A Numerical Study of Options for Improving Carburization in a Hydrogen-Intensive Direct Reduction Shaft Furnace

This study develops a computational fluid dynamics model of a shaft furnace to explore strategies for enhancing carburization performance during hydrogen-intensive direct reduction, crucial for sustainable steel production. The model is first used to study the effect of the hydrogen content in the reducing gas on the state of the furnace. Next, several technical strategies are investigated to improve the carburization under pure hydrogen reduction scenarios. The results show that an increased hydrogen content in the reducing gas leads to a clear decrease in the metallization degree and carbon content of the direct reduced iron due to the degraded thermal level in furnace triggered by the strongly endothermic nature of hydrogen reduction. A higher feed rate of reducing gas is therefore necessary to mitigate the heat shortage, improving both the metallization degree and carbon content of the product. Increasing the methane content in the carburization gas or extending the carburization/cooling zone can only increase the carbon content marginally, but a strong increase can be achieved by preheating the carburization gas to a high temperature. The results provide guidelines on how to realize more sustainable ironmaking in the future.