Air energy storage system based on natural gas cold energy utilization

Abstract

The invention discloses an air energy storage system based on natural gas cold energy utilization. The air energy storage system comprises a primary compressor for compressing air, and the inlet end of the primary compressor is connected with an air purification assembly; the first heat exchanger is arranged at the output end of the first-stage compressor; the second-stage compressor is arranged at the output end of the first heat exchanger so as to compress the air again, and a second heat exchanger is arranged at one end of the second-stage compressor; the air purification module is arranged, the dust filter and the adsorption tower are arranged at a raw material gas inlet, raw material gas is pretreated, dust is filtered, water molecules and CO2 are adsorbed, the phenomena that a pipeline is frozen and blocked and a compressor is damaged in the compression working section are avoided, the safety of equipment is improved, a unique propane heat recovery system is adopted, and the energy consumption is reduced. Heat energy generated in the low-pressure air compression process and cold energy generated by the high-pressure air turbine are exchanged, and gradient utilization and efficient conversion of energy are achieved.

Description

Technical Field

[0001] The present invention specifically relates to an air energy storage system based on the utilization of natural gas cold energy. Background Art

[0002] Traditionally, in order for low-temperature LNG to be safely introduced into the pipeline system and delivered to the user end, the liquefied natural gas must be pressurized and then heated to vaporize. Common vaporization methods include: air vaporization, seawater vaporization or natural gas supplementary combustion vaporization. This process not only leads to a large amount of waste of high-grade cold energy, but also consumes additional resources to complete the vaporization process, which is obviously contrary to the current global trend of energy conservation, emission reduction and improving energy efficiency.

[0003] The existing utility model patent 201620524259.0 introduces a compressed air energy storage system that utilizes LNG cold energy. LNG is used to cool the inlet air of each compressor stage, so that the power consumption of obtaining high-pressure air with the same working capacity is reduced, thereby realizing the recovery of LNG cold energy and converting LNG cold energy into the internal energy of compressed air; at the same time, LNG and air are exchanged in a heat exchanger, and heat exchange with a small temperature difference can be achieved through the heat exchanger, thereby maximizing the LNG cold energy recovery efficiency; Utility Model 202122357671.1 provides a low-temperature power generation integrated energy system that fully utilizes cold and heat energy and efficiently stores energy. This system can not only effectively utilize the cold released during LNG vaporization, but also effectively utilize the heat released during the compressed air process, thereby significantly improving the power generation efficiency of the waste heat power generation system. On the other hand, due to the effective utilization of low-temperature LNG cold energy, the energy storage efficiency of liquefied compressed air energy storage is also significantly improved.

[0004] From the above existing patented technology, it can be seen that the raw gas has not been processed in any way, and the air contains dust, a small amount of water molecules and CO 2 In the process of compressing air, solids are produced, which freeze the pipeline and damage the compressor. In addition, the direct heat exchange between LNG and the high-temperature air in the compression stage causes a large temperature difference in heat transfer, which makes its cold energy recovery efficiency low and its economy poor. For this reason, we propose an air energy storage system based on the utilization of natural gas cold energy. Summary of the invention

[0005] The purpose of the present invention is to provide an air energy storage system based on the utilization of natural gas cold energy to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: an air energy storage system based on natural gas cold energy utilization, comprising:

[0007] For a first-stage compressor for air compression, an inlet end of the first-stage compressor is connected to an air purification component;

[0008] A first heat exchanger is arranged at the output end of the first-stage compressor;

[0009] A secondary compressor is arranged at the output end of the first heat exchanger to re-compress the air, and one end of the secondary compressor has a second heat exchanger;

[0010] A cold box is arranged at the output end of the second heat exchanger to cool the compressed air using the cold capacity of the LNG, and the output end of the cold box is connected to a liquid air storage tank;

[0011] An energy release component connected to the output end of the liquid air storage tank to generate electricity using the energy of the liquid air during vaporization;

[0012] A propane heat storage module is connected to the output end of the first heat exchanger, and the output end of the propane heat storage module cooperates with the energy release component;

[0013] The propane cold storage module is connected to the input end of the first heat exchanger.

[0014] Preferably, the air purification component includes a first dust filter, an adsorption component and a second dust filter, the second dust filter is connected to the input end of the first-stage compressor, and the input end of the second dust filter is sequentially connected to the adsorption component and the first dust filter.

[0015] Preferably, the energy release component includes a centrifugal pump, a third heat exchanger, a first-stage expansion machine, a fourth heat exchanger, a second-stage expansion machine and a fifth heat exchanger. The centrifugal pump is connected to the output end of the liquid air storage tank, and the output end of the centrifugal pump has a third heat exchanger. One end of the third heat exchanger is connected to the first-stage expansion machine. The fourth heat exchanger is connected to the output end of the first-stage expansion machine to release cold energy to the outside. The output end of the fourth heat exchanger is connected to the second-stage expansion machine, and the third heat exchanger and the second-stage expansion machine are both connected to the external grid-connected generator set through a first pipeline. The output end of the second-stage expansion machine is connected to the fifth heat exchanger.

[0016] Preferably, the third heat exchanger, the fourth heat exchanger and the fifth heat exchanger are all connected to the input end of the propane cold storage module through the second pipeline to provide cold energy to the propane cold storage module.

[0017] Preferably, the output end of the propane heat storage module is connected to the third heat exchanger, the fourth heat exchanger and the fifth heat exchanger through a third pipeline to supplement the heat when the liquid air is vaporized.

[0018] Preferably, the input end of the propane heat storage module is connected to a heating module.

[0019] Preferably, the output end of the propane cold storage module is connected to the first heat exchanger, the second heat exchanger and the LNG storage tank through cold supply pipes respectively.

[0020] Preferably, the other output end of the cold box is connected to a three-stage compressor for pressurizing the natural gas.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) With air purification module, the raw gas in previous designs was not treated in any way, and the air contained dust, a small amount of water molecules and CO 2 In the process of compressing air, solids are generated, which freeze the pipeline and damage the compressor. This design sets a dust filter and adsorption tower at the inlet of the raw gas to pre-treat the raw gas, filter the dust and adsorb water molecules and CO at the same time. 2 , avoiding the phenomenon of pipeline freezing and compressor damage in the compression section, improving the safety of the equipment. In addition, compared with the traditional direct expansion method and compressed carbon dioxide method, the present invention compresses and liquefies air by utilizing LNG cold energy, which is convenient for improving the energy recovery rate and making more effective use of cold energy.

[0023] (2) A unique propane heat recovery system is used to exchange the heat energy generated during the low-pressure air compression process with the cold energy generated by the high-pressure air turbine, so that energy can be utilized in a cascade and converted efficiently. A heating module is added to improve the system's circulation when the heat energy is insufficient. In addition, the use of liquid air energy storage has the advantages of high energy density, clean and low carbon, high safety and direct discharge, and has great development potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] In the figure: 1. first dust filter; 2. adsorption component; 3. second dust filter; 4. primary compressor; 5. first heat exchanger; 6. secondary compressor; 7. second heat exchanger; 8. cold box; 9. LNG storage tank; 10. third compressor; 11. liquid air storage tank; 12. centrifugal pump; 13. third heat exchanger; 14. primary expander; 15. fourth heat exchanger; 16. secondary expander; 17. fifth heat exchanger; 18. propane cold storage module; 19. propane heat storage module; 20. heating module. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0027] See also Figure 1 The present invention provides a technical solution: an air energy storage system based on the utilization of natural gas cold energy, comprising:

[0028] For the first-stage compressor 4 for air compression, an inlet end of the first-stage compressor 4 is connected with an air purification component;

[0029] It is convenient to purify the air and avoid solids generated during the air compression process, which may cause freezing of the pipeline and damage to the compressor;

[0030] The first heat exchanger 5 is arranged at the output end of the first-stage compressor 4;

[0031] A secondary compressor 6 is arranged at the output end of the first heat exchanger 5 to re-compress the air, and one end of the secondary compressor 6 has a second heat exchanger 7;

[0032] Facilitates the compression of purified air;

[0033] A cold box 8 is arranged at the output end of the second heat exchanger 7 to cool the compressed air using the cold capacity of the LNG, and the output end of the cold box 8 is connected to a liquid air storage tank 11;

[0034] It is convenient to liquefy and store air for subsequent reuse;

[0035] An energy release component connected to the output end of the liquid air storage tank 11 to generate electricity using the energy of the liquid air during vaporization;

[0036] The propane heat storage module 19 is connected to the output end of the first heat exchanger 5, and the output end of the propane heat storage module 19 cooperates with the energy release component;

[0037] The propane cold storage module 18 is connected to the input end of the first heat exchanger 5 .

[0038] Compared with existing technologies, they include: 1. Direct use of LNG cold energy, such as food cold storage, plastic crushing, etc. The temperature required for cold storage is much higher than that of LNG, and the large heat transfer temperature difference leads to low cold energy recovery efficiency. 2. Direct expansion method of energy storage, first compressing liquefied natural gas into high-pressure liquid, then heated to room temperature by seawater through a heat exchanger, and then expanding through a turbine to output electrical energy. The advantage of this cycle is that the cycle process is simple and requires less equipment, but the cold energy of LNG is not fully utilized, and the energy recovery rate is low. 3. Compressed carbon dioxide energy storage, using LNG cold energy to achieve CO 2 The compression and liquefaction of liquid CO achieves energy storage. This method has strict gas source requirements. 2 After the turbine works, an additional gas storage tank is needed to store the gaseous CO 2 , increasing equipment costs.

[0039] In view of these shortcomings, the present invention makes full use of the cold energy changes in the process of LNG vaporization entering the pipeline network, realizes the purpose of energy storage by compressing and liquefying air, and releases energy to drive the generator to generate electricity during the gasification, heating and expansion process of liquid air when the power demand is tight. In addition, liquid air has the advantages of high energy storage density, wide application occasions, easy access to raw materials and direct discharge, etc. It provides a new way for the efficient use of LNG cold energy, thereby realizing the cascade utilization and efficient conversion of energy.

[0040] Preferably, the air purification component comprises a first dust filter 1, an adsorption component 2 and a second dust filter 3, the second dust filter 3 is connected to the input end of the first-stage compressor 4, and the input end of the second dust filter 3 is sequentially connected to the adsorption component 2 and the first dust filter 1;

[0041] The air first passes through the dust filter, which helps to remove solid particles, dust and other impurities in the air and protect subsequent equipment from damage. Molecular sieves and CO are used in the adsorption components. 2 Adsorbents to remove moisture and CO from the air 2 To avoid liquid formation or freezing during the subsequent compression process, which would affect system operation.

[0042] Preferably, the energy release component includes a centrifugal pump 12, a third heat exchanger 13, a first-stage expansion machine 14, a fourth heat exchanger 15, a second-stage expansion machine 16 and a fifth heat exchanger 17. The centrifugal pump 12 is connected to the output end of the liquid air storage tank 11, and the output end of the centrifugal pump 12 has a third heat exchanger 13. One end of the third heat exchanger 13 is connected to the first-stage expansion machine 14. The fourth heat exchanger 15 is connected to the output end of the first-stage expansion machine 14 to release cold energy to the outside. The output end of the fourth heat exchanger 15 is connected to the second-stage expansion machine 16, and the third heat exchanger 13 and the second-stage expansion machine 16 are both connected to the external grid-connected generator set through a first pipeline. The output end of the second-stage expansion machine 16 is connected to the fifth heat exchanger 17.

[0043] When the grid load is high and the electricity price is expensive, the system enters the energy release stage, and the liquid air passes through the centrifugal pump 12, and then is pressurized to 4MPa, and is heated to room temperature through the heat exchanger. The core of this stage is to convert the stored liquid air into gaseous air, release energy through the expander, and supply the grid with energy.

[0044] Preferably, the third heat exchanger 13 , the fourth heat exchanger 15 and the fifth heat exchanger 17 are all connected to the input end of the propane cold storage module 18 through the second pipeline to provide cold energy to the propane cold storage module 18 .

[0045] The cold energy generated during the air compression process is recovered through the cold storage module 18 and used in the subsequent air compression and cooling process, so that the cold energy of the system can be used more efficiently.

[0046] Preferably, the output end of the propane heat storage module 19 is connected to the third heat exchanger 13, the fourth heat exchanger 15 and the fifth heat exchanger 17 through a third pipeline to supplement the heat of the liquid air during vaporization.

[0047] The heat storage module 19 is used to recover the heat released by the expander, which can be used to vaporize liquid air or reheat the gas to ensure that there is no temperature imbalance when the system is running.

[0048] Preferably, the input end of the propane heat storage module 19 is connected to a heating module 20 .

[0049] If the heat storage module 19 does not have enough heat, the system provides additional heat through the heating module 20 to ensure that the compressed air can smoothly pass through the subsequent reheating and gasification process.

[0050] Preferably, the output end of the propane cold storage module 18 is connected to the first heat exchanger 5, the second heat exchanger 7 and the LNG storage tank 9 through cold supply pipes, respectively.

[0051] Preferably, the other output end of the cold box 8 is connected to a three-stage compressor 10 for pressurizing the natural gas.

[0052] After the natural gas cold energy is utilized, it is pressurized by the three-stage compressor 10 and heated to room temperature, and finally flows into the natural gas pipeline network.

[0053] Working principle and use process of the present invention: When in use, the air first passes through the first dust filter 1 to filter out impurities such as solid particles carried in the air, and then enters the adsorption component 2, which is mainly composed of an adsorption tower with double-layer fillers, namely molecular sieve and CO 2 The adsorbent removes water molecules and CO from the air. 2 Remove to avoid the generation of liquid before entering the secondary compressor 6, and prevent the pipeline from freezing and blocking. Install a second dust filter 3 at the outlet of the adsorption component 2 to prevent dust in the molecular sieve from falling and damaging the compressor. Then the purified air enters the primary compressor 4 and is pressurized to 1.8Mpa, and then enters the first heat exchanger 5 to reduce the temperature to about 40°C. The medium-pressure air enters the secondary compressor 6 again, pressurizing the air to 3.6Mpa, and then enters the second heat exchanger 7 to reduce the temperature to about 40°C. The cooled high-pressure air enters the cold box 8 for heat exchange, and the outlet temperature is reduced to -146°C. At this time, the high-pressure air is completely liquefied and enters the liquid air storage tank 11 for storage. LNG enters the cold box 8 after being pressurized from the LNG storage tank 9 as a cold logistics to exchange heat with the high-pressure air, and finally cools to about -50°C and is completely vaporized. The natural gas is pressurized by the three-stage compressor 10 and heated to room temperature, and finally flows into the natural gas pipeline network;

[0054] When the grid load is high and the electricity price is expensive, the system enters the energy release stage. At this time, the liquid air in the liquid air storage tank 11 is pressurized to 4Mpa by the centrifugal pump 12, and then heat-exchanged to room temperature by the third heat exchanger 13. The normal temperature high-pressure air passes through the first-stage expander 14 to do work externally, and the outlet pressure drops to 2Mpa. The medium-pressure air must pass through the fourth heat exchanger 15 for reheating. After reheating, the medium-pressure air passes through the second-stage expander 16. After the outlet pressure is reduced to normal pressure, the gas temperature drops sharply. The low-temperature air passes through the fifth heat exchanger 17. The cold recovery outlet is restored to normal temperature and then directly discharged; in addition, the system is also provided with a propane cold storage module 18, a propane heat storage module 19 and a heating module 20. The propane cold storage module 18 is used to recover and store the cold energy of the high-pressure air after the expansion machine, and transfer it to the first-stage compression and second-stage compression modules of the air for cooling. Heat transfer is achieved through the heat exchanger, and the transfer medium is propane. When the cooling capacity is insufficient, a small amount of LNG can be used from the LNG storage tank 9 as a cold source to exchange heat with the propane cold storage module 18 to maintain its temperature. The propane heat storage module 19 is used to recover and store the heat generated by the air compression module, which is used in the process of vaporization and reheating of the high-pressure air by the vaporization module and the expander module. The heating module 20 is a heat supplement for the propane heat storage module 19. This technical solution designs the above heat recovery system, so that the heat at each stage is fully utilized and the energy utilization rate of the system is improved;

[0055] Energy storage stage: When the power grid is at a low point or when renewable energy is in surplus, electric energy is used to drive the compressor to compress the ambient air to a high pressure state. Subsequently, the high-pressure air is heat-exchanged with the cold energy of LNG through a heat exchanger to rapidly cool and liquefy it. The liquid air is stored in a cryogenic storage tank at normal pressure and low temperature, while the compression heat generated during the compression process is recovered and stored; Energy release stage: When energy needs to be released, the liquid air is first pressurized to a higher pressure by a cryogenic pump, and then vaporized after multi-stage heating. The vaporized high-pressure air is heated to a high temperature and high pressure state to drive the turbine generator to generate electricity and connect to the grid.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An air energy storage system based on natural gas cold energy utilization, characterized in that: include: A first-stage compressor (4) for compressing air, wherein the inlet end of the first-stage compressor (4) is connected to an air purification component; A first heat exchanger (5) is arranged at the output end of the first-stage compressor (4); A secondary compressor (6) is arranged at the output end of the first heat exchanger (5) to re-compress the air, and one end of the secondary compressor (6) is provided with a second heat exchanger (7); A cold box (8) is arranged at the output end of the second heat exchanger (7) to cool the compressed air using the cold energy of the LNG, and the output end of the cold box (8) is connected to a liquid air storage tank (11); An energy release component connected to the output end of the liquid air storage tank (11) to generate electricity using the energy of the liquid air during vaporization; A propane heat storage module (19) is connected to the output end of the first heat exchanger (5), and the output end of the propane heat storage module (19) cooperates with the energy release component; The propane cold storage module (18) is connected to the input end of the first heat exchanger (5).

2. The air energy storage system based on natural gas cold energy utilization according to claim 1 is characterized in that: The air purification component comprises a first dust filter (1), an adsorption component (2) and a second dust filter (3), wherein the second dust filter (3) is connected to the input end of a first-stage compressor (4), and the input end of the second dust filter (3) is connected to the adsorption component (2) and the first dust filter (1) in sequence.

3. The air energy storage system based on natural gas cold energy utilization according to claim 1 is characterized in that: The energy release component comprises a centrifugal pump (12), a third heat exchanger (13), a first-stage expansion machine (14), a fourth heat exchanger (15), a second-stage expansion machine (16) and a fifth heat exchanger (17). The centrifugal pump (12) is connected to the output end of the liquid air storage tank (11), and the output end of the centrifugal pump (12) has a third heat exchanger (13). One end of the third heat exchanger (13) is connected to the first-stage expansion machine (14). The fourth heat exchanger (15) is connected to the output end of the first-stage expansion machine (14) to release cold energy to the outside. The output end of the fourth heat exchanger (15) is connected to the second-stage expansion machine (16). The third heat exchanger (13) and the second-stage expansion machine (16) are both connected to an external grid-connected generator set through a first pipeline. The output end of the second-stage expansion machine (16) is connected to the fifth heat exchanger (17).

4. The air energy storage system based on natural gas cold energy utilization according to claim 3 is characterized in that: The third heat exchanger (13), the fourth heat exchanger (15) and the fifth heat exchanger (17) are all connected to the input end of the propane cold storage module (18) through the second pipeline to provide cold energy to the propane cold storage module (18).

5. The air energy storage system based on natural gas cold energy utilization according to claim 3 is characterized in that: The output end of the propane heat storage module (19) is connected to the third heat exchanger (13), the fourth heat exchanger (15) and the fifth heat exchanger (17) through a third pipeline to supplement the heat generated when the liquid air is vaporized.

6. The air energy storage system based on natural gas cold energy utilization according to claim 1 is characterized in that: The input end of the propane heat storage module (19) is connected to a heating module (20).

7. The air energy storage system based on natural gas cold energy utilization according to claim 1 is characterized in that: The output end of the propane cold storage module (18) is connected to the first heat exchanger (5), the second heat exchanger (7) and the LNG storage tank (9) respectively through cold supply pipes.

8. The air energy storage system based on natural gas cold energy utilization according to claim 1 is characterized in that: The other output end of the cold box (8) is connected to a three-stage compressor (10) for pressurizing the natural gas.

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