Bo-wen Chen, Wei Wang, Wen-kang Lin, Xu-heng Chen, Ling-kun Chen, Da-wei Song, Run-sheng Xu, Jie Wang
Coke is the only solid charge component in the lower part of the blast furnace, and its strength is crucial to its production. Si and Al are the two most abundant elements in coke ash. The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests. According to the Weibull analysis, with increasing Si and Al oxide concentrations, the fracture stress range of the coke widened, the upper and lower limits decreased, the probability of fracture under the same stress conditions increased, and the randomness and dispersion of strength increased. These results can be attributed to the inhibitory effect of ash during coal pyrolysis. Ash impedes the growth and contact of mesophase, leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke. Consequently, the overall ordering of the carbon structure is reduced. Moreover, SiO2 and Al2O3 promoted the development of coke pores, thinned the coke pore wall, and significantly increased the proportion of large pores ([500 lm). Moreover, Al2O3 had more significant influences on the coke strength, carbon structure and stomatal ratio than SiO2. In addition, the position where the ash particles bonded to the carbon matrix easily produced cracks and holes, and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force, leading to structural damage. Therefore, controlling the concentration of ash could effectively reduce the number of structural defects inside coke, which is conducive to improving the strength.
