5th International Slag Valorisation Symposium
CONVERT HOT SLAG INTO VALUE-ADDED
MATERIALS BY MODIFICATION METHODS
Yu Li
Ph.D., Associate Professor
State Key Laboratory of Advanced Metallurgy(SKLAM),
University of Science and Technology of Beijing(USTB),
China
Leuven, Belgium
2017-4
Outline
1、Introduction
2、Hot slag Modification
3、Our work on modification
4、Discussion
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Steel slag dump
Introduction
Problems about slag in iron and steel industry
 Huge amount of slag and heat
*810×106 ton Crude Steel (in China, 2016)
 Blast Furnace Slag (BF slag)
slag of 250 ×106 ton (>1400 ℃)
& heat of 15 ×106 tons of standard coal equivalent (tce)
 Steel slag
slag of 100 ×106 ton (>1600,℃) & heat of 6.8 ×106 tons tce
Tapping of BF slag
 Energy: Recovering??
 Mass: Reusing ？value-added??
Tapping of steel slag
* Data from www. worldsteel.org
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How to utilize waste heat and slag?
Table 1 Successful examples for recover waste heat of hot solid or hot liquid
Hot Solid: Separate utilization of heat and mass
Examples
Process
Results of examples
Coke Dry Quenching; Firstly transformation and Coke / Ore quality must
be improved, then its
recover of heat, then use
Heat recovery
heat was recovered if
of cooled solid materials
of sintering ore
possible
Liquid iron liquid
steel by steel-making Conversion of heat and Value added materials
were produced, reprocess;
mass together into new
melting energy of raw
materials
Liquid steel used in
materials were saved
refining process
Hot Liquid: Integrated utilization of heat and mass
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How to utilize waste heat and slag?
Hot slag is solid? 
BF slag
Or liquid? √
 Method: Conversion of heat and mass
together into new materials
-- Hot slag modification
(or hot stage engineering / liquid slag
treatment, ENGSTRÖM, 2011; Dirk
MUDERSBACH,2011; KuÈ hn, M,1997)
Slag  new value-added materials
Heat Required energy for
preparing the materials
Steel slag
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Figure 1 - Two typical methods for hot slag treatments (Bisio, 1997; Fujii et al, 1982; Kasai et al,
1997; Li et al, 2011; Li, Qin, Yu, & Du, 2010; Mizuochi, Akiyama, Shimada, Kasai, & Yagi, 2001; Purwanto et al, 2006,
2010; Qin, Lv, Bai, Qiu, & Chen, 2012; Rowe, 2006;
Sun, 2005; Tiberg,1981; Tsakiridis, Papadimitriou, Tsivilis, &
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Koroneos, 2008; Wang & Cai, 2006; Wang, Zhang, & Qi, 2007; Xing, 2012; Xu, Ding, Cai, Liu, & Ye, 2007)
Hot slag modification?
Two aims for hot slag modification
1) To convert slag into value added modified slag with
improved quality
 Quality of slag*:
volume expansion,
disintegration, heavy metal
leaching, cementitious
reactivity, grindability,
and so on;
oxidation
ferrous oxide
ferric oxide
*(Drissen, Ehrenberg, Kühn, & Mudersbach, 2009; Drissen, Geiseler, Kuhn, & Schrey, 1999; Engstrom, Pontikes, Geysen,
Jones, Bjorkman, & Blanpain, 2011; Kuehn, Drissen, Geiseler, & Schrey, 2001；Engstrom, 2011; Liapis & Papayianni,
2015. Li, Zhao, Zhao, & He, 2013；Li G,5th
Ni International
H. ,2011; Dirk MUDERSBACH,
M.K., Jürgen
GEISELER and Klaus
Slag Valorisation
Symposium
KOCH,,2009)
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Hot slag modification?
2)To convert hot slag into high value added materials
 High value added materials derived slag*:
glass ceramics, mineral wool, fertilizer, foam glass
and so on.
* Pioro & Pioro ，2004 ；Dai, Li, Cang, & Liu，2014； Li, Cang, Mao, & Zhang, 2012,；
Zhang, Liu, Liu, & Yang ，2011；Wang & Liu，2014；Takahashi & Yabuta, 2002; Xiao, Y.
L.,; Liu, Y.; Li, Y. Q.,2011; Takahashi, T.; Yabuta, K., 2002; P. Colombo, G. Brusatin, E.
Bernardo, G. Scarinci. 2003;)
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 Heat consumption for melting modifiers <(>)? Sensible heat of hot slag
< crude modification
>fine modification
Basicity
Illustration for hot slag modification to produce different materials
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Analysis of Heat Balance
 Optimal amount of
Sensible heat of hot slag
Heat for melting modifiers
Sensible heat of modified slag
Basicity
modifiers ranged from 11%
/ kJ
utilization of sensible heat
Basicity
consideration of both
Heat
to 19% under the
and performance of
modified slag.
Proportion of added sand / wt. %
Fig.4 Sensible heat and basicity of modified
molten slag with different addition of sands
X Lu, Y Li, S Ma, W Dai, D Cang. Thermal equilibrium analysis and experiment of molten slag modification by use of
its sensible heat. Chinese Journal of Engineering. 2016. 38（10）: 1386-1392.
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Progress of Crude Modifications
振动器
vibrator
改质剂
Stock
料仓
Bin
Process of industrial test[9]. (a) modification
process of molten slag on site (b) transportation
process of slag pot after modification (c) tipping
process of modified slag pot
EAF
转炉/电炉
(b)
Helical
螺旋输送
Conveyor
机
Hot Slag
渣流
E-1
Platform
平台
(a)
钢质 Modifiers
软管
渣
罐
Table 3 Chemical compositions of different kinds of steel slags wt.%
Modifiers
SiO2
added
Untreated
slag
Modified
slag 1
Modified
slag 2
0
12.6
wt.%
12.0
wt.%
CaO
Al2O3 Fe2O3 MgO
MnO
Basicity
FreeCaO
17.04 40.84 3.19
27.96 3.36
3.9
2.4
5.14
21.66 34.65 6.84
23.29 4.49
4.08
1.6
1.02
21.57 34.87 10.2
20.1
3.82
1.62
0.76
4.55
(c)
[9] X. Lu, Y. Li, S. Ma, W. Dai, D. Cang, “Thermal
equilibrium analysis and experiment of molten slag
th International
5
Slag38Valorisation
modification by use of its sensible heat”, Chinese Journal of Engineering,
(10) 1386-1392Symposium
(2016).
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Grade of magnetic substances
Yield of magnetic substance
Recover rate of iron components
Grade of modified slag
Calcium ferrite ferric oxide +ferrous oxide/ RO
 Magnetite (spinel)
2
1
Fe2O5
Ca2Fe2Ca
O52相特征衍射峰
Basicity
Percent of Mixed quartz wt.%
Nonmagnetic phase
非磁含铁相：
0 Ca2Fe2O5
1 RO
Magnetic
phase
磁性矿相：
5
4
2
6
7
3
Fe3O4
MgFe2O4
MgFeAlO4
FeCr2O4
MgAl0.74Fe1.26O4
MgCr2O4
Nonmagnetic
主含钙相： silicate phase
a Ca2SiO4（#36-0642）
b Ca2SiO4（#33-0303）
c Ca3Mg(SiO4)2
2
0
0
2 b b
3
0
b 6
6 0 5
5 b
4
4
0 1
3
2
5 b
b
b
7 c
a
a
3 1
2
1 bb
b
6
5
4
b
c
7
30
a
a
2
2
3
b
2
3
3
2
5
6
5
b 4
6
5
4
b
3
2
5
b
6
5
4
c
bc
4%河沙空冷改质渣
Mixing
4% quartz
1
1
2
2
3
6
5
1 4
3
2
5
3
2
5
6
5
4
6
5
4
7
7
1
1
8%河沙空冷改质渣
Mixing 8% quartz
1
1
Mixing
12% quartz
12%河沙空冷改质渣
1
1
16%河沙空冷改质渣
Mixing
16% quartz
Mixing 20% quartz
20%河沙空冷改质渣
Magnetite
磁性矿相特征衍射峰
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Phase of different modified slag with
different percent of mixed quartz wt.%
20
a
2
1 6
5
b 4
3
2
5
6
c
5 cb
4
b
RO
RO相特征衍射峰
1
0
aa
40
c c
50
60
Mixing
24% quartz
24%河沙空冷改质渣
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80
Progress of Fine Modification
Figure 3 Sketch of slag modification by a
modifying furnace
Figure 4 Modifying furnace
(1- Modifying Chamber
(MCh), 2- Cyclone Furnace
(Cfu), 3-Hopper)
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Progress of Fine Modification
Figure 5 - Photos of slag modification in
the modifying furnace (A) view from CFu
top (B) modified slag tapping
Glassceramics
GC1
GC2
GC3
Figure 6 – Samples of glass-ceramics
from hot slag
Table 5 – mechanical properties of glass-ceramics
Sintering
Bending strength Vikers hardness Water absorption
rate / %
/ MPa
/ GPa
rate / %
10.45
146.46
6.23
0.07
9.15
120.57
6.79
1.63
3.29
17.36
None
10.01
National Standard：Bending strength > 30MPa
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Discussion
 Hot slag at 1400-1600ºC is
also a good reaction medium
to dispose hazardous solid
waste, such as municipal
solid waste (MSW), dried
sludge and CRD glass.
 If those hazardous solid
waste are directly added into
hot slag, not only melting
energy consumption of hot
slag will be saved, but also
more benefits (environment\
resources) will be obtained.
th
Figure 17
Scheme of a continuous electric cold-top
furnace. (1) Batch feeding; (2) batch; (3) melting tank; (4)
electrodes; (5) throat; (6) riser; (7) crown; (8) closing.
[13]
An electric cold top furnace is particularly
suited for the vitrification of wastes
containing a large amount of highly volatile
heavy metals.
International
SlagPress;
Valorisation
Symposium
13 Chen J. Glass Electric Melting Furnace Technology.5Beijing:
Chemical Industry
2007. (In Chinese)
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Discussion
 Recovery of valuable metals
during modification process
is another meaningful
researches trend.
 Economy could be improved
by such linkage between
recovering metals and
modifying slag.
Figure 18 The IPBM (in-plant byproduct melting process) concept [19]
MEFOS, FEhS and CRM: steel slag and other metallurgical solid wastes, such as dust,
millscale, etc were reduced by a DC furnace, and valuable metals such as Fe, Mn, V, Ni and
Cr were recovered in a metal (alloy) phase and the modified slag were converted into various
slag products, such as clinker cement material, hydraulic binder, slag stones or metallurgical
powder for steel desulfurization.
19. G. Ye, E. Burström, M. Kuhn, J. Piret, “Reduction of steel-making slags for recovery of valuable metals and oxide materials”,
5th International Slag Valorisation Symposium
Scandinavian Journal of Metallurgy, 32 7-14 (2003).
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Discussion
 Some critical issues :
1. Low viscosity（flowability）of hot slag during modification.
2. Heat conservations of hot slag after tapped；Related measures,
such as slag insulation agent, preheating slag ladle and a special
heat preservation ladle should be adopted.
3. Online quality control for raw hot slag or modified slag.
4. Performance and environmental effects of modified materials on its
application.
5. Matching of energy flow and mass flow for the whole processes,
especially for fine modification process.
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Conclusions
 As hot slag is liquid when taped, integrated utilization of
waste heat and mass to produce value-added materials (hot
slag modified method) has a higher energy and exergy
recovery efficiency
 Hot slag modified method will promote formation of a new
and high efficient industrial ecologic chain (both energy
and mass flow) among metallurgy, environment and silicate
industry in the future.
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Thank you!
Yu LI , Wenbin DAI, Daqiang CANG, Zhancheng Guo
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