What Is Nickel Pig Iron
The invention of Nickel Pig Iron (NPI) is credited to the Chinese steel makers who wanted a cheaper alternative to pure nickel, although in truth nickel pig iron was developed more than a hundred years ago.
Considered low grade, laterite nickel ores are used in the production of nickel pig iron which in turn is then used in the production of stainless steel instead of using pure nickel. At a time when nickel prices had reached an all time high the production of cheaper nickel pig iron with the added benefit of the iron also contained in the nickel pig iron gave the Chinese producers an added advantage.
Nickel laterite ores used to make nickel pig iron is mostly found in the tropical regions where the high rain fall over many millions of years has leached out much of the magnesium and silica of the original olivine-rich ultramafic rocks. Nickel laterites typically occur in regions where prolonged weathering of ultramafic rocks (containing ferro-magnesian minerals) has occurred, favoured by warm conditions with abundant rainfall. Such deposits commonly exhibit graded layers consisting of:
These laterite ores are found in abundance in Indonesia which along with the deposits in the neighbouring Philippines accounts for nearly 40% of the known world reserves.
Nickel pig iron feed stock is composed of low-grade nickel ore, coking coal, and a mixture of fluxes. The mixture is first calcined and sintered into pellets before being fed into the blast furnace with additional ore and fluxes. Impurities and slags are then removed from the reduced nickel iron melt before the molten nickel-iron is cast into the pig-moulds forming the nickel pig iron.
The Indoferro complex uses the same process to convert nickel laterites into nickel pig iron in the first nickel pig iron producing sintering plant and blast furnace outside China.