Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Investigations of Slag Properties and Reactions
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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: urn:nbn:se:kth:diva-4378ISBN: 978-91-7178-650-0 (print)OAI: oai:DiVA.org:kth-4378DiVA: diva2:12029
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
List of papers
1. Estimation of molar volumes of some binary slags from enthalpies of mixings
Open this publication in new window or tab >>Estimation of molar volumes of some binary slags from enthalpies of mixings
2007 (English)In: Steel research, ISSN 0177-4832, Vol. 78, no 2, 102-108 p.Article in journal (Refereed) Published
Abstract [en]

In an effort to interlink the thermo chemical and thermo physical properties of slags, the present workwas undertaken to derive the molar volumes of complex slags from the enthalpies of mixing of thecorresponding slags. As a first step, binary systems of the following oxides were investigated; Al2O3,CaO, FeO, MgO, MnO, and SiO2. An empirical correlation was derived between the enthalpies ofmixing and molar volumes. A comparison of the computed results on the basis of the aboverelationship with the experimental data on molar volumes available in literature shows that theagreement between the calculated results and measured densities is satisfactory in the case of mostof the binary systems, within the limits of experimentally uncertainties. The advantage of the presentapproach is that it would enable prediction of molar volumes of slags that are compatible with thethermodynamic data available.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-5611 (URN)10.2374/SRI06SP102-78-2007-102 (DOI)
Note

QC 20100812. Uppdaterad från Submitted till Published.

Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2017-12-14Bibliographically approved
2. A Thermodynamic Approach to a Density Model for Oxide Melts
Open this publication in new window or tab >>A Thermodynamic Approach to a Density Model for Oxide Melts
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.

Keyword
Density, Enthalpies, Model, Molar volume, Oxide melts, Slags, Thermodynamics
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7110 (URN)10.2374/SRI06SP108-78-2007-290 (DOI)000246510800003 ()2-s2.0-34248138538 (Scopus ID)
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2017-12-14Bibliographically approved
3. Viscosity Measurements of Some Mould Flux Slags
Open this publication in new window or tab >>Viscosity Measurements of Some Mould Flux Slags
2007 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 10, 1533-1540 p.Article in journal (Refereed) Published
Abstract [en]

Continuous casting has been the dominating process for steel casting over the past decades. During the process, mould fluxes are added to enable a smooth functioning of the process, enabling better process performance and products with less defects. The viscosity of the mould flux slag is a key parameter determining the optimum casting conditions.Several experimental studies have earlier been carried out in order to determine viscosity data for mould flux slags, both industrial ones as well as synthetic slags with compositions close to industrial mould fluxes. However, the continuous evolving of new steel grades, casting dimensions and product quality in the steel industry also demands better control and development of the mould fluxes. In industrial practice for clean steel production, the Al2O3 pick up has generally been observed to be about 2–4%. In view of this, the present study was initiated to experimentally investigate the viscosity of mould fluxes used in Swedish steel industry and the effect of dissolution of alumina in the same. The industrial implications of the slag viscosities measured in the present work are discussed.Viscosities of mould fluxes for continuous casting in steel production have been measured by the rotating cylinder method. Seven industrial mould fluxes, with different compositions, used were included in the study. The effect of the Al2O3 content in the mould fluxes was also investigated. Even relatively small additions of Al2O3 show a significant increase in viscosity. The measurements were carried out in the temperature range of 1373 to 1673 K.

Keyword
viscosity; mould flux; continuous casting; slags
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7111 (URN)10.2355/isijinternational.47.1533 (DOI)000250375700022 ()2-s2.0-37249011786 (Scopus ID)
Note
QC 20100812. Tidigare titel: Viscosities of some Mould Flux Slags. Uppdaterad från Submitted till Published 20100812.Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2017-12-14Bibliographically approved
4. Viscosities of some MnO-Containing Slags Associated with Ferromanganese Production
Open this publication in new window or tab >>Viscosities of some MnO-Containing Slags Associated with Ferromanganese Production
(English)Article in journal (Refereed) Submitted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7112 (URN)
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2010-08-12Bibliographically approved
5. Kinetic studies of fluoride evaporation from slags
Open this publication in new window or tab >>Kinetic studies of fluoride evaporation from slags
2007 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 12, 1711-1717 p.Article in journal (Refereed) Published
Abstract [en]

In view of the environmental problems associated with the evaporation of fluoride from slags and fluxes, a systematic study of the fluoride emission from slags at temperatures, relevant to steelmaking and casting, has been initiated in the present work. The loss of fluoride from slag melts was monitored by Thermogravimetric Analysis (TGA). The present paper reports the fluoride evaporation in the three binary systems Al2O3-SiO2, CaC-SiO2 and MgO-SiO2 with additions of CaF2 (ca. 3.5, 5 and 9 wt%). The thermogravimetric experiments were carried out in argon atmosphere in the isothermal mode in the temperature range 1673-1873 K. The gas flow was kept above the starvation rate in order to avoid the gas phase mass transfer step. From the results, the Arrhenius activation energies for the evaporation reaction were evaluated. The activation energies were found to be dependent on temperature and slag chemistry for the various slags studied. In binary systems, the activation energy for fluoride evaporation was found to depend on the square of the activity of SiO2 in the slag melt. This correlation obtained in the case of the binary systems could be validated in the case of the results obtained for the ternary system Al2O3-CaO-SiO2 with 5 and 10 wt% of CaF2, The present results are considered to be useful in estimating the fluoride emissions from industrial slags and mould fluxes.

Keyword
activation energy, fluoride emission, mould flux, fluorides, slags, equilibria, melts, caf2
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-17173 (URN)10.2355/isijinternational.47.1711 (DOI)000251865900002 ()2-s2.0-39149098784 (Scopus ID)
Note
QC 20100812Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Visualization of Carbon Particles in Reactive Gas and Slag Environments
Open this publication in new window or tab >>Visualization of Carbon Particles in Reactive Gas and Slag Environments
(English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153Article in journal (Refereed) Submitted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7114 (URN)
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2017-12-14Bibliographically approved

Open Access in DiVA

fulltext(7287 kB)5252 downloads
File information
File name FULLTEXT01.pdfFile size 7287 kBChecksum MD5
8d3fc41425e18551ef56a2255ca8c6f2b121c94d7943daad491521d9b2dc3ffea2e47464
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Persson, Mikael
By organisation
Materials Science and Engineering
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 5252 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1166 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf