A platen superheater system

Abstract

The present invention discloses a platen superheater system, including an inlet header, a plurality of U-shaped tube panels and an outlet header; the inlet header and the outlet header both include a large header and a plurality of small headers installed on the large header; the plurality of U-shaped tube panels are arranged along the furnace width direction of the boiler, each U-shaped tube panel includes a front row of tube panels and a rear row of tube panels arranged in parallel along the furnace depth direction of the boiler, and the front row of tube panels and the rear row of tube panels of each U-shaped tube panel are respectively connected to the same inlet small header and the same outlet small header; the inlet header and the outlet header are arranged in the upper and lower parts in the height direction, and the inlet large header and the outlet large header are arranged on the same side of the U-shaped tube panel. The present invention optimizes the layout position of the existing platen superheater large header, optimizes the flow direction of the working medium in the inlet and outlet small headers, makes the pressure difference deviation of each tube of the front and rear rows of tube panels in the inlet and outlet small headers smaller, and makes the working medium flow more uniform, so as to achieve the purpose of reducing the large systematic deviation of the outlet wall temperature on the working medium side.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler design, and more particularly to a platen superheater system capable of reducing wall temperature deviation and preventing wall temperature overheating. Background Art

[0002] The thermal deviation of the boiler heating surface mainly depends on the uneven coefficient of heat load, structure and flow rate of the heating surface. The existing supercritical pulverized coal boiler's screen superheater is arranged above the furnace, with multiple screens along the furnace width and one screen along the furnace depth, including front and rear rows of tube screens. The tube screen tubes are arranged in parallel in a U-shape. The inlet and outlet headers of the screen superheater include large and small headers, respectively, in a comb-shaped structure. The large header is parallel to the front and rear walls of the boiler, and the small header is vertically installed on the large header. The inlet and outlet headers are arranged up and down in the height direction. The early inlet and outlet large headers were located along the furnace depth direction, one in the front direction of the U-shaped tube screen furnace, and the other in the back direction of the U-shaped tube screen furnace. The U-shaped tube screen was in the middle, as shown below. Figure 1 shown.

[0003] Working fluid flow: large inlet header, small inlet header, U-shaped tube screen, small outlet header, large outlet header, that is, the working fluid flow direction relative to the inlet and outlet small headers is "Z" shaped. After actual measurement of the working fluid outlet wall temperature of the screen superheater (approximately representing the working fluid temperature), it was found that for the screen superheater arranged in this way, there is a systematic deviation of about 20°C in the working fluid outlet wall temperature values ​​of the front and rear rows of tube screens.

[0004] After analysis, the main reasons are: affected by the flow direction and flow rate of the working fluid in the small manifold, the static pressure distribution in the inlet and outlet small manifolds is different, which makes the pressure difference deviation of the front and rear tube panels corresponding to the inlet and outlet small manifolds large. The pressure difference between the inlet and outlet small manifolds of the front tube panel is large, and the pressure difference between the inlet and outlet small manifolds of the rear tube panel is small, resulting in low working fluid flow rate of the rear tube panel, large flow unevenness coefficient, and large wall temperature deviation. Summary of the invention

[0005] In view of the problem that in the prior art screen superheater system, the pressure difference deviation between the front and rear inlet and outlet small headers of a single tube of the tube panel is large, resulting in a large deviation in the working fluid flow rate, and there is a systematic deviation of about 20°C in the outlet wall temperature of the working fluid of the front and rear tube panels, which easily causes the screen superheater tube wall temperature to overheat during operation (especially under medium and low loads and deep peak-shaving conditions), the present invention proposes a screen superheater system which optimizes the layout position of the existing screen superheater large header and optimizes the flow direction of the working fluid in the inlet and outlet small headers to reduce the wall temperature deviation and prevent the wall temperature from overheating.

[0006] The present invention provides a platen superheater system, comprising an inlet header, a plurality of U-shaped tube panels and an outlet header;

[0007] The inlet header and the outlet header both include a large header and several small headers installed on the large header;

[0008] A plurality of U-shaped tube panels are arranged along the furnace width direction of the boiler, each U-shaped tube panel comprises a front row of tube panels and a rear row of tube panels arranged in parallel along the furnace depth direction of the boiler, and the front row of tube panels and the rear row of tube panels of each U-shaped tube panel are respectively connected to the same inlet small header and the same outlet small header;

[0009] The inlet header and the outlet header are arranged in upper and lower parts in the height direction, and the inlet large header and the outlet large header are arranged on the same side of the U-shaped tube panel.

[0010] According to one embodiment of the platen superheater system of the present invention, the platen superheater system is arranged above the boiler furnace, and the boiler is a counter-firing pulverized coal boiler with burners arranged on the front and rear walls of the furnace under subcritical parameters or supercritical parameters, a tangential-circle-firing pulverized coal boiler with burners arranged on the corners and furnace walls of the furnace under subcritical parameters or supercritical parameters, or a "W" flame-firing pulverized coal boiler with burners arranged on the furnace arches on the front and rear walls of the furnace under subcritical parameters or supercritical parameters.

[0011] According to an embodiment of the platen superheater system of the present invention, the inlet header and the outlet header are both comb-shaped structures, the large header is horizontally arranged parallel to the front wall or rear wall of the boiler, and the small header is horizontally arranged parallel to the side wall of the boiler and vertically installed on the large header.

[0012] According to an embodiment of the platen superheater system of the present invention, the U-shaped tube panel is vertically arranged parallel to the boiler side wall, and the front tube panel and the rear tube panel of the U-shaped tube panel each include a plurality of U-shaped tubes which are arranged in parallel and whose two ends are respectively connected to the inlet small header and the outlet small header, wherein the flow direction of the working medium in the U-shaped tube panel relative to the flow direction of the flue gas is arranged as follows: the front tube panel is in the forward flow, and the rear tube panel is in the reverse flow.

[0013] According to an embodiment of the platen superheater system of the present invention, the inlet header and the outlet header are arranged in upper and lower parts in the height direction, with the inlet header on top and the outlet header on bottom or the inlet header on bottom and the outlet header on top.

[0014] According to an embodiment of the platen superheater system of the present invention, the inlet large header and the outlet large header are arranged on the same side of the U-shaped tube panel, that is, both are arranged on the furnace front side or furnace rear side of the U-shaped tube panel.

[0015] According to an embodiment of the platen superheater system of the present invention, the working medium flow of the platen superheater system is as follows: an inlet large header, an inlet small header, a U-shaped tube screen, an outlet small header and an outlet large header, wherein the flow direction of the working medium relative to the inlet small header and the outlet small header is horizontally U-shaped.

[0016] According to an embodiment of the platen superheater system of the present invention, throttling hole structures with various diameters are arranged at the opening positions corresponding to the U-shaped tube panels on the inlet small header to finely adjust the working medium flow between the front tube panel and the rear tube panel in the U-shaped tube panel and between different U-shaped tubes in the same tube panel.

[0017] According to an embodiment of the platen superheater system of the present invention, 7 to 30 U-shaped tube panels are arranged along the furnace width direction of the boiler, and the number of U-shaped tubes in the front row and the rear row of tube panels in each U-shaped tube panel is 10 to 30 respectively.

[0018] According to an embodiment of the platen superheater system of the present invention, the tube panel lengths of the plurality of U-shaped tube panels arranged along the furnace width direction of the boiler are the same or different, the length of the front row of tube panels and the length of the rear row of tube panels in each U-shaped tube panel are the same or different, and the length, material, diameter and wall thickness of the U-shaped tubes in the front row of tube panels or the rear row of tube panels are set to be the same or different.

[0019] Compared with conventional solutions, the platen superheater system of the present invention optimizes the layout position of the existing platen superheater large header and optimizes the flow direction of the working fluid in the inlet and outlet small headers, so that the pressure difference deviation of each tube of the front and rear rows of tube panels in the inlet and outlet small headers is smaller and the working fluid flow rate is more uniform, thereby achieving the purpose of reducing the large systematic deviation of the outlet wall temperature on the working fluid side, thereby better preventing the wall temperature of the heating surface of the platen superheater from overheating, ensuring the safe operation of the heating surface, extending the service life, and ensuring that the operating parameters (steam temperature) meet the design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure shows a schematic diagram of the arrangement structure of a screen superheater system in the prior art.

[0021] Figure 2 The schematic diagram of the application structure of the platen superheater system in the present invention is shown.

[0022] Figure 3A and Figure 3B Two arrangements of the inlet header and the outlet header in a platen superheater system according to an exemplary embodiment of the present invention are respectively shown.

[0023] Figure 4A The main structure and working medium flow diagram of the platen superheater system according to the exemplary embodiment of the present invention are shown. Figure 4B It shows a schematic diagram of the left view structure and working medium flow direction of a platen superheater system according to an exemplary embodiment of the present invention. Figure 4C A schematic diagram showing the top view of the structure and working medium flow direction of a platen superheater system according to an exemplary embodiment of the present invention is shown.

[0024] Description of reference numerals:

[0025] 1-inlet large header, 2-inlet small header, 3-front row tube screen, 4-rear row tube screen, 5-outlet small header, 6-outlet large header, 7-burner, 8-furnace, 9-screen superheater system, 10-high temperature superheater, 11-low temperature superheater. DETAILED DESCRIPTION

[0026] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0027] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0028] The principle and structure of the platen superheater system of the present invention are first described in detail below.

[0029] The present invention will Figure 1 The outlet wall temperature data of the heating surface of the screen superheater in the prior art shown in the figure are tested, and the heat load unevenness coefficient, structural unevenness coefficient and flow unevenness coefficient that cause the thermal deviation of the heating surface wall of the boiler are comprehensively analyzed. When the heat load unevenness coefficient and structural unevenness coefficient of the front and rear rows of tube screens are not much different, the static distribution in the inlet and outlet small headers of the front and rear rows of tube screens is analyzed, and the pressure difference of each tube of the same screen tube is analyzed. The flow unevenness coefficient of the same screen tube can be calculated. By optimizing the layout position of the large header in the existing screen superheater and optimizing the flow direction of the working medium in the small header, the uniformity coefficient of the flow rate of the same screen tube can be calculated. Figure 1 The original arrangement in which the inlet and outlet large headers are arranged on the front side and the rear side of the U-shaped tube panel respectively and the U-shaped tube panel is arranged in the middle is optimized to an arrangement in which the inlet and outlet large headers are arranged on the same side of the "U"-shaped tube panel (including the front side or the rear side of the furnace), thereby changing the flow direction of the working fluid in the screen superheater system from a "Z" shape to a horizontal "U" shape, making the pressure difference of each tube of the front and rear rows of tube panels of the screen superheater closer in the inlet and outlet small headers, the working fluid flow rate more uniform, the working fluid enthalpy increase more uniform, and the wall temperature deviation between tubes smaller.

[0030] Figure 2 FIG. 2 shows a schematic diagram of the application structure of the screen superheater system in the present invention. Figure 2 As shown, the platen superheater system 1 of the present invention is arranged above the boiler furnace 8, a high-temperature superheater 10 is also arranged in the boiler, and a low-temperature superheater 11 is arranged in the tail flue. The specific application structure will be specifically described in Example 1.

[0031] The boiler used in the present invention can be a counter-combustion pulverized coal boiler with a burner 7 arranged on the front and rear walls of the furnace under subcritical or supercritical parameters, such as a counter-combustion boiler of 300MW (350MW), 600MW (660MW), 1000MW and higher capacity; the boiler can also be a tangential combustion pulverized coal boiler with a burner 7 arranged on the corner and furnace wall of the furnace under subcritical or supercritical parameters, or a "W" flame combustion pulverized coal boiler with a burner 7 arranged on the furnace arch on the front and rear walls of the furnace under subcritical or supercritical parameters, such as a 600MW supercritical "W" flame boiler, etc. Thus, the systematic deviation of the outlet wall temperature on the working medium side of the front and rear tube screens of the heating surface of the platen superheater can be reduced, the overheating of the wall temperature of the heating surface of the platen superheater can be better prevented, the operating parameters (steam temperature) can be guaranteed, and the deep peak regulation capability of the boiler can be improved.

[0032] Figure 3A and Figure 3B Two arrangements of the inlet header and the outlet header in a platen superheater system according to an exemplary embodiment of the present invention are respectively shown. Figure 4A The main structure and working medium flow diagram of the platen superheater system according to the exemplary embodiment of the present invention are shown. Figure 4B It shows a schematic diagram of the left view structure and working medium flow direction of a platen superheater system according to an exemplary embodiment of the present invention. Figure 4C A schematic diagram showing the top view of the structure and working medium flow direction of a platen superheater system according to an exemplary embodiment of the present invention is shown.

[0033] like FIG. 3A to FIG. 4C As shown, according to an exemplary embodiment of the present invention, the platen superheater system includes an inlet header, a plurality of U-shaped tube panels and an outlet header. The inlet header and the outlet header both include a large header and a plurality of small headers installed on the large header, that is, the inlet header includes an inlet large header 1 and an inlet small header 2, and the outlet header includes an outlet large header 6 and an outlet small header 5.

[0034] like FIG. 4A to FIG. 4C As shown, both the inlet header and the outlet header are comb-shaped structures, the large header is horizontally arranged parallel to the front wall or rear wall of the boiler, and the small header is horizontally arranged parallel to the side wall of the boiler and vertically installed on the large header.

[0035] Several U-shaped tube panels are arranged along the furnace width direction of the boiler. Each U-shaped tube panel includes a front tube panel 3 and a rear tube panel 4 arranged in parallel along the furnace depth direction of the boiler. The front tube panel 3 and the rear tube panel 4 of each U-shaped tube panel are connected to the same inlet small header and the same outlet small header respectively. The furnace depth direction is between the front wall and the rear wall of the boiler, and the furnace width direction is between the two side walls.

[0036] The U-shaped tube panel of the present invention is arranged vertically and parallel to the boiler side wall. The front tube panel 3 and the rear tube panel 4 of the U-shaped tube panel each include a plurality of U-shaped tubes arranged in parallel and connected to the inlet small header and the outlet small header at both ends, respectively. The U-shaped tubes are arranged in a U shape. The flow direction of the working medium in the U-shaped tube panel relative to the flow direction of the flue gas is arranged as follows: the front tube panel is downstream and the rear tube panel is countercurrent. Since the boiler flue gas flows from the front of the furnace to the rear of the furnace, and the working medium in the front tube panel also flows from the front of the furnace to the rear of the furnace, the two have the same direction and are downstream; while the working medium in the rear tube panel flows from the rear of the furnace to the front of the furnace, the two have opposite directions and are countercurrent.

[0037] The inlet header and the outlet header are arranged in the upper and lower parts in the height direction, and the inlet large header 1 and the outlet large header 6 are arranged on the same side of the U-shaped tube panel. Specifically, the inlet header and the outlet header are arranged in the upper and lower parts in the height direction, with the inlet header on top and the outlet header on the bottom or the inlet header on the bottom and the outlet header on top, which can be adjusted according to actual conditions.

[0038] The inlet header 1 and the outlet header 6 are arranged on the same side of the U-shaped tube panel, that is, both are arranged on the front side or the rear side of the furnace of the U-shaped tube panel. Figure 3A and Figure 3B shown.

[0039] Therefore, the working medium flow of the screen superheater system of the present invention is as follows: inlet large header 1, inlet small header 2, U-shaped tube screen, outlet small header 5 and outlet large header 6, wherein the flow direction of the working medium relative to the inlet small header and the outlet small header is horizontally U-shaped, so that the pressure difference of each tube of the front and rear rows of tube screens of the screen superheater in the inlet and outlet small headers is closer, the working medium flow rate is more uniform, the working medium enthalpy increase is more uniform and the wall temperature deviation between tubes is smaller.

[0040] In addition, the present invention provides throttling hole structures with various diameters at the opening positions corresponding to the U-shaped tube panels on the inlet small header 1 to finely adjust the working medium flow between the front tube panel and the rear tube panel in the U-shaped tube panel and between different U-shaped tubes in the same tube panel, so as to make the wall temperature deviation between the heating surface tubes smaller (reduced from about 20°C to about 5°C), and better prevent the overheating of the heating surface wall temperature of the screen superheater.

[0041] Preferably, in the present invention, 7 to 30 U-shaped tube panels are arranged along the furnace width direction of the boiler, and the number of U-shaped tubes in the front row and the rear row of tube panels in each U-shaped tube panel is 10 to 30 respectively, and the technicians can adjust it according to the actual working conditions.

[0042] In addition, in the present invention, the tube panel lengths of several U-shaped tube panels arranged along the furnace width direction of the boiler can be set to be the same or different, the length of the front tube panel and the length of the rear tube panel in each U-shaped tube panel can also be set to be the same or different, and the length, material, diameter and wall thickness of the U-shaped tube in the front tube panel or the rear tube panel can also be set to be the same or different according to the different smoke temperature and working medium temperature of the U-shaped tube, thereby the overall screen superheater is more flexible and more adjustable.

[0043] Through the application of the present invention, without increasing the boiler manufacturing cost and without causing any negative impact, the deviation of the outlet wall temperature of the working medium side of the screen superheater can be significantly reduced and the overheating of the heating surface can be avoided, so as to better ensure that the operating parameters (steam temperature) reach the design value and improve the deep peak regulation capability of the boiler.

[0044] In addition, test data show that the difference in working medium outlet wall temperature between the front and rear rows of tube panels of the screen superheater in the prior art and the screen superheater in the present invention (the rear row of tube panel wall temperature minus the front row of tube panel wall temperature) is 23.3°C and 5.3°C respectively, and the effect of reducing the wall temperature deviation is very obvious.

[0045] According to a project with two 1000MW units, annual load rate of 80%, coal price at the factory of 700 yuan / ton, 1.0℃ main steam temperature affects coal consumption by 0.088g / KWh, the application of the present invention can increase the main steam temperature by 2.0℃, the project can save 2466 tons of coal / year, and reduce expenditure by 1.726 million yuan / year; the boiler can reduce one non-stop operation in three years, and the economic loss of one non-stop operation is 9 million yuan (more conservative), that is, 3 million yuan / year, which reduces the project operation cost by 4.726 million yuan / year in total, and can reduce the emission of NOx, SO2 and dust at the same time, protecting the environment. In addition, the application of the present invention is also conducive to the recovery of equipment warranty funds (a fine of 2 million yuan will be imposed for each 1.0℃ deviation of the main steam temperature from the guaranteed value), and improves the product reputation and market competitiveness of the boiler manufacturing unit.

[0046] The present invention will be further described below in conjunction with specific embodiments.

[0047] Embodiment 1:

[0048] The present embodiment is applied to a 1000MW super (ultra) critical opposed-fired pulverized coal boiler. The platen superheater is arranged above the furnace. The U-shaped tube panels are arranged as multiple panels along the furnace width direction of the furnace and are arranged as two rows of tube panels (front tube panels and rear tube panels) along the furnace depth direction of the furnace. The U-shaped tubes in each tube panel are arranged in parallel in a U-shape. The inlet and outlet headers of the platen superheater are in a comb-shaped structure, wherein the large header is vertically arranged parallel to the front and rear walls of the boiler, and the small header is vertically installed on the large header. The inlet and outlet headers are arranged in the upper and lower parts in the height direction. In the present embodiment, the inlet header is at the bottom and the outlet header is at the top. Superheated steam enters the inlet header of the platen superheater through the steam connecting pipe from the low-temperature superheater → the inlet small header → the parallel front and rear rows of U-shaped tube panels (the front row is downstream relative to the flue gas, and the rear row is countercurrent) → the outlet small header → the outlet large header → the connecting pipes cross and then enter the inlet header of the high-temperature superheater. In the platen superheater system, the working medium flow direction relative to the inlet and outlet small headers is horizontal U-shaped. The 6-7 layers of burners are arranged in a hedged manner on the front and rear walls of the furnace (including one layer without hedge), as shown in the following figure. Figure 2 shown.

[0049] Embodiment 2:

[0050] This embodiment is applied to a 600MW supercritical (super) counter-fired pulverized coal boiler. The arrangement of the platen superheater is the same as that of Embodiment 1, including but not limited to the number of U-shaped tube plates, the number and size of U-shaped tubes in each platen, and the number of furnace sizes. 5 to 6 layers of burners are counter-arranged on the front and rear walls of the furnace (including one layer without counter-fire).

[0051] Embodiment 3:

[0052] This embodiment is applied to a 350MW supercritical (ultra) supercritical counter-fired pulverized coal boiler. The arrangement of the platen superheater is the same as that of Embodiment 1, including but not limited to the number of U-shaped tube plates, the number and size of U-shaped tubes in each platen, and the number of furnace sizes. 4 to 6 layers of burners are counter-fired on the front and rear walls of the furnace (including one layer without counter-fire).

[0053] Embodiment 4:

[0054] This embodiment is applied to a 600MW supercritical "W" flame combustion pulverized coal boiler, the furnace is provided with a furnace arch on the front and rear walls, the burner is arranged on the furnace arch, and the primary air nozzle forms a "W" flame downward. The arrangement of the screen superheater is the same as that of the embodiment 1, including but not limited to the number of U-shaped tube screens, and the number and size of the U-shaped tubes in each screen are different.

[0055] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A platen superheater system, characterized in that: It includes an inlet header, several U-shaped tube panels and an outlet header; The inlet header and the outlet header both include a large header and several small headers installed on the large header; A plurality of U-shaped tube panels are arranged along the furnace width direction of the boiler, each U-shaped tube panel comprises a front row of tube panels and a rear row of tube panels arranged in parallel along the furnace depth direction of the boiler, and the front row of tube panels and the rear row of tube panels of each U-shaped tube panel are respectively connected to the same inlet small header and the same outlet small header; The inlet header and the outlet header are arranged in the upper and lower parts in the height direction, and the inlet large header and the outlet large header are arranged on the same side of the U-shaped tube panel; The platen superheater system is arranged above the boiler furnace, and the boiler is a counter-combustion pulverized coal boiler with burners arranged on the front and rear walls of the furnace under subcritical parameters or supercritical parameters, a tangential combustion pulverized coal boiler with burners arranged on the corners and furnace walls of the furnace under subcritical parameters or supercritical parameters, or a "W" flame combustion pulverized coal boiler with burners arranged on the furnace arches on the front and rear walls of the furnace under subcritical parameters or supercritical parameters; The inlet header and the outlet header are both in a comb-shaped structure, the large header is horizontally arranged parallel to the front wall or rear wall of the boiler, and the small header is horizontally arranged parallel to the side wall of the boiler and vertically installed on the large header; The U-shaped tube panel is vertically arranged parallel to the boiler side wall, and the front tube panel and the rear tube panel of the U-shaped tube panel each include a plurality of U-shaped tubes arranged in parallel and connected at both ends to an inlet small header and an outlet small header respectively, wherein the flow direction of the working medium in the U-shaped tube panel relative to the flow direction of the flue gas is arranged as follows: the front tube panel is in a downstream direction, and the rear tube panel is in a countercurrent direction.

2. The platen superheater system according to claim 1, characterized in that: The inlet header and the outlet header are arranged in upper and lower parts in the height direction, with the inlet header on the top and the outlet header on the bottom, or with the inlet header on the bottom and the outlet header on the top.

3. The platen superheater system according to claim 1, characterized in that: The inlet large header and the outlet large header are arranged on the same side of the U-shaped tube panel, that is, both are arranged on the furnace front side or furnace rear side of the U-shaped tube panel.

4. The platen superheater system according to claim 1, characterized in that: The working medium flow of the platen superheater system is as follows: inlet large header, inlet small header, U-shaped tube screen, outlet small header and outlet large header, wherein the flow direction of the working medium relative to the inlet small header and the outlet small header is horizontal U-shaped.

5. The platen superheater system according to claim 1, characterized in that: The opening positions corresponding to the U-shaped tube panels on the inlet small header are provided with throttling hole structures of various diameters to finely adjust the working medium flow between the front tube panel and the rear tube panel in the U-shaped tube panel and between different U-shaped tubes in the same tube panel.

6. The platen superheater system according to claim 1, characterized in that: The U-shaped tube panels are arranged in a number of 7 to 30 panels along the furnace width direction of the boiler, and the number of U-shaped tubes in the front row of tube panels and the rear row of tube panels in each U-shaped tube panel is 10 to 30 respectively.

7. The platen superheater system according to claim 1, characterized in that: The tube panel lengths of the plurality of U-shaped tube panels arranged along the furnace width direction of the boiler are the same or different, the length of the front tube panel and the length of the rear tube panel in each U-shaped tube panel are the same or different, and the length, material, diameter and wall thickness of the U-shaped tubes in the front tube panel or the rear tube panel are set to be the same or different.

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