Viscous Flow and Crystallization Behaviors of P-bearing Steelmaking Slags with Varying Fluorine Content

Abstract

The role of fluorine in the CaO-SiO 2 -MgO-Al 2 O 3 -Fe t O steelmaking slags was investigated through analyzing the viscous flow and crystallization behaviors of the slags. It was found that the viscosity decreased with increasing CaF 2 content, which resulted from the decrease of the degree of polymerization (DOP) of the structures, as proved by O 1s X-ray photoelectron spectroscopy (XPS) and magic angular spinning nuclear magnetic resonance (MAS-NMR) analysis. The continuous cooling transformation (CCT) diagrams of the primary crystals were also constructed. The results showed that CaF 2 addition promoted the transformation of the primary crystal from spinel (MgFe 2 O 4 ) to flourapatite (Ca 5 (PO 4 ) 3 F), which was beneficial to the further enrichment of phosphorus. According to 19 F MAS-NMR results, F − ions mainly coordinate with Ca 2 + ions to form Ca-F bond. Furthermore, considering the greater stability of P-O-Ca than that of Si-OCa bonds, most of the F − ions behave as F-Ca-O-P band, which thus enhanced the formation of Ca 5 (PO 4 ) 3 F. Additionally, the non-isothermal crystallization kinetics was further analyzed and the activation energy for the primary crystal growth was derived.

Effect of substituting CaO with BaO on the viscosity and structure of CaO‐BaO‐SiO2‐MgO‐Al2O3 slags

“…The high‐frequency region corresponded to the [SiO 4 ]‐tetrahedral units with varying amounts of oxygen anions. Similar results have been obtained for silicate slags . The peaks shifted toward higher frequencies with an increase in BaO content, suggesting an increase in the DOP of the slag system.…”

“…Similar results have been obtained for silicate slags. 11,[30][31][32] The peaks shifted toward higher frequencies with an increase in BaO content, suggesting an increase in the DOP of the slag system. In the low-frequency region, the peak at about 480 cm À1 corresponding to the Si-O-Al stretching vibrations became pronounced with an increase in the BaO content.…”

Ionic analysis of the effect of temperature on dephosphorization capacity of silicate slags

“…Lockyer [10] pointed out that Ca 2+ preferred to associate with than with silicate species for the greater stability of P–O–M (M is cation) than of Si–O–M in the Na 2 O–CaO–SiO 2 –P 2 O 5 system, which results that an increasing P 2 O 5 addition captured more than the NBO of the [SiO 4 ]-tetrahedra and brought about the degree of polymerization of molten slag rising. Wang et al [11] showed that the addition of CaF 2 reduced the degree of polymerization of P-bearing steelmaking slags because F ions mainly coordinated with Ca 2+ ions to form Ca–F bond. And the presence of Ca–F bonds (Si–O–Ca–F) and the greater stability of P–O–Ca than that of Si–O–Ca bonds could work together to promote the formation of Si–O–Ca–F and thus the primary crystal variation from spinel (MgFe 2 O 4 ) to fluorapatite phase (Ca 5 (PO 4 ) 3 F) with the addition of CaF 2 , which was beneficial to the further study of dephosphorization process and enrichment of phosphorus.…”

Investigation on Viscosity and Nonisothermal Crystallization Behavior of P-Bearing Steelmaking Slags with Varying TiO2 Content

“…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 in the complex CaO-SiO2-MgO-Al2O3-FetO-P2O5 multiphase. [9,[18][19][20][21] A series of studies have been carried out to explore the P concentrating phase in steelmaking slags modified by Fe2O3, P2O5, Al2O3 and CaF2 additives, [22][23][24][25] where the essential structure of the slags has been systematically studied, especially Fe 3+ , P 5+ , Al 3+ and F -. Meanwhile, some other studies about the structure also replenished the investigation of the slags.…”