A multifunctional system of energy storage, carbon capture and air conditioning using LNG cold energy

Abstract

This invention discloses a multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, belonging to the field of distributed energy supply technology. It is divided according to the LNG supply sequence, comprising an LNG supply unit, a carbon capture unit, a compressed carbon dioxide energy storage and release unit, a Karina cycle power generation unit, and an air conditioning unit. The LNG supply unit is sequentially connected to the carbon capture unit, carbon dioxide energy storage and release unit, Karina cycle power generation unit, and air conditioning unit. This invention, through the combined use of the carbon capture system, carbon dioxide energy storage system, Karina cycle power generation system, and air conditioning system, rationally and scientifically solves the problems of insufficient utilization of LNG cold energy and the mismatch between LNG cold energy temperature and actual demand, realizing the cascade utilization of LNG cold energy and reducing LNG cold energy waste.

Description

Technical Field

[0001] This invention relates to a multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, belonging to the field of distributed energy supply technology. Background Technology

[0002] Distributed combined cooling, heating, and power (CCHP) systems are increasingly recognized for their significant advantages in efficiency, utility, and preferred energy supply. Various types of CCHP systems are being applied in different sectors due to their advantages, improving energy cascade utilization, matching supply and demand through energy storage and demand-side management, and contributing to the reduction of carbon dioxide emissions. Integrating and utilizing renewable energy and LNG cooling energy into CCHP systems can meet the requirements of energy sustainability.

[0003] A compressed carbon dioxide energy storage system is a novel type of energy storage system that uses carbon dioxide as the working fluid. During periods of low electricity demand, the system compresses and stores renewable energy or surplus electricity in tanks, while simultaneously recovering the heat of compression during the charging process. During periods of high electricity demand, the high-pressure carbon dioxide in the tanks is reheated, and the energy is released by using a turbine expander to perform work.

[0004] Current proposed compressed carbon dioxide energy storage systems require storage tanks to store carbon dioxide. Storing carbon dioxide in gaseous form reduces the system's energy density; storing it in liquid form necessitates the use of cryogenic cold storage devices to achieve a self-condensation process. However, this self-condensation process can reduce system cycle efficiency, and due to the temperature limitations of conventional cooling water, especially in summer conditions, the low critical temperature of CO2 (31.1℃) may have a potential negative impact on condensation activities. Therefore, cryogenic cold sources such as LNG are needed to liquefy low-pressure carbon dioxide.

[0005] LNG (Liquid Natural Gas) undergoes multiple stages of regasification before being delivered to end users. During regasification, LNG releases a significant amount of cold energy (approximately 840 kJ / kg). To avoid wasting this energy, it can be used for the condensation and liquefaction of compressed carbon dioxide, and subsequently for post-combustion carbon capture, the Kalina condensation process, and for supplying cooling to end users. The regasified natural gas can be burned as fuel, with the waste heat from the flue gas serving as a heat source for the Kalina subcycle and for supplying heat to end users.

[0006] The carbon capture system, as a subsystem of the combined heat and power generation system utilizing LNG energy, uses the cold energy of LNG to separate and capture the carbon dioxide produced during the combustion of natural gas, and finally transport it to a carbon dioxide storage tank.

[0007] As a terminal subsystem, the air conditioning system utilizes the cold energy of the high-temperature section of LNG to vaporize the LNG and use the cold energy to cool and dehumidify the outdoor air, delivering the dehumidified and cool air to the indoor user end.

[0008] The patent document with publication number CN109854320A proposes a combined power generation system based on LNG cold energy utilization, utilizing carbon dioxide storage and an organic Rankine cycle. This system aims to utilize the cold energy of LNG by combining carbon dioxide storage and release processes with an organic Rankine cycle to achieve the cascaded utilization of LNG cold energy and convert it into electricity. While this patent fully utilizes the cold energy of LNG, it does not achieve the goal of combined cooling, heating, and power (CCHP), thus reducing the cascaded utilization rate of energy.

[0009] In the patent document with authorization publication number CN115750009A, an energy storage power peak shaving system for carbon capture and liquefied natural gas cold energy utilization is proposed. It utilizes LNG cold energy to meet the cooling needs of liquid air storage and CO2 capture processes, as well as the heat energy generated by LNG combustion, but the system cannot regulate the indoor thermal environment.

[0010] The patent document with publication number CN114033517A proposes a novel geothermal power generation and heating / cooling supply system based on compressed carbon dioxide energy storage. This system utilizes a heat recovery system to collect the heat generated during compression and the waste heat from the turbine exhaust gas, which can then be used to drive a lithium bromide chiller to provide cooling, or connected to a city heating network for heating. However, due to the temperature limitations of geothermal energy, the system generates limited heat and cooling energy, making it difficult to meet the needs of diverse users.

[0011] Therefore, it is necessary to design a multifunctional system that combines LNG cold energy utilization with energy storage, carbon capture, and air conditioning to address the aforementioned issues. Summary of the Invention

[0012] This invention addresses the technical problems mentioned in the background section by aiming at a distributed energy supply technology that couples liquid carbon dioxide energy storage, LNG cold energy utilization, the Karina cycle, carbon capture, and air conditioning. This further improves the multi-level utilization rate of LNG cold energy and combustion heat, while utilizing carbon capture technology to solve the problem of flue gas emissions. It also provides users with heat, cold energy, electricity, dehumidified air, and clean water, achieving the goals of energy conservation and emission reduction. Specifically, the following technical solutions are adopted to achieve this:

[0013] A multifunctional system for LNG cold energy utilization, including energy storage, carbon capture and air conditioning, is divided according to the LNG supply sequence and includes an LNG supply unit, a carbon capture unit, a compressed carbon dioxide energy storage and release unit, a Karina cycle power generation unit and an air conditioning unit.

[0014] The LNG supply unit is sequentially connected to the carbon capture unit, the carbon dioxide storage and release unit, the Karina cycle power generation unit, and the air conditioning unit. The LNG supply unit is equipped with a first-stage LNG heat exchanger, a second-stage LNG heat exchanger, a third-stage LNG heat exchanger, and a fourth-stage LNG heat exchanger. These are used to exchange heat with the carbon capture unit through the first-stage LNG heat exchanger, with the compressed carbon dioxide storage and release unit through the second-stage LNG heat exchanger, with the Karina cycle power generation unit through the third-stage LNG heat exchanger, and with the air conditioning unit through the fourth-stage LNG heat exchanger. This provides the user side with heat, cold energy, electricity, dehumidified cold air, and clean water, realizing the function of distributed energy supply.

[0015] As a preferred example, the LNG supply unit further includes an LNG storage tank and an LNG pump;

[0016] The carbon capture unit includes a carbon capture gas-liquid separator, a liquid carbon dioxide storage tank, a flue gas reheater, a flue gas expander, and a flue gas compressor.

[0017] The air conditioning unit includes a clean water storage tank, a dew point condenser, and a fan;

[0018] The outlet of the LNG storage tank is connected to the inlet of the LNG pump via a pipeline; the outlet pipeline of the LNG pump is connected to the LNG side pipeline of the first-stage LNG heat exchanger.

[0019] The high-temperature side outlet of the first-stage LNG heat exchanger is connected to the inlet of the carbon capture gas-liquid separator. The flue gas is connected in sequence to the flue gas compressor and the high-temperature side pipeline of the first-stage LNG heat exchanger through the high-temperature side pipeline of the flue gas regenerator. The gas phase outlet of the carbon capture gas-liquid separator is connected to the low-temperature side pipeline of the flue gas regenerator. One end of the carbon capture gas-liquid separator is connected to a liquid carbon dioxide storage tank for storing the liquid carbon dioxide separated by the carbon capture gas-liquid separator in the liquid carbon dioxide storage tank. The low-temperature side pipeline outlet of the flue gas regenerator is connected to the inlet of the flue gas expander.

[0020] The refrigerant water outlet of the four-stage LNG heat exchanger is connected to the indoor user via a pipeline; the LNG side pipeline of the four-stage LNG heat exchanger is an LNG coil, which is coiled inside the dew point condenser; the fan is connected to the dew point condenser and is used to send outdoor air into the dew point condenser, and then send the dehumidified cold air to the indoor user side via the LNG coil; the water collection pan outlet at the bottom of the dew point condenser is connected to the inlet of the clean water storage tank via a pipeline; this is used to finally transport the vaporized LNG to the natural gas power plant.

[0021] Furthermore, the LNG stored in the LNG storage tank is cryogenic and low-pressure LNG (-162℃, 0.13MPa).

[0022] The low-temperature flue gas entering the carbon trap gas-liquid separator is separated into a mixture of liquid carbon dioxide and gaseous nitrogen and oxygen at -150℃ and 0.23MPa.

[0023] As a preferred example, the compressed carbon dioxide energy storage and release unit includes a low-pressure carbon dioxide storage tank, a carbon dioxide regenerator, a carbon dioxide compressor, a cold storage heat exchange device, a high-pressure carbon dioxide storage tank, a heat storage heat exchange device, a carbon dioxide expander, a cold storage medium storage tank, a heat storage medium storage tank, and a flow control valve.

[0024] The outlet of the low-pressure carbon dioxide storage tank is connected to the low-temperature side inlet of the carbon dioxide regenerator; the low-temperature side outlet of the carbon dioxide regenerator is connected to the inlet of the carbon dioxide compressor through a pipeline.

[0025] The outlet of the carbon dioxide compressor is connected to the inlet of the high-temperature side pipeline of the cold storage heat exchange device via a pipeline.

[0026] The high-temperature side pipeline outlet of the cold storage heat exchange device is connected to the high-temperature side pipeline inlet of the carbon dioxide regenerator via a pipeline; the high-temperature side pipeline outlet of the carbon dioxide regenerator is connected to the inlet of the high-pressure carbon dioxide storage tank via a pipeline; the outlet of the high-pressure carbon dioxide storage tank is connected to the low-temperature side pipeline inlet of the heat storage heat exchange device; and the low-temperature side pipeline outlet of the heat storage heat exchange device is connected to the inlet of the carbon dioxide expander via a pipeline.

[0027] The outlet of the carbon dioxide expander is connected to the high-temperature side pipeline inlet of the secondary LNG heat exchanger via a pipeline.

[0028] The high-temperature side pipeline outlet of the secondary LNG heat exchanger is connected to the inlet of the low-pressure carbon dioxide storage tank via a pipeline; the outlet of the cold storage medium storage tank is connected to the inlet of the low-temperature side pipeline of the cold storage heat exchange device; the outlet of the low-temperature side pipeline of the cold storage heat exchange device is connected to the inlet of the heat storage medium storage tank via a pipeline; the outlet of the heat storage medium storage tank is connected to two pipelines, one of which is connected to the high-temperature side pipeline inlet of the heat storage heat exchange device, and the other pipeline leads to the user side.

[0029] Furthermore, the low-pressure carbon dioxide storage tank stores low-temperature, low-pressure liquid carbon dioxide (-53℃, 0.6MPa).

[0030] The high-pressure carbon dioxide storage tank stores carbon dioxide in a critical state (55.22℃, 14MPa).

[0031] After expansion and work, the low-temperature, low-pressure carbon dioxide (-5℃, 0.6MPa) is cooled and converted into liquid carbon dioxide (-53℃, 0.6MPa) by a two-stage LNG heat exchanger and stored in a low-pressure carbon dioxide storage tank.

[0032] As a preferred example, a first throttling valve is provided on the pipeline connecting the low-pressure carbon dioxide storage tank and the carbon dioxide regenerator.

[0033] As a preferred example, a second throttle valve is also provided on the pipeline between the high-pressure carbon dioxide storage tank and the heat storage and heat exchange device.

[0034] As a preferred example, the pipeline between the cold storage medium tank and the cold storage heat exchange device is also equipped with a cold storage medium pressurization pump, which is used to transport the medium in the cold storage medium tank to the cold storage heat exchange device.

[0035] As a preferred example, one of the outlet pipes of the heat storage medium tank is connected to the user side via a flow control valve.

[0036] As a preferred example, the Karina cycle power generation unit includes a low-temperature regenerator, a high-temperature regenerator, an evaporator, a Karina cycle gas-liquid separator, and an ammonia expander;

[0037] The outlet of the high-temperature side pipeline of the three-stage LNG heat exchanger is connected to the inlet of the low-temperature side pipeline of the low-temperature regenerator via a pipeline; the outlet of the low-temperature side pipeline of the low-temperature regenerator is connected to the inlet of the low-temperature side pipeline of the high-temperature regenerator via a pipeline; the outlet of the low-temperature side pipeline of the high-temperature regenerator is connected to the inlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator via a pipeline; the outlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator is connected to the inlet of the Karina circulating gas-liquid separator via a pipeline; the gas phase outlet of the Karina circulating gas-liquid separator is connected to the inlet of the ammonia expander; the liquid phase outlet of the Karina circulating gas-liquid separator is connected to the inlet of the high-temperature side pipeline of the high-temperature regenerator; the outlet of the ammonia expander and the high-temperature side pipeline of the high-temperature regenerator are connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the high-temperature side pipeline of the low-temperature regenerator via a pipeline; the outlet of the high-temperature side pipeline of the low-temperature regenerator is connected to the inlet of the high-temperature side pipeline of the three-stage LNG heat exchanger via a pipeline.

[0038] As a preferred example, a Karina circulating working fluid pump is also installed on the connecting pipeline between the cryogenic regenerator and the three-stage LNG heat exchanger.

[0039] Furthermore, the circulating working fluid in the Karina circulating working fluid pump is a saturated ammonia water mixture with a concentration of 82%;

[0040] The ammonia solution receives low-temperature waste heat from the flue gas in the Karina circulating evaporator and then enters the Karina circulating gas-liquid separator, where it is separated into ammonia gas and lean ammonia solution.

[0041] As a preferred example, the outlet of the ammonia expander is connected to the high-temperature side pipeline of the high-temperature regenerator by a Karina circulation throttle valve.

[0042] The beneficial effects of this invention are:

[0043] 1. This invention, through the combined use of a carbon capture system, a carbon dioxide energy storage system, a Karina cycle power generation system, and an air conditioning system, rationally and scientifically solves the problems of insufficient utilization of LNG cold energy and mismatch between LNG cold energy temperature and actual demand, realizes the cascade utilization of LNG cold energy, and reduces the waste of LNG cold energy.

[0044] 2. This invention provides users with thermal energy, cold energy, electrical energy, dehumidified cold air, and clean water, realizing the function of distributed energy supply.

[0045] 3. This invention, while realizing distributed energy supply, stores carbon dioxide from the flue gas emitted by natural gas power plants in a liquid state in storage tanks, thus solving the problem of carbon dioxide emissions from natural gas power plants. (See attached figures for details.)

[0046] Figure 1 This is a schematic diagram of the structure of the present invention;

[0047] In the diagram: 1. LNG storage tank; 2. LNG pump; 3. Primary LNG heat exchanger; 4. Carbon capture gas-liquid separator; 5. Liquid carbon dioxide storage tank; 6. Flue gas regenerator; 7. Flue gas expander; 8. Flue gas compressor; 9. Secondary LNG heat exchanger; 10. Low-pressure carbon dioxide storage tank; 11. First throttle valve; 12. Carbon dioxide regenerator; 13. Carbon dioxide compressor; 14. Cold storage heat exchange device; 15. High-pressure carbon dioxide storage tank; 16. Second throttle valve; 17. Heat storage heat exchange device; 18. Carbon dioxide expander. 18; Cold storage medium tank; 19; Energy storage medium pressurization pump; 20; Heat storage medium tank; 21; Flow control valve; 22; Three-stage LNG heat exchanger; 23; Karina circulating working fluid pump; 24; Low-temperature regenerator; 25; High-temperature regenerator; 26; Karina circulating evaporator; 27; Karina circulating gas-liquid separator; 28; Ammonia expander; 29; High-temperature regenerator outlet throttle valve; 30; Mixer; 31; Four-stage LNG heat exchanger; 32; Clean water storage tank; 33; Dew point condenser; 34; Fan; 35. Detailed Implementation

[0048] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below in conjunction with specific illustrations.

[0049] like Figure 1 As shown, a multifunctional system for LNG cold energy utilization, including energy storage, carbon capture and air conditioning, comprises an LNG supply unit, a carbon capture unit, a compressed carbon dioxide energy storage and release unit, a Karina cycle power generation unit and an air conditioning unit.

[0050] The LNG supply unit is sequentially connected to the carbon capture unit, the carbon dioxide storage and release unit, the Karina cycle power generation unit, and the air conditioning unit. The LNG supply unit is equipped with a first-stage LNG heat exchanger, a second-stage LNG heat exchanger, a third-stage LNG heat exchanger, and a fourth-stage LNG heat exchanger. These are used to exchange heat with the carbon capture unit through the first-stage LNG heat exchanger, with the compressed carbon dioxide storage and release unit through the second-stage LNG heat exchanger, with the Karina cycle power generation unit through the third-stage LNG heat exchanger, and with the air conditioning unit through the fourth-stage LNG heat exchanger. This provides the user with heat, cold energy, electricity, dehumidified cold air, and clean water, realizing the function of distributed energy supply.

[0051] The LNG supply unit includes LNG storage tanks and LNG pumps;

[0052] The carbon capture unit includes a carbon capture gas-liquid separator, a liquid carbon dioxide storage tank, a flue gas reheater, a flue gas expander, and a flue gas compressor.

[0053] The air conditioning unit includes a clean water storage tank, a dew point condenser, and a fan;

[0054] The outlet of LNG storage tank 1 is connected to the inlet of LNG pump 2 via a pipeline; the outlet pipeline of LNG pump 2 is connected to the LNG side pipeline of the first-stage LNG heat exchanger 3.

[0055] The high-temperature side pipe outlet of the first-stage LNG heat exchanger 3 is connected to the inlet of the carbon capture gas-liquid separator 4. The flue gas is connected to the flue gas compressor 8 and the high-temperature side pipe of the first-stage LNG heat exchanger 3 in sequence through the high-temperature side pipe of the flue gas regenerator 6. The gas phase outlet of the carbon capture gas-liquid separator 4 is connected to the low-temperature side pipe of the flue gas regenerator 6. One end of the carbon capture gas-liquid separator is connected to the liquid carbon dioxide storage tank, which is used to store the liquid carbon dioxide separated by the carbon capture gas-liquid separator 4 in the liquid carbon dioxide storage tank 5. The low-temperature side pipe outlet of the flue gas regenerator 6 is connected to the inlet of the flue gas expander 7.

[0056] The chilled water outlet of the four-stage LNG heat exchanger 32 is connected to the indoor user via a pipeline; the LNG side pipeline of the four-stage LNG heat exchanger 32 is an LNG coil, which is coiled inside the dew point condenser 34; the fan 35 is connected to the dew point condenser 34 and is used to send outdoor air into the dew point condenser 34, and send the dehumidified cold air into the indoor user side via the LNG coil; the water collection pan outlet at the bottom of the dew point condenser 34 is connected to the inlet of the clean water storage tank 33 via a pipeline; it is used to finally transport the vaporized LNG to the natural gas power plant.

[0057] The compressed carbon dioxide energy storage and release unit includes a low-pressure carbon dioxide storage tank 10, a carbon dioxide regenerator 12, a carbon dioxide compressor 13, a cold storage heat exchange device 14, a high-pressure carbon dioxide storage tank 15, a heat storage heat exchange device 17, a carbon dioxide expander 18, a cold storage medium storage tank 19, a heat storage medium storage tank 21, and a flow control valve 22.

[0058] The outlet of the low-pressure carbon dioxide storage tank 10 is connected to the low-temperature side inlet of the carbon dioxide regenerator 12; the low-temperature side outlet of the carbon dioxide regenerator 12 is connected to the inlet of the carbon dioxide compressor 13 through a pipeline.

[0059] The outlet of the carbon dioxide compressor 13 is connected to the inlet of the high-temperature side pipeline of the cold storage heat exchange device 14 via a pipeline.

[0060] The high-temperature side pipeline outlet of the cold storage heat exchange device 14 is connected to the high-temperature side pipeline inlet of the carbon dioxide regenerator 12 via a pipeline; the high-temperature side pipeline outlet of the carbon dioxide regenerator 12 is connected to the inlet of the high-pressure carbon dioxide storage tank 15 via a pipeline; the outlet of the high-pressure carbon dioxide storage tank 15 is connected to the low-temperature side pipeline inlet of the heat storage heat exchange device 17; and the low-temperature side pipeline outlet of the heat storage heat exchange device 17 is connected to the inlet of the carbon dioxide expander 18 via a pipeline.

[0061] The outlet of the carbon dioxide expander 18 is connected to the high-temperature side pipeline inlet of the secondary LNG heat exchanger 9 via a pipeline;

[0062] The high-temperature side pipeline outlet of the secondary LNG heat exchanger 9 is connected to the inlet of the low-pressure carbon dioxide storage tank 10 via a pipeline; the outlet of the cold storage medium storage tank 19 is connected to the low-temperature side pipeline inlet of the cold storage heat exchange device 14; the low-temperature side pipeline outlet of the cold storage heat exchange device 14 is connected to the inlet of the heat storage medium storage tank 21 via a pipeline; the outlet of the heat storage medium storage tank 21 is connected to two pipelines, one of which is connected to the high-temperature side pipeline inlet of the heat storage heat exchange device 17, and the other pipeline leads to the user side.

[0063] A first throttle valve 11 is installed on the pipeline connecting the low-pressure carbon dioxide storage tank 10 and the carbon dioxide regenerator 12.

[0064] A second throttle valve 16 is also installed on the pipeline between the high-pressure carbon dioxide storage tank 15 and the heat storage and heat exchange device 17.

[0065] A storage medium pressurization pump 20 is also installed on the pipeline between the cold storage medium storage tank 19 and the cold storage heat exchange device 14, which is used to transport the medium in the cold storage medium storage tank to the cold storage heat exchange device.

[0066] One of the outlet pipes of the heat storage medium tank 21 is connected to the user side through the flow control valve 22.

[0067] The Karina cycle power generation unit includes a low-temperature regenerator 25, a high-temperature regenerator 26, an evaporator 27, a Karina cycle gas-liquid separator 28, and an ammonia expander 29.

[0068] The outlet of the high-temperature side pipeline of the three-stage LNG heat exchanger 23 is connected to the inlet of the low-temperature side pipeline of the low-temperature regenerator 25 via a pipeline; the outlet of the low-temperature side pipeline of the low-temperature regenerator 25 is connected to the inlet of the low-temperature side pipeline of the high-temperature regenerator 26 via a pipeline; the outlet of the low-temperature side pipeline of the high-temperature regenerator 26 is connected to the inlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator 27 via a pipeline; the outlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator 27 is connected to the inlet of the Karina circulating gas-liquid separator 28 via a pipeline; the Karina circulating gas... The gas phase outlet of the liquid separator 28 is connected to the inlet of the ammonia expander 29, and the liquid phase outlet of the Karina circulating gas-liquid separator 28 is connected to the high-temperature side pipeline inlet of the high-temperature regenerator 26; the outlet of the ammonia expander 29 and the high-temperature side pipeline of the high-temperature regenerator 26 are connected to the inlet of the mixer 31; the outlet of the mixer 31 is connected to the high-temperature side pipeline inlet of the low-temperature regenerator 25 through a pipeline; the high-temperature side pipeline outlet of the low-temperature regenerator 25 is connected to the high-temperature side pipeline inlet of the three-stage LNG heat exchanger 23 through a pipeline.

[0069] A circulating working fluid pump 24 is also installed on the connecting pipeline between the low-temperature regenerator 25 and the three-stage LNG heat exchanger 23.

[0070] A Karina circulation throttling valve 30 is connected to the outlet of the ammonia expander 29 and the high-temperature side pipe of the high-temperature regenerator 26.

[0071] Working principle:

[0072] 1. During the energy storage phase, only the carbon dioxide energy storage unit installed in the compressed carbon dioxide energy storage and release unit is operational, as detailed below:

[0073] The low-temperature, low-pressure (-53℃, 0.6Mpa) liquid carbon dioxide supplied by the low-pressure carbon dioxide storage tank 10 passes through the first throttle valve 11 at the outlet of the low-pressure carbon dioxide storage tank 10 (it should be noted that the first throttle valve 11 is a low-pressure throttle valve). Before entering the carbon dioxide compressor 13, it is preheated by the carbon dioxide regenerator 12. After being heated by the carbon dioxide regenerator 12, the liquid carbon dioxide is completely converted into a gas phase and enters the carbon dioxide compressor 13.

[0074] The carbon dioxide compressor 13 is driven by an electric motor to compress and pressurize gaseous carbon dioxide to obtain high-temperature and high-pressure carbon dioxide. The high-temperature and high-pressure carbon dioxide enters the hot-side pipeline of the cold storage heat exchange device 14, absorbing the cold energy stored in the cold storage medium. At the same time, the cold storage medium is heated, and its temperature rises, storing the absorbed heat of compression in the heat storage medium.

[0075] The high-temperature and high-pressure carbon dioxide, after passing through the cold storage and heat exchange device 14 and the carbon dioxide regenerator 12, is stored in the high-pressure carbon dioxide storage tank 15 in a supercritical state (55.22℃, 14MPa), thus ending the energy storage process.

[0076] 2. During the energy release phase, the LNG supply unit, carbon capture unit, carbon dioxide storage and release unit, Karina cycle power generation unit, and air conditioning unit all operate, performing functions such as carbon capture, air conditioning, providing cooling and heating energy, and generating electricity, as detailed below:

[0077] 2.1 Operation of LNG Supply Unit and Carbon Capture Unit: The low-temperature flue gas from the natural gas power plant (molar fractions of components: N2 0.85%, O2 0.1%, CO2 0.05%) undergoes initial cooling through the hot-side piping of the flue gas regenerator 6, and is then pressurized by the flue gas compressor 8. Low-temperature, low-pressure LNG (-162℃, 0.13MPa) flows out from the LNG storage tank 1 and is pressurized (to 8MPa) by the LNG pump 2, pumped to the cold-side piping of the first-stage LNG heat exchanger 3 to absorb heat and increase its temperature. Simultaneously, the flue gas in the first-stage LNG heat exchanger 3 absorbs the cold energy of the LNG, and its temperature decreases. The low-temperature flue gas enters the carbon capture gas-liquid separator 4, where it is separated into a low-temperature (-150℃, 0.23MPa) liquid carbon dioxide and a gaseous nitrogen-oxygen mixture.

[0078] Low-temperature liquid carbon dioxide is stored in liquid carbon dioxide storage tank 5; while gaseous nitrogen-oxygen mixture enters the flue gas regenerator to absorb heat from the low-temperature flue gas, and then enters the flue gas expander 7 to drive the flue gas expander 7 to do work, which in turn drives the generator to generate electricity. Moreover, the low-temperature waste heat of the flue gas from the natural gas power plant can be used as a heat source to provide heat to the Karina cycle unit and users. Thus, the carbon capture unit has achieved the functions of capturing, storing, and providing heat energy from carbon dioxide.

[0079] 2.2 When the outlet valve of the high-pressure carbon dioxide storage tank 15 is opened, the high-pressure carbon dioxide storage tank 15 supplies high-pressure supercritical carbon dioxide, which enters the second throttle valve 16 at the outlet of the high-pressure carbon dioxide storage tank 15 (it should be noted that the second throttle valve 16 is a high-pressure throttle valve) to maintain pressure stability. The carbon dioxide passing through the second throttle valve 16 enters the cold side pipeline of the heat storage and heat exchange device 17, where it absorbs the heat stored in the energy storage stage, and its temperature rises. At the same time, part of the energy storage material in the heat storage and heat exchange device 17 is cooled, and its temperature decreases, while the other part outputs heat energy according to the user's needs. After absorbing heat, the carbon dioxide changes from the supercritical state to the gas phase, and then enters the carbon dioxide expander 18, driving the carbon dioxide expander 18 to do work. The carbon dioxide expander 18 drives the generator to generate electricity for external power supply.

[0080] After expansion and work, the low-temperature, low-pressure carbon dioxide (-5℃, 0.6MPa) still does not reach the temperature required for liquid storage. Therefore, it needs to enter the hot-side pipeline of the secondary LNG heat exchanger 9 at the outlet of the carbon dioxide expander 18 to release heat and lower its temperature. At the same time, the LNG in the secondary LNG heat exchanger 9 absorbs heat and its temperature rises. The cooled carbon dioxide (-53℃, 0.6MPa) becomes liquid and enters the low-pressure carbon dioxide storage tank 10, completing the recovery of the carbon dioxide working fluid.

[0081] 2.3 The Karina cycle power generation unit operates simultaneously, generating electricity externally. LNG passes through a three-stage LNG heat exchanger 23, absorbing heat from the Karina cycle working fluid ammonia water (a saturated ammonia water mixture with a concentration of 82%) in the cold-side pipeline, causing its temperature to rise further. Simultaneously, the ammonia water releases heat in the three-stage LNG heat exchanger 23, causing its temperature to decrease. The condensed ammonia water enters the Karina cycle working fluid pump 24, where it is pressurized and pumped to the low-temperature regenerator 25. In the low-temperature regenerator 25, it absorbs heat from the ammonia solution, causing its temperature to rise. The heated ammonia solution enters the cold-side pipeline of the high-temperature regenerator 26. Simultaneously, the lean ammonia solution in the hot-side pipeline of the high-temperature regenerator 26 releases heat, causing its temperature to decrease. After two heating cycles, the ammonia solution gains low-temperature waste heat from the flue gas in the Karina cycle evaporator 27 and enters the Karina cycle gas-liquid separator 28, where it is separated into ammonia gas and lean ammonia solution. Ammonia gas enters the ammonia expander 29, which drives the ammonia gas to expand and do work. The ammonia expander 29 drives the generator to generate electricity and supply power. After the lean ammonia solution releases heat, it passes through the high-temperature regenerator outlet throttle valve 30 to reduce pressure and cool down. Then it is remixed with ammonia gas in the mixer and restored to the initial concentration.

[0082] 2.4. LNG enters the fourth-stage LNG heat exchanger 32, where the remaining cold energy of the LNG is provided to users in need via an intermediate medium. Finally, the LNG is sent to the dew point condenser 34, where its cold energy is used to generate cold dehumidified air and clean water. After passing through these units, the LNG is vaporized into NG (12℃, 8MPa), with a temperature very close to ambient temperature. The cold energy utilization rate of LNG reaches 45.07%, better realizing the cascade utilization of LNG cold energy.

[0083] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, characterized in that: According to the LNG supply sequence, it includes LNG supply unit, carbon capture unit, compressed carbon dioxide energy storage and release unit, Karina cycle power generation unit and air conditioning unit. The LNG supply unit is sequentially connected to the carbon capture unit, the carbon dioxide storage and release unit, the Karina cycle power generation unit, and the air conditioning unit. The LNG supply unit is equipped with a primary, secondary, tertiary, and quaternary LNG heat exchanger, which respectively provide heat to the carbon capture unit via the primary LNG heat exchanger, to the compressed carbon dioxide storage and release unit via the secondary LNG heat exchanger, to the Karina cycle power generation unit via the tertiary LNG heat exchanger, and to the air conditioning unit via the quaternary LNG heat exchanger. This provides the user with heat, cold energy, electricity, dehumidified air, and clean water, achieving distributed energy supply. The LNG supply unit also includes an LNG storage tank and an LNG pump. The carbon capture unit includes a carbon capture gas-liquid separator, a liquid carbon dioxide storage tank, a flue gas reheater, a flue gas expander, and a flue gas compressor. The air conditioning unit includes a clean water storage tank, a dew point condenser, and a fan; The outlet of the LNG storage tank is connected to the inlet of the LNG pump via a pipeline; the outlet pipeline of the LNG pump is connected to the LNG side pipeline of the first-stage LNG heat exchanger. The high-temperature side outlet of the first-stage LNG heat exchanger is connected to the inlet of the carbon capture gas-liquid separator. The flue gas is connected in sequence to the flue gas compressor and the high-temperature side pipeline of the first-stage LNG heat exchanger through the high-temperature side pipeline of the flue gas regenerator. The gas phase outlet of the carbon capture gas-liquid separator is connected to the low-temperature side pipeline of the flue gas regenerator. One end of the carbon capture gas-liquid separator is connected to a liquid carbon dioxide storage tank for storing the liquid carbon dioxide separated by the carbon capture gas-liquid separator in the liquid carbon dioxide storage tank. The low-temperature side pipeline outlet of the flue gas regenerator is connected to the inlet of the flue gas expander. The refrigerant water outlet of the four-stage LNG heat exchanger is connected to the indoor user via a pipeline; the LNG side pipeline of the four-stage LNG heat exchanger is an LNG coil, which is coiled inside the dew point condenser; the fan is connected to the dew point condenser and is used to send outdoor air into the dew point condenser, and then send the dehumidified cold air to the indoor user side via the LNG coil; the outlet of the water collection pan at the bottom of the dew point condenser is connected to the inlet of the clean water storage tank via a pipeline; this is used to finally transport the vaporized LNG to the natural gas power plant.

2. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 1, is characterized in that: The compressed carbon dioxide energy storage and release unit includes a low-pressure carbon dioxide storage tank, a carbon dioxide regenerator, a carbon dioxide compressor, a cold storage heat exchange device, a high-pressure carbon dioxide storage tank, a heat storage heat exchange device, a carbon dioxide expander, a cold storage medium storage tank, a heat storage medium storage tank, and a flow control valve. The outlet of the low-pressure carbon dioxide storage tank is connected to the low-temperature side inlet of the carbon dioxide regenerator; the low-temperature side outlet of the carbon dioxide regenerator is connected to the inlet of the carbon dioxide compressor through a pipeline. The outlet of the carbon dioxide compressor is connected to the inlet of the high-temperature side pipeline of the cold storage heat exchange device via a pipeline. The high-temperature side pipeline outlet of the cold storage heat exchange device is connected to the high-temperature side pipeline inlet of the carbon dioxide regenerator via a pipeline; the high-temperature side pipeline outlet of the carbon dioxide regenerator is connected to the inlet of the high-pressure carbon dioxide storage tank via a pipeline; the outlet of the high-pressure carbon dioxide storage tank is connected to the low-temperature side pipeline inlet of the heat storage heat exchange device; and the low-temperature side pipeline outlet of the heat storage heat exchange device is connected to the inlet of the carbon dioxide expander via a pipeline. The outlet of the carbon dioxide expander is connected to the high-temperature side pipeline inlet of the secondary LNG heat exchanger via a pipeline. The high-temperature side pipeline outlet of the secondary LNG heat exchanger is connected to the inlet of the low-pressure carbon dioxide storage tank via a pipeline; the outlet of the cold storage medium storage tank is connected to the inlet of the low-temperature side pipeline of the cold storage heat exchange device; the outlet of the low-temperature side pipeline of the cold storage heat exchange device is connected to the inlet of the heat storage medium storage tank via a pipeline; the outlet of the heat storage medium storage tank is connected to two pipelines, one of which is connected to the high-temperature side pipeline inlet of the heat storage heat exchange device, and the other pipeline leads to the user side.

3. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 2, is characterized in that: The pipeline connecting the low-pressure carbon dioxide storage tank and the carbon dioxide regenerator is equipped with a first throttle valve.

4. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 2, is characterized in that: A second throttle valve is also installed on the pipeline between the high-pressure carbon dioxide storage tank and the heat storage and heat exchange device.

5. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 2, is characterized in that: The pipeline between the cold storage medium tank and the cold storage heat exchange device is also equipped with a cold storage medium pressurization pump, which is used to transport the medium in the cold storage medium tank to the cold storage heat exchange device.

6. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 2, is characterized in that: One of the outlet pipes of the heat storage medium tank is connected to the user side via a flow control valve.

7. The multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 1, is characterized in that: The Karina cycle power generation unit includes a low-temperature regenerator, a high-temperature regenerator, an evaporator, a Karina cycle gas-liquid separator, and an ammonia expander. The outlet of the high-temperature side pipeline of the three-stage LNG heat exchanger is connected to the inlet of the low-temperature side pipeline of the low-temperature regenerator via a pipeline; the outlet of the low-temperature side pipeline of the low-temperature regenerator is connected to the inlet of the low-temperature side pipeline of the high-temperature regenerator via a pipeline; the outlet of the low-temperature side pipeline of the high-temperature regenerator is connected to the inlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator via a pipeline; the outlet of the low-temperature working fluid side pipeline of the Karina circulating evaporator is connected to the inlet of the Karina circulating gas-liquid separator via a pipeline; the gas phase outlet of the Karina circulating gas-liquid separator is connected to the inlet of the ammonia expander; the liquid phase outlet of the Karina circulating gas-liquid separator is connected to the inlet of the high-temperature side pipeline of the high-temperature regenerator; the outlet of the ammonia expander and the high-temperature side pipeline of the high-temperature regenerator are connected to the inlet of the mixer; the outlet of the mixer is connected to the inlet of the high-temperature side pipeline of the low-temperature regenerator via a pipeline; the outlet of the high-temperature side pipeline of the low-temperature regenerator is connected to the inlet of the high-temperature side pipeline of the three-stage LNG heat exchanger via a pipeline.

8. A multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 7, characterized in that: A circulating working fluid pump is also installed on the connecting pipeline between the cryogenic regenerator and the three-stage LNG heat exchanger.

9. A multifunctional system for LNG cold energy utilization, including energy storage, carbon capture, and air conditioning, as described in claim 7, characterized in that: The outlet of the ammonia expander is connected to the high-temperature side pipe of the high-temperature regenerator by a Karina circulation throttle valve.

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