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:
3Fe2O3 + H2 → 2Fe3O4 + H2O
Fe3O4 + H2 → 3 FeO + H2O
FeO + H2 → Fe + H2O
3Fe2O3 + CO →2Fe3O4 + CO
Fe3O4 + CO → 3 FeO + CO2
FeO + CO → Fe + CO2
CO2 + C → 2CO
There are several processes for direct reduction of iron ore:
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 Finmet / Finored gas-based process utilizes 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® direct reduction process flowsheet
Standard Energiron process flowsheet
Watch the Energiron process video below:
SLRN direct reduction process flowsheet
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