Reaction Behavior of P2O5 at the Interface between Solid 2CaO·SiO2 and Liquid CaO–SiO2–FeOx–P2O5 Slags Saturated with Solid 5CaO·SiO2·P2O5 at 1 573 K

Abstract

It is important to understand the role of solid phases such as solid CaO or 2CaO · SiO 2 in hot metal dephosphorization. In the present study, the reaction behavior of P 2 O 5 at the interface between solid 2CaO · SiO 2 and liquid CaO-SiO 2 -FeO x -P 2 O 5 slags saturated with solid 5CaO · SiO 2 · P 2 O 5 at 1 573 K was investigated.The result shows that the solid 2CaO · SiO 2 reacts with the liquid phase in the two phase mixture to form the P 2 O 5 condensed phases. Compared with the results by using the homogeneous slag as reported in the previous papers, the formation of P 2 O 5 condensed phases is more evident and the back dissolution of P 2 O 5 condensed phases into the surrounding slag is restrained in this study. These results indicate that the dissolution of P 2 O 5 condensed phases can be considerably restrained in the case that the bulk slag is saturated with solid 5CaO · SiO 2 · P 2 O 5 before reaction.KEY WORDS: multi phase flux; dephosphorization; dicalcium silicate; P 2 O 5 condensed phases; dissolution. phorization slag. Therefore, it is required to understand the reaction behavior of phosphorus in the heterogeneous flux in which the liquid phase is saturated with the solid P 2 O 5 condensed phase.Little information on this topic can be found in the literature. In the present study, the authors try to clarify the reaction mechanism between solid 2CaO · SiO 2 and the slag saturated with solid 5CaO · SiO 2 · P 2 O 5 , and also to verify the assumption that the dissolution of P 2 O 5 condensed phases can be considerably restrained when the bulk slag is saturated with solid 5CaO · SiO 2 · P 2 O 5 before reaction. However, since the phase diagram for the CaO-SiO 2 -FeO x -P 2 O 5 quaternary system is unavailable, it is impossible to make sure the accurate composition of the slag saturated with solid 5CaO · SiO 2 · P 2 O 5 in the experiment. Therefore, the heterogeneous CaO-SiO 2 -FeO x -P 2 O 5 slags containing solid 5CaO · SiO 2 · P 2 O 5 were used. The solid 2CaO · SiO 2 disc was reacted with the slags at 1 573 K. The formation mechanism of P 2 O 5 condensed phases at the interface between solid 2CaO · SiO 2 and the heterogeneous slag was discussed. The results were also compared with the findings in the previous study. 11,12) ExperimentalThe CaO-SiO 2 -FeO x -P 2 O 5 slag was prepared by mixing synthesized CaO, FeO x , reagent grade SiO 2 and 3CaO · P 2 O 5 . Powder of CaO was obtained by the calcination of reagent grade CaCO 3 for 24 h at 1 173 K in air. FeO x was synthesized by sintering an equimolar mixture of reagent grade Fe 3 O 4 and electrolytic Fe powders in iron crucible at 1 473 K with CO-CO 2 atmosphere (CO/CO 2 ϭ1) for 24 h. The initial composition of slags are listed in Table 1.The solid 2CaO · SiO 2 disc was prepared by the following method. Firstly, synthesized CaO and reagent grade SiO 2 were mixed on molar ratio of 2 : 1 and sintered in a platinum crucible at 1 773 K for 24 h in air. About 1.0 mass% 3CaO · P 2 O 5 was added into the mixture to prevent the phase transformation from b...

Selective Crystallization Behavior of CaO-SiO2-Al2O3-MgO-FetO-P2O5 Steelmaking Slags Modified through P2O5 and Al2O3

“…[8][9][10][11][12] Based on this topic, various researches have been carried out to reveal the enrichment behavior of phosphorus in recent years. [3][4][5][6][7][13][14][15][16][17][18][19][20] From the perspective of the enrichment mechanism of phosphorus, some explorations have been detected on the distribution of P 2 O 5 between solid solution in 2CaOAESiO 2 -3CaOAEP 2 O 5 (nC 2 S-C 3 P) 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 nC 2 S-C 3 P is the main P-enriched phase in the slags.…”

Phosphorus Distribution Ratio between Multi Phase CaO–FeO_t–SiO₂–P₂O₅ (6%–13%) Slags with MP Near Hot Metal Temperature and C-saturated Molten Iron at 1573 K

“…For instance, Hasegawa and Iwase 5) and Jeoungkiu IM et al 6) respectively measured the activity of Fe x O and P 2 O 5 in the 3 three-phase regions of CaO-P 2 O 5 -Fe x O system. Tsukihashi et al [7][8][9][10][11] systematically investigated the formation reaction of phosphate compound in multi phase flux and the mass transfer processes between CaO/2CaO·SiO 2 particles and molten slag. In 1982 at the earliest, Ito et al 12) measured the phos-phorus distribution between 2CaO·SiO 2 and CaO-SiO 2 -FeO-Fe 2 O 3 molten slag.…”

Activity of P₂O₅ in Solid Solution between Di-calcium Silicate and Tri-calcium Phosphate at 1823 and 1873 K

“…They also studied the phosphorous transfer behavior from CaO-Fe t O-P 2 O 5 (-SiO 2 ) slag to 2CaO•SiO 2 particles 6) and the phosphorous partition between 2CaO•SiO 2 particles and CaO-SiO 2 -Fe t O slag with the similar experimental method. 7) Kitamura et al 8) studied the mass transfer of P 2 10) and Hamano et al 11) studied the reaction mechanisms between solid CaO and CaO-SiO 2 -FeO x -P 2 O 5 slag, and Yang et al [12][13][14][15] studied the reaction mechanisms between 2CaO•SiO 2 and molten CaO-SiO 2 -FeO x -P 2 O 5 slag with the similar experimental method like Suito and Inoue's experiments. Gao et al [16][17][18] studied the phase relationship of the CaO-SiO 2 -FeO-5 mass% P 2 O 5 system by applying the chemical equilibrium method similar to the study reported by Pahlevani et al Takeshita et al 19) measured the free energies of the formation of 2CaO•SiO 2 -3CaO•P 2 O 5 solid solution by applying the gas equilibrium technique.…”