JP3276973B2 - External combustion hot stove structure - Google Patents

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 type hot blast stove in which a dome of a free standing heat storage chamber and a dome of a combustion chamber mounted on a gantry are connected without using an expansion joint.

[0002]

2. Description of the Related Art Generally, hot blast stoves, which are auxiliary equipment of a blast furnace, are roughly classified into small internal combustion hot blast stoves and large external combustion hot blast stoves. In the external combustion type hot stove, the heat storage chamber and the combustion chamber are separated,
The following two methods are used to connect the heat storage dome and the combustion chamber dome.
There is one. One of them is a hot-blast stove in which the tops of the heat storage chamber dome and the combustion chamber dome are connected by straight pipes without expansion joints. Published, Third Edition Steel Handbook II,
It is shown on page 301 for iron and steelmaking. 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.

FIG. 5 shows the structure of a conventional Coppers type hot blast stove. The heat storage chamber 1 is self-supporting, and the combustion chamber 2 is mounted on a gantry 3. The dome 10 of the heat storage chamber 1 and the dome 11 of the combustion chamber 2 are connected by a connecting pipe 4 having an expansion joint 5, so that when the internal pressure is applied, the expansion joint 5 does not expand. Further, a dome ring stiffener 6 and a tension beam 7 for receiving the internal pressure thrust are provided.
Note that reference numeral 8 in FIG. 5 denotes a connecting truss that connects the heat storage chamber 1 and the combustion chamber 2. The heat insulating range for covering the steel using a steel heat insulating material (not shown) as a measure against stress corrosion cracking of the steel is the portions of both the domes 10 and 11 above the connecting truss 8.

Meanwhile, recently, in a Coppers type hot stove, a structure that absorbs thermal expansion by the rigidity of a connecting pipe without using an expansion joint at a connecting portion aimed at reducing the weight of the hot stove structure and without an expansion joint has been considered. I have. FIG. 4 shows a hot stove structure in which an expansion joint is not used for the connecting pipe. 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 FIG. Telescopic joint 5 shown
Needless to say, the weight is reduced without the ring stiffener 6 and the tension beam 7. In addition, the heat insulation range of the iron shell is a part above the connecting truss 8 similarly to the hot stove shown in FIG.

[0005]

As described with reference to FIG. 4, when there is no expansion joint in the connecting pipe 4, the horizontal thermal expansion can escape due to the entire deformation of the heat storage chamber 1 and the combustion chamber 2. Yes, no problem in terms of stress. However, if the heat storage chamber 1 is of a self-standing type and the combustion chamber 2 is mounted on the gantry 3, the dome 10 of the heat storage chamber 1 and the dome of the combustion chamber 2
After the connection with the connection pipe 11 by the connecting pipe 4, the combustion chamber 2 is bricked, so that the height of the combustion chamber 2 is lower than that of the heat storage chamber 1 due to the bending of the gantry 3 due to the weight of the brick. Will be.

In addition, the effect of heat insulation of the steel shell for preventing stress corrosion cracking (the temperature of the insulation steel shell is 200 ° C.) and the height level between the heat storage chamber and the combustion chamber by switching between combustion and ventilation during operation of the hot stove Of the connecting pipe 4 (knuckle part)
Large stress is generated. For this reason, excessive reinforcement of the knuckle part is required, and in the worst case, the intended purpose of no expansion joint of the connecting pipe part cannot be achieved.

The present invention has been made in view of the above circumstances, and minimizes the level difference between the heat storage chamber and the combustion chamber in the height direction to reduce the stress at the knuckle connecting the connecting pipe. It is an object of the present invention to provide a structure of an external combustion type hot blast stove capable of suppressing the expansion and contraction of a connecting pipe thereby.

[0008]

According to the present invention, in order to achieve the above object, a dome of a self-supporting heat storage chamber and a dome of a combustion chamber mounted on a gantry are directly connected by a connecting pipe without using an expansion joint. In the structure of an external combustion type hot air stove, a range of a heat insulating material for covering the steel shell of the heat storage chamber and / or the combustion chamber is set based on a level difference in a height direction between the heat storage chamber and the combustion chamber. , Wherein the level difference in the height direction is offset by the thermal expansion of the steel sheath coated with the heat insulating material.

[0009]

The cause of the level difference in the height direction between the self-supporting heat storage chamber and the combustion chamber loaded on the gantry is as follows. (1) Since the brick is stacked after the self-standing heat storage chamber and the combustion chamber mounted on the gantry are joined by the connecting pipe, the gantry flexes 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 a difference in the elongation of the shell between the heat storage chamber and the combustion chamber due to switching between combustion and blowing of the hot blast stove. (3) There is a level difference in the height direction due to the difference in the heat retaining condition of the iron shell (the heat retaining range and the thermal retaining temperature condition).

[0010] Of the above three factors, the one that can be most easily adjusted is (3), so that the heat retention ranges of the heat storage chamber and the combustion chamber are changed according to the present invention, while the heat retention ranges are the same in the past. By changing, the total level difference in the height direction between the heat storage chamber and the combustion chamber in the operation process of the hot blast stove is reduced. FIG. 3 shows the level change of the combustion chamber based on the heat storage chamber of the qualitative hot stove.

That is, the level of the combustion chamber is lowered in the height direction with respect to the heat storage chamber due to the bending of the brick gantry, 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, and the level on the combustion chamber side rises due to the difference in thermal expansion. This level also becomes low during the blowing period, rises again when the temperature rises during the subsequent combustion period, and repeats during the operation of the hot-blast stove, and constantly fluctuates.

According to the present invention, the level displacement δ during the combustion period and the blowing period and the reference level of the heat storage chamber are combined so that this variation is minimized. A heat insulation range is set so as to cover the steel shell on the heat storage chamber side and / or the combustion chamber side so as to be offset by the thermal elongation of the steel shell coated with the heat insulating material. here,
Fluctuations in the period between the combustion period and the blowing period are inevitable. Therefore, when considering the load on the knuckle portion, the thermal expansion may take the value of the median δ / 2 between the levels of the blowing period during the combustion period. This is the position where the effect is greatest and is preferable. This makes it possible to achieve a hot blast stove structure using a connecting pipe without using an optimal expansion joint without reinforcing an excessive increase in the thickness of the knuckle at the base of the connecting pipe.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Generally in acid dew point or lower, such as steel shell inner surface temperature of the hot air furnace NO _X is liable furnace shell cracking is due to stress corrosion cracking in steel shell, its occurrence by coating a heat insulating material over the drum portion the connecting trusses Has been prevented.

Here, as shown in FIG. 1, a self-standing heat storage chamber 1 is directly connected to a dome 10 of a heat storage chamber 1 and a dome 11 of a combustion chamber 2 mounted on a frame by a connecting pipe 4. The upper part of the combustion chamber 2 is placed above the connecting truss 8 in the same manner as in the prior art. The area of 6540 mm indicated by oblique lines in FIG. 1 was covered with a heat insulating material 9 made of ceramic wool. In this case, the temperature of the shell in the insulated area including the domes 10 and 11 is 200
° C, and the temperature of the shell of the straight body between the other heat storage chamber 10 and the combustion chamber 11 has a distribution as shown in FIG.

In the hot blast stove in which the heat insulation 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, and the inside of the furnace was heated to a required temperature to dry bricks in the furnace. Dry the brick in the hot blast stove,
After the heat storage chamber was heated to a predetermined temperature, the hot-blast stove started regular operation in which blowing and combustion were sequentially repeated.

FIG. 2 shows the level change in the height direction of the combustion chamber 2 with respect to the heat storage chamber 1 when the connecting pipe 4 is attached in this case. In FIG. 2, the minus sign indicates a low value on the combustion chamber side and the plus sign indicates a high value on the combustion chamber side. Conventionally, as shown by the dashed line, when the loading of the brick is completed, the deflection of the gantry 3 causes the combustion chamber 2 to be 3
The level changes by 9.6 mm above the standard when the temperature rises, and 6.7 mm above the standard when the air is blown, due to the air pressure. 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 not only there is a risk of causing a crack, but also bricks in the connecting pipe 4 fall off.

Therefore, in the present invention, in order to reduce the maximum value of the level difference of 12.6 mm, the temperature difference is increased by +9.6 mm at the time of temperature rise (at the time of combustion).
And the level difference of + 6.7mm between the air blowing.
In this example, the maximum level is 12.6 so that there is an intermediate level difference.
Adjust the covering area 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. Note that 1.1 × 10 ⁻⁵ is the linear expansion coefficient of iron. In addition, 200 ° C is the temperature of the shell in the heat-insulating section, and 60 ° C is the temperature of the shell in the non-insulating section.

This is because the heat storage area on the side of the heat storage chamber is shifted in the height direction.
It means that it is sufficient to widen 5292 mm or reduce the heat insulation range on the combustion chamber side by 5292 mm in the height direction. Here, in order to promote measures against stress corrosion cracking of the steel shell, the heat insulation range of the heat storage chamber 1 is increased. The lower part of the connecting truss 8 is 5292 mm as shown in FIG.
It was decided to cover the area with the heat insulating material 9. Thus, the heat storage chamber 1 and the combustion chamber 2 during operation of the hot stove
As a result of eliminating the level difference in the height direction, cracks generated at the base of the connecting pipe 4 could be prevented.

[0019]

As described above, according to the present invention, in a hot blast stove in which a heat storage chamber and a combustion chamber are directly connected by a connecting pipe, the height of the heat storage chamber and the combustion chamber can be changed simply by changing the heat retention range. The level difference can be reduced. As a result, it is possible to prevent cracks in the steel shell and bricks that are likely to be generated at the base of the connecting pipe, thereby extending the life of the hot stove.

[Brief description of the drawings]

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

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

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

 DESCRIPTION OF SYMBOLS 1 Thermal storage room 2 Combustion chamber 3 Stand 4 Connecting pipe 5 Expansion joint 6 Dome ring stiffener 7 Tension beam 8 Connecting truss 9 Insulation material 10 Dome (heat storage room) 11 Dome (combustion chamber)

Claims (1)

(57) [Claims] 1. A structure of an external combustion type hot blast stove in which a dome of a self-supporting heat storage chamber and a dome of a combustion chamber mounted on a gantry are directly connected by a connecting pipe without using an expansion joint. The range of the heat insulator covering the heat storage chamber and / or the shell of the combustion chamber was set based on the height direction level difference between the heat insulator and the combustion chamber, and the height direction difference was covered with the heat insulator. A structure of an external combustion type hot stove characterized by being constituted so as to be offset by thermal expansion of a steel shell.