Effect of MgO Content on the Viscosity, Foaming Life, and Bonding in Liquid and Liquid/Solid CaO-SiO₂-MgO-5Al₂O₃-30FeO Slags

Abstract

The CaO-SiO2-MgO-5Al2O3-30FeO five (oxide) components slag system was studied by varying the magnesium oxide (MgO) content (5.7–13.6 wt.%.% MgO) and keeping the basicity constant). The data were analyzed using the FactSage software. It was observed that the liquid network structure and precipitation of solid particles had an impact on high-temperature viscosity and foaming life. Under the same basicity (mass ratio CaO/SiO2 = 1.5) and at a temperature of 1500 °C, the MgO content was varied as 5.7 wt.%, 7.4 wt.%, 9.6 wt.%, 11.5 wt.%, and 13.6 wt.% in A0~A5. The solid fractions of different samples were estimated with FactSage software and found to be A0–A2 (0 wt.%), A3 (2.77 wt.%), A4 (6.92 wt.%), A5 (11.7 wt.%). The viscosities of A0–A5 measured at 1500 ·C were 22, 47, 40, 76, 363, and 1088 mPa×s, respectively, and the foaming life was 2.0 min, 7.7 min, 6.2 min, 13.4 min, 16.8 min, and 18.0 min, respectively. It was found that A5 exhibits the best effective foaming life under these environmental conditions because it can ex-hibit a double foaming effect formed by the precipitation of solid particles. The Si-O-Si network in liquid slag also contributed to foaming life, when there was only liquid slag bonding in the slag, the effective foaming life was 7.7 min. In the absence of these factors, the foaming life was only 2 min.

Keywords

• slag foaming
• MgO
• viscosity
• Raman spectra
• bonding of liquid