Deposition of Bitumen and Asphaltene-Stabilized Emulsions in an Impinging Jet Cell

Abstract

Electric double-layer and van der Waals forces between emulsion droplets play an important role in coalescence phenomena. In this study, an impinging jet cell was used to investigate the effect of colloidal forces on the mass transfer of bitumen and asphaltene-stabilized mineral oil droplets to a flat collector surface. These droplet-collector interactions are analogous to droplet-droplet interactions. The droplet and collector zeta potentials, the Debye length (κ-1), and the flow Reynolds number were varied in each set of experiments and the resulting Sherwood number (dimensionless mass transfer to the collector surface) was calculated. The deposition experiments were modeled by solving the governing mass transfer and flow field equations, using analytical expressions from DLVO theory to describe the electric double-layer and van der Waals forces. Hamaker constants were calculated from Lifshitz theory. Droplet and collector zeta potentials were calculated using the Ionizable Surface Group model. Excellent agreement was found between the observed and calculated mass transfer rates for the bitumen emulsion. The results indicated that the behavior of the bitumen droplets could be predicted from DLVO theory. The calculated deposition rates for the mineral oil emulsions were consistently higher than the observed values. Subsequent coagulation experiments also suggested that the behavior of the mineral oil emulsions could not be predicted using DLVO theory. Analysis of the droplet distributions on the collector surface for the different emulsions indicated that the bitumen droplets were much more strongly attached to the collector surface than the mineral oil droplets. Finally, no dependence of the mass transfer rate on the dispersed phase viscosity was observed.