Geotechnical Behaviour of Two Novel Polymer Treatments of Oil Sands Fine Tailings

• Author / Creator

  Amoako, Kwaku Akrofi

• Reclamation of oil sands fluid fine tailings (FFT) is a challenge for mine operators in Alberta because of their high water content and slow self-weight dewatering. Chemical additives, including polymer flocculants, are used by operators as a treatment technology to reduce volumes and increase the density and strength of FFT deposits through dewatering. This research investigates the geotechnical behaviour of two novel polymer treatments on FFT with a focus on the immediate and long-term dewatering performance compared to that of an existing commercially available anionic polyacrylamide. A suite of basic and advanced laboratory characterization tests was conducted to evaluate the compressibility, hydraulic conductivity and undrained shear strength of tailings resulting from each polymer treatment and untreated FFT. Thixotropic effects on the strength and dewatering properties of polymer amended FFT were also examined.
  This study shows that the addition of each of the new polymers to FFT produces a distinct floc structure with physical and chemical properties that affect the dewatering and strength characteristics of the tailings. The neutral polymer produces rapid initial dewatering after treatment, while the cationic polymer treatment exhibits better initial dewaterability, but poor immediate dewatering efficiency. The neutral polymer achieves high early deposit strength and small long-term settlement, owing to its strong floc bonds. However, the sensitivity of these flocs to shear can affect the near-term dewatering performance of the neutral polymer treatment. In contrast, the cationic polymer treatment promotes long-term dewatering, leading to large long-term settlement and continual gain in deposit density and strength. This research also indicates the benefit of thixotropy in the strength development of polymer amended FFT after deposition. It is concluded that the new polymer treatments provide superior initial dewaterability and shear strength compared to the anionic polymer treatment. Both new polymer treatments provide improved dewatering, either in the immediate or long term, that can be potentially leveraged with further polymer modification and additional engineering to reclaim FFT deposits into acceptable landscapes with reduced risk.

• Subjects / Keywords

  • Polymer treatment
  • Large strain consolidation
  • Fluid fine tailings
  • Reclamation
  • Flocculation
  • Dewatering
  • Thixotropic strength

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-vvr6-sn60

• 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.