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A Thermodynamic Approach to a Density Model for Oxide Melts
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)In: Steel research, ISSN 0177-4832, Vol. 78, no 4, 290-298 p.Article in journal (Refereed) Published
Abstract [en]

In an attempt to estimate the densities of complex slags, a model based on the thermodynamics ofslags developed earlier by the present authors is extended to ternary and multi-component systemsin the present work. The molar volumes of ternary and higher order systems were derived from therelative integral molar enthalpies of mixing of the corresponding slags. The higher order of slagsystems has been predicted by using the parameters from the related binary sub-systems, whichhave been evaluated earlier. Comparisons of calculated results with experimental data on molarvolumes available in literature show a satisfying agreement for a number of systems, within the limitsof experimental uncertainties. The model presents a promising method to compute the molar volumeof slag systems where no experimental data is available using the abundance of thermodynamicdata available. The model would also enable the generation of density data for slags containingAl2O3, CaO, FeO, MgO, MnO, and SiO2 compatible with the corresponding thermodynamic data.

Place, publisher, year, edition, pages
2007. Vol. 78, no 4, 290-298 p.
Keyword [en]
Density, Enthalpies, Model, Molar volume, Oxide melts, Slags, Thermodynamics
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-7110DOI: 10.2374/SRI06SP108-78-2007-290ISI: 000246510800003Scopus ID: 2-s2.0-34248138538OAI: oai:DiVA.org:kth-7110DiVA: diva2:12024
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Investigations of Slag Properties and Reactions
Open this publication in new window or tab >>Investigations of Slag Properties and Reactions
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The present dissertation describes the efforts directed towards the development of computational tools to support process modeling. This work is also a further development of the Thermoslag® software developed in the Division of Materials Process Science, KTH.

The essential parts of the thesis are

a) development of a semi-empirical model for the estimation of the molar volumes/densities of multicomponent slags with a view to incorporate the same in the model for viscosities and

b) further development of the viscosity model for application towards fluoride- and manganese containing slags, as for example, mould flux slags and manganese slags used in ferromanganese production.

c) estimating fluoride emissions from industrial slags and mould fluxes.

d) study the reaction between carbon particles, hematite containing slags and in oxygen containing atmosphere.

The model for the estimation of molar volume is based on a correlation between the relative integral molar volume of a slag system and the relative integral molar enthalpies of mixing of the same system. The integral molar enthalpies of the relevant systems could be evaluated from the Gibbs energy data available in the Thermoslag® software. The binary parameters were evaluated from experimental measurements of the molar volumes. Satisfactory correlations were obtained in the case of the binary silicate and aluminate systems. The model was extended to ternary and multi component systems by computing the molar volumes using the binary parameters. The model predictions showed agreements with the molar volume data available in literature. The model was used to estimate the molar volumes of industrial slags as well as to trace the trends in molar volume due to enable prediction of molar volumes of slags that are compatible with the thermodynamic data available.

With a view to extend the existing model for viscosities to F--containing slags, the viscosities of mould flux slags for continuous casting in steel production have been investigated in the present work. The measurements were carried out utilizing the rotating cylinder method. Seven mould fluxes used in the Swedish steel industry and the impact of Al2O3 pick up by mould flux slags on viscosities were included in the study. The results showed that even relatively small additions of Al2O3 are related with a significant increase in viscosity.

A similar experimental technique was employed to estimate the viscosity of twelve synthetic slags corresponding to composition of the raw materials used in ferromanganese production. The flow rate of the liquid slag, which is determined by the slag viscosity, is an important parameter affecting the reduction rate of manganese oxide. The results show a clear correlation between manganese oxide content and viscosity. An increase of MnO in the slag lowers the viscosity. The measured viscosities have also been connected to the structure of the silicates.

The fluoride loss from the binary slag systems Al2O3-SiO2, CaO-SiO2 and MgOSiO2 with additions of CaF2 was studied by thermogravimetric (TGA) studies. The Arrhenius activation energy for the evaporation reaction of fluorides was found to be dependent on temperature and slag chemistry for the slags studied. A correlation between the activation energy for fluoride evaporation and activity of SiO2 in the slag melt was established. This relationship obtained for the binary systems appears also to be suitable for the ternary systems Al2O3-CaO-SiO2 with CaF2 addition, which indicates a possibility to estimate the fluoride emissions from industrial slags and mould fluxes.

A Confocal Scanning Laser Microscopy was used to investigate the reaction between carbon particles in hematite containing slags and in oxygen containing atmosphere. Experiments with varying temperature and slags with varying FeOx content were carried out. The general trends were that the particle size decrease was more rapid with increase of FeOx amount and/or temperature was increased.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 80 p.
Series
KTH/MSE, 2007:14
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4378 (URN)978-91-7178-650-0 (ISBN)
Public defence
2007-05-25, Salongen, KTHB, Osquars backe 31, STOCKHOLM, 10:00
Opponent
Supervisors
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2010-08-12Bibliographically approved
2. Densities and viscosities of slags: modeling and experimental investigations
Open this publication in new window or tab >>Densities and viscosities of slags: modeling and experimental investigations
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The present dissertation describes part of the efforts directed towards the development of computational tools to support process modeling. This work is also a further development of the Thermoslag software developed in the Division of Materials Process Science, KTH.

The essential parts of the thesis are

a) development of a semi-empirical model for the estimation of the molar volumes/densities of multicomponent slags with a view to incorporate the same in the model for viscosities and

b) further development of the viscosity model for application towards fluorid- containing slags, as for example, mould flux slags.

The model for the estimation of molar volume is based on a correlation between the relative integral molar volume of a slag system and the relative integral molar enthalpies of mixing of the same system. The integral molar enthalpies of the relevant systems could be evaluated from the Gibbs energy data available in the Thermoslag software. The binary parameters were evaluated from experimental measurements of the molar volumes. Satisfactory correlations were obtained in the case of the binary silicate and aluminate systems. The model was extended to ternary and multi component systems by computing the molar volumes using the binary parameters. The model predictions showed agreements with the molar volume data available in literature. The model was used to estimate the molar volumes of industrial slags as well as to trace the trends in molar volume due to compositional variations. The advantage of the present approach is that it would enable prediction of molar volumes of slags that are compatible with the thermodynamic data available.

With a view to extend the existing model for viscosities to F--containing slags, the viscosities of mould flux slags for continues casting in steel production have been investigated in the present work. The measurements were carried out utilizing the rotating cylinder method. Seven mould fluxes used in the Swedish steel industry and the impact of Al2O3 pick up by mould flux slags on viscosities were included in the study. The results showed that even relatively small additions of Al2O3 are related with a significant increase in viscosity

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 58 p.
Series
ISRN KTH/MSE--06/23--SE+THMETU/AVH
Keyword
density, nolar volume, thermodynamics, enthalpies, model, slags, oxide melts, viscosity, mould flux, continuous casting
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-3926 (URN)91-7178-336-9 (ISBN)
Presentation
2006-04-28, Sal B3, KTH, Brinellvägen 23, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20101123Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2010-11-23Bibliographically approved

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