Expansion overflow system

Abstract

The utility model discloses an expansion overflow system which comprises an expansion tank, an overflow tank and an overflow pump which are connected to form a loop, a filter exhaust system is arranged at an inlet of the overflow pump, the system consists of a pipeline, a valve and a gas-liquid separation device, and the gas-liquid separation device is connected with the bottom of a filter screen of the overflow pump through the valve and the pipeline. The top of the filter screen is provided with a valve used for discharging nitrogen in a pump inlet pipeline, the other end of the gas-liquid separation device is connected to a regeneration recovery system through a pipeline, and an exhaust automatic control valve is arranged on a connecting pipeline and used for feeding gas into the regeneration recovery system. The expansion overflow system can prevent cavitation of the pump, guarantees safe and stable work of the pump, greatly reduces tripping frequency of the overflow pump, and improves operation reliability of a photo-thermal unit.

Description

Technical Field

[0001] The utility model relates to a heat transfer oil system of a photothermal unit, in particular to an expansion overflow system which can improve the operating reliability of a heat transfer oil overflow pump system of a photothermal power station. Background Art

[0002] As an important part of my country's development of new energy, the CSP generator set has its own large-capacity, low-cost energy storage system, which can achieve 24-hour continuous, stable, low-carbon, environmentally friendly, and pollution-free advantages. As an important component of the thermal oil system of the CSP unit, the overflow pump plays a connecting role. It controls the normal liquid level of the expansion tank and ensures the safe and stable operation of the thermal oil main pump and the mirror field.

[0003] The thermal overflow pump oil pump has the following problems during operation:

[0004] 1) The density of the thermal oil changes greatly from room temperature to the rated operating temperature of 390°C, resulting in large changes in the operating current of the pump at various temperatures;

[0005] 2) When the expansion tank is running, nitrogen needs to be injected to maintain a certain pressure to prevent the thermal oil from vaporizing. The nitrogen in the tank can easily enter the overflow pump and cause cavitation, making the pump output abnormal and unable to work normally;

[0006] 3) When the expansion tank system is running, nitrogen is used to control the expansion tank pressure within the range of 5-12.6 bar. When the thermal oil system is running under low load, a large amount of nitrogen will enter the pump pipeline system;

[0007] 4) The overflow pump needs to be frequently exhausted when the unit is running. Summary of the invention

[0008] In order to solve the above problems, the purpose of the utility model is to provide an expansion overflow system for the thermal oil system of a solar thermal unit. By adjusting the overflow pump starting mode, the operation control of the expansion tank nitrogen filling valve, and the exhaust modification of the overflow pump pipeline system, the tripping and pump cavitation problems of the overflow pump can be effectively solved, thereby ensuring that the operating reliability of the overflow pump is greatly improved and the safe and stable operation of the system is guaranteed.

[0009] To achieve the above purpose, the utility model is implemented through the following technical solutions:

[0010] An expansion overflow system comprises an expansion tank, an overflow tank and an overflow pump connected into a loop, characterized in that a filter exhaust system is arranged at the inlet of the overflow pump, the system is composed of a pipeline, a first valve, a second valve and a gas-liquid separation device, the gas-liquid separation device is connected to the bottom of the overflow pump filter screen through the first valve and the pipeline, a second valve for discharging nitrogen in the pump inlet pipeline is arranged on the top of the overflow pump filter screen, the other end of the gas-liquid separation device is connected to the regeneration recovery system through a pipeline, and an exhaust automatic control valve is arranged on the connecting pipeline to send the gas into the regeneration recovery system.

[0011] Furthermore, the regeneration and recovery system includes several coolers and condensation tanks. The condensation tank is connected to a loss pump, which is connected to an overflow tank through a pipeline. The condensation tank is divided into a thermal oil condensation tank and a gas condensation tank. An activated carbon filter is connected to the top of the gas condensation tank. Non-condensable gases such as nitrogen that cannot be condensed are filtered through the activated carbon filter and released into the atmosphere.

[0012] Furthermore, a nitrogen control valve for controlling the amount of nitrogen filled in the expansion tank is provided on the expansion tank, an overflow pipe is provided between the expansion tank and the overflow tank, and a pneumatic control valve is provided on the overflow pipe. When the liquid level in the tank is high, the valve is opened to discharge oil and control the liquid level. When the liquid level in the expansion tank is low, the valve is closed. This can effectively prevent nitrogen from entering the overflow pump system from the overflow pipe.

[0013] Furthermore, the overflow pump motor is controlled by a frequency conversion cabinet, and the power supply of the overflow pump motor is a variable frequency power supply.

[0014] The utility model is simple and reliable to operate, has low technical transformation difficulty, is easy to implement, safe and reliable, greatly reduces the tripping frequency of the overflow pump, and improves the operating reliability of the solar thermal unit.

[0015] Compared with industrial frequency soft start, the utility model adopts variable frequency start to effectively adjust the shaft power of the pump, especially when starting low-temperature thermal oil. By adjusting the shaft power of the pump to match the motor power, the motor can be prevented from overloading, thereby improving the operating efficiency of the pump, reducing the power load of the pump, and being able to operate within all temperature changes of the thermal oil.

[0016] Adding electric valve control to the overflow pipe can effectively alleviate the cavitation problem of the pump, reduce the number of exhaust times of the pump and extend the exhaust interval time.

[0017] By modifying the exhaust of the pump inlet pipe and regularly exhausting the pump, cavitation problems can be prevented and the safe and stable operation of the pump can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attached Figure 1 This is a schematic diagram of the expansion overflow system of the utility model;

[0019] Attached Figure 2This is a schematic diagram of the start-up of the overflow pump motor in the expansion overflow system of the utility model;

[0020] In the figure: 1. expansion tank, 2. overflow tank, 3. overflow pump, 4. filter exhaust system, 5. pipeline, 6. first valve, 7. gas-liquid separation device, 8. overflow pump filter, 9. second valve, 10. exhaust automatic control valve, 11. cooler, 12. thermal oil condensate tank, 13. gas condensate tank, 14. loss pump, 15. activated carbon filter, 16. nitrogen control valve, 17. overflow pipe, 18. pneumatic control valve. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0022] As attached Figure 1 As shown, an expansion overflow system comprises an expansion tank 1, an overflow tank 2 and an overflow pump 3 connected into a loop, characterized in that a filter exhaust system 4 is arranged at the inlet of the overflow pump 3, the system is composed of a pipeline 5, a first valve 6, a second valve 9 and a gas-liquid separation device 7, the gas-liquid separation device 7 is connected to the bottom of the overflow pump filter 8 through the first valve 6 and the pipeline 5, a second valve 9 for discharging nitrogen in the pump inlet pipeline is arranged on the top of the overflow pump filter 8, the other end of the gas-liquid separation device is connected to the regeneration recovery system through a pipeline, and an exhaust automatic control valve 10 is arranged on the connecting pipeline for sending gas into the regeneration recovery system. The regeneration recovery system comprises a plurality of coolers 11 and a condenser tank, the condenser tank is connected to a loss pump 14, the volatilized and vaporized heat transfer oil is cooled by the cooler and condensed into a liquid state, and then sent back to the overflow tank 2 by the loss pump 14, the condenser tank is divided into a heat transfer oil condenser tank 12 and a gas condenser tank 13, the top of the gas condenser tank 13 is connected to an activated carbon filter 15, and non-condensable gases such as nitrogen that cannot be condensed are filtered by the activated carbon filter and released into the atmosphere. The expansion tank 1 is provided with a nitrogen control valve 16 for controlling the amount of nitrogen filled in the expansion tank, an overflow pipe 17 is provided between the expansion tank and the overflow tank, and a pneumatic control valve 18 is provided on the overflow pipe 17. Here, the liquid level in the expansion tank can be finely controlled by adding valve switch logic control. When the liquid level in the tank is high, the valve is opened to drain the oil and control the liquid level. When the liquid level in the expansion tank is low, the valve is closed, which can effectively prevent nitrogen from entering the overflow pump system from the overflow pipe. The overflow pump motor is controlled by a frequency conversion cabinet, and the overflow pump motor power supply is a variable frequency power supply.

[0023] During the exhaust process, the nitrogen in the pump inlet pipe is discharged through the second valve 9 on the top of the overflow pump filter 8, so that the pump is filled with thermal oil to prevent cavitation. Considering that the system works under high temperature and high pressure environment, the gas is sent to the regeneration recovery system through the exhaust automatic control valve 10. Since the cooling water flow of the cooler is limited, when all the exhaust is done, if the cooler is full of thermal oil, its cooling efficiency will be reduced, which may cause the cooling water to vaporize, threatening the safe operation of the cooling system. Therefore, the liquid level can be monitored by the gas-liquid separation device 7. When the liquid level rises, it indicates that the gas has been completely discharged. At this time, the exhaust control valve 10 needs to be closed to stop the exhaust.

[0024] Due to the large difference in oil density and viscosity between high temperature and low temperature states, the density of the thermal oil is 1051.2kg / m³ at 30°C, and 748.6kg / m³ at 350°C, which is 1.4 times different. The density decreases as the temperature rises. The shaft power of the pump varies greatly when running at different temperatures. When running at low temperatures, the shaft power of the pump is often greater than the rated power of the motor at 50HZ. The motor drives the motor through a soft starter, and the shaft power cannot be reduced by reducing the speed. The speed of the pump needs to be reduced by the frequency converter (it needs to be considered that the head of the pump at low speed can meet the operating requirements), and the shaft power of the pump is reduced to match the motor power. Therefore, the design of the overflow pump needs to consider the operating parameters of the thermal oil at low temperatures.

[0025] The original design of overflow pump motor startup was directly controlled by 400V low-voltage soft start cabinet, but now it has been changed to frequency conversion control cabinet, the pump motor power supply has been changed from industrial frequency power supply to frequency conversion power supply, and the motor secondary control circuit has been changed to frequency conversion cabinet control, which effectively avoids the influence of heat transfer oil on the pump due to density changes.

Claims

1. An expansion and overflow system, comprising an expansion tank, an overflow tank and an overflow pump connected in a loop, characterized in that: A filter exhaust system is arranged at the inlet of the overflow pump, which consists of a pipeline, a first valve, a second valve and a gas-liquid separation device. The gas-liquid separation device is connected to the bottom of the overflow pump filter through the first valve and the pipeline. A second valve for discharging nitrogen in the pump inlet pipeline is arranged on the top of the overflow pump filter. The other end of the gas-liquid separation device is connected to the regeneration and recovery system through a pipeline, and an exhaust automatic control valve is arranged on the connecting pipeline to send the gas into the regeneration and recovery system.

2. An expansion and overflow system according to claim 1, characterized in that: The regeneration and recovery system includes several coolers and condensation tanks. The condensation tank is connected to a loss pump, which is connected to an overflow tank through a pipeline. The condensation tank is divided into a thermal oil condensation tank and a gas condensation tank. An activated carbon filter is connected to the top of the gas condensation tank to release non-condensable gas into the atmosphere after filtering it through the activated carbon filter.

3. An expansion and overflow system according to claim 1, characterized in that: The expansion tank is provided with a nitrogen control valve for controlling the nitrogen filling amount in the expansion tank, an overflow pipe is provided between the expansion tank and the overflow tank, and a pneumatic control valve is provided on the overflow pipe.

4. The expansion and overflow system according to claim 1, characterized in that: The overflow pump motor is controlled by a frequency conversion cabinet, and the overflow pump motor power supply is a variable frequency power supply.

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