Carbide Capacity of CaO-SiO2-CaF2(-Na2O) Slags at 1 773 K

Abstract

The influence of CaF2, Na2O, and basicity on the solubility of carbon in the CaO-SiO2-CaF2-Na2O slag at 1 773 K was investigated on the basis of carbide capacity concept. The carbide capacity of the CaOsatd-SiO2-CaF2 system increases with increasing CaF2 content up to about 40 mass%, followed by nearly constant value. The capacity of the slags saturated with Ca2SiO4 also increases with increasing the content of CaF2 and this trend can be explained from the depolymerization reaction of silicate network by F- ions. The carbide capacity of the slags increases by increasing the ratio of (%CaF2)/(%SiO2) up to about 0.8, followed by slight increase or nearly constant value at a fixed CaO content. The capacity also increases by increasing the ratio of (%CaO)/(%SiO2) at a fixed CaF2 content. The carbide capacity of the Na2O-containing slags linearly increases with increasing the basicity, B (≡{(%CaO)+(%Na2O)}/(%SiO 2)) and the dependence of the capacity on the basicity decreases by increasing the CaF2 content. On the other hand, the capacity decreases with increasing CaF2 content at basicity, B of the slags greater than about 2.0 and vice versa in the composition of B≤2.0. The capacity of the slags containing CaF2 and Na2O could quantitatively be described by the activity of CaO rather than optical basicity.