Supercritical carbon dioxide brayton cycle system and methods of using the same

Abstract

The application discloses a supercritical carbon dioxide Brayton cycle system and a use method thereof, and the supercritical carbon dioxide Brayton cycle system comprises a heat source, an sCO2 Brayton cycle system and a heat storage device; wherein a working medium side outlet of the heat source is connected with a working medium input end of the sCO2 Brayton cycle system, and a working medium side inlet of the heat source is connected with a working medium output end of the sCO2 Brayton cycle system; the heat storage device is arranged between the working medium side outlet of the heat source and the working medium input end of the sCO2 Brayton cycle system; the heat storage device is used for storing working medium flowed out of the heat source, and adjusting a load in the system by discharging the working medium flowed out of the heat source into the sCO2 Brayton cycle system. The application discloses a supercritical carbon dioxide Brayton cycle system capable of rapidly adjusting the load, wherein the heat storage device is used for storing high-temperature and high-pressure working medium when the load is reduced, and releasing the high-temperature and high-pressure working medium when the load is increased, so that the load can be rapidly adjusted, and a high system thermal efficiency can be maintained.

Description

Technical Field

[0001] This invention relates to thermodynamic cycle system technology, specifically to a supercritical carbon dioxide Brayton cycle system for rapid load adjustment and its usage method. Background Technology

[0002] Due to energy scarcity and environmental crisis, improving energy efficiency has received widespread attention from scholars both domestically and internationally. Among numerous thermodynamic cycles, the sCO2 Brayton cycle stands out due to its high power density, simple and compact structure, high efficiency, and safe and pollution-free working fluid. Its application research has expanded to many fields such as nuclear energy, solar energy, industrial waste heat recovery, geothermal energy, and fuel cells.

[0003] The supercritical carbon dioxide Brayton cycle is a power cycle that can achieve efficient thermoelectric conversion. Using CO2 as the working fluid, it completes energy conversion through the Brayton cycle, maintaining CO2 in a supercritical state throughout the entire cycle. This cycle can utilize a wide range of heat source temperatures (400℃-700℃) and has high efficiency (40%-50%). It is suitable for multiple fields such as solar energy, nuclear energy, distributed energy, marine power, and fuel cells, and is considered one of the most promising energy conversion systems currently available.

[0004] During system operation, it is often necessary to operate under off-design conditions. How to achieve rapid load adjustment under these conditions is a key problem that urgently needs to be solved in the research process. Current load adjustment mainly includes two categories: valve bypass or throttling regulation and stock control regulation. Valve regulation bypasses or throttles high-energy working fluids, reducing energy utilization; while stock control achieves load adjustment by charging or discharging working fluids at the cold end, characterized by slow system response. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned technical problems, the present invention provides a supercritical carbon dioxide Brayton cycle system and its usage method that can quickly adjust the load by adjusting the storage state of the heat storage tank, thus solving the problem of slow system response.

[0007] (II) Technical Solution

[0008] According to one aspect of the present invention, a supercritical carbon dioxide Brayton cycle system is provided, comprising a heat source, a supercritical carbon dioxide Brayton cycle system, and a heat storage device;

[0009] The heat source's working fluid side outlet is connected to the working fluid input end of the sCO2 Brayton cycle system, and the heat source's working fluid side inlet is connected to the working fluid output end of the sCO2 Brayton cycle system.

[0010] The heat storage device is located between the working fluid outlet of the heat source and the working fluid input of the sCO2 Brayton cycle system.

[0011] The thermal storage device is used to store the working fluid flowing out of the heat source and to regulate the load in the system by discharging the working fluid flowing out of the heat source into the sCO2 Brayton cycle system.

[0012] The sCO2 Brayton cycle system includes a first turbine and a second turbine connected together. The second turbine is connected to the heat release inlet of the first regenerator, and the heat release outlet of the first regenerator is connected to the heat release inlet of the second regenerator.

[0013] The outlet of the second regenerator is connected to two loops. One loop connects to the inlet of the second regenerator through the cooler and the main compressor.

[0014] Another loop passes through the re-compressor and connects to the absorber inlet of the first regenerator together with the absorber outlet of the second regenerator.

[0015] The thermal storage device includes a hot-end storage tank and an expander;

[0016] The hot-end storage tank is connected between the heat source and the inlet of the second turbine;

[0017] The expander is coaxially connected to the first turbine, and the outlet end of the expander is connected to the outlet end of the first turbine.

[0018] The pressure in the hot end storage tank is between the main compressor inlet pressure and the re-compressor inlet pressure.

[0019] The first turbine is coaxially mounted with the main compressor.

[0020] The second turbine and the recompressor are arranged coaxially.

[0021] The cooling source for the cooler includes dry air or cooling water.

[0022] Heat sources include one or more of the following: boilers, nuclear energy, waste heat exchangers, or solar energy.

[0023] According to another aspect of the present invention, a method of using a supercritical carbon dioxide Brayton cycle system is also provided, comprising:

[0024] The working fluid absorbs heat in the heat source, generating a heat source working fluid;

[0025] When the system reduces its load, the heat source working fluid side is connected to the thermal storage device, and the thermal storage device is disconnected from the sCO2 Brayton cycle system. Part of the heat source working fluid enters the hot end storage tank in the thermal storage device, and the other part of the heat source working fluid enters the sCO2 Brayton cycle system to do work.

[0026] When the system load increases, the heat source working fluid side is disconnected from the heat storage device, and the heat storage device is connected to the sCO2 Brayton cycle system. The heat source working fluid in the heat storage device expands and enters the sCO2 Brayton cycle system to merge with the working fluid flowing in from the heat source working fluid side to do work.

[0027] After the working fluid performs work, it flows back to the heat source for recirculation and heating.

[0028] (III) Beneficial Effects

[0029] As can be seen from the above technical solution, the supercritical carbon dioxide Brayton cycle system and its usage method provided by the present invention have the following beneficial effects:

[0030] This invention discloses a supercritical carbon dioxide Brayton cycle system for rapid load adjustment. By utilizing a heat storage device, when the load decreases, the working fluid with high temperature and high pressure energy at the hot end is stored in the heat storage device. When the load increases, the high temperature and high pressure working fluid stored in the heat storage device is released into the supercritical carbon dioxide Brayton cycle system to do work. This can achieve rapid load adjustment while maintaining high system thermal efficiency.

[0031] Since the working fluid involved in the work is a high-temperature and high-pressure working fluid in the thermal storage device, the system efficiency can be improved compared to valve bypass or throttling regulation and inventory control regulation. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the supercritical carbon dioxide Brayton cycle system. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0034] Figure 1 This is a schematic diagram of the structure of the supercritical carbon dioxide Brayton cycle system.

[0035] like Figure 1 As shown, according to one aspect of the present invention, the supercritical carbon dioxide Brayton cycle system includes a heat source 1, a supercritical carbon dioxide Brayton cycle system 2, and a heat storage device 3.

[0036] Heat source 1 can heat the working fluid to increase its temperature. After passing through heat source 1, the high-pressure working fluid absorbs heat and becomes a working fluid with high temperature and high pressure. Then, the high-temperature and high-pressure working fluid is discharged into the sCO2 Brayton cycle system 2 to do work. After doing work, the working fluid returns to heat source 1 to be heated and recycled.

[0037] The working fluid side outlet of heat source 1 is connected to the working fluid input end of sCO2 Brayton cycle system 2, and the working fluid side inlet of heat source 1 is connected to the working fluid output end of sCO2 Brayton cycle system 2.

[0038] The heat storage device 3 is located between the working fluid outlet of the heat source 1 and the working fluid input of the sCO2 Brayton cycle system 2.

[0039] The heat storage device 3 is used to store the working fluid flowing out of the heat source 1 and to regulate the load in the system by discharging the working fluid flowing out of the heat source 1 into the sCO2 Brayton cycle system 2.

[0040] By setting up the heat storage device 3, the working fluid with high temperature and high pressure energy at the hot end can be stored in the heat storage device 3 when the load needs to be reduced. When the load needs to be increased, the high temperature and high pressure working fluid stored in the heat storage device 3 can be released into the sCO2 Brayton cycle system 2 to do work. This can achieve rapid load adjustment while maintaining high system thermal efficiency.

[0041] According to an embodiment of the present invention, the sCO2 Brayton cycle system 2 includes a first turbine 2-1 and a second turbine 2-2 connected together. The second turbine 2-2 is connected to the heat release end inlet of the first regenerator 2-3, and the heat release end outlet of the first regenerator 2-3 is connected to the heat release end inlet of the second regenerator 2-4.

[0042] The high-temperature and high-pressure working fluid discharged from heat source 1 enters the first turbine 2-1 and the second turbine 2-2 in sequence. The energy of the working fluid as a fluid is converted into kinetic energy when it flows through the nozzles of the first turbine 2-1 and the second turbine 2-2. When it flows through the rotor, the fluid impacts the blades and drives the rotor to rotate, thereby driving the turbine shaft to rotate. The turbine shaft drives other machinery directly or through the transmission mechanism, outputting mechanical work and converting the energy of the fluid into mechanical energy, causing the working fluid to expand into a low-pressure and high-temperature working fluid.

[0043] According to an embodiment of the present invention, the outlet of the heat release end of the second regenerator 2-4 is connected to two loops, one of which is connected to the inlet of the heat absorption end of the second regenerator 2-4 via the cooler 2-5 and the main compressor 2-6.

[0044] The low-pressure, high-temperature working fluid, after being expanded by the first turbine 2-1 and the second turbine 2-2, releases heat through the first regenerator 2-3 and the second regenerator 2-4, becoming a low-pressure, low-temperature working fluid. Subsequently, the working fluid is divided into two paths. The working fluid in one path enters the cooler 2-5 to continue releasing heat, and then enters the main compressor 2-6 for pressurization. The pressurized working fluid enters the heat absorption end of the second regenerator 2-4, where it acts as a coolant to absorb heat from the downstream working fluid, thus cooling the downstream working fluid at the heat release end of the second regenerator 2-4 and further increasing the temperature of the working fluid at the heat absorption end.

[0045] According to an embodiment of the present invention, another loop passes through the recompressor 2-7 and is connected to the absorber end inlet of the first recompressor 2-3 together with the absorber end outlet of the second recompressor 2-4.

[0046] The working fluid in the other loop directly enters the compressor 2-7 for pressurization. The pressurized working fluid merges with the working fluid at the heat absorption end outlet of the second regenerator 2-4 and enters the heat absorption end of the first regenerator 2-3 together to absorb heat as a coolant, further increasing the temperature of the working fluid at the heat absorption end. Finally, it enters the heat source 1 to be heated to the rated temperature to complete the cycle.

[0047] The heat-releasing end and the heat-absorbing end of the first regenerator 2-3 and the second regenerator 2-4 respectively use the same working fluid at different working stages of the same cycle, so that the heat between the working fluids can be circulated, which improves the working efficiency. It can also preheat the working fluid that returns to the heat source 1 after doing work, thus improving the working efficiency of the heat source 1.

[0048] According to an embodiment of the present invention, the heat storage device 3 includes a hot-end storage tank 4-1 and an expander 3-1; the hot-end storage tank 4-1 is connected between the heat source 1 and the inlet end of the second turbine 2-2; the expander 3-1 is coaxially connected to the first turbine 2-1, and the outlet end of the expander 3-1 is connected to the outlet end of the first turbine 2-1.

[0049] When the system needs to increase the load, the shaft between the expander 3-1 and the first turbine 2-1 is connected. The first turbine 2-1 can drive the expander 3-1 to rotate, so that the working fluid stored in the hot end storage tank 4-1 expands and enters the sCO2 Brayton cycle system 2.

[0050] According to an embodiment of the present invention, the pressure of the hot end storage tank 4-1 is between the inlet pressure of the main compressor 2-6 and the inlet pressure of the re-compressor 2-7.

[0051] The distance between the second regenerator 2-4 and the main compressor 2-6 and re-compressor 2-7, and the different working processes of the two working fluids, result in different friction losses during the working fluid circulation process. Therefore, it is necessary to ensure that the flow pressure of the working fluid flowing out of the hot end storage tank 4-1 is within the appropriate inlet pressure range of the main compressor 2-6 and re-compressor 2-7.

[0052] According to an embodiment of the present invention, the first turbine 2-1 is coaxially arranged with the main compressor 2-6.

[0053] The first turbine 2-1 is coaxially connected to the main compressor 2-6. When the working fluid flows and drives the blades and turbine shaft of the first turbine 2-1 to rotate, it can drive the main compressor 2-6 to work, so that the system can automatically run the compression steps and the cycle process is more continuous.

[0054] According to an embodiment of the present invention, the first turbine 2-1 and the expander 3-1 can also be coaxially connected. When the system needs to increase the load, the shaft between the expander 3-1 and the first turbine 2-1 is connected. The first turbine 2-1 can drive the expander 3-1 to rotate, so that the working fluid stored in the hot end storage tank 4-1 expands and enters the sCO2 Brayton cycle system 2.

[0055] According to an embodiment of the present invention, the second turbine 2-2 and the recompressor 2-7 are arranged coaxially.

[0056] The second turbine 2-2 is coaxially connected to the recompressor 2-7. When the working fluid flows and drives the blades and turbine shaft of the first turbine 2-1 to rotate, it can drive the main compressor 2-6 to work, so that the system can automatically run the compression steps and the cycle process is more continuous.

[0057] According to an embodiment of the present invention, the cold source for coolers 2-5 includes dry air or cooling water.

[0058] According to an embodiment of the present invention, the heat source 1 includes one or more of a boiler, nuclear energy, waste heat exchanger, or solar heat source 1.

[0059] According to another aspect of the present invention, a method of using a supercritical carbon dioxide Brayton cycle system is also provided, comprising:

[0060] The working fluid absorbs heat in heat source 1, generating working fluid for heat source 1.

[0061] During normal operation, the high-pressure working fluid first absorbs heat in heat source 1 and becomes a high-temperature and high-pressure working fluid. The high-temperature and high-pressure working fluid enters the first turbine 2-1 and the second turbine 2-2 connected in series in sequence, expands and does work, and then becomes a low-pressure working fluid. The low-pressure working fluid first enters the heat release end of the first regenerator 2-3, and then enters the heat release end of the second regenerator 2-4 to release heat. After that, the working fluid is divided into two paths.

[0062] One working fluid enters the cooler 2-5 to continue releasing heat. Then, the low-temperature, low-pressure working fluid enters the main compressor 2-6 for pressurization. The pressurized working fluid then enters the heat absorption end of the second regenerator 2-4 to absorb heat.

[0063] Another working fluid directly enters the compressor 2-7 for pressurization. The pressurized working fluid merges with the working fluid at the heat absorption end outlet of the second regenerator 2-4 and enters the heat absorption end of the first regenerator 2-3 to absorb heat. Finally, it enters the heat source 1 to be heated to the rated temperature to complete the cycle.

[0064] When the system load is reduced, the working fluid side of heat source 1 is connected to the heat storage device 3, and the heat storage device 3 is disconnected from the sCO2 Brayton cycle system 2. Part of the working fluid of heat source 1 enters the hot end storage tank 4-1 in the heat storage device 3, and the other part of the working fluid of heat source 1 enters the sCO2 Brayton cycle system 2 to do work. As the working fluid doing work is reduced, the system load is reduced.

[0065] When the system load increases, the heat source 1 working fluid side is disconnected from the heat storage device 3, and the heat storage device 3 is connected to the sCO2 Brayton cycle system 2. The heat source 1 working fluid in the heat storage device 3 expands and enters the sCO2 Brayton cycle system 2 to merge with the working fluid flowing in from the heat source 1 working fluid side to do work.

[0066] As the working fluid increases, the system load rises, and the working fluid involved in the work is a high-temperature and high-pressure working fluid in the hot-end storage tank 4-1. Therefore, compared with valve bypass or throttling regulation and storage control regulation, the system efficiency can be improved.

[0067] After the working fluid performs work, it flows back to heat source 1 for recirculation and heating.

[0068] Heat source 1 can heat the working fluid to increase its temperature. After passing through heat source 1, the high-pressure working fluid absorbs heat and becomes a working fluid with high temperature and high pressure. Then, the high-temperature and high-pressure working fluid is discharged into the sCO2 Brayton cycle system 2 to do work. After doing work, the working fluid returns to heat source 1 to be heated and recycled.

[0069] The thermal storage device 3 can store the working fluid with high temperature and high pressure energy at the hot end into the thermal storage device 3 when the load needs to be reduced. When the load needs to be increased, the high temperature and high pressure working fluid stored in the thermal storage device 3 can be released into the sCO2 Brayton cycle system 2 to do work. This can achieve rapid load adjustment while maintaining high system thermal efficiency.

[0070] The present invention is also applicable to other layouts of sCO2 Brayton cycle systems, and is not limited to the sCO2 Brayton cycle system 2 described above, nor is it limited to the layout shown in the figure. For example, other sCO2 Brayton cycle systems may employ multi-stage cooling, multi-stage compression or expansion, or different flow distribution structures, etc. Furthermore, the descriptions of high and low temperatures, high and low pressures in this invention are merely to indicate the relative temperature and pressure changes during the working fluid circulation process, and are only used as a reference for system description; they should not be taken as specific temperature and pressure ranges to limit the scope of protection of this invention.

[0071] Furthermore, implementations not illustrated or described in the accompanying drawings or the main text of the specification are all forms known to those skilled in the art and are not described in detail. Directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are merely for reference to the directions in the drawings and are not intended to limit the scope of protection of the present invention. This document may provide examples of parameters containing specific values, but these parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Moreover, in the preparation method, unless specifically described or steps must occur sequentially, the order of the above steps is not limited to those listed above and can be varied or rearranged according to the desired design.

[0072] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A supercritical carbon dioxide Brayton cycle system, comprising a heat source, a supercritical carbon dioxide Brayton cycle system, and a heat storage device; The sCO2 Brayton cycle system includes a first turbine and a second turbine connected together, a first regenerator, a second regenerator, a cooler, a main compressor, and a re-compressor, wherein... The second turbine is connected to the heat dissipation inlet of the first regenerator, and the heat dissipation outlet of the first regenerator is connected to the heat dissipation inlet of the second regenerator. The outlet of the second regenerator is connected to two circuits. A loop passes through the cooler and the main compressor and connects to the heat absorption inlet of the second regenerator; Another loop passes through a re-compressor and connects to the heat absorption end inlet of the first regenerator together with the heat absorption end outlet of the second regenerator. The thermal storage device includes a hot-end storage tank and an expander, wherein... The expander is coaxially connected to the first turbine, and the outlet end of the expander is connected to the outlet end of the first turbine. The heat storage device is used to store the working fluid flowing out of the heat source and to regulate the load in the system by discharging the working fluid flowing out of the heat source into the sCO2 Brayton cycle system. The heat source has two outlet routes on the working fluid side, wherein... The working fluid side outlet of the first route heat source is sequentially connected to the first turbine and the second turbine of the working fluid of the sCO2 Brayton cycle system. The working fluid side outlet of the second route heat source is sequentially connected to the hot end storage tank, the expander, and the second turbine. A first valve is installed between the working fluid side outlet of the route heat source and the hot end storage tank, and a second valve is installed between the hot end storage tank and the expander.

2. The supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the first turbine is coaxially arranged with the main compressor.

3. The supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the second turbine is coaxially arranged with the recompressor.

4. The supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the cold source of the cooler includes dry air or cooling water.

5. The supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the heat source includes one or more of a boiler, nuclear energy, waste heat exchanger, or solar heat source.

6. A method of using the supercritical carbon dioxide Brayton cycle system according to any one of claims 1 to 5, comprising: The working fluid absorbs heat in the heat source to generate a heat source working fluid; When the system load is reduced, the heat source working fluid side is connected to the hot end storage tank in the heat storage device, the heat storage device is disconnected from the sCO2 Brayton cycle system, a part of the heat source working fluid enters the hot end storage tank in the heat storage device, and another part of the heat source working fluid enters the sCO2 Brayton cycle system to do work. When the system load increases, the heat source working fluid side is disconnected from the heat storage device, and the heat storage device is connected to the sCO2 Brayton cycle system. The heat source working fluid in the heat storage device expands and enters the sCO2 Brayton cycle system to merge with the working fluid flowing in from the heat source working fluid side to do work. After the working fluid performs work, it flows back into the heat source for recirculation and heating.

Images