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Modeling of Reactions between Gas Bubble and Molten Metal Bath-Experimental Validation in the Case of Decarburization of Fe-Cr-C melts
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2009 (English)In: High Temperature Materials and Processes, ISSN 0334-6455, Vol. 28, no 6, 407-419 p.Article in journal (Refereed) Published
Abstract [en]

A theoretical generic model describing the mass transfer phenomena between rising gas bubbles and a metal bath has earlier been developed by the present authors, to predict the composition change in the melt as consequence of blowing different oxidant gases. In order to verify the model predictions, a series of experiments involving reactions between Fe-Cr-C melts and different O(2)-CO(2) gas mixtures were carried out. The results showed that the decarburization deviates significantly from thermodynamic paths predicted on the basis of bulk compositions and that the model was able to make reasonably reliable predictions of the changes of chromium and carbon contents in the melt as a function of time. According to the model, the compositions at the vicinity of injection point as well as at the gas-melt interface in the bubble are likely to be far from that in the bulk. The results of the present set of experiments showed, with CO(2) injection, the utilization of the available oxygen for decarburization was higher as compared to O(2) injection in the case of melts containing higher carbon levels (>1mass%). Reverse is the case in low carbon melts. The results also indicate relatively less Cr-losses from the metal bath when CO(2) is used as the oxidant. As the model predictions are found to be reasonably reliable, the model predictions are extended to predict the impact of the variation of different process parameters.

Place, publisher, year, edition, pages
2009. Vol. 28, no 6, 407-419 p.
Keyword [en]
Gas-liquid reactions, Bubbles, Simulation, Mass transfer, Decarburization, Partial pressure of oxygen, Fe-Cr-C melt
National Category
Natural Sciences
URN: urn:nbn:se:kth:diva-46956DOI: 10.1515/HTMP.2009.28.6.407ISI: 000279749700008OAI: diva2:454443
QC 20111107Available from: 2011-11-07 Created: 2011-11-07 Last updated: 2014-06-16Bibliographically 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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