Thermodynamic modeling of CO2 absorption in aqueous N-Methyldiethanolamine using Extended UNIQUAC model

• A consistent thermodynamic model for representing thermodynamic and thermal properties of CO2-MDEA-H2O system is developed.
• The Extended UNIQUAC model is developed to represent behavior of CO2-MDEA-H2O mixture.
• The Extended UNIQUAC model is significantly improved over the previous version of the model.
• A unique set of optimized parameters accurately represent different thermodynamic and thermal properties.
• Heat of absorption is calculated by the Extended UNIQUAC model, which has not been carried out before using this model.

A Thermodynamic model that can predict the behavior of the gas sweetening process over the applicable conditions is of vital importance in industry. In this work, Extended UNIQUAC model parameters optimized for the CO2-MDEA-H2O system are presented. Different types of experimental data consisting of pure MDEA vapor pressure, vapor–liquid equilibrium (VLE) (total pressure and CO2 partial pressure), freezing point depression (SLE), excess enthalpy, heat capacity and heat of absorption were used to adjust model parameters. The model was then used to predict the NMR spectroscopic data. The developed model accurately represents thermodynamic and thermal properties of the studied systems. The model parameters are valid in the temperature range from −15 to 200 °C, MDEA mass% of 5–75 and CO2 partial pressure of 0–6161.5 kPa.