Abstract
This study investigated the high-temperature hydrogen (H2) pre-reduction of oxidatively sintered chromite pellets to reduce the carbon (C) dependence during downstream ferrochrome (FeCr) production. The pellets, obtained from a South African sinter plant, were subjected to reduction temperatures and times of 1400 – 1630°C and 15 – 120 min, respectively. Iron (Fe) and chromium (Cr) metallization peaked at 93.3% and 18.8%, respectively, for samples reduced at 1460°C for 120 min. XRD showed that the as-received pellets encompassed mainly chromite and a sesquioxide phase, which is associated with oxidized chromite. SEM showed that the metallized phases that formed after H2 reduction occurred as finely distributed phases within the chromite particle interiors, which is typical for the H2 reduction of pre-oxidized chromite. This observation suggests that H2 could penetrate the particles, and that reduction was not localized at the particle edges. Prolonged H2 reduction transformed the finely distributed metallic phases into larger conglomerates, concentrated at the chromite particle surfaces. A theoretical process flow showed that the H2 required for reduction is determined by the form of Fe present in the ore. Specifically, the power required to generate the needed H2 to reduce Fe-oxides present per ton of chromite is 271.9 and 395.4 kWh if Fe occurs as FeO and Fe2O3, respectively.