Computational Fluid Dynamics Study of the Flow and Thermochemical Behaviors of a Carbon Composite Briquette in an Ironmaking Blast Furnace

A carbon composite briquette (CCB), which combines low-rank coal and iron oxides through agglomeration technology, is one promising raw material to improve energy efficiency and reduce the fuel rate for blast furnace (BF) ironmaking. However, the in-furnace behavior of CCB and its impact on BF performance is not yet clear. In this study, a computational fluid dynamics model is developed to explore the in-furnace flow and thermochemical behaviors related to CCB charging into a BF under full-scale conditions. The model features a submodel of different chemical reactions in respective coke and ore layers and an ore-CCB mixture submodel. The results show that, in comparison to non-CCB operation, the BF with CCB operation can have higher productivity and a lower coke rate and the top gas temperature is lower. This is attributed to improved thermal energy utilization efficiency in CCB operation. Moreover, the carbon mass loss fraction is compared between coke and CCB, indicating that coke carbon can be protected by CCB effectively. Then, the detailed reduction behavior of CCB and ore are analyzed throughout the BF. The thermal reserve zone temperature is found reduced when CCB is used in the BF. This model provides an effective tool to evaluate and optimize the BF performance with CCB charging for future applications.