Post on 15-Mar-2018
High Temperature Interactivity of Iron Ores in the Cohesive Zone of the Blast Furnace
Liu Xinliang, Wu Shengli, Huang Wei, Zhu Jinming
Doctoral candidate, Liu XinliangPhD supervisor, Prof. Wu Shengli
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Introduction
Iron ores materials
Reducing gas
Cohesive zone
Have great influence on the permeability of blast furnace
Affected by the softening and melting behaviors of iron ores
How does the properties of iron ores effect the formation of cohesive zone?
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Outline1. Observation of softening and melting behaviors of
respective iron ores 2. Primary‐slags properties in blast furnace of respective
iron ores 3. Influence of high temperature interaction between
sinter and acid iron ores 4. Optimization of blast furnace burdens based on high
temperature interaction
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Chemical compositions iron ores(wt%)
Samples TFe FeO CaO SiO2 Al2O3 MgO LOI P S
Sinter S 57.43 8.24 9.41 4.98 1.76 1.66 -- 0.06 0.01
Australian lump ore 57.40 1.20 0.38 5.10 2.61 0.01 9.71 0.05 0.02
South African lump ore 66.57 0.69 0.21 4.37 1.01 0.02 0.55 0.02 0.02
Acid pellet 64.65 0.55 0.30 5.93 0.35 0.59 -- 0.01 0.01
Self-fluxed pellet 65.65 1.29 2.73 2.48 0.76 0.03 -- 0.03 0.01
Raw materials
Observation of softening and melting behaviors
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Water Inlet
Gas Outlet
Gas Inlet
Water Outlet
Thermocouple
Alumina Tube
Samples
CCD Camera
Observation of softening and melting behaviors
Experiment conditionBlow 900 , 10 /min Over 900 , 5 /min Constant at 900 for 60 minReducing gas flow rate , 0.5 L/min
Reducing gas composition Temperature N2 L/min CO L/min CO2 L/min CO/(CO+CO2)
500~900 0.35 0.075 0.075 50%
900 0.35 0.09 0.06 60%
900~1000 0.35 0.105 0.045 70%
1000~1100 0.35 0.12 0.03 80%
>1100 0.35 0.15 ‐‐ 100%
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Observation of softening and melting behaviors
Softening and melting behavior of sinter
The melting of sinter mainly occurs over 1300 , and the melting rate is fast.
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Observation of softening and melting behaviors
Softening and melting behavior of Australian lump ore
The volume of the Australian lump ore slightly increases from 900 to 1050 due to the cracks produced by the reduction. The melting temperature is higher than 1250 and the melting rate is slow.
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Observation of softening and melting behaviors
Softening and melting behavior of South African lump ore
The volume of the South African lump ore obviously increases. The melting temperature is lower than 1300 and the melting rate is a little higher than that of Australian lump ore.
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Observation of softening and melting behaviors
Softening and melting behavior of acid pellet
No volume increase is observed in the softening and melting process, the melting start temperature of acid pellet is around 1250 , and the melting rate is also slow.
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Observation of softening and melting behaviors
Softening and melting behavior of self‐fluxed pellet
No volume increase is observed in the softening and melting process. The melting temperature of self‐fluxed pellet is over 1300 , and the melting rate is much higher than that of acid pellet.
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Observation of softening and melting behaviors
Compare of softening and melting behaviors
The melting temperature and melting rate of the basic iron ores are both higher than that of acid iron ores, so the melting temperature zones of basic iron ores are narrower and the position in the blast furnace are lower.
The volume of lump ores increase in the softening and melting process due to the cracks produced by the reduction, the permeability of the blast furnace decreases due to the volume increase, so the proportions of lump ores in blast furnace burdens are limited.
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Outline1. Observation of softening and melting behaviors of
respective iron ores 2. Primary‐slags properties in blast furnace of respective
iron ores 3. Influence of high temperature interaction between
sinter and acid iron ores 4. Optimization of blast furnace burdens based on high
temperature interaction
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Primary‐slags properties in blast furnace
Experiment method
The experiments are conducted using softening‐melting equipment andthe experimental conditions are as follows.
Iron ores thickness 65 mmcoke thickness 20 mmiron ore diameter 10‐12.5 mmcoke diameter 6.3‐10 mm
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Primary‐slags properties in blast furnace
Primary‐slags formation start temperature
Primary‐slags rapid formation temperature
temperature Dripping
temperature
Stop heating at Tp and cool down the samples to room temperature
Experiment methodPrimary‐
temperature
Primary‐slags formation finish temperature
15/33P, primary‐slags C, coke I, metallic iron
Distribution of primary‐slags samples
Primary‐slags properties in blast furnace
Sinter Australian lump ore
South African lump ore Acid pellet Self‐fluxed
pellet
Flooding phenomena Flooding
phenomena
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Samples FeO CaO SiO2 Al2O3 MgO
Sinter 7.60 49.74 26.51 9.31 6.84
Australian lump ore 18.61 1.92 54.71 23.59 1.17
South African lump ore 16.33 2.65 63.72 16.76 0.54
Acid Pellet 33.70 3.47 53.03 6.01 3.79
Self‐fluxed pellet 5.04 44.78 37.85 11.67 0.66
Chemical compositions of primary‐slags samples
Primary‐slags properties in blast furnace
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Liquid viscosity of primary‐slags calculated by FactSage
Australian lump ore
Primary‐slags properties in blast furnace
South African lump ore
Acid pellet Self‐fluxed Pellet
Sinter
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Primary‐slags properties in blast furnace
Compare of primary‐slags properties
The viscosity of primary‐slags of acid iron ores are much higher than basic iron ores, especially the viscosity of primary‐slags of lump ores. So too many lump ores would decrease the permeability of the blast furnace.
Obvious flooding phenomenon are observed in the primary‐slags formation process of lump ores due to the high viscosity, which would increase the pressure drop of the cohesive zone.
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Outline1. Observation of softening and melting behaviors of
respective iron ores 2. Primary‐slags properties in blast furnace of respective
iron ores 3. Influence of high temperature interaction between
sinter and acid iron ores 4. Optimization of blast furnace burdens based on high
temperature interaction
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Influence of high temperature interaction
Lump ores Lump ores
Volume increase in the softening and melting process
Wide softening and melting temperature zone with primary‐slags of high viscosity
The proportion in blast furnace burdens are limited
Must be used together with basic iron ores to decrease the disadvantages.
Basic ironores
Acid iron ores Diffusion
Ca, Si, Al∙∙∙ High temperature interaction
The interaction degree are different when mixed with different iron ores
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Basic iron ores
Acidiron ores Diffusion
Ca, Si, Al∙∙∙
Sinter Lump
Ca Si Al
950
1150
1300
High temperature interaction
Influence of high temperature interaction
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Influence of high temperature interaction
Compositions of integrated burdens
To study the influence of high temperature interaction, three integrated burdens are designed.
Composition Sinter Australian lump ore South African lump ore Acid pellet
S + ALO 77.34 22.66 ‐‐ ‐‐
S + SLO 75.12 ‐‐ 24.88 ‐‐
S + AP 79.49 ‐‐ ‐‐ 20.51
Compare of acid iron ores and integrated burdens Items Sinter ALO SLO AP S + ALO S + SLO S + AP
S value before meltingkPa∙ 55 77 48 31 30 40 33
Flooding phenomena ‐‐ Obvious Obvious Little ‐‐ ‐‐ ‐‐
Highest pressure dropKPa 2.54 3.62 2.91 2.81 2.32 1.93 1.87
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Influence of high temperature interaction
Softening and melting temperature zone
The softening and melting temperature zone of integrated burdens are all narrower than respective iron ores, and the gas permeability are all better than that of respective iron ores.
The softening and melting temperature zone of integrated burdens are all narrower than respective iron ores, and the gas permeability are all better than that of respective iron ores.
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The calculation data are calculated based proportions of respective iron ores in the integrated burdens. The results means that the actual softening and melting temperature zone are all narrower than the calculation data, and the actual permeability are much better than that of calculation data.
Influence of high temperature interaction
Softening and melting temperature zone
S+ALO S+SLO S+AP S+ALO S+SLO S+AP
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To evaluate the high temperature interaction, the high temperature
interaction indexes are calculated based on the formula
1 2 0
1 2
100aT +bT -TINI= * %aT +bT
（ ）
T1 softening and melting temperature zone of sinter
T2 softening and melting temperature zone of lump ores/pellet
T0 actual softening and melting temperature zone of integrated burdens,
a proportion of sinter in the integrated burdens
b proportion of lump ores/pellet in the integrated burdens.
Influence of high temperature interaction
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High temperature interaction index
Influence of high temperature interaction
The high temperature interaction index between sinter and Australian lump ores are much higher than that of South African lump ore and acid pellet.
S+ALO S+SLO S+AP
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Porosity Higher porosity offers more “channels” for the diffusion.
Australian lump ore > acid pellet > South African lump ore
Contact conditions
Pellet
Point contact
Sinter Sinter lump
Face contact
Influencing factors of high temperature interaction index
Influence of high temperature interaction
The high temperature interactivity of Australian lump ore is highest. The high temperature interactivity of Australian lump ore is highest.
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Outline1. Observation of softening and melting behaviors of
respective iron ores 2. Primary‐slags properties in blast furnace of respective
iron ores 3. Influence of high temperature interaction between
sinter and acid iron ores 4. Optimization of blast furnace burdens based on high
temperature interaction
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Optimization of blast furnace burdens
Two blast furnace burdens are designed based on the high temperature interaction.
Blast furnace burden A: 77% basic iron ores + 23% acid iron ores
Blast furnace burden B: 82% basic iron ores + 18% acid iron ores High temperature Interactivity, Australian lump ore>Acid pellet >South African lump ore
The high temperature interaction of blast furnace burden B is more strong.
Sinter Australian lump ore
South African lump ore
Acid pellet
Self‐fluxed pellet
Blast furnace burden A 77% ‐‐ 14% 9% ‐‐
Blast furnace burden B 70% 18% ‐‐ ‐‐ 12%
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Optimization of blast furnace burdens
The softening and melting temperature zone of blast furnace burden B is about 20 narrower than blast furnace burden A, and the permeability of blast furnace burden B is much better.
Softening and melting temperature zone
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Optimization of blast furnace burdens
Primary-slags distributionPrimary-slags distribution
Blast furnaceburden A
Blast furnaceburden B
Obvious flooding phenomena
No flooding phenomena
The lump ores of high interactivity are more benefit for the blast furnace!
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Conclusions
The volume increase in the softening and melting process, the wide softening and melting temperature zone, the high viscosity of primary‐slags for lump ores would increase the pressure drop of the cohesive zone and decrease the permeability of the blast furnace, so the proportion of lump ores are limited in blast furnace.
The softening and melting behavior and the primary‐slags properties are both improved by the high temperature interaction when sinter are mixed with acid iron ores, and the high temperature interaction are influenced by porosity and contact conditions.
Lump ores of high interactivity, high reactivity and high porosity (such as the Australian lump ore) are more suitable for the blast furnace due to the strong high temperature interaction.
Thanks for your attention !
Doctoral Candidate, Liu XinliangPhD supervisor, Prof. Wu ShengliUniversity of Science and Technology Beijing