TY - THES

T1 - Thermal treatment and cooling of metallurgical residues for use as a supplementary cementitious material

AU - Krammer, Anna

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - The metallurgical processes of steelmaking generate slags as by-products, which are often landfilled. To avoid this deposition and utilise the raw material potential, mixtures of different metallurgical residues combined with suitable correction substances were evaluated for use as a supplementary cementitious material. For this purpose, potential combinations, according to given critical values such as the basicity or the correlation of the slag masses, were calculated. These were melted to reduce the valuable metals and to separate them from the mineral fraction. The systematic cooling of the liquefied material was achieved through wet granulation. Practical implementation at laboratory scale consisted of melting the mixtures in a graphite crucible using a resistance furnace, wet granulation, and drying. The granulate was then crushed, sieved, and finally, the metallic fraction was removed by magnetic separation. The conclusions present the technological suitability of the different mixtures for cement binding, according to their chemical composition, and assess the accuracy of MS Excel Solver. Furthermore, the achievable reduction rates of iron, manganese, and chromium were determined and the separation of the valuable metals and impurities from the mineral fraction was analysed. Additionally, the composition of the accruing gas phase and possible process losses are shown by a material flow analysis.

AB - The metallurgical processes of steelmaking generate slags as by-products, which are often landfilled. To avoid this deposition and utilise the raw material potential, mixtures of different metallurgical residues combined with suitable correction substances were evaluated for use as a supplementary cementitious material. For this purpose, potential combinations, according to given critical values such as the basicity or the correlation of the slag masses, were calculated. These were melted to reduce the valuable metals and to separate them from the mineral fraction. The systematic cooling of the liquefied material was achieved through wet granulation. Practical implementation at laboratory scale consisted of melting the mixtures in a graphite crucible using a resistance furnace, wet granulation, and drying. The granulate was then crushed, sieved, and finally, the metallic fraction was removed by magnetic separation. The conclusions present the technological suitability of the different mixtures for cement binding, according to their chemical composition, and assess the accuracy of MS Excel Solver. Furthermore, the achievable reduction rates of iron, manganese, and chromium were determined and the separation of the valuable metals and impurities from the mineral fraction was analysed. Additionally, the composition of the accruing gas phase and possible process losses are shown by a material flow analysis.

KW - SCM

KW - carbothermic reduction

KW - metal recovery

KW - circular economy

KW - slag valorisation

KW - carbo-thermische Reduktion

KW - Metallrückgewinnung

KW - Kreislaufwirtschaft

KW - Schlackenverwertung

M3 - Master's Thesis

ER -