Liquid air energy storage system coupled with air separation device

Abstract

The invention provides a liquid air energy storage system coupled with an air separation device, and relates to the technical field of energy storage. The liquid air energy storage system coupled with the air separation device comprises an air compression device, a cold storage device, a liquid air tank, a rectification device, a heating device and an expansion machine device, wherein the air compression device is used for compressing air; and the cold storage device is communicated with the air compression device. The cold storage device is communicated with the rectification device, so that nitrogen and waste nitrogen generated by the rectification device can be used for supplementing cold to the cold storage device, and the scale of the cold storage device is reduced; liquid air generated in the trough electricity price period is used for directly supplementing cold for the rectification device, so that the operation cost of the rectification device is reduced; and pure air is provided for the rectification device by utilizing exhaust gas of the expansion machine device, so that the energy loss is reduced. The liquid air energy storage system is excellent in economic performance, the comprehensive utilization rate of liquid air is high, and the application range of the liquid air energy storage system is widened.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a liquid air energy storage system coupled with an air separation device. Background Art

[0002] With the depletion of fossil energy, the global energy structure is undergoing an unprecedented transformation. Renewable energy such as solar and wind energy are seen as alternatives to fossil energy because of their clean and sustainable characteristics. According to the International Energy Agency's 2023 statistics, my country's renewable energy power generation accounted for 31.2%. However, the volatility and intermittency of renewable energy pose a huge challenge to the stable operation of the power grid. The development of energy storage technology provides an effective way to solve this problem.

[0003] Liquid air energy storage technology stands out among many energy storage technologies due to its advantages such as high energy storage density, no geographical restrictions, and normal pressure storage. Liquid air energy storage technology stores energy during low power periods and releases energy during peak periods, balancing the supply and demand of the power grid and thus improving the peak-shaving capacity of the power grid. For liquid air energy storage technology, due to its deep cooling process, there are certain cleanliness requirements for the air entering the cold storage unit, so the air needs to be pre-purified to remove moisture, carbon dioxide and other impurities. During the energy release process of the energy storage system, purified air is only used for expansion and power generation, and then released to the external environment. Therefore, liquid air energy storage technology lacks the use of purified air.

[0004] Air separation technology refers to the use of related equipment and technology to separate nitrogen, oxygen and other rare gases from the air to meet the needs of various gases in industries such as metallurgy, coal chemical industry, petroleum refining, and aviation. Air separation technology generally uses a cryogenic process to separate air, which has certain requirements for air cleanliness and consumes a lot of electricity.

[0005] During the operation of the liquid air energy storage system, a molecular sieve purifier is usually required to purify the air to remove substances such as water, carbon dioxide and hydrocarbons in the air. The energy consumption of the purification process is relatively high. The liquid air energy storage system usually discharges the expanded pure air directly into the atmosphere, which will cause energy loss. In addition, the air separation unit needs to operate stably, and the electricity consumption in each time period is relatively fixed. Since industrial electricity consumption adopts a time-of-use electricity price policy, the air separation unit has the problem of high operating costs during peak electricity price periods. Summary of the invention

[0006] The present invention provides a liquid air energy storage system coupled with an air separation device, so as to solve the problems of high energy consumption and high operating cost of the existing liquid air energy storage system.

[0007] The present invention provides a liquid air energy storage system coupled with an air separation device, comprising: An air compression device, wherein the air compression device is used to compress air; A cold storage device, the cold storage device is connected to the air compression device, and the cold storage device is used to cool the high-pressure air delivered by the air compression device so as to convert part of the high-pressure air into liquid air; a liquid air tank, the liquid air tank being in communication with the cold storage device; A distillation device, wherein the distillation device is connected to the liquid air tank via a first liquid air pump, and the cold storage device is connected to the distillation device, wherein the liquid air tank is used to store liquid air, and the liquid air is transported to the distillation device via the first liquid air pump for supplementary cooling; A heating device, the heating device is connected to the liquid air tank and the distillation device, and the heating device is used to heat the liquid air output from the liquid air tank to obtain high-pressure normal-temperature air; An expander device is connected to the heating device and the air compression device, and is used to generate electricity through high-pressure and normal-temperature air during peak electricity price periods.

[0008] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the air compression device comprises: Multi-stage compressor; A multi-stage interstage cooler, wherein two adjacent stages of the compressors are connected via the corresponding interstage cooler, the air outlet of the highest-stage interstage cooler is connected to the cold storage device, and the liquid outlet and liquid inlet of each stage of the interstage cooler are connected to the expander device.

[0009] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the air compression device further comprises: A first connecting pipeline, an air outlet of one of the multiple interstage coolers is connected to the cold storage device through the first connecting pipeline.

[0010] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the cold storage device comprises: First-stage cold storage unit; The second-stage cold storage unit, the first-stage cold storage unit and the second-stage cold storage unit are connected in series to the liquid air input pipeline, the gas air output pipeline, the liquid oxygen output pipeline, the nitrogen output pipeline and the dirty nitrogen output pipeline, wherein the input end of the liquid air input pipeline is connected to the first connecting pipeline and the air outlet of the highest-level interstage cooler, the output end of the liquid air input pipeline is connected to the liquid air tank through the first liquid expander and the throttle valve in sequence; the input end of the gas air output pipeline is connected to the liquid air tank; the input ends of the liquid oxygen output pipeline, the nitrogen output pipeline and the dirty nitrogen output pipeline are all connected to the distillation device.

[0011] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the cold storage device further comprises: An air expander, wherein the liquid-phase air input pipeline between the first-stage cold storage unit and the second-stage cold storage unit is connected to the input end of the air expander, and the output end of the air expander is connected to the distillation device; A second liquid expander, the liquid-phase air input pipeline between the second-stage cold storage unit and the first liquid expander is connected to the input end of the second liquid expander, and the output end of the second liquid expander is connected to the distillation device.

[0012] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the heating device comprises: a first air heater; The second air heater, the first air heater and the second air heater are connected in series to the liquid air output pipeline, the input end of the liquid air output pipeline is connected to the liquid air tank through the second liquid air pump, and the output end of the liquid air output pipeline is connected to the expander device; the first air heater is connected to the first-stage cold storage unit through a circulation pipeline, and the second air heater is connected to the second-stage cold storage unit through a circulation pipeline.

[0013] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the expander device comprises: Multi-stage interstage heaters; A multi-stage expander, wherein two adjacent stages of the expanders are connected via the corresponding interstage heaters, and the air inlet of the interstage heater at the lowest stage is connected to the output end of the liquid-phase air output pipeline; A high-temperature water tank, wherein the liquid inlet of the high-temperature water tank is connected to the liquid outlet of each stage of the interstage cooler, and the liquid outlet of the high-temperature water tank is connected to the liquid inlet of each stage of the interstage heater; A low-temperature water tank, wherein the liquid outlet of the low-temperature water tank is communicated with the liquid inlet of each stage of the interstage cooler, and the liquid inlet of the low-temperature water tank is communicated with the liquid outlet of each stage of the interstage heater.

[0014] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the expander device further comprises: a third liquid air pump, the third liquid air pump being arranged at the liquid outlet of the high temperature water tank; a fourth liquid air pump, the fourth liquid air pump being arranged at the liquid outlet of the low-temperature water tank; A first cooler is arranged at a liquid inlet of the low-temperature water tank.

[0015] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the expander device further comprises: A return air pipeline, wherein the air inlet end of the return air pipeline is connected to the air inlet of the interstage heater of one stage, and the air outlet end of the return air pipeline is connected to the distillation device; A second cooler is connected in series to the return air pipeline.

[0016] According to a liquid air energy storage system coupled with an air separation device provided by the present invention, the expander device further comprises: a second connecting pipeline, wherein a liquid inlet end of the second connecting pipeline is connected to a liquid outlet of the third liquid air pump, and a liquid outlet end of the second connecting pipeline is connected to a liquid inlet end of the second cooler; A Rankine cycle power generation device, wherein the interstage heater of the Rankine cycle power generation device is connected in series to the second connecting pipeline.

[0017] The liquid air energy storage system coupled with the air separation device provided by the present invention can supplement the cold storage device with nitrogen and contaminated nitrogen produced by the distillation device by connecting the cold storage device with the distillation device, so as to reduce the scale of the cold storage device; the liquid air produced during the valley electricity price period can be used to directly supplement the cold of the distillation device, thereby reducing the operating cost of the distillation device; the exhaust gas of the expander device can be used to provide pure air for the distillation device, thereby reducing energy loss. The liquid air energy storage system provided by the present invention has better economic performance and a higher comprehensive utilization rate of liquid air, which broadens the application scenarios of the liquid air energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic structural diagram of the liquid air energy storage system coupled with the air separation device provided by the present invention.

[0020] Reference numerals: 1. First stage compressor; 2. Second stage compressor; 3. Third stage compressor; 4. Fourth stage compressor; 5. First stage interstage cooler; 6. Second stage interstage cooler; 7. Third stage interstage cooler; 8. Fourth stage interstage cooler; 9. Low temperature water tank; 10. High temperature water tank; 11. First stage cold storage unit; 12. Second stage cold storage unit; 13. Air expander; 14. Throttle valve; 15. Liquid air tank; 16. First liquid air pump; 17. Second liquid expander; 18. Second liquid air pump; 19. First air heater; 20. Second air heater; 21. First stage interstage heater; 22. Second stage interstage heater; 23. Third stage interstage heater; 24. Fourth stage interstage heater Heater; 25, first-stage expander; 26, second-stage expander; 27, third-stage expander; 28, fourth-stage expander; 29, second cooler; 30, distillation device; 31, first liquid expander; 32, third liquid air pump; 33, fourth liquid air pump; 34, first cooler; 36, high-temperature medium storage tank; 37, high-temperature pump; 38, low-temperature medium storage tank; 39, low-temperature pump; 40, first connecting pipeline; 41, liquid air input pipeline; 42, gas air output pipeline; 43, liquid oxygen output pipeline; 44, nitrogen output pipeline; 45, dirty nitrogen output pipeline; 46, return air pipeline; 47, Rankine cycle power generation device; 48, liquid air output pipeline; 49, second connecting pipeline. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0022] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" 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 an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0024] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0025] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0026] Combine the following Figure 1 The specific structure and working principle of the liquid air energy storage system coupled with the air separation device of the present invention are described.

[0027] like Figure 1 As shown, the liquid air energy storage system coupled with the air separation device includes an air compression device, a cold storage device, a liquid air tank 15, a distillation device 30, a heating device and an expansion device. The air compression device is used to compress air; the cold storage device is connected to the air compression device, and the cold storage device is used to cool the high-pressure air delivered by the air compression device to convert part of the high-pressure air into liquid air; the liquid air tank 15 is connected to the cold storage device. The distillation device 30 is connected to the liquid air tank 15 through the first liquid air pump 16, and the cold storage device is connected to the distillation device 30. The liquid air tank 15 is used to store liquid air and deliver liquid air to the distillation device 30 through the first liquid air pump 16 for supplementary cooling. The heating device is connected to the liquid air tank 15 and the distillation device 30, and the heating device is used to heat the liquid air output by the liquid air tank 15 to obtain high-pressure normal temperature air; the expansion device is connected to the heating device and the air compression device, and the expansion device is used to generate electricity through high-pressure normal temperature air during the peak electricity price period.

[0028] The liquid air energy storage system coupled with the air separation device provided by the present invention can supplement the cold storage device with nitrogen and contaminated nitrogen produced by the distillation device 30 by connecting the cold storage device with the distillation device 30, so as to reduce the scale of the cold storage device; the liquid air produced during the valley electricity price period can be used to directly supplement the cold of the distillation device 30, thereby reducing the operating cost of the distillation device 30; the exhaust gas of the expander device can be used to provide pure air for the distillation device 30, thereby reducing energy loss. The liquid air energy storage system provided by the present invention has better economic performance and a higher comprehensive utilization rate of liquid air, which broadens the application scenarios of the liquid air energy storage system.

[0029] In one embodiment of the present invention, the air compression device includes a multi-stage compressor and a multi-stage interstage cooler. The two adjacent compressors are connected through the corresponding interstage cooler. The air outlet of the highest-level interstage cooler is connected to the cold storage device, and the liquid outlet and liquid inlet of each interstage cooler are connected to the expander device.

[0030] Specifically, the air compression device includes a first-stage compressor 1, a second-stage compressor 2, a third-stage compressor 3, a fourth-stage compressor 4, a first-stage interstage cooler 5, a second-stage interstage cooler 6, a third-stage interstage cooler 7 and a fourth-stage interstage cooler 8. Of course, the number of compressors and the number of interstage coolers are not limited thereto and are determined according to actual needs.

[0031] The first-stage interstage cooler 5 is located between the first-stage compressor 1 and the second-stage compressor 2, and the air outlet of the first-stage compressor 1 is communicated with the air inlet of the first-stage interstage cooler 5, and the air outlet of the first-stage interstage cooler 5 is communicated with the air inlet of the second-stage compressor 2. The second-stage interstage cooler 6 is located between the second-stage compressor 2 and the third-stage compressor 3, and the air outlet of the second-stage compressor 2 is communicated with the air inlet of the second-stage interstage cooler 6, and the air outlet of the second-stage interstage cooler 6 is communicated with the air inlet of the third-stage compressor 3. The third-stage interstage cooler 7 is located between the third-stage compressor 3 and the fourth-stage compressor 4, and the air outlet of the third-stage compressor 3 is communicated with the air inlet of the third-stage interstage cooler 7, and the air outlet of the third-stage interstage cooler 7 is communicated with the air inlet of the fourth-stage compressor 4. The air inlet of the fourth-stage interstage cooler 8 is communicated with the air outlet of the fourth-stage compressor 4, and the air outlet of the fourth-stage interstage cooler 8 is communicated with the air inlet of the first-stage cold storage unit 11.

[0032] It should be noted here that the term “stage” is used in the present invention to define the compressor and the interstage cooler only for the purpose of distinguishing each compressor and each interstage cooler for the convenience of description and has no substantial meaning.

[0033] In a preferred embodiment of the present invention, a molecular sieve purifier is connected in series between the air outlet of the first-stage interstage cooler 5 and the air inlet of the second-stage compressor 2. The molecular sieve purifier is used to remove water, carbon dioxide, hydrocarbons and other substances in the air to prevent the pipeline from being blocked.

[0034] In one embodiment of the present invention, the air compression device further includes a first connecting pipeline 40, and the air outlet of one of the interstage coolers in the multi-stage interstage cooler is connected to the cold storage device through the first connecting pipeline 40. Specifically, one end of the first connecting pipeline 40 is connected to the air outlet of the second interstage cooler 6, and the other end of the first connecting pipeline 40 is connected to the air inlet of the first stage cold storage unit 11. The first connecting pipeline 40 is provided to allow part of the air to enter the first stage cold storage unit 11 to obtain cold energy, and this part of the air is cooled by the first stage cold storage unit 11, enters the air expander 13 to expand, and finally enters the distillation device 30.

[0035] In one embodiment of the present invention, the cold storage device includes a first-stage cold storage unit 11 and a second-stage cold storage unit 12. The first-stage cold storage unit 11 and the second-stage cold storage unit 12 have the same function, which is to cool the high-pressure air and finally liquefy the air. The first-stage cold storage unit 11 and the second-stage cold storage unit 12 are connected in series to the liquid air input pipeline 41, the gaseous air output pipeline 42, the liquid oxygen output pipeline 43, the nitrogen output pipeline 44 and the dirty nitrogen output pipeline 45, wherein the input end of the liquid air input pipeline 41 is connected to the first connecting pipeline 40 and the air outlet of the highest-level interstage cooler, and the output end of the liquid air input pipeline 41 is connected to the liquid air tank 15 through the first liquid expander 31 and the throttle valve 14 in turn; the input end of the gaseous air output pipeline 42 is connected to the liquid air tank 15; the input ends of the liquid oxygen output pipeline 43, the nitrogen output pipeline 44 and the dirty nitrogen output pipeline 45 are all connected to the distillation device 30.

[0036] Specifically, Figure 1 As shown, the first-stage cold storage unit 11 and the second-stage cold storage unit 12 have multiple inlets and multiple outlets respectively. An inlet on the right side of the second-stage cold storage unit 12 is connected to the liquid air tank 15 through a gas-phase air output pipeline 42, an inlet on the right side of the second-stage cold storage unit 12 is connected to the liquid oxygen outlet of the distillation device 30 through a section of liquid oxygen output pipeline 43, an inlet on the right side of the second-stage cold storage unit 12 is connected to the nitrogen outlet of the distillation device 30 through a section of nitrogen output pipeline 44, and an inlet on the right side of the second-stage cold storage unit 12 is connected to the dirty nitrogen outlet of the distillation device 30 through a section of dirty nitrogen output pipeline 45. An outlet on the right side of the second-stage cold storage unit 12 is connected to the input end of the first liquid expander 31 through a section of liquid-phase air input pipeline 41, and the output port of the first liquid expander 31 is connected to the liquid air tank 15 through a throttle valve 14.

[0037] An inlet on the right side of the first-stage cold storage unit 11 is connected to an outlet on the left side of the second-stage cold storage unit 12 through a gas-phase air output pipeline 42, an inlet on the right side of the first-stage cold storage unit 11 is connected to an outlet on the left side of the second-stage cold storage unit 12 through a liquid oxygen output pipeline 43, an inlet on the right side of the first-stage cold storage unit 11 is connected to an outlet on the left side of the second-stage cold storage unit 12 through a nitrogen output pipeline 44, and an inlet on the right side of the first-stage cold storage unit 11 is connected to an outlet on the left side of the second-stage cold storage unit 12 through a dirty nitrogen output pipeline 45. An outlet on the right side of the first-stage cold storage unit 11 is connected to an inlet on the left side of the second-stage cold storage unit 12 through a liquid air input pipeline 41. The four outlets on the left side of the first-stage cold storage unit 11 are connected one by one to a gas-phase air output pipeline 42, a liquid oxygen output pipeline 43, a nitrogen output pipeline 44 and a dirty nitrogen output pipeline 45, respectively. An inlet on the left side of the first-stage cold storage unit 11 is connected to the other end of the first connecting pipeline 40 and the air outlet of the fourth-stage interstage cooler 8 through a liquid-phase air input pipeline 41.

[0038] In one embodiment of the present invention, the cold storage device further includes an air expander 13 and a second liquid expander 17, the liquid-phase air input pipeline 41 between the first-stage cold storage unit 11 and the second-stage cold storage unit 12 is connected to the input end of the air expander 13, and the output end of the air expander 13 is connected to the distillation device 30. The liquid-phase air input pipeline 41 between the second-stage cold storage unit 12 and the first liquid expander 31 is connected to the input end of the second liquid expander 17, and the output end of the second liquid expander 17 is connected to the distillation device 30. The air expander 13 is used to expand part of the air output from the first-stage cold storage unit 11, and the expanded air enters the distillation device 30, and the second liquid expander 17 is used to expand part of the air output from the second-stage cold storage unit 12, and the expanded air enters the distillation device 30.

[0039] In one embodiment of the present invention, the heating device includes a first air heater 19 and a second air heater 20, which are connected in series to a liquid air output pipeline 48, the input end of the liquid air output pipeline 48 is connected to the liquid air tank 15 through the second liquid air pump 18, and the output end of the liquid air output pipeline 48 is connected to the expander device; the first air heater 19 is connected to the first stage cold storage unit 11 through a circulation pipeline, and the second air heater 20 is connected to the second stage cold storage unit 12 through a circulation pipeline. The first air heater 19 and the second air heater 20 are respectively used to heat the liquid air in the liquid air output pipeline 48 to gasify the liquid air.

[0040] In a specific embodiment of the present invention, the circulation pipeline includes a high-temperature medium storage tank 36, a high-temperature pump 37, a low-temperature medium storage tank 38 and a low-temperature pump 39, the output end of the high-temperature medium storage tank 36 is connected to the input end of the high-temperature pump 37, the output end of the high-temperature pump 37 is connected to the inlet of the air heater (the first air heater 19 or the second air heater 20), the outlet of the air heater (the first air heater 19 or the second air heater 20) is connected to the input end of the low-temperature medium storage tank 38, the output end of the low-temperature medium storage tank 38 is connected to the input end of the low-temperature pump 39, the output end of the low-temperature pump 39 is connected to the inlet of the cold storage unit (the first-stage cold storage unit 11 or the second-stage cold storage unit 12), and the outlet of the cold storage unit (the first-stage cold storage unit 11 or the second-stage cold storage unit 12) is connected to the input end of the high-temperature medium storage tank 36. The medium with higher temperature in the high-temperature medium storage tank 36 is pumped to the first air heater 19 or the second air heater 20 through the high-temperature pump 37 to heat the liquid air in the liquid air output pipeline 48. After the heat exchange, the temperature of the medium is reduced and enters the low-temperature medium storage tank 38. It is pumped to the first-stage cold storage unit 11 or the second-stage cold storage unit 12 through the low-temperature pump 39 to cool the air in the liquid air input pipeline 41. After the heat exchange, the medium with increased temperature returns to the high-temperature medium storage tank 36.

[0041] Furthermore, the circulation pipeline also includes a first circulation pump, a second circulation pump and a fifth interstage heater, the output end of the first circulation pump is connected to the output end of the high temperature pump 37, the input end of the second circulation pump is connected to the input end of the low temperature medium storage tank 38, the output end of the second circulation pump is connected to the inlet of the fifth interstage heater, the outlet of the fifth interstage heater is connected to the input end of the first circulation pump, and the two fifth interstage heaters are connected in series to the return air pipeline 46. When working, the medium is circulated between the air heater and the fifth interstage heater by the first circulation pump and the second circulation pump, and the air in the return air pipeline 46 can be cooled.

[0042] In one embodiment of the present invention, the expander device includes a multi-stage interstage heater, a multi-stage expander, a high-temperature water tank 10 and a low-temperature water tank 9. The two adjacent expanders are connected through the corresponding interstage heaters, and the air inlet of the lowest interstage heater is connected to the output end of the liquid air output pipeline 48.

[0043] Specifically, Figure 1As shown, the expander device includes a first-stage interstage heater 21, a second-stage interstage heater 22, a third-stage interstage heater 23, a fourth-stage interstage heater 24, a first-stage expander 25, a second-stage expander 26, a third-stage expander 27, a fourth-stage expander 28, a high-temperature water tank 10 and a low-temperature water tank 9, the air inlet of the first-stage interstage heater 21 is connected to the output end of the liquid air output pipeline 48, the air outlet of the first-stage interstage heater 21 is connected to the air inlet of the first-stage expander 25, the second-stage interstage heater 22 is located between the first-stage expander 25 and the second-stage expander 26, the air inlet of the second-stage interstage heater 22 is connected to the air outlet of the first-stage expander 25, and the air outlet of the second-stage interstage heater 22 is connected to the air inlet of the second-stage expander 26. The third-stage interstage heater 23 is located between the second-stage expander 26 and the third-stage expander 27. The air inlet of the third-stage interstage heater 23 is communicated with the air outlet of the second-stage expander 26, and the air outlet of the third-stage interstage heater 23 is communicated with the air inlet of the third-stage expander 27. The fourth-stage interstage heater 24 is located between the third-stage expander 27 and the fourth-stage expander 28. The air inlet of the fourth-stage interstage heater 24 is communicated with the air outlet of the third-stage expander 27, and the air outlet of the fourth-stage interstage heater 24 is communicated with the air inlet of the fourth-stage expander 28.

[0044] The liquid inlet of the high-temperature water tank 10 is connected to the liquid outlet of each interstage cooler, and the liquid outlet of the high-temperature water tank 10 is connected to the liquid inlet of each interstage heater; the liquid outlet of the low-temperature water tank 9 is connected to the liquid inlet of each interstage cooler, and the liquid inlet of the low-temperature water tank 9 is connected to the liquid outlet of each interstage heater.

[0045] Specifically, Figure 1 As shown, the liquid inlet of the high-temperature water tank 10 is connected to the liquid outlets of the first-stage interstage cooler 5, the second-stage interstage cooler 6, the third-stage interstage cooler 7 and the fourth-stage interstage cooler 8, the liquid outlet of the high-temperature water tank 10 is connected to the liquid inlets of the first-stage interstage heater 21, the second-stage interstage heater 22, the third-stage interstage heater 23 and the fourth-stage interstage heater 24, the liquid outlet of the low-temperature water tank 9 is connected to the liquid inlets of the first-stage interstage cooler 5, the second-stage interstage cooler 6, the third-stage interstage cooler 7 and the fourth-stage interstage cooler 8, and the liquid inlet of the low-temperature water tank 9 is connected to the liquid outlets of the first-stage interstage heater 21, the second-stage interstage heater 22, the third-stage interstage heater 23 and the fourth-stage interstage heater 24.

[0046] In one embodiment of the present invention, the expander device also includes a third liquid air pump 32, a fourth liquid air pump 33 and a first cooler 34. The third liquid air pump 32 is arranged at the liquid outlet of the high-temperature water tank 10, the fourth liquid air pump 33 is arranged at the liquid outlet of the low-temperature water tank 9, and the first cooler 34 is arranged at the liquid inlet of the low-temperature water tank 9. The first cooler 34 is used to cool the medium output by the multi-stage interstage heater, and the medium after cooling enters the low-temperature water tank 9.

[0047] In one embodiment of the present invention, the expander device also includes a return air pipeline 46 and a second cooler 29, the air inlet end of the return air pipeline 46 is connected to the air inlet of one of the interstage heaters, specifically, the air inlet end of the return air pipeline 46 is connected to the air inlet of the fourth-stage expander 28, and the air outlet end of the return air pipeline 46 is connected to the distillation device 30. The second cooler 29 is connected in series to the return air pipeline 46, and the second cooler 29 is used to cool the air in the return air pipeline 46 so that the temperature of the air reaches a predetermined room temperature.

[0048] In one embodiment of the present invention, the expander device further includes a second connecting pipeline 49 and a Rankine cycle power generation device 47, the liquid inlet end of the second connecting pipeline 49 is connected to the liquid outlet of the third liquid air pump 32, the liquid outlet end of the second connecting pipeline 49 is connected to the liquid inlet end of the second cooler 29, and the interstage heater of the Rankine cycle power generation device 47 is connected in series to the second connecting pipeline 49. The Rankine cycle power generation device 47 is composed of an interstage heater, a stage expander, a circulation pump and a cooler. The Rankine cycle power generation device 47 is an existing device in the art, and its specific connection relationship is not described in detail here. Since the compression heat cannot be completely recovered by the expanded air, if this part of the heat is discharged to the environment, part of the heat will be wasted. Therefore, a Rankine cycle power generation device 47 is added to the power generation unit to utilize the waste heat and improve the round-trip efficiency of the system.

[0049] Working principle of the liquid air energy storage system coupled with the air separation device of the present invention: During the valley electricity price period, valley electricity is supplied to the compressor group (first stage compressor 1, second stage compressor 2, third stage compressor 3 and fourth stage compressor 4) for operation. The ambient air enters the first stage compressor 1 after being purified by the air filter, and is cooled by pressurized water in the first stage interstage cooler 5. The air at high pressure room temperature is removed from water, carbon dioxide, hydrocarbons and other substances in the molecular sieve purifier. Then the compressors at the following stages continue to pressurize the air. The compression heat is recovered by the pressurized water output by the low temperature water tank 9 in each stage interstage cooler, and the generated high temperature water is stored in the high temperature water tank 10. A part of the air output by the second stage interstage cooler 6 through the first connecting pipeline 40 enters the first stage cold storage unit 11 to obtain cold capacity, and a part of the air cooled by the first stage cold storage unit 11 enters the air expander 13 for expansion, and finally enters the distillation device 30. The remaining air after being cooled by the first-stage cold storage unit 11 is cooled and liquefied in the second-stage cold storage unit 12. The liquefied liquid air first enters the air expander 13 for expansion, and then enters the throttle valve 14 for throttling. In the generated gas-liquid mixture, the liquid phase is stored in the liquid air tank 15, and the gaseous air returns to the first-stage cold storage unit 11 and the second-stage cold storage unit 12 through the gas-phase air output pipeline 42 to supplement the cooling capacity of the compressed air. Part of the liquid air in the liquid air tank 15 is extracted and sent to the distillation device 30 after being pressurized by the first liquid air pump 16.

[0050] The structure of the distillation device 30 is the same as that of the conventional air separation device, and only a brief description is given here. The gas phase and liquid phase two streams of raw materials enter the high-pressure tower for preliminary distillation, and oxygen-enriched liquid air and nitrogen are obtained at the bottom and top of the high-pressure tower respectively. The nitrogen is condensed into liquid nitrogen in the condenser evaporator, a part of which flows downward as reflux liquid, and the rest of the liquid nitrogen is sent to the low-pressure tower as reflux liquid. In the middle of the tower, a part of the oxygen-depleted liquid air is extracted and enters the subcooler together with the oxygen-enriched liquid air and liquid nitrogen for subcooling. After subcooling, the liquid nitrogen and oxygen-depleted liquid air are throttled to the corresponding pressure and enter the top and middle of the low-pressure tower respectively. The supercooled oxygen-enriched liquid air is divided into two parts, one part is throttled and sent to the middle of the low-pressure tower, and the other part enters the condenser of the crude argon tower after throttling, providing a cold source for the crude argon tower, and enters the low-pressure tower after being heated. In the low-pressure tower, a stream of air is drawn out from the argon-rich zone and sent to the crude argon tower for rectification. Argon-rich air is obtained at the top of the crude argon tower, and oxygen-rich liquid air that is basically free of argon is obtained at the bottom. The oxygen-rich liquid air is refluxed to the low-pressure tower. Finally, liquid oxygen is obtained at the bottom of the low-pressure tower and stored in a liquid oxygen tank. Nitrogen is obtained at the top of the low-pressure tower and then enters the subcooler. A large amount of dirty nitrogen is generated in the upper part of the low-pressure tower. After the dirty nitrogen and argon-rich air merge, they enter the subcooler to provide cooling for other streams.

[0051] During the period of parity electricity price, only the first-stage compressor 1 and the second-stage compressor 2 are in operation to maintain the stable operation of the distillation device 30. After being compressed, the air enters the first-stage cold storage unit 11 and the second-stage cold storage unit 12 to recover the cold of nitrogen and dirty nitrogen. The temperature and pressure of the compressed air coming out of the second-stage cold storage unit 12 do not meet the requirements of the distillation device 30, so it needs to be expanded by the second liquid expander 17 before entering the distillation device 30. At the same time, the liquid air in the liquid air tank 15 is pressurized by the first liquid air pump 16 and enters the distillation device 30 to participate in distillation. In the whole process, the operating flow of the distillation device 30 is consistent with that in the energy storage process. The products are liquid oxygen, nitrogen and dirty nitrogen. Liquid oxygen is stored in the liquid oxygen tank, and nitrogen and dirty nitrogen enter the first-stage cold storage unit 11 and the second-stage cold storage unit 12 to provide cold for the compressed air. In this process, compressed air is used to provide gaseous raw materials to the distillation device 30. Compared with the energy storage process, the flow of compressed air is much less, so the energy consumption is much lower than that of the energy storage process.

[0052] During the peak electricity price period, a large amount of liquid air is used for power generation. After being pressurized by the second liquid air pump 18, the liquid air enters the first air heater 19 and the second air heater 20, and its cold is recovered by the propane and methanol-water solution in the heater to obtain high-pressure normal temperature air. After the high-pressure normal temperature air recovers the compression heat in the first-stage interstage heater 21, the temperature rises, and then enters the first-stage expander 25 to expand, and the first-stage expander drives the generator to generate electricity. After three stages of expansion, the air pressure is close to the pressure of the distillation device 30, so a part of the expanded air is extracted and supplied to the distillation device 30 through the return air pipeline 46, and the remaining air enters the fourth-stage expander 28 after heating and expands to normal pressure. The expanded air supplied to the distillation device 30 has a temperature higher than room temperature and is cooled to room temperature in the second cooler 29 before entering the distillation device 30. In the cold storage unit, the expanded air recovers cold from the propane and methanol-water solution, and after reaching the specified temperature requirement, it enters the distillation device 30 to participate in distillation.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid air energy storage system coupled with an air separation device, characterized in that: include: An air compression device, wherein the air compression device is used to compress air; A cold storage device, the cold storage device is connected to the air compression device, and the cold storage device is used to cool the high-pressure air delivered by the air compression device so as to convert part of the high-pressure air into liquid air; a liquid air tank (15), the liquid air tank (15) being in communication with the cold storage device; A distillation device (30), the distillation device (30) is connected to the liquid air tank (15) via a first liquid air pump (16), the cold storage device is connected to the distillation device, the liquid air tank (15) is used to store liquid air, and the first liquid air pump (16) is used to transport liquid air to the distillation device (30) for supplementary cooling; a heating device, the heating device being in communication with the liquid air tank (15) and the distillation device (30), the heating device being used to heat the liquid air output from the liquid air tank (15) to obtain high-pressure normal-temperature air; An expander device is connected to the heating device and the air compression device, and is used to generate electricity through high-pressure and normal-temperature air during peak electricity price periods.

2. The liquid air energy storage system coupled with an air separation device according to claim 1, characterized in that: The air compression device comprises: Multi-stage compressor; A multi-stage interstage cooler, wherein two adjacent stages of the compressors are connected via the corresponding interstage cooler, the air outlet of the highest-stage interstage cooler is connected to the cold storage device, and the liquid outlet and liquid inlet of each stage of the interstage cooler are connected to the expander device.

3. The liquid air energy storage system coupled with an air separation device according to claim 2, characterized in that: The air compression device also includes: A first connecting pipeline (40), wherein an air outlet of one of the multiple interstage coolers is connected to the cold storage device through the first connecting pipeline (40).

4. The liquid air energy storage system coupled with an air separation device according to claim 3, characterized in that: The cold storage device comprises: A first-stage cold storage unit (11); The second-stage cold storage unit (12), the first-stage cold storage unit (11) and the second-stage cold storage unit (12) are connected in series to a liquid air input pipeline (41), a gaseous air output pipeline (42), a liquid oxygen output pipeline (43), a nitrogen output pipeline (44) and a dirty nitrogen output pipeline (45), wherein the input end of the liquid air input pipeline (41) is connected to the first connecting pipeline (40) and the gas outlet of the highest-stage interstage cooler, and the output end of the liquid air input pipeline (41) is connected to the liquid air tank (15) through the first liquid expander (31) and the throttle valve (14) in sequence; the input end of the gaseous air output pipeline (42) is connected to the liquid air tank (15); and the input ends of the liquid oxygen output pipeline (43), the nitrogen output pipeline (44) and the dirty nitrogen output pipeline (45) are all connected to the distillation device (30).

5. The liquid air energy storage system coupled with an air separation device according to claim 4, characterized in that: The cold storage device also includes: An air expander (13), wherein the liquid-phase air input pipeline (41) between the first-stage cold storage unit (11) and the second-stage cold storage unit (12) is connected to an input end of the air expander (13), and an output end of the air expander (13) is connected to the distillation device (30); A second liquid expansion machine (17), the liquid-phase air input pipeline (41) between the second-stage cold storage unit (12) and the first liquid expansion machine (31) is connected to the input end of the second liquid expansion machine (17), and the output end of the second liquid expansion machine (17) is connected to the distillation device (30).

6. The liquid air energy storage system coupled with an air separation device according to claim 4 or 5, characterized in that: The heating device comprises: A first air heater (19); a second air heater (20), the first air heater (19) and the second air heater (20) are connected in series to a liquid air output pipeline (48), the input end of the liquid air output pipeline (48) is connected to the liquid air tank (15) via a second liquid air pump (18), and the output end of the liquid air output pipeline (48) is connected to the expander device; the first air heater (19) is connected to the first-stage cold storage unit (11) via a circulation pipeline, and the second air heater (20) is connected to the second-stage cold storage unit (12) via a circulation pipeline.

7. The liquid air energy storage system coupled with an air separation device according to claim 6, characterized in that: The expander device comprises: Multi-stage interstage heaters; A multi-stage expander, wherein two adjacent stages of the expanders are connected via the corresponding interstage heaters, and the air inlet of the interstage heater at the lowest stage is connected to the output end of the liquid-phase air output pipeline (48); A high-temperature water tank (10), wherein a liquid inlet of the high-temperature water tank (10) is connected to a liquid outlet of each stage of the interstage cooler, and a liquid outlet of the high-temperature water tank (10) is connected to a liquid inlet of each stage of the interstage heater; A low-temperature water tank (9), wherein a liquid outlet of the low-temperature water tank (9) is connected to a liquid inlet of each stage of the interstage cooler, and a liquid inlet of the low-temperature water tank (9) is connected to a liquid outlet of each stage of the interstage heater.

8. The liquid air energy storage system coupled with an air separation device according to claim 7, characterized in that: The expander device further comprises: a third liquid air pump (32), the third liquid air pump (32) being arranged at a liquid outlet of the high-temperature water tank (10); a fourth liquid air pump (33), the fourth liquid air pump (33) being arranged at a liquid outlet of the low-temperature water tank (9); A first cooler (34), wherein the first cooler (34) is arranged at a liquid inlet of the low-temperature water tank (9).

9. The liquid air energy storage system coupled with an air separation device according to claim 7, characterized in that: The expander device further comprises: a return air pipeline (46), wherein an air inlet end of the return air pipeline (46) is in communication with an air inlet of the interstage heater of one stage, and an air outlet end of the return air pipeline (46) is in communication with the distillation device (30); A second cooler (29), the second cooler (29) is connected in series to the return air pipeline (46).

10. The liquid air energy storage system coupled with an air separation device according to claim 9, characterized in that: The expander device further comprises: a second connecting pipeline (49), wherein a liquid inlet end of the second connecting pipeline (49) is connected to a liquid outlet of the third liquid air pump (32), and a liquid outlet end of the second connecting pipeline (49) is connected to a liquid inlet end of the second cooler (29); A Rankine cycle power generation device (47), wherein the interstage heater of the Rankine cycle power generation device (47) is connected in series to the second connecting pipeline (49).

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