Phase development in Iron Sinter Test Pots Cooled with Liquid Nitrogen or Water

Authors:

T van den Berg and JPR de Villiers

University of Pretoria

Contribution to Colloquium: Pelletising and Sintering in the Ferroalloy and Iron Making Industry

Content

• • • • •

Introduction Experimental Procedure Results Conclusions Future work

Introduction

• • •

Sinter properties are dependent on the phase composition

–

Many studies on the final sinter product Evolution of phases during intermediate stages of the process need investigation

–

During the heating stage

– –

At maximum temperature – reducing conditions During air cooling - oxidising conditions Quench the test pot to study the reaction sequences and formation of phases in the sinter

–

Mineralogy, microstructure and their evolution can be categorized with the ultimate aim understand the sequence of reactions during sintering

Experimental Procedure

• • • • •

A normal sinter pot test was started Liquid nitrogen or water was used to quench the reactions Air suction was not stopped Pot was then opened and split through the middle Samples were then collected from the middle section of the pot

–

To eliminate edge effects

Experimental Procedure

Ore Material % 45.50

Return fines Fuel Lime Dolomite 29.00

4.71

3.20 6.42 Waste materials 6.56 Water 4.60

Experimental Procedure

•

Liquid nitrogen cooled pot test:

–

Sinter process was complete from top to bottom

–

Samples taken at numbered locations

–

Sample 8 is the grid layer that consists of sinter

Experimental Procedure

•

Water cooled pot test:

–

Sinter process was quenched

–

Samples taken at numbered locations

–

Sample 9 represents the grid layer

Experimental Procedure

• •

Liquid nitrogen cooled test:

– –

7 samples analysed with XRD Samples 2, 4 and 6 was analysed with SEM and microscope Water cooled test:

–

8 samples analysed with XRD

–

Future work will include micro analysis of the phases

Results

Nitrogen Cooled Pot Test

1600 1400 1200 1000 800 600 400 200 0 7: 00 8: 00 9: 00 10 :0 0 11 :0 0 12 :0 0 13 :0 0

Time (minutes)

14 :0 0 15 :0 0 16 :0 0 Top Middle Bottom Quench process was not effective – heating of the lower part of the pot

Results

Water Cooled Pot Test

1400 1200 1000 800 600 400 200 0 6: 59 7: 59 9: 21 10 :4 0 10 :5 8

Time (minutes)

11 :3 1 12 :1 7 Top Middle Bottom Quench process much more effective – lower part of the pot was not heated

Results

XRD Results for Liquid Nitrogen Cooled Pot Test

100 80 60 40 20 0 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 C2S 9.39

9.53

9.54

11.12

8.09

8.56

6.01

Hematite 1.7

5.36

3.31

3.54

14.66

27.89

31.56

Magnetite 73.37

71.12

72.04

77.8

59.79

49.52

46.56

SFCA 15.54

14 15.11

7.55

17.46

14.03

15.87

100 80 60 40 20 0 Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 C2S 8.6

9.75

10.17

9.2

16.28

11.34

3.27

0

Results

Water Cooled Pot Test

Hematite 4.81

6.17

3.92

12.7

3.15

13.3

30.94

72.31

Magnetite 71.08

68.5

78.5

75.2

72.39

65.73

60.2

21.23

SFCA 15.51

15.58

7.41

2.9

8.17

9.63

5.59

6.46

Top of pot: Magnetite Pore

Results

SFCA Glass Hematite

MgO

0.0

3.3

2.9

Al 2 O 3

0.3

1.2

1.6

SiO 2

0.4

1.6

5.1

CaO

0.3

4.7

8.4

Fe 2 O 3

99.0

88.0

80.9

MnO

0.0

1.2

1.2

Mineral

Hematite Magnetite SFCA

Middle of pot: Hematite SFCA

Results

Pore Magnetite

MgO

0.0

2.9

1.9

Al 2 O 3

0.0

1.1

1.4

SiO 2

0.8

0.0

4.5

CaO

0.2

1.3

8.4

Fe 2 O 3

98.9

88.9

80.3

MnO

0.0

5.9

3.6

Mineral

Hematite Magnetite SFCA

Bottom of pot: Slag SFCA

Results

Magnetite Hematite

MgO

0.1

0.0

0.4

Al 2 O 3

0.2

0.3

0.6

SiO 2

0.2

0.7

16.8

CaO

0.1

3.4

32.1

Fe 2 O 3

99.4

95.6

49.9

MnO Mineral

0.0

0.1

0.1

Hematite Magnetite Slag

Conclusions

• •

Liquid nitrogen cooled pot test:

–

It is evident from the time-temperature curves and presence of SFCA at the bottom of the pot that the pot test was not cooled effectively

–

Microscope analyses show that SFCA is associated with magnetite

–

The top and middle parts of the pot contain mainly magnetite crystals with secondary hematite on the edges

–

The bottom of the pot contains massive hematite with magnetite on the edges Water cooled pot test:

–

The time-temperature curve and SFCA content show that is was cooled efficiently

Future work

• •

Further microscopic analyses of the water cooled pot test will be conducted in order to determine which phases are associated with different temperature zones This data will then be applied in further investigation into the kinetics of SFCA formation

Acknowledgements

Prof JPR de Villiers for supervising the project Andre Dippenaar (Kumba Iron Ore) for designing and performing the pot tests Carel Coetzee for assistance with the SEM analyses Renard Chaigneau for helpful comments