JP4021948B2 - Blast furnace bottom cooling structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blast furnace bottom cooling structure for extending the life of a blast furnace bottom by strengthening cooling of a high heat load site in cooling of the bottom wall of the blast furnace.
[0002]
[Prior art]
The bottom of the blast furnace is a part that regulates the life of the blast furnace, and prevention of wear of the carbon bricks constituting the furnace bottom is the most important item for extending the life of the blast furnace. The cause of wear of the carbon bricks on the bottom wall of the furnace includes erosion due to hot metal and embrittlement due to thermal stress. Cooling strengthening of the high heat load portion is the most effective for preventing such wear.
The cooling method of the bottom wall of the blast furnace is roughly divided into cooling by stave and cooling by iron skin sprinkling. FIG. 2 shows a vertical sectional view of the bottom wall of a conventional stave cooling furnace bottom. It consists of carbon brick 4, stamp material 3, stave 5, castable 2, and iron skin 1 from the inside of the blast furnace furnace.
[0003]
Cooling is performed by cooling water flowing through the stave pipe 6 and heat dissipation from the iron skin 1, but more than 95% of the heat removal is due to cooling water flowing through the stave pipe 6, improving the cooling capacity of the bottom wall of the furnace bottom. In order to achieve this, it is effective to reduce the thermal resistance between the carbon brick 4 and the stave cooling water.
For this reason, the improvement which improves the heat conductivity (reciprocal number of thermal resistance) of the carbon brick 4 and the stamp material 3 was performed, and the cooling capacity of the furnace bottom side wall has improved. However, for the stave 5, marshallite 7 is applied to the surface of the stave pipe 6 in order to prevent carburization of the stave pipe 6 during casting at the time of casting, and the thermal resistance is large. The thermal resistance of the stave 5 was increased.
[0004]
As a countermeasure against this, an invention has been proposed in which a cooling pipe is brought into direct contact with the stamp material 3 or the carbon brick 4 as disclosed in JP-A-6-158131. In this method, since the thermal resistance of the stave 5 made of a casting is omitted, it seems that the thermal resistance between the carbon brick 4 and the cooling water can be reduced. However, in this system, since the cooling pipe is not in contact with the carbon brick 4 on the surface unlike the conventional stave 5, if the carbon brick 4 expands during operation, the difference in thermal expansion between the carbon brick 4 and the iron skin 1. As a result, the cooling pipe is compressed and the cooling pipe or the carbon brick 4 is damaged, or a gap is formed between the cooling pipe and the carbon brick 4 to increase the heat resistance.
[0005]
That is, during the operation of the blast furnace, the thermal expansion difference between the carbon brick 4 and the iron skin 1 is several tens mm or more compared with the time of construction, and this thermal expansion difference was absorbed by the shrinkage of the stamp material 3. In the invention of Japanese Patent Laid-Open No. 6-158131, this point is not taken into consideration, and there is a problem that the cooling pipe and the carbon brick 4 are damaged and the thermal resistance is increased.
On the other hand, the erosion of the carbon brick 4 on the bottom wall of the furnace bottom is deeply related to the state of the hot metal flow on the bottom of the furnace, and selecting an appropriate cooling range for the bottom wall of the furnace suppresses the wear of the carbon brick 4. It is considered effective.
[0006]
FIG. 3 shows the transition of the minimum remaining thickness (remaining thickness of the carbon brick 4) of the bottom wall and the bottom of the hearth. The hatched portion in FIG. 3 shows the thickness of the deposits present on the surface of the carbon brick 4, but in FIG. 3, the bottom of the hearth bottom is attached as in the fourth and fifth years. When the kimono is thick, the carbon brick 4 on the side wall of the furnace bottom is worn. In other words, if the bottom of the hearth is excessively cooled, the deposits formed on the bottom of the hearth will change the hot metal flow at the bottom of the furnace and increase the heat load on the side wall of the hearth. This causes wear on the side wall. Accordingly, it is necessary to set an appropriate cooling capacity in the height direction of the furnace bottom side wall.
[0007]
[Problems to be solved by the invention]
It is an object of the present invention to provide a cooling structure for a blast furnace bottom with less wear by improving the cooling capacity of a high heat load portion and optimizing the range in cooling the bottom wall of the blast furnace. To do.
[0008]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems. The gist of the present invention is that in the cooling structure of the bottom wall of the furnace bottom where the carbon brick of the large blast furnace is cooled by using a stave, 4 m below the exit opening. The stave placed between the carbon brick and the iron skin of the blast furnace bottom side wall in the range of the height is made of copper, and the blast furnace bottom side wall in the range below 4 m above the tap and the tap The stave disposed between the carbon brick and the iron skin is made of cast iron .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 7A to 7C show the structure of the copper stave as a front view, a side view, and a cross-sectional view. The cooling method is the same as that of a conventional cast iron stave. The cooling water supplied by the water supply / drainage pipe 14 passes through the water channel 15 shown in the inside of the copper stave base material 9 (as viewed in the direction of the arrows A-A in FIG. 5B). 9 is cooled.
FIG. 5 shows the heat transfer calculation results when the copper stave 5b is used on the furnace bottom side wall, and FIG. 4 shows the results of using the conventional cast iron stave 5a in the same manner.
Since the copper stave 5b is manufactured by directly perforating the copper base material 9, there is no marshalite layer 7 having a large thermal resistance unlike the cast iron stave 5a, and the thermal conductivity of the copper base material 9 is higher than that of the cast iron base material 8. Therefore, the heat transfer coefficient of the entire stave can be increased. Under the condition that the remaining thickness of the carbon brick 4 is 0.5 m, the cooling capacity (heat removal amount) is improved by 11% to 23670 kcal / m ² h in the copper stave 5b as compared with 21400 kcal / m ² h in the cast iron stave 5a. ing.
[0010]
About the arrangement | positioning position of the copper stave 5b, since the cooling capability is high, it arrange | positions to the high heat load part of a furnace bottom side wall. As shown in FIG. 3, excessive cooling of the bottom of the furnace bottom causes wear of the bottom of the furnace bottom. If a copper stave 5b having a high cooling capacity is used at the bottom of the bottom of the furnace bottom, the bottom of the furnace bottom will be excessive. Cooling is not preferable.
In the blast furnace, the high heat load part on the bottom wall of the bottom of the furnace is the most frequently located 2m below the tapping outlet, and even in the blast furnace bottom demolition investigation results, the maximum erosion part is 0.5-4m below the tapping outlet. It can be seen that the heat load at this part is particularly high. Accordingly, the range in which the copper stave is arranged is preferably in the range of 0 to 4 m below the tap hole.
In order to elucidate the reason why the maximum heat load is in the range of 0.5 to 4 m below the taphole, a water model experiment was performed to simulate the blast furnace bottom.
[0011]
Generally, coke is present at the bottom of the blast furnace, but this coke is present in the hot metal and floats from the bottom of the furnace due to the buoyancy of the hot metal. The flying height is a certain level below the spout 10 because the top surface of the hot metal is located at the spout 10. A water model experiment was performed to simulate the distribution of hot metal flow under the condition that a coke layer that floats exists.
FIG. 6 shows the experimental results. In the state where the packed bed (coke) floats and exists like the bottom of the blast furnace furnace, the hot metal flows preferentially through the void under the packed bed with low resistance, but the hot metal flow velocity changes in the height direction of the void. It was found that the lower the flow velocity, the lower the dead zone of the molten iron flow.
[0012]
That is, the part where the hot metal flow is intense is determined by the distance below the outlet, and if the hearth hearth is excessively cooled, the hot metal flow is supplied to the hearth bottom with little heat supply. Consistent with the above results that the formation of deposits is promoted.
Therefore, if a copper stave with excellent cooling performance is used in the range of 0-4m below the taphole, which is a part of high heat load, and a conventional cast iron stave is placed below the copper stave, excessive cooling of the furnace bottom hearth The high heat load portion can be strengthened by cooling without causing the wear, and the wear of the furnace bottom side wall can be prevented.
[0013]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal section of the bottom of a large blast furnace showing the present invention.
A copper stave 5b was arranged from the tap hole 10 to a range of 4 m below the tap hole 10, and a conventional cast iron stave 5 a was arranged above the tap hole 10 and below 4 m of the tap hole 10.
Although the present invention is intended for a large blast furnace, for reference, in a small blast furnace related to the present invention , the high heat load portion is at the top of the large blast furnace because the hearth diameter is small. This is to be able to understand given the similarity of hot metal flow hearth bottom, in the 1000 m ³ grade blast furnace, the arrangement position of the copper staves, and the area under 2m of taphole 10 Dezukuguchi 10 Become.
[0014]
Method of fixing the stave 5a, 5b of the furnace bottom side wall to the iron shell 1, filling method of the castable 2 between the iron shell 1 and the stave 5a, 5b of the furnace bottom side wall, the stave 5a, 5b of the furnace bottom side wall and carbon The filling method of the stamp material 3 with the brick 4, the brick stacking structure of the carbon brick 4 and the refractory brick 12 of the hearth bottom, and the hearth bottom cooling pipe 13 can be performed by a conventional method.
The thermal expansion of the carbon brick 4 during operation is absorbed by the stamp material 3 and the generated force is received by the entire stave surface, so there is no intensive force generation as in JP-A-6-158131, There is no damage to the stave pipe 6 or the carbon brick 4. Further, the stave 5a, 5b on the side wall of the furnace bottom is in surface contact with the stamp material 3, and there is no increase in thermal resistance due to the generation of a gap between the stave 5 and the stamp material 3, and the conventional furnace bottom structure Similar reliability is obtained.
[0015]
【The invention's effect】
As described above, the effects of the present invention are listed as follows.
By placing a copper stave with excellent cooling capacity at the high heat load section on the bottom wall of the blast furnace, cooling of the high heat load section on the bottom wall of the blast furnace without causing excessive cooling of the bottom furnace floor Strengthening is possible, and the blast furnace bottom life can be extended.
Like the conventional cooling structure, this structure absorbs the thermal expansion of the carbon brick 4 with the stamp material 3, so that excessive force is not applied to the stave 5, so that the stave pipe 6 and the carbon brick 4 may be damaged. There was no increase in thermal resistance due to the generation of a gap between the stave 5 and the stamp material 3, and a highly reliable bottom cooling structure was obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of the bottom of a blast furnace showing the present invention. FIG. 2 is a longitudinal sectional view of a bottom wall of a conventional stave cooling furnace bottom. FIG. Fig. 4 shows a calculation example of heat transfer calculation results when a conventional cast iron stave is used on the furnace bottom side wall. Fig. 5 shows a transmission diagram when the copper stave of the present invention is used on the furnace bottom side wall. Fig. 6 is a diagram showing a calculation example of thermal calculation results. Fig. 6 is a diagram showing water model test results of the blast furnace bottom hot metal flow simulating the blast furnace bottom. Fig. 7 (a), (b) and (c) are copper staves. Diagram showing the structure
DESCRIPTION OF SYMBOLS 1 Iron skin 2 Castable 3 Stamp material 4 Carbon brick 5 Stave 5a Cast iron stave 5b Copper stave 6 Stave pipe 7 Marshallite layer 8 Cast iron stave base material 9 Copper stave base material 10 Outlet 12 Fire resistance of the bottom of the hearth Brick 13 Furnace bottom hearth cooling pipe 14 Cooling water supply / drain pipe 15 Cooling water channel drilled in copper stave base material

Claims (1)

In the cooling structure of the bottom wall of the furnace bottom where the carbon brick of the large blast furnace is cooled using a stave,
The stave to be placed between the carbon brick and the iron skin of the blast furnace bottom side wall in the range of 4m below the exit is made of copper ,
Cooling of the bottom wall of the furnace bottom, characterized in that the stave disposed between the carbon brick and the iron skin of the bottom wall of the blast furnace furnace in the range of the height above the tap and the bottom of the tap is made of cast iron Construction.

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