Research on Reaction Mechanism of Si₃N₄ and AlF₃ in CO Atmosphere

Abstract:

The reaction between Si₃N₄ and AlF₃ had been investigated in CO atmosphere at high temperature. Experimental results are shown that the reaction between Si₃N₄ and AlF₃ is accelerated with the rise of temperature. At the temperature of 950 (aluminum electrolytic operation temperature is 935±15), there is obvious reaction between Si₃N₄ and AlF₃; under this experiment condition, Si₃N₄ converted into Si₂N₂O partly, Si₂N₂O can also react with AlF₃. The reaction products of Si₃N₄ with AlF₃ are SiF₄ (g) and AlN, while the reaction products of Si₂N₂O with AlF₃ are SiF₄ (g) and Al₈O₃N₆. So, during the usage of Si₃N₄-bonded SiC sidewall brick in aluminum electrolysis cells, the content of Si₃N₄ in Si₃N₄-SiC block are reduced which can bring down the corrosion of aluminum electrolyte to the sidewall materials.

• Periodical: Advanced Materials Research (Volumes 233-235)
• Pages: 2243-2251
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.233-235.2243
• Online since: May 2011
• Authors: Jia Ping Wang, Yong Li, Xiao Yan Zhu, Ya Wei Zhai, Jun Bo, Jian Fang Zhang
• Keywords: Si₃N₄, AlF₃, CO Atmosphere, Reaction Mechanism

References

[1] M. Sørlie and H. A. Øye, Cathodes in Aluminium Electrolysis, 2nd edition, Aluminium-Verlag Gmb, HDusseldorf, Germany, 1994.

[2] Zhuxian Qiu, Aluminium Smelting by Pre-baked slot, 3rd edition, Metallurgy Industry Press, Beijing, China, 2005. In Chinese

[3] E.Skybakmoen, H.Gudbrandsen, L. I.Stoen, Chemical resistance of sideline materials based on SiC and carbon in cryolitic melts -A laboratory study. Light metals, p.215~222.1999.

[4] E.Skybakmoen, L.I. Stoen, H.Jannicke, J.H. Kvello, O.Darell, Quality evaluation of nitride bonded silicon carbide sidelining materials. Light metals, p.773~779.2005.

DOI: 10.1007/978-3-319-48200-2_114

[5] Zh.Wang, E.Skybakmoen,T.Grande. Spent Si3N4 Bonded SiC Sidelining Materials in Aluminum Electrolysis Cells. Light metals p.353~358. 2009.

[6] Zh.Wang, E.Skybakmoen, T.Grande. Chemical Degradation of Si3N4 Bonded SiC Sidelining Materials in Aluminum Electrolysis Cells. J.Am.Ceram.Soc.92[6] pp.1296-1302, 2009.

DOI: 10.1111/j.1551-2916.2009.03020.x

[7] E.Skybakmoen, J.H. Kvello, O.Darell, H. Gudbrandsen. Test and Analysis of Nitride Bonded SiC Sideling Materials. Typical Properties Analysed 1997-2007. Light metals, pp.943-948,2008.

[8] E.Skybakmoen. Evaluation of chemical resistance/oxidation of Si3N4-SiC sidelining materials used in Al electrolysis cells. Proceedings of Unified International Technical Conference on Refractories. VolumeIII, pp.1330-1339, Cancun, Mexico, Nov 2001.

[9] Andersen, F. B., Do¨rsam, G., Stam, M., Spreij, M. Wear of Silicon Nitride Bonded SiC Bricks in Aluminium Electrolysis Cells. Light metals. p.413.2004.

[10] Zhaoyou Chen, Chemical Thermodynamics of Refractories, Metallurgy Industry Press, Beijing, China, 2005. In Chinese