Formation Mechanisms and Leachability of Hexavalent Chromium in Cr2O3-Containing Refractory Castables of Electric Arc Furnace Cover
- 80 Downloads
Cr (III)-containing refractories are widely used as electric-arc furnace cover because of their excellent corrosion resistance properties. However, the formation of hexavalent chromium [Cr(VI)] remains a matter of concern during the service and subsequent disposal of the spent refractories. Moreover, the Cr(VI) formation mechanism and total amount of Cr(VI) generated are not clearly understood. In this study, samples from different parts of a spent electric arc furnace cover were collected from a local integrated steel plant. The phase composition, microstructure, formation and leachability of Cr(VI) were investigated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and TRGS 613 leaching test (Technische Regeln für Gefahrstoffe-TRGS 613-October 2002)/multiple leaching tests. A Cr(VI)-containing phase namely CaCrO4 existed in the sample at a medium temperature range, while another Cr(VI)-containing phase namely hauyne (Ca4Al6CrO16) and a Cr(III)-containing phase (Al2O3–Cr2O3 solid solution) formed in the high temperature region. Concentrations of Cr(VI) in the leachates (as in the TRGS 613 procedure) exceeded the European permissible limit. During the leaching tests in an acid condition, Cr(VI) was reduced by Fe2+, which was primarily derived from the dissolution of FeO in the samples, while more Cr(VI) leached out with distilled water. Formation of an Al2O3–Cr2O3 solid solution can inhibit Cr(VI) generation.
This work was supported by the National Natural Science Foundation of China (No. 51604203) and the Hubei Chutian Scholar Program.
- 6.U. S Environmental Protection Agency No. 18540-29-9, Toxicological review of hexavalent chromium, USA, Washington, 1998.Google Scholar
- 8.EU directive 2003/53/EC. Restrictions on the Marketing and Use of Cements and Cement-Containing Preparations, 2003.Google Scholar
- 15.G. Ma, W. Fan, Z. Xue, W. Wang and H. Tang: Acta. Metall. Sin-Engl., 2010, vol. 23, pp. 267-276.Google Scholar
- 17.World Steel Association. World steel in figures 2016, Brussels, www.worldsteel.org; 2016.
- 19.J. Madias: in Electric Furnace Steelmaking, Treatise on Process Metallurgy, 2014, pp. 271–300.Google Scholar
- 20.R. Sun, Z. He and H. Wang: Industrial Heating., 2008, vol. 37, pp. 43-47 (in Chinese).Google Scholar
- 22.S. Song and A.M. Garbers-Craig: Refractories Worldforum., 2016, vol. 8, pp.70-74.Google Scholar
- 29.S. Mizuhara, T. Urabe, A. Yamaguchi and T. Tomoyuki:Journal of the Japan Society of Waste Management Experts., 2012, vol. 23, pp. 77-84 (in Japanese). Google Scholar
- 30.T. He and J. Kong: Machinery., 2009, vol. 47, pp. 35-37 (in Chinese).Google Scholar
- 33.‘NIST X-ray photoelectron spectroscopy database Version 2.0’, US Secretary of Commerce, 1989, Washington, DC, US Secretary of Commerce.Google Scholar
- 34.J. Chastain (Ed.): Handbook of X-ray photoelectron spectroscopy, 1992, Eden Prairie, MI, Perkin–Elmer.Google Scholar
- 36.S. Song and A.M. Garbers-Craig: in Advances in Molten Slags, Fluxes, and Salts Advances in Molten Slags, Fluxes, and Salts, 2016.Google Scholar