A microwave cavity design and optimisation for a homogeneous and faster drying process inside an industrial Agitated Nutsche Filter

Abstract

Background: Nowadays the disposal or recycling of polyethylene terephthalate (PET) material is a real-world problem. The European Union’s DEM3TO project aims at recycling PET to return it to the main chemical components with which it was produced. In a specific reactor, microwave radiation is used to quickly depolymerise the initial polymer. At the end of the de-polymerization process, a filtering and drying process through an agitated Nutsche filter (ANF) is necessary. Methods: This study aims to design and develop a High Frequency (HF) cavity inside the ANF (plugin “HF-ANF”) to speed up and improve the drying process. The effects studied are the efficiency of the HF cavity as a function of the heating process, the evaporation/drying process, and the mechanical mixing (due to the blades) of the mixture. Results: During these studies it was possible to improve the efficiency of the HF plugin and allowing to absorb more than the 95% of the microwave energy into the mixture to increase the drying speed and the drying homogeneity of the ANF. In addition, the mixture was characterised to obtain the dielectric proprieties as a function of the temperature of the ANF and the concentration of the residual water. Conclusions: The study allowed us to develop some important methodology that usually cannot to be simulated in a non-multi physics simulator. The careful modelling of certain aspects that are not normally available in EM (Electro-Magnetic) simulators, like variable geometries, mixed material, heating effect and the dielectrics characterization process are difficult and critical process but are very important steps to be undertaken in order to obtain results that can be compared with real measurements.