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Extraction of oil from crushed sunflower seeds with supercritical CO 2 was performed at 280 bar and 40 °C on a laboratory apparatus of 0.15 × 10 -3 m 3 volume and on a pilot plant of 1.5 × 10 -3 m 3 volume. CO 2 flow rate ranged between 5 and 45 kg h -1 . To study the influence of the vegetable matrix on the extraction rate, a re-extraction experiment on the extraction product was also performed on the pilot scale apparatus. A mathematical model of the supercritical extraction process was developed on the basis of the experimental evidence. The equilibrium between the solids and the fluid phase appeared to be the controlling step during the extraction process. A simplified form of a sigmoidal-shaped equilibrium curve was adopted to fit the experimental data in the whole range of CO 2 flow rates explored. The meaning of this nonlinear equilibrium relationship was also discussed.

Supercritical CO2 extraction of fennel seeds has been performed in two steps; the first step was performed at 90 bar and 50 °C to obtain the selective extraction of essential oil. The second one was performed at 200 bar and 40 °C and allowed the extraction of vegetable oil. The experiments were performed using the fractional separation of the extracts using three different CO2 flow rates (0.5, 1.0, and 1.5 kg/h). On the basis of the extraction results and of the analysis of scanning electron microscopy (SEM) images of the vegetable matter, mathematical models of the two extraction processes have been proposed. The extraction of fennel vegetable oil has been modeled using a model based on differential mass balances and on the concept of broken and intact cells as evidenced by SEM. Only one adjustable parameter has been used:  the internal mass-transfer coefficient k t. A fairly good fitting of the experimental data was obtained by setting k t = 8 × 10-8 m/s. The fennel essential oil extraction process was modeled as desorption from the vegetable matter plus a small mass-transfer resistance. The same internal mass-transfer coefficient value used for vegetable oil extraction allowed a fairly good fitting of the essential oil extraction data.