Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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
A physical modelling study to determine the influence of slag on the fluid flow in the AOD converter process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-2916-3666
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0002-1203-0181
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-1919-9964
Show others and affiliations
2018 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 45, no 10, p. 944-950Article in journal (Refereed) Published
Abstract [en]

A 1:4.6 scale physical model of a production argon oxygen decarburisation (AOD) converter was used to study the influence of top slag on the AOD process. Specifically, the gas penetration depth, fluid flow and slag behaviour under different nozzle diameters, nozzle numbers and gas flow rates were studied. The results show that the relative gas penetration depth generally increases linearly with an increased gas flow rate and a decreased nozzle size. Furthermore, the slag thickness increases linearly with an increased gas flow rate. In addition, the open-eye size was found to increase exponentially with an increased gas flow rate. Overall, three kinds of fluid flow patterns were found in the experiments: (i) a counter-clockwise rotation, (ii) a clockwise rotation and (iii) a double circulation with the plume in the middle of the converter. A counter-clockwise rotation was most common for the current experimental conditions.

Place, publisher, year, edition, pages
Taylor & Francis, 2018. Vol. 45, no 10, p. 944-950
Keywords [en]
Physical modelling, AOD, slag, side-gas injection, penetration depth
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-240764DOI: 10.1080/03019233.2017.1415012ISI: 000453823900014Scopus ID: 2-s2.0-85039167810OAI: oai:DiVA.org:kth-240764DiVA, id: diva2:1275591
Note

QC 20190107

Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2020-05-14Bibliographically approved
In thesis
1.
The record could not be found. The reason may be that the record is no longer available or you may have typed in a wrong id in the address field.
2. A Study of Parameters that Influence the Kinetics of the AOD Decarburisation Process
Open this publication in new window or tab >>A Study of Parameters that Influence the Kinetics of the AOD Decarburisation Process
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the AOD process, which is an important metallurgical reactor in stainless steel production. To be more specific, the thesis is limited to study the decarburisation step, which is the first of three process steps in the AOD converter. The main research questions is to increase the knowledge of reasons for random differences in decarburisation rates during the process. In the first part of the study, physical modeling is used to study the mixing in AOD converters. Parameters that were studied included, bath heights, gas flow rates and chemical reactions. The results showed that the mixing time decreased with an increased gas flow rate or an increased bath height. In addition, the influence of the top slag on the fluid flow and mixing time was studied. The results showed that the flow field was influenced by the slag phase and that it is of importance to account for the solid slag fractions to simulate the fluid flow and mixing time to resemble AOD converters. However, the results from this first part of the thesis illustrates that mixing is not the rate-limiting step for decarburisation in AOD converters. Instead, the focus was shifted to study if the slag was the cause for random differences in the decarburistaion rate. Slag samples were collected from an industrial AOD reactor. These slags are quite unique since they contain mainly solids and a small liquid fraction. Thus, petrography was used to study the samples and a new methodology was developed to characterize the slag samples. Methods for characterising the top slag samples from the AOD process were established, including combinations of different techniques. The common slag phases in decarburisation slag were identified. The results showed good agreement with samples analysed with SEM and EDS compared to calulations made in Thermo-Calc. Overall, it was shown that the slag characteristics changes during the decarburization period and that these changes can be determined using the new methodology. In the last part of the thesis, the commercial AOD process control model TimeAOD2 was used in combination with Thermo-Calc calculations to study how the process could be improved so that the slag composition became most beneficial for improving the kinetics of the decarburisation part of the AOD converter process. The results show that it is possible to predict the slag composition and especially the amount of liquid slag in the sample. This in turn, makes it possible to better estimate the optimal lime addition depending on the silicon content in steel and the amount of carry-over slag from the electric arc furnace.  Furthermore, it is shown that to large lime additions will lead to an increased heating time while not improving the decarburization rate.

Abstract [sv]

Denna avhandling fokuserar på AOD processen, vilken är en viktig metallurgisk reactor vid tillverkning av rostfritt stål. Mer specifikt, så är avhandlingen fokuserad på avkolningsteget, vilket är det första av tre processteg i AOD konvertern. Den huvudsakliga forskningsfrågan är att öka kunskapen gällande de slumpmässiga variationerna i avkolningshastighet i processen. I första delen av studien så används fysikalisk modellering för att studera omblandning i AOD konvertrar. Parametrar som studerades innefattade badhöjd, gasflöde och kemiska reaktioner. Resultaten visade att omblandingstiden minskade med ett ökat gasflöde och en ökad badhöjd. Dessutom så studerades inverkan av toppslaggen på stålets rörelse. Resultaten visade att stålflödet påverkades av slaggen och att det är av betydelse att även ta hänsyn till den fasta slaggfraktionen för att simulera stålflödet i AOD konvertrar. Däremot så visade resultaten från denna första del av avhandlingen att omblandningen inte är det hastighetsbestämmande steget vid avkolning i AOD konvertrar. Därför så skiftades fokus till att studera om slaggen var orsaken till slumpmässiga variationer i kolfärskningshastighet. Slaggprover togs från en industriell AOD konverter. Dessa slagger är unika eftersom de innehåller i huvudsak fasta partiklar och en liten flytande fraktion. Petrografi användes för att studera proverna och en ny metodologi utvecklades för att karakterisera slaggproverna. Detta innefattade användning av metoder för att karakterisera slaggproverna från AOD processen, inkluderande en kombination av olika tekniker. De mest vanliga slaggfaserna i slagger från avkolningssteget identifierades. Resultaten visade en god överensstämmelse mellan prover studerade med SEM och EDS jämfört med beräkningar gjorda med användande av Thermo-Calc. Sammanfattningsvis så visade resultaten att slaggkarakteristiken förändrades under avkolningsperioden och att dessa förändringar kunde bestämmas med den nyutvecklade metodologin. I den sista delen av avhandlingen så användes den kommerciella processkontrollmodellen TimeAOD2 i kombination med Thermo-Calc beräkningar för att studera hur processen skulle kunna förbättras så att slaggsammansättningen kunde vara mer fördelaktig för att förbättra kinetiken under avkolningssteget i AOD processen. Resultaten visade att det är möjligt att beräkna slaggsammansättningen och mer specifikt mängden flytande slagg som finns. Detta i sin tur gör det möjligt att bättre uppskatta den optimala kalktillsatsen vid olika kiselhalter i stål och vid olika mängder restslagg från ljusbågsugnen. Slutligen visade resultaten att an för stor kalktillsats kan leda till en ökad värmningstid utan att förbättra avkolningshastigheten.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. p. 58
Series
TRITA-ITM-AVL ; 2020:26
Keywords
AOD, decarburization, steel, slags, composition, petrography, physical modeling, industrial plant trials, AOD, avkolning, stål, slagg, sammansättning, petrografi, fysikalisk modellering, industriella försök
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering; Metallurgical process science
Identifiers
urn:nbn:se:kth:diva-273348 (URN)978-91-7873-511-2 (ISBN)
Public defence
2020-06-05, https://kth-se.zoom.us/webinar/register/WN_TpALHOTpSde-B8jj2BMo6w, http://Vid fysisk närvaro eller Du som saknar dator/ datorvana kan kontakta service@itm.kth.se (English), Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2020-05-14 Created: 2020-05-14 Last updated: 2020-06-04Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Ternstedt, PatrikNi, PeiyuanTilliander, AndersJönsson, Pär G.

Search in DiVA

By author/editor
Ternstedt, PatrikNi, PeiyuanLundqvist, NicholasTilliander, AndersJönsson, Pär G.
By organisation
Materials Science and Engineering
In the same journal
Ironmaking & steelmaking
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 10 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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