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1
Almaghrabi, Mohammednoor Naher. "Flotation of coarse particles in a modified flotation column cell." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240560.
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2
Yianatos, Juan B. "Column flotation froths." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28385.
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A fundamental study on the behaviour of flotation column froths is presented. Three main aspects were considered: hydrodynamic, cleaning (rejection of hydraulically entrained particles) and selectivity (separation between particles of different hydrophobicity).<br>Column froth hydrodynamics were studied in a two phase (gas-liquid) system. A model to estimate gas holdup from electrical conductivity was developed. Bubble coalescence was evaluated by means of local measurement of gas holdup and bubble size distribution, consequently bubble surface loss along the froth was determined. Mathematical models are developed to describe liquid entrainment and drainage throughout the froth.<br>The cleaning action was evaluated by monitoring feed water penetration at different levels in the froth, which corresponds to the boundary (worst) condition of fine particles entrainment. Laboratory and plant-scale tracer tests showed that the main cleaning action occurs close to the froth/collection zone interface.<br>Local grade and solids percentage along column froths, together with a mathematical model describing mass transport, was used to analyse mineral selectivity in column froths. Quantification of mineral loss from the froth, due to detachment and cleaning, is presented.<br>A generalized model to describe particle settling against a bubble swarm was developed. Entrainment and segregation of particles in the wake of bubbles gives insight into the characteristics of the pulp entering the froth in a flotation column.
3
Lewis, Jonathan Stretton. "A hydrodynamic investigation of platinum flotation in a pilot flotation plant." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/6082.
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Deglon, David Alan. "A hydrodynamic investigation of fine particle flotation in a batch flotation cell." Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/5375.
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5
Pazhianur, Rajesh R. "Hydrophobic Forces in Flotation." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28066.
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An atomic force microscope (AFM) has been used to conduct force measurements to better understand the role of hydrophobic forces in flotation. The force measurements were conducted between a flat mineral substrate and a hydrophobic glass sphere in aqueous solutions. It is assumed that the hydrophobic glass sphere may simulate the behavior of air bubbles during flotation. The results may provide information relevant to the bubble-particle interactions occurring during flotation. The glass sphere was hydrophobized by octadecyltrichlorosilane so that its water contact angle was 109 degrees. The mineral systems studied include covellite (CuS), sphalerite (ZnS) and hornblende (Ca₂(Mg, Fe)₅(Si₈O₂₂)(OH,F)₂). The collector used for all the mineral systems studied was potassium ethyl xanthate (KEX).
For the covellite-xanthate system, a biopotentiostat was used in conjunction with the AFM to control the potential of the mineral surface during force measurements. This was necessary since the adsorption of xanthate is strongly dependent on the electrochemical potential (Eₕ) across the solid/liquid interface. The results show the presence of strong hydrophobic forces not accounted for by the DLVO (named after Derjaguin, Landau, Verwey and Overbeek) theory. Furthermore, the potential at which the strongest hydrophobic force was measured corresponds to the potential where the flotation recovery of covellite reaches a maximum, indicating a close relationship between the two.
Direct force measurements were also conducted to study the mechanism of copper-activation of sphalerite. The force measurements conducted with unactivated sphalerite in 10⁻³ M KEX solutions did not show the presence of hydrophobic force while the results obtained with copper-activated sphalerite at pH 9.2 and 4.6 showed strong hydrophobic forces. However, at pH 6.8, no hydrophobic forces were observed, which explains why the flotation of sphalerite is depressed in the neutral pH regime.
Direct force measurements were also conducted using hornblende in xanthate solutions to study the mechanism of inadvertent activation and flotation of rock minerals. The results show the presence of long-range hydrophobic forces when hornblende was activated by heavy metal cations such as Cu²⁺ and Ni²⁺ ions. The strong hydrophobic forces were observed at pHs above the precipitation pH of the activating cation. These results were confirmed by the XPS analysis of the activated hornblende samples.
Force measurements were conducted between silanated silica surfaces to explore the relationship between hydrophobicity, advancing contact angle (CA), and the magnitude (K) of hydrophobic force. In general, K increases as Contact Angle increases and does so abruptly at Contact Angle=90°. At the same time, the acid-base component of the surface free energy decreases with increasing CA and K. At CA>90°, GammaS<sup>AB</sup> approaches zero.
Based on the results obtained in the present work a mathematical model for the origin of the hydrophobic force has been developed. It is based on the premise that hydrophobic force originates from the attraction between large dipoles on two opposing surfaces. The model has been used successfully to fit the measured hydrophobic forces using dipole moment as the only adjustable parameter. However, the hydrophobic forces measured at CA>90° cannot be fitted to the model, indicating that there may be an additional mechanism, possibly cavitation, contributing to the appearance of the long-range hydrophobic force.<br>Ph. D.
6
Ikumapayi, Fatai Kolawole. "Flotation chemistry of complex sulphide ores : recycling of process water and flotation selectivity." Licentiate thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26634.
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Recycling of flotation effluents through the ore processing plant is one of the ways of reducing both plant-operating costs and industrial impact onto the local ecosystem. Such waters named acid mine drainage (AMD), if discharged from sulphide flotation are gypsum (CaSO4.H2O) saturated and have a high salinity (on the order of 1000 ppm). As minor species, they commonly contain reduced sulphur compounds (RSC) (sulfoxyanions with sulphur in the oxidation state below (VI) such as SO32-, S2O32-, S2O52-, and S4O62-), cations of ferrous and non-ferrous metals, frothing molecules, residual chemical reagents and products of their degradation. Tailing ponds also host communities of chemolithotrophic and heterotrophic microorganisms which play an important role in dictating their aqueous and solid phase chemical speciation. Consequently, the key step towards developing scientific approaches of recycling of the tailing waters is elucidation of how, in what extent, and why the tailing water components, taken singly or jointly influence flotation of sulphides. In this work, the influence of main process water components of calcium and sulphate on chalcopyrite, galena, sphalerite and pyrite flotation has been investigated through Hallimond flotation, zeta-potential and diffuse reflectance FTIR spectroscopy measurements using pure mineral samples as well as bench scale flotation tests using complex sulphide ore. The significance of process water species in flotation has been assessed using deionised water, process water and simulated water containing calcium and sulphate ions in experiments. In addition, the effect of temperature in bench scale flotation tests has also been examined. Hallimond flotation indicated depression of chalcopyrite, galena and sphalerite and activation of pyrite in the presence of calcium and sulphate ions with potassium amyl xanthate as collector. Calcium ions have significant influence on zeta-potential characteristics and xanthate adsorption behaviour of chalcopyrite, galena, sphalerite and pyrite compared to sulphate ions. FTIR studies revealed the presence of surface oxidised sulfoxy species and surface iron and calcium carbonates on chalcopyrite in the presence of process water and water containing calcium ions, surface oxidised sulfoxy and carbonate species on galena in the presence of deionised water, process water and water containing calcium and sulphate ions, hydrated surface oxidised species and surface iron and calcium carbonates on pyrite in the presence of process water and water containing calcium ions all at pH 10.5 in which the surface species influenced xanthate adsorption. The presence of surface oxidised sulfoxy and carbonate species on sphalerite were also revealed at pH 11.5 in the presence of deionised water, process water and water containing calcium and sulphate ions in which surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that chalcopyrite recovery is better in process water than tap water and general depression of chalcopyrite at temperatures lower than 22oC in either tap water or process water, activation of chalcopyrite at all temperatures in process water and depression of chalcopyrite when tap water containing calcium and sulphate ions was used at 22oC. It also showed that galena recovery is better in tap water than process water and depression of galena at temperatures lower than 22oC in either tap water or process water. It also showed that sphalerite recovery is better in process water than in tap water better recovery of sphalerite at temperatures lower than 22oC in either tap water or process water.<br>Godkänd; 2010; 20101114 (fatiku); LICENTIATSEMINARIUM Ämnesområde: Mineralteknik/Mineral Processing Examinator: Professor Kota Hanumantha Rao, Luleå tekniska universitet Diskutant: PhD Jaakko Leppinen, Outotec, Non-Ferrous Solutions, Espoo, Finland Tid: Fredag den 10 december 2010 kl 10.00 Plats: F531 Bergrum, Luleå tekniska universitet
7
Rowley, Dylan Mark. "Investigation of Flash Flotation Technology Utilizing Centrifugal Forces and Novel Sparging Methods." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64781.
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A new processing technique, centrifugal flotation, has been developed in recent research projects to overcome the large residence times and fine particle limitations of traditional flotation technologies. The major innovation in the area of centrifugal flotation is the Air Sparged Hydrocyclone (ASH), which has proven capabilities in achieving quality products at specific capacities greater than traditional flotation methods. However, the ASH technology ultimately suffers from sparger plugging problems. Therefore, three unique flotation cyclone designs were developed utilizing external sparging systems and control features to float fine coal. The objective of each design was to create a system that mimics the behavior of the ASH technology, while providing advantages in bubble generation and retention time requirements.
The evaluation of the three designs provided evidence towards the development of an efficient centrifugal flotation technique. Evaluation of a flotation cyclone with an external Cavitation Tube yielded a single-stage product with an ash content of 4.41% and a 45% recovery rate in a retention time of 0.66 seconds. However, the system required 16 minutes to meet comparable flotation yields and recoveries. The third design achieved a multiple-stage product of 11.32% ash at a 55% recovery in 20 minutes. These two designs provided low yield, high grade products, but rejected a high percentage of hydrophobic particles and required high retention times to meet typical flotation standards. In addition, these designs suffered by requiring high frother concentrations and recovery could not be increased through increased aeration due to design limitations.<br>Master of Science
8
Schimmoller, Brian Keith. "A bubble-particle interaction model for flotation combining hydrodynamic and surface forces." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09192009-040332/.
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9
Musara, Washington Tendai. "Coal flotation : statistical comparison of a pilot flotation column and a batch mechanical cell." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29693.
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The effect of manipulated variables on the flotation response of run-of-mine coal supplied by Bullmoose Coal Mine (North East British Columbia) was studied in a pilot flotation column and a batch mechanical cell using experimental designs of the factorial class after the coal had been stage crushed and ground to about 96 percent minus 600 µm, the feed size to the flotation circuit at Bullmoose Coal Mine. The objective was to optimise statistically the two flotation units usings (1) screening designs, (2) the steepest ascent technique, and (3) central composite designs, and to compare cell performance. The efficiency index was employed as the primary optimisation criterion. The two cells yielded comparable efficiency indices, but the product ash content of clean coal from the flotation column was consistently lower.
Evaluation of the efficiency indices of individual size fractions was also carried out at the optimum conditions of each cell. The approach taken was to separate the feed into individual size fractions, retain the fractions separately, and float them separately. The flotation column yielded higher efficiency indices and lower product ash content when a feed with 15 percent solids was floated. Results obtained by floating individual size fractions at 2 percent solids indicated that it is difficult to float sizes above 300 µm in both cells at such a low pulp density. Below 300 µm, the performance of both cells was comparable.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
10
Changunda, K. "The effect of energy input on flotation kinetics in an oscillating grid flotation cell." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/14416.
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Energy is known to play an important role in particle-bubble contacting in flotation. This thesis investigates the effect of energy input (or agitation) on the flotation kinetics of quartz in a novel oscillating grid flotation cell. The effects of bubble size and particle size have been recognized as important variables affecting particle-bubble contacting in turbulent systems and are investigated in this thesis. The research work done in this thesis is a continuation of the work done by the Centre for Minerals Research by Deglon (1998) who investigated the effects of energy in a batch mechanical flotation cell. However, this system has a very complex hydrodynamic environment, resulting from the large disparities in turbulence intensity. Previously Breytenbach (1995) had constructed a hybrid flotation column cell, which was essentially a column flotation cell that could be modified into a Jameson cell or a mechanically agitated column cell. He used this to compare particle collection efficiency in these different particle-bubble contacting environments. The third phase of the work was the oscillating baffle column (OBC), a novel flotation column that attains agitation by oscillating a set of orifice baffles through the slurry, thereby producing a more uniform shear rate distribution than would be obtained in an impeller driven system (Anderson, 2008). The OBC unfortunately has significant oscillatory flow and has high shear rates, which often result in detachment effects becoming appreciable. Oscillating grids generate near ideal hydrodynamic environments, characterised by turbulence that is relatively homogeneous and isotropic. The oscillating grid flotation cell used in this study was based on the oscillatory multi-grid mixer used by Bache and Rasool (2001). The oscillatory multi-grid mixer was purchased from these authors and retrofitted to produce the oscillating grid flotation cell. The novel oscillating grid cell consists of a 10 litre tank agitated by 19 grids with a mesh size of 8 mm and grid spacing of 18 mm. The grids were oscillated at a fixed amplitude, equal to the grid spacing, and over a range of frequencies, using a variable speed drive. Frother was added at 100 ppm to be consistent with the work of Deglon (2002) and Ahmed and Jameson (1985). A low gas flow-rate (100 ml/min) and solids concentration were specifically chosen in order that there was minimal influence on the structure of turbulence in the oscillating grid cell, as Bache and Rasool (2001) took measurements in water. Flotation tests were performed on methylated quartz particles (P80 = 100 μm) over a range of power intensities (0.015–0.60 W/kg) and using three different bubble sizes, generated by sintered glass discs (0.13, 0.24 and 0.82 mm). The flotation rate constant was found to increase approximately linearly with increasing particle size for all three bubble sizes. This was due to the increased probability of collision for larger particles and is well established in the flotation literature. A number of researchers have found that the flotation rate constant for quartz particles increases almost linearly with particle size, at low power intensities. An inverse power relationship was observed between bubble size and flotation rate constant for all fine, middling and coarse particle size ranges. This inverse power relationship was due to the increased probability of collision for smaller bubbles and is also well established in the flotation literature. More significantly, the flotation rate constant was found to increase almost linearly with increasing power intensity for all particle and bubble sizes used in this study. The majority of theoretical and experimental studies have found energy input to have less of an effect than the proportional/linear dependence observed in this study. In addition, the increase in the flotation rate constant with increasing power intensity was observed to depend on particle size, but to be less dependent on bubble size. These findings suggest that energy input and bubble size may respectively play more and less of a role in promoting particle-bubble contacting in turbulent environments than was noted in the flotation literature. However, a recent study by Newell and Grano (2006) done using a stirred tank also noted this linear dependence. Given the findings of this thesis, it is strongly recommended that further work be done to investigate the OGC at higher energy intensities (~3W/kg) and to scale it up so that it can be more comparable to the widely used mechanical flotation cells. The homogeneous and nearly isotropic turbulence generated by the OGC also makes it an ideal environment to characterize floatability for different ores.
11
Mankosa, Michael James. "Scale-up of column flotation." Diss., This resource online, 1990. https://scholar.lib.vt.edu/ETD-db/ETD-catalog/manage_bound.
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Lascelles, Dominique. "Quantification of adsorbed flotation reagents." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80118.
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Collector interaction with mineral surfaces has long been studied. Little work has been done, however, on directly quantifying reagent adsorption, certainly under industrial process conditions. The use of a novel surface analysis technique, Headspace Analysis Gas-phase Infrared Spectroscopy (HAGIS), is suggested for quantification of adsorbed reagents in mineral processing.<br>As a first exercise, a test system of xanthate adsorption onto lead sulphide minerals was studied. A survey of possible calibration standards (pure xanthate, a synthetic lead-xanthate, galena (PbS) and a lead sulphide ore conditioned with xanthate) resulted in linear curves for all four cases. The quantification of isopropyl xanthate adsorption onto batch flotation products (concentrate and tail) was used to determine that ore standards gave the most accurate results.<br>The technique was also tested for quantification of adsorbed amines. Two collectors, dodecylamine and diphenylguanidine, and a depressant, triethylenetetramine, were studied. A common calibration curve was prepared using diphenylguanidine adsorbed on Inco matte. Results show that the HAGIS technique can easily be used to quantify adsorbed amines.<br>It is concluded that the HAGIS technique is a powerful new tool for the quantitative determination of adsorbed reagents. The xanthate study showed the use of ores as standards produces the best calibration. The amine study introduced the possibility of analyzing reagent mixtures.
13
Xu, Manqiu. "Sparger study in flotation columns." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64062.
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Hanumanth, G. S. "Froth flotation of china clay." Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637217.
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An experimental and theoretical study of froth flotation separation of kaolinite from other associated minerals of china clay is presented herein. A new laboratory flotation equipment has been designed and built for the above study. Its novel features are discussed. Effects of physico-chemical variables such as pH, initial solid concentration of feed, froth height and air flowrate are studied by systematically carrying out series of semi-batch kinetic experiments. pH is shown to influence both recovery and grade of the product. The effects of pH are interpreted in terms of particle/particle interactions leading to flocculation which is demonstrated to be an essential prerequisite for flotation of small particles approaching colloidal size range with the typically 1-2mm bubbles produced in the cell. Regions in a flotation cell where hydrodynamic conditions permit flocculation are identified by an analysis of pulp flow based on a distributed shear rate model. The effects of initial solid concentration on recovery and grade are interpreted in terms of floc/bubble collision frequency. Influence of floc breakup and solid drainage on pulp phase and recovery kinetics, and product grade is discussed. Pulp phase kinetics are analysed on the basis of rate-distributed species model. The selective nature of froth drainage is demonstrated by a series of kinetic experiments using different froth heights. Air flowrate can influence both pulp phase kinetics and froth drainage. These effects are studied independently by conducting two sets of experiments - one with a negligible depth of froth and the other with a deep froth. An analysis of flow and rupture forces in the froth leads to identification of two distinct zones where different floc breakup and drainage mechanisms exist. On this basis a three-phase model, consisting of a mixed pulp phase and two mixed froth phases, is developed and used to predict froth effects on flotation kinetics and selectivity.
15
Hartmann, R. (Robert). "Flotation using cellulose-based chemicals." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526219806.
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Abstract Flotation is a well-known and widely used technique for the separation of particles smaller than 250 µm, but efficient performance requires the use of various synthetic chemicals which can potentially damage the health of humans and animals and pollute the environment. Consequently, their replacement through a more environment-friendly and sustainable alternative has been demanded. One promising candidate is cellulose, which is an abundant natural polymer that is environment-friendly and can be treated chemically and physically to yield tailored properties and thus a potential for use in processes such as flotation. This work focuses on the use of cellulose-based reagents in flotation processes to replace the often harmful conventional reagents derived from mineral oil, plant oils or animal fats. The physico-chemical properties of cellulose differ from those of conventional reagents, leading to differences in performance during flotation. In particular, the chemical and morphological heterogeneity of cellulose affects its properties and thus its interaction with minerals and water. Consequently, its use requires the study of the fundamentals of flotation and their application including the physico-chemical heterogeneity of cellulose to determine the optimum conditions and enable efficient performance. This work focuses on the determination of the thermodynamic surface energetics of solid particles and changes in this after reagent adsorption, using the inverse gas chromatography technique in a dry atmosphere. Furthermore, interactions between cellulose and minerals immersed in water are investigated using the DLVO theory, the interaction forces between cellulose and the minerals being derived and correlated with flotability. The importance of free surface charges is then considered by investigating the electric surface potential of cellulose-coated minerals in connection with particle-bubble attachment efficiency. At the same time, conventional amphiphilic reagents are used and its performances are related to cellulose-based reagents<br>Tiivistelmä Vaahdotus on kaivannaisteollisuudessa laajasti käytössä oleva prosessi, jonka avulla saadaan erotettua tehokkaasti pieniä, alle 250 µm kokoisia partikkeleita. Vaahdotuksen apuaineena käytetään erilaisia synteettisiä kemikaaleja, jotka voivat aiheuttaa harmia ympäristölle. Siksi niiden korvaaminen ympäristöystävällisemmillä vaihtoehdoilla on tärkeää. Yksi lupaava vaihtoehto korvaavaksi materiaaliksi on selluloosa. Selluloosa on uusiutuva ja ympäristöystävällinen luonnonpolymeeri, josta voidaan valmistaa kemiallisesti ja fysikaalisesti käsittelemällä erilaisia biokemikaaleja. Näitä voidaan soveltaa erilaisissa prosesseissa, myös vaahdotuksessa. Tässä työssä keskitytään selluloosapohjaisten kemikaalien käyttöön vaahdotuksessa tavanomaisten, usein haitallisten synteettisten kemikaalien korvaamiseksi. Selluloosan fysikaaliskemialliset ominaisuudet eroavat synteettisten vaahdotuskemikaalien ominaisuuksista, mikä vaikuttaa niiden vuorovaikutukseen mineraalien ja veden kanssa. Erityisesti selluloosan kemiallinen ja morfologinen heterogeenisuus on keskeinen tekijä. Selluloosan hyödyntäminen tulevaisuuden vaahdotuskemikaalina edellyttää selluloosan ja mineraalien vuorovaikutuksen syvällistä ymmärtämistä. Tässä työssä tutkitaan selluloosan ja mineraalien vuorovaikutusta sekä IGC-menetelmän avulla, että DLVO-teorian että pintavarausmittausten avulla. Lisäksi tutkitaan selluloosan ja mineraalien vuorovaikutusvoimien yhteyttä vaahdotusprosessin onnistumiseen ja saavutettuja tuloksia verrataan kaupallisten reagenssien toimintaan
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Craynon, John Raymond. "The collectorless flotation of sphalerite." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45645.
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<p>The flotation of sphalerite has been demonstrated without the use
of collectors. The effect of redox potential, pH, and copper-activation
have been investigated in tests using samples of pure mineral. It has
been found that in general, collectorless flotation of sphalerite can be
accomplished at potentials greater than -200 mV, SHE, and is more
readily carried out in acidic solutions. It has also been shown that
although copper-activation was necessary to achieve flotation recoveries
above 35%, an excessive addition of cupric ions may result in a decrease
in floatability.</p>
<p>
Batch flotation experiments conducted using Elmwood Mine sphalerite
ore have shown that in addition to copper-activation, the addition of
sodium sulfide was required to obtain high grades and recoveries. If
the ratio of the addition of these reagents is maintained such that the
atomic ratio of cupric ions to sulfide ions is 0.31, good flotation is
observed over a range of reagent dosages.</p>
<p>
X-ray photoelectron spectroscopy (XPS) was conducted on pure
mineral samples after microflotation testing. Based on the sulfur
species identified on highly flotable samples, possible mechanisms for
collectorless flotation of sphalerite have been suggested. These
include: i) elemental sulfur formed under oxidizing conditions is
responsible for collectorless flotation; ii) polysulfides or metal-deficient sulfides formed as a result of mineral oxidation are
responsible for collectorless flotation; and iii) removal of HS- ions,
which may render the surface hydrophilic, under oxidizing conditions.
The third mechanism is based on the assumption that clean, unoxidized
sphalerite surfaces are naturally hydrophobic. Evidence has been
presented to suggest that the first mechanism may be responsible for
collectorless flotation in acidic solutions, while the second mechanism
may be of greater importance in nearly neutral or basic solutions where
elemental sulfur is thermodynamically less stable.</p><br>Master of Science
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Brady, Michael Richard. "Multiphase Hydrodynamics in Flotation Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28860.
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Flotation is a complex, multiphase process used to separate minerals. Four problems central to the fundamentals of the flotation process were studied. A multiphase grid turbulence experiment was conducted to verify particle collision models. The slip velocities of solid particles and bubbles were measured using Digital Particle Image Velocimetry (DPIV). The experimental results were compared with the predictions from empirical and theoretical collision models.
Time-resolved DPIV was used to measure the turbulent velocity field in a Rushton turbine around the impeller region. The turbulence quantities were found by removing the periodic component from the blade passing, which is a dominant part of the measured velocities near the impeller. We provide evidence that larger, biased dissipation and turbulent kinetic energy values are estimated in the vicinity of the impeller due to the periodic component of the blade passage. The flow was found to be anisotropic close to the impeller. Vortex detection revealed that the tip vortices travel in a nearly radial direction from the impeller for small Reynolds numbers and with a wider distribution for higher Reynolds numbers.
The rise of a buoyant bubble and its interaction with a free liquid surface was experimentally investigated using Time-Resolved Digital Particle Image Velocimetry as a function of bubble size, and surfactant concentration of the fluid medium. It is shown that the presence of a surfactant significantly affected the characteristics of the velocity field during the rise and interaction with the free surface. This difference is attributed to the adsorption coverage of the surfactant at the bubble-fluid interface. Wake profiles were compared. The presence of large vortices were observed and found to play a significant role.
Finally, Numerical and experimental results of stable and unstable foams are presented by comparing liquid fractions and bubble sizes. There was good agreement between the experiments and numerical modeling in free drainage and forced drainage experiments. In addition, foam coarsening was measured and characterized experimentally.
Each of the problems investigated have added to the understanding in the underlying physics of the flotation process and can lead to more accurate modeling. The ultimate goal of this work is to contribute to the design of more effective and efficient flotation machines.<br>Ph. D.
18
Hu, Weimeng. "Flotation circuit optimisation and design." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24805.
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Froth flotation is a widely used and versatile mineral processing method for concentrating metal ores. A finely ground ore feed is processed through a flotation circuit consisting of interlinked cells where mineral particles are separated from waste material by using their differences in surface properties. The layout of the circuit has been found to greatly affect the overall flotation performance. While industrial flotation circuit design has in the past relied on experience, due to the complex nature of the process, only small scale circuit optimisations using simple flotation models were reported in literature. This work proposes a new system capable of automatic generation of optimal circuit designs for any given feed. The system combines a circuit simulator containing detailed froth-phase flotation models with a robust genetic algorithm to search through possible layouts and to produce the global optimal result. An empirical model to predict the pulp phase flotation rate constant was developed, which was used together with physics-based models describing the froth recovery and entrainment factor to simulate the flotation process. Three feed models with different complexities were also developed. Comparable flotation performance was observed between a modelled 10-cell rougher circuit and the experimental results from Northparkes copper concentration plant. Through the genetic algorithm, optimal layouts were obtained for circuits consisted of 3 to 10 cells. Layouts containing only rougher cells were able to recover a maximum amount of mineral and were found optimal for smaller circuits, whilst inclusion of cleaner cells in the optimal layouts was found more beneficial for larger circuits. This circuit modelling and optimisation system was used to study the sensitivity of flotation performance and optimal layouts to variations in feed particle size and grade. The results showed strong correlations between the variables and froth phase behaviours which determined the concentrate recovery and grade, the optimal layouts were, however, robust and relatively resilient to the changes in feed conditions.
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Mills, Peter John Temple. "Modelling of the mixing characteristics and flotation kinetics of the collection zone in flotation columns." Doctoral thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/21987.
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Bibliography: pages 181-189.<br>Column flotation has gained worldwide acceptance in the minerals processing industry in the past decade. This has been due the operating characteristics of flotation columns which can produce improved grades and recoveries over conventional cells. Added to this, flotation columns are both simple to operate and generally less expensive than the equivalent requirement of conventional cells. Flotation columns are able to produce improved results due to a deep washed froth phase and a quiescent pulp phase in which the pulp interacts countercurrently with the air bubbles. Models describing the behaviour of particles in both of these phases have been developed over the past decade. The present study focusses specifically on the pulp phase and models presently used to describe the pulp zone hydrodynamics and kinetics are evaluated and improved. The hydrodynamics of the pulp or collection zone are evaluated using data obtained from three residence time distribution (RTD) studies performed on two pilot columns (5.4cm and 5.8cm diameter) and an industrial column (120cm diameter). Sodium chloride liquid tracers as well as radioactively labelled solid and liquid tracers were used in the RTD studies. In the study performed on a pilot column using the salt tracer the degree of mixing was found to increase both with increasing gas rate at constant bubble size and decreasing bubble size at a constant gas rate. This increase in mixing is attributed to the increase in the number of bubble$ and the subsequent increase in the tracer-bubble interactions. By extrapolating this result to industrial columns it is clear that flotation columns, which have smaller and substantially more bubbles, will be more mixed than bubble columns.
20
Massey, Wesley Thomas. "Investigating the effect of energy dissipation on flotation kinetics in an oscillating grid flotation cell." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/18475.
Full textAbstract:
This thesis investigates the effect of energy dissipation on the flotation kinetics of quartz in an oscillating grid flotation cell. Oscillating grids exhibit relatively isotropic and homogeneous turbulence, which cannot be achieved in standard impeller agitated flotation cells. Due to this they provide a potentially ideal environment in which to investigate the effects of energy dissipation on flotation kinetics. Previous work in an oscillating grid flotation cell was limited to energy dissipations of up to 0.6 kW/m³, which is low when compared to 0.6 - 3 kW/m³ commonly used in both flotation literature and industry. The current work uses a new oscillating grid cell which can operate at energy dissipations of up to 5 kW/m³. Quartz (sub 100 μm) has been floated in the new cell at energy dissipations ranging from 0.5 - 5 kW/m³ and using three discrete bubble sizes (0.13 mm, 0.24 mm and 0.82 mm). Characterisation experiments show that the new cell operates in a similar manner to the oscillating grid cell used by Changunda et al. (2008), and produces repeatable results. The effect of changing bubble and particle size on flotation kinetics is in agreement with literature findings, indicating that as a flotation device the oscillating grid cell is operating as expected.
21
Edwards, Robert Paul. "Expert system control of a flotation circuit." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29600.
Full textAbstract:
Expert systems technology is a discipline of artificial intelligence that has recently emerged from the research environment and is currently making significant inroads into business and industry. The proponents of expert systems make many attractive claims. Two of the claims are that expert systems can capture the knowledge of the experts and can be programmed by non-programmers. To date, most uses of this technology in the process industry are in off-line applications, that is, applications that are not directly tied to operating environments. Moreover, those that are used in on-line environments are used as advisors and only suggest changes, human operators are required to close-the-loop to the process. This technology should be applicable to operating environments and should the claims of its proponents be valid, then it should also be better than existing tools currently in use. In an operating environment it could use the knowledge of experienced operators as an intelligent controller and apply it directly to a process without the intervention of human operators.
In this thesis the prospect of using an expert system as an intelligent controller is investigated. The thesis offers background to expert systems, how expert systems are related to artificial intelligence and what the generic components of an expert system are. As a test of the technology an expert system was developed as an intelligent controller in a mineral processing application. The prototype expert system was developed as a supervisory controller in the copper flotation circuit in the concentrator at Brenda Mines Ltd..
The expert system operated on-line and controlled the process in real-time. It read sensor data and using the operating experience of Brenda's flotation
operators, manipulated regulatory controller setpoints as deemed necessary. The expert system was able to manipulate directly reagent flowrates and process air flowrates. Also, it suggested changes to other process variables not directly under its control. The manipulated variables were collector and frother reagent flowrates, the air flowrate to a bank of scavenger flotation cells and the air flowrate to four flotation columns. The operators were allowed to, and sometimes required to, intervene in instances of large process upsets. Results of a month long trial period in the flotation circuit indicated the success of the application. The expert system was indeed able to maintain metallurgical performance at a level approximating that of the operating experts, however, no direct comparison between the performance of the circuit under expert system control, versus performance under operator control, was possible. A rudimentary comparison was made between the circuit's performance under expert system control and its historic performance. The results were favourable. A less tangible measure, though as important, were the attitudes of the operators toward the system. Almost unanimously, the operators felt the system eased the task of circuit operation and was responsible for better circuit performance.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
22
Harbort, Gregory J. "A study of the hydrodynamics, bubble-particle interaction and flotation within the high intensity zone of a flotation machine and its implication for flotation machine design /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19448.pdf.
Full text
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Harris, T. A. "The development of a flotation simulation methodology towards an optimisation study of UG2 platinum flotation circuits." Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5322.
Full textAbstract:
Bibliography: p. [251]-266.<br>The design of new flotation plants is still based substantially on experience obtained from prior plant designs. Design criteria are typically based on rule of thumb procedures that often prove to be highly ineffective. The development of appropriate models of the flotation process is a means of addressing these problems so that flotation plant simulations can be performed to identify the true potential of existing plants as well as in the design of new flotation plants. This thesis addresses the complex issue of developing a robust methodology for use in flotation circuit modelling and simulation, based on the operation of pilot-scale flotation equipment. The investigation is focussed on the processing of platinum bearing ores from the UG2 reef in South Africa. The UG2 reef is of considerable economic importance, containing a substantial proportion of the world wide reserves of platinum group metals. However, UG2 ore has very complex mineralogy, and a high degree of association with chromite, which renders processing of this ore relatively difficult. Consequently, optimising the design of flotation circuits to treat this ore has proved challenging, and has been the focus of much attention by major platinum producers over the last 10 to 20 years.The primary aim of this thesis is to identify, evaluate and refine appropriate flotation models and modelling procedures reported in the literature, and use these models to develop a flotation circuit simulation procedure that can be used to provide a sound basis for the evaluation of current UG2 circuit design trends, and as an optimisation tool for the design of UG2 circuits in the future. The processing of UG2 ore from three different locations is evaluated, using two continuous pilot plants of different size, each operated in a variety of different configurations. The investigation required extensive modification of the pilot plant facility that was used, to facilitate the acquisition of the data required by the selected models.The basis and implications of these modifications with respect to the design and operation of pilot plants as a tool for design and optimisation is extensively covered. The modelling approach adopted in this study is based on the separation of the factors affecting flotation into those arising from the characteristics of the ore (floatability) and those arising owing to the hydrodynamics in the equipment, in both the pulp and froth zones of the cell. It is proposed that the pulp zone performance can best be related to the bubble surface area flux based on the work of Gorain et al (1997), while ore floatability is modelled using a distributed floatability model, based on the approach developed by Runge et al (1997) and Harris (1997). The performance of the froth phase with respect to minerals recovered by true flotation is modelled based on the approach proposed by Harris (1997) and Gorain et al (1998), while entrainment in the froth is modelled using the approach proposed by Savassi et al (1998).
24
Healy, Daniel Francis. "The depression of sphalerite during carbon pre-flotation and lead flotation at the Century Mine concentrator." Thesis, Curtin University, 2005. http://hdl.handle.net/20.500.11937/1787.
Full textAbstract:
The differential lead-zinc flotation process has been practised since 1912, yet selectivity in the process remains a significant technical issue in many operations. The minerals processing operation at Zinifex Limited's Century Mine, which uses differential flotation, began in November 1999 and the flotation behavior of the ore remains a major research interest. The present study was aimed to determine the possible mechanisms of sphalerite recovery during carbon pre-flotation and lead flotation in this operation including identification of the variables that affect these two flotation stages and also identify depressants for sphalerite that offer better selectivity during these stages. To achieve this aim, the study was undertaken in two stages: a review of literature related to selectivity during lead-zinc flotation, and an experimental program consisting of bench-scale flotation tests wherein the various experimental variables were systematically varied. A comparison between the data generated to those of the plant was also undertaken. The review of literature revealed four basic mechanisms of sphalerite recovery: activation of the sphalerite surface, composite particle flotation with galena and gangue, graphitic inclusions in the mineral surface and entrainment in the froth. The depression or rejection of sphalerite on the other hand could be affected by grinding, froth washing and the use of chemical depressants including cyanides, zinc sulfate, abraded iron and iron sulfate, sodium sulfide, sodium sulfite and metabisulfite, and organic depressants derived from selective collectors.The results from the experimental program indicate that: (a) activation of the sphalerite surface as a mechanism of sphalerite recovery during lead flotation was not significant at the Century Mine concentrator, (b) the recovery of sphalerite during the carbon pre-flotation was predominantly due to a bulk flotation action and entrainment in the froth, (c) composite particle recovery was a significant contributing factor in the recovery of sphalerite in lead flotation, and (d) mineral oxidation was only significant for galena and occurred mostly during pre-flotation, but the use of cyanide adequately counters any effect on sphalerite recovery. The investigation on the variables that affect the pre-flotation and lead flotation circuits revealed that: (a) reducing the pulp density and the amount of frother added during pre-flotation significantly reduced the bulk flotation action and entrainment of sphalerite in the froth, b) grinding the ore finer (P80 = 40 μm) reduced the recovery of sphalerite as composite particles during lead flotation, and (c) the pulp pH was best maintained at natural pH during pre-flotation and at an elevated alkaline pH (pH 9.5) during lead flotation for optimal selectivity. In terms of depressants it was found that zinc sulfate specifically depressed sphalerite during lead flotation.
25
Healy, Daniel Francis. "The depression of sphalerite during carbon pre-flotation and lead flotation at the Century Mine concentrator." Curtin University of Technology, Western Australian School of Mines, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16397.
Full textAbstract:
The differential lead-zinc flotation process has been practised since 1912, yet selectivity in the process remains a significant technical issue in many operations. The minerals processing operation at Zinifex Limited's Century Mine, which uses differential flotation, began in November 1999 and the flotation behavior of the ore remains a major research interest. The present study was aimed to determine the possible mechanisms of sphalerite recovery during carbon pre-flotation and lead flotation in this operation including identification of the variables that affect these two flotation stages and also identify depressants for sphalerite that offer better selectivity during these stages. To achieve this aim, the study was undertaken in two stages: a review of literature related to selectivity during lead-zinc flotation, and an experimental program consisting of bench-scale flotation tests wherein the various experimental variables were systematically varied. A comparison between the data generated to those of the plant was also undertaken. The review of literature revealed four basic mechanisms of sphalerite recovery: activation of the sphalerite surface, composite particle flotation with galena and gangue, graphitic inclusions in the mineral surface and entrainment in the froth. The depression or rejection of sphalerite on the other hand could be affected by grinding, froth washing and the use of chemical depressants including cyanides, zinc sulfate, abraded iron and iron sulfate, sodium sulfide, sodium sulfite and metabisulfite, and organic depressants derived from selective collectors.<br>The results from the experimental program indicate that: (a) activation of the sphalerite surface as a mechanism of sphalerite recovery during lead flotation was not significant at the Century Mine concentrator, (b) the recovery of sphalerite during the carbon pre-flotation was predominantly due to a bulk flotation action and entrainment in the froth, (c) composite particle recovery was a significant contributing factor in the recovery of sphalerite in lead flotation, and (d) mineral oxidation was only significant for galena and occurred mostly during pre-flotation, but the use of cyanide adequately counters any effect on sphalerite recovery. The investigation on the variables that affect the pre-flotation and lead flotation circuits revealed that: (a) reducing the pulp density and the amount of frother added during pre-flotation significantly reduced the bulk flotation action and entrainment of sphalerite in the froth, b) grinding the ore finer (P80 = 40 μm) reduced the recovery of sphalerite as composite particles during lead flotation, and (c) the pulp pH was best maintained at natural pH during pre-flotation and at an elevated alkaline pH (pH 9.5) during lead flotation for optimal selectivity. In terms of depressants it was found that zinc sulfate specifically depressed sphalerite during lead flotation.
26
Smith, Christopher David. "Flotation Response to Gas Distribution Management." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486926.
Full textAbstract:
Froth f1otation.is the most widely used mineral concentration process in the world. Experimental work has shown different gas distribution profiles to a bank of flotation cells elicit different metallurgical responses; with an increasing profile yielding the highest cumulative recovery. However, this same response has not been seen on flotation models, it is believed this· is due to a lack of a distinct, physics based, froth zone model these flotation models. Recent research work has focused upon developipg physics based computer simulations of flotation froths able to yield mineral grade and recovery results achieved experimentally. FrothSim, a physics based model of flotation froths, has been used to develop aJT10del of a bank of flotation cells from experimental results, the model is. a very good representation of the bank. Additional models have been developed to enable froth output parameters, such as the air recovery and overflowing bubble size, to be predicted after changes to operating variables, such as air rate, have been made. These models have been incorporated into the froth simulation package FrothSim and used to predict flotation performance for the bank of cells modelled, at different air distribution profiles. One of these profiles was predicted to improve the performance of the bank by ncreasing the grade of the valuable minerals at the head of the bank and increasing the cumulative recovery of the same minerals at the tail of the bank, maximising potential profit from the bank. The predicted improvement in performance was confirmed on a subsequent industrial sampling campaign, on the same bank,.with the same air distribution profile. A very good agreement between the predicted and experimental performance was obtained for all minerals in the model, both selectively floated valuable minerals and non-selec~ively entrained gangue minerals. Therefore, FrothSim is able to be used as a tool to optimise gas distribution off-line, reducing the requirement for costly, and time-consuming, on-plant experimentation.
27
Ding, Kejian. "Zero-conditioning time concept in flotation." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/30776.
Full textAbstract:
In the particle-to-bubble attachment process collector species are needed at the
attachment point to render the mineral surface hydrophobic. It is common to assume that
such species are transported toward mineral particles via diffusion/mixing and render the
mineral surface hydrophobic by adsorption. However, collector species can also be brought
to the point of attachment by bubbles carrying the species on their surfaces. That ensures
that the collector is at the right time at the point where it is needed to facilitate the
attachment of the particle to the bubble.
It is generally accepted that flotation with amines is very rapid and that only a short
conditioning time is required in such a cationic flotation. This indicates that the
transportation of the collector species toward mineral particles is very favorable when
amines are applied. This implies that in such systems the major portion of amine is brought
to the mineral surface by bubbles, and that the conventional introduction of such flotation
reagents to the pulp via dissolution in the pulp does not constitute the best way of utilizing
such reagents.
These ideas were tested in a reverse coal flotation process. In this process a
quaternary aliphatic amine, dodecyltrimethyl ammonium chloride (DTAC), was used as a
collector to float gangue while depressing coal particles. The process is interesting because
low rank/oxidized coals float poorly, and because of the possible utilization of such clean
coal products in the form of coal-water slurries. However, to float gangue efficiently the
process requires very high dosages of the quaternary amine since adsorption of the amine
onto coal is very high. However, if amine is transported with bubbles then it should be
possible to carry out the process at "zero conditioning time" that would (i) reduce the
amount of the amine adsorbed by coal thus reducing its overall consumption and (ii)
improve gangue flotation. The process can be carried out either without any conditioning
step prior to flotation, or, more efficiently, with the amine introduced to the flotation
system with the stream of bubbles. The experiments confirmed entirely the hypothesized
mechanism in which amine is mainly transported by bubbles, and showed that, with the zero conditioning tests, coal reverse flotation could be successfully carried out at reduced
amine consumption.
However, in order to become a viable option the coal reverse flotation process
requires a very substantial reduction of the quaternary amine consumption. In search for
the ways of reducing the collector dosage in this process the attention was turned to
polymers which in potash flotation are utilized as blinders. The batch flotation tests carried
out using a mechanical cell confirmed that some polyacrylamides worked very well as
blinders in the coal reverse flotation process. At the same time the standard flocculation
tests showed that the polyacrylamides acted as total non-selective flocculants. This obvious
discrepancy revealed the importance of conditioning in selective flocculation. Reverse
flotation with a simultaneous use of polyacrylamide, which significantly reduced
consumption of amine collector, can be selective only after sufficient conditioning. It was
found that the polyacrylamides with a different degree of anionicity responded differently
to conditioning. Only the addition of the polymers with a lower degree of anionicity
promoted the flotation of gangue. The flocculation turned out to be significantly more
selective after more intense conditioning with polyacrylamide.
Since in reverse flotation coal is not recovered as a hydrophobic froth product but
as a hydrophilic concentrate, it is much easier to utilize such a product to produce a coalwater
slurry. The rheological measurements indicate that the viscosity reducing chemical
additives are not needed when the slurries are prepared from the reverse flotation clean
coal product.
Additionally, since coal reverse flotation increases the column carrying capacity
because of the reduced yield of froth product, it could minimize the associated problems in
the use of flotation columns in coal flotation.
While this thesis deals specifically with coal reverse flotation, these results have
much broader implications since amines and polyacrylamides are widely applied in
flotation and flocculation.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
28
Crawford, Russell J., and n/a. "Particle size, hydrophobicity and flotation response." Swinburne University of Technology, 1986. http://adt.lib.swin.edu.au./public/adt-VSWT20070828.150946.
Full textAbstract:
Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of.
surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles.
Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface
methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher
surface coverages are less than those anticipated by the Cassie
equation.
The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of
flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour.
Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study.
Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface
coverage. It was found that the dependence of rate constant on particle size is essentially linear.
29
Watson, Jeffrey A. "Deinking recycled paper using column flotation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29636.pdf.
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Watson, Jeffrey A. 1971. "Deinking recycled paper using column flotation." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27262.
Full textAbstract:
The degree of waste paper recycling has been increasing steadily in North America over the last decade. Flotation is a popular method for removing ink from fibres (deinking) and is traditionally performed in mechanical cells. Column flotation has been proposed as an alternative to mechanical cells. In this work, open and packed laboratory and pilot-scale columns were operated to determine their relative merits and how they compare to a circuit of mechanical cells.<br>It was found that the type of sparger was critical for obtaining high flotation efficiencies. Fine porous stainless steel spargers (0.5 $ mu$m) produced flotation efficiencies which were equal to those of the mechanical cells. Packing was effective in increasing flotation efficiency when the coarse porous stainless steel sparger (100 $ mu$m) was used in the laboratory column and when the variable gap sparger was used in the pilot column.<br>The organic loss from all column configurations (laboratory and pilot-scale) was less than 3%.<br>The scale up procedure was evaluated using data from the laboratory column and pilot column dimensions. Finally, using data from the laboratory column, industrial columns were designed.
31
Yu, Shaning. "Particle collection in a flotation column." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66002.
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Zhou, Zhi-ang. "Gas nucleation and cavitation in flotation." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40477.
Full textAbstract:
The role of gas nucleation and cavitation in flotation has been systemically studied. It was shown theoretically that about a 10 m high recovery zone is required to ensure at least one collision between a particle less than 10 $ mu$m and a bubble, under conventional column flotation conditions, indicating that the collision is the rate limiting step for fine particle flotation. Direct formation of small bubbles on the hydrophobic particle surfaces and in slurry by gas nucleation and cavitation has, therefore, been exploited as a way to accelerate the fine particle collection rate.<br>Experimentally, the existence of gas nuclei in water was demonstrated from coagulation, sedimentation and filtration tests of fine coal (d$ sb{50} approx 5 mu$m) and silica (d$ sb{50} approx 3.5 mu$m) particles. Small bubbles are generated, from the expansion of the pre-existing gas nuclei, by hydrodynamic cavitation induced by flow of liquid through a nozzle at a velocity of 8-15 m/s, depending on nozzle diameter and length. This velocity of bubble initiation is reduced 5-7 m/s when the liquid is gas-supersaturated. Surfactants do not affect the on-set of bubble formation by cavitation, but increase the amount of bubbles formed. The addition of a small amount of hydrophobic particles in gas-supersaturated systems increases the quantity of bubbles generated, while the presence of hydrophilic particles reduces bubble formation.<br>Dissolved air (or carbon dioxide) flotation of fine silica (d$ sb{50} approx 1.6 mu$m) has shown that recovery increases with the slurry flow velocity, regardless of the saturation pressures applied (102-310 kPA). Releasing the gas-supersaturated slurry into a solution gives a higher recovery than releasing the gas-supersaturated slurry into a slurry. These observations suggest that bubble nucleation is a better mechanism for enhancing particle collection compared with the direct particle-bubble contact.<br>Flotation results using a newly designed flotation reactor indicate that adding a cavitation tube and a small amount of air in the feed stream increases recovery significantly, and that bubbles formed by hydrodynamic cavitation play a role in improving flotation kinetics, even in the absence of added gas in the stream.
33
Kaya, Muammer. "Froth washing in mechanical flotation cells." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74232.
Full textAbstract:
This basic research project was aimed at assessing the potential of wash water for mechanical flotation machines. Test work at laboratory scale first examined the nature of entrainment; froth structures with and without wash water; and the location, geometry, and flowrate of wash water addition. The relationship between slurry, total water recovery and gangue recovery was characterized. Confirmatory work at pilot plant was completed.<br>The effect of wash water on metallurgical performance was tested with various streams from the Falconbridge Strathcona mill at laboratory and pilot and full plant scale, and with the secondary cleaner stage at the Eastmaque Kirkland Lake mill.<br>Results show that mechanical entrainment is the major means of gangue transport up to the slurry-froth interface. Transport into the froth is mostly hydraulic, although entrapment becomes dominant at low water recoveries. Free gangue recovery was closely related to slurry water recovery at all three scales. Wash water at an optimum superficial rate of 0.03 to 0.07 cm/s reduced entrainment by anywhere from 30 to 70%, typical values being around 50%.<br>Wash water can be further assisted by mechanical and ultrasonic vibration of the froth, difficult to achieve at plant scale, or with warm wash water, which becomes attractive if a waste heat source is available. A further rejection of 10 to 20% then becomes possible.<br>Distributor geometry was aimed at washing the entire froth surface at laboratory and pilot scale. It was observed that the recovery of hydrophobic minerals generally increased because the froth was stabilized. At plant scale, two perforated pipes close to the concentrate weir yielded the most reject. Froth stabilization was lost, and recoveries decreased.
34
Zhang, Lingyu. "Enhanced phosphate flotation using novel depressants." UKnowledge, 2013. http://uknowledge.uky.edu/mng_etds/10.
Full textAbstract:
Froth flotation is the most efficient method for phosphate separation, which is a physic-chemical separation process based on the difference of surface properties between the valuable minerals and unwanted gangue minerals. However, the presence of clay slimes in the slurry after grinding consumes a large amount of reagents, decreases the collision probability between bubbles and minerals, prevents phosphate particle attachment to air bubbles, and thus considerably reduces flotation recovery and concentrate grade. Georgia Pacific Chemical, LLC has recently developed novel depressants, i.e., clay binders, which are a series of low molecular weight specialty polymers to help improve phosphate flotation performance by selectively agglomerating and depressing clay particles, thus lowering their surface area and reducing the adsorption of surfactants.
This thesis addresses the effects of clay binders on phosphate flotation performance and their adsorption behavior on different minerals in a sedimentary phosphate ore. Quartz Crystal Microbalance with Dissipation technique (QCM-D) was used to study adsorption characteristics of clay binders and batch flotation tests were performed under different conditions to investigate phosphate flotation performance. The experimental results have shown that clay binders significantly improved phosphate flotation selectivity and reduced the dosages of collector and sodium silicate used as dispersant in the industry.
35
Marson, Andrew D. "Air flotation drying of paper pulp." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613430.
Full textAbstract:
Although much academic research has been devoted to the fields of paper drying and air impingement heat transfer, little of the resulting information is in a form usable to dryer manufacturers. The aim of this research was therefore to develop a model suitable for the designing the flotation dryers often used in the production of market pulps. The heat transfer characteristics of several commercial nozzle designs, namely flotation nozzles, slot nozzles and arrays of round orifices, were determined under conditions relevant to pulp drying. Empirical correlations for the Nusselt number for the nozzles were obtained using the property ratio method to account for the variation of the physical properties of air with temperature. The proposed correlations were shown to be in excellent agreement with the experimental results and were sufficiently accurate for use in industrial dryer design. The effect of the nozzle exit velocity and nozzle-to-surface spacing on the profile of static pressure at the impingement surface was also determined for a typical flotation nozzle design. The influence of nozzle conditions and sheet properties on the drying characteristics of papermaking pulp was determined through batch drying experiments. Over 400 experiments were performed using samples produced from four furnishes at basis weights in the range 120 g/m" to 2125 g/m2 and oven dry densities in the range 175 kg/mt to 900 kg/m'. Drying was achieved using heated air emerging from flotation nozzles at air temperatures in the range 100°C to 250°C with nozzle velocities between 15 mls and 55 mls. Temperature profiles through handsheets of both pressed and unpressed pulp were also measured during drying, which showed the presence of a quasi-constant temperature.
36
Chow, Ping-Sheng. "Separation of mixed plastics by flotation." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318720.
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Wallin, Peter John. "The mathematical modelling of flotation kinetics." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314632.
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38
Hale, Waverly Mitchell. "Surface chemical aspects of microbubble flotation." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45816.
Full textAbstract:
<p>In order to demonstrate the ability of microbubble
flotation to superclean coal to ash levels of less than
2%, several Eastern U. S. coals have been tested. The
results show that the process is capable of producing
superclean coal with improved recovery as compared to the
conventional flotation process.<p>
<p>
To further improve and understand the microbubble
flotation process, electrokinetic studies of the
hydrocarbon oils used in flotation as collectors have been
conducted. Also, the effect of oil emulsifiers on the zeta
potential of oil droplets has been studied. In general,
oil droplets are negatively charged and negative zeta
potential is reduced with the addition of nonionic and
cationic surfactants. On the other hand, the negative
charge is increased with the addition of an anionic
reagent. It has also been shown that the negative zeta
potential of oil droplets increases with increasing
hydrocarbon chain length.<p>
<p>The effects of different collectors on induction time
and flotation have been determined by conducting
microflotation and induction time experiments using an
Elkhorn seam coal sample. The results show that industrial
oils combined with the coal have the shortest induction
times and, therefore, the highest flotation yields as
compared to pure hydrocarbon oils. It has also been shown
that oil emulsifiers tend to increase flotation yield and
reduce particle/bubble induction time.<p><br>Master of Science
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An, Dongbo, and Dongbo An. "Improved Flotation of Bastnaesite and Chalcopyrite." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624299.
Full textAbstract:
The present study is targeted on the optimization of the flotation conditions for the improvement of the industrial flotation practice. Part I is focused on the improvement of the flotation of Mountain Pass mine ore for the beneficiation of rare earth elements. The objective is to improve the rare earth recovery of Mountain Pass ore by developing a novel flotation reagents' scheme, meanwhile reducing the flotation temperature to a cost-efficient level and simplifying the flowsheet. Surface chemistry study by contact angle, zeta potential and microflotation tests indicate that a mixed collector consisting of oleic acid (OA) and sodium octanohydroxamate hydrate (OHA) is beneficial for rare earth flotation. More importantly, salicylhydroxamic acid (SHA) is also a promising collector due to the high selectivity. Lab-scale flotation tests using SHA as collector show that 80-90% REE recovery and <20% gangue recovery are achieved at 40°C~60°C, which yield a rougher concentrate of 30%~40% REO. A novel flotation scheme has been developed towards Mountain Pass rare earth mine. The new scheme is of both high selectivity and high recovery, meanwhile the dosage of reagent required is much less, and the flotation temperature is also significantly reduced. Interactive adsorption models are built up through FT-IR and AFM study. The interaction of collector with bastnaesite surface is illustrated. Hydroxamic acid collectors (OHA and SHA) adsorb on bastnaesite surface by forming stable chelating complex. The selectivity of collectors towards bastnaesite flotation is summarized as SHA>OHA>OA.
Part II is focused on the improvement of the flotation of Resolution Copper's Superior mine ore at an elevated temperature for the beneficiation of chalcopyrite. Because the Resolution Copper ore is mined from a deep, hot, underground mine, the temperature of ROM (run of mine ore) is much higher than that of the ore usually processed in a typical open-pit copper mine. The ore temperature will still be high during flotation. It is therefore critical to carry out a systemic study on the flotation of Resolution Copper ore at elevated temperatures and clarify the impact on flotation. An overall beneficial effect is observed in high temperature flotation through a lab-scale flotation study. Further action of temperature control is not necessary. The contact angle results indicate that surface hydrophobicity is enhanced at elevated temperature, of which the surface morphology change (shown by AFM images) of xanthate adsorption species (dixanthogen) is the key factor.
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Schmidt, Dale C. "Flotation deinking of toner-printed papers /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9828.
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Christie, Jevan Craig. "The sensitivity of direct faecal examination, faecal flotation and centrifugal sedimentation / flotation in the diagnosis of canine spirocercosis." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/24987.
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A variety of faecal examination methods have shown variable sensitivity in identifying larvated Spirocerca lupi (S. lupi) eggs. The purpose of this study was to determine which faecal examination method, including a novel modified centrifugal flotation method, was most sensitive in the diagnosis of spirocercosis. Faeces were collected from 33 dogs diagnosed with spirocercosis by oesophageal endoscopy at the Onderstepoort Veterinary Academic Hospital between 2008 and 2009. If the first evaluation was negative, a second faecal sample was evaluated 24-48 h later. Ten faecal examinations using 1 g aliquots of faeces were performed per sample. Four faecal examination methods were evaluated; direct faecal examination using saline, direct faecal flotation, a modified faecal centrifugal flotation and a laboratory performed faecal sedimentation/flotation. The direct and modified centrifugal flotation methods were each performed using four faecal flotation solutions; NaNO3 (Specific gravity (SG) 1.22), MgSO4 (SG 1.29), ZnSO4 (SG 1.30) and saturated sugar (SG 1.27). The sedimentation/flotation method utilized MgSO4 (SG 1.29). The modified centrifugal flotation method required centrifugation (1400 G) of a prepared faecal suspension (1 g faeces suspended in 5 ml of flotation solution) after which 0.1 ml of the supernatant was aspirated from the surface using an adjustable volume micropipette for microscopic examination. The 10 faecal examination tests were statistically analysed using the Friedman test (nonparametric equivalent of analysis of variance) p=0.000, z value = 0.05. The sensitivity of the tests ranged between 42 % and 67 %, with the NaNO3 solution showing the highest sensitivity in both the direct and modified centrifugal flotation methods. The modified NaNO3 centrifugal method ranked first with the highest mean egg cell count (45.24 ± 83). The modified centrifugal NaNO3 method was found to be superior (i.e. higher egg counts) and significantly different (p<0.001) compared with the routine saturated sugar, ZnSO4 and MgSO4 flotation methods. The direct flotation method/technique using NaNO3 flotation fluid was also superior and significantly different (p<0.001) when compared to the same technique using ZnSO4 or MgSO4 flotation fluids. Neoplastic transformation of oesophageal nodules was confirmed in 15 % (n=5) of dogs and a further 18 % (n=6) had both neoplastic and non-neoplastic oesophageal nodules. S. lupi eggs were demonstrated in 40 % of dogs with neoplastic nodules and in 72.9 % of dogs with non-neoplastic nodules. The mean egg count in the non-neoplastic group (61) was statistically greater (p=0.02) than that of the neoplastic group (1). The results show that faecal examination using the direct and modified centrifugal flotation methods with the NaNO3 flotation fluid are the most sensitive methods in the diagnosis of spirocercosis. The modified centrifugal flotation method using this solution has the highest mean egg count. The study also found that dogs with neoplastic nodules shed significantly fewer eggs than dogs with non-neoplastic nodules. Copyright<br>Dissertation (MMedVet)--University of Pretoria, 2011.<br>Companion Animal Clinical Studies<br>unrestricted
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Goodall, Craig Michael. "The effects of flotation variables on the bubble size, mixing characteristics and froth behaviour in column flotation cells." Thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/23802.
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Hobert, Andrew Reid. "Development of a Novel Air Sparging Device." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/71828.
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Column flotation is commonly employed in the processing and recovery of fine mineral particles due to an increase in flotation selectivity unattainable using conventional flotation methods. Such an increase in selectivity is due to the employment of wash water, minimizing hydraulic entrainment of fine gangue particles, and the presence of quiescent operating conditions assisted by the use of various air sparging technologies. High performance air spargers increase the probability of collision and attachment between air bubbles and particles, thereby improving recovery of fine and coarse mineral particles otherwise misplaced to the tailings fraction in conventional flotation cells. Although many high-pressure spargers, including the static mixer and cavitation tube, are currently employed for the aeration of column cells, a low pressure sparger capable of providing equivalent performance while resisting a reduction in aeration efficiency does not exist.
In light of escalated energy requirements for operation of air compressors necessary to provide high pressure air to existing external and internal spargers, a low-pressure and porous sparger capable of resisting plugging and scaling was developed. Following the design, construction, and optimization of such a prototype, air holdup and flotation performance testing was completed to verify the viability of the sparger as a replacement to existing aerators. Performance evaluations suggest that the sparger is capable of providing similar functionality to currently employed sparging technologies, but further work is required with regards to manipulation of the porous medium to prevent sparger fouling and sustain high aeration efficiencies.<br>Master of Science
44
Ozun, Savas. "Flotation Characteristics Of Minerals In Feldspar Ores." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614273/index.pdf.
Full textAbstract:
Albite (Na-feldspar) and orthoclase (K-feldspar) are the major feldspar minerals used in the production of glass and ceramics. They are found together with impurities like biotite, muscovite, quartz and rutile which are not desired for ceramics and glass industries. Therefore, these have to be removed to make the ore available for industrial use. In order to shed light on the actual feldspar ores, in this study<br>the flotation characteristics of albite, biotite, muscovite, orthoclase, quartz and rutile were investigated separately in their pure forms. In the investigation, the electrokinetic potential measurements and micro-flotation studies have been carried out to get information about their flotation characteristics under the effect of three different collectors, Aero 704, Aero 3000C and Aero 825, and the pH of the medium. The flotation recoveries were found to be pH dependent and the effective between the pH range of 7.0 and 11.5 in the presence of Aero 704. In the case of flotation with Aero 3000C, the recoveries reached up to 95.0% at certain concentrations and pH values and decreased sharply below pH 3.0 and above pH 9.5 for all the minerals tested. In the presence of Aero 825, the flotation recoveries of the minerals except for rutile, were found to be insufficient even with its highest concentration. In order to evaluate the adsorption mechanism of the collectors, Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses were carried out. From the AFM results it might be deduced that the behavior of Aero 3000C and Aero 825 was found to be almost similar for biotite and muscovite as monolayer adsorption and for the remaining minerals, albite, orthoclase, quartz and rutile, as monolayer and bilayer adsorption together. In the case of Aero 704, for albite and orthoclase, the adsorption of the collector might be the reason for monolayer and bilayer formation on their surfaces. The strength of the interaction of the collectors on the mineral surfaces was followed by FTIR analyses before and after acetone washing. The interaction of all the collectors was found to be weak in the case of albite, orthoclase, quartz and rutile whereas the interaction of Aero 704 and Aero 3000C was found to be strong in the case of biotite and muscovite.
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Ajersch, Michael John. "Mechanisms of pulp loss in flotation deinking." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30126.pdf.
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Guo, Jun-Xiang. "Development and theory of centrifugal flotation cells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65675.pdf.
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Ajersch, Michael. "Mechanisms of pulp loss in flotation deinking /." *McMaster only, 1997.
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Emerson, Zachery Ian. "Particle and bubble interactions in flotation systems." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Spring%20Dissertations/EMERSON_ZACHERY_45.pdf.
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Hosseini, Seyed Hamid. "Physicochemical studies of oxide zinc mineral flotation /." Luleå : Division of Mineral Processing, Department of Chemical Engineering and Geosciences, Luleå University of Technology, 2008. http://epubl.ltu.se/1402-1544/2008/17/.
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Mohamed, Ahmed. "Frother blends in flotation: polyglycols and alcohols." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104699.
Full textAbstract:
Frothers are non ionic surfactants, commonly alcohols and polyglycols, used to provide two functions in flotation, namely to reduce bubble size and stabilize froth. Both functions imply an impact on the properties of the air-water interface (bubble surface) but there is no consensus on the mechanism, particularly with regard to bubble size reduction. Blending frothers is becoming common in flotation practice arguably enhancing performance by permitting independent control of the two frother functions. However, there have been no studies to determine this blend possible action. The blends used here focused on a small addition of polyglycol (F150 and DF250) to alcohols (1-pentanol and MIBC). The effect of blends on gas dispersion properties (bubble size and gas holdup) and froth properties (froth height and water overflow rate) was measured in three units, bubble column, 800 L and 5.5 L mechanical cells. Froth height and water overflow rate showed a strong blend effect, both increasing significantly compared to individual frothers. However, while the bubble size was decreased at blend concentration below the critical coalescence concentration (CCC) of the alcohol frother, bubble size was significantly larger above the alcohol CCC. Gas holdup data supported these effects on bubble size. This bubble size effect compromised testing the hypothesis of independent function control using blends. The thesis focussed on explaining the bubble size observations by designing coalescence and beak-up experiments. Coalescence time of bubbles generated from two horizontal capillaries did not show a blend effect. Break-up tests for one-bubble-at-a-time and from an air stream conducted for F150 – pentanol blends showed that the blend reduced bubble break-up compared to single frothers. The increase in bubble size above the base CCC therefore appears to due to decreased break-up. A mechanism based on the Marangoni effect is introduced to explain this phenomenon.<br>Les moussants sont des surfactants non ioniques. Ceux-ci sont communément des alcools et des polyglycols, utilisés en flottation pour assumer deux fonctions : réduire la taille de la bulle et stabiliser la mousse. Ces deux fonctions exercent une influence sur les propriétés de l'interface air-eau (surface des bulles). Cependant il n'existe pas de consensus sur le mécanisme, particulièrement en ce qui a trait à la réduction de la taille des bulles. Mélanger des moussants devient une pratique généralement acceptée en flottation, laquelle sans doute renforce la performance en permettant le contrôle indépendant des deux fonctions de moussants. Toutefois, aucune étude n'a été réalisée pour déterminer l'action possible du mélange des moussants. Le mélange utilisé dans ce travail est un ajout d'une petite quantité de polyglycol (F150 et DF250) aux alcools (1-pentanol et MIBC). L'effet des mélanges sur les propriétés de dispersion de gaz (taille des bulles, rétention de gaz) que sur celles de la mousse (hauteur de la mousse, vitesse du flux du trop plein d'eau) a été mesurée en trois unités, colonne à bulles, 800 L et 5.5 L cellules mécaniques. La hauteur de la mousse et la vitesse du flux du trop plein d'eau ont révélé un fort effet de mélange puisque les deux paramètres accusent dans le cas du mélange une augmentation significative en comparaison aux moussants individuels. Alors que la taille des bulles avait diminué lorsque la concentration du mélange avait atteint une valeur inferieure à la concentration critique de coalescence (CCC) de la mousse d'alcool, la taille de la bulle était devenue largement supérieure à celle d'alcool CCC, contre toute attente. Les données sur la rétention de gaz ont aussi corroboré ces effets affectant la taille des bulles. Cet effet de taille de la bulle compromise tester l'hypothèse de la contrôle indépendante de fonction utilisant des mélanges. Le pivot de cette thèse est l'explication des observations de la taille des bulles par le biais des tests de coalescence et de rupture. Le temps de coalescence de bulles générées à partir de deux capillaires horizontaux n'a pas démontré un effet du mélange. Les tests de rupture réalisés avec une seule bulle à la fois et à partir d'un courant d'air pour le mélange F150 – pentanol, démontre que le mélange a réduit la possibilité de rupture par rapport à un seul moussant. L'augmentation de la taille de la bulle au-delà de la base CCC pourrait être due à la diminution de l'effet de rupture. Afin d'expliquer ce phénomène, un mécanisme basé sur l'effet de Marangoni est introduit.