Thermodynamic simulation on mineralogical composition of CaO–SiO2–Al2O3–MgO quaternary slag system

It is necessary to elucidate the crystallization thermodynamic of mineralogical phases during the cooling process of the molten BFS with different chemical composition, because the high-melting point mineral phase maybe crystallized during the fiber forming and thereafter cooling process. Thermodynamic calculation software FactSage6.4 and the hot remelting experiments were performed to explore the influence of basicity, Al2O3 content and MgO content on the crystallization of mineralogical components and their transformation. The results showed that the main mineralography of the CaO-SiO2-Al2O3-MgO quaternary slag system was melilite, and a certain amount of anorthite and calcium metasilicate. The crystallographic temperature of melilite is increased with the increasing of basicity, MgO and Al2O3 content, which has a significant impact on the utilization performance of the mineral wool prepared with the hot blast furnace slag directly. With the increasing of basicity, there was a tendency that crystallographic amount of melilite increased to the summit and then declined, while the amount of anorthite and calcium metasilicate decreased consistently. Finally, these two mineralogical components could be replaced by magnesium rhodonite and spinel with the increasing of basicity. When the basicity and MgO content were 1.0 and 9 %, the crystallographic mass ratio of melilite and anorthite increased, while that of calcium silicate declined, and replaced by spinel finally with the increasing of Al2O3 content. When the basicity and Al2O3 content were 1.0 and 13 %, the crystallographic mass ratio of melilite increased, while that of anorthite and calcium silicate declined, and replaced by pyroxene and spinel with the increasing of MgO content. To decline fiberization temperature of the melt BFS, the basicity, MgO and Al2O3 content should be decreased during the modification process of chemical composition, because the crystallization temperature of the primary crystalline phase in the slag system without modification.