high temperature interactivity of iron ores in the ... · pdf filehigh temperature...

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


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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Softening and melting behavior of sinter

The melting of sinter mainly occurs over 1300 , and the melting rate is fast.

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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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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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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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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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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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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 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


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


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Liquid viscosity of primary‐slags calculated by FactSage

Australian lump ore


South African lump ore

Acid pellet Self‐fluxed Pellet

Sinter

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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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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


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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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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.



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.


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High temperature interaction index


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


The high temperature interactivity of Australian lump ore is highest. The high temperature interactivity of Australian lump ore is highest.

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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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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.


345322

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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

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