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Recovery of iron and manganese values from metallurgical slags by the oxidation route
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
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.
Keyword [en]
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
Identifiers
URN: urn:nbn:se:kth:diva-24534ISBN: 978-91-7415-722-2 (print)OAI: oai:DiVA.org:kth-24534DiVA: diva2:351739
Public defence
2010-10-08, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20100916Available from: 2010-09-16 Created: 2010-09-13 Last updated: 2010-09-17Bibliographically approved
List of papers
1. Kinetics of oxidation of divalent iron to trivalent state in liquid FeO-CaO-SiO2 slags
Open this publication in new window or tab >>Kinetics of oxidation of divalent iron to trivalent state in liquid FeO-CaO-SiO2 slags
2010 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 6, 1230-1239 p.Article in journal (Refereed) Published
Abstract [en]

This work was devoted to the kinetics studies of the oxidation of divalent iron in liquid FeO-CaO-SiO2 slags to the trivalent state. The experiments were carried out using a thermogravimetric technique (TGA) in the temperature range of 1623 K to 1773 K (1350 °C to 1500 °C) in an oxidizing atmosphere. The reaction products after oxidation were analyzed by X-ray diffraction and optical and scanning electron microscopy. The results obtained show that during the first 10 to 15 minutes of oxidation, 70 to 90 pct of the Fe2+ in the slag was oxidized. Kinetic analysis of the TGA results indicates that the oxidation process may consist of three distinct steps, viz an initial incubation period, followed by a chemical-reaction-controlled stage, and later, a diffusion-control stage. Appropriate mathematical relationships were set up for the first two consecutive steps. After combining these equations suitably as the mechanism of oxidation shifts from one form to another, the experimental results for the first two parts could be reproduced. A linear correlation was found between the thermodynamic activity of FeO in the slag and the degree of oxidation.

Keyword
Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24551 (URN)10.1007/s11663-010-9425-x (DOI)000284326900010 ()2-s2.0-78650796392 (Scopus ID)
Note
QC 20100916Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
2. Confocal Scanning Laser Microscopy studies of crystal growth during oxidation of a liquid FeO-CaO-SiO2 slag
Open this publication in new window or tab >>Confocal Scanning Laser Microscopy studies of crystal growth during oxidation of a liquid FeO-CaO-SiO2 slag
Show others...
2011 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 3, 471-476 p.Article in journal (Refereed) Published
Abstract [en]

The oxidation of FeO in 30 wt pct FeO-35 wt pct CaO-35 wt pct SiO2 slag was investigated as part of a wider study on the recovery of Fe units through magnetic separation. A confocal scanning laser microscopy (CSLM) technique was used to visualize the oxidation of FeO in the liquid slag. The formation event was observed in situ under the CSLM and the onset of precipitation on a surface of the slag liquid was recorded at various temperatures in an oxidizing atmosphere. A Time-Temperature-Transformation (TTT) diagram was constructed based on the CSLM results. Samples obtained from the CSLM heating chamber were analyzed by a scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer (EDS).

National Category
Metallurgy and Metallic Materials Materials Engineering
Identifiers
urn:nbn:se:kth:diva-24550 (URN)10.1007/s11663-011-9505-6 (DOI)000290688300005 ()2-s2.0-79959533824 (Scopus ID)
Note
QC 20100916. Updated from submitted to published, 20120316Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
3. The Kinetics of Oxidation of Liquid FeO-MnO-CaO-SiO2 Slags in Air
Open this publication in new window or tab >>The Kinetics of Oxidation of Liquid FeO-MnO-CaO-SiO2 Slags in Air
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.

Keyword
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
Identifiers
urn:nbn:se:kth:diva-24549 (URN)10.1007/s11663-011-9576-4 (DOI)000299327800006 ()2-s2.0-84861828106 (Scopus ID)
Funder
Mistra - The Swedish Foundation for Strategic Environmental Research
Note

QC 20100917. Updated from submitted to published, 20120315

Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
4. Confocal Microscopic Studies on Evolution of Crystals during oxidation of the FeO-CaO-SiO2-MnO Slags
Open this publication in new window or tab >>Confocal Microscopic Studies on Evolution of Crystals during oxidation of the FeO-CaO-SiO2-MnO Slags
Show others...
2010 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 5, 940-945 p.Article in journal (Refereed) Published
Abstract [en]

The current work investigates dynamic phenomena at the microstructural level during iron and manganese recovery from the liquid FeO-CaO-SiO2-MnO slags using an oxidation method. A hot-stage-equipped confocal scanning laser microscope (CSLM) was used to analyze the kinetic behavior of crystallization in synthetic slags. Based on observed precipitations on cooling in the 1273 K (1000 °C) to 1873 K (1600 °C) temperature range, a time–temperature–transformation (TTT) diagram has been created. The crystallization studies were conducted in air.

National Category
Materials Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24552 (URN)10.1007/s11663-010-9392-2 (DOI)000284333700003 ()2-s2.0-79951516928 (Scopus ID)
Note
QC 20100916Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
5. Investigation of the potential way of the magnetite particles separation from liquid EAF slags
Open this publication in new window or tab >>Investigation of the potential way of the magnetite particles separation from liquid EAF slags
2010 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Other academic) Submitted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24553 (URN)
Note
QS 20120316Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
6. Recovery of manganese ferrite in nanoform from the metallurgical slags
Open this publication in new window or tab >>Recovery of manganese ferrite in nanoform from the metallurgical slags
2011 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 1, 2-4 p.Article in journal (Refereed) Published
Abstract [en]

The present work investigates the formation of manganese ferrite of nanosize by oxidation of MnO- and FeO-containing slag. A horizontal resistance furnace was used as an experimental setup. The experiment was conducted in the temperature range of 1573 K to 1673 K (1300 A degrees C to 1400 A degrees C) in an oxidizing atmosphere. The samples were quenched to the cold end of the furnace and were analyzed by X-ray diffraction (XRD). The XRD patterns of the products showed the presence of two phases-manganese ferrite and calcium silicate. The particle size of the manganese ferrite was estimated by the Scherrer formula to be in the range of nanometers.

Keyword
Experimental setup, Horizontal resistance, Manganese ferrites, Metallurgical slags, Nano-size, Nanoforms, Oxidizing atmosphere, Scherrer formula, Temperature range, XRD patterns, Calcium silicate, Ferrite, Furnaces, Iron oxides, Manganese, Manganese oxide, Silicates, Slags, X ray diffraction
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24554 (URN)10.1007/s11663-010-9457-2 (DOI)000286942500001 ()2-s2.0-79951515539 (Scopus ID)
Note
QC 20100916 Uppdaterad från submitted till published (20110318).Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
7. Synthesis of nano-manganese ferrite by an oxalate method and its magnetic properties characterization
Open this publication in new window or tab >>Synthesis of nano-manganese ferrite by an oxalate method and its magnetic properties characterization
2010 (English)Report (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH, 2010
Identifiers
urn:nbn:se:kth:diva-24555 (URN)KTH/MSE--10/43--SE+THMETU/ART (ISRN)
Note
QC 20100916Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2010-09-17Bibliographically approved

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