Effects of Operation Condition and Casting Strategy on Drainage Efficiency of the Blast Furnace Hearth

Abstract

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...

Pressure Drop in the Blast Furnace Hearth with a Sitting Deadman

“…An efficient and strictly controlled tapping is necessary for guaranteeing a stable operation and high productivity of the BF. Many recent investigations [1][2][3][4][5][6][7][8][9] on this subject have revealed that the pressure drop caused by fluid flow through the deadman in the hearth is a significant factor governing hearth drainage. However, due to the hostile environment, the possibilities to directly measure internal variables are practically nonexistent.…”

Flow Patterns of Iron and Slag in the Blast Furnace Taphole

“…In this respect, the experimental system is equivalent to the case where the coke-free zone extends above the taphole level, which can be caused by excessively high liquid levels in the BF hearth. 5,6) Even though a coke bed in the hearth could have an influence on the flow patterns in the taphole, it would be almost impossible to consider the effect in an appropriate way since the exact configuration of the coke particles next to the taphole is unknown.…”

“…It has been reported that the taphole diameter (or taphole expansion rate during tapping) can significantly influence the slag residual ratio and casting duration. [5][6][7][8] Also, steeper taphole inclination could lead to higher productivity and longer casting duration since more iron can be drained out below the taphole level. However, the effect of taphole diameter and inclination angle on the taphole flow patterns has, to the best of our knowledge, not been reported.…”

“…[1][2][3][4][5][6][7][8][9][10] Most investigators were concerned about the effect of various in-furnace conditions, including coke size, dead man porosity and coke-free zone on multiphase (gas, iron and slag) flow in the BF hearth. The taphole flow, however, has been given very little attention and was usually ignored or strongly simplified.…”

Research Status and Development Trend of Numerical Simulation on Blast Furnace Lining Erosion

“…In the early, researchers [27][28][29]32,[35][36][37][38][39][40] supposed the dead-man was cylinder or hemisphere, owed uniform voidage, and filled the hearth along the radial. The simulation results 29,32) revealed the volume of free coke in the hearth significantly affect the line erosion, the narrower the space, the faster the metal flow, the heavier the erosion.…”