Transient behaviors of flow and accumulation of fine powders in packed bed

Powder behavior in blast furnace is one of the important issues to maintain stable operation of the furnace. This study discussed transient flow and accumulation behaviors of fine coke powders in packed bed of coarse alumina spheres. In the experiments two phase flow of air and fine coke is introduced from the bottom of the packed column. The variation of the pressure drop along the bed axis and the amount of the powder discharged from the top of the bed were continuously measured. After certain powder feeding time, all the materials in the packed column were taken out, and the fine powders and the coarse particles were separated to determine the static hold-up, which is the amount of the fine powders accumulated in a unit volume of the packed bed. The pressure drop and the static hold-up in the bed increase with the progress of powder injection time. The flow and the accumulation behaviors can be generally classified by the diameter ratio of the fine powders to the packed coarse particles. In small diameter ratio cases, the two phase flow would approach to a steady state. Contrarily blockage would occur in large diameter ratio cases. These behaviors could be explained through a simple consideration about the packing structure of the packed bed. Additionally local blockage, in which the powder cluster locally blocked the interstice in the bed, was observed.