Calculation of solubility of CO2 and H2S acid gases in aqueous MDEA solution applicable in gas sweetening processes

Three molecular activity coefficient models with the aid of ion pair concept are used to model the solubility of CO2 and H2S acid gases in the aqueous methyldiethanolamine(MDEA) solution. The gas phase nonideality is considered using the SRK equation of state. For the liquid phase, an activity local composition model is applied that the Pitzer-Debye-Hückel theory is used as a shortrange term. The N-Wilson-NRF, NRTL-NRF and UNIQUAC-NRF activity coefficient models are used as the short-range term. The interaction parameters of the binary MDEA-H2O, CO2-H2O and H2S-H2O systems are obtained using the corrosponding solubility data of literature. Using the optimazed binary parameters, the other binary interaction parameters for the two ternary systems of MDEA-CO2-H2O and MDEA-H2S-H2O are caculated. A good agreement between the experimental data and the correlated results are obtained .

Keywords:

solubility , activity coefficient , MDEA , N-Wilson-NRF , NRTL-NRF , UNIQUAQNRF