Slag formation path during dephosphorization process in a converter

Abstract

The slag formation path is important for efficient dephosphorization in steelmaking processes. The phosphorus capacity and the melting properties of the slag are critical parameters for optimizing the slag formation path. Regarding these two factors, the phosphorus partition ratio was calculated using the regular solution model (RSM), whereas the liquidus diagrams of the slag systems were estimated using the FactSage thermodynamic package. A slag formation path that satisfies the different requirements of dephosphorization at different stages of dephosphorization in a converter was thus established through a combination of these two aspects. The composition of the initial slag was considered to be approximately 15wt%CaO–44wt%SiO₂–41wt%FeO. During the dephosphorization process, a slag formation path that follows a high-iron route would facilitate efficient dephosphorization. The composition of the final dephosphorization slag should be approximately 53wt%CaO–25.5wt%SiO₂–21.5wt%FeO. The composition of the final solid slag after dephosphorization is approximately 63.6wt%CaO–30.3wt%SiO₂–6.1wt%FeO.

Keywords

steelmaking / dephosphorization / slag composition / optimization

References

[1] Li P.C., Zhang J.L. A prediction model of phosphorus distribution between CaO-SiO₂-MgO-FeO-Fe₂O₃-P₂O₅ slags and liquid iron. ISIJ Int., 2014, 54(4): 756.

[2] Xie S.L., Wang W.L., Liu Y.Z., Matsuura H. Effect of Na₂O and B₂O₃ on the distribution of P₂O₅ between solid solution and liquid phases slag. ISIJ Int., 2014, 54(4): 766.

[3] Monaghan B.J., Romfret R.J., Coley K.S. The kinetics of dephosphorization of carbon-saturated iron using an oxidizing slag. Metall. Mater. Trans. B, 1998, 29(1): 111.

[4] Ogasawara Y., Miki Y., Uchida Y., Kikuchi N. Development of high efficiency dephosphorization system in decarburization converter utilizing FetO dynamic control. ISIJ Int., 2013, 53(10): 1786.

[5] Kitamura S.Y., Yonezawa K., Ogawa Y., Sasaki N. Improvement of reaction efficiency in hot metal dephosphorisation. Ironmaking Steelmaking, 2002, 29(2): 121.

[6] Naito K., Wakoh M. Recent change in refining process in Nippon Steel Corporation and metallurgical phenomena in the new process. Scand. J. Metall., 2005, 34(6): 326.

[7] Ohnishi T., Takagi H., Ogura T., Hajika K., Yabata T., Yoshida Y. A pretreatment technique for hot metal using a newly-developed refining furnace. Kobe Res. Dev., 1986, 36(1): 9.

[8] Wu W., Zou Z.S., Guo Z.H., Wu D.R., Zhao G.G. Optimum slag forming route for BOF with top and bottom blowing oxygen. J. Iron Steel Res., 2004, 16(1): 21.

[9] Basu S., Lahiri A.K., Seetharaman S., Halder J. Change in phosphorus partition during blowing in a commercial BOF. ISIJ Int., 2007, 47(5): 766.

[10] Dahlin A. Influence of Ladle-slag Additions on BOF-process Parameters, 2011, Stockholm, Royal Institute of Technology, 23.

[11] Swinnerton M. The Influence of Slag Evolution on BOF Dephosphorisation, 2005, Wollongong, University of Wollongong, 22.

[12] Huang X.H. Ferrous Metallurgy Theory, 2002, Beijing, Metallurgical Industry Press, 180.

[13] Eisenhüttenleute V.D. Slag Atlas, 1995, Düsseldorf, Verlag Stahleisen GmbH, 126.

[14] Zhao J.X., Li X.M., Guo J.L., Huang M. Study on effect of P₂O₅ in converter slag on hot metal dephosphorization. China Metall., 2008, 18(10): 8.

[15] Wen Y.C., Dong Y.H., Wang T., Du D.X. Study of manganese ore direct alloying for increasing [Mn] content in steel in steelmaking process. Iron Steel Vanadium Titanium, 1998, 19(3): 7.

[16] Cicutti C., Valdez M., Pérez T., Donayo R., Petroni J. Analysis of slag foaming during the operation of an industrial converter. Lat. Am. Appl. Res., 2002, 32(3): 237.

[17] Kreijger P.J., Boom R. Slag formation in large scale BOF steelmaking. Can. Metall. Q., 1982, 21(4): 339.

[18] Wang X.B., Feng M.X., Zou Z.S., Zhao G.G., Liu Z.X. Slag forming route and dephosphorization of BOF dephosphorizing pretreatment and direct Steelmaking. Iron Steel, 2009, 44(1): 23.

[19] Li W.C. Metallurgical Thermodynamics, 1995, Beijing, Metallurgical Industry Press, 128.

[20] Matsui A., Nabeshima S., Matsuno H., Kikuchi N., Kishimoto Y. Kinetics behavior of iron oxide formation under the condition of oxygen top blowing for dephosphorization of hot metal in the basic oxygen furnace. Tetsu-to-Hagane, 2009, 95(3): 207.

[21] Sun L.M. Duplex melting process of converter and its features. Shanghai Met., 2005, 27(2): 44.

[22] Qiu X., Xie B., Jiang L., Zhang X., Diao J., Li H.Y. Experimental study of phosphorus distribution between slag and metal during duplex dephosphorus converter processing. Proceedings of the 4th International Symposium on High-Temperature Metallurgical Processing, 2013 199.