XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1857
Sample Characterization
The metallization degree (MD) was used as the evaluation
indicator for the reduction experiment, as shown in Eq. (1):
MD =MFe/TFe*100% (1)
where MFe and TFe represented the metallic iron and total
iron content of reduced products, respectively.
RESULTS AND DISCUSSION
Effect of Reduction Parameters on Metallization
Degree
Effect of Temperature
Temperature determined the reduction rate of iron miner-
als, and had an essential influence on MD. The effect of
reduction temperature on MD was studied at H2 concen-
tration of 50% and reduction time of 40 min. Figure 5
shows the relationship between MD and temperature.
As the reduction temperature increased from 500 °C
to 550 °C, the MD increased from 44.52% to 59.59%.
However, above 600 °C, there was a significant drop in
MD. When the temperature was increased to 650 °C,
the MD significantly decreased to 42.96%. According to
the previous studies, below 570 °C, the reaction path of
magnetite was Fe3O4 → Fe, while above 570 °C, the reac-
tion path of magnetite was Fe3O4→ FeO→ Fe (Schenk,
2011 Spreitzer and Schenk, 2019b). Previous kinetic stud-
ies suggested that magnetite could be rapidly reduced to
wüstite, and the rate-limiting reaction step was FeO to Fe
(Kim et al., 2021). Therefore, the variation of the reduc-
tion pathway of magnetite may lead to a decrease in MD
at a temperature range of 600 °C–650 °C. Above 700 °C,
MD increased steadily. It was found that at the tempera-
ture of 850 °C, the particles in the bed adhered together
and the defluidization occurred. Therefore, in subsequent
experiments, the reduction behavior of boron-bearing iron
concentrate was investigated at 550 °C and 800 °C.
Effect of H2 Concentration
Reducing agent concentration determined the reduc-
tion rate of iron oxides. The variation of MD in the range
of H2 concentration from 40 to 90% was investigated at a
fixed experimental condition of reduction temperature of
550 °C and 800 °C, reduction time of 40 min, and the
results are shown in Figure 6.
As shown in Figure 6, at 550 °C, the MD increased
substantially with the acceleration of H2 concentration, and
then remained stable. When the reduction temperature was
800 °C, the MD increased almost linearly. With an increase
in H2 concentration, the concentration difference of reduc-
tant between the iron oxide-metallic iron reaction interface
and the particle surface-reducing gas interface increased,
which promoted the diffusion of H2 to the reaction inter-
face and improved the reaction rate. The increase in MD
was not evident when the H2 concentration exceeded 80%,
Figure 5. Effect of reduction temperature on MD
Sample Characterization
The metallization degree (MD) was used as the evaluation
indicator for the reduction experiment, as shown in Eq. (1):
MD =MFe/TFe*100% (1)
where MFe and TFe represented the metallic iron and total
iron content of reduced products, respectively.
RESULTS AND DISCUSSION
Effect of Reduction Parameters on Metallization
Degree
Effect of Temperature
Temperature determined the reduction rate of iron miner-
als, and had an essential influence on MD. The effect of
reduction temperature on MD was studied at H2 concen-
tration of 50% and reduction time of 40 min. Figure 5
shows the relationship between MD and temperature.
As the reduction temperature increased from 500 °C
to 550 °C, the MD increased from 44.52% to 59.59%.
However, above 600 °C, there was a significant drop in
MD. When the temperature was increased to 650 °C,
the MD significantly decreased to 42.96%. According to
the previous studies, below 570 °C, the reaction path of
magnetite was Fe3O4 → Fe, while above 570 °C, the reac-
tion path of magnetite was Fe3O4→ FeO→ Fe (Schenk,
2011 Spreitzer and Schenk, 2019b). Previous kinetic stud-
ies suggested that magnetite could be rapidly reduced to
wüstite, and the rate-limiting reaction step was FeO to Fe
(Kim et al., 2021). Therefore, the variation of the reduc-
tion pathway of magnetite may lead to a decrease in MD
at a temperature range of 600 °C–650 °C. Above 700 °C,
MD increased steadily. It was found that at the tempera-
ture of 850 °C, the particles in the bed adhered together
and the defluidization occurred. Therefore, in subsequent
experiments, the reduction behavior of boron-bearing iron
concentrate was investigated at 550 °C and 800 °C.
Effect of H2 Concentration
Reducing agent concentration determined the reduc-
tion rate of iron oxides. The variation of MD in the range
of H2 concentration from 40 to 90% was investigated at a
fixed experimental condition of reduction temperature of
550 °C and 800 °C, reduction time of 40 min, and the
results are shown in Figure 6.
As shown in Figure 6, at 550 °C, the MD increased
substantially with the acceleration of H2 concentration, and
then remained stable. When the reduction temperature was
800 °C, the MD increased almost linearly. With an increase
in H2 concentration, the concentration difference of reduc-
tant between the iron oxide-metallic iron reaction interface
and the particle surface-reducing gas interface increased,
which promoted the diffusion of H2 to the reaction inter-
face and improved the reaction rate. The increase in MD
was not evident when the H2 concentration exceeded 80%,
Figure 5. Effect of reduction temperature on MD