Kinetische Untersuchungen zur Reduktion von zink- und eisenhaltige Reststoffen mittels Wasserstoff

Translated title of the contribution: Kinetic Studies on the Reduction of Zinc- and Iron-Containing Residues Using Hydrogen

Maximilian Haller

Research output: ThesisMaster's Thesis


The Waelz process is the most applied technique to recover zinc from steel mill dust through carbothermic reduction. Products include Waelz oxide containing around 55¿60 wt.% zinc and Waelz slag containing around 5 wt. % zinc. This thesis aimed to investigate the feasibility of zinc recovery using hydrogen reduction to replace the Waelz kiln or to further reduce the Waelz slag. For this, kinetic study was performed for a representative Waelz feed mixture and various Waelz slag samples. For the Waelz slag, a metal yield of over 95 wt.% was achieved, but the reaction kinetics proved to be poor. Therefore, a thermomechanical pretreatment was carried out before the reduction tests to explore whether it could improve the kinetics. The results showed that the pretreatment significantly enhanced achievable reduction degree and reaction rate which could be attributed to the improved material porosity and permeability. Utilizing hydrogen in the Waelz process itself could contribute to drastically reduce its CO2 emissions. Thereby, understanding the rate-limiting steps and selecting optimal process parameters are crucial. A literature review identified temperature, reducing gas composition, and sample characteristics as key parameters. Thermogravimetric analysis investigated the effects of these parameters on the reduction kinetics for the representative Waelz feed mixture. It was demonstrated that higher temperatures improved overall reaction rates, while gas flow rates increased diffusion velocity and, consequently, reaction rates in every phase of the reaction. Increased hydrogen concentration enhanced the diffusivity of the reducing gas, leading to higher reaction rates, especially in the beginning and middle phases of the reduction. The effects of larger pellets varied depending on the hydrogen concentration and gas flow rate. Using Helium instead of Nitrogen as purge gas, improved diffusivity and heat transfer leading to better kinetics throughout beginning and middle phase of the reduction.
Translated title of the contributionKinetic Studies on the Reduction of Zinc- and Iron-Containing Residues Using Hydrogen
Original languageGerman
Awarding Institution
  • Montanuniversität
  • Leuchtenmüller, Manuel, Supervisor (external)
  • Steinlechner, Stefan, Supervisor (internal)
Award date30 Jun 2023
Publication statusPublished - 2023

Bibliographical note

embargoed until 16-06-2028


  • Reduction
  • Steel Mill Dust
  • Hydrogen
  • Reaction Kinetics

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