锆英石对铝铬锆砖抗侵蚀性能及六价铬形成的影响

铝铬锆砖因具有优异的抗渣侵蚀性能,被作为炉衬材料广泛应用于工作环境恶劣的危废焚烧炉。然而,铝铬锆砖在制备和服役过程中可能形成有毒的水溶性Cr(VI),相关研究工作却未见报道。本研究分别以单斜氧化锆和锆英石为氧化锆源制备了两种铝铬锆砖,研究了铝铬锆砖在四种不同组成危废焚烧炉渣中的侵蚀行为及熔渣侵蚀前后砖中Cr(VI)的含量。结果表明,锆英石高温下分解形成单斜氧化锆和无定形的二氧化硅,促进化学稳定性较好的(Al,Cr)₂O₃固溶体的形成,提高了铝铬锆砖的致密化程度,同时改善了铝铬锆砖的抗渣侵蚀性能。此外,生成的二氧化硅可以还原砖中Cr(VI)化合物,降低铝铬锆砖中的Cr(VI)含量。熔渣侵蚀后,铝铬锆砖渗透层中Cr(VI)含量与熔渣成分密切相关。在被高碱性氧化物含量的熔渣侵蚀后,铝铬锆砖渗透层中的Cr(VI)含量较高,但锆英石作为氧化锆源的铝铬锆砖在不同熔渣中侵蚀前后的原砖层和渗透层内的Cr(VI)含量均低于欧盟限制标准。

Effect of Zircon on Corrosion Resistance of Al2O3-Cr2O3-ZrO2 Bricks and Hexavalent Chromium Formation

Al₂O₃-Cr₂O₃-ZrO₂ bricks are widely used as lining material in hazardous waste incinerators because of their excellent slag corrosion resistance. However, toxic water-soluble Cr(VI) may be formed during the preparation and service of Al₂O₃-Cr₂O₃-ZrO₂ bricks, and the related research work has not been reported. In present study, two kinds of Al₂O₃-Cr₂O₃-ZrO₂ bricks were prepared using monoclinic zirconia and zircon as zirconia sources. The corrosion behavior of the bricks in four kinds of hazardous waste incinerator slags and the content of Cr(VI) in the bricks before and after slag corrosion were studied. The results show that zircon decomposes into monoclinic zirconia and amorphous silica at high temperatures, which promotes the formation of highly chemical stable (Al,Cr)₂O₃ solid solution and improves the densification as well as corrosion resistance of the Al₂O₃-Cr₂O₃-ZrO₂ bricks. Furthermore, the formed silica can reduce Cr(VI) compound, which lowers the content of Cr(VI) in Al₂O₃-Cr₂O₃-ZrO₂ bricks. The content of Cr(VI) in the penetration layer of Al₂O₃-Cr₂O₃-ZrO₂ bricks is closely related to the composition of slag. There is higher Cr(VI) content in the penetration layer after being corroded by the slag with high alkaline oxide content, while Cr(VI) content in the origin and penetration layer of Al₂O₃-Cr₂O₃-ZrO₂ bricks with zircon is lower than the EU limit standard in the four kinds of slag.