A secondary reheat boiler

Abstract

The present invention relates to the technical field of secondary reheat boilers, and provides a secondary reheat boiler, which at least includes: a boiler main body containing a front flue, a middle flue and a rear flue inside; a first regulating baffle arranged at the outlet of the front flue and adapted to regulate the flue gas volume of the front flue; a second regulating baffle arranged at the outlet of the middle flue and adapted to regulate the flue gas volume of the middle flue; a third regulating baffle arranged at the outlet of the rear flue and adapted to regulate the flue gas volume of the rear flue; a primary low-temperature reheater arranged in the front flue; a secondary low-temperature reheater arranged in the rear flue; and a primary superheater arranged in the middle flue. For this secondary reheat boiler, the regulation of steam temperature can be achieved without setting up a flue gas recirculation system, there is no additional plant power consumption caused by the operation of the recirculation fan, and there will be no wear of the recirculation fan either, so the reliability and economy are higher; during low-load operation, the combustion will not be affected by adopting flue gas recirculation, and the safety is higher.

Description

Technical Field

[0001] This invention relates to the field of double reheat boiler technology, and specifically to a double reheat boiler. Background Technology

[0002] Currently, the temperature control method of double reheat tower boilers is basically to use flue gas recirculation + dual flue gas regulating baffles. The primary low-temperature reheater and the secondary low-temperature reheater are arranged in the front and rear flues respectively. First, the temperature of the primary and secondary reheat steam is regulated as a whole by flue gas recirculation. When one of the reheat steam temperatures reaches the rated value, the balance of heat absorption of the primary and secondary reheat is adjusted by flue gas baffles.

[0003] However, using flue gas recirculation as the main temperature control method will increase plant power consumption during operation, resulting in low economic efficiency. Furthermore, wear and tear on the recirculation fan is unavoidable, leading to poor reliability, long-term maintenance, and high costs. Moreover, as the boiler load decreases, the proportion of recirculated flue gas will gradually increase, which will have a certain impact on combustion during low-load operation. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that the existing technology uses flue gas recirculation as the main temperature control method, which increases plant power consumption during operation, is not economical, and the wear of the recirculation fan is unavoidable, resulting in poor reliability, requiring long-term maintenance and high cost; moreover, as the boiler load decreases, the proportion of recirculated flue gas will gradually increase, which will have a certain impact on combustion during low-load operation, thus providing a secondary reheat boiler.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A double reheat boiler includes at least: a boiler body containing three parallel flues, referred to as a front flue, a middle flue, and a rear flue; a first regulating baffle disposed at the outlet of the front flue, adapted to regulate the flue gas volume of the front flue; a second regulating baffle disposed at the outlet of the middle flue, adapted to regulate the flue gas volume of the middle flue; a third regulating baffle disposed at the outlet of the rear flue, adapted to regulate the flue gas volume of the rear flue; a primary low-temperature reheater disposed in the front flue; a secondary low-temperature reheater disposed in the rear flue; and a primary superheater disposed in the middle flue.

[0007] Furthermore, the inlet section of the first-stage superheater includes a first suspended pipe and a second suspended pipe arranged parallel to each other along the flue gas conveying direction; the first suspended pipe is wrapped with flat steel to form a front partition wall and a rear partition wall, which divide the flue inside the boiler body into the front flue, the middle flue, and the rear flue; at least a portion of the first suspended pipe extends downward to the first low-temperature reheater and then bends to form the first-stage superheater, and the remaining portion of the first suspended pipe continues downward together with the second suspended pipe to form a screen-type superheater at the bottom of the boiler body.

[0008] Furthermore, the secondary reheat boiler also includes a high-temperature superheater, which is located within the boiler body and downstream of the screen-type superheater along the flue gas conveying path. The outlet of the screen-type superheater is connected to the inlet of the high-temperature superheater.

[0009] Furthermore, the secondary reheat boiler also includes a primary high-temperature reheater and a secondary high-temperature reheater, both of which are located within the boiler body and downstream of the high-temperature superheater along the flue gas conveying path.

[0010] Furthermore, the pipes of the primary high-temperature reheater and the secondary high-temperature reheater are alternately arranged on a plane perpendicular to the flue gas conveying direction, and the interval between two adjacent pipes is suitable for the passage of flue gas.

[0011] Furthermore, the secondary reheat boiler also includes a first economizer, a second economizer, and a third economizer; the first economizer is located in the front flue and downstream of the primary low-temperature reheater along the flue gas conveying direction; the second economizer is located in the middle flue and downstream of the primary superheater along the flue gas conveying direction; the third economizer is located in the rear flue and downstream of the secondary low-temperature reheater along the flue gas conveying direction.

[0012] Furthermore, the inlet section of the first-stage superheater includes six rows of suspended tubes arranged in parallel, wherein the two middle rows of suspended tubes are the first suspended tubes, and the remaining four rows of suspended tubes on both sides are the second suspended tubes.

[0013] Furthermore, the primary superheater is connected to the screen-type superheater via a pipeline.

[0014] Furthermore, the primary superheater is suspended from the front partition wall or the rear partition wall via structural components.

[0015] Furthermore, the second economizer is suspended from the front partition wall or the rear partition wall via structural components.

[0016] The technical solution of this invention has the following advantages:

[0017] The double reheat boiler provided by this invention, during temperature adjustment, firstly, keeps the opening of the third regulating baffle constant, and controls the opening of the first and second regulating baffles to bring the average steam temperature of the primary and secondary reheat close to the target temperature value; then, keeps the opening of the second and third regulating baffles constant, and controls the opening of the first regulating baffle to adjust the steam temperature of both the primary and secondary reheat to the target temperature value. Compared with existing double reheat boilers, this application can achieve steam temperature adjustment without setting up a flue gas recirculation system, without the increased plant power consumption due to the operation of the recirculation fan, and without the wear and tear of the recirculation fan, resulting in higher reliability and economy; under low load operation, the use of flue gas recirculation will not affect combustion, resulting in higher safety. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the secondary reheat boiler in an embodiment of the present invention;

[0020] Figure 2 for Figure 1 A magnified schematic diagram of a local structure;

[0021] Figure 3 This is a schematic diagram of three flues in the secondary reheat boiler of the present invention.

[0022] Figure 4 This is a top view of the primary high-temperature reheater and the secondary high-temperature reheater in the secondary reheat boiler of the present invention embodiment.

[0023] Figure 5 This is a schematic diagram showing the steam flow path in the secondary reheat boiler according to an embodiment of the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Boiler body; 2. Front flue; 3. Middle flue;

[0026] 4. Rear flue; 5. Front partition wall; 6. Rear partition wall;

[0027] 7. First suspension pipe; 8. Second suspension pipe; 9. First adjusting baffle;

[0028] 10. Second adjusting baffle; 11. Third adjusting baffle; 12. First economizer;

[0029] 13. Second economizer; 14. Third economizer; 15. First-stage superheater;

[0030] 16. Primary low-temperature reheater; 17. Secondary low-temperature reheater; 18. Primary high-temperature reheater;

[0031] 19. Secondary high-temperature reheater; 20. High-temperature superheater; 21. Screen-type superheater;

[0032] 22. Steam-water separator; 23. Inlet section of the first-stage superheater. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Figure 1 This is a schematic diagram of the overall structure of the secondary reheat boiler in an embodiment of the present invention; Figure 2 for Figure 1 A magnified schematic diagram of a local structure; Figure 3 This is a schematic diagram of the three flues in the secondary reheat boiler of this invention; as shown. Figure 1 , Figure 2 as well as Figure 3 As shown, this embodiment provides a double reheat boiler, comprising at least: a boiler body 1 containing three parallel flues, denoted as a front flue 2, a middle flue 3, and a rear flue 4; a first regulating baffle 9, disposed at the outlet of the front flue 2, suitable for regulating the flue gas volume of the front flue 2; a second regulating baffle 10, disposed at the outlet of the middle flue 3, suitable for regulating the flue gas volume of the middle flue 3; a third regulating baffle 11, disposed at the outlet of the rear flue 4, suitable for regulating the flue gas volume of the rear flue 4; a primary low-temperature reheater 16 disposed within the front flue 2; a secondary low-temperature reheater 17 disposed within the rear flue 4; and a primary superheater 15 disposed within the middle flue 3. The structures of the first regulating baffle 9, the second regulating baffle 10, and the third regulating baffle 11 are all consistent with those used in existing double reheat boilers employing flue gas recirculation and dual flue regulation.

[0038] The double reheat boiler provided in this embodiment, during temperature adjustment, firstly, keeps the opening of the third regulating baffle 11 unchanged, and controls the opening of the first regulating baffle 9 and the second regulating baffle 10 to bring the average steam temperature of the primary and secondary reheat close to the target temperature value; then, keeps the opening of the second regulating baffle 10 and the third regulating baffle 11 unchanged, and controls the opening of the first regulating baffle 9 to adjust the steam temperature of both the primary and secondary reheat to the target temperature value. Compared with the double reheat boilers in the prior art, this application can achieve steam temperature adjustment without setting up a flue gas recirculation system, without the increased plant power consumption due to the operation of the recirculation fan, and without the wear and tear of the recirculation fan, resulting in higher reliability and economy; when operating at low load, the use of flue gas recirculation will not affect combustion, resulting in higher safety.

[0039] After steam exits from the steam-water separator 22, it enters the inlet section 23 of the first-stage superheater through the connecting pipe. The inlet section 23 of the first-stage superheater includes a first suspension pipe 7 and a second suspension pipe 8 arranged parallel to each other along the flue gas conveying direction. For example, the inlet section 23 of the first-stage superheater includes six rows of suspension pipes arranged in parallel, wherein the two rows of suspension pipes in the middle are the first suspension pipes 7, and the remaining four rows of suspension pipes on both sides are the second suspension pipes 8. The first suspended tube 7 is wrapped with flat steel to form the front partition wall 5 and the rear partition wall 6. The front partition wall 5 and the rear partition wall 6 divide the flue inside the boiler body 1 into the front flue 2, the middle flue 3 and the rear flue 4. The number of tubes in each row of the first suspended tube 7 is twice the number of tubes in each row of the second suspended tube 8. At least a portion of the tubes in each row of the first suspended tube 7 extends downward to the same height as the first low temperature reheater 16 and then bends in the middle to form the first-stage superheater 15. The remaining portion of the tubes in each row of the first suspended tube 7 does not bend and continues downward together with the second suspended tube 8 to form a screen-type superheater 21 at the bottom of the boiler body 1.

[0040] The secondary reheat boiler also includes a high-temperature superheater 20, which is installed inside the boiler body 1 and located downstream of the screen-type superheater 21 along the flue gas conveying path. The outlet of the screen-type superheater 21 is connected to the inlet of the high-temperature superheater 20.

[0041] Figure 4 This is a top view of the primary high-temperature reheater and the secondary high-temperature reheater in the double reheat boiler of this invention embodiment; as shown... Figure 4 As shown, the double reheat boiler also includes a primary high-temperature reheater 18 and a secondary high-temperature reheater 19, both of which are located within the boiler body 1 and downstream of the high-temperature superheater 20 along the flue gas transport direction. For example, the pipes of the primary high-temperature reheater 18 and the secondary high-temperature reheater 19 are alternately arranged along a plane perpendicular to the flue gas transport direction, and the spacing between two adjacent pipes is suitable for flue gas passage.

[0042] The secondary reheat boiler further includes a first economizer 12, a second economizer 13, and a third economizer 14. The first economizer 12 is located in the front flue duct 2 and downstream of the primary low-temperature reheater 16 along the flue gas conveying direction. The second economizer 13 is located in the middle flue duct 3 and downstream of the primary superheater 15 along the flue gas conveying direction. The third economizer 14 is located in the rear flue duct 4 and downstream of the secondary low-temperature reheater 17 along the flue gas conveying direction. The first economizer 12, the second economizer 13, and the third economizer 14 are connected in parallel.

[0043] The primary superheater 15 can be connected to the screen superheater 21 via a pipeline. The working fluid in the primary superheater 15 can flow into the screen superheater 21, and the working fluid in the screen superheater 21 can then flow into the high-temperature superheater 20.

[0044] Both the primary superheater 15 and the secondary economizer 13 can be suspended from the front partition wall 5 or the rear partition wall 6 by structural components. For example, the structural components can be fasteners such as bolts.

[0045] The tops of the first suspension pipe 7 and the second suspension pipe 8 can be fixed to the inner top wall of the boiler body 1. At this time, the high-temperature superheater 20, the primary high-temperature reheater 18, the secondary high-temperature reheater 19, the primary low-temperature reheater 16, the second low-temperature reheater, the first economizer 12, and the third economizer 14 can all be suspended and installed using the first suspension pipe 7 or the second suspension pipe 8 as the point of force.

[0046] In this embodiment of the double reheat boiler, during operation, the flue gas generated by the combustion of fuel and air in the furnace passes through the upper part of the furnace, sequentially through the screen-type superheater 21, the high-temperature superheater 20, the primary high-temperature reheater 18, and the secondary high-temperature reheater 19, and then enters the tail flue. In the front flue 2, the flue gas sequentially passes through the primary low-temperature reheater 16 and the first economizer 12; in the middle flue 3, the flue gas sequentially passes through the primary superheater 15 and the second economizer 13; in the rear flue 4, the flue gas sequentially passes through the secondary low-temperature reheater 17 and the third economizer 14; finally, the flue gas merges together after passing through the three tail flues and enters the denitrification device and air preheater, etc.

[0047] When adjusting the temperature, first keep the opening of the third adjusting baffle 11 unchanged, and use the first adjusting baffle 9 and the second adjusting baffle 10 to adjust the average value of the first reheat and second reheat steam temperature, so that the average value is close to the set target steam temperature, such as 623℃. Then, keep the opening of the second adjusting baffle 10 and the third adjusting baffle 11 unchanged, and use the first adjusting baffle 9 to adjust the deviation between the first reheat and second reheat steam temperatures, so that the steam temperatures of the first reheat and second reheat are close to or even reach the target steam temperature, such as 623℃.

[0048] Except for the primary superheater 15 and the second economizer 13 in the middle flue 3, which are suspended on the front partition wall 5 and the rear partition wall 6, the remaining heating surfaces are suspended by suspension pipes, and the final load is transferred to the boiler top beam.

[0049] Figure 5 This is a schematic diagram of the steam flow path in the secondary reheat boiler according to an embodiment of the present invention, as shown below. Figure 5 As shown, the superheater is arranged in three stages. The first-stage superheater 15 is located in the middle flue 3, and the screen-type superheater 21 and the high-temperature superheater 20 are arranged sequentially at the furnace outlet. The superheater steam flow is as follows: Figure 5 As shown.

[0050] In summary, the double reheat boiler with three flue baffle temperature control method proposed in this application has advantages in investment cost and subsequent operation and maintenance cost, while not affecting the combustion conditions inside the furnace, and has higher reliability, safety and economy.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method of temperature control of a double-reheat boiler, characterized by, At least including: The boiler body contains three parallel flues, referred to as the front flue, middle flue, and rear flue. The first adjusting baffle is located at the outlet of the front flue and is suitable for adjusting the flue gas volume of the front flue. The second adjusting baffle is located at the outlet of the middle flue and is suitable for adjusting the flue gas volume of the middle flue. The third adjusting baffle is located at the outlet of the rear flue and is suitable for adjusting the flue gas volume of the rear flue. A low-temperature reheater is installed inside the front flue. A secondary low-temperature reheater is installed inside the rear flue. A primary superheater is installed inside the intermediate flue. The inlet section of the primary superheater includes a first suspension pipe and a second suspension pipe that are arranged parallel to each other along the flue gas conveying direction; The first suspension pipe is wrapped with flat steel to form a front partition wall and a rear partition wall, which divide the flue inside the boiler body into the front flue, the middle flue and the rear flue. At least a portion of the first suspension tube extends downward to the first low-temperature reheater and then bends to form the first-stage superheater. The remaining portion of the first suspension tube continues downward and together with the second suspension tube forms a screen-type superheater at the bottom of the boiler body. During temperature adjustment, firstly, the opening of the third regulating baffle remains unchanged, and the opening of the first regulating baffle and the second regulating baffle is controlled so that the average steam temperature of the first reheat and the second reheat is close to the target temperature value; then, the opening of the second regulating baffle and the third regulating baffle remains unchanged, and the opening of the first regulating baffle is controlled so that the steam temperature of the first reheat and the second reheat is adjusted to the target temperature value. The inlet section of the primary superheater includes six rows of suspended tubes arranged in parallel, wherein the two middle rows of suspended tubes are the first suspended tubes, and the remaining four rows of suspended tubes on both sides are the second suspended tubes. The primary superheater is connected to the screen-type superheater via a pipeline.

2. The temperature control method for a double reheat boiler according to claim 1, characterized in that, It also includes a high-temperature superheater, which is installed inside the boiler body and located downstream of the screen-type superheater along the flue gas conveying route. The outlet of the screen-type superheater is connected to the inlet of the high-temperature superheater.

3. The temperature control method for a double reheat boiler according to claim 2, characterized in that, It also includes a primary high-temperature reheater and a secondary high-temperature reheater, both of which are located inside the boiler body and downstream of the high-temperature superheater along the flue gas conveying path.

4. The temperature control method for a double reheat boiler according to claim 3, characterized in that, The pipes of the primary high-temperature reheater and the secondary high-temperature reheater are alternately arranged on a plane perpendicular to the flue gas conveying direction, and the interval between two adjacent pipes is suitable for the passage of flue gas.

5. The temperature control method for a double reheat boiler according to claim 1, characterized in that, It also includes the first economizer, the second economizer, and the third economizer; The first economizer is located in the front flue and downstream of the primary low-temperature reheater along the flue gas conveying direction; The second economizer is located in the middle flue and downstream of the first-stage superheater along the flue gas conveying direction; The third economizer is located in the rear flue and downstream of the secondary low-temperature reheater along the flue gas conveying direction.

6. The temperature control method for a double reheat boiler according to claim 1, characterized in that, The primary superheater is suspended from the front partition wall or the rear partition wall via structural components.

7. The temperature control method for a double reheat boiler according to claim 5, characterized in that, The second economizer is suspended from the front partition wall or the rear partition wall via structural components.

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