TY - THES

T1 - Optimization of Reaction Parameters for Hydrogen Reduction of Electric Arc Furnace Dust

AU - Keuschnig, Aaron

N1 - no embargo

PY - 2024

Y1 - 2024

N2 - The recycling of galvanized scrap generates a zinc-containing dust fraction, usually called Electric Arc Furnance Dust EAFD, which is currently mainly treated in the carbon-based Waelz process. While the process is efficient in terms of zinc-recovery and process economy, it produces a secondary zinc concentrate with a large carbon footprint and underutilizes other valuable elements that are present in the EAFD. Climate change mitigation efforts require the substitution of carbon-based processes with carbon-neutral alternatives, such as hydrogen. To achieve this objective, it is important to have a fundamental understanding of the reaction kinetics of the reduction reactions with hydrogen. The present work investigates the influence of the temperature and H2O/H2 ratio on the reaction kinetics during the EAFD reduction. Experiments were conducted in a Thermogravimetric Analyzer TGA that was coupled with a Mass Spectrometer MS. The second objective was to develop an algorithm, that allows to distinguish between the reduction of zinc-oxide and iron-oxide by coupling the TGA and MS datasets. Experimental data demonstrated a full recovery of zinc (¿ 99 %) within a 60-minute hydrogen reduction period. The remaining solid material, which can be described as secondary-grade direct reduced iron (DRI), exhibited a high degree of metallization and a high iron concentration (¿ 70 %). Up to 1.150 °C, the reaction kinetics increased with the temperature. Above this point, the reactivity of the material decreased rapidly. During the reduction, the material shrinkage increased within reaction temperatures of 900-1.050 °C, but stagnated above that temperature. Interestingly, the H2O/H2 ratio of the atmosphere influenced the shrinkage behavior. A higher H2O concentration in the gas led to a higher material shrinkage. In contrast, the reaction kinetics decreased with higher H2O concentrations. The influence of the process parameters on the reaction kinetics of the EAFD could be identified. Additionally, the experimental setup was optimized to facilitate further investigations of the reaction kinetics.

AB - The recycling of galvanized scrap generates a zinc-containing dust fraction, usually called Electric Arc Furnance Dust EAFD, which is currently mainly treated in the carbon-based Waelz process. While the process is efficient in terms of zinc-recovery and process economy, it produces a secondary zinc concentrate with a large carbon footprint and underutilizes other valuable elements that are present in the EAFD. Climate change mitigation efforts require the substitution of carbon-based processes with carbon-neutral alternatives, such as hydrogen. To achieve this objective, it is important to have a fundamental understanding of the reaction kinetics of the reduction reactions with hydrogen. The present work investigates the influence of the temperature and H2O/H2 ratio on the reaction kinetics during the EAFD reduction. Experiments were conducted in a Thermogravimetric Analyzer TGA that was coupled with a Mass Spectrometer MS. The second objective was to develop an algorithm, that allows to distinguish between the reduction of zinc-oxide and iron-oxide by coupling the TGA and MS datasets. Experimental data demonstrated a full recovery of zinc (¿ 99 %) within a 60-minute hydrogen reduction period. The remaining solid material, which can be described as secondary-grade direct reduced iron (DRI), exhibited a high degree of metallization and a high iron concentration (¿ 70 %). Up to 1.150 °C, the reaction kinetics increased with the temperature. Above this point, the reactivity of the material decreased rapidly. During the reduction, the material shrinkage increased within reaction temperatures of 900-1.050 °C, but stagnated above that temperature. Interestingly, the H2O/H2 ratio of the atmosphere influenced the shrinkage behavior. A higher H2O concentration in the gas led to a higher material shrinkage. In contrast, the reaction kinetics decreased with higher H2O concentrations. The influence of the process parameters on the reaction kinetics of the EAFD could be identified. Additionally, the experimental setup was optimized to facilitate further investigations of the reaction kinetics.

KW - Reaction Kinetics

KW - Electric Arc Furnace Dust

KW - Decarbonization

KW - Hydrogen Reduction

KW - Zinc Recovery

KW - Reaktionskinetik

KW - Stahlwerksstaub

KW - Zinkrückgewinnung

KW - Wasserstoffreduktion

KW - Dekarbonisierung

M3 - Master's Thesis

ER -