Verwertungsstrategien von Wälzschlacke

Translated title of the contribution: Utilisation strategies from waelz slag

Christoph Pichler

Research output: ThesisDoctoral Thesis


Within the scope of the research project “Utilisation strategies from waelz slag” an evaluation of different possibilities to recycle waelz slag was done. Theoretical fundamentals built the basics for the various performed investigations from lab scale, up to an extended technical scale, to determine the most suitable strategy. The main input material of the waelz process has its origin in the production of steel through the electric arc furnace. In this case the zinc enters the process with the scrap and gets vaporized at the present temperatures. The oxidizing conditions in the off-gas stream lead to the formation of zinc oxide, which accumulates in the filter dust. About 9.7 million tons of filter dusts are generated in the current steel production but only 43 % of them get recycled. The main process to treat the electric arc furnace dust is the waelz process with a market share of 80 %. The obtained product out of this treatment is the waelz oxide, which is used as input material for the primary production of zinc. The remaining waelz slag unfortunately shows too high amounts of elutable compounds, which does not allow a usage as secondary raw material in various cases. Currently most of this material is dumped. Because of still existing valuable metals and possible problems in the future by the landfilling of metallurgical residues, different possibilities to recycle the waelz slag were developed and evaluated within this thesis. One option is the removal of zinc and lead with solid carbon carriers or a pyrolysis gas, which results from the carbonization of biomass. Investigations with a retort were done up to extended technical scale trials. Furthermore, a simultaneous metal recovery was investigated to realize a Zero-Waste process. As products flue dust, an iron alloy and an inert slag were generated. The produced metal could be used in different metallurgical applications. The flue dust allows to go into the same market as the waelz oxide and the remaining slag shows an elute behaviour, which enables a usage as secondary resource. In this case the necessary requirements for an application in the cement industry were determined. Practical trial in the lab scale defined the possible parameters to perform investigations on a “Top Blown Rotary Converter” and a “Submerged Arc Furnace” in the technical scale.
Translated title of the contributionUtilisation strategies from waelz slag
Original languageGerman
  • Friedrich, Bernd, Assessor A (external), External person
  • Antrekowitsch, Jürgen, Assessor A (internal)
Publication statusPublished - 2015

Bibliographical note

embargoed until 11-02-2020


  • waelz slag
  • recycling
  • zinc oxide
  • steel mill dust
  • residues

Cite this