JPH05239519A - Structure of outer combustion type hot stove - Google Patents

Abstract

PURPOSE:To reduce the height level difference between two chambers and to prevent cracking of an iron shell developed at the connecting part of a connecting tube and fall-down of bricks only by changing heat insulating range in an outer combustion type hot stove directly connecting a regenerator and a combustion chamber with the connecting tube. CONSTITUTION:A top dome 10 in a self-standing type regenerator 1 and a top dome 11 in a combustion chamber 2 put on a frame base 3 in an outer combustion type hot stove are directly connected with a connecting tube 4. Successively, the combustion chamber 2 is lowered in the height directional level lower than the self-standing regenerator 1 by deflection of the frame base 3 with the wt. of bricks for laying in the combustion chamber 2 and large stress is developed to the connecting part of the connecting tube 4, thereby the corrosion crack of the iron shell based on the stress in this part is developed. In order to prevent this cracking, the range 9 of the heat insulating material coated on the iron shell in the combustion chamber 2 is widened or the range 9 constituted of heat insulating material in the regenerator 1 is reduced to make the difference of the height directional level between the combustion chamber 2 and the regenerator 1 the min., thus the development of the stress to the connecting part of the connecting tube 4 is prevented, and the development of the cracking of the iron shell caused by the stress and the falling-down accident of the bricks are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an external combustion hot-air stove in which a dome of a self-supporting heat storage chamber and a dome of a combustion chamber mounted on a stand are connected without using expansion joints.

[0002]

2. Description of the Related Art In general, a hot blast stove, which is an auxiliary facility of a blast furnace, is roughly classified into a small internal combustion hot stove and a large external combustion hot stove. In the external combustion hot stove, the heat storage chamber and the combustion chamber are separated,
For the connection method between the heat storage dome and the combustion chamber dome, the following 2
There is one. One is a hot-air stove in which the tops of the heat storage chamber dome and the combustion chamber dome are connected by a straight pipe without expansion joints, which is commonly called the Martin type or Dadeer type. For example, Maruzen Co., Ltd. October 1979. Published, 3rd Edition Steel Handbook II,
Ironmaking and steelmaking Shown on page 301. The other is a so-called Coppers type in which the side walls of the heat storage chamber dome and the combustion chamber dome are connected by a straight pipe having an expansion joint, which is disclosed in JP-A-50-104707 and JP-A-53-13190.
No. 6 and Japanese Utility Model Publication No. 55-4285 are available.

FIG. 5 shows the structure of a conventional Coppers type hot air stove. The heat storage chamber 1 is a self-supporting type, and the combustion chamber 2 is loaded on a pedestal 3. The dome 10 of the heat storage chamber 1 and the dome 11 of the combustion chamber 2 are connected by the connecting pipe 4 having the expansion joint 5, so that the expansion joint 5 does not expand when the internal pressure is applied to both domes 10 and 11. Further, a dome ring stiffener 6 and a tension beam 7 which are responsible for the internal pressure thrust are provided.
In addition, 8 in FIG. 5 is a connecting truss that connects the heat storage chamber 1 and the combustion chamber 2. The heat insulation range for covering the iron skin with an iron skin heat insulating material (not shown) as a measure against stress corrosion cracking of the iron skin is the portion of both the domes 10 and 11 above the connecting truss 8.

By the way, recently, in the Coppers type hot-blast stove, a structure in which the weight of the hot-blast stove structure is reduced and the joint for the purpose of eliminating the expansion joint is used to absorb the thermal expansion by the rigidity of the connecting pipe without using the expansion joint. There is. Fig. 4 shows a hot-blast stove structure that does not use expansion joints for the connecting pipes. In this case, the dome 10 of the heat storage chamber 1 and the dome 11 of the combustion chamber 2 are directly connected by the connecting pipe 4, and in Fig. 5. Expansion joint 5 shown
Of course, the ring stiffener 6 and the tension beam 7 are also lightened. In addition, the heat insulation range of the iron skin is a portion above the connecting truss 8 as in the hot air stove shown in FIG.

[0005]

As described with reference to FIG. 4, when the connecting pipe 4 has no expansion joint, the heat expansion in the horizontal direction can escape due to the deformation of the heat storage chamber 1 and the combustion chamber 2 as a whole. It is possible, and there is no problem in terms of stress. However, if the heat storage chamber 1 is self-supporting and the combustion chamber 2 is loaded on the pedestal 3, the dome 10 of the heat storage chamber 1 and the dome of the combustion chamber 2
After connecting 11 and 11 by the connecting pipe 4, the bricks of the combustion chamber 2 are stacked. Therefore, the level of the combustion chamber 2 in the height direction lowers with respect to the heat storage chamber 1 due to the bending of the pedestal 3 due to the weight of the brick. It will be.

[0006] In addition, the effect of heat insulation of the steel shell (the temperature of the heat insulating portion is 200 ° C) as a countermeasure against stress corrosion cracking, and the level in the height direction between the heat storage chamber and the combustion chamber due to combustion / blast switching during hot stove operation. Change of the connection pipe 4 joint root (knuckle part)
A large stress is generated in. Therefore, the knuckle portion needs to be excessively reinforced, and in the worst case, the intended purpose of not having the expansion joint of the connecting pipe portion cannot be achieved.

The present invention has been made in view of the above situation, and minimizes the level difference in the height direction between the heat storage chamber and the combustion chamber to reduce the stress in the knuckle connecting the connecting pipes. It is an object of the present invention to provide a structure of an external combustion hot-air stove in which expansion and contraction joints of connecting pipes can be suppressed and thereby omitted.

[0008]

According to the present invention for achieving the above object, a dome of a self-supporting heat storage chamber and a dome of a combustion chamber loaded on a stand are directly connected by a connecting pipe without using an expansion joint. In the structure of an external combustion hot-air stove, the range of the heat insulating material for coating the iron skin of the heat storage chamber and / or the combustion chamber is set based on the level difference in the height direction between the heat storage chamber and the combustion chamber. The structure of an external combustion hot-air stove is characterized in that the height difference in the height direction is offset by the thermal expansion of the iron shell coated with the heat insulating material.

[0009]

The function of the level difference in the height direction between the self-supporting heat storage chamber and the combustion chamber loaded on the pedestal is as follows. (1) Since the bricks are stacked after the self-supporting heat storage chamber and the combustion chamber loaded on the pedestal are joined by the connecting pipe, the pedestal bends due to the weight of the brick, and a level difference occurs in the height direction between the heat storage chamber and the combustion chamber. (2) A level difference in the height direction occurs due to the difference in the expansion of the skins of the heat storage chamber and the combustion chamber due to the switching between hot air stove combustion and blowing. (3) A level difference occurs in the height direction due to the difference in the heat retention condition of the iron skin (heat retention range and heat retention temperature condition).

Among the above three factors, the one which can be adjusted most easily is (3), and therefore the conventional heat retention range is the same, whereas in the present invention, the heat retention chamber and the combustion chamber are kept warm. By changing it, the total level difference in the height direction between the heat storage chamber and the combustion chamber in the process of operating the hot stove is reduced. FIG. 3 shows the level change of the combustion chamber based on the qualitative heat storage chamber of the hot stove.

That is, the level of the combustion chamber in the height direction is lowered with respect to the heat storage chamber due to the bending of the brick base as described above at the stage of completing the brick stacking after the connection pipe is attached. Next, when the temperature rises, the temperature on the combustion chamber side becomes higher, so the level on the combustion chamber side rises due to the difference in thermal expansion. This level also becomes low during the blast period, rises again when the temperature rises in the subsequent combustion period, and repeats during hot blast stove operation, and will constantly fluctuate.

In the present invention, the level displacement amount δ in the combustion period and the blower period and the reference level of the heat storage chamber are combined so as to minimize this fluctuation amount, and between the levels in the combustion period and the blower period in the figure. The heat-retaining range is set so as to cover the heat storage chamber-side and / or combustion-chamber-side iron skins, and the thermal expansion of the steel skins covered with the heat insulating material is offset. here,
The fluctuations between the combustion period and the blast period are unavoidable. Therefore, when considering the load on the knuckle part, the heat expansion may be taken so that the median value δ / 2 between the levels of the blast period is obtained in the combustion period. This is the position where the effect is greatest and is preferable. By doing so, it is possible to achieve an optimum hot-blast stove structure using a connecting pipe that does not use an expansion joint, without reinforcing the knuckle portion of the connecting pipe root by an excessive increase in plate thickness.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. Generally, when the inner surface temperature of the hot-air stove is below the acid dew point such as NO _{X, the} iron-skin crack easily occurs due to stress corrosion cracking, so the drum part above the connecting truss is covered with a heat insulating material. Is being prevented.

Here, as shown in FIG. 1, in a self-supporting type heat storage chamber 1, the dome 10 of the heat storage chamber 1 and the dome 11 of the combustion chamber 2 mounted on a pedestal are directly connected by a connecting pipe 4. In the same way as the conventional method, the heat insulating range is set above the connecting truss 8, but the combustion chamber 2 uses the dome 11 as well as the straight trunk iron shell directly below the connecting truss 8 in the height direction in order to prevent stress corrosion of the iron shell. The area of 6540 mm indicated by diagonal lines in FIG. 1 was covered with the heat insulating material 9 made of ceramic wool. In this case, the temperature of the iron shell in the heat-insulating area including the domes 10 and 11 is 200
C., and the temperatures of the other straight body shells of the heat storage chamber 10 and the combustion chamber 11 have the distributions shown in FIG.

In the hot stove in which the heat-retaining range of the combustion chamber 2 is expanded as described above, the dome 10 of the heat storage chamber 1 and the dome 11 of the combustion chamber 2 are connected by the connecting pipe 4, and then the bricks are placed in both chambers. Stacking was performed, the temperature in the furnace was raised to the required temperature, and the bricks in the furnace were dried. Dry the bricks in the hot stove,
When the heat storage chamber was heated to a predetermined temperature, the hot-air stove was put into steady operation in which air blowing and combustion were repeated in sequence.

FIG. 2 shows a level change in the height direction of the combustion chamber 2 with the heat storage chamber 1 as a reference when the connecting pipe 4 is attached in this case. In FIG. 2, minus is low on the combustion chamber side, and plus is high on the combustion chamber side. Conventionally, as shown by the broken line, when the bricks are completely stacked, the combustion chamber 2 is set to 3
The mm level decreases, the temperature rises 9.6 mm above the standard when the temperature rises, and the level changes when the blast pressure increases 6.7 mm above the standard, and the maximum level difference reaches 12.6 mm.
If the level change is repeated as it is, a large stress is generated at the base of the connecting pipe 4 and there is a risk of cracking, and the brick in the connecting pipe 4 falls off.

Therefore, in the present invention, in order to reduce the maximum value of this level difference of 12.6 mm, +9.6 mm at the time of temperature rise (during combustion)
This is to eliminate the +6.7 mm level difference when blowing.
In this example, the maximum level value is 12.6 so that there is an intermediate level difference.
Adjust the coating range of the heat insulating material so that mm is reduced to [3.0 + (9.6-6.7) / 2] = 4.45 mm. That is (200 ° -60
°) × 1.1 × 10 ^-5 L = (12.6-4.45) mm, L = 5292mm
Is obtained. In addition, 1.1 × 10 ^-5 is the coefficient of linear expansion of iron. Further, 200 ° C is the temperature of the heat insulation part and 60 ° C is the temperature of the non-heat insulation part.

This is because the heat retention range on the heat storage chamber side is set in the height direction.
It means that it should be expanded by 5292 mm or the heat insulation range on the combustion chamber side should be reduced by 5292 mm in the height direction, but here, in order to promote measures against stress corrosion cracking of the iron shell, The lower part of the connecting truss 8 is 5292 mm as shown in FIG.
It was decided to cover the range of 1 with the heat insulating material 9. In this way, the heat storage chamber 1 and the combustion chamber 2 during the operation of the hot stove
As a result of eliminating the level difference in the height direction, it was possible to prevent cracks occurring at the base of the connecting pipe 4.

[0019]

As described above, according to the present invention, in the hot stove in which the heat storage chamber and the combustion chamber are directly connected by the connecting pipe, the heights of the heat storage chamber and the combustion chamber can be changed only by changing the heat retention range. The level difference can be reduced. As a result, it is possible to prevent cracking of the iron shell that tends to occur at the base of the connecting pipe and falling of the brick, so that the life of the hot stove can be extended.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a graph showing the level change in the height direction of the combustion chamber with reference to the heat storage chamber according to the embodiment of the present invention.

FIG. 3 is a graph showing the level change in the height direction of the combustion chamber with respect to the heat storage chamber, for explaining the concept of the present invention.

FIG. 4 is a side view showing a conventional example.

FIG. 5 is a side view showing another conventional example.

[Explanation of symbols]

 1 heat storage chamber 2 combustion chamber 3 pedestal 4 connecting pipe 5 expansion joint 6 dome ring stiffener 7 tension beam 8 connecting truss 9 heat insulating material 10 dome (heat storage chamber) 11 dome (combustion chamber)

Claims (1)

[Claims] 1. A structure of an external combustion hot-air stove in which a dome of a self-supporting heat storage chamber and a dome of a combustion chamber mounted on a mount are directly connected by a connecting pipe without using expansion joints, and the heat storage chamber is provided. Based on the height direction level difference between the heat storage chamber and / or the combustion chamber, the range of the heat retaining material that covers the iron skin of the combustion chamber is set, and the height direction level difference is coated with the heat retaining material. The structure of an external combustion hot-air stove, which is configured to be offset by the heat expansion of the iron shell.