Experimental investigation of the residence time distribution in a screw-type apparatus designated to extract artemisinin

A continuous solid-liquid counter-current extraction process in a screw-type extractor is characterized using residence time distribution (RTD) measurements. The goal is to design an efficient process for the extraction of artemisinin from Artemisia Annua L. leaves. Artemisinin is used as an efficient anti-malaria drug. The study focuses on evaluating operating conditions and capturing the relevant hydrodynamic features. The RTD behavior has been investigated using pulse injections of a tracer material. The estimated average solid-phase Bodenstein number of approximately 45 indicates rather low axial dispersion. The mean solid-phase residence time of approximately 15 min allows an extraction efficiency of artemisinin in toluene above 95 %. The obtained experimental data will be used for validating companion simulations based on Computational Fluid Dynamics (CFD), in order to further optimize the extractor design.