Slag metallurgy for recycling of Ta

Recycling of process residues, tin slags and sludges via chlorination or production of synthetic tantalum concentrate (syncon) constitutes an evolving alternative to the production of tantalum from ores mined primarily in Central Africa. For the pyrometallurgical syncon production the metal / slag separation is crucial to ensure product quality and yield. Therefore, melting behaviour and viscosity of such slags depict arbitrative indication. Hot stage microscope tests of synthetic slags are performed to investigate their characteristics in a temperature range of 1000 to 1600 °C under reducing (CO / CO2) and inert (Ar) atmosphere. The experimental results are compared to thermodynamic calculations realized with FactSage 7.1 to get a better understanding of the process and more detailed information on the melting range as well as the viscosity, which are heavily dependent on the slag composition.