Abstract

Column flotation is a technique used to recover particles or species of interest in air-water-particle or air-water systems. Air or gas is fed under pressure through dispersers or mechanical means to generate the dispersed phase in the continuous phase. Dispersion characteristics (bubble diameter, gas volume and bubble surface area) are a very important aspect that must be adjusted to each separation application and on which the capture and recovery efficiency of valuable species depends; unfortunately, the average bubble diameter cannot be measured directly in practice because flotation devices are not transparent; moreover, there is no control over the characteristics of the dispersions generated by most gas dispersers; in this last case, effective and reliable simulation of gas dispersers becomes important to control the characteristics of the dispersion that suits each specific application, whether mineral or non-mineral. In this work, the diameters of bubbles generated by a venturi-type disperser installed in a transparent laboratory flotation column were measured. These diameters measured from photographic evidence were compared with the bubble sizes estimated by solving the Drift Flux model and with the diameters predicted by the CFD simulation of the laboratory column used.

The comparison results shows that the measured, estimated and predicted bubble diameters reasonably converge within a difference range of less than 20%. The above allows us to establish the feasibility of controlling the characteristics of the dispersion of gases generated with the venturi, and to estimate with reasonable precision the characteristics of the dispersion generated in an air-water system, in addition to concluding that the design through CFD simulation of venturi-type dispersers under particular operating conditions of a flotation device is reliable.

Keywords:Bubble diameter; Drift flux; CFD; Column flotation; Bubble surface area flux