Modelling and experimental study of separators for co-solvent recovery in a supercritical extraction process

Co-solvent recovery in supercritical extraction is addressed here through a theoretical description of the behaviour of a CO2 + co-solvent mixture into a cascade of cyclonic separators, such as those existing in conventional fractionation processes based on depressurisation cascades. Conversely to the conventional simplified approach that considers a separator as a plain theoretical stage, our study proposes a dynamic modelling that accounts for the probable droplet entrainment by the light phase and the re-vaporisation phenomenon after the valve. Fractionation experiments of CO2 + n-propyl alcohol mixtures were operated in a three-stage fractionation pilot, and experimental results are compared with simulation ones. The study demonstrates the relevance of our modelling, and points out the importance of entrainment effects, especially for low-pressure operated separators.