E. Reverchon et al., Supercritical fractional extraction of fennel seed oil and essential oil: Experiments and mathematical modeling, IND ENG RES, 38(8), 1999, pp. 3069-3075
Supercritical CO2 extraction of fennel seeds has been performed in two step
s; the first step was performed at 90 bar and 50 degrees C to obtain the se
lective extraction of essential oil. The second one was performed at 200 ba
r and 40 degrees C and allowed the extraction of vegetable oil. The experim
ents were performed using the fractional separation of the extracts using t
hree 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 (SE
M) images of the vegetable matter, mathematical models of the two extractio
n processes have been proposed. The extraction of fennel vegetable oil has
been modeled using a model based on differential mass balances and on the c
oncept of broken and intact cells as evidenced by SEM. Only one adjustable
parameter has been used: the internal mass-transfer coefficient kt. A fairl
y good fitting of the experimental data was obtained by setting k(t) = 8 x
10(-8) m/s. The fennel essential oil extraction process was modeled as deso
rption from the vegetable matter plus a small mass-transfer resistance. The
same internal mass-transfer coefficient value used for vegetable oil extra
ction allowed a fairly good fitting of the essential oil extraction data.