Computational fluid dynamics study of re-blowin operation in an ironmaking blast furnace

Abstract

Blast furnace (BF) is an efficient but complex chemical reactor for converting iron ore to liquid iron. In BF practice, after the planned blast-off operations, air may be re-blown in gradually, usually integrated with pulverised coal injection (PCI) operation so as for resuming stable raceway and production, but the in-furnace phenomena in re-blowin process are not clear yet. A three-dimensional (3D) computational fluid dynamics (CFD) model is developed and used to describe the re-blowin process in an industrial-scale BF. The model offline integrates a raceway model and a PCI model. The models are validated against the experimental measurements. The in-furnace phenomena of four key steady states in the normal re-blowin operation are illustrated using the industrial-scale model, in terms of the flow field, temperature field, distribution and concentration of gas species within the raceway and the surrounding coke bed. The simulation results indicate a larger blast volume can enlarge the size of the recirculation region of the raceway and can help recover the raceway operation quickly. On the other hand, starting PCI operation with O2 enrichment are tested, and indicate insignificant enhancement on the re-blowin process. This model provides a cost-effective way to understand the re-blowin operation for operation design and optimisation.