Model studies of liquid flow in the blast furnace lower zone

The non-wetting flow of liquid iron in the blast furnace lower zone is simulated experimentally using a two dimensional raceway model with water, air and 4.1 mm diameter polyethylene beads to represent liquid iron, blast furnace gas and the coke bed respectively. An X-ray technique is used to visualise liquid flow in the packed bed and the distribution of liquid from the bottom of the bed is measured. The liquid percoates through the packed bed as series of rivulets which are continuously breaking up and rejoining. The direction and magnitude of the percolation velocity is determined by the balance between three forces acting on the liquid-gravity, gas drag and bed resistance. The gas drag has a very strong effect on the liquid distribution, forcing the liquid away from the raceway region. This effect increases with increasing gas flow rate. At high gas flow rate, the liquid flow rate and distribution at the top of the bed do not effect the liquid distribution leaving the bed. Near the raceway, the packed bed is dry. The size of the dry region increases with increasing gas flow rate. Above the raceway, beyond the dry packed bed, is a region of high liquid holdup. Liquid dripping into this region has a high residence time compared to liquid falling through the deadman zone. A mathematical model for liquid fow is outline which gives good agreement with experimentally observed liquid flow patterns in the cold raceway model and could be suitable for predicting the liquid flow pattern under real blast furnace conditions. This study confirms that the effect of gas drag on the flow of liquid iron through the blast furnace lower zone is important and should not be neglected.