Optimized arrangement structure of flue flow field from flue gas heater outlet to chimney inlet of thermal power generating unit

Abstract

The utility model relates to the technical field of flues, and discloses a thermal power generating unit flue gas heater outlet to chimney inlet flue flow field optimization arrangement structure which comprises a first branch flue, a second branch flue and a converging flue, and the first branch flue is a rectangular flue and is used for connecting an A flue gas heater and the converging flue; the branch flue I is a rectangular flue and is used for connecting the flue gas heater B and the converging flue; and the converging flue is used for converging the branch flue I and the branch flue II, and is connected into the chimney inlet section flue after converging. The utility model provides a brand new technical route for optimizing and transforming the flue from the outlet of the flue gas heater to the inlet of the chimney, has the advantages of low investment cost, good implementation effect, small on-site modification amount and the like, is suitable for large-scale popularization and application on various thermal power generating units in China, and has very wide market application prospect.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas used in a flue gas system of a coal-fired power plant, and in particular to a flue gas flow field optimization arrangement structure from a flue gas heater outlet to a chimney inlet of a thermal power unit. Background Art

[0002] The boiler smoke and air duct of the power station is responsible for the transportation and distribution of boiler smoke and coal powder. The design of the boiler smoke and air duct of the power station and the selection of the power station fan affect the energy consumption of the boiler smoke and coal powder system and the operation of the boiler, air preheater, dust collector, induced draft fan, desulfurization absorption tower and other equipment. For the conventionally arranged flue from the outlet of the flue gas heater to the chimney entrance, the on-site layout is often very compact due to limited space. The bends of the flue are very sharp, and the flue outlet flue on both sides have a hedging effect due to the confluence of the flue gas heat exchanger outlets. Therefore, the resistance of this section of the flue is often at a very high level.

[0003] In order to solve the above problems, the utility model proposes a flue flow field optimization layout structure from the flue gas heater outlet to the chimney inlet of a thermal power unit, and realizes the flow field optimization inside the flue by reasonably arranging guide plates inside the branch flues and the merging flues on both sides of the flue gas heater outlet, while avoiding the impact effect when the flue gases in the flues on both sides merge, thereby significantly reducing the flue resistance and achieving the flue depth optimization effect. Utility Model Content

[0004] The purpose of the utility model is to provide an optimized arrangement structure of guide plates inside the flue from the flue gas heater outlet to the chimney entrance section of a thermal power unit under the premise of keeping the overall structure of the flue from the flue gas heater outlet to the chimney entrance section unchanged, by optimizing the arrangement of guide plates inside the flue from the flue gas heater outlet to the chimney entrance section, so as to achieve the flow field optimization inside the flue, and avoid the impact effect of the airflow on both sides when the flues on both sides merge, thereby significantly reducing the flue resistance and achieving the flue depth optimization effect.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A flue flow field optimization layout structure from the flue gas heater outlet to the chimney inlet of a thermal power unit comprises a branch flue 1, a branch flue 2 and a merging flue, wherein the branch flue 1 is a rectangular flue used to connect the A flue gas heater and the merging flue; the branch flue 1 is a rectangular flue used to connect the B flue gas heater and the merging flue; the merging flue is used to achieve the merging of the branch flue 1 and the branch flue 2, and after the merging, they are connected to the chimney inlet section flue.

[0007] The utility model is further improved in that the elbow guide plate is composed of two guide plates, namely elbow guide plate 1 and elbow guide plate 2, which are arranged at the first elbow of the branch flue 1 to optimize the flow field of the airflow in the elbow flue 1. The two guide plates are shaped as follows: the inner turning radius of the elbow 1 is R 2-1 , the outer turning radius of elbow 1 is R 2-2 , the first and second guide plates of the elbow are both 90° arc plates, and the two guide plates are linearly and evenly arranged at one part of the elbow, and the radius of curvature of the arcs of the two satisfy: The height of the two guide plates is consistent with the height of the elbow and the flue.

[0008] The utility model is further improved in that the guide plate of elbow 2 is composed of five guide plates, namely, guide plate 1 of elbow 2, guide plate 2 of elbow 2, guide plate 3 of elbow 2, guide plate 4 of elbow 2 and guide plate 5 of elbow 2, which are arranged at the second elbow of branch flue 1 to optimize the flow field of the airflow in the flue of elbow 2. Among them, the shape of the five guide plates is: the inner turning radius of elbow 2 is R 3-1 , the outer turning radius of elbow 2 is R 3-2 The five guide plates at elbow 2 are all 90° arc plates. The five guide plates are linearly and evenly arranged at elbow 2, and the radius of curvature of the arc meets the following requirements: R 3-1 ≤R 31 ≤R 32 ≤R 33 ≤R 34 ≤R 35 ≤R 3-2 ∈[1000,6000]mm, and the leading edges of the arc curves of the five guide plates are tangent to the horizontal center line of the upstream rectangular flue, and the trailing edges of the arc curves are tangent to the horizontal center line of the downstream rectangular flue. The height of the five guide plates is consistent with the height of the second flue at the elbow.

[0009] The further improvement of the utility model is that the elbow three guide plate is composed of two guide plates, namely elbow three guide plate 1 and elbow three guide plate 2, which are arranged at the first elbow of branch flue 2 to optimize the flow field of the airflow in the elbow three flue. The shape structure and installation position of the two guide plates are completely consistent with the corresponding features of elbow one guide plate 1 and elbow one guide plate 2.

[0010] The further improvement of the utility model is that the elbow four guide plate is composed of five guide plates, namely elbow four guide plate 1, elbow four guide plate 2, elbow four guide plate 3, elbow four guide plate 4 and elbow four guide plate 5, which are arranged at the second elbow of the branch flue 2 to optimize the flow field of the airflow in the elbow four flue. The shape structure and installation position of these five guide plates are completely consistent with the corresponding features of elbow two guide plate 1, elbow two guide plate 2, elbow two guide plate 3, elbow two guide plate 4 and elbow two guide plate 5.

[0011] A further improvement of the utility model is that the converging flue guide plate is composed of nine guide plates, namely, converging flue guide plate one, converging flue guide plate two, converging flue guide plate three, converging flue guide plate four, converging flue guide plate five, converging flue guide plate six, converging flue guide plate seven, converging flue guide plate eight and converging flue guide plate nine, for achieving low-loss converging of the airflow in the converging flue and flow field optimization, and the height of the nine guide plates is consistent with the height of the converging flue.

[0012] The utility model is further improved in that the modeling method of the converging flue guide plate 1, the converging flue guide plate 2 and the converging flue guide plate 3 is as follows: the above three guide plates are composed of 90° arc plates and rectangular straight plates, and the above three guide plates are linearly and evenly arranged at the upper part of the converging flue, that is, The radius of curvature of the arc of the above three guide plates meets the following requirements: 500mm≤R 61 <R 62 <R 63 ≤6000mm, and the leading edges of the arc curves of the three guide plates are tangent to the horizontal centerline of the upstream rectangular flue, and the trailing edges of the arc curves are tangent to the horizontal centerline of the converging flue. The trailing edge points extend along the horizontal centerline of the converging flue to be flush with the outer wall of the first flue of the branch flue, forming a straight line segment. The arc curve and the straight line segment are stretched in the vertical direction to complete the three-dimensional structural modeling of the three guide plates;

[0013] The utility model is further improved in that the converging flue guide plate six, converging flue guide plate seven, and converging flue guide plate eight are shaped as follows: the above three guide plates are composed of 90° arc plates and rectangular straight plates, and the three guide plates are linearly and evenly arranged at the upper part of the converging flue, that is, The radius of curvature of the arc of the above three guide plates meets the following requirements: 500mm≤R 66 <R 67 <R 68 ≤6000mm; the converging flue guide plate 6, converging flue guide plate 7, converging flue guide plate 8 and the converging flue guide plate 1, converging flue guide plate 2, and converging flue guide plate 3 are symmetrically arranged, and the shape structure and corresponding installation position are completely consistent;

[0014] The utility model is further improved in that the shapes of the converging flue guide plate 4, the converging flue guide plate 5 and the converging flue guide plate 9 are: the converging flue guide plate 4 and the converging flue guide plate 9 are all 90° arc plates, the leading edges of the arc curves are tangent to the inner wall of the branch flue, the trailing edges of the arc curves are tangent to the horizontal centerline direction of the converging flue, and meet the following requirements: R 64 =R 69 ∈[1000,10000]mm, the converging flue guide plate five is a rectangular straight plate, which is the tangent point of the arc curve tail edges of the converging flue guide plate four and the converging flue guide plate nine, extending along the horizontal center line of the converging flue to the outer wall of the branch flue one, forming a straight line segment, and the straight line segment is stretched in the vertical direction to complete the three-dimensional structural modeling of the converging flue guide plate five.

[0015] A further improvement of the utility model is that all guide plates are steel plates, which are welded and installed, and their thickness is δ, and satisfies δ∈[6,20]mm.

[0016] The utility model has the following beneficial effects:

[0017] 1) The utility model provides a flow field optimization arrangement structure of the flue from the flue gas heater outlet to the chimney inlet of a thermal power unit, under the premise of keeping the overall structure of the flue from the flue gas heater outlet to the chimney inlet unchanged. The flow guide plates are optimally arranged inside the flue from the flue gas heater outlet to the chimney inlet, so as to achieve the flow field optimization inside the flue, and avoid the impact effect of the airflow on both sides when the flues on both sides merge, thereby significantly reducing the flue resistance and achieving the depth optimization effect of the flue.

[0018] 2) The utility model provides a new technical route for optimizing and transforming the flue from the flue gas heater outlet to the chimney inlet, which has the advantages of low investment cost, good implementation effect, and small amount of on-site modification. It is suitable for large-scale promotion and application in various types of thermal power units across the country and has a very broad market application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a three-dimensional model of the arrangement structure of the guide plate inside the flue gas outlet of the flue gas heat exchanger of the utility model;

[0020] Figure 2 This is a schematic diagram of a three-dimensional model of the outlet flue structure of the practical flue gas heat exchanger;

[0021] Figure 3 It is a two-dimensional structural modeling diagram of an elbow and a guide plate of the utility model;

[0022] Figure 4 It is a two-dimensional structural modeling diagram of the second guide plate of the elbow of the utility model;

[0023] Figure 5 It is a two-dimensional structural modeling diagram of the converging flue guide plate of the utility model;

[0024] In the figure: 1. Flue gas heat exchanger outlet flue; 2. Elbow 1 guide plate; 3. Elbow 2 guide plate; 4. Elbow 3 guide plate; 5. Elbow 4 guide plate; 6. Converging flue guide plate; 11. Branch flue 1; 12. Branch flue 2; 13. Converging flue; 21. Elbow 1 guide plate 1; 22. Elbow 1 guide plate 2; 31. Elbow 2 guide plate 1; 32. Elbow 2 guide plate 2; 33. Elbow 2 guide plate three; 34, elbow 2 guide plate four; 35, elbow 2 guide plate five; 61, merge flue guide plate one; 62, merge flue guide plate two; 63, merge flue guide plate three; 64, merge flue guide plate four; 65, merge flue guide plate five; 66, merge flue guide plate six; 67, merge flue guide plate seven; 68, merge flue guide plate eight; 69, merge flue guide plate nine;

[0025] R 2-1 R is the inner turning radius of the elbow. 2-2 R is the outer turning radius of the elbow. 21 R is the radius of curvature of the arc of elbow guide plate. 22 R is the radius of curvature of the arc of elbow 1 guide plate 2, 3-1 R is the inner turning radius of the elbow. 3-2 R is the second outer turning radius of the elbow, 31 R is the radius of curvature of the arc of the guide plate 1 of the elbow 2, 32 R is the radius of curvature of the arc of the second guide plate of the elbow, 33 R is the radius of curvature of the arc of the elbow 2 guide plate 3, 34 R is the radius of curvature of the arc of the elbow second guide plate four, 35 R is the radius of curvature of the arc of the guide plate 5 of the elbow 2, 61 R is the radius of curvature of the arc of the converging flue guide plate 1, 62 R is the radius of curvature of the arc of the second flue gas duct guide plate, 63 R is the radius of curvature of the arc of the converging flue guide plate 3, 64 R is the radius of curvature of the arc of the converging flue guide plate 4, 66 R is the radius of curvature of the arc of the converging flue guide plate 6, 67 R is the radius of curvature of the arc of the converging flue guide plate 7, 68 R is the radius of curvature of the arc of the converging flue guide plate 8, 69 is the radius of curvature of the arc of the converging flue guide plate 9, D is the width of the converging flue, L 11 is the width of branch flue 1, L 12 is the width of branch flue 2, all the above units are mm. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] like Figure 1-5 As shown, the utility model provides a flue flow field optimization arrangement structure from the flue gas heater outlet to the chimney inlet of a thermal power unit, including a flue gas heater outlet flue 1, which is led out from the flue gas heater outlets on the A side and the B side and merged into a merged flue, including a branch flue 11, a branch flue 2 12, and a merged flue 13; an elbow first guide plate 2, which is arranged at an elbow of the branch flue 11 to optimize the flow field of the airflow in the elbow first flue; an elbow second guide plate 3, which is arranged at The second elbow of the branch flue 11 is used to achieve flow field optimization of the airflow in the elbow second flue; the third elbow guide plate 4 is arranged at the third elbow of the branch flue 12 to achieve flow field optimization of the airflow in the elbow three flue; the fourth elbow guide plate 5 is arranged at the fourth elbow of the branch flue 12 to achieve flow field optimization of the airflow in the elbow four flue; the converging flue guide plate 6 is arranged in the converging flue 13 to achieve low-loss confluence and flow field optimization of the airflow in the converging flue.

[0028] The branch flue 11 is used to connect the flue gas heater A and the converging flue 13. A first elbow guide plate 2 is provided at the top elbow of the branch flue 11 to optimize the flow field of the airflow in the first elbow flue; a second elbow guide plate 3 is provided at the second elbow of the bottom to optimize the flow field of the airflow in the second elbow flue;

[0029] The structure of the elbow guide plate 2 and the elbow guide plate 4 is the same, both of which are composed of two guide plates, including the elbow guide plate 1 21 and the elbow guide plate 2 22. The above two guide plates are 90° arc plates, and the height of the two guide plates is consistent with the height of the flue at the elbow one or the elbow three.

[0030] The branch flue 12 is used to connect the B flue gas heater and the converging flue 13. The three elbows at the top of the branch flue 12 are provided with three guide plates 4 to optimize the flow field of the airflow in the elbow three flue; the four elbows at the bottom are provided with four guide plates 5 to optimize the flow field of the airflow in the elbow three flue;

[0031] The elbow guide plate 5 has the same structure as the elbow guide plate 3, and is composed of five guide plates, including elbow guide plate 1 31, elbow guide plate 2 32, elbow guide plate 3 33, elbow guide plate 4 34 and elbow guide plate 5 35.

[0032] The converging flue 13 is used to realize the converging of the branch flue 11 and the branch flue 2 12, and is connected to the chimney inlet flue after converging, so as to realize the low-loss converging and flow field optimization of the airflow in the converging flue; a converging flue guide plate 6 is provided inside the converging flue 13 between the outlets of the branch flue 11 and the branch flue 2 12 to prevent the converging and counter-attacking of the airflow;

[0033] The merging flue guide plate 6 is composed of nine guide plates, including merging flue guide plate one 61, merging flue guide plate two 62, merging flue guide plate three 63, merging flue guide plate four 64, merging flue guide plate five 65, merging flue guide plate six 66, merging flue guide plate seven 67, merging flue guide plate eight 68 and merging flue guide plate nine 69.

[0034] Example

[0035] The flue section from the flue gas heater outlet to the chimney inlet of a domestic 660MW unit has a very high resistance because there is a direct hedging effect between the flue gases inside the flue when the flue gas heater outlets on the A and B sides merge. According to on-site measurements, the resistance value of this flue section is above 1000Pa.

[0036] Aiming at the problem of too high resistance of the flue gas heater outlet, the utility model of the utility model proposes an optimized layout structure of the flue gas heater outlet to the chimney inlet flow field of the thermal power unit, including the flue gas heater outlet 1, the elbow first guide plate 2, the elbow second guide plate 3, the elbow third guide plate 4, the elbow fourth guide plate 5 and the converging flue guide plate 6. The guide plate thickness δ = 10mm, and other specific parameters are set as follows:

[0037] 1) Elbow-guide plate 2: R 2-1 =1000mm, R 21 =3000mm, R 22 =5000mm, R 2-2 =7000mm;

[0038] 2) Elbow second guide plate 3: R 3-1 =1500mm, R 31 =1625mm, R 32 =1750mm, R 33 =1875mm, R 34 =2000mm, R 35 =2125mm, R 3-2 =2250mm;

[0039] 3) Elbow three guide plate 4: R 4-1 =1000mm, R 41 =3000mm, R 42=5000mm, R 4-2 =7000mm;

[0040] 4) Elbow four guide plate 5: R 5-1 =1500mm, R 51 =1625mm, R 52 =1750mm, R 53 =1875mm, R 54 =2000mm, R 55 =2125mm, R 5-2 =2250mm;

[0041] 5) Combined flue guide plate 6: R 61 =R 66 =643mm, R 62 =R 67 =1301mm, R 63 =R 68 =1952mm, R 64 =R 69 =2639mm, D=5200mm, L 11 =L 12 =5800mm.

[0042] The implementation effect of the utility model: before the modification of the flue section from the flue gas heater outlet to the chimney inlet, the measured resistance of this section of the flue was 1021Pa under the 660MW working condition; after the modification of the optimized arrangement structure of the internal guide plate of the flue section from the flue gas heater outlet to the chimney inlet of the thermal power unit, the resistance of this section of the flue was measured to be 669Pa under the 660MW working condition. After calculation, it can be found that after the optimization arrangement modification of the internal guide plate of the flue, the resistance of this section of the flue decreased by 352Pa. Therefore, the implementation effect of the utility model is good, which significantly reduces the resistance of the flue section from the flue gas heater outlet to the chimney inlet, improves the flow field conditions inside the flue, and optimizes the confluence mode of the flue, thereby achieving the deep energy-saving optimization effect of the flue.

Claims

1. A flue flow field optimization layout structure from the flue gas heater outlet to the chimney inlet of a thermal power unit, comprising a branch flue 1 (11), a branch flue 2 (12) and a converging flue (13), wherein the branch flue 1 (11) is used to connect the A flue gas heater and the converging flue (13), the branch flue 2 (12) is used to connect the B flue gas heater and the converging flue (13), and the converging flue (13) is used to realize the converging of the branch flue 1 (11) and the branch flue 2 (12), and after the converging, the branch flue 1 (11) and the branch flue 2 (12) are connected to the chimney inlet section flue; characterized in that: The branch flue 1 (11) is provided with a first bend guide plate (2) at one bend of the top, and a second bend guide plate (3) at two bends at the bottom; the branch flue 2 (12) is provided with a third bend guide plate (4) at three bends of the top, and a fourth bend guide plate (5) at four bends at the bottom; and a converging flue guide plate (6) for preventing airflow from converging and colliding is provided inside the converging flue (13) between the outlets of the branch flue 1 (11) and the branch flue 2 (12).

2. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 1 is characterized in that: The elbow one guide plate (2) and the elbow three guide plate (4) have the same structure, and are both composed of two guide plates, including elbow one guide plate one (21) and elbow one guide plate two (22). The two guide plates are both 90° arc plates. The two guide plates are linearly and evenly arranged at elbow one or elbow three, and the height of the two guide plates is consistent with the height of the flue at elbow one or elbow three.

3. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 2 is characterized in that: The curvature radius of the arc of the elbow guide plate (21) satisfies: The curvature radius of the arc of the elbow first guide plate second (22) satisfies: The inner turning radius of elbow 1 is R 2-1 , the outer turning radius of elbow 1 is R 2-2 .

4. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 1 is characterized in that: The structure of the second bend guide plate (3) and the fourth bend guide plate (5) is the same, and both are composed of five guide plates, including the first bend guide plate (31), the second bend guide plate (32), the third bend guide plate (33), the fourth bend guide plate (34) and the fifth bend guide plate (35). The leading edges of the circular arc curves of the five guide plates are all tangent to the horizontal center line direction of the upstream flue, and the trailing edges of the circular arc curves are all tangent to the horizontal center line direction of the downstream flue. The five guide plates are all 90° circular arc plates. The five guide plates are linearly and evenly arranged at the second bend or the fourth bend, and the height of the five guide plates is consistent with the height of the flue at the second bend or the fourth bend.

5. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 4, characterized in that: The arc curvature radius of the elbow second guide plate one (31), elbow second guide plate two (32), elbow second guide plate three (33), elbow second guide plate four (34) and elbow second guide plate five (35) meets the following requirements: R 3-1 ≤R 31 ≤R 32 ≤R 33 ≤R 34 ≤R 35 ≤R 3-2 ∈[1000,6000]mm, where the inner turning radius of elbow 2 is R 3-1 , the outer turning radius of elbow 2 is R 3-2 .

6. The optimized arrangement structure of flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 1, characterized in that: The combined flue guide plate (6) is composed of nine guide plates, including a combined flue guide plate one (61), a combined flue guide plate two (62), a combined flue guide plate three (63), a combined flue guide plate four (64), a combined flue guide plate five (65), a combined flue guide plate six (66), a combined flue guide plate seven (67), a combined flue guide plate eight (68) and a combined flue guide plate nine (69).

7. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 6, characterized in that: The converging flue guide plate 1 (61), the converging flue guide plate 2 (62), and the converging flue guide plate 3 (63) are all composed of a combination of a 90° arc plate and a rectangular straight plate; the three guide plates are linearly and evenly arranged on the upper part of the converging flue (13), and the arc curvature radius of the three guide plates meets the following requirements: 500mm≤R 61 <R 62 <R 63 ≤6000mm, and the leading edges of the arc curves of the above three guide plates are tangent to the horizontal centerline of the upstream flue, and the trailing edges of the arc curves are tangent to the horizontal centerline of the converging flue, and the trailing edge points extend along the horizontal centerline of the converging flue to be flush with the outer wall of the branch flue (11), forming a straight line segment.

8. The optimized arrangement structure of the flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 6, characterized in that: The converging flue guide plate six (66), converging flue guide plate seven (67), and converging flue guide plate eight (68) are all composed of a 90° arc plate and a rectangular straight plate. The three guide plates are linearly and evenly arranged on the upper part of the converging flue. The arc curvature radius of the three guide plates meets the following requirements: 500mm≤R 66 <R 67 <R 68 ≤6000mm, and the leading edges of the arc curves of the above three guide plates are tangent to the horizontal centerline of the upstream rectangular flue, and the trailing edges of the arc curves are tangent to the horizontal centerline of the merged flue, and the trailing edge points extend along the horizontal centerline of the merged flue to be flush with the outer wall of the branch flue two (12), forming a straight line segment.

9. The optimized arrangement structure of flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 6, characterized in that: The converging flue guide plate four (64) and the converging flue guide plate nine (69) are both 90° arc plates, the leading edges of the arc curves are tangent to the inner wall of the branch flue, the trailing edges of the arc curves are tangent to the horizontal centerline of the converging flue, and meet the following conditions: R 64 =R 69 ∈[1000,10000]mm; the merged flue guide plate five (65) is a rectangular straight plate, which is a straight line segment formed by the tangent point of the arc curve tail edges of the merged flue guide plate four (64) and the merged flue guide plate nine (69) extending along the horizontal center line of the merged flue to the outer wall of the branch flue one (11) or the branch flue two (12) flush with the flue.

10. The optimized arrangement structure of flue flow field from the flue gas heater outlet to the chimney inlet of a thermal power plant according to claim 1, characterized in that: All the guide plates (2) of the first elbow, the guide plates (3) of the second elbow, the guide plates (4) of the third elbow, the guide plates (5) of the fourth elbow, and the guide plates (6) of the combined flue gas duct are steel plates, and their thickness is δ, and satisfies δ∈[6,20]mm.

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