Modelling of CO₂ solubility in phase separation solvent composed of amine/ether/water system for CO₂ capture

Phase separation solvents for CO₂ absorption constructed with amine/ether/water have been designed which transform into two liquid phases after CO₂ absorption. We also found that phase separation solvent can reduce the temperature difference between absorber and desorber that can reduce the required energy for CO₂ capture. In this study, we develop a model for the CO₂ solubility of phase-separation type CO₂ absorbent which is necessary for process simulation. Ion species in the liquid phase was estimated by ¹³C NMR, and the ion association form was inferred from the Walden plot based on conductivity and viscosity. The CO₂ solubility model expressed the vapour-liquid equilibrium as the Henry's law constant, the liquid-liquid equilibrium as the non-random two-liquid activity coefficient model, and the liquid phase CO₂ chemical absorption as the equilibrium constant. The model can predict CO₂ solubility at temperature range (313–363 K) and CO₂ partial pressure range (1–100 kPa) and compositions of CO₂-lean and CO₂-rich phases can be calculated when phase separation occurs.