Modeling supercritical CO2 drying of potato starch: A BET-coupled CFD simulation approach

Supercritical carbon dioxide (ScCO 2 ) is being investigated as an alternative drying medium for potato starch because it allows drying under relatively mild temperature conditions and avoids use of hot drying air. This study explores the influence of initial moisture content (15%, 20%, and 30% w/w) on the drying behavior using a continuous ScCO 2 extraction system operated at 100 bar, 50 °C, and 50 g·min -1 CO 2 mass flow rate. Experimental drying kinetics were quantified via Karl Fischer titration, while complementary BET (Brunauer-Emmett-Teller) analysis provided specific surface area and adsorption parameters required to describe water–starch interactions. A model was developed and calibrated in COMSOL Multiphysics of the packed starch bed, incorporating adsorption equilibria through a BET-based multilayer formulation. Simulations reproduced the drying trends observed experimentally, showing that higher initial moisture content leads to faster water removal and lower final equilibrium moisture. The fitted effective parameters vary in this way with initial moisture, which is consistent with, but does not prove, a larger fraction of weakly retained water. The calibrated CFD (Computational Fluid Dynamics) model provides a framework for interpreting the coupled flow, mass-transfer and adsorption phenomena governing ScCO 2 -based starch drying and offers a basis for future process optimization and scale-up studies.