SPONGE IRON, DIRECT ALSO CALLED REDUCED IRON (DRI), [1] IS PRODUCED FROM THE DIRECT REDUCTION OF IRON ORE (IN THE FORM OF LUMPS, PELLETS, OR FINES) INTO IRON BY A REDUCING GAS OR ELEMENTAL CARBON PRODUCED FROM NATURAL GAS OR COAL. MANY ORES ARE SUITABLE FOR DIRECT REDUCTION.

DIRECT REDUCTION REFERS TO SOLID-STATE PROCESSES WHICH REDUCE IRON OXIDES TO METALLIC IRON AT TEMPERATURES BELOW THE MELTING POINT OF IRON. REDUCED IRON DERIVES ITS NAME FROM THESE PROCESSES, ONE EXAMPLE BEING HEATING IRON ORE IN A FURNACE AT A HIGH TEMPERATURE OF 800 TO 1,200 °C (1,470 TO 2,190 °F) IN THE PRESENCE OF THE REDUCING GAS SYNGAS, A MIXTURE OF HYDROGEN AND CARBON MONOXIDE.[2]

DIRECT REDUCTION PROCESSES CAN BE DIVIDED ROUGHLY INTO TWO CATEGORIES: GAS-BASED, AND COAL-BASED. IN BOTH CASES, THE OBJECTIVE OF THE PROCESS IS TO REMOVE THE OXYGEN CONTAINED IN VARIOUS FORMS OF IRON ORE (SIZED ORE, CONCENTRATES, PELLETS, MILL SCALE, FURNACE DUST, ETC.), IN ORDER TO CONVERT THE ORE TO METALLIC IRON, WITHOUT MELTING IT (BELOW 1,200 °C (2,190 °F)).

THE DIRECT REDUCTION PROCESS IS COMPARATIVELY ENERGY EFFICIENT. STEEL MADE USING DRI REQUIRES SIGNIFICANTLY LESS FUEL, IN THAT A TRADITIONAL BLAST FURNACE IS NOT NEEDED. DRI IS MOST COMMONLY MADE INTO STEEL USING ELECTRIC ARC FURNACES TO TAKE ADVANTAGE OF THE HEAT PRODUCED BY THE DRI PRODUCT.[3]