Liquid nitrogen vaporization cold energy utilization system

Abstract

The utility model relates to a liquid nitrogen vaporization cold energy utilization system which comprises a liquid nitrogen vaporizer and a circulating cooling water return pipe and further comprises a box body, a top end water inlet and a bottom end water outlet of the box body are communicated with a water inlet pipe and a water outlet pipe respectively, and the water outlet pipe is connected with a water pump. The liquid nitrogen vaporizer is mounted in the box body; the circulating cooling water return pipe is sequentially communicated with the water inlet pipe and the water outlet pipe in the water flow direction. Return water of process circulating cooling water of the lithium battery plant serves as a hot water source to exchange heat with the liquid nitrogen vaporizer, so that the surface of the liquid nitrogen vaporizer is prevented from being frozen, effective operation of the liquid nitrogen vaporizer is guaranteed, and liquid nitrogen vaporization efficiency is maintained; and meanwhile, the circulating cooling water absorbs the cooling capacity to be cooled, is pressurized by the water pump to return into the circulating cooling water return pipe, and is mixed with the original circulating cooling water in the circulating cooling water return pipe, so that the overall water temperature of the circulating cooling water in the circulating cooling water return pipe is reduced, the energy consumption of the circulating cooling water system is further reduced, and the efficient utilization of the liquid nitrogen cooling capacity is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of energy recovery and utilization, in particular to a liquid nitrogen vaporization cold utilization system. Background Art

[0002] A large amount of nitrogen is required in the production process of lithium batteries, and the supply of nitrogen is usually supplied by a combination of liquid nitrogen vaporization and nitrogen generators. Liquid nitrogen is usually vaporized using a liquid nitrogen vaporizer. During the vaporization process of liquid nitrogen, a large amount of cold is directly discharged into the air without being recycled, resulting in energy waste. In addition, the air around the liquid nitrogen vaporizer is easily condensed and frozen, resulting in a decrease in the heat exchange effect of the liquid nitrogen vaporizer, which seriously affects the vaporization effect of liquid nitrogen. At the same time, the process circulating water supply temperature of the lithium battery plant is about 20°C, while the cooling water return temperature is about 25°C, resulting in a high overall energy consumption of the entire circulating cooling water system. Utility Model Content

[0003] Based on this, it is necessary to address the technical problems that the current liquid nitrogen vaporization cooling energy is not recycled, resulting in energy waste, and the overall energy consumption of the entire circulating cooling water system of the lithium battery plant is high. The utility model provides a liquid nitrogen vaporization cooling energy utilization system.

[0004] The utility model provides a liquid nitrogen vaporization cold capacity utilization system, which comprises a liquid nitrogen vaporizer and a circulating cooling water return pipe, and also comprises a box body, a top water inlet and a bottom water outlet of the box body are respectively connected with a water inlet pipe and a water outlet pipe, and a water pump is connected to the water outlet pipe; the liquid nitrogen vaporizer is installed in the box body; along the water flow direction, the circulating cooling water return pipe is sequentially connected with the water inlet pipe and the water outlet pipe.

[0005] The utility model utilizes the return water of the process circulating cooling water of the lithium battery plant as the hot water source to exchange heat with the liquid nitrogen vaporizer. The liquid nitrogen in the liquid nitrogen vaporizer absorbs the heat of the circulating cooling water and vaporizes. The flowing circulating cooling water is utilized to take away the coldness of the liquid nitrogen to prevent the surface of the liquid nitrogen vaporizer from freezing, thereby ensuring the effective operation of the liquid nitrogen vaporizer and maintaining the vaporization efficiency of the liquid nitrogen. At the same time, the circulating cooling water absorbs the coldness and is cooled down and is pressurized by a water pump and returned to the circulating cooling water return pipe, where it is mixed with the original circulating cooling water in the circulating cooling water return pipe, thereby reducing the overall water temperature of the circulating cooling water in the circulating cooling water return pipe, thereby reducing the energy consumption of the circulating cooling water system, saving costs, and realizing the efficient use of the coldness of the liquid nitrogen.

[0006] As a further improvement of the above scheme of the utility model, it also includes a reclaimed water inlet pipe; an electric valve 1 is arranged on the water inlet pipe; one end of the reclaimed water inlet pipe is connected to the water inlet pipe and the connection point between the reclaimed water inlet pipe and the water inlet pipe is located downstream of the electric valve 1, and an electric valve 2 is arranged on the reclaimed water inlet pipe. By setting the reclaimed water inlet pipe, when the circulating cooling water system of the lithium battery plant is shut down and cannot provide circulating cooling water, reclaimed water can be used as a water source for liquid nitrogen vaporization heat exchange to ensure the normal operation of the liquid nitrogen vaporizer; through the electric valve 1 and the electric valve 2, the switching between circulating cooling water and reclaimed water can be conveniently performed.

[0007] As a further improvement of the above solution of the utility model, an electric valve 3 is also provided on the water inlet pipe, which is located downstream of the electric valve 1, and the connection point between the reclaimed water inlet pipe and the water inlet pipe is located between the electric valve 1 and the electric valve 3. The electric valve 3 can control the on and off of the water source at the water inlet at the top of the box.

[0008] As a further improvement of the above solution of the utility model, a flow meter is also provided on the water inlet pipe, and the flow meter is located downstream of the electric valve 3. The water inlet flow rate of the box can be adjusted by the flow meter, and the flow rate of the water pump should be equivalent to the water inlet flow rate of the box, so that the liquid level in the box is maintained within a predetermined liquid level range.

[0009] As a further improvement of the above scheme of the utility model, a liquid level meter and a temperature sensor are arranged on the box body, a water spray pipe is arranged at the top of the box body, the water spray pipe is connected to the water inlet at the top of the box body, and a plurality of water spray holes are distributed at the bottom of the water spray pipe. The liquid level and water temperature in the box body are monitored in real time by the liquid level meter and the opening and closing of the water pump are adjusted according to the liquid level monitored by the liquid level meter. When the liquid level in the box body is at a low alarm water level, the water pump stops; when the liquid level in the box body is at a normal water level, the water pump starts; when the liquid level in the box body is at a high alarm water level, the water pump increases the frequency until the water level returns to the normal water level, and the flow rate of the water pump is adjusted so that the pressure value of the pressure sensor 1 is between the pressure values ​​of the pressure sensor 2 and the pressure sensor 3. The openings of electric valve 1 and electric valve 3 are adjusted according to the temperature of the water flow in the box detected by the temperature sensor to maintain the water temperature in the box within a predetermined range. When the water temperature in the box is too low, the openings of electric valve 1 and electric valve 3 can be increased to increase the water inlet flow rate of the box. When the water temperature in the box is too high, the openings of electric valve 1 and electric valve 3 can be reduced to reduce the water inlet flow rate.

[0010] As a further improvement of the above scheme of the utility model, a sewage outlet is provided at the bottom of the box body and the sewage outlet is connected to a sewage pipe, and an electric valve 4 is provided on the sewage pipe. The sewage inside the box body can be cleaned and discharged through the sewage pipe, and it is only opened when the box body needs to be cleaned, mud is discharged and emptied. The box body can be rinsed with the reclaimed water through the reclaimed water inlet pipe. After cleaning, the electric valve 4 is opened to discharge sewage through the sewage pipe.

[0011] As a further improvement of the above scheme of the utility model, it also includes a reclaimed water outlet pipe; the outlet pipe is provided with an electric valve 5 located downstream of the water pump; one end of the reclaimed water outlet pipe is connected to the outlet pipe and the connection point between the reclaimed water outlet pipe and the outlet pipe is located between the water pump and the electric valve 5, and the reclaimed water outlet pipe is provided with an electric valve 6. When reclaimed water is used as the heat exchange water source of the liquid nitrogen heat exchanger, the prepared cold water can be introduced into the air compressor cooling tower through the water pump and the reclaimed water outlet pipe to replenish the air compressor cooling tower.

[0012] As a further improvement of the above solution of the utility model, a backflow preventer 1 is also provided on the water outlet pipe and is located downstream of the electric valve 5. The backflow preventer 1 prevents water from flowing back.

[0013] As a further improvement of the above solution of the utility model, a pressure sensor 1 is also provided on the water outlet pipe, which is located downstream of the backflow preventer 1. The water inlet pressure of the box is monitored in real time by the pressure sensor 1.

[0014] As a further improvement of the above scheme of the utility model, along the water flow direction, the circulating cooling water return pipe is provided with pressure sensor 2, backflow preventer 2, and pressure sensor 3 in sequence, the connection point between the water inlet pipe and the circulating cooling water return pipe is located between pressure sensor 2 and backflow preventer 2, and the connection point between the water outlet pipe and the circulating cooling water return pipe is located between backflow preventer 2 and pressure sensor 3. Backflow preventer 2 can prevent the water flow in the circulating cooling water return pipe from flowing back, and the head of the water pump is adjusted according to the water pressure values ​​detected by pressure sensor 1, pressure sensor 2, and pressure sensor 3, so that the pressure value detected by pressure sensor 1 is between the pressure values ​​detected by pressure sensor 2 and pressure sensor 3.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] The utility model utilizes the return water of the process circulating cooling water of the lithium battery plant as the hot water source to exchange heat with the liquid nitrogen vaporizer. The liquid nitrogen in the liquid nitrogen vaporizer absorbs the heat of the circulating cooling water and vaporizes. The flowing circulating cooling water is utilized to take away the coldness of the liquid nitrogen to prevent the surface of the liquid nitrogen vaporizer from freezing, thereby ensuring the effective operation of the liquid nitrogen vaporizer and maintaining the vaporization efficiency of the liquid nitrogen. At the same time, the circulating cooling water absorbs the coldness and is cooled down and is pressurized by a water pump and returned to the circulating cooling water return pipe, where it is mixed with the original circulating cooling water in the circulating cooling water return pipe, thereby reducing the overall water temperature of the circulating cooling water in the circulating cooling water return pipe, thereby reducing the energy consumption of the circulating cooling water system, saving costs, and realizing the efficient use of the coldness of the liquid nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a liquid nitrogen vaporization cold utilization system proposed in an embodiment of the utility model;

[0018] Figure 2 This is a schematic diagram of the structure of a box in a liquid nitrogen vaporization cold energy utilization system proposed in an embodiment of the utility model.

[0019] Figure numerals: 1. liquid nitrogen vaporizer; 2. circulating cooling water return pipe; 3. box; 4. water inlet pipe; 5. water outlet pipe; 6. water pump; 7. grey water inlet pipe; 8. electric valve one; 9. electric valve two; 10. electric valve three; 11. flow meter; 12. liquid level meter; 13. temperature sensor; 14. water spray pipe; 15. sewage pipe; 16. electric valve four; 17. grey water outlet pipe; 18. electric valve five; 19. electric valve six; 20. backflow preventer one; 21. pressure sensor one; 22. pressure sensor two; 23. backflow preventer two; 24. pressure sensor three. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0021] This embodiment aims to solve the technical problems that the liquid nitrogen vaporization cooling capacity is not recycled, resulting in energy waste, and the overall energy consumption of the entire circulating cooling water system of the lithium battery plant is high. A liquid nitrogen vaporization cooling capacity utilization system is provided to effectively utilize the liquid nitrogen vaporization cooling capacity and reduce the overall energy consumption of the entire circulating cooling water system of the lithium battery plant. Figure 1 , Figure 2 The liquid nitrogen vaporization cold energy utilization system provided in this embodiment includes a liquid nitrogen vaporizer 1, a circulating cooling water return pipe 2 and a box body 3, and may also include a reclaimed water inlet pipe 7 and a reclaimed water outlet pipe 17.

[0022] The circulating cooling water return pipe 2 of this embodiment directly adopts the circulating cooling water return pipe 2 in the lithium battery plant process, and the cooling water temperature in the circulating cooling water return pipe 2 is about 25°C. Pressure sensor 2 22, backflow preventer 23, and pressure sensor 3 24 are connected in sequence along the water flow direction of the circulating cooling water return pipe 2. The pressure sensor 22 and pressure sensor 3 24 monitor the water pressure at their locations, and the backflow preventer 23 can prevent water from flowing back.

[0023] The box body 3 is used to provide a cold utilization chamber. The top of the box body 3 is provided with a top water inlet and the bottom of the box body 3 is provided with a bottom water outlet and a sewage outlet. The top water inlet, the bottom water outlet and the sewage outlet are connected to the water inlet pipe 4, the water outlet pipe 5 and the sewage outlet 15 respectively. The top of the box body 3 is provided with a water spray pipe 14 connected to the top water inlet, and a plurality of water spray holes are distributed at the bottom of the water spray pipe 14. When the water flow is introduced into the top water inlet pipe 4, the water spray holes of the water spray pipe 14 will spray water downward, and at the same time, the water flow in the box body 3 can be led to the outside through the water outlet pipe 5. Electric valve 1 8, electric valve 3 10 and flow meter 11 are arranged in sequence along the water flow direction on the water inlet pipe 4. The water flow of the water inlet pipe 4 can be controlled by electric valve 1 8 and electric valve 2 9, and the flow rate of the water entering the top water inlet can be adjusted by the flow meter 11. The water pump 6, the electric valve 5 18, the backflow preventer 120, and the pressure sensor 121 are connected to the water outlet pipe 5 in sequence along the water flow direction. The water pump 6 provides power to lead the water flow from the bottom of the box body 3. The electric valve 5 18 can control the water flow of the water outlet pipe 5, and the backflow preventer 120 can prevent the water flow from flowing back. The electric valve 4 16 is provided on the sewage pipe 15, and the on and off of the sewage pipe 15 is controlled by the electric valve 4 16. When the electric valve 4 16 is opened, the sewage pipe 15 can be used to clean and drain the inside of the box body 3. It is only opened when the box body 3 needs to be cleaned, drained and emptied. In order to facilitate the observation of the liquid level and water temperature in the box body 3, a liquid level meter 12 and a temperature sensor 13 are also provided on the box body 3. The water pump 6 adopts a variable frequency pump, and the frequency of the water pump 6 changes with the change of the water inlet flow rate. The opening and closing of the water pump 6 is adjusted according to the liquid level monitored by the liquid level meter 12. When the liquid level in the box 3 is at the low alarm water level, the water pump 6 stops; when the liquid level in the box 3 is at the normal water level, the water pump 6 starts; when the liquid level in the box 3 is at the high alarm water level, the frequency of the water pump 6 is increased until the water level returns to the normal water level. The flow rate of the water pump 6 is adjusted to make the pressure value of the pressure sensor 1 21 between the pressure values ​​of the pressure sensor 2 22 and the pressure sensor 3 24.

[0024] The liquid nitrogen vaporizer 1 is arranged inside the box 3. When the water flow is introduced into the water inlet pipe 4, the water spray pipe 14 sprays the water evenly on the surface of the liquid nitrogen vaporizer 1, and the liquid nitrogen in the liquid nitrogen vaporizer 1 absorbs heat and vaporizes. In this embodiment, the liquid nitrogen vaporizer 1 can adopt an air-type vaporizer in the prior art, and its working principle is known and will not be described in detail here.

[0025] One end of the recycled water inlet pipe 7 is connected to the water inlet pipe 4 and the connection point between the recycled water inlet pipe 7 and the water inlet pipe 4 is located between the electric valve 1 8 and the electric valve 3 10. The other end of the recycled water inlet pipe 7 is connected to the recycled water source. The electric valve 2 9 is provided on the recycled water inlet pipe 7, and the electric valve 2 9 can be used to control the on and off of the water flow in the recycled water inlet pipe 7.

[0026] One end of the reclaimed water outlet pipe 17 is connected to the water outlet pipe 5, and the connection point between the reclaimed water outlet pipe 17 and the water outlet pipe 5 is located between the water pump 6 and the electric valve five 18. The other end of the reclaimed water outlet pipe 17 can be connected to the air compressor cooling tower. An electric valve six 19 is provided on the reclaimed water outlet pipe 17, and the electric valve six 19 can control the on and off of the water flow in the reclaimed water outlet pipe 17.

[0027] It should be noted that the electric valve 1 8, electric valve 2 9, electric valve 3 10, electric valve 4 16, recycled water outlet pipe 17, electric valve 5 18, and electric valve 6 19 involved in this embodiment all adopt electric flow control valves known in the prior art, and their working principles are known and will not be elaborated here.

[0028] Through the above structural setting, the working principle of this embodiment is as follows:

[0029] During normal operation, the electric valve 1 8 and the electric valve 3 10 are opened, and the circulating cooling water with a temperature of about 25°C in the circulating cooling water return pipe 2 is introduced into the water spray pipe 14 through the water inlet pipe 4. The circulating cooling water is sprayed from the water spray hole to the surface of the liquid nitrogen vaporizer 1 in the box body 3. When the circulating cooling water flows through the surface of the liquid nitrogen vaporizer 1, the liquid nitrogen in the liquid nitrogen vaporizer 1 is vaporized by absorbing heat, and the flowing circulating cooling water takes away the coldness of the liquid nitrogen vaporizer in time, thereby effectively suppressing the supercooling and icing of the surface of the liquid nitrogen vaporizer 1, and maintaining the liquid nitrogen vaporizer 1. The cooling water is operated efficiently, and the temperature of the circulating cooling water is reduced due to heat exchange; the flow rate is adjusted by the flow meter 11, and the opening of the electric valve 18 and the electric valve 3 10 is adjusted according to the temperature of the water flow in the box 3 detected by the temperature sensor 13, so that the water temperature in the box 3 is maintained within a predetermined range. When the water temperature in the box 3 is too low, the opening of the electric valve 18 and the electric valve 3 10 can be increased to increase the water flow rate of the box 3. When the water temperature in the box 3 is too high, the opening of the electric valve 18 and the electric valve 3 10 is reduced to reduce the water flow rate;

[0030] When the liquid level meter 12 detects that the liquid level in the box body 3 reaches the predetermined water level, the water pump 6 is started and the electric valve five 18 is opened, and the electric valve six 19 is kept closed, and the circulating cooling water cooled in the box body 3 is pumped into the circulating cooling water return pipe 2 through the water pump 6, and mixed with the original circulating cooling water in the circulating cooling water return pipe 2, which can reduce the overall water temperature in the circulating cooling water return pipe 2, thereby reducing the energy consumption of the circulating cooling water system in the lithium battery production process and saving costs; the head of the water pump 6 is adjusted according to the water pressure values ​​detected by the pressure sensor one 21, the pressure sensor two 22, and the pressure sensor three 24, so that the pressure value detected by the pressure sensor one 21 is between the pressure values ​​detected by the pressure sensor two 22 and the pressure sensor three 24; when the liquid level in the box body 3 exceeds the predetermined water level and reaches the high alarm level, the frequency of the water pump 6 is increased until the liquid level in the box body 3 returns to the predetermined water level; when the liquid level in the box body 3 is lower than the predetermined water level and reaches the low alarm level, the water pump 6 is turned off;

[0031] When the circulating cooling water system of the lithium battery plant is shut down and cannot provide circulating cooling water, in order to ensure the normal operation of the liquid nitrogen vaporizer 1, the electric valve 1 8 and the electric valve 5 18 are closed, and the electric valve 2 9 is opened, and the liquid nitrogen vaporizer 1 is heat exchanged using reclaimed water as the water source. The obtained cold water flows into the air compressor cooling tower through the water pump 6 and the reclaimed water outlet pipe 17 to replenish the air compressor cooling tower with water;

[0032] When the box body 3 needs to be cleaned and drained, the electric valve 1 8 and the electric valve 5 18 are closed, and the box body 3 is rinsed with recycled water. After cleaning, the electric valve 4 16 is opened to drain the sewage through the sewage pipe 15.

[0033] It should be noted that the water inlet pipe 4, the water outlet pipe 5, the recycled water inlet pipe 7 and the recycled water outlet pipe 17 in this embodiment are all made of the same material as the circulating cooling water return pipe 2 and are provided with an external insulation layer.

[0034] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more related listed items.

[0036] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A liquid nitrogen vaporization cold energy utilization system, comprising a liquid nitrogen vaporizer (1) and a circulating cooling water return pipe (2), characterized in that: It also comprises a box body (3), wherein a top water inlet and a bottom water outlet of the box body (3) are respectively connected to a water inlet pipe (4) and a water outlet pipe (5), and the water outlet pipe (5) is connected to a water pump (6); a liquid nitrogen vaporizer (1) is installed in the box body (3); and along the direction of water flow, a circulating cooling water return pipe (2) is sequentially connected to the water inlet pipe (4) and the water outlet pipe (5).

2. The liquid nitrogen vaporization cold energy utilization system according to claim 1, characterized in that: It also includes a recycled water inlet pipe (7); an electric valve 1 (8) is arranged on the water inlet pipe (4); one end of the recycled water inlet pipe (7) is connected to the water inlet pipe (4), and the connection point between the recycled water inlet pipe (7) and the water inlet pipe (4) is located downstream of the electric valve 1 (8); and an electric valve 2 (9) is arranged on the recycled water inlet pipe (7).

3. The liquid nitrogen vaporization cold energy utilization system according to claim 2, characterized in that: The water inlet pipe (4) is also provided with an electric valve three (10) located downstream of the electric valve one (8), and the connection point between the recycled water inlet pipe (7) and the water inlet pipe (4) is located between the electric valve one (8) and the electric valve three (10).

4. The liquid nitrogen vaporization cold energy utilization system according to claim 3, characterized in that: A flow meter (11) is also provided on the water inlet pipe (4), and the flow meter (11) is located downstream of the electric valve three (10).

5. The liquid nitrogen vaporization cold energy utilization system according to claim 1, characterized in that: A liquid level meter (12) and a temperature sensor (13) are provided on the box body (3), and a water spray pipe (14) is provided at the top end of the box body (3). The water spray pipe (14) is connected to a water inlet at the top end of the box body (3), and a plurality of water spray holes are distributed at the bottom of the water spray pipe (14).

6. The liquid nitrogen vaporization cold energy utilization system according to claim 1, characterized in that: A sewage outlet is provided at the bottom of the box body (3), and the sewage outlet is connected to a sewage pipe (15), and an electric valve four (16) is provided on the sewage pipe (15).

7. The liquid nitrogen vaporization cold energy utilization system according to claim 2, characterized in that: It also includes a medium water outlet pipe (17); the outlet pipe (5) is provided with an electric valve five (18) located downstream of the water pump (6); one end of the medium water outlet pipe (17) is connected to the outlet pipe (5), and the connection point between the medium water outlet pipe (17) and the outlet pipe (5) is located between the water pump (6) and the electric valve five (18); and the medium water outlet pipe (17) is provided with an electric valve six (19).

8. The liquid nitrogen vaporization cold energy utilization system according to claim 7, characterized in that: The water outlet pipe (5) is also provided with a backflow preventer (20) located downstream of the electric valve (18).

9. The liquid nitrogen vaporization cold energy utilization system according to claim 8, characterized in that: The water outlet pipe (5) is also provided with a pressure sensor (21) located downstream of the backflow preventer (20).

10. The liquid nitrogen vaporization cold energy utilization system according to claim 9, characterized in that: Along the water flow direction, a second pressure sensor (22), a second backflow preventer (23), and a third pressure sensor (24) are sequentially arranged on the circulating cooling water return pipe (2); a connection point between the water inlet pipe (4) and the circulating cooling water return pipe (2) is located between the second pressure sensor (22) and the second backflow preventer (23); and a connection point between the water outlet pipe (5) and the circulating cooling water return pipe (2) is located between the second backflow preventer (23) and the third pressure sensor (24).

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