Pelletization of a Low-Grade Indian Chromite Overburden: Optimizing the Induration Parameters and Understanding the Consolidation Behavior

High-quality pellets have been developed from a low-grade Indian chromite overburden containing high silica in the present study. The thermodynamic, hot-stage microscopic, and thermogravimetric analyses of the overburden and pellet mixes predict the temperature of formation of low melting slag phases at various basicity. A temperature in the range of 1200 °C to 1300 °C and basicity between 0.10 and 0.15 have been found ideal for the initiation of the slag phases, whereas higher conditions lead to softening of the pellets. The effect of basicity, binder content, induration temperature, and time on the physical and metallurgical properties of the indurated pellets has been investigated. A binder content of 1 wt pct, basicity of 0.15, induration temperature of 1250 °C, and a time of 20 minutes are optimum to provide the desired properties to the pellets. X-ray diffraction and Scanning Electron Microscopy coupled with Energy Dispersion Spectroscopy analysis reveal that under the optimum conditions, hematite recrystallization and slag formation impart the needed strength (133.8 kg/pellet), porosity (27.8 pct), tumbler index (99.2 pct), RI (76.2 pct), and RDI (1.2 pct). Conversely, increasing the basicity and the induration temperature results in the melting of the slag phases and, therefore, impair the consolidation of the pellets.