EXPERIMENTAL DESIGN OF ROSEMARY OLEORESIN
EXTRACTION IN AN IMMERSED FIXED BED PERCOLATOR
KRIM Scheherazade, BAIT Malek, BENTAHAR Fatiha
Laboratoire des Phénomènes de Transfert, Département de Génie chimique et de
Cryogénie, Faculté de Génie Mécanique et de Génie des Procédés, Université des
Sciences et de la Technologie Houari Boumediene. B.P. 32 El Alia 16111 Bab-Ezzouar,
ALGER, Tél./Fax : (213) 21 24 71 69. Sch_Krim@yahoo.fr Fatihabentahar@yahoo.fr
Abstract
Rosemary (Rosmarinus officinalis L.) leaves from Algiers have been extracted
continuously by hexane in an immersed fixed bed percolator. In order to improve the
extraction yields of rosemary oleoresin, different operating conditions have been tested both
on extraction yields and rates as well as on the kinetics and the passage time. Results showed
that intraparticle diffusion is rate-governing step of the process. The extractions all proceeded
in two stages: a fast initial washing stage, and a slower stage. The former has a constant rate
while the latter has a decreasing one. The operating parameters studied were the operating
temperature, the volumetric solvent flow rate, the vegetal height and the column diameter.
Negative effects have been shown by increasing vegetal height (and/or the vegetal weight)
and column diameter while positive effects have been obtained by increasing the operating
temperature and the volumetric solvent flow rate. The oleoresin yield decreases, in the worst
case of 2mL/min of solvent flow rate, of 44% when the vegetal height increases from 17.5 cm
to 49 cm and increases of about 56% for the latter and about 33% for the former when the
operating temperature increases from 35 to 45 °C for any solvent flow rate ranging from 2 to
10 mL/min. Likewise, increasing flow rate in the studied range, leads to increase the
oleoresin yield of around 28% and 76%, respectively, for a bed height of 17.5 and 49 cm, for
any temperature ranging from 35 and 45°C. The best yield of extracted oleoresin was 6.82%
according and the following operating conditions: a solvent flow rate of 10mL/min, a bed
height of 17.5cm and an operating temperature of 45°C. Furthermore, a close relation between
the extraction yields and the residence time has been brought to the fore. It has been shown
that the former is negatively affected by increasing the latter. Indeed, the most significant
parameter studied, being the solvent flow rate, which is inversely proportional to residence
time, seems to control the values of the extraction yields. In the other hand, the porosity and
the height of the active bed are also linked to the residence time. A complementary study is
then necessary to bring to the fore the individual and conjugated effects of these parameters
with that of the solvent flow rate by the mean of an experimental design. In order to obtain
different porosities by making constant the active bed height as well as its vegetal weight a
package of glass balls has been used. Thus, porosities ranging from 0.86 to 0.6 can be
obtained. Yield of extracted oleoresin increases with decreasing of bed porosity from 0.86 to
0.756, where is the highest and decreases with further decreasing of bed porosity to 0.6. The
best yield obtained was about 7% according to a bed porosity of 0.756. Positive effects have
been shown by increasing the volumetric solvent flow rate for all the operating conditions
tested while negative effects have been obtained by increasing the vegetal height (and/or the
vegetal weight). Increasing the bed porosity between 0.71 and 0.8 was without any effect. The
best yield of extracted oleoresin was 7.33% according to a passage time of 25.41 min and the
following operating conditions: a solvent flow rate of 10mL/min, a bed height of 17.5cm and
a porosity of 0.74.