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Basic Agglomeration Technique, Pellet Simulator and other testing facilities at RDCIS

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1. Introduction
1. Sintering and Pelletisation
2. Preparation of Raw Materials
2. Sintering Process
1. Sintering process description
2. Bonding mechanism

3. Pelletisation

• Process Stages
• Advantages of usages of pellets in Blast Furnace
• Pellet testing facilities at RDCIS
• Pilot Scale heat hardening pelltisation unit (60 kg per batch)
• CCS, Porosity, Swelling Index, Blaine no, RDI, RI
• X-Ray CT, XRD

Content

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Agglomeration Processes

1. Sintering 2. Pelletizing 3. Briquetting

• Briquetting: Iron ore fines pressed mechanically with the addition of water or another binder.
• Sintering:
• Presently the most important agglomeration process is down-draught sintering.
• Heating up of the granulated mix to slightly above the softening.
• The spongy sinter cake of size 5- 50 mm obtained.

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• During mining operation of iron ore, about 70% fines (- 8 mm) & 30% lump (8-40 mm) are generated
• Most of the fines contain Fe to the tune of 60% but it can not be charged in the blast furnace due to the size restriction
• Permeability plays a vital role in the blast furnace for production of hot metal
• Blast furnace process is based on counter- current principle basis i.e. charge descends from top and air is supplied from bottom

Why Sintering

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• It is essential to agglomerate the fines to a desired size which can be charged in the blast furnace
• Sintering is techno-economically viable
• Use of sinter has many fold advantages in the blast furnace like :
• Utilization of fines / fines conservation
• Pre-reduced material
• High softening temperature
• Use of flux through sinter
• Higher reducibility of sinter

Why Sintering

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I/o fines 0-10mm (generated )

flux fines 0-3mm (crushed)

fuel fines 0-3mm ( crushed)

wastes 0-3mm (generated in plant)

mill scale 0-10mm (generated in plant)

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• Mixing and Nodulization in balling drum/high intensity mixer with water addition
• Preparation of sinter mix exerts considerable influence on productivity, quality (RDI,RI etc.), consistency of sinter chemistry as well as machine operation

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Raw material preparation for Sintering

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Sintering can be defined as agglomeration of fines into a porous mass by incipient fusion due to the heat generated within the mass itself

Raw Material – Product Sinter

Sintering process

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Sinter Machine

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Different zones in sintering

Typical sintering process

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• Slag Bonding

During sintering liquid slag forms and covers the unmelted ore particles.

• Diffusion bonding

Diffusion bond is based on recrystallisation of the same kind of material.

Recrystallisation is transfer of atoms resulting crystals become bigger due to diffusion. When crystal lattice is heated, vibration of atoms becomes stronger and atoms transfer from original position to another position.

To get good recrystallisation :

Contact among grains of iron ore fines to be increased by

• Small particle size
• High bulk density.

Bonding mechanism

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Solid state reactions during sintering

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Pelletisation- A way Forward for sustainable steel Making…..�

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Why Pelletization

• Various iron ore mines have huge amount of dumped fines & slimes (low grade iron ores) as waste
• Use of these low grade ores in future
• These ores are ground upto micron level at first for its beneficiation
• Utilization of these micro fines is limited in sintering process
• Pelletization is the established route for its effective utilization
• Study in the field of grinding, green pellet preparation and development of proper induration cycle

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Why Pelletization

Pellet improves Blast Furnace Performance:

• more permeability in the stack region resulting in uniform pressure drop
• higher iron content per unit furnace volume due to high bulk density
• more reducible due to high micro-porosity
• high strength (250 kg/pellet)
• higher softening temperature compared to lump ore
• Increase in B.F/c productivity and decrease in coke rate

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Pellet

• Pellets are balls produced from concentrates / natural iron ore fines with some remarkable properties
• Pellets have different mineralogical and chemical composition
• Pellets are produced from the micro-fines of ores (Blaine no range: 1500-3000 cm²/g) with some binders/additives

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Pellet Properties

• Uniform size distribution within a main range of 9-15 mm diameter
• High and even porosity of 25-30%
• High iron content of more than 63% iron
• Practically no loss on ignition or volatiles
• High and uniform mechanical strength
• Low tendency to abrasion and good behaviour during transportation
• Sufficient mechanical strength even at thermal stress under reducing atmosphere

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Size Distribution of Pellets

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Pellet vs Sinter

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Process stages for pellet production

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• Ore and additives are ground
• Ground ore is homogenised and mixed with additives (binding and fluxing agents) such as bentonite or slaked lime and also limestone
• Mixing is carried out by intensive mixers

Grinding, Homogenising and Mixing�

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Production of Green balls in Disc Pelletizer

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Stages of Drying of Green Balls

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Pellet Induration Systems

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Straight Grate vs Grate Kiln Technology

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Compression Strength and Firing Temperature for

Typical Hematite and Magnetite Pellets

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Pilot Pellet Heat Hardening System

Pellet Testing Facilities at RDCIS SAIL

Pellet Heat Hardening System (PHHS), is first of its kind in India, in which all types of iron ores can be tested in auto mode for their amenability to Pelletization. Main features of this equipment are as follows:

• The experimental Pot is designed for 60 kg of green pellet capacity

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• Can simulate the actual pelletization condition, i.e. Pellet induration

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• The pelletization parameters of the in-duration cycle can be optimized for any type of iron ore for achieving the desired quality of pellets

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• PHHS is a Pilot Plant system for simulation of the industrial process steps of Up draft drying, Downdraft drying, Downdraft heating, Down draft firing, Down draft soaking and Up draft cooling in a continuous sequential manner for heat hardening of the pellets

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• Regular experiments conducted with different types of ore/ varying basicity/binder/in-duration cycle to optimise the productivity and quality of pellets

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Pellet Testing Facilities at RDCIS SAIL

Schematic diagram of Pilot Pellet Heat Hardening System

There’s a little bit of SAIL in everybody’s life

There’s a little bit of SAIL in everybody’s life

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Pellet testing Facilities at RDCIS SAIL

All the testing facilities required for pellets are available in RDCIS, Ranchi laboratory. Major available equipments for testing of pellets are as follows:

• Blaine Apparatus
• Laboratory Scale Planetary Mixer
• Laboratory Scale Disc Pelletizer
• Raising Hearth Furnace
• High Temperature Furnace
• CCS Measurement Equipment
• Automatic Mercury Intrusion Porosimeter
• Swelling Apparatus
• RDI and RI Equipment
• Automatic X-Ray Diffractometer (XRD) system
• X-ray Computed Tomography System

Disc Pelletizer

High Temperature Furnace

Mercuy Porosimeter

Swelling/RDI/RI Apparatus

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X-ray Computed Tomography System

• A CT scan or computed tomography scan makes use of computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional (tomographic) images (virtual "slices") of specific areas of a scanned object, allowing the user to see inside the object without cutting.
• Digital geometry processing is used to further generate a three-dimensional volume of the inside of the object from a small series of two-dimensional radiographic images taken around a single axis of rotation.
• An X-ray CT system usually consists of an X-ray source, a sample manipulation system, a radiation detector and a computer system to analyze data.
• The v|tome|x s is a versatile high resolution system for 2D x-ray inspection and 3D failure- and structure analysis. To allow high flexibility, the v|tome|x equipped with both, a 240 kV / 320 W micro-focus tube.
• We do regular characterization of Sinter, Pellet, Coke, Steel (welding, fracture), Aluminium, casting samples of internal and external customers.

X-Ray CT machine

3D image analysis of Iron Ore sinter

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Automatic X-Ray Diffractometer (XRD) system

• Fully Automatic XRD system (Rigaku SmartLab 3 kw)
• Used for phase identification & quantification of Iron ore, sinter, pellet, refractory, flux, waste materials, steel samples etc
• Capable for qualitative and quantitative phase analysis with both standard and standard less method

Pellet testing Facilities at RDCIS SAIL

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X-ray Computed Tomography System

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