Competitive H2S – CO2 absorption in reactive aqueous methyldiethanolamine solution: Prediction with ePC-SAFT

Reactive absorption of CO2 and H2S in aqueous methyldiethanolamine (MDEA) solutions is considered within the ePC-SAFT equation of state. We demonstrate that ePC-SAFT can be employed in a predictive manner without regression of additional temperature-correlated terms. Mixed system predictions are tested using a consistent set experimental data covering a wide range of temperatures (313 K–413 K), partial pressures (0.001 kPa–1000 kPa), and MDEA mass fractions (0.05–wMDEA 0.75 wMDEA). Predicted partial pressures for acid gas absorption show good agreement for low MDEA fractions (wMDEA < 0.5). Absorption selectivity in binary H2S + CO2 absorption is correctly predicted, with absolute average deviations of 57.18% and 79.32% for partial pressures of CO2 and H2S. We identify a significant deterioration in ePC-SAFT predictive power for the high-MDEA regime (wMDEA > 0.5), likely originating from underlying assumptions in the Debye-Hückel electrolyte free energy treatment and representation of ionic species