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A Study on the Effect of Temperature and Pressure on the Removal of Cyclohexane from Non-Aqueous Extraction Gangue
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- Author / Creator
- Renaud, Richard
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Solvent based extraction has the potential to supplant the current hot water based extraction process as the industry standard method for recovering bitumen from mined oil sand. It has the potential for higher bitumen recovery that is less sensitive to the grade of oil sand ore being processed. More importantly, it can prevent the further accumulation of tailings ponds because it does not produce aqueous tailings. Instead, a mixture of sand with residual solvent and bitumen, referred to as extraction gangue, is produced. When solvent is recovered from extraction gangue, the remaining mixture is suitable for backfilling a mined out area. While solvent based recovery processes have been thoroughly studied, gaps remain in the literature regarding the recovery of solvent from extraction gangue, which is critical for the process to be economically viable. Experiments were performed on extraction gangue from high and low grade oil sand ores that had bitumen extracted using cyclohexane. The effects of temperature and pressure on the removal of cyclohexane from extraction gangue were tested. An apparatus was designed that could accurately measure and control both temperature and pressure and separately measure the evaporation of both cyclohexane and water. Tests were performed drying high and low grade extraction gangue between 25 and 95 °C with increments of 10 °C combined with pressures of 300, 500, 700 mbar, as well as a simulation atmospheric pressure condition above 900 mbar. Tests were conducted in duplicate with 2 additional runs at 105 °C and the atmospheric pressure simulation for a total of 66 tests per grade of gangue. In comparing the gangue produced by the different grades of oil sand ore, mass flux was higher in all stages of the cyclohexane removal process for high grade gangue. This was attributed partly to the higher water content in low grade gangue with a mean initial concentration of 12.5% ± 1.9% (n=66) by mass compared to just 2.1% ± 1.1% (n=66) for high grade gangue. Higher mass flux in high grade gangue in the final drying stages may have been attributed to a lower fines content prior to extraction of 11.2% ± 0.7% (n=3) by mass compared to 19.4% ± 0.9% (n=2) in low grade ore. The amount of cyclohexane remaining at the transition point between high and low mass flux cyclohexane removal was also higher for low grade gangue, so more cyclohexane needed to be recovered at a lower mass flux. All in all, total completion time was an average of 3.2 ± 0.9 (n=33) times longer in low grade gangue than in high grade gangue for experiments conducted at the same temperature and pressure. It was found that increasing temperature and decreasing pressure both had the effect of increasing mass flux of evaporating cyclohexane. Total time required to reach a goal residual cyclohexane concentration of 250 ppm was found to decay following a power law relationship with both increasing temperature and decreasing pressure, and the benefits of adding more energy through use of vacuum or heating were found to lose significance at higher temperatures. Energy analysis of these batch experiments found that while minimum energy input would occur at atmospheric pressure and 25 °C temperature, operating at higher temperatures and applying vacuum would drastically reduce the time required to recover cyclohexane without dramatically increasing the required energy input.
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- Graduation date
- Spring 2015
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- 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.