A Thermodynamic Model for Predicting Phosphorus Partition between CaO-based Slags and Hot Metal during Hot Metal Dephosp
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AN, Research Professors, are with the Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China. Contact e-mails: [email protected] JIN-YAN LI, Ph.D. Candidate and Joint-Training Student, is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P. R. China, and also with the Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences. GUO-MING CHAI, formerly Ph.D. Candidate with the Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, is now with the No. 2 Steelmaking Plant, Shanxi Taigang Stainless Steel Corporation Limited, Taiyuan 030003, P.R. China. JIAN ZHANG, Professor Emeritus, is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing. Manuscript submitted October 1, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
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INTRODUCTION
EXTRACTING phosphorus from iron-based melts is pivotal to refine low or ultra–low phosphorus steel products with high performances. Due to limited dephosphorization ability during blast furnace ironmaking process and most secondary refining processes of molten steel, dephosphorization operations in both hot meat pretreatment and converter steelmaking process play important roles in fulfilling requirement of phosphorus content in iron-based melts after refining in routine metallurgical process. Technologies on hot metal pretreatment as desiliconization, dephosphorization, and
desulfurization have been developed using CaO-based or Na2CO3-based or mixture of CaO and Na2CO3 fluxes or slags since the 1970s.[1,2] Although the twin-converter steelmaking process[3] has been developed and applied in some metallurgical companies since the 1990s, dephosphorization pretreatment of hot metal is still important to decrease the required mission of extracting phosphorus from iron-based melts during converter steelmaking process. In comparison with tremendous studies on dephosphorization of molten steel[1–79] by oxidizing slags since the 1920s,[4] thermodynamic study on hot metal dephosphorization has not widely been reported[22,62,65,74] because oxidizing slags containing more or less iron oxides FetO can gradually be reduced by carbon in hot metal to form CO bubbles, i.e., chemical reaction equilibrium cannot really be reached.[22] In order to overcome this congenital difficulty, Ito and Sano[22] used solid iron and molten slags to determine phosphorus partition LP between basic slags and carbon-saturated hot metal by keeping chemical potential of phosphorus in solid iron (c–Fe) the same as that in hot metal. However, very long experimental period about 12 h should be used to reach real chemical reaction equilibrium between solid iron and applied slags. Furthermore, the prediction models of LP between CaO-based slags and hot metal such as by Kawai et al.[26] as well as by Lee and Fruehan[74] ar
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