THE EFFECT OF SHEAR ON SWEEP FLOCCULATION IN STABLE WATER-IN-OIL EMULSIONS

• Author / Creator

  Bhargava, Aakanksha

• Naphthenic Froth Treatment (NFT) is employed to remove water droplets and solids from the bitumen froth recovered from the extracted oilsands ore. In the process, bitumen froth is diluted with naphtha to reduce the viscosity and induce density difference to promote settling of water droplets and solids. The diluted bitumen froth is then mixed with a demulsifier and passed through Inclined Plate Settlers (IPSs) and centrifuges. The IPS units separate most water and solids from the diluted bitumen froth, leaving the final concentration of around 1.5 -2.5 wt % water and 0.5 wt% solids in the final product. The remaining water is present in the form of very stable droplets that are difficult to separate without the assistance of induced flocculation or coalescence. These water droplets in diluted bitumen are detrimental to upgrading facilities as they may cause corrosion problems. The selection of operating conditions for separating equipment (IPS) such as demulsifier selection/optimal concentration depends on the data obtained from laboratory scale bottle or jar tests. These tests are done under static conditions that are not representative of the shear/flow experienced at the industrial scale. The main objective of the project is to understand the effect of shear on the flocculation of water droplets. This project uses water-in-light mineral oil emulsions as analogs for water-in-diluted bitumen emulsions.
  Several experiments were conducted to determine the effect of shear rate on the flocculation of water droplets in water-in-light mineral oil emulsions. The effect of shear was studied using a custom-built Couette cell, which has a shear rate range similar to IPS. The shear rate selected is 12.2 – 29.3 s-1, similar to that experienced by the water droplets between the parallel plates in an IPS. The emulsion was sheared in the Couette cell using a precisely defined protocol and then allowed to settle for one hour. 
  The laminar shear rate (12.2 – 29.3 s-1) induced in the water-in-light mineral oil emulsion forces water droplets/ flocs to come in contact with each other, increasing the number of collisions and promoting floc formation. Furthermore, the formed flocs have higher settling velocities than individual droplets. The faster settling flocs sweep away single water droplets or small flocs present in their settling path, leading to further growth of the flocs, which increases their settling velocity; this mechanism is called sweep flocculation. Sweep flocculation promotes the removal of small water droplets from the oil that would otherwise take many days or hours to settle. It can be inferred from the experiments that shearing the emulsion promotes the formation of flocs, which further induces sweep flocculation in the emulsion and results in a cleaner oil as compared to the emulsions, that have not been sheared in the Couette cell.

• Subjects / Keywords

  • Sweep flocculation
  • Emulsions
  • Shear

• Graduation date

  Spring 2022

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-gj3g-re41

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.