What is sponge iron

Sponge iron, also name as direct reduced iron (DRI), is the resulting product (with a metallization degree greater than 82 percent) of solid state reduction of iron ores or agglomerates (generally of high grade), the principal constituents of which are Metallic iron, residual iron oxides carbon’ and impurities such as phosphorus, sulphur and gangue (principally silica and alumina).

Sponge iron/DRI has gained great prominence in some countries as a substitute of steel scrap (partially) in steel making in electric arc furnace and in induction furnace. Direct Reduction is a metallurgical process of producing sponge iron from iron oxides (mainly from lump iron ores or pellets) directly in the solid phase. The product of this solid state route has a honey comb structure with minute pores. Hence this product is most commonly known as sponge iron/direct reduced iron (DRI). In addition to the metallic iron content sponge iron contains some unreduced iron oxides and gangue. Since there is no separation of impurities in DR process, all the gangue present in the original oxide (silica, alumina, oxides of phosphorous) goes in to the product sponge iron. In fact concentration of these oxides increases due to the removal of oxygen to a level of plus 90%.

Chemical Composition of Sponge Iron

Grade Total Iron Metallic Iron
SiO2 + AI2O3
Sio2 Sulphur Phos Combined total of Pb, Zn, Cu,Sn, Cr,Ni,As

1 Plus 91 Plus 82 5 4 0.02 0.06 0.015 2 89- 91 78- 82 6 4 0.03 0.07 0.015 3 85- 91 76-78 8 6 0.03 0.10 0.015

different types

Hot DRI (HBI)

HBI means briquettes made out of sponge iron/DRI produced in gas based direct reduction processes at elevated temperature by the application of external pressure in a more or less close mould.

Hot DRI in the form of pellets, lumps, fines at a temperature of 650-850 deg C is passed through hot briquetting machine where the product is pressed between the rolls at extremely high pressure to produce highly compacted pillow shaped material called hot briquetted iron (HBI).

Cold DRI

While producing sponge iron some amount of sponge fines of minus 4mm is also generated. This sponge fines is briquetted in cold condition using binders in the cold roller press to produce highly compacted pillow shaped material called as cold briquetted iron. (CBI)

The DRI grade chart

Why make sponge iron briquette
For most of the cases in sponge iron briquette making is to deactivate.
Sponge iron is a kind of raw material

1. When using the iron ore to produce
The sponge iron briquette machine

Cold DRI briquette machine

Hot HBI briquette machine

Sponge iron briquette process