Surface Tension of the Molten Blast Furnace Slag Bearing TiO2: Measurement and Evaluation

The influence of TiO2 content and basicity on the surface tension of the molten blast furnace slag has been investigated using the dispensed drop method at 1 673 K under the Argon atmosphere (Pressure approximate to 1.2 atm). The measurement shows that TiO2 plays a role as a surfactant in the CaO-SiO2-MgO-Al2O3-TiO2 system, and the decrease of the surface tension of the melt results from both the compositional changes and the structural change along with the composition variation. The surface tension of the slag rises from 413 mN/m up to 456 mN/m along with CaO/SiO2 mass ratio increasing from 0.90 to 1.20, while the structural variation only attenuates the rise of the surface tension of the slag. The thermodynamic model for determining the surface tension of molten slag by considering the surface tension and molar volume of the pure oxide components, and their ionic radii was applied to this molten slag bearing TiO2. The temperature dependence of the surface tension for pure TiO2 has been determined by comparing the measurement and the model calculation. The calculated surface tensions based on the present model are in good agreement with the experimental values. The maximum error and the average error are -7.52% and 3.27%, respectively. The influence of MgO and Al2O3 in the 5-component slag system has also been studied, and the addition of MgO or Al2O3 can increase the surface tension of the slag.