Investigation on the evolution of structure and strength of iron coke during carbonization: Carbon structure, pore structure, and carbonization mechanism

Iron coke has attracted great interest in low-carbon ironmaking due to its environmental friendliness and efficient utilization of resources. However, the low strength of iron coke limits the potential applications. Herein, the evolution mechanism of the structure and strength of iron coke during carbonization was examined to elucidate the impact of iron ore on iron coke strength. The findings indicate a significant reduction in the tensile strength of iron coke when the iron ore addition exceeds 15%, and improving carbonization temperature positively impacts the tensile strength of iron coke. Additionally, XRD and Raman analyses demonstrate that iron ore destroys the microcrystalline layers of iron coke, thus weakening the cohesiveness of carbon structure. The volume expansion resulting from crystal transformation during iron ore reduction generates cracks within the carbon matrix, which further destroys the structural integrity of iron coke. Furthermore, the panorama reveals that the coupling reactions of iron ore reduction and carbon gasification intensify the consumption of carbon matrix, causing the erosion and dissolution of pore walls. The porosity and heterogeneity of macroscopic pores are hence increased, which reduces the iron coke strength. Compared to macroscopic pores, the influence of micropores on iron coke strength is relatively insignificant.