Presentation - Third International Slag Valorisation Symposium

IMPROVED SLAG 

QUALITIES BY LIQUID SLAG 

TREATMENT 

D. MUDERSBACH, 

P. DRISSEN, H. MOTZ

IMPROVED SLAG QUALITIES BY LIQUID SLAG TREATMENT 

Introduction 

2 Second International Slag Valorisation Symposium │ D. MUDERSBACH 

28/04/2011


Production of Iron and Steel Slag in Europe 

2008: 45.6 million tonnes 

BOS 

20 % 

EAF S 

2 % 

EAF C 

12 % 

SecMS 

4 % 

BFS 

62% 

Internal use for 

metallurgical 

purposes 

3% 

Fertilizer 

2% 

Hydraulic 

engineering 

1% 

Road 

construction 

38 % 


Use of Iron and Steel Slag in Europe 

2008: 46.9 million tonnes 

Interim storage 

5 % Final deposit 

2% Others 

1 % 

Cement 

production 

48 % 

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6,6 % 

2,3 8,0 % % 

7,7 mio. t Blast Furnace Slags in Germany 2010 

5,4 9,3 % 

504515 

178765 

714126 

70,0 % 

11,8 % 

903922 

5365115 


ABS 

GBS cement 

GBS other 

internal use 

stock 

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31.3 % 

14.3 % 

29.4 % 

19.6 % 

Cement production and CO 2 emissions 

- Benefits of slag cements - 

Calcination:0.55 t / t Cl 

CEM I 32.5 R (= 100 %) CEM II/B-S with 30 % slag (= 72 %) 

1011 

kg/t 

539 

kg/t 

51.0 % 

54.4 % 

30.4 % 

16.9 % 

CEM III/A with 50 % slag (= 53 %) CEM III/B with 75 % slag (= 30 %) 

Electr.energy:651 g/kWh 

26.4 % 

27.8 % 


730 

kg/t 

45.8 % 

52.8 % 

300 

kg/t 

Therm.energy:331 g/kWh 

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3,9 % 

8,0 8,0 % % 

231171 

1508238 

5,4 % 

472603 

6 mio. t Steel Slags in Germany 2010 

320959 

25,4 % 

13512 

57,1 % 

3388050 


BOF-S 

EAF-C-S 

EAF-S-S 

LF-S 

AOD-/VOD-S-S 

other 

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Increasing the quality 

of water granulated 

blast furnace slags 


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Druckfestigkeit in N/mm 2 

60 

50 

40 

30 

20 

10 

0 

original 

HOS D 

Mörtel-Druckfestigkeit (Zement: Mischung HS/Kl 75/25, 4200 cm 2 /g) 

Versuche mit SEKS: 51% CaO; 36% Al2O3 

Al2O3=11,4% 

C/S=1,10 

+3% 

SEKS 

+6% 

SEKS 

Al2O3=14,8% 

+10% 

SEKS 

C/S=1,39 

+20% 

SEKS 

Al2O3=11,8% 

C/S=1,17 

HOS D HOS C 

original 

HOS C 

+3% 

SEKS 


+6% 

SEKS 

Al2O3=15,3% 

C/S=1,40 

+10% 

SEKS 

2d 

7d 

28d 

+20% 

SEKS 

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low basicity CaO/SiO 2 � 

low compressive strength of 

mortar/concrete 

low concentration of Al 2O 3 � 

retarded development of (early) strength 

Injection of lime/Al 2O 3 

into the main runner 

10 Second International Slag Valorisation Symposium │ D. MUDERSBACH 28/04/2011 

10



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CaO/SiO2-ratio 

1,50 

1,45 

1,40 

1,35 

1,30 

1,25 

1,20 

1,15 

1. Start 

< 1t slag/min 

2. Start 

CaO/SiO2-ratio = f(CaO-injection) [spoon sample] 

08:25 

08:33 

08:39 

08:42 

08:48 

08:54 

08:57 

09:03 

09:06 

09:12 

09:18 

3. Start 

09:27 

09:30 

09:36 

09:42 

09:51 

09:57 

10:00 

10:06 


4. Start 

5. Start 

time 

6. Start 

10:15 

7. Start 

10:24 

8. Start 

10:33 

10:36 

10:42 

10:45 

9. Start 

10:54 

11:03 

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compressive strength [N/mm2] 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

compressive strength of mortar prisms as function of gbfs's 

basicity CaO/SiO2 

unbehandelt 2 4 

C/S = 1,17 C/S = 1,25 

C/S = 1,29 


2d 

7d 

28d 

C/S 

1,30 

1,25 

1,20 

1,15 

1,10 

C/S= Basicity CaO/SiO2 

28/04/2011



of basic oxygen 

furnace slags for the 

use in road 

construction 


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BOF/EAF slag might have some free CaO 

(free lime) & free MgO (periclase). In the 

presence of humidity the hydration of 

both minerals causes 100 % increase in 

volume of the crystals. 


The hydration is a 

serious problem in 

using steel slag as 

construction material ! 

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28/04/2011


O 2 + 2 FeO Fe 2O 3 + energy 

2 CaOfree + SiO2 2 CaOxSiO2 2 CaOfree + Fe2O3 2 CaOxFe2O3 by injection of sand and oxygen: 

� additional heat is generated 

- to keep slag liquid 

- to heat up and dissolve the sand 

� CaO/SiO 2 is reduced 

� free lime is dissolved and chemically bound 


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of basic oxygen 

furnace slags for the 

use as fertiliser 


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Vermartung in Tonnen 


3.000.000 

2.500.000 

2.000.000 

1.500.000 

1.000.000 

500.000 

0 

1945 1955 1965 1975 1985 1995 2005 2015 

Jahr 


Thomasphosphat 

Konverterkalk 

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Aim: 

sewage sludge ash + BOFS �� „Thomasphosphate 2 nd Generation“ 

~ 20 % P 2O 5 ~ 1,5 % P 2O 5 ~ 10 % P 2O 5 

with ~ 40 % ~ 95 % ~ 99 % available for plants 

Whitlockite + Dicalciumsilicate � Calcium-Phosphate-Silicate 

Ca 3(PO 4) 2 + 6 Ca 2Si 1-xP xO 4 � Ca 15(PO 4) 2(SiO 4) 6 

Approach: 

dissolution of the ash in the liquid slag 


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Problems 

with the 

physical 

properties 

of the 

liquid slag 

Homogeneous 

mixture of 

sewage sludge 

ash and liquid 

BOF slag 


Zugabe in t 

16 

14 

12 

10 

8 

6 

4 

2 

0 

Zugabe zu 20 t LDS mit 1,1 M.-% P2O5 

Zugabe Klärschlammasche mit 

21,8 M.-% P2O5 in t 

4,7 

2,5 

Problems 

with 

handling 

and 

dust 

Zugabe 

Tierkörperverbrennungsasche mit 

37,0 M.-% P2O5 in t 

9,9 

Mixture: 

20t BOFS + 8t ash 

(liquid) 4,7(solid) 

3 4 5 6 7 8 9 10 11 

M.-% P 2O 5 im Produkt 

15,1 

6,7 

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Converter lime: 

rich in lime but 

pure in P 2O 5 

Sewage sludge 

ash: rich in P 2O 5 

but P 2O 5 only 40 % 

available for plants 


Thomasphosphate 

of 2 nd generation 

Rich in lime and in 

P 2O 5 with 99 % 

available for plants 

28/04/2011


Optimising the 

metallurgical work of 

electric furnace slags 


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hoch 

legiert 

Stahlerzeugung 

Fe 2O 3 SiO 2 CaO Cr 2O 3 NiO ZnO PbO 

niedrig 

legiert 

Steel EAF-Slag 

25 - 40 3 - 7 3 - 5 5 - 15 0,5 - 3 5 - 30 0,1 - 0,2 

Staubzusammensetzung 

25 - 45 3 - 7 3 - 5 1 - 5 0,1 - 1 15 - 35 0,1 - 1,5 

Recycling/Utilisation: 

Scandust/Valera 


Internal Recycling 

Stope filling 

Waelz 

Oxide 

Waelz kiln 

Waelz 

Slag 

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filterhouse 

dustsilo 

for external 

recycling 

dusttransmitter 


caol 

O 2 

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wt.-% Zn in dust; 

kg dust/t liquid steel 

35 

30 

25 

20 

15 

10 

5 

Zn-content in dust [wt.-%] 

External output of dust in kg/t liquid steel 

Recycled dust quantity in % 

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 


70 

60 

50 

40 

30 

20 

10 

0 

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Recycled dust quantity in %


ratio (Cr 2O 3)/[Cr] 

1,2 

1,0 

0,8 

0,6 

0,4 

0,2 

0,0 

w/o dust-Recycling, 

only stirring with N 2 

Chrome scorification as function of treatment 

only dust-Recycling 

with C 

additional FeSi 

with air injection 


additional FeSi 

with N 2 injection 

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of stainless steel 

slags 


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Mineral: 

Idealisied 

Formula: 

% of 

Mineral: 

Compared to 19 wt.-% Cr2O3 in solid 

material, the leaching of 0.7 mg Cr/liter 

slag is surprisingly low. 

95 % of the total Cr is fixed as chromite, a 

Spinel-type mineral. 

(Me 2+ Me 2 3+ O4, with Me 2+ = Fe 2+ , Mg 2+ , Ni 2+ 

and Me 3+ = Fe 3+ , Al 3+ , Cr 3+ ) are known to be 

very stable under environmental conditions. 

Further progress is possible by stimulating 

the formation of spinels. 

Electron Microprobe Analyses of Minerals [wt.-%] 

SiO 2 Al 2 O 3 CaO MgO Cr 2 O 3 MnO Fe 2 O 3 NiO MoO 2 P 2 O 5 S 

Factor SP = 0.2 MgO + 1.0 Al 2O 3 + n Fe total + 0.5 Cr 2O 3 

Spinel Me 3+ 

2Me2+ O4 35 0,3 6,9 1,6 14,6 51,4 5,8 4,5 0,10 0,04 0,03 0,01 

Melilithe Ca 2 Al 2 SiO 7 20 33,3 14,1 37,9 2,2 0,1 10,9 0,1 0,03 0,00 0,10 0,53 

Bredigite Ca 7 MgSi 4 O 8 45 34,3 0,1 46,5 10,4 1,4 2,4 2,5 0,01 0,01 0,08 0,02 


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Crtotal (leachate) in mg/l 

0,30 

0,25 

0,20 

0,15 

0,10 

0,05 

0,00 

EAF-slags: original and laboratory modified 

(original slag: Fe total -parts < 1,0 %-wt.) 

XRD-investigation: 

point: no (Mg,Fe)-(Fe,Al,Cr)-spinel and 

square: (Mg,Fe)-(Fe,Al,Cr)-spinel 

sp 0,05 mg/l 

operational test: without bauxite-addition 

operational test: with bauxite-addition 

0 5 10 15 20 25 30 35 40 45 

factor sp = (0,2xMgO + 1,0xAl 2O 3 [+ 4,0xFe total] lab.- 0,5xCr 2O 3) in %-wt. 


sp >25 %-wt. : Crtotal in leachate



Operational tests 

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Spent refractories 


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and optimising the 

recycling 

of secondary 

metallurgy slags 


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During solidification of secondary steelmaking slag 

some dicalciumsilicate (C 2S) is built, mostly. By 

further cooling C 2S transforms from � - to � - 

modification. The transformation is accompanied by 

an increase in volume of 11 % of the crystals. The 

increase in volume destroys the structure of slag. 

The transformation causes several problems: 

� formation of dust, 

� fine grained materials are hardly used in 

civil engineering, 

� progressive leaching according to 

the high specific surface area. 


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� Solution 1 : rapid cooling of the slag 

SiO2 8,5 

Al2O3 32,7 

CaO 45,1 

CaO frei 1 - 5 

porous 

< 1 

amorphous 

Periclase 

(MgO) 

beta-C2S 

X X 

* 

(Ca2SiO4) gamma-C2S 

X 

fine X X X 

X 

X 

(Ca2SiO4) Mayenite 

(Ca12Al14O33) X 

X 

X 

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Borgehalt im Feststoff [mg/kg] 

15000 

13500 

12000 

10500 

9000 

7500 

6000 

4500 

3000 

1500 

0 

02399 

02406 

Abhängigkeit der Borkonzentration im S4-Eluat vom Borgehalt im Feststoff 

02407 

02397 

02405 

02394 

02398 

02408 

02393 

02411 

02412 

02409 

02410 

02400 

02414 

02401 

02416 

02403 

�-C 2S 

Borgehalt Feststoff 

Borkonzentration Eluat 

Trendlinie der Eluatkonzentration 

45 kg Glassrock (B-&P-haltig) 

60 kg Glassrock (B-&P-haltig) 

02404 

02402 

02413 

02424 

02415 

02422 

02417 

02418 

02420 

02421 

02423 

02425 

02419 


30 

25 

20 

15 

10 

5 

0 

Borkonzentration im S4-Eluat [mg/l] 

GFS Bor 

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Conclusion 


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28/04/2011

Presentation - Third International Slag Valorisation Symposium

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