Stabilization of MgCr2O4 spinel in slags of the SiO2-CaO-MgO-Cr2O3 system

The objective of this study is to analyze the effect of MgO content and the slag basicity on the stability of the mineralogical species of the SiO2-CaO-MgO-Cr2O3 system. Slag samples were prepared in equilibrium at 1600 degrees C tinder reducing conditions (pO(2) = 10(-9) atm). The MgO content ranged from 0 to 12 mass%, Cr2O3 was 10% and the slag basicity was held at 1 and 1.5. A thermodynamic analysis was carried out to estimate the most stable mineral phases in the slag. Experimental and calculated results show that Cr2O3 is mainly bound into MgCr2O4 spinel phase, even at low MgO content. SEM-EDS results show the evidence of three crystalline structures: (A) Octahedrons which correspond to MgCr2O4 spinel-type compound; (B) Elongated crystals which belong to calcium silicate compounds and (C) Massive grains that correspond to calcium silicates with impurites of Mg and Cr that did not crystallize completely.