Modeling the supercritical fluid extraction of hazelnut and walnut oils

Data from supercritical fluid extraction of hazelnut and walnut oils were modeled using the Sovová's mass transfer model. The extractions were carried out at temperature ranging from 308–321 K and pressure 18–23.4 MPa. For the hazelnut oil, the influence of superficial velocity of the fluid (CO 2 ) was studied in the range (4.42–7.10) × 10 −4 ms −1 , for ground hazelnut with D p = 0.7 mm. For the walnut oil, the influence of particle size was studied, in the range 0.01–0.5 mm, for 6.8 × 10 −4 ms −1 of superficial velocity of the fluid. The overall mass transfer coefficients in the solvent phase and in the solid phase, the fraction of the solute directly exposed to the solvent, and the void fraction in the bed were selected as adjustable parameters. For hazelnut oil, values of these parameters were: ε = 0.273; f k = 0.668; K f = (1.29–3.65) × 10 −2 s −1 ; and K s = (8.97–28.1) × 10 −5 s −1 . The K f calculated by the Sherwood equations varied from 1.61 × 10 −2 to 2.62 × 10 −2 s −1 , agreeing very well with values determined by the Sovová's model. For the walnut oil, ε varied from 0.142 to 0.225; f k = (0.339–0.581); K f = (1.04–3.62) × 10 −2 s −1 ; and K s = (5.17–16.0) × 10 −5 s −1 . The K f calculated by the Sherwood equations varied from 1.49 × 10 −2 to 5.46 × 10 −2 s −1 , agreeing well with those obtained by Sovová's model. © 2007 American Institute of Chemical Engineers AIChE J, 2007