Mass Transfer from Solid Material in Gas Extraction

Extraction rates of substances from solid substrates by supercritical gases have been determined for coffee beans and for rape oil seeds. In case of the indestructed coffee beans an unsteady extraction process prevails, which is determined by the transport of caffeine in the solid material. An approximate solution of the differential equations and a steady state approach are applicable to the long time part of the extraction process. In case of the crushed seeds a steady state mass transfer prevails which can be calculated by mass transfer calculations.