(771a) Numerical Simulations of the Simultaneous Absorption of Carbon Dioxide and Hydrogen Sulfide In Membrane Contactors with Typical Alkanolamine Solutions

The simultaneous removal of acid gas impurities, such as CO₂ and H₂S, from sour gas streams is a significant operation in natural gas processing. These acid components react with the aqueous alkanolamine solution via an exothermic reversible reaction in a hollow fiber gas-liquid contactor. A comprehensive mathematical model for acid gases absorption in aqueous alkanolamine solutions has been developed assuming radial diffusion inside the fiber, through the membrane, and within the shell. The reactive absorption mechanism was built based on momentum and mass transport conservation laws in all three compartments involved in the process, i.e. the gas phase, the membrane barrier and the liquid phase. The liquid velocity in the fiber bore is assumed to obey a fully developed laminar flow, whereas that of the gas mixture in the shell side is characterized by the Navier-Stokes momentum balance equations. Three typical alkanolamine solutions used very often in industrial processes, namely monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA) were employed as absorbents in the present analysis. This model could be a useful tool to predict the theoretical performance of the simultaneous absorption rates of CO₂ and H₂S in various industrial alkanolamine aqueous solutions in the conditions where both gases have a mutual interaction on the respective rates. Effects of gas to liquid flow ratio, initial alkanolamine concentrations on the extent of H₂S removal and mass transfer performance were investigated.