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The Kinetics of Oxidation of Liquid FeO-MnO-CaO-SiO2 Slags in Air
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2012 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 1, 56-63 p.Article in journal (Refereed) Published
Abstract [en]

The oxidizing kinetics of the liquid FeO-MnO-CaO-SiO(2) slags in air has been studied in the temperature range of 1500 K to 1600 K (1227 A degrees C to 1327 A degrees C) by using a thermogravimetric analysis (TGA). The reaction products after oxidation were analyzed by X-ray diffraction analysis (XRD). The surface topography of the obtained samples was analyzed by scanning electron microscopy (SEM). The products after oxidation showed the presence of manganese ferrite/magnetite and calcium silicate for all the samples in the experimental temperatures range. The oxidation process was developed through the following three consequent steps: (1) incubation period followed by a chemical reaction controlled stage (2) and later (3) diffusion of oxygen through the product layer. Appropriate mathematical relationships were constructed for these steps. Combining equations corresponding to the mechanism of oxidation, the experimental results were consistently reproduced, validating thereby the theoretical analysis.

Place, publisher, year, edition, pages
2012. Vol. 43, no 1, 56-63 p.
Keyword [en]
Incubation periods, Kinetics of oxidation, Manganese ferrites, Mathematical relationship, Mechanism of oxidation, Oxidation process, Product layer, Temperature range, XRD
National Category
Materials Engineering Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-24549DOI: 10.1007/s11663-011-9576-4ISI: 000299327800006ScopusID: 2-s2.0-84861828106OAI: diva2:351730
Mistra - The Swedish Foundation for Strategic Environmental Research

QC 20100917. Updated from submitted to published, 20120315

Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2014-04-29Bibliographically approved
In thesis
1. Recovery of iron and manganese values from metallurgical slags by the oxidation route
Open this publication in new window or tab >>Recovery of iron and manganese values from metallurgical slags by the oxidation route
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the modern practice, a sustainable development strategy in a domain of wasteutilization is shifting its focus from a general completeness of recycling to a morespecific attention to efficiently utilize elements in the wastes. This is well-illustrated bythe steelmaking slag industries. The major waste product from the steelmaking practiceis slag and its main constituents are: CaO, SiO2, Al2O3, MnO, FeO and so on. The mainfield of application for the steelmaking slags is civil engineering, especially for road andwaterway construction. However, a significant amount of the slag remains in the dumps,damaging the environment as well as requiring a land for secure storage. Efficientrecycling of these materials is of increasing interest worldwide as a result of increasingsustainability in processes with respect to increasing raw material costs and wastereduction.In order to find a practical solution, joint efforts are currently made at the RoyalInstitute of Technology, Sweden and National Metallurgical Academy of Ukraine. Theconcept is based on transformation of non-magnetic wüstite (FeO) to magneticmagnetite (Fe3O4) using an oxidizing atmosphere was proposed.In order to verify the feasibility of the proposed way of slag utilization, experiments onthe ternary CaO-FeO-SiO2 and quaternary CaO-FeO-SiO2-MnO slags systems,accompanied by thermodynamic and kinetic modelling, were performed. The crystalprecipitation during synthetic slag oxidation was observed by Confocal Scanning LaserMicroscopy (CSLM). Precipitated phases were found to be magnetite and manganeseferrite in the spinel form.Obtained magnetite and manganese ferrite can be separated from the slag by magneticseparation.The formation of nanosize manganese ferrite from the CaO-FeO-SiO2-MnO slag systemduring oxidation was investigated. Experiments were conducted in a horizontalresistance furnace in an oxidizing atmosphere (air). The final product was analysed by Xraydiffraction (XRD). The particles size of the manganese ferrite was estimated by theScherrer formula and was found to be of the order of 23-25 nm. In order to get anunderstanding of the magnetic properties of the manganese ferrite recovered from slagtreatment, it was necessary to synthesize a reference compound from pure precursors.The MnFe2O4 nanopowder was synthesized by the oxalate route. The size effects on themagnetic properties of manganese ferrite particles were investigated.IIThe potential way of the magnetite particles separation from liquid slags was investigatedby cold model studies. The experimental technique of mobilising non-conducting,nonmagnetic particles in conducting liquid in crossed electric and magnetic fields wasinvestigated in order to find the way of the particle separation from the liquidsteelmaking slags. The effects of the current density, magnetic field, size and shape ofthe particle on the particle velocity under action of the electromagnetic buoyancy force(EBF) in the electrolyte were analyzed.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. X, 64 p.
oxidation, metallurgical slag, recycling, FeO, iron recovery, manganese recovery, manganese ferrite, nano-ferrites, oxidation process, TTT, crystallization, kinetics studies, thermodynamic studies, modelling, cold-model studies, electromagnetic buoyancy force
National Category
Metallurgy and Metallic Materials Metallurgy and Metallic Materials Materials Engineering
urn:nbn:se:kth:diva-24534 (URN)978-91-7415-722-2 (ISBN)
Public defence
2010-10-08, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
QC 20100916Available from: 2010-09-16 Created: 2010-09-13 Last updated: 2010-09-17Bibliographically approved

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