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Frother persistence / F. Azgomi in Minerals engineering, Vol. 22 N° 9/10 (Août/Septembre 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 9/10 (Août/Septembre 2009) . - pp. 874–878 Titre : Frother persistence : A measure using gas holdup Type de document : texte imprimé Auteurs : F. Azgomi, Auteur ; C.O. Gomez, Auteur ; J.A. Finch, Auteur Année de publication : 2009 Article en page(s) : pp. 874–878 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Flotation  frothers Résumé : Persistence here refers to the how long a frother remains effective in producing small bubbles, one of its prime functions in flotation. One way to evaluate is to track gas holdup over time while air is sparged into a column: if frother is depleted bubble size will start to increase consequently increasing bubble rise velocity and hence decreasing gas holdup. Persistence of nine frothers was evaluated in this manner. Polyglycol frothers exhibited high persistence with gas holdup virtually constant over 50 h compared with alcohol frothers. The alcohols divided into two groups, one showing steady decline in gas holdup, e.g., 1-hexanol, and a second group exhibiting a sharp decline at a given time, e.g., MIBC. Tests on MIBC showed increasing concentration extended persistence while increasing gas velocity and increasing bubble size decreased persistence. The decrease in gas holdup was related directly to measured decrease in frother concentration. It appears that the transport of frother to and through the froth and from froth to atmosphere needs to be considered. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900096X [article] Frother persistence : A measure using gas holdup [texte imprimé] / F. Azgomi, Auteur ; C.O. Gomez, Auteur ; J.A. Finch, Auteur . - 2009 . - pp. 874–878. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 9/10 (Août/Septembre 2009) . - pp. 874–878 Mots-clés : Flotation  frothers Résumé : Persistence here refers to the how long a frother remains effective in producing small bubbles, one of its prime functions in flotation. One way to evaluate is to track gas holdup over time while air is sparged into a column: if frother is depleted bubble size will start to increase consequently increasing bubble rise velocity and hence decreasing gas holdup. Persistence of nine frothers was evaluated in this manner. Polyglycol frothers exhibited high persistence with gas holdup virtually constant over 50 h compared with alcohol frothers. The alcohols divided into two groups, one showing steady decline in gas holdup, e.g., 1-hexanol, and a second group exhibiting a sharp decline at a given time, e.g., MIBC. Tests on MIBC showed increasing concentration extended persistence while increasing gas velocity and increasing bubble size decreased persistence. The decrease in gas holdup was related directly to measured decrease in frother concentration. It appears that the transport of frother to and through the froth and from froth to atmosphere needs to be considered. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S089268750900096X

On the role of cavitation in particle collection in flotation – A critical review. II / Z.A. Zhou in Minerals engineering, Vol. 22 N° 5 (Avril 2009) 

Public ISBD [article]  in Minerals engineering > Vol. 22 N° 5 (Avril 2009) . - pp. 419–433 Titre : On the role of cavitation in particle collection in flotation – A critical review. II Type de document : texte imprimé Auteurs : Z.A. Zhou, Auteur ; Zhenghe Xu, Auteur ; J.A. Finch, Auteur Année de publication : 2009 Article en page(s) : pp. 419–433 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Bubbles  Hydrodynamic  cavitation  Flotation  Coal  Oil  sands Résumé : Research in applying hydrodynamic cavitation to recovery of natural resources during the last decade is reviewed. The existence and formation of tiny bubbles or gas nuclei (with diameter from microns down to nano sizes) in natural water were verified from both direct and in-direct measurements, thus providing a foundation for applying hydrodynamic cavitation to flotation systems. The interactions between tiny bubbles and fine particles in aqueous slurry were analysed based on particle surface properties and types of gas nuclei present in water. Tiny bubbles generated by hydrodynamic cavitation were found to increase contact angle of solids and hence attachment force, bridge fine particles to form aggregates, minimize slime coating, remove oxidation layers on particle surfaces, and in consequence reduce reagents consumption. Experiments on generating tiny bubbles by hydrodynamic cavitation revealed that the energy dissipation levels for cavity formation in a flowing liquid could be much lower than predicted, depending on the content of dissolved gases, presence of free gas nuclei and design of cavitation tubes. Application of hydrodynamic cavitation to fine and coarse particle flotation, high intensity conditioning, oil agglomeration of fine coal, and oil sands processing has confirmed the role of tiny bubbles formed by cavitation in improving recovery efficiency. Based on the characteristics of vapor cavity bubbles, increased flotation kinetics by hydrodynamic cavitation could be attributed to a dual role: some collapsing cavity bubbles serving to break interfacial layers on particle surfaces, while other cavity bubbles attaching to those freshly exposed mineral surfaces. The role of water vapor and other gases within cavity bubbles in particle–bubble attachment remains to be explored, as does the action of frothers. Incorporating hydrodynamic cavitation into flotation systems to take advantage of its unique features is expected to develop the next generation of flotation machines. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508002847 [article] On the role of cavitation in particle collection in flotation – A critical review. II [texte imprimé] / Z.A. Zhou, Auteur ; Zhenghe Xu, Auteur ; J.A. Finch, Auteur . - 2009 . - pp. 419–433. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 22 N° 5 (Avril 2009) . - pp. 419–433 Mots-clés : Bubbles  Hydrodynamic  cavitation  Flotation  Coal  Oil  sands Résumé : Research in applying hydrodynamic cavitation to recovery of natural resources during the last decade is reviewed. The existence and formation of tiny bubbles or gas nuclei (with diameter from microns down to nano sizes) in natural water were verified from both direct and in-direct measurements, thus providing a foundation for applying hydrodynamic cavitation to flotation systems. The interactions between tiny bubbles and fine particles in aqueous slurry were analysed based on particle surface properties and types of gas nuclei present in water. Tiny bubbles generated by hydrodynamic cavitation were found to increase contact angle of solids and hence attachment force, bridge fine particles to form aggregates, minimize slime coating, remove oxidation layers on particle surfaces, and in consequence reduce reagents consumption. Experiments on generating tiny bubbles by hydrodynamic cavitation revealed that the energy dissipation levels for cavity formation in a flowing liquid could be much lower than predicted, depending on the content of dissolved gases, presence of free gas nuclei and design of cavitation tubes. Application of hydrodynamic cavitation to fine and coarse particle flotation, high intensity conditioning, oil agglomeration of fine coal, and oil sands processing has confirmed the role of tiny bubbles formed by cavitation in improving recovery efficiency. Based on the characteristics of vapor cavity bubbles, increased flotation kinetics by hydrodynamic cavitation could be attributed to a dual role: some collapsing cavity bubbles serving to break interfacial layers on particle surfaces, while other cavity bubbles attaching to those freshly exposed mineral surfaces. The role of water vapor and other gases within cavity bubbles in particle–bubble attachment remains to be explored, as does the action of frothers. Incorporating hydrodynamic cavitation into flotation systems to take advantage of its unique features is expected to develop the next generation of flotation machines. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687508002847