Cooling system and control method of thermal power generating unit

Abstract

The invention discloses a cooling system of a thermal power generating unit and a control method, the cooling system comprises a cooling tower, a spraying device is arranged in the cooling tower, and a water collecting tank is arranged below the spraying device along the height direction; a circulation pipeline is arranged in the condenser and used for conducting heat exchange on dead steam discharged by the thermal power generating unit, and an inlet of the circulation pipeline of the condenser communicates with the water collecting tank through a water outlet pipe; the first water return pipe is communicated with the spraying device and an outlet of a circulating pipeline of the condenser; and the second water return pipe is communicated with the water collecting tank and an outlet of the circulating pipeline of the condenser. By arranging the second water return pipeline, high-temperature circulating water generated after heat exchange of the condenser can directly flow back to the water collecting tank, heat dissipation is not needed, and therefore the problem that the temperature of the water outlet assembly is affected or even frozen due to the fact that the temperature of circulating water in the water collecting tank is too low can be prevented, the phenomenon that the temperature of the water outlet assembly is too low can be prevented, and the service life of the water outlet assembly is prolonged. The temperature of the circulating water inlet meets the requirement.

Description

Technical Field

[0001] The invention relates to the technical field of cooling of thermal power plants, and in particular to a cooling system and a control method for a thermal power unit. Background Art

[0002] At present, wet-cooled thermal power units are usually cooled by hyperbolic natural ventilation cooling water towers. During the cooling process, the hyperbolic natural ventilation cooling water tower will exchange heat with the external environment, thereby achieving the purpose of cooling the circulating water. However, in the winter, during the heat exchange between the hyperbolic natural ventilation cooling water tower and the external environment, there is a problem of ice forming inside the hyperbolic natural ventilation cooling water tower.

[0003] In order to avoid ice formation in the cooling water tower and ensure that the circulating water inlet temperature is within an appropriate range to ensure the safety and economy of the wet-cooled thermal power unit, a louvered wind shield is usually used to block the air inlet position of the cooling water tower. By changing the angle of the louver, the air inlet volume of the cooling water tower is changed, thereby changing the cooling effect of the circulating water in the cooling water tower, that is, achieving the purpose of temperature regulation of the circulating water inlet of the cooling water tower.

[0004] However, in the northern region, the ambient temperature can reach -30℃ during extremely cold weather in winter. Even if all the shutters are closed, the circulating water inlet temperature is still lower than the minimum specified value, which cannot meet the circulating water inlet temperature requirement. There is even the problem of ice formation in the cooling water tower, resulting in no circulating water circulation at the circulating water inlet, seriously affecting the safe operation of the unit.

[0005] Therefore, how to provide a cooling system for a thermal power unit so that the temperature of the circulating water inlet meets the requirements is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In view of this, an embodiment of the present invention provides a cooling system of a thermal power unit, so that the temperature of the circulating water inlet meets the requirement. In addition, an embodiment of the present invention also provides a control method of the cooling system of a thermal power unit.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A cooling system for a thermal power unit, comprising:

[0009] A cooling tower, wherein a spray device is provided in the cooling tower, and a water collecting tank is provided below the spray device in the height direction;

[0010] A condenser, wherein a circulation pipeline is arranged in the condenser for heat exchange with exhaust steam discharged from the thermal power unit, and an inlet of the circulation pipeline of the condenser is connected with the water collecting tank through a water outlet pipe;

[0011] a first water return pipe, the first water return pipe being connected to the outlet of the circulation pipeline of the spray device and the condenser;

[0012] A second water return pipe is connected to the outlet of the circulation pipeline of the water collecting tank and the condenser.

[0013] Preferably, in the cooling system of the above-mentioned thermal power unit, a solenoid valve for controlling the opening of the second water return pipe is provided on the second water return pipe.

[0014] Preferably, the cooling system of the thermal power unit further comprises:

[0015] A shutter is used to cover the air inlet of the cooling tower.

[0016] Preferably, the cooling system of the thermal power unit further comprises:

[0017] A temperature sensor, the temperature sensor is used to detect the temperature of the water outlet pipe;

[0018] A controller, the controller is connected to the temperature sensor and controls the opening of the solenoid valve and the opening of the shutter;

[0019] When the shutter is closed, when the temperature of the water outlet pipe is not greater than a first preset value, the opening of the solenoid valve is 100%; when the temperature of the water outlet pipe is greater than the first preset value and not greater than a second preset value, the opening of the solenoid valve is 50%; when the temperature of the water outlet pipe is greater than the second preset value and not greater than a third preset value, the opening of the solenoid valve is 0%;

[0020] The first preset value is smaller than the second preset value, and the second preset value is smaller than the third preset value.

[0021] A control method for a cooling system of a thermal power unit, applied to a cooling device of any of the thermal power units described above, comprising:

[0022] After determining that the shutter is closed for a first preset time, determining that the temperature of the water outlet pipe is not greater than a first preset value and that the temperature of the water outlet pipe is on a downward trend, the antifreeze mode is activated;

[0023] If it is determined that the pressure value in the condenser is greater than the preset pressure value and the temperature of the water outlet pipe is not greater than the first preset value, the solenoid valve opening is controlled to 100% until the temperature of the water outlet pipe is greater than the first preset value and not greater than the second preset value, then the solenoid valve opening is controlled to 50% until the temperature of the water outlet pipe is greater than the second preset value and not greater than the third preset value, then the solenoid valve opening is controlled to 0% until the temperature of the water outlet pipe is greater than the third preset value and the temperature of the water outlet pipe shows an upward trend, then the antifreeze mode is exited.

[0024] Preferably, in the above-mentioned control method for the cooling system of a thermal power unit, the starting antifreeze mode comprises:

[0025] Activate the sound and light alarm device;

[0026] The blinds are switched to manual adjustment.

[0027] Preferably, in the above-mentioned control method for the cooling system of a thermal power unit, the exiting the antifreeze mode comprises:

[0028] Turn off the sound and light alarm device;

[0029] The blinds switch to automatic adjustment.

[0030] Preferably, in the above-mentioned control method for the cooling system of a thermal power unit, the detection method of the temperature of the water outlet pipe showing a downward trend includes:

[0031] Obtain a first temperature value of the water outlet pipe at a first time point, obtain a second temperature value of the water outlet pipe at a second time point, and obtain a third temperature value of the water outlet pipe at a third time point, wherein the second time point is a time point equal to the first time point plus a second preset time, and the third time point is a time point equal to the second time point plus the second preset time;

[0032] It is determined that the first temperature value is greater than the second temperature value, and the second temperature value is greater than the third temperature value, and the temperature of the water outlet pipe is on a downward trend.

[0033] Preferably, in the above-mentioned control method for the cooling system of a thermal power unit, the detection method of the rising trend of the temperature of the water outlet pipe includes:

[0034] Obtain a fourth temperature value of the water outlet pipe at a fourth time point, obtain a fifth temperature value of the water outlet pipe at a fifth time point, and obtain a sixth temperature value of the water outlet pipe at a sixth time point, wherein the fifth time point is a time point equal to the fourth time point plus a third preset time, and the sixth time point is a time point equal to the fifth time point plus the third preset time;

[0035] It is determined that the fourth temperature value is less than the fifth temperature value, and the fifth temperature value is less than the sixth temperature value, and the temperature of the water outlet pipe is on an upward trend.

[0036] Preferably, in the above-mentioned control method for the cooling system of a thermal power unit, after the antifreeze mode is started,

[0037] Make sure that the pressure value in the condenser is not greater than the preset pressure value, and the opening of the solenoid valve remains unchanged.

[0038] The embodiment of the present invention discloses a cooling system for a thermal power unit. By setting a second return water pipeline, high-temperature circulating water generated after heat exchange in a condenser can be directly returned to a water collecting tank without heat dissipation, thereby preventing the circulating water temperature in the water collecting tank from being too low and affecting the temperature of a water outlet component or even freezing, and is conducive to preventing the phenomenon of too low temperature at the water outlet component, even if the temperature of the circulating water inlet meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 A schematic diagram of the structure of a cooling system for a thermal power unit disclosed in an embodiment of the present invention;

[0041] Figure 2 A top view of a cooling system of a thermal power unit disclosed in an embodiment of the present invention;

[0042] Figure 3 A flow chart of a method for controlling a cooling system of a thermal power unit disclosed in an embodiment of the present invention;

[0043] Figure 4 A detailed flow chart of a control method for a cooling system of a thermal power unit disclosed in an embodiment of the present invention.

[0044] Among them, 1 is a cooling tower, 2 is a spray device, 3 is a water collection tank, 4 is a first return water pipeline, 5 is a second return water pipeline, 6 is a solenoid valve, 7 is a condenser, 8 is a water outlet pipe, and 9 is a circulating water pump. DETAILED DESCRIPTION

[0045] The embodiment of the present invention discloses a cooling system of a thermal power unit, which makes the temperature of the circulating water inlet meet the requirements. In addition, the embodiment of the present invention also discloses a control method of the cooling system of the thermal power unit.

[0046] 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.

[0047] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0048] At present, wet-cooled thermal power units are usually cooled by hyperbolic natural ventilation cooling water towers. During the cooling process, the hyperbolic natural ventilation cooling water tower will exchange heat with the external environment, thereby achieving the purpose of cooling the circulating water. However, in the winter, during the heat exchange between the hyperbolic natural ventilation cooling water tower and the external environment, there is a problem of ice forming inside the hyperbolic natural ventilation cooling water tower.

[0049] In order to avoid ice formation in the cooling water tower and ensure that the circulating water inlet temperature is within an appropriate range to ensure the safety and economy of the wet-cooled thermal power unit, a louvered wind shield is usually used to block the air inlet position of the cooling water tower. By changing the angle of the louver, the air inlet volume of the cooling water tower is changed, thereby changing the cooling effect of the circulating water in the cooling water tower, that is, achieving the purpose of temperature regulation of the circulating water inlet of the cooling water tower.

[0050] However, in the northern region, the ambient temperature can reach -30℃ during extremely cold weather in winter. Even if all the shutters are closed, the circulating water inlet temperature is still lower than the minimum specified value, which cannot meet the circulating water inlet temperature requirement. There is even the problem of ice formation in the cooling water tower, resulting in no circulating water circulation at the circulating water inlet, seriously affecting the safe operation of the unit.

[0051] Based on this, the embodiments of the present application are combined Figure 1 and Figure 2 A cooling system for a thermal power unit is provided, which is used to cool a wet-cooled thermal power unit and prevent the cooling water tower from freezing, thereby ensuring the safe operation of the unit. Figure 1 A schematic diagram of the structure of a cooling system for a thermal power unit disclosed in an embodiment of the present invention; Figure 2 The figure is a top view of the cooling system of a thermal power unit disclosed in an embodiment of the present invention.

[0052] like Figure 1 and Figure 2 The cooling system shown includes: a cooling tower 1, a spray device 2, a water collecting tank 3, a return water component, a condenser 7 and a water outlet component.

[0053] The cooling tower 1 is a hyperbolic tower body, and the size of the cooling tower 1 can be set according to different needs. Filling is arranged in the cooling tower 1. The spray device 2 is located in the cooling tower 1, and the water collection tank 3 is located at the bottom of the cooling tower 1. The spray device 2 is opposite to the water collection tank 3, and the spray device 2 is at a height of the water collection tank 3.

[0054] The return water assembly is communicated with the cooling tower 1 and connected to the outlet of the circulation pipeline of the condenser 7. One end of the water outlet assembly is communicated with the water collecting tank 3, and the other end is communicated with the inlet of the circulation pipeline of the condenser 7.

[0055] The exhaust steam generated during the operation of the wet-cooled thermal power unit is discharged to the outdoor condenser 7 through the turbine exhaust pipe. The exhaust steam outside the tube undergoes convection heat transfer with the low-temperature circulating water in the tube of the condenser 7. The exhaust steam releases heat and condenses into water, while the low-temperature circulating water absorbs heat and becomes high-temperature circulating water. The high-temperature circulating water flows back to the cooling system and is cooled by the cooling system.

[0056] During the cooling process of the high-temperature circulating water by the cooling system: the high-temperature circulating water flows back to the spraying device 2, and the high-temperature circulating water is sprayed from top to bottom onto the filler in the cooling tower 1 by the spraying device 2, and during the spraying process, the high-temperature circulating water exchanges heat with the cold air rising from the cooling tower 1 to achieve cooling of the high-temperature circulating water. The cooled high-temperature circulating water is collected in the collecting tank 3, and the collecting tank 3 is used to provide low-temperature circulating water to the condenser 7.

[0057] The water return assembly of the embodiment of the present application includes a first water return pipeline 4 and a second water return pipeline 5 .

[0058] Among them, one end of the first water return pipe 4 is connected to the spray device 2 of the cooling tower 1, and the other end of the first water return pipe 4 is connected to the condenser 7. One end of the second water return pipe 5 is connected to the water collection tank 3, and the other end of the second water return pipe 5 is connected to the condenser 7. Exemplarily, the spray device 2 is connected to the central shaft in the cooling tower 1, and the first water return pipe 4 is connected to the central shaft.

[0059] The return water component of the embodiment of the present application is provided with a second return water pipeline 5, so that the high-temperature circulating water generated after the heat exchange of the condenser 7 can be directly returned to the collecting tank 3 without the need for heat dissipation, thereby preventing the circulating water temperature in the collecting tank 3 from being too low and affecting the temperature of the water outlet component, and is conducive to preventing the problem of too low temperature at the water outlet component.

[0060] In some embodiments, the second water return pipeline 5 is provided with a solenoid valve 6 for controlling the on-off of the second water return pipeline 5. It should be noted that the opening of the solenoid valve 6 is adjustable, so that the solenoid valve 6 is used to adjust the flow rate of the second water return pipeline 5, thereby changing the temperature of the circulating water in the water collection tank 3.

[0061] like Figure 2 As shown, the water outlet assembly includes a water outlet pipe 8 and a circulating water pump 9.

[0062] One end of the water outlet pipe 8 is connected to the water collecting tank 3, and the other end of the water outlet pipe 8 is connected to the condenser 7. The circulating water pump 9 is arranged on the water outlet pipe 8, and is used to provide power for the circulating water flowing from the water collecting tank 3 to the condenser 7. By changing the power of the circulating water pump 9, the heat exchange effect of the condenser 7 can be adjusted.

[0063] In some embodiments, the cooling system of the thermal power unit further includes shutters (not shown in the figure).

[0064] The shutter is arranged on the cooling tower 1 and is opposite to the air inlet of the cooling tower 1. The opening angle of the shutter is adjustable, and the adjustment method of the opening angle of the shutter in the embodiment of the present application includes manual adjustment and electric adjustment.

[0065] Optionally, the cooling system of the thermal power unit disclosed in the embodiment of the present application also includes a temperature sensor and a controller.

[0066] Among them, the temperature sensor is used to detect the temperature of the water outlet pipe 8 to determine the temperature of the circulating water provided by the water collecting tank 3 to the condenser 7. Specifically, the temperature sensor is installed at the position where the water collecting tank 3 is connected to the water outlet pipe 8 or at the position where the water outlet pipe 8 is connected to the condenser 7.

[0067] Of course, a plurality of temperature sensors may be arranged on the water outlet pipe 8 along the setting direction of the water outlet pipe 8, and the temperature of the circulating water provided by the water collecting tank 3 to the condenser 7 may be obtained by calculating the average value of these temperature sensors.

[0068] The controller is connected to the temperature sensor, and the controller can control the opening degree of the solenoid valve 6 according to the temperature value detected by the temperature sensor.

[0069] For example, when the shutter is closed, when the temperature of the water outlet pipe 8 is not greater than the first preset value, the opening of the solenoid valve 6 is 100%; when the temperature of the water outlet pipe 8 is greater than the first preset value and not greater than the second preset value, the opening of the solenoid valve 6 is 50%; when the temperature of the water outlet pipe 8 is greater than the second preset value and not greater than the third preset value, the opening of the solenoid valve 6 is 0%. In the embodiment of the present application, the first preset value is less than the second preset value, and the second preset value is less than the third preset value.

[0070] It should be noted that in winter, in order to prevent the circulating water inlet (i.e., the outlet pipe 8) from being too low and causing ice to form in the cooling tower 1, thus affecting the safety of the unit, and to prevent the circulating water inlet temperature from being too high, causing the vacuum of the condenser 7 to decrease and the economic efficiency of the thermal power unit to decline, the circulating water inlet temperature is usually set between 3°C and 15°C.

[0071] In this application, it is set that when the circulating water inlet temperature is lower than 3°C, all the shutters are closed. The temperature setting value when the shutters are closed can be adjusted according to the actual situation.

[0072] Based on the above temperature settings, illustratively, the first preset value is 3°C, the second preset value is 8°C, and the third preset value is 15°C.

[0073] In addition, combined Figure 3 and Figure 4 As shown, the embodiment of the present application also discloses a control method for a cooling system of a thermal power unit, wherein: Figure 3 This is a flow chart of a method for controlling a cooling system of a thermal power unit disclosed in an embodiment of the present invention. Figure 4 A detailed flow chart of a control method for a cooling system of a thermal power unit disclosed in an embodiment of the present invention.

[0074] The control method of the cooling system of a thermal power unit disclosed in the embodiment of the present application comprises the following steps:

[0075] S1: Get the status of the blinds.

[0076] The state of the shutter is detected. The state of the shutter can be detected by obtaining the ventilation volume of the air inlet of the cooling tower. If there is no air inlet, it is determined that the shutter is in a closed state.

[0077] S2: Get the temperature and trend of the circulating water inlet.

[0078] After detecting that the shutter is in the closed state for the first preset time, the outlet pipe temperature (ie, the circulating water inlet temperature of the condenser 7) is detected. If the outlet pipe temperature is not greater than the first preset value and the outlet pipe temperature shows a downward trend.

[0079] Among them, the detection method for the downward trend of the temperature of the water outlet pipe includes: obtaining a first temperature value of the water outlet pipe at a first time point, obtaining a second temperature value of the water outlet pipe at a second time point, and obtaining a third temperature value of the water outlet pipe at a third time point, the second time point being the first time point plus the second preset time, and the third time point being the second time point plus the second preset time.

[0080] The controller compares the first temperature value, the second temperature value and the third temperature value. If the first temperature value is greater than the second temperature value, and the second temperature value is greater than the third temperature value, the temperature of the water outlet pipe shows a downward trend.

[0081] This article only takes the temperature values ​​at three time points as an example for explanation. In other optional embodiments, the temperature trend can also be determined by detecting the temperature at more time points, which will not be repeated here.

[0082] Optionally, the first preset time is 5 minutes, the first preset value is 3° C., and the second preset time is 5 minutes.

[0083] S3: Activate antifreeze mode.

[0084] When the controller determines that the temperature of the water outlet pipe is not greater than the first preset value and the temperature of the water outlet pipe is on a downward trend, the controller starts the antifreeze mode.

[0085] Starting the antifreeze mode includes: starting the sound and light alarm device, switching the shutters to manual adjustment, and detecting the pressure value in the condenser and the temperature of the water outlet pipe.

[0086] The shutters are switched from automatic to manual adjustment and remain closed to prevent the shutters from opening and closing frequently due to the circulating water inlet temperature varying around the critical value, thereby causing the solenoid valve to open and close frequently.

[0087] S4: Get the pressure of the condenser.

[0088] The pressure value in the condenser is detected. If the pressure value in the condenser is not greater than the preset pressure value, the opening of the solenoid valve remains unchanged. If the pressure value in the condenser is greater than the preset value, S5 is executed.

[0089] It should be noted that in the antifreeze mode, in order to avoid the problem that the vacuum of the condenser 7 drops too much after the circulating water temperature rises after the solenoid valve 6 is opened, causing the thermal power unit to trip due to low vacuum protection, the control method of the embodiment of the present application adds the detection of the pressure value in the condenser. When the pressure value in the condenser is detected to be not greater than the preset pressure value, the opening of the solenoid valve remains unchanged, and an audible and visual alarm is issued to remind the operator to make adjustments in time.

[0090] The above-mentioned preset pressure value is -80kpa to -70kpa, and optionally, the preset pressure value is -78kpa.

[0091] S5: Adjust the opening of the solenoid valve.

[0092] If it is detected that the pressure value in the condenser is greater than the preset pressure value, and the temperature of the water outlet pipe is not greater than the first preset value, the controller controls the opening of the solenoid valve to 100% until the temperature of the water outlet pipe is greater than the first preset value and not greater than the second preset value, then the controller controls the opening of the solenoid valve to 50% until the temperature of the water outlet pipe is greater than the second preset value and not greater than the third preset value, then the controller controls the opening of the solenoid valve to 0% until the temperature of the water outlet pipe is greater than the third preset value and the temperature of the water outlet pipe shows an upward trend.

[0093] The second preset value is 8°C, and the third preset value is 15°C.

[0094] In some embodiments, the method for detecting that the temperature of the water outlet pipe is decreasing includes:

[0095] The fourth temperature value of the water outlet pipe at the fourth time point is obtained, the fifth temperature value of the water outlet pipe at the fifth time point is obtained, and the sixth temperature value of the water outlet pipe at the sixth time point is obtained. The fifth time point is the time point of the fourth time point plus the third preset time, and the sixth time point is the time point of the fifth time point plus the third preset time.

[0096] The controller compares the fourth temperature value, the fifth temperature value and the sixth temperature value. If the fourth temperature value is smaller than the fifth temperature value and the fifth temperature value is smaller than the sixth temperature value, the temperature of the water outlet pipe shows an upward trend.

[0097] This article only takes the temperature values ​​at three time points as an example for explanation. In other optional embodiments, the temperature trend can also be determined by detecting the temperature at more time points, which will not be repeated here.

[0098] In the embodiment of the present application, the control method adopts three temperature sections for adjustment, and at temperatures outside the three temperature sections, the solenoid valve maintains the current state unchanged, thereby avoiding frequent disturbances to the thermal power unit and affecting the normal use of the thermal power unit.

[0099] S6: Exit antifreeze mode.

[0100] When the controller determines that the temperature of the water outlet pipe is greater than the third preset value and the temperature of the water outlet pipe is on an upward trend, the controller exits the antifreeze mode.

[0101] Exiting the antifreeze mode includes: turning off the sound and light alarm devices and switching the blinds to automatic adjustment.

[0102] The cooling system and control method of the thermal power unit disclosed in the embodiment of the present application can ensure that the circulating water inlet temperature is maintained above 3°C when the wind shield of the cooling tower cannot meet the antifreeze requirements in extremely cold weather in northern regions, which can effectively prevent the cooling tower from freezing and ensure the safe operation of the thermal power unit. At the same time, the circulating water inlet temperature can be automatically adjusted between 3°C and 15°C to enable the thermal power unit to operate at the optimal temperature and pressure, thereby improving the efficiency of the steam turbine and the economy of the thermal power unit.

[0103] In addition, the cooling system and control method of the thermal power unit disclosed in the embodiment of the present application both emit audible and visual alarms when starting and exiting the antifreeze mode to remind the operating personnel to pay attention and make adjustments in time, thereby effectively avoiding the occurrence of unsafe incidents.

[0104] The sound and light alarms involved in the present application include sound alarms and light alarms. The sound alarms include but are not limited to beeps, and the light alarms include but are not limited to flashing red lights.

[0105] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0106] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cooling system for a thermal power unit, characterized in that: include: A cooling tower, wherein a spray device is provided in the cooling tower, and a water collecting tank is provided below the spray device in the height direction; A condenser, wherein a circulation pipeline is arranged in the condenser for heat exchange with exhaust steam discharged from the thermal power unit, and an inlet of the circulation pipeline of the condenser is connected with the water collecting tank through a water outlet pipe; a first water return pipe, the first water return pipe being connected to the outlet of the circulation pipeline of the spray device and the condenser; A second water return pipe is connected to the outlet of the circulation pipeline of the water collecting tank and the condenser.

2. The cooling system of a thermal power unit according to claim 1, characterized in that: The second water return pipe is provided with a solenoid valve for controlling the opening of the second water return pipe.

3. The cooling system of a thermal power unit according to claim 2, characterized in that: Also includes: A shutter is used to cover the air inlet of the cooling tower.

4. The cooling system of a thermal power unit according to claim 3, characterized in that: Also includes: A temperature sensor, the temperature sensor is used to detect the temperature of the water outlet pipe; A controller, the controller is connected to the temperature sensor and controls the opening of the solenoid valve and the opening of the shutter; When the shutter is closed, when the temperature of the water outlet pipe is not greater than a first preset value, the opening of the solenoid valve is 100%; when the temperature of the water outlet pipe is greater than the first preset value and not greater than a second preset value, the opening of the solenoid valve is 50%; when the temperature of the water outlet pipe is greater than the second preset value and not greater than a third preset value, the opening of the solenoid valve is 0%; The first preset value is smaller than the second preset value, and the second preset value is smaller than the third preset value.

5. A control method for a cooling system of a thermal power unit, applied to the cooling device of a thermal power unit according to any one of claims 1 to 4, characterized in that: include: After determining that the shutter is closed for a first preset time, determining that the temperature of the water outlet pipe is not greater than a first preset value and that the temperature of the water outlet pipe is on a downward trend, the antifreeze mode is activated; If it is determined that the pressure value in the condenser is greater than the preset pressure value and the temperature of the water outlet pipe is not greater than the first preset value, the solenoid valve opening is controlled to 100% until the temperature of the water outlet pipe is greater than the first preset value and not greater than the second preset value, then the solenoid valve opening is controlled to 50% until the temperature of the water outlet pipe is greater than the second preset value and not greater than the third preset value, then the solenoid valve opening is controlled to 0% until the temperature of the water outlet pipe is greater than the third preset value and the temperature of the water outlet pipe shows an upward trend, then the antifreeze mode is exited.

6. The control method of the cooling system of a thermal power unit according to claim 5, characterized in that: The starting antifreeze mode comprises: Activate the sound and light alarm device; The blinds are switched to manual adjustment.

7. The control method of the cooling system of a thermal power unit according to claim 5, characterized in that: The exiting antifreeze mode comprises: Turn off the sound and light alarm device; The blinds switch to automatic adjustment.

8. The control method of the cooling system of a thermal power unit according to claim 5, characterized in that: The detection method of the temperature of the water outlet pipe showing a downward trend includes: Obtain a first temperature value of the water outlet pipe at a first time point, obtain a second temperature value of the water outlet pipe at a second time point, and obtain a third temperature value of the water outlet pipe at a third time point, wherein the second time point is a time point equal to the first time point plus a second preset time, and the third time point is a time point equal to the second time point plus the second preset time; It is determined that the first temperature value is greater than the second temperature value, and the second temperature value is greater than the third temperature value, and the temperature of the water outlet pipe is on a downward trend.

9. The control method of the cooling system of a thermal power unit according to claim 5, characterized in that: The detection method of the rising trend of the temperature of the water outlet pipe includes: Obtain a fourth temperature value of the water outlet pipe at a fourth time point, obtain a fifth temperature value of the water outlet pipe at a fifth time point, and obtain a sixth temperature value of the water outlet pipe at a sixth time point, wherein the fifth time point is a time point equal to the fourth time point plus a third preset time, and the sixth time point is a time point equal to the fifth time point plus the third preset time; It is determined that the fourth temperature value is less than the fifth temperature value, and the fifth temperature value is less than the sixth temperature value, and the temperature of the water outlet pipe is on an upward trend.

10. The control method for the cooling system of a thermal power unit according to any one of claims 5 to 9, characterized in that: After the antifreeze mode is activated, Make sure that the pressure value in the condenser is not greater than the preset pressure value, and the opening of the solenoid valve remains unchanged.

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