A Comparative Evaluation of Friction Theory, Free-Volume Theory, Entropy Scaling, and Helmholtz Energy Scaling Viscosity Models Coupled with the PρT-SAFT Equation of State for Pure and Binary Mixtures of Ethylene Glycols and Alkanolamines

Ethylene glycols and alkanolamines play a crucial role in various industrial processes, particularly in natural gas processing. Accurate viscosity modeling for these substances is essential for designing and optimizing industrial operations. This study evaluates the performance of five semi-theoretical viscosity models, namely Friction Theory (FT), Free-Volume Theory (FVT), Entropy Scaling (ES1 and ES2), and Helmholtz Energy Scaling (HES), coupled with the PρT-SAFT equation of state (EoS). The study focuses on modeling the viscosity of pure monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), and their binary mixtures. Model parameters were determined using Random Search and Conjugate Gradient optimization methods. The HES model demonstrates the highest accuracy for pure ethylene glycols and alkanolamines. No binary interaction parameters were included in the mixture calculations. Based on available data, five binary mixtures of ethylene glycols and alkanolamines were studied. The HES model consistently provides the most accurate predictions across a wide range of pressures and temperatures. The overall average absolute deviations (%AAD) for the FT, FVT, ES1, ES2, and HES models coupled with the PρT-SAFT EoS for all pure compounds and mixtures are respectively: 119, 28, 13, 14, and 11. These results confirm that the HES and ES models offer the most reliable viscosity predictions for pure and mixed ethylene glycol and alkanolamine systems.