Role of Residual Bitumen on the Solvent Removal from Alberta Oil Sands Gangue

  • Author / Creator
  • Non-aqueous extraction technologies are currently being investigated as an alternative to the conventional water based process for extracting bitumen from oil sands. The reduced dependence on fresh water and land for creation of tailing ponds makes non-aqueous technologies a greener alternative. The recovery of solvent from the extracted waste termed as ‘gangue’ to industrially as well as environmentally acceptable limits remains a major challenge. Preliminary drying experiments under ambient conditions of the gangue obtained from rich grade ore extraction using cyclohexane exhibited an interesting albeit unexpected physical process. The residual bitumen in the gangue migrated along with the solvent (cyclohexane) to the top of the bed forming a dark bitumen enriched top layer. The deposition of bitumen in the pores could hinder the solvent connectivity and removal from the bed. Understanding the effect of this bitumen migration process on solvent recovery was vital. The residual bitumen and initial cyclohexane composition in extracted gangue were highly variable. To gain an insight into the residual bitumen-solvent interaction during the gangue drying process a control was needed on the composition of the components making up the gangue. An experimental protocol was developed to prepare control samples termed henceforth as ‘reconstituted gangue’. These reconstituted gangue samples were representative of the extracted gangue samples obtained after the non-aqueous extraction process. Reconstituted gangue samples were prepared with residual bitumen as would be expected in extracted gangue for bitumen recoveries in the range 84-96%. Two initial solvent contents of 12 and 8% by net weight of gangue were selected. The water content was kept constant. The drying experiments were performed with reconstituted gangue inside a fume-hood under ambient conditions for 2 hrs. Three bed heights of 0.6,1 and 1.4 cm were chosen for sample packing. The drying curves had two stages, a fast drying stage and a slow drying stage separated by a breakpoint termed as ‘transition time’. It was concluded that the transition time needed to be reached before ending the drying process so as to obtain residual cyclohexane content < 600 ppm. For any bed height, for reconstituted gangue samples with initially 12% cyclohexane, the samples with highest residual bitumen content had the highest final pore volume saturation in the top layer with bitumen, lowest initial 10 min flux and the maximum delay in transition time to occur. Exactly opposite observations were seen with the samples with the lowest residual bitumen content. Higher bitumen migration was observed for reconstituted gangue samples with 12% initial cyclohexane compared to 8% initial cyclohexane. An initial flux reduction was also seen in reconstituted gangue samples with 8% initial cyclohexane with increase in residual bitumen content though not as obvious as for the 12% initial cyclohexane samples. For reconstituted samples with 8% initial cyclohexane content, the delay in transition time with increase in residual bitumen content though apparent wasn’t gradual as in samples with 12% initial cyclohexane but more like a step change after a significant increase in residual bitumen content. For achieving the goal residual cyclohexane content of <260 ppm in 2 hr of drying at ambient conditions the residual bitumen content should be <1.8 wt. % and the bed height <1 cm.

  • Subjects / Keywords
  • Graduation date
    Spring 2016
  • 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.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Specialization
    • Chemical Engineering
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Choi,Phillip (Chemical and Materials Engineering)
    • Semagina,Natalia (Chemical and Materials Engineering)
    • Chung,Hyun-Joong (Chemical and Materials Engineering)
    • Liu,Qi (Chemical and Materials Engineering)