Separation of fish oil ethyl esters with supercritical carbon dioxide

Abstract

Fatty acid ethyl esters from fish oil (FAEE) were continuously fractionated with supercritical carbon dioxide (SCCO 2). A pilot plant countercurrent extraction column with an inner diameter of 68 mm and an effective height of 12 m packed with Sulzer CY wire mesh packing was used for the experiments. The operating conditions varied in the temperature range of T=40–80°C and the pressure range of p=6.5–19.5 MPa. All experiments focused on a separation between the low-molecular-weight components (LMC), with carbon numbers from C14 to C18, and the high-molecular-weight components (HMC), C20 and C22. This separation represents a possible first step in an enriching process for the commercial interesting components EPA and DHA. HMC concentrations greater than 95 wt% at a yield greater than 95% were achieved with this set-up. The pilot plant was equipped with a sampling system to measure the concentration profile along the column. These experiments allow the height of a theoretical plate to be calculated. Previously published phase equilibrium data [V. Riha, G. Brunner, Phase equilibrium of fish oil ethyl esters with supercritical carbon dioxide, J. Supercrit. Fluids 15 (1999) 33–50] are employed as base information for these calculations. The methods of McCabe-Thiele and Ponchon-Savarit (R.E. Treybal, Mass-transfer Operations. Classic Textbook Reissue, 3rd edition, McGraw-Hill, New York, 1987) and a multi-component simulation with the flowsheeting program Aspen+ are used to compute the theoretical number of plates for each experimental run. All methods yield similar results. A height of approximately 0.3 m can be assumed for a theoretical plate with this set-up.