A Thermodynamic Model of Phosphate Capacity for CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -MnO-Al 2 O 3 -P 2 O 5 Slags Equilibrated wi

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IN a conventional steelmaking process arrangement, dephosphorization is an important metallurgical function of a top–bottom combined blown converter because the subsequent secondary refining process cannot provide additional phosphorus removal. The  phosphorus distribution ratio LP ¼ ðpct P2 O5 Þ ½pct P]2 ;  00 000 LP ¼ ðpct PO3 4 Þ ½pct P]; or LP ¼ ðpct P2 O5 Þ=½pct P] has been widely used to express the phosphorus removal ability of a slag because of its simple meaning and XUE-MIN YANG, Research Professor, is with the State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China. Contact e-mail: [email protected] CHENG-BIN SHI, Ph.D. Candidate and Joint-Training Student, and MENG ZHANG, Master Degree Student and Joint-Training Student, are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China, and with the Institute of Process Engineering, Chinese Academy of Sciences. JIAN-PING DUAN, Senior Engineer, is with the Technology Center, Shanxi Taigang Stainless Corporation Limited, Taiyuan 030003, P. R. China. JIAN ZHANG, Professor, is with the School of Metallurgical and Ecological Engineering, University of Science and Technology. Manuscript submitted March 5, 2011. Article published online June 4, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS B

because it can be calculated easily. The dephosphorization potential of a slag has been defined by Wagner[1] in the 1970s as phosphate capacity CPO3 or phosphide 4 capacity CP3 based on slag–gas equilibrium; similarly, the phosphate capacity index CPO3 ;index has been also 4 proposed by Yang et al.[2,3] in the 1990s and applied by many researchers based on slag–metal equilibrium. It should be emphasized that the phosphate capacity index CPO3 ;index can be easily confused with phosphate capacity 4 CPO3 : Therefore, the phosphate capacity index CPO3 ;index 4 4 is used to distinguish phosphate capacity CPO3 and 4 phosphate capacity index CPO3 ;index in this article. 4 Large amounts of phosphate capacity CPO3 data for 4 various slags have been measured based on slag–gas equilibrium reaction since the 1970s after it was proposed by Wagner[1]; meanwhile, a lot of phosphate capacity index CPO3 ;index data have been also measured 4 based on slag–metal equilibrium reaction, although some researchers did not distinguish the concept of phosphate capacity CPO3 and phosphate capacity index 4 CPO3 ;index .[4–9] Some prediction models for calculating 4 phosphate capacity CPO3 and phosphate capacity index 4 CPO3 ;index had been developed, such as Selin’s model[10] 4 for CaO-SiO2-CaF2 slags, Mori’s model[11] for CaO-MgO-SiO2-FetO slags, Suito’s model[6,12] for VOLUME 42B, OCTOBER 2011—951

CaO-MgO-FetO-SiO2 slags, Young’s models[13] for CaO-SiO2-MgO-MnO slags, and Kunisada’s model[14] for soda-based slags. It should be emphasized that the original meaning of the applied CP3 ;index ¼ ðpct P)= ½pct P] 

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