Modeling of Fluid Flow, Mixing and Inclusion Motion in...

Univ. of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • L. Zhang, 2004, 1

Modeling of Fluid Flow, Mixing and Inclusion Motion in Bottom Gas-

Stirred Molten Steel Vessel— Development of a Process to Continuously Melt, Refine, and Cast

High-Quality Steel

Lifeng Zhang, Brian G. ThomasUniversity of Illinois

May 10, 2004


Acknowledgements

- Continuous Casting Consortium at UIUC- UMR (Prof. Kent Peaslee, Prof. David

Robertson, Mr. Jorg Peter)- Department of Energy (DOE)- Fluent Inc.- National Center for Supercomputing

Applications at UIUC


heated holding ladle (for EAF or tundish),or pig the steel

0

1

2

3

4

5

6

7

8

9

10

11

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16length (meters)

heig

ht o

r wid

th (m

eter

s)

Ar Ar Ar

Ar

Ar

Ar

mold

CO,Ar

0.15%C

2890ºF

measure

measure

measure

measure

heating rods

Ca wire

wire feeding adjustment?

Deo

xidi

zer,

CaO

, MgO

CaO, MgO

alloys

Side view

Top viewlooking at steel surface

Conceptual layout for 110 tph process

27 t20 t20 t30 min 50 t

2910ºF 2880ºF2870ºF

2830ºF

+ 12 min + 12 min + 21 min = 75 min

melt

oxidize

reduce

homogenize & float

?

O2 + Ar

7 t –

23 t

Figure from Jorg Peter, UMR

Vessel II


Geometry of Vessel II Geometry of Vessel II

Inlet

Vessel II

Outlet SEN

Outlet Launder

Gas Injection inlets:Position: 1/4 and 3/4 diameter of the bottomDin=0.2m

Inlet Launder


Geometry of Vessel IIGeometry of Vessel II

Inlet(Din=0.14m, Dout=0.2m,Submergence depth:0.15mSimulated inlet SEN length: 0.5mDistance of inlet center line to left wall: 0.2mVin=0.23m/sKin=0.01m2/s2

in=0.06m2/s3)

Vessel II(Din=1.4m,Depth: 2.0m) Outlet SEN

(Din=0.14m, Dout=0.2m,Length: 1.1m, no slide gateDistance of outlet center

line to right wall: 0.2m)

Outlet Launder:Thickness:0.3m

Inlet Launder:Left depth: 0.3mRight depth:0.6mLength: 1mThickness:0.3m

0.3m

0.4m

0.4m

1.1m

0.7m0.9m

0.3m

ε


Geometry of Vessel IIGeometry of Vessel II

Inner diameter: D=1.4mSteel bath height: Hsteel= 2.0mSlag depth: Hslag=0.2mDiameter of gas porous plug: 0.2m (two plugs)Inlet nozzle inner diameter: Dsteel, in=0.14mInlet nozzle outer diameter: 0.2mInlet submergence depth: 0.15mInlet SEN length: 1.1mModeled inlet length: 0.5mDistance from inlet center line to right side wall: 0.2mMolten Steel temperature: To=1900K Inlet and outlet launders on opposites of vessels and directed radially


Input Flow ConditionsInput Flow Conditions

Steel flow rate: 99.5 tons/hourSteel density: 7020 kg/m3

Mean inlet velocity: 0.232 m/s

Cold argon gas flow rate: 0.49 m3/minHot argon gas flow rate: 1.314 m3/minMean bubble injection velocity: 0.35 m/sMean bubble size: 48mm

Discrete multiphase transient flow input: 19 bubbles/0.1s at each of the two gas inlets at the bottom


Fluid Flow and Particle Motion with Argon

Injection


Fluid Flow with Argon Injection Fluid Flow with Argon Injection

Fluid flow velocity Gas concentration


Fluid Flow with Argon InjectionFluid Flow with Argon Injection

Turbulent Energy Dissipation RateTurbulent Energy


Typical Trajectories of Alumina Inclusions Typical Trajectories of Alumina Inclusions (300(300µµm, 3500 kg/mm, 3500 kg/m33) (With Argon Injection)) (With Argon Injection)


Transient Fluid Flow with Argon Injection Transient Fluid Flow with Argon Injection

500 Bubbles injection per seconds


Fluid Flow and Particle Motion without Argon

Injection


Fluid Flow VelocitiesFluid Flow Velocities


Typical Trajectories of Tracer Particle Typical Trajectories of Tracer Particle (Without Random Motion)(Without Random Motion)


Typical Trajectories of Particles (With Typical Trajectories of Particles (With Random Motion)Random Motion)

Tracer particles Alumina Inclusions


Fluid Flow, Particle Motion, and Mixing in a

Argon-Stirred Ladle(300 ton, 4.5m height, 0.5 m3/min argon injection, bubble

size: 33mm)


Fluid Flow Fluid Flow

(m)

(m)

00.511.52

0

0.5

1

1.5

2

2.5

3

3.5

4

4.50.0 0.3 0.5 0.8 1.0

speed (m/s)

(m)0 0.5 1 1.5 2

1m/s

Velocities

0 0.5 1 1.5 2(m)

(m)

00.511.52

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0.0001 0.0006 0.0040 0.0251 0.1585 1.0000

gas concentraction (kg/m3)

Gas Concentration


Particle Motion and Mixing Time Particle Motion and Mixing Time

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

1

2

3

4

5

6

7

Calculated gas column shape (0.001 isoline of the gas volume fraction)

50µm 100µm 300µm

(m)Inclusion Trajectories

0.1 1 10 100 100010

100

1000

123456

50t ASEA-SKF 50t Ar-stirred 58.9t Ar-stirred 6t Ar-stirred 200RH 65kg Water model

τ=523ε - 0.4

Current 300tonne Ar-stirred ladle

Mix

ing

time,

τ (s

)Stirring power, ε (Watt/ton)Mixing Time

Average Moving path length before reaching top surface:- 100µm inclusion: 47.0m (285s); - 33mm bubble: 5.0m (3.9s)


Dissolution of Aluminum Alloy in Ladle Dissolution of Aluminum Alloy in Ladle

0s 3s


Overall process summary Overall process summary

50s10s


ConclusionsConclusions

1. The developed Lagrangian-Lagrangian multiphase model can predict the fluid flow, inclusion motion and mixing in vessels of this continuous steelmaking process

2. Without gas injection- Generating short circuiting flow pattern (from the

inlet launder quickly and directly to the outlet launder), very detrimental for the process.

- The inlet jet impinges strongly against the shallow bottom of the inlet launder, so possible splashing and erosion of the refractory bricks

- Possible improvement: making the outlet launder not align directly across the vessel from the inlet.


ConclusionsConclusions

3. With gas injection- Generating a strong recirculation in the whole height of the

vessel.- Particles recirculate a long time,good for reactions.

4. Useful researches for this project (now and future):- Solute mixing (such as alloy dissolution) (done by L. Zhang and

J.Aoki for gas stirred ladles)- Reactions such as deoxidation, impurity element and

inclusion removal, depending on mixing phenomena at the interface of slag / metal and gas/metal.

- Modeling inclusion nucleation, growth, collision (done by Lifeng )and interact with gas bubbles (done by Lifeng and Jun Aoki in gas stirred ladles)

- Investigating the emulsification of the top slag

Modeling of Fluid Flow, Mixing and Inclusion Motion in...

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