1824 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The FeO contents of roasted ore in different cooling
processes were 1.64%, 8.54%, and 14.94%, respectively.
Compared with the nitrogen cooling process, the FeO con-
tent significantly decreased in the air cooling process. This
is because the synthetic magnetite was oxidized by the O2,
and part Fe2+ was oxidized into Fe3+, and the FeO content
decreased. It is also found that the synthetic magnetite was
also partly oxidized in the water quenching process, which
may be caused by the oxygen in the water.
XRD Analysis
To further investigate the mineral phase transformation
in air cooling processes, XRD analysis of roasted ore and
iron concentrate was studied, and the results are shown
in Figure 3. According to the XRD analysis results, the
primary mineral composition of roasted ores was mag-
netite, maghemite, and quartz. However, magnetite and
maghemite are both spinel structure phases, which are
different to identify because of their similar diffraction
characteristic peaks. The gangue mineral in roasted ore was
mainly quartz. Due to its great differences in magnetism
with magnetite and maghemite, it was easily separated from
iron minerals and went into tailings. Thus, the mineral
phase of magnetic iron concentrate was primarily magne-
tite and maghemite. In previous studies, it was believable
that magnetite is very easily oxidized into hematite in the
air-cooling process. Based on Figure 3(b), however, no
hematite characteristic peaks were found in the roasted ore.
Additionally, according to the decrease of FeO content in
roasted ore and magnetic iron concentrate, as shown in
Figure 2(a–b), the synthetic magnetite must be oxidized in
the air cooling process. Combined with the XRD results, it
indicated that most synthetic magnetite was oxidized into
maghemite in the air-cooling process.
VSM Analysis
The Magnetic hysteresis loops of different cooling ores
were analysed using VSM, and the results are shown in
Figure 2. The magnetising roasting and cooling experiments of limonite ore. (a) roasted ore (b) magnetic concentrate (c)
magnetic tailing (d) magnetic separation index

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Extracted Text (may have errors)

1824 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The FeO contents of roasted ore in different cooling
processes were 1.64%, 8.54%, and 14.94%, respectively.
Compared with the nitrogen cooling process, the FeO con-
tent significantly decreased in the air cooling process. This
is because the synthetic magnetite was oxidized by the O2,
and part Fe2+ was oxidized into Fe3+, and the FeO content
decreased. It is also found that the synthetic magnetite was
also partly oxidized in the water quenching process, which
may be caused by the oxygen in the water.
XRD Analysis
To further investigate the mineral phase transformation
in air cooling processes, XRD analysis of roasted ore and
iron concentrate was studied, and the results are shown
in Figure 3. According to the XRD analysis results, the
primary mineral composition of roasted ores was mag-
netite, maghemite, and quartz. However, magnetite and
maghemite are both spinel structure phases, which are
different to identify because of their similar diffraction
characteristic peaks. The gangue mineral in roasted ore was
mainly quartz. Due to its great differences in magnetism
with magnetite and maghemite, it was easily separated from
iron minerals and went into tailings. Thus, the mineral
phase of magnetic iron concentrate was primarily magne-
tite and maghemite. In previous studies, it was believable
that magnetite is very easily oxidized into hematite in the
air-cooling process. Based on Figure 3(b), however, no
hematite characteristic peaks were found in the roasted ore.
Additionally, according to the decrease of FeO content in
roasted ore and magnetic iron concentrate, as shown in
Figure 2(a–b), the synthetic magnetite must be oxidized in
the air cooling process. Combined with the XRD results, it
indicated that most synthetic magnetite was oxidized into
maghemite in the air-cooling process.
VSM Analysis
The Magnetic hysteresis loops of different cooling ores
were analysed using VSM, and the results are shown in
Figure 2. The magnetising roasting and cooling experiments of limonite ore. (a) roasted ore (b) magnetic concentrate (c)
magnetic tailing (d) magnetic separation index

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1823
was processed using low-intensity magnetic separation
with a magnetic intensity of 85.19 kA/m. Finally, the iron
concentrate and magnetic tailing of the roasted ore were
obtained. The yield and recovery were calculated based on
the equations (1–2). In the final stage, the samples were
characterized via chemical element analysis, XRD, and
VSM.
γ= (α-θ)/(β-θ)×100% (1)
φ =(β/α)·(α-θ)/(β-θ)×100% (2)
where α, β, and θ are the iron grades of the roasted ore,
magnetic concentrates, and tailings, respectively, γ is the
yield, and φ is the iron recovery.
Characterization
The chemical elemental analyses of raw ore were con-
ducted the Fe and FeO were determined using chemical
titration method the SiO2, Al2O3, MgO, CaO, and P were
determined using X-ray fluorescence (XRF) spectrometry
(Primus II, Japan) the S was determined using a LECO
SC-144DR sulfur analyzer. The mineralogical composition
of limonite samples was detected by a polycrystalline X-ray
diffractometer (PW3040, PANalytical B.V., Netherlands).
The polycrystalline X-ray diffractometer was equipped
with a 2.2 kW Cu anode with a long, fine-focus ceramic
X-ray tube for generating Cu Ka radiation. Scanning range
during detection was 5–90°, scanning speed was 12°/min.
The XRD patterns were analyzed using the software Jade
(6.5) The PDF cards of magnetite (#19-0629), maghemite
(#39-1346), and quartz (#46-1045) were used to identify
the mineral phase. Hysteresis loops were collected using a
vibrating sample magnetometer (JDAW-2000D, China) at
room temperature. A sample of 50.00 mg was weighed and
placed in the holder, after which the hysteresis loops were
measured within the magnetic field in a range of –915–915
kA/m. Magnetic parameters of saturation magnetization,
remanent magnetization, and coercivity were obtained
based on the hysteresis loops.
RESULTS AND DISCUSSION
Magnetising Roasting and Cooling Experiments
The Magnetising roasting of limonite ore was conducted,
and the high-temperature roasted ores were cooled in air
and nitrogen atmospheres and water quenching, respec-
tively. The elemental analysis of cooling ores and magnetic
separation index are shown in Figure 2(a-d). In the tradi-
tional water quenching and nitrogen cooling process, the
high-temperature magnetite was protected from oxidation.
Thus, the iron concentrate can be easily recovered by mag-
netic separation. According to Figure 3(a), an iron concen-
trate with a grade of 58.12% and recovery of 92.27% was
obtained in nitrogen cooling. Compared with the nitrogen
cooling process, the high-temperature synthetic magnetite
was directly exposed to the air atmosphere in air cooling.
However, a good magnetic separation index with an iron
grade of 55.94% and 93.39% was achieved. Generally, the
high-temperature magnetite would be oxidized into hema-
tite, which is an antiferromagnetic mineral and affects the
subsequent magnetic recovery. Based on Figure 2(d), the
most synthetic magnetite must be oxidized into maghemite
but not hematite. Maghemite is a ferrimagnetic mineral
and can be easily recovered.
Figure 1. The schematic diagram of the laboratory magnetising roasting and cooling experiments of limonite ore

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1823
was processed using low-intensity magnetic separation
with a magnetic intensity of 85.19 kA/m. Finally, the iron
concentrate and magnetic tailing of the roasted ore were
obtained. The yield and recovery were calculated based on
the equations (1–2). In the final stage, the samples were
characterized via chemical element analysis, XRD, and
VSM.
γ= (α-θ)/(β-θ)×100% (1)
φ =(β/α)·(α-θ)/(β-θ)×100% (2)
where α, β, and θ are the iron grades of the roasted ore,
magnetic concentrates, and tailings, respectively, γ is the
yield, and φ is the iron recovery.
Characterization
The chemical elemental analyses of raw ore were con-
ducted the Fe and FeO were determined using chemical
titration method the SiO2, Al2O3, MgO, CaO, and P were
determined using X-ray fluorescence (XRF) spectrometry
(Primus II, Japan) the S was determined using a LECO
SC-144DR sulfur analyzer. The mineralogical composition
of limonite samples was detected by a polycrystalline X-ray
diffractometer (PW3040, PANalytical B.V., Netherlands).
The polycrystalline X-ray diffractometer was equipped
with a 2.2 kW Cu anode with a long, fine-focus ceramic
X-ray tube for generating Cu Ka radiation. Scanning range
during detection was 5–90°, scanning speed was 12°/min.
The XRD patterns were analyzed using the software Jade
(6.5) The PDF cards of magnetite (#19-0629), maghemite
(#39-1346), and quartz (#46-1045) were used to identify
the mineral phase. Hysteresis loops were collected using a
vibrating sample magnetometer (JDAW-2000D, China) at
room temperature. A sample of 50.00 mg was weighed and
placed in the holder, after which the hysteresis loops were
measured within the magnetic field in a range of –915–915
kA/m. Magnetic parameters of saturation magnetization,
remanent magnetization, and coercivity were obtained
based on the hysteresis loops.
RESULTS AND DISCUSSION
Magnetising Roasting and Cooling Experiments
The Magnetising roasting of limonite ore was conducted,
and the high-temperature roasted ores were cooled in air
and nitrogen atmospheres and water quenching, respec-
tively. The elemental analysis of cooling ores and magnetic
separation index are shown in Figure 2(a-d). In the tradi-
tional water quenching and nitrogen cooling process, the
high-temperature magnetite was protected from oxidation.
Thus, the iron concentrate can be easily recovered by mag-
netic separation. According to Figure 3(a), an iron concen-
trate with a grade of 58.12% and recovery of 92.27% was
obtained in nitrogen cooling. Compared with the nitrogen
cooling process, the high-temperature synthetic magnetite
was directly exposed to the air atmosphere in air cooling.
However, a good magnetic separation index with an iron
grade of 55.94% and 93.39% was achieved. Generally, the
high-temperature magnetite would be oxidized into hema-
tite, which is an antiferromagnetic mineral and affects the
subsequent magnetic recovery. Based on Figure 2(d), the
most synthetic magnetite must be oxidized into maghemite
but not hematite. Maghemite is a ferrimagnetic mineral
and can be easily recovered.
Figure 1. The schematic diagram of the laboratory magnetising roasting and cooling experiments of limonite ore