Decarbonizing Ferrochrome Production Through Hydrogen Pre-reduction of Oxidatively Sintered Chromite Pellets

Abstract

Abstract This study evaluates hydrogen as a pre-reductant for oxidatively sintered chromite pellets to reduce carbon (C) emissions during ferrochrome (FeCr) production. Industrial pellets from four South African sinter plants were reduced with hydrogen at 1100 °C for up to 120 min. Higher Fe metallization (48.1–69.2%) was achieved in pellets exhibiting higher degrees of oxidation (more pronounced Fe-enriched sesquioxide phases), whereas Cr metallization remained negligible (< 2.5%), consistent with its thermodynamic resistance to hydrogen reduction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed that oxidative sintering liberated spinel-bound Fe, improving reducibility. Hydrogen pre-reduction decreased pellet break strength to values comparable to traditional C pre-reduced (Premus-type) pellets, indicating potential suitability for industrial smelting. A preliminary cost analysis showed that the reductant cost to smelt chromite by incorporating a hydrogen pre-reduction step would increase the cost to process 1 kmol of chromite from 4.60 USD (75.65 ZAR, if smelted using anthracite) to up to 15.99 USD (262.83 ZAR, if pre-reduced with hydrogen and then smelted with anthracite). It was demonstrated that integrating oxidative sintering with hydrogen pre-reduction using a vertical moving bed reactor can theoretically reduce C emissions by 25% (assuming pure chromite, i.e., FeCr 2 O 4 ). For the pellets considered here, C emissions may be reduced by 19.7–29.3%, based on their respective Fe- and Cr-oxide contents. Such a decrease corresponds to an estimated reduction of 921 960 – 1 371 240 t CO 2 /annum. These results highlight both the potential and trade-offs of combining oxidative sintering with hydrogen pre-reduction to decarbonize FeCr production. Graphical Abstract