| There are abundant vanadium titano magnetite in Panzhihua area of Sichuan province in China.In the smelting of vanadium titano magnetite in blast furnace process,Ti oxides are more difficult to be reducted by C than Fe oxides,which leads to Ti element transfored into blast furnace slag.The slag is known as Ti-bearing slag and containing more than 20%TiO2.The Ti-bearing slag has been considered as a valuable secondary resource due to the high TiO2 content,and a lot of processes have been proposed for treating the Ti-bearing slag.The Ti element is finely dispersed in many different kinds of Ti-containing phases,which makes it is very difficult to extracting Ti resource from Ti-bearing slag system.However,the thermodynamic information especially the phase diagram data for Ti-bearing slag system has rarely been investigated,which severely restrict the comprehensive utilization of the Ti resources.,hence,the determination of the phase relations and liquidus temperatures for Ti-bearing slag system becomes more and more important not only for the supplement of the phase diagram information,but also for the comprehensive utilization of the Ti resources.In present project,the CaO-SiO2-MgO-Al2O3-TiO2 system was selected based on the compositions in Ti-bearing slag system.The melting temperatures and equilibrium phase relations of CaO-SiO2-MgO-Al2O3-TiO2 system were systermatic studied using the SHTT technique and high temperature equilibrium technique followed by X-Ray Fluoroscopy(XRF),X-Ray Diffraction(XRD),Scanning Electron Microscope(SEM)and Energy Dispersive X-ray spectroscope(EDS)analysis.The liquidus surface and equilibrium phase relations were finally obtained based on the thermodynamic theory for CaO-SiO2-5%MgO-(10%-30%)Al2O3-TiO2 system.Within the experimental conditions in present study,the main conclusions could be obtained as follows:(1)The melting temperatures in the specific area of CaO-SiO2-5%MgO-(10%-20%)Al2O3-TiO2 system were studied by SHTT technique.In the composition range of present work,the melting temperature increased with the increase of w(CaO)/w(SiO2),The lowest melting temperature was 1250? when TiO2 content was 5.15%and w(CaO)/w(SiO2)was 0.88,while the highest melting temperature was 1541? when TiO2 content was 22.57%and w(CaO)/w(SiO2)was 1.46.(2)The relationships of melting temperature change with w(CaO)/w(SiO2)were determined based on the thermodynamic theory.The 1300?-1500? liquidus lines were then calculated and plotted for CaO-SiO2-5%MgO-(10%-20%)Al2O3-TiO2 system.In the composition range of present work,liquidus temperature increased with the increase of w(CaO)/w(SiO2).(3)The equilibrium phase relations at 1300?-1450? were experimental determined by high temperature equilibrium technique.In the composition range of present work,the equilibria phases of(C2MS2,C2AS)SS,2CaO.Al2O3.SiO2,CaO TiO2,CaO.SiO2,2CaO.SiO2,Ca(Ti,Mg,Al)(Si,Al)2O6,(MT2,AT)ss and MgO.Al2O3 were confirmed.(4)Based on the SHTT results,high temperature equilibrium experimental results and related phase diagram information,the 1300?-1500? liquidus lines and the distribution of equilibria phases of(C2MS2,C2AS)ss,2CaO·Al2O3 SiO2,CaO TiO2,CaO SiO2,2CaO.SiO2,Ca(Ti,Mg,Al)(Si,Al)2O6,(MT2,AT)ss and Mg·Al2O3 were obtained.(5)Based on the equilibrium thermodynamic theory,the composition range of 1300?-1450? liquidus surfaces were calculated when the liquid phase equilibrium with CaO·TiO2,(C2MS2,C2AS)ss and MgO.A12O3,respectively.The composition range of the liquid phase coexisting with CaO·TiO2 and(C2MS2,C2AS)ss was also calculated.In the composition range of present study,the primary crystal field of(C2MS2,C2AS)ss exist in high w(CaO)/W(SiO2)area with TiO2 content lower than 12.67%.The primary crystal field of MgO·Al2O3 exist in low w(CaO)Aw(SiO2)area with A12O3 content higher than 26.07%.The primary crystal field of CaO TiO2 exist in high iw(CaO)/w(SiO2)area when TiO2 content is between 5.83%-25.98%.(MT2,AT)ss will appear when TiO2 content is higher than 25.98%,while the primary crystal field of Ca(Ti,Mg,Al)(Si,Al)2O6 exist in low w(CaO)/w(SiO2)area with Al2O3 content lower than 26.07%. |
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