High-power-density wide-load-regulation supercritical CO2 circulation system and method

Abstract

The invention belongs to the field of power generation / power circulation systems, and discloses a high-power-density wide-load-regulation supercritical CO2 circulation system and method.The system comprises a high-temperature heat source, a turbine-generator system, a heat recovery system and a multi-stage compression system which are connected, and circulation of supercritical CO2 is achieved; the system combines a multi-stage compression form of turbine split-flow expansion acting and pre-compression and recompression, the recompression cycle efficiency is further improved, meanwhile, the operating condition range of a cycle system is widened, the power density of the system is further improved based on the advantage of high efficiency of the cycle system, and the power efficiency of the system is improved. A power generation / power system simultaneously meets the ultrahigh requirements of multiple indexes such as high efficiency, wide load adjusting range and high power density; the circulating system is efficient, compact, high in safety and reliability and high in flexibility and maneuverability, efficient heat-work conversion can be achieved, sufficient power sources can be provided for various special application scenes such as power generation / power, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation / power cycle systems, and in particular relates to a supercritical CO2 cycle system and method with high power density and wide load regulation. Background Art

[0002] Supercritical CO2 is a special state of CO2 with a density close to that of liquid and a viscosity close to that of gas. The specific heat capacity at constant pressure changes dramatically with temperature and pressure. Therefore, supercritical CO2 has special advantages such as low compression power consumption, small flow resistance, and strong heat and mass transfer capabilities. It is regarded as a very promising circulating working fluid. The circulation system with supercritical CO2 as the working fluid has the advantages of high thermal efficiency, high compactness, low noise, safety and reliability. It is a revolutionary new power generation / power technology and one of the technologies with the greatest potential to replace the traditional steam Rankine cycle. It can be widely used in nuclear energy, solar energy, coal-fired, waste heat utilization, ship power and other fields.

[0003] At present, supercritical CO2 cycles mainly adopt two forms: simple cycle and recompression cycle. The feasibility of the two methods has been proved through experimental tests. Among them, the simple cycle is favored because of its simple structure and easy operation, but it has certain limitations in terms of efficiency and operating load adjustment range. Although the recompression cycle improves some efficiency, it also increases the complexity of the system structure, and the operating load adjustment range has not been improved. Although these two conventional cycles have advantages at the level of single indicators, they perform poorly in overall performance and are difficult to meet the growing demand for high efficiency and wide load adjustment.

[0004] It can be seen that the existing supercritical CO2 circulation method only has advantages at the level of a single indicator, but performs poorly in overall performance and is unable to meet the growing operational needs for high efficiency and wide load regulation. Summary of the invention

[0005] The present invention provides a supercritical CO2 circulation system and method with high power density and wide load regulation, so as to solve the technical problem that the existing supercritical CO2 circulation method has advantages only at the level of a single indicator, but performs poorly in overall performance and is difficult to meet the growing operational requirements of high efficiency and wide load regulation.

[0006] In order to achieve the above object, the present invention adopts the following technical contents: A supercritical CO2 circulation system with high power density and wide load regulation, comprising: High temperature heat source for heating supercritical CO2; The high temperature heat source is connected to a turbine-generator system for outputting electrical power by expanding the heated supercritical CO2 to do work; The turbine-generator system is connected to a heat recovery system for recovering the heat of the supercritical CO2 after expansion and work; The heat recovery system is connected to a multi-stage compression system for performing at least two-stage compression on the supercritical CO2 after heat recovery to increase the pressure of the supercritical CO2; The working fluid output end of the multi-stage compression system is connected to the high-temperature heat source through a heat recovery system to form a closed circulation system.

[0007] Further, the turbine-generator system includes a first turbine-generator set and a second turbine-generator set; The high-temperature heat source outlet working fluid is divided into three branches, among which: The first branch is connected to the turbine inlet of the first turbine-generator set through a three-way valve and a first flow regulating valve; The second branch is connected to the turbine inlet of the second turbine-generator set through a three-way valve and a second flow regulating valve; After passing through the turbine bypass valve, the third branch merges with the turbine outlets of the first turbine-generator set and the second turbine-generator set; after merging, the third branch is connected to the hot side inlet of the heat recovery system.

[0008] Furthermore, the heat recovery system includes a connected high-temperature regenerator and a low-temperature regenerator; the hot side inlet of the high-temperature regenerator is connected to the turbine-generator system; the hot side outlet of the low-temperature regenerator is connected to the multi-stage compression system; and the cold side outlet of the high-temperature regenerator is connected to the supercritical CO2 side inlet of the high-temperature heat source.

[0009] Furthermore, the outlet of the recompression compressor of the multi-stage compression system and the cold side outlet of the low-temperature regenerator are connected to the cold side inlet of the high-temperature regenerator.

[0010] Further, the multi-stage compression system includes a pre-compression compressor, a main-pressure compressor and a re-compression compressor; The working medium inlet of the pre-compression compressor is connected to the hot side outlet of the heat recovery system through a pre-cooler; The first branch of the pre-compression compressor is connected to the main pressure compressor through a third flow regulating valve and an interstage cooler; The second branch of the pre-compression compressor is connected to the re-compression compressor; The main pressure compressor is communicated with a cold side inlet of a low-temperature regenerator of the heat recovery system, and the re-pressure compressor is communicated with a cold side inlet of a high-temperature regenerator of the heat recovery system.

[0011] Furthermore, the first branch of the main pressure compressor is connected to the cold side inlet of the low-temperature regenerator of the heat recovery system, and the second branch is connected in sequence with a third back pressure valve and a storage tank, and the tank outlet merges with the hot side outlet of the heat recovery system and is connected to the hot side inlet of the precooler.

[0012] Furthermore, the high temperature heat source adopts one of nuclear energy, solar energy, coal and gas, and the temperature range is 400~800℃.

[0013] A control method for a supercritical CO2 circulation system with high power density and wide load regulation is provided, based on the above-mentioned supercritical CO2 circulation system with high power density and wide load regulation, comprising: The high temperature heat source heats the supercritical CO2, and the heated supercritical CO2 is transported to the turbine-generator system to perform work on the expansion of the supercritical CO2; The heat recovery system recovers the heat of the supercritical CO2 after expansion and transports the supercritical CO2 to the multi-stage compression system; The multi-stage compression system compresses the supercritical CO2 in at least two stages, and circulates the pressurized supercritical CO2 to the high-temperature heat source through the heat recovery system.

[0014] Furthermore, the outlet working fluid of the high-temperature heat source is divided into three branches, the first branch enters the first turbine-generator set through the three-way valve and the first flow regulating valve, and the second branch enters the second turbine-generator set through the three-way valve and the second flow regulating valve; the third branch is controlled by the turbine bypass valve, and the system output power can be adjusted and controlled in the range of 0 to 100% by adjusting the turbine bypass valve and the first flow regulating valve and the second flow regulating valve; After the supercritical CO2 passes through the turbine bypass valve, the first turbine-generator set and the second turbine-generator set, it enters the high-temperature regenerator and the low-temperature regenerator to release heat to heat the cold-side supercritical CO2. After that, the supercritical CO2 enters the precooler and is cooled to the inlet state of the pre-compression compressor. After being compressed in the pre-compression compressor, the supercritical CO2 is divided into two paths. One path enters the re-compression compressor to be compressed again, and the other path passes through the flow control valve and the interstage cooler to be cooled to the inlet state of the main pressure compressor and then enters the main pressure compressor. The supercritical CO2 compressed by the main pressure compressor enters the low-temperature regenerator through the second flow regulating valve of the main pressure compressor, absorbs the heat of the supercritical CO2 on the hot side, and then merges with the supercritical CO2 at the outlet of the re-pressure compressor and enters the high-temperature regenerator to absorb heat and heat up again. The flow entering the main pressure compressor and the re-pressure compressor is controlled by adjusting the third flow regulating valve and the first back pressure valve to adjust the clamping point position of the low-temperature regenerator and improve the efficiency of the low-temperature regenerator; the first back pressure valve is connected to the outlet of the re-pressure compressor.

[0015] Furthermore, when the supercritical CO2 at the outlet of the main pressure compressor is over-pressured, the third back-pressure valve is opened, and the supercritical CO2 passing through the third back-pressure valve is stored in the storage tank until the pressure is restored and then closed; when the pressure at the inlet of the precooler is too low, the pressure regulating valve of the storage tank is opened, and supercritical CO2 is filled into the system until the pressure is restored and then closed.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a supercritical CO2 circulation system with high power density and wide load regulation. The system comprises a connected high-temperature heat source, a turbine-generator system, a heat recovery system and a multi-stage compression system, thereby realizing the circulation of supercritical CO2. The system combines the turbine split flow expansion work, pre-compression and re-compression in a multi-stage compression form, thereby further improving the re-compression cycle efficiency and broadening the operating condition range of the circulation system. Based on the advantage of the high efficiency of the circulation system, the power density of the system is further improved, thereby realizing that the power generation / power system simultaneously meets the ultra-high requirements of multiple indicators such as high efficiency, wide load regulation range and high power density. The circulation system is efficient and compact, has high safety and reliability, and is highly flexible and maneuverable. It can realize efficient heat-to-work conversion, and can provide sufficient power sources for a variety of special application scenarios such as power generation / power, and has broad application prospects.

[0017] Preferably, in the present invention, the system divides the high-temperature heat source outlet working fluid into three branches through a three-way valve and a flow regulating valve, which respectively enter two turbine-generator sets and a bypass path; the system is equipped with two sets of turbine-generator sets, which can increase the system output power adjustment range and can also be used as one main and one auxiliary. This design enables the system to flexibly adjust the output power according to load requirements, thereby improving the flexibility and stability of the system.

[0018] Preferably, in the present invention, the heat recovery system includes a high-temperature regenerator and a low-temperature regenerator connected to each other, thereby improving the efficiency of the regenerator and significantly improving the net output power and efficiency of the supercritical CO2 circulation system.

[0019] Further preferably, in the present invention, the secondary compression outlet of the multi-stage compression system and the cold side outlet of the low-temperature regenerator are connected to the cold side inlet of the high-temperature regenerator; in this way, the heat of the high-temperature supercritical CO2 can be absorbed again, and the effective utilization of heat and further increase of pressure are achieved through the confluence connection, thereby enhancing the overall performance of the circulation system.

[0020] Preferably, in the present invention, the multi-stage compression system includes a pre-compression compressor, a main-pressure compressor and a re-compression compressor. The arrangement of the pre-compression compressor, the main-pressure compressor and the re-compression compressor forms a two-stage compression, which greatly increases the maximum pressure of the system, enables the system to flexibly adjust the compression ratio according to needs, and improves the adaptability and stability of the system.

[0021] Further preferably, in the present invention, a storage tank and a back-pressure valve are added to the outlet of the main pressure compressor, so that the system can store excess supercritical CO2 when overpressure occurs, and charge supercritical CO2 into the system when the pressure is too low. The storage tank is used to adjust the maximum and minimum pressures of the system. When the maximum pressure of the system is overpressured, the back-pressure valve opens until the pressure returns to the set pressure. This part of the supercritical CO2 is stored in the storage tank. When the inlet pressure of the precooler is too low, the pressure regulating valve opens until the pressure returns to the set pressure. Such a design realizes self-dynamic leveling of the maximum and minimum pressures of the circulation system, without the need to charge CO2 into the system from the outside, thereby ensuring the stable operation of the system.

[0022] Preferably, in the present invention, the high temperature heat source can be any energy source of nuclear energy, solar energy, coal, and gas with a temperature range of 400-800°C.

[0023] The present invention also provides a control method for a supercritical CO2 circulation system with high power density and wide load regulation. Based on the above-mentioned supercritical CO2 circulation system with high power density and wide load regulation, the method heats the supercritical CO2 by a high-temperature heat source, and transports the heated supercritical CO2 to a turbine-generator system to expand the supercritical CO2 and perform work; a heat recovery system recovers the heat of the supercritical CO2 after expansion and performs work, and transports the supercritical CO2 to a multi-stage compression system; finally, the multi-stage compression system compresses the supercritical CO2 for at least two stages, and circulates the pressurized supercritical CO2 from the heat recovery system to the high-temperature heat source; the use of this method makes the circulation system perform well in overall performance, and can meet the growing operational requirements of high efficiency and wide load regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic structural diagram of a supercritical CO2 circulation system with high power density and wide load regulation provided by the present invention.

[0025] Reference numerals: 1-high temperature heat source, 2-three-way valve, 3-first turbine-generator set, 4-second turbine-generator set, 5-main pressure compressor, 6-interstage cooler, 7-pre-pressure compressor, 8-re-pressure compressor, 9-precooler, 10-storage tank, 11-low temperature regenerator, 12-high temperature regenerator, 111-turbine bypass valve, 112-first flow regulating valve, 113-second flow regulating valve, 114-third flow regulating valve, 115-first back pressure valve, 116-second back pressure valve, 117-third back pressure valve, 118-pressure regulating valve. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings: Example 1 As described in the above background technology, the current supercritical CO2 cycle mainly adopts two forms: simple cycle and recompression cycle. The feasibility of the two methods has been proved through experimental tests. Among them, the simple cycle is favored because of its simple structure and easy operation, but it has certain limitations in terms of efficiency and operating load adjustment range; and the recompression cycle improves some efficiency, but also increases the complexity of the system structure, and the operating load adjustment range has not been improved. Although these two conventional cycles have advantages at the level of single indicators, they perform poorly in overall performance and are difficult to meet the growing demand for high efficiency and wide load adjustment.

[0034] In order to solve the above problems, this embodiment provides a supercritical CO2 circulation system with high power density and wide load regulation. The system can meet the requirements of high efficiency, high compactness, flexibility, low noise, safety and reliability.

[0035] like Figure 1 As shown, this embodiment provides a supercritical CO2 circulation system with high power density and wide load regulation, including: The high-temperature heat source 1, turbine-generator system, heat recovery system and multi-stage compression system are connected in sequence, wherein the working fluid output end of the multi-stage compression system is also connected to the high-temperature heat source 1 through the heat recovery system to realize the working fluid circulation; the specific structure is as follows: The turbine-generator system comprises a first turbine-generator set 3 and a second turbine-generator set 4; The heat recovery system includes a low-temperature regenerator 11 and a high-temperature regenerator 12; The multi-stage compression system includes a pre-compression compressor 7, a main pressure compressor 5 and a re-compression compressor 8; In this embodiment, a more specific connection structure is as follows: The system includes a high-temperature heat source 1, a three-way valve 2, a first turbine-generator set 3, a second turbine-generator set 4, a main pressure compressor 5, an interstage cooler 6, a pre-pressure compressor 7, a re-pressure compressor 8, a pre-cooler 9, a storage tank 10, a low-temperature regenerator 11, a high-temperature regenerator 12, a turbine bypass valve 111, a first flow regulating valve 112, a second flow regulating valve 113, a third flow regulating valve 114, a first back pressure valve 115, a second back pressure valve 116, a third back pressure valve 117 and a pressure regulating valve 118. The working fluid at the outlet of high-temperature heat source 1 is divided into three routes: One path is connected to the turbine inlet of the first turbine-generator set 3 through the three-way valve 2 and the first flow regulating valve 112; One path is connected to the turbine inlet of the second turbine-generator set 4 through the three-way valve 2 and the second flow regulating valve 113; The other path passes through the turbine bypass valve 111 and merges with the turbine outlets of the first turbine-generator set 3 and the second turbine-generator set 4; after merging, it is connected to the hot side inlet of the high-temperature regenerator 12, and the hot side outlet of the high-temperature regenerator 12 is connected to the hot side inlet of the low-temperature regenerator 11. The hot side outlet of the low-temperature regenerator 11 is connected to the hot side inlet of the precooler 9 after merging with the outlet of the pressure regulating valve 118, and the hot side outlet of the precooler 9 is connected to the inlet of the pre-compression compressor 7; the outlet working fluid of the pre-compression compressor 7 is divided into two paths, one of which is connected to the inlet of the re-compression compressor 8, and the other is connected to the interstage cooler through the flow regulating valve 114. 6, the hot side outlet of the interstage cooler 6 is connected to the inlet of the main pressure compressor 5, the outlet of the main pressure compressor 5 is connected to the cold side inlet of the low-temperature regenerator 11 through the back pressure valve 116, under certain conditions, part of the working fluid enters the storage tank 10 through the back pressure valve 117, the outlet of the storage tank 10 is connected to the precooler 9 after merging with the hot side outlet of the low-temperature regenerator 11 through the pressure regulating valve 118, the cold side outlet of the low-temperature regenerator 11 is connected to the cold side inlet of the high-temperature regenerator 12 after merging with the working fluid of the outlet of the re-compression compressor 8 through the back pressure valve 115, and the cold side outlet of the high-temperature regenerator 12 is connected to the cold side inlet of the high-temperature heat source 1.

[0036] The high-temperature heat source 1 is used to heat supercritical CO2, and the high efficiency of the supercritical CO2 circulation system is achieved by increasing the temperature of supercritical CO2. The heating form can be direct heating or indirect heating. Among them, the temperature range of the high-temperature heat source is 400℃~800℃, and the heat source can be nuclear energy, solar energy, coal, high-temperature gas, etc.

[0037] The pre-compression compressor 7, the main pressure compressor 5, and the re-compression compressor 8 are used to compress supercritical CO2 and increase the pressure of supercritical CO2. The pre-compression compressor 7 is used as the first-stage compression, and the main pressure compressor 5 and the re-compression compressor 8 are used as the second-stage compressors. The multi-stage compression of CO2 makes the circulation pressure ratio break through the existing technical level, while further improving the efficiency of the circulation system, and also improving the system power density. Among them, the outlet of the pre-compression compressor 7 is divided into two routes, one is connected to the re-compression compressor 8 through a three-way valve, and the other is connected to the main pressure compressor 5 through a three-way valve and an interstage cooler 6; this embodiment uses the pre-compression compressor 7 as the first-stage compression, the main pressure compressor 5 and the re-compression compressor 8 as the second-stage compression, and the maximum system pressure can reach more than 20MPa.

[0038] In this embodiment, a flow splitter is provided at the outlet of the pre-compression compressor 7, and the pinch point position of the low-temperature regenerator is controlled by adjusting the working medium flow rates of the main pressure compressor 5 and the re-compression compressor 8.

[0039] In addition, an interstage cooler 6 is provided at the inlet of the main pressure compressor 5 , thereby reducing the power consumption of the main pressure compressor 5 .

[0040] The first turbine-generator set 3 and the second turbine-generator set 4 are used to expand high-temperature and high-pressure supercritical CO2 to drive the turbine impeller and drive the generator to generate electricity. The net output power of the circulation system is controlled by adjusting the flow rate and temperature of the supercritical CO2 entering the turbine and the pressure ratio of the multi-stage compressor, which can achieve 0-100% operating load adjustment of the circulation system and meet the requirements of the wide load adjustment range of the system; it can be seen that by using two turbine-generator sets and adding a turbine bypass valve, the system can quickly adjust the output power within the range of 0-100%, which is more flexible and maneuverable.

[0041] The high-temperature regenerator 12 and the low-temperature regenerator 11 are used to recover the heat of the supercritical CO2 after expansion and work, and transfer the heat to the supercritical CO2 after compression and pressure increase to increase its temperature, which can reduce the power of the heat source to improve the cycle thermal efficiency.

[0042] In this embodiment, the precooler 9 and the interstage cooler 6 are used to further cool the supercritical CO2 to the inlet temperature of the pre-compression compressor 7 and the main pressure compressor 5. The cold source can be water cooling or air cooling.

[0043] In this embodiment, the storage tank 10 is used to adjust the maximum pressure and the minimum pressure of the system. When the maximum pressure of the system is overpressured, the back pressure valve opens until the pressure returns to the set pressure. This part of the supercritical CO2 is stored in the storage tank. When the precooler inlet pressure is too low, the pressure regulating valve opens until the pressure returns to the set pressure.

[0044] This embodiment uses a pre-compression compressor, a main pressure compressor, and a re-compression compressor to form a two-stage compression, greatly increasing the maximum pressure of the system, and adjusting the compressor outlet pressure through the speed and back pressure valve, thereby adjusting the operating conditions of the system; The present invention utilizes the third flow regulating valve 114 to regulate the flow into the main pressure compressor 5 and the re-pressure compressor 8, thereby regulating the supercritical CO2 flow on the cold side of the low-temperature regenerator 11 and the inlet and outlet temperatures of the hot and cold sides, and controlling the clamping point of the low-temperature regenerator 11 to be located outside, thereby improving the efficiency of the low-temperature regenerator 11 and enabling the system to obtain higher system efficiency under any operating conditions.

[0045] This embodiment uses the third back pressure valve 117, the storage tank 10, and the pressure regulating valve 118 to control the maximum pressure and the minimum pressure level of the system. When the maximum pressure of the system is too high, the third back pressure valve 117 opens, and part of the supercritical CO2 enters the storage tank 10 until the maximum pressure is restored, and the third back pressure valve 117 is closed; when the minimum pressure of the system is too low, the pressure regulating valve 118 opens, and the high-pressure supercritical CO2 in the storage tank 10 is filled into the pipeline until the minimum pressure is restored, and the pressure regulating valve 118 is closed.

[0046] It can be seen that the present embodiment provides a supercritical CO2 circulation system with high power density and wide load regulation. The system includes a high temperature heat source, two sets of turbine-generator sets, a high temperature regenerator, a low temperature regenerator, a precooler, a pre-compression compressor, an interstage cooler, a main pressure compressor, a re-compression compressor set, a storage tank, a valve, etc.; a multi-stage compressor is used to increase the maximum pressure of the system, an interstage cooler is added to reduce the compression power consumption, and a high and low temperature regenerator is used to improve the efficiency of the regenerator, so that the net output power and efficiency of the supercritical CO2 circulation system are significantly improved. In addition, the system is equipped with two sets of turbine-generator sets, which can increase the system output power adjustment range, and can also be used as one main and one auxiliary. The system uses control strategies such as motor active control unit, valve group, storage tank, etc. to realize the wide load regulation of the system. The supercritical CO2 circulation system with high power density and wide load regulation provided by the present system is efficient, compact, safe and reliable, flexible and maneuverable, and realizes efficient heat-to-work conversion. It can provide sufficient power sources for a variety of special application scenarios such as power generation / power, and has broad application prospects.

[0047] Example 2 This embodiment also provides a control method for a supercritical CO2 circulation system with high power density and wide load regulation. Based on the supercritical CO2 circulation system provided in Example 1, the specific implementation is as follows: In this embodiment, when the supercritical CO2 circulation system with high power density and wide load regulation is in operation, the critical CO2 is heated in the high-temperature heat source 1, enters the turbines of the first turbine-generator set 3 and the second turbine-generator set 4 to expand and perform work, pushes the turbine impeller, and drives the generator to generate electricity. The supercritical CO2 after expansion and work successively enters the high-temperature regenerator 12 and the low-temperature regenerator 11 for heat recovery, and then enters the precooler 9 for further cooling to the inlet state of the pre-compression compressor 7; the supercritical CO2 close to the critical point is compressed in the pre-compression compressor 7 and is divided into two paths, one path enters the re-compression compressor 8 for secondary compression, and the other path enters the main pressure compressor 5 for secondary compression after being cooled by the interstage cooler 6, and then enters the low-temperature regenerator 11 to absorb the heat of the high-temperature supercritical CO2, and then merges with the supercritical CO2 in the re-compression compressor 8 circuit and enters the high-temperature regenerator 12 to absorb the heat of the high-temperature supercritical CO2 again, and then enters the high-temperature heat source 1 to be heated to the turbine inlet state.

[0048] Specifically, in this embodiment, the outlet working fluid of the high-temperature heat source 1 is divided into three branches. The first branch enters the first turbine-generator set 3 through the three-way valve 2 and the first flow regulating valve 112, and the second branch enters the second turbine-generator set 4 through the three-way valve 2 and the second flow regulating valve 113; the third branch is controlled by the turbine bypass valve 111, and the system output power can be adjusted and controlled in the range of 0 to 100% by adjusting the turbine bypass valve 111 and the first flow regulating valve 112 and the second flow regulating valve 113; After the supercritical CO2 passes through the turbine bypass valve 111, the first turbine-generator set 3 and the second turbine-generator set 4, it enters the high-temperature regenerator 12 and the low-temperature regenerator 11 to release heat to heat the cold-side supercritical CO2, and then the supercritical CO2 enters the precooler 9 to be cooled to the inlet state of the pre-compression compressor 7; after being compressed in the pre-compression compressor 7, the supercritical CO2 is divided into two paths, one path enters the re-compression compressor 8 to be compressed again, and the other path passes through the flow control valve 114 and the interstage cooler 6 to be cooled to the inlet state of the main pressure compressor and then enters the main pressure compressor 5; The supercritical CO2 compressed by the main-pressure compressor 5 enters the low-temperature regenerator 11 through the second flow regulating valve 116 of the main-pressure compressor 5, absorbs the heat of the supercritical CO2 on the hot side, and then merges with the supercritical CO2 at the outlet of the re-pressure compressor 8 to enter the high-temperature regenerator 12 to absorb heat and heat up again. The flow entering the main-pressure compressor 5 and the re-pressure compressor 8 is controlled by adjusting the third flow regulating valve 114 and the first back-pressure valve 115 to adjust the clamping point position of the low-temperature regenerator 11 and improve the efficiency of the low-temperature regenerator 11; the first back-pressure valve 115 is connected to the outlet of the re-pressure compressor 8.

[0049] The present embodiment provides a control method for a supercritical CO2 circulation system with high power density and wide load regulation, which can increase the system efficiency to more than 40%, the power can reach more than 10MW, and the output power can be switched arbitrarily within the range of 0-100%. It not only achieves a significant improvement in system efficiency, but also the system is compact and small in size, and is very suitable for offshore power generation / power platforms.

[0050] In this embodiment, flow regulating valves and turbine bypass valves are used to adjust the flow into the turbines of the first turbine-generator set and the second turbine-generator set, thereby controlling the output power of the two turbine-generator sets and the net output power of the system, so that the system can achieve 0-100% output power regulation.

[0051] In this embodiment, a pre-compression compressor, a main pressure compressor, and a re-compression compressor are used to form a two-stage compression, which greatly increases the maximum pressure of the system, and the compressor outlet pressure is adjusted by the speed and back pressure valve, thereby adjusting the operating conditions of the system; In this embodiment, the flow rate regulating valve is used to adjust the flow rate into the main pressure compressor and the re-pressure compressor, so as to adjust the supercritical CO2 flow rate on the cold side of the low-temperature regenerator and the inlet and outlet temperatures on the hot and cold sides, and control the clamping point of the low-temperature regenerator to be located outside, thereby improving the efficiency of the low-temperature regenerator and enabling the system to obtain higher system efficiency under any working conditions; This embodiment uses the third back pressure valve 117, the storage tank 10, and the pressure regulating valve 118 to control the maximum pressure and the minimum pressure level of the system. When the maximum pressure of the system is too high, the third back pressure valve 117 opens, and part of the supercritical CO2 enters the storage tank 10 until the maximum pressure is restored, and the third back pressure valve 117 is closed; when the minimum pressure of the system is too low, the pressure regulating valve 118 opens, and the high-pressure supercritical CO2 in the storage tank 10 is filled into the pipeline until the minimum pressure is restored, and then the pressure regulating valve 118 is closed, thereby realizing self-dynamic leveling of the maximum pressure and the minimum pressure of this circulation system.

[0052] The present invention provides a supercritical CO2 circulation system and method with high power density and wide load regulation. Compared with existing circulation measures, the system has the following advantages: First, the high power density and wide load regulation supercritical CO2 circulation system realizes the efficient recycling of supercritical CO2 by integrating high temperature heat source, turbine-generator system, heat recovery system and multi-stage compression system, which significantly improves the power density and energy utilization efficiency of the system. Secondly, by adopting multi-stage compression system and heat recovery system, the system can effectively recover and utilize the heat of supercritical CO2 after expansion work, reduce energy waste and improve the overall efficiency of the system. Furthermore, the turbine-generator system includes two turbine-generator sets and is equipped with three branches, which can adjust the system output power according to actual needs, realize the wide load regulation function, and enhance the flexibility and adaptability of the system. In addition, the pre-compression compressor, main pressure compressor and re-compression compressor in the multi-stage compression system work together, and the flow entering each compressor is accurately adjusted through control elements such as flow control valve and back pressure valve, which optimizes the clamping point position of the low-temperature regenerator and further improves the efficiency and stability of the system. Finally, the system also has overpressure protection and pressure regulation functions. When the outlet of the main pressure compressor is overpressured, the supercritical CO2 can be stored in the storage tank by opening the back pressure valve. When the pressure at the inlet of the precooler is too low, supercritical CO2 can be charged into the system to ensure the safe and stable operation of the system. It can be seen that the system has shown significant beneficial effects in improving energy utilization efficiency, enhancing system flexibility, optimizing system performance, and ensuring safe and stable operation of the system.

[0053] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A supercritical CO2 circulation system with high power density and wide load regulation, characterized in that: include: A high temperature heat source (1) for heating supercritical CO2; The high temperature heat source (1) is connected to a turbine-generator system for outputting electrical power by expanding the heated supercritical CO2 to produce work; The turbine-generator system is connected to a heat recovery system for recovering the heat of the supercritical CO2 after expansion and work; The heat recovery system is connected to a multi-stage compression system for performing at least two-stage compression on the supercritical CO2 after heat recovery to increase the pressure of the supercritical CO2; The working fluid output end of the multi-stage compression system is connected to the high-temperature heat source (1) via a heat recovery system to form a closed circulation system.

2. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 1 is characterized in that: The turbine-generator system comprises a first turbine-generator set (3) and a second turbine-generator set (4); The outlet working fluid of the high temperature heat source (1) is divided into three branches, among which: The first branch is connected to the turbine inlet of the first turbine-generator set (3) through a three-way valve (2) and a first flow regulating valve (112); The second branch is connected to the turbine inlet of the second turbine-generator set (4) through the three-way valve (2) and the second flow regulating valve (113); After passing through the turbine bypass valve (111), the third branch is merged with the turbine outlets of the first turbine-generator set (3) and the second turbine-generator set (4); after merging, the third branch is connected to the hot side inlet of the heat recovery system.

3. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 1 is characterized in that: The heat recovery system comprises a high-temperature regenerator (12) and a low-temperature regenerator (11) connected to each other; the hot side inlet of the high-temperature regenerator (12) is connected to the turbine-generator system; the hot side outlet of the low-temperature regenerator (11) is connected to the multi-stage compression system; and the cold side outlet of the high-temperature regenerator (12) is connected to the supercritical CO2 side inlet of the high-temperature heat source (1).

4. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 3 is characterized in that: The outlet of the recompression compressor of the multi-stage compression system and the cold side outlet of the low-temperature regenerator (11) are connected to the cold side inlet of the high-temperature regenerator (12).

5. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 1 is characterized in that: The multi-stage compression system comprises a pre-compression compressor (7), a main-pressure compressor (5) and a re-compression compressor (8); The working medium inlet of the pre-compression compressor (7) is connected to the hot side outlet of the heat recovery system through a pre-cooler (9); The first branch of the pre-pressure compressor (7) is connected to the main-pressure compressor (5) via a third flow regulating valve (114) and an interstage cooler (6); The second branch of the pre-compression compressor (7) is in communication with the re-compression compressor (8); The main pressure compressor (5) is in communication with a cold side inlet of a low-temperature regenerator of the heat recovery system, and the re-pressure compressor (8) is in communication with a cold side inlet of a high-temperature regenerator of the heat recovery system.

6. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 5 is characterized in that: The first branch of the main pressure compressor (5) is connected to the cold side inlet of the low-temperature regenerator of the heat recovery system, and the second branch is connected in sequence to a third back pressure valve (117) and a storage tank (10), and the outlet of the storage tank (10) merges with the hot side outlet of the heat recovery system and is connected to the hot side inlet of the precooler (9).

7. The supercritical CO2 circulation system with high power density and wide load regulation according to claim 1 is characterized in that: The high temperature heat source (1) is one of nuclear energy, solar energy, coal and gas, and has a temperature range of 400-800°C.

8. A control method for a supercritical CO2 circulation system with multiple high power density and wide load regulation, characterized in that: The supercritical CO2 circulation system with high power density and wide load regulation according to any one of claims 1 to 7 comprises: The high temperature heat source (1) heats the supercritical CO2, and transmits the heated supercritical CO2 to the turbine-generator system to perform work on the expansion of the supercritical CO2; The heat recovery system recovers the heat of the supercritical CO2 after expansion and transports the supercritical CO2 to the multi-stage compression system; The multi-stage compression system compresses the supercritical CO2 in at least two stages, and circulates the pressurized supercritical CO2 to the high-temperature heat source (1) through the heat recovery system.

9. The control method of the supercritical CO2 circulation system with multi-high power density and wide load regulation according to claim 8 is characterized in that: The outlet working fluid of the high-temperature heat source (1) is divided into three branches, the first branch enters the first turbine-generator set (3) through the three-way valve (2) and the first flow regulating valve (112), and the second branch enters the second turbine-generator set (4) through the three-way valve (2) and the second flow regulating valve (113); the third branch is controlled by the turbine bypass valve (111), and the system output power can be adjusted and controlled within the range of 0 to 100% by adjusting the turbine bypass valve (111), the first flow regulating valve (112), and the second flow regulating valve (113); After the supercritical CO2 passes through the turbine bypass valve (111), the first turbine-generator set (3) and the second turbine-generator set (4), it enters the high-temperature regenerator (12) and the low-temperature regenerator (11) to release heat to heat the cold-side supercritical CO2, and then the supercritical CO2 enters the precooler (9) to be cooled to the inlet state of the pre-compression compressor (7); after being compressed in the pre-compression compressor (7), the supercritical CO2 is divided into two paths, one path enters the re-compression compressor (8) to be compressed again, and the other path passes through the flow control valve (114) and the interstage cooler (6) to be cooled to the inlet state of the main pressure compressor and then enters the main pressure compressor (5); The supercritical CO2 compressed by the main pressure compressor (5) enters the low-temperature regenerator (11) through the second flow regulating valve (116) of the main pressure compressor (5), absorbs the heat of the hot-side supercritical CO2, and then merges with the supercritical CO2 at the outlet of the re-pressure compressor (8) and enters the high-temperature regenerator (12) to absorb heat and heat up again. The flow entering the main pressure compressor (5) and the re-pressure compressor (8) is controlled by adjusting the third flow regulating valve (114) and the first back pressure valve (115) to adjust the clamping point position of the low-temperature regenerator (11) and improve the efficiency of the low-temperature regenerator (11); the first back pressure valve (115) is connected to the outlet of the re-pressure compressor (8).

10. The control method of the supercritical CO2 circulation system with multi-high power density and wide load regulation according to claim 9 is characterized in that: When the supercritical CO2 at the outlet of the main pressure compressor (5) is over-pressured, the third back-pressure valve (117) is opened, and the supercritical CO2 passing through the third back-pressure valve (117) is stored in the storage tank (10) until the pressure is restored and then closed; when the pressure at the inlet of the precooler (9) is too low, the pressure regulating valve (118) of the storage tank (10) is opened to charge the system with supercritical CO2, and the valve is closed until the pressure is restored and then closed.

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