Dissolution of dolomite and doloma in silicate slag

Dissolution mechanisms of dolomite CaMg(CO3)(2), and doloma CaO.MgO, in a m odel basic oxygen furnace (BOF) slag based on the CaO-MgO-SiO2-FeO-MnO syst em have been characterised with regard to the reaction product phases at th e dolomite/slag and doloma/slag interfaces by post-mortem microstructural a nalysis. It was found that after 1 h immersion at 1350 degrees C in a stagn ant molten slag, the CaO and MgO in doloma react with SiO2 and FeO in the s lag forming dicalcium silicate (2CaO.SiO2 or C2S), MgO-rich magnesiowustite ((Fe,Mg)O), and dicalcium ferrite (2CaO.Fe2O3 or C2F). The formation of (F e,Mg)O and C2F breaks up the C2S layer, leaving it discontinuous. Similar r eactions take place in dolomite, but at a later stage of dissolution since they are retarded by the intermediate decomposition of dolomite in which ra pid CO2 gas evolution quenches the resulting C2S layer and forms a fap betw een the resulting doloma and slag. A more complete and continuous dicalcium silicate layer was observed in dolomite compared with doloma.