Localized Heating and Reduction of Magnetite Ore with Coal in Composite Pellets Using Microwave Irradiation

Abstract

Magnetite iron ore-coal composite pellets were microwave irradiated in N₂ atmosphere with a power supply gradually increased in 2 min intervals from 0.2 up to 2 kW at 2.45 GHz. Electron probe microanalysis (EPMA), X-ray image of SEM micrographs, back scattered electron image (BSE) and Fe, O, S and C mappings of composite pellets irradiated up to different temperatures were obtained. Under the present experimental conditions, pellets heated up to about 800°C without reduction. Above this temperature the reduction occurred stepwise; Fe₃O₄ reduced to FeO between about 800°C and 1000°C and then FeO reduced to Fe from about 1000 to 1250°C average temperatures. The measured temperature appears to reasonable represent the average temperature of the pellet. However inside of the reacting mass localized slightly different temperatures may exist. Point carbon contents of reduced iron inside the composite pellet irradiated up to 1150°C were from almost 0% to 2% with no correlation between with their spatial location inside the pellet. It is concluded that carbon in the microwave irradiated pellet acting as a reducing and heating agent at the same time generates localized reduction microenvironments.