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High-temperature mass spectrometric study of the vaporization processes of V2O3 and vanadium-containing slags
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
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2010 (English)In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 24, no 16, 2420-2430 p.Article in journal (Refereed) Published
Abstract [en]

A Knudsen effusion mass spectrometric method was used to study the vaporization processes and thermodynamic properties of pure V2O3 and 14 samples of vanadium-containing slags in the CaO-MgO-Al2O3-SiO2 system in the temperature range 1875-2625 K. The system was calibrated using gold in the liquid state as the standard. Vaporization was carried out from double tungsten effusion cells. First it was shown that, in vapor over V2O3 and the vanadium-containing slags in the temperature range 1875-2100 K, the following vapor species were present: VO2, VO, O, WO3 and WO2, with the latter two species being formed as a result of interaction with the tungsten crucibles. The temperature dependencies of the partial pressures of these vapor species were obtained over V2O3 and the slags. The ion current comparison method was used for the determination of the V2O3 activities in slags as a function of temperature with solid V2O3 as a reference state. The V2O3 activity coefficients in the slags under investigation indicated positive deviations from ideality at 1900 K and a tendency to ideal behavior at 2100K. It was shown that the V2O3 activity as a function of the slag basicity decreased at 1900 K and 2000 K and was practically constant in the slag melts at 2100K. The results are expected to be valuable in the optimization of slag composition in high-alloy steelmaking processes as well as for their environmental implications. Copyright (C) 2010 John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
2010. Vol. 24, no 16, 2420-2430 p.
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:kth:diva-26866DOI: 10.1002/rcm.4657ISI: 000280687200014ScopusID: 2-s2.0-77955359931OAI: diva2:373700
QC 20101201Available from: 2010-12-01 Created: 2010-11-29 Last updated: 2012-03-28Bibliographically approved
In thesis
1. Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys
Open this publication in new window or tab >>Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With the progress of high alloy steelmaking processes, it is essential to minimize the loss of valuable metals, like chromium and vanadium during the decarburization process, from both economic as well as environmental view points. One unique technique to realize this aim, used in the present work, is the decarburization of high alloy steel grades using oxygen with CO2 in order to reduce the partial pressure of oxygen. In the present work, the investigation on the oxidation of iron-chromium and iron-vanadium molten alloys under CO2-O2 mixtures was carried out and presented in this dissertation.

For oxidation study on Fe-Cr molten alloy with CO2-O2 mixtures, on the basis of thermodynamic analysis, energy balance calculation and modeling results, experimental validation in laboratory was carried out, and later on, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts under controlled partial pressure of oxygen was investigated. Thermodynamics calculation and energy balance estimation demonstrated that, it is possible to use CO2 or CO2-O2 mixtures as decarburizers during EAF process and high initial carbon contents in the steel can be adopted at the beginning in order to reduce the cost.

A generic model has been developed to describe the overall process kinetics prevailing in metallurgical reactors containing liquid metal and gas bubbles. This model is general and can be extended further to consider any gas liquid reactions in any chemical engineering reactor, and especially the metallurgical ones, like AOD. In the present dissertation, the model is applied in predicting the evolution of Cr and C contents in a Fe-C-Cr melt during injection of different O2-CO2 mixtures. The related simulation results illustrated that CO2 is efficient in Cr retention.

In order to verify the modeling results, 1kg induction furnace experiments were carried out in the present laboratory. The results indicated that the predictions of the model are in good agreement with the experimental results. Meanwhile, the experimental results indicated that the Cr-losses can be significantly lowered by replacing the oxygen with CO2 in the injected gas, specifically for Fe-Cr-C melts with carbon levels higher than about 0.8 mass%. Subsequently, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts was investigated under different CO2-O2 mixtures. It is indicated that, the oxidation rate is controlled by the chemical reaction at the initial stage and the reaction rate can be expressed as  at the Cr range of 11-21 mass% in the Fe-Cr melt.

For oxidation study on Fe-V liquid alloy, the investigation of the oxidation kinetics was carried out under CO2-O2 mixtures, which is followed by the study on thermodynamic properties of vanadium containing slags. During oxidation of Fe-V melt, in the case of alloys with vanadium contents exceeding 10 mass%, there exists an incubation period before the chemical reactions prevail the process. In addition, the ‘incubation time’ increased with the increase of temperature and the vanadium content, whereas it decreased with the increase of oxygen partial pressure in the oxidant gas.

High-temperature mass spectrometric method was used to determine the activity of the vanadium oxide in CaO-MgO-Al2O3-SiO2-V2O3 slags, whereas, the oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOxslag system was studied by XANES method. The results indicated that, higher basicities stabilize higher vanadium oxidation state, whereas, higher temperature stabilizes lower vanadium oxidation state.

The present work, which was carried out within the ECO-STEELMAKING project funded by MISTRA via Jernkontoret is expected to lead to implementation of some modifications in high alloy steel production based on fundamental concepts towards more environment-friendly steel processing.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. viii, 58 p.
Theses in Risk and Safety from the Division of Philosophy at the Royal Institute of Technology, ISSN 1654-627X
Oxidation, High-alloy steelmaking, Retention, CO2-O2, Fe-Cr melt, Fe-Cr-C melt, Fe-V melt, Vanadium containing slags, Kinetics, Thermodynamics properties.
National Category
Metallurgy and Metallic Materials Materials Engineering
urn:nbn:se:kth:diva-12955 (URN)978-91-7415-638-6 (ISBN)
Public defence
2010-05-31, Salongen, KTHB, Osquars Backe 31, Stockholm, 10:00 (English)


Available from: 2010-05-21 Created: 2010-05-20 Last updated: 2014-06-16Bibliographically approved

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