| Description |
The supercritical fluid extraction (SFE) of bitumens from the Whiterocks, Asphalt Ridge, PR Spring and Sunnyside oil sand deposits has been investigated in a semicontinuous system. The extraction experiments were conducted with the Asphalt Ridge and Sunnyside bitumens at five different operating conditions using commercial propane as the solvent. The results indicted that the cumulative extraction yields increased with an increase in pressure at constant temperature and decreased with increase in temperature at constant pressure. The extraction yields increased with an increase in solvent density. The composition of the feedstock was a major factor in controlling the extraction yields. The four bitumens from the Uinta Basin, Utah, varied significantly in their physical and chemical properties. The propane extraction yields were inversely proportional to the bitumen asphaltene content and directly proportional to the bitumen resin content. The cumulative extraction yields increased with an increase in bitumen volatility and saturates and aromatics contents for the Whiterocks, PR Spring and Sunnyside bitumens. The asphaltenes appeared to concentrate in the residual fraction and were not extracted. Furthermore, they hindered the extraction of other solubility classes. The extracted phases were upgraded relative to the bitumens as indicated by their volatilities. The volatilities of the extract phases were considerably higher than those of the bitumens. The fractionation of the residual fractions into solubility fractions indicated that saturates and aromatics were preferentially extracted from the bitumen relative to the asphaltenes and resins. This phenomenon was confirmed by the reduction in the measured hydrogen/carbon ratios of the residual fractions. The SFE of Asphalt Ridge and Sunnyside bitumen was modeled using continuous thermodynamics principles and the Peng-Robinson equation of state. A process flow diagram was suggested to upgrade bitumens using supercritical fluid extraction and separation technology. Suitable operating conditions such as pressure, temperature and solvent-to-feed ratio were identified for the proposed extraction and separation process concept. The modeling successfully fit the experimental observations. A high temperature simulated distillation technique was developed along with a software to extend the ASTM D2887 and D5307 techniques to estimate the boiling point distribution of heavy oils from 811 K to 973 K. |
