An experimental thermodynamic study of CO2 capture using chemical absorbents.

AfficheA method to fight against global warming consists in reducing CO2 emissions. Industrial CO2 capture processes developed to remove CO2 from industrial effluents are based on repeated absorption-desorption cycles of CO2 in selective absorbents such as aqueous solutions of amines. Research and development are actually carried out on both absorbent selection [1,2,3] and process optimization in order to reduce total cost of CO2 capture. Thermodynamic properties are of major importance to study gas dissolution and to design capture process units. Demixing amines are the absorbents considerate in this study. The singularity of aqueous solutions of demixing amines with CO2 is a liquid-liquid phase separation at a specific temperature and CO2 loading. Therefore, in regeneration step, the stripper receives only the CO2 rich phase. In these conditions, some improvements in the CO2 capture process could be done in order to reduce cost of solvent regeneration. Liquid-liquid equilibria (LLE), excess molar enthalpies of mixing and molar heat capacities were measured for different {water - amine} systems. Calorimetric investigations were performed to study the systems {water - amine - CO2} in order to determine the enthalpies of solution and the limits of gas solubility. The different experimental techniques used in this study are presented here. LLE were measured using both a microDSCIII apparatus from Setaram and an equilibrium cell SPM20 from Thar Technologies. Molar heat capacities of aqueous solution of amine in the one phase region were obtained from microDSCIII measurements. Excess molar enthalpies of mixing were measured by a flow calorimetric technique using a BT2.15 from Setaram. The calorimeter was equipped with a mixing cell developed in the laboratory. In the same way the enthalpies of mixing of CO2 with absorbent are performed using a C-80 from Setaram. The techniques and the different results are reported in this presentation. [1] L. Rodier, K. Ballerat-Busserolles, J-Y. Coxam, J. Chem. Thermodynamics, 42, 773-780 (2010). [2] H. Arcis, L. Rodier, K. Ballerat-Busserolles, J-Y. Coxam, J. Chem. Thermodynamics, 39, 878-887 (2007) [3] H. Arcis, L. Rodier, K. Ballerat-Busserolles, J-Y. Coxam, J. Chem. Thermodynamics, 40, 1022-1029 (2008) [4] Y. Coulier, K. Ballerat-Busserolles, L. Rodier, J-Y. Coxam, Fluid Phase Equilibria, 296, 206-212 (2010