Microwave Processing of Materials, Benefits and Challenges

About half of the global energy consumption is use for the generation of heat, and 50% out of that is used for industrial process heat. Although great efforts are being made worldwide to increase the share of renewable energies in process heat, this cannot compensate for the growing demand for process heat . There is still a long way to go that may benefit from electrification of process heat by using electromagnetic heating. But there are still many challenges to be solved along the way.
The Institute for Pulsed Power and Microwave Technology (IHM) at KIT is conducting applied research and development in the field of materials processing with microwaves within the Helmholtz Program Materials and Technologies for the Energy Transition (MTET). Starting with high temperature processing of materials such as ceramics, glasses and metals about 30 years ago, these microwave activities have been continuously expanded to novel applications, such as the curing of fiber-reinforced plastics, pultrusion, 3D printing, plasma chemistry and others, using industrial microwave sources like magnetrons and solid-state microwave amplifiers.
All those activities are motivated by increasing productivity and energy efficiency while reducing CO2 emissions by replacing fossil energy sources with microwave energy powered by renewable electricity. ... mehrAn overview of related developments at KIT and latest research results will be presented.
For a successful development of microwave systems and processes and for the transfer of technology from laboratory to industrial scale, knowledge of the dielectric properties of the processed materials in the relevant parameter range is essential. In general, knowing dielectric properties only at room temperature is not sufficient, as these properties can change significantly during the process due to temperature, potential phase transitions or chemical reactions. Furthermore, the dielectric properties reported in literature are not necessarily representative for the material of interest, in particular if the composition, purity, or porosity of the material is not identical or if the measurement was performed at different frequencies. Thus, direct dielectric characterization of the material to be processed is recommended. Different methods for dielectric measurement will be discussed. The influence of measurement results on the design of microwave system and process development will be explained on the basis of some specific applications.