File(s) under permanent embargo
Reason: This item is currently closed access.
Phase field modelling of spinodal decomposition in the oil/water/asphaltene system
In this paper the quantitative applicability of van der Sman/van der Graaf type Ginzburg–Landau theories
of surfactant assisted phase separation [van der Sman et al., Rheol. Acta, 2006, 46, 3] is studied for real
systems displaying high surfactant concentrations at the liquid–liquid interface. The model is applied for
the water/heptane/asphaltene system (a model of heavy crude oil), for which recent molecular dynamics
(MD) simulations provide microscopic data needed to calibrate the theory. A list of general requirements
is set up first, which is then followed by analytical calculations of the equilibrium properties of the system,
such as the equilibrium liquid densities, the adsorption isotherm and the interfacial tension. Based on the
results of these calculations, the model parameters are then determined numerically, yielding a reasonable
reproduction of the MD density profiles. The results of time-dependent simulations addressing the
dynamical behaviour of the system will also be presented. It will be shown that the competition between
the diffusion and hydrodynamic time scales can lead to the formation of an emulsion. We also address the
main difficulties and limitations of the theory regarding quantitative modelling of surfactant assisted liquid
phase separation.
Funding
This work has been supported by the VISTA basic research programme project No. 6359 ‘‘Surfactants for water/CO2/hydrocarbon emulsions for combined CO2 storage and utilization’’ of the Norwegian Academy of Science and Letters and the Statoil.
History
School
- Science
Department
- Mathematical Sciences