1854 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
2012 Wang et al., 2018 Ye et al., 2022). The EAF method
is a mature ironmaking technology, and the key issue is that
the melting boron-rich slag needs to be cooled slowly to
ensure the alkali leaching rate of boron (Wang et al., 2012
Zhan et al., 2007). In addition, adding sodium salt during
coal-based reduction roasting could improve the reactivity
of boron, but sodium salt is not friendly to the environ-
ment and equipment (Li et al., 2016 Zhu et al., 2020).
The consensus of the pyrometallurgical process is that iron
minerals should be selectively reduced to metallic iron. In
contrast, the boron minerals remain oxides, then boron
and iron are separated by subsequent processes. However,
coal-based solid-state high-temperature reduction processes
(1050–1300 °C) cannot avoid the volatilization of boron
due to the long reduction time, and emits considerable
amounts of greenhouse gases (Han et al., 2016 Li et al.,
2014 Li et al., 2022). Therefore, a low-temperature, fossil-
free roasting method for the rapid reduction of boron-bear-
ing iron concentrate is urgently required.
With the continued global concern about the energy
crisis and greenhouse effect, hydrogen storage and produc-
tion technology is developing rapidly, and the production
method has gradually shifted from fossil to renewable energy
(Li et al., 2023). It is found that the reduction speed of H2
as a reducing agent for iron ore is much higher than that of
CO due to its small volume and rapid mass transfer (Du et
al., 2022 Ma et al., 2022 Prabowo et al., 2022 Spreitzer
and Schenk, 2020). Furthermore, the reduction product of
hydrogen is water vapor, which is much more environmen-
tally friendly than fossil fuels. (Vogl et al., 2018). Besides,
the fluidized bed reduction process has recently been widely
discussed. It can directly use fine-grained ores with superior
reaction kinetic advantages, and become the mainstream
hydrogen reduction process in the future (Du et al., 2022
Schenk, 2011 Spreitzer and Schenk, 2019a).
On this basis, a fluidized hydrogen reduction method
was proposed to achieve the rapid metallization of boron-
bearing iron concentrate. The relationship between the
metallization degree and process parameters was inves-
tigated. Besides, the phase transformation and micro-
structure changes at fluidized bed operating temperatures
were discussed comprehensively. As a result, the reduc-
tion behavior of boron-bearing iron concentrate under a
hydrogen atmosphere was revealed, providing a necessary
reference for the low temperature and clean reduction of
boron-bearing iron concentrate.
MATERIALS AND METHODS
Materials
The material was the magnetic separation concentrate
from Fengcheng in Liaoning Province, China. Table 1 and
Figure 1 display the chemical composition and XRD pattern
(PW3040, PANalytical B.V, Netherlands) of the material,
respectively. The result indicated that the TFe content was
50.94%, mainly in magnetite (Fe3O4). The boron-bearing
minerals were ludwigite ((Mg, Fe)2Fe(BO3)O2)) and szai-
belyite (MgBO2(OH)), with B2O3 content of 6.44%. The
gangue mineral was chrysotile (Mg3Si2O5(OH)4), with a
SiO2 content of 4.64%. Figure 2 shows the particle size
distribution of the material (MS 2000, Malvern, England).
The particle size range based on volume was 30–120 μm,
and the average particle size was 72 μm.
The raw material was set in resin and polished. The
microstructure of the sample was recorded using SEM-
EDS (Apreo 2C, Thermo Scientific, American) and the
results are reported in Figure 3. Based on the elemental
distribution, the bright areas in Figure 3 (a) were magne-
tite, the dark gray particles contained Mg, Fe and O ele-
ments, which were identified as ludwigite. Combined with
the Mg, Si and O elements distribution, the szaibelyite and
chrysotile were present in the black regions. These minerals
coexisted closely and had dense structures.
Experimental Procedure
The experimental apparatus for fluidized reduction and
activation roasting of boron-bearing iron concentrate with
H2 is demonstrated in Figure 4. The inner diameter of the
reactor was 25 mm, and a porous quartz plate with a poros-
ity of 15% was in the middle. For the reduction experi-
ment, 10.0 g sample was put into the quartz plate and
nitrogen was introduced to replace the air in the reactor.
After reaching the reaction temperature, the nitrogen was
quickly changed to a mixture of H2 and N2 at a flow rate
of 1000 mL/min under ambient pressure. At the end of the
reaction, the sample was cooled under the protection of N2
to avoid oxidation.
Table 1. Chemical composition of the material
Composition TFe B2O3 FeO SiO2 Al2O3 MgO CaO P S LOI
Content (wt%) 50.94 6.44 24.31 4.70 0.25 13.31 0.51 0.011 0.833 4.63
*TFe: Total Fe content LOL: Loss on ignition.
2012 Wang et al., 2018 Ye et al., 2022). The EAF method
is a mature ironmaking technology, and the key issue is that
the melting boron-rich slag needs to be cooled slowly to
ensure the alkali leaching rate of boron (Wang et al., 2012
Zhan et al., 2007). In addition, adding sodium salt during
coal-based reduction roasting could improve the reactivity
of boron, but sodium salt is not friendly to the environ-
ment and equipment (Li et al., 2016 Zhu et al., 2020).
The consensus of the pyrometallurgical process is that iron
minerals should be selectively reduced to metallic iron. In
contrast, the boron minerals remain oxides, then boron
and iron are separated by subsequent processes. However,
coal-based solid-state high-temperature reduction processes
(1050–1300 °C) cannot avoid the volatilization of boron
due to the long reduction time, and emits considerable
amounts of greenhouse gases (Han et al., 2016 Li et al.,
2014 Li et al., 2022). Therefore, a low-temperature, fossil-
free roasting method for the rapid reduction of boron-bear-
ing iron concentrate is urgently required.
With the continued global concern about the energy
crisis and greenhouse effect, hydrogen storage and produc-
tion technology is developing rapidly, and the production
method has gradually shifted from fossil to renewable energy
(Li et al., 2023). It is found that the reduction speed of H2
as a reducing agent for iron ore is much higher than that of
CO due to its small volume and rapid mass transfer (Du et
al., 2022 Ma et al., 2022 Prabowo et al., 2022 Spreitzer
and Schenk, 2020). Furthermore, the reduction product of
hydrogen is water vapor, which is much more environmen-
tally friendly than fossil fuels. (Vogl et al., 2018). Besides,
the fluidized bed reduction process has recently been widely
discussed. It can directly use fine-grained ores with superior
reaction kinetic advantages, and become the mainstream
hydrogen reduction process in the future (Du et al., 2022
Schenk, 2011 Spreitzer and Schenk, 2019a).
On this basis, a fluidized hydrogen reduction method
was proposed to achieve the rapid metallization of boron-
bearing iron concentrate. The relationship between the
metallization degree and process parameters was inves-
tigated. Besides, the phase transformation and micro-
structure changes at fluidized bed operating temperatures
were discussed comprehensively. As a result, the reduc-
tion behavior of boron-bearing iron concentrate under a
hydrogen atmosphere was revealed, providing a necessary
reference for the low temperature and clean reduction of
boron-bearing iron concentrate.
MATERIALS AND METHODS
Materials
The material was the magnetic separation concentrate
from Fengcheng in Liaoning Province, China. Table 1 and
Figure 1 display the chemical composition and XRD pattern
(PW3040, PANalytical B.V, Netherlands) of the material,
respectively. The result indicated that the TFe content was
50.94%, mainly in magnetite (Fe3O4). The boron-bearing
minerals were ludwigite ((Mg, Fe)2Fe(BO3)O2)) and szai-
belyite (MgBO2(OH)), with B2O3 content of 6.44%. The
gangue mineral was chrysotile (Mg3Si2O5(OH)4), with a
SiO2 content of 4.64%. Figure 2 shows the particle size
distribution of the material (MS 2000, Malvern, England).
The particle size range based on volume was 30–120 μm,
and the average particle size was 72 μm.
The raw material was set in resin and polished. The
microstructure of the sample was recorded using SEM-
EDS (Apreo 2C, Thermo Scientific, American) and the
results are reported in Figure 3. Based on the elemental
distribution, the bright areas in Figure 3 (a) were magne-
tite, the dark gray particles contained Mg, Fe and O ele-
ments, which were identified as ludwigite. Combined with
the Mg, Si and O elements distribution, the szaibelyite and
chrysotile were present in the black regions. These minerals
coexisted closely and had dense structures.
Experimental Procedure
The experimental apparatus for fluidized reduction and
activation roasting of boron-bearing iron concentrate with
H2 is demonstrated in Figure 4. The inner diameter of the
reactor was 25 mm, and a porous quartz plate with a poros-
ity of 15% was in the middle. For the reduction experi-
ment, 10.0 g sample was put into the quartz plate and
nitrogen was introduced to replace the air in the reactor.
After reaching the reaction temperature, the nitrogen was
quickly changed to a mixture of H2 and N2 at a flow rate
of 1000 mL/min under ambient pressure. At the end of the
reaction, the sample was cooled under the protection of N2
to avoid oxidation.
Table 1. Chemical composition of the material
Composition TFe B2O3 FeO SiO2 Al2O3 MgO CaO P S LOI
Content (wt%) 50.94 6.44 24.31 4.70 0.25 13.31 0.51 0.011 0.833 4.63
*TFe: Total Fe content LOL: Loss on ignition.