Dilational Elasticity of Emulsified Bitumen Droplet Surfaces

Kevin Moran

Syncrude Canada Ltd., Edmonton Research Centre, 9421 – 17 Avenue

Edmonton, AB, Canada, T6N 1H4

moran.kevin@syncrude.com

Considerable emphasis has been placed on the processing of bitumen, an extremely viscous heavy crude oil extracted from oil sands ores.  In commercial water-based extraction processes, the ore is mixed with water, air and process aids.  Small bitumen droplets (~10-40 microns in diameter) represent a significant fraction of the total hydrocarbon in the resulting aqueous slurry.  It is advantageous to promote the coalescence of these droplets in order to improve recovery via gravity-based separation.  Clearly, coalescence is a function of the mechanical surface properties of emulsified droplets. A reasonable understanding of these properties may provide insights into droplet interaction and coalescence mechanisms.

Conservative properties of an interface can be calculated by measuring its deformations in response to static applied forces. In this study, a micropipette-based technique is used to mechanically deform emulsified bitumen droplets; the applied force is quantified through the deflection of a sensitive cantilever. In describing the stress-strain response, at relatively small deformations, a model is developed that captures the relevant conservative material properties of the interface: These are the equilibrium tension and dilational elasticity. The dilational elasticity and equilibrium tension of bitumen droplet surfaces, emulsified in industrially relevant aqueous environments, are examined. It is demonstrated that the interfacial dilational elasticity of bitumen droplets depends on temperature and droplet age, while the tension is relatively invariant to these variables.