Abstract

Column flotation is a separation method applied to recover mineral species of interest or to clean effluents contaminated with heavy metals or with organics; in these cases, control of gas dispersion characteristics (bubble diameter, gas volume, and bubble surface area) is important for flotation devices to operate efficiently. Mathematical modeling was carried out using Computational Fluid Dynamics (CFD), for 6 Venturi-type gas disperser designs, varying the diameter ratio (convergent and divergent diameter/vena contracta diameter), and for different air inlets to the disperser. The venturi was simulated and coupled to a laboratory flotation column. The simulation results show that with the diameter ratio in the Venturi equal to 3, the pressure drop values are more stable and represent more homogeneous dispersion characteristics. Regarding the number of air inlets to the disperser, it is concluded that 4 of them at 45° is the most efficient, because it maintains the laminar flow, and the pressure differential is sufficiently large. The feasibility of applying the simulation tool for the design of Venturi-type dispersers installed in a flotation column is shown, by predicting values of gas fractions of up to 18%, and bubble diameters of 0.5 to 2mm.

Keywords:Venturi-type disperser; Gas disperser; Gas holdup; Bubbles design; CFD simulation; Flotation columns