Seal structure of boiler, and repair method for seal structure of boiler

Abstract

To provide a seal structure of a boiler that is hardly affected by thermal deformation.SOLUTION: A seal structure of a boiler according to an embodiment comprises a skin casing for sealing a gap between at least one pipe penetrating the interior and exterior of a combustion gas passage of the boiler and a wall part defining the combustion gas passage. The skin casing comprises a first end part on the side of the pipe, and a second end part on the side of the wall part. A cross-sectional shape of the skin casing along an extending direction of the pipe includes three or more curved parts having curved shapes between the first end part and the second end part in at least a partial region when viewed from the extending direction.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a boiler seal structure and a method for repairing a boiler seal structure. [Background technology]

[0002] For example, a large boiler such as a coal-fired boiler has a hollow furnace that is installed vertically, and a plurality of combustion burners are arranged along the circumferential direction on the furnace wall. In addition, in the coal-fired boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is arranged in the flue. The combustion burner injects a mixture of fuel and air into the furnace to form a flame, and combustion gas is generated and flows into the flue. The heat exchanger is installed in the area where the combustion gas flows, and water or steam flowing inside a heat transfer tube that constitutes the heat exchanger is heated to generate superheated steam.

[0003] In such a boiler, the furnace wall and the ceiling wall defining the upper part of the furnace are so-called membrane walls equipped with furnace wall tubes. In addition, a penthouse is provided above the ceiling wall in which the headers of the heat exchangers (superheater, reheater, etc.) are arranged. That is, a part of the heat transfer tubes constituting the heat exchanger is provided so as to penetrate the ceiling wall. If the combustion gas generated in the furnace flows into the penthouse, the headers and the like may be damaged by the heat and components of the combustion gas. Therefore, in order to prevent the combustion gas from flowing into the penthouse, a gas seal structure may be provided at the portion of the ceiling wall through which the heat transfer tubes penetrate (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-101320 A Summary of the Invention [Problem to be solved by the invention]

[0005] When a gas sealing structure is applied in which the penetration portion is covered with a casing (skin casing), the skin casing is welded to the member on the ceiling wall side and the member on the heat transfer tube side. The skin casing is heated by heat from the combustion gas and the high-temperature fluid flowing inside the heat transfer tube, and thermal deformation occurs. The skin casing is formed, for example, so that the cross-sectional shape along the extension direction of the heat transfer tube has a bent portion so that it can absorb such thermal deformation. However, depending on the material of the plate and the dimensions of the bent portion, the plate may not be able to fully absorb the thermal deformation, which may result in cracks occurring in the bent portion or in the welded portions with the components on the ceiling wall side or the components on the heat transfer tube side.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a boiler seal structure that is less susceptible to thermal deformation, and a method for repairing a boiler seal structure. [Means for solving the problem]

[0007] (1) A seal structure of a boiler according to at least one embodiment of the present disclosure, A seal structure for a boiler, comprising: a skin casing for sealing between at least one tube penetrating an inside and an outside of a combustion gas passage of a boiler and a wall portion defining the combustion gas passage, The skin casing has a first end on a tube side and a second end on a wall side, The cross-sectional shape of the skin casing along the extension direction of the tube includes three or more curved portions having a curved shape between the first end and the second end, in at least a portion of the region when viewed from the extension direction.

[0008] (2) A method for repairing a seal structure of a boiler according to at least one embodiment of the present disclosure, A method for repairing a seal structure of a boiler having a skin casing for sealing between at least one tube penetrating an inside and an outside of a combustion gas passage of the boiler and a wall portion defining the combustion gas passage, comprising: removing at least a portion of an existing skin casing to be repaired from the boiler; Attaching a new skin casing to the boiler from which at least a portion of the existing skin casing has been removed, the new skin casing having a first end on a tube side and a second end on a wall side, the new skin casing having a cross-sectional shape along the extension direction of the tubes including three or more curved portions having a curved shape between the first end and the second end; Equipped with. Effect of the Invention

[0009] According to at least one embodiment of the present disclosure, it is possible to provide a boiler seal structure that is less susceptible to thermal deformation, and a method for repairing a boiler seal structure. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram showing a coal-fired boiler according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a heat exchanger and steam and water supply systems provided in a coal-fired boiler. [Diagram 3] FIG. 2 is a schematic side view showing the superheater of FIG. [Figure 4] 4 is an enlarged view of the main part of FIG. 3, and is a side view showing the main part of the seal structure according to the present embodiment. FIG. [Diagram 5] 5 is a view taken along the arrow VV in FIG. 4, showing the seal structure shown in FIG. 4 from above. [Figure 6] 6 is a view taken along the line VI-VI in FIG. 5. [Figure 7] FIG. 7 is a view taken along the line VII-VII of FIG. 5. [Figure 8] 4 is a flowchart showing a procedure of a process in a method for repairing a seal structure of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such a configuration, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to rectangular shapes, cylindrical shapes, etc. in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions excluding the presence of other elements.

[0012] FIG. 1 is a schematic configuration diagram showing a coal-fired boiler according to the present embodiment.

[0013] The boiler of this embodiment is a coal-fired (pulverized coal-fired) boiler that uses pulverized coal made by pulverizing coal as pulverized fuel (carbon-containing solid fuel), burns this pulverized coal with a combustion burner, and recovers the heat generated by this combustion and exchanges it with feed water or steam to generate superheated steam. In the following explanation, up and above refer to the upper side in the vertical direction, and below and below refer to the lower side in the vertical direction.

[0014] In this embodiment, as shown in Fig. 1, a coal-fired boiler 10 has a furnace 11, a combustion device 12, and a flue (combustion gas flow path) 13. The furnace 11 has a hollow rectangular cylinder shape and is installed along the vertical direction. The furnace wall that constitutes the furnace 11 is composed of multiple evaporation tubes and fins that connect them, and suppresses the temperature rise of the furnace wall by exchanging heat with feed water and steam.

[0015] The combustion device 12 is provided on the lower side of the furnace wall that constitutes the furnace 11. In this embodiment, the combustion device 12 has a plurality of combustion burners (e.g., 21, 22, 23, 24, 25) attached to the furnace wall. For example, the combustion burners 21, 22, 23, 24, 25 are arranged at equal intervals along the circumferential direction as one set, and are arranged in a plurality of stages along the vertical direction. However, the shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

[0016] Each of the combustion burners 21, 22, 23, 24, 25 is connected to a pulverizer (mill) 31, 32, 33, 34, 35 via a pulverized coal supply pipe 26, 27, 28, 29, 30. Although not shown, the pulverizers 31, 32, 33, 34, 35 are configured such that, for example, a rotary table is supported in a housing so as to be driven and rotatable, and a plurality of rollers are supported above the rotary table so as to be rotatable in conjunction with the rotation of the rotary table. When coal is fed between the plurality of rollers and the rotary table, it is pulverized to a predetermined pulverized coal size, and the pulverized coal classified by a carrier gas (primary air) can be supplied to the combustion burners 21, 22, 23, 24, 25 from the pulverized coal supply pipes 26, 27, 28, 29, 30.

[0017] Furnace 11 is provided with a wind box 36 at the mounting positions of combustion burners 21, 22, 23, 24, and 25, and one end of an air duct 37 is connected to this wind box 36. Air duct 37 is provided with a blower 38 at the other end.

[0018] Furthermore, the furnace 11 is provided with an additional air nozzle 39 above the mounting positions of the combustion burners 21, 22, 23, 24, and 25. An end of a branch air duct 40 branched off from the air duct 37 is connected to the additional air nozzle 39. Therefore, the combustion air (air for fuel gas combustion / secondary air) sent by the blower 38 can be supplied from the air duct 37 to the wind box 36 and then supplied from this wind box 36 to the combustion burners 21, 22, 23, 24, and 25, and the additional combustion air (additional air) sent by the blower 38 can be supplied from the branch air duct 40 to the additional air nozzle 39.

[0019] The flue 13 is connected to the vertical upper part of the furnace 11. The flue 13 is provided with superheaters 41, 42, 43, reheaters 44, 45, and economizers 46, 47 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated by combustion in the furnace 11 and the feed water or steam flowing through each heat exchanger.

[0020] A gas duct 48, through which the combustion gas that has undergone heat exchange is discharged, is connected to the downstream side of the flue 13. An air heater (air preheater) 49 is provided between the gas duct 48 and the air duct 37, and heat exchange is performed between the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48, thereby making it possible to raise the temperature of the combustion air to be supplied to the combustion burners 21, 22, 23, 24, and 25.

[0021] The flue 13 is provided with a denitration catalyst 50 at a position upstream of the air heater 49. The denitration catalyst 50 supplies a reducing agent having the effect of reducing nitrogen oxides, such as ammonia or urea water, into the flue 13, and promotes a reaction between the nitrogen oxides and the reducing agent in the combustion gas to which the reducing agent has been supplied, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 48 connected to the flue 13 is provided with a dust treatment device (electrostatic precipitator, desulfurization device) 51, an induced draft fan 52, and the like at a position downstream of the air heater 49, and a chimney 53 is provided at the downstream end.

[0022] On the other hand, when the pulverizers 31, 32, 33, 34, 35 are driven, the generated pulverized coal is supplied to the combustion burners 21, 22, 23, 24, 25 through the pulverized coal supply pipes 26, 27, 28, 29, 30 together with the conveying air. In addition, the heated combustion air is supplied to each of the combustion burners 21, 22, 23, 24, 25 from the air duct 37 through the wind box 36. Then, the combustion burners 21, 22, 23, 24, 25 blow the pulverized fuel mixture, which is a mixture of the pulverized coal and the conveying gas (primary air), into the furnace 11 and also blow the combustion air into the furnace 11, and at this time, the combustion air is ignited to form a flame. A flame is generated at the bottom of the furnace 11, and the combustion gas rises inside the furnace 11 and is discharged into the flue 13.

[0023] In the furnace 11, a pulverized fuel mixture and combustion air (secondary air) combust in the lower region A to generate a flame. Here, the furnace 11 is set so that the amount of air supplied is less than the theoretical amount of air relative to the amount of pulverized coal supplied, thereby maintaining a reducing atmosphere inside. That is, in region B, NOx generated by the combustion of pulverized coal is reduced in the furnace 11, and then additional air is additionally supplied from the additional air nozzle 39 to complete the oxidative combustion of the pulverized coal, thereby reducing the amount of NOx generated by the combustion of pulverized coal.

[0024] The combustion gas then undergoes heat exchange in superheaters 41, 42, 43, reheaters 44, 45, and economizers 46, 47, which are arranged in the flue 13. After that, nitrogen oxides are reduced and removed by a denitration catalyst 50, and particulate matter and sulfur are removed in a dust treatment device 51, and the gas is discharged into the atmosphere through a chimney 53.

[0025] Next, the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47 provided in the flue 13 as heat exchangers will be described in detail. Fig. 2 is a schematic diagram showing the heat exchangers and the steam and feedwater system provided in the coal-fired boiler 10. Note that Fig. 2 is a diagram for explaining the steam and feedwater system, and does not accurately show the positions of the heat exchangers (the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47) in the flue 13.

[0026] 2, in this embodiment, the flue 13 is provided with a combustion gas passage 60 through which the combustion gas passes, and the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47 are arranged in this combustion gas passage 60. The superheaters 41, 42, 43 may be arranged in series via headers, but these headers are omitted in FIG.

[0027] The steam turbine 61 operated by the steam generated in the coal-fired boiler 10 is composed of, for example, a high-pressure turbine 62 and a low-pressure turbine 63. A condenser 64 is connected to the low-pressure turbine 63, and the steam that drives the low-pressure turbine 63 is cooled by cooling water (for example, seawater) in the condenser 64 to become condensed water. The condenser 64 is connected to an inlet header 65 of the first economizer 47 via a feedwater line L1. The inlet header 65 is provided in the combustion gas passage 60, and the feedwater line L1 is provided with a feedwater pump 66 outside the combustion gas passage 60. The second economizer 46 is disposed above the first economizer 47, and an intermediate header 67 is provided between the economizers 46, 47. An outlet header 68 is connected to the upper part of the second economizer 46, and the outlet header 68 is disposed outside the combustion gas passage 60.

[0028] The outlet header 68 is connected to a steam drum 69 arranged outside the combustion gas passage 60 via a water supply line L2. The steam drum 69 is connected to each heat transfer tube (not shown) of the furnace wall, and is also connected to the superheaters 41, 42, and 43 via an inlet header 74. The superheaters 41, 42, and 43 are connected to the high-pressure turbine 62 via a steam line L3. An outlet header 75 is provided on the steam line L3. The high-pressure turbine 62 is connected to an inlet header (header) 70 of the first reheater 45 via a steam line L4. The inlet header 70 is provided in the combustion gas passage 60, the first reheater 45 is connected to the second reheater 44 via an intermediate header 71, and the second reheater 44 has an outlet header 72 connected to its upper portion, and the intermediate header 71 and the outlet header 72 are arranged outside the combustion gas passage 60. The outlet header 72 is connected to the low-pressure turbine 63 via a steam line L5 to rotate the low-pressure turbine 63.

[0029] Therefore, when the combustion gas flows through the combustion gas passage 60 of the flue 13, the heat of the combustion gas is recovered in the order of the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47. On the other hand, the water supplied from the feedwater pump 66 is preheated by the economizers 47, 46, and then supplied to the steam drum 69. The water is heated while being supplied to each heat transfer tube of the furnace wall (not shown) and becomes saturated steam, and is returned to the steam drum 69. The saturated steam in the steam drum 69 is introduced into the superheaters 41, 42, 43 and is superheated by the combustion gas. The superheated steam generated by the superheaters 41, 42, 43 is supplied to the high-pressure turbine 62 and drives the high-pressure turbine 62 to rotate. The steam discharged from the high-pressure turbine 62 is introduced into the reheaters 45, 44 and superheated again, and then supplied to the low-pressure turbine 63 to drive the low-pressure turbine 63 to rotate. A generator is connected to the rotating shaft of the steam turbine 61 to generate electricity. The steam discharged from the low-pressure turbine 63 is cooled in the condenser 64 to become condensed water, and is sent to the economizers 47, 46 again.

[0030] Furthermore, the flue 13 may have a soot blower (injection device) 80 disposed between the inlet header 70 and the economizer 47. The soot blower 80 extends in a direction parallel to the longitudinal direction of the inlet header 70 and is disposed at a position facing the inlet header 70. The soot blower 80 is an injection device that injects steam (gas) in a direction perpendicular to the axial direction of the longitudinal direction of the inlet header 70, and can also vary the injection direction. The steam injected from the soot blower 80 toward the economizer 47 removes combustion ash accumulated on the surface of the heat transfer tube of the economizer 47.

[0031] Next, a seal structure 90 between the heat transfer tube 89 and the ceiling wall 82 provided in at least one of the superheaters 41, 42, and 43 provided in the flue 13 of this embodiment will be described in more detail with reference to Figs. 3 to 7. Note that the seal structures 90 between the heat transfer tube 89 and the ceiling wall 82 provided in at least one of the superheaters 41, 42, and 43 have substantially the same configuration, so in the following description, the superheater 41 will be described as a representative, and descriptions of the other superheaters 42 and 43 will be omitted. In the following description and Figs. 3 to 7, the Z direction indicates the vertical up-down direction, the X direction indicates the arrangement direction of the multiple heat transfer tubes 89 penetrating the ceiling wall 82, and the Y direction indicates the direction perpendicular to the Z direction and the X direction.

[0032] FIG. 3 is a schematic side view showing the superheater of FIG. FIG. 4 is an enlarged view of the main part of FIG. 3, and is a side view showing the main part of the seal structure according to this embodiment. 5 is a view of the seal structure shown in FIG. 4 as seen from above in the direction of arrows VV in FIG. FIG. 6 is a view taken along the line VI-VI in FIG. FIG. 7 is a view taken along line VII-VII of FIG.

[0033] As shown in FIG. 3, the flue 13 has a wall portion 81 that defines the side of the combustion gas passage 60 provided therein, and a ceiling wall 82 that defines the upper side of the combustion gas passage 60. 3, a penthouse 86 in which the inlet header 74 and the outlet header 75 of the superheater 41 and the like are arranged is provided above the ceiling wall 82. The ceiling wall 82 is also formed with a through hole 84a through which a heat transfer tube 89 constituting the superheater 41 described below is inserted. The through hole 84a communicates between the internal space of the flue 13 (the combustion gas passage 60 in this embodiment) continuing to the furnace 11 and the external space of the furnace 11 (the space within the penthouse 86 in this embodiment).

[0034] 1, the superheater 41 is a heat exchanger provided at the most upstream side of the combustion gas passage 60. The superheater 41 is provided vertically above the furnace 11, and is provided in the vicinity of the wall portion 81 of the flue 13, as shown in FIG.

[0035] The superheater 41 is composed of a plurality of heat transfer tubes 89 connecting the inlet header 74 and the outlet header 75. Each heat transfer tube 89 includes a first vertical pipe section 89a extending substantially vertically downward from the inlet header 74, a horizontal pipe section 89b bending from the lower end of the first vertical pipe section 89a and extending in the X direction toward the wall section 81, and a second vertical pipe section 89c bending from the end of the horizontal pipe section 89b and extending substantially vertically upward. That is, the first vertical pipe section 89a and the second vertical pipe section 89c extend along the up-down direction (Z direction). As described above, the inlet header 74 and the outlet header 75 are provided in the penthouse 86, and therefore the first vertical pipe section 89a and the second vertical pipe section 89c are arranged to penetrate the ceiling wall 82 of the flue 13. Specifically, as shown in Figures 6 and 7, the first vertical pipe section 89a and the second vertical pipe section 89c are inserted through through holes 84a formed in the ceiling wall 82. A plurality of through holes 84a are formed at predetermined intervals in the X direction (the extension direction of the ceiling pipe 83 in this embodiment) so as to correspond to the first vertical pipe section 89a and the second vertical pipe section 89c of the plurality of heat transfer tubes 89. Note that although Figures 6 and 7 show the second vertical pipe section 89c, the first vertical pipe section 89a has a similar configuration.

[0036] A seal structure 90 is provided in the penthouse 86 to prevent combustion gas from flowing into the penthouse 86 through the through-hole 84a. 4 to 7, the seal structure 90 includes a skin casing 91 welded to the ceiling wall 82 via a mounting plate 94 to cover the through hole 84a, a support plate 93 welded to the heat transfer tube 89 (specifically, the second vertical tube portion 89c), and a blocking plate 92 provided between the support plate 93 and the skin casing 91. The length of the seal structure 90 in the longitudinal direction (X direction) is, for example, approximately 5 m to 15 m.

[0037] The skin casing 91 is a cover-like member extending in the X direction, and has an upper end (first end) 911 fixed to the support plate 93 by welding or the like via a closing plate 92 or directly without the closing plate 92, and a lower end (second end) 912 fixed to the ceiling wall 82 by welding or the like via a mounting plate 94 as described above. The skin casing 91 covers from above a plurality of through holes 84a formed at predetermined intervals in the X direction. That is, the skin casing 91 forms a space inside and seals the space. The skin casing 91 is formed of, for example, carbon steel or low alloy steel (for example, 0.5 to 2.25 Cr steel, etc.). The skin casing 91 separates the internal space of the flue 13 (the combustion gas passage 60 in this embodiment) which is continuous with the furnace 11 from the external space of the furnace 11 (the space within the penthouse 86 in this embodiment).

[0038] 6 and 7, in the skin casing 91 of this embodiment, the cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89 of the skin casing 91 includes three or more curved portions 914 having a curved shape between the first end 911 and the second end 912 in at least a part of the region when viewed from the extension direction (Z direction). In the example shown in Fig. 6 and 7, the cross-sectional shape S of the skin casing 91 includes three curved portions 914 having a curved shape between the first end 911 and the second end 912.

[0039] FIG. 6 shows the cross-sectional shape S of a skin casing 91 arranged to surround the first tube 891, which is a heat transfer tube 89 arranged at the end of a tube row PL formed by a plurality of heat transfer tubes 89 penetrating the ceiling wall 82. FIG. 7 also shows the cross-sectional shape S of a skin casing 91 arranged to cover the side of a second tube 892, which is a heat transfer tube 89 arranged in the central region (central region CR) of the tube row PL.

[0040] In the example shown in Figures 6 and 7, the cross-sectional shape S of the skin casing 91 includes, in order from the curved portion 914 closest to the first end 911, a first curved portion 915, a second curved portion 916, and a third curved portion 917. In the example shown in FIGS. 6 and 7, the cross-sectional shape S of the skin casing 91 includes a straight portion 918 having a straight line shape between the first end 911 and the second end 912.

[0041] The first curved portion 915, in its cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89, is curved so as to protrude from the external space OA toward the internal space IA (in this embodiment, the combustion gas passage 60) of the flue 13 continuing from the furnace 11, for example, so that the center of the radius of curvature R1 is in the external space OA of the furnace 11 (in this embodiment, the space within the penthouse 86).

[0042] The second curved portion 916, in its cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89, is curved so as to protrude from the internal space IA toward the external space OA, for example, so that the center of the curvature radius R2 is located in the internal space IA of the furnace 11.

[0043] The third curved portion 917, in its cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89, is curved so as to protrude from the external space OA toward the internal space IA, for example, so that the center of the curvature radius R3 is in the external space OA.

[0044] In the skin casing 91 arranged so as to surround the periphery of the first pipe 891 shown in FIG. 6, the first curved portion 915 and the second curved portion 916 are directly connected without an intervening straight portion 918 . In the skin casing 91 arranged to surround the periphery of the first pipe 891 shown in Fig. 6, the straight portion 918 exists between the first end portion 911 and the first curved portion 915, and between the second curved portion 916 and the third curved portion 917. Note that in the skin casing 91 shown in Fig. 6, the first end portion 911 and the first curved portion 915 may be directly connected without the straight portion 918, and the second curved portion 916 and the third curved portion 917 may be directly connected without the straight portion 918.

[0045] In the skin casing 91 arranged to cover the side of the second pipe 892 shown in Fig. 7, the straight portion 918 exists between the first end portion 911 and the first curved portion 915, between the first curved portion 915 and the second curved portion 916, and between the second curved portion 916 and the third curved portion 917. In the skin casing 91 shown in Fig. 7, the first end portion 911 and the first curved portion 915 may be directly connected without the straight portion 918, the first curved portion 915 and the second curved portion 916 may be directly connected without the straight portion 918, and the second curved portion 916 and the third curved portion 917 may be directly connected without the straight portion 918.

[0046] The curvature radius R1 of the first curved portion 915 in the skin casing 91 shown in FIG. 6 is preferably larger than the curvature radius R1 of the first curved portion 915 in the skin casing 91 shown in FIG. The radius of curvature R2 of the second curved portion 916 in the skin casing 91 shown in FIG. 6 is preferably larger than the radius of curvature R2 of the second curved portion 916 in the skin casing 91 shown in FIG. The radius of curvature R3 of the third curved portion 917 in the skin casing 91 shown in FIG. 6 may be larger than or the same as the radius of curvature R3 of the third curved portion 917 in the skin casing 91 shown in FIG.

[0047] In the skin casing 91 of this embodiment, thermal deformation occurs due to heating by heat from the combustion gas and the superheated steam flowing inside the heat transfer tube 89. The skin casing 91 is formed to have the curved portion 914 described above so as to be able to absorb such thermal deformation. In the sealing structure 90 of this embodiment, the skin casing 91 is formed to include three curved portions 914 having a curved shape between the first end 911 and the second end 912 in order to enhance the ability to absorb thermal deformation. This makes it possible to better absorb thermal deformation of the skin casing 91 compared to a case in which the cross-sectional shape S includes two or less curved portions 914. This makes it possible to make the seal structure 90 less susceptible to the effects of thermal deformation.

[0048] In the skin casing 91 of this embodiment, the radius of curvature R1 of the first curved portion 915 closest to the first end 911 when viewed from the extension direction (Z direction) is preferably larger than the radii of curvature R2, R3 of the other curved portions 914 (the second curved portion 916, the third curved portion 917). As a result of careful investigation, the inventors have found that a relatively large stress is generated in curved portion 914 located near first end 911 due to thermal deformation of skin casing 91 . According to the above configuration, the radius of curvature R1 of the first curved portion 915 closest to the first end 911 is made larger than the radii of curvature R2, R3 of the other curved portions 914 (the second curved portion 916, the third curved portion 917), thereby effectively reducing stress in the first curved portion 915 closest to the first end 911, where relatively large stress may be generated.

[0049] In the skin casing 91 of this embodiment, among the pairs of two adjacent curved portions 914 when viewed from the extension direction (Z direction) (the pair of the first curved portion 915 and the second curved portion 916, and the pair of the second curved portion 916 and the third curved portion 917), it is preferable that in at least one pair, the two adjacent curved portions 914 are directly connected to each other without a straight portion 918 that extends linearly when viewed from the extension direction (Z direction). In the skin casing 91 shown in FIG. 6, in the pair of the first curved portion 915 and the second curved portion 916, the first curved portion 915 and the second curved portion 916 are directly connected to each other without a straight portion 918. This makes it possible to increase the radius of curvature R of the curved portion 914 while preventing the size of the skin casing 91 from increasing, compared to when two adjacent curved portions 914 are connected via a straight portion 918, making it easier to reduce stress in the curved portion 914.

[0050] The sealing structure 90 of this embodiment may include a blocking plate 92 that is provided between the first end 911 and the heat transfer tube 89, has a radially outer end 921 centered on the central axis AX of the heat transfer tube 89 connected to the first end 911, and has a radially inner end 922 directly or indirectly connected to the heat transfer tube 89, and is arranged in at least a portion of the circumferential area so as to surround the heat transfer tube 89 in the circumferential direction centered on the central axis AX. In the seal structure 90 of the present embodiment, the blocking plate 92 is provided in the vicinity of the first pipe 891 so as to surround the periphery of the first pipe 891. In the seal structure 90 of the present embodiment, a radially inner end 922 of the blocking plate 92 is fixed to the outer circumferential surface of the support plate 93 by welding or the like and is connected to the heat transfer pipe 89 via the support plate 93, but may be directly connected to the heat transfer pipe 89.

[0051] By configuring the skin casing 91 so that it is positioned at a position radially outward rather than a position closer to the central axis AX of the heat transfer tube 89, stress generated in the skin casing 91 due to thermal deformation tends to decrease. However, if the skin casing 91 is positioned at a position radially outward from the central axis AX of the heat transfer tube 89 without significantly changing the cross-sectional shape along the extension direction (Z direction) of the heat transfer tube 89, such as the shape of the curved portion 914 of the skin casing 91, the gap between the first end 911 and the heat transfer tube 89 opens in the radial direction and becomes large. According to the above configuration, the gap can be blocked by the blocking plate 92, so that the skin casing 91 can be positioned radially outwardly away from the central axis AX of the heat transfer tube 89, thereby reducing the stress generated in the skin casing 91 due to thermal deformation.

[0052] In the seal structure 90 of the present embodiment, the first end 911 and the second end 912 may be spaced apart in the extension direction (Z direction). The inner end 922 of the closing plate 92 may be farther away from the second end 912 along the extension direction (Z direction) than the outer end 921 of the closing plate 92. That is, the inner end 922 of the closing plate 92 may be located higher than the outer end 921 of the closing plate 92. As a result, the position of the inner end 922 of the closing plate 92 and the position of the outer end 921 of the closing plate 92 are misaligned in the above-mentioned extension direction (Z direction), so that the closing plate 92 is inclined with respect to the heat transfer tube 89. As a result, if the closing plate 92 and a member (e.g., the support plate 93) on the tube side (heat transfer tube 89 side) are connected by welding, the stress generated in this welded portion (welded portion at the end 922) due to thermal deformation of the skin casing 91 can be reduced.

[0053] In the seal structure 90 of the present embodiment, the skin casing 91 is formed so as to surround the periphery of the tube row PL when viewed from the above-mentioned extension direction (Z direction). This makes it possible to seal between the tube row PL and the wall portion (ceiling wall 82) that defines the combustion gas passage (combustion gas passage 60).

[0054] In the skin casing 91 of this embodiment, the cross-sectional shape S may include three or more curved portions 914 between the first end 911 and the second end 912 in at least a portion of a circumferential region centered on the first central axis AX1 of the first tube 891 arranged at the end of the row of tubes PL.

[0055] As a result of careful investigation, the inventors found that the stress generated in the skin casing 91 due to thermal deformation of the skin casing 91 is relatively greater in the vicinity of the first tube 891 arranged at the end of the row than in the central region (central region CR) of the tube row PL. According to the above configuration, the cross-sectional shape S includes three or more curved portions 914 in the vicinity of the first pipe 891, where the stress generated in the skin casing 91 is relatively large, thereby effectively reducing the stress generated in the skin casing 91 in the vicinity of the first pipe 891.

[0056] In the sealing structure 90 of this embodiment, when viewed from the above-mentioned extension direction (Z direction), among the distances between the line segment LS connecting the central axes AX of the multiple heat transfer tubes 89 and the second end 912, a first distance Ld1 at the position of the first central axis AX1 is preferably greater than a second distance Ld2 at the position of the second central axis AX2 of the second tube 892 arranged in the central region CR of the row of tube rows PL (see Figure 5).

[0057] As described above, the stress generated in the skin casing 91 due to thermal deformation of the skin casing 91 is relatively large in the vicinity of the first tubes 891 arranged at the ends of the row than in the central region (central region CR) of the tube row PL. Furthermore, as described above, by configuring the skin casing 91 so that it is positioned at a position radially outward rather than closer to the central axis AX of the heat transfer tube 89, the stress generated in the skin casing 91 due to thermal deformation tends to be reduced. According to the above configuration, the skin casing 91 can be positioned radially outward from the central axis AX of the heat transfer tube 89 in the vicinity of the first tube 891 compared to the vicinity of the second tube 892, thereby effectively reducing the stress generated in the skin casing 91 in the vicinity of the first tube 891, where the stress generated in the skin casing 91 is relatively large.

[0058] In the seal structure 90 of the present embodiment, it is preferable that the radius of curvature R of at least one of the three or more curved portions 914 included in the cross-sectional shape S is 10 times or more the plate thickness t of the skin casing. The larger the radius of curvature R of the curved portion 914 relative to the plate thickness t of the skin casing 91, the more the stress generated in the curved portion 914 due to thermal deformation of the skin casing 91 can be reduced. According to the above configuration, the stress generated in the curved portion 914 can be effectively reduced.

[0059] (How to repair the seal structure) A method for repairing the seal structure will be described below. For example, in the case of an existing coal-fired boiler 10, if there is a risk that continued use will cause damage to the skin casing 91, at least a portion of the existing skin casing 91 can be removed and replaced with at least a portion of the seal structure 90 having the characteristics described above.

[0060] The method for repairing a sealing structure in this embodiment is a method for repairing a sealing structure 90 that includes a skin casing 91 for sealing between at least one tube (e.g., a heat transfer tube 89) that penetrates the inside and outside of a combustion gas passage 60 of an existing coal-fired boiler 10 and a wall portion (e.g., a ceiling wall 82) that defines the combustion gas passage 60. FIG. 8 is a flowchart showing the procedure of the process in the method for repairing the seal structure of the present embodiment. The method for repairing a seal structure according to this embodiment includes step S10 of removing at least a portion of the existing skin casing, and step S20 of attaching a new skin casing.

[0061] (Step S10 of removing at least a portion of the existing skin casing) Step S10 of removing at least a portion of the existing skin casing is a step of removing at least a portion of the existing skin casing 91 to be repaired from the existing coal-fired boiler 10. In step S10 of removing at least a portion of the existing skin casing, a worker repairing the coal-fired boiler 10 may remove only a portion of the existing skin casing 91, or may remove a front portion of the existing skin casing 91. In step S10 of removing at least a portion of the existing skin casing, the worker may also remove at least a portion of the portion corresponding to the blocking plate 92.

[0062] In addition, in step S10 of removing at least a portion of the existing skin casing, if the cross-sectional shape S of the existing skin casing 91 includes two or less curved portions 914, the worker may remove the entire existing skin casing 91.

[0063] (Step S20: Installing a new skin casing) Step S20 of installing a new skin casing is a step of installing a new skin casing 91 to an existing coal-fired boiler 10 from which at least a portion of the existing skin casing 91 has been removed, the new skin casing 91 having a first end 911 on the tube side and a second end 912 on the wall side, and having, for example, three or more curved portions 914 whose cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89 has a curved shape between the first end 911 and the second end 912. In step S20 of installing a new skin casing, at least a portion of the new skin casing 91 including an area corresponding to the removal range is installed on the existing coal-fired boiler 10 so as to cover the opening formed by removing at least a portion of the existing skin casing 91 in step S10 of removing at least a portion of the existing skin casing.

[0064] If the cross-sectional shape of the existing skin casing includes three or more curved portions, in step S20 of attaching the new skin casing, it is preferable that the radius of curvature R of at least one of the three or more curved portions 914 included in the cross-sectional shape S of the new skin casing 91 be larger than the radius of curvature R of any of the curved portions 914 in the existing skin casing 91. As a result, by increasing the radius of curvature of the curved portion 914, the stress generated in the curved portion 914 can be reduced, so that the seal structure 90 of the existing coal-fired boiler 10 can be made less susceptible to the effects of thermal deformation due to repair.

[0065] If the entire existing skin casing 91 is removed in step S10 of removing at least a portion of the existing skin casing, in step S20 of installing a new skin casing, workers install a new skin casing 91 to the existing coal-fired boiler 10 from which the entire existing skin casing 91 has been removed. As a result, the cross-sectional shape S of the new skin casing 91 includes three or more curved portions 914, so that the new skin casing 91 can better absorb thermal deformation compared to the existing skin casing 91 in which the cross-sectional shape S includes two or fewer curved portions. Therefore, the seal structure 90 of the existing coal-fired boiler 10 can be made less susceptible to the effects of thermal deformation through repair.

[0066] According to the repair method for the sealing structure of this embodiment described above, for example, by installing a new skin casing 91 in which the cross-sectional shape S along the extension direction (Z direction) of the heat transfer tube 89 includes three or more curved sections 914 having a curved shape between the first end 911 and the second end 912, the sealing structure 90 of the existing coal-fired boiler 10 can be made less susceptible to the effects of thermal deformation.

[0067] The present disclosure is not limited to the above-described embodiments, and includes modifications to the above-described embodiments and appropriate combinations of these modifications. For example, the fuel for the boiler according to the above-described embodiment is coal (fine powder), but the fuel is not limited to coal and may be other fuels such as biomass, ammonia, etc. In other words, the present disclosure is also applicable to boilers that use fuels other than coal, such as biomass, ammonia, etc.

[0068] The contents described in each of the above embodiments can be understood, for example, as follows. (1) A boiler seal structure 90 according to at least one embodiment of the present disclosure is a boiler seal structure 90 including a skin casing 91 for sealing between at least one tube (heat transfer tube 89) penetrating the inside (internal space IA) and the outside (external space OA) of a combustion gas passage 60 of a boiler (coal-fired boiler 10) and a wall portion (ceiling wall 82) defining the combustion gas passage 60. The skin casing 91 has a first end 911 on the tube side (heat transfer tube 89 side) and a second end 912 on the wall side (ceiling wall 82 side). A cross-sectional shape S of the skin casing 91 along the extension direction (Z direction) of the tube (heat transfer tube 89) includes three or more curved portions 914 having a curved shape between the first end 911 and the second end 912 in at least a part of the region when viewed from the extension direction (Z direction).

[0069] According to the above configuration (1), since the cross-sectional shape S of the skin casing 91 includes three or more curved portions 914, the skin casing 91 can absorb more thermal deformation than when the cross-sectional shape S includes two or less curved portions 914. This makes it possible to make the boiler seal structure 90 less susceptible to the effects of thermal deformation.

[0070] (2) In some embodiments, in the configuration of (1) above, the radius of curvature R (radius of curvature R1) of the curved portion 914 (first curved portion 915) closest to the first end 911 when viewed from the extension direction (Z direction) may be larger than the radius of curvature R of the other curved portions 914.

[0071] According to the above configuration (2), the radius of curvature R (radius of curvature R1) of the curved portion 914 (first curved portion 915) closest to the first end 911 is made larger than the radius of curvature R of the other curved portions 914, thereby effectively reducing stress in the curved portion 914 (first curved portion 915) closest to the first end 911, where relatively large stress may be generated.

[0072] (3) In some embodiments, in the configuration of (1) or (2) above, among the pairs of two adjacent curved portions 914 when viewed from the extension direction (Z direction) (the pair of the first curved portion 915 and the second curved portion 916, and the pair of the second curved portion 916 and the third curved portion 917), at least one pair may be such that the two adjacent curved portions 914 are directly connected to each other without passing through a straight portion 918 that extends linearly when viewed from the extension direction (Z direction).

[0073] According to the above configuration (3), compared to the case where two adjacent curved portions 914 are connected via the straight portion 918, the radius of curvature R of the curved portion 914 can be increased while preventing the size of the skin casing 91 from increasing, making it easier to reduce stress in the curved portion 914.

[0074] (4) In some embodiments, in any of the configurations (1) to (3) above, a blocking plate 92 may be provided between the first end 911 and the tube (heat transfer tube 89), the blocking plate 92 having an outer end 921 in the radial direction centered on the central axis AX of the tube (heat transfer tube 89) connected to the first end 911 and an inner end 922 in the radial direction connected directly or indirectly to the tube (heat transfer tube 89), and the blocking plate 92 is disposed in at least a portion of the circumferential area so as to surround the tube (heat transfer tube 89) in the circumferential direction centered on the central axis AX.

[0075] According to the above configuration (4), the blocking plate 92 can block the gap between the first end 911 and the tube (heat transfer tube 89), so that the skin casing 91 can be positioned radially outwardly away from the central axis AX of the tube (heat transfer tube 89), thereby reducing the stress generated in the skin casing 91 due to thermal deformation.

[0076] (5) In some embodiments, in the configuration of (4) above, the first end 911 and the second end 912 may be spaced apart in the extension direction (Z direction). The inner end 922 of the closing plate 92 may be farther away from the second end 912 in the extension direction (Z direction) than the outer end 921 of the closing plate 92.

[0077] According to the above configuration (5), the position of the inner end 922 of the closing plate 92 and the position of the outer end 921 of the closing plate 92 are misaligned in the above extension direction (Z direction), so that the closing plate 92 is inclined with respect to the tube (heat transfer tube 89). As a result, if the closing plate 92 and a member (e.g., the support plate 93) on the tube side (heat transfer tube 89 side) are connected by welding, the stress generated in the welded portion due to thermal deformation of the skin casing 91 can be reduced.

[0078] (6) In some embodiments, in any of the configurations (1) to (5) above, the at least one tube (heat transfer tube 89) may include a plurality of tubes (heat transfer tubes 89). The plurality of tubes (heat transfer tubes 89) may form a tube row PL spaced apart in a direction (X direction) intersecting the extension direction (Z direction). The skin casing 91 may be formed so as to surround the periphery of the tube row PL when viewed from the extension direction (Z direction).

[0079] According to the above configuration (6), the gap between the tube row PL and the wall portion (ceiling wall 82) that defines the combustion gas passage 60 can be sealed.

[0080] (7) In some embodiments, in the configuration of (6) above, the cross-sectional shape S may include three or more curved portions 914 between the first end 911 and the second end 912 in at least a portion of a circumferential region centered on the first central axis AX1 of the first tube 891 arranged at the end of the row of tubes PL.

[0081] According to the above configuration (7), the cross-sectional shape S includes three or more curved portions 914 in the vicinity of the first pipe 891, where the stress generated in the skin casing 91 is relatively large, so that the stress generated in the skin casing 91 in the vicinity of the first pipe 891 can be effectively reduced.

[0082] (8) In some embodiments, in the configuration of (7) above, when viewed from the extension direction (Z direction), among the distances between the line segment LS connecting the central axes AX of the multiple tubes (heat transfer tubes 89) and the second end 912, a first distance Ld1 at the position of the first central axis AX1 may be greater than a second distance Ld2 at the position of the second central axis AX2 of the second tube 892 arranged in the central region CR of the row of the tube array PL.

[0083] According to the above configuration (8), the skin casing 91 can be positioned radially outwardly from the central axis AX of the tube (heat transfer tube 89) in the vicinity of the first tube 891 compared to the vicinity of the second tube 892, so that the stress generated in the skin casing 91 in the vicinity of the first tube 891, where the stress generated in the skin casing 91 is relatively large, can be effectively reduced.

[0084] (9) In some embodiments, in any of the configurations (1) to (8) above, the radius of curvature R of at least one of the three or more curved portions 914 included in the cross-sectional shape S may be 10 times or more the plate thickness t of the skin casing 91.

[0085] According to the above configuration (9), the stress generated in the curved portion 914 can be effectively reduced.

[0086] (10) A method for repairing a sealing structure of a boiler according to at least one embodiment of the present disclosure is a method for repairing a sealing structure 90 of a boiler (coal-fired boiler 10) that includes at least one tube (heat transfer tube 89) that penetrates between the inside (inner space IA) and the outside (external space OA) of the combustion gas passage 60 of the boiler (coal-fired boiler 10) and a skin casing 91 for sealing between a wall portion (ceiling wall 82) that defines the combustion gas passage 60. A method of repairing a boiler sealing structure according to at least one embodiment of the present disclosure includes a step S10 of removing at least a portion of an existing skin casing 91 to be repaired from a boiler (coal-fired boiler 10), and a step S20 of attaching to the boiler (coal-fired boiler 10) from which at least a portion of the existing skin casing 91 has been removed a new skin casing 91 having a first end 911 on the tube side (heat transfer tube 89 side) and a second end 912 on the wall side (ceiling wall 82 side), and whose cross-sectional shape S along the extension direction (Z direction) of the tube (heat transfer tube 89) includes three or more curved portions 914 having a curved shape between the first end 911 and the second end 912.

[0087] According to the above method (10), by attaching a new skin casing 91 in which the cross-sectional shape S along the extension direction (Z direction) of the above tube (heat transfer tube 89) includes three or more curved sections 914 having a curved shape between the first end 911 and the second end 912, it is possible to make the sealing structure 90 of the boiler (coal-fired boiler 10) less susceptible to the effects of thermal deformation.

[0088] (11) In some embodiments, in the method (10) above, in step S20 of attaching a new skin casing, if the cross-sectional shape S of the existing skin casing 91 includes three or more curved portions 914, the radius of curvature R of at least one of the three or more curved portions 914 included in the cross-sectional shape S of the new skin casing 91 is preferably larger than the radius of curvature of any of the curved portions 914 in the existing skin casing 91.

[0089] According to the above method (11), it is possible to reduce the stress generated in the curved portion 914 by increasing the radius of curvature R of the curved portion 914. This makes it possible to make the seal structure 90 of the boiler (coal-fired boiler 10) less susceptible to the effects of thermal deformation due to repair.

[0090] (12) In some embodiments, in the method of (10) above, in the removing step S10, if the cross-sectional shape S of the existing skin casing 91 includes two or less curved portions 914, the existing skin casing 91 may be entirely removed. In the installing step S20 of a new skin casing, the new skin casing 91 may be installed on the boiler (coal-fired boiler 10) from which the existing skin casing 91 has been entirely removed.

[0091] As described above, since the cross-sectional shape S of the new skin casing 91 includes three or more curved portions 914, the new skin casing 91 can better absorb thermal deformation compared to the existing skin casing 91 in which the cross-sectional shape S includes two or less curved portions 914. According to the above method (12), the seal structure 90 of the boiler (coal-fired boiler 10) can be made less susceptible to the effects of thermal deformation through repair. [Explanation of symbols]

[0092] 10 Coal-fired boiler 11 Furnace 12 Combustion equipment 13 Flue (combustion gas flow path) 41,42,43 Superheater 44,45 Reheater 60 Combustion gas passage 82 Ceiling Wall 89 Heat transfer tube 89a First vertical pipe section 89b Horizontal pipe section 89c Second vertical pipe section 90 Seal structure 91 Skin Casing 92 Closing plate 93 Support Plate 94 Mounting plate 891 1st pipe 892 2nd pipe 911 Upper end (first end) 912 Lower end (second end) 914 Curved section 915 1st curve section 916 Second curve section 917 Third curve section 918 Straight section 921 End 922 End

Claims

1. A seal structure for a boiler, comprising: a skin casing for sealing between at least one tube penetrating an inside and an outside of a combustion gas passage of a boiler and a wall portion defining the combustion gas passage, The skin casing has a first end on a tube side and a second end on a wall side, A cross-sectional shape of the skin casing along the extension direction of the tube includes three or more curved portions having a curved shape between the first end and the second end in at least a part of a region when viewed from the extension direction. Boiler seal structure.

2. A radius of curvature of the curved portion closest to the first end when viewed from the extending direction is larger than the radius of curvature of the other curved portions. The boiler seal structure according to claim 1.

3. Among the pairs of two adjacent curved portions when viewed from the extension direction, at least one pair is such that the two adjacent curved portions are directly connected to each other without a straight portion that extends linearly when viewed from the extension direction. The boiler seal structure according to claim 1 or 2.

4. a blocking plate provided between the first end and the pipe, the blocking plate having an outer end in a radial direction centered on a central axis of the pipe connected to the first end and an inner end in the radial direction connected directly or indirectly to the pipe, and the blocking plate being disposed in at least a part of a region in the circumferential direction so as to surround the pipe in the circumferential direction centered on the central axis; Equipped with The boiler seal structure according to claim 1 or 2.

5. The first end and the second end are spaced apart in the extending direction, The inner end of the closing plate is farther from the second end along the extension direction than the outer end of the closing plate. The boiler seal structure according to claim 4.

6. the at least one tube comprises a plurality of tubes; The plurality of tubes form a tube row spaced apart in a direction intersecting the extension direction, The skin casing is formed so as to surround the periphery of the tube row when viewed from the extending direction. The boiler seal structure according to claim 1 or 2.

7. the cross-sectional shape includes three or more curved portions between the first end and the second end in at least a portion of a circumferential region about a first central axis of a first tube disposed at an end of the tube row, the curved portion being located at three or more positions between the first end and the second end. The boiler seal structure according to claim 6.

8. a first distance between a line segment connecting central axes of the plurality of tubes when viewed from the extending direction and the second end portion, at a position of the first central axis, is greater than a second distance at a position of a second central axis of a second tube disposed in a central region of the tube array; The boiler seal structure according to claim 7.

9. The radius of curvature of at least one of the three or more curved portions included in the cross-sectional shape is 10 times or more the plate thickness of the skin casing. The boiler seal structure according to claim 1 or 2.

10. A method for repairing a seal structure of a boiler having a skin casing for sealing between at least one tube penetrating an inside and an outside of a combustion gas passage of the boiler and a wall portion defining the combustion gas passage, comprising the steps of: removing at least a portion of an existing skin casing to be repaired from the boiler; a step of attaching a new skin casing to the boiler from which at least a portion of the existing skin casing has been removed, the new skin casing having a first end on a tube side and a second end on a wall side, the new skin casing having a cross-sectional shape along the extension direction of the tubes including three or more curved portions having a curved shape between the first end and the second end; Equipped with How to repair a boiler's sealing structure.

11. In the step of attaching the new skin casing, if the cross-sectional shape of the existing skin casing includes three or more curved portions, the radius of curvature of at least one of the three or more curved portions included in the cross-sectional shape of the new skin casing is larger than the radius of curvature of any of the curved portions of the existing skin casing. A method for repairing a seal structure of a boiler according to claim 10.

12. In the removing step, when the cross-sectional shape of the existing skin casing includes two or less curved portions, the entire existing skin casing is removed, In the step of installing a new skin casing, the new skin casing is installed to the boiler from which the entire existing skin casing has been removed. A method for repairing a seal structure of a boiler according to claim 10.

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