A model of foam growth in the presence of antifoam emulsion

Theoretical predictions of foam growth rates in the presence of antifoam emulsion are compared with the results of foam rise experiments. The model is based on the assumption that the rate of bubble coalescence is determined by the rate of heterocoagulation of antifoam emulsion droplets with air bubbles in the liquid phase. The main features of the experimental data were predicted by the model. These include: high antifoam concentration prevents foam growth until the antifoam concentration in the liquid phase is depleted; linear foam rise curves (i.e. volume vs time) are obtained when the antifoam concentration is low; and antifoam is active for a longer time when treating larger bubbles.