An initial pH of 1.5 retards the precipitation of jarosite, allowing temperatures as high as 80°C to result in copper extraction yields close to 100%. However, if a thermophile with a poor capacity to form Fe3+ is employed, 100% copper extractions can also be obtained at pH 2.5, because ORP is low as result of low amounts of Fe3+ in solution. Optimum temperatures for the growth of thermophiles did not always mean high copper extraction yields. Conversely, high biomass concentrations depending on the capacity of the thermophile strain to leach iron as Fe3+, can result in excess Fe3+ in solution, leading to the precipitation of large amounts of Fe3+ as jarosite. The bioleaching capacity of A. brierleyi was reduced or suppressed when insufficient initial Fe3+ was pro-vided to trigger the leaching reaction, whereas S. metallicus and M. sedula were less sensitive to the initial availability of Fe3+. This result confirmed that a direct enzymatic attack on the mineral surface could initiate the leaching reaction, but later ORP governed the leaching rate of chalcopyrite.

Jan 1, 2014

Dielectrophoresis is a separation technique that uses a non-uniform electrical field to separate particles on the basis of their permittivity. There are many areas of mineral processing that might benefit from the application of dielectrophoresis. These include: coarse removal of gangue, recovery of ultrafine particles, upgrading of flotation concentrates or simply as a laboratory analysis technique. In order to determine the potential value of dielectrophoresis to the mineral processing industry, the response of composite particles was investigated. The electrical properties of composites involve complex relationships between the shape, distribution and permittivity of the individual grains within the rock. The relationship between mineral composition and dielectrophoretic force was measured on single particles from two ore types. The results were used to populate a model that could predict the separation characteristics of the ore. The insights gained from this model separator allowed potential applications of the technology to be examined and their performance evaluated.

Sep 1, 2012

By Cagri Emer

In conventional mechanical flotation cells, when the size of particles exceed a particular value, that is of the order of 100 µm for metal sulphides, the recovery of particles decline rapidly. It appears that the turbulence in the agitated vessel is sufficiently intense to rupture the forces of attraction between the particles and the bubbles, so the large particles are flung off the bubbles in the turbulent field. It has recently been suggested, that a fluidized bed would be a very favorable environment in which to contact bubbles and the particles. In a fluidized bed, particles are supported by rising flow of fluid, which separates them from each other and allows them to move freely while remaining close together. In this novel method, bubbles injected into the fluidized bed are able to rise through it, colliding with hydrophobic particles, transporting them to the top of the column where they can form a froth layer that overflows into a launder. The flow in a fluidized bed is generally slow and nonturbulent, and preliminary experiments have shown, that it is possible to collect mineral particles as large as 1 mm and coal particles as large as 5.5 mm. If the upper particle size limit can be extended, there could be significant reductions in the overall energy consumption in concentrators. Calculations show for example that if the top size for flotation could be increased from 100 µm to 400 µm, there would be a reduction in grinding energy of the order of 40%. It is therefore, important to study the mechanism of coarse particle capture in fluidized beds. In this work, the factors governing the capture rate of particles, particularly the particle and bubble size, the fluidization velocity and the superficial gas velocity have been investigated, and the results will be presented.

Sep 1, 2012

By I. Yu. Rasskazov, A. V. Rasskazova, N. M. Litvinova, N. A. Lavrik, V. G. Kryukov

The possibility of the intensification of the gravity processing of complex iron-manganese ore, which contains the finely dispersed inclusions of gold and platinum is shown. Clear mineral fractions of precious metals were sorted out of the different types of ores (quartz-braunite and carbonate- magnetite ore, ferruginous quartzite, carbon-containing shale, breccia-limestone and dolomite breccia). Composition and structures of precious-metals particles was detailed. The industrial content of platinum and gold was found. Precious-metals mineralization is character for all types of ores. High content of platinum is indicated in the carbonate-magnetite (up to 11.3 mg/kg) and quartz –braunite (up to 10 mg/kg) types of ore. Gold is presented in the ferruginous quartzite (up to 1.29 mg/kg) according to the data of the reduced mineralogical analysis. The composition of native platinum depends on the type of the ores: 1) quartz-braunite type contains isoferroplatinum (Pt3Fe) with Cu, Rh, Ir, Ru; 2) carbonate-magnetite type contains isoferroplatinum with Cu, Sn, Ni, Rh, Ir, Os; 3) pyritic-carbon ore contains isoferroplatinum with Sn, Ni; 4) ferruginous quartzite contains isoferroplatinum without admixtures. The ultrasonic treatment of mineral aggregates (P = 41.5 Watt, I = 15 W/cm2) made possible the liberation of fine particles of precious metals. Smooth-shaped or crystalline mineral aggregates are effectively liberated after acoustic treatment. Their surface is freed from impurities. The aggregates with the complex form and structure, which consist of the numerous plates and the grains, are not effectively liberated from impurities. It is shown that the ultrasonic treatment of aggregates with the fine inclusions of precious metals contributes to the liberation of the particles of platinum and gold and intensification of the gravity processing of refractory ore. This approach contributes the increase of the raw-material base of precious metals.

Jan 1, 2018

By C. Eswaraiah

A drop weight tester (DWT) is designed and fabricated for the purpose of analyzing single particle impact breakage characteristics of different ores. The test results were evaluated through the breakage distributions of different size fractions at five different input energy levels. The breakage parameter, t10 (Narayanan, 1986) is used to represent the degree of size reduction, which is assumed to be representative of the breakage product size distribution obtained from single particle breakage. Representation of breakage distribution with this method consist one more breakage dependent parameter (a). To evaluate the impact breakage characteristic of different ores, a mathematical relationship was established to analyze the dependency of breakage parameters, t10 and a on specific input energy (EIS) or fracture energy (Tavares et al, 1998, Fandrich, 1998), specimen size (?) and Bond?s operating work index (WI0). Mathematical results developed gives adequate model for all ball mill modeling. It can be concluded that the drop weight test method is a useful and practical way of evaluating the impact strengths of various ores and results of which can be used in modeling mills.

Sep 1, 2012

By E. V. Mezentseva, S. M. Okunev

"In the article there is set forth a development experience of JSC LEBEDINSKY GOK Beneficiation Plant concerning the plan of increase in the production volumes of the iron ore concentrate with Fe content more than 69.5%. There are considered the issues regarding implementation of the updated process scheme of the concentrate beneficiation using fine screening operation, its industrial tests have shown an exploitability of this development direction. There are described the issues relating to the ceramic filters for dehydration of the additionally-beneficiated concentrate, there are given the production and process figures achieved during the exploitation. The methods of the research. In the paper there have been used the following scientific research methods: the methods of system analysis, mathematical statistics, classification, comparison, modelling, observance, experiment. INTRODUCTION JSC LEBEDINSKY GOK is the largest leading enterprise for iron ore beneficiation and the unique RF producer of the merchant hot briquetted sponge iron (HBI) highly demanded by the consumers. Raw materials for hot briquetted iron production are fluxed pellets produced from iron ore concentrate with Fe content more than 69.5% (additionally-beneficiated concentrate). Strategic program of the plant’s development foresees expansion of production of the highly demanded products that imposes a necessity of expending capacity of the enterprise and implementation in production of modern processes and equipment having low resource intensity and ensuring in addition a high efficiency. Construction of the third stage of the HBI Plant became one of directions for the strategic development of JSC LEBEDINSKY GOK implemented in 2017 that caused a demand in the production volumes and filtration of the iron ore concentrate with Fe content more than 69.5%. Purpose of the work – to develop and to provide a rationalization for efficiency of the production process and filtration of the iron ore concentrate with Fe content more than 69.5% ensuring increase of production volumes and its prime cost."

Jan 1, 2018

By Paul W. Cleary

"DEM application in mineral processing has for many years been heavily focused on simulating mills of various types. This method can be used to simulate many other aspects of mineral processing operations and can be used both to enhance understanding of the underlying flows and of issues such a breakage, wear, blockage, product degradation, segregation and mixing. The application of DEM to four important classes of non-comminution problems and equipment commonly found in or near mineral processing plants are described. These are:- Particle transport (examples include a conveyor belt and an inclined screw conveyor)- Sampling (assessment of sample bias for cross-stream samplers)- Separation (the efficiency of vibrating screens)- Storage and reclaim (discharge from a multi-port hopper and segregation in a splitter bin with asymmetric ingoing and outgoing conveyor belts, apron feeders and impact plate)."

Jan 1, 2003

By Christopher Tucker, Marcello Veiga

Social issues are increasingly recognized as significant inhibitors to mineral development projects. Increasingly social risk is being recognized as a key factor determining the success of a mineral investment. Groups opposed to a mine for social or political reasons often use environmental impacts, real or perceived, to prevent mine development. These risk factors depend largely on cultural perceptions of mining activities and must be understood as such in order to be appropriately managed. A first step to addressing social issues is inclusive, transparent and meaningful engagement of stakeholders. This process allows stakeholders to understand what the other parties value in order to collectively establish a common currency for development and the creation of mutual value. Expanding the scope of benefits and values a mine can bring is of increasing importance to mining companies who typically consult outside specialists remote from the mine site and late in the development timeline for this purpose. Training technical staff, engineers and geologists, who make initial and ongoing contact with local interests, in a holistic approach to mine development is crucial to successful and economic mineral development projects. Further extending this conversation to the general public, media governments and non-governmental organizations is a necessary step in developing a meaningful discourse on the benefit of mining activities.

Jan 1, 2014

By Q. Zhang

This paper, by studying the surface properties of pure dolomite minerals separated from representative marine sedimentary rare earth-bearing phosphate ores in Zhijin, Guizhou, aims to study the effect of different anions on the ? potential of dolomite. The research findings showed that the dolomite mineral had a point of zero charge (PZC) at pH 6.5, and the PZC shifted towards lower pH values with addition of anion SiO32- and PO43-. However, addition of anion CO32- and F- resulted in higher PZC values. Keywords: dolomite, ? potential, PZC, anion

Sep 1, 2012

By D. Z. Wei

Amine collectors with different structures and length of carbon-chain have been widely used in oxide minerals flotation. In this paper, we synthesized one kind of binary amine, N-dodecylethyl- enediamine, and studied its flotation performance. From the results, we can see N-dodecylethylenediamine which has excellent frothability, is a new type of chelating surfactants. And it also has fine catchability to quartz and hematite. The recoveries of quartz and hematite increase with the augment of N-dodecylethylenediamine concentration. When the dosage of collector reaches 100g/t, the recoveries of quartz and hematite achieve 95.30% and 87.89% respectively. Meanwhile, the influence of pH on the flotation recovery of hematite is studied and test results showed that, as pH increases, the flotation recovery rises until pH=9. And the recovery reaches its maximum in alkalescence. The collector has better flotation capability to quartz than to hematite. And the maximum recovery of quartz is gained in alkaline media, which reaches 97.87%. Finally, the flotation mechanism of N-dodecylethylenediamine is discussed through the measurement of infrared spectroscopy.

Jan 1, 2014

By Kirsten Corin, Margreth Tadie, Michael Nicol, Cyril O’Connor, Jenny Wiese

"The recovery of base metal sulfides has been emphasized in the study of the flotation of platinum group minerals (PGMs). However, in some ore bodies such as the Platreef of the Bushveld Complex, sulfide minerals do not make up the majority of the more significant PGM mineralization. It is therefore important to develop a fundamental understanding of how non-sulfide and sulfide PGMs respond respectively to the current reagents being used in the flotation of these minerals. The interactions between platinum and palladium sulfides and tellurides with the thiol collectors, ethyl xanthate and diethyl dithiophosphate, have been studied using the electrochemical techniques of mineral rest potential and voltammetry measurements. The differences in the interaction between the two types of minerals with these reagents were of key interest. Rest potential measurements indicated stronger electrochemical interactions of the minerals with ethyl xanthate than diethyl dithiophosphate. These measurements also indicated that there are different forms of oxidized collector present on the mineral surfaces after interaction with ethyl xanthates. Voltammetry measurements support these observations and suggest differences of adsorption on Pt and Pd sulfides than on Pt and Pd tellurides. Voltammetry also showed that there was minimal electrochemical interaction between the Pt and Pd minerals and diethyl dithiophosphate."

Jan 1, 2014

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

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

Jan 1, 2014

By Anatoly Usov

The detailed researches of a broad circle of problems connected to development of the electric pulse method destruction materials (EPD) of a various nature and area of use are executed. The electrical and power characteristics of process, physical fundamentals of selectivity of a breakdown and destruction are investigated, the device of electric pulse (EP) disaggregation and ?omminution of materials are developed, the technological efficiency of disintegration of industrial minerals estimated. Due to its technological advantages, the EPD could have a great potential in minerals mining and processing technologies. Low specific power and weight-and-size characteristics of EP installations based on the existing out-of-date electric equipment are at present the main reasons hindering the effective application of the method in mining and processing technologies. The main studies carried out in Russia in the field of electro technical equipment development for EP technology are presented. The pulse capacitors service life affects greatly the economic efficiency of the process because the capacitors cost accounts for a considerable, and in some cases, the most part of the operational costs. Determined and analyzed in the study are the ways which could significantly improve the specific characteristics of high voltage pulse generators (VPG), such as to use of high-frequency voltage transformation to develop a charger; to use pulse transformers (PT) with iron magnetic circuits made of materials characterized by high magnetic permeability, in pulse generating circuits; as well as to use special ways which could produce voltage pulses with a short front. The experiments have proved the possibility to adapt these technological solutions for EP devices, and a further strategy of the EP technologies development and application has been suggested on this base. Keywords: electric pulse disaggregation, electric pulse installation, charger battery, high voltage pulse generator

Sep 1, 2012

By Ghislain Bournival, Seher Ata, Yesenia Saavedra Moreno

"In froth flotation, frothers are commonly added to the pulp to modify the interfacial properties of bubbles. These properties may be modelled using commercial software packages. The volume of fluid (VOF) method was used to track the interface motion during the post-rupture oscillation of the newly formed bubble. The aim of this research was to provide an insight into the modelling of viscoelastic phenomena through the coalescence dynamics of two bubbles in solutions of various surface tensions using a three-dimensional computational study. Different surface tensions were used to simulate changes in methyl isobutyl carbinol (MIBC) concentration. The computational results were evaluated by comparing the oscillatory motion of the newly formed bubble for the different MIBC concentrations. For known MIBC concentrations, the deviations of the computational damping constants from the experiments were quantified, revealing possible deviations in the VOF surface tension model. In addition, the analysis provided insight into the flow patterns of the fluids and the effect of frother concentration on the velocity magnitude in the liquid and air phases. This analysis provided a further understanding of coalescence dynamic and post-rupture oscillation in froth flotation. Such a process is believed to affect the stability of particles at the interface due to the release of surface energy when the bubble surface is reduced.INTRODUCTIONIn froth flotation, bubble coalescence is an important phenomenon that is highly dependent on the interfacial properties of the liquid film between bubbles. It is known that the frother adsorption at the liquid-air interface changes the interfacial properties, resulting in an increase of surface elasticity and reduction of surface energy (Pugh, 2016). However, in a two-phase system, it is the frother type, concentration, frother molecule conformation at the interface and viscoelasticity properties that dictate film stability (Pugh, 2016). The viscoelasticity phenomena can be explained in terms of surface viscosity, which quantifies the energy dissipation at the interface and surface elasticity that represents the energy absorbed at the interface as result of bubble oscillation (Pugh, 2016). In the case of systems stabilized by nonionic frothers, it has been shown that surface forces alone do not account for film stability, but the viscoelasticity represents the ability to damp external disturbances in the thin film separating the bubbles and prevent coalescence (Santini et al., 2007)."

Jan 1, 2018

By Andrey Kozlov

The results of mineralogical?technological studies of PGM mineralization in zoned mafic?ultramafic complexes of the Ural?Alaskan type are given. The most important technological specificity of PGM mineralization hosted in dunites is its occurrence only in the form of free mineral species with predominance of Fe?Pt alloys (ferrous platinum, isoferroplatinum, and tetraferroplatinum). Technological properties, grain size, and good opening of PGM ore in grain size class +80 µm make it possible to concentrate ore using gravity methods with stadial comminution and between cycle separation of relatively large grains and nuggets into high-grade concentrates at the early stage of disintegration. Keywords: platiniferous dunites, PGM mineralization, mineralogical?technological studies and processibility research, recovery technology, gravity methods

Sep 1, 2012

By Bern Klein, Givemore Sakuhuni

Flotation is the dominant base metal extraction technique and it requires ore to be ground below the liberation size for effective recovery due to its dependence on mineral surface properties. For a poly-metallic ore, differential hardness of constituent minerals leads to over grinding of softer minerals before the harder minerals are fully liberated, which makes selection of a target grind size complex, and the complexity increases when treating leaner ores. Flotation recovery deteriorates above 100 and below 10 microns causing significant loses of valuable minerals in most flotation circuits. Although enhanced gravity concentration is known to be effective at recovering particles above 100 microns, which are difficult to hydro-dynamically transport, exploiting differential specific gravity for base metal separation was not an option in the past. This was partly due to the absence of high mass yield gravity techniques. The advent of continuous gravity concentrators with flexible mass yields, in the past two decades, has necessitated investigation of possible base metal applications. The Knelson CVD, one of the continuous discharge centrifugal concentrators, has an established application niche for sulphides associated with gold. However, its base metal applications have never been rigorously tested. Considering the dependence of flotation recovery on particle size, continuous discharge centrifugal concentration can be integrated in flotation circuits to capture flotation non-recoverable coarse particles. This paper explores how particle size, liberation and mineral hardness influence application of continuous centrifugal technology to regulate galena deportment in a polymetallic base metal plant. The results show that particle size affects galena recovery more than liberation. In view of these results, the CVD can be integrated in the primary grinding circuit to pre-concentrate the heavy sulphides at a coarser grind size with potential grinding energy savings.

Jan 1, 2014