Modeling steam distillation of essential oils: Application to lavandin super oil

Steam distillation of essential oil was studied to develop a phenomenological model able to reproduce oil recovery yield vs. collected floral water volume of aromatic plants with oil glandular trichomes. The model considers three stages in the oil obtaining process: (1) thermal oil exudation from the glandular trichomes, (2) vapor-liquid equilibrium at the interface, considering individual oil components, and (3) vapor phase oil mass transfer. Oil exudation was confirmed by SEM, and first order release kinetics was assumed for this stage. Lavandin super oil steam distillation experimental data were collected at a bench scale plant, using different steam flows and bed porosities. Experimental data were used to correlate model parameters: (1) the thermal exudation rate constant (0.072 min(-1)), and (2) the oil spots average thickness in the oil-aqueous layer (115 mu m). The average oil recovery yield was 1.36 +/- 0.14% w/w. The main compounds of essential oil were identified and quantified by GC/MS. (c) 2008 American Institute of Chemical Engineers.