Tiejun Lu

Modelling the extraction of essential oils with compressed carbon dioxide

Abstract Three models were used to describe the extraction of essential oils from oregano bracts using compressed carbon dioxide. They were developed on the basis of a plate-like geometry of the particles and were tested experimentally using various bract pre-treatments, pressures, temperatures and solvent flow rates. The two particle phase derived models applied, the Single Plate model (SP model) and the Simple Single Plate model (SSP model), differ only by the allowance or not for a film coefficient (kf) and have as the only adjustable parameter the matrix diffusivity (Dm). The third model, the Fluid Phase/Simple Single Plate model (FP/SSP model), considers both the particle mass balance and a detailed description of the fluid mass balance. In addition to the matrix diffusivity the FP/SSP model may require the adjustment of the fraction of oil leached by the solvent during the pressurisation procedure (f0). All models gave a good fit to the experimental data though the FP/SSP model gave the best fit. However, the matrix diffusivities found correlated very poorly with the estimated diffusivity of essential oils in carbon dioxide (D12), which indicates a complex intraparticle transport.

Extraction of useful components from herbs using supercritical CO2: Experimental findings and data modelling

Abstract Extraction of Thyme and Rosemary with CO 2 at 25 and 40°C and pressures up to 250 bar is described and the results modelled, Single Sphere Models being best. Good data fits were obtained for both herbs when effective diffusivities D e were fitted at each temperature and pressure but variations of D e with temperature and pressure were physically more convincing for Thyme.

Effect of Flow Rate on the Extraction of Volatile Concentrates and Resinoid Compounds from Origanum vulgare L. ssp. virens (Hoffm. et Link) letswaart using Compressed CO2

Abstract The effect of CO2 flow rate on the extraction of the volatile concentrate and resinoid compounds from Origanum vulgare L. ssp. virens (Hoffm. et Link) letswaart was studied at liquid (300 K, 70 bar) and supercritical (310 K, 100 bar) conditions. The mass flow rate of CO2 was varied between 0.3 kg/h to 0.9 kg/h with 0.2 kg/h increments. The degree and rate of extraction of the volatile concentrate was little dependent on CO2 flow rate and was controlled by intraparticle resistances. An extract slightly richer in volatile concentrate was collected at liquid CO2 conditions. The extraction of the resinoid compounds was mostly dependent on the flow rate of CO2 and was limited by their solubility in compressed CO2.