Abstract
The Al2O3-CaO-Cr2O3 systems are widely regarded as highly corrosion-resistant refractory castables, but leading a Cr(VI) problem after service. In the present paper, different contents (0–13.33 wt%) of MS (micro-silica) were added to the castables’ matrix system and heat-treated at 110–1500 °C in an air atmosphere. XRD, SEM-EDS, and leaching tests were done to study the influence of MS content on the formation, inhibition, and leaching kinetics of Cr(VI) phases. The formation of silicate phases is more favorable over Cr(VI) phases at higher temperatures and lower CaO/SiO2 ratios. With increasing MS content, the Cr(VI) compounds decrease gradually until disappearing at the C/S ratio of 0.36. Simultaneously, calcium aluminum garnet, gehlenite, and anorthite phases were formed gradually. When the MS content reached 13.33% (C/S = 0.36%), the total leachable Cr(VI) is decreased by 70% at 700 °C and 100% at 1100 °C respectively. The leaching kinetics experiment indicated that the Cr(VI) leaching process was governed by diffusion via product layers.
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