Dissolution mechanism of dolomite in converter slag at 1873 K

Abstract

The mechanism of dolomite dissolution in converter slag was studied and found to proceed by two steps: decomposition of dolomite into CaO and MgO and dissolution of the product into the slag. The first step was found to be controlled by heat transfer, which was confirmed by theoretical calculation. The decomposed dolomite had many pores, which allowed easy slag penetration. A discontinuous 2CaO.SiO₂ layer along with MgO.Fe₂O₃ particles was found on the surface of the samples. Some 2CaO.SiO₂ islands were found in the vicinity of the samples in the slag, revealing that the dissolution was dominated by peeling-off of the layer of 2CaO.SiO₂–MgO.Fe₂O₃ mixture. 2CaO.SiO₂, (Mg, Fe)O_ss along with super cooled liquid phases were found inside dolomite samples close to the surface. 2CaO.SiO2 phase was replaced gradually by 3CaO.SiO₂ towards the centre of the decomposed sample. While addition of small amounts of dolomite directly into the slag could be considered in steelmaking converter, too much would result in slow dissolution and waste of the raw materials.

Keywords:

• Dolomite
• Dissolution
• Decomposition
• Converter slag

Acknowledgements

The authors are thankful to Professor Patrice Nortier and Dr Thierry Chopin for their valuable suggestions and stimulating discussions. Financial support and lime samples from Lhoist are gratefully acknowledged.