Effects of differential permeability on packed bed supercritical extractors: A theoretical insight

This paper analyses the effects on the extraction kinetics of a solvent flow which is non-uniform in the extraction column bed cross-section. When modeling the extraction kinetics of a solute from a solid matter (for instance of oil from seeds), the solvent motion is normally assumed as consisting in plug flow, eventually corrected by the axial dispersion coefficient. Some experimental evidence put into question this simplified description. We have shown to which extent the effects of a non-uniform extraction bed permeability reflect on the extraction kinetics: in particular conditions, these effects could be even more significant than the effects due to the mass transport resistances governing the extraction of the solute out from the matrix.