Direct-Reduced Iron (DRI)
Definition - What does Direct-Reduced Iron (DRI) mean?
Direct-reduced iron (DRI) is a type of alternative iron produced from heating iron ore by a reducing gas generated from natural gas or coal. DRI is used as feedstock in electric-arc furnaces, blast furnaces and in other iron and steel-making processes.
It contains from 90 to 97 percent pure iron, the rest being mainly carbon with trace amounts of other impurities. Since the reduction process consumes enormous amounts of natural gas, it is economically viable only where natural gas is abundant and relatively cheap.
Direct-reduced iron is also known as sponge iron due to its porous nature.
Corrosionpedia explains Direct-Reduced Iron (DRI)
Direct reduced iron is a metallic iron product made from iron ore pellets, lumps or fines which is reduced (by removing only the oxygen) from the ore at a temperature below the melting point of the iron.
DRI product is made by converting iron ore into purer, metallic iron without actually melting the ore. There are several specific processes to achieve this that are differentiated by the furnace type, reductant fuel (coal or natural gas) and the form of iron ore input (lump, pellet, fines). Although there are many ways to make direct-reduced iron products, the method using a moving-bed-stack furnace, natural gas and iron ore pellets has become the most common and is often referred to as DRI.
Directly reduced iron is highly susceptible to oxidation and rusting if left unprotected, and is normally quickly processed further to steel. The bulk iron can also catch fire since it is pyrophoric.
DRI is not useful by itself, but can be processed to create wrought iron. It is removed from the furnace, called a bloomery, and repeatedly beaten with heavy hammers and folded over to remove the slag, oxidize any carbon or carbide and weld the iron together. This treatment usually creates wrought iron with about three percent slag and a fraction of a percent of other impurities. Further treatment may add controlled amounts of carbon, allowing various kinds of heat treatment.