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The study focuses on the use of microwave energy in the reduction roasting followed by magnetic separation studies of an Indian Banded Hematite Jasper (BHJ) ore assaying about 48% Fe. Two coals having different origins have been used as the reductants, and the effects of their petrographical characteristics on the microwave-assisted carbothermic reduction have been discussed. The impacts of various process variables such as microwave power, time, ore and coal size have been studied and subsequently optimized using the Taguchi based statistical design. Microwave power and time are found to be the most influential factors, while the particle sizes of the ore and coal play less significant roles. The coal having higher vitrinite reflectance and lower mineral matter is found to be a better reductant in the microwave roasting as it has given rise to a magnetic concentrate of ~64% Fe with a recovery of 68.4% at process conditions such as a power of 6 kW, time of 16 min and C/Fe ratio of 0.15. In contrast, even at the same C/Fe ratio, the coal having lower vitrinite reflectance and higher mineral matter could generate a concentrate with an iron recovery of 34.59%. The X-Ray Diffraction, optical micrographic, Scanning Electron Microscopic (SEM) and Vibrating Saturation Magnetometry (VSM) studies have been used to characterize the microwave roasted products with an intention to understand the phase changes. [ABSTRACT FROM AUTHOR]

The reduction of iron ore using biomass-based reductants has opened up a new chapter because of its contribution to energy conservation and emission reduction. In this connection, the application of waste coconut shells (CS) as the reductant in the reduction roasting-magnetic separation of an iron ore overburden sample is explored. Characterization studies on the overburden having 49% Fe suggest that the sample is mostly a goethitic ore containing kaolinite as the major gangue mineral. A concentrate with 63.2% Fe at an iron recovery of 66.2% has been obtained from the low-intensity magnetic separation of the overburden roasted at a temperature of 800 °C, time of 60 min and a CS to feed ratio of 0.2. Characterization studies indicate the formation of magnetite and hematite under these optimum conditions, whereas roasting at a temperature of 900 °C and a reductant to feed ratio of 0.3 is found to form feebly magnetic phases like wustite, fayalite and complex iron aluminosilicates resulting in poor iron recovery. The thermo-gravimetric analysis studies explain the disintegration of the biomass and reduction of the iron ore thereby validating the reduction sequence as predicted using the characterization studies. Unlabelled Image • Novel application of coconut shell as a substitute to coal based reductants. • Iron recovery from iron ore overbudren using reduction roasting-magnetic separation. • Product with 63% Fe with an iron recovery of 66% from a feed of 49% Fe. • In-depth mineralogical characterization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pellets prepared from low-grade BHQ using conventional beneficiation and magnetization roasting. • Pellet properties are compared as a function of induration temperature. • Pellets of synthesized magnetite at 1250 °C and hematite at 1360 °C have CCS > 250 kg/pellet, porosity > 25%. • Synthesized magnetite pellet achieved 3.49% RDI, 80.21% RI and 19.38% SI. • Mineralogical changes confirmed using TG-DTA, optical microscope, XRD, FESEM and EDS. A compressive pelletization study, for the utilization of an Indian Banded Hematite Quartzite ore, is presented in this communication. Iron ore concentrates have been generated utilizing the conventional beneficiation process and also by the approach of reduction roasting-magnetic separation. The Fe contents of the hematite and the synthesized magnetite concentrate were found to be 64.22 and 63.80%, respectively. The influence of different factors on the respective physical, chemical, and metallurgical properties of the fired pellets, generated through both the routes, have been compared. The pellets prepared from the synthesized magnetite attain the threshold Cold Crushing Strength (CCS) of 50 kg/pellet at a lower temperature of 1050 °C in comparison to hematite pellets (1100 °C). Also, the threshold CCS of 250 kg/pellet is attained by synthesized magnetite pellets at a lower temperature of 1250 °C compared to hematite pellets (1360 °C). The fired synthesized magnetite pellets also achieve the desired metallurgical properties i.e., Reduction Degradation Index (RDI), Reducibility Index (RI), and Swelling Index (SI) at par with the hematite pellets. Moreover, unlike the hematite pellets, the synthesized magnetite pellets do not need the addition of external carbon during the pellet making. [ABSTRACT FROM AUTHOR]