Coupling system for liquefied natural gas re-gasification and liquid air energy storage

Abstract

A coupling system for liquefied natural gas re-gasification (LNG-RG) and liquid air energy storage (LAES). The coupling system comprises an LNG-RG system and an LAES system. The LNG-RG system comprises a heat exchanger-natural gas, and a liquefied natural gas re-gasification path passes through the heat exchanger-natural gas. The LAES system comprises a cold dewar, and a main gas liquefaction path and a liquefied main gas re-gasification path pass through the cold dewar, wherein in the cold dewar, the main gas liquefaction path and the liquefied main gas re-gasification path are the same path but have opposite air flow directions; and the cold dewar performs cold energy exchange with the main gas liquefaction path and the liquefied main gas re-gasification path by means of a cold storage medium in the cold dewar. A hot end of the heat exchanger-natural gas is connected to a hot end of the cold dewar, and a cold end of the heat exchanger-natural gas is connected to a cold end of the cold dewar, thereby forming a heat exchange cycle where cold energy exchange is performed with a heat exchange medium. In the system, regardless of whether the LAES system is in a charging working situation, a standing working situation or a discharging working situation, effective coupling utilization of cold energy and heat energy between the LAES system and the LNG-RG system can be realized, the coupling system is improved, the effective coupling utilization rate of cold energy and heat energy between the systems is improved, and the output requirements for the LNG-RG system and the LAES system are met in multiple working situations.

Description

Coupled system of liquefied natural gas regasification and liquid air energy storage

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. CN202410401319.9 filed on April 3, 2024. The full text of the above-mentioned Chinese patent application is hereby cited as part of this application. Technical Field

[0003] The present invention belongs to the technical field of large-scale energy storage, and in particular relates to a coupling system of liquefied natural gas regasification and liquid air energy storage. Background Art

[0004] Liquid Air Energy Storage (LAES), as a type of energy storage technology, uses cheap valley electricity to absorb air from the environment, then cools it until it becomes liquid for storage. During peak electricity consumption, the liquid air is released from the tank and pressurized and heated, and then enters the expander to generate work and generate electricity, realizing valley electricity peak utilization. It can play an important role in peak regulation of the power grid, but there will be a loss of cold energy during the charging and discharging process. In order to replenish the lost cold energy, additional electricity is usually required to supplement the cold energy, which is costly.

[0005] In recent years, the proportion of natural gas in energy consumption has steadily increased as a clean energy source. With improvements in natural gas liquefaction technology and reductions in LNG (Liquefied Natural Gas) transportation costs, LNG has gained widespread application and attention. LNG receiving terminals often involve the LNG regasification (RG) process. The regasification of LNG into natural gas releases a significant amount of cold energy, making the coupled application of LAES and LNG-RG systems highly practical and promising.

[0006] At present, scholars and manufacturers at home and abroad have proposed multiple coupling models for the LAES system and the LNG-RG system. However, they have not considered the coupled continuous operation of the LNG-RG system and the LAES system under various working conditions. Therefore, the coupling system is imperfect and the effective coupling utilization rate of the cold and heat energy between the systems is low. Summary of the Invention

[0007] In view of this, an object of the present invention is to propose a coupling system of LNG-RG and LAES to solve the problems in the prior art of imperfect coupling system between LAES system and LNG-RG system and low effective coupling utilization rate of cold energy and heat energy between the systems.

[0008] In some illustrative embodiments, the coupled LNG-RG and LAES system includes an LNG-RG system and a LAES system, wherein the LNG-RG system includes a natural gas heat exchanger with a liquefied natural gas regasification path running through the natural gas heat exchanger, and the LAES system includes a cold storage tank with a main gas liquefaction path and a liquefied main gas regasification path running through the cold storage tank. Within the cold storage tank, the main gas liquefaction path and the liquefied main gas regasification path are the same path but have opposite air flow directions. The cold storage tank exchanges cold energy with the main gas liquefaction path and the liquefied main gas regasification path, respectively, via a cold storage medium therein. The natural gas heat exchanger and the cold storage tank are connected at their hot ends and cold ends, respectively, forming a heat exchange cycle in which cold energy is exchanged using a heat exchange medium.

[0009] In some optional embodiments, when the LNG-RG system is running and the LAES system is in a charging condition, a stationary condition, a discharging condition, or a condition change, the heat exchange medium in the heat exchange cycle maintains a flow cycle of the cold end of the natural gas heat exchanger, the cold end of the cold storage tank, the hot end of the cold storage tank, and the hot end of the natural gas heat exchanger, and exchanges cold energy with the cold storage medium in the cold storage tank in the cold storage tank.

[0010] In some optional embodiments, when the LAES system is in a charging condition, the main gas under the charging condition of the LAES system enters from the hot end of the cold storage tank and flows out from the cold end of the cold storage tank, and exchanges cold energy with the cold storage medium in the cold storage tank inside the cold storage tank.

[0011] In some optional embodiments, when the LAES system is in a discharge condition, the liquefied main gas under the discharge condition of the LAES system enters from the cold end of the cold storage tank and flows out from the hot end of the cold storage tank, and exchanges cold energy with the cold storage medium in the cold storage tank inside the cold storage tank.

[0012] In some optional embodiments, when the LNG-RG system is in operation and the LAES system is out of operation or has excess cold storage, the cold energy generated by the LNG-RG system is output to the ambient air through a gas phase path, bypassing the LAES system.

[0013] In some optional embodiments, the cold storage tank includes: a shallow cold tank and a cryogenic tank; the natural gas heat exchanger includes: a cryogenic natural gas heat exchanger and a shallow cold natural gas heat exchanger arranged in sequence along the liquefied natural gas regasification direction on the liquefied natural gas regasification path; the heat exchange medium includes: a shallow cold heat exchange medium and a cryogenic heat exchange medium; the shallow cold tank and the cryogenic tank are arranged in sequence along the air liquefaction direction on the main gas liquefaction path, and the cryogenic tank and the shallow cold tank are also arranged in sequence along the air regasification direction on the liquefied main gas regasification path. The heat exchange cycle comprises: a shallow cold closed circuit for exchanging cold energy between the shallow cold natural gas heat exchanger and the shallow cold tank using a shallow cold heat exchange medium; and a cryogenic closed circuit for exchanging cold energy between the cryogenic natural gas heat exchanger and the cryogenic tank using a cryogenic heat exchange medium; wherein, in the shallow cold closed circuit, the hot ends of the shallow cold natural gas heat exchanger and the shallow cold tank are respectively connected, and the cold ends of the deep cold closed circuit are respectively connected, and the hot ends of the deep cold natural gas heat exchanger and the cryogenic tank are respectively connected.

[0014] In some optional embodiments, the shallow cold tank includes: a first shallow cold tank and a second shallow cold tank arranged in sequence along the air liquefaction direction on the main gas liquefaction path; the deep cold tank, the second shallow cold tank and the first shallow cold tank are arranged in sequence along the air regasification direction on the liquefied main gas regasification path; the shallow cold natural gas heat exchanger, the first shallow cold tank and the second shallow cold tank form the shallow cold closed loop for exchanging cold energy with a shallow cold exchange medium; wherein, the hot ends and cold ends of the shallow cold natural gas heat exchanger, the first shallow cold tank and the second shallow cold tank are respectively connected.

[0015] In some optional embodiments, when the LNG-RG system is running and the LAES system is in a charging condition, a stationary condition, a discharging condition, or a condition change, the shallow cooling closed loop supports: the shallow cooling heat exchange medium circulates in the flow direction of the shallow cooling natural gas heat exchanger cold end, the first shallow cooling tank cold end, the first shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end; and / or the shallow cooling heat exchange medium circulates in the flow direction of the shallow cooling natural gas heat exchanger cold end, the second shallow cooling tank cold end, the second shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end.

[0016] In some optional embodiments, when the LAES system is in a charging condition, the main gas under the LAES system charging condition passes through the first shallow cold tank, the second shallow cold tank and the deep cold tank in sequence, and exchanges cold energy with the cold storage medium therein in sequence; when the LAES system is in a discharging condition, the liquefied main gas under the LAES system discharging condition passes through the deep cold tank, the second shallow cold tank and the first shallow cold tank in sequence, and exchanges cold energy with the cold storage medium therein in sequence.

[0017] In some optional embodiments, the coupling system further includes: a compressor, a cryogenic expander, a liquid-gas separator and a liquid air storage tank arranged in sequence along the air liquefaction direction on the main gas liquefaction path; wherein, the first shallow cold tank is arranged in front of the main gas inlet of the compressor, and the second shallow cold tank is arranged between the compressor and the cryogenic expander; the deep cold tank is arranged between the second shallow cold tank and the cryogenic expander.

[0018] In some optional embodiments, the cold storage tank further includes: an ultra-cold tank arranged between the cryogenic tank and the low-temperature expander on the main gas liquefaction path, the gas phase outlet of the liquid-gas separator passes through the ultra-cold tank, the cryogenic tank and the main gas outlet of the first shallow cold tank and the main gas inlet of the compressor in sequence, forming a reflux main gas path for the cascade recovery of ultra-cold energy, cryogenic energy and shallow cold energy.

[0019] In some optional embodiments, the coupling system further includes: a liquid air storage tank and an expander arranged in sequence along the air regasification direction on the liquefied main gas regasification path; the cryogenic tank, the second shallow cold tank and the first shallow cold tank are arranged in sequence between the liquid air storage tank and the expander along the air regasification direction on the liquefied main gas regasification path.

[0020] In some optional embodiments, the expander includes: a first expander and a second expander; the cryogenic tank, the second shallow cold tank, the first expander, the first shallow cold tank and the second expander are arranged in sequence along the air regasification direction on the liquefied main gas regasification path.

[0021] In some optional embodiments, the cold storage tank is a solid packed bed.

[0022] In some optional embodiments, the cold storage medium in the cold storage tank has anisotropic thermal conductivity.

[0023] Compared with the existing technology, this application has the following advantages:

[0024] The coupling system in this embodiment of the present invention not only meets the coupling requirements between the LNG-RG system's operating conditions and the LAES system's charging conditions, but also meets the coupling requirements between the LNG-RG system's operating conditions and the LAES system's stationary and discharging conditions. Regardless of whether the LAES system is in any of the charging, stationary, or discharging conditions, it can effectively couple and utilize cooling and thermal energy with the LNG-RG system, improving the coupling system and increasing the effective coupling utilization of cooling and thermal energy between the systems. Furthermore, while ensuring the continuous operation of the LNG-RG system coupled with the LAES system under various operating conditions, the LAES system can switch operating conditions according to its actual needs, meeting the output requirements of both the LNG-RG and LAES systems under multiple operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a structural example 1 of a coupling system of an LNG-RG system and a LAES system according to an embodiment of the present invention;

[0026] FIG2 is an example of a first coupling working condition of a coupling system according to an embodiment of the present invention;

[0027] FIG3 is an example 1 of a second coupling working condition of the coupling system according to an embodiment of the present invention;

[0028] FIG4 is an example 1 of a third coupling working condition of the coupling system according to an embodiment of the present invention;

[0029] FIG5 is an example 1 of a fourth coupling working condition of the coupling system according to an embodiment of the present invention;

[0030] FIG6 is an example 1 of the fifth coupling working condition of the coupling system according to an embodiment of the present invention;

[0031] FIG7 is a second example of a fifth coupling operating condition of the coupling system according to an embodiment of the present invention;

[0032] FIG8 is a second structural example of a coupling system of an LNG-RG system and a LAES system according to an embodiment of the present invention;

[0033] FIG9 is a second example of a first coupling working condition of a coupling system according to an embodiment of the present invention;

[0034] FIG10 is a second example of a second coupling working condition of the coupling system according to an embodiment of the present invention;

[0035] FIG11 is a second example of a third coupling working condition of the coupling system according to an embodiment of the present invention;

[0036] FIG12 is a second example of a fourth coupling operating condition of the coupling system according to an embodiment of the present invention;

[0037] FIG13 is a third example of the fifth coupling working condition of the coupling system according to an embodiment of the present invention;

[0038] FIG14 is a fourth example of the fifth coupling operating condition of the coupling system according to an embodiment of the present invention;

[0039] FIG15 is a third structural example of a coupling system of an LNG-RG system and a LAES system according to an embodiment of the present invention;

[0040] FIG16 is a third example of the first coupling working condition of the coupling system in an embodiment of the present invention.

[0041] Figure symbols: Natural gas heat exchanger HX-NG (Heat Exchanger-Natural Gas), cryogenic natural gas heat exchanger HX-NG1 (Heat Exchanger-Natural Gas 1), shallow natural gas heat exchanger HX-NG2 (Heat Exchanger-Natural Gas 2); Cold storage tank CD (Cold Dewar), first shallow cold tank SCD1 (Shallow Cold Dewar 1), second shallow cold tank SCD2 (Shallow Cold Dewar 2), cryogenic tank DCD (Deep Cold Dewar); ultra-cold tank UCD (Ultra Cold Dewar); compressor C (Compressor), cryogenic expander CE (Cryogenic Expander), liquid-gas separator LAS (Liquid Air Separator), liquid air storage tank LAD (Liquid Air Dewar), cryogenic pump CP (Cryogenic Pump), expander E (Expander), first expander E1 (Expander 1), second expander E2 (Expander 2). DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making creative efforts shall fall within the scope of protection of the present invention.

[0043] It should be noted that the various technical features in the embodiments of the present invention can be combined with each other without conflict.

[0044] Terminology Notes:

[0045] LNG-RG system, liquefied natural gas regasification system, is used to realize the conversion of liquefied natural gas (LNG) into natural gas (NG). It has a liquefied natural gas regasification path. LNG is converted into NG in the process of releasing cold energy (and absorbing heat energy) on the liquefied natural gas regasification path.

[0046] The LAES system, a liquid air energy storage system, is used to convert main gas (air) into liquefied main gas (liquid air) for energy storage through electric energy during the charging process, and to generate electric energy in the process of converting liquefied main gas into regasified main gas during the discharge process. It has a main gas liquefaction path and a liquefied main gas regasification path. The main gas is converted into liquefied main gas in the process of absorbing cold energy (and releasing heat energy at the same time) on the main gas liquefaction path, and the liquefied main gas is converted into regasified main gas in the process of releasing cold energy (and absorbing heat energy) on the liquefied main gas regasification path.

[0047] Under the charging condition of the LAES system, the main gas refers to the part of air that is purified, passes through the main gas liquefaction path, and finally becomes liquid air, excluding the return air that needs to recover cold energy; under the discharging condition of the LAES system, the liquefied main gas refers to liquid air and regasified liquid air.

[0048] The embodiment of the present invention discloses a coupled system of liquefied natural gas regasification (LNG-RG) and liquid air energy storage (LAES). Specifically, as shown in FIG1 , FIG1 is a structural example 1 of the coupled system of LNG-RG and LAES in the embodiment of the present invention; the coupled system includes an LNG-RG system and a LAES system. The LNG-RG system includes: a natural gas heat exchanger HX-NG, a liquefied natural gas regasification path passes through the natural gas heat exchanger HX-NG, and the LAES system includes: a cold storage tank CD, a main gas-liquid The main gas liquefaction path and the liquefied main gas regasification path run through the cold storage tank CD. Inside the cold storage tank CD, the main gas liquefaction path and the liquefied main gas regasification path are the same path, but the air flows in opposite directions. The cold storage tank CD exchanges cold energy with the main gas liquefaction path and the liquefied main gas regasification path respectively through the cold storage medium therein. A heat exchange cycle for exchanging cold energy using the heat exchange medium is formed between the natural gas heat exchanger HX-NG and the cold storage tank CD. The hot ends and cold ends of the natural gas heat exchanger HX-NG and the cold storage tank CD are respectively connected.

[0049] In some embodiments, the main gas liquefaction path of the LAES system includes: an air purification device (not shown), a cold storage tank CD, a compressor C, a cryogenic expander CE, a liquid-gas separator LAS, and a liquid air storage tank LAD, which are connected in sequence; the cold storage tank CD is located between the compressor C and the cryogenic expander CE; and the liquefied main gas regasification path of the LAES system includes: a liquid air storage tank LAD, a cryogenic pump CP, a cold storage tank CD, and an expander E, which are connected in sequence. The cold storage tank is located between the cryogenic pump CP and the expander E.

[0050] The LAES system in the existing technology usually configures a heat storage tank to recover and store the compression heat energy of the main gas compressed by the compressor unit, and uses it to heat and expand the regasified main gas under the discharge condition of the LAES system. However, the actual value of this compression heat energy is low, and the heat storage and maintenance costs are high. Therefore, heat energy can be provided by an external heat source.

[0051] As shown in FIG2 , FIG2 is an example 1 of a first coupling working condition of a coupling system according to an embodiment of the present invention, and is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0052] When the LNG-RG system is running and the LAES system is in the charging condition, the heat exchange medium in the heat exchange cycle circulates in the flow direction of the natural gas heat exchanger HX-NG cold end, the cold end of the cold storage tank CD, the hot end of the cold storage tank CD, and the hot end of the natural gas heat exchanger HX-NG. The cold energy generated during the LNG regasification process of the LNG-RG system and the cold energy previously stored in the LAES system's own cold storage tank CD are jointly output to the main gas under the charging condition of the LAES system, realizing the cooling of the main gas and the regasification of LNG, thereby achieving effective coupled utilization of cold energy and heat energy between the LNG-RG system and the LAES system.

[0053] As shown in FIG3 , FIG3 is an example 1 of a second coupling working condition of the coupling system according to an embodiment of the present invention, and is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0054] When the LNG-RG system is running and the LAES system is in a static working condition, the heat exchange medium in the heat exchange cycle circulates in the flow direction of the natural gas heat exchanger HX-NG cold end, the cold end of the cold storage tank CD, the hot end of the cold storage tank CD, and the hot end of the natural gas heat exchanger HX-NG, outputting the cold energy generated during the LNG regasification process of the LNG-RG system to the cold storage medium in the cold storage tank CD of the LAES system, thereby realizing the regasification of LNG while increasing the cold energy storage capacity of the cold storage tank CD, and achieving effective coupled utilization of cold energy and heat energy between the LNG-RG system and the LAES system.

[0055] The static operating condition of the LAES system in the embodiment of the present invention includes the static operating condition after the LAES system is charged and the static operating condition after the LAES system is discharged.

[0056] As shown in FIG4 , FIG4 is a third coupling working condition example 1 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0057] When the LNG-RG system is operating and the LAES system is in the discharge condition, the heat exchange medium in the heat exchange cycle circulates in the flow direction of the natural gas heat exchanger HX-NG cold end, the cold end of the cold storage tank CD, the hot end of the cold storage tank CD, and the hot end of the natural gas heat exchanger HX-NG. The cold energy generated during the LNG regasification process of the LNG-RG system and the cold energy generated during the regasification process of the liquefied main gas under the discharge condition of the LAES system are jointly output to the cold storage medium in the cold storage tank CD of the LAES system. At the same time, the regasification of LNG and the regasification of the liquefied main gas under the discharge condition of the LAES system are realized, thereby achieving effective coupled utilization of cold energy and heat energy between the LNG-RG system and the LAES system.

[0058] The coupling system in the embodiment of the present invention not only satisfies the coupling between the operating condition of the LNG-RG system and the charging condition of the LAES system, but also satisfies the coupling between the operating condition of the LNG-RG system and the static condition and the discharging condition of the LAES system. Regardless of whether the LAES system is in any of the charging, static, and discharging conditions, effective coupling utilization of cold energy and heat energy with the LNG-RG system can be achieved, thereby improving the coupling system and enhancing the effective coupling utilization rate of cold energy and heat energy between the systems.

[0059] In addition, when the LNG-RG system is operating and the LAES system is in a charging condition, a stationary condition, a discharging condition, or a condition change, the flow direction of the heat exchange medium in the heat exchange cycle remains unchanged.

[0060] Furthermore, in the embodiment of the present invention, the LNG-RG system and the LAES system exchange cold energy with the main gas through other heat exchange media as cold energy carriers, which can avoid placing high-pressure natural gas and high-pressure air in the same equipment, causing operational risks.

[0061] As shown in FIG5 , FIG5 is a fourth coupling operating condition example 1 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0062] In some embodiments, when the LNG-RG system is operating and the LAES system is shut down or has excess cold storage, the cold energy generated by the LNG-RG system can be output to the ambient air through the gas phase path, bypassing the LAES system.

[0063] Specifically, the LAES system in this embodiment of the present invention further includes a gas phase path extending through the natural gas heat exchanger HX-NG. This path is used to transport purified ambient air through the gas phase path, exchanging cold energy with the LNG-RG system within the natural gas heat exchanger HX-NG to achieve LNG regasification when the system is operating and the LAES system is shut down or the cold storage tank CD has excess cold energy. This gas phase path can be independent of the natural gas regasification path HX-NG and the heat exchange circulation path within the natural gas heat exchanger HX-NG, or it can be directly formed by the heat exchange circulation path within the natural gas heat exchanger HX-NG.

[0064] In this embodiment, the LAES system is generally shut down during the maintenance period of the LAES system. At this time, the main equipment of the LAES system is unavailable and therefore cannot support the supply of heat energy to the LNG-RG system. Excess cold storage in the LAES system is generally prone to occur during the static period of the LAES system. At this time, the cold energy temperature of LNG regasification has been fully reached inside the cold storage equipment of the LAES system, and therefore it can no longer provide heat energy to the LNG-RG system. Therefore, an additional heat source needs to be introduced.

[0065] In this embodiment, the operating conditions of the LNG-RG system are coupled with the conditions of the LAES system being shut down and having excess cold storage. This ensures that the LNG-RG system can maintain continuous operation by directly providing a heat source for the LNG-RG system by introducing external ambient air when the LAES system is shut down or has excess cold storage. This also prevents the LNG-RG system from continuing to exchange cold energy with the LAES system when the LAES system has excess cold storage, which could result in insufficient cold energy release from LNG, reduced regasification efficiency, and consequently reduced production. Furthermore, the risk of low temperature damage to transmission pipelines and container equipment could be avoided due to the regasified natural gas being too cold.

[0066] In some embodiments, the coupling system may further satisfy the following requirements: when the LNG-RG system is shut down, the heat exchange cycle between the LNG-RG system and the LAES system is cut off, thereby allowing the LAES system to operate independently from the LNG-RG system.

[0067] As shown in FIG6 , FIG6 is a fifth coupling operating condition example 1 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0068] When the LAES system is in the charging condition, the main gas under the charging condition of the LAES system enters from the hot end of the cold storage tank CD and flows out from the cold end of the cold storage tank CD, exchanges cold energy with the cold storage medium in the cold storage tank CD, and directly consumes the cold energy of the cold storage tank CD to achieve cooling of the main gas.

[0069] As shown in FIG7 , FIG7 is a fifth coupling operating condition example 2 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 1 of the coupling system shown in FIG1 ;

[0070] When the LAES system is in the discharge condition, the liquefied main gas under the discharge condition enters from the cold end of the cold storage tank CD and flows out from the hot end of the cold storage tank CD, exchanges cold energy with the cold storage medium in the cold storage tank CD, and directly recovers the cold energy released during the regasification process of the liquefied main gas through the cold storage tank CD, thereby realizing the regasification of the liquefied main gas.

[0071] In some embodiments, the main gas liquefaction path of the LAES system includes: an air purification device (not shown), a cold storage tank CD, a compressor C, a cryogenic expander CE, a liquid-gas separator LAS, and a liquid air storage tank LAD, which are connected in sequence; the cold storage tank CD is located between the compressor C and the cryogenic expander CE; and the liquefied main gas regasification path of the LAES system includes: a liquid air storage tank LAD, a cryogenic pump CP, a cold storage tank CD, and an expander E, which are connected in sequence. The cold storage tank is located between the cryogenic pump CP and the expander E.

[0072] In some embodiments, the cold energy involved between the two systems is divided into deep cold energy and shallow cold energy according to the quality of the cold energy, wherein the quality of deep cold energy is higher than that of shallow cold energy; by dividing the cold energy into deep cold energy and shallow cold energy; the cold energy exchange between the two systems is further divided into shallow cold energy exchange and deep cold energy exchange.

[0073] As shown in FIG8 , FIG8 is a second structural example of a coupling system of an LNG-RG system and a LAES system according to an embodiment of the present invention;

[0074] Specifically, the cold storage tank CD includes: shallow cold tanks (e.g., SCD1 and SCD2) for storing and releasing shallow cold energy, and a cryogenic tank DCD for storing and releasing deep cold energy; wherein the shallow cold tanks and the cryogenic tank DCD are arranged sequentially along the air liquefaction direction on the main gas liquefaction path, and the cryogenic tank DCD and the shallow cold tank are also arranged sequentially along the air regasification direction on the liquefied main gas regasification path;

[0075] The natural gas heat exchanger HX-NG includes: a deep-cooled natural gas heat exchanger HX-NG1 and a shallow-cooled natural gas heat exchanger HX-NG2 arranged in sequence along the liquefied natural gas regasification path;

[0076] Heat exchange media include: shallow cooling heat exchange media and deep cooling heat exchange media.

[0077] The heat exchange cycle includes: a shallow cooling closed circuit between the shallow cooling natural gas heat exchanger HX-NG2 and the shallow cooling tank, in which a shallow cooling heat exchange medium is used to exchange cold energy; and a cryogenic closed circuit between the deep cooling natural gas heat exchanger HX-NG1 and the cryogenic tank DCD, in which a cryogenic heat exchange medium is used to exchange cold energy;

[0078] Among them, the hot ends and cold ends of the shallow cooling natural gas heat exchanger HX-NG2 and the shallow cooling tank in the shallow cooling closed loop are connected respectively; the hot ends and cold ends of the deep cooling natural gas heat exchanger HX-NG1 and the deep cooling tank DCD in the deep cooling closed loop are connected respectively.

[0079] The shallow heat exchange medium in the embodiment of the present invention only needs to maintain a stable fluid state within the temperature range of the shallow cold energy defined; preferably, methanol can be used as the shallow heat exchange medium; similarly, the deep cold heat exchange medium only needs to maintain a stable fluid state within the temperature range of the deep cold energy defined; preferably, propane can be used as the deep cold heat exchange medium.

[0080] In some embodiments, the shallow cold tank includes: a first shallow cold tank SCD1 and a second shallow cold tank SCD2 arranged in sequence along the air liquefaction direction on the main gas liquefaction path; the deep cold tank DCD, the second shallow cold tank SCD2 and the first shallow cold tank SCD1 are arranged in sequence along the air regasification direction on the liquefied main gas regasification path; a shallow cold closed loop for exchanging cold energy using a shallow cold exchange medium is formed between the shallow cold natural gas heat exchanger HX-NG2, the first shallow cold tank SCD1 and the second shallow cold tank SCD2; wherein the hot ends and cold ends of the shallow cold natural gas heat exchanger HX-NG2, the first shallow cold tank SCD1 and the second shallow cold tank SCD2 are respectively connected.

[0081] The following example shows the operating conditions of the coupled system after the cold energy is split into shallow cold energy and deep cold energy:

[0082] When the LNG-RG system is operating and the LAES system is in charging, stationary, discharging, or changing operating conditions, the shallow cooling closed loop supports the following: the shallow cooling heat exchange medium circulates along the shallow cooling natural gas heat exchanger cold end, the first shallow cooling tank cold end, the first shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end; and / or the shallow cooling heat exchange medium circulates along the shallow cooling natural gas heat exchanger cold end, the second shallow cooling tank cold end, the second shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end. The cryogenic closed loop supports the cryogenic heat exchange medium circulates along the cryogenic natural gas heat exchanger cold end, the cryogenic tank cold end, the cryogenic tank hot end, and the cryogenic natural gas heat exchanger hot end.

[0083] As shown in FIG9 , FIG9 is a second example of a first coupling working condition of a coupling system according to an embodiment of the present invention, and is applicable to the second structural example of the coupling system shown in FIG8 ;

[0084] When the LNG-RG system is operating and the LAES system is in charging mode, the shallow cooling heat exchange medium in the shallow cooling closed loop circulates along the cold end of the shallow cooling natural gas heat exchanger HX-NG2, the cold end of the first shallow cooling tank SCD1, the hot end of the first shallow cooling tank SCD2, and the hot end of the shallow cooling natural gas heat exchanger HX-NG2; and along the cold end of the shallow cooling natural gas heat exchanger HX-NG2, the cold end of the second shallow cooling tank SCD2, the hot end of the second shallow cooling tank SCD2, and the hot end of the shallow cooling natural gas heat exchanger HX-NG. Simultaneously, the cryogenic heat exchange medium circulates along the cold end of the cryogenic natural gas heat exchanger HX-NG1, the cold end of the cryogenic tank DCD, the hot end of the cryogenic tank DCD, and the hot end of the cryogenic natural gas heat exchanger HX-NG1. The main gas in the LAES system's charging mode passes through the first shallow cooling tank SCD1, the second shallow cooling tank SCD2, and the cryogenic tank DCD in sequence, exchanging cold energy with the cold storage medium therein. Realize the cooling of main gas and regasification of LNG.

[0085] As shown in FIG10 , FIG10 is a second coupling working condition example 2 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 2 of the coupling system shown in FIG8 ;

[0086] When the LNG-RG system is operating and the LAES system is at rest, the shallow cooling heat exchange medium in the shallow cooling closed loop circulates between the cold end of the shallow cooling natural gas heat exchanger HX-NG2, the cold end of the first shallow cooling tank SCD1, the hot end of the first shallow cooling tank SCD1, and the hot end of the shallow cooling natural gas heat exchanger HX-NG2; and between the cold end of the shallow cooling natural gas heat exchanger HX-NG2, the cold end of the second shallow cooling tank SCD2, the hot end of the second shallow cooling tank SCD2, and the hot end of the shallow cooling natural gas heat exchanger HX-NG2. Simultaneously, the cryogenic heat exchange medium circulates between the cold end of the cryogenic natural gas heat exchanger HX-NG1, the cold end of the cryogenic tank DCD, the hot end of the cryogenic tank DCD, and the hot end of the cryogenic natural gas heat exchanger HX-NG1. This regasifies the LNG and simultaneously increases the shallow cooling energy storage capacity of the first and second shallow cooling tanks SCD1 and SCD2, and the cryogenic energy storage capacity of the cryogenic tank DCD.

[0087] As shown in FIG11 , FIG11 is a third coupling working condition example 2 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 2 of the coupling system shown in FIG8 ;

[0088] When the LNG-RG system is running and the LAES system is in the discharge condition, the shallow cooling heat exchange medium in the shallow cooling closed loop circulates in the flow direction of the shallow cooling natural gas heat exchanger HX-NG2 cold end, the first shallow cooling tank SCD1 cold end, the first shallow cooling tank SCD2 hot end, and the shallow cooling natural gas heat exchanger HX-NG2 hot end; and circulates in the flow direction of the shallow cooling natural gas heat exchanger HX-NG2 cold end, the second shallow cooling tank SCD2 cold end, the second shallow cooling tank SCD2 hot end, and the shallow cooling natural gas heat exchanger HX-NG2 hot end; at the same time, the cryogenic heat exchange medium circulates in the flow direction of the cryogenic natural gas heat exchanger HX-NG1 cold end, the cryogenic tank DCD cold end, the cryogenic tank DCD hot end, and the cryogenic natural gas heat exchanger HX-NG1 hot end. Among them, the liquefied main gas under the discharge condition of the LAES system passes through the cryogenic tank DCD, the second shallow cold tank SCD2 and the first shallow cold tank SCD1 in turn, and exchanges cold energy with the cold storage medium therein in turn; at the same time, the regasification of LNG, the regasification of the liquefied main gas under the discharge condition of the LAES system, the increase of the shallow cold energy storage of the first shallow cold tank SCD1 and the second shallow cold tank SCD2, and the increase of the deep cold energy storage of the cryogenic tank DCD are realized.

[0089] As shown in FIG12 , FIG12 is a fourth coupling working condition example 2 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 2 of the coupling system shown in FIG8 ;

[0090] The gas-phase pathway in this embodiment of the present invention sequentially passes through the shallow-cooled natural gas heat exchanger HX-NG2 and the cryogenic natural gas heat exchanger HX-NG1. When the LNG-RG system is operating and the LAES system is shut down, or when the cold storage tank has excess cold energy, the pathway can transport purified ambient air, exchanging cold energy with the LNG-RG system in the shallow-cooled natural gas heat exchanger HX-NG2 and the cryogenic natural gas heat exchanger HX-NG1, thereby regasifying LNG. Within the natural gas heat exchanger, this gas-phase pathway can be independent of the natural gas regasification path and heat exchange circulation path, or it can be directly formed by the heat exchange circulation path within the natural gas heat exchanger.

[0091] As shown in FIG13 , FIG13 is a fifth coupling operating condition example 3 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 2 of the coupling system shown in FIG8 ;

[0092] When the LNG-RG system is shut down and the LAES system is charging, the main gas passes through the first shallow cold tank SCD1, the second shallow cold tank SCD2 and the deep cold tank DCD in sequence, and exchanges cold energy with the cold storage medium therein in sequence, consuming the shallow cold energy and deep cold energy of the first shallow cold tank SCD1, the second shallow cold tank SCD2 and the deep cold tank DCD in sequence to cool the main gas;

[0093] As shown in FIG14 , FIG14 is a fifth coupling operating condition example 4 of the coupling system according to an embodiment of the present invention, which is applicable to the structural example 2 of the coupling system shown in FIG8 ;

[0094] When the LNG-RG system is shut down and the LAES system is in the discharge condition, the liquefied main gas under the discharge condition of the LAES system passes through the cryogenic tank DCD, the second shallow cold tank SCD2 and the first shallow cold tank SCD1 in sequence, and exchanges cold energy with the cold storage medium therein in sequence. The cryogenic energy and shallow cold energy released during the regasification process of the liquefied main gas are recovered in sequence through the cryogenic tank DCD, the second shallow cold tank SCD2 and the first shallow cold tank SCD1, thereby realizing the regasification of the liquefied main gas.

[0095] Furthermore, the coupling system also includes: a compressor C, a cryogenic expander CE, a liquid-gas separator LAS and a liquid air storage tank LAD arranged in sequence along the air liquefaction direction on the main gas liquefaction path; wherein, the first shallow cold tank SCD1 is arranged in front of the main gas inlet of the compressor C, and the second shallow cold tank SCD2 is arranged between the compressor C and the deep cold tank DCD; the deep cold tank DCD is arranged between the second shallow cold tank SCD2 and the cryogenic expander CE.

[0096] When the LNG-RG system is running and the LAES system is in a charging condition, the shallow cold energy generated by the LNG-RG system and stored by the LAES system can be jointly output to the main gas in the LAES system that has undergone air purification but has not undergone one or more stages of compression, as well as the main gas that has undergone one or more stages of compression but has not absorbed deep cold energy; and, the deep cold energy generated by the LNG-RG system and stored by the LAES system can be jointly output to the main gas in the LAES system that has absorbed shallow cold energy but has not been expanded and liquefied.

[0097] By exporting shallow cooling energy to the main gas that has undergone air purification but has not yet undergone one or more stages of compression, the LNG-RG system's shallow cooling energy can be used to initially cool the main gas before compression in the LAES system, thereby reducing power consumption during the subsequent compression process. Furthermore, air purification of the main gas before cooling can remove dust, water, and carbon dioxide from the incoming ambient air, preventing condensation and crystallization of water and carbon dioxide after cooling, which can cause pipeline blockage and damage.

[0098] Furthermore, the coupling system also includes: a liquid air storage tank LAD, a cryogenic pump CP and an expander E arranged in sequence along the air regasification direction on the liquefied main gas regasification path; a deep cold tank DCD, a second shallow cold tank SCD2 and a first shallow cold tank SCD1 arranged in sequence between the cryogenic pump CP and the expander E along the air regasification direction on the liquefied main gas regasification path.

[0099] Furthermore, the expander E includes: a first expander E1 and a second expander E2; the cryogenic tank DCD, the second shallow cold tank SCD2, the first expander E1, the first shallow cold tank SCD1 and the second expander E2 are arranged in sequence along the air regasification direction on the liquefied main gas regasification path; wherein, not shown, along the liquefied main gas regasification path, an external heat source can be connected between the second shallow cold tank SCD2 and the first expander E1, and an external heat source can be connected between the first shallow cold tank SCD1 and the second expander E2.

[0100] As shown in Figures 15-16, Figure 15 is a third structural example of a coupling system of an LNG-RG system and a LAES system according to an embodiment of the present invention, which adds a super-cold tank DCD for recovering and utilizing super-cold energy on the basis of the second structural example of the coupling system shown in Figure 8; Figure 16 is a third first coupling operating condition example of the coupling system according to an embodiment of the present invention, which is applicable to the second structural example of the coupling system shown in Figure 15;

[0101] In some embodiments, the cold storage tank also includes: an ultra-cold tank UCD arranged between the cryogenic tank DCD and the low-temperature expander CE on the main gas liquefaction path, and the gas phase outlet of the liquid-gas separator LAS passes through the ultra-cold tank DCD, the cryogenic tank DCD and the main gas outlet of the first shallow cold tank SCD1 and the main gas inlet of the compressor E in sequence, forming a reflux main gas path for the cascade recovery of ultra-cold energy, cryogenic energy and shallow cold energy.

[0102] In some embodiments, preferably, the cold storage tank is a solid packed bed.

[0103] Furthermore, the cold storage medium in the cold storage tank has anisotropic thermal conductivity. This means that the axial thermal conductivity (direction of the heat exchange pipeline) of the cold storage medium is lower than its radial thermal conductivity, the axial thermal conductivity of the heat exchange pipeline is lower than its radial thermal conductivity, and the axial thermal conductivity of the cold storage medium is equal to or higher than the axial thermal conductivity of the heat exchange pipeline. This selection of thermal conductivity allows the radial temperature of the solid medium to converge during cold storage or release, creating a thermoclinic layer distributed along the axial direction of the solid medium.

[0104] The cold storage tanks (such as the first shallow cold tank, the second shallow cold tank, and the deep cold tank) in the LAES system in the embodiment of the present invention can adopt one or more series / parallel tank structures, and can be specifically designed according to the cold storage capacity requirements of the cold storage tanks in the LAES system.

[0105] In this embodiment of the present invention, the shallow refrigeration tank's hot-end temperature is between ambient temperature and zero degrees Celsius, but not below zero degrees Celsius. Its cold-end temperature is the shallow refrigeration temperature. The deep refrigeration tank's hot-end temperature is the shallow refrigeration temperature, while its cold-end temperature is the liquid-to-gas phase transition temperature during LNG regasification. The shallow refrigeration temperature is determined by the LAES system's operating parameters and the compressor's actual low-temperature operating performance and parameters.

[0106] Those skilled in the art should understand that the coupling system in the embodiment of the present invention may include a number of valve bodies to control the switching between various paths, cycles, and loops (between various coupling working conditions) in the coupling system; among them, using valve bodies to control the on-off state of pipelines is a conventional technology in this field. In addition, through the diagrams in the coupling working condition examples in the embodiments of the present invention, the solid line indicates connection (activation) and the dotted line indicates blocking (shutdown), which can also clearly indicate the on-off state under various working conditions. The present invention will not elaborate on this.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A LNG-RG and LAES coupling system, comprising an LNG-RG system and a LAES system, characterized in that: The LNG-RG system includes: a natural gas heat exchanger, a liquefied natural gas regasification path passes through the natural gas heat exchanger, and the LAES system includes: a cold storage tank, a main gas liquefaction path and a liquefied main gas regasification path pass through the cold storage tank; Wherein, in the cold storage tank, the main gas liquefaction path and the liquefied main gas regasification path are the same path but the air flows in opposite directions, and the cold storage tank exchanges cold energy with the main gas liquefaction path and the liquefied main gas regasification path respectively through the cold storage medium therein; The natural gas heat exchanger and the cold storage tank are connected at their hot ends and cold ends, respectively, to form a heat exchange cycle for exchanging cold energy using a heat exchange medium.

2. The coupling system according to claim 1, characterized in that When the LNG-RG system is running and the LAES system is in a charging condition, a stationary condition, a discharging condition, or a condition change, the heat exchange medium in the heat exchange cycle maintains a flow cycle of the cold end of the natural gas heat exchanger, the cold end of the cold storage tank, the hot end of the cold storage tank, and the hot end of the natural gas heat exchanger, and exchanges cold energy with the cold storage medium in the cold storage tank in the cold storage tank.

3. The coupling system according to claim 1, characterized in that When the LAES system is in a charging state, the main gas in the LAES system in the charging state enters from the hot end of the cold storage tank and flows out from the cold end of the cold storage tank, and exchanges cold energy with the cold storage medium in the cold storage tank in the cold storage tank; When the LAES system is in a discharging condition, the liquefied main gas under the discharging condition enters from the cold end of the cold storage tank and flows out from the hot end of the cold storage tank, and exchanges cold energy with the cold storage medium in the cold storage tank.

4. The coupling system according to claim 1, characterized in that When the LNG-RG system is running and the LAES system is shut down or has excess cold storage, the cold energy generated by the LNG-RG system during operation bypasses the LAES system and is output to the ambient air through the gas phase path.

5. The coupling system according to claim 1, characterized in that The cold storage tank includes: a shallow cold tank and a cryogenic tank; the natural gas heat exchanger includes: a cryogenic natural gas heat exchanger and a shallow cold natural gas heat exchanger arranged in sequence along the liquefied natural gas regasification direction on the liquefied natural gas regasification path; the heat exchange medium includes: a shallow cold heat exchange medium and a cryogenic heat exchange medium; The shallow cold tank and the deep cold tank are arranged in sequence along the air liquefaction direction on the main gas liquefaction path, and the deep cold tank and the shallow cold tank are also arranged in sequence along the air regasification direction on the liquefied main gas regasification path; The heat exchange cycle includes: a shallow cold closed circuit for exchanging cold energy between the shallow cold natural gas heat exchanger and the shallow cold tank using a shallow cold heat exchange medium; and a cryogenic closed circuit for exchanging cold energy between the cryogenic natural gas heat exchanger and the cryogenic tank using a cryogenic heat exchange medium. Among them, the hot ends and cold ends of the shallow cooling natural gas heat exchanger and the shallow cooling tank in the shallow cooling closed circuit are connected respectively; the hot ends and cold ends of the deep cooling natural gas heat exchanger and the deep cooling tank in the deep cooling closed circuit are connected respectively.

6. The coupling system according to claim 5, characterized in that The shallow cold tank comprises: a first shallow cold tank and a second shallow cold tank arranged in sequence along the air liquefaction direction on the main gas liquefaction path; the deep cold tank, the second shallow cold tank and the first shallow cold tank are arranged in sequence along the air regasification direction on the liquefied main gas regasification path; The shallow cooling natural gas heat exchanger, the first shallow cooling tank and the second shallow cooling tank form the shallow cooling closed circuit for exchanging cold energy with a shallow cooling medium; The shallow cooling natural gas heat exchanger, the first shallow cooling tank and the second shallow cooling tank are connected at their hot ends and cold ends respectively.

7. The coupling system according to claim 6, characterized in that When the LNG-RG system is operating and the LAES system is in a charging condition, a stationary condition, a discharging condition, or a condition change, the shallow cooling closed circuit supports: The shallow cooling heat exchange medium circulates in the flow direction of the shallow cooling natural gas heat exchanger cold end, the first shallow cooling tank cold end, the first shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end; and / or, The shallow cooling heat exchange medium circulates in the flow direction of the shallow cooling natural gas heat exchanger cold end, the second shallow cooling tank cold end, the second shallow cooling tank hot end, and the shallow cooling natural gas heat exchanger hot end.

8. The coupling system according to claim 6, characterized in that When the LAES system is in a charging state, the main gas in the LAES system in the charging state passes through the first shallow cold tank, the second shallow cold tank, and the deep cold tank in sequence, and exchanges cold energy with the cold storage medium therein in sequence; When the LAES system is in a discharging condition, the liquefied main gas in the discharging condition of the LAES system passes through the deep cold tank, the second shallow cold tank and the first shallow cold tank in sequence, and exchanges cold energy with the cold storage medium therein in sequence.

9. The coupling system according to claim 6, characterized in that Also includes: A compressor, a cryogenic expander, a liquid-gas separator and a liquid air storage tank are arranged in sequence along the air liquefaction direction on the main gas liquefaction path; wherein, the first shallow cold tank is arranged in front of the main gas inlet of the compressor, and the second shallow cold tank is arranged between the compressor and the cryogenic expander; the deep cold tank is arranged between the second shallow cold tank and the cryogenic expander.

10. The coupling system according to claim 8, characterized in that The cold storage tank also includes: an ultra-cold tank arranged between the cryogenic tank and the low-temperature expander on the main gas liquefaction path, and the gas phase outlet of the liquid-gas separator passes through the ultra-cold tank, the cryogenic tank and the main gas outlet of the first shallow cold tank and the main gas inlet of the compressor in sequence, forming a reflux main gas path for the cascade recovery of ultra-cold energy, cryogenic energy and shallow cold energy.

11. The coupling system according to claim 6, characterized in that Also includes: The liquid air storage tank and the expander are arranged in sequence along the air regasification direction on the liquefied main gas regasification path; the deep cold tank, the second shallow cold tank and the first shallow cold tank are arranged in sequence between the liquid air storage tank and the expander along the air regasification direction on the liquefied main gas regasification path.

12. The coupling system according to claim 10, characterized in that The expander includes: a first expander and a second expander; The cryogenic tank, the second shallow cryogenic tank, the first expander, the first shallow cryogenic tank and the second expander are arranged in sequence along the air regasification direction on the liquefied main gas regasification path.

13. The coupling system according to claim 1, wherein: The cold storage tank is a solid packed bed.

14. The coupling system according to claim 1, wherein: The cold storage medium in the cold storage tank has anisotropic thermal conductivity.

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