2001 Volume 87 Issue 5 Pages 373-379
Permeability in coke bed in the lower part of blast furnace is believed to have important functions to affect the operation. Accordingly, elucidation of the renewal mechanism and packed structure of deadman coke is expected. The renewal motion may be related with such a motion that the coke bed floats due to the buoyancy force when the molten liquid is stored beyond a critical depth in the hearth. In the present study, a semi-three dimensional model of blast furnace with semicircular cross section was used. The model can approximate more adequately practical furnace in the stress field than two-dimensional model. The moving trajectory of individual particle of deadman packed bed was observed under the repetition of floating to sinking motion of the bed, using water and model particles in place of molten liquid, coke and ore, respectively. The following results were obtained. The height of particle-free space formed above the hearth when the bed floated, had a close correlation with the total depth of water within the bed. The particle renewal did not take place in the whole deadman region, but was restricted within a particular region determined depending on the free space height. The two renewal paths were recognized. First, the particles forced up due to buoyancy towards the deadman surface, joined with the fast moving particles in the funnel flow region to move into the raceway. Second, the particles which descended within the deadman, turned gradually to the direction to move towards the raceway.