Understanding the Role of Caustic Addition in Oil Sands Processing

  • Author / Creator
    Zhu, Qian
  • Sodium hydroxide (NaOH) is used as a chemical additive to enhance bitumen recovery from oil sands by surface-mining extraction process. The addition of NaOH adjusts the pH of the slurry water to pH ~8.5 (approximate pH of process water). The change in pH of oil sand slurry affects the process performance. In the current study, the effect of pH was investigated by varying the caustic usage up to about 0.7 wt. % (based on the mass of oil sand). Many parameters such as: Naphthenic acid, divalent cations and the surface charges of particles, bitumen and air bubbles have a significant impact on bitumen recovery and froth quality. A Study of the extraction process at a fundamental level improves our understanding of the key parameters that govern bitumen recovery. Four oil sand ores of different composition were studied. Two ores were classified as high fines (CN912 and AS), and two as average fines (MA and AZ). Using Denver cell flotation, the recovery of high fines ores was observed to be caustic dependent, in contrast to little variation in bitumen recovery with increasing pH for average fines ores. Unlike recovery, the froth quality showed a general improvement with increasing pH for all the ores tested. Such behavior is believed to be related to the fundamental steps of bitumen extraction process such as: air-bitumen attachment (induction) time and slime coating defined as the coating of bitumen droplets by ultrafine particles. The induction time is shown to increase almost linearly with increasing pH for all the ores, while slime coating is shown to be most severe at low pH, improving with increasing pH. The severity of slime coating is shown to be somewhat dependent on the type of ores.

  • Subjects / Keywords
  • Graduation date
    Spring 2013
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • 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.