LAUSR

The specific heat capacity (Cp) of blast furnace (BF) slag critically impacts BF smelting and reports on the Cp of BF slag with high Al2O3 are rare. Mineral transform and Cp characterization of synthesized BF slag (CaO–SiO2–MgO–Al2O3) with high Al2O3 in the heating process are herein discussed. Differential scanning calorimetry curves show a major exothermic peak at a low temperature and multiple endothermic peaks at elevated temperatures. The exothermic peak at approximately 920 °C appears when amorphous SiO2 (or SiO2 in silicate) becomes crystal SiO2 (or SiO2 in silicate). The endothermic peak between 1224–1254 °C is attributed to the reverse eutectic reaction, CaO·Al2O3·2SiO2 + 2CaO·0.5MgO·0.5Al2O3·1.5SiO2 → Liquid, along a eutectic line. CaO·Al2O3·2SiO2 + MgO·SiO2 → Liquid + 2MgO·SiO2 (reverse peritectic reaction) or CaO·Al2O3·2SiO2 + 2MgO·SiO2 → Liquid (reverse eutectic reaction) at approximately 1268 °C will occur with an endothermic reaction in some cases. The sharp endothermic peak between 1282 and 1303 °C is the reverse eutectic reaction, CaO·SiO2 + 2CaO·Al2O3·SiO2 → Liquid. The blunt endothermic peak between 1388 and 1447 °C is the residual slag melting, Solid → Liquid. The relationships of Cp with temperatures and compositions (R, ratio of w(MgO)/w(Al2O3), and w(Al2O3)) are established with a good fit.