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配加铁钛氧化物对复合焦炭性能与结构的影响

Influence of adding iron/titanium oxides on the properties and structure of composite coke

  • 摘要: 新型低碳炼铁炉料的开发和利用是高炉实现降碳减排的重要途径,尽管高反应性铁焦能够提升煤气利用率,但其热强度较低。目前,配加TiO2炼焦在改善焦炭热强度方面已展现出优势。本文通过在炼焦煤中加入Fe2O3和TiO2,采用坩埚焦试验制备铁钛复合焦炭,结合拉曼光谱和N2吸附等表征方法,研究了Fe2O3和TiO2对焦炭形貌、落下强度、碳微晶结构、孔隙结构的影响规律,并利用FactSage软件计算分析了结焦过程中铁钛氧化物的矿相转变规律。结果表明,与原煤制备焦炭相比,添加Fe2O3的焦炭形貌裂纹多,落下强度下降了35~85个百分点;添加TiO2的焦炭形貌规整,落下强度仅降低了2~15个百分点;两者复合添加后焦炭形貌保持良好,落下强度介于铁焦与钛焦之间,当两者总配比(质量分数)为5%时焦炭落下强度可达原煤炼焦强度的94.65%。碳微晶结构演变表明,Fe2O3在高温阶段(850 ℃)缺陷结构增加,而TiO2在高温阶段(超过650 ℃)促进石墨微晶有序排列,两者复合添加实现了炼焦过程全温域碳结构有序度的协同提升。在孔隙结构方面,Fe2O3在450、650 ℃促进介孔发育与贯通,提高了比表面积与孔容;TiO2则在高温阶段(不低于850 ℃)凭借金红石相热稳定性抑制孔隙塌陷。矿物相演变进一步表明,Fe2O3还原过程(Fe3+→Fe2+→Fe)引发体积“膨胀-收缩”,诱发缺陷;TiO2通过与FeO的强结合促使钛铁矿低温生成,抑制铁橄榄石生成,缓解晶格应力。本研究为高质量铁钛复合焦炭的制备及性能优化提供了重要的理论支撑。

     

    Abstract: The development and application of novel low-carbon ironmaking burden materials represent a critical pathway for blast furnaces to achieve carbon reduction and emission abatement. Although highly reactive iron coke can improve gas utilization, it suffers from low thermal strength. The incorporation of TiO2 in the coking process is demonstrated to enhance the thermal strength of coke. In this study, iron-titanium composite coke was prepared by adding Fe2O3 and TiO2 to coking coal through crucible coke experiments. The influence of adding Fe2O3 and TiO2 on the morphology,shatter strength,carbon microcrystalline structure,and pore structure of the coke were investigated using Raman spectroscopy,N2 adsorption,and other characterization methods. Furthermore,the mineral phase transformation of iron and titanium oxides during the coking process was calculated and analyzed using FactSage software. The results indicate that,compared with coke produced from raw coal,coke with added Fe2O3 is observed to exhibit more morphological cracks,and its shatter strength is reduced by 35 to 85 percent points. Conversely,coke containing added TiO2 exhibits regular coke morphology,with a shatter strength decreases of only 2 to 15 percent points. Subsequent to the amalgamation of two additives,the morphology of the coke remains intact,and its shatter strength is positioned between that of iron coke and titanium coke. When the total blend ratio reaches 5%,the shatter strength of the iron-titanium composite coke attains 94.65% of that derived from raw coal. The evolution of the microcrystalline structure indicates that the defect structure is increased by Fe2O3 at elevated temperatures(850 ℃),whereas the ordered arrangement of graphite microcrystals is enhanced by TiO2 at temperatures exceeding 650 ℃. A synergistic enhancement in the ordering degree of the carbon structure throughout the entire coking temperature range is achieved by the composite addition of the two. In terms of pore structure, the development and interconnection of mesopores are facilitated by Fe2O3 within the temperature range of 450 ℃ to 650 ℃,thereby increasing both specific surface area and pore volume. Conversely, pore collapse during the high-temperature stage(≥850 ℃)is prevented by TiO2 due to the thermal stability of the rutile phase. The evolution of mineral phases indicates that a volume "expansion-contraction" phenomenon is induced by the reduction of Fe2O3(Fe3+→Fe2+→Fe),which in turn induces defects. Conversely,the low-temperature formation of ilmenite is promoted by TiO2 through strong binding with FeO,the formation of iron olivine is inhibited,and lattice stress is mitigated. This study provides significant theoretical support for the preparation and performance optimization of high-quality iron-titanium composite coke.

     

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