Parameterization and uncertainty analysis of binary interaction parameters for triethylene glycol and ethane/propane

Formation of gas hydrates in natural gas saturated with water threatens the integrity of subsea pipelines, therefore effort must be put into inhibiting these processes. A commonly used inhibition method is gas dehydration with triethylene glycol (TEG), which is the molecule of interest in this work. In our previous study, new multicomponent vapour-liquid-equilibria (VLE) data for TEG/water/natural gas systems were published, along with the Cubic-Plus-Association (CPA) equation of state (EoS) thermodynamic modelling. Some of the binary interaction parameters (BIP) used in this previous work, however, were only available in the literature for the 4C association scheme for TEG. In this context, new BIPs for TEG-Ethane and TEG-Propane using the different association schemes (4F, 5F, 6F and 5C) for TEG were optimised in this work. The older binary interaction parameter values for the 4C scheme were also improved. The confidence intervals for the fitted parameters were derived from statistical bootstrapping uncertainty analysis. Results revealed a low degree of uncertainty (±0.70%) for the TEG-Ethane parameter, while the linear correlation between the two terms in the BIP of TEG-Propane generated higher uncertainties (±61%). The newly fitted parameters were, then, used to model the same multicomponent VLE data previously mentioned. Minor improvements for the classical 4C scheme further confirmed this association scheme as the best choice for TEG in the CPA framework.