An air-cooled island deactivation protection method and system for a large-scale air-cooled generating unit

Abstract

The present invention discloses a method and system for deactivation protection of an air-cooled island of a large air-cooled generating unit. The method includes: extracting ammonia gas from the denitration system of a thermal power plant; conveying the extracted ammonia gas to a control cabinet; the control cabinet conveys the ammonia gas to the exhaust pipe of the low-pressure cylinder of the condenser, and through the exhaust pipe of the low-pressure cylinder, conveys the ammonia gas into the main steam pipeline at the bottom of the air-cooled island with an elevation of zero; installing an ammonia gas concentration meter and an ammonia gas pressure gauge on the air extraction pipe from the air-cooled island to the vacuum pump, and according to the ammonia gas concentration signal displayed by the ammonia gas concentration meter and the ammonia gas pressure signal displayed by the ammonia gas pressure gauge, the control cabinet controls the ammonia gas inlet volume. The system includes: the condenser is connected to the air-cooled island, the air-cooled island is connected to the vacuum pump, an ammonia gas concentration meter and a pressure gauge are arranged on the air extraction pipe, the ammonia gas concentration meter and the pressure gauge are electrically connected to the control cabinet, and the control cabinet is connected to an ammonia gas inlet valve, which has the advantages of simple process, easy operation and good safety performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of generator sets, and particularly relates to a method and system for deactivation protection of an air-cooled island of a large air-cooled generator set. Background Art

[0002] During the shutdown and standby periods of an air-cooled unit, oxygen and carbon dioxide in the air will enter the air-cooled system, resulting in serious corrosion of the carbon steel material components of the air-cooled system.

[0003] The carbon steel material components in the air-cooled island are the key to the entire deactivation maintenance. Carbon steel is prone to corrosion in a humid atmosphere with a low pH value and oxygen. Increasing the pH value, reducing the dissolved oxygen, or drying the air can effectively prevent the corrosion of carbon steel. However, in reality, the structure of the air-cooled island system is huge and complex, and it is almost impossible to completely drain the internal accumulated water to dry the internal air. Therefore, only by increasing the pH value and reducing the dissolved oxygen can the corrosion of the air-cooled island be prevented.

[0004] The method of increasing the pH value in the air-cooled island is usually to increase the ammonia addition amount to the feed water before shutdown. The method of reducing the dissolved oxygen in the air is usually to indirectly reduce the oxygen in the air by the method of nitrogen filling. Among them, by increasing the pH value through the method of adding ammonia to the feed water, since the air-cooled island cannot be 100% sealed after shutdown, after a period of time, the oxygen inside the equipment is saturated, and the pH value of the water and moisture will gradually decrease due to the dissolution of CO 2 in the air, thus corrosion will occur. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method and system for deactivation protection of an air-cooled island of a large air-cooled generator set.

[0006] The specific solutions are as follows:

[0007] A method for deactivation protection of an air-cooled island of a large air-cooled generator set, including a denitration system of a thermal power plant, a control cabinet, a condenser, a vacuum pump, and an air-cooled island, characterized in that: the method for deactivation protection of the air-cooled island includes the following steps:

[0008] S1): Leading out ammonia gas from the ammonia gas emission point of the denitration system of the thermal power plant;

[0009] S2): Introducing the led-out ammonia gas into a control cabinet capable of controlling the ammonia gas inlet amount and ammonia gas concentration;

[0010] S3): The control cabinet transports the ammonia gas to the low-pressure cylinder exhaust pipe of the condenser, and transports the ammonia gas to the main steam pipe at the bottom of the air-cooled island with a zero elevation through the low-pressure cylinder exhaust pipe;

[0011] S4): Install an ammonia concentration meter and an ammonia pressure gauge on the suction pipe from the air-cooled island to the vacuum pump. According to the ammonia concentration signal displayed by the ammonia concentration meter and the ammonia pressure signal displayed by the ammonia pressure gauge, the control cabinet controls the ammonia inlet volume so that the ammonia concentration range in the air-cooled island is 300 - 400 mg / L, and the ammonia pressure control range in the air-cooled island is 0.05 - 0.1 MPa.

[0012] In step S1), when ammonia is led out from the ammonia emission point of the thermal power plant denitration system, the air-cooled island is in a shutdown state.

[0013] In step S1), the ammonia extraction point of the thermal power plant denitration system is selected behind the evaporator of the liquid ammonia tank of the thermal power plant or in front of the blowdown valve where the ammonia for denitration enters the boiler side of the thermal power plant.

[0014] An ammonia inlet valve is provided on the control cabinet. The ammonia inlet valve closes when the ammonia concentration exceeds the first concentration set value or the ammonia pressure exceeds the first pressure set value, and the ammonia inlet valve opens when the ammonia concentration is less than the second concentration set value or the ammonia pressure is less than the second pressure set value.

[0015] The first concentration set value is 400 mg / L, the first pressure set value is 0.1 MPa, the second concentration set value is 300 mg / L, and the second pressure set value is 0.05 MPa.

[0016] An air-cooled island shutdown protection system for a large air-cooled generating unit. The condenser is connected to the air-cooled island through a pipeline. A suction pipe is provided between the air-cooled island and the vacuum pump. The air-cooled island is connected to the vacuum pump through the suction pipe. A concentration meter and a pressure gauge are provided on the suction pipe. The concentration meter and the pressure gauge are electrically connected to the control cabinet. An ammonia inlet valve is provided on the control cabinet. The control cabinet is connected to the thermal power plant denitration system through the ammonia inlet valve.

[0017] The condenser includes a low-pressure cylinder of the steam turbine and a steam exhaust device of the steam turbine. A main steam pipeline is provided at the bottom of the air-cooled island. Among them, the main steam pipeline is connected to the steam exhaust device of the steam turbine, and the steam exhaust device of the steam turbine is connected to the low-pressure cylinder of the steam turbine.

[0018] The control cabinet is a PLC control cabinet. An ammonia inlet channel, an ammonia discharge channel, and a PLC main controller are provided in the PLC control cabinet. A controller input end and a controller output end are provided on the PLC main controller. Among them, the concentration meter and the pressure gauge are both electrically connected to the controller input end, the controller output end is electrically connected to the ammonia inlet valve, and the ammonia inlet channel is connected to the ammonia inlet valve through a pipeline.

[0019] A low-pressure cylinder exhaust pipe is provided on the steam turbine exhaust device. The condenser is connected to the ammonia discharge channel through the low-pressure exhaust pipe, and the low-pressure cylinder exhaust pipe is connected to the main steam pipe.

[0020] An outlet pipe is also provided between the steam turbine exhaust device and the air-cooled island. The steam turbine exhaust device is connected to the air-cooled island through the outlet pipe.

[0021] The present invention discloses a method and structure for protecting an air-cooled island of a large air-cooled generating unit from being out of service. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The ammonia in the thermal power plant comes from the ammonia used for denitrification, with a simple source and convenient use.

[0023] (2) Adding ammonia can offset the influence of carbon dioxide in the air and indirectly increase the water and moisture in the air-cooled island.

[0024] (3) The present invention uses the ammonia from the boiler denitrification of the thermal power plant to fill ammonia into the air-cooled island irregularly, so that the pH of the water vapor reaches the pH value required for out-of-service protection. Since the molecular weight of ammonia is only 17, ammonia is relatively light. When ammonia is input into the main pipe with a bottom elevation of zero in the steam turbine exhaust device of the air-cooled island, ammonia can diffuse to the top of the air-cooled island and fill the gas space, with good protection effect, which is better than that of the gas-phase corrosion inhibitor.

[0025] (4) After maintenance, the qualified time of the water vapor quality during the start-up of the thermal power generating unit is greatly shortened, saving a large amount of water and coal, with significant economic benefits;

[0026] (5) Using this method does not require a large amount of modification of the original pipeline, so the process is simple, the operation is easy, and the safety is good. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the present invention. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0029] A method for protecting an air-cooled island of a large air-cooled generating unit from being out of service includes a thermal power plant denitrification system, a control cabinet, a condenser, a vacuum pump, and an air-cooled island. The method for protecting the air-cooled island from being out of service includes the following steps:

[0030] S1): Draw out ammonia from the ammonia emission point of the thermal power plant denitration system;

[0031] S2): Introduce the drawn-out ammonia into a control cabinet that can control the ammonia inflow and ammonia concentration;

[0032] S3): The control cabinet transports ammonia to the exhaust pipe of the low-pressure cylinder of the condenser, and transports the ammonia through the exhaust pipe of the low-pressure cylinder into the main steam pipe at the bottom of the air-cooled island with an elevation of zero;

[0033] S4): Install an ammonia concentration meter and an ammonia pressure gauge on the suction pipe from the air-cooled island to the vacuum pump. According to the ammonia concentration signal displayed by the ammonia concentration meter and the ammonia pressure signal displayed by the ammonia pressure gauge, the control cabinet controls the ammonia inflow so that the ammonia concentration in the air-cooled island ranges from 300 to 400 mg / L, and the ammonia pressure control range in the air-cooled island is from 0.05 to 0.1 MPa.

[0034] In step S1), when drawing out ammonia from the ammonia emission point of the thermal power plant denitration system, the air-cooled island is in a shutdown state.

[0035] In step S1), the ammonia extraction point of the thermal power plant denitration system is selected after the evaporator of the liquid ammonia tank of the thermal power plant or before the drain valve where the ammonia for denitration enters the boiler side of the thermal power plant. In this embodiment, after the air-cooled island system is shut down, preferably, a stainless steel pipe with a diameter of φ59×4.5 mm is led from the thermal power plant denitration system. The extraction point of the stainless steel pipe of the thermal power plant denitration system can be selected after the evaporator of the liquid ammonia tank of the thermal power plant or before the drain valve where the ammonia for denitration enters the boiler side of the thermal power plant.

[0036] The thermal power plant denitration system is mainly used to decompose nitrogen oxides in the flue gas discharged from the boiler into harmless nitrogen and water. Liquid nitrogen is sent from the liquid ammonia tank truck to the liquid ammonia storage tank by a unloading compressor, and after being evaporated into ammonia in the evaporator, it enters the boiler area through the ammonia buffer tank and the conveying pipeline. In this embodiment, preferably, the ammonia discharged after the evaporator of the liquid ammonia tank is used to be input into the control cabinet.

[0037] An ammonia inlet valve is provided on the control cabinet. The ammonia inlet valve closes when the ammonia concentration exceeds the first concentration set value or the ammonia pressure exceeds the first pressure set value, and the ammonia inlet valve opens when the ammonia concentration is less than the second concentration set value or the ammonia pressure is less than the second pressure set value.

[0038] The first concentration set value is 400 mg / L, the first pressure set value is 0.1 MPa, the second concentration set value is 300 mg / L, and the second pressure set value is 0.05 MPa.

[0039] Preferably, the upper and lower limits of the ammonia concentration and the upper and lower limits of the ammonia pressure can be set according to the on-site commissioning results of the environmental humidity where the thermal power plant is located. After the ammonia concentration meter accumulates to the first set concentration value or the first set pressure value, the ammonia inlet valve is automatically closed. After the ammonia inlet valve is automatically closed, it can only be reopened after manual reset to play a safety protection role.

[0040] As Figure 1 shown, a protection system for deactivating an air-cooled island of a large air-cooled generator set. The condenser 1 is connected to the air-cooled island 3 through a pipeline. An air extraction pipe 10 is arranged between the air-cooled island 3 and the vacuum pump 2. The air-cooled island 3 is connected to the vacuum pump 2 through the air extraction pipe 10. A concentration meter 5 and a pressure gauge 6 are arranged on the air extraction pipe 10. The concentration meter 5 and the pressure gauge 6 are electrically connected to the control cabinet 4. An ammonia inlet valve 411 is arranged on the control cabinet 4. The control cabinet 4 is connected to the denitration system pipeline of the thermal power plant through the ammonia inlet valve 411.

[0041] The condenser 1 includes a low-pressure cylinder 8 of a steam turbine and an exhaust steam device 9 of the steam turbine. A main steam pipeline 11 is arranged at the bottom of the air-cooled island. Among them, the main steam pipeline 11 is connected to the exhaust steam device 9 of the steam turbine through a pipeline, and the exhaust steam device 9 of the steam turbine is connected to the low-pressure cylinder 8 of the steam turbine through a pipeline.

[0042] The control cabinet 4 is a PLC control cabinet. An ammonia inlet channel 41, an ammonia discharge channel 42 and a PLC main controller 43 are arranged in the PLC control cabinet. A controller input end and a controller output end are arranged on the PLC main controller 43. Among them, the concentration meter 5 and the pressure gauge 6 are both electrically connected to the controller input end, the controller output end is electrically connected to the ammonia inlet valve 411, the ammonia inlet channel 41 is connected to the ammonia inlet valve 411 through a pipeline. The concentration meter 5 is used to measure the ammonia concentration in the air extraction pipe 10, the pressure gauge 6 is used to test the air pressure value in the air extraction pipe 10. The concentration meter 5 and the pressure gauge 6 are both communicatively connected to the PLC main controller 43. The concentration meter 5 and the pressure gauge 6 can transmit the measured concentration value and pressure value to the PLC main controller 43. The PLC main controller 43 controls the closing of the ammonia inlet valve 411 according to the received ammonia concentration value and ammonia pressure value. Preferably, when the ammonia concentration in the air extraction pipe 10 exceeds 400 mg / L, or the ammonia pressure in the air extraction pipe 10 exceeds 0.1 MPa, the ammonia gas volume in the air-cooled island has met the requirements. At this time, the PLC main controller 43 will send an electrical signal to close the ammonia inlet valve 411. The ammonia inlet valve 411 is preferably a solenoid valve.

[0043] The steam turbine exhaust device 9 is provided with a low-pressure cylinder exhaust pipe 12. The condenser 1 is connected to the ammonia discharge channel 42 through the low-pressure exhaust pipe 12, and the low-pressure cylinder exhaust pipe 12 is connected to the main steam pipe 11 through pipes.

[0044] The steam turbine exhaust device 9 is connected to the air-cooled island 3 through an outlet pipe 7.

[0045] In this embodiment, the ammonia discharged from the ammonia discharge channel 42 can enter the condenser 1 through the low-pressure exhaust pipe 12, or can enter the air-cooled island through the low-pressure exhaust pipe 12 and the main steam pipe 11. In addition, the ammonia entering the condenser 1 can also enter the air-cooled island 3 through the outlet pipe 7.

[0046] The present invention discloses a method and system for protecting an air-cooled island of a large air-cooled generating unit. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) The ammonia in the thermal power plant comes from the ammonia used for denitrification, with a simple source and convenient use.

[0048] (2) Adding ammonia can offset the influence of carbon dioxide in the air and indirectly improve the water and moisture in the air-cooled island.

[0049] (3) The present invention uses the ammonia for boiler denitrification in the thermal power plant to fill ammonia into the air-cooled island irregularly, so that the pH of the water vapor reaches the pH value required for shutdown protection. Since the molecular weight of ammonia is only 17, ammonia is relatively light. When ammonia is input into the main pipe with a bottom elevation of zero in the exhaust device of the air-cooled island, ammonia can diffuse to the top of the air-cooled island and can fill the gas space, with good protection effect and better effect than the gas-phase corrosion inhibitor.

[0050] (4) After maintenance, the qualified time of the water vapor quality during the startup of the thermal power generating unit is greatly shortened, saving a large amount of water and coal, and having significant economic benefits;

[0051] (5) Using this method does not require a large amount of modification of the original pipeline, so the process is simple, the operation is easy, and the safety is good.

[0052] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A method for protecting an air-cooled island of a large air-cooled generating unit during shutdown, including a denitration system of a thermal power plant, a control cabinet, a condenser, a vacuum pump and an air-cooled island, Characterized in that: The method for protecting the air-cooled island during shutdown includes the following steps: S1): Extract ammonia gas from the ammonia gas emission point of the denitration system of the thermal power plant; S2): Introduce the extracted ammonia gas into a control cabinet that can control the amount of ammonia gas entering and the ammonia gas concentration; S3): The control cabinet transports the ammonia gas to the exhaust pipe of the low-pressure cylinder of the condenser, and transports the ammonia gas to the main steam pipeline at the bottom of the air-cooled island with a zero elevation through the exhaust pipe of the low-pressure cylinder; S4): Install an ammonia gas concentration meter and an ammonia gas pressure gauge on the air extraction pipe from the air-cooled island to the vacuum pump. According to the ammonia gas concentration signal displayed by the ammonia gas concentration meter and the ammonia gas pressure signal displayed by the ammonia gas pressure gauge, the control cabinet controls the amount of ammonia gas entering so that the ammonia gas concentration in the air-cooled island ranges from 300 to 400 mg / L, and the pressure control range of the ammonia gas in the air-cooled island is 0.05 to 0.1 MPa; In step S1), the ammonia gas extraction point of the denitration system of the thermal power plant is selected after the evaporator of the liquid ammonia tank of the thermal power plant, or before the blowdown valve where the ammonia gas for denitration enters the boiler side of the thermal power plant; The denitration system of the thermal power plant decomposes nitrogen oxides in the flue gas discharged from the boiler into harmless nitrogen and water. Liquid nitrogen is sent from the liquid ammonia tank truck to the liquid ammonia storage tank by a discharging compressor, evaporated into ammonia gas after passing through the evaporator, and enters the boiler area through the ammonia buffer tank and the conveying pipeline. The ammonia gas discharged after the evaporator of the liquid ammonia tank is used to be input into the control cabinet; An ammonia gas inlet valve is provided on the control cabinet. The ammonia gas inlet valve closes when the ammonia gas concentration exceeds the first set value or the ammonia gas pressure exceeds the first set value, and the ammonia gas inlet valve opens when the ammonia gas concentration is less than the second set value or the ammonia gas pressure is less than the second set value.

2. The method for protecting an air-cooled island of a large air-cooled generating unit during shutdown according to claim 1, Characterized in that: In step S1), when extracting ammonia gas from the ammonia gas emission point of the denitration system of the thermal power plant, the air-cooled island is in a shutdown state.

3. The method for protecting an air-cooled island of a large air-cooled generating unit during shutdown according to claim 1, Characterized in that: The first set value of the concentration is 400 mg / L, the first set value of the pressure is 0.1 MPa, the second set value of the concentration is 300 mg / L, and the second set value of the pressure is 0.05 MPa.

4. An air-cooled island shutdown protection system for a large air-cooled generating unit, which adopts the method for protecting an air-cooled island of a large air-cooled generating unit during shutdown according to any one of claims 1 to 3, Characterized in that: The condenser (1) is connected to the air-cooled island (3) through pipelines. An extraction pipe (10) is provided between the air-cooled island (3) and the vacuum pump (2). The air-cooled island (3) is connected to the vacuum pump (2) through the extraction pipe (10). A concentration meter (5) and a pressure gauge (6) are provided on the extraction pipe (10). The concentration meter (5) and the pressure gauge (6) are electrically connected to the control cabinet (4). An ammonia inlet valve (411) is provided on the control cabinet (4). The control cabinet (4) is connected to the denitration system pipeline of the thermal power plant through the ammonia inlet valve (411).

5. The air-cooled island shutdown protection system for a large air-cooled generating unit according to claim 4, characterized in that: The condenser (1) includes a low-pressure cylinder of the steam turbine (8) and a steam exhaust device of the steam turbine (9). A main steam pipeline (11) is provided at the bottom of the air-cooled island. Among them, the main steam pipeline (11) is connected to the steam exhaust device of the steam turbine (9) through pipelines, and the steam exhaust device of the steam turbine (9) is connected to the low-pressure cylinder of the steam turbine (8) through pipelines.

6. The air-cooled island shutdown protection system for a large air-cooled generating unit according to claim 5, characterized in that: The control cabinet (4) is a PLC control cabinet. An ammonia inlet channel (41), an ammonia outlet channel (42) and a PLC main controller (43) are provided in the PLC control cabinet. A controller input end and a controller output end are provided on the PLC main controller (43). Among them, the concentration meter (5) and the pressure gauge (6) are both electrically connected to the controller input end, the controller output end is electrically connected to the ammonia inlet valve (411), and the ammonia inlet channel (41) is connected to the ammonia inlet valve (411) through pipelines.

7. The air-cooled island shutdown protection system for a large air-cooled generating unit according to claim 6, characterized in that: A low-pressure cylinder exhaust pipe (12) is provided on the steam exhaust device of the steam turbine (9). The condenser (1) is connected to the ammonia outlet channel (4) through the low-pressure exhaust pipe (12). The low-pressure cylinder exhaust pipe (12) is connected to the main steam pipeline (11) through pipelines.

8. The air-cooled island shutdown protection system for a large air-cooled generating unit according to claim 7, characterized in that: An air outlet pipeline (7) is further provided between the steam exhaust device of the steam turbine (9) and the air-cooled island (3). The steam exhaust device of the steam turbine (9) is connected to the air-cooled island (3) through the air outlet pipeline (7).

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