Role of Clays in Bitumen Extraction of Water-Based Oil Sands Processing

• Author / Creator

  Li, An

• Fines , especially clays, in oil sands ores have a significant impact on the processability of the ore, or performance of bitumen extraction from the ore. The main focus of this research is to understand the effects of the type and wettability of clays on the performance of bitumen extraction from mined oil sands to develop a viable solution in dealing with clay/fines in operations.
  The results from batch extraction tests showed a detrimental role of doping hydrophilic clays (kaolinite, illite, and montmorillonite) in suppressing bitumen recovery with montmorillonite being the worst. With 1 ~ 5 wt.% of clays addition, bitumen recovery reduced from the baseline of 88% to 78 ~ 25, 73 ~ 13, and 61 ~ 4% when doped with kaolinite, illite, and montmorillonite, respectively. The presence of clays in bitumen froth was found to be carried over by their attachment to bitumen. The crucial role of clays in bitumen slime-coating was studied through atomic force microscopy (AFM), ζ potential distribution measurement, and clay deposition test. For the hydrophilic clays, repulsive long-range forces with small adhesions between bitumen and the model basal planes of clays were measured by AFM. These forces could not explain the bitumen-clay hetero-coagulation observed in ζ potential distribution measurements in solutions of high clay to bitumen ratios. The deposition tests showed that clay concentration was an essential parameter in determining the bitumen-clay hetero-coagulation process. Strong slime-coating of clay particles on bitumen droplets occurred only above a critical clay concentration for a given type of clays. This critical concentration varied with clay type and water chemistry. In contrast to the results from earlier studies, kaolinite in this study was found to deposit strongly on bitumen surfaces. Under the conditions of extraction tests, the critical concentrations for kaolinite, illite, and montmorillonite were determined to be 12.9, 8.6, and 5.8 g/L, respectively. Increasing pH of the slurry could improve the critical clay concentrations while the presence of monovalent or divalent cations was found to reduce the critical clay concentrations. To reduce slime-coating in oil sands operations, the concentration of clays in process water should be controlled to be lower than the critical concentration.
  Hydrophilic clays were contaminated by soaking in toluene-diluted-bitumen solutions to exam the effect of solid hydrophobicity on bitumen extraction. In this case, different clays had a similar impact on bitumen extraction performance with a bitumen recovery of 68 ~ 29% because their surfaces were covered with similar materials during the soaking process. Due to different surface properties, hydrophobic clays had a less significant depression on bitumen recovery but a more significant deterioration on froth quality than hydrophilic clays. Similar slime-coating was observed among the different clays once contaminated by diluted bitumen, with the results being closely related to the hydrophobicity of contaminated clays. Furthermore, the presence of a large number of clays in bitumen extraction could result in excessive emulsification of bitumen into small droplets, contributing to low bitumen recovery.
  A simple and robust method based on the use of X-ray fluorescence (XRF) spectroscopy to measure potassium content was developed as a tool for the determination of the clay/fines content in oil sands. Both the XRF method and the conventional methylene blue titration (MBT) method were used to analyze various solid samples, including model solids with and without surface contamination as well as the solids extracted from bitumen froth and tailings stream. The results showed that the XRF method was more tolerant to surface contamination and therefore more reliable in characterizing clay/fines content in oil sands and relevant processing streams than the MBT method. The high potassium content of froth solids determined by the XRF method served as a marker of low bitumen recovery discussed in this study.
  To alleviate or eliminate the negative impact of high fines (clay) content in oil sands on bitumen extraction, NaOH addition and ore blending were tested as the coping strategies. It was found that both were effective in enhancing bitumen recovery.

• Subjects / Keywords

  • bitumen extraction
  • clays
  • oil sands

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-8saa-8952

• License

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