Nucleation and growth control for iron- and phosphorus-rich phases from a modified steelmaking waste slag

Abstract

Recovering the iron (Fe) and phosphorus (P) contained in steelmaking slags not only reduces the environmental burden caused by the accumulated slag, but also is the way to develop a circular economy and achieve sustainable development in the steel industry. We had previously found the possibility of recovering Fe and P resources, i.e., magnetite (Fe₃O₄) and calcium phosphate (Ca₁₀P₆O₂₅), contained in steelmaking slags by adjusting oxygen partial pressure and adding modifier B₂O₃. As a fundamental study for efficiently recovering Fe and P from steelmaking slag, in this study, the crystallization behavior of the CaO—SiO₂—FeO—P₂O₅—B₂O₃ melt has been observed in situ, using a confocal scanning laser microscope (CLSM). The kinetics of nucleation and growth of Fe- and P-rich phases have been calculated using a classical crystallization kinetic theory. During cooling, a Fe₃O₄ phase with faceted morphology was observed as the 1st precipitated phase in the isothermal interval of 1300–1150°C, while Ca₁₀P₆O₂₅, with rod-shaped morphology, was found to be the 2nd phase to precipitate in the interval of 1150—1000°C. The crystallization abilities of Fe₃O₄ and Ca₁₀P₆O₂₅ phases in the CaO—SiO₂—FeO—P₂O₅—B₂O₃ melt were quantified with the index of (T _U − T _I)/T _I (where T _I represents the peak temperature of the nucleation rate and T _U stands for that of growth rate), and the crystallization ability of Fe₃O₄ was found to be larger than that of Ca₁₀P₆O₂₅ phase. The range of crystallization temperature for Fe₃O₄ and Ca₁₀P₆O₂₅ phases was optimized subsequently. The Fe₃O₄ and Ca₁₀P₆O₂₅ phases are the potential sources for ferrous feedstock and phosphate fertilizer, respectively.

Keywords

steelmaking slag / magnetite / calcium phosphate / nucleation / growth / kinetics

References

[1] I. Sosa, C. Thomas, J.A. Polanco, J. Setién, and P. Tamayo, High performance self-compacting concrete with electric arc furnace slag aggregate and cupola slag powder, Appl. Sci., 10(2020), No. 3, art. No. 773.

[2] G.M.P. Kumara and K. Kawamoto, Steel slag and autoclaved aerated concrete grains as low-cost adsorbents to remove Cd²⁺ and Pb²⁺ in wastewater: Effects of mixing proportions of grains and liquid-to-solid ratio, Sustainability, 13(2021), No. 18, art. No. 10321.

[3] Wu QS, Huang ZC. Preparation and performance of lightweight porous ceramics using metallurgical steel slag. Ceram. Int., 2021, 47(18): 25169.

[4] Tang ZJ, Liang J, Jiang WH, et al. Preparation of high strength foam ceramics from sand shale and steel slag. Ceram. Int., 2020, 46(7): 9256.

[5] Lin L, Liu YQ, Zhi JG, et al. Influence of slag temperature on phosphorus enrichment in P-bearing steelmaking slag. Ironmaking Steelmaking, 2021, 48(3): 334.

[6] Matsuura H, Yang X, Li GQ, Yuan ZF, Tsukihashi F. Recycling of ironmaking and steelmaking slags in Japan and China. Int. J. Miner. Metall. Mater., 2022, 29(4): 739.

[7] Seetharaman S, Wang LJ, Wang HJ. Slags containing transition metal (chromium and vanadium) oxides—Conversion from ticking bombs to valuable resources: Collaborative studies between KTH and USTB. Int. J. Miner. Metall. Mater., 2022, 29(4): 750.

[8] Zhao JH, Yan PY, Wang DM. Research on mineral characteristics of converter steel slag and its comprehensive utilization of internal and external recycle. J. Cleaner Prod., 2017, 156, 50.

[9] Juckes LM. The volume stability of modern steelmaking slags. Trans. Inst. Min. Metall. Sect. C, 2003, 112(3): 177.

[10] Engström F, Adolfsson D, Yang Q, Samuelsson C, Björkman B. Crystallization behaviour of some steelmaking slags. Steel Res. Int., 2010, 81(5): 362.

[11] Gomes JFP, Pinto CG. Leaching of heavy metals from steelmaking slags. Rev. Metal., 2006, 42(6): 409.

[12] Chen LJ, Wan Y, Xia XJ, Li J, Yang YD, Mclean A. Dephosphorisation of hot metal containing moderate amounts of chromium with CaO—FeO_x—Cr₂O₃—CaF₂ slag. Ironmaking Steelmaking, 2021, 48(7): 868.

[13] Min DJ, Han JW, Chung WS. A study of the reduction rate of FeO in slag by solid carbon. Metall. Mater. Trans. B, 1999, 30(2): 215.

[14] Fan DQ, Elzohiery M, Mohassab Y, Sohn HY. The kinetics of carbon monoxide reduction of magnetite concentrate particles through CFD modelling. Ironmaking Steelmaking, 2021, 48(7): 769.

[15] A. Heidari, N. Niknahad, M. Iljana, and T. Fabritius, A review on the kinetics of iron ore reduction by hydrogen, Materials, 14(2021), No. 24, art. No. 7540.

[16] Semykina A, Nakano J, Sridhar S, Shatokha V, Seetharaman S. Confocal microscopic studies on evolution of crystals during oxidation of the FeO—CaO—SiO₂—MnO slags. Metall. Mater. Trans. B, 2010, 41(5): 940.

[17] Semykina A. The kinetics of oxidation of liquid FeO—MnO—CaO—SiO₂ slags in air. Metall. Mater. Trans. B, 2012, 43(1): 56.

[18] Semykina A, Nakano J, Sridhar S, Shatokha V, Seetharaman S. Confocal scanning laser microscopy studies of crystal growth during oxidation of a liquid FeO—CaO—SiO₂ slag. Metall. Mater. Trans. B, 2011, 42(3): 471.

[19] Duan WJ, Yu QB, Wu TW, Yang F, Qin Q. The steam gasification of coal with molten blast furnace slag as heat carrier and catalyst: Kinetic study. Int. J. Hydrogen Energy, 2016, 41(42): 18995.

[20] Li JC, Bhattacharjee D, Hu XJ, Zhang DW, Sridhar S, Li ZS. Crystallization behavior of liquid CaO—SiO₂—FeO—MnO slag in relation to its reaction with moisture. Metall. Mater. Trans. B, 2019, 50(4): 1931.

[21] Li JC, Bhattacharjee D, Hu XJ, Zhang DW, Sridhar S, Li ZS. Effects of slag composition on H₂ generation and magnetic precipitation from molten steelmaking slag—steam reaction. Metall. Mater. Trans. B, 2019, 50(2): 1023.

[22] Malvoisin B, Brunet F, Carlut J, et al. High-purity hydrogen gas from the reaction between BOF steel slag and water in the 473–673 K range. Int. J. Hydrogen Energy, 2013, 38(18): 7382.

[23] Wang WZ, Liang B, Zhang JR. Experimental study on low temperature flotation recovery of apatite from a magnetic tailings. Appl. Mech. Mater., 2014, 522–524, 1501.

[24] Matsubae-Yokoyama K, Kubo H, Nagasaka T. Recycling effects of residual slag after magnetic separation for phosphorus recovery from hot metal dephosphorization slag. ISIJ Int., 2010, 50(1): 65.

[25] Li C, Gao JT, Wang FQ, Guo ZC. Enriching Fe-bearing and P-bearing phases from steelmaking slag melt by super gravity. Ironmaking Steelmaking, 2018, 45(1): 44.

[26] Li C, Gao JT, Guo ZC. Separation of phosphorus- and iron-enriched phase from CaO—SiO₂—FeO—MgO—P₂O₅ melt with super gravity. Metall. Mater. Trans. B, 2016, 47(3): 1516.

[27] Li C, Gao JT, Guo ZC. Isothermal enrichment of P-concentrating phase from CaO—SiO₂—FeO—MgO—P₂O₅ melt with super gravity. ISIJ Int., 2016, 56(5): 759.

[28] Zhang YY, Xue QG, Wang G, Wang JS. Gasification and migration of phosphorus from high-phosphorus iron ore during carbothermal reduction. ISIJ Int., 2018, 58(12): 2219.

[29] Sugata M, Sugiyama T, Kondo SI. Reduction of iron oxide contained in molten slags with solid carbon. ISIJ Int., 1974, 14(2): 88.

[30] Takeuchi S, Sano N, Matsushita Y. Separate recovery of iron and phosphorus from BOF slags by using Fe—Si alloys. Tetsu-to-Hagane, 1980, 66(14): 2050.

[31] C.M. Du, X. Gao, S. Ueda, and S.Y. Kitamura, Separation and recovery of phosphorus from steelmaking slag via a selective leaching-chemical precipitation process, Hydrometallurgy, 189(2019), art. No. 105109.

[32] Teratoko T, Maruoka N, Shibata H, Kitamura SY. Dissolution behavior of dicalcium silicate and tricalcium phosphate solid solution and other phases of steelmaking slag in an aqueous solution. High Temp. Mater. Process., 2012, 31(4–5): 329.

[33] Numata M, Maruoka N, Kim SJ, Kitamura SY. Fundamental experiment to extract phosphorous selectively from steelmaking slag by leaching. ISIJ Int., 2014, 54(8): 1983.

[34] H.M. Xue, J. Li, Y.J. Xia, Y. Wan, L.J. Chen, and C.J. Lv, Mechanism of phosphorus enrichment in dephosphorization slag produced using the technology of integrating dephosphorization and decarburization, Metals, 11(2021), No. 2, art. No. 216.

[35] J.M. Gonzalez, C.J. Penn, and S.J. Livingston, Utilization of steel slag in blind inlets for dissolved phosphorus removal, Water, 12(2020), No. 6, art. No. 1593.

[36] Ye GF, Yang J, Zhang RH, Yang WK, Sun H. Behavior of phosphorus enrichment in dephosphorization slag at low temperature and low basicity. Int. J. Miner. Metall. Mater., 2021, 28(1): 66.

[37] Li GX, Liang JS, Long J, et al. A novel process for separation of magnetite and phosphorous phases from a CaO—SiO₂—FeO—P₂O₅ slag. ISIJ Int., 2022, 62(7): 1556.

[38] Turnbull D. Formation of crystal nuclei in liquid metals. J. Appl. Phys., 1950, 21(10): 1022.

[39] Turnbull D. Under what conditions can a glass be formed?. Contemp. Phys., 1969, 10(5): 473.

[40] Fisher JC, Hollomon JH, Turnbull D. Rate of nucleation of solid particles in a subcooled liquid. Science, 1949, 109(2825): 168.

[41] Uhlmann DR. A kinetic treatment of glass formation. J. Non-Cryst. Solids, 1972, 7(4): 337.

[42] Barin I. Thermochemical Data of Pure Substances, 1995, 3rd ed. Weinheim, VCH Verlagsgesellschaft mbH, 478.

[43] Li B, Sui ZT. Glass crystallization kinetics of CaO—MgO—Fe₂O₃—Al₂O₃—SiO₂ slags. Chin. J. Mater. Res., 1999, 13(4): 412.

[44] Zhang PX, Sui ZT, Luo DM, Ma RJ. Study on crystallization kinetics of component containing boron in MgO—B₂O₃—SiO₂—Al₂O₃—CaO slag. Chin. J. Mater. Res., 1995, 9(1): 66.

[45] Zhang X, Xie B, Diao J, Li XJ. Nucleation and growth kinetics of spinel crystals in vanadium slag. Ironmaking Steelmaking, 2012, 39(2): 147.

[46] Lan X, Gao JT, Wang ZW, Guo ZC. Viscosity of RE-bearing slag systems and kinetics of nucleation and growth for RE-phases. Ceram. Int., 2022, 48(9): 13304.

[47] Mills KC, Sridhar S. Viscosities of ironmaking and steelmaking slags. Ironmaking Steelmaking, 1999, 26(4): 262.

[48] Bordes-Richard E. Multicomponent oxides in selective oxidation of alkanes theoretical acidity versus selectivity. Top. Catal., 2008, 50, 82.

[49] Lei XF, Xue XX. Preparation, characterization and photocatalytic activity of sulfuric acid-modified titanium-bearing blast furnace slag. Trans. Nonferrous Met. Soc. China, 2010, 20(12): 2294.

[50] Zong YB, Cang DQ, Zhen YP, Li Y, Bai H. Component modification of steel slag in air quenching process to improve grindability. Trans. Nonferrous Met. Soc. China, 2009, 19(Suppl. 3): s834.

[51] Chen G, Chen J, Peng JH, Wan RD. Green evaluation of microwave-assisted leaching process of high titanium slag on life cycle assessment. Trans. Nonferrous Met. Soc. China, 2010, 20(Suppl.1): s198.

[52] Wang WL, Dai SF, Zhang TS, Li ZM, Xie YJ. Effect of isothermal and cooling rate on crystallization and viscosity of silicomanganese waste slag. Ceram. Int., 2021, 47(10): 13622.

[53] Wu JH, Zhang FQ, Chen GH. A new method to estimate the ability of forming amorphous solids. Phys. Status Solidi A, 1987, 101(1): K1.

[54] Johnson WA, Mehl RF. Reaction kinetics in processes of nucleation and growth. Trans. AIME, 1939, 135, 416.