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.