Reduction Behaviors of Hematite to Metallic Iron …
115
where f (X) is the mechanism model [27], k r is the rate constant. Logarithm treatment
on both sides of Eq. (2) yields
ln
d X
dt
= ln(A) + ln[ f (X )] −
E
RT
(3)
Results and Discussion
According to Huang [28], the intermediate phase, FeO phase, within the process of
Fe 2 O 3 reduction cannot occur at an arbitrary temperature such as reaction temperature
is lower than 570 °C. Consequently, when the reaction temperature T < 570 °C, the
reduction of hematite to iron is described into two reaction processes as [15]
Fe 2 O 3 + 1/3 H 2 = 2/3 Fe 3 O 4 + 1/3 H 2 O
( 4 )
Fe 3 O 4 + 4H 2 = 3Fe + 4H 2 O
( 5 )
Effect of Inlet Gas Flow
As well known, the gas flow rate U g is the main factor affecting external diffusion. Xu
et al. [22, 29] reported that the effect of the external diffusion could be weakened by
increasing the gas flow rate in MFBRA. To explore the effect of U g on the reduction of
hematite, five gas flow rates were selected as 300, 350, 400, 500, and 600 mL/min.
Figure 3 shows the reduction process at different gas flow rates under 500 °C, it
illustrates that the reaction rate increase with increasing U g until U g is higher than
400 mL/min. Thus, the external diffusion is considered to be eliminated significantly
when U g is 400 mL/min, which is finally selected as the gas flow rate in this study.
Effect of Temperature
Figure shows that, with 20% H2-80% Ar, the reduction of Brazilian hematite to
iron at the temperature range from 400 to 570 °C. As Fig. 4b illustrates, for 400
and 500 °C, the reaction rate increased with increasing reaction time at the initial
reaction stage (about X < 0.05), decreased above X = 0.05 until it reached minimum
value (around X = 0.11), and then increased again at the middle stage, and finally
slowly decreased (about X > 0.35); and for 540 and 570 °C, the reaction rate also
115
where f (X) is the mechanism model [27], k r is the rate constant. Logarithm treatment
on both sides of Eq. (2) yields
ln
d X
dt
= ln(A) + ln[ f (X )] −
E
RT
(3)
Results and Discussion
According to Huang [28], the intermediate phase, FeO phase, within the process of
Fe 2 O 3 reduction cannot occur at an arbitrary temperature such as reaction temperature
is lower than 570 °C. Consequently, when the reaction temperature T < 570 °C, the
reduction of hematite to iron is described into two reaction processes as [15]
Fe 2 O 3 + 1/3 H 2 = 2/3 Fe 3 O 4 + 1/3 H 2 O
( 4 )
Fe 3 O 4 + 4H 2 = 3Fe + 4H 2 O
( 5 )
Effect of Inlet Gas Flow
As well known, the gas flow rate U g is the main factor affecting external diffusion. Xu
et al. [22, 29] reported that the effect of the external diffusion could be weakened by
increasing the gas flow rate in MFBRA. To explore the effect of U g on the reduction of
hematite, five gas flow rates were selected as 300, 350, 400, 500, and 600 mL/min.
Figure 3 shows the reduction process at different gas flow rates under 500 °C, it
illustrates that the reaction rate increase with increasing U g until U g is higher than
400 mL/min. Thus, the external diffusion is considered to be eliminated significantly
when U g is 400 mL/min, which is finally selected as the gas flow rate in this study.
Effect of Temperature
Figure shows that, with 20% H2-80% Ar, the reduction of Brazilian hematite to
iron at the temperature range from 400 to 570 °C. As Fig. 4b illustrates, for 400
and 500 °C, the reaction rate increased with increasing reaction time at the initial
reaction stage (about X < 0.05), decreased above X = 0.05 until it reached minimum
value (around X = 0.11), and then increased again at the middle stage, and finally
slowly decreased (about X > 0.35); and for 540 and 570 °C, the reaction rate also