EFFECT OF TEMPERATURE ON MgO ACTIVITY IN THE CaO-SiO2-MgO-Al2O3 SYSTEM MEASURED BY MOLTEN TIN

Blast-furnace slag is one of the main by-products produced in the process of blast-furnace ironmaking. Its metallurgical properties have an important impact on the smooth operation and long life of blast furnaces. In this paper, the activity of MgO in a CaO-SiO2-MgO-Al2O3 quaternary slag system was measured using the reference-slag method at 1773–1873 K. The effects of temperature on MgO activity and the activity coefficient of Mg in Sn of the CaO-SiO2-MgO-Al2O3 quaternary slag system were discussed. The results showed that when w(MgO)/w(Al2O3) = 0.40, B(w(CaO)/w(SiO2)) = 1.30 and w(Al2O3) = (12 %; 15 %; 18 %; 20 %), the activity of the MgO and the activity coefficient of the Mg in Sn increased with increasing temperature. With increasing temperature, the grooves in the SiO4 tetrahedral structure at wavenumbers of 800–1200 cm–1 gradually became shallow and flat, indicating that the complex silicate structure synthesized in the form of SiO2 decreased and the activity of the MgO increased. According to the CaF2-MgO binary phase diagram, the dissolution enthalpy of MgO was calculated to be –16.409 kJ/mol.