JPH0967604A - Blast furnace bottom structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the service lift of a blast furnace without obstructing efficient and stable production of a pig iron. SOLUTION: In order to form the structure of a furnace bottom refractory having no coke-free layer formation at the peripheral part of side wall thereof, the furnace bottom surface is formed slant by from the range of 0.5-0.8R distance (R is the furnace radius at the tuyere height of the blast furnace) from the furnace bottom surface center toward a furnace bottom side wall at inclination of >=45 deg.. Further, the contact position of the furnace bottom surface with the furnace bottom side wall is higher than the position of an iron tapping hole.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a refractory structure at the bottom of a blast furnace for the purpose of extending the life of the blast furnace.

[0002]

2. Description of the Related Art In recent years, the size of blast furnaces has increased and the internal volume has reached 5,000.
There are quite a few that exceed m ³ . Since repairing such a large blast furnace costs a huge amount of money, in recent blast furnace operations, it is important to extend the life of the furnace as much as possible, as well as to stably produce pig iron. There is. The life of a blast furnace is judged based on the degree of damage to the furnace body, except for blow-offs in line with the production plan.
The criterion for this is whether or not it is possible to maintain the furnace body necessary to continue operation by repairing during a downwind. Since the start of operation, repairs have been carried out from the inner surface of the furnace on a regular basis or when necessary when there is a blast, but the side wall above the tuyere in the blast furnace furnace body is maintained to some extent due to the progress of repair technology. Although it is possible, the side wall and bottom of the furnace body below the tuyere are the parts where molten pig iron is present, and the contents below the tuyere cannot be emptied easily. It is impossible to radically repair damage to the same area. In other words, it can be considered that significant damage to the side wall and bottom of the tuyere (hereinafter referred to as “furnace bottom side wall” and “furnace bottom bottom”, respectively) determines the life of the blast furnace, and the key to extending the life of the furnace is It can be said that this is to prevent damage to the bottom wall and bottom of the furnace.

More specifically, the damage to the bottom wall and bottom of the furnace means the erosion and damage of the refractory bricks on the inner surface of the furnace, and the brick wear mechanism is complicated, but the main cause is that of the hot metal. It is said that the brick melts due to flow.
If the hot metal flow is active, the wear progresses. Therefore, it can be said that the suppression of brick wear is to reduce the heat load by lowering the hot metal flow velocity near the same part.

Conventionally, in order to protect the furnace bottom, charging of a Ti-containing iron source ore or blowing of a Ti-containing ore from a tuyere has been carried out. These are intended to reduce the hot metal flow rate due to an increase in the hot metal viscosity near the bottom wall of the furnace bottom. However, Ti-containing ores are not cheap ones, and there is a big cost disadvantage in using them all the time. In addition, there is a risk that the pig iron residue will deteriorate even if used in large quantities. On the other hand, when considering the hot metal flow rate from the aspect of liquid permeability, the presence or absence of the hot metal-only region (hereinafter referred to as the "coke-free layer") that occurs in the blast furnace hearth becomes a problem.

FIG. 1 shows a schematic view of the hearth of the blast furnace. Above the bottom 3 of the bottom of the furnace, there are a coke filling layer 1 and a coke-free layer 2, which are composed of an upper layer of slag 6 + coke 8 and a lower layer of hot metal 7 + coke 8. Further, tuyere 5 is provided at an upper portion of the furnace bottom side wall 4 at regular intervals in the circumferential direction, and tapholes 9 are provided at a lower part thereof. The height of the taphole 9 from the bottom of the furnace is 10 Say.

In this way, the coke-free layer 2 is formed on the bottom of the blast furnace.
Since the liquid permeability of that portion is significantly better than that of the coke-filled layer 1, the hot metal flow rate increases and the heat load increases at the portion where the coke-free layer exists. Therefore, it has a great influence on the hot metal flow, and especially when it occurs only on the side wall of the furnace bottom, the hot metal flow becomes an annular flow to promote brick wear of the same part.

There are several techniques for protecting the hearth by paying attention to this coke-free layer. For example, in Japanese Examined Patent Publication No. 5-7443, an ore / coke (hereinafter “O /
(Referred to as "C") ratio to increase the charge load in the center of the furnace to suppress the floating of the coke packed bed at the bottom of the furnace. However, increasing the O / C ratio in the central part of the furnace also affects the radial gas flow distribution in the upper part of the furnace, which impedes the effective progress of the pig iron reaction in the blast furnace and further hinders stable operation. There is a risk of

Further, the technique disclosed in Japanese Patent Application Laid-Open No. 4-45213 proposes a furnace bottom shape in which the coke-free layer is buried after the shape is estimated by experiments. Specifically, the structure of the bottom surface of the hearth is inclined at an angle range of 20 to 45 degrees with respect to the horizontal plane from the center of the furnace to the periphery of the furnace, and the coke-free layer is not generated in the hearth to improve the hot metal flow rate. Controlled to prevent brick wear. However, in the actual blast furnace, since tapping is performed intermittently, the molten metal surface position fluctuates and the coke packed bed also floats. Also,
It is thought that it may float depending on the operating conditions, especially the charging O / C ratio. At a slope of 45 degrees, which is almost the same as the angle of repose, the coke-filled bed floats up significantly, so that the ultra-thin coke-free layer spreads from the center of the furnace to the entire periphery of the furnace, and at the angle smaller than 45 degrees, that is, locally thin coke. Free layer is generated,
At that portion, there is a high possibility that the hot metal will flow at a high speed and abnormal wear will occur, and in the blast furnace operation, there is a risk that such rapid wear will delay the countermeasure.

[0009]

In view of the above-mentioned problems, an object of the present invention is to extend the furnace life of a blast furnace without hindering the efficient and stable production of pig iron which is the basic mission of the blast furnace. The purpose is to develop a blast furnace bottom structure that can be used.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies on the suppression of the wear of the furnace bottom side wall and the furnace bottom side brick, and as a result, the furnace bottom refractory structure is formed with a coke-free layer around the furnace bottom side wall. Focusing on the fact that the brick wear of the same part can be suppressed by adopting a non-existent structure, and assuming that the furnace radius at the tuyere height of the blast furnace is R, this is contrary to the recognition found in the above-mentioned JP-A-4-45213. Furthermore, the inventors have invented a blast furnace bottom refractory structure characterized by increasing the inclination angle formed by the bottom surface of the furnace bottom and the horizontal plane to more than 45 degrees from the range of 0.5 R or more and 0.8 R or less from the center.

Here, the bottom surface of the furnace bottom means a projection surface of the furnace bottom,
The angle between the bottom surface of the furnace bottom and the horizontal plane is defined as positive in the counterclockwise direction. In a preferred mode thereof, the boundary position between the bottom surface of the furnace bottom and the side wall of the furnace bottom having the above-described inclination angle may have a molten metal pool depth equal to or higher than the height of the tap hole.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Here, the reason why the above-mentioned configuration is adopted in the present invention will be described in detail together with its operation.

The results of past blast furnace dismantling surveys are shown in FIG. In the figure, the state of erosion below the tuyere 5 is shown, but particularly remarkable erosion is seen below the tap hole 9, and the maximum erosion line 11 is largely eroded from the brick surface 12 during furnace construction. I understand. 13 is an iron skin, 14 is a chamotte brick, and 15 is a carbon brick.

It should be noted here that the furnace bottom is eroded by a long-term operation, but the erosion is not so remarkable above the tap hole 9, while the brick wear of the furnace bottom side wall is particularly remarkable. That is. It is considered that the main reason for this is the annularization of the hot metal flow toward the taphole, and it is presumed that the coke-free layer generated at this site has a very large effect on brick wear on the side wall of the furnace bottom. It

Therefore, in order to understand the heat load applied to the bricks on the side wall and bottom of the furnace bottom by the shape of the coke-free layer, the shape of the furnace bottom shown in FIG. 3 (the shape of the coke-free layer:
Numerical analysis was carried out using a bottom flow model of the furnace bottom, with A, B, and C) as preconditions.

The amounts of heat flux at three points were determined for each of the coke-free layer shapes A, B, and C, and the results are shown in FIG. As can be seen from these results, even if the shape of the coke-free layer is changed greatly at the bottom of the furnace, the heat flux does not change so much. However, the presence or absence of a coke-free layer at the calculation site on the bottom wall of the furnace significantly changes the heat load, and without the coke-free layer, the heat flux decreases by more than 20%. Further, when the heat loads are compared, the side wall is larger than the bottom part.

Therefore, in the furnace bottom refractory structure, it is always necessary to consider so that the coke-free layer is not generated in the vicinity of the furnace bottom side wall portion immediately below the taphole. There is a reference that was obtained by a flat plate model experiment on the top surface shape of the coke-free layer and the boundary shape with the coke packed bed. "Ironmaking 54th Committee Material 54 Committee-186
4 ". It is said that the top surface shape of the coke-free layer changes at an inclination angle of 0 to 44.0 degrees. However, in the present invention, by forming a furnace bottom structure having an inclination not less than this inclination angle, even if a coke-free layer is formed at the bottom of the furnace bottom, the side wall of the bottom of the furnace near the taphole is always occupied by the coke-filled layer, The formation of the coke-free layer shape that causes the flow to be circularized is suppressed. Therefore, in the present invention, the tilt angle is determined to be a value larger than 45 degrees.

However, the shape of the coke-free layer is determined by factors such as the buoyancy of the molten pig iron, the load from above, the blowing pressure and the density of the packing. Increasing the depth of the pool and decreasing the load from the top (decreasing the O / C ratio) may cause the coke-filled layer to float, and a coke-free layer may be generated in the entire bottom of the furnace. Therefore, if the contact point between the bottom of the furnace bottom and the side wall of the furnace bottom, that is, the boundary position, is the depth of the molten metal pool that is equal to or higher than the taphole height, it is possible to suppress the occurrence of local coke-free layers near the taphole to the maximum extent. Even if it occurs, a local hot metal flow cannot occur because it has already formed a coke-free layer in a wide area at the bottom of the furnace bottom.

Further, a model experiment was conducted to estimate the shape of the coke-free layer. The device is a full-circle model device (1/20
The stress applied to the bottom of the equipment was measured in a state where the equipment was filled with sinter having a grain size of 0.5 to 1.0 mm and then unloading.

The measurement results are shown in FIG. From the results shown in the figure, it can be seen that the stress applied to the bottom of the device is almost constant from the central part to the middle part and sharply decreases from the middle part to the wall side. If such a stress distribution is applied in the vertical direction as it is even in the case of an actual blast furnace, the bottom of the coke packed bed is a distance of 0.5 from the center, where R is the radius of the blast furnace at the tuyere height. Almost flat in the range less than R, 0.5
It is considered that when R or more, the shape rises toward the wall side.

Therefore, in the present invention, the distance from the center
When it is 0.5 R or more, the inclination angle formed by the bottom surface of the furnace bottom and the horizontal plane is increased, and the inclination angle is made larger than 45 degrees toward the bottom side wall. Also, if the absolute value of the angle between the horizontal surface of less than 0.5 R and the bottom surface of the furnace bottom is about 10 degrees, there is no problem even if the center part is higher than the middle part. However, the distance from the center is 0.
At 8 R, the vertical stress already applied to the bottom of the device is about 30% or less of the center and middle parts. Moreover, since it is already close enough to the furnace wall even if tilted from more than 0.8 R,
It is predicted that the coke-free layer will be generated on the furnace wall side, and the effect cannot be expected so much. Therefore, 0.8 R was decided as the upper limit. More preferably, the distance is 0.5R to 0.8R,
The angle of inclination is also 45 to 70 degrees.

[0022]

EXAMPLES The operation and effects of the present invention will be described in detail below with reference to specific examples. It is considered that the coke packed bed floats and sinks depending on the operating conditions. Therefore, in each of the hearth bottom structures shown in Cases 1 to 5 in FIG. 6, when the A series: coke packed bed is submerged,
(a) to (f) B series: When the coke-filled layer floats by 0.3R, the coke-free layer of the coke-free layer is assumed based on the bottom normal stress distribution of Fig. 5 assuming Fig. 6 (g) to (l). Each shape was estimated.

In the figure, indicates the center position of the furnace bottom, indicates the position of the side wall of the furnace bottom, and the reference numeral 9 indicates the tap hole,
Reference numeral 12 indicates the brick surface at the time of furnace construction, and the hatched portion indicates the coke-free layer 2.

Based on these preconditions, a numerical analysis was carried out using a furnace bottom hot water flow model. The boundary conditions used in the calculation were set appropriately with reference to the blast furnace operating conditions with a furnace volume of 4800 m ³ and a hearth radius of 7.3 m.

The heat flux at the center position of the furnace bottom and the side wall position of the furnace bottom (position at a certain distance from the tap hole) was obtained, and the heat flux was measured for each of the A and B series bases (Fig. 6 (e)
, (K)) and cases 1 to 5 were compared and relative evaluation was performed. The bases are the results when the conditions of both A and B series are close to those of the conventional blast furnace. Table 1 shows the results for the A series and Table 2 for the B series, respectively, and Table 3 shows a comprehensive evaluation of these two results.

In case 3 and case 5 corresponding to the furnace bottom structure proposed by the present invention, the heat load is suppressed in any series, that is, regardless of whether the coke packed bed is floating or sinking. On the other hand, in the furnace bottom structure with an inclination angle of 25 degrees (Case 1), the coke packed bed rises (see Fig. 6 (g)),
A part of the thin coke-free layer is locally generated between the center of the furnace bottom and the tap hole, and the entire coke-free layer is connected. Therefore, in this situation, the hot metal flow velocity increases in the thin portion of the coke-free layer, and the heat load increases significantly.

When the inclination angle is set to 30 degrees from 0.5R or more as in case 2, the coke-free layer sinks.
As shown in (b), a coke-free layer is generated in the vicinity of the side wall, which causes the hot metal flow to be circularized and the heat load is significantly increased. Further, the base (Fig. 6 (e)) or case 4 (Fig. 6 (d)) corresponding to the bottom structure of the conventional blast furnace also has the same situation because the coke-free layer is generated at the corner portion.

As described above, as a result of the numerical analysis using the furnace bottom molten metal flow model, it was confirmed that the furnace bottom refractory structure of the present invention can constantly suppress the heat load on the furnace bottom side wall and is effective in suppressing brick wear. .

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

According to the present invention, the distance from the center is 0.
By increasing the angle between the bottom surface of the furnace bottom and the horizontal surface within the range of 5 R or more and 0.8 R or less and making the inclination angle greater than 45 degrees toward the bottom side wall, a refractory structure at the bottom of the blast furnace is provided. It becomes difficult to generate a coke-free layer in the vicinity of the bottom wall of the furnace bottom, the annular flow of the hot metal flow is prevented, and the brick wear on the side wall of the furnace bottom can be significantly suppressed. Therefore, the life extension of the blast furnace can be expected without hindering stable operation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a structure of a general furnace bottom portion of a blast furnace.

FIG. 2 is a schematic diagram showing a furnace bottom brick erosion line based on a blast furnace dismantling investigation result.

FIG. 3 is a schematic diagram showing the shape of a coke-free layer used for calculating a furnace bottom molten metal flow model.

FIG. 4 is a graph showing changes in heat flux at 3 points (furnace bottom 1, furnace bottom 2, side wall) when the coke-free layer is changed.

FIG. 5 is a graph showing a radial distribution of a vertical stress at the bottom in a model test.

6 (a) to 6 (l) show the bottom structure and the coke-free layer shape used for the calculation when the bottom flow model was used to confirm the effect of the present invention. It is a schematic diagram.

[Explanation of symbols]

 1: Coke filling layer 2: Coke-free layer 3: Bottom of furnace bottom 4: Side wall of furnace bottom 5: Tuyere 6: Slag 7: Hot metal 8: Coke 9: Tap hole 10: Depth of pool 11: Maximum erosion line 12: Brick surface during furnace construction 13: Iron crust 14: Chamotte brick 15: Carbon brick

Claims (2)

[Claims] 1. When the furnace radius at the tuyere height of the blast furnace is R, the bottom surface shape of the bottom of the blast furnace is within a range of 0.5 R or more and 0.8 R or less from the center. Blast furnace bottom structure characterized by increasing the angle of inclination to over 45 degrees. 2. The blast furnace furnace according to claim 1, wherein the boundary position between the bottom surface of the furnace bottom and the side wall of the furnace bottom having the inclination angle has a depth of the pool of water equal to or higher than the height of the tap hole. Bottom structure.