Thermodynamic model for {CO2 –H2O- alkanolamine} systems.
Résumé
Alkanolamine processes are the most common used for the removal of acid gases present in industrial effluents. The capture of the gas by the absorbent solution is a combination of acido-basic reactions and physical dissolution. The development of thermodynamic models to correlate and predict the vapour-liquid equilibria of {CO2-H2O-alkanolamine} systems requires consistent experimental data such as enthalpies and solubilities. These models are based on a system of equations for the chemical and phase equilibria, the charge and the mass balance. Different models are available in the literature [1,2,3,4].The main objective of this work is to test the ability of a thermodynamic model to predict enthalpy of solution and to compare the relative importance of the different enthalpic contributions due to the chemical reactions and to the physical equilibria. We have chosen a gamma-phi model to represent the vapour-liquid equilibria. The interaction parameters in the liquid phase in the model are fitted using literature solubility data. The enthalpies of solution are calculated from the chemical and physical equilibria equations by temperature derivation. The model is tested by comparing calculated enthalpies of solution with experimental enthalpies of solution in aqueous solutions of alkanolamine [5,6].