Modeling of Transport Properties Using the SAFT-VR Mie Equation of State

Carbon capture and storage (CCS) has been presented as one of the most promising methods to counterbalance the CO₂ emissions from the combustion of fossil fuels. Density, viscosity and interfacial tension (IFT) are, among others properties, crucial for the safe and optimum transport and storage of CO₂-rich steams and they play a key role in enhanced oil recovery (EOR) operations. Therefore, in the present work the capability of a new molecular based equation of state (EoS) to describe these properties was evaluated by comparing the model predictions against literature experimental data. The EoS considered herein is based on an accurate statistical associating fluid theory with variable range interaction through Mie potentials (SAFT-VR Mie EoS). The EoS was used to describe the vapor-liquid equilibria (VLE) and the densities of selected mixtures. Phase equilibrium calculations are then used to estimate viscosity and interfacial tension values. The viscosity model considered is the TRAPP method using the single phase densities, calculated from the EoS. The IFT was evaluated by coupling this EoS with the density gradient theory of fluids interfaces (DGT). The DGT uses bulk phase properties from the mixture to readily estimate the density distribution of each component across the interface and predict interfacial tension values. To assess the adequacy of the selected models, the modeling results were compared against experimental data of several CCVrich systems in a wide range of conditions from the literature. The evaluated systems include five binaries (CO₂/O₂, CO₂/N₂, CO₂/Ar, CO₂/n-C₄ and CO₂/n-C₁₀) and two multicomponent mixtures (90%CO₂/5%O₂/2%Ar/3%N₂ and 90%CO₂/6%n-C₄/4%n-C₁₀). The modeling results showed low absolute average deviations to the experimental viscosity and IFT data from the literature, supporting the capabilities of the adopted models for describing thermophysical properties of CO₂-rich systems.