(155g) A Semi-Empirical Approach to Predict Solids Stabilized Emulsion Size

Authors: 
Tsabet, E., NSERC/TOTAL Industrial chair, Montreal Polytechnic
Fradette, L., NSERC/TOTAL Industrial chair, Montreal Polytechnic

The droplet size of concentrated solids stabilized emulsions produced in an agitated reactor is modelled using a semi-empirical approach. The modelling procedure estimates the coverage and the interface generation potential and assumes that the theoretical stabilized interface is equal to the lowest potential. The coverage potential is obtained by considering the solids properties while the interface generation is deduced from the correlation developed by Calabrese R.V. et al. (1986). The initial Calabrese correlation was modified to include the coalescence effect due to the oil concentrations of up to 20% considered. The effect of particles on both breakage and coalescence processes is also taken into account. Assuming that stabilization by particles is achieved by covering the droplets with a particles network, the stabilization is analysed at two scales: the droplet and the particle. Four steps are used to model particles absorption and four efficiencies are defined. At the particle scale, the particle/droplet attachment should be achieved concomitantly with the collision, then the three phase contact line should be formed and finally the attachment force should be strong enough to avoid detachment. At the d droplet scale the coverage rate should be higher than the coalescence rate. Combining the analysis at the two scales, a good agreement with experimental results is obtained for a wide range of viscosities, for many impeller speeds and solids concentrations of up to 20%. An adapted form of the Calabrese correlation is finally proposed to account for a wider range of conditions than initially and include the presence of solids as stabilizers. The role of the four efficiencies on the modelling approach is highlighted and the impact of operating conditions is emphasised.