Methodology for process modelling of supercritical fluid fractionation processes illustrated for the separation of alkane/alcohol isomer mixtures using CO2

• Methodology for process modelling of supercritical fluid fractionation.
• Use binary solvent/solute experimental data to fit simple thermodynamic model.
• Applied to supercritical CO2 fractionation of C10 alkanes and alcohols.
• Experimental data for CO2/(alkane + alcohol) mixture and pilot plant fractionation.

A methodology to determine the technical feasibility of a supercritical fluid fractionation process is presented. A limited amount of solvent/solute phase equilibrium data is used to fit a simple thermodynamic model, after which the process is modelled in a commercial simulator using an equilibrium stage liquid–liquid extraction column to model the extraction column and a flash drum to model the separator. The methodology is illustrated for the supercritical CO2 fractionation of a mixture of C10 alkane and alcohol isomers using Aspen Plus® as the process simulator. The RK ASPEN property method (modified SRK equation of state) was fitted to previously measured solvent/solute data and the fit verified against experimentally measured bubble and dew point data for the system CO2/(C10 alkanes + alcohols). Comparison of the developed Aspen Plus® process model, using the fitted RK ASPEN property method, with experimentally measured pilot plant data revealed that the component flow rates in the two product streams can be predicted with reasonable accuracy, thus verifying the validity of the methodology.

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