Enhancing Oil Sands Tailings Treatment by Lime Addition

• Author / Creator

  Tan, Yang

• This research aims to improve oil sands tailings treatment by applying a combination of quick lime (calcium oxide) and anionic or cationic polymers in the flocculation process. A procedure including mixing lime, dilution of mature fine tailings (MFT) in the lime supernatant and addition of polymeric flocculants optimizes settling efficiency of MFT solids. An improvement of flocculation is obtained as shown by achieving significantly higher initial settling rate, lower turbidity of recycled water and higher solid content sediments with less amount of polymers. Both anionic polymer Magnafloc336 and cationic polymer Zetag8110 are tested separately.In order to study the mechanism and explain why the best performance appears with the intermediate dosage of lime, focus beam reflectance measurement (FBRM) is applied to observe the floc size change during the flocculation process. Zeta potentials of tailings particles are measured by zeta phoremeter in solutions of different ion concentrations and pH. The results together with settling test results and ion chromatography measurements are analyzed. We find that the increased concentration of calcium monohydroxide ions (Ca(OH)+) is the key species influencing zeta potentials of tailings particles and flocculation process. Finally, quartz crystal microbalance with dissipation monitoring (QCMD) is applied study the adsorption mechanism and conformational changes of polymers on tailings particles. We find that increasing the lime concentration can enhance the adsorption of both anionic and cationic polymers.The increased calcium ions and hydrolyzed ions are shown to reduce the negative charges of the particle surface and also screen the strong repulsions between segments of polymer chains. The conformational changes of polymers are detected by dissipation monitoring on QCMD. The more compact conformations of polymers may facilitate the adsorption but could also hinder the bridging effect of flocculation process. With excessive concentrations of lime, we observe a decay of flocculation performance.

• Subjects / Keywords

  • Tailings
  • Calcium oxide
  • Flocculation
  • Oil sands

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-e8k7-kb13

• License

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