JPH057443B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention adjusts the O/C [ratio of the amount of ores (sintered ore + lump ore + pellets) to the amount of coke] of the charge charged to the blast furnace to improve the O/C of the charge charged to the blast furnace. The present invention relates to a blast furnace operating method that suppresses erosion of bricks or deposits. [Prior Art] Bricks or deposits at the bottom of a blast furnace are constantly subject to physical and chemical erosion, and it is extremely important to suppress this erosion in order to extend the life of the blast furnace. be. Various methods for suppressing this erosion have been proposed in the past. For example, Japanese Patent Publication No. 60-41124 and Japanese Patent Publication No. 61-
As proposed in Publication No. 139608, the temperature of the blast furnace bottom bricks is measured, the O/C of the entire blast furnace charge is calculated based on this measured temperature level, and the O/C is adjusted to the calculated value. There is a method to suppress erosion of the furnace bottom bricks or deposits. [Problems to be Solved by the Invention] However, since both of these publications use the O/C of the entire charge as an adjustment factor, for example, increasing the O/C will lower the overall position of the cohesive zone. ,
Adverse effects will occur on blast furnace operation. In other words, since the shape of the bottom part B of the blast furnace shown in FIG. . This deposit that has grown and grown prevents the contents from falling on the furnace wall side, making the rate of descent uneven in the radial direction of the furnace, causing slips or drops, and hindering stable blast furnace operation. Yes O/
The increase adjustment range for C is small. Furthermore, since the O/C of the entire charge is adjusted based only on the measured temperature level, the O/C of the entire charge is adjusted regardless of the erosion rate, resulting in early corrosion of the bottom bricks or deposits. It was impractical as it could not prevent this. [Means for Solving the Problems] With the aim of preventing erosion of blast furnace bottom bricks or deposits while maintaining stable operation of blast furnaces, the present inventors have repeatedly conducted various experiments and studies. The increase in temperature of the bottom brick is caused by the thickness of deposits on the bottom of the furnace or the thickness of the bottom brick. It was found that this phenomenon was dominated by the flow of molten metal at the bottom of the furnace, and that the flow of molten metal was closely related to the ups and downs of the furnace core. That is, when considering the balance of forces applied to the furnace core 3, which is estimated to have a conical shape as shown in FIG. weight of the charge) W ₁ and the force that tries to float the furnace core 3 (ventilation resistance during air blowing = [air blowing pressure from tuyere 5] - [pressure at the top of the furnace])
W ₂ is in balance, and as this balance changes, the furnace core 3 rises and falls. For example, if the furnace core 3 sinks, the furnace core 3 and deposits 1
1 (or the hearth bottom bricks 7) decreases or disappears, the flow of the hot metal in the hearth bottom 7 becomes poor, and the deposits 11 gradually adhere to the hearth bottom 7 and become thicker, and the temperature of the hearth bottom 7 bricks decreases. . On the other hand, when the furnace core 3 floats up, the distance d between the furnace core 3 and the deposit 11 (or the furnace bottom 7) increases, and the furnace bottom 7
It is thought that as the flow of the molten metal becomes better, the deposits 11 on the furnace bottom 7 are gradually melted and thinned, and the temperature of the furnace bottom bricks increases. As a method of floating and sinking this furnace core 3, the above-mentioned furnace core 3
A method of changing the weight of the charge in the lumpy zone 1 on the furnace core 3, a method of changing the pressure at the top of the furnace (furnace top pressure), a method of changing the blowing pressure from the tuyere 5 is possible. However, since this method involves fluctuations in the amount of tapped iron, it is not practical in the current situation where production volume is strictly controlled. The method described above, without the drawbacks of
It was found to be the best method with almost no negative impact on the furnace condition. Furthermore, it was found that the temperature of the hearth bricks did not rise gradually, but showed a rapid change once the temperature began to rise. This is because when the distance d between the furnace core 3 and the deposits 11 becomes thinner as the deposits 11 are sequentially melted and eroded, the distance d gradually becomes wider and the flow of the melt at the furnace bottom 7 becomes better. It is thought that the temperature increases at an accelerating rate because the melting rate of deposits 11 increases in proportion to the flow of the molten metal. In order to confirm this, we investigated the relationship between the O/C of the lumpy zone 1 above the furnace core 3 and the temperature rise of the furnace bottom 7 bricks in a 5000 m class ³ blast furnace. 3 O/C of upper lumpy zone 1 and hearth bottom 7
Since it was found that there was a negative relationship with the amount of temperature rise of the brick, the validity of the above explanation was supported. The present invention has been made based on the above knowledge, and its gist is to measure the hearth bottom temperature with a thermometer installed in the hearth brick at or near the center of the blast furnace bottom, and If the amount of upward change exceeds the corresponding allowable control value for the amount of erosion at the bottom, erosion of the bottom of the blast furnace can be prevented by increasing the O/C on the center side without increasing the O/C on the wall side of the contents inside the blast furnace. This is a method of operating a blast furnace characterized by suppressing. [Function] The present invention utilizes the bulk specific gravity difference (O: 2.00, C: 0.50) between O (ores) and C (coke) in the blast furnace charge, and transfers the heavy O, which has a heavy specific gravity, to the central part of the furnace, i.e. By charging a large amount only onto the furnace core 3 (within the dotted line A),
The weight on the furnace core 3 is increased, the furnace core 3 is lowered, and the distance between the bottom surface of the furnace core 3 and the furnace bottom surface 7 is decreased or the distance between the bottom surface of the furnace core 3 and the furnace bottom surface 7 is reduced, and the flow between the bottom surface of the furnace core 3 and the furnace bottom surface 7 is reduced. This is to inactivate the blast furnace bottom 7 surface, prevent the deposits 11 from dissolving from the furnace bottom 7 at an early stage, and suppress corrosion of the furnace bottom bricks or the deposits 11. Moreover, since the O/C is not increased outside the dotted line A in FIG. 1, that is, on the furnace wall side, stable operation can be maintained without lowering the position of the root C of the cohesive zone 2 and causing slips or drops. Furthermore, since the O/C adjustment index on the furnace core 3 is the temperature rise of the furnace bottom brick, the erosion rate, that is, the erosion rate of the deposits 11 on the blast furnace bottom 7 can be estimated.
Since the O/C is adjusted according to the amount of temperature rise,
Erosion of deposits 11 can be suppressed in a short period of time. To adjust the O/C on the furnace core 3, for example, as shown in Fig. 2, the amount of adjustment of the O/C on the furnace core 3 and the whole is determined, and the amount of movement of the armor plate provided at the upper part of the blast furnace inside , ore, and coke, and in the case of a bellless blast furnace, the chute angle of the rotating chute may be controlled by replacing it with an armor plate. [Example] An example of the present invention will be described with reference to FIGS. 1, 2, and 4. Introducing the measured values from thermometers 8 for temperature measurement installed at 10 locations below the furnace core 3 in the hearth bottom 7 bricks, the calculator 10 performs the following calculations as shown in FIG. The measured value of the thermometer 8 is read at 60 second intervals to determine the average value for the day, and this average value is compared with the average value of the previous day to calculate the amount of temperature change and determine whether the temperature change is an increase or a decrease. Determine if there is a change. If the change is an upward change, compare the increased temperature change with each of the following control values (1) to (3) shown in Figure 3, and determine whether the temperature change is the control value (1), (2), ( Determine which of 3) applies. ●Furnace bottom allowable melt damage control value (1): Dead zone taking into account the measurement error of the thermometer 8 mentioned above and the complexity of the O/C adjustment operation above the furnace core 3 ●Furnace bottom melt damage suppression allowable control value (2) ): Erosion suppression zone that adjusts the O/C above the furnace core 3 and the O/C of the entire blast furnace ●Erosion abnormality control value at the bottom of the furnace (3): Erosion rate is too high, and the blast furnace is closed. An erosion suppression zone that stops the movement of molten metal at the bottom of the furnace and suppresses erosion at the bottom of the furnace.If the amount of change in temperature rise is within the control value (1), adjust the O/C above the furnace core 3. Otherwise, if it is within the control value (2), the amount of O/C increase on the furnace core 3 is calculated based on the amount of change in temperature increase. If it is within the control value (3), a blast furnace wind shutdown command is output to the display 12. Based on the amount of O/C increase on the furnace core and the predetermined amount of O/C change per unit movement of the armor plate 9 toward the inside of the furnace, a large bell (not shown) in the blast furnaces is determined. ) Calculate the amount of movement of the armor plate 9 provided below in the direction of the furnace (in the case of a bellless blast furnace, calculate the chute angle of the rotating chute). An armor plate drive signal is output to the armor plate drive device 9 based on the calculated armor plate movement amount. (In the case of a bellless blast furnace, a shute drive signal is output to the shute drive device based on the calculated shute angle.) On the other hand, the overall O/C is not changed based on the amount of O/C increase on the furnace core 3 calculated above. Calculate the amount of O/C drop on the furnace wall side in this case. The allowable increase in furnace wall heat load is calculated based on the current furnace wall heat load, the managed furnace wall heat load upper limit, and the calculated furnace wall heat load increase amount. Based on this allowable increase in heat load on the furnace wall, the allowable increase in C on the furnace wall side is determined. The amount of change in O/C on the furnace wall side is determined based on the allowable increase in C on the furnace wall side and the radial direction of the furnace and the overall ventilation condition. The amount of change in the overall O/C is determined based on the amount of change in O/C on the furnace wall side and the amount of increase in O/C on the furnace core calculated above. Based on the amount of change in the overall O/C calculated above, a cutting change amount signal is output to the cutting control device 13 of the ore hopper and coke hopper (not shown). In this way, the drive device 9a receives the armor plate drive signal output from the computer 10.
is operated to move the armor plate 9 to the inside of the furnace when charging O (in the case of a bellless blast furnace, adjust the chute angle of the rotating chute), and the cutting control device 13 moves the ore hopper and coke hopper. Control the cutting amount. By doing this, the lumpy zone 1 above the furnace core 3
Partial O/C increases, and overall O/C changes as necessary. In this state, the amount of temperature change is monitored by the computer 10, and if the amount of temperature change continues to increase after about 10 days, the same operation as above is repeated to eliminate the temperature change. As soon as the wind shutdown command is output from the computer 10 and displayed on the display 12, the wind is shut down and the furnace condition is adjusted. By carrying out the operation as described above, the erosion of the deposits 11 on the blast furnace bottom 7 is stopped. The results of this adjustment are shown in Tables 1 and 2 below. Table 1 shows the case of the route in Fig. 2, and Table 2 shows the case of the route in Fig. 2. As can be seen from Tables 1 and 2, the furnace core 3
10 days after adjusting the above O/C, the bottom temperature stopped rising and started to drop, and 20 days later, this temperature drop became smaller and the bottom temperature began to stabilize. In other words, it can be seen that on the 10th day after the action, the erosion of the furnace bottom was stopped and deposits 11 began to adhere to the furnace bottom. At this time, thermometers 8a-8b and 8c-8d were installed at two points in the height direction inside the bricks at the bottom of the blast furnace.
As a result of estimating the remaining thickness of the furnace bottom using a known model formula for estimating the remaining furnace bottom based on the temperature between points,
In the case shown in Table 1, there was only about 15 mm of erosion on the 5th day after the action, and there was no subsequent erosion. In addition, in the case of Table 2, there was only about 20 mm of erosion on the 7th day after the action, but there was no subsequent erosion. In Fig. 1, 4 is a raceway and 6 is a taphole.

【table】

[Table] [Effects of the invention] The present invention raises the O/C of the blocky zone above the furnace core without raising the O/C of the furnace wall side, thereby lowering the furnace core and lowering the blast furnace bottom and furnace. By reducing the flow rate of hot metal between the core and the core, corrosion of the blast furnace bottom bricks or deposits is suppressed, so stable operation of the blast furnace can be maintained without fluctuations in the amount of iron tapped, and O/ The adjustment range for C can be widened, and since O/C is adjusted according to the degree of corrosion, the corrosion of bottom bricks or deposits takes about 1/2 to 1/3 of the time compared to conventional methods. The amount of corrosion can also be suppressed to about 1/3 to 1/4, making it possible to extend the life of the blast furnace.

[Brief explanation of the drawing]

FIG. 1 is a simplified explanatory diagram showing one embodiment of the present invention;
Fig. 2 is a block process diagram showing an embodiment of the present invention; Fig. 3 is a diagram showing the relationship between the O/C of the lumpy zone above the furnace core and the temperature change rate of the blast furnace bottom brick;
FIG. 4 is a diagram showing the relationship between the furnace bottom temperature change and the amount of furnace bottom erosion.

Claims (1)

[Claims] 1. When the hearth temperature is measured using a thermometer installed in the hearth bricks at or near the center of the blast furnace bottom, and the amount of change in temperature rise exceeds the corresponding allowable control value for the amount of furnace bottom erosion. A method of operating a blast furnace characterized by suppressing erosion of the bottom of the blast furnace by raising the O/C of the contents at the center of the furnace without raising the O/C of the furnace wall side.