A Thermodynamic Model of Phosphate Capacity of CaO–SiO2–MgO–FetO–P2O5 Steelmaking Slags

Abstract

Abstract: According to the ion and molecule coexistence theory (IMCT), a thermodynamic model of phosphate capacity of CaO–SiO2–MgO–FetO–P2O5 steelmaking slags has been developed and verified by the experimental data. The predicted phosphate capacity of CaO–SiO2–MgO–FetO–P2O5 steelmaking slags at 1873 K and 1923 K by the developed IMCT–Cp model have higher accuracy than the measured phosphate capacity as well as the predicted phosphate capacity by other phosphate capacity models. The developed IMCT–Cp model can calculate not only the total phosphate capacity of the slags but also the respective phosphate capacity of ion pairs (Ca2++O2?)、(Mg2++O2?) and (Fe2++O2?) in the slags

Key words: CaO–SiO2–MgO–FetO–P2O5 steelmaking slags, phosphate capacity, the ion and molecule coexistence theory, basic oxides, dephosphorization contribution ratio

References

[1] Wagner C. The concept of the basicity of slags[J]. Metall. Mater. Trans. B, 1975, 6(3): 405–409
[2] Suito H and Inoue R. Effects of Na2O and BaO additions on phosphorus distribution between CaO–MgO–FetO–SiO2 slags and liquid iron[J]. Trans. ISIJ, 1984, 24(1): 47–53.
[3] Ito K and Sano N. Phosphorus distribution between basic slags and carbon–saturated iron at hot–metal temperatures[J]. Trans. ISIJ, 1985, 25(5): 355–62.
[4] Muraki M, Fukushima H and Sano N. Phosphorus distribution between CaO–CaF2–SiO2 melts and carbon–saturated iron[J]. Trans. ISIJ, 1985, 25(10): 1025–1030.
[5] Pak J J, Fruhan R J. Soda slag system for hot metal dephosphorization[J]. Metall. Mater. Trans. B, 1986, 17(3): 797–804.
[6] Nassaralla C, Fruehan R J. Phosphate capacity of CaO–Al2O3 slags containing CaF2, BaO, Li2O or Na2O[J]. Metall. Mater. Trans. B, 1992, 23(2): 117–179.
[7] Morales A T and Fruehan R J. Thermodynamics of MnO, FeO and phosphorus in steelmaking slags with high MnO contents[J]. Metall. Mater. Trans. B, 1997, 28(6): 1111–1118.
[8] Selin R, Dong Y and Wu Q. Uses of lime–based fluxes for simultaneous removal of phosphorus and sulphur in hot metal pretreatment[J]. Scand. J. Metall., 1990, 19(3): 98–109.
[9] Mori T. On the phosphorus distribution between slag and metal[J]. Bull. Jpn. Inst. Met., 1984, 23(4): 354–56.
[10] Suito H, Inoue R and Takada M. Phosphorus distribution between liquid iron and MgO saturated slags of the system CaO–MgO–FeOx–SiO2[J]. ISIJ Int., 1981, 21(4): 250–259.
[11] Young R W, Duffy J A, Hassall G J et al. Use of optical basicity concept for determining phosphorus and sulphur slag–metal partitions[J]. Ironmaking and steelmaking, 1992, 19(3): 201–219.
[12] Deo B, Halder J, Snoeijer B et al. Effect of MgO and Al2O3 variations in oxygen steelmaking(BOF) slag on slag morphology and phosphorus distribution[J]. Ironmaking and Steelmaking, 2005, 32(1), 54–60.
[13] Zhang J. Computational Thermodynamics of Metallurgical Melts and Solutions[M]. Beijing: Metallurgical Industry Press, 2007: 379
[14] Zhang J. The applicability of the law of mass action in combination with the coexistence theory of slag structure to the multicomponent slag systems[J]. Acta Metallurgica Sinica, 2001, 14(3): 177–190
[15] Zhang J. Applicability of mass action law to sulphur distribution between slag melts and liquid iron[J]. J Univ Sci Technol Beijing, 2002, 9(2): 90–98
[16] Zhang J. Applicability of annexation principle to the study of thermodynamic properties of ternary molten salts CaCl2–MgCl2–NaCl[J]. Rare Metals, 2004, 23(3): 209–213
[17] Yang X M, Jiao J S, Ding R C et al. A thermodynamic model for calculating sulphur distribution ratio between CaO–SiO2–MgO–Al2O3 ironmaking slags and carbon saturated hot metal based on the ion and molecule coexistence theory[J]. ISIJ Int, 2009, 49(12): 1828–1837
[18] Shi C B, Yang X M, Jiao J S et al. A sulphide capacity prediction model of CaO–SiO2–MgO–Al2O3 ironmaking slags based on the ion and molecule coexistence theory[J]. ISIJ Int, 2010, 50(10): 1362–1372
[19] Yang X M, DUAN J P, Shi C B, et al. A Thermodynamic Model of Phosphorus Distribution Ratio between CaO–SiO2–MgO–FeO–Fe2O3–MnO–Al2O3–P2O5 Slags and Molten Steel during Top–Bottom Combined Blown Converter Steelmaking Process Based on the Ion and Molecule Coexistence Theory[J]. Metallurgical and Material Transactions B, 2011, 42B(4):738–770.
[20] Turkdogan E T. Activities of constituents of iron and steelmaking slags[J]. J Iron Steel Inst, 1953, 175: 398–401.
[21] Chen J X. Handbook of Common Figures, Tables and Data for Steelmaking[M], Metallurgical Industry Press, Beijing, China, 2010:157.
[22] Herty C H. Phosphorus capacities in some multi component slag systems[J]. Trans. AIME, 1926, 73: 1107–1112
[23] Basu S, Lahiri A K, and Seetharaman S. Phosphorus partition between liquid steel and CaO–SiO2–P2O5–MgO slag containing low FeO[J]. Metall. Mater. Trans. B, 2007, 38(3): 357–366.
[24] Wrampelmeyer J C, Dimitrov S and Janke D. Dephosphorization equilibria between pure molten iron and CaO–saturated FeOn–CaO–CaF2 slags[J]. Steel Res., 1990, 61(1): 1–7.
[25] Gaskell D R. On the correlation between the distribution of phosphorus between slag and metal and the theoretical optical basicity of the slag[J]. Trans ISIJ, 1982, 22(12): 997–1000.
[26] Nagabayashi R, Hino M and Ban-ya S. Solubilities of CaO, MgO, SiO2 and 2CaO?SiO2, and ferric–ferrous equilibrium in FetO–(CaO+MgO)–(SiO2+P2O5) phosphate slags[J]. Tetsu–to–Hagané, 1988, 80(8): 1577–1584.