DRI production

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.

The chemical reactions involved in the direct reduction of iron are the following:

With H2

3Fe₂O₃ + H₂ → 2Fe₃O₄ + H₂O
Fe₃O₄ + H₂ → 3 FeO + H₂O
FeO + H₂ → Fe + H₂O

With CO

3Fe₂O₃ + CO →2Fe₃O₄ + CO
Fe₃O₄ + CO → 3 FeO + CO₂
FeO + CO → Fe + CO₂

With Solid Carbon in reaction

CO₂ + C → 2CO

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.

Overview of direct reduction process types

Direct reduction furnace types

Direct reduction processes for iron

Illustrations of the principal processes are shown below. The Midrex® and Energiron gas-based processes use predominantly iron ore pellets as feedstock, but sometimes with inclusion of lump ore in the furnace charge. The Circored and Finmet / Finored gas-based processes utilize iron ore fines as feedstock.The SLRN coal-based rotary kiln process uses lump ore and, increasingly, pellets as feedstock. There are variants of these processes which are described on the websites of the various technology providers.

Midrex® process

Midrex® direct reduction process flowsheet

Energiron process

Standard Energiron process flowsheet

Watch the Energiron process video below:

Metso:Outotec Circored process

Finmet / Finored Megatrain process

SLRN process

SLRN direct reduction process flowsheet