CONTINUOUS FRACTIONATION OF FRIED OIL BY SUPERCRITICAL CO2 AND HEXANE

Fractionation of fried oils by Supercritical Carbon Dioxide (SC-CO2) might be a suitable purification technique, since a selective separation of the oil components can be attained [1, 2, 3]. Unfortunately, the specific quantity of CO2 with respect the oil is fairly high [2, 3] and thus the operating cost is estimated to be high [4]. The use of hexane as cosolvent has been tested to reduce it. The influence of the hexane concentration at selected operating condition (P = 35 MPa and T = 50°C) has been tested at constant ratio oil-hexane (60% vol). Ratio between CO2 and oil has been reduced from 52 down to a 22 kg/kg at constant CO2 flow rate. Fractionation yields and composition of products has been analysed and discussed. Experimental results indicate that the use of hexane can allow a significant CO2 flow rate reduction maintaining the oil composition and recovery substantially constant at column top. Nevertheless, the presence of some percentage of hexane residue in the oil has been detected and further treatments are necessary