Steam turbine No. 3 high pressure heater leakage detection method, device and system

Abstract

The present invention relates to a method, device and system for detecting leakage of No. 3 high-pressure heater of a steam turbine. By establishing a fault model of No. 3 high-pressure heater, 7 leakage criteria are obtained, and boundary conditions for triggering leakage warning of No. 3 high-pressure heater are provided. Compared with the prior art, the present invention develops different fault judgment models according to different leakage modes of No. 3 high-pressure heater, and can give an early warning for leakage from the water side of No. 3 high-pressure heater to the steam side, and can also give an early warning for leakage from the steam side of No. 3 high-pressure heater to the drain side. Leakage of the high-pressure heater can be discovered in time and an early warning can be given, which can effectively prevent the leakage from further expanding and avoid causing safety accidents.

Description

Technical Field

[0001] The present invention relates to the field of steam turbine high-pressure heaters, and in particular to a method, device and system for detecting leakage of a No. 3 high-pressure heater of a steam turbine. Background Art

[0002] Under the new situation of the power industry, the low-load operation time of coal-fired power generation units has increased, and the start-up and shutdown are frequent, which has an adverse impact on the safety of unit operation. At the same time, the requirements for the safety of coal-fired power generation units are constantly increasing, and the use of new technologies to improve the safety level of units has become an urgent need.

[0003] As a heat conversion device, the high-pressure heater is widely used in the steam extraction and heat recovery system of large thermal power units. Its working principle is: extract high-temperature and high-pressure superheated steam from the steam turbine, heat the feed water in the high-pressure heater, reduce the temperature difference between the feed water entering the boiler and the furnace, and improve the heat exchange efficiency. In the mainstream steam turbine system, there are three high-pressure heaters, namely the first high-pressure heater, the second high-pressure heater and the third high-pressure heater. The third high-pressure heater is the No. 3 high-pressure heater. The No. 3 high-pressure heater is a surface structure. There is a temperature difference between steam and feed water, and a large pressure difference between the water side and the steam side. The working environment is worse than that of the No. 1 and No. 2 high-pressure heaters. In addition, the thermal stress generated during frequent startup and insufficient preheating are factors that easily cause the heater to leak. The impact of leakage on the safety and economy of the unit is as follows:

[0004] 1. The leaking pipe creates a high-pressure water supply impact on the surrounding pipe bundles, causing an increase in the number of leaking pipe bundles and increasingly serious leakage.

[0005] 2. Leakage from the steam side to the drain side forms a steam-water two-phase flow in the drain pipe, which can easily cause steam-water shock in the pipe and affect the safe operation of the unit.

[0006] 3. The leakage causes the water level in the high-pressure heater to rise, posing risks such as the high-pressure heater being disconnected and the unit's load capacity being reduced.

[0007] 4. Leakage causes the outlet water temperature of the heater to decrease, and the high-quality heat is not fully utilized, which affects the final feed water temperature and reduces the economic efficiency of the unit operation.

[0008] It can be seen that the leakage of No. 3 high-pressure heater has an important impact on the safety and economy of the unit operation. Therefore, it is very necessary to detect the leakage of the high-pressure heater in a timely and accurate manner, and take operating measures in time to effectively prevent the leakage accident from expanding; reduce the problem of decreased unit operating economy caused by leakage; and avoid a substantial increase in unit coal consumption due to serious leakage.

[0009] In the prior art, leakage of the No. 3 high-pressure heater is mainly judged manually by humans, who observe relevant data such as the operating end difference of the heater and the feed water temperature and rely on rich operating experience to make judgments, which requires high capabilities and experience of the operating personnel. When the personnel discover that the relevant parameters of the No. 3 high-pressure heater are abnormal, an obvious leakage has occurred, which has an adverse effect on the safe and economical operation of the unit. There is a lack of intelligent early warning methods for leakage of the No. 3 high-pressure heater. Summary of the invention

[0010] The purpose of the present invention is to provide a method, device and system for detecting leakage of the No. 3 high-pressure heater of the steam turbine, which can timely detect the leakage of the No. 3 high-pressure heater of the steam turbine and issue a leakage warning to prevent the leakage from further expanding and avoid causing safety accidents. It can also issue a warning for leakage from the water side of the No. 3 high-pressure heater to the steam side, and can also issue a warning for leakage from the steam side of the No. 3 high-pressure heater to the drain side.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A method for detecting leakage of a No. 3 high-pressure heater of a steam turbine, comprising:

[0013] Step S1: collecting the opening of the drain valve of the No. 3 high-pressure heater under the set working condition, and judging whether the opening exceeds the first set threshold value, if yes, executing step S4, otherwise, executing step S2;

[0014] Step S2: obtaining the water inlet temperature and the drain temperature of the No. 3 high-pressure heater, and determining whether the difference between the drain temperature and the water inlet temperature is greater than a third set threshold value. If yes, executing step S3; otherwise, returning to step S1;

[0015] Step S3: determining whether the temperature rise of the No. 3 high-pressure heater under the set working condition exceeds the fourth set threshold value, if yes, executing step S5, otherwise, returning to step S1;

[0016] Step S4: Determine whether any two of the following conditions are met:

[0017] 1) Whether the difference between the water inlet flow rate and the water outlet flow rate of the No. 3 high-pressure heater exceeds the second set threshold value,

[0018] 2) Whether the water level of No. 3 high-pressure heater reaches the high I value,

[0019] 3) Whether the temperature rise of the No. 3 high-pressure heater exceeds the fourth set threshold value under the set working condition,

[0020] 4) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold,

[0021] 5) Whether the speed of the water supply pump increases to the sixth set threshold under the set working conditions,

[0022] If yes, it is determined that leakage has occurred, otherwise, it returns to step S1;

[0023] Step S5: Determine whether any one of the following conditions is met:

[0024] 1) Whether the water level of No. 3 high-pressure heater reaches the high I value

[0025] 2) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold,

[0026] If yes, it is determined that leakage has occurred, otherwise, the process returns to step S1.

[0027] The method further comprises:

[0028] Step S6: When it is determined that a leak has occurred, an alarm signal is outputted externally.

[0029] The first set threshold is 12%.

[0030] The second set threshold is 30t / h.

[0031] The third set threshold is 12°C, and the fourth set threshold is 4°C.

[0032] The fifth set threshold is 2.5 degrees Celsius.

[0033] The sixth set threshold is 300 rpm.

[0034] A detection device as described above is implemented, comprising a third high-pressure heater, a second high-pressure heater and a first high-pressure heater connected in sequence, the input end of the third high-pressure heater is connected to the intermediate-pressure cylinder of the steam turbine through a three-stage steam extraction pipeline, and the input end is connected to the deaerator through a feed water pump, a third drain regulating valve is provided at the bottom of the third high-pressure heater, an inlet water temperature sensor is provided at the input end, and an outlet water temperature sensor is provided at the output end, an inlet steam pressure sensor is provided on the three-stage steam extraction pipeline, the device also includes an environmental pressure sensor for measuring atmospheric pressure, a drain temperature sensor is provided between the third high-pressure heater and the third drain regulating valve, an inlet steam temperature sensor is also provided on the three-stage steam extraction pipeline, the output end of the first high-pressure heater is connected to the boiler, an inlet water flow meter is provided between the third high-pressure heater and the feed water pump, a water outlet flow meter is provided between the second high-pressure heater and the third high-pressure heater, the third high-pressure heater is also provided with a water level gauge, and a speed sensor is provided on the feed water pump.

[0035] A steam turbine system comprises a boiler, a deaerator, a steam turbine high-pressure cylinder and a steam turbine intermediate-pressure cylinder, and a detection device as described above, wherein the first steam outlet of the boiler is connected to the input end of the steam turbine high-pressure cylinder through a main steam pipeline, the output end of the steam turbine high-pressure cylinder is connected to the boiler through a high-pressure cylinder exhaust pipeline and then connected to the input end of the steam turbine intermediate-pressure cylinder through an intermediate-pressure cylinder steam inlet pipeline via a second steam outlet of the boiler, and the input end of the deaerator is connected to a condensate pipeline.

[0036] The invention also includes a first-stage steam extraction pipeline and a second-stage steam extraction pipeline. Two ends of the first-stage steam extraction pipeline are respectively connected to the high-pressure cylinder of the steam turbine and the first high-pressure heater. Two ends of the second-stage steam extraction pipeline are respectively connected to the high-pressure cylinder of the steam turbine and the second high-pressure heater.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) It can timely detect the leakage of the third high-pressure heater of the steam turbine and issue a leakage warning to prevent the leakage from further expanding and avoid causing safety accidents. It can also issue a warning for the leakage from the water side of the third high-pressure heater to the steam side, and it can also issue a warning for the leakage from the steam side of the third high-pressure heater to the drain side.

[0039] 2) A one-to-one correspondence between leakage and multiple operating parameters is established. The early warning logic includes a comprehensive analysis of multiple judgment bases to avoid interference from accidental factors and improve the accuracy of early warning.

[0040] 3) It has wide applicability and is suitable for units in the design stage of commissioning, units that are frequently started and stopped after commissioning or operate at low load for a long time, and units that have experienced leakage of the third high-pressure heater. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a structural diagram of an application system according to an embodiment of the present invention;

[0042] Figure 2 is a partial schematic diagram of a high-voltage heater according to an embodiment of the present invention;

[0043] Among them: 1. The first high-pressure heater, 2. The second high-pressure heater, 3. The third high-pressure heater, 4. Deaerator, 11. Boiler, 12. Turbine high-pressure cylinder, 13. Turbine intermediate-pressure cylinder, 14. Generator, 15. Feedwater pump, 21. First-stage steam extraction pipeline, 22. Second-stage steam extraction pipeline, 23. Third-stage steam extraction pipeline, 24. Fourth-stage steam extraction pipeline, 31. Main steam pipeline, 32. High-pressure cylinder exhaust pipeline, 33. Reheat steam pipeline, 34. Intermediate-pressure cylinder exhaust pipeline, 35. Condensate pipeline, 36. Feedwater pipeline, 41. First drain regulating valve, 42. Second drain regulating valve, 43. Third drain regulating valve, 51. Inlet flow meter, 52. Outlet flow meter, 53. Water level meter, PT 3, steam inlet pressure sensor, PT 0 , Environmental pressure sensor, TT 3jq , Inlet temperature sensor, TT 3ss , Hydrophobic temperature sensor, TT 3js , water inlet temperature sensor, TT 3cs , water outlet temperature sensor, RPM, water feed pump speed measurement point. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0045] The leakage of No. 3 high-pressure heater of coal-fired power generation unit has an important impact on the operating safety and economy of the unit. It is very necessary to detect the leakage of No. 3 high-pressure heater in a timely and accurate manner.

[0046] like Figure 1 and Figure 2 As shown, the whole system includes a third high-pressure heater 3, a second high-pressure heater 2, a first high-pressure heater 1, a deaerator 4, a boiler 11, a turbine high-pressure cylinder 12, a turbine intermediate-pressure cylinder 13, a generator 14, a feed water pump 15, a first-stage steam extraction pipeline 21, a second-stage steam extraction pipeline 22, a third-stage steam extraction pipeline 23, a fourth-stage steam extraction pipeline 24, a main steam pipeline 31, a high-pressure cylinder exhaust pipeline 32, an intermediate-pressure cylinder steam inlet pipeline 33, an intermediate-pressure cylinder exhaust pipeline 34, a condensate pipeline 35, and a feed water pipeline 36. A first drain regulating valve 41 is provided at the bottom of the first high-pressure heater 1, a second drain regulating valve 42 is provided at the bottom of the second high-pressure heater 2, and a third drain regulating valve 43 is provided at the bottom of the third high-pressure heater 3.

[0047] The input end of the third high pressure heater 3 is provided with a water inlet temperature sensor TT 3js , the output end is equipped with a water temperature sensor TT 3cs The third-stage extraction steam pipeline 23 is provided with a steam inlet pressure sensor PT 3 The device also includes an ambient pressure sensor PT for measuring atmospheric pressure 0 A hydrophobic temperature sensor PP is provided between the third high pressure heater 3 and the third hydrophobic regulating valve 43. 3ss The third-stage extraction steam pipeline 23 is also provided with a steam inlet temperature sensor TT. 3jq The output end of the first high-pressure heater 1 is connected to the boiler 11. An inlet flow meter 51 is provided between the third high-pressure heater and the feed water pump, and an outlet flow meter 52 is provided between the second high-pressure heater and the third high-pressure heater.

[0048] By studying the influence of leakage of No. 3 high-pressure heater on operating parameters, the quantitative relationship between leakage and related operating parameters is given, and the following 7 criteria are determined:

[0049] Criteria 1: The normal drain valve opening of No. 3 high-pressure heater is 12% higher than that under the same load condition;

[0050] Criteria 2: No. 3 high-pressure heater water inlet flow rate G 1 With water flow G 2 Deviation G 1 -G 2 ≥30t / h;

[0051] Criteria 3: No. 3 high pressure heater water level high I value;

[0052] Criteria 4: No. 3 high-pressure heater water inlet temperature t 3js and hydrophobic temperature t 3ss The difference, that is, the lower end difference t 3ss -t 3js ≥12℃;

[0053] Criteria 5: Temperature rise of No. 3 high-voltage heater (t 3cs -t 3js ) and the design temperature rise under the same load condition (t 03cs -t 03js ) difference, that is, (t 03cs -t 03js )-(t 3cs -t 3js )≥4℃;

[0054] Criterion 6: No. 3 high-pressure heater water outlet temperature t 3cs With extraction steam pressure P 3 The corresponding saturation temperature pswsat_t(P 3 +P 0 ) difference, that is, the upper difference pswsat_t(P 3 +P 0 )-t 3cs ≥2.5℃;

[0055] Criterion 7: Under the same load condition, the speed of the water supply pump increases by 300 rpm.

[0056] Based on the above 7 criteria, a program is developed. When criterion 1 is met, as long as any one of criteria 2, 3, 5, 6, and 7 is met, it is determined that a leakage has occurred; or, when criterion 4 and criterion 5 are met, as long as any one of criteria 3 and criterion 6 is met, it is also determined that a leakage has occurred.

[0057] The specific program design is as follows, perform the following steps:

[0058] Step S1: collecting the opening of the drain valve of the No. 3 high-pressure heater under the set working condition, and judging whether the opening exceeds the first set threshold value, if yes, executing step S4, otherwise, executing step S2;

[0059] Step S2: obtaining the water inlet temperature and the drain temperature of the No. 3 high-pressure heater, and determining whether the difference between the drain temperature and the water inlet temperature is greater than a third set threshold value. If yes, executing step S3; otherwise, returning to step S1;

[0060] Step S3: determining whether the temperature rise of the No. 3 high-pressure heater under the set working condition exceeds the fourth set threshold value, if yes, executing step S5, otherwise, returning to step S1;

[0061] Step S4: Determine whether any two of the following conditions are met:

[0062] 1) Whether the difference between the water inlet flow rate and the water outlet flow rate of the No. 3 high-pressure heater exceeds the second set threshold value,

[0063] 2) Whether the water level of No. 3 high-pressure heater reaches the high I value,

[0064] 3) Whether the temperature rise of the No. 3 high-pressure heater exceeds the fourth set threshold value under the set working condition,

[0065] 4) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold,

[0066] 5) Whether the speed of the water supply pump increases to the sixth set threshold under the set working conditions,

[0067] If yes, it is determined that leakage has occurred, otherwise, it returns to step S1;

[0068] Step S5: Determine whether any one of the following conditions is met:

[0069] 1) Whether the water level of No. 3 high-pressure heater reaches the high I value

[0070] 2) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold,

[0071] If yes, it is determined that leakage has occurred, otherwise, the process returns to step S1.

[0072] Among them, the first set threshold is 12%, the second set threshold is 30t / h, the third set threshold is 12°C, the fourth set threshold is 4°C, the fifth set threshold is 2.5 degrees Celsius, and the sixth set threshold is 300rpm.

[0073] In some embodiments, the method further includes: Step S6: when it is determined that a leakage has occurred, an alarm signal is outputted externally.

[0074] Taking a 600MW unit of a power plant as an example, the example is analyzed. The unit is equipped with three high-pressure heaters and one deaerator. The above equipment is installed and numbered according to the schematic diagram of the embodiment, the first high-pressure heater 1, the second high-pressure heater 2, the third high-pressure heater 3, and the deaerator 4.

[0075] Under the rated power of 600MW, the design parameters of the No. 3 high-pressure heater are: the upper end difference is 0℃, the lower end difference is 5.6℃, and the heater temperature rise is 43℃. The unit operates stably and all operating parameters are normal. With the increase in the number of unit starts and stops and the operating time, the No. 3 high-pressure heater drain temperature gradually increases under the rated power condition of the unit, and the lower end difference reaches 12℃. At this time, the water level of the No. 3 high-pressure heater begins to fluctuate, and the outlet water temperature of the No. 3 high-pressure heater begins to decrease. When the lower end difference of the No. 3 high-pressure heater reaches 14℃ and the heater temperature rise decreases by 4℃, the upper end difference reaches 2.5℃, triggering the alarm of the No. 3 high-pressure heater steam side leaking to the drain side. On-site inspection found that the No. 3 high-pressure heater drain pipe was shaking, which further clarified the fact that the No. 3 high-pressure heater steam side leaked to the drain side.

[0076] The unit operators took measures to disconnect the high-pressure heater, exited the steam-side and water-side operation of the high-pressure heater, and switched to water-side bypass operation. The No. 3 high-pressure heater drain pipe was cut on site, and the drain cooling section cladding on the same side of the drain pipe was inspected. It was found that there were holes in the cladding caused by scouring, and there were gaps caused by scouring at the weld between the cladding and the end tube sheet, which verified the accuracy of the alarm system.

[0077] Through the leakage warning device of the No. 3 high-pressure heater of the steam turbine, it can be seen that the impact of the intelligent warning device of the No. 3 high-pressure heater on the safety and economy of the operation of the steam turbine is mainly reflected in the following aspects.

[0078] (1) Timely and accurate discovery of the No. 3 high-pressure heater leak and early warning, inspection of the cladding for holes caused by scouring, and verification of the accuracy of the analysis and judgment;

[0079] (2) After the warning, the unit operators take timely measures to effectively prevent the leakage accident from expanding, avoid safety accidents caused by the leakage, and even the risk of the unit not being able to shut down;

[0080] (3) If the leakage of the high-pressure heater is not discovered in time, the leakage will cause the heat exchange effect to deteriorate, the operating end difference to increase, and the feed water temperature to decrease, causing the unit's coal consumption to increase by more than 1.2g / (kW·h), affecting the unit's operating economy.

[0081] The leakage warning device of the No. 3 high-pressure heater of the steam turbine is studied and analyzed. The influence of the leakage of the No. 3 high-pressure heater on the operating parameters is established, and the leakage warning device of the No. 3 high-pressure heater is established. The logical basis of the leakage warning is clarified, which can timely and accurately judge the leakage of the high-pressure heater and prevent the leakage from further expanding and causing safety accidents. The warning device is highly practical and has broad development prospects.

Claims

1. A detection device for realizing a leakage detection method for a No. 3 high-pressure heater of a steam turbine, It is characterized in that Detection methods include: Step S1: collecting the opening of the drain valve of the No. 3 high-pressure heater under the set working condition, and judging whether the opening exceeds the first set threshold value, if yes, executing step S4, otherwise, executing step S2; Step S2: obtaining the water inlet temperature and the drain temperature of the No. 3 high-pressure heater, and determining whether the difference between the drain temperature and the water inlet temperature is greater than a third set threshold value. If yes, executing step S3; otherwise, returning to step S1; Step S3: determining whether the temperature rise of the No. 3 high-pressure heater under the set working condition exceeds the fourth set threshold value, if yes, executing step S5, otherwise, returning to step S1; Step S4: Determine whether any two of the following conditions are met: 1) Whether the difference between the water inlet flow rate and the water outlet flow rate of the No. 3 high-pressure heater exceeds the second set threshold value, 2) Whether the water level of No. 3 high-pressure heater reaches the high I value, 3) Whether the temperature rise of the No. 3 high-pressure heater under the set working condition is lower than the fourth set threshold, 4) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold, 5) Whether the speed of the water supply pump increases to the sixth set threshold under the set working conditions, If yes, it is determined that leakage has occurred, otherwise, it returns to step S1; Step S5: Determine whether any one of the following conditions is met: 1) Whether the water level of No. 3 high-pressure heater reaches the high I value, 2) Whether the upper end difference of the No. 3 high-pressure heater is greater than the fifth set threshold, If yes, it is determined that leakage has occurred, otherwise, it returns to step S1; The detection device comprises a third high-pressure heater (3), a second high-pressure heater (2) and a first high-pressure heater (1) which are connected in sequence, wherein the input end of the third high-pressure heater (3) is connected to the intermediate-pressure cylinder (13) of the steam turbine via a three-stage steam extraction pipeline (23), and the input end is connected to the deaerator (4) via a feedwater pump (15), a third drain regulating valve (43) is provided at the bottom of the third high-pressure heater (3), and a water inlet temperature sensor (TT 3js ), the output end is equipped with a water outlet temperature sensor (TT 3cs ), the third-stage steam extraction pipeline (23) is provided with a steam inlet pressure sensor (PT 3 ), the device also includes an ambient pressure sensor (PT 0 ), a hydrophobic temperature sensor (TT) is provided between the third high-pressure heater (3) and the third hydrophobic regulating valve (43). 3ss ), the third-stage steam extraction pipeline (23) is also provided with a steam inlet temperature sensor (TT 3jq ), the output end of the first high-pressure heater (1) is connected to the boiler (11), a water inlet flow meter (51) is provided between the third high-pressure heater (3) and the feed water pump (15), a water outlet flow meter (52) is provided between the second high-pressure heater (2) and the third high-pressure heater (3), the third high-pressure heater (3) is also provided with a water level meter (54), and a speed sensor (RPM) is provided on the feed water pump (15).

2. The detection device according to claim 1, It is characterized in that The method further comprises: Step S6: When it is determined that a leak has occurred, an alarm signal is outputted externally.

3. The detection device according to claim 1, It is characterized in that The first set threshold is 12%.

4. The detection device according to claim 1, It is characterized in that The second set threshold is 30t / h.

5. The detection device according to claim 1, It is characterized in that The third set threshold is 12°C, and the fourth set threshold is 4°C.

6. The detection device according to claim 5, It is characterized in that The fifth set threshold is 2.5 degrees Celsius.

7. The detection device according to claim 1, It is characterized in that The sixth set threshold is 300 rpm.

8. A leakage detection system for the No. 3 high-pressure heater of a steam turbine, It is characterized in that The invention comprises a boiler (11), a deaerator (4), a steam turbine high-pressure cylinder (12) and a steam turbine intermediate-pressure cylinder (13), and a detection device as claimed in claim 1, wherein the first steam outlet of the boiler (11) is connected to the input end of the steam turbine high-pressure cylinder (12) through a main steam pipeline (31), the output end of the steam turbine high-pressure cylinder (12) is connected to the boiler (11) through a high-pressure cylinder exhaust pipeline (32), and then connected to the input end of the steam turbine intermediate-pressure cylinder (13) through a second steam outlet of the boiler (11) through an intermediate-pressure cylinder steam inlet pipeline (33), and the input end of the deaerator (4) is connected to a condensate pipeline (35).

9. The detection system according to claim 8, It is characterized in that The detection system further comprises a first-stage steam extraction pipeline (21) and a second-stage steam extraction pipeline (22), wherein two ends of the first-stage steam extraction pipeline (21) are respectively connected to the steam turbine high-pressure cylinder (12) and the first high-pressure heater (1), and two ends of the second-stage steam extraction pipeline (22) are respectively connected to the steam turbine high-pressure cylinder (12) and the second high-pressure heater (2).

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