Cascade cold storage device for storing and conveying LNG (Liquefied Natural Gas) cold energy by utilizing various phase-change materials

Abstract

The invention discloses a cascade cold storage device for storing and conveying LNG (Liquefied Natural Gas) cold energy by utilizing various phase-change materials, which comprises an LNG tank and a natural gas tank, and is provided with an ultralow-temperature phase-change material energy storage system, a low-temperature phase-change material energy storage system, a CO2 capturing, liquefying and energy storage system and a low-temperature power generation system which are connected with the LNG tank, the natural gas tank is connected with the low-temperature power generation system; the LNG cold energy utilization temperature is partitioned, the phase change materials with different melting temperatures are used for storing the LNG cold energy in different temperature regions, and the cold energy utilization rate and the use temperature matching degree are increased; different cold energy storage and conveying methods are formulated according to the phase change materials in different temperature zones; lNG cold energy can be utilized step by step and is not influenced by adjustment or shutdown of a single series system; and independent operation of cold energy utilization systems in different temperature zones can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change cold storage, and in particular relates to a cascade cold storage device which utilizes a variety of phase change materials to store and transport LNG cold energy. Background Art

[0002] With the transformation of the global energy structure and the growth of clean energy demand, liquefied natural gas (LNG) is becoming more and more widely used as a clean and efficient energy carrier. As a fuel, LNG generally undergoes a gasification process. The cooling capacity of LNG is 830-860 kJ / kg, and its gasification temperature is about -162°C, which can be used as high-grade cold energy. At present, the recovery and utilization methods of LNG cold energy are mainly divided into direct utilization and indirect utilization. The utilization of LNG cold energy still faces several major difficulties. First, the utilization method of cold energy is single. Most of the existing cold energy utilization projects are for recovery in a single temperature zone, and the cold energy outside the temperature zone is not effectively recovered and utilized, resulting in a low utilization rate of LNG cold energy. Second, the downstream demand for natural gas fluctuates significantly with day and night and seasons, while cold users often require continuous and stable supply. Third, the planning of the LNG cold energy utilization industry is lagging behind. The design and construction of the receiving station and gasification station ignore the surrounding cold users, resulting in insufficient space for subsequent planning and limiting the construction of large-scale utilization devices.

[0003] In order to solve the problem of single utilization mode of LNG cold energy, it is necessary to classify the cold energy in different temperature zones of LNG and recover it step by step, so as to match the LNG temperature zone with the usage scenario while improving the utilization rate of LNG cold energy. In order to solve the problem that the downstream demand of natural gas fluctuates significantly with day and night and season, it is necessary to store LNG cold energy when there is surplus cold energy and release it when there is a shortage of cold energy to meet the stable supply of cold energy users. In order to solve the problem of lagging planning of LNG cold energy utilization industry, it is necessary to strengthen the simple and fast cold energy transportation system to quickly transport LNG cold energy to where it is needed.

[0004] Phase change material is a material that uses phase change to store and release cold energy. Different phase change materials have different phase change temperatures, and can store LNG cold energy in different temperature ranges; at the same time, it can store a large amount of cold energy during the phase change process, greatly reducing the size of the LNG cold energy storage and release system; in addition, the phase change material after storing cold energy is generally solid or liquid, which facilitates the transmission of cold energy. Therefore, phase change materials play a very important role in the recycling of LNG cold energy, and the development of a LNG cold energy cascade utilization system that couples multiple phase change materials has important significance.

[0005] The existing invention patent with patent number CN111102027B provides a LNG cold energy cascade utilization system and control method, which can ensure that when an abnormal operating condition occurs in one of the processes of the refrigerant expansion subsystem, the cold storage area subsystem, and the data center area subsystem, other areas will not be affected and continue to produce. The invention patent with patent number CN11757760A discloses a high-efficiency heat exchange phase change energy storage system based on cryogenic fluid. The high-efficiency heat exchange phase change energy storage system is a phase change energy storage cycle. Through switching control, the energy storage cycle and the energy release cycle share a set of system pipelines, which simplifies the system layout. The heat exchange plate group in the energy storage water tank can take into account both energy storage heat exchange and energy release heat exchange, improve heat exchange efficiency, increase the effective heat exchange space in the energy storage water tank, and reduce the volume of the energy storage water tank by more than one third.

[0006] In the existing technology, the utilization of LNG cold energy mainly focuses on a single application in a certain field, such as air separation, cryogenic crushing, dry ice manufacturing, refrigeration and cold storage, and cold energy power generation technology, etc., ignoring the utilization of LNG cold energy in multiple temperature zones. Or a small number of studies only focus on the utilization of LNG cold energy in multiple temperature zones, while ignoring the storage and transportation of LNG cold energy. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention proposes a cascade cold storage device that uses a variety of phase change materials to store and transport LNG cold energy. The device divides the utilization temperature of LNG cold energy into zones, and uses phase change materials with different melting temperatures to store the cold energy of LNG in different temperature zones, thereby improving the cold energy utilization rate and the matching degree of the use temperature. Secondly, different cold energy storage and transportation methods are formulated for phase change materials in different temperature zones. Finally, through the design of the system control method, the LNG cold energy can be utilized step by step, and it is not affected by the adjustment or shutdown of a single series system; it can also realize the independent operation of the cold energy utilization systems in different temperature zones.

[0008] In order to achieve the above-mentioned invention object, the specific technical solution of this application is as follows:

[0009] A cascade cold storage device for storing and transporting LNG cold energy using a variety of phase change materials, comprising an LNG tank and a natural gas tank, having an ultra-low temperature phase change material energy storage system connected to the LNG tank, a low temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system, and a low temperature power generation system; the natural gas tank is connected to the low temperature power generation system;

[0010] The ultra-low temperature phase change material energy storage system includes an ultra-low temperature cold energy transport vehicle equipped with a cold storage heat exchange tube and a cold release heat exchange tube. LNG output from the LNG tank enters the cold storage heat exchange tube and is transferred to the liquid phase change material in the cold release heat exchange tube for energy storage; the cold-stored LNG is used to be output to the low temperature phase change energy storage system and / or the low temperature power generation system;

[0011] The low-temperature phase-change energy storage system comprises a first low-temperature heat exchanger and a second low-temperature heat exchanger. The incoming LNG flows through the second low-temperature heat exchanger and the first low-temperature heat exchanger in sequence, exchanges heat with the low-temperature phase-change material to store energy, and the LNG after the heat exchange enters the CO2 capture, liquefaction and energy storage system and / or the low-temperature power generation system.

[0012] The CO2 capture, liquefaction and energy storage system comprises a first CO2 liquefaction heat exchanger, a second CO2 liquefaction heat exchanger and an air dehydrator, the incoming LNG flows through the second CO2 liquefaction heat exchanger, the first CO2 liquefaction heat exchanger and the air dehydrator in sequence, and the LNG after heat exchange enters the low-temperature power generation system;

[0013] The low-temperature power generation system includes an LNG direct expander. The input LNG is directly expanded by the LNG direct expander to generate electricity, and after releasing the cold, it becomes gaseous natural gas and is stored in a natural gas tank.

[0014] Preferably, the ultra-low temperature cold energy transport vehicle has an energy storage stage and an energy release stage; in the energy storage stage, LNG enters the cold storage heat exchange tube and is transferred to the liquid phase change material, the phase change material gradually solidifies, and the energy storage is completed; in the energy release stage, the cold release heat exchange tube is connected to the ultra-low temperature cold energy heat exchange tube, the heat exchange medium enters the cold release heat exchange tube, the cold energy of the phase change material is gradually transferred to the heat exchange medium, and the phase change material gradually melts.

[0015] Preferably, the low-temperature phase change energy storage system is provided with a low-temperature phase change material storage tank, a low-temperature cold energy heat exchanger and a gaseous low-temperature phase change material compressor connected in sequence; after the liquid phase change material flows through the first low-temperature cold energy heat exchanger and the second low-temperature cold energy heat exchanger in sequence, the temperature gradually drops and is stored in the first low-temperature phase change material storage tank, and then flows through the low-temperature cold energy heat exchanger to release the cold energy and the temperature becomes a gaseous phase change material, and the gaseous phase change material is pressurized into a liquid by the gaseous low-temperature phase change material compressor for circulating heat exchange with LNG.

[0016] Preferably, the LNG entering the low-temperature phase change energy storage system comes from an ultra-low-temperature phase change material energy storage system and / or an LNG tank that completes energy storage.

[0017] Preferably, the LNG entering the CO2 capture, liquefaction and energy storage system comes from a low-temperature phase change material energy storage system and / or an LNG tank that performs energy storage.

[0018] Preferably, the CO2 capture, liquefaction and energy storage system also includes an air pump, an air-water separator, a first air-CO2 separator, a second air-CO2 separator and a first liquid CO2 storage tank; the pumped air enters the air dehydrator and the cold energy of LNG solidifies the water in the air; the air-water separator is used to remove solid water in the air; the air after dehydration is liquefied through the first CO2 liquefaction heat exchanger and the second CO2 liquefaction heat exchanger; the first air-CO2 separator is used to separate the liquid CO2 in the first CO2 liquefaction heat exchanger; the second air-CO2 separator is used to separate the liquid CO2 in the second CO2 liquefaction heat exchanger; the first liquid CO2 storage tank is used to store liquid CO2.

[0019] Preferably, the CO2 capture, liquefaction and energy storage system also includes a second liquid CO2 storage tank connected to the first liquid CO2 storage tank, and is provided with a liquid CO2 heat exchanger connected to the second liquid CO2 storage tank; the liquid CO2 heat exchanger is used to release cold energy.

[0020] Preferably, the LNG fed into the low-temperature power generation system comes from an ultra-low temperature phase change material energy storage system, a low temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system and / or an LNG tank.

[0021] Preferably, the low-temperature power generation system includes an LNG-ORC working fluid heat exchanger, through which LNG transfers cold energy to ORC working fluid; an ORC working fluid-seawater or low-temperature heat source heat exchanger and an ORC expander connected to the LNG-ORC working fluid heat exchanger, wherein the ORC working fluid used for ORC power generation is pumped into the ORC working fluid-seawater or low-temperature heat source heat exchanger and enters the ORC expander to generate electricity after being heated.

[0022] Preferably, there is a first LNG-seawater or low-temperature heat source heat exchanger connected to the LNG-ORC working fluid heat exchanger, and the LNG heated by the first LNG-seawater or low-temperature heat source heat exchanger enters the LNG direct expansion machine to generate electricity; and there is a second LNG-seawater or low-temperature heat source heat exchanger connected to the LNG direct expansion machine, which is used to release the LNG output by the LNG direct expansion machine and convert it into gaseous natural gas for storage in a natural gas tank.

[0023] Compared with the prior art, the invention has the following innovative features and beneficial effects:

[0024] (1) The present invention divides the utilization temperature of LNG cold energy into different zones, and uses phase change materials with different melting temperatures to store the cold energy of LNG in different temperature zones. The final cold energy is combined with seawater or a low-temperature heat source to perform an organic Rankine cycle and direct expansion power generation, thereby improving the cold energy utilization rate and the matching degree of LNG utilization temperature.

[0025] (2) The present invention uses a solid-liquid phase change material with a phase change temperature close to the liquefaction temperature of LNG to store the ultra-low temperature cold energy of LNG through a heat storage heat exchanger, and uses an ultra-low temperature cold energy transport vehicle to transport the cold energy; The present invention uses a phase change material with a phase change temperature between the liquefaction temperature of LNG and the liquefaction temperature of CO2 to store the low temperature cold energy of LNG, and transports it through a working fluid pipeline, thereby extending the use range of LNG cold energy and increasing the convenience of cold energy transportation.

[0026] (3) The present invention uses cold energy close to the liquefaction temperature of CO2 to capture and liquefy CO2 in the air, and transports the liquid CO2 through a pipeline, thereby providing convenience for surrounding users who need liquid CO2 while utilizing LNG cold energy for decarbonization.

[0027] (4) The four systems of the present invention utilizing LNG cold energy use a temperature that gradually decreases from top to bottom, which can be connected in series to gradually utilize the cold energy of LNG, or can be operated independently by adjusting related valves when the demand for this part is high, thereby improving the independence of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of a cascade cold storage device for storing and transporting LNG cold energy using a variety of phase change materials according to the present invention;

[0029] Figure 2 This is a schematic diagram of an ultra-low temperature cold energy transport vehicle;

[0030] Figure 3 It is a schematic diagram of heat exchange tubes for storing and releasing cold;

[0031] Among them: 1. LNG tank; 2. Flow regulating valve 1; 3. LNG pump; 4. Flow regulating valve 2; 5. Flow regulating valve 3; 6. Flow regulating valve 4; 7. Flow regulating valve 5; 8. Valve 1; 9. Valve 2; 10. Valve 3; 11. Valve 4; 12. Valve 5; 13. Natural gas tank; 1-1. Ultra-low temperature cold energy transport vehicle; 1-2. Cold storage heat exchange pipe; 1-3. Cold release heat exchange pipe; 1-4. Ultra-low temperature cold energy heat exchanger; 1-5. Ultra-low temperature phase change material energy storage system outlet temperature probe; 2-1. Flow regulating valve 6; 2-2. Low temperature phase change material energy storage System inlet temperature probe; 2-3, first low-temperature cold energy heat exchanger; 2-4, second low-temperature cold energy heat exchanger; 2-5, first low-temperature phase change material storage tank; 2-6, first low-temperature liquid phase change material pump; 2-7, second low-temperature phase change material storage tank; 2-8, second low-temperature liquid phase change material pump; 2-9, low-temperature cold energy heat exchanger; 2-10, gaseous low-temperature phase change material pump; 2-11, gaseous low-temperature phase change material compressor; 2-12, low-temperature phase change material energy storage system outlet temperature probe; 3-1, flow control valve 7; 3-2, CO2 capture, liquefaction and storage Energy system inlet temperature probe; 3-3, air pump; 3-4, air dehumidifier; 3-5, air-water separator; 3-6, first CO2 liquefaction heat exchanger; 3-7, first air-CO2 separator; 3-8, first liquid CO2 storage tank; 3-9, second CO2 liquefaction heat exchanger; 3-10, second air-CO2 separator; 3-11, first liquid CO2 pump; 3-12, second liquid CO2 storage tank; 3-13, second liquid CO2 pump; 3-14, liquid CO2 heat exchanger; 3-15, CO2 capture, liquefaction and energy storage System outlet temperature probe; 4-1, flow control valve 8; 4-2, flow control valve 9; 4-3, low-temperature power generation system inlet temperature probe; 4-4, LNG-ORC working fluid heat exchanger; 4-5, ORC working fluid pump; 4-6, ORC working fluid-seawater or low-temperature heat source heat exchanger; 4-7, ORC expander; 4-8, first LNG-seawater or low-temperature heat source heat exchanger; 4-9, LNG direct expander; 4-10, valve 3; 4-11, second LNG-seawater or low-temperature heat source heat exchanger; 4-12, low-temperature power generation system outlet temperature probe. DETAILED DESCRIPTION

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0034] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0035] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] like Figure 1-3 As shown, in this embodiment, a cascade cold storage device for storing and transporting LNG cold energy using a variety of phase change materials includes an LNG tank 1 and a natural gas tank 13, and has an ultra-low temperature phase change material energy storage system connected to the LNG tank 1, a low temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system, and a low temperature power generation system; the natural gas tank 13 is connected to the low temperature power generation system;

[0038] The ultra-low temperature phase change material energy storage system includes an ultra-low temperature cold energy transport vehicle equipped with a cold storage heat exchange pipe 1-2 and a cold release heat exchange pipe 1-3. The LNG outputted from the LNG tank 1 enters the cold storage heat exchange pipe 1-2 and is transferred to the liquid phase change material in the cold release heat exchange pipe 1-3 for energy storage; the cold stored LNG is used to be output to the low temperature phase change energy storage system and / or the low temperature power generation system;

[0039] The low-temperature phase-change energy storage system includes a first low-temperature cold energy heat exchanger 2-4 and a second low-temperature cold energy heat exchanger 2-3. The incoming LNG flows through the second low-temperature cold energy heat exchanger 2-4 and the first low-temperature cold energy heat exchanger 2-3 in sequence, exchanges heat with the low-temperature phase-change material for energy storage, and the LNG after the heat exchange enters the CO2 capture, liquefaction and energy storage system and / or the low-temperature power generation system;

[0040] The CO2 capture, liquefaction and energy storage system includes a first CO2 liquefaction heat exchanger 3-6, a second CO2 liquefaction heat exchanger 3-9 and an air dehydrator 3-4. The incoming LNG flows through the second CO2 liquefaction heat exchanger, the first CO2 liquefaction heat exchanger and the air dehydrator in sequence. After the heat exchange, the LNG enters the low-temperature power generation system.

[0041] The low temperature power generation system includes LNG direct expanders 4-9. The input LNG is directly expanded by the LNG direct expanders to generate electricity, and after releasing the cold, it becomes gaseous natural gas and is stored in the natural gas tank.

[0042] In this embodiment, the four systems utilizing LNG cold energy use cold energy at a temperature that gradually decreases from top to bottom, so that a series connection can be formed to gradually utilize the cold energy of LNG.

[0043] like Figure 1 As shown, the LNG tank 1 is connected to the ultra-low temperature phase change material energy storage system, the low temperature phase change material energy storage system, the CO2 capture, liquefaction and energy storage system, and the low temperature power generation system through the flow regulating valve 2 and the LNG pump 3; the natural gas tank 13 is connected to the low temperature power generation system. By adjusting the opening of the flow regulating valve 2, the LNG flow pumped out of the LNG tank 1 and the LNG flow flowing into different systems can be controlled. In addition, the ultra-low temperature phase change material energy storage system is connected to the low temperature phase change material energy storage system through the valve 10 flow regulating valve 2-1, and is connected to the low temperature power generation system through the valve 8 and the flow regulating valve 4-2. The low temperature phase change material energy storage system is also connected to the CO2 capture, liquefaction and energy storage system through the valve 11 and the flow regulating valve 3-1, and is connected to the low temperature power generation system through the valve 9 and the flow regulating valve 4-2. The CO2 capture, liquefaction and energy storage system is also connected to the low temperature power generation system through the valve 12 and the flow regulating valve 4-1.

[0044] The ultra-low temperature cold energy transport vehicle 1-1 is equipped with a cold storage heat exchange pipe 1-2 and a cold release heat exchange pipe 1-3, and the two groups of heat exchange pipes are arranged alternately. In the heat storage stage, the cold storage heat exchange pipe 1-2 is connected to the system pipeline through the flow regulating valve 4 and the valve 10. After the ultra-low temperature cold energy transport vehicle 1-1 is transported over a long distance, the cold release heat exchange pipe 1-3 is connected to the ultra-low temperature cold energy heat exchanger 1-4. The ultra-low temperature phase change material energy storage system outlet temperature probe 1-5 is installed at the system outlet.

[0045] The low-temperature phase change material energy storage system inlet temperature probe 2-2, the second low-temperature cold energy heat exchanger 2-4, the first low-temperature cold energy heat exchanger 2-3 and the low-temperature phase change material energy storage system outlet temperature probe 2-12 are connected in sequence. In addition, the first low-temperature cold energy heat exchanger 2-3, the second low-temperature cold energy heat exchanger 2-4, the first low-temperature phase change material storage tank 2-5, the first low-temperature liquid phase change material pump 2-6, the second low-temperature phase change material storage tank 2-7, the second low-temperature liquid phase change material pump 2-8, the low-temperature cold energy heat exchanger 2-9, the gaseous low-temperature phase change material pump 2-10, and the gaseous low-temperature phase change material compressor 2-11 are connected in sequence.

[0046] In the CO2 capture, liquefaction and energy storage system, the CO2 capture, liquefaction and energy storage system inlet temperature probe 3-2, the second CO2 liquefaction heat exchanger 3-9, the first CO2 liquefaction heat exchanger 3-6 and the CO2 capture, liquefaction and energy storage system outlet temperature probe 3-14 are connected in sequence. The air pump 3-3, the air dehydrator 3-4, the air-water separator 3-5, the first CO2 liquefaction heat exchanger 3-6, the first air-CO2 separator 3-7, and the first liquid CO2 storage tank 3-8 are connected in sequence. In addition, the first air-CO2 separator 3-7 is also connected to the second CO2 liquefaction heat exchanger 3-9, the second air-CO2 separator 3-10 and the first liquid CO2 storage tank 3-8 in sequence. The first liquid CO2 storage tank 3-8, the first liquid CO2 pump 3-11, the second liquid CO2 storage tank 3-12, the second liquid CO2 pump 3-13, and the liquid CO2 heat exchanger 3-14 are connected in sequence.

[0047] The low-temperature power generation system inlet temperature probe 4-3, LNG-ORC working fluid heat exchanger 4-4, first LNG-seawater or low-temperature heat source heat exchanger 4-8, LNG direct expansion generator 4-9, second LNG-seawater or low-temperature heat source heat exchanger 4-11 and low-temperature power generation system outlet temperature probe 4-12 are connected in sequence. In addition, the LNG-ORC working fluid heat exchanger 4-4 is also connected to the ORC working fluid pump 4-5, ORC working fluid-seawater or low-temperature heat source heat exchanger 4-6, and ORC expander 4-7 in sequence. In addition, the ORC working fluid-seawater or low-temperature heat source heat exchanger 4-6, the first LNG-seawater or low-temperature heat source heat exchanger 4-8, and the second LNG-seawater or low-temperature heat source heat exchanger 4-11 are also connected to seawater or a low-temperature heat source.

[0048] In another preferred embodiment, the ultra-low temperature cold energy transport vehicle has an energy storage stage and an energy release stage; in the energy storage stage, LNG enters the cold storage heat exchange tube 1-2 and is transferred to the liquid phase change material, and the phase change material gradually solidifies to complete the energy storage; in the energy release stage, the cold release heat exchange tube 1-3 is connected to the ultra-low temperature cold energy heat exchange tube 1-4, and the heat exchange medium enters the cold release heat exchange tube, and the cold energy of the phase change material is gradually transferred to the heat exchange medium, and the phase change material gradually melts.

[0049] The LNG in the LNG tank 1 is pumped out by adjusting the opening of the flow regulating valve 2 and using the LNG pump 3. The pumped LNG is regulated by the flow regulating valve 4 and enters the cold storage heat exchange pipe 1-2 in the ultra-low temperature cold energy transport vehicle 1-1 of the ultra-low temperature phase change energy storage system. At this time, the phase change material (isopentane, 2-methylpentane, isoprene, etc.) loaded in the ultra-low temperature cold energy transport vehicle 1-1 is in a liquid state. As the cold energy of the LNG is transferred to the liquid phase change material, the LNG gradually vaporizes and the temperature gradually rises (its temperature is monitored by the ultra-low temperature phase change material energy storage system outlet temperature probe 1-5), and the phase change material gradually solidifies. After completing the energy storage, the solid phase change material is transported to a place where cold energy is needed by the ultra-low temperature cold energy transport vehicle 1-1 over a long distance, and the cold release heat exchange pipe 1-3 of the ultra-low temperature cold energy transport vehicle 1-1 is connected to the ultra-low temperature cold energy heat exchange pipe 1-4, and the heat exchange medium enters the cold release heat exchange pipe 1-3, and the cold energy of the phase change material is gradually transferred to the heat exchange medium, the phase change material gradually melts, and the temperature of the heat exchange medium gradually decreases. The heat exchange medium then transfers cold energy to other media in the ultra-low temperature cold energy heat exchanger 1-4. After the cold release is completed, the ultra-low temperature cold energy transport vehicle 1-1 returns to the cold storage location to continue the next cycle. The LNG that has completed cold storage can enter the low temperature phase change energy storage system through valve 10 and flow control valve 2-1, or directly enter the low temperature power generation system through valve 10, valve 8, and flow control valve 4-2.

[0050] In a preferred embodiment, the LNG entering the low-temperature phase change energy storage system comes from an ultra-low-temperature phase change material energy storage system or an LNG tank that completes energy storage, or it can be a mixture of the two.

[0051] The temperature of LNG entering the low-temperature phase change material energy storage system can be monitored by the low-temperature phase change material energy storage system inlet temperature probe 2-2. LNG comes from the ultra-low temperature phase change material energy storage system or LNG tank 1 that completes energy storage and can adjust the flow rate or temperature through the flow control valve 2-1 and the flow control valve 5. After mixing, LNG flows through the second low-temperature cold energy heat exchanger 2-4 and the first low-temperature cold energy heat exchanger 2-3 in sequence, and its flow direction is opposite to the flow direction of the low-temperature phase change material, and the cold energy of LNG can be used step by step. After completing the heat exchange, LNG can enter the CO2 capture, liquefaction and energy storage system through valve 11 and flow control valve 3-1, or directly enter the low-temperature power generation system through valve 11, valve 9 and flow control valve 4-2. In addition, the temperature of the high-temperature liquid phase change material (nitrogen trifluoride, etc.) gradually decreases after flowing through the first low-temperature cold energy heat exchanger 2-3 and the second low-temperature cold energy heat exchanger 2-4 in sequence, and can then be stored in the first low-temperature phase change material storage tank 2-5. Subsequently, it can be transported to the second low-temperature phase change material storage tank 2-7 where cold energy is needed through the first low-temperature phase change material pump 2-6 and pipeline, and released through the low-temperature cold energy heat exchanger 2-9 through the second low-temperature phase change material pump 2-8 to gradually increase the temperature and become a gaseous phase change material. Finally, it is transported to the cold storage place through the gaseous low-temperature phase change material pump 2-10 and pipeline, and the gaseous low-temperature phase change material compressor 2-11 is used to pressurize the gaseous phase change material into a liquid state, and continue the next cycle.

[0052] In this embodiment, the LNG entering the CO2 capture, liquefaction and energy storage system comes from a low-temperature phase change material energy storage system or an LNG tank that completes energy storage, or may be a mixture of the two.

[0053] The temperature of LNG entering the CO2 capture, liquefaction and energy storage system can be monitored by the CO2 capture, liquefaction and energy storage system inlet temperature probe 3-2. LNG comes from the low-temperature phase change material energy storage system or LNG tank 1 that completes energy storage and can adjust the flow rate or temperature through the flow control valve 3-1 and the flow control valve 6. After mixing, LNG flows through the second CO2 liquefaction heat exchanger 3-9, the first CO2 liquefaction heat exchanger 3-6 and the air dehydrator 3-4 in sequence. Its flow direction is opposite to the air flow direction, and the cold energy of LNG can be used step by step. After completing the heat exchange, LNG enters the low-temperature power generation system through valve 12, flow control valve 4-1 and flow control valve 4-2. The air is first pumped into the air dehydrator 3-4 by the air pump 3-3, and the cold energy of LNG is used to condense the water in the air, and then the solid water is removed through the air-water separator 3-5. The dehydrated air passes through the first CO2 liquefaction heat exchanger 3-6 to liquefy part of the CO2 therein, and the liquid CO2 is separated in the subsequent first air-CO2 separator 3-7 and stored in the first liquid CO2 storage tank 3-8. The remaining gas enters the second CO2 liquefaction heat exchanger 3-9 to liquefy most of the CO2, and the liquid CO2 is separated in the subsequent second air-CO2 separator 3-10 and stored in the first liquid CO2 storage tank 3-8. The liquid CO2 in the first liquid CO2 storage tank 3-8 is transported to a location where liquid CO2 and cold energy are required through the first liquid CO2 pump 3-11 and the pipeline and stored in the second liquid CO2 storage tank 3-12. The liquid CO2 can then be used directly or transported to the liquid CO2 heat exchanger 3-14 to release cold energy.

[0054] In this embodiment, the LNG fed into the low-temperature power generation system comes from an ultra-low temperature phase change material energy storage system, a low-temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system and / or an LNG tank, and can also be a mixture of at least two of the above LNG.

[0055] The temperature of LNG entering the low-temperature power generation system can be monitored by the low-temperature power generation system inlet temperature probe 4-3. LNG comes from the above three systems or LNG tank 1 and can adjust the flow or temperature through flow regulating valve 4-1, flow regulating valve 7 and flow regulating valve 4-2. After mixing, LNG first passes through LNG-ORC working fluid heat exchanger 4-4 to transfer the cold energy of LNG to ORC working fluid, and the temperature of LNG gradually rises and the temperature of ORC working fluid gradually decreases. Then LNG flows through the first LNG-seawater or low-temperature heat source heat exchanger 4-8, the temperature of LNG increases and the pressure increases, and it is directly expanded through LNG direct expander 4-9 to generate electricity. Finally, LNG passes through the second LNG-seawater or low-temperature heat source heat exchanger 4-11, and after releasing the cold, it becomes gaseous natural gas and is stored in the natural gas tank 13. The ORC working fluid used for ORC power generation is pumped into the ORC working fluid-seawater or low-temperature heat source heat exchanger 4-5, the temperature of ORC increases, and enters the ORC expander 4-7 for power generation. The high-temperature ORC working fluid flows into the LNG-ORC working fluid heat exchanger 4-4 and the temperature drops, and the next cycle continues. In addition, LNG from the above three systems or LNG tank 1 can also be directly introduced into the second LNG-seawater or low-temperature heat source heat exchanger 4-11 through valve 4-10 to quickly supply natural gas or reduce the shortage of natural gas supply caused by failure of the above four systems.

[0056] In addition, the four energy storage or power generation systems in the present invention can also realize the independent operation of a single or multiple systems by adjusting valves or flow control valves, thereby increasing the flexibility of using LNG cold energy. For example, to realize the operation of a single CO2 capture, liquefaction and energy storage system and shut down the other systems, the regulating valve 2, regulating valve 6, valve 12, regulating valve 4-1, and valve 4-10 can be opened, and the other valves can be closed to realize the independent operation of the system without affecting other systems. If only the low-temperature phase change material energy storage system and the low-temperature power generation system are to be operated, the regulating valve 2, regulating valve 5, valve 11, valve 9, and regulating valve 4-2 need to be opened, and the other valves need to be closed to realize the operation of only the low-temperature phase change material energy storage system and the low-temperature power generation system.

[0057] The above description is only an example of a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cascade cold storage device for storing and transporting LNG cold energy using a variety of phase change materials, comprising an LNG tank and a natural gas tank, characterized in that: It has an ultra-low temperature phase change material energy storage system, a low temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system, and a low temperature power generation system connected to the LNG tank; the natural gas tank is connected to the low temperature power generation system; The ultra-low temperature phase change material energy storage system includes an ultra-low temperature cold energy transport vehicle equipped with a cold storage heat exchange tube and a cold release heat exchange tube. LNG output from the LNG tank enters the cold storage heat exchange tube and is transferred to the liquid phase change material in the cold release heat exchange tube for energy storage; the cold-stored LNG is used to be output to the low temperature phase change energy storage system and / or the low temperature power generation system; The low-temperature phase-change energy storage system comprises a first low-temperature heat exchanger and a second low-temperature heat exchanger. The incoming LNG flows through the second low-temperature heat exchanger and the first low-temperature heat exchanger in sequence, exchanges heat with the low-temperature phase-change material to store energy, and the LNG after the heat exchange enters the CO2 capture, liquefaction and energy storage system and / or the low-temperature power generation system. The CO2 capture, liquefaction and energy storage system comprises a first CO2 liquefaction heat exchanger, a second CO2 liquefaction heat exchanger and an air dehydrator, the incoming LNG flows through the second CO2 liquefaction heat exchanger, the first CO2 liquefaction heat exchanger and the air dehydrator in sequence, and the LNG after heat exchange enters the low-temperature power generation system; The low-temperature power generation system includes an LNG direct expander. The input LNG is directly expanded by the LNG direct expander to generate electricity, and after releasing the cold, it becomes gaseous natural gas and is stored in a natural gas tank.

2. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 1 is characterized in that: The ultra-low temperature cold energy transport vehicle has an energy storage stage and an energy release stage; in the energy storage stage, LNG enters the cold storage heat exchange tube and is transferred to the liquid phase change material, the phase change material gradually solidifies, and the energy storage is completed; in the energy release stage, the cold release heat exchange tube is connected to the ultra-low temperature cold energy heat exchange tube, the heat exchange medium enters the cold release heat exchange tube, the cold energy of the phase change material is gradually transferred to the heat exchange medium, and the phase change material gradually melts.

3. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 1 is characterized in that: The low-temperature phase change energy storage system is provided with a low-temperature phase change material storage tank, a low-temperature cold energy heat exchanger and a gaseous low-temperature phase change material compressor which are connected in sequence; after the liquid phase change material flows through the first low-temperature cold energy heat exchanger and the second low-temperature cold energy heat exchanger in sequence, the temperature gradually drops and is stored in the first low-temperature phase change material storage tank, and then flows through the low-temperature cold energy heat exchanger to release the cold energy and the temperature changes into a gaseous phase change material, and the gaseous phase change material is pressurized into a liquid by the gaseous low-temperature phase change material compressor for circulating heat exchange with LNG.

4. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 3 is characterized in that: The LNG entering the low-temperature phase change energy storage system comes from the ultra-low-temperature phase change material energy storage system and / or the LNG tank that completes the energy storage.

5. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 1 is characterized in that: The LNG entering the CO2 capture, liquefaction and energy storage system comes from the low-temperature phase change material energy storage system and / or LNG tank that completes the energy storage.

6. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 5 is characterized in that: The CO2 capture, liquefaction and energy storage system also includes an air pump, an air-water separator, a first air-CO2 separator, a second air-CO2 separator and a first liquid CO2 storage tank; the pumped air enters the air dehydrator and the cold energy of LNG condenses the water in the air; the air-water separator is used to remove solid water in the air; the air after dehydration is liquefied through the first CO2 liquefaction heat exchanger and the second CO2 liquefaction heat exchanger; the first air-CO2 separator is used to separate the liquid CO2 in the first CO2 liquefaction heat exchanger; the second air-CO2 separator is used to separate the liquid CO2 in the second CO2 liquefaction heat exchanger; the first liquid CO2 storage tank is used to store liquid CO2.

7. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 6 is characterized in that: The CO2 capture, liquefaction and energy storage system also includes a second liquid CO2 storage tank connected to the first liquid CO2 storage tank, and is provided with a liquid CO2 heat exchanger connected to the second liquid CO2 storage tank; the liquid CO2 heat exchanger is used to release cold energy.

8. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 1 is characterized in that: The LNG fed into the low-temperature power generation system comes from an ultra-low temperature phase change material energy storage system, a low temperature phase change material energy storage system, a CO2 capture, liquefaction and energy storage system and / or an LNG tank.

9. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 8, characterized in that: The low-temperature power generation system includes an LNG-ORC working fluid heat exchanger, through which LNG transfers cold energy to an ORC working fluid; an ORC working fluid-seawater or low-temperature heat source heat exchanger and an ORC expander connected to the LNG-ORC working fluid heat exchanger, wherein the ORC working fluid used for ORC power generation is pumped into the ORC working fluid-seawater or low-temperature heat source heat exchanger, and after being heated, enters the ORC expander to generate electricity.

10. The cascade cold storage device for storing and transporting LNG cold energy using multiple phase change materials according to claim 9, characterized in that: A first LNG-seawater or low-temperature heat source heat exchanger is provided which is connected to the LNG-ORC working medium heat exchanger, and the LNG heated by the first LNG-seawater or low-temperature heat source heat exchanger enters the LNG direct expander to generate electricity; A second LNG-seawater or low-temperature heat source heat exchanger connected to the LNG direct expander is provided to release the LNG outputted by the LNG direct expander and convert it into gaseous natural gas to be stored in a natural gas tank.

Images