CN111351066A

CN111351066A - Sealing structure for boiler, and method for operating boiler

Info

Publication number: CN111351066A
Application number: CN201911315202.4A
Authority: CN
Inventors: 本村航平; 岩本匡
Original assignee: Mitsubishi Hitachi Power Systems Ltd
Current assignee: Mitsubishi Power Ltd
Priority date: 2018-12-21
Filing date: 2019-12-18
Publication date: 2020-06-30
Also published as: JP2020101320A

Abstract

A sealing structure of a boiler, the boiler, and a method for operating the boiler. A sealing structure (90) for a boiler is provided with: a ceiling wall (82) having a through hole (84a) for communicating the internal space of the furnace with the external space of the furnace, and defining the upper part of the furnace; a superheater that has a heat transfer pipe (89) inserted through the through hole (84a) and is made of a material different from that of the ceiling wall (82); an outer jacket shell (91) which has a lower flange (91c) and is fixed to the top wall (82) so as to cover the through hole (84 a); and a support plate (93) that has an upper flange (93b) and is fixed to the heat transfer pipe (89). The lower flange (91c) and the upper flange (93b) are slidable in the longitudinal direction. The purpose of the present invention is to suppress leakage of combustion gas generated in a furnace.

Description

Sealing structure for boiler, and method for operating boiler

Technical Field

The present invention relates to a sealing structure of a boiler, and a method for operating a boiler.

Background

A large boiler such as a coal-fired boiler disclosed in patent document 1 has a hollow hearth provided in a vertical direction, and a plurality of burners are arranged in a circumferential direction on a hearth wall of the hearth. Further, the coal-fired boiler has a flue connected to a vertically upper portion of the furnace, and a heat exchanger for generating steam is disposed in the flue. The burner injects a mixture of fuel and air into the furnace to form a flame, generates combustion gas, and flows the combustion gas into the flue. A heat exchanger is provided in a region where the combustion gas flows, and water or steam flowing through a heat transfer pipe constituting the heat exchanger is heated to generate superheated steam.

In such a boiler, the furnace wall and a ceiling wall defining an upper part of the furnace are so-called film walls including the furnace wall tubes. Further, a ceiling chamber in which a header of a heat exchanger (such as a superheater or a reheater) is disposed above the ceiling wall. That is, a part of the heat transfer tubes constituting the heat exchanger is provided so as to penetrate the ceiling wall. When the combustion gas generated in the furnace flows into the top chamber, the header pipe 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 dome chamber, a gas seal structure may be provided in a portion penetrating the dome through which the heat transfer pipe penetrates (for example, patent document 1).

Prior art documents

Patent document

Patent document 1: japanese Kokai publication Hei-2-100004

In the case of applying a structure in which the through portion is covered with the case as a gas sealing structure, the case is welded and fixed to the member on the top wall side and the member on the heat transfer pipe side.

In the heat exchanger located above the ceiling wall, the fluid flowing through the heat transfer tubes is at a high temperature (e.g., 500 ℃ or higher). Therefore, the heat-transfer-tube-side member becomes high in temperature due to the influence of the fluid flowing inside the heat transfer tube. On the other hand, the fluid flowing inside the furnace wall tube of the ceiling wall is lower in temperature than the fluid flowing inside the heat transfer tube of the heat exchanger. Therefore, the member on the top wall side does not become a higher temperature than the member on the heat transfer pipe side. Thus, there is a temperature difference between the member on the heat transfer pipe side and the member on the ceiling wall side.

In particular, in recent years in which the temperature of steam generated in a boiler has been increased, in a superheater or the like, the temperature of fluid flowing through the heat transfer tube has become higher (for example, approximately 600 ℃), and a temperature difference between a member on the heat transfer tube side and a member on the ceiling wall side of the superheater has become more significant.

Further, in consideration of the influence of the further increase in temperature of the fluid flowing through the heat transfer tube such as the superheater on the strength of the heat transfer tube, a member having higher heat resistance may be used as the material of the furnace wall tube of the conventional ceiling wall as the member on the heat transfer tube side, and for example, in the case of using austenitic stainless steel or the like, the member has a higher thermal expansion coefficient than the conventional steel material.

Therefore, as the temperature of the heat transfer tube-side member rises and the heat transfer tube material has a large thermal expansion coefficient, the thermal elongation of the heat transfer tube-side member becomes larger than that of the ceiling wall-side member. Therefore, stress concentration generated by the expansion of the heat-transfer-pipe-side member being restricted by the ceiling-wall-side member (including the case fixed to the ceiling-wall-side member) is likely to occur at a stress greater than that in the conventional case, and the possibility of deformation or damage of the heat-transfer-pipe-side member and the case increases.

In this way, when the members and the casing on the heat transfer pipe side constituting the gas sealing structure are deformed or damaged, the sealing property of the sealing structure is lowered, and there is a possibility that the combustion gas leaks from the inside of the furnace. If the combustion gas leaks from the furnace, the high-temperature combustion gas flows into the top chamber, and the header may be damaged. In addition, since ash contained in the combustion gas is accumulated in the top chamber, it is necessary to clean the ash when the boiler is stopped. In addition, there is a possibility that the ceiling pipe is deformed by the accumulated ash load.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a seal structure of a boiler, and a method of operating a boiler, which can suppress leakage of combustion gas generated in a furnace.

In order to solve the above problems, the following aspects are adopted in the sealing structure of the boiler, and the operation method of the boiler according to the present invention.

In accordance with one embodiment of the present invention, there is provided a seal structure for a boiler that generates steam using combustion gas generated in a furnace, the seal structure including: a ceiling wall having a through hole for communicating an internal space of the furnace with an external space of the furnace, and defined above the furnace; a heat exchanger having a heat transfer pipe inserted through the through hole and made of a material different from that of the ceiling wall; a first fixing member having a first contact surface, covering the through hole to seal the external space, and fixed to the top wall; and a second fixing member that has a second contact surface that directly or indirectly comes into contact with the first contact surface, is fixed to the heat transfer pipe, and is made of a material different from that of the first fixing member, wherein the first contact surface and the second contact surface are slidable in a thermal expansion direction of the second fixing member.

In the above configuration, the first fixing member covers the through hole, thereby making an external space communicating with the through hole a closed space. Thus, even when the combustion gas generated in the furnace passes through the through-hole, the combustion gas is sealed in the space inside the first fixing member (i.e., the external space). Therefore, the leakage of the combustion gas to the outside of the first fixing member can be suppressed.

In the above configuration, the first contact surface of the first fixing member directly or indirectly comes into contact with the second contact surface of the second fixing member fixed to the heat transfer pipe. That is, the first contact surface and the second contact surface are in a sealed arrangement so that the combustion gas does not leak from between the first contact surface and the second contact surface. This makes it difficult for the combustion gas to leak from between the first fixing member covering the through hole and the member on the heat transfer pipe side. Therefore, leakage of the combustion gas to the outside of the first fixing member can be more appropriately suppressed.

The heat exchanger and the top wall are heated by heat generated in the boiler, respectively. The heat exchanger and the ceiling wall have different temperature rise degrees due to different environments and the like. Thus, the heat exchanger and the top wall are formed of different materials. In this way, the second fixing member and the first fixing member, which are fixed to the heat exchanger and the ceiling wall having different temperature increases, are made of different materials. The second fixing member fixed to the heat transfer pipe of the heat exchanger may thermally extend relative to the first fixing member due to heat of steam flowing through the heat transfer pipe. Further, since the second fixing member and the first fixing member are formed of different materials, thermal elongation of the second fixing member with respect to the first fixing member may become significant.

In the above structure, the second contact surface of the second fixing member is in direct or indirect surface contact with the first contact surface of the first fixing member in a slidable manner. That is, the first fixing member and the second fixing member are relatively movable. Thereby, the second fixing member is not constrained by the first fixing member. Therefore, even in the case where the second fixing member is thermally elongated, concentration of stress to the second fixing member due to the restraint of the first fixing member does not occur. Therefore, deformation and damage of the second fixing member can be suppressed. In addition, since the first contact surface and the second contact surface slide in the thermal expansion direction of the second fixing member, the contact between the first contact surface and the second contact surface is not released. Therefore, the deformation and damage of the second fixing member due to thermal elongation can be suppressed while maintaining the sealing property between the first contact surface and the second contact surface.

As an example of the heat exchanger made of a material different from that of the ceiling wall, a superheater provided in a boiler or the like can be mentioned.

In the seal structure of a boiler according to the one embodiment of the present invention, the first fixing member may have a plate-like first flange formed with a plurality of first bolt holes penetrating therethrough in a plate thickness direction, the second fixing member may have a plate-like second flange formed with a plurality of second bolt holes penetrating therethrough in the plate thickness direction, the first contact surface may be a plate surface of the first flange, the second contact surface may be a plate surface of the second flange, and the first flange and the second flange may be fixed by a plurality of bolts inserted through the plurality of first bolt holes and the plurality of second bolt holes.

In the above structure, the first flange having the first contact surface and the second flange having the second contact surface are fixed by a plurality of bolts. Therefore, the first contact surface and the second contact surface can be brought into contact with each other more stably. Therefore, the sealing property between the first contact surface and the second contact surface can be improved.

The first fixing member and the second fixing member are fixed to each other by a flange provided on each member and a plurality of bolts inserted through the flanges. Therefore, the first fixing member and the second fixing member can be fixed with a relatively simple structure.

In the seal structure of a boiler according to the one embodiment of the present invention, the plurality of first bolt holes may include long holes extending in the thermal expansion direction of the first flange.

In the above structure, the plurality of first bolt holes include long holes extending in the thermal expansion direction of the second fixing member. Thus, even when the second fixing member is thermally expanded relatively largely with respect to the first fixing member and the bolt fixed to the second fixing member is moved in the thermal expansion direction, interference between the edge of the first bolt hole and the bolt can be suppressed. Therefore, the sliding of the first contact surface and the second contact surface can be more favorably permitted. Therefore, concentration of stress on the second fixing member and the first fixing member can be suppressed, and deformation and damage of the first fixing member and the second fixing member can be more appropriately suppressed.

In the seal structure of a boiler according to the one embodiment of the present invention, the plurality of second bolt holes may include long holes extending in the thermal expansion direction of the second flange.

In the above structure, the plurality of second bolt holes include long holes extending in the thermal expansion direction of the second fixing member. Thus, even when the second fixing member is thermally expanded largely with respect to the first fixing member, interference between the edge of the second bolt hole and the bolt can be suppressed. Therefore, the sliding of the first contact surface and the second contact surface can be more favorably permitted. Therefore, concentration of stress on the second fixing member and the first fixing member can be suppressed, and deformation and damage of the first fixing member and the second fixing member can be more appropriately suppressed.

In the seal structure of a boiler according to the one embodiment of the present invention, the plurality of first bolt holes may be arranged at predetermined intervals along the thermal expansion direction of the first flange, and the first bolt hole arranged at the center in the thermal expansion direction may be a circular hole.

In the above-described configuration, the first bolt hole arranged at the center in the thermal expansion direction among the plurality of first bolt holes is a circular hole. Accordingly, the starting point of thermal expansion of the second fixing member can be set to the center in the thermal expansion direction, and therefore the length of the second fixing member to be thermally expanded (that is, the length from the starting point of thermal expansion to the end in the thermal expansion direction) becomes shorter. Therefore, the thermal elongation at both ends of the second fixing member in the thermal expansion direction can be suppressed. Therefore, deformation and damage of the first fixing member and the second fixing member can be more appropriately suppressed.

In the seal structure of a boiler according to the one embodiment of the present invention, the second flange may have a plurality of the second bolt holes, the plurality of the second bolt holes may be arranged at predetermined intervals along the thermal expansion direction of the second flange, and the second bolt hole arranged at the center in the thermal expansion direction among the plurality of the second bolt holes may be a circular hole.

In the above configuration, the second bolt hole arranged at the center in the thermal expansion direction among the plurality of second bolt holes is a circular hole. Accordingly, the starting point of thermal expansion of the second fixing member can be set to the center in the thermal expansion direction, and therefore the length of the second fixing member to be thermally expanded (that is, the length from the starting point of thermal expansion to the end in the thermal expansion direction) becomes shorter. Therefore, the thermal elongation at both ends of the second fixing member in the thermal expansion direction can be suppressed. Therefore, deformation and damage of the first fixing member and the second fixing member can be more appropriately suppressed.

In the seal structure of a boiler according to the embodiment of the present invention, the first fixing member and the second fixing member may be made of metals having different thermal expansion coefficients.

In the case where the first fixing member and the second fixing member are formed of metals having different thermal expansion coefficients, thermal elongation of the second fixing member with respect to the first fixing member becomes significant. In the above configuration, even in such a case, the deformation and damage of the second fixing member due to thermal expansion can be suppressed while maintaining the sealing property between the first contact surface and the second contact surface.

In the seal structure of a boiler according to the embodiment of the present invention, the first contact surface and the second contact surface may indirectly come into contact with each other with a gasket interposed therebetween.

In the above structure, the spacer is provided between the first contact surface and the second contact surface, and the first contact surface and the second contact surface are indirectly in contact with each other. By providing the spacer, the first contact surface and the second contact surface can be more appropriately slid. Further, by providing the gasket, it is possible to improve the sealing property between the first contact surface and the second contact surface, and to suppress leakage of the combustion gas more appropriately.

In the seal structure of a boiler according to the embodiment of the present invention, a plurality of the second fixing members may be provided, and the plurality of the second fixing members may be arranged in parallel along the thermal expansion direction.

In the above configuration, the plurality of second fixing members are arranged in line along the thermal expansion direction. This can shorten the length of each second fixing member in the thermal expansion direction. Therefore, the thermal elongation of each second fixing member can be suppressed. Therefore, deformation and damage of each second fixing member can be more appropriately suppressed.

In the seal structure of a boiler according to the embodiment of the present invention, a length of the first contact surface in the thermal expansion direction may be longer than a length of the second contact surface in the thermal expansion direction.

In the above configuration, the length of the second contact surface in the thermal expansion direction is longer than the length of the first contact surface in the thermal expansion direction. Thus, even when the second fixing member is more thermally elongated than the first fixing member, the surface contact between the first contact surface and the second contact surface can be made less likely to be released. Therefore, the sealing property between the first contact surface and the second contact surface can be improved.

The boiler according to an embodiment of the present invention employs the seal structure described in any one of the above.

In accordance with one embodiment of the present invention, there is provided a method for operating a boiler that generates steam using combustion gas generated in a furnace, the boiler including: a ceiling wall having a through hole for communicating an internal space of the furnace with an external space of the furnace, and defined above the furnace; a heat exchanger having a heat transfer pipe inserted through the through hole and made of a material different from that of the ceiling wall; a first fixing member having a first contact surface, covering the through hole to seal the external space, and fixed to the top wall; and a second fixing member that has a second contact surface that is in direct or indirect contact with the first contact surface and is fixed to the heat transfer tube, wherein the method for operating the boiler includes a step of sliding the first contact surface and the second contact surface in a thermal expansion direction of the second fixing member.

Effects of the invention

According to the present invention, leakage of combustion gas generated in the furnace can be suppressed.

Drawings

Fig. 1 is a schematic configuration diagram showing a coal-fired boiler according to an embodiment of the present invention.

Fig. 2 is a schematic view showing a heat exchanger and a steam and water supply system provided in the coal-fired boiler of fig. 1.

FIG. 3 is a schematic side view showing the superheater of FIG. 1.

Fig. 4 is an enlarged view of a main portion (portion IV) of fig. 3, and is a side view showing a main portion of a seal structure according to an embodiment of the present invention.

Fig. 5 is a front view of the sealing structure of fig. 4.

Figure 6 is a top view of the sealing structure of figure 4.

Fig. 7 is a plan view showing an end portion of the seal structure of the present embodiment.

Description of reference numerals:

a coal fired boiler (boiler);

a hearth;

a combustion apparatus;

a flue;

a superheater;

a second reheater;

45.. a first reheater;

a second economizer;

a first economizer;

a gas conduit;

a denitration catalyst;

an inlet header;

an outlet header;

wall portion;

82.. a top wall;

a roof-wall pipe;

a fin;

a through hole;

85.. a hanger;

86.. a top chamber;

a bolt;

89.. a heat transfer tube;

90.. sealing structure;

an outer jacket shell (first securing member);

a first outer shield shell;

a second outer shield shell;

a connection portion of the outer protective shell;

a lower inclined portion;

an upper inclined portion;

a lower flange (first flange);

bending a face;

a lower flange connection;

92.. sealing plate;

93.. a support plate (second fixation member);

93a.. first support plate;

a second support plate;

a support plate coupling portion;

a plumb portion;

93b.. upper flange (second flange);

an upper flange connection;

94... bolt;

95.. a nut;

96... first bolt hole;

a second bolt hole.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment, and when there are a plurality of embodiments, the present invention also includes a configuration in which the respective embodiments are combined.

Fig. 1 is a schematic configuration diagram showing a coal-fired boiler according to the present embodiment.

The boiler of the present embodiment is a coal-fired (pulverized coal-fired) boiler as follows: pulverized coal obtained by pulverizing coal is used as a fine powder fuel (carbon-containing solid fuel), and the fine powder coal is combusted by a burner, and heat generated by the combustion is recovered and heat-exchanged with water supply and steam, whereby superheated steam can be generated. In the following description, the upper and upper sides denote the upper side in the vertical direction, and the lower and lower sides denote the lower side in the vertical direction.

In the present embodiment, as shown in fig. 1, a coal-fired boiler 10 includes a furnace 11, a combustion device 12, and a flue (combustion gas flow path) 13. The furnace 11 is a hollow square tube and is provided along the vertical direction. The furnace wall constituting the furnace 11 is composed of a plurality of evaporation tubes and fins connecting the plurality of evaporation tubes, and suppresses temperature rise of the furnace wall by heat exchange with the feed water and the steam.

The combustion device 12 is provided on the lower side of the furnace wall constituting the furnace 11. In the present embodiment, the combustion apparatus 12 has a plurality of burners (e.g., 21, 22, 23, 24, 25) attached to the furnace wall. For example, the

burners

21, 22, 23, 24, and 25 are arranged in a plurality of stages in the vertical direction, with one set of burners arranged at equal intervals in the circumferential direction. However, the shape of the furnace, the number of burners in one stage, and the number of stages are not limited to those in the embodiment.

The

burners

21, 22, 23, 24, and 25 are connected to pulverizers (grinders) 31, 32, 33, 34, and 35 via pulverized

coal supply pipes

26, 27, 28, 29, and 30. Although not shown, the

grinders

31, 32, 33, 34, and 35 are configured such that, for example, a rotary table is supported in a housing so as to be able to rotate, and a plurality of rollers are supported above the rotary table so as to be able to rotate in conjunction with the rotation of the rotary table. When coal is put between the plurality of rollers and the rotating table, the coal can be pulverized to a predetermined size of fine coal, and the fine coal classified by the conveyance gas (primary air) can be supplied to the

burners

21, 22, 23, 24, and 25 from the fine

coal supply pipes

26, 27, 28, 29, and 30.

Further, in the furnace 11, a wind box 36 is provided at the mounting position of each of the

burners

21, 22, 23, 24, and 25, and one end of the wind box 36 is connected to an air duct 37. A blower 38 is provided at the other end of the air duct 37.

In addition, the additional air nozzle 39 is provided in the furnace 11 above the mounting position of each of the

burners

21, 22, 23, 24, and 25. The additional air nozzle 39 is coupled to an end of a branch air duct 40 branched from the air duct 37. Therefore, the combustion air (fuel gas combustion air/secondary air) sent from the blower 38 can be supplied from the air duct 37 to the wind box 36 and supplied from the wind box 36 to the

burners

21, 22, 23, 24, and 25, and the additional combustion air (additional air) sent from the blower 38 can be supplied from the branch air duct 40 to the additional air nozzle 39.

The flue 13 is connected to the upper portion of the furnace 11 in the vertical direction. In the flue 13,

superheaters

41, 42, 43,

reheaters

44, 45, and

coal economizers

46, 47 are provided as heat exchangers for recovering heat of the combustion gas, and heat exchange is performed between the combustion gas generated by combustion in the furnace 11 and the feed water and steam flowing through the heat exchangers.

A gas duct 48 for discharging the heat-exchanged combustion gas is connected to the downstream side of the flue 13. The gas duct 48 is provided with an air heater (air preheater) 49 between the air duct 37 and the air duct 37, and the combustion air supplied to the

burners

21, 22, 23, 24, and 25 can be heated by exchanging heat between the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48.

Further, in the flue duct 13, a denitration catalyst 50 is provided at a position on the upstream side of the air heater 49. The denitration catalyst 50 supplies a reducing agent having an action of reducing nitrogen oxides such as ammonia and urea water into the flue 13, and accelerates a reaction between the nitrogen oxides and the reducing agent in the combustion gas to which the reducing agent is supplied, thereby removing and reducing the nitrogen oxides in the combustion gas. The gas duct 48 connected to the flue 13 is provided with a coal dust treatment device (electrostatic precipitator, desulfurizer) 51, an induced draft fan 52, and the like at a position downstream of the air heater 49, and is provided with a chimney 53 at a downstream end.

On the other hand, when the

pulverizers

31, 32, 33, 34, 35 are driven, the produced fine coal is supplied to the

burners

21, 22, 23, 24, 25 through the fine

coal supply pipes

26, 27, 28, 29, 30 together with the conveying air. The heated combustion air is supplied from the air duct 37 to the

burners

21, 22, 23, 24, and 25 through the wind box 36. Then, the

burners

21, 22, 23, 24, and 25 can form a flame by ignition when a fine powder fuel mixture gas obtained by mixing fine powder coal and a carrier gas (primary air) is blown into the furnace 11 and combustion air is blown into the furnace 11. A flame is generated in a lower portion of the furnace 11, and the combustion gas rises in the furnace 11 and is discharged to the flue 13.

In the furnace 11, in the lower region a, the fine powder fuel mixture and the combustion air (secondary air) are combusted to generate flames. Here, in the furnace 11, the amount of air supplied is set to be smaller than the theoretical amount of air with respect to the amount of fine coal supplied, and the inside is maintained in a reducing atmosphere. That is, in the region B, NOx generated by the combustion of the fine coal is reduced in the furnace 11, and thereafter, additional air is supplied from the additional air nozzle 39 to complete the oxidation combustion of the fine coal, thereby reducing the amount of NOx generated by the combustion of the fine coal.

Thereafter, the combustion gas is heat-exchanged in the

superheaters

41, 42, and 43, reheaters 44 and 45, and

coal economizers

46 and 47 disposed in the flue 13, and thereafter, nitrogen oxides are reduced and removed by the denitration catalyst 50, particulate matter is removed by the coal dust treatment device 51, sulfur components are removed, and the combustion gas is discharged to the atmosphere from the stack 53.

Next, the

superheaters

41, 42, and 43, reheaters 44 and 45, and

economizer

46 and 47 provided in the flue 13 will be described in detail as heat exchangers. Fig. 2 is a schematic diagram showing a heat exchanger and a steam and water supply system provided in coal-fired boiler 10. Fig. 2 is a diagram for explaining the steam and water supply system, and is a diagram that does not accurately show the positions of the heat exchangers (

superheaters

41, 42, 43,

reheaters

44, 45, and coal economizers 46, 47) in the flue 13.

As shown in fig. 2, in the present embodiment, the flue 13 is provided therein with a combustion gas passage 60 through which combustion gas passes, and the

superheaters

41, 42, 43, the

reheaters

44, 45, and the

coal economizers

46, 47 are disposed in the combustion gas passage 60. It should be noted that the

superheaters

41, 42, 43 may be arranged in series via a header, but the header is omitted in fig. 2.

The steam turbine 61 operated by the steam generated in the coal-fired boiler 10 is constituted by, for example, a high-pressure turbine 62 and a low-pressure turbine 63. The low-pressure turbine 63 is connected to a condenser 64, 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 the inlet header 65 of the first economizer 47 via a water supply line L1. The inlet header 65 is provided to the combustion gas passage 60, and the water supply line L1 is provided with a water supply 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. The second economizer 46 is connected at an upper portion thereof with an outlet header 68, and the outlet header 68 is disposed outside the combustion gas passage 60.

The outlet header 68 is connected to a steam drum 69 disposed outside the combustion gas passage 60 via a water supply line L2. The steam drum 69 is connected to heat transfer pipes (not shown) of the furnace wall, and is connected to the

superheaters

41, 42, and 43 via an inlet header 74. Further, 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 in the steam line L3. Further, the high-pressure turbine 62 is connected to an inlet header (proximity pipe) 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, the second reheater 44 is connected to an outlet header 72 at an upper portion thereof, and the intermediate header 71 and the outlet header 72 are disposed outside the combustion gas passage 60. The outlet header 72 is connected to the low-pressure turbine 63 via a steam line L5, and rotationally drives the low-pressure turbine 63.

Therefore, when the combustion gas flows through the combustion gas passage 60 of the flue 13, the combustion gas recovers heat in the order of the

superheaters

41, 42, and 43, the

reheaters

44 and 45, and the

economizer

46 and 47. On the other hand, the water supplied from the water supply pump 66 is preheated by the

economizer

47, 46, supplied to the steam drum 69, heated to become saturated steam while being supplied to each heat transfer pipe of the furnace wall, not shown, and returned to the steam drum 69. The saturated steam of the steam drum 69 is introduced into the

superheaters

41, 42, and 43, and superheated by the combustion gas. The superheated steam generated by the

superheaters

41, 42, and 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 and 44, is reheated, is then supplied to the low-pressure turbine 63, and drives 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 again to the

coal economizers

47 and 46.

Further, in the flue 13, a sootblower (injection device) 80 may be disposed between the inlet header 70 and the economizer 47. The sootblowers 80 extend in a direction parallel to the longitudinal direction of the inlet header 70 and are disposed at positions facing the inlet header 70. The sootblower 80 is a spraying device that is axially oriented in the longitudinal direction of the inlet header 70, sprays steam (gas) in a direction orthogonal to the axial direction, and the spraying direction can be changed. The steam injected from the sootblower 80 toward the economizer 47 removes combustion ash accumulated on the surface of the heat transfer pipe of the economizer 47.

Next, the support method of at least any one of the

superheaters

41, 42, and 43 provided in the flue 13 and the seal structure 90 of the heat transfer pipe 89 and the ceiling wall 82 provided in at least any one of the

superheaters

41, 42, and 43 according to the present embodiment will be described in more detail with reference to fig. 3 to 7. Note that, since the support form of at least any one of the

superheaters

41, 42, and 43 and the seal structure 90 provided to the heat transfer pipe 89 and the ceiling wall 82 of at least any one of the

superheaters

41, 42, and 43 are substantially the same in configuration, the superheater 41 will be described as a representative in the following description, and the descriptions of the other superheaters 42 and 43 will be omitted. In the following description and fig. 3 to 7, the Z direction represents a vertical up-down direction, the X direction represents an extending direction of the ceiling pipe 83, and the Y direction represents a direction orthogonal to the Z direction and the X direction.

As shown in fig. 3, the flue 13 includes: a wall portion 81 defining a side of the combustion gas passage 60 provided therein; and a ceiling wall 82 defining an upper portion of the combustion gas passage 60.

As shown in fig. 5, the ceiling wall 82 is a so-called film wall having a plurality of ceiling-wall tubes 83 extending in the horizontal direction (more specifically, the X direction) through which the refrigerant flows, and plate-like fins 84 connecting the adjacent ceiling-wall tubes 83 to each other, similarly to the furnace wall. As shown in fig. 3, a ceiling chamber (plenum) 86 in which the inlet header 74 and the outlet header 75 of the superheater 41 and the like are disposed is provided above the ceiling wall 82. The ceiling wall 82 is formed with a through hole 84a through which a heat transfer pipe 89 constituting the superheater 41 described later is inserted. The through-hole 84a communicates the internal space of the flue 13 (in the present embodiment, the combustion gas passage 60) continuous with the furnace 11 with the external space of the furnace 11 (in the present embodiment, the space in the top chamber 86).

As shown in fig. 1, the superheater 41 is a heat exchanger provided on the most upstream side of the combustion gas passage 60. The superheater 41 is provided vertically above the furnace 11 and, as shown in fig. 3, is provided in the vicinity of a wall 81 of the flue 13. The superheater 41 is fixed to a boiler steel frame (not shown) and supported by a hanger 85 suspended from the boiler steel frame.

The superheater 41 is constituted by a plurality of heat transfer tubes 89 that connect the inlet header 74 and the outlet header 75. Each heat transfer pipe 89 includes a first vertical pipe portion 89a extending substantially vertically downward from the inlet header 74, a horizontal pipe portion 89b bent from a lower end of the first vertical pipe portion 89a and extending in the X direction toward the wall portion 81, and a second vertical pipe portion 89c bent from an end portion of the horizontal pipe portion 89b and extending substantially vertically upward. That is, the first vertical pipe portion 89a and the second vertical pipe portion 89c extend in the vertical direction (Z direction). As described above, since the inlet header 74 and the outlet header 75 are provided in the top chamber 86, the first vertical pipe portion 89a and the second vertical pipe portion 89c are disposed so as to penetrate the top wall 82 of the flue 13. Specifically, as shown in fig. 5, the first vertical pipe portion 89a and the second vertical pipe portion 89c are inserted through the through hole 84a of the fin 84 formed in the top wall 82. The plurality of through holes 84a are formed at predetermined intervals in the X direction (in the present embodiment, the extending direction of the top-wall tube 83) so as to correspond to the first vertical tube portion 89a and the second vertical tube portion 89c of the plurality of heat transfer tubes 89. Although the first vertical pipe portion 89a is illustrated in fig. 5, the second vertical pipe portion 89c has the same configuration.

A seal structure 90 is provided in the top chamber 86 so that the combustion gas does not flow into the top chamber 86 from the through hole 84a.

As shown in fig. 4 and 5, the seal structure 90 includes an outer jacket case (first fixing member) 91 welded and fixed to the top wall 82 and covering the through hole 84a, a seal plate 92 welded and fixed to the heat transfer pipe 89 (specifically, the first vertical pipe portion 89a), a support plate (second fixing member) 93 welded and fixed to the seal plate 92, and bolts 94 and nuts 95 fastening and fixing the outer jacket case 91 and the support plate 93. The length of the seal structure 90 in the longitudinal direction (X direction) is, for example, approximately 5m to 15 m.

The outer jacket 91 is a hood-shaped member extending in the X direction, and the lower end thereof is fixed to the upper portion of the ceiling pipe 83 of the ceiling wall 82 by welding or the like. The outer jacket 91 covers a plurality of through holes 84a formed at predetermined intervals in the X direction from above. That is, the outer jacket 91 has a space formed therein and seals the space. The outer jacket 91 is made of low alloy steel (e.g., 0.5 to 2.0Cr steel) as in the case of the top wall 82.

The outer jacket 91 includes a first outer jacket 91A fixed to the first top wall pipe 83A positioned on one side of the through hole 84a, a second outer jacket 91B fixed to the second top wall pipe 83B positioned on the other side of the through hole 84a (the opposite side to the one side across the through hole 84a), and an outer jacket connecting portion 91C connecting the first outer jacket 91A and the second outer jacket 91B. In the present embodiment, for example, the first outer jacket case 91A and the second outer jacket case 91B are configured to be substantially symmetrical with each other with the through hole 84a interposed therebetween, and therefore, the first outer jacket case 91A will be described below, and the second outer jacket case 91B will not be described.

The first outer jacket 91A includes, for example, a plate-like lower inclined portion 91A extending obliquely upward from the upper portion of the ceiling wall pipe 83 toward the heat transfer pipe 89, a plate-like upper inclined portion 91b bent from the upper end of the lower inclined portion 91A and extending obliquely upward toward the heat transfer pipe 89, and a plate-like lower flange (first flange) 91c extending in a substantially horizontal direction from the upper end of the upper inclined portion 91b.

The lower end of the lower inclined portion 91a is fixed to the top wall 82 above the ceiling pipe 83 by welding or the like (see W1 in fig. 5). The upper end of the upper inclined portion 91b is located near the side surface of the support plate 93. The lower inclined portion 91a and the upper inclined portion 91b are formed by bending a single plate material so as to protrude toward a space formed inside. The shape of the first outer jacket case 91A is not limited to the shape of the present embodiment. That is, the inclination angles of the lower inclined portion 91a and the upper inclined portion 91b may be other inclination angles. The lengths of the lower inclined portion 91a and the upper inclined portion 91b may be different. In addition, the first outer jacket 91A may be formed partially or entirely by a curved surface.

One end of the lower flange 91c and the upper end of the upper inclined portion 91b are fixed by welding or the like (see W2 in fig. 5). The lower flange 91c is a plate-like member extending substantially horizontally. The upper surface (first contact surface) of the lower flange 91c is disposed so as to directly or indirectly come into contact with a lower surface (second contact surface) of an upper flange 93b (described later) (hereinafter, referred to as "seal disposition"). The lower flange 91c has a plurality of first bolt holes 96 penetrating therethrough in the plate thickness direction. The first bolt holes 96 are arranged at substantially equal intervals along the longitudinal direction (X direction). The plurality of first bolt holes 96 are circular holes having a diameter larger than the cross-sectional diameter of the threaded portion of the bolt 94 or long holes long in the longitudinal direction, and the bolt 94 is inserted therethrough.

As shown in fig. 7, the outer shield shell coupling portion 91C is provided at both ends of the outer shield shell 91 in the longitudinal direction (X direction). The outer shield shell connection portion 91C includes a curved surface portion 91d that connects the end portions of the lower inclined portion 91A and the upper inclined portion 91B of the first outer shield shell 91A and the end portions of the lower inclined portion 91A and the upper inclined portion 91B of the second outer shield shell 91B, and a lower flange connection portion 91e that connects the lower flange 91C of the first outer shield shell 91A and the lower flange 91C of the second outer shield shell 91B. The outer jacket coupling portion 91C is curved to have a predetermined curvature in a plan view. The end of the upper flange 93b, which is sealed and disposed opposite to the end of the lower flange 91c, is formed to have a predetermined curvature in a plan view.

As shown in fig. 4 and 5, the seal plate 92 is a member having a substantially コ -shaped cross section extending in the X direction and the Z direction, and has holes through which the plurality of heat transfer pipes 89 arranged in the X direction penetrate. The length of the seal plate 92 in the Y direction is set to be longer than the diameter of the heat transfer pipe 89 so that the outer peripheral surface of the heat transfer pipe 89 is not exposed. In the present embodiment, the steam flowing through the heat transfer tubes 89 of the superheater 41 is at a higher temperature (e.g., about 600 ℃) than the steam flowing through the ceiling wall tubes 83 constituting the ceiling wall 82. Therefore, the superheater 41 is made of a material having a heat resistance superior to that of the ceiling wall pipe 83 constituting the ceiling wall 82. The heat transfer pipe 89 of the superheater 41 is formed of, for example, austenitic stainless steel (SUS304 or the like). The seal plate 92 is preferably made of the same material as the heat transfer pipe 89 when connected thereto, and is made of, for example, austenitic stainless steel (SUS304 or the like) because it is heated to a high temperature by heat from the heat transfer pipe 89. The seal plate 92 and the outer peripheral surface of the heat transfer pipe 89 are fixed by welding or the like.

The support plate 93 is preferably the same material as the seal plate 92, and is also high-temperature, and thus is formed of, for example, austenitic stainless steel (SUS304 or the like). The support plate 93 is fixed to the hanger 85. The support plate 93 includes a first support plate 93A disposed on the first outer shield case 91A side, a second support plate 93B disposed on the second outer shield case 91B side, and a support plate coupling portion 93C that couples the first support plate 93A and the second support plate 93B. The first support plate 93A and the second support plate 93B are disposed substantially in parallel with each other with the heat transfer pipe 89 interposed therebetween. Since the first support plate 93A and the second support plate 93B are symmetrically configured with the through hole 84a interposed therebetween, the first support plate 93A will be described below, and the second support plate 93B will not be described.

The first support plate 93A includes a plate-shaped vertical portion 93A extending along a side surface of the seal plate 92, and a plate-shaped upper flange (second flange) 93b extending in a substantially horizontal direction from a vertically intermediate region (for example, a substantially central region) of the vertical portion 93A.

The plate surface of the vertical part 93a is in surface contact with the side surface of the sealing plate 92. The upper end of the vertical portion 93a is located below the upper end of the sealing plate 92. The upper end of the hanging portion 93a is fixed to the side surface of the sealing plate 92 by welding or the like (see W3 in fig. 5). Further, the lower portion of the hanger 85 is fixed to the outer side surface of the hanging portion 93a by a bolt 87. The lower end of the vertical portion 93a is located below the upper end of the upper inclined portion 91b of the outer jacket 91. That is, the lower end of the vertical portion 93a is positioned in a space formed inside the outer jacket 91. In fig. 5, the hanger 85 is not shown for the sake of illustration.

One end of the upper flange 93b and a side surface of the vertical portion 93a are fixed by welding or the like (see W4 in fig. 5). The upper flange 93b is a plate-like member extending substantially horizontally. The lower surface of the upper flange 93b is disposed in a sealing manner so as to be slidable in opposition to the upper surface of the lower flange 91c. The length of the upper flange 93b in the short direction (Y direction) is substantially the same as the length of the lower flange 91c in the short direction. The upper flange 93b has a plurality of second bolt holes 97 penetrating in the plate thickness direction. The second bolt holes 97 are arranged at substantially equal intervals along the longitudinal direction (X direction). Bolts 94 are inserted through the second plurality of bolt holes 97. Of the plurality of second bolt holes 97, only the second bolt hole 97a located at the center in the longitudinal direction of the upper flange 93b is formed in a circular hole shape. The other second bolt holes 97 are formed in a long hole shape long in the longitudinal direction. Each second bolt hole 97 is provided at a position corresponding to the first bolt hole 96. That is, each second bolt hole 97 is formed at a position communicating with the first bolt hole 96. The shapes of the corresponding first bolt hole 96 and second bolt hole 97 may be reversed. Specifically, the plurality of second bolt holes 97 of the lower flange 91c and the second bolt hole 97a located at the center may be circular holes, only the first bolt hole 96 of the upper flange 93b corresponding to the second bolt hole 97a located at the center in the longitudinal direction may be circular holes, and the other first bolt holes 96 may be long holes in the longitudinal direction. The shapes of the corresponding first bolt holes 96 and second bolt holes 97 may be the same, and the second bolt holes 97a located only at the center in the longitudinal direction may be formed in a circular hole shape and the other second bolt holes 97 may be formed in an elongated hole shape that is long in the longitudinal direction in both the upper flange 93b and the lower flange 91c.

A gasket material (not shown) (e.g., a non-asbestos material) is provided between the upper flange 93b and the lower flange 91c.

As shown in fig. 7, the support plate coupling portions 93C are provided at both ends of the support plate 93 in the longitudinal direction (X direction). The support plate coupling portion 93C has a bent portion 93C that connects an end of the vertical portion 93A of the first support plate 93A and an end of the vertical portion 93A of the second support plate 93B, and an upper flange coupling portion 93d that connects the upper flange 93B of the first support plate 93A and the upper flange 93B of the second support plate 93B. The curved portion 93c is curved to have a predetermined curvature in a plan view. The upper flange connecting portion 93d is formed to have a predetermined curvature in a plan view.

The length of the upper flange 93b in the longitudinal direction is set to be shorter than the length of the lower flange 91c in the longitudinal direction. That is, the longitudinal end of the lower flange connection portion 91e is located on the outer side in the longitudinal direction than the longitudinal end of the upper flange connection portion 93d. Thus, a gap G is provided between the end portion of the vertical portion 93a in the longitudinal direction and the lower flange connection portion 91e.

The bolts 94 are inserted through the first bolt holes 96 and the second bolt holes 97 from above or below. Further, the lower end of the bolt 94 is fastened by a nut 95. The bolt 94 can control the torque so that the upper flange 93b and the lower flange 91c can slide. At this time, for example, after the bolt 94 is completely tightened, the bolt 94 is rotated by half a turn in the direction of loosening the tightening of the bolt 94, whereby the upper flange 93b and the lower flange 91c can be made to slide, and the torque management can be easily performed.

Note that the bolt 94 and the lower flange 91c may be spot welded to prevent rotation. By performing the rotation stop, the fastening force of the bolt 94 can be maintained.

According to the present embodiment, the following operational effects are exhibited.

In the present embodiment, the outer jacket 91 covers the through hole 84a to seal an external space communicated with the through hole 84a. Thus, even when the combustion gas generated in the furnace 11 passes through the through-hole 84a, the combustion gas is sealed in the space inside the outer jacket 91. Therefore, the leakage of the combustion gas to the outside of the outer jacket 91 (into the top chamber 86) can be suppressed.

In the present embodiment, the lower flange 91c of the outer jacket 91 and the upper flange 93b of the support plate 93 fixed to the heat transfer pipe 89 via the seal plate 92 are disposed in a sealed manner so as to face each other. This makes it difficult for the combustion gas to leak from between the outer jacket 91 covering the through hole 84a and the support plate 93. Therefore, the leakage of the combustion gas to the outside of the outer jacket 91 can be suppressed more effectively.

During operation of the boiler, the seal plate 92 and the support plate 93 fixed to the heat transfer tubes 89 of the superheater 41 rise in temperature due to the heat of the steam flowing through the heat transfer tubes 89, and thermally expand. In the present embodiment, the steam flowing through the heat transfer tubes 89 of the superheater 41 has a higher temperature (e.g., about 600 ℃) than that of the conventional steam (e.g., about 500 to 560 ℃). Therefore, the support plate 93 is also at a higher temperature than in the related art due to the influence of the steam having a higher temperature than in the related art flowing through the heat transfer pipe 89. Conventionally, a low alloy steel (e.g., 0.5 to 2Cr steel) has been used as the support plate 93 as the same material as the outer jacket 91, but in the present embodiment, a high temperature resistant material different from the material of the outer jacket 91 is used. That is, the support plate 93 is formed of a high-temperature resistant material (e.g., an austenitic stainless steel material) having a large thermal expansion coefficient and being easily thermally elongated, which is different from the thermal expansion coefficient of the low alloy steel forming the outer jacket 91. Further, the thermal elongation is increased because the temperature is higher than that in the conventional art.

On the other hand, the steam flowing through the top wall pipe 83 is lower in temperature than the steam flowing through the heat transfer pipe 89 of the superheater 41. Therefore, the outer jacket 91 is not heated to a higher temperature than the support plate 93. Therefore, the outer jacket 91 is formed of a low alloy steel which is less susceptible to thermal elongation than the high-temperature resistant material (e.g., austenitic stainless steel material) forming the support plate 93, and therefore has a relatively small thermal expansion coefficient as compared with the high-temperature resistant material, and the temperature itself is relatively low, and therefore the amount of thermal elongation is small. In this way, the thermal elongation during boiler operation differs between the outer casing 91 and the support plate 93 depending on the temperature and material. Therefore, the outer shield shell 91 and the support plate 93 are relatively moved by thermal elongation. In particular, the relative movement amount of the outer shield case 91 and the support plate 93 in the X direction (thermal expansion direction) as the longitudinal direction is increased.

In the present embodiment, the outer shield case 91 has a lower inclined portion 91a and an upper inclined portion 91b. By making the inclination angles of the lower inclined portion 91a and the upper inclined portion 91b different, relative movement of the support plate 93 and the outer shield case 91 in the Z direction and the Y direction due to a difference in thermal elongation is allowed, so that generation of stress concentration is suppressed.

In the present embodiment, the upper flange 93b of the support plate 93 and the lower flange 91c of the outer jacket case 91 are slidably and hermetically disposed to face each other. That is, the outer jacket 91 and the support plate 93 are movable relative to each other in the X direction (thermal expansion direction) which is the longitudinal direction. Thereby, the support plate 93 is not restrained by the outer jacket 91. Therefore, the thermal expansion coefficient of the support plate 93 is relatively large and relatively high temperature, and therefore, even when the thermal elongation of the support plate 93 is larger than that of the outer jacket 91, concentration of stress to the support plate 93 due to the constraint of the outer jacket 91 can be suppressed. Therefore, deformation and damage of the support plate 93 and the outer jacket case 91 can be suppressed. Further, since the lower flange 91c and the upper flange 93b slide in the longitudinal direction (X direction) of the support plate 93, even when the support plate 93 thermally expands in the X direction, the state in which the lower flange 91c and the upper flange 93b are arranged to face each other and sealed is not released. Therefore, the lower flange 91c and the upper flange 93b can maintain the sealing property therebetween, and deformation and damage of the support plate 93 and the outer jacket case 91 due to thermal elongation can be suppressed.

In the present embodiment, the first flange and the second flange are fixed by the bolts 94. Therefore, the upper flange 93b and the lower flange 91c can be maintained in a more stable state of being opposed to each other and being sealed. Therefore, the sealability between the upper flange 93b and the lower flange 91c can be maintained.

The outer jacket 91 and the support plate 93 are fixed to each other by bolts 94 provided to the flanges of the respective members and inserted through the flanges. Therefore, the outer jacket 91 and the support plate 93 can be fixed with a relatively simple structure. In addition, maintenance is also facilitated.

In the present embodiment, the second bolt hole 97 provided in the upper flange 93b of the support plate 93 or the lower flange 91c of the outer jacket 91 other than the center in the longitudinal direction (X direction) is an elongated hole extending in the X direction. Thus, even when the support plate 93 thermally expands in the X direction, interference between the edge of the second bolt hole 97 and the bolt 94 can be suppressed. Therefore, the sliding of the upper flange 93b and the lower flange 91c can be more favorably permitted. Therefore, concentration of stress to the outer jacket case 91 due to the restraint of the support plate 93 or concentration of stress to the support plate 93 due to the restraint of the outer jacket case 91 can be suppressed, and deformation and damage of the support plate 93 or the outer jacket case 91 can be more appropriately suppressed.

In the present embodiment, of the plurality of second bolt holes 97, the second bolt hole 97a disposed at the center in the longitudinal direction (X direction) of the upper flange 93b of the support plate 93 or the lower flange 91c of the outer jacket 91 is a circular hole. This enables the starting point of thermal expansion of the support plate 93 (see reference numeral S in fig. 6) to be set at the center in the X direction. Therefore, the thermal expansion direction extends in two directions from the center in the X direction as a starting point, and the thermal expansion amount at both ends in the longitudinal direction of the support plate 93 can be suppressed. Therefore, deformation and damage of the support plate 93 can be more appropriately suppressed.

In the present embodiment, a gasket is provided between the upper flange 93b and the lower flange 91c. By providing the gasket, the upper flange 93b and the lower flange 91c can be more favorably slid. Further, by providing the gasket, the sealability between the upper flange 93b and the lower flange 91c can be improved.

In the present embodiment, the length of the lower flange 91c in the longitudinal direction (X direction) is longer than the length of the upper flange 93b in the X direction. This can suppress interference during thermal expansion in the X direction, which is the longitudinal direction, and make it difficult to release the sealing arrangement between the lower flange 91c and the upper flange 93b. Therefore, the sealability between the lower flange 91c and the upper flange 93b can be maintained.

Further, the longitudinal end of the lower flange connection portion 91e is located on the outer side in the longitudinal direction than the longitudinal end of the upper flange connection portion 93d, and a gap G is provided between the longitudinal end of the vertical portion 93a and the lower flange connection portion 91e. Thus, even when the support plate 93 is thermally extended in the X direction, which is the longitudinal direction, relatively larger than the outer jacket 91, the support plate 93 and the lower flange 91c can be configured to suppress interference.

The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit and scope of the invention.

For example, a plurality of support plates 93 may be provided, and the support plates 93 may be arranged in line along the X direction. That is, a plurality of support plates 93 may be provided for one outer jacket case 91. In the case of such a configuration, the length of each support plate 93 in the X direction is, for example, about 3 to 5m, and, for example, 30 to 40 second bolt holes 97 may be formed.

With this configuration, the length of each support plate 93 in the X direction can be shortened. Therefore, the thermal elongation in the X direction of each support plate 93 can be suppressed. Therefore, deformation and damage of each support plate 93 can be more appropriately suppressed.

In the above-described embodiment, an example has been described in which, among the plurality of second bolt holes 97 formed in the upper flange 93b or the lower flange 91c, only the second bolt hole 97a located at the center in the longitudinal direction of the upper flange 93b or the lower flange 91c is formed in a circular hole shape, but the present invention is not limited thereto. The position of the second bolt hole 97 formed in a circular hole shape may not be the center in the longitudinal direction of the upper flange 93b or the lower flange 91c.

In the above embodiment, an example in which the seal structure 90 of the present invention is applied to the seal structure between the superheater 41 and the ceiling wall 82 has been described, but the present invention is not limited to this. For example, the seal structure 90 may also be applied to seal structures between

other superheaters

42, 43 and the top wall 82. Further, the present invention may be applied to a seal structure between another heat exchanger (e.g., reheater 44) and ceiling wall 82.

Claims

1. A sealing structure of a boiler for generating steam using combustion gas generated in a furnace, wherein,

the sealing structure of the boiler is provided with:

a ceiling wall having a through hole for communicating an internal space of the furnace with an external space of the furnace, and defined above the furnace;

a heat exchanger having a heat transfer pipe inserted through the through hole and made of a material different from that of the ceiling wall;

a first fixing member having a first contact surface, covering the through hole to seal the external space, and fixed to the top wall; and

a second fixing member that has a second contact surface that directly or indirectly comes into contact with the first contact surface, is fixed to the heat transfer pipe, and is made of a material different from that of the first fixing member,

the first contact surface and the second contact surface are slidable in a thermal expansion direction of the second fixing member.

2. The sealing structure of a boiler according to claim 1,

the first fixing member has a plate-like first flange formed with a plurality of first bolt holes penetrating in a plate thickness direction,

the second fixing member has a plate-like second flange formed with a plurality of second bolt holes penetrating in a plate thickness direction,

the first contact surface is a plate surface of the first flange,

the second contact surface is a plate surface of the second flange,

the first flange and the second flange are fixed by a plurality of bolts inserted through the plurality of first bolt holes and the plurality of second bolt holes.

3. The sealing structure of a boiler according to claim 2,

the plurality of first bolt holes include long holes extending in the thermal expansion direction of the first flange.

4. The sealing structure of a boiler according to claim 2,

the plurality of second bolt holes include long holes extending in the thermal expansion direction of the second flange.

5. The sealing structure of a boiler according to claim 3,

the plurality of first bolt holes are arranged at predetermined intervals along the thermal expansion direction of the first flange,

the first bolt hole disposed at the center in the thermal expansion direction is a circular hole.

6. The sealing structure of a boiler according to claim 4,

the plurality of second bolt holes are arranged at predetermined intervals along the thermal expansion direction of the second flange,

the second bolt hole disposed at the center in the thermal expansion direction is a circular hole.

7. The sealing structure of a boiler according to claim 1,

the first fixing member and the second fixing member are formed of metals having different thermal expansion coefficients.

8. The sealing structure of a boiler according to claim 1,

the first contact surface and the second contact surface indirectly make contact with each other via a pad provided between the first contact surface and the second contact surface.

9. The sealing structure of a boiler according to claim 1,

the second fixing member is provided in plurality,

the plurality of second fixing members are arranged in line along the thermal expansion direction.

10. The sealing structure of a boiler according to any one of claims 1 to 9,

the length of the first contact surface in the thermal expansion direction is longer than the length of the second contact surface in the thermal expansion direction.

11. A boiler, wherein the boiler is provided with a boiler,

the boiler is applied with a sealing structure of the boiler of any one of claims 1 to 10.

12. A method for operating a boiler for generating steam using combustion gas generated in a furnace, wherein,

the boiler is provided with:

a second fixing member that has a second contact surface that is in direct or indirect surface contact with the first contact surface and is fixed to the heat transfer pipe,

the method of operating the boiler includes a step of sliding the first contact surface and the second contact surface in a thermal expansion direction of the second fixing member.