Influence of Coal Reactivity on Carbon Composite Briquette …
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(stage 5); and when the temperature was above 1150 K, the CCB carbon was gasified
by BF gas (stage 6).
The above analysis indicates that the initial temperature of self-reduction in sample
A was 850 K. In the stages with CCB self-reduction involved, sample A presented
a high reaction rate. When the temperature was higher than 1000 K, the reaction of
sample A can increase the local CO partial pressure and decrease the local CO 2 partial
pressure in BF gas (at 1000 K, P CO /P CO2 = 1.0 in BF gas), indicating that the reaction
in sample A has the effects of BF energy-saving (suppressing coke gasification and
prompting sinter reduction). The dominant temperature range for BF energy-saving
was from 1000 to 1150 K. From Fig. 3, it could be observed that the final reduction
fraction of sample A was 1.0 and the final carbon conversion of sample B was 0.90.
High Coal Reactivity
Higher coal reactivity could be represented by decreasing the activation energy of coal
gasification. The reaction development of the CCB with E C = 118 kJ/mol (sample
B) was analyzed, and the results are shown in Fig. 4. From Fig. 4, it is known that
temperature ranges of all individual stages in sample B are stage 1: 500–750 K, stage
2: 750–800 K, stage 3: 800–820 K, stage 4: 820–880 K, stage 5: 880–1140 K, and
stage 6: >1140 K. The initial temperature of self-reduction in sample B was 750 K,
and the dominant temperature range in the reaction of sample B for BF energy-saving
was from 880 to 1140 K. Form Fig. 4, it could be observed that both its final reduction
fraction and its final carbon conversion were close to 1.0.
Therefore, compared to sample A, the initial temperature of self-reduction in
sample B became lower, and the temperature range in the reaction of sample B for
BF energy-saving became wider, and the final carbon conversion in sample B was
higher.
From the above analysis, it is known that to improve the coal reactivity in CCB
could intensify the effect of CCB reaction on BF energy-saving.
Low Coal Reactivity
Lower coal reactivity could be represented by increasing the activation energy of
coal gasification. The reaction development of CCB sample with E C = 158 kJ/mol
(sample C) was analyzed and the results are shown in Fig. 5. Figure 5 shows that
temperature ranges of each stage in sample C are: stage 1: 550–980 K, stage 2: 980–
1150 K, stage 3:1150–1155 K, stage 4: 1155–1170 K, stage 5:1170–1180 K, and
stage 6: >1180 K. Therefore, the initial temperature of self-reduction in sample C
was 980 K, and the dominant temperature range in the reaction of sample C for BF
energy-saving was from 1155 to 1180 K. From Fig. 5, it could be seen that its final
reduction fraction was 1.0, while its final carbon conversion was 0.4.
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(stage 5); and when the temperature was above 1150 K, the CCB carbon was gasified
by BF gas (stage 6).
The above analysis indicates that the initial temperature of self-reduction in sample
A was 850 K. In the stages with CCB self-reduction involved, sample A presented
a high reaction rate. When the temperature was higher than 1000 K, the reaction of
sample A can increase the local CO partial pressure and decrease the local CO 2 partial
pressure in BF gas (at 1000 K, P CO /P CO2 = 1.0 in BF gas), indicating that the reaction
in sample A has the effects of BF energy-saving (suppressing coke gasification and
prompting sinter reduction). The dominant temperature range for BF energy-saving
was from 1000 to 1150 K. From Fig. 3, it could be observed that the final reduction
fraction of sample A was 1.0 and the final carbon conversion of sample B was 0.90.
High Coal Reactivity
Higher coal reactivity could be represented by decreasing the activation energy of coal
gasification. The reaction development of the CCB with E C = 118 kJ/mol (sample
B) was analyzed, and the results are shown in Fig. 4. From Fig. 4, it is known that
temperature ranges of all individual stages in sample B are stage 1: 500–750 K, stage
2: 750–800 K, stage 3: 800–820 K, stage 4: 820–880 K, stage 5: 880–1140 K, and
stage 6: >1140 K. The initial temperature of self-reduction in sample B was 750 K,
and the dominant temperature range in the reaction of sample B for BF energy-saving
was from 880 to 1140 K. Form Fig. 4, it could be observed that both its final reduction
fraction and its final carbon conversion were close to 1.0.
Therefore, compared to sample A, the initial temperature of self-reduction in
sample B became lower, and the temperature range in the reaction of sample B for
BF energy-saving became wider, and the final carbon conversion in sample B was
higher.
From the above analysis, it is known that to improve the coal reactivity in CCB
could intensify the effect of CCB reaction on BF energy-saving.
Low Coal Reactivity
Lower coal reactivity could be represented by increasing the activation energy of
coal gasification. The reaction development of CCB sample with E C = 158 kJ/mol
(sample C) was analyzed and the results are shown in Fig. 5. Figure 5 shows that
temperature ranges of each stage in sample C are: stage 1: 550–980 K, stage 2: 980–
1150 K, stage 3:1150–1155 K, stage 4: 1155–1170 K, stage 5:1170–1180 K, and
stage 6: >1180 K. Therefore, the initial temperature of self-reduction in sample C
was 980 K, and the dominant temperature range in the reaction of sample C for BF
energy-saving was from 1155 to 1180 K. From Fig. 5, it could be seen that its final
reduction fraction was 1.0, while its final carbon conversion was 0.4.