8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

In a modern blast furnace (BF) operation, the hearth is a critical area influencing both the routine casting performance and campaign life, where the liquid flow distribution, coke bed structure and condition, and the in-service refractory profile are all contributing factors. However, direct measurement is nearly impossible because of the high temperature conditions in the hearth. In practice, the refractory temperature distribution is a valuable measurement for assessing the hearth condition, e.g. the coke bed state and/or refractory erosion. However, for both normal furnace operations and long maintenance shutdown periods, the refractory temperature cannot fully provide a comprehensive and necessary assessment of this condition. In this regard, mathematical modelling, often coupled with physical modelling, has played an important role in interpreting the refractory temperature distribution in terms of liquid flow distribution, coke bed properties, hearth wear condition, and so forth. One aspect of the present investigation involved using a new, improved conjugate heat transfer model to describe the flow of liquid iron coupled with liquid-refractory heat transfer in the hearth of Port Kembla No. 5 Blast Furnace, under normal operating conditions. The model was carefully validated through a comparison between measured refractory data and model predictions. Results show that the actual range in measured pad temperature fluctuation over the course of the present campaign were well within the temperature difference expected for the float/sink movement of the coke bed. In the second aspect involved the development and application of a new transient numerical model developed to simulate hearth cooling during an extended maintenance shutdown period. In this model, the mushy zone was tracked so as to predict the temporal variation of refractory temperatures and critically, the extent of liquid bath cooling during extended shutdowns of several days duration. During the course of the shutdown, these results proved to be a very useful guide for furnace and maintenance engineers.