Dissolution of dolomite and doloma in silicate slag

Dissolution mechanisms of dolomite CaMg( CO3)2, and doloma CaO.MgO, in a model basic oxygen furnace (BOF) slag based on the CaO-MgO-SiO2-FeO-MnO system have been characterised with regard to the reaction product phases at the dolomite/slag and doloma/slag interfaces by post-mortem microstructural analysis. It was found that after I h immersion at 1350(degree) C in a stagnant molten slag, the CuO and MgO in doloma react with SiO2 and FeO in the slag forming dicalcium silicate (2CaO.SiO2 or C2S), MgO-rich magnesiowiistite ((Fe,Mg)O), and dicalcium ferrite (2CaO.Fe2O3 or C2F). The formation of (Fe,Mg)0 and C2F breaks up the C2S layer, leaving it discontinuous. Similar reactions take place in dolomite, but at a later stage of dissolution since they are retarded by the intermediate decomposition of dolomite in which rapid CO2 gas evolution quenches the resulting C2S layer and forms a gap between the resulting doloma and slag. A more complete and continuous dicalcium silicate layer was observed in dolomite compared with doloma. BCT/352