Microstructure characteristics of coke during solution loss reaction in the mixed atmosphere of water vapour and CO 2

Abstract

Injecting coke oven gas or hydrogen gas in a blast furnace (BF), which is a potential low-carbon iron-making technology, alters the atmospheric conditions of the coke gasification reaction. Understanding the characteristics of the solution loss reaction and the performance of coke in a mixed atmosphere of water vapour and CO₂ is essential for targeted adjustments of coke quality in hydrogen-enriched BF. This study carried out the experiment of reaction between coke and the mixed atmosphere of water vapour and CO₂ using a coupling device of a tube furnace and water vapour generator. Simultaneously, the pore structure parameters of cokes prepared under different conditions were measured through image analysis and nitrogen adsorption methods at different scales, and the optical texture of coke was analysed using the point counting method with an automatic microscopic analysis system. The findings reveal that mixing water vapour in reactant gas markedly intensifies the extent of solution loss reaction of coke leading to increase in coke porosity. At 1150°C, water vapour promoted the expansion of nanopores, while at temperatures between 950∼1050°C, it promoted the expansion of micropores. Moreover, an increase in water vapour content led to a decrease in the proportion of textures like fusinite and fragmental texture, fine mosaic texture, and isotropic texture, indicating that water vapour in the reaction atmosphere accelerated the consumption of these textures. This result suggests that water vapour selectively reacts with textures exhibiting high isotropy.