EVALUATION OF IRON ORE SINTERS AND PELLETS FOR BF AND DR USE

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EVALUATION OF IRON ORE SINTERS AND PELLETS FOR BF
AND DR USE

• Presented by MS Mashao
• Kumba Iron Ore

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OVERVIEW

• List of most popular tests performed
• Tumble Strength (ISO 3271)
• Crushing Strength (ISO 4700)
• Swelling Index (ISO 4698)
• Size range
• Reducibility (ISO 4695)
• Relative Reducibility (ISO 7215)
• Reduction Disintegration (ISO 4695)
• Reduction Disintegration and metallization for DR
  feedstock (ISO 11257)

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OVERVIEW

• List of most popular tests performed
• Corex tests
• REAS (Reduktion Erweichung und Abschmelzung)
• Drop tests

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PHYSICAL PROPERTIES

• Important properties
• Size distribution
• Strength
• Degradation

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PHYSICAL PROPERTIES
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PHYSICAL PROPERTIES

• Tumble Strength
• Percentage of 6.3mm fraction gives TI
• Percentage of 0.5mm fraction in gives AI
• Criterion of acceptance
• 70 for TI
• Less than 5 for AI

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PHYSICAL PROPERTIES

• Compression Strength
• Criterion of acceptance
• 250 kg/pellet

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PHYSICAL PROPERTIES

• Characterize material susceptibility to
• Breakage
• Degradation

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METALLURGICAL PROPERTIES

• Important properties
• Reduction Disintegration
• Reducibility
• Swelling
• Sticking
• Softening and melting

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METALLURGICAL PROPERTIES
RDI
RI RR
REAS RUL
REAS
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REDUCTION DISINTEGRATION

• RDI for blast furnace
• RDI for Midrex
• RDI for Corex

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REDUCTION DISINTEGRATION
Blast Furnace Direct Reduction Direct Reduction
- 3.15 mm lt 40
- 0.5 mm lt 5
Acceptable Preferred
-3.36 5 Max. 2
Metallization 91 Min 93
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REDUCTION DISINTEGRATION

• Decrease in burden permeability
• Poor gas distribution
• Scaffolding
• Increases fuel consumption
• Lower productivity
• Increased dust load in off gas
• Material more susceptible between (400-600)C

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REDUCIBILITY
RI RR
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REDUCIBILITY

• Reducibility Index
• Relative Reducibility

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REDUCIBILITY

• Reducibility for sinters generally higher
• Typical values for sinters (1.1 -1.4)/min
• Typical values for pellets (0.8 -1.4)/min
• Final degree of reduction
• Typical value for sinters (60-70)
• Typical value for pellets (50-60)

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REDUCIBILITY

• Productivity requires reducible feedstock
• Reducibility depends on
• Porosity
• Surface area
• Gas-solid contact

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FREE SWELLING INDEX

• General criterion for acceptance
• Swelling not be higher than (25-30)
• Noted that alkalis promote excessive swelling

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FREE SWELLING INDEX

• Increase in volume which in turn decreases voids
  in charge
• Impedes gas flow
• Pressure drop

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STICKING INDEX

• Impact on maximum bustle gas temperature
• Bustle temperature determines overall productivity

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METALLURGICAL PROPERTIES
REAS
REAS
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REAS

• Ideal BF conditions
• Temperature profile increases from ambient to
  1600C in 8hrs
• Sample subjected to a fixed load

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REAS

• Softening temperature
• Melting temperature
• Dripping temperature
• Differential pressure (dP)
• Degree of reduction at time and temperature
• Compaction at time and temperature
• Mass of dripping melt at time

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REAS
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REAS

• General criterion for acceptance
• Cohesive zone should be small but at high
  temperatures
• Relative drip mass at least 70 per cent
• Shape of dP curve
• Width
• Height
• Position of peak(s)

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PELLET vs. SISHEN 20mm
Pellet 20 mm ore
Size Range
9 x 16 mm 85 - Min 95 Pref. 83.5
Fines 5 Max lt 3 Pref. 3.9
Tumble Strength
6.3 mm 92 88
- 0.5 mm 6 4.4
Hot Load
Metallization 98 98
Clustering 0 0
Linder
Metallization 91 95
lt 3.36 5 2.4 (10)
Price /tonne 240 205