Chromium: A Double-Edged Sword in Preparation of Refractory Materials from Ferronickel Slag

This study reports the role of chromium as a double-edged sword in the preparation of refractory materials from ferronickel slag with the addition of sintered magnesia based on the thermodynamic analysis and experimental exploration of the phase transformation of ferronickel slag during the sintering process. The results of thermodynamic calculation, X-ray diffraction, and electron probe microanalysis revealed that in the presence of sintered magnesia (20 wt %) and Cr2O3 (0-6 wt %), forsterite, donathite (instead of magnesium chromate spinel generated without addition of Cr2O3), magnesium aluminate spinel, and enstatite were formed. The forsterite and spinel phases contributed to high refractoriness of the prepared material by sintering. However, with excessive addition of Cr2O3 (>6 wt %), the quantity of enstatite increased obviously, which would lower the refractoriness of refractory material. For this reason, the addition of chromium or its content in the slag should be carefully controlled to fully exert its advantage in promoting the properties of the refractory material. Based on these findings, a superior refractory material with refractoriness of 1840 degrees C, bulk density of 2.68 g/cm(3), apparent porosity of 15.19%, and compressive strength of 96.28 MPa was obtained by sintering at 1350 degrees C for 3 h with additions of 20 wt % sintered magnesia and 6 wt % Cr2O3. Because of its better comprehensive properties than the commercial counterparts and those obtained without addition of Cr2O3, the present study offers a very promising method for utilizing the hazardous element in preparing high-quality refractory materials from industrial waste, exhibiting great environmental and economic benefits.