TY - THES

T1 - Kinetic Aspects of the Selective Reduction of Zinc Ferrite with H2 in the Processing of Electric Arc Furnace Dust

AU - Hoffelner, Felix

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - EAF dust is currently recycled via processes that rely on carbothermal reduction. The implementation of an H2-based reduction process could help reduce greenhouse gas emissions in a way that would allow recyclers to contribute their part to the European Green Deal. Although some studies already proved technical feasibility, a definitive process has yet to be established. A key role plays the reaction kinetics between the solid EAF dust constituents and the gaseous H2. This work investigates the relevant reactions in thermogravimetric experiments using high-purity ZnFe2O4 and Fe2O3 powders. The results from the pure substances were then compared to experiments using pure EAF dust. The objective was to study the kinetics of the individual sequential reduction steps. Kinetic models for the individual reduction steps of ZnFe2O4 and Fe2O3 could be found, but some ambiguities remained for the Fe2O3 results. The results indicate a different behaviour between iron oxide reduction from ZnFe2O4 and Fe2O3. The main difference lies in the first two reduction steps up to FeO, which for ZnFe2O4 is rate limited by nucleation and diffusion. The limiting mechanisms for Fe2O3 appear to be nucleation and growth. The final reduction step to metallic Fe proceeds in a similar overall manner for both materials and follows a geometric contraction model. The behaviour of EAF dust shows similarities with that of ZnFe2O4. Although, a comprehensive kinetic study with a special focus on EAF dust has yet to be conducted. Further experiments should investigate the same reactions in an extended parameter area for temperature and gas composition and the results would benefit from tweaks to the gas flow rates.

AB - EAF dust is currently recycled via processes that rely on carbothermal reduction. The implementation of an H2-based reduction process could help reduce greenhouse gas emissions in a way that would allow recyclers to contribute their part to the European Green Deal. Although some studies already proved technical feasibility, a definitive process has yet to be established. A key role plays the reaction kinetics between the solid EAF dust constituents and the gaseous H2. This work investigates the relevant reactions in thermogravimetric experiments using high-purity ZnFe2O4 and Fe2O3 powders. The results from the pure substances were then compared to experiments using pure EAF dust. The objective was to study the kinetics of the individual sequential reduction steps. Kinetic models for the individual reduction steps of ZnFe2O4 and Fe2O3 could be found, but some ambiguities remained for the Fe2O3 results. The results indicate a different behaviour between iron oxide reduction from ZnFe2O4 and Fe2O3. The main difference lies in the first two reduction steps up to FeO, which for ZnFe2O4 is rate limited by nucleation and diffusion. The limiting mechanisms for Fe2O3 appear to be nucleation and growth. The final reduction step to metallic Fe proceeds in a similar overall manner for both materials and follows a geometric contraction model. The behaviour of EAF dust shows similarities with that of ZnFe2O4. Although, a comprehensive kinetic study with a special focus on EAF dust has yet to be conducted. Further experiments should investigate the same reactions in an extended parameter area for temperature and gas composition and the results would benefit from tweaks to the gas flow rates.

KW - Zinkferrit

KW - Lichtbogenofenstaub

KW - EAF Staub

KW - Wasserstoffreduktion

KW - Kinetik

KW - zinc ferrite

KW - electric arc furnace dust

KW - EAF dust

KW - hydrogen reduction

KW - kinetics

M3 - Master's Thesis

ER -