Supercritical extraction of essential oil from Echium amoenum seed : Experimental, modeling and genetic algorithm parameter estimation

Abstract

Mathematical modeling of supercritical CO2 extraction of essential oil from Echium amoenum seed was carried out. The effect of process variables such as pressure (15, 20, 25 and 30 MPa), temperature (313, 318, 323 and 328 K) and CO2 flow rate (0.6, 0.9, 1.2 and 1.5 ml/min) on the recovery of essential oil extraction was investigated in a series of experiments conducted in a laboratory scale apparatus. The chemical composition of recovered essential oil (fatty acids) was analyzed by GC-FID. The mathematical model was developed utilizing diffusion-controlled regime in the pore and film mass transfer resistances with axial dispersion of the mobile phase at dynamic conditions. Henry's law was used to describe the equilibrium state of solid and pore fluid phases. The obtained mass transfer equations for the mobile and stationary phases were solved using the numerical explicit method of line, and the modeling pre- dictions of oil extraction recovery were validated via comparison with experimental data. Genetic algorithm (GA) was applied to estimate the optimum value of the Henry constant. Finally, applying the validated model the extraction re- covery was investigated as a function of effective variables such as dynamic extraction time and supercritical fluid temperature, pressure and flow rate. A set of optimal operating conditions were determined via modeling parametric analysis to achieve the objective function of maximum recovery.