Modeling of turbulent drop coalescence in the presence of electrostatic forces

• New coalescence model for dispersions containing ionic species was derived.
• Destabilization effect of salt is predicted by new model.
• Importance of additional disruptive stress due to interfacial tension difference was proved.
• Good agreement between predictions of breakage and coalescence models with experiments.

The influence of ionic surfactant (SDS) on the drop size distribution in stirred liquid–liquid dispersions was considered. The destabilizing effect of a salt (NaBr) on the dispersion was also discussed. A new model for drop coalescence in turbulent flow in the presence of repulsive forces was derived. The film drainage between rigid and deformed droplets was taken into account. The influence of interfacial tension and electrostatic repulsion on the behavior of the dispersion in different zones of a stirred tank was predicted. It was also shown that, additional disruptive stresses, resulting from interfacial tension difference, due to surfactant desorption, increase drop breakage rate. In both breakage and coalescence models local intermittency was taken into account by using the multifractal formalism. Drop size distributions were predicted, by solving the population balance equation, and compared with experimental data.