Various workers have shown the asphaltene fraction of crude oil to be responsible for the highly stable W/O emulsions formed after marine oil spillages. Electron microscope studies on crude oil emulsions using the freeze etching technique showed the oil/water interface to be smooth on the aqueous side but to have a particulate structure on the oil side. In Brega crude oil emulsions, waxy plates were aligned along the interface. Also observed were the coherence of the interfacial film and droplet coalescence. Allowing a method error of ± 10%, good agreement was found between computer calculated droplet diameters from the log-normal distribution equation and standard statistical mean diameters. Sc (interfacial area/unit volume oil phase) was larger for salt water emulsions. An equation proposed for Sc as a function of stirring time fitted very well for all three crude oil emulsions. The maximum Sc increased with φ (volume fraction) indicating a minimum possible diameter droplet fold by the stirrer. A rate parameter in the equation is probably related to the asphaltene diffusion to the interface. A good fit with the data was obtained when the equation was modified to account for detergent addition delaying emulsion formation. A second rate parameter may reflect the irreversible replacement of detergent at the interface by asphaltenes. Ageing studies showed that once stabilisation was complete, detergent present only slowly affected coalescence. A heating effect explained the non-linearity of Kuwait and Tia Juana emulsion rheograms. The greater viscosity of Tia Juana stabilised emulsions was explained by a thicker supporting asphaltene layer. The elasticity of the-interfacial film accounted for anomalous behaviour in emulsions of asphaltenes dispersed in m-xylene/n-octane. The extrapolated yield point and critical shear rate were used as empirical measures of deformability and attractive forces respectively.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:474411 |
| Date | January 1975 |
| Creators | Symonds, John David |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/11473/ |
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