化工学报 ›› 2019, Vol. 70 ›› Issue (11): 4143-4152.DOI: 10.11949/0438-1157.20190931
收稿日期:
2019-08-13
修回日期:
2019-09-16
出版日期:
2019-11-05
发布日期:
2019-11-05
通讯作者:
杜占
基金资助:
Received:
2019-08-13
Revised:
2019-09-16
Online:
2019-11-05
Published:
2019-11-05
Contact:
Zhan DU
摘要:
从热力学角度出发,揭示了还原条件对高温气基还原过程中颗粒表面铁析出行为的影响规律,提出了通过改变还原气氛调控铁析出形貌的操控方法。研究表明在CO中混入H2可以加快铁晶粒的生长速率,同时增加还原初期矿粉表面的铁形核数量,导致矿粉表面新生成的金属铁由晶须状转变为致密状。随着CO-CO2中CO2含量的升高,矿粉表面新生成的金属铁会由“锋利”的晶须状转变为“仙人掌状”,并且表面铁的分布密度会变小。随着还原温度的降低,矿粉表面铁晶须的强度会变弱。
中图分类号:
杜占. 颗粒表面金属铁析出规律的热力学研究[J]. 化工学报, 2019, 70(11): 4143-4152.
Zhan DU. Thermodynamic studies on behavior of newly formed metallic iron on surface of particles[J]. CIESC Journal, 2019, 70(11): 4143-4152.
Composition | Content /%(mass) |
---|---|
TFe | 61.13 |
FeO | 25.43 |
CaO | 0.83 |
MgO | 4.32 |
Al2O3 | 0.84 |
SiO2 | 6.02 |
TiO2 | 0.11 |
表1 智利精粉的化学组成
Table 1 Chemical composition of Chilean iron ore
Composition | Content /%(mass) |
---|---|
TFe | 61.13 |
FeO | 25.43 |
CaO | 0.83 |
MgO | 4.32 |
Al2O3 | 0.84 |
SiO2 | 6.02 |
TiO2 | 0.11 |
图2 流化还原系统装置
Fig.2 Experimental apparatus used for fluidized bed reduction1—gas cylinder; 2—shutoff valve; 3—mass flowmeter; 4—fluidized bed; 5—electric resistance furnace; 6—thermocouple; 7—temperature controller; 8—pressure sensor; 9—computer
图4 800℃下矿粉在不同比例CO-H2中还原后的表面铁析出形貌(金属化率约为22%)
Fig.4 Surface morphology of as-reduced samples in CO-H2 mixtures at 800℃(metallization degree is about 22%)
图5 纯H2和纯CO中铁矿粉还原初期的剖面图(金属化率约为5%)
Fig.5 Cross sectional views of as-reduced samples in H2 and CO during initial reduction period(metallization degree is about 5%)
图7 铁矿粉在800℃下H2/(H2+CO)=30%(vol)中预还原5 min,然后再在纯CO中还原至金属化率为22%左右时的表面形貌
Fig.7 Surface morphology of as-reduced sample by pre-reduction in H2/(H2+CO)=30%(vol) for 5 min, metallization degree is about 22%
CO2 /(CO+CO2)/%(vol) | ΔG/ (kJ/mol) |
---|---|
10 | -33.8 |
20 | -18.3 |
30 | -8.7 |
CO2 Fe/oxide eq=41.1%(vol) | 0 |
表2 800℃下不同比例CO-CO2中的热力学驱动力
Table 2 Thermodynamic driving forces in CO-CO2 mixtures at 800℃
CO2 /(CO+CO2)/%(vol) | ΔG/ (kJ/mol) |
---|---|
10 | -33.8 |
20 | -18.3 |
30 | -8.7 |
CO2 Fe/oxide eq=41.1%(vol) | 0 |
图9 800℃下矿粉在不同比例CO-CO2中还原后的铁析出形貌(金属化率约为15%)
Fig.9 Surface morphology of as-reduced samples in CO-CO2 mixtures at 800℃(metallization degree is about 15%)
图11 矿粉在纯CO中不同温度下还原后的铁析出形貌(金属化率约为20%)
Fig.11 Surface morphology of as-reduced samples in CO at different temperatures(metallization degree is about 20%)
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