REVIEWING THE EXPERIMENTAL PROCEDURE TO DETERMINE THE CARRYING CAPACITY IN FLOTATION COLUMNS

• Published in: Canadian metallurgical quarterly 2004, Vol.43 (4), p.513-520
• Main Authors: LI, H., VILLAR, R. DEL, GOMEZ, C.O.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Metallurgical fundamentals; Metals. Metallurgy; Production of metals
• ISSN: 0008-4433; 1879-1395
• DOI: 10.1179/cmq.2004.43.4.513

Carrying capacity is a parameter required in the sizing of flotation columns that depends on the characteristics of the generated bubble population and on the mineral density and particle size distribution. Two alternatives were originally proposed by Espinosa-Gomez et al. in the mid-80s for its evaluation: a semi-empirical model based on then available data and an experimental procedure for direct estimation. The model has been improved since, but its calibration still depends on values obtained using the original experimental procedure. To re-evaluate the experimental procedure, tests for different combinations of collection and froth zone heights were performed at three different gas velocities in a laboratory column processing a mixture of hematite/silica particles. The column was instrumented to allow for the continuous calculation of bubble surface area flux which was used to account for changes in the characteristics of the bubble population generated in the column and to explain concentrate particle size variations by the estimation of particle coverage of the bubble surface. The experimental results demonstrate that the collection and froth zone heights as well as the gas rate affect the determination of the carrying capacity. Particle coverage was between 10 and 18% and showed almost no variation in spite of the large increase in the concentrate solids rate. This increase was compensated by the reduction in concentrate particle size. These results lead to the conclusion that both the concept of carrying capacity and its experimental determination method require a deep revision. La capacité de transport, un des paramètres requis pour le dimensionnement des colonnes de flottation, dépend des caractéristiques de la population de bulles générées et de la distribution granulométriques des particules minérales à flotter. Deux alternatives pour estimer sa valeur furent proposées par Espinosa et al. lors de l'introduction de ce paramètre dans les années 80: un model semi-empirique basé sur les données alors disponibles et une procédure expérimentale pour son estimation directe. Le modèle a été amélioré par la suite, mais pour son calibrage, des valeurs encore obtenues par la méthode expérimentale originale sont requises. À objet de re-évaluer cette procédure, des essais réalisés avec différentes combinaisons de hauteur de collecte et de nettoyage à trois taux d'aération différents furent complétés dans une colonne de laboratoire traitant un mélange de pa