(424e) Predicting the Effect of Homogenization Pressure On Emulsion Drop Size Distributions

Emulsions constitute numerous natural as well as processed products with a wide variety of applications like foods, pharmaceuticals, cosmetics etc. We have developed a population balance equation (PBE) model to predict drop size distributions obtained from high pressure homogenization. Starting with the simple case of dilute oil?in?water emulsions, we identified the need for two breakage mechanisms to adequately describe the experimental model system (Raikar et al., 2009). We then advanced our PBE model to incorporate multiple daughter drop formation, which tremendously improved the model predictions over the case of binary breakage. We have also added coalescence to make the model applicable to more industrially relevant emulsion systems with high disperse phase volume fractions.

The quality of the final emulsion is strongly affected by the type and concentration of the ingredients used as well as the method used for preparation. We have tested the extensibility of our model for changes in formulation variables as well as processing conditions. The model could capture the effect of changes in formulation variables but failed to describe the effect of the operating pressure. The operating pressure was incorporated through the energy dissipation rate for the homogenizing valve. Our current description lacks extensibility for changes in pressure, and the present contribution is focused on identifying deficiencies in the energy dissipation rate function and identifying alternative functional forms that allow improved predictions. Computational fluid dynamics (CFD) simulations are used to understand the variation of the energy dissipation rate across the homogenizing value and to relate the local dissipation rate to the local pressure and to the applied pressure. The CFD results are used to construct alternative energy dissipation rate functions that provide improved drop size distribution predictions across a range of applied pressures.

Raikar N.B., Bhatia S.R., Malone M.F. and Henson M.A, ?Experimental Studies and Population Balance Equation Models for Breakage Prediction of Emulsion Drop Size Distributions?, Chemical Engineering Science, 64 , 2433-2447 (2009)