Investigation of the Reaction Kinetics of a Sinter-Reduction Process in the Thermal Reserve Zone of a Blast Furnace Using a Modified Sectioning Method

Abstract

With the development of large-scale and high-performing blast furnaces, it is necessary to extensively study the reaction characteristics and related kinetic parameters of sinters in their heat reserve area. Under reducing atmosphere conditions, the reduction of iron oxide in sinter is closely related to the gasification reaction of coke. Based on a simulation experiment, the transition point from chemical reactions to diffusion and the related kinetic parameters were determined through a sectioning method. The results showed that increasing the proportion of low-grade coke increased the chemical-reaction rate, but it slightly decreased the mass-transfer and diffusion rates. An increase in the coke particle size increased the chemical-reaction, mass-transfer, and diffusion rates. However, an increase in the CO2 volume fraction in gas reduced the chemical-reaction, diffusion, and mass-transfer rates. The mixing ratio of coke and sinters increased the chemical-reaction rate, but it decreased the mass-transfer and diffusion rates. The rate constant of the chemical reactions in the early stage was three orders of magnitude higher than that of the diffusion and mass-transfer coefficients, and the fitting degree was obviously better than that of the molecular diffusion in the later stage. Based on the thermodynamics of irreversible processes, the interference of the chemical reactions with the diffusion and mass transfer in the near-equilibrium region was tentatively established, the method of controlling coke diffusion and mass transfer in the later reaction stage was given and related kinetic parameters were corrected, and further improvement of the modified sectioning method was completed.