Prediction of CO2 and H2S solubility and enthalpy of absorption in reacting N-methyldiethanolamine /water systems with ePC-SAFT

The major goal of this work was the prediction of the solubility of CO2 and H2S in aqueous methyldiethanolamine (MDEA) reacting systems using the electrolyte equation of state ePC-SAFT with focus on MDEA weight fractions wMDEA> 0.3 (related to the binary water/MDEA system). Predictions in this work mean that no parameters were adjusted to the experimental gas solubility data in aqueous MDEA solutions. In order to obtain improved prediction results compared to state-of-the-art literature models, binary interaction parameters kij between water-MDEAH+ , water-HCO3− , and water-HS− were introduced; these kij values were fitted to osmotic-coefficient data measured in this work and from literature. This new possibility to access these kij parameters allowed improved predictions of CO2 solubility, and the predictions were validated by new experimental data at wMDEA = 0.6. Even more, the influence of the inert gas CH4 on CO2 solubility was predicted reasonably correct. Further, the solubility of H2S in aqueous MDEA solutions was accurately predicted in the temperature range 298 K < T < 393 K at wMDEA = 0.32 and 0.48. In the final part of this work enthalpy of absorption was predicted for 353 K < T < 393 K at wMDEA = 0.3 for varying gas loadings. In summary, prediction results were satisfying considering the fact that ePC-SAFT parameters were fitted only to experimental data of pure fluids or binary systems.