Study On Fluidity And Thermal Stability Of Chlorine-Containing Blast Furnace Titanium Slag

With the development of steel industry,the charge structure and raw fuel conditions of iron and steel enterprises have changed.The chlorine brought into the blast furnace by imported ores and raw fuels continues to increase,and the chlorine will be absorbed by the blast furnace slag.The properties especially viscosity and thermal stability would be affected.Up to now,there are few studies related to the effect chlorine viscous behavior of blast furnace titanium slag,and the evolution mechanism of chlorine on the slag structure is unclear.In this paper,the chlorine-containing blast furnace titanium slag（Ca O-Si O2-Mg O-Al2O3-Ti O2-Ca Cl2）is used as the research object,and the effects of chlorine content,basicity,Al2O3 content and Ti O2 content on the properties of slag are studied,and the conclusion as below:The viscosity of the pre-melted slag was measured by the rotating cylinder method.And the experimental results showed that each group of slag samples had obvious turning points,which showing the obvious"short slag"characteristics.The increased of chlorine content in the slag reduced the melt viscosity,viscous flow activation energy and melting temperature,as well as effectively improved the fluidity of the slag.At low temperature,the chlorine content had a great influence on the slag viscosity.Due to the volatilization behavior of chlorine at high temperatures,the chlorine content gradually decreased as the viscosity test temperature decreased.The effect of basicity and Ti O2 content on the viscosity was consistent.The slag viscosity and viscous flow activation energy gradually increased as the Al₂O₃ content increased.The melt structure of the quenched samples was analyzed by infrared spectroscopy and Raman spectroscopy.The addition of chloride in the slag to form Si-Cl bonds destroyed the complex silicon-oxygen tetrahedral structure of the melt,and made the complex anions agglomerate into simple structural units.The replacement of free oxygen ions continued to destroy the structure in the slag,and the Ti-O-（Ti or Si）structure was simplified to Ti-O and O-Ti-O structure,which reduced the stability of the slag.With the increased of basicity and Ti O2 content,the amount of free oxygen in the slag increased,and the complex siloxane groups were depolymerized.With the increase of Al₂O₃ content,Al³⁺replaces Si⁴⁺to form[Al O₄]^5-tetrahedron,which increases the complexity of the slag structure.The concept of"Extreme Heat Release of Slag"（EHRS）was proposed to quantify the stability of slag.The heat capacity,enthalpy and EHRS of the chlorine-containing blast furnace titanium slag were calculated by thermodynamic equations.The slag heat capacity and enthalpy of slag were linearly related to the chlorine content,and gradually decreased with the increased of chlorine content,while the EHRS value increased gradually.The increase of chlorine content enhanced the resistance of the slag temperature to heat fluctuations,and the effect on slag viscosity was reduced,as well as was beneficial to ensure the stability of the slag,thereby maintaining the stability of blast furnace smelting.The heat capacity and enthalpy of slag decreased linearly with the increased of basicity and TiO₂ content,and increased linearly with the increased of Al₂O₃ content.