Thermodynamic modeling of hydrogen sulfide absorption by aqueous N-methyldiethanolamine using the Extended UNIQUAC model

• A consistent thermodynamic model for representing thermodynamic and thermal properties of H2S–H2O and H2S–MDEA–H2O systems is developed.
• A unique set of optimized parameters accurately represent properties such as: total pressure, H2S partial pressure, pure H2S vapor pressure and heat of H2S absorption into aqueous MDEA.
• For the first time the Extended UNIQUAC model has been applied for representing thermodynamics of H2S absorption process by use of alkanolamines.

Aqueous MDEA is the most commonly used solvent for H2S removal from natural gas. A reliable thermodynamic model is required for the proper design of natural gas sweetening processes. In this study, a rigorous thermodynamic model is developed to represent properties of the H2S–MDEA–H2O ternary system. The Extended UNIQUAC model is used to represent the system behavior. The model is created based on models for the constituent binary subsystems. The developed model provides accurate representation of VLE and heat of absorption for the studied system and subsystem in the temperature range of 0–180 °C, H2S partial pressure of 0.0033–8329.71 kPa, MDEA mass% of 0–50 and loading range of 0–2.17.