Particle size distribution and stratification of pelletized oilseeds affects cumulative supercritical CO2 extraction plots

Abstract

This work studies the effect of the substrate particle size distribution and stratification on the SuperCritical (SC) CO2 extraction of oilseeds. Cumulative SC-CO2 extraction curves of small (S, dpe = 2 mm) and large (L, dpe = 4 mm) cylindrical cranberry seed pellets were modeled simultaneously using a Linear Driving Force (LDF) model empirically modified to consider the experimental oil partition isotherm and using oil solubility in SC-CO2 (Csat) and effective oil diffusivity in the substrate (De) at 40 °C and 30 MPa as best-fitting parameters. The mathematical model was adapted for a substrate with a particle size distribution and experimentally validated for random and stratified 1:1 (w/w) mixtures of S and L pellets. Cumulative extraction curves of substrates with same measurement of central tendency (Sauter mean diameter) changed depending on the particle size distribution, because of the negative impact of slow-extracting large particles, particularly at the vessel exit.