Settling Behavior in the Dewatering Process for Bitumen Froth with Different Qualities

• Author / Creator

  Xu,Runzhi

• The formation of extremely fine water drops (<10µm) during bitumen extraction causes trouble in downstream processing since chlorides in the water form hypo-chloric acids in the hydrogenation process, which corrodes equipment and leads to extensive maintenance costs. Hence, bitumen must be treated with demulsifier to improve settling by helping coalescence and flocculation. The effect of mixing on demulsifier performance has been studied on diluted bitumen and bitumen froth for many years, where mixing conditions during the addition of demulsifier have been shown to influence the settling of water and solids and affect the performance of the demulsifier.

  Bitumen froth of varying qualities was initially treated as the same substance, adding the same amount of demulsifier and operating under the same mixing conditions. However, the settling behavior of water and solids in different qualities of froths can be different. This project sets out to compare the settling behavior of water and solids in bitumen froths of average and poor qualities, including average-quality, high-water and high-solids froth. In previous thesis projects, standardized experiments were performed using the Confined Impeller Stirred Tank (CIST) to study mixing effects on demulsifier performance in average-quality and high-water froth. Most of the water and solids in average-quality froth finishes settling within the first 10 minutes once the impellers are turned off. By contrast, high-water froth shows an induction time, which can be up to 40 minutes. In this thesis project, high-solids froth was added to the data set. High-solids froth can also show an induction time which is somewhat shorter: up to 25 minutes. If the settling behavior of average-quality froth is set as a benchmark, both high-water and high-solids concentrations can lead to an induction time during separation. However, high-water concentration leads to a longer induction time than high-solids concentration. Although there is no measurable water settling during the induction time, coalescence and flocculation can still occur. In the last part of this work, microscope images are analyzed to determine the types of structures present in the froth. Under the microscope, irregularly-shaped large free water is dominant for high-water froth, but many spherical water drops are observed for high-solids froth. The identification and characterization of induction time in froth settling can be used to improve both the design of equipment and operating conditions. The most important lesson of this work is that froths with different qualities should be treated differently in order to obtain better dewatering efficiency.

• Subjects / Keywords

  • Settling Behavior
  • Bitumen Froth Treatment
  • Mixing

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3SB3XF12

• License

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