Method and system for generating power by balancing pressure energy of gas storage through compression energy storage

Abstract

The invention provides a method and a system for generating power by balancing pressure energy of a gas storage by using compression energy storage, which can realize stable output of converting the pressure energy into electric energy in a gas recovery process of the gas storage, maximally recover the pressure energy and realize energy-saving operation. The method at least comprises the steps that dehydrated qualified dry gas is used as a circulating medium, and the low-pressure storage tank is stamped till the pressure is balanced; when the main process natural gas expands to generate power, the low-pressure natural gas in the low-pressure storage tank is boosted, and after being subjected to heat exchange and cooling, the boosted high-pressure qualified dry gas is introduced into the high-pressure storage tank to be stored; when the main process natural gas expansion generating capacity is insufficient, after heat exchange and temperature rise are conducted on high-pressure qualified dry gas in the high-pressure storage tank, the high-pressure qualified dry gas is introduced into the energy storage expansion machine independent of the main expansion machine to generate power, and therefore main process natural gas expansion generating power is supplemented.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field surface engineering and relates to energy storage power generation technology, specifically a method and system for generating electricity by using compressed energy storage to balance the pressure energy of a gas storage tank. Background Technology

[0002] The gas extraction period for underground gas storage facilities is mainly concentrated between November and March of the following year. During this period, natural gas undergoes a series of treatments to meet quality standards before being transported to the external natural gas pipeline network. In this process, the pressure of the natural gas decreases from the formation pressure to the external pipeline network pressure, and the recovery of pressure energy primarily relies on the expansion and power generation process of the natural gas. Taking a complete gas extraction cycle of a storage facility as an example, assuming a total of 1.6 billion cubic meters of natural gas is extracted during that cycle, its gathering and injection station can theoretically generate approximately 0.19 billion kilowatt-hours of electricity through pressure energy recovery, equivalent to the energy produced by burning 2,336 tons of standard coal. However, the expansion and power generation process of natural gas does not fully capture and utilize this energy.

[0003] On the other hand, during the gas extraction process, the formation pressure in the gas storage facility tends to decrease continuously, and the daily extracted natural gas volume and inlet pressure also fluctuate. Simultaneously, the pressure in the external natural gas pipeline network is also affected by various external factors, resulting in irregular fluctuations. These fluctuations collectively lead to the instability of natural gas expansion power generation. Stable power output is one of the necessary conditions to ensure the smooth grid connection and effective utilization of electricity.

[0004] In summary, although there are existing methods for recovering some pressure energy using expander power generation, achieving stable power output is difficult due to multiple factors such as formation pressure, gas production volume, and external pipeline pressure. When the main process power generation exceeds the grid-agreed power generation, a small amount of fluctuating natural gas usually needs to be switched to JT valve groups for throttling to achieve stable output, resulting in significant pressure energy waste. Conversely, when the main process power generation is less than the grid-agreed power generation, effective balancing and supplementary power generation are not possible, potentially impacting the grid. How to effectively balance these fluctuating factors, ensure stable expansion power generation, and fully utilize the pressure energy from the gas extraction process in gas storage facilities has become a pressing technical challenge. Summary of the Invention

[0005] To overcome the problems of unstable power generation from natural gas expansion and insufficient utilization of pressure energy during gas extraction in existing technologies, this invention provides a method and system for generating electricity by balancing the pressure energy of gas storage facilities using compressed energy storage. This method can achieve a stable output of pressure energy converted into electrical energy during gas extraction, maximize the recovery of pressure energy, and achieve energy-saving operation.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A method for generating electricity by utilizing compressed energy storage to balance the pressure energy of a gas storage tank, comprising at least the following steps:

[0008] Use qualified dry gas after dehydration as the circulating medium to pressurize the low-pressure storage tank until the pressure is balanced;

[0009] While generating electricity from natural gas in the main process, the low-pressure natural gas in the low-pressure storage tank is pressurized, and after heat exchange and cooling of the pressurized high-pressure qualified dry gas, it is passed into the high-pressure storage tank for storage.

[0010] When the power generation from the main process natural gas expansion is insufficient, the high-pressure qualified dry gas in the high-pressure storage tank is heated by heat exchange and then fed into an energy storage expander that is set up independently of the main expander to generate electricity, in order to supplement the power generation from the main process natural gas expansion.

[0011] Furthermore, the steps also include: during power generation, the control center calculates the circulating natural gas flow rate based on the pressure of the low-pressure storage tank, the pressure of the high-pressure storage tank, and the calculated power generation from expansion, and balances the power generation through valve control.

[0012] Furthermore, the method for pressurizing the low-pressure natural gas in the low-pressure storage tank is as follows: a small amount of natural gas with fluctuating flow rate is used as a driving source and fed into a secondary expander to generate electricity. The secondary expander drives a coaxial compressor to rotate, thereby compressing and pressurizing the low-pressure natural gas in the low-pressure storage tank.

[0013] Furthermore, the heat exchange and cooling of the pressurized qualified dry gas is specifically as follows: the pressurized qualified dry gas from the coaxial compressor is introduced into a two-way heat exchanger to exchange heat with the natural gas before expansion and cool down. The cooled qualified dry gas is then introduced into a high-pressure storage tank for storage.

[0014] Furthermore, the expanded natural gas in the auxiliary expander merges with the expanded natural gas from the main process in the main expander at the inlet of the cryogenic separator and enters the cryogenic separator.

[0015] Furthermore, the high-pressure qualified dry gas in the high-pressure storage tank is introduced into a two-way heat exchanger, where it exchanges heat with the natural gas before expansion and is then introduced into the first-stage expander of the energy storage system for expansion and power generation. The expanded natural gas in the first-stage expander is then introduced into an expansion heat exchanger for further heating and then into a second-stage expander for expansion and power generation. The expanded natural gas in the second-stage expander is then introduced into an outlet heat exchanger for further heating and then into a low-pressure storage tank for storage.

[0016] The present invention also provides a system for generating electricity by utilizing compressed energy storage to balance the pressure energy of a gas storage tank, for implementing the method described above, comprising at least:

[0017] The auxiliary expander is connected to the main process natural gas power generation pipeline via a branch line to introduce a small amount of natural gas with fluctuating flow rate, which serves as a power device for compressed energy storage.

[0018] A coaxial compressor is connected between the auxiliary expander and the low-pressure storage tank. It is used to provide power from the auxiliary expander to the coaxial compressor to compress the low-pressure natural gas in the low-pressure storage tank to a high-pressure state. The coaxial compressor is also connected to the main process natural gas power generation pipeline.

[0019] The low-pressure storage tank is used for storing low-pressure natural gas and is also connected to the main process natural gas power generation pipeline and the outlet heat exchanger.

[0020] High-pressure storage tanks are used for storing high-pressure natural gas and are connected to the main process natural gas power generation pipeline.

[0021] The primary energy storage expander is used to supplement power generation and is connected to the high-pressure storage tank and the secondary energy storage expander respectively through the main process natural gas power generation pipeline.

[0022] The secondary energy storage expander is used to supplement power generation and is also connected to the outgoing heat exchanger.

[0023] Furthermore, it also includes a control center, which is electrically connected at least to the electric valves of the primary energy storage expander, the electric valves of the secondary energy storage expander, and the flow meter and regulating valve b installed between the high-pressure storage tank and the main process natural gas power generation pipeline.

[0024] Furthermore, the main process natural gas power generation pipeline includes a main heat exchanger, a preheater, a bidirectional heat exchanger, an expansion heat exchanger, a liquid separator, a main expander, and a cryogenic separator connected in sequence via pipelines. The main heat exchanger is used for centralized heat exchange of the produced natural gas and is also connected to a low-pressure storage tank, a high-pressure storage tank, a cryogenic separator, and an outlet heat exchanger. The bidirectional heat exchanger is also connected to a high-pressure storage tank, a primary energy storage expander, and a coaxial compressor. The expansion heat exchanger is also connected to a primary energy storage expander and a secondary energy storage expander. The pipeline at the rear end of the liquid separator is connected to the auxiliary expander via a branch.

[0025] Furthermore, the auxiliary expander is also connected to the front end pipeline of the cryogenic separator, so that the expanded natural gas in the auxiliary expander and the expanded natural gas in the main expander can be combined and then enter the cryogenic separator.

[0026] The beneficial effects of this invention include:

[0027] By utilizing compressed energy storage technology, when the power generation from natural gas expansion in the main process is insufficient, high-pressure qualified dry gas in the high-pressure storage tank can be used to supplement power generation, thereby ensuring a stable output of electricity and solving the problem of unstable power generation from natural gas expansion. Through equipment such as auxiliary expanders, coaxial compressors, low-pressure storage tanks, high-pressure storage tanks, and energy storage expanders, the pressure energy during the gas extraction process in the gas storage facility is fully and effectively converted into electrical energy, maximizing the recovery of pressure energy and improving energy utilization efficiency. Through the calculation of circulating natural gas flow and valve control by the control center, the natural gas flow can be adjusted according to actual power generation needs, achieving energy-saving operation and reducing operating costs. Using equipment such as bidirectional heat exchangers and expansion heat exchangers, effective heat exchange of natural gas before and after expansion is achieved, improving heat exchange efficiency and reducing energy loss.

[0028] In summary, this method achieves a stable output of pressure energy converted into electrical energy during the gas extraction process of the gas storage facility, maximizes the recovery of pressure energy, and realizes energy-saving operation. This technology avoids the waste of pressure energy resources and contributes to the achievement of the "dual carbon" target while ensuring the safe and stable operation of the gas storage facility project. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention.

[0030] In the diagram: 1-Main heat exchanger, 2-Preheater, 3-Bidirectional heat exchanger, 4-Expansion heat exchanger, 5-Divider tank, 6-Main flow meter, 7-Regulating valve a, 8-Main expander, 9-Cryogenic separator, 10-Secondary flow meter, 11-Secondary expander, 12-Coaxial compressor, 13-Low-pressure storage tank, 14-High-pressure storage tank, 15-Primary energy storage expander, 16-Secondary energy storage expander, 17-Outlet heat exchanger, 18-JT valve, 19-High-pressure tank charging valve, 20-Low-pressure tank charging valve, 21-External flow meter, 22-Control center, 23-Flow meter, 24-Regulating valve b. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] This invention relates to a method and system for generating electricity by balancing the pressure energy of a gas storage facility using compressed energy storage. The system uses qualified dry gas obtained after dehydration from the gas storage facility as the circulating medium. While generating electricity through the expansion of natural gas in the main process, a small amount of natural gas with fluctuating flow rate is used as the driving source. The low-pressure natural gas is compressed to a high-pressure state and stored through a coaxial compressor. When the power generation from the expansion of natural gas in the main process is insufficient, it is supplemented by generating electricity through an energy storage expander, thereby achieving the purpose of balancing the power generation.

[0034] This method mainly consists of three parts:

[0035] The first part is the compression energy storage section. Dehydrated, qualified dry gas is used as the circulating medium to pressurize the low-pressure storage tank until pressure equilibrium is reached. While the main process involves the metered natural gas entering the main expander for power generation, a small amount of fluctuating natural gas enters the auxiliary expander, driving a coaxial compressor to pressurize the natural gas in the low-pressure storage tank. The heat energy generated during compression is recovered through heat exchange between the unexpanded natural gas and the pressurized circulating natural gas. The cooled circulating natural gas then enters the high-pressure storage tank for storage. The fluctuating small amount of natural gas mixes with the metered natural gas from the main process and enters a cryogenic separator for dehydrocarbonization and dehydration.

[0036] The second part is the supplementary power generation section. When the main process's fixed-quantity natural gas power generation is insufficient to meet the stable power output, the circulating natural gas stored in the high-pressure storage tank exchanges heat with the pre-expansion natural gas and then enters the energy storage expander to generate electricity to supplement the power generation. The expanded low-pressure, low-temperature natural gas in the energy storage expander exchanges heat with qualified external dry gas and then enters the low-pressure storage tank for storage after being heated.

[0037] The third part is the circulating natural gas flow control section. During power generation, the control center calculates the circulating natural gas flow based on the pressure of the low-pressure and high-pressure storage tanks and the calculated power generation from expansion, and controls it through valves to maintain stable power generation.

[0038] Example 1

[0039] refer to Figure 1 This embodiment will describe in detail the structure of a system for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank:

[0040] First, the system includes a main process natural gas power generation pipeline for power generation from the main process natural gas expansion. The main process natural gas power generation pipeline includes a main heat exchanger 1, a preheater 2, a bidirectional heat exchanger 3, an expansion heat exchanger 4, a liquid separator 5, a main expander 8, and a cryogenic separator 9, which are connected in sequence via pipelines. The main heat exchanger 1 is used for centralized heat exchange of the produced natural gas. It is also directly connected to the cryogenic separator 9 and the outlet heat exchanger 17. A JT valve 18 is installed on the connecting pipeline between the main heat exchanger 1 and the cryogenic separator 9. An external flow meter 21 is installed on the qualified dry gas external transmission pipeline at the rear end of the outlet heat exchanger 17. A main flow meter 6 and a regulating valve a7 are installed on the connecting pipeline between the liquid separator 5 and the main expander 8.

[0041] The system also includes a secondary expander 11, a coaxial compressor 12, a low-pressure storage tank 13, a high-pressure storage tank 14, a primary energy storage expander 15, a secondary energy storage expander 16, and an outlet heat exchanger 17. The secondary expander 11 is connected to the rear pipeline of the separator 5 via a branch line to introduce a small amount of natural gas with fluctuating flow rate as a power device for compression energy storage. The secondary expander 11 is connected to the coaxial compressor 12, which is connected to the low-pressure storage tank 13. The secondary expander 11 provides power to the coaxial compressor 12 to compress the low-pressure natural gas in the low-pressure storage tank 13 to a high-pressure state. The secondary expander 11 is also connected to the front pipeline of the cryogenic separator 9 so that the expanded natural gas in the secondary expander 11 merges with the expanded natural gas in the primary expander 8 before entering the cryogenic separator 9. The coaxial compressor 12 is also connected to the bidirectional heat exchanger 3; the low-pressure storage tank 13 is used for low-pressure natural gas storage, and the low-pressure storage tank 13 is also connected to the main heat exchanger 1 and the outlet heat exchanger 17 respectively. A low-pressure tank pressure valve 20 is provided on the connecting pipeline between the low-pressure storage tank 13 and the main heat exchanger 1; the high-pressure storage tank 14 is used for high-pressure natural gas storage, and the high-pressure storage tank 14 is connected to the main heat exchanger 1 and the bidirectional heat exchanger 3 respectively. A high-pressure tank pressure valve 19 is provided on the connecting pipeline between the high-pressure storage tank 14 and the main heat exchanger 1; the first-stage energy storage expander 15 is used for supplementary power generation, and it is directly connected to the bidirectional heat exchanger 3 and the expansion heat exchanger 4 respectively; the second-stage energy storage expander 16 is used for supplementary power generation, and it is directly connected to the expansion heat exchanger 4 and the outlet heat exchanger 17 respectively.

[0042] It also includes a control center 22, which is electrically connected to at least the electric valves of the primary energy storage expander 15, the electric valves of the secondary energy storage expander 16, and the flow meter 23 and regulating valve b24 located between the high-pressure storage tank 14 and the bidirectional heat exchanger 3.

[0043] Example 2

[0044] Based on the system structure described in Embodiment 1, this embodiment will describe in detail the steps of the method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank. The numerical values ​​involved in the step description are illustrative examples to facilitate understanding of the system's operation: Initially, a small amount of natural gas is used to start the system through the throttling cooling process via valve 18 (JT valve 18). Simultaneously, qualified dry gas (5.5 MPa) is discharged from the main heat exchanger 1, while the low-pressure tank pressurization valve 20 and the high-pressure tank pressurization valve 19 are opened to pressurize the low-pressure storage tank 13 and the high-pressure storage tank 14 (5 MPa). Once the system is running smoothly and the gas processing capacity increases, the process is switched to the expansion power generation process.

[0045] Main process natural gas expansion power generation flow: Taking the gas extraction process in the gathering and injection station as an example, the extracted natural gas (10MPa, 25℃, 7.43 million cubic meters / day) is heated by the main heat exchanger 1 and then enters the preheater 2 for heating. After being heated by the bidirectional heat exchanger 3 and the expansion heat exchanger 4, it enters the separator 5 to separate free droplets. After being measured by the main flow meter 6 and the regulating valve a7 (9.8MPa, 25℃, 7 million cubic meters / day), it enters the main expander 8 for power generation. The expanded low-temperature natural gas (5.5MPa, -13℃, 7 million cubic meters / day) enters the low-temperature separator 9 for gas-liquid separation. The separated qualified dry gas and condensate are returned to the main heat exchanger 1 for heat exchange. The condensate goes to the subsequent processing unit. The qualified dry gas is heated by the outlet heat exchanger 17 and measured by the external flow meter 21 before being transported to the natural gas pipeline network.

[0046] A small amount of natural gas (9.8 MPa, 25°C, 430,000 m³ / day) used to power the compressed energy storage is driven by a secondary expander 11 to rotate a coaxial compressor 12, compressing the qualified dry gas (277,000 m³ / day, ambient temperature, 5 MPa) in the low-pressure storage tank 13 to 10 MPa. The expanded natural gas (5.5 MPa, -13°C, 380,000 m³ / day) in the secondary expander 11 is then combined with the main process natural gas at the inlet of the cryogenic separator 9 and processed. The high-pressure qualified dry gas (62°C, 10 MPa) compressed by the coaxial compressor 12 is cooled (to 45°C) in the two-way heat exchanger 3 and then stored in the high-pressure storage tank 14. During this process, the pressure in the low-pressure storage tank 13 drops from 5 MPa to a minimum of 1 MPa, while the pressure in the high-pressure storage tank 14 rises from 5 MPa to 10 MPa.

[0047] When the system needs to generate additional power, the high-pressure natural gas (150,000 cubic meters / day, ambient temperature, 10 MPa) in high-pressure storage tank 14 is heated to 35°C in bidirectional heat exchanger 3, then expanded to -10°C, 5 MPa in primary energy storage expander 15, heated to 30°C in expansion heat exchanger 4, expanded to -57°C, 1 MPa in secondary energy storage expander 16, and then exchanged at 5°C in outlet heat exchanger 17 before being stored in low-pressure storage tank 13. During this process, the pressure in low-pressure storage tank 13 increases from 1 MPa to a maximum of 5 MPa, while the pressure in high-pressure storage tank 14 decreases from 10 MPa to 5 MPa.

[0048] Taking a low-pressure storage tank (13) with a capacity of 1440 cubic meters and a high-pressure storage tank (14) with a capacity of 1150 cubic meters, a storage time of 5 hours, a power generation time of 4 hours, and a power generation capacity of 380 kW as an example, calculations show that during power generation, the expansion gas volume of high-pressure natural gas in the high-pressure storage tank (14) gradually increases from 150,000 cubic meters / day to 250,000 cubic meters / day to ensure stable power generation of 380 kW.

[0049] By applying the above methods, it is possible to generate electricity by utilizing the pressure energy of the gas storage tank through compressed energy storage, maximize the recovery of system pressure energy, and achieve stable output of power generation.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank, characterized by the following steps: At least including: Use qualified dry gas after dehydration as the circulating medium to pressurize the low-pressure storage tank until the pressure is balanced; While generating electricity from natural gas in the main process, the low-pressure natural gas in the low-pressure storage tank is pressurized, and after heat exchange and cooling of the pressurized high-pressure qualified dry gas, it is passed into the high-pressure storage tank for storage. When the power generation from the main process natural gas expansion is insufficient, the high-pressure qualified dry gas in the high-pressure storage tank is heated by heat exchange and then fed into an energy storage expander that is set up independently of the main expander to generate electricity, in order to supplement the power generation from the main process natural gas expansion.

2. The method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank according to claim 1, characterized by the following steps: It also includes: during power generation, the control center calculates the circulating natural gas flow rate based on the pressure of the low-pressure storage tank, the pressure of the high-pressure storage tank, and the calculated power generation from expansion, and balances the power generation through valve control.

3. A method for generating electricity using the pressure energy of a gas storage tank based on compressed energy storage according to claim 1 or 2, characterized in that, The method for increasing the pressure of low-pressure natural gas in a low-pressure storage tank is as follows: a small amount of natural gas with fluctuating flow rate is used as a driving source to generate electricity through a secondary expander. The secondary expander drives a coaxial compressor to rotate, thereby compressing and increasing the pressure of the low-pressure natural gas in the low-pressure storage tank.

4. The method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank according to claim 3, characterized in that, The heat exchange and cooling of the high-pressure qualified dry gas after pressurization is specifically as follows: the high-pressure qualified dry gas after pressurization by the coaxial compressor is introduced into the bidirectional heat exchanger to exchange heat with the natural gas before expansion and cool down. The cooled high-pressure qualified dry gas is then introduced into the high-pressure storage tank for storage.

5. A method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank, as described in claim 3, characterized in that, The expanded natural gas in the auxiliary expander merges with the expanded natural gas from the main process in the main expander at the inlet of the cryogenic separator and then enters the cryogenic separator.

6. The method for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank according to claim 1, characterized in that, The high-pressure qualified dry gas in the high-pressure storage tank is introduced into a two-way heat exchanger, where it exchanges heat with the natural gas before expansion and is then introduced into the first-stage expander of the energy storage system for expansion and power generation. The expanded natural gas in the first-stage expander is then introduced into an expansion heat exchanger for further heat generation, and then into a second-stage expander for further expansion and power generation. The expanded natural gas in the second-stage expander is then introduced into an outlet heat exchanger for further heat exchange and is then introduced into a low-pressure storage tank for storage.

7. A system for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank, for implementing the method as described in any one of claims 1-6, characterized in that, At least including: The auxiliary expander (11) is connected to the main process natural gas power generation pipeline through a branch line to introduce a small amount of natural gas with fluctuating flow rate as a power device for compressed energy storage; A coaxial compressor (12) is connected between the auxiliary expander (11) and the low-pressure storage tank (13) to provide power from the auxiliary expander (11) to the coaxial compressor (12) to compress the low-pressure natural gas in the low-pressure storage tank (13) to a high-pressure state; the coaxial compressor (12) is also connected to the main process natural gas power generation pipeline; The low-pressure storage tank (13) is used for low-pressure natural gas storage and is also connected to the main process natural gas power generation pipeline and the outlet heat exchanger (17). High-pressure storage tank (14) is used for high-pressure natural gas storage and is connected to the main process natural gas power generation pipeline; The primary energy storage expander (15) is used to supplement power generation. It is connected to the high-pressure storage tank (14) and the secondary energy storage expander (16) through the main process natural gas power generation pipeline. The secondary energy storage expander (16) is used to supplement power generation and is also connected to the outlet heat exchanger (17).

8. A system for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank, as described in claim 7, is characterized in that... It also includes a control center (22), which is electrically connected to at least the electric valves of the primary energy storage expander (15), the electric valves of the secondary energy storage expander (16), and the flow meter (23) and regulating valve b (24) located between the high-pressure storage tank (14) and the main process natural gas power generation pipeline.

9. A system for generating electricity using the pressure energy of a gas storage tank based on compressed energy storage as described in claim 7 or 8, characterized in that, The main process natural gas power generation pipeline includes a main heat exchanger (1), a preheater (2), a bidirectional heat exchanger (3), an expansion heat exchanger (4), a liquid separator (5), a main expander (8), and a cryogenic separator (9) connected in sequence by pipelines. The main heat exchanger (1) is used for centralized heat exchange of the extracted natural gas and is also connected to a low-pressure storage tank (13), a high-pressure storage tank (14), a cryogenic separator (9), and an outlet heat exchanger (17). The bidirectional heat exchanger (3) is also connected to the high-pressure storage tank (14), the first-stage energy storage expander (15), and the coaxial compressor (12), respectively. The expansion heat exchanger (4) is also connected to the first-stage energy storage expander (15) and the second-stage energy storage expander (16), respectively. The pipeline at the rear end of the liquid separator (5) is connected to the auxiliary expander (11) through a branch.

10. A system for generating electricity using compressed energy storage to balance the pressure energy of a gas storage tank, as described in claim 9, characterized in that, The auxiliary expander (11) is also connected to the front end pipeline of the cryogenic separator (9) so that the expanded natural gas in the auxiliary expander (11) and the expanded natural gas in the main expander (8) can be combined and then enter the cryogenic separator (9).

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