Modeling and simulation of the supercritical CO 2 extraction of vegetable oils

Abstract

The model of broken and intact cells has been applied to the experimental results on oil seed supercritical extraction obtained by various authors and on several species of seeds. The results analyzed are related to various extraction apparatus ranging from very low laboratory scale to pilot plants. Moreover, a wide range of operating conditions has been covered, CO 2 flow rates ranging between 1.5 and 750 g/min, extraction pressures from 240 to 550 bar, temperatures between 25 and 50°C and particle diameters from 0.25 to 4 mm have been considered. Besides, the experimental results existing in the literature, systematic scanning electron microscope (SEM) analysis have been performed on seed particles belonging to the different seed species studied, thus obtaining data about the microscopic cells that bear the oil that are characteristic of the different seed structures. Operating in this manner the differential mass balances that characterize this kind of models have been supported by microscopic information on seed structure and the number of adjustable parameters in the model has been reduced to only one, the internal mass transfer coefficient ( k i). A fair good fitting of all the available experimental results has been obtained using best fit k i values ranging between 2.4×10 −7 and 9.2×10 −8 m/s and producing a coherent description of the extraction process. Some simulation tests have also been performed that evidenced the role of particle size and of internal mass transfer and of their interaction on the overall performance of the extraction process.