Technologies Available

Different Technologies are available for converting Iron ore fines into pellets like Vertical shaft Furnace technology, Rotary kiln technology, etc. But the most proven and accepted technology for Hematite Ore  is the straight traveling grate technology. In-fact major Pelletization Plants in India and around the world are working on Straight Grate Technology.

Different Technologies for Pelletization:

Vertical Shaft Kiln Technology.

• Old Technology.
• Heating of Green Balls in small quantity.
• Output - Poor Quality.
• Suitable for Magnetite Ore (with specific Grade) Only.

Rotary Grate Kiln Technology

• Preferably suited for magnetite ores.
• Drying, preheating, Indurations, Cooling cycles are carried out in different units like straight grate for pre-heating rotary grate kiln annular cooler
• Many transfer points, hence heavy generation of fines.
• Fines create accretion problems and affect the productivity.
• Power and fuel consumption higher because of seal leakage.
• Less efficient thermal process.
• Difficult waste heat recovery system.
• Technology not in use internationally. No plants in India, yet !
• Higher wear of refractories because kiln refractories are subjected to thermal cycling each revolution & abrasion from pellets.
• All repairs of the grate component occur “off line”.
• The complex chain grate in the grate kiln process must be shut down & cooled for maintenance.
• Single Burner in Rotary Kiln - Low Flexibility.

The Grate-Kiln-Technology was earlier developed by a American company Allis Chalmer. Similar technology is now offered by Chinese Companies.

Basically, this technology is suitable for Magnetite Ore (Fe₃O₄). In their Technology, material moves on Straight-Travelling-Grate-bar till it attains the temperature of 800°C  to 1000°C . Thereafter it is transferred to rotary kiln where the temperature is further raised up-to 1250 - 1300°C.
At 800°C, the Magnetite Ore gets converted into Hematite Ore (Fe₂O₃) in an exothermic reaction. The liberated heat hardens the green balls which is helpful in withstand the tumbling impact in the Rotary kiln. Thus the green balls in the kiln do not break.

In the case of Hematite Ore, which is abundantly available in India, the exothermic reaction is not possible and hence the hardening of the balls simply does not take place.

TISCO have put up Pelletizing Plant with Grate Kiln Technology similar to Chinese design at Noamundi. But, due to difficulties, finally the plant was scrapped.

Practically, for using the above technology for hematite ore, the extra long Straight Travelling Grate-bar system with Stainless Steel alloy is required which can withstand temperature more than 1200°C by which green balls attain necessary strength at 1200°C so that  they will not crack while transporting to rotary kiln as well as will withstand the tumbling pressure of rotary kiln. along with Rotary Kiln and cooler which not only make it expensive against Straight Travelling Grate technology but also it needs a high maintenance.