1922 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
concentrate fluctuated in the range of 56.06% to 56.58%.
As the reduction time exceeded 25 min, the iron grade sta-
bilized within the range of 56.34% to 56.67%, and the iron
recovery in concentrate increased from 94.03% to 96.47%.
Therefore, the optimal reduction time of 40 min was iden-
tified to obtain concentrate with an iron grade and iron
recovery in concentrate of 56.49%, 95.21%, respectively.
Effect of Reductant Concentration
The effect of reductant concentration is a crucial factor
affecting the separation index of concentrate. The concen-
tration of reductant required during the experiment is con-
tinuously controlled, and the CO:H2 ratio of the reductant
is kept constant. The effect of reductant concentration was
performed at a reduction temperature of 540 °C, reduc-
tion time of 40 min, total gas flow of 600 mL/min, and
the reductant concentration ranging from 20% to 40%
(CO:H2=1:3). The results were shown in Figure 5.
When the reductant concentration increased from
20% to 40%, the iron grade in concentrate essentially sta-
bilized, ranging from 56.04% to 56.32%, while the iron
recovery in concentrate gradually increased from 95.24%
to 96.18%. This indicates that the increasing reductant
concentration enhances the transformation rate of hema-
tite to magnetite. Therefore, the corresponding separation
index was achieved, with an iron grade in concentrate of
56.31% and iron recovery in concentrate of 95.43%, at the
optimal reductant concentration of 30%.
Effect of Hydrogen Content in Reductant
The effect of hydrogen content in reductant on the sepa-
ration indexes of the concentrate was examined, and the
results are shown in Figure 6. The effect of hydrogen con-
tent in reductant was investigated in the range of 500 °C
to 600 °C, under other conditions including a reduction
temperature at 540 °C, a reduction time of 40 min, a total
gas flow at 600 mL/min, a reductant concentration of 40%,
and hydrogen as a reductant.
Figure 6 emphasized that the iron recovery in concen-
trate increased from 86.67% to 95.85% and the iron grade
in concentrate decreased from 57.00% to 56.37% as the
hydrogen content in reductant increased from 0% to 75%.
When the hydrogen content in reductant further increased
to 100%, the iron grade and recovery in concentrate
increased from 56.37% to 56.84%, 95.85% to 96.31%,
respectively. In summary, the optimal hydrogen content in
reductant was determined to be 100%, resulting in an iron
grade in concentrate of 56.84% and iron recovery in con-
centrate of 96.31%.
Phase Transformation
The samples at different reduction temperatures and times
were determined by XRD, as depicted in Figure 7. Figure 8
illustrates the XRD pattern of the samples before and after
minerals phase transformation.
As shown in Figure 7(a), with the increase of the
reduction temperature, the intensity of diffraction peaks of
Figure 4. Effect of reduction time on separation indexes
concentrate fluctuated in the range of 56.06% to 56.58%.
As the reduction time exceeded 25 min, the iron grade sta-
bilized within the range of 56.34% to 56.67%, and the iron
recovery in concentrate increased from 94.03% to 96.47%.
Therefore, the optimal reduction time of 40 min was iden-
tified to obtain concentrate with an iron grade and iron
recovery in concentrate of 56.49%, 95.21%, respectively.
Effect of Reductant Concentration
The effect of reductant concentration is a crucial factor
affecting the separation index of concentrate. The concen-
tration of reductant required during the experiment is con-
tinuously controlled, and the CO:H2 ratio of the reductant
is kept constant. The effect of reductant concentration was
performed at a reduction temperature of 540 °C, reduc-
tion time of 40 min, total gas flow of 600 mL/min, and
the reductant concentration ranging from 20% to 40%
(CO:H2=1:3). The results were shown in Figure 5.
When the reductant concentration increased from
20% to 40%, the iron grade in concentrate essentially sta-
bilized, ranging from 56.04% to 56.32%, while the iron
recovery in concentrate gradually increased from 95.24%
to 96.18%. This indicates that the increasing reductant
concentration enhances the transformation rate of hema-
tite to magnetite. Therefore, the corresponding separation
index was achieved, with an iron grade in concentrate of
56.31% and iron recovery in concentrate of 95.43%, at the
optimal reductant concentration of 30%.
Effect of Hydrogen Content in Reductant
The effect of hydrogen content in reductant on the sepa-
ration indexes of the concentrate was examined, and the
results are shown in Figure 6. The effect of hydrogen con-
tent in reductant was investigated in the range of 500 °C
to 600 °C, under other conditions including a reduction
temperature at 540 °C, a reduction time of 40 min, a total
gas flow at 600 mL/min, a reductant concentration of 40%,
and hydrogen as a reductant.
Figure 6 emphasized that the iron recovery in concen-
trate increased from 86.67% to 95.85% and the iron grade
in concentrate decreased from 57.00% to 56.37% as the
hydrogen content in reductant increased from 0% to 75%.
When the hydrogen content in reductant further increased
to 100%, the iron grade and recovery in concentrate
increased from 56.37% to 56.84%, 95.85% to 96.31%,
respectively. In summary, the optimal hydrogen content in
reductant was determined to be 100%, resulting in an iron
grade in concentrate of 56.84% and iron recovery in con-
centrate of 96.31%.
Phase Transformation
The samples at different reduction temperatures and times
were determined by XRD, as depicted in Figure 7. Figure 8
illustrates the XRD pattern of the samples before and after
minerals phase transformation.
As shown in Figure 7(a), with the increase of the
reduction temperature, the intensity of diffraction peaks of
Figure 4. Effect of reduction time on separation indexes