Vapor-Liquid Equilibrium Measurements and Cubic-Plus-Association Modeling of Triethylene Glycol + Water + Methane Systems at 6.0 and 12.5 MPa

As a part of a series of studies that aim to expand the experimental database used to assist the design of novel technologies in the field of subsea gas processing, 18 new vapor–liquid equilibrium data points were measured for the system triethylene glycol (1) + water (2) + methane (3) at 6.0 and 12.5 MPa, temperature range between 288 and 323 K, and a glycol content above 95 wt %. The new data include both gas [glycol (y₁) and water (y₂)] and liquid [methane solubility (x₃)] phase composition, with relative experimental uncertainties below 18%. It was observed that one of the experimental data sets available in the literature is not in agreement with the experimental data measured in this work. Furthermore, an important target was to reevaluate the cubic-plus-association (CPA) equation-of-state modeling capability, which has been previously used for triethylene glycol–methane systems. CPA using a 4C association scheme for TEG and one interaction parameter per binary has provided a good description of the newly measured data, with the average absolute relative deviation ranging between 9 and 43%. Binary interaction parameters regressed solely from the corresponding binary data were used for all ternary predictions with CPA.