Numerical study on the solid phase residence time distribution in a counter-current screw extractor

Abstract

The application of a highly efficient continuous counter-current extraction to extract Artemisinin from Artemisia Annua leaves is desirable since Artemisinin is efficiently used as anti-malaria drug. The residence time distribution (RTD) of the solid and liquid phases are most important for understanding this process since they influence the reaction efficiency. This work is devoted to the numerical investigation of the solid-phase RTD in a fully-filled screw extractor by using computational fluid dynamics (CFD). The solid phase is considered as a liquid Eulerian phase with a high viscosity. To track it, the commonly used species model has been implemented in a frozen quasi-steady-state simulation. Validation experiments have been performed by using dry leaves. A very good agreement between numerical and experimental residence times can be observed, with a relative error lower than 12 %. As a next step the model will be extended to predict the RTD in a multiphase flow model including the liquid solvent.