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A comparison of the critical impeller speed for solids suspension in a bench-scale and a pilot-scale mechanical flotation cell / O.A. Lima in Minerals engineering, Vol. 22 N° 13 (Octobre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 13 (Octobre 2009) . - pp. 1147–1153 Titre : A comparison of the critical impeller speed for solids suspension in a bench-scale and a pilot-scale mechanical flotation cell Type de document : texte imprimé Auteurs : O.A. Lima, Auteur ; D.A. Deglon, Auteur ; L.S. Leal Filho, Auteur Année de publication : 2009 Article en page(s) : pp. 1147–1153 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Froth  flotation  Flotation  machines  Solids  suspension Résumé : This paper compares the critical impeller speed results for 6 L Denver and Wemco bench-scale flotation cells with findings from a study by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2007. Evaluation of solids suspension in a pilot-scale mechanical flotation cell: the critical impeller speed. Minerals Engineering 20, 233–240; Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621–629] conducted in a 125 L Batequip flotation cell. Understanding solids suspension has become increasingly important due to dramatic increases in flotation cell sizes. The critical impeller speed is commonly used to indicate the effectiveness of solids suspension. The minerals used in this study were apatite, quartz and hematite. The critical impeller speed was found to be strongly dependent on particle size, solids density and air flow rate, with solids concentration having a lesser influence. Liquid viscosity was found to have a negligible effect. The general Zwietering-type critical impeller speed correlation developed by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621–629] was found to be applicable to all three flotation machines. The exponents for particle size, solids concentration and liquid viscosity were equivalent for all three cells. The exponent for solids density was found to be less significant than that obtained by the previous authors, and to be consistent with values reported in the general literature for stirred tanks. Finally, a new dimensionless critical impeller speed correlation is proposed where the particle size is divided by the impeller diameter. This modified equation generally predicts the experimental measurements well, with most predictions within 10% of the experimental. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001320 [article] A comparison of the critical impeller speed for solids suspension in a bench-scale and a pilot-scale mechanical flotation cell [texte imprimé] / O.A. Lima, Auteur ; D.A. Deglon, Auteur ; L.S. Leal Filho, Auteur . - 2009 . - pp. 1147–1153. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 13 (Octobre 2009) . - pp. 1147–1153 Mots-clés : Froth  flotation  Flotation  machines  Solids  suspension Résumé : This paper compares the critical impeller speed results for 6 L Denver and Wemco bench-scale flotation cells with findings from a study by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2007. Evaluation of solids suspension in a pilot-scale mechanical flotation cell: the critical impeller speed. Minerals Engineering 20, 233–240; Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621–629] conducted in a 125 L Batequip flotation cell. Understanding solids suspension has become increasingly important due to dramatic increases in flotation cell sizes. The critical impeller speed is commonly used to indicate the effectiveness of solids suspension. The minerals used in this study were apatite, quartz and hematite. The critical impeller speed was found to be strongly dependent on particle size, solids density and air flow rate, with solids concentration having a lesser influence. Liquid viscosity was found to have a negligible effect. The general Zwietering-type critical impeller speed correlation developed by Van der Westhuizen and Deglon [Van der Westhuizen, A.P., Deglon, D.A., 2008. Solids suspension in a pilot scale mechanical flotation cell: a critical impeller speed correlation. Minerals Engineering 21, 621–629] was found to be applicable to all three flotation machines. The exponents for particle size, solids concentration and liquid viscosity were equivalent for all three cells. The exponent for solids density was found to be less significant than that obtained by the previous authors, and to be consistent with values reported in the general literature for stirred tanks. Finally, a new dimensionless critical impeller speed correlation is proposed where the particle size is divided by the impeller diameter. This modified equation generally predicts the experimental measurements well, with most predictions within 10% of the experimental. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001320

Flotation in a novel oscillatory baffled column / C. J. Anderson in Minerals engineering, Vol. 22 N° 12 (Octobre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 12 (Octobre 2009) . - pp. 1079–1087 Titre : Flotation in a novel oscillatory baffled column Type de document : texte imprimé Auteurs : C. J. Anderson, Auteur ; M.C. Harris, Auteur ; D.A. Deglon, Auteur Année de publication : 2009 Article en page(s) : pp. 1079–1087 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Flotation  machines  Column  flotation  Flotation  kinetics  Fine  particle  processing Résumé : This paper presents an evaluation of an oscillatory baffled column (OBC) as a novel flotation device. The cell is based on a standard column design but employs a novel agitation mechanism where a series of baffle plates are oscillated sinusoidally through the fluid. This type of agitation has been shown to produce a more evenly distributed shear rate in the cell and allows the effect of agitation on particle–bubble contacting to be decoupled from gas dispersion effects. The column was first characterised in terms of mixing and gas dispersion, before being flotation tested using a quartz-amine system. Results indicated that the OBC was able to improve the flotation rate constant by up to 60% for fine particles (<30 μm) and by between 30% and 40% for coarser particles, relative to a standard flotation column. Interestingly, optimal flotation performance was obtained at power intensities orders of magnitude lower than those found in similar studies in stirred systems. This is believed to arise from the even distribution of shear in the OBC together with the oscillatory motion of the fluid in the cell. This oscillatory motion does not contribute to the average power intensity in the fluid and therefore results in more fluid motion per unit energy than would be obtained in a conventional stirred system. The OBC was therefore able to significantly improve flotation rates at power intensities orders of magnitude lower than those found in conventional cells. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001174 [article] Flotation in a novel oscillatory baffled column [texte imprimé] / C. J. Anderson, Auteur ; M.C. Harris, Auteur ; D.A. Deglon, Auteur . - 2009 . - pp. 1079–1087. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 12 (Octobre 2009) . - pp. 1079–1087 Mots-clés : Flotation  machines  Column  flotation  Flotation  kinetics  Fine  particle  processing Résumé : This paper presents an evaluation of an oscillatory baffled column (OBC) as a novel flotation device. The cell is based on a standard column design but employs a novel agitation mechanism where a series of baffle plates are oscillated sinusoidally through the fluid. This type of agitation has been shown to produce a more evenly distributed shear rate in the cell and allows the effect of agitation on particle–bubble contacting to be decoupled from gas dispersion effects. The column was first characterised in terms of mixing and gas dispersion, before being flotation tested using a quartz-amine system. Results indicated that the OBC was able to improve the flotation rate constant by up to 60% for fine particles (<30 μm) and by between 30% and 40% for coarser particles, relative to a standard flotation column. Interestingly, optimal flotation performance was obtained at power intensities orders of magnitude lower than those found in similar studies in stirred systems. This is believed to arise from the even distribution of shear in the OBC together with the oscillatory motion of the fluid in the cell. This oscillatory motion does not contribute to the average power intensity in the fluid and therefore results in more fluid motion per unit energy than would be obtained in a conventional stirred system. The OBC was therefore able to significantly improve flotation rates at power intensities orders of magnitude lower than those found in conventional cells. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509001174

Numerical modelling of non-Newtonian slurry in a mechanical flotation cell / C. W. Bakker in Minerals engineering, Vol. 22 N° 11 (Octobre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 11 (Octobre 2009) . - pp. 944–950 Titre : Numerical modelling of non-Newtonian slurry in a mechanical flotation cell Type de document : texte imprimé Auteurs : C. W. Bakker, Auteur ; C.J. Meyer, Auteur ; D.A. Deglon, Auteur Année de publication : 2009 Article en page(s) : pp. 944–950 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Modelling  Computational  fluid  dynamics  Froth  flotation  Fine  particle  processing  Agitation Résumé : Certain mineral slurries used in the minerals processing industry have been shown to exhibit non-Newtonian rheologies, particularly with finer particle sizes and at higher solid concentrations. Research has also shown that a cavern containing yielded fluid surrounded by stagnant fluid form around the impeller during the agitation of non-Newtonian fluids exhibiting yield stresses, and this is therefore hypothesised to occur inside mechanical flotation cells which may adversely affect fluid hydrodynamics. A single phase non-Newtonian fluids was modelled using CFD, using the Herschel–Bulkley non-Newtonian model with constants derived from experimentally determined Bindura nickel ore slurry, known to be rheologically complex due to the presence of fibrous mineral types, such as serpentine. The modelling methodology was first validated against published experimental results in a stirred tank, and results were experimentally validated using piezoelectric pressure transducers to measure the magnitude of pressure fluctuations due to the fluid velocity in order to define the cavern boundary. Both experimental and numerical findings show that a cavern forms around the stator, with its size depending on slurry yield stress. It was also found that the shear–stress transport (SST) k–ω turbulence model predicted the cavern boundary most accurately. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509000958 [article] Numerical modelling of non-Newtonian slurry in a mechanical flotation cell [texte imprimé] / C. W. Bakker, Auteur ; C.J. Meyer, Auteur ; D.A. Deglon, Auteur . - 2009 . - pp. 944–950. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 11 (Octobre 2009) . - pp. 944–950 Mots-clés : Modelling  Computational  fluid  dynamics  Froth  flotation  Fine  particle  processing  Agitation Résumé : Certain mineral slurries used in the minerals processing industry have been shown to exhibit non-Newtonian rheologies, particularly with finer particle sizes and at higher solid concentrations. Research has also shown that a cavern containing yielded fluid surrounded by stagnant fluid form around the impeller during the agitation of non-Newtonian fluids exhibiting yield stresses, and this is therefore hypothesised to occur inside mechanical flotation cells which may adversely affect fluid hydrodynamics. A single phase non-Newtonian fluids was modelled using CFD, using the Herschel–Bulkley non-Newtonian model with constants derived from experimentally determined Bindura nickel ore slurry, known to be rheologically complex due to the presence of fibrous mineral types, such as serpentine. The modelling methodology was first validated against published experimental results in a stirred tank, and results were experimentally validated using piezoelectric pressure transducers to measure the magnitude of pressure fluctuations due to the fluid velocity in order to define the cavern boundary. Both experimental and numerical findings show that a cavern forms around the stator, with its size depending on slurry yield stress. It was also found that the shear–stress transport (SST) k–ω turbulence model predicted the cavern boundary most accurately. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687509000958

The development of a cavern model for mechanical flotation cells / C. W. Bakker in Minerals engineering, Vol. 23 N° 11-13 (Octobre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 968–972 Titre : The development of a cavern model for mechanical flotation cells Type de document : texte imprimé Auteurs : C. W. Bakker, Auteur ; C.J. Meyer, Auteur ; D.A. Deglon, Auteur Année de publication : 2011 Article en page(s) : pp. 968–972 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Modelling  Computational  fluid  dynamics  Froth  flotation  Fine  particle  processing  Agitation Résumé : Certain fine particle and high solid concentration mineral slurries used in the froth flotation process have been shown to exhibit non-Newtonian rheologies, including a yield stress. The mixing characteristics of these fluids are often problematic as a cavern of yielded fluid forms around the impeller whilst the rest of the fluid remains stagnant and therefore unmixed. This paper aims to develop a semi-empirical model to calculate the height of caverns forming in non-Newtonian mineral slurries in a mechanical flotation cell. Cavern shapes in a pilot-scale Batequip flotation cell were numerically determined for a range of mineral slurries using an experimentally validated Computational Fluid Dynamics (CFD) model. Development of the cavern height model was based on the assumption that the cavern boundary was formed where the shear stress imposed on the slurry equaled the fluid yield stress and also that the flow along the cell walls could be represented by an annular wall jet. It was found that the cavern height was directly proportional to the product of the slurry density and the square of the impeller tip speed, and inversely proportional to the slurry yield stress. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000725 [article] The development of a cavern model for mechanical flotation cells [texte imprimé] / C. W. Bakker, Auteur ; C.J. Meyer, Auteur ; D.A. Deglon, Auteur . - 2011 . - pp. 968–972. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 968–972 Mots-clés : Modelling  Computational  fluid  dynamics  Froth  flotation  Fine  particle  processing  Agitation Résumé : Certain fine particle and high solid concentration mineral slurries used in the froth flotation process have been shown to exhibit non-Newtonian rheologies, including a yield stress. The mixing characteristics of these fluids are often problematic as a cavern of yielded fluid forms around the impeller whilst the rest of the fluid remains stagnant and therefore unmixed. This paper aims to develop a semi-empirical model to calculate the height of caverns forming in non-Newtonian mineral slurries in a mechanical flotation cell. Cavern shapes in a pilot-scale Batequip flotation cell were numerically determined for a range of mineral slurries using an experimentally validated Computational Fluid Dynamics (CFD) model. Development of the cavern height model was based on the assumption that the cavern boundary was formed where the shear stress imposed on the slurry equaled the fluid yield stress and also that the flow along the cell walls could be represented by an annular wall jet. It was found that the cavern height was directly proportional to the product of the slurry density and the square of the impeller tip speed, and inversely proportional to the slurry yield stress. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000725

The effect of ore blends on the mineral processing of platinum ores / E. Van Tonder in Minerals engineering, Vol. 23 N° 8 (Juillet 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 8 (Juillet 2010) . - pp. 621–626 Titre : The effect of ore blends on the mineral processing of platinum ores Type de document : texte imprimé Auteurs : E. Van Tonder, Auteur ; D.A. Deglon, Auteur ; T.J. Napier-Munn, Auteur Année de publication : 2011 Article en page(s) : pp. 621–626 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Ore  blends  Grinding  Froth  flotation Résumé : This paper investigates whether blends of platinum ores display linear grinding and flotation characteristics or whether non-linear effects occur, i.e. synergistic/antagonistic effects. Ores from four different shafts are used in the study, i.e. Salene, Waterval UG2, Paardekraal and Townlands. Laboratory grinding and flotation tests are conducted on blends of the four ores using a statistical simplex lattice mixture design. Grinding results show no evidence that blends of ores display non-linear grinding characteristics. Flotation results show significant antagonistic effects in binary blends of the Salene ore with the other ore types. On the other hand, ternary/quaternary blends of ores result in synergistic effects. The study concludes that blends of platinum ores display non-linear (non-additive) characteristics when there are large differences in metallurgical properties between the ore types. The study demonstrates that appropriately designed mixtures experiments are an effective way to study the performance of ore blends in the laboratory. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000440 [article] The effect of ore blends on the mineral processing of platinum ores [texte imprimé] / E. Van Tonder, Auteur ; D.A. Deglon, Auteur ; T.J. Napier-Munn, Auteur . - 2011 . - pp. 621–626. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 8 (Juillet 2010) . - pp. 621–626 Mots-clés : Ore  blends  Grinding  Froth  flotation Résumé : This paper investigates whether blends of platinum ores display linear grinding and flotation characteristics or whether non-linear effects occur, i.e. synergistic/antagonistic effects. Ores from four different shafts are used in the study, i.e. Salene, Waterval UG2, Paardekraal and Townlands. Laboratory grinding and flotation tests are conducted on blends of the four ores using a statistical simplex lattice mixture design. Grinding results show no evidence that blends of ores display non-linear grinding characteristics. Flotation results show significant antagonistic effects in binary blends of the Salene ore with the other ore types. On the other hand, ternary/quaternary blends of ores result in synergistic effects. The study concludes that blends of platinum ores display non-linear (non-additive) characteristics when there are large differences in metallurgical properties between the ore types. The study demonstrates that appropriately designed mixtures experiments are an effective way to study the performance of ore blends in the laboratory. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510000440