A supercritical carbon dioxide cycle system

Abstract

This invention discloses a supercritical carbon dioxide circulation system, belonging to the field of thermodynamic cycle technology, applicable to various energy utilization scenarios. In this system, the turbine outlet is sequentially connected to the high-temperature side of a high-temperature regenerator and a low-temperature regenerator. The high-temperature side outlet of the low-temperature regenerator is divided into two paths: one path connects to the main compressor inlet via a working fluid purification device and a cooler, and the other path directly connects to the re-compressor inlet, with the re-compressor outlet connected to the low-temperature side of the low-temperature regenerator. After the two working fluids exchange heat and converge, they sequentially flow back to the turbine via the low-temperature regenerator and the low-temperature side of the high-temperature regenerator, forming a closed loop. The carbon dioxide working fluid storage tank is connected in parallel with the circulation loop through a pressure balancing module, which can stably replenish the circulating working fluid. This invention adds a working fluid purification and pressure balancing structure, effectively improving the purity of the working fluid and the stability of system operation, optimizing equipment working status, and featuring a compact overall structure, high circulation efficiency, and strong practicality and adaptability.

Description

Technical Field

[0001] This invention relates to the field of thermal cycle equipment technology, and more particularly to a supercritical carbon dioxide cycle system. Background Technology

[0002] Supercritical carbon dioxide circulation systems use supercritical carbon dioxide as the working fluid, offering significant advantages such as high circulation efficiency, compact system structure, and environmentally friendly and non-toxic working fluid, making them a research hotspot in the energy field in recent years. Compared to traditional steam circulation systems, supercritical carbon dioxide circulation systems have a higher working fluid density and lower viscosity, which can significantly reduce equipment size and floor space, thereby lowering system investment costs.

[0003] However, existing supercritical carbon dioxide circulation systems suffer from problems during operation, including working fluid loss, poor circulation stability, limited heat recovery efficiency, difficulty in ensuring working fluid purity, and compressor surge. On the one hand, during long-term operation, the working fluid may be lost due to pipeline leaks or inadequate equipment sealing, leading to insufficient total circulating working fluid and affecting normal system operation. Simultaneously, solid impurities and moisture can easily mix into the working fluid during circulation, affecting equipment operating efficiency and lifespan. On the other hand, large fluctuations in the temperature and pressure of the circulating working fluid can reduce the operating efficiency of core equipment such as turbines and compressors, even affecting their lifespan. Furthermore, the pressure difference between the carbon dioxide working fluid storage tank and the circulation loop is difficult to control, easily leading to unstable working fluid delivery and further exacerbating system fluctuations. In addition, some existing circulation systems have unreasonable regenerative structure designs, resulting in low heat recovery efficiency, and compressors lack effective anti-surge protection, further restricting the improvement of overall system circulation efficiency and operational reliability.

[0004] Therefore, there is an urgent need for a supercritical carbon dioxide circulation system that can supplement and stabilize the total amount of circulating working fluid, improve circulation stability and heat recovery efficiency, ensure working fluid purity, and protect core equipment, in order to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to address the deficiencies in the existing technology by proposing a supercritical carbon dioxide cycle system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A supercritical carbon dioxide circulation system includes a turbine, a high-temperature regenerator, a low-temperature regenerator, a cooler, a main compressor, a re-compressor, a carbon dioxide working fluid storage tank, a working fluid purification device, and a pressure balancing module. The high-temperature side outlet of the high-temperature regenerator is connected to the high-temperature side inlet of the low-temperature regenerator; the high-temperature side outlet of the low-temperature regenerator is divided into two paths, one path is connected to the inlet of the main compressor via a working fluid purification device and a cooler, and the other path is connected to the low-temperature side inlet of the low-temperature regenerator via a re-compressor; the low-temperature side outlet of the low-temperature regenerator is connected to the low-temperature side inlet of the high-temperature regenerator. The low-temperature outlet of the high-temperature regenerator is connected to the inlet of the turbine, and the outlet of the turbine is connected to the high-temperature inlet of the high-temperature regenerator, forming a closed loop. The carbon dioxide working medium storage tank is installed in the closed loop via a pressure balancing module to replenish and stabilize the total amount of circulating working medium; the pressure balancing module is used to adjust the pressure difference between the carbon dioxide working medium storage tank and the closed loop.

[0007] Furthermore, the connection point between the carbon dioxide working fluid storage tank and the closed loop is located on the pipeline between the low-temperature side outlet of the high-temperature regenerator and the turbine inlet, and the pressure balance module is connected in series in the closed loop.

[0008] Furthermore, the working fluid purification device includes a filtration unit and a drying unit connected in sequence. The filtration unit is used to filter solid impurities in the working fluid, and the drying unit is used to remove moisture from the working fluid. The inlet of the working fluid purification device is connected to the high-temperature side outlet of the low-temperature regenerator, and the outlet is connected to the inlet of the cooler.

[0009] Furthermore, the pressure balancing module includes a pressure reducing valve, a check valve, and a pressure sensor. The pressure sensor is connected to the closed loop and the carbon dioxide working medium storage tank respectively, and is used to collect the pressure data of both in real time. The pressure reducing valve is connected in series with the check valve, and the conduction direction of the check valve is from the carbon dioxide working medium storage tank to the closed loop. The pressure reducing valve adjusts its opening degree according to the pressure data collected by the pressure sensor.

[0010] Furthermore, the cooler is a partition wall heat exchanger, and a temperature regulating unit is provided inside the cooler to cool the carbon dioxide working fluid discharged from the high-temperature side outlet of the low-temperature regenerator to the inlet temperature of the main compressor. The temperature regulating unit is electrically connected to the inlet temperature sensor of the main compressor.

[0011] Furthermore, both the main compressor and the re-compressor are centrifugal compressors. The centrifugal compressors are equipped with a flow regulating device and an anti-surge protection unit. The anti-surge protection unit is used to monitor the operating status of the centrifugal compressor, and the flow regulating device is used to regulate the input flow of the centrifugal compressor when there are signs of surge.

[0012] Furthermore, both the high-temperature regenerator and the low-temperature regenerator are counter-flow regenerators, and the regenerators are equipped with heat exchange enhancement structures, which are either finned structures or spiral flow guiding structures.

[0013] Furthermore, the carbon dioxide working fluid storage tank is equipped with a pressure monitoring device, a temperature monitoring device, and a filling / draining valve. The pressure monitoring device and the temperature monitoring device are used to monitor the pressure and temperature of the working fluid in the storage tank, respectively. The filling / draining valve is linked with the pressure balance module for automatic control of working fluid replenishment and discharge.

[0014] Furthermore, the closed loop is equipped with a flow monitoring device and a pressure regulating valve. The flow monitoring device is used to monitor the flow rate of the circulating working fluid, and the pressure regulating valve is used to regulate the overall pressure within the closed loop.

[0015] Furthermore, the pressure balancing module is connected to the closed loop via a buffer pressure stabilizing branch. The buffer pressure stabilizing branch is sequentially provided with a multi-stage damping pressure stabilizing structure, a flow slow-release chamber, and a buffer pressure stabilizing valve. The branch pipe is connected to the closed loop via the buffer pressure stabilizing valve. The multi-stage damping pressure stabilizing structure consists of multiple layers of porous damping plates, which are staggered within the branch pipe. The flow slow-release chamber is an expanded-diameter buffer chamber, located between the buffer pressure stabilizing valve and the multi-stage damping pressure stabilizing structure.

[0016] Beneficial effects

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: By adding a pressure balancing module and combining it with the reasonable connection between the carbon dioxide working medium storage tank and the closed loop, the pressure difference between the storage tank and the loop can be precisely adjusted to achieve stable delivery of the working medium. At the same time, the working medium lost during the circulation process can be replenished in real time to stabilize the total amount of circulating working medium and avoid abnormal system operation due to insufficient working medium or pressure fluctuations, thus significantly improving the system's operational stability and reliability.

[0018] By adding a working fluid purification device, solid impurities in the working fluid can be effectively filtered out and moisture removed, ensuring the purity of the circulating working fluid, preventing impurities from wearing away and moisture from corroding core equipment, extending the service life of the equipment, and avoiding the impact of insufficient working fluid purity on circulation efficiency, thereby further improving the stability of system operation.

[0019] The system adopts a dual-regeneration structure with a high-temperature regenerator and a low-temperature regenerator connected in series, and sets up a heat exchange enhancement structure inside the regenerator. This allows the high-temperature working fluid at the turbine outlet to release heat by passing through the high-temperature regenerator and the low-temperature regenerator in sequence, thus fully preheating the circulating working fluid, maximizing the recovery of waste heat from the working fluid, reducing heat loss, and effectively improving the system's heat recovery efficiency and overall circulation efficiency. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0021] Figure 1 This is a schematic diagram of the connection structure of a supercritical carbon dioxide cycle system.

[0022] In the diagram: 1. Turbine, 2. High-temperature regenerator, 3. Low-temperature regenerator, 4. Cooler, 5. Main compressor, 6. Recompressor, 7. Carbon dioxide working fluid storage tank, 8. Working fluid purification device. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Reference Figure 1 This invention provides a supercritical carbon dioxide circulation system, comprising a turbine 1, a high-temperature regenerator 2, a low-temperature regenerator 3, a cooler 4, a main compressor 5, a recompressor 6, a carbon dioxide working fluid storage tank 7, a working fluid purification device 8, and a pressure balancing module; the outlet of the turbine 1 is connected to the high-temperature side inlet of the high-temperature regenerator 2, and the high-temperature side outlet of the high-temperature regenerator 2 is connected to the high-temperature side inlet of the low-temperature regenerator 3; the high-temperature side outlet of the low-temperature regenerator 3 is divided into two paths, one path connecting to the inlet of the main compressor 5 via the working fluid purification device 8 and the cooler 4, and the other path connecting to the recompressor 6. The low-temperature inlet of the low-temperature regenerator 3 is connected to the low-temperature inlet of the high-temperature regenerator 2, and the low-temperature outlet of the high-temperature regenerator 2 is connected to the inlet of the turbine 1, forming a closed loop 8. The carbon dioxide working fluid storage tank 7 is connected in parallel with the closed loop 8 through a pressure balancing module. The specific connection point is set on the pipeline between the low-temperature outlet of the high-temperature regenerator 2 and the inlet of the turbine 1, which is used to supplement and stabilize the total amount of circulating working fluid. The pressure balancing module is used to adjust the pressure difference between the carbon dioxide working fluid storage tank 7 and the closed loop 8 to achieve stable delivery of the working fluid.

[0026] In other preferred embodiments, the working fluid purification device 8 includes a filtration unit and a drying unit connected in sequence. The filtration unit uses a high-precision filter element, which can filter solid impurities with a diameter greater than 5μm. The drying unit uses an adsorption dryer, which can reduce the moisture content in the working fluid to below 10ppm, effectively ensuring the purity of the working fluid. The pressure balance module includes a pressure reducing valve, a one-way valve, and a pressure sensor. The pressure sensor has a measurement accuracy of ±0.1MPa and can collect pressure data in the closed loop 8 and the carbon dioxide working fluid storage tank 7 in real time. The pressure reducing valve automatically adjusts its opening according to the pressure data, with an adjustment range of 0-100%. The one-way valve can prevent the working fluid from flowing backward and ensure stable delivery of the working fluid.

[0027] In other preferred embodiments, the cooler 4 adopts a partitioned water-cooled heat exchanger, and the internal temperature regulation unit includes a temperature sensor and a flow regulating valve. The temperature sensor is connected to the air inlet of the main compressor 5 to collect the air inlet temperature in real time. When the air inlet temperature deviates from the suitable range (30-40℃), the temperature regulation unit automatically adjusts the cooling water flow rate to achieve closed-loop control of the working fluid cooling temperature. Both the main compressor 5 and the re-compressor 6 are centrifugal compressors. Their anti-surge protection units can monitor the inlet and outlet pressure ratio and flow rate of the compressor. When the pressure ratio is lower than the set value or the flow rate fluctuates abnormally, the flow regulating device is automatically adjusted to prevent the compressor from surging.

[0028] In other preferred embodiments, both the high-temperature regenerator 2 and the low-temperature regenerator 3 adopt a counter-flow structure, and the internal heat exchange enhancement structure is a finned structure. The fins are made of stainless steel, which can increase the heat exchange area by 30%-50%, making the heat exchange between the hot and cold working fluids more complete, and improving the heat recovery efficiency by more than 20% compared with the existing structure. The carbon dioxide working fluid storage tank 7 is equipped with a pressure monitoring device 9, a temperature monitoring device, and a filling and discharging valve. The pressure monitoring device 9 and the temperature monitoring device provide real-time feedback on the working fluid status in the storage tank. The filling and discharging valve is linked with the pressure balance module. When the working fluid pressure in the closed loop 8 is lower than the set value (e.g., 8MPa), the filling and discharging valve automatically opens, and the pressure balance module adjusts the pressure difference, allowing the working fluid to enter the loop smoothly. When the pressure in the loop is higher than the set value (e.g., 12MPa), the filling and discharging valve opens in reverse, and the excess working fluid is discharged into the storage tank, achieving stable control of the total amount of working fluid.

[0029] The flow monitoring device installed on the closed loop 8 is an electromagnetic flow meter with a measurement range of 0-100 m³ / h and an accuracy of ±0.5%, which can monitor the flow rate of the circulating working medium in real time. The pressure regulating valve is an electric regulating valve, which can manually or automatically adjust the overall pressure in the loop according to the system operating conditions to ensure stable system operation.

[0030] The buffer pressure stabilizing branch is an integrated disturbance elimination and pressure stabilizing structure, including the branch pipe body, buffer pressure stabilizing valve, multi-stage damping pressure stabilizing structure, flow slow release cavity and pipeline throttling bushing. All structures are integrated in series inside the feeding branch.

[0031] Among them, the buffer pressure regulating valve is an electrically controlled adaptive regulating valve that works in conjunction with the system pressure balance module. It can dynamically adjust the valve opening according to the real-time pressure of the circulation loop and the output pressure of the storage tank. The multi-stage damping pressure regulating structure adopts a staggered arrangement of multi-layer porous damping plates, which are set up step by step along the flow direction of the working fluid. It can decelerate and stabilize the high-speed flowing replenishment working fluid in layers. The flow release chamber is an expanded-diameter buffer chamber located at the rear end of the damping structure. It can temporarily accumulate the replenishment working fluid with small fluctuations to achieve a smooth transition of the working fluid flow. The pipeline throttling bushing is matched with the flow characteristics of supercritical carbon dioxide working fluid to avoid pressure shock and flow field turbulence caused by excessive local flow velocity in the pipeline.

[0032] The working process of this invention is as follows: Supercritical carbon dioxide working fluid expands and performs work within turbine 1, driving turbine 1 to operate. After performing work, the temperature and pressure of the working fluid decrease. It exits from the turbine 1 outlet and enters the high-temperature side of high-temperature regenerator 2, where it exchanges heat with the low-temperature working fluid on the low-temperature side of regenerator 2, releasing some heat. The working fluid then enters the high-temperature side of low-temperature regenerator 3, continuing to exchange heat with the working fluid on the low-temperature side of regenerator 3, further releasing heat. Subsequently, the working fluid at the high-temperature side outlet of low-temperature regenerator 3 is divided into two paths. One path enters the working fluid purification device 8, where impurities and moisture are removed through filtration and drying before entering the cooler 4, where it is cooled to a suitable temperature under the control of the temperature regulation unit. The working fluid then enters the main compressor 5 for compression. The anti-surge protection unit monitors the compressor's operating status in real time to prevent surge. Another path directly enters the re-compressor 6 for compression, which also operates stably under the protection of the anti-surge protection unit. After the working fluid is compressed by the main compressor 5 and the re-compressor 6, it enters the low-temperature side of the low-temperature regenerator 3. Through the heat exchange enhancement structure, it absorbs the heat released by the high-temperature working fluid. After the temperature rises, it enters the low-temperature side of the high-temperature regenerator 2. It continues to absorb the heat released by the high-temperature working fluid through the heat exchange enhancement structure. The temperature rises further to the suitable inlet temperature of the turbine 1. After the pressure is adjusted by the pressure regulating valve, it enters the turbine 1 again to expand and do work, completing a closed cycle.

[0033] Throughout the entire cycle, the flow monitoring device monitors the working fluid flow rate in real time, and the pressure regulating valve adjusts the overall pressure of the loop. The carbon dioxide working fluid storage tank 7 is linked with the closed loop 8 through the pressure balancing module to replenish the lost working fluid and adjust the loop pressure in real time, ensuring the stable, efficient and safe operation of the circulation system.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A supercritical carbon dioxide cycle system, characterized in that, It includes a turbine, a high-temperature regenerator, a low-temperature regenerator, a cooler, a main compressor, a re-compressor, a carbon dioxide working fluid storage tank, a working fluid purification device, and a pressure balance module; The high-temperature side outlet of the high-temperature regenerator is connected to the high-temperature side inlet of the low-temperature regenerator; the high-temperature side outlet of the low-temperature regenerator is divided into two paths, one path is connected to the inlet of the main compressor via a working fluid purification device and a cooler, and the other path is connected to the low-temperature side inlet of the low-temperature regenerator via a re-compressor; the low-temperature side outlet of the low-temperature regenerator is connected to the low-temperature side inlet of the high-temperature regenerator. The low-temperature outlet of the high-temperature regenerator is connected to the inlet of the turbine, and the outlet of the turbine is connected to the high-temperature inlet of the high-temperature regenerator, forming a closed loop. The carbon dioxide working medium storage tank is installed in the closed loop via a pressure balancing module to replenish and stabilize the total amount of circulating working medium; the pressure balancing module is used to adjust the pressure difference between the carbon dioxide working medium storage tank and the closed loop.

2. The supercritical carbon dioxide cycle system according to claim 1, characterized in that, The connection point between the carbon dioxide working fluid storage tank and the closed loop is located on the pipeline between the low-temperature side outlet of the high-temperature regenerator and the turbine inlet, and the pressure balance module is connected in series in the closed loop.

3. The supercritical carbon dioxide cycle system according to claim 1, characterized in that, The working fluid purification device includes a filtration unit and a drying unit connected in sequence. The filtration unit is used to filter solid impurities in the working fluid, and the drying unit is used to remove moisture from the working fluid. The inlet of the working fluid purification device is connected to the high-temperature side outlet of the low-temperature regenerator, and the outlet is connected to the inlet of the cooler.

4. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, The pressure balancing module includes a pressure reducing valve, a check valve, and a pressure sensor. The pressure sensor is connected to the closed loop and the carbon dioxide working medium storage tank respectively, and is used to collect the pressure data of both in real time. The pressure reducing valve and the check valve are connected in series. The conduction direction of the check valve is from the carbon dioxide working medium storage tank to the closed loop. The pressure reducing valve adjusts its opening degree according to the pressure data collected by the pressure sensor.

5. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, The cooler is a partition wall heat exchanger, and a temperature regulating unit is installed inside the cooler to cool the carbon dioxide working fluid discharged from the high temperature side outlet of the low temperature regenerator to the main compressor inlet temperature. The temperature regulating unit is electrically connected to the main compressor inlet temperature sensor.

6. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, Both the main compressor and the re-compressor are centrifugal compressors. The centrifugal compressors are equipped with a flow regulating device and an anti-surge protection unit. The anti-surge protection unit is used to monitor the operating status of the centrifugal compressor, and the flow regulating device is used to regulate the input flow of the centrifugal compressor when there are signs of surge.

7. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, Both the high-temperature regenerator and the low-temperature regenerator are counter-flow regenerators, and the regenerators are equipped with heat exchange enhancement structures, which are either finned structures or spiral flow guiding structures.

8. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, The carbon dioxide working medium storage tank is equipped with a pressure monitoring device, a temperature monitoring device, and a filling / draining valve. The pressure monitoring device and the temperature monitoring device are used to monitor the pressure and temperature of the working medium in the storage tank, respectively. The filling / draining valve is linked with the pressure balance module for automatic control of working medium replenishment and discharge.

9. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, The closed loop is equipped with a flow monitoring device and a pressure regulating valve. The flow monitoring device is used to monitor the flow rate of the circulating working fluid, and the pressure regulating valve is used to regulate the overall pressure within the closed loop.

10. A supercritical carbon dioxide cycle system according to claim 1, characterized in that, The pressure balancing module is connected to the closed loop through a buffer pressure stabilizing branch. The buffer pressure stabilizing branch is sequentially provided with a multi-stage damping pressure stabilizing structure, a flow slow-release chamber, and a buffer pressure stabilizing valve. The branch pipe is connected to the closed loop through the buffer pressure stabilizing valve. The multi-stage damping pressure stabilizing structure is a multi-layer porous damping plate, which is staggered in the branch pipe. The flow slow-release chamber is an expanded diameter buffer chamber, which is located between the buffer pressure stabilizing valve and the multi-stage damping pressure stabilizing structure.

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