Sintering Behavior Research Of Calcium Aluminate With Calcium Silicate During High-temperature Eutectic Reaction

Extracting alumina from low-grade aluminum-containing resources with lime sinter process has the advantages of dry sintering and clinkers self-pulverization.However,high lime dosage,high amounts of leached residues and poor alumina leaching property of clinkers inhibit its application and development.Therefore reducing lime dosage and improving alumina leaching property are always the fundamental development direction in the lime sinter process.In this paper,the phase formation,phase transformation and micromorphology of CaAl₂O₄?CA?-Ca₂SiO₄?C₂S?and Ca₁₂Al₁₄O₃₃(C₁₂A₇)-C₂S during high temperature eutectic reaction were studied by XRD,SEM,FTIR and TG-DSC.The pulverization property of sintered clinkers were determined by particle size analysis.Chemical stability in Na₂CO₃-NaOH solution were studied by standard dissolution.The formation mechanism and chemical stability of gehlenite also studied.The phase transformation mechanism and chemical stability of CA-C₂S clinkers were studied when the sintering temperature ranges from 1300?to 1500°C.Increasing sintering temperature and duration can promote the transformation process that CA reacts with C₂S into C₂AS and C₁₂A₇.The main phases of clinkers sintered at 1450°C for 2.0h are C₂AS,C₁₂A₇ and?-C₂S,as well as some CA and?-C₂S.C₂AS can reduce the pulverization property of clinkers,which is also difficult to react with Na₂CO₃ solution.The alumina leaching rate of sintered clinkers is 56.17%.The main phases of clinkers when sintered at 1500?for 2.0h are CA and?-C₂S,as well as some C₂AS,C₁₂A₇ and?-C₂S.The alumina leaching rate is 96.22%.The phase transformation and chemical stability of C₁₂A₇-C₂S clinkers were studied when the sintering temperature is 1300¹500°C.C₁₂A₇ reacts with C₂S to form C₂AS when sintered temperature at 1498°C for 2.0h.The main phases are C₁₂A₇ and C₂S as well as some C₂AS when the sintering temperature is 1500°C.The alumina leaching property increases first and then decreases with the increase of sintering temperature.The alumina leaching rate is 99.47%sintered at 1450°C for 2.0h.