Transport processes in liquid
steel : challenge for chemical
engineers
Kamil Wichterle
VSB – Technical University of Ostrava, Czech Republic
Classical image of iron metallurgy:
Reduction of iron oxides
FeO(s) + CO(g)  Fe(?) + CO2(g)
• (?)=(s) … Direct reduction - smelting
• (?)=(l) … Blast furnace reduction
Iron ore
Charcoal
CO2
,N2
Smelting furnace, T<1000oC
Gas - Solid reaction
Air
Iron bloom (solid Fe)
hammering, forging,
carburization, quenching
Steel
IRONWORKS
(Technical museum of Brno)
1st milenium
18th century
http://www.technicalmuseum.cz/pamatky.html
Genesis
1. Adam
2. Cain
3. Enoch
4. Irad
…Tubalcain, an instructor
5. Mehuajel
6. Methushael
of
every
artificer
in
brass
7. Lamech
and iron …
8. Tubalcain
9. …
Genesis 4:22
10. …Noah
THE GREAT FLOOD
IRON BLOOM
English Heritage Archaeology Day 22 June 2002
http://www.brad.ac.uk/acad/archsci/depart/resgrp/amrg/Rievaulx02/Rievaulx.htm
HAMMERING
http://www.cassovia.sk/stm/v3.php3
Iron ore
Coke
CO, CO2 ,N2
o
T>1500 C
Blast furnace,
Gas – Liquid - Solid reaction
Hot air
Pig iron (liquid Fe – Fe3C)
Molding
Cast iron (high carbon %)
STEEL
(wrought iron) less than 2% C
ductile, malleable
CAST IRON
more than 2% C
brittle
STEEL - CAST IRON
Prague 1891
Petřín tower
Hannau Pavillon
MAIN REASON FOR
STEELMAKING
Removing of
carbon
Steel – less than 2% C
Special steels 99.9% Fe
liquid steel process
LIQUID STEEL
Fe – C
Temperature oC
1638oC
Lowest melting point
STEEL
Fe
1153oC
CAST IRON
Weight Percent Carbon
Fe3
C
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 } → <Fe> + [Fe-C] + {CO }
•Mechanical separation of solid steel
lumps from the „puddle“
The Crucible Steel Furnace Shop at Abbeydale
http://www.woodberry.org/acad/hist/irwww/Metallurgy/Biography/Henry_Cort.htm
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)
Sir Henry Bessemer 1813 - 1898
http://www.history.rochester.edu/ehp-book/shb/illus.htm
EFFECT OF THE LINING - 1875
Sidney Gilchrist Thomas and Percy Gilchrist
Dephosphorization in the converter
MgO, CaO lining (basic)
The lining enters following reactions:
[Fe-P] + {O2 } + <CaO> → [Fe] + (Ca3(PO4)2)
metal melt
gas
solid non-metal metal melt non-metal melt (slag)
slag => fertilizer „Thomas powder“
Other reactions:
[Fe-S] + {O2 } + <CaO> → [Fe] + (CaS)
[Fe-Si] + {O2 } + <CaO> →[Fe] + (CaSiO3)
CONVERTER
CONVERTER 1936
1936
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
1950
• Iron- and steelworking - fully matured
industry, using proven processes
• Limited demand for a scientific
approach to the technology
Revolution in steelworking
since 1960
• Basic oxygen process
• Continuous casting
• Environmental issues
Revolution in steelworking
CONTINUOUS CASTING
Revolution in steelworking
OXYGEN PROCESS
FURNACES
Oxygen in steelmaking
• Prof. Robert Durrer
(pilot-plant experiments Gerlafingen,
Switzerland 1948)
• The first industrial oxygen converter
(VOEST Linz-Donawitz 1952)
Advantage of pure Oxygen
Absence of inert nitrogen:
•
•
•
•
Faster reaction than with air
More efficient employment of heat
Higher temperature
Suppressed formation of nitrides
BOS - Basic Oxygen Steelmaking
BOP - Basic Oxygen Process
BOF - Basic Oxygen Furnace
[Fe-C] + {O2 } → [Fe] + {CO }
[Fe-P-S-Si] + {O2 } + <CaO> → [Fe] + (P,S,Si in slag)
Source of iron for steelworking
• Liquid pig iron from blast furnace 30-40%
(higher content of C, Si, P, S,…)
• Steel scrap
60-70%
(variable composition - also Cu, Zn, Pb, Cd,…)
• Iron from direct reduction process < 10%
(bloom, sponge, briquettes – quite pure Fe)
Scrap
BOS
Liquid
steel
Ladle
Oxygen
Lance
Steel batch 200 000 kg
O2 : 500 normal m3/min
20 min
Superficial velocity 1.5 m/s
250 vvm
Gas power input 60 kW/m3
(or 8 W/kg)
Mixing time 10-100 s
Whole cycle 50 min
Oxygen tuyere
http://www.bhpsteel.com.au/bhp/steel/steelenv/steelpath/steelbos.cfm
Steel
Slag
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
Production of Oxygen
cryogenic process and liquid air distillation
Largest 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
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, …)
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)
LIQUID IRON FOR STEELMAKING
•
•
•
•
•
BLAST FURNACE
TORPEDO LADLE
ELECTRIC ARC
GAS - OXYGEN COMBUSTION
HEAT OF OXIDATION C, Si, … (Fe)
BLAST FURNACE
TORPEDO LADLE
(up to 100 km from the blast furnace)
ELECTRIC ARC FURNACE
ALSO WITH OXYGEN
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
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
ARGON –VACUUM TREATMENT
• Argon gas-lift for agitation (10-300 W/m3)
• Vacuum for desorption of soluble gases
Superficial gas
velocity:
0.001 m/s … bottom
> 1 m/s … level
(CO, O2, H2, N2)
Atmospheric pressure:
1420 mm Fe
RH
Ruhrstaal - Heraeus
DH
Dortmund-Hoerde
ENVIRONMENTAL:
• Gas emissions (CO)
• Airborn particles
(Fe,Zn,Pb,Cd,Cu, …)
• Slag
TUNDISH
• Batch input 
continuous output
• Turbulence suppression
• Argon agitation
• Argon inert atmosphere
• Last slag separation 
particles < 50μm
• Tundish refractories 
steel quality
tundish
mold
solidification
cooling
HYDRODYNAMICS
MULTIPHASE FLOW
HEAT TRANSFER
CFD
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, …)
Our contribution
Department of Chemistry
Faculty of Metallurgy and
Material Engineering
Technical University of
Ostrava
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
ρ
Liquid
oC
kg/m3
dynamic
kinematic surface
Laplace
Laplace
viscosity
viscosity tension
length
velocity
μ
ν
σ
(σ/(ρg))1/2 (σg/ρ)1/4
Pas
m2/s
N/m
m
m/s
molten steel 1500
7200
5*10-3
0.7*10-6
1.4
4.5*10-3
0.21
water
25
1000
1.0*10-3
1.0*10-6
0.073
2.7*10-3
0.16
mercury
25
13500
1.5*10-3
1.1*10-6
0.46
1.8*10-3
0.14
Wood metal
80
10600
3*10-3
0.3*10-6
0.4
1.9*10-3
0.14
hexane
25
650
0.35*10-3
0.5*10-6
0.018
1.6*10-3
0.13
DECREASING PRESSURE - INCREASING VOLUME
BREAK-UP
HIGH HYDROSTATIC ("FERROSTATIC")
PRESSURE AT THE LADLE BOTTOM
SMALL SINGLE ARGON BUBBLES
DECREASING PRESSURE - INCREASING VOLUME
BREAK-UP
FAST DECREASE OF PRESSURE
INCREASING BUBBLES
RETARDED BREAKUP
Experimental
History of Metallurgical
Engineering
DE RE METALLICA
LIBRI XIIGeorgius
Chemnitz
Agricola (Georg Bauer)
(1494-1555)
Glauchau
Leipzig
Jáchymov
(Joachimsthal)
Basel
Padova
Bologna
Dukedom Saxony
Czech Kingdom
Georgius Agricola
(Georg Bauer)
(1494-1555)
Agricola
1556
Cascade of
CSTR
Impeller
manufacture
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
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
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