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Mathematical modeling of selected ladle operations
KTH, Superseded Departments, Metallurgy.
1998 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The traditional approach to modeling ladle processes involvea critical survey of the thermodynamic aspects of the processincluding mass and heat balantes at the macroscopic level. Onthe other hand, the macrokinetics, specific to the reactor haveoften been studied separately, using computational fluiddynamits. Over the years, it has been realized that traditionalmethods have obvious limitations in providing an understandingof heterogeneous processes. In a long range perspective, acomplete description of ladle metallurgy and a fundamentalunderstarrding of the underlying process phenomena require aconsideration of all the individual reactions involved andtheir interrelations. This, in tum, clearly requiressimultaneous solution of thermodynamics, heat and fluid flow.The salient features of the present study are the considerationof fundamental transport equations and establishedthermodynamic relationships so that mathematital models takinginto account both thermodynamics and fluid flow could beachieved.

A technique to' incorporate the slag phase in two-phasefluid-flow models for ladle treatment is introduced in thisthesis. This development enabled, for the first time,predictions of fluid flow conditions in the important steelklagregion. Good agreement is shown between predictions andphysical modeling reported in literature, regarding thecriteria for initiation of entrapment of a lighter phase into aheavier phase.

Furthermore, a method to combine fluid dynamits andthermodynamics to model slag/metal reactions is introduced andis demonstrated in the case of sulphur refining during gasstirring. By considering the volume of mixing between slag andmetal and the thermodynamic equilibrium in the two-phase zone,the calculations of interfacial area and the mass-transfercoeffcients for different elements are avoided. In this way,the combined effect of fluid-flow and thermodynamic conditionscould be predicted from fundamental transport equations.Comparison between predicted data and plant data demonstratesthat the method could be used to predict the desulphurizationwith an acceptable accuracy.

A new method to model ladle processes involving gas-liquidreactions is also introduced in this thesis. In the cases wherethe interfacial reaction and mass transfer in the gas-phase arerapid, the overall mass transfer resistance could be expressedby the mass-transfer in the melt. The hydrogen refinementprocess during vacuum degassing in an ASEA-SKE ladle furnacehas been taken as an example. The predictions have beencompared with data from production scale experiments carriedout at Ovako Steel. Good agreement between the calculatedhydrogen toncentrations and the hydrogen tontent in the sampletaken after vacuum degassing substantiates the feasibility ofthis technique.

Key words:Slag-Metal Reactions, Metal-Gas Reactions,Ladle Metallurgy, Sulphur Refining, Hydrogen Refining, VacuumDegassing, Combined Kinetics and Thermodynamics, 3-Phase Model,Gas Stirring, Modeling, CAS-OB, CFD

Place, publisher, year, edition, pages
Stockholm: KTH , 1998. , 49 p.
Series
Trita-MEL, 192
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-2634ISBN: 91-7170-240-7 (print)OAI: oai:DiVA.org:kth-2634DiVA: diva2:8300
Public defence
1998-05-19, 00:00
Note
QC 20100623Available from: 2000-01-01 Created: 2000-01-01 Last updated: 2010-06-23Bibliographically approved
List of papers
1. A model of gas-stirred ladle
Open this publication in new window or tab >>A model of gas-stirred ladle
1995 (English)In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 24, no 5-6, 194-206 p.Article in journal (Refereed) Published
Abstract [en]

Background/aims: A research program with the objective of studying the separation of non-metallic inclusions is currently being undertaken by the Swedish Steel Producers' Association. The aim is to develop a pc-based model that can easily be used by the participating steel companies. important inputs to the model are, among other parameters, data for steel velocities and dissipation of turbulent kinetic energy. Results and conclusion: A 2-dimensional two-phase mathematical model for a gas-stirred ladle has been developed. This model differs from existing models in that the nozzle and plume areas have been modeled more realistically. The predicted data of gas fraction and velocity in a water model agree well with experimental data found in the literature. The calculated surface velocities in an argon gas-stirred ladle are of the same order of magnitude as experimental data. However, the experimental surface velocity measurements are not sufficiently accurate to permit a closer comparison. Predicted bubble rising velocities for an argon-stirred steel ladle agree well with existing experimental data.

Keyword
gas-stirring, ladle metallurgy, modelling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13647 (URN)A1995UH30900002 ()
Note

QC 20100622

NR 20140804Available from: 2010-06-22 Created: 2010-06-22 Last updated: 2017-12-12Bibliographically approved
2. A model of oxygen flow from slag to steel in the ladle
Open this publication in new window or tab >>A model of oxygen flow from slag to steel in the ladle
1996 (English)In: Proceedings of the International conference MSMM, 1996, 309-313 p.Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13648 (URN)
Conference
International conference MSMM
Note

QC 20100622

NR 20140804Available from: 2010-06-22 Created: 2010-06-22 Last updated: 2013-02-24Bibliographically approved
3. Modeling of the fluid flow conditions around the slag/metal interface in a gas-stirred ladle
Open this publication in new window or tab >>Modeling of the fluid flow conditions around the slag/metal interface in a gas-stirred ladle
1996 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 36, no 9, 1127-1134 p.Article in journal (Refereed) Published
Abstract [en]

A three-phase model of a gas-stirred steel bath covered with a slag layer has been developed. Predicted steel surface velocities have been shown to be in at least five times greater agreement with experimental data compared to predicted velocities from a model which excludes the effect of a slag phase. It has also been shown that it is possible to predict the amount of slag dispersed into the steel.

Keyword
3-phase model, gas stirring, ladle metallurgy, slag/metal interface, MASS-TRANSFER, METALLURGY
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13649 (URN)A1996VG97800003 ()
Note
QC 20100622Available from: 2010-06-22 Created: 2010-06-22 Last updated: 2017-12-12Bibliographically approved
4. Viscosities of ld slags and their impact on ladle refining
Open this publication in new window or tab >>Viscosities of ld slags and their impact on ladle refining
1997 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, no 5, 484-491 p.Article in journal (Other academic) Published
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13651 (URN)
Note

QC 20100622

NR 20140804Available from: 2010-06-22 Created: 2010-06-22 Last updated: 2017-12-12Bibliographically approved
5. Three-phase (steel, slag, gas) modeling of the CAS-OB process
Open this publication in new window or tab >>Three-phase (steel, slag, gas) modeling of the CAS-OB process
1997 (English)Conference paper, Published paper (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13676 (URN)
Conference
80th Steelmaking conference
Note
QC 20100623Available from: 2010-06-23 Created: 2010-06-23 Last updated: 2010-06-23Bibliographically approved
6. A new approach to model sulphur refining in a gas-stirred ladle: A couple CFD and thermodynamic model of sulphur refiningin a gas-stirred ladle
Open this publication in new window or tab >>A new approach to model sulphur refining in a gas-stirred ladle: A couple CFD and thermodynamic model of sulphur refiningin a gas-stirred ladle
1998 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 38, no 3, 260-267 p.Article in journal (Refereed) Published
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13677 (URN)
Note

QC 20100623

NR 20140804Available from: 2010-06-23 Created: 2010-06-23 Last updated: 2017-12-12Bibliographically approved
7. Prediction and experimental verification of hydrogen refining parameters during vacuum degrassing in a  ladle furnace: Part 1 - theoretical model
Open this publication in new window or tab >>Prediction and experimental verification of hydrogen refining parameters during vacuum degrassing in a  ladle furnace: Part 1 - theoretical model
1998 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460Article in journal (Other academic) Accepted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13678 (URN)
Note
QC 20100623Available from: 2010-06-23 Created: 2010-06-23 Last updated: 2017-12-12Bibliographically approved
8. Prediction and experimental verification of hydrogen refining parameters during vacuum degrassing in a  ladle furnace: Part 2 - Plant trials and verifications
Open this publication in new window or tab >>Prediction and experimental verification of hydrogen refining parameters during vacuum degrassing in a  ladle furnace: Part 2 - Plant trials and verifications
1998 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460Article in journal (Other academic) Accepted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13679 (URN)
Note
QC 20100623Available from: 2010-06-23 Created: 2010-06-23 Last updated: 2017-12-12Bibliographically approved

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