Tube panel and header anti-tension-crack structure

Abstract

The invention provides an anti-tension-crack structure for a tube panel and a header, and relates to the technical field of power station boilers. Comprising a plurality of heating surface tube panels and a header, and one end of each heating surface tube panel is inserted into a water cooling wall; the header is communicated with a plurality of pipe joints, and the other end of the heating surface pipe panel is connected with the pipe joints; the heating surface tube panel comprises a horizontal section and an inclined section, the horizontal section is inserted into the water cooling wall, and the inclined section is located outside the water cooling wall; one end of the inclined section is connected with the horizontal section, and the other end is connected with the pipe joint; the vertical distance between the end, close to the pipe joint, of the inclined section and the boiler center line is smaller than that between the end, close to the horizontal section, of the inclined section and the boiler center line. According to the invention, the heating surface tube panel is arranged in an offset manner, so that after the normal operation of the boiler, the inclined tensile stress concentration caused by the expansion difference between the heating surface tube panel and the pipe joint of the header can be effectively eliminated, the problem that the pipe joint of the header is easy to crack due to tension is effectively solved, and the safety and stability of the boiler are improved.

Description

Technical Field

[0001] This invention relates to the field of power plant boiler technology, and more specifically, to a structure for preventing the pipe screen and header from cracking. Background Technology

[0002] To improve the absorption capacity of renewable energy, coal-fired power units with good peak-shaving potential are playing a crucial role as the basic regulating energy source in the power grid. With the vigorous promotion and development of new energy sources, the proportion of new energy connected to the grid will continue to increase in the future, and the current peak-shaving load of thermal power units may not be able to meet the requirements of the future new power system. To address the increased volatility and uncertainty brought about by the increased proportion of renewable energy generation, future thermal power units will need to handle lower and more extreme peak-shaving loads. During frequent peak-shaving, due to large temperature changes, cracking can easily occur at the pipe joints of the high-temperature heating surface headers. The following explanation uses the heating surface of a tower furnace as an example.

[0003] like Figures 1-3 As shown, the heating surface tube panel 1 inside the ultra-supercritical tower boiler is arranged horizontally, passing through the water-cooled wall 4 and then connecting to the pipe joints 5 of the inlet header 2 and outlet header 3 outside the boiler. The heating surface tube panel 1 is rigidly sealed at the point where it passes through the water-cooled wall 4. The conventional design in the prior art is as follows: Figure 2 As shown, a single heating surface tube panel 1 is arranged horizontally in a straight line. The lateral pitch b of the heating surface tube panel 1 is equal to the lateral pitch a of the pipe joint 5 on the inlet header 2 or outlet header 3, and a and b are equal. The heating surface tube panel 1 expands freely into the furnace in the depth direction and expands synchronously with the water-cooled wall 4 in the width direction. The operating temperature of the water-cooled wall 4 is much lower than the operating temperatures of the inlet header 2 and the outlet header 3. For the heating surface of the high-temperature reheater of a high-efficiency ultra-supercritical boiler, the operating temperature of the outlet header 3 is about 620℃, and the operating temperature of the water-cooled wall 4 at the wall penetration is about 450-470℃. The deviation in unit expansion is large, and the pipe joint 5 of the outlet header 3 is easily cracked due to the large deviation in expansion between the water-cooled wall 4 and the outlet header 3 in the width direction of the furnace.

[0004] like Figure 2 As shown, the zero point of boiler expansion along the width direction is set at the boiler centerline. Details of the expansion amounts of the water-cooled wall 4 and the outlet header 3 along the furnace width direction are provided in [link to details]. Figure 4As shown, the heat-receiving tube screen 1 closest to the boiler centerline is the first piece, followed by the second piece, the third piece, and so on, until the heat-receiving tube screen 1 closest to the centerline of the left wall water-cooled wall is the Nth piece. The expansion deviation between the water-cooled wall 4 and the outlet header 3 corresponding to the first heat-receiving tube screen 1 is 0.2mm. The expansion deviation increases as the tube screen gets closer to the furnace side. The expansion deviation between the water-cooled wall 4 and the outlet header 3 corresponding to the Nth heat-receiving tube screen 1 reaches more than 15mm. Therefore, the pipe joint 5 of the outlet header 3 corresponding to the outermost heat-receiving tube screen 1 is easily cracked, reducing the safety and stability of the boiler. Summary of the Invention

[0005] The purpose of this invention is to provide a structure for preventing the pipe screen and header from cracking. By offsetting the heating surface pipe screen, it can effectively eliminate the concentration of tilting tensile stress between the pipe joints of the heating surface pipe screen and the header due to the expansion difference after the boiler is running normally. This effectively solves the problem of easy cracking of the pipe joints of the header and improves the safety and stability of the boiler.

[0006] The technical solution adopted in this invention is as follows:

[0007] This application provides a structure for preventing the cracking of a tube screen and a header, including a heated surface tube screen and a header. The heated surface tube screen is multiple and one end of it is inserted into the water-cooled wall. The header is connected to multiple pipe joints, and each pipe joint corresponds to a heated surface tube screen. The other end of the heated surface tube screen is connected to a pipe joint.

[0008] The heated surface tube panel includes a horizontal section and an inclined section. The horizontal section is inserted into the water-cooled wall, and the inclined section is located outside the water-cooled wall. One end of the inclined section is connected to the horizontal section, and the other end of the inclined section is connected to the pipe joint. The vertical distance from the end of the inclined section near the pipe joint to the center line of the boiler is less than the vertical distance from the end of the inclined section near the horizontal section to the center line of the boiler.

[0009] Furthermore, in some embodiments of the present invention, the vertical distance from the end of the inclined section of any heat-receiving tube screen near the pipe joint to the horizontal section of the heat-receiving tube screen is the offset ΔH, and the ΔH value corresponding to the heat-receiving tube screen that is closer to the boiler centerline is smaller.

[0010] Furthermore, in some embodiments of the present invention, the heating surface tube panels are numbered 1, 2, 3...N sequentially from the boiler centerline to the side wall water-cooled wall centerline. The formula for calculating the offset ΔH value corresponding to the Nth heating surface tube panel is as follows:

[0011] △H=0.5×(L2-L1);

[0012] in:

[0013] L1 is the thermal expansion along the width direction at the point where the Nth heated surface tube screen penetrates the water-cooled wall.

[0014] L2 represents the thermal expansion along the width direction at the pipe joint corresponding to the Nth heated surface tube panel.

[0015] Furthermore, in some embodiments of the present invention, the calculation formula for L1 is as follows:

[0016] L1=ɑ1×(N-0.5)×b×(T1-T0)mm;

[0017] The formula for calculating L2 is as follows:

[0018] L2=ɑ2×(N-0.5)×b×(T2-T0)mm;

[0019] in:

[0020] T1 (°C) is the operating temperature of the water-cooled wall, a1 (mm / mm.°C) is the linear expansion coefficient of the water-cooled wall, T2 (°C) is the operating temperature of the header, a2 (mm / mm.°C) is the linear expansion coefficient of the header, T0 (°C) is the ambient temperature, and b (mm) is the transverse pitch of the heated surface tube panel.

[0021] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0022] This application sets an inclined section, thus offsetting the heating surface tube panel towards the boiler centerline. The offset ΔH varies at different locations. After the boiler is in normal operation, the expansion at the pipe joints of the header is large, while the expansion at the connection between the heating surface tube panel and the water-cooled wall is small. Therefore, as the boiler continues to operate normally, the offset ΔH will continuously decrease, that is, the inclination angle of the inclined section gradually decreases. This can effectively eliminate the concentration of inclined tensile stress caused by the difference in expansion between the heating surface tube panel and the pipe joints of the header, thereby effectively solving the problem of easy cracking of the pipe joints of the header and improving the safety and stability of the boiler. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the tube panel and header in the existing technology;

[0025] Figure 2 for Figure 1 Top view in the middle;

[0026] Figure 3 for Figure 1The right view in the middle;

[0027] Figure 4 for Figure 2 A graph showing the expansion amount along the width of the furnace.

[0028] Figure 5 This is a structural schematic diagram provided for an embodiment of the present invention.

[0029] Icons: 1-Heated surface tube panel; 11-Horizontal section; 12-Inclined section; 2-Inlet header; 3-Outlet header; 4-Water-cooled wall; 5-Pipe fitting; 6-Header. Detailed Implementation

[0030] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0031] Example

[0032] Please refer to Figure 5 This embodiment provides a structure for preventing the tearing of a tube screen and header, including a heating surface tube screen 1 and a header 6. Multiple heating surface tube screens 1 are included, with one end inserted into a water-cooled wall 4. The header 6 is connected to multiple pipe joints 5, each corresponding to a heating surface tube screen 1. The other end of each heating surface tube screen 1 is connected to a pipe joint 5. Each heating surface tube screen 1 includes a horizontal section 11 and an inclined section 12. The horizontal section 11 is inserted into the water-cooled wall 4, and the inclined section 12 is located outside the water-cooled wall 4. One end of the inclined section 12 is connected to the horizontal section 11, and the other end is connected to a pipe joint 5. The vertical distance from the end of the inclined section 12 closest to a pipe joint 5 to the boiler centerline is less than the vertical distance from the end of the inclined section 12 closest to the horizontal section 11 to the boiler centerline. The vertical distance from the end of the inclined section 12 of any heating surface tube screen 1 closest to a pipe joint 5 to the horizontal section 11 of that heating surface tube screen 1 is the offset ΔH. The closer the heating surface tube screen 1 is to the boiler centerline, the smaller the corresponding ΔH value. The heating surface tube panels 1 are numbered sequentially from the boiler centerline towards the side wall water-cooled wall centerline as 1, 2, 3...N. The formula for calculating the offset ΔH value corresponding to the Nth heating surface tube panel 1 is as follows:

[0033] △H=0.5×(L2-L1);

[0034] in:

[0035] L1 is the thermal expansion along the width direction at the point where the Nth heated surface tube screen 1 penetrates the water-cooled wall;

[0036] L2 represents the thermal expansion along the width direction at the pipe joint 5 corresponding to the Nth heated surface tube screen 1.

[0037] like Figure 5 As shown, in some implementations, the formula for calculating L1 is as follows:

[0038] L1=ɑ1×(N-0.5)×b×(T1-T0)mm;

[0039] The formula for calculating L2 is as follows:

[0040] L2=ɑ2×(N-0.5)×b×(T2-T0)mm;

[0041] in:

[0042] T1 (°C) is the operating temperature of the water-cooled wall, a1 (mm / mm.°C) is the linear expansion coefficient of the water-cooled wall, T2 (°C) is the operating temperature of the header, a2 (mm / mm.°C) is the linear expansion coefficient of the header, T0 (°C) is the ambient temperature, and b (mm) is the transverse pitch of the heated surface tube panel.

[0043] This application, by setting an inclined section 12, offsets the heating surface tube panel 1 towards the boiler centerline. Furthermore, the offset ΔH varies at different locations of the heating surface tube panel 1. Thus, after the boiler begins normal operation, the expansion at the pipe joint 5 of the header 6 is large, while the expansion at the connection between the heating surface tube panel 1 and the water-cooled wall 4 is small. Therefore, as the boiler continues to operate normally, the offset ΔH will continuously decrease, meaning the inclination angle of the inclined section 12 will gradually decrease. This effectively eliminates the concentrated tensile stress caused by the difference in expansion between the heating surface tube panel 1 and the pipe joint 5 of the header 6, thereby effectively solving the problem of easy cracking of the pipe joint 5 of the header 6 and improving the safety and stability of the boiler. It should be noted that the anti-crack structure for the tube panel and header provided in this application is applicable to both the inlet header and the outlet header.

[0044] Furthermore, unless otherwise explicitly specified or limited, the terms "installation" and "connection" in this application embodiment should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. The terms "upper," "lower," "left," "right," "inner," "outer," and "side," etc., are merely for reference to the direction in the accompanying drawings or the usual placement of the product during use. They are only for clearly describing this application and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limitations on this application. The terms "first," "second," etc., are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance; "multiple" refers to at least two. In this application embodiment, the limitations on relative positional relationships such as parallel, perpendicular, and aligned are all relative to the current technological level and are not absolutely strict limitations. Slight deviations are allowed; approximations of parallel, perpendicular, and aligned are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 degrees and 10 degrees.

[0045] The above are only some embodiments and implementation methods of this application. The protection scope of this application is not limited thereto. In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. Any combination of features in different embodiments is also within the protection scope of this application. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A structure for preventing the cracking of a tube screen and header, comprising a heated surface tube screen (1) and a header (6), wherein the heated surface tube screen (1) is multiple and one end of each is inserted into a water-cooled wall (4); the header (6) is connected to multiple pipe joints (5), each pipe joint (5) corresponding one-to-one with a heated surface tube screen (1), and the other end of each heated surface tube screen (1) is connected to a pipe joint (5); characterized in that: The heated surface tube panel (1) includes a horizontal section (11) and an inclined section (12). The horizontal section (11) is inserted into the water-cooled wall (4), and the inclined section (12) is located outside the water-cooled wall (4). One end of the inclined section (12) is connected to the horizontal section (11), and the other end of the inclined section (12) is connected to the pipe joint (5). The vertical distance from the end of the inclined section (12) near the pipe joint (5) to the center line of the boiler is less than the vertical distance from the end of the inclined section (12) near the horizontal section (11) to the center line of the boiler.

2. The anti-tear-crack structure for pipe screens and headers according to claim 1, characterized in that, The vertical distance from the inclined section (12) of any of the heating surface tube screens (1) near the pipe joint (5) to the horizontal section (11) of the heating surface tube screen (1) is the offset ΔH. The closer the heating surface tube screen (1) is to the center line of the boiler, the smaller the corresponding ΔH value.

3. The anti-tear-crack structure for pipe screens and headers according to claim 2, characterized in that, The heating surface tube panels (1) are numbered sequentially from the boiler centerline to the side wall water-cooled wall centerline as 1, 2, 3...N. The formula for calculating the offset ΔH value corresponding to the Nth heating surface tube panel (1) is as follows: △H=0.5×(L2-L1); in: L1 is the thermal expansion along the width direction of the Nth heated surface tube screen (1) at the point where it penetrates the water-cooled wall; L2 is the thermal expansion along the width direction at the pipe joint (5) corresponding to the Nth heated surface tube screen (1).

4. The anti-tear-crack structure for pipe screens and headers according to claim 3, characterized in that, The formula for calculating L1 is as follows: L1=ɑ1×(N-0.5)×b×(T1-T0)mm; The formula for calculating L2 is as follows: L2=ɑ2×(N-0.5)×b×(T2-T0)mm; in: T1 (°C) is the operating temperature of the water-cooled wall, α1 (mm / mm.°C) is the linear expansion coefficient of the water-cooled wall, T2 (°C) is the operating temperature of the header, α2 (mm / mm.°C) is the linear expansion coefficient of the header, T0 (°C) is the ambient temperature, and b (mm) is the transverse pitch of the heated surface tube panel.

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