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Bubble size measurement in electroflotation / Md. Shahjahan Kaisar Alam Sarkar in Minerals engineering, Vol. 23 N° 11-13 (Octobre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 1058–1065 Titre : Bubble size measurement in electroflotation Type de document : texte imprimé Auteurs : Md. Shahjahan Kaisar Alam Sarkar, Auteur ; G.M. Evans, Auteur ; S.W. Donne, Auteur Année de publication : 2011 Article en page(s) : pp. 1058–1065 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Electroflotation  Detached  bubble  diameter  Bubble  generation  rate Résumé : A feature of electroflotation is the ability to create very fine bubbles, which are known to improve flotation performance of fine particles. This study was aimed at determining the hydrogen bubble size generated as a function of current density and electrode geometry. Experiments were performed in a viewing cell that allowed direct visualization of hydrogen bubbles being generated and transported away from platinum wire electrodes of 90, 120 and 190 μm in diameter. The detached bubble diameters varied between 15 and 23 μm in diameter, and for each wire diameter, were little influenced by the applied current in the range 150–350 A/m2. The measurements were consistent with those predicted from a simple force balance analysis based on a H2–Pt–0.2M Na2SO4 contact angle of 0.18°. Interestingly, upon detachment, the bubble size increased rapidly, recording up to an 8-fold increase in volume in the first few millimeters of rise, before approaching the steady state diameter of between 30 and 50 μm in the bulk. This increase in bubble size was found to be mostly due to the transfer of dissolve hydrogen into growing bubble while moving through the electrolyte super saturated by dissolved hydrogen gas. The equilibrium bulk diameter was found to be a function of the rate of hydrogen production, bubble nucleation rate, and dissolved gas concentration field. Consequently, electroflotation cells need to be designed to optimise the contact between the supersaturated liquid and the rising bubble plume. By doing this, the volumetric flux of bubbles will be maximised leading to improved flotation performance. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510002141 [article] Bubble size measurement in electroflotation [texte imprimé] / Md. Shahjahan Kaisar Alam Sarkar, Auteur ; G.M. Evans, Auteur ; S.W. Donne, Auteur . - 2011 . - pp. 1058–1065. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 1058–1065 Mots-clés : Electroflotation  Detached  bubble  diameter  Bubble  generation  rate Résumé : A feature of electroflotation is the ability to create very fine bubbles, which are known to improve flotation performance of fine particles. This study was aimed at determining the hydrogen bubble size generated as a function of current density and electrode geometry. Experiments were performed in a viewing cell that allowed direct visualization of hydrogen bubbles being generated and transported away from platinum wire electrodes of 90, 120 and 190 μm in diameter. The detached bubble diameters varied between 15 and 23 μm in diameter, and for each wire diameter, were little influenced by the applied current in the range 150–350 A/m2. The measurements were consistent with those predicted from a simple force balance analysis based on a H2–Pt–0.2M Na2SO4 contact angle of 0.18°. Interestingly, upon detachment, the bubble size increased rapidly, recording up to an 8-fold increase in volume in the first few millimeters of rise, before approaching the steady state diameter of between 30 and 50 μm in the bulk. This increase in bubble size was found to be mostly due to the transfer of dissolve hydrogen into growing bubble while moving through the electrolyte super saturated by dissolved hydrogen gas. The equilibrium bulk diameter was found to be a function of the rate of hydrogen production, bubble nucleation rate, and dissolved gas concentration field. Consequently, electroflotation cells need to be designed to optimise the contact between the supersaturated liquid and the rising bubble plume. By doing this, the volumetric flux of bubbles will be maximised leading to improved flotation performance. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510002141