Rs. Sanders et al., DEPOSITION OF BITUMEN AND ASPHALTENE-STABILIZED EMULSIONS IN AN IMPINGING JET CELL, Journal of colloid and interface science, 174(1), 1995, pp. 230-245
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.