Sponge Iron Plant Model
A small model image of DRI Plant



Introduction to the Sponge Iron Processing

As we familiar with sponge iron many more questions arise. When we want to know about Sponge Iron, then it is very important for us to know its raw material. In the Sponge Iron Processing, we give more attention to these industries for steel making.  Direct Reduced Iron is called as Sponge iron. Generally, we adopted the Coal base DRI (Direct Reduced Iron) rotary kiln process successfully. This is because of the high presence of raw material. We also know the process as SL/RN process. The SL/RN process stands as Stelco-Lurgi (SL) and Steel National Lead (SN).

Besides, Sponge Iron Processing has many parameters to increase the quality. This process also takes a suitable operation for productivity throughout the process.

Sketch Diagram of sponge Iron Plant
Sketch Diagram of Dri Plant

Uses of Non-coking coal

That is to say, Sponge Iron Processing uses Non-coking coal tremendously. Because this is the source of reductant in the reduction of iron oxide. Effective production of the sponge iron from the raw material iron ore.

This depends upon various process parameters. So, this is responsible for consistency in the quality product throughout the operation.


Process Summary of 100 Tpd rotary kiln

The Sponge Iron Processing is called a reduction of iron ore in solid-state. So, that it means reduction takes place without the melting of the iron ore. So, this reduction is done by Sub-Bituminous coal as a reductant.

Moreover, the reduction happens under a controlled atmosphere at the desired temperature and pressure.

Raw material feeding to The Rotary Kiln

Popuri Engineering designed the Rotary Kiln. The kiln length is 42m. and the diameter is 3m. As they designed in such a manner, that solid feedstock runs under kiln bed. This reacts with the gaseous atmosphere throughout the length of the kiln in rotary action.

Within the kiln, the reduction reaction takes place to get the desired metallic Iron. In this way, the rotary action of the kiln makes the hot materials to avoid sticking on the inner surface of kiln.

Discharging of hot material through the cooler

Subsequently, the hot solid metallic Iron (or reduced material) from kiln discharge end flows in rotary action in a Cooler. The cooler length is 22m and the diameter is 2.3m. Then, the hot material cools near about 1000c to avoid reoxidation of hot materials.

So, the principle of rotary action must require positive pressure throughout the whole kiln and cooler. Finally, the materials fell in a belt from the cooler discharge end.

Storing of the sponge Iron

After that, the cooler discharge materials in the belt. This shifts the material to the Product Separation House. Here, magnetic separator separates the charcoal mixed reduced iron. The separations are Sponge lumps, sponge fines, and charcoal.

Electric Furnaces accepts it largely. These Furnaces use these products as raw material for making steel.

Sponge Iron Plant
DRI 100 tpd kiln


First of all, we have strange feelings when we hear that this is a sponge iron. Then we get curious to know it. Since we found Iron ore abundantly as Hematite and Magnetite on earth’s crust in oxide form. By analysis, We found more than 27% Oxygen in Hematite or magnetite ore in Oxide form. These oxygen particles occupy between the Iron ore in compound form in nature.

While performing Sponge Iron Processing in solid-state reduction, only the oxygen part of oxide ore reacts with a gaseous reductant. These reductants remove Oxygen from the ore body making the number of micro holes of cavities in the solid.


The term sponge iron named because of the spongy appearance of the porous solid. But this is not due to the spongy effect of the solid. Due to solid-state reduction, sponge iron retains all other impurities as present in iron ore. Only, Oxygen removal reduces weight.

The concept of sponge iron

For, Sponge Iron Processing, First of all, the concept of sponge iron should be determined. We know the concept when iron ore forms sponge iron.  As we know, Hematite iron ore is the most important raw material for making Sponge Iron. Therefore, Hematite iron ore needs to be studied. The chemical formula for hematite iron ore is Fe2O3.

During reduction, Hematite iron ore changes to metallic iron. This happens after a series of reductions. This solid metallic iron is called sponge iron. The sponge iron is so-called because of its microscopic appearance. A large number of microporous has seen just like a sponge.

The concentration of oxygen in Hematite iron ore

First of all, we have to found oxygen content in hematite ore(Fe2O3). Determination of concentration of oxygen in Hematite iron ore in the following way.

                Fe2O3→ 2Fe + 3O2 → 2 × 55.85  + 3 ×  16

( atomic mass of iron = 55.85u and atomic mass of oxygen = 16u ).

So, this means hematite iron ore Fe2O3 has 11 1.70 parts of iron parts. These parts of iron combine with 48 parts of oxygen.

When 65% of Fe Parts contained in Iron Ore.


The oxygen part is calculated as-.

Since 111.7 parts of     Fe contains     =  48   Parts of    O2.

Similarly,        1 part of     Fe contains             = 48/111.7  Parts of    O2.

Similarly,     65    parts of     Fe contains     = 48×65/111.7 Parts of    O2. = 27.93 (approx.) Parts of    O2.

Composition of Hematite Iron Ore

As we know, Hematite Iron ore contains Fe, O2, and rest are Gangue particle and Loss on ignition(LOI).

Gangue particles such as –

Silicate(SiO2), Aluminates (Al2O3), Calcium Oxide (CaO), Magnesium Oxide (MgO).

lead(Pb),Copper(Cu), Zinc(Zn),Vanadium(V), Sulphur (S),Phosphorous(P).

In the reduction process, when solid metallic Iron is formed, only O2 and LOI are removed. But other elements remain present in the metallic Iron.

This solid metallic Iron is called Sponge Iron. This metallic Iron is lighter than Iron Ore. This is due to the removal of Oxygen and LOI.

Hematite ore contains the chemical composition

If, Hematite Ore has 65% of Fe. Let us know the chemical composition of Hematite ore.


Chemical Composition of Hematite Iron Ore

After Reduction Reaction, Sponge Iron Contains –

The following image shows the chemical composition of sponge iron.

Chemical Composition Of Sponge Iron


Pie Chart

We easily understand the difference between Iron ore and Sponge Iron by the Pie Chart. So, the Pie Chart shows the difference between Iron ore and Sponge Iron.


Pie-Chart Of Iron Ore And Sponge Iron

Characteristics Of Sponge Iron

1) Sponge iron does not contain Oxygen.

2) Attracted by the magnet.

3) Size does not change. That means the same size as of  Iron ore.

4) Picks up little carbon and slightly sulfur.

5) Highly reactivity with moisture.

6) Blackish appearance.



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