Effect of particle size composition of iron ore fines on the suitable amount of bonding phase in sintering process
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摘要: 铁酸钙是高碱度烧结矿的主要黏结相，其生成量与烧结矿质量有着密切关系，而适宜的黏结相量也是烧结过程中节能降碳的一个重要因素。以铁酸一钙（CF）为初始黏结相，用赤铁矿（Fe2O3）模拟铁矿粉，研究铁矿粉粒度组成对烧结中适宜的黏结相量的影响。结果表明，随着铁矿粉粒级的增加，获得同一抗压强度时烧结试样所需的黏结相量增加。相同粒度范围下，随着CF含量增加，抗压强度呈先增大后减小的变化趋势，其最大值对应于该粒度下适宜的黏结相量。不同粒级范围下，随着Fe2O3粒级的增加，最大抗压强度呈下降趋势。同时，适宜黏结相量向增加方向偏移。试验还发现，CF与Fe2O3反应有低熔点液相—高铁铁酸钙（Ca3.6Fe14.4O25.2）生成，增加了烧结中黏结相量。新相Ca3.6Fe14.4O25.2的生成随着CF含量增加和Fe2O3粒级减小而增加，揭示了初始黏结相与实际黏结相生成量的关系。Abstract: Calcium ferrite is main bonding phase in high-basicity sinter, its formation is closely related to the sinter quality, and the appropriate amount of bonding phase is also an important factor of energy saving and carbon reduction in the sintering process. In this work, mono-calcium ferrite (CF) as an initial bonding phase and pre-sintered hematite (Fe2O3) powder as iron ore fines were used to investigate the influence of particle size composition of iron ore fines on the appropriate amount of bonding phase in sintering process. The results show that the amount of bonding phase needed for obtaining the same compressive strength of sintered samples increases with the increase of iron ore fines size. At same particle size range of iron ore fines, the compressive strength increases first and then decreases with increase of CF addition, and its maximum value should be corresponding to the suitable amount of bonding phase. At different particle size range, the maximum compressive strength decreases with increase of iron ore fines size, simultaneous the suitable amount of bonding phase shiftes to the direction of increasing bonding phase amount. Besides, CF reacts with Fe2O3 to form a calcium rich-ferrate (Ca3.6Fe14.4O25.2) with the low melting point, increasing the amount of bonding phase in sintering process. The Ca3.6Fe14.4O25.2 formation as a new phase increases with the increase of CF addition and the decrease of iron ore fines size, which revealed the relationship of amount between actual bonding phase and initial one in sintering process.
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Key words:
- sinter /
- iron ore fines /
- particle size /
- bonding phase /
- CF /
- compression strength
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图 1 IPP 6.0对试样断面光学照片上物相的定量流程
Figure 1. IPP 6.0 quantitative process of phase on the optical photos of sample cross-section
图 2 1250 ℃下粒级≤0.15 mm赤铁矿粉加入不同量CF烧结10 min后试样断面光学形貌
Figure 2. Optical photos of cross-section of sample where adding different amount of CF into hematite fines with particle size ≤0.15 mm after sintering at 1250 ℃ for 10 min
图 3 1250 ℃下烧结10 min粒级≤0.15 mm赤铁矿粉试样黏结相生成量与加入CF量的关系
Figure 3. Relationship of bonding phase amount with CF added in hematite samples with particle size ≤ 0.15 mm after sintering at 1250 ℃ for 10 min
图 4 加入10%和20%CF不同粒级赤铁矿粉1250 ℃烧结10 min试样黏结相量变化
Figure 4. Relationship of bonding phase amount of sample with different particle size of hematite fines addition of 10% and 20% CF respectively afrer sintering at 1250 ℃ for 10 min
图 5 加入10%和20%CF不同粒级赤铁矿粉试样1250 ℃烧结10 min的断面光学照片
Figure 5. Optical photos of cross-section of samples with different particle size hematite fines addition of 10% and 20%CF respectively after sintering at 1250 ℃ for 10 min
图 6 1250 ℃烧结10 min后不同粒级赤铁矿粉中加入不同量CF烧结试样的抗压强度变化
Figure 6. Variation curve of compressive strength of sintered samples with different amount of CF in different particle size of hematite fines
图 7 不同粒级赤铁矿粉试样1250 ℃烧结10 min对应的适宜黏结相量变化
Figure 7. Relationship of suitable amount of bonding phase with particle size of hematite fines in sample sintered at 1250 ℃ for 10 min
图 8 粒级≤0.15 mm赤铁矿粉中加入不同量CF在1250 ℃烧结10 min后试样内平均孔径变化
Figure 8. Relationship of average pore diameter with different amounts of CF in samples with particle size ≤ 0.15 mm hematite after sintered at 1250 ℃ for 10 min
图 9 1250 ℃烧结10 min后不同粒级赤铁矿粉中不加CF试样的断面光学照片
Figure 9. Optical photo of cross-section of samples with different particle size of hematite fines without CF after sintered at 1250 ℃ for 10 min
图 10 1250 ℃烧结10 min后不同粒级Fe2O3中不加CF试样的抗压强度和平均孔径关系
Figure 10. Relationship of compressive strength with average pore diameter in samples with different particle sizes of hematite fines without CF after sintered at 1250 ℃ for 10 min
图 11 粒级≤0.15 mm 赤铁矿粉加入不同CF量在1250 ℃烧结10 min试样XRD谱
Figure 11. XRD pattern of samples with particle size ≤0.15 mm hematite fines with different amounts of CF after sintered at 1250 ℃ for 10 min
图 12 不同粒级赤铁矿粉中加入20% CF试样1250 ℃烧结10 min后XRD谱
Figure 12. XRD pattern of samples with different particle size hematite fines and 20% CF after sintered at 1250 ℃ for 10 min
图 13 粒级≤0.15 mm赤铁矿粉中加入不同量CF在1250 ℃烧结10 min试样断面的SEM形貌及能谱
Figure 13. SEM photos and EDS images of samples of ≤ 0.15 mm hematite fines with different amounts of CF after sintered at 1250 ℃ for 10 min
表 1 试样的混合组成
Table 1. Mixed compositions of samples
试样 成分组成/g w(CF)/% w(Fe2O3)/% CF Fe2O3 1 0.00 4.00 0 100 2 0.20 3.80 5 95 3 0.40 3.60 10 90 4 0.60 3.40 15 85 5 0.80 3.20 20 80 6 1.20 2.80 30 70 7 1.60 2.40 40 60 8 2.00 2.00 50 50 
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表 2 粒级≤0.15 mm赤铁矿粉中加入不同量CF烧结试样断面EDS分析结果
Table 2. EDS result of cross-section of sintered sample of ≤0.15 mm hematite fines with different amounts of CF
w(CF)/% 位置 元素含量（y/%） 物相 Fe Ca O 10 P1 28.9 14.4 56.7 CF P2 32.0 8.0 60.0 Ca3.6Fe14.4O25.2 P3 42.5 0.2 57.3 Fe2O3 20 P4 27.9 14.1 58.0 CF P5 32.5 7.6 59.9 Ca3.6Fe14.4O25.2 P6 41.8 0.2 58.0 Fe2O3
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