Reducing gas catalysts for DRI / Midrex processes
The DRI process and reducing gas production
Direct reduced iron (DRI) has become an ever increasing important source of raw material for steel making. DRI is made by reducing iron oxide to metallic iron without melting. In a typical DRI process a reducing gas, containing high concentrations of CO and H2, is fed to a shaft furnace and reacts with iron oxide feed. The chemically bound oxygen is then removed from the iron oxide and consequently oxidises the CO and H2 components of the reducing gas into CO2 and H2O:
- Fe2O3 + 3 CO = 2Fe + 3CO2
- Fe2O3 + 3H2 = 2Fe + 3H2O
The reducing gas may be generated in several ways: traditional steam reforming, Midrex® type low pressure CO2 reforming and coal based gasification methods.
The unique features of the Midrex® type reforming process are that the spent gas from the shaft furnace is partly recycled as the feed gas for the CO2 reformer, and the operating pressure is low.
The catalysts used in CO2 reformers are typically made of toughened alumina supports with nickel as the active catalytic phase. In order to minimise the adverse carbon formation catalysts of varying activities are used in different reactor sections. Additives/promoters are also often used to increase the catalyst activity and selectivity.
The Magcat range of catalysts for DRI processes
Magma has developed the Magcat range of reforming catalysts specifically designed for the Midrex® type reformers. Nickel oxide and promoters are impregnated onto high strength catalyst carriers to provide a range of low, medium and high activity catalysts suitable for a wide range of natural gas compositions.