DEPOSITION OF BITUMEN AND ASPHALTENE-STABILIZED EMULSIONS IN AN IMPINGING JET CELL

Electric double-layer and van der Waals forces between emulsion drople ts play an important role in coalescence phenomena. In this study, an impinging jet cell was used to investigate the effect of colloidal for ces on the mass transfer of bitumen and asphaltene-stabilized mineral oil droplets to a flat collector surface, These droplet-collector inte ractions are analogous to droplet-droplet interactions, The droplet an d collector zeta potentials, the Debye length (kappa(-1)), and the flo w Reynolds number were varied in each set of experiments and the resul ting Sherwood number (dimensionless mass transfer to the collector sur face) was calculated, The deposition experiments were modeled by solvi ng the governing mass transfer and flow field equations, using analyti cal expressions from DLVO theory to describe the electric double-layer and van der Waals forces. Hamaker constants were calculated from Lifs hitz theory. Droplet and collector zeta potentials were calculated usi ng the Ionizable Surface Group model, Excellent agreement was found be tween the observed and calculated mass transfer rates for the bitumen emulsion, The results indicated that the behavior of the bitumen dropl ets could be predicted from DLVO theory, The calculated deposition rat es for the mineral oil emulsions were consistently higher than the obs erved values, Subsequent coagulation experiments also suggested that t he behavior of the mineral oil emulsions could not be predicted using DLVO theory, Analysis of the droplet distributions on the collector su rface for the different emulsions indicated that the bitumen droplets were much more strongly attached to the collector surface than the min eral oil droplets. Finally, no dependence of the mass transfer rate on the dispersed phase viscosity was observed. (C) 1995 Academic Press, Inc.