Cubic-plus-association equation of state parameterization of liquid-liquid equilibrium of propane + n-butane + bitumen and dimethyl ether + bitumen systems

Abstract

Steam-based oil recovery processes are energy-intensive, leading to excessive greenhouse gas emissions. Solvent-assisted oil recovery methods have become of considerable significance as oil industry is moving toward developing new recovery processes with less environmental impact. As a result, thermodynamic modeling of the phase equilibria of oil/solvent systems is essential in designing and optimizing the new recovery processes. In this work, liquid-liquid equilibria (LLE) of bitumen/ liquefied petroleum gas (LPG, a mixture of propane and normal butane) and bitumen/dimethyl ether (DME) are studied. The cubic plus association equation of state (CPA EoS) is utilized to calculate the fugacity coefficient of each component in the two liquid phases. Finally, the experimental weight fractions of the two light and heavy liquid phases are used to tune the model parameters. The model parameters for bitumen/ LPG are considered a linear function of temperature. The tuning over all temperatures resulted in an absolute average relative deviation (AARD) of 8.6 % in predicting the experimental weight fractions. The model also provided acceptable predictions of density, heavy yield, and K-values. For the bitumen/DME system, the tuning was conducted separately for each temperature. The tuned parameters show a meaningful relationship with the test temperature, and the overall AARD in the prediction of the experimental weight fractions is 9.7 %. The tuned EoS model predicted the density and heavy yield reasonably but failed to predict K-values for the bitumen/DME system.