Inhibition of Cr(VI) in the Al2O3-CaO-Cr2O3 castables by using (Al1-x,Crx)2O3 solid solution

Abstract

Al2O3-CaO-Cr2O3 castables are required for various furnaces due to excellent corrosion resistance and sufficient early strength. However, generation of toxic Cr(VI) caused subsequent problems with disposal. The present work aimed at achieving Cr(VI) reduction by replacing Cr2O3 with (Al1 − x,Crx)2O3 solid solution. The phase evolutions and Cr(VI) formation in castables were systemically investigated. Compared with Cr2O3, stability of (Al1 − x,Crx)2O3 in CAC was much higher and improved gradually with Al3+ proportion. The substitution of Cr2O3 with (Al1 − x,Crx)2O3 completely inhibited CaCrO4 formation at 300–1100 oC, and drastically suppressed Ca4Al6CrO16 generation at 900–1300 °C. Thus, a remarkable Cr(VI) reduction of 98.1% could be achieved. Moreover, In comparison with CA and CA2, CA6 was much more stable, which would not take chemical reaction with (Al1 − x,Crx)2O3. Thus, incorporating some Al2O3 powders in Al2O3-CaO-Cr2O3 castables to form CA6 at temperature above 1300 oC was also essential for inhibiting Cr(VI) formation when using (Al1 − x,Crx)2O3 as substitute for Cr2O3.