Modeling of CO2 solubility in aqueous N-methyldiethanolamine solution using electrolyte modified HKM plus association equation of state

- An electrolyte mHKM-CPA equation of state is developed for solubility calculation of acid gases in alkanolamines.
- Using the present EoS, VLE calculation is carried out for CO2 solubility in aqueous MDEA systems.
- The results of AAD % was 12.14 for the CO2-MDEA-H2O system.
- The results are given in wide ranges of temperature, pressure, acid gas loading, and amine concentration.

In this work, a new type of electrolyte cubic plus association equation of state as emHKM-CPA EoS has been developed and was used to modeling the CO2 solubility in aqueous alkanolamine such as N-methyldiethanolamine (MDEA) and diethanolamine (DEA) solutions. This EoS consists of the several terms as the cubic HKM part for dispersion contribution, electrolyte part and association term. The Mean Spherical Approximation (MSA) term together with Born term are used for electrostatic long-range interaction and charging processes, respectively, and for association the Wertheim equation was applied. Using the present EoS, the solubility of CO2 in aqueous MDEA solutions is modeled so that the 470 experimental solubility data were used at the different solution compositions, temperatures, pressures and acid gas loadings. At first, the pure components parameters were obtained through regression of the pure components vapor pressure and saturated liquid density experimental data. Consequently, the binary interaction parameters were calculated using the binary vapor-liquid equilibrium data. Finally, the ternary H2O-CO2-MDEA and H2O-CO2-DEA systems were modeled using a reactive bubble point pressure calculation method. Moreover, the present EoS is applied for LLE calculation of heptane-MEA system. The results showed that the calculated values were in good agreement with the experimental data. For the H2O-CO2-MDEA and H2O-CO2-DEA systems, the percentage of Absolute Average Deviation (AAD%) were 12.14 and 9.17, respectively, that shows emHKM- CPA is an efficient EoS which can be successfully applied to representation of the solubility of CO2 in aqueous alkanolamine solutions in wide ranges of temperature, pressure, acid gas loading, and amine concentration.