Investigation on Viscosity and Nonisothermal Crystallization Behavior of P-Bearing Steelmaking Slags with Varying TiO 2
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THE production of crude steel in China surpassed 800 million tons in 2015, disposing nearly 80 to 100 million tons of steelmaking slags.[1] Nevertheless, only about 30 wt pct of steelmaking slags were recycled as construction materials, soil conditioners, fertilizers, recovery of metals or recovered in iron- and steelmaking process, etc.[2–7] Among these utilization methods, the most effective way of using the steelmaking slags was recycled into the iron- and steelmaking process, which may inevitably result in the enrichment of phosphorus in the slags and further increase the burden in the following dephosphorization process.[8–10] Thus, the lowering of the phosphorus content in steelmaking slags is of primary concern for further utilization of P-bearing steelmaking slags. The selective crystallization and phase separation (SCPS) method has been proved to
ZHANJUN WANG, Doctoral Candidate, and MEI ZHANG, Professor, are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 100083 Beijing, P.R. China. YONGQI SUN, Doctoral Candidate, is with the College of Engineering, Peking University, 100871 Beijing, P.R. China. SEETHARAMAN SRIDRAR, Professor, is with the Advanced Steel Research Centre, WMG, Steels Processing Research Centre, University of Warwick, Coventry CV4 7AL, U.K. ZUOTAI ZHANG, Professor, is with the School of Environmental Science and Engineering, South University of Science and Technology of China, 518055 Shenzhen, P.R. China. Contact e-mail: [email protected] Manuscript submitted July 19, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
be the most efficient way to recycle the phosphorous in steelmaking slags.[11–13] During the SCPS process, the selective crystallization is the key step to enrich phosphorous successfully into a certain phase, which can be separated and used as phosphorus fertilizer, and the residues may be recycled into the iron- and steelmaking process. During the early 1960s and 1980s, several investigations were conducted to detect the dephosphorization process.[14–17] These investigations were mainly based on the CaO-SiO2-FetO-P2O5 system to study the mechanism of dephosphorization, and the n(2CaOÆSiO23CaOÆP2O5) (nC2S-C3P) solid solution was considered to be the efficient P-enriched phase. Based on these investigations, various studies have been explored to reveal how to boost the phosphorus content in nC2S-C3P solid solution through adding different additives into the complex CaO-SiO2-MgO-Al2O3FetO-P2O5 multiphase.[9,18–21] A series of studies has been carried out to explore the P concentrating phase in steelmaking slags modified by Fe2O3, P2O5, Al2O3, and CaF2 additives,[22–25] where the essential structure of the slags has been systematically studied, especially Fe3+, P5+, Al3+, and F. Meanwhile, some other studies about the structure also replenished the investigation of the slags.[26–29] Nevertheless, the existing data are still too limited to cover all of the slag compositions. Some studies showed that TiO2 can also be used
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