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

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Presentation on theme: "Transport processes in liquid steel : challenge for chemical engineers Kamil Wichterle VSB – Technical University of Ostrava, Czech Republic."— Presentation transcript:

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

3 Classical image of iron metallurgy: Reduction of iron oxides FeO(s) + CO(g)  Fe(?) + CO 2 (g) (?)=(s) … Direct reduction - smelting (?)=(l) … Blast furnace reduction

4 Smelting furnace, T<1000 o C Iron ore Charcoal Air CO 2,N 2 Iron bloom (solid Fe) hammering, forging, carburization, quenching Steel Gas - Solid reaction

5 IRONWORKS (Technical museum of Brno) 1st milenium 18th century

6 Genesis …Tubalcain, an instructor of every artificer in brass and iron … Genesis 4:22 1.Adam 2.Cain 3.Enoch 4.Irad 5.Mehuajel 6.Methushael 7.Lamech 8.Tubalcain 9.… 10.…Noah THE GREAT FLOOD

7 English Heritage Archaeology Day 22 June IRON BLOOM

8 HAMMERING

9 Iron ore Coke Hot air CO, CO 2,N 2 Pig iron (liquid Fe – Fe 3 C) Molding Cast iron (high carbon %) Gas – Liquid - Solid reaction Blast furnace, T>1500 o C

10 STEEL CAST IRON ( wrought iron) less than 2% C more than 2% C ductile, malleable brittle

11 Prague 1891 STEEL - CAST IRON Petřín towerHannau Pavillon

12 MAIN REASON FOR STEELMAKING Removing of carbon Steel – less than 2% C Special steels 99.9% Fe liquid steel process

13 FeFe 3 C Weight Percent Carbon Temperature o C CAST IRON Lowest melting point 1153 o C 1638 o C LIQUID STEEL STEEL OXYGEN PROCESS – DURRER 1950 CONVERTER -BESSEMER 1856 PUDDLING - CORT 1780 OPEN HEARTH - SIEMENS-MARTIN Fe – C

14 PUDDLING - Henry Cort 1780 The Crucible Steel Furnace Melted high carbon iron (pig iron) + air + flue gas Reaction: Fe-C(ℓ) + O 2 (g) → Fe( s ) + Fe-C(ℓ) + CO(g) or: [Fe-C] + {O 2 } → + [Fe-C] + {CO } Mechanical separation of solid steel lumps from the „puddle“

15 The Crucible Steel Furnace Shop at Abbeydale

16 CONVERTER – Sir Henry Bessemer 1856 The Converter Melted high carbon iron (pig iron) + bottom injected air Fast reaction: [Fe-C] + {O 2 } → [Fe] + {CO } Minor reaction [Fe] + {O 2 } → (FeO) Liquid steel product SiO 2 lining (acidic)

17 Sir Henry Bessemer

18 EFFECT OF THE LINING Sidney Gilchrist Thomas and Percy Gilchrist Dephosphorization in the converter MgO, CaO lining (basic) The lining enters following reactions: [Fe-P] + {O 2 } + → [Fe] + (Ca 3 (PO 4 ) 2 ) metal melt gas solid non-metal metal melt non-metal melt (slag) slag => fertilizer „Thomas powder“ Other reactions: [Fe-S] + {O 2 } + → [Fe] + (CaS) [Fe-Si] + {O 2 } + →[Fe] + (CaSiO 3 )

19 CONVERTER 1936

20 OPEN HEARTH FURNACE 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

21 1950 Iron- and steelworking - fully matured industry, using proven processes Limited demand for a scientific approach to the technology

22 Basic oxygen process Continuous casting Environmental issues Revolution in steelworking since 1960

23 Revolution in steelworking CONTINUOUS CASTING

24 Revolution in steelworking OXYGEN PROCESS FURNACES ELECTRIC ARC OPEN HEARTH OXYGEN

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

26 Advantage of pure Oxygen Absence of inert nitrogen: Faster reaction than with air More efficient employment of heat Higher temperature Suppressed formation of nitrides

27 BOS - Basic Oxygen Steelmaking BOP - Basic Oxygen Process BOF - Basic Oxygen Furnace [Fe-C] + {O 2 } → [Fe] + {CO } [Fe-P-S-Si] + {O 2 } + → [Fe] + (P,S,Si in slag)

28 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% < 10%

29 Ladle Steel Scrap Slag Oxygen tuyere Oxygen Lance BOS Steel batch kg O 2 : 500 normal m 3 /min 20 min Superficial velocity 1.5 m/s 250 vvm Gas power input 60 kW/m 3 (or 8 W/kg) Mixing time s Whole cycle 50 min Liquid steel

30 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

31 Production of Oxygen cryogenic process and liquid air distillation Largest facilities in steelworks consumption normal m 3 per ton of steel delivery rates normal m 3 /min pressure of 1.5 MPa 99.5% O 2 ; the major impurity is Argon byproducts: Argon and Nitrogen energy consumption 0.45 kWh per normal m 3

32 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, …)

33 REFRACTORY LINING Up to 1 m thickness Errosion, abrasion, thermal cycling Losses 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 runs)

34 LIQUID IRON FOR STEELMAKING BLAST FURNACE TORPEDO LADLE ELECTRIC ARC GAS - OXYGEN COMBUSTION HEAT OF OXIDATION C, Si, … (Fe)

35 BLAST FURNACE

36 TORPEDO LADLE (up to 100 km from the blast furnace)

37 ELECTRIC ARC FURNACE ALSO WITH OXYGEN

38 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

39 SECONDARY METALLURGY Desorption of diluted gases N, CO, H, O Sedimentation - floating of slag particles Addition of alloying metals De-oxidation Homogenization Removing of solid non-metal particles Homogenization of temperature and composition ARGON – VACUUM LADLE TUNDISH

40 ARGON –VACUUM TREATMENT Argon gas-lift for agitation ( W/m 3 ) Vacuum for desorption of soluble gases (CO, O 2, H 2, N 2 ) Atmospheric pressure: 1420 mm Fe Superficial gas velocity: m/s … bottom > 1 m/s … level DH Dortmund-Hoerde RH Ruhrstaal - Heraeus

41 ENVIRONMENTAL: Gas emissions (CO) Airborn particles (Fe,Zn,Pb,Cd,Cu, …) Slag

42 TUNDISH Batch input  continuous output Turbulence suppression Argon agitation Argon inert atmosphere Last slag separation  particles < 50μm Tundish refractories  steel quality

43 HYDRODYNAMICS MULTIPHASE FLOW HEAT TRANSFER CFD

44 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, …)

45 Our contribution Department of Chemistry Faculty of Metallurgy and Material Engineering Technical University of Ostrava

46 BUBBLE BEHAVIOR IN LIQUID STEEL From the viewpoint of two-phase hydrodynamics (density, viscosity and surface tension), water and liquid steel are quite similar ! densitydynamic kinematic surfaceLaplace Laplace viscosity viscosity tension length velocity Liquid ρ μ ν σ(σ/(ρg)) 1/2 (σg/ρ) 1/4 o Ckg/m 3 Pasm 2 /sN/mmm/s molten steel * * * water * * * mercury * * * Wood metal * * * hexane * * *

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50 Experimental

51 History of Metallurgical Engineering

52 Georgius Agricola (Georg Bauer) ( ) Basel Jáchymov (Joachimsthal) Glauchau Leipzig Chemnitz Padova Bologna Georgius Agricola (Georg Bauer) ( ) DE RE METALLICA LIBRI XII Dukedom Saxony Czech Kingdom

53 Agricola 1556 Cascade of CSTR Impeller manufacture

54 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

55 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

56 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


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