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

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.