Direct Reduced Iron (DRI), also called sponge iron,[1] is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) into iron by a reducing gas which either contains elemental carbon (produced from natural gas or coal) or hydrogen.

Direct reduction of iron is the removal of oxygen from iron ore or other iron bearing materials in the solid state, i.e. without melting, as in the blast furnace. The reducing agents are carbon monoxide and hydrogen, coming from reformed natural gas, syngas or coal. Iron ore is used mostly in pellet and/or lumpy form.

Direct Reduction Processes

There are several processes for direct reduction of iron ore:

• gas-based shaft furnace processes (Midrex® and Energiron being the main ones) – accounting for 75.8% of 2019 DRI production (total 108.1 million tonnes);
• gas-based fluidized bed processes (the Finmet / Finored process being the only commercial scale one in operation) – accounting for 0.2% of 2019 DRI production
• coal based rotary kiln furnaces (mainly in India) – accounting for 24% of 2019 production.

Generic illustrations of the types of process are shown in the graphics below.

Direct-reduced iron has about the same iron content as pig iron, typically 90–94% total iron (depending on the quality of the raw ore) so it is an excellent feedstock for the electric furnaces used by mini mills, allowing them to use lower grades of scrap for the rest of the charge or to produce higher grades of steel.