Almond oil extraction by supercritical CO2:: experiments and modelling

Oil from crushed almond seeds was extracted with supercritical CO2 at 350 bar and 40 degrees C. Almond particles of three different mean sizes were tested. Extraction of the smaller particles was performed at two different solvent flow rates. Oil yields were obtained with asymptotic values at large extraction times that were close to the values obtained by Soxhlet extraction. An extraction model based on the physical evidence of broken and intact oil cells has been developed. It accounts for a former equilibrium regime and a latter finite mass transfer regime. All model parameters except the internal mass transfer coefficient and the oil concentration at solvent saturation have been determined with independent experiments. The model solution was calculated with a finite difference numerical technique. A good agreement was obtained between model curves and the experimental data for an internal mass transfer coefficient of 7.5 x 10(-9) m/s. Solute concentration profiles within the extractor were evaluated with our model. (C) 1998 Elsevier Science Ltd. All rights reserved.