Kinetic Study and Optimization of the Operating Conditions of the Extraction by Steam Distillation of the Essential Oil of Thymus numidicus (Poiret) of Algeria

Abstract

In order to study the process of extraction of the essential oil of Tymus numidicus kabylica extracted by steam distillation, kinetic studies as well as an optimization of the operating conditions were achieved. The optimization was carried out by a parametric study and experiments planning method. Three operational parameters were chosen: thyme mass, steam water flow rate and porosity of the bed. The obtained results underscored a kinetic of order one with two steps. The first is faster with a recovery of more than 94 % of essential oil. The optimal conditions obtained by the parametric study correspond to a : mass of 35 g, steam flow rate of 6.3 g/min. and porosity of 0.9155. The study by experiments planning realized by adopting the factorial planning of two levels of the three parameters 23, allowed on one hand, the estimation of the simple, combined interactions and triple effects of the parameters on the essential oil yield, and on the other hand, the establishment of a mathematical model describing the variations of the yield according to the studied parameters. The results reveal that the simple effect of the bed porosity is preponderant in comparison to the simple effects of the mass and the steam water flow rate. Concerning the combined effects of two parameters, the steam water flow rate and the bed porosity, is the more important. The yield is also affected by the interaction of the three parameters.