Fin device for preventing water wall tube leakage caused by fin cracking of coal-fired boiler

Abstract

The invention relates to the technical field of coal-fired power plant boiler protection equipment, and discloses a fin device used for avoiding water wall tube leakage caused by fin cracking of a coal-fired boiler, the fin device comprises a butterfly-shaped sealing shell plate welded in a boiler tube switching connection part, and the end face, away from a boiler tube, of the butterfly-shaped sealing shell plate is of an open structure. X-shaped forcep nails are arranged in the butterfly-shaped sealing shell plate, high-temperature-resistant sealing filler is smeared in the butterfly-shaped sealing shell plate, and the butterfly-shaped sealing shell plate is filled with the filler which covers the boiler pipe conversion connecting part. The high-temperature-resistant sealing filler is prepared from the following components in percentage by mass: 30%-40% of ceramic fiber, 15%-25% of silica powder, 12%-20% of alumina powder, 8%-12% of kaolin, 5%-10% of mica powder, 3%-6% of borate glass powder and 4%-10% of an additive, and the sum of the component raw materials is 100%. The sealing device has the advantages of being good in applicable sealing performance, capable of preventing leakage of boiler pipes due to stress concentration, capable of reducing the production cost of a coal-fired power plant and stable in sealing effect.

Description

Technical Field

[0001] This invention relates to a fin device for preventing water-cooled wall tube leakage caused by fin cracking in coal-fired boilers, belonging to the technical field of boiler protection equipment for coal-fired power plants. Background Technology

[0002] Currently, in common large-scale supercritical coal-fired power plant boilers, the transition connection between the spiral water-cooled wall and the vertical water-cooled wall is mostly sealed using wide metal fins welded to the water-cooled wall tubes. However, due to the high temperature in this area during unit operation, the heat in the middle of the wide fins cannot be carried away by the medium inside the tubes in time. This easily leads to carbonization and cracking in the middle of the wide fins. Furthermore, affected by load changes, these cracks will gradually extend and expand to the heated surface tubes, which can easily cause tube leaks. Once a tube leaks, the unit needs to be shut down, and then scaffolding or a lifting platform needs to be erected to replace the leaking tubes, which consumes a lot of manpower and resources, seriously affecting the safe, stable, and economical operation of the unit.

[0003] To address this, Chinese patent application CN202410122652.6 provides a device for preventing cracking of the water-cooled wall fins in boilers. The device includes a crack-prevention body for the water-cooled wall fins, comprising two T-shaped ceramic fins, two inverted T-shaped fins, multiple water-cooled wall tubes, and multiple fins. One end of each T-shaped ceramic fin is overlapped, and the other end is snapped into place with another T-shaped fin. The free end of each T-shaped fin is alternately connected to multiple water-cooled wall tubes and multiple fins. By arranging T-shaped ceramic fins at the left and right center expansion points of the boiler wall, and because these fins are high-temperature flexible ceramics, the device ensures good sealing of the fins after slight thermal expansion and maintains good mechanical properties after thermal expansion. This prevents cracking of the boiler wall water-cooled wall fins, which could lead to leaks in the water-cooled wall tubes and cause non-shutdown accidents, thus reducing unnecessary economic losses. However, while T-type ceramic fins possess advantages such as high chemical stability and high temperature resistance, they still present the following problems in practical applications: 1. The overall shape of T-shaped ceramic fins is fixed. Even when combined with inverted T-shaped fins, their overall shape remains fixed and can only adapt to regular installation positions. However, the common transition connection between spiral water-cooled walls and vertical water-cooled walls often involves cutting and welding, resulting in irregular installation positions. This makes it difficult to install T-shaped ceramic fins and adapt to irregular installation positions, leading to gaps between them and the tubes after installation, which cannot effectively prevent media leakage.

[0004] 2. T-type ceramic fins have high manufacturing process and performance requirements, which leads to relatively high production costs, which may impose a certain economic burden on boiler manufacturers.

[0005] 3. Due to the characteristics of ceramic materials, the flexibility of T-shaped ceramic fins is limited to the high flexibility of ceramic materials. In fact, the overall brittleness is still relatively large, making it difficult to withstand deformation. Coal-fired boiler tubes are prone to vibration due to water flow. When this vibration is transmitted to the T-shaped ceramic fins, it is more likely to cause them to break. Summary of the Invention

[0006] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a fin device for preventing water-cooled wall tube leakage caused by fin cracking in coal-fired boilers.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a high-temperature resistant sealing filler, which, by mass percentage, is composed of the following components: 30% to 40% ceramic fiber, 15% to 25% silica powder, 12% to 20% alumina powder, 8% to 12% kaolin, 5% to 10% mica powder, 3% to 6% borate glass powder, and 4% to 10% additives, the total of the above components being 100%.

[0008] Further, the additive, by weight percentage, consists of the following components: 2%–4% binder, 1%–3% lubricant, 0.5%–1.5% antioxidant, and 0.5%–1.5% coupling agent.

[0009] Furthermore, the ceramic fiber is a high-alumina ceramic fiber with an alumina content of not less than 55%, a fiber diameter of 3-8 μm, and a length of 10-50 mm.

[0010] Furthermore, the silicon micropowder has a specific surface area of ​​15-25 m² / g, an average particle size of 0.5-1.5 μm, and a silicon dioxide content of not less than 98% in its chemical composition.

[0011] Furthermore, the alumina powder is α-alumina powder with a purity of not less than 99% and an average particle size of 1–5 μm.

[0012] Furthermore, the kaolin is a water-washed kaolin with a flaky crystal structure, a flake diameter-to-thickness ratio of not less than 10:1, a particle size of 325-500 mesh, a silica content of 45%-55%, an alumina content of 35%-45%, and a loss on ignition of 12%-15%.

[0013] Furthermore, the mica powder is muscovite powder with a Mohs hardness of 2-3, an aspect ratio of 30-50, a particle size of 200-400 mesh, and a chemical composition containing 45%-50% silicon dioxide, 30%-35% aluminum oxide, 9%-11% potassium oxide, and no more than 0.5% iron oxide.

[0014] Furthermore, the borate glass powder has a softening temperature of 500–600℃, a particle size of 10–50 μm, a boron trioxide content of 30%–40%, a silicon dioxide content of 20%–30%, an alkali metal oxide content of 10%–20%, and a coefficient of thermal expansion of (6–10) × 10⁻⁶. -6 / ℃.

[0015] Secondly, the present invention provides a method for preparing the aforementioned high-temperature resistant sealing filler, comprising the following steps: Step 1: Raw material preparation; weigh each raw material according to the formula; Step 2: Premixing; ceramic fiber, silica powder, alumina powder, kaolin, and mica powder are placed in a mixer for preliminary mixing; Step 3: Additive treatment and mixing; silica sol is added directly to the mixer, stearic acid is heated until completely melted and then added to the mixer through a pipe, antioxidants and coupling agents are prepared into solutions with anhydrous ethanol and then added to the mixer, and then stirring and mixing are continued; Step 4: Viscosity adjustment; Use a viscometer to test the viscosity of the packing material in the mixer. Stop mixing once the viscosity of the packing material meets the design standard. Step 5: Packaging; Place the filler into a suitable packaging container and seal it for storage.

[0016] Thirdly, the present invention provides a fin device for preventing water-cooled wall tube leakage caused by fin cracking in a coal-fired boiler, comprising a butterfly-shaped sealing shell plate welded to the boiler tube transition connection. The end face of the butterfly-shaped sealing shell plate away from the boiler tube is configured with an open structure. The butterfly-shaped sealing shell plate is provided with X-shaped grab studs inside. The butterfly-shaped sealing shell plate is coated with the aforementioned high-temperature resistant sealing filler. The high-temperature resistant sealing filler fills the butterfly-shaped sealing shell plate and also covers the boiler tube transition connection.

[0017] The present invention has the following beneficial effects: 1. This invention provides a high-temperature resistant sealing filler made from materials such as ceramic fiber, silica powder, alumina powder, kaolin, mica powder, and borate glass powder. This filler has the advantage of good heat insulation, which can isolate heat transfer and thus ensure the temperature stability of the coating location. Its raw materials are widely available and inexpensive, and the production process does not require the complex manufacturing process and high-precision equipment of T-shaped ceramic fins, resulting in low production costs. Before curing, this filler also has good plasticity, which can easily adapt to various irregular installation positions to form a seamless sealing layer, thus providing good sealing performance. This filler also has good flexibility, which can better withstand deformation and vibration, and is not prone to cracking, thus ensuring the stability of the sealing effect.

[0018] 2. This invention provides a finned device that incorporates a butterfly-shaped sealing shell plate within the boiler tube transition connection. High-temperature resistant sealing filler is applied to the butterfly-shaped sealing shell plate. This filler possesses excellent heat insulation properties, preventing heat transfer from the boiler tubes to the transition connection, thus preventing carbonization and cracking of the butterfly-shaped sealing shell plate at this location. Furthermore, the high-temperature resistant sealing filler exhibits good plasticity and flexibility, completely filling the transition connection area to effectively prevent media leakage. The high-temperature resistant sealing filler is not prone to leakage or cracking due to pipeline vibration. It also has a lower manufacturing cost, which can reduce the production cost of coal-fired power plants. The clamping nail 2 can evenly distribute external stresses such as thermal stress caused by thermal expansion and mechanical stress generated by boiler tube vibration when the butterfly-shaped sealing shell plate 1 and the high-temperature resistant sealing filler 3 are subjected to external stresses, such as thermal stress caused by thermal expansion and mechanical stress generated by boiler tube vibration. This can prevent leakage caused by stress concentration in boiler tubes. Compared with the existing technology, it has the advantages of good sealing performance, prevention of leakage caused by stress concentration in boiler tubes, reduction of production costs of coal-fired power plants, and stable sealing effect. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the fin device of the present invention in use.

[0020] The reference numerals in the figure are as follows: 1. Butterfly-shaped sealing shell plate; 2. Clamping nail; 3. High-temperature resistant sealing filler; 4. Boiler tubes. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] Example 1: Please refer to Figure 1This embodiment provides a fin device for preventing water-cooled wall tube leakage caused by fin cracking in a coal-fired boiler. It includes a welded butterfly-shaped sealing shell plate 1 in each transition connection of the boiler tube 4. The end face of the butterfly-shaped sealing shell plate 1 away from the boiler tube 4 is set with an open structure. Each butterfly-shaped sealing shell plate 1 is fixedly provided with an X-shaped grab nail 2. A specific high-temperature resistant sealing filler 3 is applied to the inside of the butterfly-shaped sealing shell plate 1. The high-temperature resistant sealing filler 3 fills the butterfly-shaped sealing shell plate 1 and also covers the transition connection of the boiler tube 4, so that it can form a plate-shaped sealing protective layer structure after curing, thereby achieving protection of the transition connection of the boiler tube 4. When the high-temperature resistant sealing filler 3 is applied inside the butterfly-shaped sealing shell plate 1, the grab pins 2 can be embedded into the high-temperature resistant sealing filler 3. This allows the high-temperature resistant sealing filler 3 and the butterfly-shaped sealing shell plate 1 to be bonded not only by the physical adsorption force of the filler itself, but also by the mechanical anchoring force provided by the grab pins 2. This greatly enhances the adhesion between the high-temperature resistant sealing filler 3 and the butterfly-shaped sealing shell plate 1. At the same time, the grab pins 2 can also evenly distribute external stresses such as thermal stress from thermal expansion and mechanical stress from boiler pipe vibration when the butterfly-shaped sealing shell plate 1 and the high-temperature resistant sealing filler 3 are subjected to external stresses, such as thermal stress from thermal expansion and mechanical stress from boiler pipe vibration, to ensure the integrity and stability of the subsequently formed plate-shaped sealing protective layer structure.

[0023] In this specific embodiment, during the overhaul of a coal-fired boiler, if the large fins at the transition connection of boiler tube 4 are found to be cracked due to high-temperature carbonization, the original large sealing fins are cut off, and their edges are rounded off. Then, a butterfly-shaped sealing shell plate 1 is spot-welded to the fin mounting area at the transition connection of boiler tube 4. Next, a retaining nail 2 is welded inside the butterfly-shaped sealing shell plate 1. Then, high-temperature resistant sealing filler 3 is applied to the butterfly-shaped sealing shell plate 1 until it is completely filled, and then applied again until the high-temperature resistant sealing filler 3 covers the transition connection of boiler tube 4. After the high-temperature resistant sealing filler 3 dries and solidifies, the resulting plate-like sealing protective layer structure ensures that dust and high-temperature flue gas inside the furnace do not leak out, and also prevents the problem of fins cracking due to heat from extending to the boiler tube 4.

[0024] In this embodiment, the high-temperature resistant sealing filler 3, by mass percentage, consists of the following components: 30% ceramic fiber, 25% silica powder, 20% alumina powder, 12% kaolin, 10% mica powder, 6% borate glass powder, and 10% additives, with the total of the above components being 100%. The addition of ceramic fiber provides high-temperature resistance and flexibility to withstand high-temperature thermal stress and fill voids. The addition of silica powder enhances density and strength. The addition of alumina powder improves hardness and high-temperature resistance, thereby enhancing chemical stability. The addition of mica powder improves insulation and high-temperature resistance. Borate glass powder can form a glassy phase at high temperatures, thereby enhancing sealing and adhesion.

[0025] In this embodiment, the additive, by mass percentage, comprises the following components: 4% binder, 3% lubricant, 1.5% antioxidant, and 1.5% coupling agent. The addition of the binder enhances the adhesion between components; the binder can be silica sol. The addition of the lubricant improves its processing performance and prevents clumping in the equipment during subsequent processing; the lubricant can be stearic acid. The addition of the antioxidant prevents high-temperature oxidation; the antioxidant can be 2,6-di-tert-butyl-p-cresol. The addition of the coupling agent enhances the binding force between inorganic and organic components; the coupling agent can be a silane coupling agent.

[0026] In this embodiment, high-alumina ceramic fibers are selected, with an alumina content of not less than 55%, a fiber diameter of 3–8 μm, and a length of 10–50 mm. The specific alumina content allows the high-temperature resistant sealing filler 3 to withstand higher temperatures, preventing deformation, melting, or decomposition under high-temperature conditions. This ensures the performance and reliability of the high-temperature resistant sealing filler 3 under extreme high-temperature conditions. The specific fiber diameter and length range allows the ceramic fibers to form a good interwoven structure within the high-temperature resistant sealing filler 3, thereby enhancing its mechanical strength and toughness. In this embodiment, the specific surface area of ​​the silica powder is 15–25 m² / g, the average particle size is 0.5–1.5 μm, and the silica content in the chemical composition is not less than 98%. The specific surface area and average particle size allow for better filling of the voids in other raw materials, resulting in a denser structure for the high-temperature resistant sealing filler 3. This improves the sealing performance and overall strength of the high-temperature resistant sealing filler 3. The specific silica content also enables the high-temperature resistant sealing filler 3 to resist the erosion of various chemical substances, thereby maintaining stable performance.

[0027] In this embodiment, the alumina powder is selected as α-alumina powder with a purity of not less than 99% and an average particle size of 1-5 μm. α-alumina has high hardness, and α-alumina powder with a purity of not less than 99% can significantly improve the hardness and wear resistance of the high-temperature resistant sealing filler 3. Furthermore, α-alumina powder with a specific particle size can have good activity during the sintering process, thereby promoting the sintering reaction of the high-temperature resistant sealing filler 3 and enabling the high-temperature resistant sealing filler 3 to have higher density and strength after sintering.

[0028] In this embodiment, the kaolin is a water-washed kaolin with a flaky crystalline structure, a flake diameter-to-thickness ratio of not less than 10:1, a particle size of 325-500 mesh, and a silica content of 45%-55%, an alumina content of 35%-45%, and a loss on ignition of 12%-15%. The flaky structure and specific flake diameter and thickness can increase the resistance to gas and liquid permeation, thereby improving the sealing performance of the high-temperature resistant sealing filler 3. The specific particle size setting ensures that the kaolin can not only be uniformly dispersed in the high-temperature resistant sealing filler 3, but also be fully mixed with other raw materials. The specific silica content, alumina content, and loss on ignition ensure the stability of the kaolin's performance during high-temperature sintering.

[0029] In this embodiment, the mica powder is muscovite powder with a Mohs hardness of 2-3, an aspect ratio of 30-50, a particle size of 200-400 mesh, and a chemical composition containing 45%-50% silica, 30%-35% alumina, 9%-11% potassium oxide, and no more than 0.5% iron oxide. The specific Mohs hardness prevents the muscovite powder from causing excessive wear on equipment during processing and allows for better mixing with other raw materials. The specific aspect ratio and particle size enable the mica powder to form a good lamellar overlap structure in the high-temperature resistant sealing filler 3, thereby improving the barrier properties, strength, and toughness of the high-temperature resistant sealing filler 3. The specific silica, alumina, potassium oxide, and iron oxide contents endow the muscovite powder with good high-temperature resistance, insulation, and chemical stability.

[0030] In this embodiment, the borate glass powder has a softening temperature of 500–600°C, a particle size of 10–50 μm, a boron trioxide content of 30%–40%, a silicon dioxide content of 20%–30%, an alkali metal oxide content of 10%–20%, and a coefficient of thermal expansion of (6–10) × 10⁻⁶. -6 / ℃. A specific softening temperature allows the glass powder to soften when it reaches the corresponding temperature during boiler operation, thereby filling the tiny pores in the high-temperature resistant sealing filler 3 and further improving the sealing performance. Specific particle size, boron trioxide content, silicon dioxide content, and alkali metal oxides can give the glass powder good adhesion, which helps it to form a stable sealing structure with other components at high temperatures. Specific thermal expansion coefficient can reduce the internal stress caused by the difference in thermal expansion during temperature changes and prevent the high-temperature resistant sealing filler 3 from cracking, falling off, etc.

[0031] In this embodiment, the preparation method of the above-mentioned high-temperature resistant sealing filler includes the following steps: Step 1: Raw material preparation; accurately weigh each raw material according to the formula. A high-precision electronic scale can be used to ensure that the weighing error is controlled within ±0.05%. The process should be carried out in a normal temperature (20~25℃) and normal humidity (40%~60%) environment.

[0032] Step 2: Premixing; ceramic fiber, silica powder, alumina powder, kaolin, and mica powder are placed in a mixer for preliminary mixing. The mixing speed is 1000-1200 r / min, the mixing time is 10-15 min, and the mixing temperature is 20-25℃.

[0033] Step 3: Additive treatment and mixing; add the binder directly to the mixer; heat the lubricant to 75-85℃ to completely melt it, and then slowly add it to the mixer through the pipeline; prepare the antioxidant and coupling agent into 12%-15% solutions with anhydrous ethanol and add them to the mixer, continue to stir and mix at a speed of 800-1000 r / min for 20-25 min, and control the stirring temperature at 30-40℃.

[0034] Step 4: Viscosity adjustment; Use a viscometer to test the viscosity of the filler in the mixer, set the filler viscosity to 7000~12000mPa·s (25℃), and stop stirring after the filler viscosity meets the design standard.

[0035] Step 5: Packaging; The filler is placed into a suitable packaging container and sealed for storage for later use.

[0036] Example 2: Please refer to Figure 1 This embodiment provides a fin device for preventing water-cooled wall tube leakage caused by fin cracking in coal-fired boilers. The difference between this embodiment and Embodiment 1 is that the composition of the high-temperature resistant sealing filler 3 is different. Specifically, in this embodiment, the high-temperature resistant sealing filler 3 is composed of the following components by mass percentage: 38% ceramic fiber, 15% silica powder, 12% alumina powder, 12% kaolin, 9% mica powder, 5% borate glass powder, and 9% additives. The total of the above components is 100%. In this embodiment, the additive consists of the following components by mass percentage: 4% binder, 3% lubricant, 1% antioxidant and 1% coupling agent.

[0037] Example 3: Please refer to Figure 1This embodiment provides a fin device for preventing water-cooled wall tube leakage caused by fin cracking in coal-fired boilers. The difference between this embodiment and Embodiment 1 is that the composition of the high-temperature resistant sealing filler 3 is different. Specifically, in this embodiment, the high-temperature resistant sealing filler 3 is composed of the following components by mass percentage: 40% ceramic fiber, 20% silica powder, 20% alumina powder, 8% kaolin, 5% mica powder, 3% borate glass powder, and 4% additives. The total of the above components is 100%. In this embodiment, the additive consists of the following components by mass percentage: 2% binder, 1% lubricant, 0.5% antioxidant and 0.5% coupling agent.

[0038] Example 4: This example compares the above Examples 1, 2, and 3 with common ceramic fins used for heat insulation. Please see Table 1 below for details.

[0039] Table 1

[0040] Based on the table above, it can be seen that the fin devices provided in Examples 1, 2, and 3, while ensuring that the temperature resistance is similar to that of ceramic fins, have the advantages of low manufacturing cost, consistent chemical stability, good sealing performance, good flexibility, and low construction difficulty. Therefore, they are more suitable for use in a wide range of coal-fired power plants.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-temperature resistant sealing filler, characterized in that: It is composed of the following components by mass percentage: 30%–40% ceramic fiber, 15%–25% silica powder, 12%–20% alumina powder, 8%–12% kaolin, 5%–10% mica powder, 3%–6% borate glass powder, and 4%–10% additives, with the total of the above components being 100%.

2. The high-temperature resistant sealing filler according to claim 1, characterized in that: The additive, by weight percentage, consists of the following components: 2%–4% binder, 1%–3% lubricant, 0.5%–1.5% antioxidant, and 0.5%–1.5% coupling agent.

3. The high-temperature resistant sealing filler according to claim 1, characterized in that: The ceramic fiber is a high-alumina ceramic fiber with an alumina content of not less than 55%, a fiber diameter of 3-8 μm, and a length of 10-50 mm.

4. The high-temperature resistant sealing filler according to claim 1, characterized in that: The silicon micropowder has a specific surface area of ​​15-25 m² / g, an average particle size of 0.5-1.5 μm, and a silicon dioxide content of not less than 98% in its chemical composition.

5. The high-temperature resistant sealing filler according to claim 1, characterized in that: The alumina powder is α-alumina powder with a purity of not less than 99% and an average particle size of 1-5 μm.

6. The high-temperature resistant sealing filler according to claim 1, characterized in that: The kaolin is a water-washed kaolin with a flaky crystal structure, a flake diameter-to-thickness ratio of not less than 10:1, a particle size of 325-500 mesh, a silica content of 45%-55%, an alumina content of 35%-45%, and a loss on ignition of 12%-15%.

7. The high-temperature resistant sealing filler according to claim 1, characterized in that: The mica powder is muscovite powder with a Mohs hardness of 2-3, an aspect ratio of 30-50, a particle size of 200-400 mesh, and a chemical composition containing 45%-50% silicon dioxide, 30%-35% aluminum oxide, 9%-11% potassium oxide, and no more than 0.5% iron oxide.

8. The high-temperature resistant sealing filler according to claim 1, characterized in that: The borate glass powder has a softening temperature of 500–600℃, a particle size of 10–50 μm, a boron trioxide content of 30%–40%, a silicon dioxide content of 20%–30%, an alkali metal oxide content of 10%–20%, and a coefficient of thermal expansion of (6–10) × 10⁻⁶. -6 / ℃.

9. A method for preparing a high-temperature resistant sealing filler as described in any one of claims 1 to 8, characterized in that: Includes the following steps: Step A1: Raw material preparation; weigh each raw material according to the formula; Step A2: Premixing; ceramic fiber, silica powder, alumina powder, kaolin, and mica powder are placed in a mixer for preliminary mixing; Step A3: Additive treatment and mixing; silica sol is added directly to the mixer, stearic acid is heated until completely melted and then added to the mixer through a pipe, antioxidants and coupling agents are prepared into solutions with anhydrous ethanol and then added to the mixer, and then stirring and mixing are continued; Step A4: Viscosity adjustment; Use a viscometer to test the viscosity of the packing material in the mixer. Stop stirring and mixing once the viscosity of the packing material meets the design standard. Step A5: Packaging; Place the filler into a suitable packaging container and seal it for storage.

10. A finned device for preventing water-cooled wall tube leakage caused by fin cracking in coal-fired boilers, characterized in that: The butterfly sealing shell plate (1) is welded to the transition connection part of the boiler tube (4). The end face of the butterfly sealing shell plate (1) away from the boiler tube (4) is set with an open structure. The butterfly sealing shell plate (1) is provided with X-shaped grab nails (2) inside. The butterfly sealing shell plate (1) is coated with high temperature resistant sealing filler (3) as described in any one of claims 1 to 8. The high temperature resistant sealing filler (3) fills the butterfly sealing shell plate (1) and also covers the transition connection part of the boiler tube (4).

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