Mass and Energy Balance of an EAF for Tantalum Recycling

Georg Schnalzger

Research output: ThesisMaster's Thesis


Tantalum represents an important refractory metal for many key technologies (e.g., capacitors and superalloys). Thus, the market demand has increased over the last 10–15 years and the European Commission put it on the list of “critical metals” in 2017 due to its high industrial value. Today´s main tantalum resource comprises coltan (columbite-tantalite ores), which is mainly excavated in artisanal and small-scale mines in Central Africa (e.g., Democratic Republic Congo and Ruanda). However, these mining activities often contribute to rebel funding. Thus, feedstocks are considered as a case of conflict mineral. For enhancing transparency and traceability along the supply chain different organizations started to certify a non-conflicting origin, as some electronic companies claim this. Tantalum recycling from electronic devices still plays a minor role due to technological and economic challenges. However, synthetic concentrates (syncon) mainly produced from slags of tin plants have become a considerable secondary resource and contribute to a certain security of supply in Europe. In Laufenburg (Germany) H.C. Starck has been operating a syncon production line for more than 60 years and built up extensive recycling competence. With the launch of the KIC project “OpTaRec (Optimization of Tantalum Recycling)” in 2017 a broad investigation of the process and its performance started. The present master thesis constitutes a part of the project and aims at the establishment of a mass and energy balance (MEB) for the first thermal stage of syncon production (i.e., carbothermal reduction) in Microsoft Excel. This work is based on knowledge from literature, thermochemical calculations in FactSage and especially measurements of process parameters on-site during operation. The quantification of the MEB for selected batches shows a significant influence of chemical energies contained in materials on the outcome. In addition, it adds up to the conclusion that for future investigations the accuracy of temperature measurements should be increased. Although further sophistications and an extensive validation are required, the developed balances are beneficial tools for the identification and assessment of energy saving potentials. Based on current results, especially the reduction of heat losses to the surrounding is an effective lever to decrease the overall energy demand.
Translated title of the contributionMassen- und Energiebilanz eines Elektrolichtbogenofens zum Recyling von Tantal
Original languageEnglish
Awarding Institution
  • Montanuniversität
  • Hofer, Dominik, Co-Supervisor (internal)
  • Luidold, Stefan, Supervisor (internal)
Award date14 Dec 2018
Publication statusPublished - 2018

Bibliographical note

embargoed until 30-10-2023


  • tantalum
  • recycling
  • mass balance
  • energy balance
  • syncon

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