Influence Of Typical Gangue Composition Characteristics On Iron Ore Sintering Mineralization And Metallurgical Properties

Iron ore powder sintering,as the front step of the long process of iron and steel production,plays an important role in improving the properties of iron making materials and stabilizing the structure of blast furnace charge.With the gradual shortage of high grade iron ore resources,improving the ratio of low grade iron ore powder has become one of the most important means to reduce cost and increase efficiency in sintering process.However,the complex gangue composition in low-grade iron ore powder has a great influence on the metallurgical properties of sinter.Comprehensive study on the characteristics of typical gangue composition（basicity,Al₂O₃/SiO₂ ratio,MgO/Al₂O₃ratio）is of great significance to optimize the mineralization characteristics and improve metallurgical properties of sinter.Based on the raw material structure of sintering site,the optimization guidance of sintering mineralization and properties under different gangue composition characteristics was realized by calculating the reasonable component characteristic interval based on thermodynamics theory and combining with the experimental study of optimized ore blending in laboratory.Thermodynamic study showed that temperature,basicity,Al₂O₃/SiO₂ ratio,MgO/Al₂O₃ ratio and other factors have significant effects on the liquid content,mineral composition and liquid composition in sintering process.In the temperature range of 1200-1400℃,sinter included liquid phase,spinel,calcium silicate,plagioclase and other oxides.The increase of temperature and basicity led to the increase of liquid phase.When the basicity increased from 1.85 to 2.00,calcium silicate and spinel phases increased in mineral composition.The contents of SiO₂,Ca O and MgO in liquid phase also showed the same pattern,but the contents of Fe O and Fe₂O₃decreased in different degrees.When the Al₂O₃/SiO₂ ratio increased from 0.34 to 0.37,the contents of Fe O and Fe₂O₃ in the liquid phase,plagioclase and the liquid phase increased,while the contents of calcium silicate and oxide decreased.With the increase of MgO/Al₂O₃ ratio from 0.68 to 0.83,the contents of Fe₂O₃ and Al₂O₃ in the liquid phase,feldspar,oxide and liquid phase components decreased to varying degrees,while the contents of spinel,Ca O,SiO₂ and MgO components increased,and Fe O showed a trend of first increasing and then decreasing.Combined with the basic characteristics of iron ore powder sintering at high temperature,the sintering cup test of optimized ore blending under the condition of on-site raw materials was carried out.The test showed that:With the increase of basicity from 1.85 to 2.00,the indexes of sinter yield,drum index and utilization coefficient were optimized.When the basicity was 1.95,the above indexes were optimal,and the reducibility and low temperature reducibility of sinter were also optimal.At this basicity,the content of acicular calcium ferrite in the ore phase of sinter was higher,and there were fewer silicates and pores,which was consistent with the above results.With the increase of Al₂O₃/SiO₂ ratio from 0.34 to 0.37,the quality index of sinter mineral reaches the optimal value at 0.36.At this time,the mineral phase structure was more uniform,and the mineral phase was mainly interwoven corrosion structure formed by acicular calcium ferrite and magnetite,with fewer holes and silicates.The low temperature reduction degradation performance of sinter was gradually improved,and the reduction degree was the highest at 0.36.As MgO/Al₂O₃ ratio increases from 0.68to 0.83,the yield of sinter,tumle index and reduction performance were optimal at 0.78.At this time,the content of hematite in ore phase was low,and calcium ferrite phase increases significantly,which was mostly needle-like and dendritic,forming interwoven corrosion structure with magnetite,and the low temperature reduction degradation performance of sinter increased gradually.Through thermodynamic analysis and experimental verification,the appropriate sintering parameters were as follows:basicity 1.95,Al₂O₃/SiO₂ ratio 0.36,MgO/Al₂O₃ratio 0.78.Under these conditions,the sintering yield,drum strength and metallurgical properties of sinter reached the best level.The structure of produced sinter was uniform,showing interleaved erosion structure.And the mineral calcium ferrite content was high,mainly in acicular calcium ferrite.