Transport processes in liquid steel : challenge for chemical engineers Kamil Wichterle VSB – Technical University of Ostrava, Czech Republic

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Transport processes in liquid steel challenge
for chemical engineers Kamil WichterleVSB
Technical University of Ostrava, Czech Republic
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Classical image of iron metallurgyReduction of
iron oxides FeO(s) CO(g) ? Fe(?) CO2(g)

• (?)(s) Direct reduction - smelting
• (?)(l) Blast furnace reduction

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Smelting furnace, Tlt1000oC
Iron ore Charcoal Air
CO2 ,N2
Gas - Solid reaction
Iron bloom (solid Fe)
hammering, forging, carburization, quenching
Steel
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IRONWORKS (Technical museum of Brno)
1st milenium
18th century
http//www.technicalmuseum.cz/pamatky.html
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Genesis

• Adam
• Cain
• Enoch
• Irad
• Mehuajel
• Methushael
• Lamech
• Tubalcain
• Noah THE GREAT FLOOD

Tubalcain, an instructor of every artificer in
brass and iron Genesis 422
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English Heritage Archaeology Day 22 June
2002http//www.brad.ac.uk/acad/archsci/depart/res
grp/amrg/Rievaulx02/Rievaulx.htm
IRON BLOOM
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HAMMERING
http//www.cassovia.sk/stm/v3.php3
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Blast furnace, Tgt1500oC
Iron ore Coke Hot air
CO, CO2 ,N2
Gas Liquid - Solid reaction
Pig iron (liquid Fe Fe3C)
Molding
Cast iron (high carbon )
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STEEL CAST IRON
(wrought iron) less than 2 C more
than 2 Cductile, malleable
brittle
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STEEL - CAST IRON
Prague 1891
Petrín tower
Hannau Pavillon
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MAIN REASON FOR STEELMAKING

• Removing of carbon

Steel less than 2 C Special steels 99.9 Fe
liquid steel process
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Fe C
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PUDDLING - Henry Cort 1780

• The Crucible Steel Furnace
• Melted high carbon iron (pig iron)
• air flue gas
• Reaction
• Fe-C(l) O2 (g) ? Fe(s) Fe-C(l) CO(g)
• or
• Fe-C O2 ? ltFegt Fe-C CO
• Mechanical separation of solid steel lumps from
  the puddle

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The Crucible Steel Furnace Shop at Abbeydale
http//www.woodberry.org/acad/hist/irwww/Metallurg
y/Biography/Henry_Cort.htm
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CONVERTER Sir Henry Bessemer 1856

• The Converter
• Melted high carbon iron (pig iron)
• bottom injected air
• Fast reaction
• Fe-C O2 ? Fe CO
• Minor reaction
• Fe O2 ? (FeO)
• Liquid steel product
• SiO2 lining (acidic)

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Sir Henry Bessemer 1813 - 1898
http//www.history.rochester.edu/ehp-book/shb/illu
s.htm
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EFFECT OF THE LINING - 1875Sidney Gilchrist
Thomas and Percy Gilchrist
Dephosphorization in the converter MgO, CaO
lining (basic) The lining enters following
reactions Fe-P O2 ltCaOgt ? Fe
(Ca3(PO4)2) metal melt gas
solid non-metal metal melt non-metal melt
(slag) slag gt fertilizer Thomas powder
Other reactions Fe-S O2 ltCaOgt ?
Fe (CaS) Fe-Si O2 ltCaOgt ?Fe
(CaSiO3)
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CONVERTER 1936
CONVERTER 1936
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OPEN HEARTH FURNACE - 1863 Sir Charles William
Siemens Émile et Pierre Martin

• Melted iron (pig iron scrap)
• hot air
• flue gas
• magnesite lining
• CaO powder

Slower process than this in the
converters However higher quality of the product
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1950

• Iron- and steelworking - fully matured industry,
  using proven processes
• Limited demand for a scientific approach to the
  technology

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Revolution in steelworkingsince 1960

• Basic oxygen process
• Continuous casting
• Environmental issues

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Revolution in steelworkingCONTINUOUS CASTING
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Revolution in steelworkingOXYGEN PROCESS
FURNACES
OXYGEN
ELECTRIC ARC
OPEN HEARTH
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Oxygen in steelmaking

• Prof. Robert Durrer (pilot-plant experiments
  Gerlafingen, Switzerland 1948)
• The first industrial oxygen converter (VOEST
  Linz-Donawitz 1952)

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Advantage of pure Oxygen Absence of inert
nitrogen

• Faster reaction than with air
• More efficient employment of heat
• Higher temperature
• Suppressed formation of nitrides

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BOS - Basic Oxygen SteelmakingBOP - Basic Oxygen
Process BOF - Basic Oxygen Furnace
Fe-C O2 ? Fe CO Fe-P-S-Si O2
ltCaOgt ? Fe (P,S,Si in slag)
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Source of iron for steelworking

• Liquid pig iron from blast furnace (higher
  content of C, Si, P, S,)
• Steel scrap (variable composition - also
  Cu, Zn, Pb, Cd,)
• Iron from direct reduction process (bloom,
  sponge, briquettes quite pure Fe)

30-40 60-70 lt 10
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BOSSteel batch 200 000 kg O2 500 normal
m3/min 20 min Superficial velocity 1.5 m/s250
vvm Gas power input 60 kW/m3 (or 8 W/kg) Mixing
time 10-100 sWhole cycle 50 min
http//www.bhpsteel.com.au/bhp/steel/steelenv/stee
lpath/steelbos.cfm
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OXYGEN INTRODUCTION

• Tuyere above the liquid bath (L-D)
• Tuyere under the liquid level (Quiet)
• Bottom blown ladles (converters)
• Introduction of CaO powder in the oxygen stream
• Water cooled lance
• Hydrocarbon gas cooled lance

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Production of Oxygen cryogenic process and liquid
air distillationLargest facilities in steelworks

• consumption 50-60 normal m3 per ton of steel
• delivery rates 500-800 normal m3/min
• pressure of 1.5 MPa
• 99.5 O2 the major impurity is Argon
• byproducts Argon and Nitrogen
• energy consumption 0.45 kWh per normal m3

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OTHER AIMS OF STEELMAKING

• Removing of P, S, Si
• Removing of metals Zn, Cu, Pb, Cd, Al,
• Removing of diluted gases N, CO, H, O
• Removing of solid non-metal particles
• Addition of alloying metals (e.g. Ni, Cr, Co, Mo,
  Mn, Si, V, )

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REFRACTORY LINING

• Up to 1 m thickness
• Errosion, abrasion, thermal cycling
• Losses 0.5-1 mm per run
• Laser controlled thickness
• Slower wall dissolution when CaO added
• Life more than 1000 runs (classical
  converters 100 runs)
• Regeneration of walls by slag spray (up to 10
  000 runs)

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LIQUID IRON FOR STEELMAKING

• BLAST FURNACE
• TORPEDO LADLE
• ELECTRIC ARC
• GAS - OXYGEN COMBUSTION
• HEAT OF OXIDATION C, Si, (Fe)

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BLAST FURNACE
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TORPEDO LADLE (up to 100 km from the blast
furnace)
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ELECTRIC ARC FURNACE
ALSO WITH OXYGEN
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GAS COMBUSTION WITH OXYGEN

• less expensive (40) than the electric arc
• lower temperature than with the electric arc -
  limited heavy metal emissions
• can be combined with the electric heating

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SECONDARY METALLURGY
ARGON VACUUM LADLE

• Desorption of diluted gases N, CO, H, O
• Sedimentation - floating of slag particles
• Addition of alloying metals
• De-oxidation
• Homogenization

TUNDISH

• Removing of solid non-metal particles
• Homogenization of temperature and composition

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ARGON VACUUM TREATMENT

• Argon gas-lift for agitation (10-300 W/m3)
• Vacuum for desorption of soluble gases
  (CO, O2, H2, N2)

Superficial gas velocity 0.001 m/s bottom gt 1
m/s level
Atmospheric pressure 1420 mm Fe
RH Ruhrstaal - Heraeus
DH Dortmund-Hoerde
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ENVIRONMENTAL

• Gas emissions (CO)
• Airborn particles (Fe,Zn,Pb,Cd,Cu, )
• Slag

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TUNDISH

• Batch input ? continuous output
• Turbulence suppression
• Argon agitation
• Argon inert atmosphere
• Last slag separation ? particles lt 50µm
• Tundish refractories ? steel quality

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HYDRODYNAMICSMULTIPHASE FLOWHEAT
TRANSFERCFD
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Transformation of Metallurgy

• Material engineering merging with polymer
  science, ceramics, electronics materials
• Process engineering adoption of chemical
  engineering method (chemical reactors
  gas-liquid-solid, non-isothermal processes,
  mechanical separation, transport phenomena,
  scale-up methods, modelling, simulation, CFD, )

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Our contributionDepartment of Chemistry
Faculty of Metallurgy and Material
EngineeringTechnical University of Ostrava
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BUBBLE BEHAVIOR IN LIQUID STEEL

• From the viewpoint of two-phase hydrodynamics
  (density, viscosity and surface tension),
• water and liquid steel are quite similar !

density dynamic kinematic surface Laplace
Laplace viscosity viscosity tension
length velocity Liquid ? µ ?
s (s/(?g))1/2 (sg/?)1/4
oC kg/m3 Pas m2/s N/m m m/s molten steel 1500
7200 510-3 0.710-6 1.4 4.510-3 0.21 water
25 1000 1.010-3 1.010-6 0.073 2.710-3 0.1
6 mercury 25 13500 1.510-3 1.110-6 0.46
1.810-3 0.14 Wood metal
80 10600 310-3 0.310-6 0.4 1.910-3 0.14 hexane
25 650 0.3510-3 0.510-6 0.018 1.61
0-3 0.13
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Experimental
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History of Metallurgical Engineering
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Georgius Agricola (Georg Bauer)(1494-1555)
DE RE METALLICA LIBRI XII
Chemnitz
Glauchau
Leipzig
Jáchymov (Joachimsthal)
Dukedom Saxony
Czech Kingdom
Basel
Padova
Georgius Agricola (Georg Bauer) (1494-1555)
Bologna
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Agricola1556Cascade of CSTRImpeller
manufacture
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Metallurgy ? ? Chemical Engineering

• Transformation of one journal
• 1902 Electrochemical Industry
• 1905 Electrochemical and Metallurgical
  Engineering
• 1910 Metallurgical and Chemical Engineering
• 1913 Chemical and Metallurgical Engineering
• 1946 Chemical Engineering

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CONCLUSIONS

• At the end of 20th century steelmaking became a
  fast developing chemical technology
• Chemical engineering education should also turn
  its attention to the processes in liquid steel
• In metallurgy, there are challenging jobs for
  chemical engineers

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Thank you for the attention
Financial support by the Grant Agency of the
Czech Republic (grants No.106/98/0050 and No.
104/01/0547) is greatly appreciated