Materials Transactions, Vol. 52, No. 8 (2011) pp. 1705 to 1708
#2011 The Japan Institute of Metals
RAPID PUBLICATION
Upgrading of Manganese from Waste Silicomanganese Slag
by a Mechanical Separation Process
Byung-Su Kim1 , Soo-Bock Jeong1; * , Mi-Hee Jeong1 and Jae-Wook Ryu2
1
Korea Institute of Geoscience & Mineral Resources (KIGAM), 92 Gwahang-no, Yuseong-gu, Daejeon 305-350, Korea
Korea Research Association of New Iron and Steel Making Technology, 19F Posteel Tower,
735-3 Yeoksam-dong, Kangnam-gu, Seoul 135-923, Korea
2
Large amounts of silicomanganese slag are generated and discarded from the silicomanganese alloy smelting furnaces that treat
ferromanganese slag to produce silicomanganese alloy, which contain 10–14 mass% Mn. It is thus important to find a possibility for recovering
manganese from silicomanganese slag in terms of environmental and economic points of view. Upgrading of manganese from the
silicomanganese slag for recycling the slag back to the silicomanganese furnaces must be necessary to decrease the slag volume which causes
irregularities in their operation. In this study, a physical separation process for the upgrading of manganese from silicomanganese slag discarded
has been suggested. The process first grinds silicomanganese slag between 500 mm and +75 mm, followed by the dry magnetic separation
process to separate and concentrate manganese from the ground slag. Based on the results obtained, a manganese rich slag which contains over
20 mass% manganese was calculated to be separated and concentrated from silicomanganese slag under a magnetic field of about 6,000 Tesla
using the proposed process. The manganese rich slag obtained should be used as a manganese resource for manufacturing silicomanganese alloy.
[doi:10.2320/matertrans.M2011114]
(Received April 14, 2011; Accepted May 25, 2011; Published July 25, 2011)
Keywords: recycling, manganese, silicomanganese alloy, silicomanganese slag, magnetic separation
1.
Introduction
In a typical semi electric arc smelting furnace operation for
manufacturing silicomanganese alloy, production of 1 kg of
silicomanganese alloy is accompanied by generation of about
1.2 kg of silicomanganese slag. Currently, about 84,000 tons
of silicomanganese slag is produced each year from semi
electric arc smelting furnace during the production of
silicomanganese alloy at Dongbu Metal Company in Korea,
which is simply used as a road pavement material or
discarded at dump sites. Since the natural manganese oxide
concentrates are becoming low grade and complex and the
use of manganese continues to increase in the special steel
industry, the amount of the slag generated in the silicomanganese alloy smelting processes will rise concurrently.
The discarded slag usually contains 10–14 mass% Mn that
can be recovered. It was thus highly desirable to develop a
novel process for recovering manganese from the slag in
order to utilize effectively manganese resources and minimize the environmental problems caused by the slag of which
the generation amount will increase in the future.
Recycling of silicomanganese slag back into the silicomanganese alloy smelting furnace would not only reduce an
environmental liability caused by its dump-site but also
decrease manganese ore consumption by recovering manganese contained in the slag. However, the gangue materials
contained in the slag beside manganese have to be removed
prior to feeding the slag into the silicomanganese alloy
smelting furnace. This is due to the increase in slag volume,
which can cause detrimental effects in the smelting operation.
Thus, the upgrading of manganese from the silicomanganese
slag must be required to recycle the slag back into the
silicomanganese alloy smelting furnace. So far, a few
*Corresponding
author, E-mail: [email protected]
hydrometallurgical processes to recover manganese from
secondary manganese sources like waste batteries and spent
electrodes, spent catalysts, steel scrap, sludge and ferromanganese slag are suggested.1,2) However, very little data on
the utilizing of silicomanganese slag as a manganese resource
are available. Specially, the upgrading of manganese from
silicomanganese slag by physical separation processes has
not been reported in literature.
Therefore, the present research is concerned with experimental investigations for the upgrading of manganese from
silicomanganese slag by a physical separation process that is
relatively simple and without generating any water wastes.
The proposed process involves grinding and magnetic
separation steps. It is thus thought that the physical separation
process is relatively simple and low cost investment
compared with conventional hydrometallurgical processes.
The aim of this study is to investigate a feasibility process for
the upgrading of manganese from silicomanganese slag to
utilize it as a manganese resource for manufacturing
silicomanganese alloy.
2.
Experimental
The raw material used in the experiments was a
silicomanganese slag discarded from semi electric arc
smelting furnace during the production of silicomanganese
alloy at Dongbu Metal Company in Korea. The slag was
verified to has a complex amorphous structure with a
composition mainly of MnO-SiO2 -CaO-Al2 O3 system by Xray analysis. Table 1 shows the average chemical compositions of the slag. The main ingredients contained in the
slag are 14.1 mass% Mn, 38.6 mass% SiO2 , 15.7 mass%
CaO and 14.8 mass% Al2 O3 . In the study, the slag was first
ground by a jaw, hammer and pulverizer. The particle size
of the powder ranged under 500 mm. The powder was then
1706
B.-S. Kim, S.-B. Jeong, M.-H. Jeong and J.-W. Ryu
Table 1 Average chemical composition of the slag used in this study
(mass%).
Zn
Pb
Mn
Cr
Al2 O3 CaO MgO
P
Na
K
Fe
Silicomanganese slag
Jaw crushing
SiO2
0.02 0.01 14.10 0.01 14.76 15.67 4.83 0.09 0.62 2.25 0.77 38.61
Hammer crushing
Pulverizing
Sieving
-500 ~ +280 µm
-280 ~ +200 µm
-200 ~ +150 µm
-150 ~ +75 µm
Magnetic separation
Fig. 2 The experimental flow sheet.
20
90
Mn
Fe
Results and Discussion
It is already known that manganese minerals are separated
in commercial magnetic separators.3,4) The magnetic separation technology was thus chosen to separate and concentrate
manganese from waste silicomanganese slag in this study.
In order to feed the silicomanganese slag into the dry
magnetic separator, the slag was first ground into under
15
30
1
Yield (%)
sieved to four sizes, +0.280 mm, +0.200 mm, +150 mm and
+75 mm. After that, dry magnetic separation was conducted
at a magnetic field range of 5;00010;000 Tesla for each the
particle sizes. The dry magnetic separator used was one
of the cross-belt types made by ERIEZ manufacturing
company (Model: H.C.B), of which the maximum magnetic
field strength was 15,000 Tesla. Figure 1 is a schematic
diagram of the magnetic separator apparatus. In the
magnetic separation experiment, the particles were continuously fed into magnetic field by an induced roll. Then,
non-magnetic particles were thrown off the roll into the
tailings compartment, whereas magnetic were gripped,
carried out of the influence of the field and deposited into
the magnetic compartment. Figure 2 shows the experimental
flow sheet. Samples before and after the separation experiments were analyzed for Fe by a potassium dichromate
titration method and Si by the loss in weight on volatilization with hydrofluoric acid. Also, Mn, Al, Ca, Mg, Zn, K
and Na were determined by the inductively coupled plasma
(ICP) method (JY-38 plus, Horiba Ltd., Kyoto, Japan). The
solution for ICP analysis was prepared by decomposition
with concentrated inorganic acids. Also, the morphological
characterization of the samples was performed using a
scanning electron microscope (SEM, JSM-6380LV, JEOL
Ltd., Tokyo, Japan) equipped with an energy dispersive
X-ray spectrometer (EDS, Link Isis 3.0, Oxford Instrument
plc, Oxon, U.K).
3.
60
Schematic diagram of the magnetic separator apparatus.
Content (mass%)
Fig. 1
10
0
0
-500 ~ +280 -280 ~ +200 -200 ~ +150 -150 ~ +75
Particle size, µm
Fig. 3 The relationship between the contents of manganese and iron and
the percentage yield of each particle sizes.
500 mm, and then the powder was sieved into several sizes.
Figure 3 shows the relationship between the contents of
manganese and iron and the percentage yield of each particle
sizes. The figure shows that the contents of manganese
and iron for all particle sizes are almost steady to be 14–
15 mass% and under 1 mass%, respectively. Thus, it was
verified that the particle separation on the upgrading of
manganese form silicomanganese slag is not effective.
The magnetic separation for the upgrading of manganese
form silicomanganese slag was carried out at a magnetic field
range of 5;00010;000 Tesla using the dry magnetic
separator. Figure 4 shows the relationship between the
contents of manganese and iron and the percentage yield of
magnetic particles with the magnetic field strength for each
the particle sizes. Shown in the figure is that the contents of
manganese and iron in the magnetic particles separated
increases with decreasing in the magnetic field strength for
all particle sizes. This might be the reason why most of
manganese contained in the raw silicomanganese slag exists
in a mixture consisting of Mn, Mn-Fe, MnO and Mn-Fe-O
compounds which are para-magnetic.3,4) Figure 5 shows
SEM-EDS results of the raw silicomanganese slag particles.
Upgrading of Manganese from Waste Silicomanganese Slag by a Mechanical Separation Process
75
Mn
Fe
25
30
5
0
0.5
0.7
45
15
30
10
15
5
0
0
15
0
0.5
1
Magnetic strength, Tesla
30
(c) Particle size=-200 µm ~ +150 µm
25
0.7
1
Magnetic strength, Tesla
30
Mn
Fe
75
(d) Particle size=-150 µm ~ +75 µm
15
5
Content (mass%)
30
60
20
15
45
10
30
5
Yield (%)
45
Yield (%)
Content (mass%)
60
15
75
Mn
Fe
25
20
10
60
20
Yield (%)
45
15
75
Mn
Fe
25
20
10
(b) Particle size=-280 µm ~+200 µm
60
Yield (%)
Content (mass%)
30
(a) Particle size=-500 µm ~ +280 µm
Content (mass%)
30
1707
15
0
0
0
0
0.5
0.7
1
0.5
Magnetic strength, Tesla
0.7
1
Magnetic strength, Tesla
Fig. 4 The relationship between the contents of manganese and iron and the percentage yield of magnetic particles with the magnetic field
strength for each particle sizes.
Element
Mn
Fe
O
Si
Ca
Al
Mg
1
0.00
0.00
43.73
1.77
53.07
0.71
0.71
2
7.32
0.00
43.65
34.84
6.50
4.31
0.94
Content (mass%)
Particle number
3
4
12.71
59.46
0.00
5.87
40.78
19.20
24.00
4.56
8.73
6.00
7.58
1.63
2.06
1.21
5
16.65
8.56
31.12
19.92
9.93
8.81
3.30
6
18.36
8.49
25.31
18.17
13.82
6.81
2.56
Fig. 5 SEM micrograph of the raw silicomanganese slag with EDS of
selected particles.
The figure indicates that manganese-rich particles (particles
4-6) contain relatively much iron compared with manganesepoor particles (particles 1-3), while the manganese-poor
particles (particles 1-3) contain a lot of gangue minerals like
silicon, calcium and aluminum instead of iron. Thus, it was
thought that since the manganese-poor particles which are
relatively non-magnetic tend to be separated into the
magnetic particles at strong magnetic field, the contents
of manganese and iron in the magnetic particles separated
decreases with increasing in the magnetic field strength. But,
it was very difficult to measure experimentally the magnetic
strength for each particle in the study. From Fig. 4, it was
also examined that the content of manganese in the magnetic
particles separated from all particle sizes is over 20 mass% at
a magnetic field of 5,000 Tesla. Thus, the magnetic particles
separated should be used as a manganese resource for
manufacturing silicomanganese alloy because manganese
rich slag containing over 20 mass% manganese has been
used for production of silicomanganese alloy in the duplex
processing.5) Based on the magnetic separation experimental
results, Fig. 6 shows the relationship between the content of
manganese, the percentage recovery of manganese and the
percentage yield of magnetic particles with the magnetic field
strength. From the figure, manganese rich slag containing
over 20 mass% manganese was calculated to be obtained
from the magnetic separation process under the condition of a
magnetic field of about 6,000 Tesla for the silicomanganese
slag ground into the particle size range of 500 mm þ75 mm. At the conditions, the percentage recovery of
manganese and the percentage yield were calculated to be
33% and 24%, respectively. Under the experimental con-
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B.-S. Kim, S.-B. Jeong, M.-H. Jeong and J.-W. Ryu
4.
30
100
Conclusion
Yield(Ymp )
80
Mn Contents(C Mn )
Mn Content 20mass%
20
60
40
Mn Recovery 33%
10
Yield 24%
20
Contents (mass%)
Recovery ratio of Mn and
yield of magnetic particles (%)
Mn Recovery(RMn )
0
0
0.5
0.7
1.0
Magnetic strength, Tesla
Fig. 6 The relationship between the content of manganese, the percentage
recovery of manganese and the percentage yield of magnetic particles with
the magnetic field strength. (Particle size: 500 mm þ75 mm).
ditions considered in the study, the relationship equation for
the percentage recovery of manganese and percentage yield
of magnetic particles at each magnetic field strength is also
given
RMn ¼ 0:071 Ymp CMn
A physical separation process to separate and concentrate
manganese from silicomanganese slag discarded from semi
electric arc furnace during the production of silicomanganese
alloy was suggested in the study. The proposed process
consisted of two major steps, grinding and magnetic
separation steps. The content of manganese in the magnetic
particles separated by the magnetic separation process was
over 20 mass% for the particle size range of 500 mm þ75 mm at a magnetic field strength of 5,000 Tesla. Using the
process suggested, the manganese rich slag containing over
20 mass% manganese from the silicomanganese slag was
calculated to be obtained at a magnetic field of about 6,000
Tesla for the silicomagnese slag ground into the particle size
range of 500 mm þ75 mm.
Acknowledgement
This research was supported by the Research Project
funded by the Ministry of Knowledge and Economy of
Korea.
REFERENCES
ð1Þ
where RMn is the percentage recovery of Mn, Ymp is the
percentage yield and CMn is the content (mass%) of Mn in the
magnetic particles separated. Therefore, it was considered
that the process developed is a possible method to separate
and concentrate manganese from the silicomanganese slag
discarded from semi electric arc furnace during the production of silicomanganese alloy.
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