Fluid phase equilibria modeling of mixtures with CO2, water and n-alkanes/n-alcohols homologues series using GCA-EoS

M. GONZALEZ PRIETO; F. A. SANCHEZ; S. PEREDA

Eindhoven

Simposio; 27th European Symposium on Applied Thermodynamics; 2014

Carbon dioxide is a highly-studied chemical compound. It is a product of the biological life cycle, fuel and biomass combustion, as well as other biomass processing pathways like pyrolysis, hydrolysis or gasification. Moreover, CO2 is present in nature in a wide range of conditions from atmospheric to that of petrochemical reservoirs, in mixtures with hydrocarbons, water and different organic compounds. It plays a major role in many processes like enhanced oil recovery, carbon dioxide sequestration and injection in ocean waters as a disposal method. Moreover, because of its low reactivity, toxicity and cost, it has been proposed for many processes as supercritical solvent not only as extracting agent but also as reaction media. In this context, an accurate representation of thermodynamic properties of mixtures containing CO2 is required for the design and operation of processing units. Furthermore, a predictive thermodynamic model for properties estimation is a highly useful tool for exploratory purposes in the emerging technologies for biomass processing.In this work, the group-contribution with association equation of state, namely GCA-EoS [1], has been successfully applied to represent vapor-liquid and liquid-liquid equilibria of carbon dioxide mixtures. The previous table of parameters [2] was revisited in order to model multicomponent mixtures of carbon dioxide with water and compounds of the homologues series of n-alkanes and n-alcohols by group contribution. Parameters for hydrocarbons and polar compounds were taken from previous work [3]. Using a single set of parameters obtained from binary data, the model is able to predict the phase behavior of binary mixtures not included in the parameterization procedure. Moreover, GCA-EoS predicts correctly the change in type of phase behavior, according to the van Konynenburg and Scott [4] classification, in all the analyzed cases. In addition, ternary mixtures are also well predicted. The model was evaluated against an experimental database covering temperatures from 250 K to 647 K and pressures up to 1500 bar.