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Studies on High Alumina Blast Furnace Slags
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In the present work, viscosities and sulphide capacities of high alumina blast furnace slags were investigated. The systems investigated were four component CaO-SiO2-MgO-Al2O3 quaternary system, CaO-SiO2-MgO-Al2O3-TiO2 and CaO-SiO2-MgO-Al2O3-CaF2 quinary systems.

Viscosities of high alumina blast furnace slags were experimentally determined by the rotating cylinder method using Brookfield digital viscometer model LVDV-II+ pro. Experiments were conducted in the temperature range of 1573- 1873 K. The effects of temperature, basicity, TiO2, CaF2 and silica activity of slags on viscosity were studied. Viscosity decreases with basicity for high alumina blast furnace slags with increase in basicity and CaF2. At higher basicity (~0.8), slag viscosity decreases even with small amount of TiO2 (~2%) addition in the slag. With increase in silica activity in the range of 0.1 to 0.4,viscosity of slag increases and the increase is steeper below liquidus temperature.

Sulphide capacity of the slag was measured using gas-slag equlibria. The liquid slag was equilibrated with Ar-CO-CO2-SO2 gas mixture. The slag systems studied were the same as in the case of viscosity measurements. Experiments were conducted in the temperature range of 1773 to 1873 K. Effect of temperature, basicity, MgO,TiO2 and CaF2 contents of slags on sulphide capacity were studied. As expected, sulphide capacity was found to increase with increase in temperature and basicity. At higher experimental temperature (~ 1873 K) TiO2 was found to decrease the sulphide capacity of slags. But, at lower temperature, there was no significant effect of TiO2 on the sulphide capacity. Sulphide capacity increases with increase in MgO content of slag if MgO content is more than 5%.

Based on above experimental data, models were developed for estimation of viscosity and sulphide capacity of blast furnace slags. These models were later on applied for designing the slags for achieving the optimum slag characteristics so that slag volume can be reduced. With the help of these models slag volume was reduced to the extent of 5-10 kg per ton hot metal and also silicon content of the hot metal was reduced by around 10% with some improvement in slag viscosity and sulphide capacity of the slag.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , 43 p.
Series
KTH/MSE, 2007:38
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-4431ISBN: 978-91-7178-710-1 (print)OAI: oai:DiVA.org:kth-4431DiVA: diva2:12293
Public defence
2007-06-15, Sal B1, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100818Available from: 2007-06-08 Created: 2007-06-08 Last updated: 2010-08-18Bibliographically approved
List of papers
1. Experimental investigation of the viscosities in CaO-SiO2-MgO-Al2O3 and CaO-SiO2-MgO-Al2O3-TiO2 slags
Open this publication in new window or tab >>Experimental investigation of the viscosities in CaO-SiO2-MgO-Al2O3 and CaO-SiO2-MgO-Al2O3-TiO2 slags
2007 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 6, 911-915 p.Article in journal (Refereed) Published
Abstract [en]

The viscosities of high alumina blast furnace slags were experimentally determined by the rotating cylinder method using the Brookfield digital viscometer model LVDV-II + pro. Two different slag systems were considered for the current study, the CaO-SiO2-MgO-Al2O3 quaternary and the CaO-SiO2-MgO-Al2O3-TiO2 quinary system. Experiments were conducted in the temperature range of 1650 to 1873 K. The effects of temperature, basicity, TiO2, and silica activity of slags on viscosity were studied. The viscosity decreases with basicity for high alumina blast furnace slags with basicity in the range of 0.46 to 0.8. At high basicity (similar to 0.8), slag viscosity decreases even with a small amount of TiO2 (similar to 2 pct) addition in the slag. With an increase in silica activity in the range of 0.1 to 0.4, the slag viscosity increases, the increases being steeper below the liquidus temperature.

Keyword
Alkalinity; Alumina; Blast furnaces; Silica; Viscometers; Viscosity measurement; Digital viscometer models; Liquidus temperature; Quinary systems; Slags
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-17182 (URN)10.1007/s11663-007-9087-5 (DOI)000251925700008 ()2-s2.0-37249038999 (Scopus ID)
Note
QC 20100818Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-08-18Bibliographically approved
2. Estimation of viscosties of high alumina blast furnace slags
Open this publication in new window or tab >>Estimation of viscosties of high alumina blast furnace slags
(English)In: Ironmaking & steelmaking, ISSN 0301-9233Article in journal (Refereed) Accepted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7317 (URN)
Note
QC 20100818Available from: 2007-06-08 Created: 2007-06-08 Last updated: 2010-08-18Bibliographically approved
3. Sulphur partition between hot metal and high alumina blast furnace slag
Open this publication in new window or tab >>Sulphur partition between hot metal and high alumina blast furnace slag
2006 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, Vol. 33, no 5, 413-418 p.Article in journal (Refereed) Published
Abstract [en]

The sulphur partition ratio between hot metal and high alumina blast furnace slag (> 18% alumina) has been examined on cast by cast basis for G blast furnace of Tata Steel. Equilibrium sulphur partition ratio was calculated from sulphide capacity with the help of oxygen activity in the melt. Oxygen activity was calculated from SiO2/Si, MnO/Mn and CO/C equilibria. The equilibrium sulphur distribution calculated by considering the reaction [C] + [O]=(CO)(g) in equilibrium for estimation of oxygen activity was very close to measured sulphur distribution ratio on cast by cast basis. Use of MnO/Mn pairs gives very high oxygen activity compared with SiO2/Si and CO/C pairs.

Keyword
Optical basicity; Oxygen activity; Sulphide capacity; Sulphur partition ratio; Alkalinity; Alumina; Blast furnaces; Metals; Oxygen; Silica; Sulfur; Sulfur compounds; slags
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7318 (URN)10.1179/174328106X113968 (DOI)000241457300010 ()
Note
QC 20100818Available from: 2007-06-08 Created: 2007-06-08 Last updated: 2010-08-18Bibliographically approved
4. Sulfide capacity of high alumina blast furnace slags
Open this publication in new window or tab >>Sulfide capacity of high alumina blast furnace slags
2006 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, 941-947 p.Article in journal (Refereed) Published
Abstract [en]

Sulfide capacities of high alumina blast furnace slags were experimentally determined using the gas-slag equilibration technique. Two different slag systems were considered for the current study, namely, CaO-SiO2-MgO-Al2O3 quaternary and CaO-SiO2-MgO-Al2O3-TiO2 quinary system. The liquid slag was equilibrated with the Ar-CO-CO2-SO2 gas mixture. Experiments were conducted in the temperature range of 1773 to 1873 K. The effects of temperature, basicity, and the MgO and TiO2 contents of slags on sulfide capacity were studied. As expected, sulfide capacity was found to increase with the increase in temperature and basicity. At the higher experimental temperature, titania decreases the sulfide capacity of slag. However, at the lower temperature, there was no significant effect of titania on the sulfide capacity of slag. Sulfide capacity increases with the increase in MgO content of slag if the MgO content is more than 5 pct.

Keyword
Alkalinity; Alumina; Blast furnaces; Sulfide minerals; Thermal effects; Titanium dioxide; Gas-slag equilibration technique; Liquid slags; MgO; TiO2; Slags
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7319 (URN)10.1007/BF02735016 (DOI)000242967000012 ()2-s2.0-33846250338 (Scopus ID)
Note
QC 20100818Available from: 2007-06-08 Created: 2007-06-08 Last updated: 2010-08-18Bibliographically approved

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