This paper presents an experimental and numerical study of the two-phase flow in a particle packed bed, under conditions related to a blast furnace hearth. In these models, drainage velocities, slag ratio, tapping time, and maximum slag level in hearth are studied. The coke free space formed at tap hole level forms a circumference slag flow and significantly improves the hearth drainage efficiency. When the coke free space surround a part of packed bed, the effect is in proportion to the surrounded packed bed size. Such a nonaxisymmetric coke free space causes the imbalances of tap time and slag ratio.

A mathematical model is developed to quantify the effect of operation conditions and casting strategy on residual amount of slag and metal in hearth. The model is validated by a physical scale model experiment. Calculated results show that the residual amount of slag increases in proportion to the square of production. The effect of hearth permeability on the residual amount of slag is larger than slag viscosity. Then high permeability is necessary under high productivity operation condition. Although a load is not small, increasing tapping rod diameter and shortening cast duration are the effective way to decease maximum slag level. High durability filling mud is necessary to keep cast duration.KEY WORDS: blast furnace; hearth; liquid; tow-phase flow; drainage; residual; slag; mathematical mode; scale model; coke; packed bed; tapping; casting. volumes are measured. Procedures of experiment are same as BF tapping operation. At first, drainage velocity is smaller than liquid supply velocities. As the flow control valve opens, drainage velocity increases When nitrogen gas in the vessel comes out through the flow control valve, the valve is closed and another valve is opened. Liquid sampling is carried out after reaching steady cyclic condition of the alternative casting. Scale condition focused to reproduce liquid surface shape in a blast furnace hearth, because it affects on stability of operation as described in the former section. Figure 2 shows the schematic diagram of the slag surface. When slag velocities of supply and drainage are same, slag surface shape is constant, and the pressures at P and PЈ should be same. The pressure drop between P and PЈ caused by liquid flow DP flow should be compensated by hydrostatic pressure DP gravity · DP flow can be described by Kozeny-Carman equation:.............. (1) where d p (m), e (Ϫ), m slag (Pa · s) and v (m/s) are particle diameter, packed bed porosity, slag viscosity and liquid velocity respectively. To keep the inclination q, the pressure drop has to be compensated by the hydraulic pressure DP gravity , which can be described as following equation: Experimental Result and DiscussionMeasured drainage velocities, HCFC ratio and liquid levels are shown in Fig. 3. HCFC velocity increases in first 60 s and saturates. On the other hand, paraffin velocity increases after 60 s. Consequently the ratio of HCFC to total liquid velocity becomes the maximum at 60 s. Although the liquid level of paraffin becomes the maximum at 90 s, which is half cast duration 180 s, the level of HCFC is the maximum at 60 s. HCFC ratio and level are the maximum at same time under all of other experimental condition. These results show that the HCFC ratio is in proportion to the level of itself. Although it is omitted in this paper, this relation is confirmed by many other condition experiments. Measured casting velocity of an actual BF, which production is 10 000 t/d and hearth diameter is 15 m, is shown in Fig. 4. Although time scale is 85 times larger than the scale model (Table 1), the fea...

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