Original Article

Surface morphology and structural evolution of coke under hydrogen-rich conditions and dissolution mechanism based on active sites

¹ Hebei Iron and Steel Laboratory, North China University of Science and Technology, Tangshan 063210, PR China
² College of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063210, PR China

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Received: 16 December 2025
Accepted: 10 March 2026

Abstract

More in-depth studies on the gasification behavior and mechanism of coke by H₂O are needed due to blast furnace (BF) hydrogen-rich smelting becomes a popular topic. This paper focuses on the gasification dissolution loss experiment of coke by H₂O. The results indicate that: As the H₂O content increases, the coke surface becomes noticeably rougher, the changes on coke surface can be divided into two situations. The peaks on coke surface are consumed again and again, the coke surface is gradually eroded in this cycle. The degree of unevenness on coke surface shows that the baseline of gasification reaction has been decreased as the reaction progresses. After 60 minutes of gasification, the overall average of pores has expanded, and the distribution of pores on coke surface is no longer uniform. The proportion of isotropic structure decreases with the prolongation of gasification dissolution loss time and temperature. Even in anisotropic structure, the proportions of each structure are changing, and this evolution may be the fundamental reason for the changes in macroscopic properties of coke. In the infrared spectral curve, aromatic ring (C = C stretching vibration) and free hydroxyl group (stretching vibration of O–H) have been discovered. The number of free hydroxyl group has decreased due to the consumption of free hydroxyl group in the gasification reaction. High temperature promotes the separation of free hydroxyl group from H₂O, There are more media provided, which is the microscopic reason for the intense gasification. The entire process of coke dissolution by H₂O is summarized, the gasification dissolution mechanism based on active sites is proposed to understand the behavior of coke. On active sites, the adsorption of reactants first occurs. The adsorption saturation of active sites is defined to clarify the adsorption and desorption on active sites.