Modelling detachment rates of hydrophobic particles from bubbles in a froth phase

Abstract

In the current study, computational fluid dynamics (CFD) simulations were used to investigate the detachment rate of hydrophobic particles in the froth phase of a flotation column reactor. A stable froth was formed by injecting the air through a slurry of water at 20 °C and silica (SiO2) solid particles. The slurry inside pulp zone was assumed to be perfectly mixed. A number of sub models representing various processes of the bubble-bubble interaction and bubble-particle interaction in the pulp and froth zones were included in the present work through user defined subroutines coupled to commercial CFD software AVL FIRE v2017. Modelling calculations were conducted using a Eulerian–Eulerian multiphase approach to solve multiphase flow equations for the conservation of mass, momentum and turbulence quantities. The standard k–ε dispersed turbulence model was used in the present study for its accuracy. The effect of solid concentration and gas flow rate on the detachment of hydrophobic particles from the froth was studied. The predicted results were in reasonable agreement with experimental observations and available literature results. It was found that the froth height increased with the increase of gas flow rate, and decreased with the increasing of solid concentration. The dynamic froth stability factor was observed to decrease by 16–35 % with the increase of gas flow rate. Depending on the operating conditions, the increase in the detachment rate was in the 25–225% range as Q was increased from 1.4 L/min to 2.1 L/min. The main observation of the present study was that the increase of solid concentration and gas flow rate have a significant effect on the detachment rate of hydrophobic particles in froth layer and thus its stability.