高炉焦炭微观结构演变的多尺度表征及应用

doi:10.13228/j.boyuan.issn0449-749x.20220269

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Abstract Coke is an important raw material for blast furnace smelting, and the multi-scale characterization of its microstructural evolution plays a crucial role in the rational evaluation of coke quality and blast furnace operation. During carbon loss reaction, different degrees of degradation gradients generate inside the porous structure of coke, which have a very important impact on coke behavior, but the current coke evaluation system fail to take this factor into account. The ratio of the reaction rate constant k_rea to the diffusion coefficient D_eff (k_rea/D_eff) was proposed to characterize the effect of the carbon loss reaction on the deterioration of the coke's spatial structure, it could provide a basis for further accurate characterization and prediction of the degradation gradient inside the coke, thus optimizing the coke quality. The matrix reaction characteristics and pore structure evolution characteristics of coke with different particle size were studied. The composition and pore structure parameters of different carbon loss cokes were analyzed by Fourier transform infrared spectroscopy, optical microscope, SEM-EDS and BET specific surface area pore size distribution analyzer. The results show that with the deepening of coke's carbon loss, minerals gradually precipitate on the surface of coke, and play a catalytic role in the process of carbon loss, resulting in a decrease in activation energy Ea and an increase in k_rea. At this point, the micropores in coke expand and merge into mesopores and macropores, the diffusion path of CO₂ molecule decreases, the diffusion activation energy E_D decreases, and D_eff increases gradually. In the middle and late period of carbon loss reaction, the active components in coke are consumed and a large amount of ash in coke is precipitated, which increases the activation energy E_a and decreases the k_rea. Moreover, the number of macropores in coke is further increased, and the tortuous degree of porous structure is greatly reduced, which leads to the decrease of diffusion activation energy E_D and the increase of D_eff. Sudying the ratio of coke k_rea and D_eff shows that k_rea/D_eff decreases rapidly with the increase of carbon loss reaction. And the larger the k_rea/D_eff is, the larger the deterioration gradient inside the coke is, and the coke powder is easily generated from the coke surface, which is not conducive to the actual production of the blast furnace. Therefore, on the basis of reducing the coke dissolution loss rate or CSR, controlling k_rea/D_eff within a reasonable range is an effective measure to further improve the coke quality.

Key words： coke microstructure multi-scale kinetics carbon loss reaction

Received: 21 April 2022

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	Articles by authors
	LIU Qi-hang
	WANG Di
	ZHAO Xiao-wei
	YANG Shuang-ping
	HU Qu

Cite this article:

LIU Qi-hang,WANG Di,ZHAO Xiao-wei等. Multiscale characterization and application of microstructural evolution of blast furnace coke[J]. Iron and Steel, 2022, 57(10): 43-54.

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http://www.chinamet.cn/Jweb_gt/EN/10.13228/j.boyuan.issn0449-749x.20220269 OR http://www.chinamet.cn/Jweb_gt/EN/Y2022/V57/I10/43

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