Modified temperature-dependent volume translation model in PC-SAFT equation of state for carbon dioxide

Abstract

Statistical associating fluid theory (SAFT)-type equations of state (EOSs) have been widely used to model the phase behavior of pure compounds (e.g., carbon dioxide). One issue with the conventional SAFT-type EOSs is that they fail to accurately reproduce the critical pressure and critical temperature of pure compounds. To address this limitation, the three parameters in SAFT-type EOSs (i.e., m, σ, and ε/k) must be adjusted to exactly reproduce the critical temperature and critical pressure of pure compounds, leading to the development of the critical-point perturbed-chain SAFT (CPPC-SAFT). However, this is achieved by sacrificing the accuracy of the liquid-density predictions. As such, a fourth parameter, that is, the volume translation parameter, is indispensable for improving the accuracy of liquid density predictions. In this study, a new nonlinear temperature-dependent volume translation model is introduced into the perturbed-chain SAFT EOS (PC-SAFT EOS) for more accurate prediction of CO2 density. The newly developed volume-translated and critical-point PC-SAFT EOS (VT-CPPC-SAFT EOS) is found to be superior to the previously developed models, such as the original PC-SAFT (Gross and Sadowski, 2001), CPPC-SAFT (Anoune et al., 2021), and industrialized version of PC-SAFT EOS (I-PC-SAFT) (Moine et al., 2019), because it can provide more accurate density predictions for CO2 in different phase states. In addition, the VT-CPPC-SAFT EOS accurately reproduces the critical pressure and critical temperature of CO2.