Mass transfer modeling of apricot kernel oil extraction with supercritical carbon dioxide

Effects of process parameters on extraction of apricot (Prunus armeniaca L.) kernel oil with supercritical carbon dioxide (SC-CO2) were investigated. The parameters included particle size (mean particle diameter < 0.425-1.5 mm), solvent flow rate (1-5 g/min), pressure (300-600 bar), temperature (40-70 degrees C) and co-solvent concentration (up to 3.0 wt.% ethanol). The model of broken and intact cells represented the apricot kernel oil extraction well. Grinding was necessary to release the oil from intact oil cells of kernel structure. About 99% apricot kernel oil recovery was possible if particle diameter decreased below 0.425 mm. Two extraction periods were distinguished. The released oil on the surface of particles was extracted in the fast extraction period while the unreleased oil in the intact cells was extracted in the slow extraction period. The amount oil recovered in the slow extraction period was negligible compared to the amount recovered in the fast extraction period. Extraction rate in the fast extraction period increased with increase in solvent flow rate, pressure, temperature, and ethanol addition. Mass transfer coefficients in the fluid phase and in the solid phase changed between 0.7 and 3.7 min(-1), and between 0.00009 and 0.0005 min(-1), respectively. Mass transfer coefficient in the fluid phase increased with decrease in particle size and pressure, and with increase in solvent flow rate, temperature and ethanol concentration