Effects of MgO and Fe₂O₃ Addition for Upgrading the Refractory Characteristics of Magnesite Ore Mining Waste/By-Products

Abstract

In the context of a circular economy/zero-waste, the conversion of extractive wastes into new products is of particular importance. At the Grecian Magnesite SA mine (Chalkidiki, N. Greece), millions of tons of waste accumulate in the operation field. To achieve these goals, the effect of caustic calcined magnesia (MgO) at 10, 15, and 20 wt.% was investigated in combination with 0.5, 1, 2.5, and 5 wt.% Fe2O3 at 1300 °C and 1600 °C for 120 min. The main refractory properties were determined along with the mineralogical content. The morphological examination has been performed by SEM-EDS analysis. The addition of MgO increases the desired olivine and eliminates the unwanted pyroxenes, causing the formation of magnesium-ferrite and periclase. MgO wt.% addition resulted in the decrease of firing shrinkage at 1300 °C but increased with Fe2O3. At 1600 °C, firing shrinkage had a minimum value at the optimum MgO dose. Mechanical strength at 1600 °C achieved a maximum value at the optimum MgO dose plus 5 wt.% MgO and 2.5 wt.% Fe2O3 due to sintering process/magnesioferrite formation. These results indicate that MgO and Fe2O3 upgrade the refractoriness of magnesite mining wastes due to the diffusion of Fe2O3 in MgO excess.

Keywords

• magnesite mining waste
• MgO additive
• Fe₂O₃ additive
• forsterite (olivine)
• thermal treatment
• refractory products