In this study, possible leaching control mechanisms for Cr and V in electric arc furnace slags were investigated by using a multi-methodological approach. Aside from chemical and mineralogical bulk analyses, special emphasis was given to surface investigations of the slags prior to and after leaching. In addition, pH dependence leaching tests were performed and the obtained data were evaluated with hydrogeochemical models. Investigations revealed that Cr and V are mainly bound in spinel and wuestite as well as minor amounts of olivine. Spinel and wuestite do not dissolve during water leaching for 48 h, whereas, depending on the composition of olivine, this phase either dissolves and releases V and Cr congruently, or does not dissolve but may hydrate. Melilite may also hydrate, but neither V nor Cr were detected in this phase. It appears that leached V is subsequently adsorbed onto these newly hydrated phases. The combination of the applied methods further showed that the abundance of calcium silicates, spinel, and wuestite is influenced by the FeO/SiO2 and CaO/SiO2 ratio in the slag. Therefore, it is assumed that the leaching of V and Cr can be minimized by changing these ratios to favor the formation of Fe bearing calcium silicate and spinel instead of wuestite.
Gestiegene Umweltauflagen sowie hohe Metallpreise führten in den letzten Jahren zu intensiven Forschungsbemü-hungen auf dem Gebiet des Recyclings von Stahlwerksstäuben. Diese waren jedoch häufig geprägt durch die rasche Entwicklung von Verfahren, um möglichst schnell wirtschaftliche Aufarbeitungswege anbieten zu können. Wenig wurde aber in die Charakterisierung und Untersuchung des Schmelz-und Reduktionsverhaltens der Stäube investiert, sodass sich in Optimierungsfragen bzw. in der Entwicklung neuer Verfahrenswege häufig ein deutlicher Mangel an Grundlageninformationen zeigt. In der vorliegenden Arbeit werden die Daten hinsichtlich Charakterisierung und Verhalten aus der Literatur zusammengefasst, mit Ergebnissen eigener Untersuchungen ergänzt und offene Fragen bzw. zukünftige Problemstellungen aufgezeigt.
Characterization and Behaviour of Zinc-, Lead-and Halogen Compounds during the Recycling of Electric Arc FurnaceDusts. Environmental legislation as well as high metal prices led to an intensive research in the area of steel mill dust recycling. First of all this research was done to develop process routes to enable an economical recycling of the steel mill dust. Beside this, only low efforts were made concerning characterization and behaviour during melting and reduction of the used materials. Therefore, often a lack in fundamental information becomes obvious during optimization of existing or development of new processes. The present work summarizes the available information concerning characterization and behaviour from literature, complemented with data from own investigations and discusses open items and possible problems of the future.
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