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Z. Yu et al.
production, the BF accounts for approximately 50% of the total energy consumption and generating most CO 2 . Consequently, decreasing energy consumption and
reducing CO 2 emission in BF is important.
Carbon composite briquette (CCB) represents a class of materials produced by
agglomerating fine powders of carbonaceous materials with iron ore fines. Charging
CCB in BF is considered to be a state-of-the-art technology to achieve these targets
[1]. Much work has been performed on the preparation method of CCB [2–4] and
some types of CCB have been adopted in commercial plants [4, 5]. Presently, to
understand CCB reaction behavior in BF becomes important as the CCB reaction
directly related to the change of sinter reduction and coke gasification in the BF upper
part, and thus to the improvement of BF energy efficiency. CCB reaction behavior in
BF could be influenced by many factors. Generally, the reactivity of the employed
carbon material plays significant roles. Presently, all of these studies were carried
out under simulated BF conditions. However, in actual practice, the BF is with high
pressure. Therefore, these researches are still insufficient to understand how the coal
reactivity influences CCB reaction in BF.
This research aimed to reveal correctly the CCB reaction in BF by modeling.
Thereafter, the influence of coal reactivity on CCB reaction behavior in BF was
investigated.
Method of Numerical Investigation
CCB Reaction Model
The CCB model developed by the present authors [6] was applied. The CCB model
is applied to describe CCB reaction behavior above the cohesive zone (CZ) in BF
(the temperature range of CZ is from 1473 to 1673 K). The gangue in CCB usually
includes SiO 2 , CaO, Al 2 O 3 , and so on. In the BF upper part, CCB softening or
melting could not occur and reactions involving gangue components are not active
because the solid temperature is less than 1473 K, so they are not considered in the
model. The following is the outline. The model is established for the reaction of a
single spherical CCB in BF and thus is one dimensional in the radial direction. The
model includes reactions that occurred in CCB, the internal gas diffusion, and the
mass transfer between CCB and BF gas. The concept of the model is shown in Fig. 1.
Both the gas phase and the solid phase are considered in the model. The gas phase is
an ideal gas and includes CO, CO 2 , and N 2 . The solid phase includes Fe 2 O 3 , Fe 3 O 4 ,
FeO, Fe, and C. Assumptions in the model are (1) CCB volume is constant in the
reaction process, (2) mass transfer by convection is not considered, (3) the involved
reactions are the reactions given in Table 1.
Governing equations of the gas phase are built based on the mass conservation of
CO and CO 2 in the CCB. They are Eqs. (1, 2).
Z. Yu et al.
production, the BF accounts for approximately 50% of the total energy consumption and generating most CO 2 . Consequently, decreasing energy consumption and
reducing CO 2 emission in BF is important.
Carbon composite briquette (CCB) represents a class of materials produced by
agglomerating fine powders of carbonaceous materials with iron ore fines. Charging
CCB in BF is considered to be a state-of-the-art technology to achieve these targets
[1]. Much work has been performed on the preparation method of CCB [2–4] and
some types of CCB have been adopted in commercial plants [4, 5]. Presently, to
understand CCB reaction behavior in BF becomes important as the CCB reaction
directly related to the change of sinter reduction and coke gasification in the BF upper
part, and thus to the improvement of BF energy efficiency. CCB reaction behavior in
BF could be influenced by many factors. Generally, the reactivity of the employed
carbon material plays significant roles. Presently, all of these studies were carried
out under simulated BF conditions. However, in actual practice, the BF is with high
pressure. Therefore, these researches are still insufficient to understand how the coal
reactivity influences CCB reaction in BF.
This research aimed to reveal correctly the CCB reaction in BF by modeling.
Thereafter, the influence of coal reactivity on CCB reaction behavior in BF was
investigated.
Method of Numerical Investigation
CCB Reaction Model
The CCB model developed by the present authors [6] was applied. The CCB model
is applied to describe CCB reaction behavior above the cohesive zone (CZ) in BF
(the temperature range of CZ is from 1473 to 1673 K). The gangue in CCB usually
includes SiO 2 , CaO, Al 2 O 3 , and so on. In the BF upper part, CCB softening or
melting could not occur and reactions involving gangue components are not active
because the solid temperature is less than 1473 K, so they are not considered in the
model. The following is the outline. The model is established for the reaction of a
single spherical CCB in BF and thus is one dimensional in the radial direction. The
model includes reactions that occurred in CCB, the internal gas diffusion, and the
mass transfer between CCB and BF gas. The concept of the model is shown in Fig. 1.
Both the gas phase and the solid phase are considered in the model. The gas phase is
an ideal gas and includes CO, CO 2 , and N 2 . The solid phase includes Fe 2 O 3 , Fe 3 O 4 ,
FeO, Fe, and C. Assumptions in the model are (1) CCB volume is constant in the
reaction process, (2) mass transfer by convection is not considered, (3) the involved
reactions are the reactions given in Table 1.
Governing equations of the gas phase are built based on the mass conservation of
CO and CO 2 in the CCB. They are Eqs. (1, 2).