Effects of shaft angle on the performance of an ironmaking blast furnace: A CFD study

Abstract

An ironmaking blast furnace (BF) is a key chemical reactor for producing hot metal from iron oxides ore rapidly while the shaft profile significantly affects the flow-thermal-chemical behaviors inside a BF; however, the design is largely based on empirical correlations. In this article, a recent multi-fluid blast furnace model is adopted to quantitatively study the influence of shaft angle on the performance of a BF, in terms of in-furnace phenomena of flow-, thermal-, and chemical-behaviors as well as the overall performance indices. The results show that, the relatively small shaft angle is beneficial for the development of central gas flow while largely increasing the possibility of the formation of mixed region near periphery area. Meanwhile, the gas residence time increases with the increased shaft angle but in a quite limited range. In addition, the overall furnace performance indices including top gas utilization and coke rate can be affected with the changed shaft angle. Finally, the reasons behind the selection/design and evolvement of shaft angle with the increased furnace inner volume are explored, and the corresponding strategies to ensure the smooth operation are discussed. This model provides a useful tool for shaft angle design of ironmaking BFs.