JPH0445213A - Structure of furnace hearth in blast furnace - Google Patents

Abstract

PURPOSE:To restrain annular flow of molten iron and to prevent erosion of brick at surrounding part of furnace hearth by inclining the hearth face shape at the furnace hearth part at the specific angle to the horizontal plane from the furnace center part toward the furnace peripheral part. CONSTITUTION:In the furnace hearth in the blast furnace, the horizontal part 8A in the furnace bottom 8 is formed over the desired range as centering the furnace core Z. The inclining part 8B is arranged as continuing to the horizontal part 8A toward the furnace wall. At this time, ratio H/R of distance H from an iron tapping hole 6 to the furnace bottom 8 to distance R from the furnace core Z to the iron tapping hole 6 is desirably set to 0.45 - 0.60. By this method, the annular flow of molten iron at the time of tapping the molten iron, can be restrained and as the heat load to refractory at the peripheral part of furnace hearth 8 can be reduced, the service life of the blast furnace can be extended.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention aims to suppress the annular flow of hot metal accompanying tap slag, prevent local erosion of the bottom brick wall, and thereby extend the life of the blast furnace. This invention relates to a blast furnace hearth structure that has an optimal hearth shape to achieve this.

(Prior art) As shown in the schematic cross-sectional view of Fig. 3, the structure of a blast furnace is, from the top, a furnace mouth (1), a furnace chest (2), a furnace belly (3), a morning glory (4),
Water basin (5), taphole (6), hearth {7} and hearth bottom (8)
) is well known.

As shown in the schematic cross-sectional view in Figure 4, the hearth structure is lined with chamotte bricks and carbonaceous bricks to protect the hearth, and the hearth bottom is horizontal to the horizontal plane, making it dimensionless. The hearth depth H/R (H: tap hole from the hearth inner wall, R, hearth radius) is configured to be about 0.35.

The structure of a blast furnace is generally as described above, and in order to extend the life of the blast furnace, various furnace body protection and repair techniques have been developed and put into practical use.

In other words, the lifespan of the blast furnace from the chest (2) to the morning glory (4) has been significantly extended due to the development of new furnace wall cooling devices and advances in reduction and repair technology.

In particular, for the hearth part, techniques to prevent brick erosion have been applied by selecting the material of the bricks at the time of hearth construction, the shape of the hearth at the time of hearth construction, and operational management.

Recently, cedar techniques have been developed to prevent erosion of hearth wall bricks by controlling the annular flow of hot metal during tapping by appropriately controlling the depth of the taphole (6).

In particular, reducing the stress on the hearth wall by optimizing the flow of hot metal in the hearth is of fundamental importance.

The basic factors governing the flow of hot metal in the hearth are: ■ Formation of an area where only hot metal exists at the bottom of the pool (hereinafter referred to as free space), ■ Hearth filling structure, ■ Tapping port. Many theoretical and experimental considerations have been made in the past, taking into account depth, cooling conditions for the reactor wall, etc. However, there are only a few examples of research on the effects related to both hot metal flow and hearth autobiographical thermal behavior.

In particular, there is only a few examples of information on free space, which is thought to have a large effect on hot metal flow, and the formation behavior of free space has not yet been sufficiently elucidated.

(Invention or problem to be solved) As mentioned above, what are the results of experiments regarding the formation behavior of hearth hot metal flow, which is said to be important in various measures to extend blast furnace life? , the following was clarified.

As mentioned above, the basic factors that control the flow of hot metal in the hearth are ■ Formation of a region where only hot metal exists at the bottom of the pool, ■ Hearth filling structure, ■ Depth of tap hole, and ■ Furnace wall cooling. Given the current situation where there is very little information on free space, which is thought to have a major impact on hot metal flow, the inventors investigated the formation behavior of free space using a hearth model. Based on the results obtained, the effects of the above items 1 to 2 on the flow of hot metal in the hearth and heat transfer behavior (temperature distribution) including the hearth refractories were examined through numerical calculations.

First, according to the dismantling investigation of the blast furnace body, as shown in the schematic cross-sectional view in Figure 5, a free space P was formed in which only hot metal existed, and this existence is closely related to the erosion of the hearth wall W. That seems to be the case.

Since the formation of free space P is predicted to have a very large effect on the flow of hot metal, the formation behavior of free space P in the hearth was observed using the apparatus shown in FIG.

In the experiment, a model was filled with foamed polystyrene resin beads having a particle size of 3.5++ un, and a raceway was formed by blowing room-temperature air through the slats (9). Thereafter, water was repeatedly stored and drained from the center of the bottom plate C1) of the apparatus without allowing the sediment layer to fall.

As a result, as shown in Figure 7A, B, C, and D, the process progresses from the initial state (Figure 7A), and when the water is stored in Figure 7B, the hearth (
It was observed that particles present in 7) were discharged upward toward the raceway.

With this upward movement of particles, a free space P is formed in a part αυ of the hearth bottom corner (Fig. 7C), and the inclination angle of the lower surface of the particle layer (hereinafter referred to as the free space angle) increases the water storage level. It increased as the temperature increased, and at the maximum of 210, it became constant at 1゛. On the other hand, during draining (FIG. 7D), the packed particles started to fall from the furnace wall side, and the inclination angle of the free space became gentler as the transition level decreased.

In addition, it was found that the maximum inclination angle of the free space coincides with the inclination angle θφ (angle of repose) of the top surface of the particle layer, as shown in Figure 7E, and is independent of the viscosity and density of the liquid. .

As described above, when the level of stored pig iron slag is maintained high during blast furnace operation, the rise and fall of the stored pig iron slag level causes an upward movement of the hearth coke toward the raceway, resulting in a free space P in a part of the hearth bottom corner. is formed.

For this reason, an annular flow of hot metal is generated in the free space P, and the resulting heat load accelerates brick erosion.

The present invention has been made based on the above-mentioned viewpoints, and includes:
The purpose of this is to suppress the annular flow of hot metal that causes erosion of the hearth bricks by supplementing the coke-free area with refractory bricks, thereby preventing brick erosion around the hearth and extending the life of the blast furnace. It's there.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a blast furnace hearth structure in which the floor surface shape of the blast furnace hearth part made of refractory bricks is changed from the furnace center to the furnace periphery. An invention relating to a hearth structure tilted at an angle of 20 to 45 degrees with respect to the opposite horizontal plane, and a furnace configured to have a dimensionless hearth depth H/R set in a range of 0.45 to 0.60. It uses a floor structure.

(Function) As mentioned above, the present invention has a blast furnace hearth structure in which the floor surface shape of the blast furnace hearth part is inclined at an angle range of 20 to 45 degrees with respect to the horizontal plane from the furnace center to the furnace periphery. A configuration in which the dimensionless hearth depth H/R was set in the range of 0.45 to 0.60 was adopted for the hearth structure, and the reason for adopting these configurations is as follows.

That is, the reason why the configuration in which the floor surface shape of the hearth section is inclined at an angle of 20 to 45 degrees with respect to the horizontal plane from the center of the furnace toward the periphery of the furnace is as follows.

That is, as shown in Figures 8A and B to Figure 10A and B, which show the relationship between the flow velocity vector of the hot metal annular flow and the isotemperature line, the free space P formed in the hearth is calculated from the results of the above experiments. The angle of inclination was estimated to be 0° to 45° (corresponding to the angle of repose of 1°), and the following three cases were considered.

Example A - Free space P with an inclination angle of 20° (however, the bottom of the hearth is in contact with the hearth bottom) Example B - Free space P with an inclination angle of 20' (however, the bottom of the hearth is not in contact with the hearth bottom) (Contact) Example C - Case where the hearth is filled with coke and there is no free space P In Example A, the flow of hot metal near the bottom of the furnace is as shown in Figures 8A and B. An annular flow is generated that flows around the coke layer, and the flow velocity is fast in the free space P on the side wall below the taphole and in the bottom corner on the opposite side of the taphole, and conversely in the bottom corner of the taphole. The flow velocity is fastest in the packed bed at the bottom corners and the center of the bottom.

The temperature of the refractory brick in contact with the hot metal corresponds to the hot metal flow rate.In other words, the temperature of the refractory brick in contact with the hot metal is higher in places where the hot metal flow rate is faster.
It is also low at slow points.

Therefore, it can be seen that the flow rate of hot metal is strongly related to the heat transfer between hot metal and refractory bricks.

Regarding Example B, the hot metal flow in the coke packed bed exhibits the same behavior as that of Example A described above, as shown in FIGS. 9A and 9B.

However, the flow of hot metal in the free space P does not become an annular flow but heads toward the taphole (6) via the shortest path.

For this reason, the flow velocity near the center of the furnace bottom increases, and in response to the flow of hot metal, the temperature of the refractory bricks increases over the entire area except for the corner of the furnace bottom below the taphole.

As mentioned above, although the heat load on the refractory bricks near the center of the furnace bottom surface is reduced due to the large increase in the thickness of the free space P, it can be seen that a relatively large heat load is still placed on the refractory bricks.

Regarding Example C, the hot metal dripped into the puddle passes through the deeper part of the puddle as the dripping point moves away from the tap hole, and as shown in the figure, a gentle flow with little bias is formed throughout the hearth bottom. has been done.

In other words, the flow velocity is fastest in the side wall below the taphole and becomes slower as it moves away from the taphole, and the temperature of the refractory bricks near the hot metal is lower overall than in the case of the example. , only the side wall below the taphole is slightly higher.

This was discovered from the experimental results of numerical calculations of the hot metal flow velocity distribution during tapping when a coke-free region, in other words, a region containing only hot metal, occurs in the blast furnace hearth. The fact that the heat load on the bricks around the bottom is large can be understood by looking at the temperature distribution inside the bricks.

Based on the above experimental results, we adopted a configuration in which the floor surface shape of the blast furnace hearth is inclined at an angle range of 20 to 45 degrees with respect to the horizontal plane from the furnace center to the furnace periphery, and the free space P is compensated with bricks. This structure was adopted at the time of furnace construction to suppress hot metal reflux and reduce the heat load around the bottom of the furnace.

Next, the reason why the dimensionless hearth depth H/R was set to 045 to 0°60 is as follows.

That is, it was discovered from the relationship between the dimensionless hearth depth H/R (H: depth of the taphole from the inner wall of the hearth, R1 refers to the hearth radius), hot metal flow, and heat transfer behavior, Calculations were made by changing the tap hole position to three levels as shown in Figure 1).

However, the shape of the free space P was set to be the same as in Example A.

Based on the above settings, it is estimated that the hearth depth will be extended from the relationship between the hot metal flow velocity vector and the isothermal line at each position of the taphole, as shown in Figure 12 ASB to Figure 14 A and B. It is seen that the annular flow is suppressed as the depth of the hearth increases, and as the position of the hot metal suction port decreases as the depth of the hearth increases, the flow velocity of hot metal increases near the bottom of the furnace below.

Corresponding to this change in hot metal flow, it can be seen that the brick temperature decreases at the corners of the furnace bottom, and conversely increases near the center of the furnace bottom surface.

It was also found that the circumferential balance of brick temperature became more uniform as the taphole depth increased.

Furthermore, it can also be found from the relationship between the hearth depth and the hot metal flow velocity in the free space P.

That is, as shown in the graphs of FIGS. 15A and 15B, the flow velocity of hot metal in the fleece base P increases as H/R increases, and
When /R is 0.40 or more, it becomes almost constant, and Fig. 15B
From the relationship between the hot metal flow and H/R, the flow velocity at the center of the furnace bottom is H.
Since it increases almost monotonically as /H increases,
In order to suppress the annular flow, it is considered best to maintain H/R=0.45 to 0.60.

From the above viewpoint, in the present invention, the dimensionless hearth depth H/R is set to 0.
．． It was set at 45-0.60.

(Example) An example of the blast furnace hearth structure of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows an example of a structure having a horizontal part at the hearth bottom (8),
Fig. 2 shows an example of a forest-like hearth structure.

That is, in the hearth structure shown in FIG. 1, a horizontal part (8A) is formed in the hearth bottom (8) over a desired range centered on the hearth Z, and the hearth is continuous with this horizontal part (8A). Approximately 24° toward the wall (
θ) An inclined slope part (8B) is provided, and a tap hole (6
) to the hearth bottom (8) is 3.15 m, the distance R from the furnace core Z to the taphole (6) is 7 m, and the ratio of both H/
This is a hearth structure with R of 0.45.

In addition, in FIG. 2, as in FIG. 1, the furnace bottom (8) is inclined at an angle of about 20° (θ) from the furnace core 2 toward the furnace wall (8B).
), and the distance H from the taphole (6) to the hearth bottom (8) is 3.15 m, the distance R from the furnace core Z to the taphole (6) is 7m, and the ratio of the two is H/R. This is a hearth structure with 0.45.

As a result of numerical analysis of the above hearth structure, it was found that the hearth annular flow was suppressed, the heat load on the refractories around the hearth could be reduced, and this was effective in preventing hearth erosion.

(Effects of the Invention) The present invention provides a blast furnace hearth structure in which the floor surface shape of the blast furnace hearth part is 20 to 45
Configuration for tilting in the angular range of ° and dimensionless hearth depth H/
Since the configuration in which R is set in the range of 0.45 to 0.60 is adopted, it is possible to suppress the annular flow of hot metal during tapping slag, and it is possible to reduce the thermal load on the refractories around the bottom of the furnace.

Therefore, it is possible to prevent local erosion of the bricks placed in the hearth, and the life of the blast furnace can be dramatically extended.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views showing one embodiment of the blast furnace hearth structure of the present invention, FIG. 3 is a schematic cross-sectional view showing a conventional blast furnace structure, and FIG. 4 is a schematic cross-sectional view showing a conventional blast furnace structure. A schematic cross-sectional view showing an example of a hearth structure, FIG. 5 is a schematic cross-sectional view showing the formation behavior of a coke-free region, and FIG. 6 is a schematic cross-sectional view showing an example of a method for confirming the formation behavior of a coke ratio filling region in the hearth. Figure 7 A, B
, C1D are schematic diagrams showing the formation behavior of the coke-free region, FIG. 7E is a schematic diagram showing the relationship between the coke-free region inclination angle and the angle of repose of particles, and FIGS. 8A, B to 1O. A
, B is a schematic explanatory diagram showing the numerical calculation results of the hot metal flow velocity distribution and temperature distribution in the brick during tapping when there is a coke-unfilled region, and the first) diagram shows the dimensionless hearth depth, hot metal flow, and hearth Figures 12A and B to 14A and B are schematic diagrams showing the measurement method for measuring the relationship with the heat transfer behavior within the steel. FIG. 15 is a schematic explanatory diagram showing the numerical calculation results of the distribution and temperature distribution in the brick, and is a graph showing the relationship between the hearth depth and the hot metal flow velocity in the coke-free region. The names of the codes are as follows. (1) ... hearth mouth, (21- hearth chest, (3) ... hearth belly, (4) - morning glory, (5) - hot water pool, (6) --
One taphole, (7) --- one hearth, (8) --- hearth bottom,
(8A) - Horizontal part of the hearth bottom, (8B) - Inclined part of the hearth bottom, (
91-tuyere, Z-furnace core, R...-distance from furnace core to taphole, H.1. Distance from hearth bottom to taphole, patent applicant Kobe Steel, Ltd.

Claims (2)

[Claims] (1) A blast furnace characterized in that the floor surface of the blast furnace hearth made of refractory bricks is inclined at an angle of 20 to 45 degrees with respect to the horizontal plane from the furnace center to the furnace periphery. floor structure. (2) The dimensionless hearth depth H/R, which is the ratio of the taphole depth H from the hearth inner wall to the hearth radius R, according to claim (1), is set in the range of 0.45 to 0.60. The blast furnace hearth structure according to claim 1, characterized in that: