High Temperature Phase Relations in FeO<I><SUB>X</SUB></I>(<I>X</I>=1 and 1.33)&ndash;CaO&ndash;SiO<SUB>2</SUB> Systems under Various Oxygen Partial Pressure

Abstract

As a fundamental study of slags in metallurgical processes, liquidus lines in the FeO(wüstite)-CaO-SiO 2 and Fe 3 O 4 (spinel)-CaO-SiO 2 systems were determined at temperatures between 1573 and 1673 K and partial pressures of oxygen between 10 À4 and 36 Pa using a quenching method with a crucible of platinum foil. It was found that the two phases (solid wüstite and liquid) region in the FeO-CaO-SiO 2 system (1573 K) increased remarkably by changing the partial pressure of oxygen from 10 À4 to 10 À3 Pa. It was also found that the two phases (solid spinel and liquid) region in the Fe 3 O 4 -CaO-SiO 2 system (1573 K) at PO 2 of 10 À2 Pa was a little larger than that in the FeO-CaO-SiO 2 system at PO 2 of 10 À3 Pa but it was extended considerably when the oxygen pressure was increased to 10 À1 Pa. However, the two liquids region did no change too much in the range of oxygen pressure above 10 À1 Pa even though the liquidus line became almost parallel to the Fe 3 O 4 -CaO axis in the ternary diagram when the oxygen pressure was increased. Furthermore, it was found that the two phase region in the Fe 3 O 4 -CaO-SiO 2 system at PO 2 of 10 À1 Pa decreased remarkably with increasing temperature. On the basis of the obtained and reported data, the homogeneous liquid regions in the FeO X -CaO-SiO 2 systems (1573 K) at PO 2 of 10 À3 Pa, 10 À1 Pa and in air were compared.

Thermodynamic Calculation of Liquidus Surface of FeOx–CaO–SiO2 System

“…However, the MPE fit to the liquidus of the FeO xCaO-SiO 2 system in the air is not accurate. In the present study, two Fe 2 O 3 -CaO-SiO 2 ternary parameters were introduced and the SiO 2 -Fe 2 O 3 binary parameters were re-optimized to fit the liquidus data of FeO x -CaO-SiO 2 system in the air at 1 573 K. 5,7,12,13) Figure 1 compares the liquidus surface of the FeO x -CaO-SiO 2 system in air at 1 573 K and 1 513 K measured by Henao et al, 5) by Nikolic et al, 7) by Phillips and Muan, 12) by Pownceby et al 13) and the model calculation. There is general agreement between these sets of data except for the region of SiO 2 content ranging from 10 to 20 mass%.…”

“…The comparison of calculated liquidus in the SiO 2 and magnetite saturation region at the oxygen partial pressure of 4ϫ10 Ϫ4 atm and 1 573 K with the experimental data by Henao et al 5) and Nikolic et al 7) is plotted in Fig. 3.…”

“…The literature data available up to Year 2000 on the effect of oxygen partial pressure and additions of Al 2 O 3 and MgO on the liquid region of the FeO x -CaO-SiO 2 and its sub-systems are critically reviewed by Yazawa. 2) More experimental [3][4][5][6][7][8] and modelling efforts 9,10) have since been made on the FeO x -CaO-SiO 2 system under the compositional conditions and oxygen partial pressures more relevant to the iron ore sintering process. However, the model prediction 9,10) does not agree with the experimental data by Shigaki et al, 11) particularly in magnetite saturation region.…”

“…ture [3][4][5][6][7][8][11][12][13] and between the experimental data [3][4][5][6][7][8]11) and modelling results. 9,10) In this paper, a modified version of the computational package: Multi-Phase Equilibrium (MPE) software developed by CSIRO, 14,15) was used to quantify the liquidus surface of the FeO x -CaO-SiO 2 system containing Al 2 O 3 and MgO at various intermediate oxygen partial pressures.…”

Subsolidus Phase Relations in the CaO–SiO₂–Nb₂O₅–La₂O₃ Quarternary System at 1273 K

“…In order to avoid nonequilibrium phase exists during the experiment, the sample was heated to 1 873 K to ensure that it completely melted again, and then cooling to the equilibrium temperature, this process can improve the accuracy of the experiment. The equilibrium temperature involved in the experiment was 1 273 K and 1 473 K, the equilibrium time lasted 24 hours based on experiences reported by previous authors, [13][14][15] repeat experiments with longer equilibrium time were performed for some samples to check whether the equilibrium was achieved. After the equilibrium, the sample was rapidly taken out from the furnace and quenched to 273 K by icewater, the quenching process was completed in 2 seconds to ensure that all samples maintained the high temperature equilibrium phase composition.…”