Process design methodology for fractionation of fatty acids from palm fatty acid distillates in countercurrent packed columns with supercritical CO2

Abstract

In this work, the fractionation of fatty acids from palm oil deodorizer distillates, a by-product of the physical refining process of palm oil, has been investigated in a laboratory scale countercurrent packed column with supercritical CO2 as solvent. Experiments were carried out at 26 and 29 MPa and 373 K. Phase equilibria for the mixture palm fatty acids distillates + CO2 have been investigated experimentally by the static method at 333, 353, and 373 K and pressures between 20 and 29 MPa. The chemical identification of free fatty acids has been performed by gas chromatography. Hydrodynamic experiments were carried out for the systems palm fatty acids distillates + CO2 at 333, 353, and 373 K and pressures between 20 and 29 MPa in order to compute the column hydraulic capacity. A separation analysis based on phase equilibrium data (gas loading and selectivity) as well as hydrodynamic experiments (density of the coexisting liquid–gaseous phase and column hydraulic capacity) has been performed in order to optimize the best operation conditions. Process data (solvent and feed flow rates, reflux ratio, and mass fractions in feed and product streams) as well as phase equilibrium data of the multi-compound system fatty acids/carbon dioxide were used to compute the number of stages by the McCabe-Thiele and Jänecke methods. The mass transfer efficiency of the process was analyzed in terms of HETP as a function of liquid load, solvent-to-feed ratio and reflux ratio. HETP values lies between 0.8 and 2.5 m. The results show that palmitic acid was enriched from an initial content of 52.51 wt.% in the feed to 74.39 wt.% in the extract, while the oleic + linoleic acids were enriched from 46.27 wt.% in the feed to 59.00 wt.% in the raffinate showing that countercurrent gas extraction using carbon dioxide as solvent is suitable for fractionation and enriching of fatty acids from palm fatty acids distillates.