Population balance modelling of a continuous static mixer-based emulsification process

Abstract

Emulsions preparation using static mixers is investigated in this work. First, it is demonstrated that a fully continuous emulsification process is experimentally feasible through the direct pumping of the two immiscible phases individually into a set of static mixers. This process is advantageous, especially in the case of highly viscous fluids, compared to that employing a pre-emulsification step in stirred tanks which creates inhomogeneity in the sample in terms of the droplet size. Second, a population balance model is employed to predict the droplet size distribution at the process outlet. To do so, a recently modified breakage kernel of Coulaloglou and Tavlarides, accounting for droplet breakage within the inertial and dissipation subranges of isotropic turbulence, is used. In this work, we propose to calculate the second-order longitudinal structure function using semi-empirical formulas. Moreover, the kernel considers the droplet cohesive force due to the viscosity of the dispersed. While this term is sometimes neglected in the literature, we found that this is certainly due to limited variation of the dispersed phase viscosity in the set used for parameter identification. The developed model is validated against a wide range of experimental data and showed very good prediction capabilities.