Mathematical models for supercritical extraction of olive husk oil

Olive husk oil was extracted from olive husk under pressures of 12.0 to 18.0 MPa and temperatures of 308 to 330 It with supercritical carbon dioxide. Olive husk was supplied by an olive oil factory. The effects of pressure, temperature, extractor capacity and superficial velocity on the extraction rate of olive husk oil were studied. Extraction curves were evaluated by an empirical model, a 'hot sphere' model and by the extended Lack's plug-flow model and the relative merits of the models are demonstrated. The results are compared with those obtained in the literature. Good agreement between the extended Lack's plug-flow model and our experimental measurements was obtained. The empirical model (in which only one adjustable parameter varied with extraction conditions) also fitted the data well. The 'hot sphere' model, as currently applied, gave acceptable results at the higher superficial velocities studied but gave a very poor fit at the lowest velocities. The effects on the parameters in this model of allowing rapid equilibration to occur between the pore fluid and adjacent adsorbed solute are examined and discussed in the light of the experimental findings. (C) 1999 Elsevier Science B.V. All rights reserved.