Pilot Trial of Detoxification of Chromium Slag in Cyclone Furnace and Preparation of Glass-Ceramics with the Water-Quenched Melt

Pilot trial of the detoxification of chromium slag in cyclone furnace and the preparation of glass-ceramics were investigated in a power plant in China. 10 wt.% chromium slag were mixed with pulverized bituminous coal and limestone as the raw materials of the cyclone furnace. Cr(VI) in chromium slag was reduced to Cr2O3 inside the cyclone furnace. The melt was water-quenched into frit and then fired into glass-ceramics with a laboratory ceramic roller kiln. The preparation and crystallization behavior of glass-ceramics were investigated with differential thermal analysis (DTA), physical and mechanical properties testing, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optimal flexural strength exceeding 90 MPa were achieved in firing temperature zone of 1170–1200 °C. Anorthite (CaAl2Si2O8) and diopside [Ca(Mg, Fe)Si2O6] can be identified in the glass-ceramics and CaAl2Si2O8 is the predominant crystal phase. Fine particles with average diameter of 200 nm distributed uniformly in the glass-ceramics. Granular crystals are intensively interconnected and constituted a crystal skeleton soaked in the glass matrix. Leaching toxicity test detected Cr(VI) of 0.016 and 0.010 mg/L of the water-quenched frit and glass-ceramics, respectively. This method provides an effective and comprehensive technique for the detoxification and utilization of chromium slag at low cost and large-scale.