Transient Modeling of the Direct Reduction Shaft Furnace: Moving From Natural Gas to Hydrogen

Hydrogen‐based direct reduction of iron ore in shaft furnaces is a promising option for deep decarbonization of steelmaking. In addition to this, the process offers better opportunities for flexible operation compared to the traditional process of blast furnace. To provide insight into the dynamic evolution of in‐furnace states, this work develops, for the first time, a two‐dimensional transient computational fluid dynamics model of the shaft furnace process. The model is first applied to analyze the temporal variation of both gas and solid phases when the reducing gas composition is shifted from natural gas‐based to hydrogen‐based operation, which is an interesting future scenario. The results reveal that the gas phase responds within a few seconds, with the top gas composition stabilizing after about 5 s, while the solid metallization degree evolves much more slowly, showing an inverse response to a new steady state in more than 50 h. Increasing gas feed rate and decreasing solid feed rate are studied as potential countermeasures. The results demonstrate that the model can be used to gain an understanding of the effect of disturbances and to design control measures under changing boundary conditions.