Heat storage cascade centralized compressed air and air separation coupling system

Abstract

The invention belongs to the technical field of energy storage and utilization, and discloses a heat storage cascade centralized compressed air and air separation coupling system. The system comprises a compressed air energy storage unit and an air separation unit, the compressed air energy storage unit comprises multi-stage compression equipment, heat storage equipment and multi-stage expansion equipment, the multi-stage compression equipment can compress air through electric energy, the heat storage equipment can absorb heat energy in air, and the multi-stage expansion equipment can utilize expanded air and generate electric energy; and the air separation unit is in heat conduction connection with the heat storage equipment and is connected with the air outlet end of the multi-stage expansion equipment. In the system, the heat energy in the heat storage equipment is fully utilized, the energy consumption of the air separation unit is reduced, meanwhile, the air exhausted through expansion can be input into the air separation unit, the energy consumption required by the compressed air for separation can be reduced, and the air has high cleanliness, so that a filtering device is omitted, and the energy consumption of the air separation unit is reduced. And meanwhile, the purity and cleanliness of the product can be improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage and utilization technology, and in particular to a thermal storage cascade centralized compressed air and air separation coupling system. Background Technology

[0002] Compressed air energy storage (CAES) is an energy storage method that uses electricity to drive a compressor during periods of low electricity demand to compress air to a high-pressure state and store it. During periods of high electricity demand, the high-pressure air is released to drive an expander to generate electricity. This technology can balance grid load and promote the consumption of renewable energy, but it suffers from problems such as insufficient thermal storage utilization and limited system efficiency. Air separation technology (ASU) typically relies on large compressors to compress air and then separate it into products such as oxygen and nitrogen through cryogenic distillation. This process is energy-intensive, especially the compressor, which consumes a significant portion of the energy.

[0003] Existing technologies combine CAES (Compressed Energy Storage System) with ASU (Air Separation Unit), utilizing high-pressure air provided by the energy storage system as a feedstock for air separation, reducing the energy consumption of the air separation compressor, and using resources such as liquid nitrogen and cooling energy generated during the air separation process to serve the energy storage system, achieving bidirectional energy utilization. However, this approach suffers from low thermal energy storage efficiency and insufficient energy recovery.

[0004] Therefore, a cascaded centralized compressed air and air separation coupling system for thermal storage is needed to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a cascaded centralized compressed air and air separation coupling system for thermal energy storage, which can improve thermal energy storage utilization efficiency and energy recovery rate while coupling CAES and ASU.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A cascaded centralized compressed air and air separation coupling system for thermal storage includes:

[0008] A compressed air energy storage unit includes a multi-stage compression device, a heat storage device, and a multi-stage expansion device. The multi-stage compression device can compress air using electrical energy, the heat storage device can absorb heat energy from the air, and the multi-stage expansion device can use the heat energy from the heat storage device to heat the air and generate electricity. The heat storage device includes a thermochemical heat storage device and a sensible heat storage device. The thermochemical heat storage device is used to absorb and store high-quality heat, and the sensible heat storage device is used to absorb and store low-quality heat.

[0009] An air separation unit is thermally connected to the heat storage device and connected to the air outlet of the multi-stage expansion device. The air separation unit can use the heat energy in the heat storage device to heat the air flowing out of the multi-stage expansion device to separate components.

[0010] In some embodiments, the thermal storage device further includes a high-pressure gas tank connected between the thermochemical thermal storage device and the sensible thermal storage device.

[0011] In some embodiments, the thermal storage device includes two sensible thermal storage devices, and the high-pressure gas tank is connected between the two sensible thermal storage devices.

[0012] In some embodiments, the thermal storage device further includes a latent heat storage device connected between the thermochemical thermal storage device and the sensible heat storage device, the latent heat storage device being used to absorb and store medium-mass heat.

[0013] In some embodiments, the thermochemical thermal storage device includes a high-temperature reactive material, and the reaction temperature range of the high-temperature reactive material is 200-1200 degrees Celsius.

[0014] In some embodiments, the latent heat storage device includes molten salt, the reaction temperature range of which is 100-200 degrees Celsius.

[0015] In some embodiments, the sensible heat storage device includes rock, the reaction temperature range of which is 30-100 degrees Celsius.

[0016] In some embodiments, the air separation unit and the air inlet of the multi-stage expansion device are connected, and the nitrogen produced by the air separation unit can enter the multi-stage expansion device to generate electrical energy.

[0017] In some embodiments, the air separation unit is capable of producing high-pressure nitrogen and low-pressure nitrogen, and the multi-stage expansion device includes at least two expanders connected in sequence, with the operating pressure range of two adjacent expanders decreasing in a direction away from the heat storage device, the low-pressure nitrogen being input to the expander away from the heat storage device, and the high-pressure nitrogen being input to the expander close to the heat storage device.

[0018] In some embodiments, the multi-stage compression device includes at least two compressors connected in sequence, the operating pressure range of two adjacent compressors is increased in the direction close to the heat storage device, and the outlet ends of at least two compressors are connected to the heat storage device by gas input pipes.

[0019] The beneficial effects of this invention are as follows: In this thermal storage cascade centralized compressed air and air separation coupling system, on the one hand, the thermal energy in the thermal storage equipment can be fully utilized to reduce the energy consumption of the air separation unit. On the other hand, the air discharged from the compressed air energy storage unit (usually at a pressure higher than atmospheric pressure) can be input into the air separation unit. This not only reduces the energy consumption of compressed air to meet the separation requirements, but also ensures that the air entering the air separation unit has a high degree of cleanliness. This eliminates the need for the filtration device required by the air separation unit, while also improving the purity and cleanliness of the products produced by the air separation unit, as well as improving the thermal storage utilization efficiency and energy recovery rate. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the thermally conductive connection of the cascaded centralized compressed air and air separation coupling system in the first embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the thermally conductive connection of the cascaded centralized compressed air and air separation coupling system in the second embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the thermally conductive connection of the cascaded centralized compressed air and air separation coupling system in the third embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the heat conduction connection of the thermal storage cascade centralized compressed air and air separation coupling system in the fourth embodiment of the present invention.

[0024] In the picture:

[0025] 1. Compressed air energy storage unit; 11. Multi-stage compression equipment; 111. Compressor; 121. Thermochemical heat storage device; 122. Sensible heat heat storage device; 123. High-pressure gas tank; 124. Latent heat heat storage device; 125. Purifier; 126. Throttling valve; 127. Booster; 13. Multi-stage expansion equipment; 131. Expander; 14. Gas input pipeline; 15. Gas output pipeline;

[0026] 2. Air separation unit; 21. Main heat exchanger; 22. Cooling expander; 23. High-pressure tower; 24. Low-pressure tower; 25. Condenser. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," "fixed," and "abutting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0030] In the description of this embodiment, the terms "upper," "lower," "right," and "left," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0031] The following is based on Figures 1 to 4 This invention introduces a cascaded centralized compressed air and air separation coupling system for thermal energy storage provided in an embodiment of the present invention. This cascaded centralized compressed air and air separation coupling system mainly includes a compressed air energy storage unit 1 and an air separation unit 2, which are thermally coupled and simultaneously facilitate material transport.

[0032] Specifically, such as Figure 1As shown, the compressed air energy storage unit 1 includes a multi-stage compression device 11, a heat storage device, and a multi-stage expansion device 13. The multi-stage compression device 11 includes at least two compressors 111 connected sequentially. Each compressor 111 can compress air to different pressure ranges, thus utilizing electrical energy to compress air to a high-pressure state during off-peak electricity demand. The heat storage device is connected to the multi-stage compression device 11, and the air temperature gradually increases during compression. When the high-temperature, high-pressure air flows through the heat storage device, the device absorbs and stores the heat. The multi-stage expansion device 13 includes at least two expanders 131 connected sequentially. Each expander 131 can generate electricity by being driven by gas within different pressure ranges. When high-pressure, room-temperature gas passes through the multi-stage expansion device 13, it can drive multiple expanders 131 to generate electricity, thereby producing electrical energy to meet electricity demand during peak periods. The thermal storage equipment includes a thermochemical thermal storage device 121 and a sensible thermal storage device 122. The thermochemical thermal storage device 121 is used to absorb and store high-quality heat, while the sensible thermal storage device 122 is used to absorb and store low-quality heat, so as to achieve full absorption and storage of air heat.

[0033] Simultaneously, the air separation unit 2 is thermally connected to the thermal storage device and connected to the outlet of the multi-stage expansion device 13. Clean air flowing out of the multi-stage expansion device 13 can be input into the air separation unit 2, where it can utilize the heat energy in the thermal storage device to heat the air and separate components. This connection method, on the one hand, fully utilizes the heat energy in the thermal storage device, reducing the energy consumption of the air separation unit 2. On the other hand, it allows the air discharged from the compressed air energy storage unit 1 (usually at a pressure higher than atmospheric pressure) to be input into the air separation unit 2. This not only reduces the energy consumption of compressed air to meet the separation requirements but also ensures that the air entering the air separation unit 2 has a high degree of cleanliness. This eliminates the need for a filtration device in the air separation unit 2, while also improving the purity and cleanliness of the products produced by the air separation unit 2, as well as increasing the efficiency of thermal storage and energy recovery.

[0034] Preferably, such as Figure 1 As shown, in this embodiment, the thermal storage device also includes a high-pressure gas tank 123, which is connected between the thermochemical thermal storage device 121 and the sensible thermal storage device 122. This high-pressure gas tank 123 can buffer the high-pressure air, thereby helping to smooth out fluctuations caused by peak and off-peak electricity demand. In some embodiments, the high-pressure gas tank 123 can also be directly connected to the air separation unit 2, further utilizing the high-pressure air in the high-pressure gas tank 123 to directly input or mix with the air discharged from the multi-stage expansion device before inputting it into the air separation unit 2, thereby further reducing the air compression energy consumption of the air separation unit 2.

[0035] Furthermore, in this embodiment, as Figure 1 , Figure 2 As shown, the thermal storage device also includes two sensible thermal storage devices 122, with a high-pressure gas tank 123 connected between them. The two sensible thermal storage devices 122 not only increase the overall thermal storage capacity of the device, but also allow the high-temperature gas to exchange heat sequentially with each device, thus absorbing more heat from the gas and providing more heat to the air separation unit 2.

[0036] Optionally, in this embodiment, as Figures 1 to 3 As shown, the thermal storage device also includes a latent heat storage device 124, which is connected between the thermochemical thermal storage device 121 and the sensible heat storage device 122. The latent heat storage device 124 is used to absorb and store medium-quality heat. Specifically, in this embodiment, the high-quality heat absorbed and stored by the thermochemical thermal storage device 121 refers to the heat released to the thermochemical thermal storage device 121 when the gas is above 200 degrees Celsius. The medium-quality heat absorbed and stored by the latent heat storage device 124 refers to the heat released to the latent heat storage device 124 when the gas is between 100 degrees Celsius and 200 degrees Celsius. The low-quality heat absorbed and stored by the sensible heat storage device 122 is the heat released to the sensible heat storage device 122 when the gas is between 30 and 100 degrees Celsius. Of course, as... Figure 4 As shown, in some embodiments, the latent heat storage device 124 may not be provided, and the thermochemical heat storage device 121 and the sensible heat storage device 122 may be directly connected, which is also within the scope of protection of this invention.

[0037] More specifically, in this embodiment, the thermochemical heat storage device 121 is equipped with a high-temperature reactive material, which can undergo an endothermic reaction within a temperature range of 200-1200 degrees Celsius, thereby absorbing heat from the air. Preferably, in this embodiment, a direct fixed bed and a high-temperature reactive material are used in combination, allowing the high-temperature gas to directly contact the high-temperature reactive material, thereby absorbing heat from the high-temperature air.

[0038] The latent heat storage device 124 includes molten salt and an indirect fixed bed, where the high-temperature gas does not directly contact the molten salt after being introduced. The reaction temperature range of the molten salt is 100-200 degrees Celsius, thus reducing the gas temperature to around 100 degrees Celsius. The sensible heat storage device 122 includes rock and an indirect fixed bed, where the high-temperature gas also does not directly contact the rock after being introduced. The reaction temperature range of the rock is 30-100 degrees Celsius, thus reducing the gas temperature to around 30 degrees Celsius.

[0039] Furthermore, in this embodiment, the compressed air energy storage unit 1 also includes a purifier 125, which can be used to filter impurities in the air. The purifier 125 is connected between the high-pressure gas tank 123 and the sensible heat storage device 122, and can not only filter impurities in the compressed air energy storage unit 1, but also improve the purity of the gas input to the air separation unit 2. Optionally, a throttle valve 126 is also provided between the high-pressure gas tank 123 and the purifier 125, which can regulate the pressure and prevent mechanical damage or vibration loss of control caused by instantaneous flow of high-pressure gas.

[0040] Optionally, in this embodiment, the outlet ends of at least two compressors 111 in the multi-stage compression device 11 are connected to the thermal storage device via gas input pipes 14. It should be noted that the at least two compressors 111 are connected sequentially, with the outlet end of the last compressor 111 connected to the thermal storage device via the gas input pipe 14. The operating pressure range of adjacent compressors 111 increases towards the thermal storage device, resulting in a significant increase in gas pressure as the number of compressors 111 increases. Simultaneously, the outlet end of another compressor 111 is also connected to the thermal storage device via a gas input pipe 14, allowing the multi-stage compression device 11 to selectively or in combination input compressed gas into the thermal storage device via the gas input pipe 14. In other words, the multi-stage compression device 11 can rationally select the compression level according to power consumption, thereby matching energy storage needs.

[0041] Preferably, the heat storage device also includes a booster compressor 127 to increase the gas pressure input to the multi-stage expansion device 13. The booster compressor 127 can be located between the outlet of the sensible heat storage device 122 and the high-pressure gas tank 123, between the outlet of the sensible heat storage device 122 and the latent heat storage device 124, or between the outlet of the sensible heat storage device 122 and the multi-stage expansion device 13. The number and location of the booster compressors 127 are not specifically limited in this invention, as long as they effectively increase the gas pressure.

[0042] Similarly, the multi-stage expander 13 also includes at least two expanders 131, and the inlet ends of at least two expanders 131 are connected to the heat storage device via gas outlet pipes 15. The at least two expanders 131 are connected sequentially, with the inlet end of the foremost expander 131 connected to the heat storage device via the gas outlet pipe 15. The operating pressure range of adjacent expanders 131 decreases with increasing distance from the heat storage device, resulting in a greater decrease in gas pressure as the number of expanders 131 increases. Simultaneously, the inlet end of another expander 131 is also connected to the heat storage device via a gas outlet pipe 15, allowing the heat storage device to selectively or partially input the gas to be expanded into the multi-stage expander 13 via the gas outlet pipe 15. In other words, the compressed air energy storage unit 1 can rationally select the degree of expansion based on power consumption, air compression, etc., to match the energy storage needs or the input pressure required by the air separation unit 2.

[0043] Air separation unit 2 includes a main heat exchanger 21, a cooling expander 22, a high-pressure tower 23, a low-pressure tower 24, and a condenser 25. The main heat exchanger 21 and the sensible heat storage device 122 are thermally connected, allowing compressed air to be deeply cooled to below its liquefaction temperature in the main heat exchanger 21. At this time, the sensible heat storage device 122 can also store the heat from the compressed air, achieving higher energy utilization. Subsequently, the compressed air enters the cooling expander 22, which provides cooling to drive deep liquefaction of the air. The liquefied air flows into the high-pressure tower 23 and the low-pressure tower 24, achieving component separation. During the separation process, high-pressure nitrogen and low-pressure nitrogen are generated. These high-pressure and low-pressure nitrogen absorb heat from the heat storage device and mix with high-temperature air before entering the expander 131 from the inlet of the multi-stage expander 13. This increases the system's output power, improves the system's grid regulation capability, and requires no external heat supply during nitrogen pressurization. Optionally, low-pressure nitrogen can be introduced into an expander 131 located away from the thermal storage device, while high-pressure nitrogen can be introduced into an expander 131 located close to the thermal storage device. This increases the work done by the expander 131 and also matches different operating pressure ranges of the expander 131.

[0044] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A cascaded centralized compressed air and air separation coupling system for thermal energy storage, characterized in that, include: A compressed air energy storage unit (1) includes a multi-stage compression device (11), a heat storage device, and a multi-stage expansion device (13). The multi-stage compression device (11) can use electrical energy to compress air, the heat storage device can absorb the heat energy in the air, and the multi-stage expansion device (13) can use the heat energy of the heat storage device to heat the air and generate electrical energy. The heat storage device includes a thermochemical heat storage device (121) and a sensible heat storage device (122). The thermochemical heat storage device (121) is used to absorb and store high-quality heat, and the sensible heat storage device (122) is used to absorb and store low-quality heat. An air separation unit (2) is thermally connected to the heat storage device and connected to the outlet of the multi-stage expansion device (13). The air separation unit (2) can use the heat energy in the heat storage device to heat the air flowing out of the multi-stage expansion device (13) to separate components.

2. The thermal storage cascade centralized compressed air and air separation coupling system according to claim 1, characterized in that, The thermal storage device also includes a high-pressure gas tank (123), which is connected between the thermochemical thermal storage device (121) and the sensible thermal storage device (122).

3. The thermal storage cascade centralized compressed air and air separation coupling system according to claim 2, characterized in that, The thermal storage device includes two sensible thermal storage devices (122), and the high-pressure gas tank (123) is connected between the two sensible thermal storage devices (122).

4. The thermal storage cascaded centralized compressed air and air separation coupling system according to any one of claims 1-3, characterized in that, The thermal storage device also includes a latent heat storage device (124), which is connected between the thermochemical thermal storage device (121) and the sensible heat storage device (122). The latent heat storage device (124) is used to absorb and store medium-mass heat.

5. The thermal storage cascade centralized compressed air and air separation coupling system according to claim 1, characterized in that, The thermochemical thermal storage device (121) includes a high-temperature reaction material, and the reaction temperature range of the high-temperature reaction material is 200-1200 degrees Celsius.

6. The thermal storage cascaded centralized compressed air and air separation coupling system according to claim 4, characterized in that, The latent heat storage device (124) includes molten salt, the reaction temperature range of which is 100-200 degrees Celsius.

7. The thermal storage cascaded centralized compressed air and air separation coupling system according to claim 1, characterized in that, The sensible heat storage device (122) includes rocks, and the reaction temperature range of the rocks is 30-100 degrees Celsius.

8. The thermal storage cascaded centralized compressed air and air separation coupling system according to claim 1, characterized in that, The air separation unit (2) and the multi-stage expansion device (13) are connected at their inlet ends, and the nitrogen produced by the air separation unit (2) can enter the multi-stage expansion device (13) to generate electricity.

9. The thermal storage cascaded centralized compressed air and air separation coupling system according to claim 8, characterized in that, The air separation unit (2) is capable of producing high-pressure nitrogen and low-pressure nitrogen. The multi-stage expansion device (13) includes at least two expanders (131) connected in sequence. The working pressure range of two adjacent expanders (131) is set to decrease in the direction away from the heat storage device. The low-pressure nitrogen is input to the expander (131) away from the heat storage device, and the high-pressure nitrogen is input to the expander (131) close to the heat storage device.

10. The thermal storage cascaded centralized compressed air and air separation coupling system according to claim 1, characterized in that, The multi-stage compression device (11) includes at least two compressors (111) connected in sequence. The working pressure range of two adjacent compressors (111) is increased in the direction close to the heat storage device. The outlet of at least two compressors (111) is connected to the heat storage device by a gas input pipe (14).

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