Abstract:
Ochre is a naturally occurring, friable material commonly associated with different types of iron ore in the Singhbhum Craton of eastern India. It appears in various colors, including yellow, red, gray, and black. The present study focuses on the mineralogical and geochemical characteristics of yellow ochre sourced from the Daitari Iron Ore Mines in Odisha, India, and their processing for potential value addition. Typically, ochre is low in iron content and powdery, often regarded as waste. However, the yellow ochre studied in this article contains ~ 60% iron, ~ 3% combined alumina and silica, and ~ 10% loss on ignition (LOI). This composition is due to the presence of micron-sized hematite and goethite phases. Although laboratory investigations classify this material as a supplement to medium-grade iron ore, it is unsuitable for direct reduction due to its fine particle size and high LOI. To address this, attempts were made to convert the ochre into pellets by optimizing the pelletization process parameters, such as basicity and induration cycles. Pellets with basicity ranging from 0.3 to 0.4 and indurated at 1280 °C for 5 min achieved the desired cold compressive strength (CCS) and porosity values. Additional characterization studies supported the experimental findings, including X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The study demonstrated that the recrystallization of hematite phases during the induration process enhanced the mechanical strength and other properties of the pellets. However, slightly higher basicity and induration parameters negatively impacted pellet porosity by creating low-melting slag phases that filled the pores during the induration process. Finally, reduction tests on these indurated pellets showed that those with a basicity of 0.4, when indurated at 1280 °C and subjected to direct reduction at 1250 °C for 4 h, achieved a metallization rate of 87.23%.
