Thermodynamic Analysis and Formation Law of Q Phase of Calcium Aluminate Clinker

The research on lime sintering process to treat low grade bauxite becomes the hotspot, because it can realize dry sintering and decrease the energy consumption. But during the sintering process the existence of MgO, which is trace element and contained in lime, will lead to the phase formation from 12CaO·7Al₂O₃ (C₁₂A₇) to 20CaO·13Al₂O₃·3MgO·3SiO₂ (Q phase) whose alumina leaching property is worse than the former. The alumina leaching ratio decreases obviously. The double parameter model is used to calculate the thermodynamic data of the quaternary compound, and the formation law of alumina-containing phases is obtained by Factsage software. The results indicate that low temperature and high lime addition are benefit to the formation of C₁₂A₇. The Q phase is found in clinker when sintering temperature is 1325 °C. The content of Q phase increases obviously when the temperature is higher than 1400 °C.