Fixing device for inner sleeve of waste heat boiler

Abstract

The invention relates to the technical field of waste heat boilers, in particular to a waste heat boiler inner sleeve fixing device which comprises a main pipeline and an inner sleeve. According to the device, a traditional positioning screw is replaced by an axial and circumferential composite positioning system (a positioning pull block and a rotary positioning mechanism), thermal expansion is allowed to be free, and the fatigue fracture risk is eliminated; the shaking of the inner sleeve is inhibited through a multi-stage radial limiting system (a plurality of circles of limiting screws); final mechanical protection is provided through an anti-failure safety system (a tail limiting block). The hole diameter of the connector of the desuperheater is increased to prevent jamming, a gap welding check block is arranged to optimize a flow field, and thermal stress is reduced. The problem of abnormal displacement of the inner sleeve caused by cold and heat alternation is systematically solved, and the safety and reliability of operation of the waste heat boiler are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of power plant boiler equipment technology, specifically to a device for fixing the inner sleeve of the superheater or reheater desuperheating pipe of a waste heat boiler, which is particularly suitable for fixing the inner sleeve to resist displacement and fatigue under conditions of large temperature and cold alternation. Background Technology

[0002] Waste heat boilers are key equipment in gas-fired combined cycle units, and their reheater and superheater systems are typically equipped with desuperheating devices to regulate steam temperature. The injection of desuperheating water subjectes the inner sleeve of the downstream pipe of the desuperheater to severe alternating thermal stress. Currently, the axial and radial positions of the inner sleeve are commonly fixed by welding positioning screws.

[0003] However, this fixing method has inherent drawbacks: the main pipe (usually high-chromium steel such as P91) and the inner sleeve (usually low-chromium steel such as 12Cr1MoV) are made of different materials, resulting in significant differences in their coefficients of linear expansion. During the unit's start-up and shutdown, and the cycle of desuperheating water activation and deactivation, the different amounts of thermal expansion cause the welded positioning screws to bear enormous alternating tensile and compressive stresses, making them highly susceptible to metal fatigue and breakage. Once the positioning screws break, the inner sleeve will axially shift under the scouring of steam, and may even jam the desuperheater nozzle, making normal disassembly and maintenance impossible and seriously threatening the safe and stable operation of the unit.

[0004] Although existing technologies employ other limiting blocks or support blocks, most of them do not systematically address the complex mechanical problems caused by material expansion differences, alternating hot and cold temperatures, and steam impacts. They lack a comprehensive fixing solution that can simultaneously allow free thermal expansion, effectively suppress vibration, and provide backup in case of failure. Summary of the Invention

[0005] Purpose of the invention: The primary purpose of this invention is to overcome the shortcomings of the prior art and provide a waste heat boiler inner sleeve fixing device that can effectively adapt to the different thermal expansion of the main pipe and the inner sleeve and eliminate the risk of fatigue fracture of the fixing parts.

[0006] Another objective of this invention is to provide a fixing device that can limit abnormal movement of the inner sleeve (axial displacement, radial jitter, circumferential rotation) in multiple dimensions and has a failure-proof safety mechanism.

[0007] Another objective of this invention is to provide an inner sleeve fixing scheme that facilitates maintenance and disassembly, and optimizes the internal flow field to reduce thermal stress.

[0008] Technical solution: A waste heat boiler inner sleeve fixing device, comprising: a main pipe and an inner sleeve coaxially disposed inside it, characterized in that the fixing device includes: The axial and circumferential composite positioning system includes a number of positioning pull blocks fixed to the outer wall of the inner sleeve and a rotary positioning mechanism that restricts the circumferential rotation of the inner sleeve. A thermal expansion gap is provided between the positioning pull blocks and the inner wall of the main pipe (1). A multi-stage radial limiting system includes a multi-turn limiting screw group spaced apart along the axial direction of the inner sleeve. Each turn of the limiting screw group includes multiple circumferentially distributed limiting screws. The limiting screws are installed on the main pipe and abut against the outer wall of the inner sleeve. The failure prevention system includes several tail limiting blocks disposed at the tail end of the inner sleeve, and a safety gap is provided between the tail limiting blocks and the inner wall of the main pipe or the fixed structure.

[0009] In a further embodiment, the inner sleeve has a flared section with an inner diameter larger than that of its standard section in the area where the corresponding desuperheater nozzle is inserted.

[0010] In a further embodiment, a flow field optimization structure is also included, wherein the flow field optimization structure is a gap welded block disposed on the air inlet side between the main pipe and the inner sleeve, the gap welded block being fixed by intermittent welding points and forming a flow gap for fluid to pass through.

[0011] In a further embodiment, the rotary positioning mechanism includes a positioning key fixed to the inner wall of the main pipe and a keyway disposed on the outer wall of the inner sleeve, wherein the positioning key and the keyway cooperate with each other.

[0012] In a further embodiment, the number of positioning pull blocks is 6 to 8 sets, and they are evenly distributed along the circumference of the inner sleeve.

[0013] In a further embodiment, the multi-stage radial limiting system has 5 to 7 sets of limiting screws, each set of limiting screws including 3 circumferentially evenly distributed limiting screws.

[0014] In a further embodiment, the number of tail limiting blocks is 6 to 8 sets, and they are welded to the outer wall of the tail of the inner sleeve.

[0015] In a further embodiment, the gap welding stop is an annular component that matches the shape of the main pipe and the inner sleeve, and is fixed by multiple intermittent welding points.

[0016] In a further embodiment, the gap welding block is composed of a plurality of independent sector blocks arranged at intervals along the circumference.

[0017] In a further embodiment, the main pipe is made of SA-335M P91 material, and the inner sleeve is made of 12Cr1MoV material.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. Fundamentally solve fatigue fracture: By eliminating the rigidly welded positioning screws and adopting positioning pull blocks that allow relative sliding, the alternating stress generated at the fixed point due to the different thermal expansion coefficients of the materials is completely eliminated, fundamentally solving the persistent problem of fatigue fracture of positioning components.

[0019] 2. Enhanced multidimensional stability: Through axial and circumferential composite positioning and multi-ring and multi-point radial limiting, a spatial stability constraint system is formed, which effectively suppresses the axial movement, radial vibration and circumferential rotation that may occur in the inner sleeve during operation, and improves the stability of equipment operation.

[0020] 3. High safety and reliability: The introduced failure protection system adds a safety barrier to the inner sleeve, which can avoid catastrophic consequences even if the main fixing structure fails in extreme cases, greatly improving the reliability of the equipment.

[0021] 4. Facilitates maintenance and repair: The enlarged desuperheater interface diameter design solves the practical problem of the inner sleeve shifting and jamming the nozzle, which leads to difficult maintenance and shortens downtime for maintenance.

[0022] 5. Active thermal stress control: By optimizing the flow field through gap welding baffles, the temperature difference between the inner and outer jacket pipes is actively reduced when the desuperheating water is put into use, thereby reducing the driving force that causes relative displacement from the source, which is a fundamental solution. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the present invention.

[0024] Figure 2 This is a cross-sectional view at point AA of the present invention.

[0025] Figure 3 This is a cross-sectional view of section BB of the present invention.

[0026] Figure 4 This is a cross-sectional view at the CC section of the present invention.

[0027] Figure 5 This is a detailed description of the present invention. Figure I Enlarged view of a specific area.

[0028] Figure 6 This is a detailed description of the present invention. Figure II Enlarged view of a specific area. Figure 7 This is the estimated expansion amount of the main pipeline in this invention.

[0029] Reference numerals: 1. Main pipe; 2. Inner sleeve; 3. Positioning pull block; 4. Rotary positioning mechanism; 41. Positioning key; 42. Keyway; 5. Limiting screw; 6. Tail limiting block; 7. Gap welding stop. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] A waste heat boiler inner sleeve fixing device includes: an inner sleeve comprising a main pipe and coaxially sleeved inside it, wherein the fixing structure of the inner sleeve includes: Axial and circumferential composite positioning system: This system replaces the traditional axial positioning screw and includes several positioning pull blocks distributed circumferentially along the inner sleeve and at least one set of rotary positioning mechanisms. The positioning pull blocks are fixed to the outer wall of the inner sleeve, with a thermal expansion gap between their outer sides and the inner wall of the main pipe, allowing relative displacement between the two in the radial and axial directions. The rotary positioning mechanism is fixedly connected to the inner wall of the main pipe and engages with a corresponding structure on the inner sleeve to restrict the circumferential rotation of the inner sleeve relative to the main pipe.

[0032] Multi-stage radial limiting system: This system includes a group of multiple limiting screws arranged at intervals along the axial direction of the inner sleeve. Each group of limiting screws includes multiple limiting screws evenly distributed circumferentially. These screws are screwed into threaded seats fixed on the main pipe and abut against the outer wall of the inner sleeve to constrain the radial position of the inner sleeve and suppress its vibration during operation.

[0033] Fail-safe system: This system is located at the tail end of the inner sleeve (downstream of the steam pipe) and includes several tail limit blocks. These limit blocks have a predetermined safety clearance between themselves and the inner wall of the main pipe or the structure fixed to it. When the main positioning system malfunctions and causes the inner sleeve to displace beyond its limit, the tail limit blocks will contact the main pipe, forming a final mechanical block to prevent the inner sleeve from completely detaching or causing more severe blockage.

[0034] Anti-interference structure for desuperheater interface: The inner diameter of the inner sleeve corresponding to the insertion position of the desuperheater nozzle is specially enlarged to form a flared section, ensuring that even if the inner sleeve undergoes slight displacement, it will not jam against the outer wall of the desuperheater nozzle, thus ensuring the normal assembly and disassembly of the desuperheater.

[0035] Flow field optimization and thermal stress relief structure: On the inlet side (upstream of steam) between the main pipe and the inner sleeve, the original closed spacer ring has been optimized into a gap-welded baffle. This baffle is connected to the main pipe and the inner sleeve through intermittent welds, forming several flow gaps. This increases the steam flow rate into the interlayer between the inner sleeve and the main pipe, thereby enabling faster balancing of the inner and outer pipe wall temperatures when desuperheating water is used, reducing the temperature difference and thermal expansion difference between them.

[0036] Example 1: like Figures 1 to 5 As shown, the waste heat boiler inner sleeve fixing device in this embodiment is mainly used for the reheater desuperheating pipeline. The main pipeline 1 is made of SA-335MP91, and the inner sleeve 2 is made of 12Cr1MoV. The inner sleeve 2 is fixed inside the main pipeline 1 by the following structure: Axial and circumferential composite positioning system: Eight sets of positioning pull blocks 3 are welded along the outer wall of the upstream section of the inner sleeve 2, and they are evenly distributed circumferentially. A 1.5mm thermal expansion gap 9 is maintained between the positioning pull blocks 3 and the inner wall of the main pipe 1. Near the center, a set of rotary positioning mechanisms 4 is installed, such as... Figure 3 As shown, the mechanism includes a positioning key 41 fixed to the inner wall of the main pipe 1 and a keyway 42 opened on the outer wall of the inner sleeve 2. The keyway 42 has a range of motion in the axial and radial directions, and only restricts circumferential rotation.

[0037] Multi-stage radial limiting system: Seven sets of limiting screws are arranged along the axial direction of the inner sleeve 2. Each set consists of three limiting screws 5 evenly distributed circumferentially. The limiting screws 5 are screwed into the threaded seats welded to the main pipe 1, and their spherical ends abut against the outer wall of the inner sleeve 2, thereby limiting the radial movement of the inner sleeve 2. A total of 21 screws greatly enhance the anti-vibration capability.

[0038] Fail-safe system: Eight tail limit blocks 6 are welded to the tail of the inner sleeve 2. A 10mm safety gap 10 is reserved between these limit blocks 6 and the inner wall of the main pipe 1. This gap is greater than the maximum thermal expansion displacement of the inner sleeve 2 under normal operating conditions and only functions in the event of failure of the main positioning.

[0039] Anti-interference structure for desuperheater interface: The inner diameter of the section on the inner sleeve 2 corresponding to the desuperheater nozzle is machined to be 5mm larger than the standard section to form a flared opening, ensuring that the nozzle can be freely inserted and removed.

[0040] Flow field optimization and thermal stress relief structure: At the steam inlet end, a baffle 7 is welded with gaps to replace the original closed baffle ring. The baffle body is connected to the main pipe 1 and the inner sleeve 2 through multiple intermittent welding points, forming a flow gap between adjacent welding points, allowing some of the main steam to enter the interlayer and improve heat exchange.

[0041] Example 2: The main difference between this embodiment and Embodiment 1 lies in the structure of the gap welding block.

[0042] like Figure 5As shown, in this embodiment, the gap welding block 7 is designed as an independent sector-shaped block, with multiple sector-shaped blocks arranged at circumferential intervals to form a ring-shaped blocking structure. Each sector-shaped block is fixed to the main pipe 1 and the inner sleeve 2 respectively through welding points on both sides. This structure creates a larger and more regular flow gap, further optimizing the steam flow path and resulting in better heat balance. This design is particularly suitable for applications with larger pipe diameters and higher requirements for uniform flow distribution.

[0043] Example 3: This embodiment mainly illustrates the application of the present invention in different piping systems. Its basic structure is the same as in Embodiment 1, but the structural parameters have been adaptively adjusted according to the actual situation of the superheater desuperheating pipe (main pipe size φ273×28.58): The number of positioning pull blocks 3 is reduced to 6 sets.

[0044] The number of turns of the limit screw group is reduced to 5 turns, with 3 screws per turn.

[0045] The number of tail limit blocks 6 is reduced to 6 sets.

[0046] The thermal expansion gap and safety gap 1 have been recalculated and set according to the specific thermal expansion of the superheater pipe.

[0047] This embodiment demonstrates that the core fixing concept and structural combination of the present invention can be flexibly scaled up and applied to boiler pipes of different sizes and operating conditions, and can exert its excellent effects of anti-displacement and anti-fatigue.

[0048] Example 4: This embodiment mainly illustrates the improvement direction of the present invention based on actual conditions: First, the positioning bolts were removed, and the inner sleeve was upgraded to 8 sets of positioning pull blocks + 2 sets of rotary positioning. This ensures free expansion between the inner sleeve and the main pipe under hot cooling conditions, while preventing the inner sleeve from rotating on its own, and further improving the strength of the positioning blocks.

[0049] The number of limit screws has been increased to 3 screws per turn, for a total of 21 screws in 7 turns. The axial limit has been increased from 4 turns to 7 turns, and the number of screws has been increased from 16 to 21, in order to reduce the vibration of the inner sleeve.

[0050] Eight sets of limit blocks are added at the tail of the inner sleeve as a last-line safety measure in case the positioning block fails or the inner sleeve breaks.

[0051] Increase the diameter of the inner sleeve at the desuperheater to prevent the inner sleeve from jamming the nozzle and affecting the disassembly and assembly of the desuperheater.

[0052] The air inlet spacer between the inner sleeve and the main pipe has been optimized into a gap-welded stop, increasing the air intake flow between them. This ensures an appropriate increase in the amount of desuperheating water used while reducing the temperature difference between the inner sleeve and the main pipe during desuperheating water operation and minimizing the metal expansion difference on both sides. See details below. Figures 1 to 5 .

[0053] thermal expansion Based on the pipeline's hot temperature of 560℃, the axial displacement of the inner sleeve is 41.70 mm, which is less than the axial displacement clearance of 50 mm. See details... Figure 7 .

[0054] As previously calculated, the main pipe is 560℃ in hot condition. After the desuperheating water is put into use (the inner sleeve is estimated to be 300℃), the radius deviation of the estimated expansion of the main pipe and the inner sleeve is 1.088mm (positive deviation), which is less than the reserved gap of 3mm. Furthermore, the positioning bolts of the inner sleeve fixing structure have been eliminated and replaced with positioning pull blocks, which eliminates the hidden danger of metal fatigue fracture of the inner sleeve fixing components and welds after the desuperheating water is put into use. Pipe replacement The inlet pipe of the lower header of the reheater section was replaced with an optimized version of the new pipe provided by Wuxi Huaguang Boiler, and the reinstallation and welding have been completed. Weld 1 and weld 2 were heat-treated according to the welding specifications after welding, and the weld hardness was retested and 100% UT / RT flaw detection was performed. The non-destructive testing has passed. Under normal unit operation, the reheat reducer valve is maintained at 19% opening, and the desuperheating water flow rate is maintained at 6.27 T / h. The superheat reducer valve operates once every 24 hours depending on the load, with a maximum opening of 18% and a maximum desuperheating water flow rate of 4.76 T / h. The reheat reducer valve is continuously in operation, while the superheat reducer valve is intermittently in operation, playing a major role in desuperheating the steam. The reheat and superheat reducer valves are basically kept closed, providing auxiliary desuperheating for the steam. Therefore, the inner sleeve of the reheat reducer main pipeline bears the most frequent alternating hot and cold stress, followed by the inner sleeve of the superheat reducer main pipeline, and the inner sleeves of the superheat and reheat reducer main pipelines bear the least.

[0055] The reheat main pipeline has a diameter of Φ558.8×22.23 and is made of SA-335MP91. The inner sleeve has a diameter of Φ495×10 and is made of 12Cr1MoV. The superheat main pipeline has a diameter of φ273×28.58 and is made of SA-335MP91. Therefore, the diameter of the reheat main pipeline is significantly larger than that of the superheat main pipeline. According to the thermal expansion calculation table, after the desuperheating water is put into use, the expansion and contraction of the inner sleeve of the reheat main pipeline under cold and hot conditions is significantly greater than that of the inner sleeve of the reheat main pipeline.

[0056] In summary, this invention systematically solves the problem of abnormal displacement of the inner sleeve of a waste heat boiler through an innovative combined fixing structure, and has extremely high engineering application value and promotion prospects.

[0057] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A waste heat boiler inner sleeve fixing device, comprising: The main pipe and the inner sleeve coaxially disposed therein, characterized in that the fixing device includes: The axial and circumferential composite positioning system includes a number of positioning pull blocks fixed to the outer wall of the inner sleeve and a rotary positioning mechanism that restricts the circumferential rotation of the inner sleeve. A thermal expansion gap is provided between the positioning pull blocks and the inner wall of the main pipe (1). A multi-stage radial limiting system includes a multi-turn limiting screw group spaced apart along the axial direction of the inner sleeve. Each turn of the limiting screw group includes multiple circumferentially distributed limiting screws. The limiting screws are installed on the main pipe and abut against the outer wall of the inner sleeve. The failure prevention system includes several tail limiting blocks disposed at the tail end of the inner sleeve, and a safety gap is provided between the tail limiting blocks and the inner wall of the main pipe or the fixed structure.

2. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, The inner sleeve has a flared section with an inner diameter larger than that of its standard section in the area where the corresponding desuperheater nozzle is inserted.

3. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, It also includes a flow field optimization structure, which is a gap welded block set on the air inlet side between the main pipe and the inner sleeve. The gap welded block is fixed by intermittent welding points and forms a flow gap for fluid to pass through.

4. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, The rotary positioning mechanism includes a positioning key fixed to the inner wall of the main pipe and a keyway provided on the outer wall of the inner sleeve, wherein the positioning key and the keyway cooperate with each other.

5. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, The number of positioning blocks is 6 to 8 sets, and they are evenly distributed along the circumference of the inner sleeve.

6. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, The multi-stage radial limiting system has 5 to 7 sets of limiting screws, each set of limiting screws including 3 circumferentially evenly distributed limiting screws.

7. The waste heat boiler inner sleeve fixing device according to claim 1, characterized in that, The number of tail limiting blocks is 6 to 8 sets, and they are welded to the outer wall of the tail of the inner sleeve.

8. The waste heat boiler inner sleeve fixing device according to claim 3, characterized in that, The gap welding stop is an annular component that matches the shape of the main pipe and the inner sleeve, and is fixed by multiple intermittent welding points.

9. The waste heat boiler inner sleeve fixing device according to claim 3, characterized in that, The gap welding stop is composed of multiple independent sector-shaped blocks arranged at intervals along the circumference.

10. The waste heat boiler inner sleeve fixing device according to any one of claims 1 to 9, characterized in that, The main pipe is made of SA-335M P91 material, and the inner sleeve is made of 12Cr1MoV material.

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