Dissolution of Lime in Synthetic ‘FeO’‐SiO2 and CaO‐‘FeO’‐SiO2 Slags

Dissolution of different CaO samples into molten synthetic ‘FeO’‐SiO₂ and ‘FeO’‐SiO₂‐CaO slags was carried out in a closed tube furnace at 1873 K. The slag was kept stagnant. It was found that the dissolution rate was very fast when CaO rod was dipped into ‘FeO’‐SiO₂ slag. In the case of ‘FeO’‐SiO₂‐CaO slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). Only less than 16 percent CaO reacted with the slag, irrespective of the type of lime. Three phase‐regions were identified in the reacted part of the lime rod by SEM‐EDS analysis. The formation of these regions was explained thermodynamically. A dense layer of 2CaO · SiO₂ was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO · SiO₂ layer would be of essence to obtain a high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag to reach a reliable conclusion regarding the relevance of the reactivity obtained by water ATSM test to the real reactivity of lime in high temperature slag.