Multi-scale experimental study and modeling of the supercritical fractionation process

• Supercritical fractionation of water-ethanol mixtures by carbon dioxide was carried out at 10.1 MPa and 333 K.
• Laboratory, pilot and industrial-scale units were used and good agreement was found between the experimental results.
• An equilibrium-stage model predicts well the tendencies of the extract and raffinate compositions as a function of the solvent-to-feed ratio and feed composition.
• On the laboratory column, entrainment was detected at solvent velocity of 12 mm s−1 but was not present at velocities between 20 and 40 mm s−1.

In this work, the fractionation of water–ethanol mixtures by supercritical carbon dioxide at 333 K and 10.1 MPa was used as a model system to compare experimental extract and raffinate compositions and overhead loadings at laboratory, pilot and industrial scales to contribute toward a sizing methodology for counter-current supercritical fractionation columns. A series of three columns with an internal diameter of 19, 58 and 126 mm and with a height of 2, 4 and 8 m respectively were used for the different scales, meaning scaling factors from 9 to 44 between columns. The massic solvent-to-feed ratio was varied between 5.2 and 78.8. Experimental results at the different scales are analyzed and compared from the thermodynamic, mass transfer and column hydrodynamics points of view; and also using process simulation by equilibrium-stage models. In total, 42 successful experimental runs are taken into account, including 6 at a pilot scale unit and 2 at an industrial scale.

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