The sulphide capacities of CaO-SiO2-MgO-Al2O3-BaO slags were measured at 1773 K and 1823 K using the gas-slag equilibration method to estimate the desulphurization ability of the blast furnace slags that contained barium. The effects of basicity, the Al2O3 and BaO content of slags on the sulphide capacity of slags were studied. The relationship between the sulphide capacity and the optical basicity of the slags was also investigated. The experimentally determined results were compared with the sulphide capacities estimated by some previously reported models. The results showed that the sulphide capacity increased significantly when the basicity (CaO/SiO2) increased from 1.0 to 1.2, but decreased when the Al2O3 content increased in the slag. The increasing BaO content increased the sulphide capacity. The desulphurizing ability decreased when the BaO content was more than 3.5%. There was a linearly increasing relationship between the optical basicity and the sulphide capacity. The experimentally determined sulphide capacities were closest to the predicted values obtained by the Sosinsky and Sommerville’s model.

The present work was carried out to study the evaporation of fluoride from CaF 2 -CaO-Al 2 O 3 -MgO-Li 2 O-(TiO 2 ) slag with different TiO 2 contents. The evaporation ratio is determined by monitoring the weight change of the slag by isothermal thermogravimetric analysis in the temperature range of 1470-1530°C. The results show that the evaporation ratio of fluoride is promoted by increasing temperature and adding TiO 2 content from 0 to 13.28 wt-%. It has a slight effect to enhance the fluoride evaporation ratio when the TiO 2 content exceeds 8.67 wt-%. CaF 2 and AlF 3 are major constituents of the evaporation substances. The evaporation of fluoride is affected by the vapour pressure of AlF 3 and the viscosity of slag. The evaporation process for TiO 2 -containing slags is controlled by a chemical reaction in the beginning, followed by a mixed reaction-mass transfer regime, and the limiting factor is the liquid-phase mass transport in the end.

This study presents the evaporation mechanism of fluoride from CaF2–CaO–Al2O3–MgO–Li2O–(TiO2) slag and their melting characteristics at different TiO2 contents by thermogravimetric analysis and melting‐temperature‐characteristic testing. FactSage is used to identify the major components evaporating from the tested slags. The results show that the slag melting point decreases with an increase in the TiO2 content. In addition, X‐ray diffraction analysis reveal that with an increase in the TiO2 content, the total CaF2 and Ca12Al14F2O32 content increase while the MgAl2O4 content decrease. The gaseous species easily evaporating from slags, including LiF and CaF2, are the primary contributors to fluoride loss. The apparent activation energy for LiF evaporation is calculated to be in the range of 116.75–227.62 kJ mol−1 and this process can be described as 3D diffusion. In the case of CaF2 evaporation, the apparent activation energy is calculated to be in the range of 365.98–492.33 kJ mol−1 and this process followed the mechanism of random nucleation and growth.

A kinetic model for the reactions between the low-fluoride slag CaF2–CaO–Al2O3–MgO–Li2O–TiO2 and Incoloy 825 alloy was proposed based on the two-film theory. The applicability of the model was verified to predict the variation of components in the slag–metal reaction process. The results show that the controlling step of the reaction 4[Al] + 3(TiO2) = 3[Ti] + 2(Al2O3) is the mass transfer of Al and Ti in the liquid alloy and the controlling step of the reactions 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3) and [Si] + (TiO2) = [Ti] + (SiO2) is the mass transfer of SiO2 in the molten slag. With increasing TiO2 content in the slag from 3.57% to 11.27%, the Al content in the alloy decreased whereas the Ti content increased gradually. The Si content continued to decrease during the slag–metal reaction. Soluble oxygen in the alloy reacts with Al, Ti, and Si, resulting in a decrease of the oxygen content in the alloy. The variations of TiO2 content were in good agreement with the calculated results by the kinetic model whereas the measured results of Al2O3 and SiO2 in the slag were lower than the calculated results, which is mainly due to the volatilization of fluoride.