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Some Aspects on Macroscopic Mixing in a Tundish
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.ORCID iD: 0000-0001-7953-1127
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Two aspects on macroscopic mixing in a continuous flow system – metallurgical tundish were studied. Specifically, 1) the first focus was on salt solution tracer mixing, which is important for tundish design from perspectives of tracer technology and Residence Time Distributions (RTD) as well as for the understanding of the macroscopic mixing in tundishes. The different amounts of salt solution tracer mixing in a tundish were studied by using both physical models and mathematical models. The disturbance of KCl salt tracer on the flow in the tundish with respect to different amounts is like the “butterfly effect”, i.e. only a slight increase of the amount of tracer, the flow field might be disturbed. This, in turn, will result in a shifted RTD curve. 2) The second focus was on Eulerian modeling of inclusions macroscopic transport and removal, which is important for tundish design from perspectives of inclusions removal and to provide information of macroscopic removal of inclusions. In the study, an approach that combined the meso-scale inclusions deposition at turbulent boundary layers of steel-slag interface and the macroscopic transport of inclusions in the tundish was used. The theoretical calculation results showed that the effect of the roughness on the deposition velocity of small inclusions (radius of 1 μm) were more pronounced than that for the big inclusions (up to the radius of 9 μm). The dynamic inclusions removal studies showed that the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5 μm, 7 μm and 9 μm) than that of the case without weirs and dams. However, the tundish without weirs and dams showed a higher removal ratio of smaller inclusions (radius of 1 μm).

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2015. , x, 24 p.
Keyword [en]
continuous reactor, tundish, tracer, macroscopic mixing, water model, CFD, turbulence models, inclusions removal, inclusions deposition, dynamic removal
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-168402ISBN: 978-91-7595-632-9 (print)OAI: oai:DiVA.org:kth-168402DiVA: diva2:816312
Public defence
2015-08-28, B2, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150615

Available from: 2015-06-15 Created: 2015-06-02 Last updated: 2015-06-15Bibliographically approved
List of papers
1. Effects of Salt Tracer Amount, Concentration and Kind on the Fluid Flow Behavior in a Hydrodynamic Model of Continuous Casting Tundish
Open this publication in new window or tab >>Effects of Salt Tracer Amount, Concentration and Kind on the Fluid Flow Behavior in a Hydrodynamic Model of Continuous Casting Tundish
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2012 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 12, 1141-1151 p.Article in journal (Refereed) Published
Abstract [en]

The hydrodynamic modeling method that widely used to simulate the fluid flow was reconsidered and discussed in this paper. The effects of injected salt tracer amount, concentration and kind on the fluid flow behavior in a hydrodynamic model tundish were investigated. The results were compared with the mathematical modeling calculation results, that the tracer density effect was eliminated. The residence time distribution (RTD) curve of tracer introduced deviated to the left side of the calculated curve, besides the deviation was increased as dimensionless tracer amount (the ratio of tracer amount to hydrodynamic model tundish volume) increased from 0.202 × 10−3 to 1.008 × 10−3. The results of tracer concentration study were similar, namely the deviation was increased with concentration increased; on the other hand, the deformation of a “stair-shape” RTD curve occurred when tracer concentration was much lower (at dimensionless tracer amount of 0.168 × 10−3 with converting to saturated solution). Besides, the effect of tracer kind on the accuracy of hydrodynamic modeling was also studied; the measurements of KCl solution with lower density than that of NaCl solution exhibited more of accuracy. Finally, the optimized tracer in hydrodynamic model tundish of present work is saturated KCl solution with dimensionless tracer amount of 0.202 × 10−3.

Place, publisher, year, edition, pages
John Wiley & Sons, 2012
Keyword
hydrodynamic model method;tundish;residence time distribution;tracer;continuous casting
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-168396 (URN)10.1002/srin.201200086 (DOI)000312153200004 ()2-s2.0-84870540588 (Scopus ID)
Note

QC 20150615

Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2017-12-04Bibliographically approved
2. A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish
Open this publication in new window or tab >>A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish
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2015 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 1, 169-190 p.Article in journal (Refereed) Published
Abstract [en]

A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD+ WSD, KMD+ KV, and KMD+ WSD+ KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i. e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace. The breakthrough time and peak concentration of RTD curves of model predictions and water modeling results showed a good agreement (all difference within 12.5 pct) for the 100, 150, and 250 mL KCl cases.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2015
Keyword
Continuous casting, Diffusion in liquids, Flow patterns, Fluid dynamics, Forecasting, Mathematical models, Mixing, Molecules, Nozzles, Breakthrough time, Continuous casting tundish, Molecule diffusion, Peak concentrations, Scalar transport equation, Solution viscosity, Tracer concentration, Water self diffusions
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-160382 (URN)10.1007/s11663-014-0190-0 (DOI)000348199900022 ()2-s2.0-84925537308 (Scopus ID)
Note

QC 20150618. Correction in: Metallurgical and materials transactions. B, process metallurgy and materials processing science, vol. 46, issue. 6 page 2721. Doi: 10.1007/s11663-015-0448-1. WOS: 000367067600033

Available from: 2015-02-26 Created: 2015-02-19 Last updated: 2017-12-04Bibliographically approved
3. A Mathematical Modeling Study of the Influence of Small Amounts of KCl Solution Tracers on Mixing in Water and its Residence Time Distribution in a Continuous Flow Reactor-Metallurgical Tundish
Open this publication in new window or tab >>A Mathematical Modeling Study of the Influence of Small Amounts of KCl Solution Tracers on Mixing in Water and its Residence Time Distribution in a Continuous Flow Reactor-Metallurgical Tundish
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2015 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 137, 914-937 p.Article in journal (Other academic) Published
Abstract [en]

In an earlier research (Chen et al., 2015a) a mathematical model was established to simulate tracer mixing (a KCl solution). The predicted Residence Time Distribution (RTD) curves showed good agreements with experimental RID curves for larger amounts of tracer additions. However, for smaller additions (50 mL) of a KCl solution into water, the predicted RID curves tended to deviate from the experimental RTD curves for a tundish (a continuous flow reactor). The current paper focuses on the possibilities that the predictability for smaller additions could be resolved by using a suitable turbulence model. The performance of five different turbulence models representing different modeling techniques and levels of complexity were tested in combination with using a density-coupled mixed composition fluid model to simulate the mixing, i.e. the following models: LVEL, Chen-Kim k-epsilon, MMK k-epsilon, Explicit Algebraic Reynolds Stress Model (EARSM), and Large Eddy Simulation (LES): Wall-Adapting Local Eddy-viscosity (WALE). The results indicate that models that tend to resolve turbulence structures renders better predictions of the mixing process of smaller tracer amounts. In addition, the influence of different tracer amounts on the flow in tundish was assessed. The simulation results for 75 mL, 100 mL, 150 mL, and 250 mL KCl tracer additions were compared. The results showed that in an upward flow the tracer will, sooner or later (dependent on the tracer amount), sink to the bottom. This is due to the higher density of the tracer compared to the density of water. From a physical modeling perspective, this issue is like the "butterfly effect". It is showed that for a slight increase of the amount of tracer, the flow field might be disturbed. This, in turn, will result in a shifted RTD curve.

Place, publisher, year, edition, pages
Pergamon Press, 2015
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-168398 (URN)10.1016/j.ces.2015.07.037 (DOI)000361772400084 ()2-s2.0-84939812058 (Scopus ID)
Note

Updated from "Manuscript" to "Article". QC 20151207

Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2017-12-04Bibliographically approved
4. Application of a Unified Eulerian Model to Study the Inclusions Deposition at a Steel-Slag Interface in a Tundish
Open this publication in new window or tab >>Application of a Unified Eulerian Model to Study the Inclusions Deposition at a Steel-Slag Interface in a Tundish
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(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-168399 (URN)
Note

QS 2015

Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2015-06-15Bibliographically approved
5. A CFD Model Study of the Macroscopic Transport and Dynamic Removal of Inclusions at a Steel-Slag Interface for Different Tundish Designs
Open this publication in new window or tab >>A CFD Model Study of the Macroscopic Transport and Dynamic Removal of Inclusions at a Steel-Slag Interface for Different Tundish Designs
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(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-168400 (URN)
Note

QS 2015

Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2015-06-15Bibliographically approved

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