Water-Assisted Solvent Extraction of Bitumen from Oil Sands

Water-assisted solvent extraction processes (WASEPs) were developed by introducing a water layer between the oil sands and solvent to extract bitumen from oil sands. The extraction condition was well investigated using the naphtha as the extraction solvent. Considering the extraction cost, the advised extraction processes for industrial application were conducted under stirring at temperature of 50-60 degrees C for 30 min using a ratio of oil sands to naphtha to water in 1:1:0.5 (wt/wt/wt). At such conditions, bitumen recovery of about 72-74% was obtained on processing a weathered ore. In the case of some types of oil sands such as the weathered ore, surfactant needs to be added in the aqueous phase to eliminate the solids aggregation suspended in the oil-water interface. The function of the water layer introduced in the WASEPs is to reduce the fines content in the extracted bitumen solution and make it easy to separate the bitumen solution from the solids. In the examination of the solvent recovery, it was found that there was 7% of the solvent still remaining in the solids. The loss of the solvent greatly depends upon the surface wettability of the solids. Studies on the effect of various solvents on bitumen recovery indicated that using toluene as the extraction solvent gave the highest bitumen recovery of about 95%. However, considering the extraction cost and environmental problems, the water-assisted naphtha extraction processes were advised and might find its application in the oil sands processing industry, although some issues need to be resolved in the future work.