JP7650167B2 - Seal box - Google Patents

Description

The present invention relates to a seal box that covers the gap between the boiler ceiling wall and a group of heat transfer tubes that penetrate the boiler ceiling wall, preventing combustion ash and the like from entering the penthouse.

A large number of heat transfer tubes that make up heat exchangers such as superheaters are suspended inside the boiler furnace, and these heat transfer tubes penetrate the boiler ceiling wall, which is the water wall tube, and are connected to each header (also called a header). Each header is connected to a manifold installed in the penthouse of the boiler building, and the fluid flowing through the heat transfer tubes is collected in the manifold via the header.

The combustion ash generated in the furnace can enter the penthouse through the gap between the boiler ceiling wall and the group of heat transfer tubes that penetrate the boiler ceiling wall, so a seal box is installed inside the penthouse to prevent this.

This type of seal box is formed in a box shape that covers a large number of heat transfer tubes, and the lower end of the peripheral wall of the seal box is fixed to the boiler ceiling wall by welding, and the ceiling wall of the seal box is fixed to the header by welding. Since there is a significant temperature difference between the boiler ceiling wall and the manifold, thermal stress acts on the seal box in the vertical direction due to the difference in thermal expansion between the two. To absorb this thermal stress, the seal box is provided with, for example, a W-shaped expansion (see Patent Document 1).

Japanese Patent Application Publication No. 11-223303

In recent years, the temperature of combustion gas inside furnaces has been rising, and the temperature of the fluid (steam) flowing through headers and manifolds has also been rising. This has resulted in a larger difference in thermal expansion, and the thermal stress acting on the seal box in the vertical direction has also increased. If the seal box is unable to absorb the thermal stress and cracks, combustion ash will enter the penthouse through the cracks, so the seal box needs to be structured to absorb thermal stress more than ever before.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to provide a sealed box that can absorb greater thermal stress.

In order to achieve the above object, one aspect of the present invention is a sealed box that is provided in a penthouse, which is a space above a boiler ceiling wall, and that surrounds a group of heat transfer tubes that penetrate the boiler ceiling wall, the sealed box being formed in a box shape with a peripheral wall consisting of a front wall, a rear wall, a left wall, and a right wall, and a ceiling wall that covers the peripheral wall from above, the ceiling wall being fixed by welding to a header to which the group of heat transfer tubes is connected, the lower end of the peripheral wall being fixed by welding to the boiler ceiling wall, and the peripheral wall being provided with a vertical slit that continues from the front wall to the ceiling wall and the rear wall.

In order to achieve the above object, another aspect of the present invention is a seal box that is provided in a penthouse, which is a space above a boiler ceiling wall, and surrounds a group of heat transfer tubes that penetrate the boiler ceiling wall, the seal box being formed in a box shape having a peripheral wall consisting of a front wall, a rear wall, a left side wall, and a right side wall, and a ceiling wall that covers the peripheral wall from above, the ceiling wall being fixed by welding to a header to which the group of heat transfer tubes is connected, and the lower end of the peripheral wall is fixed to the boiler ceiling wall by welding, and a horizontal slit is provided that is continuous across the front wall, the left side wall, and the rear wall, and across the front wall, the right side wall, and the rear wall, and an expansion for absorbing thermal stress is provided over the entire longitudinal direction of the seal box in the front wall and the rear wall, and the expansion protrudes outward from the peripheral wall, and the expansion is provided so as to be continuous with the horizontal slit at the same height position as the horizontal slit .

The present invention can absorb larger thermal stresses. Problems, configurations, and effects other than those described above will become clear from the description of the embodiments below.

1 is a side view showing the overall structure of a boiler to which the present invention is applied. FIG. 2 is an external perspective view of the seal box according to the first embodiment; FIG. 13 is an external perspective view of the seal box with the slits covered with heat-resistant cloth. 4 is a vertical cross-sectional view of the seal box shown in FIG. 3 cut along a virtual plane P and viewed from a direction A. 4 is a cross-sectional view showing the heat-resistant cloth attached to the ceiling wall, taken along the line BB in FIG. 3 . FIG. 4 is a cross-sectional view showing the state in which the heat-resistant cloth is attached to the front wall, taken along the CC direction in FIG. 3; FIG. FIG. 11 is an external perspective view of a seal box according to a second embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

First Embodiment
Fig. 1 is a side view showing the overall structure of a boiler. The seal box according to the present invention is applied to, for example, the boiler 1 shown in Fig. 1. In this specification, the front-rear, up-down, and left-right directions are defined as shown in each drawing.

The boiler 1 shown in FIG. 1 is installed, for example, in a power generation facility. The boiler 1 includes a furnace 2 for burning fuel such as pulverized coal, a cage section 3, and a secondary side wall 4 connecting the furnace 2 and the cage section 3. The combustion gas generated in the furnace 2 flows through the secondary side wall 4 and the cage section 3, which are the flow path of the combustion gas, and is then discharged into the atmosphere via a gas treatment device (not shown).

The furnace 2 has a furnace side wall 5 and a furnace ceiling wall (boiler ceiling wall) 6, and is suspended from a steel frame 10 by hanging bolts 11. The furnace side wall 5 and the furnace ceiling wall 6 are fabricated into a wall shape by alternately welding heat transfer tubes and fin bars (not shown), and are configured so that water flows inside each heat transfer tube.

Inside the furnace 2, the auxiliary side wall 4, and the cage section 3, multiple heat exchangers consisting of a large number of heat transfer tubes (heat transfer tube group) 15 are installed. These heat exchangers include, for example, superheaters, reheaters, and economizers. As the high-temperature combustion gas flows through the furnace 2, the auxiliary side wall 4, and the cage section 3, it exchanges heat with the fluid in the heat transfer tube group 15. This generates high-temperature superheated steam.

A penthouse (ceiling room) 13 is provided above the furnace ceiling wall 6 (the space between the furnace ceiling wall 6 and the steel frame 10). A header (pipe header) 16 and a manifold 17 are suspended from the penthouse 13 by suspension bolts 12. The heat transfer tube group 15 is connected to the header 16 and is suspended within the furnace 2 by passing through a heat transfer tube penetration 7 (see Figure 4) opened in the furnace ceiling wall 6.

Here, in order to prevent combustion ash from entering the penthouse 13 through the gap between the heat transfer tube penetration portion 7 and the heat transfer tube group 15, a seal box 20 is provided in the penthouse 13 so as to surround the heat transfer tube group 15. The structure of the seal box 20 according to the first embodiment of the present invention will be described below.

(Seal box structure)
FIG. 2 is an external perspective view of the sealed box 20 according to the first embodiment, FIG. 3 is an external perspective view of the sealed box 20 with the slits covered with heat-resistant cloth, and FIG. 4 is a longitudinal sectional view of the sealed box shown in FIG. 3 cut by imaginary plane P and viewed from direction A.

As shown in these figures, the seal box 20 is formed in a box shape with a peripheral wall 25 consisting of a front wall 21, a rear wall 22, a left side wall 23, and a right side wall 24, and a ceiling wall 26 that covers the peripheral wall 25 from above. The ceiling wall 26 is fixed to the header 16 by welding, and the lower end of the peripheral wall 25 is fixed to the furnace ceiling wall 6 by welding. As a result, the space R (see FIG. 4) between the furnace ceiling wall 6 and the header 16 is sealed by the seal box 20.

Furthermore, the seal box 20 is provided with a vertical slit 28 and multiple horizontal slits 29 (29a, 29b). Specifically, the vertical slit 28 is provided continuously with a predetermined width across the front wall 21, the ceiling wall 26, and the rear wall 22. The vertical slit 28 has both ends extending to a position slightly higher than the lower ends of the front wall 21 and the rear wall 22 (see FIG. 6). Note that in FIG. 2, one vertical slit 28 is provided approximately in the center in the longitudinal direction (left-right direction in FIG. 2), but the number is not limited to one. In other words, multiple vertical slits 28 may be provided at intervals in the longitudinal direction.

The two left-side horizontal slits (first horizontal slits) 29a are provided on the left side of the seal box 20 with a vertical gap between them. Each horizontal slit 29a is provided continuously with a predetermined width across the front wall 21, the left side wall 23, and the rear wall 22. Similarly, the two right-side horizontal slits (second horizontal slits) 29b are provided on the right side of the seal box 20 with a vertical gap between them. Each horizontal slit 29b is provided continuously with a predetermined width across the front wall 21, the right side wall 24, and the rear wall 22. In FIG. 2, the horizontal slits 29a and 29b are provided at the same height position, but they may be provided at different height positions. The number of horizontal slits 29 is not limited to two. The number of horizontal slits 29 may be one, or three or more.

Furthermore, two expansions 27 for absorbing thermal stress are provided on the front wall 21 and the rear wall 22 of the peripheral wall 25 of the seal box 20, extending over almost the entire longitudinal direction and spaced apart in the vertical direction. As shown in FIG. 4, the expansions 27 have a U-shaped cross section and protrude outward from the peripheral wall 25 (front wall 21, rear wall 22). The expansions 27 are provided at the same height as the horizontal slits 29 so as to be continuous with the horizontal slits 29. The shape of the expansions 27 may be other than U-shaped in cross section as long as they can absorb thermal stress acting in the vertical direction of the seal box 20.

As shown in FIG. 3, the seal box 20 is provided with a heat-resistant cloth (first sheet member) 35 that entirely covers the vertical slit 28, and multiple heat-resistant cloths (second sheet members) 36 that entirely cover each horizontal slit 29. These heat-resistant cloths 35, 36 are formed into a cloth-like shape by weaving a heat-resistant fiber material (such as glass fiber) that can be used up to 500°C, for example, and have a thickness of about 30 mm, but the material and thickness can be selected as appropriate as long as they are suitable for the usage environment. Note that the heat-resistant cloth 36 that covers the left horizontal slit 29a is not shown in FIG. 3.

Next, the mounting structure of the heat-resistant cloths 35, 36 will be described. Note that the mounting structures of the heat-resistant cloths 35 and 36 are the same, so the mounting structure of the heat-resistant cloth 35 will be described as an example. Figure 5 is a cross-sectional view showing the heat-resistant cloth 35 mounted on the ceiling wall 26, taken along the line B-B in Figure 3. Figure 6 is a cross-sectional view showing the heat-resistant cloth 35 mounted on the front wall 21, taken along the line C-C in Figure 3.

As shown in FIG. 5, the heat-resistant cloth 35 is placed on the upper surface of the ceiling wall 26 so as to cover the vertical slit 28, and both edges of the heat-resistant cloth 35 are fixed to the ceiling wall 26 by bolts 41 and nuts 42 via a pressure plate 40. This ensures airtightness inside the sealed box 20. That is, the heat-resistant cloth 35 is attached so as to be in close contact with the ceiling wall 26 so that no gap is created between the heat-resistant cloth 35 and the ceiling wall 26. The pressure plate 40 is made of, for example, a metal plate, but any material can be used as long as it is heat-resistant.

As shown in FIG. 6, the heat-resistant cloth 35 is arranged on the front surface of the front wall 21 so as to cover the vertical slit 28, and both edges of the heat-resistant cloth 35 are fixed to the front wall 21 by bolts 41 and nuts 42 via a pressing plate 40. As shown in FIG. 6, the lower end of the heat-resistant cloth 35 is fixed to the front wall 21 at a position slightly higher than the furnace ceiling wall 6 while completely covering the vertical slit 28. In other words, the heat-resistant cloth 35 is not fixed to the furnace ceiling wall 6. This is because the furnace ceiling wall 6 is composed of a heat transfer tube and fin bars, making it difficult to attach the heat-resistant cloth 35. Although not shown in the figure, the heat-resistant cloth 35 is also fixed to the rear wall 22 in the same manner as in FIG. 6.

The seal box 20 according to the first embodiment configured in this way can provide the following effects:

The seal box 20 is provided with an expansion 27, so that it can absorb thermal stress acting in the vertical direction of the seal box 20. Moreover, since the seal box 20 is provided with a vertical slit 28 and a horizontal slit 29, the deformation of the seal box 20 due to the difference in thermal expansion between the manifold 17 and the furnace ceiling wall 6 can be absorbed by the vertical slit 28 and the horizontal slit 29. As a result, it is possible to prevent cracks from occurring in the seal box 20 (especially the welded parts), and to prevent combustion ash from entering the penthouse 13 through the cracks. In addition, it is easy to inspect the piping arranged in the penthouse 13. In this way, since this embodiment is provided with a vertical slit 28 and a horizontal slit 29, it is even more effective in harsh operating environments where the expansion 27 alone cannot absorb the thermal stress acting on the seal box 20.

In addition, the vertical slits 28 and horizontal slits 29 are completely covered by the heat-resistant cloths 35, 36, ensuring the airtightness of the sealed box 20. Even if the sealed box 20 is deformed by heat, the heat-resistant cloths 35, 36 bend in response to the deformation, so that the vertical slits 28 and horizontal slits 29 are always kept covered by the heat-resistant cloths 35, 36. Therefore, combustion ash will not get into the penthouse 13.

Second Embodiment
7 is an external perspective view of a seal box 120 according to the second embodiment. The seal box 120 according to the second embodiment is different from the seal box 20 according to the first embodiment in that the seal box 120 according to the second embodiment does not have the vertical slits 28 and the horizontal slits 29. Therefore, in the second embodiment, the heat-resistant cloths 35 and 36 are not provided.

In the second embodiment, two expansions 27 with a U-shaped cross section are provided in the vertical direction, so that the thermal stress acting on the seal box 120 in the vertical direction can be sufficiently absorbed. Moreover, since there are no slits, in addition to the structure being simple, there is no need to provide a heat-resistant cloth, which is expected to reduce costs. The seal box 120 according to the second embodiment is effective when used in an environment where the temperature difference is relatively small compared to the first embodiment.

The present invention is not limited to the above-described embodiment, but includes various modified examples. The above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the configurations described.

For example, if the thermal stress acting on the seal box 20 is relatively small, the horizontal slits 29a and 29b do not need to be provided. In other words, the seal box 20 may have a box shape with a vertical slit 38 and an expansion 27.

Depending on the conditions of the usage environment, the seal box 20 may be provided with at least one of the vertical slits 28 and the horizontal slits 29, and the expansion 27 may be omitted. In other words, the expansion 27 may be removed from the seal box 20 shown in FIG. 3, and a seal box with the vertical slits 28 and the horizontal slits 29 optionally provided may be installed inside the penthouse 13.

1 Boiler 2 Furnace 3 Cage section 4 Sub-side wall 5 Furnace side wall 6 Furnace ceiling wall (boiler ceiling wall)
Reference Signs List 7 Heat transfer tube penetration 10 Steel frame 11, 12 Suspension bolt 13 Penthouse 15 Heat transfer tube group 16 Header 17 Manifold 20 Seal box 21 Front wall 22 Rear wall 23 Left side wall 24 Right side wall 25 Peripheral wall 26 Ceiling wall 27 Expansion 28 Vertical slit 29 (29a, 29b) Horizontal slit (first horizontal slit, second horizontal slit)
35 Heat-resistant cloth (first sheet member)
36 Heat-resistant cloth (second sheet member)
40 Retaining plate 41 Bolt 42 Nut

Claims (12)

A seal box is provided in a penthouse, which is a space above a boiler ceiling wall, and surrounds a heat transfer tube group penetrating the boiler ceiling wall,
The seal box is formed in a box shape having peripheral walls including a front wall, a rear wall, a left side wall, and a right side wall, and a ceiling wall covering the peripheral walls from above,
The ceiling wall is fixed to a header to which the heat transfer tube group is connected by welding,
The lower end of the peripheral wall is fixed to the boiler ceiling wall by welding,
A sealed box, characterized in that the peripheral wall is provided with a vertical slit that continues from the front wall to the ceiling wall to the rear wall. The seal box according to claim 1,
A seal box characterized in that the vertical slits are provided in a plurality of positions spaced apart from each other in the longitudinal direction of the seal box. The seal box according to claim 1 or 2,
A sealed box, characterized in that the vertical slit is covered with a first sheet member having heat resistance. The seal box according to claim 3,
A seal box, characterized in that the first sheet member is fixed to the peripheral wall by bolts via a pressure plate. The seal box according to claim 4,
A sealed box, characterized in that a lower end of the first sheet member is fixed at a position higher than a lower end of the peripheral wall. The seal box according to any one of claims 1 to 5,
A sealed box, characterized in that at least the front wall and the rear wall of the peripheral walls have expansions for absorbing thermal stress provided throughout the entire longitudinal direction of the sealed box. The seal box according to claim 6,
A seal box characterized in that the expansion has a U-shaped cross section and protrudes outward from the peripheral wall. The seal box according to any one of claims 1 to 7,
A sealed box characterized in that the peripheral wall is provided with a first horizontal slit that continues between the front wall, the left side wall, and the rear wall, and a second horizontal slit that continues between the front wall, the right side wall, and the rear wall. The seal box according to claim 8,
A sealed box characterized in that the first horizontal slit and the second horizontal slit are each provided in a plurality of positions spaced apart from each other in the vertical direction. The seal box according to claim 8 or 9,
A sealed box, characterized in that the first horizontal slit and the second horizontal slit are covered by a second sheet member having heat resistance. A seal box is provided in a penthouse, which is a space above a boiler ceiling wall, and surrounds a heat transfer tube group penetrating the boiler ceiling wall,
The seal box is formed in a box shape having peripheral walls including a front wall, a rear wall, a left side wall, and a right side wall, and a ceiling wall covering the peripheral walls from above,
The ceiling wall is fixed to a header to which the heat transfer tube group is connected by welding,
The lower end of the peripheral wall is fixed to the boiler ceiling wall by welding,
a horizontal slit is provided between the front wall, the left side wall, and the rear wall, and between the front wall, the right side wall, and the rear wall;
The front wall and the rear wall of the peripheral wall are provided with expansions for absorbing thermal stress over the entire longitudinal direction of the seal box,
The expansion protrudes outward from the peripheral wall ,
A sealed box characterized in that the expansion is arranged so as to be continuous with the horizontal slit at the same height position as the horizontal slit . The seal box according to claim 11,
A sealed box characterized in that the expansions are provided in multiple spaces spaced apart from each other in the vertical direction of the peripheral wall.

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