additions of industrial engineering of stainless steel slags · additions of industrial residues...
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Additions of industrial residues for hot stage engineering ofstainless steel slags
Y. Pontikes, L. Kriskova, X. Wang, D. Geysen, S. Arnout, E. Nagels, Ö. Cizer, T. Van Gerven, J. Elsen, M. Guo, P. T. Jones, B. Blanpain
Stainless steel production
3-step process (before casting)- EAF: scrap melting
- AOD/VOD: de-C and de-S
- Ladle refining: de-S
EAF slag125 kg/ton
steel
De-C slag180 kg/ton
steel
Ladle slag20 kg/ton
steel
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Steel production sites in Belgium
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Stainless steel/slag in Belgium
ArcelorMittal, Genk
- steel: 900 kt/year
- slag: 250 kt/year
ArcelorMittal, Charleroi
- steel: 700 kt/year
- slag: 200 kt/year
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Atomium: 1958-2008
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Pyramid of Brussels: every 15 years
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Slag valorisation chain
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Slag valorisation chain
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Slag valorisation chain
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Slag valorisation chain
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Slag valorisation chain
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Motivation
Slag disintegrates during cooling and can not be used as aggregate. Goes to land-filling with increased cost per ton.
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Different unit cells = different ions can stabilise the non-γ phases =Flexibility = opportunities
C. J. Chan, M. W. Kriven and J. F. Young,. J. Am. Ceram. Soc., 1992, 75, (6), 1621-1627.
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Transformations of C2S
Goal
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Jean-Marie Delbecq, Steel Slags as cementitious materials, Seminário Internacional – Aplicação de Escória deAciaria, Belo Horizonte, Nov. 22 2010
Stabilise stainless steel slag towards aggregates or a hydraulic binder
Is a hydraulic binder feasible?
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Al2O
3+Fe
2O
30 10 20 30 40 50 60 70 80 90 100
SiO2
0
10
20
30
40
50
60
70
80
90
100
CaO+MgO
0
10
20
30
40
50
60
70
80
90
100
High alumina cement
Trass brick
dust pozzolana
Blast furnace slag
Blast furnace slag cement
Portland cement
AOD experimental
CC experimental
CaO MgO Fe2O3 FeO MnO SiO2 Al2O3 CaF2
AOD slag 45-60 5-12 < 1 < 1 < 1 30-40 < 5 4-6
LM slag 60-70 ~ 10 < 1 < 1 < 1 15-25 < 1 8-12
Belite-rich clinker 60-63 <1 3-6 - - 25-30 3-7 -
CEMENT SLAG
Raw materials Limestone, shale, clay minerals (bauxite, iron mills, fly ash, blast furnace slag, etc)
Limestone, dolomite, fluorite, quartz sand
Processing Sintering Melting
Cooling Fast Depends (overlooked)
Post-processing Milling, additions etc Depends (overlooked)
Cement VS slag
Hydration of C2S
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Slow cooling results to γ-C2S that does not hydrate (activation can change this, see poster by F. Zhang et al.)
There is need for β, α΄, α forms; β is the one typically found in cement clinkers.
chemical stabilisation by ions
change in slag chemistry
fast cooling
How to stabilise the slag?
α
α΄H
α΄L
β Β2Ο3, Na2O, K2O, BaO, MnO2, CrO3
MgO, Al2O3, Fe2O3, BaO, K2O, P2O5, CrO3
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Stabilisation by ions
19
Production in Kirka Plant: 600.000t/y
Annual Report - www.etimaden.gov.tr
Tincal ore
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Boron plants in Turkey
20
•Annual quantity of solid boron wastes (BW): 300.000 - 400.000t.•Content of B2O3 varies from 3.5wt% to 26wt%.
ST/EIPPCB/MTWR_BREF_FINAL July2004
•Crushing•Washing•Screening
•Dissolving
•SettlingBoron wastes
Tincal ore
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Production flow sheet of refined borates
Fly ash – Lignite combustion
Megalopolis, Greece
Fly ash: 10 MT/year
rich in Al2O3 and Fe2O3
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http://www.industcards.com/st-coal-greece.htm
Raw materials
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SiO2 Al2O3 Fe2O3 CaO MgO SrO K2O Na2O B2O3 SO3 TiO2 CaF2 other
Synthetic slag
28.4 1.3 - 56.7 6.5 - - - - - 1.1 6.0 -
Boron waste
21.9 3.6 1.0 18.2 14.1 2.8 2.4 9.2 25.8 n.d. n.d. n.d. 1.0
Fly ash 50.2 19.5 9.2 11.7 2.5 n.d. 2.2 0.3 n.d. 3.0 0.8 n.d. 0.6
Boron waste is composed of tincalconite Na2B4O7·5H2O and dolomite CaMg(CO3)2.
Sanidine KAlSi3O8, calcite CaCO3, chlorite (Mg,Fe2+)10Al2[(Si6Al2)O20](OH)16,montmorillonite(0.5Ca,Na)0.7(Al,Mg,Fe)4[(Si,Al)8O20](OH)4·nH2O and most probably searlesite NaBSi2O5(OH)2,are also present as minor phases.
Fly ash is composed of quartz (SiO2), anorthite (CaAl2Si2O8), magnetite (Fe3O4), anhydrite (CaSO4) and gehlenite (Ca2Al2SiO7).
FactSage thermodynamic calculations: reference slag
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FactSageequilibrium cooling
FactSageScheil-Gulliver cooling
Phase constitution of reference slag
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Phase distribution in BW stabilised
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Backscattered electron image after chemical etching
Backscattered electron image after chemical etching
C2S
C2S
C2S
C2S
MgO
180μm
120μm
Phase distribution in BW stabilised
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Backscattered electron image (left) and phase distribution based on image stacking from elemental maps (right) of 1 wt% boron waste-stabilized slag.
Phase constitution of BW stabilised slag
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Phase distribution in fly ash stabilised
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Backscattered electron image (left) and phase distribution based on image stacking from elemental maps (right) of the 22 wt% fly ash stabilized stainless steel slag.
FactSage thermodynamic calculations: fly ash stabilised
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FactSage Scheil-Gulliver cooling
FactSage equilibrium cooling
Phase constitution of fly ash stabilised
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Will BW stabilised slag react with water?
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0 20 40 60 80 100 120 140 160 1800
2
4
6
8
10
12
14 rate
cumulative
time [h]
rate
of
heat
rele
ase [
J/h
.g]
0
1000
2000
3000
4000
5000
6000
cum
ula
tive h
eat re
lease [J
/g]
Will BW stabilised slag react with water?
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3 days 7 days
YES, IT WILL!
Will also B-stabilised AOD slag hydrate?
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Industrial sample of AOD from ferritic steel production, stabilisedwith borates, after 3, 7 and 28 days of hydration
82
84
86
88
90
92
94
96
98
100
AOD FER 4
we
igh
t lo
ss [%
]
3D
7D
28D
100 200 300 400 500 600 700 800 900 1000
C-S-H ?
AOD FER4
DT
G [m
g/m
g/°
C]
temperature [°C]
3D
7D
28D
Mg(OH)2
Ca(OH)2
0 20 40 60 80 100 120 140 160 180 200 220
0
2
4
6
8
10
AOD FER4
rate
cumulative
Time (h)
rate
of
heat
rele
ase [
J/h
.g]
0
1000
2000
3000
4000
5000
6000
7000
cum
ula
tive h
eat re
lease [J
/g]
Conclusions
C2S-driven disintegration during cooling
1 wt% addition of boron: stabilisation of a slag with basicity (CaO/SiO2) = 2.
22 wt% addition of fly ash stabilises the slag
boron stabilised slag hydraulic properties.
Further analysis is required.
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Thank you
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