Updated E-NRTL Model for High-concentration MEA Aqueous Solution by Regressing Thermodynamic Experimental Data at High Temperatures

Chemical absorption using amine solutions is a promising technology for post combustion CO2 Capture (PCC) from flue gas. Monoethanolamine (MEA) aqueous solution has been used in many projects as a benchmark solution and its research results are widely shared with many literatures. Aspen Plus® is a useful computational simulation software to design the PCC system totally including operating conditions. It provides example files of rate-based MEA models using electrolyte NRTL methods. Basically, these models can compute nearly accurate results fitting to experimental data within a limited operating temperature and concentration range. However, there are a non-negligible difference between experimental and calculation results, especially in the vapor-liquid equilibrium (VLE) at high temperatures and high MEA concentrations. This report offers the updated electrolyte NRTL model of 30wt% and higher concentrations MEA solution by regressing specific heat capacity, heat of CO2 absorption and VLE experimental data obtained at high temperatures. Since these thermodynamic properties are mutually dependent and affected by internal model parameters like activity coefficients, standard enthalpy change of formation of principal ions, we tried to fit all properties in the MEA-H2O-CO2 ternary system that is consistent with the MEA-H2O binary system by using a combination method of the provided data regression functionality and external spread-sheet software. The updated model reflected the above modification can more accurately simulate thermodynamic properties of high concentration MEA solutions at high temperatures.