A three-stage bypass system for thermal power plants

Abstract

The present invention discloses a three-stage bypass system of a thermal power plant, including a boiler superheater, a connecting block, a movable block, a limit plate, a counterweight block and a limit cylinder. A safety valve upper cover is arranged above the safety valve body, a fastening bolt is installed at the connection between the safety valve body and the safety valve upper cover, a limit spring is arranged inside the safety valve upper cover, a connecting block is arranged below the limit spring, a movable block is installed below the connecting block, a limit plate is arranged at the end of the movable block, the limit plate is connected to the end of the connecting pipe, a counterweight block is connected above the connecting block, a limit cylinder is arranged outside the counterweight block, and the limit cylinder is installed above the safety valve upper cover. The three-stage bypass system of the thermal power plant is provided with a high-pressure bypass and a medium-pressure bypass arranged on the boiler side, fully considering the rationality of the overall layout of the turbine bypass system, facilitating the two-row layout of the steam turbine room, and reducing the engineering cost of the steam turbine room.

Description

Technical Field

[0001] The invention relates to the field of main reheat steam and bypass systems of thermal power plants, in particular to a three-level bypass system of a thermal power plant. Background Art

[0002] At present, in order to adapt to the constant pressure and sliding pressure operation of the unit, improve the startup performance of the unit in cold, warm and hot states, and ensure that the reheater does not dry burn, the million-level secondary reheat ultra-supercritical units all adopt a high-pressure, medium-pressure and low-pressure three-stage series bypass system. The high-pressure bypass is connected from the two main steam pipes before the inlet of the ultra-high pressure cylinder of the turbine, and is connected to the cold primary reheat steam pipe after temperature and pressure reduction. The medium-pressure bypass is connected from the two branches of the primary reheat hot section steam before the inlet of the high-pressure cylinder of the steam turbine, and is connected to the secondary reheat cold section steam pipe after temperature and pressure reduction. The low-pressure bypass is connected from the two branches of the secondary reheat hot section steam before the inlet of the intermediate-pressure cylinder of the steam turbine, and is connected to the condenser after pressure reduction and temperature reduction.

[0003] In the existing design bill, the high-pressure bypass is generally arranged at about 13.7m in the turbine room, without a safety door function; the medium- and low-pressure bypass devices are start-up bypasses, the medium-pressure bypass valve is arranged at 8.60m in front of the furnace, and the low-pressure bypass is arranged at 8.60m in the turbine room. There are two problems:

[0004] (1) The high-pressure bypass is arranged at about 13.7m above the turbine room. A safety valve must be designed at the boiler superheater outlet. The safety valve has a high pressure rating and is prone to not returning to its seat when operated, which can easily lead to internal leakage.

[0005] (2) The high, medium and low pressure bypasses are all arranged in the turbine room, which will cause the turbine room space to be occupied and the unreasonable layout will increase the project cost;

[0006] Therefore, we proposed a three-level bypass system for thermal power plants to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a three-level bypass system for a thermal power plant to solve the problem that the safety valve has a high pressure level and is prone to not returning to its seat when moved and is prone to internal leakage; the high, medium and low pressure bypasses are all arranged in the steam engine room, which will cause the space of the steam engine room to be occupied and the unreasonable layout will increase the project cost.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a three-stage bypass system of a thermal power plant, comprising a boiler superheater, a connecting block, a movable block, a limiting plate, a counterweight block and a limiting cylinder, wherein the high-pressure bypass is provided with a boiler superheater, a VHP bypass valve, a VHP regulating valve, a VHP ventilation valve and an ultra-high-pressure cylinder VHP, the medium-pressure bypass is provided with a first-stage reheater RH1, an HP bypass valve, an HP regulating valve, an HP check valve, a high-pressure cylinder HP and an HP ventilation valve, the low-pressure bypass is provided with a second-stage reheater RH2, an IP regulating valve, an IP bypass valve and a medium-pressure cylinder IP, a connecting pipe is provided inside the end of the safety valve body, a safety valve upper cover is provided above the safety valve body, and the safety valve body A fastening bolt is installed at the connection with the upper cover of the safety valve, a limiting spring is arranged inside the upper cover of the safety valve, a connecting block is arranged below the limiting spring, a movable block is installed below the connecting block, a limiting plate is arranged at the end of the movable block, the limiting plate is connected to the end of the connecting pipe, a counterweight block is connected above the connecting block, a limiting cylinder is arranged on the outside of the counterweight block, and the limiting cylinder is installed above the upper cover of the safety valve, the high-pressure bypass is arranged at about 80m floor of the boiler room, the medium-pressure bypass is arranged at 8.6m floor in front of the furnace, and the low-pressure bypass is arranged at 8.6m on the steam engine room, the interior of the limiting cylinder is a hollow structure, and the counterweight block inside the limiting cylinder constitutes an up and down sliding structure through the connecting block.

[0009] Preferably, the high-pressure bypass adopts a three-way valve system with a safety valve function, with a capacity of 100% BMCR. The capacities of the medium-pressure bypass and the low-pressure bypass are set to meet the unit startup flow requirements. The VHP bypass valve, HP bypass valve and IP bypass valve are all hydraulically controlled.

[0010] Preferably, the safety valve body and the safety valve upper cover are fixedly connected by fastening bolts, and the limiting cylinder and the safety valve upper cover are fixedly connected.

[0011] Preferably, the movable block forms an up-and-down movable structure inside the safety valve upper cover through a limit spring.

[0012] Compared with the prior art, the invention has the following beneficial effects: the three-stage bypass system of the thermal power plant is provided with:

[0013] (1) The high-pressure bypass and medium-pressure bypass are arranged on the boiler side, which fully considers the rationality of the overall layout of the turbine bypass system, facilitates the two-row layout of the turbine room, and reduces the construction cost of the turbine room;

[0014] (2) The high-pressure bypass valve has a safety gate function, eliminating the boiler superheater outlet safety gate, reducing investment, and eliminating the risk of internal leakage of the ultra-high-pressure safety gate, fully considering the operating safety of the turbine bypass system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the position layout of the present invention;

[0016] Figure 2 This is a schematic diagram of the main cross-sectional structure of the safety valve of the present invention;

[0017] Figure 3 For the present invention Figure 2 Schematic diagram of the structure at point A in the middle.

[0018] In the figure: 1. boiler superheater; 2. VHP bypass valve; 3. VHP regulating valve; 4. VHP ventilation valve; 5. ultra-high pressure cylinder VHP; 6. primary reheater RH1; 7. HP bypass valve; 8. HP regulating valve; 9. HP check valve; 10. high pressure cylinder HP; 11. HP ventilation valve; 12. secondary reheater RH2; 13. IP regulating valve; 14. IP bypass valve; 15. medium pressure cylinder IP; 16. low pressure cylinder LP; 17. condenser; 18. high pressure bypass; 19. medium pressure bypass; 20. low pressure bypass; 21. safety valve body; 22. connecting pipe; 23. safety valve upper cover; 24. fastening bolts; 25. limit spring; 26. connecting block; 27. movable block; 28. limit plate; 29. ​​counterweight block; 30. limit cylinder. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1-3The present invention provides a technical solution: a three-stage bypass system of a thermal power plant, comprising a boiler superheater 1, a VHP bypass valve 2, a VHP regulating valve 3, a VHP ventilation valve 4, an ultra-high pressure cylinder VHP5, a primary reheater RH16, an HP bypass valve 7, an HP regulating valve 8, an HP check valve 9, a high pressure cylinder HP10, an HP ventilation valve 11, a secondary reheater RH212, an IP regulating valve 13, an IP bypass valve 14, a medium pressure cylinder IP15, a low pressure cylinder LP16, a condenser 17, a high pressure bypass 18, a medium pressure bypass 19, and a low pressure bypass 20. , safety valve body 21, connecting pipe 22, safety valve upper cover 23, fastening bolts 24, limit spring 25, connecting block 26, movable block 27, limit plate 28, counterweight block 29 and limit cylinder 30, the high-pressure bypass 18 is provided with boiler superheater 1, VHP bypass valve 2, VHP regulating valve 3, VHP ventilation valve 4 and ultra-high pressure cylinder VHP5, the medium-pressure bypass 19 is provided with primary reheater RH16, HP bypass valve 7, HP regulating valve 8, HP check valve 9, high-pressure cylinder HP10 and HP ventilation valve 11, the low-pressure bypass 20 is provided with Secondary reheater RH212, IP regulating valve 13, IP bypass valve 14 and medium pressure cylinder IP15, a connecting pipe 22 is arranged inside the end of the safety valve body 21, a safety valve upper cover 23 is arranged above the safety valve body 21, a fastening bolt 24 is installed at the connection between the safety valve body 21 and the safety valve upper cover 23, a limit spring 25 is arranged inside the safety valve upper cover 23, a connecting block 26 is arranged below the limit spring 25, a movable block 27 is installed below the connecting block 26, a limit plate 28 is arranged at the end of the movable block 27, and the limit plate 28 It is connected to the end of the connecting pipe 22, and a counterweight block 29 is connected to the top of the connecting block 26. A limiting cylinder 30 is arranged on the outside of the counterweight block 29, and the limiting cylinder 30 is installed above the safety valve cover 23. The high-pressure bypass 18 is arranged at about 80m in the boiler room, the medium-pressure bypass 19 is arranged at 8.6m in front of the furnace, and the low-pressure bypass 20 is arranged at 8.6m in the steam engine room. The rationality of the overall layout of the turbine bypass system is fully considered. The interior of the limiting cylinder 30 is a hollow structure, and the counterweight block 29 inside the limiting cylinder 30 forms an up and down sliding structure through the connecting block 26.

[0021] The high-pressure bypass 18 adopts a three-way valve system with a safety valve function, with a capacity of 100% BMCR. The capacities of the medium-pressure bypass 19 and the low-pressure bypass 20 are set to meet the unit startup flow requirements. The VHP bypass valve 2, HP bypass valve 7 and IP bypass valve 14 are all hydraulically controlled, taking into account the operational safety of the turbine bypass system.

[0022] The safety valve body 21 and the safety valve upper cover 23 are fixedly connected by fastening bolts 24, and the limiting cylinder 30 and the safety valve upper cover 23 are fixedly connected to maintain the sealing of the device.

[0023] The movable block 27 forms an up-and-down movable structure inside the safety valve upper cover 3 through the limit spring 25 .

[0024] Working principle: When using the three-stage bypass system of the thermal power plant, first, the first-stage bypass BP1, that is, the bypass of the ultra-high pressure cylinder VHP5, steam is discharged from the boiler superheater outlet to the turbine ultra-high pressure cylinder VHP5, and enters the first-stage reheater RH16. The steam entering the ultra-high pressure cylinder VHP5 enters the first-stage reheater RH16 after being discharged from the ultra-high pressure cylinder VHP5. During startup, the pressure of the first-stage reheater RH16 is ≯4MPa to avoid the exhaust temperature of the ultra-high pressure cylinder VHP5 exceeding the maximum limit of 530℃. A VHP ventilation valve 4 is configured on the exhaust cylinder of the ultra-high pressure cylinder VHP5. This valve does not participate in startup. Its main function is to quickly exhaust steam when the load is dropped. The high-pressure bypass 18 valve group and the oil station are arranged on the 80m floor of the boiler room. The high-pressure bypass 18 system adopts a three-purpose valve system with a safety valve function, and the boiler superheater outlet safety door is cancelled.

[0025] The medium-pressure bypass 19, i.e. the bypass of the high-pressure cylinder HP10, the bypass steam is discharged from the outlet of the first-stage reheater RH16 into the second-stage reheater RH212, that is, it is connected to the exhaust steam of the high-pressure cylinder HP10. The steam entering the high-pressure cylinder HP10 is discharged from the exhaust steam cylinder of the high-pressure cylinder HP10 and also enters the second-stage reheater. The function of the medium-pressure bypass 19 is to control the pressure of the first-stage reheater RH16. During startup, the pressure of the second-stage reheater RH212 is 0.5MPa~1.3MPa to avoid the maximum limit of 500℃ of the exhaust steam temperature of the high-pressure cylinder HP10. The exhaust steam of the high-pressure cylinder HP10 is also equipped with an HP ventilation valve. Similarly, this valve does not participate in the startup. Its main function is to quickly exhaust steam when the load is dropped. The medium-pressure bypass 19 is arranged at the 8.60m layer in front of the furnace.

[0026] The low-pressure bypass 20, that is, the outlet of the secondary reheater RH212 to the condenser 17, plays the role of controlling the pressure of the secondary reheater RH212. For the double reheat steam turbine, the pressure of the secondary reheater RH212 has the opposite effect on the exhaust temperature of the high-pressure cylinder HP10 and the exhaust temperature of the medium-pressure cylinder IP15 (low-pressure inlet). Therefore, the setting of the secondary reheater RH212 pressure during startup must ensure that the exhaust temperature of the high-pressure cylinder HP10 and the exhaust temperature of the medium-pressure cylinder IP15 are both within the safe range. The low-pressure bypass 20 is arranged on the 8.60m floor of the steam engine room. And the contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0027] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-stage bypass system for a thermal power plant, comprising a boiler superheater (1), a high-pressure bypass (18), a medium-pressure bypass (19), a low-pressure bypass (20), a safety valve body (21), a connecting block (26), a movable block (27), a stop plate (28), a counterweight block (29) and a stop cylinder (30), characterized in that: The high-pressure bypass (18) is provided with a boiler superheater (1), a VHP bypass valve (2), a VHP regulating valve (3), a VHP ventilation valve (4) and an ultra-high-pressure cylinder VHP (5); the medium-pressure bypass (19) is provided with a primary reheater RH1 (6), an HP bypass valve (7), an HP regulating valve (8), an HP check valve (9), a high-pressure cylinder HP (10) and an HP ventilation valve (11); the low-pressure bypass (20) is provided with a secondary reheater RH2 (12), an IP regulating valve (13), an IP bypass valve (14) and an intermediate-pressure cylinder IP (15); a connecting pipe (22) is provided inside the end of the safety valve body (21); a safety valve upper cover (23) is provided above the safety valve body (21); a fastening bolt (24) is installed at the connection between the safety valve body (21) and the safety valve upper cover (23); the safety valve upper cover (23) is provided with a connecting pipe (22); A limit spring (25) is arranged inside, a connection block (26) is arranged below the limit spring (25), a movable block (27) is installed below the connection block (26), a limit plate (28) is arranged at the end of the movable block (27), the limit plate (28) is connected to the end of the connection pipe (22), a counterweight (29) is connected above the connection block (26), a limit cylinder (30) is arranged outside the counterweight (29), and the limit cylinder (30) is installed above the safety valve upper cover (23), the high-pressure bypass (18) is arranged at about 80m above the boiler room, the medium-pressure bypass (19) is arranged at 8.6m above the furnace, and the low-pressure bypass (20) is arranged at 8.6m above the turbine room, the interior of the limit cylinder (30) is a hollow structure, and the counterweight (29) inside the limit cylinder (30) forms an up and down sliding structure through the connection block (26).

2. A three-stage bypass system for a thermal power plant according to claim 1, characterized in that: The high-pressure bypass (18) adopts a three-way valve system with a safety valve function, and its capacity is 100% BMCR. The capacities of the medium-pressure bypass (19) and the low-pressure bypass (20) are set to meet the unit startup flow requirements. The VHP bypass valve (2), the HP bypass valve (7) and the IP bypass valve (14) are all hydraulically controlled.

3. A three-stage bypass system for a thermal power plant according to claim 1, characterized in that: The safety valve body (21) and the safety valve upper cover (23) are fixedly connected via fastening bolts (24), and the limiting cylinder (30) and the safety valve upper cover (23) are also fixedly connected.

4. A three-stage bypass system for a thermal power plant according to claim 1, characterized in that: The movable block (27) forms an upper and lower movable structure inside the safety valve upper cover (3) via a limit spring (25).

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