A steam turbine unit suitable for ultra-low load operation and an operating method thereof

Abstract

The present invention discloses a steam turbine unit suitable for ultra-low load operation and an operating method thereof. The steam turbine unit includes a steam generator, a high-pressure cylinder connected to the steam generator, a main steam pipeline and an auxiliary steam pipeline. The main steam pipeline is arranged between the steam generator and the high-pressure cylinder. A main steam valve and a main regulating valve are provided on the main steam pipeline. The main regulating valve is arranged between the main steam valve and the high-pressure cylinder. The inlet of the auxiliary steam pipeline is connected to the air inlet end of the main steam valve, and the outlet of the auxiliary steam pipeline is connected to the air outlet end of the regulating valve. A bypass stop valve and a bypass regulating valve are provided on the auxiliary steam pipeline. An auxiliary steam pipeline is added to the main steam pipeline between the steam generator and the high-pressure cylinder. The auxiliary steam pipeline is used to enable the steam turbine to operate under low load for a long time, protect the main steam valve and the main regulating valve on the main steam pipeline, and ensure the safety and reliability of the steam turbine unit.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbines, and in particular to a steam turbine unit suitable for ultra-low load operation and an operating method thereof. Background Art

[0002] Thermal power units operating at low or even ultra-low loads can lead to a host of problems. One such issue is operating the control valve at a small opening. At low loads, the system often switches from sequence valves to single-valve control mode to ensure uniform thermal expansion of the cylinder. However, due to the small valve opening, severe throttling occurs in the gap between the control valve body and the valve seat. This throttling effect generates high temperatures at the valve seat, which directly heats the cylinder through heat transfer from the valve casing, causing the cylinder's thermal expansion to exceed the design value. At this time, the temperature after the control stage is relatively low, causing the rotor's thermal expansion to fall below the design value. This can lead to severe negative expansion of the turbine, impacting normal operation.

[0003] Moreover, when the control valve is opened too small, the flow channel gap is too small, the medium flow rate is too large, and the valve core and valve seat are severely eroded, which may cause the control valve to be scrapped in a short period of time; the load span is large, and the drastic pressure and flow rate changes, when exceeding the stiffness of the control valve, cause the control valve to vibrate violently, and also greatly reduce the valve life; if the control valve is opened too small, there will be jump closing and jump opening phenomena. The control valve cannot be adjusted normally at this opening, and the safety of the unit operation will also be threatened. Summary of the Invention

[0004] Therefore, in order to overcome the defects in the prior art that the steam turbine operates at low load for a long time, and the wear of the main steam valve and regulating valve of the steam turbine seriously affects the operating safety and stability of the steam turbine unit, the present invention provides a steam turbine unit suitable for ultra-low load operation.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] A steam turbine unit suitable for ultra-low load operation, comprising a steam generator, a high-pressure cylinder connected to the steam generator; a main steam pipeline and an auxiliary steam pipeline, the main steam pipeline being arranged between the steam generator and the high-pressure cylinder, a main steam valve and a main regulating valve being provided on the main steam pipeline, the main regulating valve being arranged between the main steam valve and the high-pressure cylinder; the inlet of the auxiliary steam pipeline being connected to the air inlet end of the main steam valve, the outlet of the auxiliary steam pipeline being connected to the air outlet end of the main regulating valve, and the auxiliary steam pipeline being provided with a bypass stop valve and a bypass regulating valve.

[0007] According to some embodiments of the present invention, the bypass regulating valve is arranged between the bypass stop valve and the high-pressure cylinder, the bypass regulating valve is used to adjust the flow rate of the secondary steam pipeline, and the bypass stop valve is used to control the on-off of the secondary steam pipeline.

[0008] According to some embodiments of the present invention, an accumulator is provided on the bypass stop valve.

[0009] According to some embodiments of the present invention, the main steam pipeline includes a first branch and a second branch connected in parallel, the first branch is provided with a first main steam valve, a first main regulating valve and a third main regulating valve, and the second branch is provided with a second main steam valve, a second main regulating valve and a fourth main regulating valve; there are two auxiliary steam pipelines, and the two auxiliary steam pipelines are respectively connected in parallel with the first branch and the second branch.

[0010] According to some embodiments of the present invention, the first branch is provided with a first parallel regulating pipeline, the third main regulating valve is provided on the first parallel regulating pipeline, and the third main regulating valve is connected in parallel with the first main regulating valve; the second branch is provided with a second parallel regulating pipeline, the fourth main regulating valve is provided on the second parallel regulating pipeline, and the fourth main regulating valve is connected in parallel with the second main regulating valve.

[0011] According to some embodiments of the present invention, the two auxiliary steam pipelines are respectively a first bypass and a second bypass, the first bypass is provided with a first bypass stop valve and a first bypass regulating valve, and the second bypass is provided with a second bypass stop valve and a second bypass regulating valve;

[0012] The first bypass regulating valve is disposed between the first bypass cut-off valve and the high-pressure cylinder, and the second bypass regulating valve is disposed between the second bypass cut-off valve and the high-pressure cylinder.

[0013] According to some embodiments of the present invention, the total flow rate of the secondary steam pipeline is 15-25% of the heat rate acceptance condition flow rate of the main steam pipeline.

[0014] According to some embodiments of the present invention, the auxiliary steam pipeline includes multiple bypasses, and the total flow rate of the multiple bypasses is 15-25% of the heat rate acceptance operating condition flow rate, and the multiple bypass flows are distributed according to the parallel branch flow ratio.

[0015] The present invention also provides an operating method for a steam turbine unit suitable for ultra-low load operation, comprising the following steps:

[0016] When the operating load of the steam turbine unit drops below the heat rate acceptance condition of 15-25%, gradually open the bypass regulating valve. When the opening of the bypass regulating valve reaches 30%, open the bypass stop valve.

[0017] While gradually opening the bypass regulating valve, gradually close the main regulating valve. When the bypass regulating valve is opened to the required flow capacity, close the main steam valve.

[0018] When the load of the steam turbine unit gradually increases to above the heat rate acceptance condition of 15-25%THA, gradually open the main control valve. When the main control valve is opened to 30% of the flow rate of the heat rate acceptance condition of 15-25%, open the main steam valve.

[0019] While gradually opening the main regulating valve, gradually close the bypass regulating valve. When the main regulating valve is opened to the required flow capacity, close the bypass stop valve.

[0020] The technical solution of the present invention has the following advantages:

[0021] 1. The present invention provides a steam turbine unit suitable for ultra-low load operation, in which an auxiliary steam pipeline is added to the main steam pipeline of the steam generator and the high-pressure cylinder. The inlet of the auxiliary steam pipeline is connected to the air inlet end of the main steam valve, and the outlet of the auxiliary steam pipeline is connected to the air outlet end of the main regulating valve. A bypass stop valve and a bypass regulating valve are provided on the auxiliary steam pipeline. The auxiliary steam pipeline enables the steam turbine to operate under low load for a long time, protects the main steam valve and the main regulating valve on the main steam pipeline, and ensures the safety and reliability of the steam turbine unit.

[0022] 2. The present invention provides a steam turbine unit suitable for ultra-low load operation. An accumulator is installed in the bypass stop valve. When the energy is too large, the energy is converted and stored. When the steam turbine unit needs it, the energy is converted and released and resupplied to the steam turbine unit to ensure normal pressure of the entire steam turbine unit.

[0023] 3. The present invention provides an operating method for a steam turbine unit operating at ultra-low load. The bypass steam pipeline utilizes a method that activates the bypass regulating valve first, followed by the shut-off valve. This effectively protects the bypass regulating valve, preventing damage to the bypass regulating valve caused by large pressure differentials during startup. This method is simple to operate, eliminates wear issues with the turbine unit's main steam valve and main line regulating valve, and ensures safe and stable unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1A schematic diagram of the connection between the main steam pipeline and the auxiliary steam pipeline of a steam turbine unit provided in one embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the connection between the main steam pipeline and the auxiliary steam pipeline of a steam turbine unit provided in another embodiment of the present invention.

[0027] Explanation of the accompanying symbols: 1. Main steam pipeline; 2. Auxiliary steam pipeline; 3. Main steam valve; 4. Main line regulating valve; 5. Bypass stop valve; 6. Bypass regulating valve; 7. Accumulator; 8. High-pressure cylinder; 11. First branch; 12. Second branch; 13. First parallel regulating pipeline; 14. Second parallel regulating pipeline; 21. First bypass; 22. Second bypass; 31. First main steam valve; 32. Second main steam valve; 41. First main line regulating valve; 42. Second main line regulating valve; 43. Third main line regulating valve; 44. Fourth main line regulating valve; 51. First bypass stop valve; 52. Second bypass stop valve; 61. First bypass regulating valve; 62. Second bypass regulating valve. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present 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.

[0030] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0031] In addition, 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.

[0032] Reference Figure 1 As shown, the present invention proposes a steam turbine unit suitable for ultra-low load operation, including a steam generator, a high-pressure cylinder 8 connected to the steam generator, a main steam pipeline 1 and an auxiliary steam pipeline 2. The main steam pipeline 1 is arranged between the steam generator and the high-pressure cylinder 8. A main steam valve 3 and a main regulating valve 4 are provided on the main steam pipeline 1. The main regulating valve 4 is arranged between the main steam valve 3 and the high-pressure cylinder 8; the inlet of the auxiliary steam pipeline 2 is connected to the air inlet end of the main steam valve 3, and the outlet of the auxiliary steam pipeline 2 is connected to the air outlet end of the main regulating valve 4. A bypass stop valve 5 and a bypass regulating valve 6 are provided on the auxiliary steam pipeline 2.

[0033] Specifically, an auxiliary steam pipeline 2 is added to the main steam pipeline 1 of the steam generator and the high-pressure cylinder 8. The inlet of the auxiliary steam pipeline 2 is connected to the air inlet end of the main steam valve 3, and the outlet of the auxiliary steam pipeline 2 is connected to the air outlet end of the main regulating valve 4. A bypass stop valve 5 and a bypass regulating valve 6 are provided on the auxiliary steam pipeline 2. The auxiliary steam pipeline 2 is used to enable the steam turbine to operate under low load for a long time, protect the main steam valve 3 and the main regulating valve 4 on the main steam pipeline 1, and ensure the safety and reliability of the steam turbine unit.

[0034] In some embodiments of the present invention, the bypass regulating valve 6 is arranged between the bypass stop valve 5 and the high-pressure cylinder 8. The bypass regulating valve 6 is used to adjust the flow rate of the auxiliary steam pipeline 2, and the bypass stop valve 5 is used to control the on and off of the auxiliary steam pipeline 2.

[0035] Specifically, the bypass stop valve 5 and the bypass regulating valve 6 are arranged in series on the auxiliary steam pipeline 2. During the operation of the turbine unit, the bypass regulating valve 6 is started first and then the bypass stop valve 5 is started to avoid damage to the bypass regulating valve 6 caused by the pressure difference shock during startup. This can well protect the bypass regulating valve 6 and extend the service life of the bypass regulating valve 6.

[0036] In some embodiments of the present invention, an accumulator 7 is provided on the bypass stop valve 5 .

[0037] Specifically, an accumulator 7 is installed on the bypass stop valve 5. When the bypass stop valve 5 is subjected to excessive energy, the energy is converted and stored. When the steam turbine unit needs it, the energy is converted and released and resupplied to the steam turbine unit to ensure normal pressure of the entire steam turbine unit.

[0038] In some embodiments of the present invention, the main steam pipeline 1 includes a first branch 11 and a second branch 12 in parallel, the first branch 11 is provided with a first main steam valve 31, a first main regulating valve 41 and a third main regulating valve 43, and the second branch 12 is provided with a second main steam valve 32, a second main regulating valve 42 and a fourth main regulating valve 44; there are two auxiliary steam pipelines 2, and the two auxiliary steam pipelines 2 are respectively connected in parallel with the first branch 11 and the second branch 12.

[0039] Specifically, the main steam pipeline 1 is configured as a first branch 11 and a second branch 12 connected in parallel. If either branch 11 or 12 becomes blocked, the other unobstructed branch ensures normal steam supply, ensuring the normal operation of the steam turbine. Two auxiliary steam pipelines 2 are connected in parallel with the first branch 11 and the second branch 12, respectively, to protect the main steam valve 3 and main regulating valve 4 on the first and second branches 11, 12, and improve the safety and reliability of the steam turbine.

[0040] Reference Figure 2 As described above, in some embodiments of the present invention, the first branch 11 is provided with a first parallel regulating pipeline 13, the third main regulating valve 43 is provided on the first parallel regulating pipeline 13, and the third main regulating valve 43 is connected in parallel with the first main regulating valve 41; the second branch 12 is provided with a second parallel regulating pipeline 14, the fourth main regulating valve 44 is provided on the second parallel regulating pipeline 14, and the fourth main regulating valve 44 is connected in parallel with the second main regulating valve 42.

[0041] Specifically, the two auxiliary steam pipelines 2 should be connected in parallel with the first main regulating valve 41 and the second main regulating valve 42, or connected in parallel with the third main regulating valve 43 and the fourth main regulating valve 44, respectively, to balance the valve pressure.

[0042] In some embodiments of the present invention, the two auxiliary steam pipelines 2 are respectively a first bypass 21 and a second bypass 22. The first bypass 21 is provided with a first bypass stop valve 51 and a first bypass regulating valve 61, and the second bypass 22 is provided with a second bypass stop valve 52 and a second bypass regulating valve 62; the first bypass regulating valve 61 is arranged between the first bypass stop valve 51 and the high-pressure cylinder 8, and the second bypass regulating valve 62 is arranged between the second bypass stop valve 52 and the high-pressure cylinder 8.

[0043] Specifically, the first bypass 21 is connected in parallel with the first branch 11, and the second bypass 22 is connected in parallel with the second branch 12. The first bypass stop valve 51 and the first bypass regulating valve 61 provided on the first bypass 21 are used to protect the first main steam valve 31, the first main line regulating valve 41, and the third main line regulating valve 43 on the first branch 11. The second bypass stop valve 52 and the second bypass regulating valve 62 provided on the second bypass 22 are used to protect the second main steam valve 32, the second main line regulating valve 42, and the fourth main line regulating valve 44 on the second branch 12. When the first bypass 21 and the second bypass 22 are put into operation, the first bypass regulating valve 61 and the second bypass regulating valve 62 are opened first, and then the first bypass stop valve 51 and the second bypass stop valve 52 are opened. This prevents damage to the first bypass regulating valve 61 and the second bypass regulating valve 62 caused by the large impact force generated by the steam at the moment of opening, thereby improving the stability of the steam turbine unit.

[0044] According to some embodiments of the present invention, the total flow rate of the auxiliary steam pipeline 2 is 15-25% of the flow rate of the main steam pipeline 1 under heat rate acceptance conditions.

[0045] Specifically, the total flow rate of the auxiliary steam pipeline 2 is determined according to the size of the steam turbine unit. In some embodiments of the present invention, the total flow rate of the auxiliary steam pipeline 2 is 20% of the heat rate acceptance operating condition flow rate of the main steam pipeline 1.

[0046] In some embodiments of the present invention, the auxiliary steam pipeline 2 includes multiple bypasses, and the total flow rate of the multiple bypasses is 15-25% of the heat rate acceptance operating flow rate, and the multiple bypass flows are distributed according to the parallel branch flow ratio.

[0047] Specifically, the multiple bypasses distribute the flow rate in proportion to the parallel branches, protecting the main steam valve 3 and the main regulating valve 4 on the branches, thereby ensuring the safe and stable operation of the steam turbine unit.

[0048] The present invention also provides an operating method for a steam turbine unit suitable for ultra-low load operation, comprising the following steps:

[0049] When the operating load of the steam turbine unit drops below the heat rate acceptance condition of 15-25%, the bypass regulating valve 6 is gradually opened. When the opening of the bypass regulating valve 6 reaches 30%, the bypass stop valve 5 is opened.

[0050] Specifically, opening the bypass regulating valve 6 first and then opening the bypass stop valve 5 can avoid excessive impact force of steam at the moment the stop valve is opened, which may cause pressure on the bypass regulating valve 6, reduce the impact of steam on the bypass regulating valve 6, and avoid damage to the bypass regulating valve 6; it can extend the service life of the bypass regulating valve 6 and improve the reliability of the steam turbine unit.

[0051] While gradually opening the bypass regulating valve 6, gradually close the main regulating valve 4. When the bypass regulating valve 6 is opened to the required flow capacity, close the main steam valve 3. At this time, the main steam pipeline 1 is in a shutdown state, and the auxiliary steam pipeline 2 is successfully put into operation.

[0052] When the load of the steam turbine unit gradually increases to above the flow rate of the acceptance condition of 15-25% heat rate, gradually open the main regulating valve 4. When the main regulating valve 4 opens to 30% of the flow rate of the acceptance condition of 15-25% heat rate, open the main steam valve 3.

[0053] While gradually opening the main regulating valve 4, the bypass regulating valve 6 is gradually closed. When the main regulating valve 4 is opened to the required flow capacity, the bypass stop valve 5 is closed.

[0054] Specifically, the auxiliary steam line 2 operates by first activating the bypass regulating valve 6 and then the bypass stop valve 5. This effectively protects the bypass regulating valve 6, preventing damage to the bypass regulating valve 6 caused by the large pressure differential during startup. This operating method is simple to operate and, when the steam turbine unit is operating at ultra-low load, can eliminate wear issues on the main steam valve 3 and main line regulating valve 4, while ensuring safe and stable operation of the unit.

[0055] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for operating a steam turbine unit suitable for ultra-low load operation, characterized in that: The steam turbine unit comprises a steam generator and a high-pressure cylinder (8) connected to the steam generator; a main steam pipeline (1), wherein the main steam pipeline (1) is arranged between the steam generator and the high-pressure cylinder (8); a main steam valve (3) and a main regulating valve (4) are provided on the main steam pipeline (1); the main regulating valve (4) is arranged between the main steam valve (3) and the high-pressure cylinder (8); an auxiliary steam pipeline (2), wherein the inlet of the auxiliary steam pipeline (2) is connected to the air inlet end of the main steam valve (3), and the outlet of the auxiliary steam pipeline (2) is connected to the air outlet end of the main regulating valve (4); and a bypass stop valve (5) and a bypass regulating valve (6) are provided on the auxiliary steam pipeline (2); The method comprises the following steps: When the operating load of the steam turbine unit is reduced to below the heat rate acceptance condition of 15-25%, the bypass regulating valve (6) is gradually opened. When the opening of the bypass regulating valve (6) reaches 30%, the bypass stop valve (5) is opened. While gradually opening the bypass regulating valve (6), gradually closing the main regulating valve (4); when the bypass regulating valve (6) is opened to the required flow capacity, closing the main steam valve (3); When the load of the steam turbine unit gradually increases to above the heat rate acceptance condition of 15-25%, the main regulating valve (4) is gradually opened. When the main regulating valve (4) is opened to 30% of the flow rate of the heat rate acceptance condition of 15-25%, the main steam valve (3) is opened. While gradually opening the main regulating valve (4), the bypass regulating valve (6) is gradually closed. When the main regulating valve (4) is opened to the required flow capacity, the bypass stop valve (5) is closed.

2. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 1, characterized in that: The bypass regulating valve (6) is arranged between the bypass stop valve (5) and the high-pressure cylinder (8), the bypass regulating valve (6) is used to adjust the flow rate of the auxiliary steam pipeline (2), and the bypass stop valve (5) is used to control the on-off of the auxiliary steam pipeline (2).

3. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 1, characterized in that: An accumulator (7) is provided on the bypass stop valve (5).

4. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 1, characterized in that: The main steam pipeline (1) comprises a first branch (11) and a second branch (12) connected in parallel, wherein the first branch (11) is provided with a first main steam valve (31), a first main regulating valve (41) and a third main regulating valve (43), and the second branch (12) is provided with a second main steam valve (32), a second main regulating valve (42) and a fourth main regulating valve (44); and there are two auxiliary steam pipelines (2), and the two auxiliary steam pipelines (2) are respectively connected in parallel with the first branch (11) and the second branch (12).

5. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 4, characterized in that: The first branch (11) is provided with a first parallel regulating pipeline (13), the third main regulating valve (43) is provided on the first parallel regulating pipeline (13), and the third main regulating valve (43) is connected in parallel with the first main regulating valve (41); the second branch (12) is provided with a second parallel regulating pipeline (14), the fourth main regulating valve (44) is provided on the second parallel regulating pipeline (14), and the fourth main regulating valve (44) is connected in parallel with the second main regulating valve (42).

6. The operating method of a steam turbine unit suitable for ultra-low load operation according to claim 4, characterized in that: The two auxiliary steam pipelines (2) are respectively a first bypass (21) and a second bypass (22); the first bypass (21) is provided with a first bypass stop valve (51) and a first bypass regulating valve (61); the second bypass (22) is provided with a second bypass stop valve (52) and a second bypass regulating valve (62); The first bypass regulating valve (61) is arranged between the first bypass stop valve (51) and the high-pressure cylinder (8), and the second bypass regulating valve (62) is arranged between the second bypass stop valve (52) and the high-pressure cylinder (8).

7. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 1, characterized in that: The total flow rate of the auxiliary steam pipeline (2) is 15-25% of the flow rate of the main steam pipeline (1) under the heat rate acceptance working condition.

8. The method for operating a steam turbine unit suitable for ultra-low load operation according to claim 7, characterized in that: The auxiliary steam pipeline (2) comprises multiple bypasses, the total flow rate of the multiple bypasses is 15-25% of the heat rate acceptance condition flow rate, and the multiple bypass flows are distributed according to the flow ratio of the parallel branches.

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