| Description |
Oil sand is an unconventional crude oil resource that contains bitumen, which can be recovered for oil production. Hot Water Extraction of bitumen from oil sands is used in Canada as the only commercialized method of extraction. However, it has not been proven for Utah oil sands, which are more difficult to process because of the higher viscosity of the bitumen and the lack of a connate water layer between the bitumen and the sand surface. The current method requires a large amount of water and produces an equally large amount of contaminated water and tailings, which create a tremendous environmental burden that must be addressed. This research has developed and tested a new pressure cycles-assisted extraction (PCAE) technique on both oil sands from Alberta, Canadian and Utah, USA. The new process has shown a bitumen recovery rate over 92%, and the coefficient of separation over 0.70 under optimal conditions. The PCAE process makes use of successive pressurization and depressurization cycles with the CO2 gas, in which the expanding microbubbles created during depressurization assist the recovery of bitumen in its liberation from the sand surface and subsequent floatation, concertedly leading to good separation of the bitumen from the spent sands. The PCAE process requires no chemical addition and results in a process water that can be readily treated for reuse as well as spent sands that settle and dewater readily. An alternative solvent-based extraction method was also developed to extract iv bitumen from oil-wet Utah oil sands that completely eliminates the requirement of water in the process. The two-solvent relay method uses an primary extraction solvent to dissolve bitumen from oil sands, and a relay solvent to disrupt the solvent capability of the primary solvent in the bitumen extract; this results in the formation of bitumen precipitate for collection followed by separation of the solvents by distillation for reuse. The solvent-based method uses environmentally friendly solvents such as d-limonene (orange oil) and methanol that can be completely recycled. The bitumen recovery rate has been found to exceed 92% for Utah oil sands when a proper pair of solvents is employed. |
