Model study of central coke charging on ironmaking blast furnace performance: Effects of charging pattern and nut coke

Ironmaking blast furnace (BF) is a slow-moving bed chemical reactor and is facing many challenges such as low-grade raw materials. Central coke charging (CCC) can accommodate low-grade materials including low-grade iron ore, low-grade coal and nut coke (a low-grade coke) and meanwhile helping stabilize BF operations, but it lacks systematic and quantitative studies. In this work, a multi-fluid BF model, which considers flow-thermal chemical behaviors of gas, solid and liquid phase is further developed, featuring a CCC burden profile sub model and an ore-nut coke mixture sub-model. It is used to study the influences of CCC patterns including CCC opening radius and nut coke rate (NCR) on BF performance and identify the optimal CCC operational conditions. The results show that, when CCC opening radius increases from 1/64 to 1/4, carbon solution-loss reaction is further suppressed while top gas temperature and coke rate encounter an increase by similar to 200 K and similar to 43 kg/ton hot metal (kg/tHM), respectively. On the other hand, when NCR increases, BF performance varies non-linearly; the highest BF performance indices are attained at the NCR of 20 kg/tHM, namely the optimal NCR. This model provides a cost-effective way to systematically study and design CCC operation in BF practice. (C) 2019 Elsevier B.V. All rights reserved.