Comparative Evaluation of Vapor-Phase Nonideality Models for CO ₂ –MEA–H ₂ O VLE: Virial and Nakamura Approaches Coupled with eUNIQUAC and eNRTL

High Resolution Image Download MS PowerPoint Slide This study provides a critical assessment of the role of vapor-phase nonidealities in vapor–liquid equilibrium (VLE) modeling for a CO 2 –MEA–H 2 O system. The investigation employs eUNIQUAC and eNRTL models for the liquid phase, while the vapor phase is described using the Nakamura and virial equations of state. Unlike previous works that predominantly emphasize liquid-phase modeling, this study underscores the significance of vapor-phase modeling choices on the predictive accuracy of thermodynamic models. All models were implemented in MATLAB with literature-sourced parameters and validated against experimental data from the literature. Results demonstrate that combining the virial equation of state with eUNIQUAC yields excellent predictive performance across a temperature range of 313–393 K at 7 m MEA, achieving a global average deviation of 8.01%. In contrast, pairing the virial equation of state with eNRTL results in a higher average deviation of 10.77% for temperatures between 353 and 373 K and MEA molalities from 2.89 to 7 m. Under comparable conditions, the Nakamura equation of state with eNRTL offers slightly improved agreement (9.76% global average deviation) compared to its combination with eUNIQUAC (10.47%). Overall, the study finds that all modeling approaches deliver consistent predictions. Future improvements in predictive capability are anticipated through targeted parameter estimation.