Schlackenmetallurgie beim Recycling von niedrig tantalhaltigen Reststoffen

Research output: ThesisDoctoral Thesis


Organisational units


Tantalum (Ta), with a high melting point of 2996 °C, is part of the so-called refractory metal group. Thanks to unique mechanical and chemical properties, its main applications are high-tech products (e.g. capacitors, super alloys or sputtering targets). Due to the tremendous economic importance and supply risk, Ta was classified as a critical raw material for the European Union in 2017. Improved recycling processes offer promising opportunities with regard to future price stability, reduced import dependency and an increase in the end-of-life recycling rate, which currently accounts for less than one percent. Synthetic concentrate production in a multi-stage pyrometallurgical process with the emergence of huge amounts of high melting slag constitutes state of the art for secondary practice. Comprehensive investigations regarding melting behaviour, composition and viscosity carried out within the framework of this research work form the basis for replicating the process in laboratory scale. Therefore, the determination of characteristic temperatures throughout several hot stage microscope test series plays a decisive role, as does their validation by thermodynamic calculations using FactSage. In addition to established viscosity models, measurements in a high-temperature rheometer help to better understand the block smelting process. The use of selected additives or a two-stage slag operation accelerate the metal/slag separation, which enables a reduced energy demand due to a faster treatment time as well as an increased process yield. Smelting experiments in an induction and electric arc furnace lay the groundwork for upscaling of the developments to small industrial scale. Innovative recycling processes provide the best means to achieve future economic and ecological goals as well as to ensure a sustainable supply of conflict-free tantalum.


Translated title of the contributionSlag metallurgy for the recycling of low grade tantalum bearing residues
Original languageGerman
Awarding Institution
Publication statusPublished - 2020