Selective Crystallization Behavior of CaO-SiO 2 -Al 2 O 3 -MgO-Fe t O-P 2 O 5 Steelmaking Slags Modified through P 2 O 5

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CHINA has become the biggest crude steel producer since 2005.[1] The steelmaking slags accounting for about 10 to 20 wt pct crude steel; however, the utilization of steelmaking slags is relatively low as a result that the majority of steelmaking slags have been dumped after recycling of Fe, causing a series of environmental problems and waste of resources.[1] Although the recycling of slag in iron- and steelmaking process can enforce the internal reuse of the slag, the inevitable enrichment of phosphorus will subsequently increase the burden of further dephosphorization. On this occasion, the principle of selective crystallization and phase separation (SCPS) method was put forward, which has been extensively investigated to treat the slags with phosphorus or vanadium.[1–6] For the P-bearing steelmaking slags, the selective crystallization is the key step to successfully extract P-enriched phase through modifying the slags.[3–5,7] ZHANJUN WANG, Doctoral Candidate, and MEI ZHANG and MIN GUO Professors, are with the State Key Laboratory of Advanced Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] YONGQI SUN, Doctoral Candidate, and ZUOTAI ZHANG, Professor, are with the Department of Energy and Resources Engineering and Beijing Key Laboratory for Solid Waste Utilization and Management, College of Engineering, Peking University, Beijing 100871, P.R. China. Contact e-mail: [email protected] SEETHARAMAN SRIDHAR, Professor, is with the Steels Processing Research Centre, Advanced Steel Research Centre, WMG, University of Warwick, Coventry CV4 7AL, UK. Manuscript submitted February 5, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B

A number of investigations on the dephosphorization have been put forward between the early 1960 and 1980s.[8–12] Based on this topic, various researches have been carried out to reveal the enrichment behavior of phosphorus in recent years.[3–7,13–20] From the perspective of the enrichment mechanism of phosphorus, some explorations have been detected on the distribution of P2O5 between solid solution in 2CaOÆSiO2-3CaOÆP2O5 (nC2S-C3P) and liquid solution in the molten slag phase,[13,18] the behavior of phosphorous transfer,[20] and the formation reaction of P-enriched phase,[17] etc. Based on the above investigations, it can be summarized that the solid solution nC2S-C3P is the main P-enriched phase in the slags. In order to enhance the phosphorus solubility in the enriched phase, the steelmaking slags were also modified by different additives, such as Al2O3,[3] SiO2,[4] CaF2,[5] and TiO2,[7] which were beneficial to the enhancement of the solubility of phosphorus. However, the precipitation behavior of Fe- or Penriched phases under the different cooling rates has not been investigated so far; how the additives introduction into the steelmaking slags influence the structure and further affect the phase transformation has not been studied; and the kinetics of the pre

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