additions of industrial engineering of stainless steel slags · additions of industrial residues...

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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