Influence of Coal Petrography on Microwave-assisted Carbothermic Reduction Roasting of Banded Hematite Jasper Ore

Abstract

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 similar to 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.