Thermodynamic modeling for CO₂ absorption in aqueous MEA solution with electrolyte NRTL model

Accurate modeling of thermodynamic properties of CO₂ absorption in aqueous alkanolamine solutions is essential for simulation and design of such CO₂ capture processes. In this study, we use the Electrolyte Nonrandom Two-liquid activity coefficient model in Aspen Plus to develop a rigorous and thermodynamically consistent representation for the MEA-H₂O-CO₂ system. Vapor-liquid equilibrium (VLE), heat capacity and excess enthalpy data for the binary aqueous amine system (MEA-H₂O) are used to determine the NRTL interaction parameters for the MEA-H₂O binary. VLE, enthalpy of absorption, heat capacity and NMR spectroscopic data for the MEA-H₂O-CO₂ ternary system are used to identify the electrolyte NRTL interaction parameters for the molecule-electrolyte binaries and the previously unavailable standard state properties of the amine ions, MEA protonate and carbamate. The predicted VLE, enthalpy of absorption, heat capacity and speciation for the MEA-H₂O-CO₂ system are compared favorably to experimental data.