(480c) Phase-Inversion and Coalescence in Turbulent Liquid/Liquid-Dispersions

Understanding the dispersions of immiscible liquids is still very challenging. A detailed understanding of the opposed phenomena of drop breakage and coalescence is necessary for a successful mathematical modelling. A further difficulty handling such dispersed systems is the possible danger of a phase inversion (PI). Does this phenomenon occur spontaneously during an industrial process, it can have fatal consequences for product and equipment [1]. Therefore also a deeper understanding and modelling of this phenomenon is desirable.

A turbulent liquid/liquid system was investigated. The operation parameters dispersed phase fraction and surfactant concentration have been varied systematically to reliably achieve PI. The transient drop sizes as the instable behaviour of the water and organic phase have been observed using an in-situ microscope [2]. The drop size was measured using a fully automated image analysis tool [3]. Furthermore, the simulation of the drop size was carried out using population balance equation (PBE).

By using the named measurement technique, it was possible to detect the starting point of the PI. Furthermore the occurrence of double emulsions was observed during the procedure. The drop size was fluctuating. The change of the droplet sizes with variation of the operating parameters mentioned was successfully simulated with the help of the PBE. A simulation of the occurrence of PI using PBE was not predictable with the used model.

[1] Nienow, A. W., Adv. Colloid Interface Sci. 2004, 108, 95-103.

[2] Maaß, S., Wollny, S., Voigt, A., Kraume, M., Exp. Fluids 2011, 50, 259-269.

[3] Maaß, S., Rojahn, J., Hänsch, R., Kraume, M., Comput. Chem. Eng. 2012, 45: 27-37.