新型铁酸钙型熔剂制备及其在钒钛磁铁矿氧化球团中的应用
Preparation of innovative calcium ferrite flux and its application in oxidized pellets of vanadium titano-magnetite
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摘要: 传统烧结工艺能耗高、污染大,这一问题在处理钒钛磁铁矿等复杂低品位铁矿粉时尤为突出。与烧结工艺相比,球团工艺是一种更为清洁的造块工艺。因此,提高钒钛磁铁矿球团矿入炉比例已成为高炉低碳冶炼的重要发展方向。本研究针对钒钛磁铁矿球团氧化困难、易形成核壳结构、强度低等问题,基于烧结法或球团法制备铁酸钙型钙质熔剂,并将其作为新型添加剂配入钒钛磁铁矿球团中以改善球团的固结特性。试验结果表明,烧结法制备的铁酸钙型熔剂以针状、板块状复合铁酸钙为主,大于5 mm粒级产品中复合铁酸钙有效含量达78.54%(面积分数)以上;球团法制备的铁酸钙型熔剂主要以铁酸一钙和铁酸二钙形式存在,复合铁酸钙有效含量达97.30%(面积分数)。配加2%(质量分数)球团法制备的铁酸钙型熔剂后,钒钛磁铁矿球团中形成的钙铁橄榄石等液相很好地充当了晶粒间固结的桥梁,钛赤铁矿晶粒尺寸明显长大,再结晶互联程度紧密,球团孔隙率降低,相同预热焙烧条件下,球团抗压强度同比提高26.2%,这为钒钛磁铁矿高炉高球团配比冶炼奠定了良好的理论与数据基础。Abstract: Conventional sintering methods are characterized by elevated energy consumption and significant environmental pollution, particularly when processing complex low-grade iron ores, such as vanadium titano-magnetite. In contrast, pelletizing represents a more environmentally friendly technique for producing agglomerated iron ore products. Consequently, the increased utilization of pellet burden of vanadium titano-magnetite in blast furnace low-carbon ironmaking process has emerged as a critical advancement in the field. To overcome challenges associated with vanadium titano-magnetite pellets such as poor oxidation behavior, the propensity to develop core-shell structures, and low mechanical strength, a calcium ferrite flux was synthesized via sintering and pelletizing techniques and introduced as an innovative additive to improve pellet consolidation characteristics. Experimental findings indicate that the calcium ferrite flux produced by sintering predominantly comprises acicular or tabular silico-ferrite of calcium and aluminum (SFCA), achieving an effective content of SFCA exceeding 78.54%(area fraction) in particles larger than 5 mm. In contrast, the flux prepared through pelletizing mainly consists of monocalcium ferrite and dicalcium ferrite, with an effective content of SFCA of 97.30% (area fraction). The addition of 2.0%(mass fraction) pelletized calcium ferrite flux to vanadium titano-magnetite pellets facilitates the formation of liquid phase, such as calcic iron olivine, which acts as effective bridging agents promoting intergranular consolidation. This results in a marked increase in titanium hematite grain size, enhances recrystallization bonding and decreases pellet porosity. 26.2% improvement in pellet compressive strength under consistent preheating and calcination conditions is achieved.
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