Vapor-Liquid Equilibrium and Enthalpy of Absorption of the CO₂-MEA-H₂O System

Abstract

Amine scrubbing is widely used to remove acid gases, mainly CO2 and H2S, from various process gaseous streams, because of the enhancement due to chemical reactions occurring in the liquid phase. For designing the acid gas removal plant, information on the heats of absorption of carbon dioxide in amine aqueous solutions is of paramount importance. Due to the exothermicity of reactions, a temperature increase occurs in the absorber, affecting the equilibrium and the amount of absorbed acid gas, while in the regenerator the energy requirement at the reboiler strongly depends on the heat of desorption. This work is focused on the removal of CO2, a powerful greenhouse gas, from flue gases by means of aqueous solutions of monoethanolamine (MEA), an industrial technology which is part of carbon capture and sequestration, to limit global warming. The aim is the study of the CO2-MEA-water system, in particular as for thermodynamics. The Electrolyte- NRTL model is used for the description of Vapor-Liquid Equilibrium as well as for the computation of the heat of absorption, considering the influence exerted by thermodynamic parameters. The obtained parameters, checked against experimental data of VLE and of heat of absorption, can be implemented in the commercial software ASPEN Plus® and employed for simulations of the amine scrubbing scheme.