Numerical analysis on behavior of unburned char and fine coke in blast furnace

A mathematical model of blast furnace operation, which is able to estimate the behaviors of the unburned char and the fine coke simultaneously, has been developed. The model based on the multi-fluid theory treats dynamic powders that are moving entrained by the gas stream as individual phases and static powders as solid components. The former takes conservation equations of momentum, thermal energy, chemical species and continuity. The latter takes only mass balance equations of chemical species, and shares fields of flow and temperature with the other solid components, such as lump coke, sinter, and so on. In the simulations, the unburned char is derived from the pulverized coal injected from the tuyere, and there is no difference in model treatment between the unburned char and the pulverized coal. The fine coke is generated uniformly in the raceway region from the coke particles, and the generation rate is determined by a kinetic treatment. The simulation of the blast furnace operation by this model revealed that the unburned char and the fine coke having different diameters and densities show different flow patterns especially in the cohesive zone and deadman. Consequently these two powders formed different areas of accumulation and reactions while large amount of powders were deposited in the deadman zone regardless of difference in flow patterns.