An unusual state during the production of solid stabilized emulsions in stirred tanks paste

2013-11-03
Ayrancı Tansık, İnci
Fradette, Louis
Solid stabilized emulsions (SSEs) are alternatives to conventional surfactant based emulsions. In SSEs the particles get adsorbed at the oil-water interface irreversibly, giving a more stable emulsion than the conventional emulsions. This is advantageous when the production of an emulsion is targeted. It may, however, be disadvantageous if undesired emulsions form in the presence of the three phases � oil-water-solids. An example of that is in oil sands processing. The small particles adsorbed at the oil-water interface form very small and very stable water droplets that are difficult to separate from the oil. In either case, whether the SSEs are the desired or the undesired product, there is a lack of knowledge of the necessary process conditions for the production. The current research on SSEs is limited to geometries that are not directly applicable to industry such as hand-shaken vials or cells stirred with homogenizers at overwhelmingly high Reynolds numbers, and to characterizing the emulsions. Our global objective is to demonstrate the impact of the process conditions on the production of SSEs in stirred tanks. This work focuses on an unusual state that the SSEs go through during production: paste state. Under continuous mixing, when the three phases, oil and water-solids slurry, are brought together first a normal SSE forms. Shortly after, the emulsion turns into a paste of particles in oil and water. Depending on the process conditions the time it takes to reach the paste state can be very short, or very long. The paste is not a proper emulsion, but it is not a complete separation of three phases. This paste state is similar to the rag layer that is seen during oil sands processing. The rag layer consists of some small droplets, oil and water phases and sand. Over time, as mixing of the paste is continued the paste turns back into a normal solid stabilized emulsion. The specific objective of this work is to determine the parameters that affect the formation of the paste, and to analyze how they affect the formation, and the time it takes to reach a paste. � The salt concentration, particle diameter, wettability of the particles, solids concentration, hydrodynamics and Reynolds number were found to affect the formation of the paste and time required for pasting. The tests were run for two impellers, a Rushton turbine and a pitched blade turbine, at varying Reynolds numbers, with or without baffles (with an off-centred impeller).� Phase diagrams that show the regions where paste forms for each impeller at varying oil, water and solids concentrations were generated. The emulsion formed after continued mixing of the paste also exhibited surprising behaviour by completely separating into three phases. The time required for this separation to occur varies based on the process conditions.
Citation Formats
İ. Ayrancı Tansık and L. Fradette, “An unusual state during the production of solid stabilized emulsions in stirred tanks paste,” presented at the American Institute of Chemical Engineers (AIChE), (3 - 08 Kasım 2013), 2013, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/78867.