Since 1980, this process is realized by means of an external reformer coupled with the typical reduction circuit, including the reactor, in which the reducing gas is circulated in counter current with solid material, that is moving downwards by gravity.
The steam reformer converts the natural gas into H2 and CO (reducing agents) at high temperature and in presence of a Nickel-based catalyst. Hydrogen and Carbon Monoxide are used to carry out the reduction reactions, which transform iron oxide into metallic iron in the reactor. Finally, the ENERGIRON III consists of the typical ENERGIRON ZR reduction circuit coupled with an external steam reformer. This process configuration is selected when the reducing source contains high concentrations of heavy hydrocarbons (HHC). This solution is preferable to other technologies using stoichiometric reformers, because a stoichiometric reformer would require the addition of a turbo-expander to get rid of HHC; on the contrary, by means of the ENERGIRON III technology, the reforming reaction is carried out with excess of steam. Even Sulphur contained in natural gas, which may represent a potential hazard of poisoning the reformer catalyst, for the ENERGIRON III technology is not a limitation, because a natural gas desulphurizing unit is a package included in the steam reformer.
Finally, several advantages can be obtained by using a steam reformer placed off-line from the reducing circuit:
- the reformer is not affected by contaminants coming from the pellets (Sulfur and other poisons for the reformer catalyst)
- the reformer operation is not affected either by upset conditions in the process gas, such as the CO2 and CH4 content
- the reducing circuit can be easily fed with reformed gas only or any mixture of other reducing agents .