Pelletization of synthesized magnetite concentrate obtained by magnetization roasting of Indian low-grade BHQ iron ore

Abstract In India, the use of iron ore pellets in the blast furnace, electric arc furnace, or sponge iron production is continuously optimized, considering different aspects of the production chain from the run of mining (ROM) to metallic iron depending upon the industrial need and ore availability (recent aggressive iron ore mining auction 2020 in India). The scarcity of high-grade iron ore resource and availability of the considerable quantity of low-grade iron ore fines, banded hematite quartzite (BHQ) ore in mines (mostly in Bihar, Odisha, Madhya Pradesh, and Karnataka), has to lead the way to beneficiate and utilized the concentrate as pellet feed for the steelmaking process. Banded iron ore such as BHQ is one of the potential resources of iron having a total iron content, i.e., Fe (T) of 35–48 wt%, which is lying unutilized in most of the Indian iron ore mines. The challenge before the policymakers and researchers is to think of a sustainable process technology to utilize these iron ore resources wisely. The conventional beneficiation of this type of siliceous BHQ iron ore resource having low iron content is not advisable. Therefore, pelletization of synthesized magnetite concentrate obtained from the magnetization roasting of BHQ emerged as an alternative energy-saving and ore conserving process that may be scaled up and commercialized for low-grade banded iron ores. The pelletization of magnetite concentrate is an independent heat hardening process; thereby requirement of anthracite coal fines as a fossil fuel additive to maintain the temperature gradient from core to the periphery of the pellet can be avoided. Physical properties such as cold crushing strength (CCS) and porosity of the pellets were optimized to study their suitability in the steelmaking process. In this regard, characterization studies of the pellets were performed using X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope, and X-ray micro-computed tomography to understand the microstructural properties of the pellets. The CCS of 255.8 kg/pellet and porosity of 25.42% were achieved at the optimized induration temperature and residence time of 1250 °C (50 °C to 80 °C less than conventional hematite pellet induration) and 10 min, respectively. The properties studied are encouraging and comparable with the pellet prepared from the natural magnetite/hematite ore.