Effect of TiO₂ on fluoride evaporation from CaF₂–CaO–Al₂O₃–MgO–Li₂O–(TiO₂) slag

ABSTRACT

The present work was carried out to study the evaporation of fluoride from CaF₂–CaO–Al₂O₃–MgO–Li₂O–(TiO₂) slag with different TiO₂ 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 TiO₂ content from 0 to 13.28 wt-%. It has a slight effect to enhance the fluoride evaporation ratio when the TiO₂ content exceeds 8.67 wt-%. CaF₂ and AlF₃ are major constituents of the evaporation substances. The evaporation of fluoride is affected by the vapour pressure of AlF₃ and the viscosity of slag. The evaporation process for TiO₂-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.

KEYWORDS:

• Electroslag remelting
• TiO₂
• fluoride evaporation
• thermogravimetric analysis
• vapour pressure
• evaporation kinetics
• viscosity
• apparent activation energy

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under grant number 51774225.