Article ID: ISIJINT-2024-300
Introducing hydrogen gas into the blast furnace to partially substitute pulverised coal or coke, is a promising solution to decrease CO2 emissions of ironmaking process. However, increased H2O concentration alters the thermal and chemical conditions in the furnace, impacting the gasification reaction rate and degradation mechanism of coke. This research developed a modified random pore model (RPM) to integrate internal diffusion and interfacial chemical reaction processes, aiming to study reaction mechanisms and structural changes in coke under simulated conventional and H2-enriched blast furnace conditions. High-temperature thermogravimetric analysis was used to evaluate the gasification of coke lumps with varying initial quality. The experiments were performed isothermally between 1173-1473 K. Results indicated that coke reactivity in an H2-rich environment is up to 1.5 times higher than the conventional case. Moreover, low CRI coke exhibited a lower reaction rate in the H2-rich case, indicating the importance of coke quality for modified blast furnace operations. Modelling results showed that in the conventional blast furnace case, reactions occur more uniformly across the coke radius, indicating that chemical reaction is the dominant mechanism. In contrast, in the H2-rich blast furnace case, gas diffusion becomes the dominant rate limiting factor at higher temperatures (i.e., 1473 K), leading to higher mass loss near the coke surface and leaving a less-reacted core. These effects are more pronounced in low CRI coke due to its lower diffusivity coefficient. The results suggest that low CRI coke in an H2-rich blast furnace helps minimise coke degradation and maintain structural integrity.
