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The crystallography of the Ca2SiO4-Ca3P2O8 solid solutions in the dephosphorization slag in current steelmaking process was determined in this study. Understanding the physical and chemical properties of these Ca2SiO4-Ca3P2O8 solid solutions is a preliminary step towards understanding the role of the Ca2SiO4-Ca3P2O8 solid solutions in the dephosphorization process. The range of Ca3P2O8 in the Ca2SiO4-Ca3P2O8 solid solutions synthesized for analysis varied from 10 to 90 mol pct, with an incremental increase of 10 mol pct per solid solution. In solid solutions with a Ca3P2O8 content of up to 40 mol pct, the crystal structure at 1773 K was found to be hexagonal, while the solid solutions with a Ca3P2O8 content over 70 mol pct had a trigonal structure. The silicocarnotite solid solutions observed when the Ca3P2O8 content was 50 to 60 mol pct were likely formed by phase transformation during cooling. In the stable solid solution with a Ca3P2O8 content of 50 to 60 mol pct at 1773 K before the occurrence of transformation, the crystal structure is trigonal since it is in the Ca3P2O8-rich range. A linear increase in the lattice parameters c of the solid solutions in the range of (0, 40 mol pct) and (70 mol pct, 100 mol pct) was found with increasing Ca3P2O8 content. The lattice parameter a, however, was almost independent of the Ca3P2O8 content in the solid solutions.

In ironmaking, maintaining gas permeability in blast furnace with low coke rate operation is essential to reduce carbon emissions. The high pressure loss in the cohesive zone decreases the gas permeability and affects the productivity of blast furnace. In order to increase the gas permeability in the cohesive zone, the thickness of the cohesive layer should be decreased. For this purpose, increasing softening temperature and decreasing dripping temperature of the iron ore are desired. In this study, softening, melting, and permeation of SiO2-FeO-CaO-Al2O3-MgO on a coke bed were investigated. The oxide sample in a tablet form was heated under CO/CO2 atmosphere, and the shape of the tablet was observed. The softening and melting temperatures of the SiO2-FeO-CaO system changed with the addition of Al2O3 and MgO. Oxide tablets with and without Al2O3 softened below and above the solidus temperature, respectively. The melting temperatures varied with the ratio of CO/CO2 in the gas. The permeation temperature was independent of the melting temperature, but dependent on the wettability.

The thermodynamic properties of aluminum, magnesium, and calcium in molten silicon were investigated using a chemical equilibration technique at 1723 to 1848 K, 1698 to 1798 K, and 1723 to 1823 K, respectively. The activity coefficient of aluminum in molten silicon was determined by equilibrating molten silicon-aluminum alloys with solid Al2O3 and Al6Si2O13, that of magnesium was determined by equilibrating molten silicon-magnesium alloys and MgO-SiO2-Al2O3 melts doubly saturated with MgSiO3 and SiO2, and that of calcium was determined by equilibrating molten silicon-calcium alloys with SiO2-saturated CaO-SiO2 melts. The activity coefficients at infinite dilution relative to the pure liquid state were determined as follows: $$\begin{array}{*{20}c} {log \gamma _{Al(l) in Si}^ \circ = - \frac{{1570}}{T} + 0.236 (1723 to 1848 K)} \\ {log \gamma _{Mg(l) in Si}^ \circ = - \frac{{4900}}{T} + 1.96 (1698 to 1798 K)} \\ {log \gamma _{Ca(l) in Si}^ \circ = - \frac{{7670}}{T} + 1.53 (1723 to 1823 K)} \\ \end{array} $$

Titanium and iron in silicon are known as harmful “lifetime killer” impurities, which shorten the lifetime of excited carriers in silicon solar cell and disturb power generation. Therefore, the removal of titanium and iron is one of the most important topics for the production of solar grade silicon. Thermodynamic properties of titanium and iron in molten silicon were determined at 1723 K by equilibrating molten silicon-titanium alloys or molten silicon-iron alloys with molten lead, which has a limited mutual solubility for both alloys. The activity coefficients of infinite dilution, self-interaction coefficients of titanium and iron in molten silicon, and the Gibbs energy change of mixing for silicon-titanium and silicon-iron at 1723 K relative to pure liquid silicon, titanium, and iron were determined.