Study On The Ecological Preparation Technology Of Glass-ceramics From Blast Furnace Slag After Extracting Titanium

Blast furnace slag after extracting titanium?BST?is a solid waste,which was formed by the treatment of Ti-bearing blast furnace slag by“high temperature carbonization-low temperature chlorination”process.BST has both hazardous attributes and resource characteristics.Based on phase composition and chemical composition of BST,BST was used as raw material,the glass-ceramics with good performance were prepared by direct sintering method without adding or adding little auxiliary materials.The mineralogical characteristics of BST,the phase composition and transformation of the calcined slag,and the dechlorination efficiency of BST were studied systematically.The influence of the addition amount of auxiliary materials and heat treatment process parameters on the phase composition,microstructure and properties of BST glass-ceramics were studied.The relationship between multiple performances were analyzed.The aim is to provide reference for the resource utilization and harmless utilization of BST.The results show that:?1?The crystal phase and the amorphous phase coexist in the BST,the crystal phases are khamrabaevite and carbon,the main chemical components are CaO,Al₂O₃,SiO₂,and some Fe₂O₃,MgO,TiO₂,Cl,etc.?2?When the calcining temperatures were 300⁶00°C,the phase composition in calcined slag remained steady;at 700°C,the characteristic diffraction peak of carbon disappeared completely,and perovskite appeared;at 800°C,the characteristic diffraction peaks of akermanite and diopside appeared.The amorphous phase disappeared completely at 900¹100°C.?3?After calcining at different temperatures,the content of chlorine in the slag gradually reduced.At 1000°C,the residual amount of chloride in the slag was 0.06%,and the dechlorination efficiencywas98%.?4?During the process of calcining,a layer of white powder adhered to the wall of tube furnace,according to qualitative analysis,the crystal phases in the white powder are halite and sylvite.?5?The concentration of chloride ion in the absorption liquid is greatly affected by the calcining temperature.When the calcining temperature was 1000°C,the chloride ion concentration in the absorption liquid was the lowest,9.26 ppm.?6?Via direct sintering method,glass-ceramics with akermanite,diopside and perovskite were prepared from using BST as full raw material,The utilization rate of BST was 100%;with the change of heating treatment process,the crystal phase of glass-ceramics remains unchanged,while the microstructure and properties of glass-ceramics change greatly.The interlaced structure formed by the crystal phase and the liquid phase could be observed in the glass-ceramics with fine microstructure,meanwhile the pore is small and isolated distribution.Under the optimized heat treatment process,the linear shrinkage rate,bulk density,water absorption and bending strength of the prepared glass-ceramics were14.41%,2.50 g/cm³,1.45%and 51.52 MPa,respectively.?7?BST was used as the main raw material and adding a small amount of sodium carbonate as auxiliary material,glass-ceramics with akermanite,diopside and perovskite were prepared by direct sintering method.The optimal addition amount of sodium carbonate was 3%,the utilization rate of BST was 97%;the addtion of sodium carbonate has obvious destructive effect on the crystal structure of diopside,that inhibits the growth and development of diopside,when the addition amount was 10%,diopside disappeared in the glass-ceramcs.Under different sintering condition,the crystal phase of the glass-ceramics remains steady,and the influence degree of the sintering process parameters on each crystal phase is:diopside>akermanite>perovskite.Under the optimized sintering process,the linear shrinkage rate,bulk density and bending strength of the prepared glass-ceramics were 15.89%,2.76 g/cm³,56.93 MPa and the water absorption rate was 0.08%.