Isothermal and non-isothermal CO2 gasification kinetics of charging coke and raceway coke used in a blast furnace

The composition and microstructure of charging coke and raceway coke (R-coke) of a blast furnace were studied by various detection methods. The gasification reactivity and reaction activation energy of the two samples were compared by thermogravimetric method under non isothermal and isothermal conditions. The results show that the R-coke level spacing d002 is slightly smaller than that of the coke, and the graphite layer accumulation height Lc and graphite layer size are significantly higher than that of the coke. The coke undergoes chemical erosion and physical wear in the blast furnace with microscopic pore development and increased surface structural irregularity. The high overlap of alkali metal K and Na with Si and Al elemental distribution positions on the surface of R-coke indicates the generation of complex compounds. In the non-isothermal gasification process, the rate-controlling of the gasification process gradually shifts from chemical reaction to diffusion as the conversion of the sample increases. Diffusion becomes the only limiting link of the reaction during isothermal gasification, and the pore structure is the main factor affecting the gasification rate. Since the pore structure of R-coke is more developed than that of coke, the activation energy of the reaction is lower, which is conducive to the diffusion of CO2 molecules to the reaction interface and the diffusion of the product CO to distant places, thus making the reaction rate of R-coke higher than that of coke.