ZINC STRIPPING FROM STEELWORK DUST Kamil Wichterle, Jan Cieslar, Jana Wichterlov

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ZINC STRIPPING FROM STEELWORK DUSTKamil
Wichterle, Jan Cieslar, Jana Wichterlová
VSB-Technical University of Ostrava, 70833
Ostrava Poruba, Czech Republic kamil.wichterle_at_vsb
.cz
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What is the steelwork dust ?
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World steel production
40
O2
Oxygen steelmaking BOF (basic oxygen furnace)
Electric steelmaking EAF (electric arc furnace)
CaO
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Dust composition depends mostly on the quality of
scrap
Statistics for USA and Canada (year 2000) for
EAF mostly (50) Fe 15-30 Zn 12-25 Pb
1-2 Cd 0,02-0,05
Percentage of iron is higher and percentage of
the heavy metals is lower in the dust from BOF
process (as the heavy metals are absent in the
entering pig iron)
In particular our samples from the tandem
furnaces Arcelor Mittal contained Fe about 50
Zn 8-16 Pb 1 Cd 0,02
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Dust as a basic neutralizing agent
1 tonne PRICE NaOH 400 CaO
25 ZnFe2O4 -20
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Steelmaking dust processing
Pyrometalurgy Reduction roasting at
1000-2000C Distillation of Zn (boiling point
907C) and its condensation in oxidizing
environment in form of ZnO
problems
problems
Hydrometalurgy Total dissolution (both Fe and Zn
oxides) in conc. H2SO4 or HCl Hydrolysis at
increasing pH in large volume of water leads to
iron precipitation haematite, goethite, or
jarosite Filtration
problems
Chlorine metalurgy Reaction of Cl2 or HCl with
the dust chlorides formation The iron chlorides
decompose at higher temperature to oxides and
HCl ZnCl2 (boiling point 756C) is volatile and
it condenses as a water-soluble salt
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Experimental studiesof the reactions of HCl with
metallurgy dust

• VŠB -Technical University of Ostrava
• Faculty of Metallurgy and Material Engineering
• Department of Chemistry
• Jan Cieslar
• Šárka Langová
• Juraj Leško
• Dalibor Matýsek
• Radim Škuta
• Jana Wichterlová
• Kamil Wichterle

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Arcelor Mittal Steel Tandem Furnaces
The dust in Arcelor Mittal Steel plant is
separated by textile filtres and collected as a
water suspension after a sedimenttion in Dorr
thickenners the mud is dumped in deposits
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The dust in Arcelor Mittal Steel plant is
collected by textile filtres and transferred to
water suspension after a sedimenttion in Dorr
thickenners the mud is dumped in deposits
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Mineralogy of the sample TP
  w/w Zn distribution Zn
Hematit 3,2    
Magnetit 35,6    
Wuestit 3,2    
Franklinit 36,6 9,9 69,0
Grafit 4,4    
Zinkit 5,6 4,5 31,0
amorphous 11,4    
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Inlet HCl
Quartz tube
Oven
Condenser
Laboratory equipment
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EQUILIBRIUM DATA
2 HCl(g) 1/3 Fe2O3(s) 2/3 FeCl3(s,l,g)
H2O(g) (1) 2 HCl(g) 1/4 Fe3O4(s) 1/4
FeCl2(s,l,g) 1/2 FeCl3(s,l,g) H2O(g) (2) 2
HCl(g) FeO (s) FeCl2(s,l,g)
H2O(g) (3) 2 HCl(g) ZnO (s) ZnCl2(s,l,g)
H2O(g) (4) 2 HCl(g) 1/4 ZnFe2O4(s) 1/4
ZnCl2(s,l,g) 1/2 FeCl3(s,l,g) H2O(g) (5) 2
HCl(g) ZnFe2O4(s) ZnCl2(s,l,g) Fe2O3(s)
H2O(g) (6) FeCl2(s,l,g) ZnFe2O4(s)
ZnCl2(s,l,g) Fe2O3(s) FeO (s) (7) 2/3
FeCl3(s,l,g) ZnFe2O4(s) ZnCl2(s,l,g) 4/3
Fe2O3(s) (8)
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Evidently, iron chlorides are unstable at
temperatures higher than 300C. Zinc chloride is
generally chemically stable up to 700C However,
ZnCl2 at higher temperatures leaves the reaction
space as a vapor (its boiling point is 756C)
which affects the equilibrium
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Therefore, higher temperatures are suitable to
separate ZnCl2 vapors from the solid residuum of
iron oxides
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Zn, Fe, and HCl conversions as functions of
temperature for the TP dust sample (45 minutes
reaction)
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Zn, Fe, and HCl conversions as functions of
reaction time for the TP dust sample (temperature
900C)
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World steel production
40
O2
Oxygen steelmaking BOF (basic oxygen furnace)
Electric steelmaking EAF (electric arc furnace)
CaO
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World zinc production
2009 8 millions tonnes Zn China (continental)
2.9 Peru 1.4 Australia 1.3 United States
0.7 Canada 0.7
Zinc lossed in steelmaking dust 3 millions
tonnes of Zn
!!!!!!
1 tonne of Zn 1500 - 2500 (2009-2010)
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Efficient way of zinc recycling is worth to be
studied
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Thank you for the attention