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Experimental Study of Phase Equilibria in CaO-SiO2-MgO-Al2O3-V2O3 Slags
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2014 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 12, 1588-1596 p.Article in journal (Refereed) Published
Abstract [en]

Thermodynamic data with regard to slags containing vanadium oxide are scarce and scattered. In the present study, the classic gas-slag equilibrium technique has been adopted to investigate the phase relationships in the CaO-SiO2-MgO-Al2O3-V2O3 slags. The phase equilibria in the slag systems in the temperature range of 1773-1823K (1500-1550 degrees C) at oxygen partial pressures of 10(-5) Pa and 0.21 x 10(5) Pa were characterized. CaVO3 was precipitated in samples with basicity 1.5 and 1.8 treated in air at 1773 K (1550 degrees C) while all vanadium was dissolved in equilibrium phases in samples treated at oxygen partial pressure of 10(-5) Pa. Vanadium distribution between the slags and solid Pt and phase compositions were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffractomer (XRD) techniques. The effects of temperature, oxygen partial pressure, and slag basicity on the phase compositions in the slags are presented. Activities of VO1.5 were also calculated using the value of vanadium activity in the Pt-V alloy.

Place, publisher, year, edition, pages
2014. Vol. 85, no 12, 1588-1596 p.
Keyword [en]
vanadium oxide, phase equilibrium, activity, thermodynamics, steelmaking slags
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-158282DOI: 10.1002/srin.201400017ISI: 000345832000002Scopus ID: 2-s2.0-84913616789OAI: oai:DiVA.org:kth-158282DiVA: diva2:778092
Note

QC 20150109

Available from: 2015-01-09 Created: 2015-01-07 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Investigation of vanadium-containing oxide systems: CALPHAD and experiments
Open this publication in new window or tab >>Investigation of vanadium-containing oxide systems: CALPHAD and experiments
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fundamental studies on thermodynamic properties of vanadium-containing oxides systems are essential to understand practical vanadium metallurgical process. The CALPHAD technique is here applied to the thermodynamic modelling of the V-O, Ca-V-O and Ti-V-O systems. The compound energy formalism is used for all the solution phases. All optimization processes and calculations are performed using the Thermo-Calc software package. The present work attempts to develop a self-consistent thermodynamic database of all phases in the studied systems. The obtained datasets can be used to calculate thermodynamic properties, stable as well as metastable phase equilibria and driving forces for oxidation etc.

Steelmaking slag is an important secondary source for vanadium extraction. The phase relationships and vanadium distribution in the CaO-SiO2-MgO-V2O3-Al2O3 synthetic slags, whose compositions were chosen based on the relevance to the steel producers, are also studied. Phase equilibria in the temperature range of 1773 to 1823 K at oxygen partial pressure of 10-10 bar and 0.21 bar were characterized.

An investigation of the volatilization of vanadium oxide was also carried out in the present work. Isothermal evaporation of vanadium pentoxide in the temperature range between 1723 and 1873 K was investigated by Thermogravimetric Analysis under different oxygen partial pressures, viz. oxygen, air or CO2. The Arrhenius activation energy for the evaporation reaction in various atmospheres was calculated from the experimental results. A mathematical model was developed to describe the kinetics of the evaporation process. Evaporation coefficients and enthalpies in various atmospheres were also estimated. The present results may have some implications in recovering vanadium from different vanadium-bearing sources.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 47 p.
Keyword
Calphad; thermodynamic modelling; compound energy formalism; evaporation kinetics, activation energy, TGA, activity
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-197292 (URN)978-91-7729-169-5 (ISBN)
Public defence
2016-11-25, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161202

Available from: 2016-12-02 Created: 2016-12-01 Last updated: 2016-12-02Bibliographically approved

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