XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1843
concentration of 60%, reduction time of 20 min, and gas
flow rate of 800 mL/min.
As observed in Figure 4(a), the metallization rate grad-
ually increased with rising temperatures, accompanied by
a decrease in FeO content. At 800 °C, the metallization
rate reached 76.89%. Further temperature increase did
not significantly alter the metallization rate. At 900 °C, a
slight decrease in metallization rate was observed, with an
approximately 3% increase in ferrous content. This could
be attributed to changes in the morphology of iron or the
formation of iron agglomerates as the temperature rises,
hindering the contact of some FeO with the reduction
gas. Additionally, due to the distinctive oolitic structure,
enclosed hematite within gangue may not fully reduce.
With rising temperatures, iron oxides which have not been
reduced to iron might react with gangue, yielding new
iron-containing substances.
Effect of H2 Concentration
Under the experimental conditions of a reduction tem-
perature of 800 °C, H2 concentration ranging from 10%
to 90%, a reduction time of 20 min, and a gas flow rate of
800 mL/ min, the influence of reduction H2 concentration
on the degree of metallization of reduction products was
examined, as presented in Figure 4(b).
Figure 4(b) illustrated the impact of different concen-
trations on the metallization rate of the reduced products. It
was observed that the metallization rate gradually increased
with concentration. Below 40%, the metallization rate rose
rapidly from 3.63% to 66.13%, with the reaction being
most rapid. Beyond 60%, the increase in metallization rate
became less pronounced. It was likely that some iron min-
erals in the ore were closely embedded with gangue, mak-
ing it difficult to come into contact with gas. Considering
industrial practicality, along with cost and safety concerns
associated with high-concentration hydrogen use, a hydro-
gen concentration of 60% was chosen for the test.
Effect of Reduction Time
Figure 4(c) explored the effect of reduction time on the
degree of metallization of reduction products under the
conditions of reduction temperature of 800 °C, H2 concen-
tration of 60%, reduction time of 0–30 min, and gas flow
rate of 800 mL/min.
From Figure 4(c), it can be seen that the metallization
rate gradually increased with the increase of time, and when
the time was 20min, the metallization rate was 76.45%,
and continued to extend the time, the metallization rate
did not change much. While observing the content of FeO,
at 2.5 min, the ferrous iron content was very low, this was
because a large amount of hematite or magnetite have not
been reduced, the reaction was not enough. When the reac-
tion was started at 5 min, most of the hematite has been
reduced to wüstite or magnetite, and at this time, the con-
tent of FeO can be up to 42.13%. As the time continues to
increase, the FeO content gradually decreased. When the
reaction time was 25 minutes, increasing the time further
did not cause significant changes in the ferrous content.
This may be due to the generated iron layer covering the
surface of the iron oxide, preventing the diffusion of hydro-
gen gas.
Effect of Particle Size
In order to consider the actual industrialization, there may
be 0.074~0.038 mm ultra-fine particles in the fluidization.
Therefore, the metallization degree of 0.15~0.074 mm and
0.074~0.038 mm reduction products was further studied
under the conditions of reduction temperature of 800 °C,
H2 concentration of 60%, reduction time of 20 min, and
gas flow rate of 800 mL/min.
As shown in Figure 4(d), when comparing the metalli-
zation rates of the two particle sizes at the same temperature,
it was observed that the reaction of fine particles was signifi-
cantly faster than that of coarse particles. For instance, at a
temperature of 750 °C, the metallization rate of fine par-
ticles reached the maximum value of 80.93%, which was
10% higher than that of coarse particles. Additionally, it
was noted that the FeO content continued to increase with
a rise in temperature, indicating that it might not be an
error but rather a phenomenon worthy of exploration.
Process Mechanism Analysis
X-Ray Diffraction Analysis
In order to study the phase transformation of oolitic hema-
tite during the reduction roasting process of fluidized
hydrogen, the reduction products were analyzed by XRD.
The results were shown in Figure 5–7.
Figure 5 presented the XRD patterns of the reduced
samples at different temperatures. From Figure 5(a), it
could be observed that the diffraction peak corresponding
to metallic iron gradually increases with the rise in reduc-
tion temperature. After the temperature reached 800°C, the
change in the diffraction peak of metallic iron became less
pronounced, indicating a relatively stable content of metal-
lic iron in the mineral beyond 800°C, and no new metallic
iron was formed. On the other hand, there was an obvious
magnetite diffraction peak below 750°C, and the magne-
tite diffraction peak gradually weakened with the increase
of temperature. When the temperature exceeded 750 °C,
the peak of magnetite became very small, and at this point,
concentration of 60%, reduction time of 20 min, and gas
flow rate of 800 mL/min.
As observed in Figure 4(a), the metallization rate grad-
ually increased with rising temperatures, accompanied by
a decrease in FeO content. At 800 °C, the metallization
rate reached 76.89%. Further temperature increase did
not significantly alter the metallization rate. At 900 °C, a
slight decrease in metallization rate was observed, with an
approximately 3% increase in ferrous content. This could
be attributed to changes in the morphology of iron or the
formation of iron agglomerates as the temperature rises,
hindering the contact of some FeO with the reduction
gas. Additionally, due to the distinctive oolitic structure,
enclosed hematite within gangue may not fully reduce.
With rising temperatures, iron oxides which have not been
reduced to iron might react with gangue, yielding new
iron-containing substances.
Effect of H2 Concentration
Under the experimental conditions of a reduction tem-
perature of 800 °C, H2 concentration ranging from 10%
to 90%, a reduction time of 20 min, and a gas flow rate of
800 mL/ min, the influence of reduction H2 concentration
on the degree of metallization of reduction products was
examined, as presented in Figure 4(b).
Figure 4(b) illustrated the impact of different concen-
trations on the metallization rate of the reduced products. It
was observed that the metallization rate gradually increased
with concentration. Below 40%, the metallization rate rose
rapidly from 3.63% to 66.13%, with the reaction being
most rapid. Beyond 60%, the increase in metallization rate
became less pronounced. It was likely that some iron min-
erals in the ore were closely embedded with gangue, mak-
ing it difficult to come into contact with gas. Considering
industrial practicality, along with cost and safety concerns
associated with high-concentration hydrogen use, a hydro-
gen concentration of 60% was chosen for the test.
Effect of Reduction Time
Figure 4(c) explored the effect of reduction time on the
degree of metallization of reduction products under the
conditions of reduction temperature of 800 °C, H2 concen-
tration of 60%, reduction time of 0–30 min, and gas flow
rate of 800 mL/min.
From Figure 4(c), it can be seen that the metallization
rate gradually increased with the increase of time, and when
the time was 20min, the metallization rate was 76.45%,
and continued to extend the time, the metallization rate
did not change much. While observing the content of FeO,
at 2.5 min, the ferrous iron content was very low, this was
because a large amount of hematite or magnetite have not
been reduced, the reaction was not enough. When the reac-
tion was started at 5 min, most of the hematite has been
reduced to wüstite or magnetite, and at this time, the con-
tent of FeO can be up to 42.13%. As the time continues to
increase, the FeO content gradually decreased. When the
reaction time was 25 minutes, increasing the time further
did not cause significant changes in the ferrous content.
This may be due to the generated iron layer covering the
surface of the iron oxide, preventing the diffusion of hydro-
gen gas.
Effect of Particle Size
In order to consider the actual industrialization, there may
be 0.074~0.038 mm ultra-fine particles in the fluidization.
Therefore, the metallization degree of 0.15~0.074 mm and
0.074~0.038 mm reduction products was further studied
under the conditions of reduction temperature of 800 °C,
H2 concentration of 60%, reduction time of 20 min, and
gas flow rate of 800 mL/min.
As shown in Figure 4(d), when comparing the metalli-
zation rates of the two particle sizes at the same temperature,
it was observed that the reaction of fine particles was signifi-
cantly faster than that of coarse particles. For instance, at a
temperature of 750 °C, the metallization rate of fine par-
ticles reached the maximum value of 80.93%, which was
10% higher than that of coarse particles. Additionally, it
was noted that the FeO content continued to increase with
a rise in temperature, indicating that it might not be an
error but rather a phenomenon worthy of exploration.
Process Mechanism Analysis
X-Ray Diffraction Analysis
In order to study the phase transformation of oolitic hema-
tite during the reduction roasting process of fluidized
hydrogen, the reduction products were analyzed by XRD.
The results were shown in Figure 5–7.
Figure 5 presented the XRD patterns of the reduced
samples at different temperatures. From Figure 5(a), it
could be observed that the diffraction peak corresponding
to metallic iron gradually increases with the rise in reduc-
tion temperature. After the temperature reached 800°C, the
change in the diffraction peak of metallic iron became less
pronounced, indicating a relatively stable content of metal-
lic iron in the mineral beyond 800°C, and no new metallic
iron was formed. On the other hand, there was an obvious
magnetite diffraction peak below 750°C, and the magne-
tite diffraction peak gradually weakened with the increase
of temperature. When the temperature exceeded 750 °C,
the peak of magnetite became very small, and at this point,