Low-load drainage switching detection system for high-pressure heater

Abstract

The utility model relates to the technical field of steam turbine detection, and provides a low-load drainage switching detection system for a high-pressure heater. Comprising a boiler, a high-pressure cylinder and an intermediate-pressure cylinder which are sequentially connected to form a main steam loop; the first high-pressure heater, the second high-pressure heater and the third high-pressure heater are sequentially connected in series; the deaerator is connected to a drain outlet of the third high-pressure heater through a third normal drain pipeline, and a third normal drain valve is arranged on the third normal drain pipeline; the condenser drain flash tank is connected to a drain outlet of the third high-pressure heater through a third critical drain pipeline, and a third critical drain valve is arranged on the third critical drain pipeline; the input end of the DCS control system is connected with the pressure detection device and the output end of the deaerator pressure sensor, and the output end of the DCS control system is connected with a third normal drain valve and a third emergency drain valve. By accurately controlling the drainage switching of the final-stage high-pressure heater, the problem of response lag of traditional manual operation is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steam turbine detection technology, in particular to a low-load drain switching detection system for high-pressure heater. BACKGROUND

[0002] In the design of thermal power plants, multiple stages of non-regulated steam extraction are provided for steam turbines to supply various stages of heaters, and the steam turbines supply steam to various stages of heaters according to sliding parameters during startup of the unit. The drain of various stages of high-pressure heaters adopts a scheme of step-by-step series connection of drain from high to low pressure in the heater, and the drain of the last stage of high-pressure heater is to the deaerator during normal operation, and the feedwater after deaeration by the deaerator is sent to the boiler for heating. The deaerator adopts an auxiliary steam supply constant pressure operation mode during the low-load startup stage, and is switched to a sliding pressure operation mode of corresponding steam extraction only when the deaerator reaches the constant pressure operation parameters. The internal pressure of the last stage of high-pressure heater is lower than the internal pressure of the deaerator during the startup stage, at which time the last stage of high-pressure heater drains to the condenser drain expansion vessel, and is switched to normal drain when the internal pressure of the last stage of high-pressure heater is higher than the pressure of the deaerator by a certain value.

[0003] In the existing scheme, manual switching to normal drain is required according to experience, the control is not accurate enough, heat source loss is caused, and the unit self-starting and stopping control requirements cannot be met. CONTENT OF THE UTILITY MODEL

[0004] Therefore, the present application provides a low-load drain switching detection system for high-pressure heater, which can automatically and accurately switch the drain of the last stage of high-pressure heater during low load, so as to reduce the labor intensity of the operating personnel, save coal resources, improve resource utilization, and provide conditions for one-key start-stop control of the unit.

[0005] The low-load drain switching detection system for high-pressure heater provided by the present application comprises:

[0006] The boiler, the high-pressure cylinder and the medium-pressure cylinder are connected in sequence to form a main steam loop;

[0007] The first high-pressure heater, the second high-pressure heater and the third high-pressure heater are connected in series for drain;

[0008] The deaerator is connected to the drain outlet of the third high-pressure heater through a third normal drain pipeline, and a third normal drain valve is arranged on the third normal drain pipeline;

[0009] The condenser drain expansion vessel is connected to the drain outlet of the third high-pressure heater through a third emergency drain pipeline, and a third emergency drain valve is arranged on the third emergency drain pipeline;

[0010] A DCS control system is connected to the output end of the pressure detection device and the deaerator pressure sensor, and is connected to the third normal drain valve and the third emergency drain valve respectively.

[0011] The high-pressure heater low-load drain switching detection system of the embodiment of the application comprises a boiler, a high-pressure cylinder, and a medium-pressure cylinder connected in sequence to form a main steam loop; a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater connected in sequence; a deaerator connected to the drain outlet of the third high-pressure heater through a third normal drain pipeline, wherein a third normal drain valve is arranged on the third normal drain pipeline; a condenser drain flash tank connected to the drain outlet of the third high-pressure heater through a third emergency drain pipeline, wherein a third emergency drain valve is arranged on the third emergency drain pipeline; and a DCS control system connected to the output end of the pressure detection device and the deaerator pressure sensor, and connected to the third normal drain valve and the third emergency drain valve respectively. The drain switching of the last-stage high-pressure heater is accurately controlled, and the problem of response lag in traditional manual operation is solved. The DCS control system judges the drain path based on the real-time pressure difference, and avoids the mis-switching caused by pressure fluctuation. The double-path drain pipeline design ensures the stable operation of the system under low load and normal conditions, reduces heat loss, provides a hardware basis for unit self-starting and stopping control, reduces the labor intensity of operating personnel, saves coal resources, improves resource utilization, and provides conditions for one-key starting and stopping control of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0013] Figure 1 FIG. 1 is a structural schematic diagram of a high-pressure heater low-load drain switching detection system provided by an embodiment of the application.

[0014] In the diagram: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. First high-pressure heater; 5. Second high-pressure heater; 6. Third high-pressure heater; 7. Deaerator; 8. Feedwater pump turbine; 9. Drainage expansion tank; 10. Condenser; 11. High-pressure cylinder exhaust check valve; 12. First-stage extraction steam electric valve and check valve; 13. Second-stage extraction steam electric valve and check valve; 14. Third-stage extraction steam electric valve and check valve; 15. Fourth-stage... 16. Electric steam extraction valve and check valve for deaerator; 17. Electric steam extraction valve and check valve for deaerator; 18. Electric steam extraction valve and regulating valve for deaerator; 19. First normal steam trap; 20. Second normal steam trap; 21. Third normal steam trap; 22. First emergency steam trap; 23. Second emergency steam trap; 24. Third emergency steam trap; 25. Steam extraction pressure detection device; 26. Pressure detection device; 27. Deaerator pressure detection device. Detailed Implementation

[0015] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0016] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0017] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0018] like Figure 1 As shown, this application provides a high-pressure heater low-load condensate switching detection system, comprising:

[0019] Boiler 1, high-pressure cylinder 2, and intermediate-pressure cylinder 3 are connected in sequence to form the main steam circuit;

[0020] The first high-pressure heater 4, the second high-pressure heater 5 and the third high-pressure heater 6 are connected in series;

[0021] The deaerator 7 is connected to the drain outlet of the third high-pressure heater 6 through a third normal drain pipe, and a third normal drain valve 20 is arranged on the third normal drain pipe;

[0022] The condenser drain expansion vessel 9 is connected to the drain outlet of the third high-pressure heater 6 through a third emergency drain pipe, and a third emergency drain valve 23 is arranged on the third emergency drain pipe;

[0023] The DCS control system is connected to the output ends of the pressure detection device 25 and the deaerator pressure sensor 27, and is connected to the third normal drain valve 20 and the third emergency drain valve 23 respectively.

[0024] In application, the main steam circuit is driven by high-temperature and high-pressure steam generated by the boiler to drive the high-pressure cylinder and the medium-pressure cylinder in sequence. The drain of the high-pressure heater is arranged in series, and the third high-pressure heater is used as the last-stage heater. The drain outlet of the third high-pressure heater is connected to the deaerator and the condenser drain expansion vessel through two independent pipes respectively. When the unit is started, the steam source of the deaerator is from the auxiliary steam (constant-pressure operation, the pressure is adjusted to a specified value of 0.147 MPa), and when the pressure of the steam source of the deaerator reaches 0.147 MPa, the steam for deaeration is switched to the steam extraction sliding pressure operation. The DCS control system collects the pressure of the shell side of the third high-pressure heater and the pressure of the deaerator in real time through the pressure detection device 25 and the deaerator pressure sensor 27, and calculates the difference between the two pressures. When the pressure difference reaches a preset threshold value (for example, 0.2 MPa), the DCS outputs a control signal to switch the drain path, thereby improving the thermal efficiency of the unit and creating conditions for realizing the self-starting and stopping control of the unit. The pressure detection device is preferably an intelligent instrument, and the measurement accuracy can reach ±0.1% FS. The deaerator pressure sensor is installed in the steam space at the top of the deaerator. The third normal drain valve and the emergency drain valve adopt a pneumatic actuator, and the valve body material needs to meet the requirements of high-temperature and high-pressure working conditions.

[0025] The embodiment solves the problem of response lag of traditional manual operation by accurately controlling the drain switching of the last-stage high-pressure heater. The DCS control system judges the drain path based on the real-time pressure difference, thereby avoiding the mis-switching caused by pressure fluctuation. The double-path drain pipe design ensures the stable operation of the system under low load and normal conditions, reduces heat loss, provides a hardware basis for the self-starting and stopping control of the unit, reduces the labor intensity of the operating personnel, saves coal resources and improves resource utilization, and provides conditions for the one-key starting and stopping control of the unit.

[0026] In one embodiment, the outlet of the boiler 1 is connected to the inlet of the high-pressure cylinder 2 of the steam turbine through a main steam pipe, and the outlet of the high-pressure cylinder 2 of the steam turbine is connected to the inlet of the reheater of the boiler 1 through a high-pressure cylinder exhaust electric valve and a check valve 11, and the outlet of the reheater is connected to the inlet of the intermediate-pressure cylinder 3 of the steam turbine through a hot reheated steam pipe.

[0027] In application, the superheated steam generated by the boiler enters the high-pressure cylinder through the main steam pipe to do work, and the steam after work returns to the reheater of the boiler for secondary heating through the high-pressure cylinder exhaust check valve 11. The reheated steam enters the intermediate-pressure cylinder through the hot reheated steam pipe to continue to do work. The function of the high-pressure cylinder exhaust check valve 11 is to prevent steam backflow and ensure the stability of the steam pressure at the inlet of the reheater. The connection between the hot reheated steam pipe and the inlet of the intermediate-pressure cylinder adopts a welded structure to ensure the sealing reliability under high temperature and high pressure conditions. Among them, the main steam pipe can adopt ASTM A335 P91 material, the design pressure is 25 MPa, and the temperature can reach 600°C. The high-pressure cylinder exhaust check valve prevents steam backflow, and an expansion joint is arranged between the inlet of the reheater and the outlet of the high-pressure cylinder to compensate for thermal displacement, and the material of the bellows of the expansion joint is Inconel 625. The hot reheated steam pipe adopts a double-layer insulation structure, the outer layer is aluminum silicate fiber felt, and the inner layer is nano aerogel composite material, which ensures that the surface temperature of the pipe is lower than 50°C. The valve plate of the check valve adopts a hinge structure, and the valve seat sealing surface is stacked with stellite alloy to ensure the sealing reliability under frequent opening and closing conditions.

[0028] This embodiment optimizes the main steam loop structure design to improve energy conversion efficiency. The high-pressure cylinder exhaust valve effectively prevents equipment damage caused by steam backflow, and the reheater pipe insulation design reduces heat loss by about 8%. The special structure design of the check valve enables it to respond quickly under high pressure difference conditions, reduces the risk of valve jamming, and prolongs the service life of the equipment.

[0029] In one embodiment, it also includes a feed water pump turbine 8, and the inlet is connected to the four-stage extraction port of the intermediate-pressure cylinder 3 of the steam turbine.

[0030] In application, the driving steam source of the feed water pump turbine 8 comes from the four-stage extraction of the intermediate-pressure cylinder. The four-stage extraction port is located downstream of the last stage blade of the intermediate-pressure cylinder, and low-pressure steam is extracted to supply the feed water pump turbine. Valves and check devices are arranged on the extraction pipe to prevent steam backflow. The feed water pump turbine converts steam heat energy into mechanical energy to drive the feed water pump to supply water to the boiler, forming a closed-loop energy utilization system. Among them, the feed water pump turbine can adopt a back pressure type structure, the rated power is 5 MW, and the inlet pressure is 1.2 MPa. The four-stage extraction port is located behind the last stage blade of the intermediate-pressure cylinder, and a steam-water separator is arranged on the extraction pipe with a separation efficiency of ≥98%.

[0031] The embodiment recovers low-pressure steam of the medium-pressure cylinder to drive the feed water pump, reduces the consumption of auxiliary power, and improves the overall energy utilization rate. The valve setting of the steam extraction pipeline enhances the system regulation flexibility and meets the operation requirements under different loads.

[0032] In one embodiment, a cascade drainage structure is formed between the first high-pressure heater 4, the second high-pressure heater 5, the third high-pressure heater 6, and the deaerator 7.

[0033] The drainage outlet of the first high-pressure heater 4 is connected to the drainage inlet of the second high-pressure heater 5 through a first normal drainage pipeline, and is connected to the condenser drainage flash tank 9 through a first emergency drainage pipeline. The first normal drainage pipeline is provided with a first normal drainage valve 18, and the first emergency drainage pipeline is provided with a first emergency drainage valve 21.

[0034] The drainage outlet of the second high-pressure heater 5 is connected to the drainage inlet of the third high-pressure heater 6 through a second normal drainage pipeline, and is connected to the condenser drainage flash tank 9 through a second emergency drainage pipeline. The second normal drainage pipeline 19 is provided with a second normal drainage valve 19, and the second emergency drainage pipeline is provided with a second emergency drainage valve 22.

[0035] In application, during normal operation, the steam extracted from the shell side of the high-pressure heater and the feed water flowing through the inner tube side of the high-pressure heater are heated, and then the working medium water (steam) in the shell side is drained to the next stage (the last high-pressure heater is drained to the deaerator) in sequence from high to low pressure (the first high-pressure heater is drained to the second high-pressure heater through the normal drainage valve, the second high-pressure heater is drained to the third high-pressure heater through the normal drainage valve, and the third high-pressure heater is drained to the deaerator through the normal drainage valve), thus completing the corresponding thermodynamic cycle. When the water level of a certain stage of the heater is abnormal or the downstream equipment fails, the corresponding emergency drainage valve (21 or 22) is opened to directly drain the drainage to the condenser drainage flash tank. The opening and closing of the valve is automatically controlled by the DCS system according to the water level and pressure signals.

[0036] The cascade drainage structure of the embodiment realizes the step-by-step recovery of heat energy, reduces the waste of high-quality steam, and improves the system fault tolerance by independently setting the emergency drainage valve to ensure safe operation in the event of a local fault.

[0037] In one embodiment, the steam extraction inlet of the first high-pressure heater 4 is connected to a one-stage steam extraction port of the high-pressure cylinder 2 of the steam turbine, the steam extraction inlet of the second high-pressure heater 5 is connected to a two-stage steam extraction port of the high-pressure cylinder 2 of the steam turbine, the steam extraction inlet of the third high-pressure heater 6 is connected to a three-stage steam extraction port of the medium-pressure cylinder 3 of the steam turbine, and the steam extraction inlet of the deaerator 7 is connected to a four-stage steam extraction port of the medium-pressure cylinder 3 of the steam turbine.

[0038] In application, the first and second stage extraction steam of the high pressure cylinder provides heating steam for the first and second high pressure heaters respectively, the third stage extraction steam of the medium pressure cylinder provides steam for the third high pressure heater, and the fourth stage extraction steam provides steam for the deaerator and the feed water pump turbine. The extraction port positions are arranged in sequence along the turbine flow passage to form a step distribution of pressure from high to low. The extraction pipe of each stage is provided with an electric valve and a check valve for adjusting the extraction amount and preventing steam backflow. The first stage extraction pressure can be set to 8 MPa, the second stage to 5 MPa, the third stage to 2.5 MPa, and the fourth stage to 0.8 MPa to form a step extraction pressure distribution.

[0039] The embodiment of the present application optimizes the heat exchange efficiency of the heater by reasonably distributing the steam supply circuit. The setting of the extraction valve group enables the system to flexibly adjust the steam usage according to load changes, thereby improving the operation economy.

[0040] In one embodiment, a first stage extraction electric valve and check valve 12 are arranged between the extraction inlet of the first high pressure heater 4 and the first stage extraction port of the high pressure cylinder 2 of the turbine, a second stage extraction electric valve and check valve 13 are arranged between the extraction inlet of the second high pressure heater 5 and the second stage extraction port of the high pressure cylinder 2 of the turbine, a third stage extraction electric valve and check valve 14 are arranged between the extraction inlet of the third high pressure heater 6 and the third stage extraction port of the medium pressure cylinder 3 of the turbine, and a fourth stage extraction electric valve and check valve 15 and a deaerator extraction inlet electric valve and check valve 16 are arranged between the extraction inlet of the deaerator 7 and the fourth stage extraction port of the medium pressure cylinder 3 of the turbine.

[0041] In application, the first to third stage extraction pipes are respectively provided with a combination of electric valve and check valve (12, 13, 14) for controlling the extraction on-off and preventing backflow. The fourth stage extraction pipe adopts a double valve series design (15 and 16) to improve reliability. The electric valve receives a DCS control signal to adjust the opening degree, and the check valve is automatically opened and closed by pressure difference. The sealing performance of the valve needs to meet the requirements of high temperature and high pressure working conditions to prevent steam leakage.

[0042] The double valve series design of the embodiment enhances the safety of the fourth stage extraction system, avoiding steam out of control caused by single valve failure. The remote control function of the electric valve realizes accurate adjustment of the extraction amount, improving the system response speed.

[0043] In one embodiment, extraction pressure detection devices are arranged on the extraction inlet pipelines of the first high pressure heater 4, the second high pressure heater 5, the third high pressure heater 6 and the feed water pump turbine 8.

[0044] In application, the extraction pressure detection devices 24 are installed at the upstream position of each stage extraction pipe to monitor the extraction pressure in real time and transmit it to the DCS system. The detection device adopts a standard pressure detection device with an output of 4-20 mA analog signal.

[0045] The embodiment provides data support for system optimization operation by comprehensively monitoring the extraction steam pressure. Real-time feedback of the pressure data enables the DCS to quickly respond to working condition changes, maintain the heat exchange efficiency of each heater and reduce steam waste. The DCS automatically and accurately controls the drain switching of the last-stage high-pressure heater according to the pressure data, solving the problem of response lag in traditional manual operation.

[0046] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A high pressure heater low load drain switch detection system, characterized by, It comprises: A boiler (1), a high-pressure cylinder (2), and a medium-pressure cylinder (3) are sequentially connected to form a main steam circuit; A first high-pressure heater (4), a second high-pressure heater (5), and a third high-pressure heater (6) are sequentially connected to form a drain circuit; A deaerator (7) is connected to the drain outlet of the third high-pressure heater (6) through a third normal drain pipeline, and a third normal drain valve (20) is arranged on the third normal drain pipeline; A condenser drain expansion vessel (9) is connected to the drain outlet of the third high-pressure heater (6) through a third emergency drain pipeline, and a third emergency drain valve (23) is arranged on the third emergency drain pipeline; A DCS control system is connected to the output ends of a pressure detection device (25) and a deaerator pressure sensor (27) at the input end, and is connected to the third normal drain valve (20) and the third emergency drain valve (23) at the output end.

2. The high pressure heater low load drain switch detection system of claim 1, wherein, The outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (2) of a steam turbine through a main steam pipeline, the exhaust port of the high-pressure cylinder (2) of the steam turbine is connected to the inlet of the reheater of the boiler (1) through a high-pressure cylinder exhaust electric valve and a check valve (11), and the outlet of the reheater is connected to the steam inlet of the medium-pressure cylinder (3) of the steam turbine through a hot reheat steam pipeline.

3. The high pressure heater low load drain switch detection system of claim 1, wherein, A feedwater pump turbine (8) is further provided, and the steam inlet is connected to the four-stage extraction port of the medium-pressure cylinder (3) of the steam turbine.

4. The high pressure heater low load drain switch detection system of claim 1, wherein, A cascade drain structure is formed between the first high-pressure heater (4), the second high-pressure heater (5), the third high-pressure heater (6), and the deaerator (7): The drain outlet of the first high-pressure heater (4) is connected to the drain inlet of the second high-pressure heater (5) through a first normal drain pipeline, and is connected to the condenser drain expansion vessel (9) through a first emergency drain pipeline, a first normal drain valve (18) is arranged on the first normal drain pipeline, and a first emergency drain valve (21) is arranged on the first emergency drain pipeline; The drain outlet of the second high-pressure heater (5) is connected to the drain inlet of the third high-pressure heater (6) through a second normal drain pipeline, and is connected to the condenser drain expansion vessel (9) through a second emergency drain pipeline, a second normal drain valve (19) is arranged on the second normal drain pipeline, and a second emergency drain valve (22) is arranged on the second emergency drain pipeline.

5. The high pressure heater low load drain switch detection system of claim 1, wherein, The extraction inlet of the first high-pressure heater (4) is connected to the one-stage extraction port of the high-pressure cylinder (2) of the steam turbine, the extraction inlet of the second high-pressure heater (5) is connected to the two-stage extraction port of the high-pressure cylinder (2) of the steam turbine, the extraction inlet of the third high-pressure heater (6) is connected to the three-stage extraction port of the medium-pressure cylinder (3) of the steam turbine, and the extraction inlet of the deaerator (7) is connected to the four-stage extraction port of the medium-pressure cylinder (3) of the steam turbine.

6. The high pressure heater low load drain switch detection system of claim 5, wherein, The first high-pressure heater (4) is provided with a first-stage extraction electric valve and check valve (12) between the extraction inlet and the first-stage extraction port of the high-pressure cylinder (2) of the steam turbine, the second high-pressure heater (5) is provided with a second-stage extraction electric valve and check valve (13) between the extraction inlet and the second-stage extraction port of the high-pressure cylinder (2) of the steam turbine, the third high-pressure heater (6) is provided with a third-stage extraction electric valve and check valve (14) between the extraction inlet and the third-stage extraction port of the intermediate-pressure cylinder (3) of the steam turbine, and the deaerator (7) is provided with a fourth-stage extraction electric valve and check valve (15) and a deaerator extraction inlet electric valve and check valve (16) between the extraction inlet and the fourth-stage extraction port of the intermediate-pressure cylinder (3) of the steam turbine.

7. The high pressure heater low load drain switch detection system of claim 3, wherein, The extraction inlet pipelines of the first high-pressure heater (4), the second high-pressure heater (5), the third high-pressure heater (6) and the feed water pump turbine (8) are all provided with extraction pressure detection devices.

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