Simulation of a Packed Bed Extraction Vessel for Designing a Supercritical Fluid Extraction Plant for Solid Substrates

Being interested in the sizing and optimization of supercritical fluid extraction plants for solid substrates, we are developing a computational tool to estimate changes in residual solute content in a solid substrate within one of the extraction vessels in a multi-vessel plant with a simulated counter-current contact between the solid substrate and continuously flowing supercritical CO2. In this contribution we are illustrating the use of our computational tool to assess the productivity of vegetable oil of plants with six cubic meters of total extraction volume and having three or four vessels with an inner diameter of 68.3 cm using 5 mmdiameter pre-pressed rapeseed pellets (equivalent diameter = 6.67 mm, bulk density = 500 kg/m) as the substrate, and 2400-to-6000 kg/h of CO2 at 40 °C and 30 MPa as the solvent. For the purpose of assessing the annual productivity we assumed the plant operated continuously (24 h/day) during 300 day/year using 60 oC and 8 MPa as the separation conditions. As expected, the productivity of the plant increased as the number of the extraction vessels or as the mass flow rate of CO2 increased. However, this increased productivity should be associated with increased investment and operational costs which were not estimated as part of our work. Thus, our main result at present is a map of vegetable oil productivity as a function of plant configuration that we plan to use for the economic optimization of the process.