Supercritical extraction of oil seed rape: Energetic evaluation of process scale

• Supercritical CO2 extraction of oil seed rape at different scales (1 L and 16 L).
• Optimum conditions were 35 °C and 55.0 MPa, yielding 95% of a heptane extraction.
• Energy consumption of the process divided into cooling, heating and pumping.
• 9.7 and 10.2 kW h/kg of extracted oil needed in small and pilot scale, respectively.

This study focuses upon the supercritical CO2 extraction of oil seed rape (Brassica napus) and the energy consumption associated with it in two different scales (1 L and 2 × 16 L). Experiments were carried out to determine the influence of pressure, temperature and flow rate on the extraction yield. The yield varied from 37 to 97% of the one for n-heptane. The energy consumption in both extraction plants allowed an analysis of the different components involved in the extraction process, namely pumping, heating and cooling. This energy consumption was analysed depending on the amount of CO2 used, so the calculations can be extrapolated to any supercritical fluid extraction process undertaken in those plants. In the particular case of the supercritical extraction of oil seed rape, the best conditions in our experimental range were achieved at 55 MPa and 35 °C, yielding 100.3 g of oil per kW h. This yield was comparable to that obtained in the pilot plant of 97.4 g oil/kW h. An accurate energetic evaluation of the extraction process at different scales has provided further evidence to encourage the change to supercritical fluid extraction as an economically viable industrial process.

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