A downcomer and steam module industrial boiler for absorbing expansion
By introducing a combination of bent and straight pipes in the downcomer, combined with the design of the boiler steel frame and buffer components, the problem of weld cracking caused by downcomer expansion was solved, thus achieving stable boiler operation and extended component life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DATANG (JINHUA) CLEAN ENERGY CO LTD
- Filing Date
- 2025-06-23
- Publication Date
- 2026-05-29
AI Technical Summary
In existing large-scale steam modular industrial boilers, the thrust generated by the downcomer when it expands under heat directly acts on the weld joint, causing the weld joint to crack and affecting the stability of boiler operation.
The system employs a downcomer structure consisting of a first straight pipe, a second straight pipe, a first bend, and a second bend. The expansion displacement is absorbed by the elastic deformation of the bend, and the elastic deformation path is extended by the third straight pipe to disperse the expansion stress. Combined with the boiler steel frame and buffer design, it allows for slight displacement of the steam drum to release the expansion thrust.
This effectively avoids the expansion thrust acting directly on the weld joint, reduces the risk of weld joint cracking, extends the service life of the downcomer and related components, and ensures stable operation of the boiler under high temperature and high pressure.
Smart Images
Figure CN224302059U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of large-scale steam module industrial boilers, and in particular to a downcomer for absorbing expansion and a steam module industrial boiler. Background Technology
[0002] In large-scale industrial boilers with steam modules, the main function of the downcomer is to transport water from the top steam drum to the bottom water connection header, and then distribute it to the lower headers at the bottom of the furnace module and the bottom of the convection module to maintain normal water circulation in the boiler. In existing technology, the downcomer adopts a distributed straight pipe structure. The steam drum is fixed to the boiler body steel frame, and the water connection header is usually fixed to the ground. The two ends of the downcomer are rigidly connected to the steam drum and the water connection header, respectively. The water connecting pipes are welded and connect the water connection header, the lower header at the bottom of the furnace module, and the lower header at the bottom of the convection module.
[0003] However, as the downcomer expands during heating, the thrust generated by the expansion acts directly on the bottom water connection header. The water connection header is forced to release the thrust generated by the expansion through the weld, which intensifies the stress on the weld between the water connection pipe and the lower header, causing the weld to crack and seriously affecting the stability of boiler operation. Utility Model Content
[0004] In view of the shortcomings of the existing technology, one of the objectives of this utility model is to provide an industrial boiler with a downcomer and steam module for absorbing expansion.
[0005] First aspect:
[0006] This application provides a downcomer for absorbing expansion, which adopts the following technical solution:
[0007] A downcomer for absorbing expansion includes a first straight pipe, a second straight pipe, a first bend, and a second bend. One end of the first straight pipe is connected to a top water tank, and the other end is connected to the first bend. One end of the second bend is connected to the end of the first bend, and the other end is connected to the second straight pipe. The end of the second straight pipe away from the second bend is connected to a bottom water tank. The first bend and the second bend are used to absorb the displacement caused by the thermal expansion of the pipe body.
[0008] By adopting the above technical solution, when the boiler is running and the downcomer body expands due to heat, the elastic deformation of the first and second bends can effectively absorb the expansion displacement. This avoids the thrust generated by the expansion acting directly on the weld joint, reduces stress concentration at the weld joint, lowers the risk of weld cracking, and extends the service life of the downcomer and related components.
[0009] Preferably, it also includes a third straight pipe, the two ends of which are respectively connected to the first bend and the second bend.
[0010] By adopting the above technical solution, the setting of the third straight pipe extends the distance between the first bend and the second bend, forming a longer elastic deformation path, which enables the entire downcomer to adapt to a larger expansion displacement. When the pipe is heated and elongated, the third straight pipe can act as an independent buffer unit to undergo axial or radial deformation, working in conjunction with the first and second bends to disperse the expansion stress to a longer pipe section and avoid local stress concentration.
[0011] Preferably, the bending radius of the first bend and the second bend is at least four times the nominal diameter of the pipe.
[0012] By adopting the above technical solution, the larger bending radius of the first and second bends significantly reduces the curvature of the bends, allowing the pipe body to absorb expansion displacement through greater elastic bending when heated.
[0013] The second aspect:
[0014] This application provides a steam module industrial boiler, which adopts the following technical solution:
[0015] A steam modular industrial boiler, employing any of the aforementioned downcomers for absorbing expansion, further includes a boiler steel frame, a steam drum, a water connection header, a water connection pipe assembly, a riser assembly, a furnace module, and a convection module. The boiler steel frame is placed on the ground, the steam drum is located on top of the boiler steel frame, and the furnace module and convection module are fixedly installed inside the boiler steel frame. One end of the downcomer is connected to the steam drum, and the other end is connected to the water connection header. One end of the water connection pipe assembly is connected to the water connection header, and the other end is connected to both the convection module and the furnace module. One end of the riser assembly is connected to the steam drum, and the other end is connected to both the convection module and the furnace module.
[0016] By adopting the above technical solution, the boiler steel frame serves as the basic support structure, firmly supporting core components such as the steam drum, furnace module, and convection module, ensuring that each component maintains a precise installation position under high temperature and high pressure conditions. The steam drum delivers water to the water connection header through the downcomer, and then distributes it to the furnace module and convection module through the water connection pipe assembly. In the furnace module, the water absorbs the high heat of fuel combustion to complete partial vaporization, and in the convection module, it further absorbs waste heat to complete partial vaporization. The resulting steam-water mixture returns to the steam drum through the riser assembly for separation. The separated water mixes with the feedwater and continues to participate in the circulation.
[0017] Preferably, the boiler steel frame includes a support base plate for supporting the steam drum, a frame body, and two support seats. The support base plate is located at the bottom of the steam drum, and the two support seats are fixed to the top of the frame body and located at both ends of the support base plate. A hinge pin is provided on the outside of the support seat. The hinge pin passes through the support base plate and the support seat, so that the steam drum and the support base plate can rotate slightly about the hinge pin.
[0018] By adopting the above technical solution, the downcomer expands under heat and generates thrust, which acts directly on the steam drum. The hinged pin acts as a fulcrum for rotation, allowing slight displacement of the steam drum and releasing the expansion displacement of the downcomer caused by temperature changes, thus effectively protecting the weld joint.
[0019] Preferably, two buffer members are provided above the boiler steel frame, and the two buffer members are located below both ends of the support base plate. The buffer members are used to support the steam drum and the support base plate and to buffer small displacements.
[0020] By adopting the above technical solution, the elastic deformation characteristics of the buffer can effectively absorb the vertical displacement of the steam drum caused by thermal expansion. In coordination with the rotation of the hinge pin, the steam drum can make slight adjustments when it receives the thrust of the downcomer, thereby converting the thrust generated by expansion into the elastic deformation of the buffer.
[0021] Preferably, the furnace module includes a furnace, water-cooled wall tubes, a first lower manifold, and a first upper manifold. The water-cooled wall tubes are arranged inside the furnace. One end of the water-cooled wall tube is connected to the first lower manifold, and the other end is connected to the first upper manifold. The first lower manifold is connected to the water pipe assembly, and the first upper manifold is connected to the riser pipe assembly.
[0022] By adopting the above technical solution, the water-cooled wall tubes are arranged around the furnace walls to form a fully enclosed radiant heating surface, maximizing the absorption of high-temperature radiant heat generated by fuel combustion in the furnace. The connection design between the bottom of the water-cooled wall tubes and the first lower header, and the top of the water-cooled wall tubes and the first upper header, together with the bubble, downcomer, water connection pipe assembly and water connection header, constructs a steam-water circulation loop. The density difference between steam and water forms a natural circulation force, ensuring the continuous flow of the working fluid in the water-cooled wall tubes and avoiding abnormal operating conditions such as stagnation and backflow.
[0023] Preferably, the convection module includes a convection tube bundle, a second lower manifold, and a second upper manifold. One end of the convection tube bundle is connected to the second lower manifold, and the other end is connected to the second upper manifold. The second lower manifold is connected to the water connection pipe assembly, and the second upper manifold is connected to the riser pipe assembly.
[0024] By adopting the above technical solution, the convection tube bundle effectively absorbs the heat of the medium-temperature flue gas discharged from the furnace, causing the water inside the tube to partially evaporate after absorbing the heat. At the same time, the connection structure between the bottom end of the convection tube bundle and the second lower header, and the top end and the second upper header, together with the bubble, downcomer, water connection pipe assembly and water connection header, effectively utilizes the waste heat to vaporize the water.
[0025] In summary, this application includes at least one of the following beneficial technical effects:
[0026] 1. When the boiler is running and the downcomer body expands due to heat, the elastic deformation of the first and second bends can effectively absorb the expansion displacement. This avoids the thrust generated by the expansion acting directly on the weld joint, reduces stress concentration at the weld joint, lowers the risk of weld cracking, and extends the service life of the downcomer and related components.
[0027] 2. The setting of the third straight pipe extends the distance between the first bend and the second bend, forming a longer elastic deformation path, which enables the entire downcomer to adapt to a larger expansion displacement. When the pipe is heated and elongated, the third straight pipe can act as an independent buffer unit to undergo axial or radial deformation, working in conjunction with the first and second bends to disperse the expansion stress to a longer pipe section and avoid local stress concentration.
[0028] 3. A larger bending radius significantly reduces the curvature of the bend, making the pipe more flexible and allowing the pipe body to absorb expansion displacement through greater elastic bending when heated. Attached Figure Description
[0029] Figure 1 This embodiment of the application is a schematic diagram illustrating the structure of a downcomer used to absorb expansion;
[0030] Figure 2 This embodiment of the application is a schematic diagram illustrating the structure of a steam module industrial boiler;
[0031] Figure 3 This is a structural schematic diagram illustrating the supporting base plate, supporting seat, and buffer component in an embodiment of this application.
[0032] Reference numerals: 1. First straight pipe; 2. Second straight pipe; 3. First bend; 4. Second bend; 5. Third straight pipe; 6. Boiler steel frame; 61. Support base plate; 62. Support seat; 63. Frame body; 7. Steam drum; 8. Water connection header; 9. Water connection pipe assembly; 10. Riser pipe assembly; 11. Furnace module; 111. Furnace; 112. Water-cooled wall tube; 113. First lower header; 114. First upper header; 12. Convection module; 121. Convection tube bundle; 122. Second lower header; 123. Second upper header; 13. Hinge pin; 14. Buffer component. Detailed Implementation
[0033] The following is in conjunction with the appendix Figure 1 - Appendix Figure 3 This application will be described in further detail.
[0034] This application discloses a downcomer for absorbing expansion, with its two ends connected to two water tanks respectively. It is used to divert water from the top water tank to the bottom water tank and reduce the force on the two water tanks due to the expansion of the pipe when heated.
[0035] Reference Figure 1 A downcomer for absorbing expansion includes a first straight pipe 1, a second straight pipe 2, a first bend 3, and a second bend 4. One end of the first straight pipe 1 is connected to the top water tank, and the other end is connected to the first bend 3. One end of the second bend 4 is connected to the end of the first bend 3, and the other end is connected to the second straight pipe 2. The end of the second straight pipe 2 away from the second bend 4 is connected to the bottom water tank. The first bend 3 and the second bend 4 are used to absorb the displacement caused by the thermal expansion of the pipe body. This embodiment discloses a plurality of downcomers for absorbing expansion, evenly connected to the top and bottom water tanks. When the downcomer body expands due to heat during boiler operation, the first bend 3 and the second bend 4 undergo elastic deformation, absorbing the expansion displacement and preventing the thrust generated by the expansion from being directly transmitted to the weld joint.
[0036] Furthermore, the downcomer for absorbing expansion disclosed in this embodiment also includes a third straight pipe 5, with its two ends connected to the first bend 3 and the second bend 4, respectively. The third straight pipe 5 serves as a buffer section between the first bend 3 and the second bend 4, enabling the downcomer to accommodate a larger amount of expansion. This optimizes the situation where the first bend 3 and the second bend 4 are directly connected, and the resulting small gap prevents the downcomer from absorbing a significant amount of expansion displacement.
[0037] Preferably, the bending radius of the first bend 3 and the second bend 4 is at least four times the nominal diameter of the pipe. When the bending radius of the first bend 3 and the second bend 4 is less than four times the nominal diameter of the pipe, the curvature of the first bend 3 and the second bend 4 is large, the deformation during expansion is small, and they can only absorb a small amount of displacement. The remaining displacement is converted into weld thrust, which easily causes weld cracking. Moreover, the first bend 3 and the second bend 4 absorb excessive displacement multiple times, which easily leads to cracking of the first bend 3 and the second bend 4. When the bending radius of the first bend 3 and the second bend 4 is greater than four times the nominal diameter of the pipe, the curvature of the first bend 3 and the second bend 4 is small, and they can absorb more displacement through elastic bending.
[0038] This application also discloses a steam module industrial boiler.
[0039] Reference Figure 2A steam modular industrial boiler includes the aforementioned downcomer for absorbing expansion, and also includes a boiler steel frame 6, a steam drum 7, a water connection header 8, a water connection pipe assembly 9, a riser assembly 10, a furnace module 11, and a convection module 12. The boiler steel frame 6 is placed on the ground, the steam drum 7 is located on top of the boiler steel frame 6, the furnace module 11 and the convection module 12 are fixedly installed inside the boiler steel frame 6, the top end of the downcomer is connected to the bottom of the steam drum 7, and its bottom end is connected to the top of the water connection header 8, one end of the water connection pipe assembly 9 is connected to the water connection header 8, and the other end is connected to and welded to the convection module 12 and the furnace module 11 respectively, and one end of the riser assembly 10 is connected to the steam drum 7, and the other end is connected to the convection module 12 and the furnace module 11 respectively.
[0040] The treated softened water is pumped into the steam drum 7 and stored in the water space at the bottom of the steam drum 7. The water in the steam drum 7 flows downwards through the downcomer to the water connection header 8 under gravity. The water connection header 8 distributes the water evenly to the furnace module 11 and the convection module 12 via the water connection pipe assembly 9. Subsequently, the water absorbs heat generated inside the furnace module 11 and the convection module 12, and some of the water evaporates to form a steam-water mixture, which decreases in density and flows upwards back into the steam drum 7 through the riser assembly 10. Next, the steam-water mixture enters the steam drum 7 and is separated by the built-in separator. The steam accumulates at the top of the steam drum 7 and is transported to the superheater or used directly for industrial purposes via steam pipes. The separated water mixes with the feedwater and continues to participate in the circulation.
[0041] Furthermore, referring to Figure 3 The boiler steel frame 6 includes a support base plate 61 for supporting the steam drum 7, a frame body 63, and two support seats 62. The support base plate 61 is located at the bottom of the steam drum 7 and is used to support the steam drum 7. The two support seats 62 are fixed to the top of the frame body 63 and are located at both ends of the support base plate 61. A high-temperature resistant hinge pin 13 is provided on the outer side of the support seat 62. The high-temperature resistant hinge pin 13 is horizontally inserted through the support base plate 61 and the support seats 62 to form a hinge support, allowing the steam drum 7 and the support base plate 61 to rotate slightly around the high-temperature resistant hinge pin 13. Two buffer members 14 are provided above the boiler steel frame 6. Specifically, the buffer members 14 disclosed in this embodiment are high-temperature resistant springs. The two buffer members 14 are located below both ends of the support base plate 61, and both ends of the support base plate 61 are placed on the buffer members 14, which can support the steam drum 7 and the support base plate 61 and buffer small displacements. The downcomer expands under heat, generating thrust and vertical displacement, which is then applied to the steam drum 7. If the steam drum 7 and the downcomer are rigidly fixed, the thermal expansion of the downcomer will generate huge tensile or thrust forces on the connected steam drum 7 and water connection header 8, which can easily lead to weld cracking. The high-temperature resistant hinge pin 13 and buffer 14 release the thermal expansion displacement of the downcomer caused by temperature changes, preventing the force generated by the expansion from being transmitted to the weld.
[0042] Specifically, refer to Figure 2 The furnace module 11 includes a furnace 111, water-cooled wall tubes 112, a first lower header 113, and a first upper header 114. The water-cooled wall tubes 112 are arranged inside the walls surrounding the furnace 111. The bottom end of the water-cooled wall tubes 112 is connected to the first lower header 113, and the top end is connected to the first upper header 114. The first lower header 113 is welded to and connected to the water connection pipe assembly 9, and the first upper header 114 is connected to the riser pipe assembly 10. The water connection header 8 distributes water to the first lower header 113 through the water connection pipe assembly 9, and the water flows into the water-cooled wall tubes 112. The water in the water-cooled wall tubes 112 absorbs heat from the furnace 111, and part of it evaporates into a steam-water mixture that enters the first upper header 114 and is then sent to the steam drum 7 through the first riser pipe.
[0043] The convection module 12 includes a convection tube bundle 121, a second lower header 122, and a second upper header 123. The bottom end of the convection tube bundle 121 is connected to the second lower header 122, and the top end is connected to the second upper header 123. The second lower header 122 is welded to and connected to the water connecting pipe assembly 9, and the second upper header 123 is connected to the riser assembly 10. The water connecting header 8 distributes water to the second lower header 122 through the water connecting pipe assembly 9, and the water flows into the convection tube bundle 121. The convection tube bundle 121 absorbs the heat from the flue gas discharged from the furnace 111, causing part of the water in the tubes to evaporate into a steam-water mixture, which enters the second upper header 123 and then enters the steam drum 7 through the second riser.
[0044] The implementation principle of this application embodiment is as follows:
[0045] After the boiler starts up, the treated softened water is injected into the lower water space of the steam drum 7 by the feedwater pump. Then, under the action of gravity, it flows to the water connection header 8 through the evenly distributed downcomers at the bottom of the steam drum 7. At the same time, the downcomers are displaced due to thermal expansion. The bends absorb the expansion through elastic deformation, and the third straight pipe 5 further disperses the stress, preventing the expansion thrust from being directly transmitted to the weld between the water connection header 8 and the lower header, thereby preventing the weld from cracking.
[0046] Water is diverted from the water header 8 to the furnace module 11 and the convection module 12. In the furnace module 11, water enters the first lower header 113 via the water connector assembly 9, and then flows into the water-cooled wall pipes 112 surrounding the furnace 111 wall. After absorbing high-temperature radiant heat, some of the water vaporizes into a steam-water mixture, which returns to the steam drum 7 via the first upper header 114 and the riser assembly 10. In the convection module 12, water enters the convection tube bundle 121 via the second lower header 122, absorbs waste heat from the flue gas to form a steam-water mixture, and returns to the steam drum 7 via the second upper header 123 and the riser assembly 10.
[0047] After the steam-water mixture is separated by a built-in separator inside the steam drum 7, the steam is output from the top for industrial use, and the separated water is mixed with the makeup water to re-enter the circulation. To cope with thermal expansion, the bottom of the steam drum 7 is designed with a hinge pin 13 supporting the base plate 61 to release expansion displacement, and the buffers 14 at both ends effectively absorb vertical displacement.
[0048] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A downcomer for absorbing expansion, characterized in that, It includes a first straight pipe (1), a second straight pipe (2), a first bend (3), and a second bend (4). One end of the first straight pipe (1) is connected to the top water tank, and the other end is connected to the first bend (3). One end of the second bend (4) is connected to the end of the first bend (3), and the other end is connected to the second straight pipe (2). The end of the second straight pipe (2) away from the second bend (4) is connected to the bottom water tank. The first bend (3) and the second bend (4) are used to absorb the displacement caused by the thermal expansion of the pipe body.
2. A downcomer for absorbing expansion according to claim 1, characterized in that, It also includes a third straight pipe (5), the two ends of which are connected to the first bend (3) and the second bend (4), respectively.
3. A downcomer for absorbing expansion according to claim 1, characterized in that, The bending radius of the first bend (3) and the second bend (4) is at least four times the nominal diameter of the pipe.
4. A steam module industrial boiler, employing a downcomer for absorbing expansion as described in any one of claims 1-3, characterized in that, It also includes a boiler steel frame (6), a steam drum (7), a water connection header (8), a water connection pipe assembly (9), a riser assembly (10), a furnace module (11), and a convection module (12). The boiler steel frame (6) is placed on the ground, the steam drum (7) is located on top of the boiler steel frame (6), the furnace module (11) and the convection module (12) are fixedly installed inside the boiler steel frame (6), one end of the downcomer is connected to the steam drum (7), and the other end is connected to the water connection header (8). One end of the water connection pipe assembly (9) is connected to the water connection header (8), and the other end is connected to the convection module (12) and the furnace module (11) respectively. One end of the riser assembly (10) is connected to the steam drum (7), and the other end is connected to the convection module (12) and the furnace module (11) respectively.
5. A steam module industrial boiler according to claim 4, characterized in that, The boiler steel frame (6) includes a support base plate (61), a frame body (63), and two support seats (62) for supporting the steam drum (7). The support base plate (61) is located at the bottom of the steam drum (7). The two support seats (62) are fixed to the top of the frame body (63) and located at both ends of the support base plate (61). A hinge pin (13) is provided on the outside of the support seat (62). The hinge pin (13) passes through the support base plate (61) and the support seats (62), so that the steam drum (7) and the support base plate (61) can rotate slightly around the hinge pin (13).
6. A steam module industrial boiler according to claim 5, characterized in that, Two buffers (14) are provided above the boiler steel frame (6), and the two buffers (14) are located below both ends of the support base plate (61). The buffers (14) are used to support the steam drum (7) and the support base plate (61) and to buffer small displacements.
7. A steam module industrial boiler according to claim 4, characterized in that, The furnace module (11) includes a furnace (111), a water-cooled wall tube (112), a first lower header (113), and a first upper header (114). The water-cooled wall tube (112) is arranged inside the furnace (111). One end of the water-cooled wall tube (112) is connected to the first lower header (113), and the other end is connected to the first upper header (114). The first lower header (113) is connected to the water pipe assembly (9), and the first upper header (114) is connected to the riser assembly (10).
8. A steam module industrial boiler according to claim 4, characterized in that, The convection module (12) includes a convection tube bundle (121), a second lower manifold (122), and a second upper manifold (123). One end of the convection tube bundle (121) is connected to the second lower manifold (122), and the other end is connected to the second upper manifold (123). The second lower manifold (122) is connected to the water pipe assembly (9), and the second upper manifold (123) is connected to the riser assembly (10).