Use of the foam drainage equation to model water flow in flotation froth

Abstract

The standard foam drainage equation (Leonard and Lemlich, 1965; Goldfarb et al., 1988) was taken to model froth water flow in laboratory flotation column, using polypropylene glycols (PPG 425 and PPG 725) as frothers. Simulations were run to investigate the sensitivity of the model with respect to operating parameters. In the absence of particles, the model is in agreement with the experiments within a certain range of frother concentration; below and above which, it failed. Experimentally measured water flow rate was overestimated by the model at low and high frother concentration. Such discrepancies may be attributed to the assumptions accompanying the standard foam drainage equation. For instance, the model was modified to accommodate the effect of surface shear viscosity, which was measured using a deep channel surface shear viscometer. When plotted against frother concentration, surface shear viscosity follows the same trend as that of net water flow rate. It showed a maximum value within an intermediate range of frother concentration. The modified foam drainage equation that takes into account the interfacial properties of the gas-liquid interface significantly reduced the discrepancies between the model and experiment. However, a further improvement of the model is necessary to be applicable to three phase flowing froths in mineral processing industry.