Gasification and physical-chemical characteristics of carbonaceous materials in relation to HIsarna ironmaking process

HIsarna ironmaking process is one of the emerging technologies being developed to mitigate the increasing carbon footprint from the steel making industry. This innovative process offers flexibility with the type of reductants used in the smelting reduction vessel for the conversion of iron ore to liquid hot metal. Natural gas is well known for being a relatively clean fossil fuel producing carbon black and hydrogen when it undergoes thermal decomposition. The gasification reactivity of carbon black compared to the carbonaceous materials used in HIsarna process is investigated in this work using isothermal gravimetric analysis (TGA) method at 1250 °C, 1350˚C and 1450 °C under atmospheric pressure. Furthermore, physical-chemical characteristics of the individual carbonaceous materials, which may influence the reactivity, are evaluated systematically. The experimental results show that carbon black is the least reactive followed by thermal coal and charcoal. It was found that the effect of the morphology of the carbonaceous materials on the reactivity is dominant compared to the surface area of the materials. In addition, the reactivity increases with the alkali index (AI) and the level of the amorphousness of the material's structure. Three well-known kinetic models, i.e. the volumetric model (VM), the grain model (GM) and the random pore model (RPM) were applied to predict the gasification behaviour of the three carbonaceous materials. The random pore model best describes the gasification reaction of the selected samples due to the influence of the pore diffusion on the reaction. It is observed that the activation energy of the samples are not following the order of reactivity, this can be explained by the kinetic compensation effect.