Direct reduction
Directly reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) by a reducing gas or elemental carbon produced from natural gas or coal. Many minerals are suitable for direct reduction.
Reduced iron derives its name from the chemical change that iron ore undergoes when heated in a furnace at high temperatures in the presence of gases rich in hydrocarbons, carbon monoxide, or elemental carbon. Direct reduction refers to processes that reduce iron oxides to metallic iron at temperatures below the melting point of iron. The product of such solid-state processes is called directly reduced iron (DRI).
The reducing gas is a mixture of gases, mainly hydrogen (H2) and carbon monoxide (CO). The process temperature is typically 800 to 1200 °C.