PHASE-BEHAVIOR OF CO2-BITUMEN FRACTIONS

The phase behaviour of Cold Lake bitumen and its five fractions (or "cuts") saturated with carbon dioxide is examined. The two lightest fractions (bp < 510-degrees-C) were clear liquids, whereas the third and fourth fractions were dark and viscous, i.e. much like the whole bitumen. The fifth fraction was a glass-like solid, with a softening temperature of approximately 100-degrees-C. The vapour-liquid equilibrium (VLE) data for the bitumen and bitumen fractions saturated with CO2 were collected at temperatures from 25 to 150-degrees-C and pressures up to 10 MPa. Experiments were also performed at conditions under which pure CO2 exists as a liquid. The VLE and LLE data were correlated with the Peng-Robinson equation of state by modeling each bitumen fraction as one pseudocomponent whose critical properties and acentric factor were estimated from correlations available in the literature. The CO2-solubility and density data were used to develop generalized correlations for the critical pressure and the binary interaction parameter (k(ij)) in terms of molar mass and critical temperature. The model was subsequently used to predict the solubility of CO2 in the whole bitumen which was represented as a 5-component mixture. A correlation for Cut i-Cut j binary interaction parameter (k(ij)) was developed in terms of temperature and the difference in hydrocarbon molar masses. The average deviation in the predicted and experimental CO2-solubility in the whole Cold Lake bitumen was less than 7%.