LNG and freeze-dried carbon dioxide energy storage system and working method

Abstract

The present invention provides a carbon dioxide energy storage system combined with LNG and freeze drying, including a low-pressure liquid storage tank, a high-pressure liquid storage tank, freeze drying equipment and an LNG station, wherein the low-pressure liquid storage tank and the high-pressure liquid storage tank are respectively connected through an energy storage pipeline and an energy release pipeline to form a circulation pipeline, and a first heat exchanger is provided on the energy storage pipeline, and the first heat exchanger and the LNG station are respectively connected to the freeze drying equipment and are respectively used to provide cold energy for the freeze drying equipment during nighttime energy storage and daytime LNG gasification. The carbon dioxide energy storage system combined with LNG and freeze drying of the present invention has low manufacturing cost and use cost, high energy utilization rate, energy saving and environmental protection, and reliable system operation, stable temperature and good use effect.

Description

Technical Field

[0001] The present invention relates to an energy storage system, and in particular to a carbon dioxide energy storage system combined with LNG and freeze drying and a working method thereof. Background Art

[0002] Vacuum freeze drying technology is one of the most advanced food processing technologies. However, as a large energy consumer, vacuum freeze drying equipment consumes hundreds of millions of electricity each year, which greatly increases the power generation pressure of local power systems. Of the large amount of energy consumed by freeze drying equipment, about 70% is used for refrigeration, the purpose of which is to capture the sublimated gaseous water in food for a long time and at a temperature below -40°C. Such high energy consumption will be more competitive if it can be combined with current compressed air energy storage technology and LNG technology.

[0003] Compressed air technology is to store the abandoned electricity in the off-peak period of the power system in the form of heat energy and carbon dioxide potential energy, and release it in the form of electrical energy during the peak period of the power system, which will greatly reduce the peak load of the power system. Carbon dioxide energy storage (CES) technology is a new physical energy storage technology based on compressed air energy storage (CAES) and Brayton power generation cycle. The energy storage time can exceed 16 hours and the energy release power can reach GW level. It has the advantages of high energy storage density, long operating life, and compact system equipment. It is suitable for large-scale long-term energy storage and has good development and application prospects. In the existing technical application, during the low electricity price period, the atmospheric gaseous carbon dioxide is converted into high-pressure liquid carbon dioxide through a multi-stage compressor, and the electrical energy is converted into the form of carbon dioxide internal energy for storage; during the peak period of electricity consumption, the high-pressure liquid carbon dioxide is expanded into atmospheric gaseous carbon dioxide through a multi-stage expander to generate electricity, and finally realize the storage and release of electrical energy.

[0004] LNG is a form of energy that is made by cooling gaseous natural gas to about -162°C under normal pressure and condensing it into liquid form. Its main component is methane, and it may also contain a small amount of other components such as ethane, propane, and nitrogen. LNG has been widely used in the energy field due to its high efficiency, economy and cleanliness.

[0005] China has developed rapidly in the field of LNG, and has built multiple LNG receiving stations and planned coastal LNG receiving stations and transmission pipelines to meet the domestic demand for clean energy. However, a large amount of ultra-low temperature cold energy generated by LNG is discharged into the sea due to the inability to find suitable application scenarios, becoming waste energy.

[0006] At the same time, the traditional carbon dioxide energy storage system has the following disadvantages: 1. The cost investment is huge, and its cost includes multi-stage compressors, multi-stage expanders, and atmospheric pressure carbon dioxide gas storage bags, etc. The cost of technology promotion cannot be ignored; 2. The energy conversion efficiency is low. The system converts electrical energy into internal energy storage with the help of carbon dioxide, outputs electrical energy when releasing internal energy, and finally generates benefits by doing work with electrical energy. Although the electricity generated is widely used, the system is inefficient due to multiple energy conversions. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a carbon dioxide energy storage system combined with LNG and freeze drying which has a compact structure, low production cost and use cost, high energy conversion rate, and is energy-saving and environmentally friendly.

[0008] The present invention provides a carbon dioxide energy storage system combined with LNG and freeze drying, comprising a low-pressure liquid storage tank 1, a high-pressure liquid storage tank 7, freeze drying equipment 4 and an LNG station. The low-pressure liquid storage tank 1 and the high-pressure liquid storage tank 7 are respectively connected through an energy storage pipeline and an energy release pipeline to form a circulation pipeline. A first heat exchanger 31 is provided on the energy storage pipeline. The first heat exchanger 31 and the LNG station are respectively connected to the freeze drying equipment 4 and are respectively used to provide cold energy for the freeze drying equipment 4 during energy storage at night and LNG gasification during the day.

[0009] Furthermore, the output end of the low-pressure liquid storage tank 1 is connected to the high-pressure liquid storage tank 7 through a first pipeline, and the first pipeline is provided with a first expansion valve 21, a first heat exchanger 31, a compressor 5, a second heat exchanger 32 and a third heat exchanger 33 in sequence to form the energy storage pipeline, and the second heat exchanger 32 and the third heat exchanger 33 cool down the medium in the pipe in sequence and liquefy it; the output end of the high-pressure liquid storage tank 7 is connected to the low-pressure liquid storage tank 1 through a second pipeline, and the second expansion valve 22, a fourth heat exchanger 34, a fifth heat exchanger 35 and an expansion generator 9 are provided on the second pipeline in sequence to form an energy release pipeline, and the fourth heat exchanger 34 and the fifth heat exchanger 35 heat up the medium in the pipe in sequence, and internal heat exchange can be achieved between the second heat exchanger 32, the third heat exchanger 33, the fourth heat exchanger 34 and the fifth heat exchanger 35.

[0010] Furthermore, it also includes a heat storage tank 11 and a cold storage tank 12. The output end of the heat storage tank 11 is connected to the cold storage tank 12 after passing through the first circulation pump and the fifth heat exchanger 35 in sequence, so as to heat the fifth heat exchanger 35 and transport the cold medium after heat exchange to the cold storage tank 12; the output end of the cold storage tank 12 is connected to the heat storage tank 11 after passing through the second circulation pump and the second heat exchanger 32 in sequence, so as to cool down the second heat exchanger 32 and transport the hot medium after heat exchange to the heat storage tank 11.

[0011] Furthermore, it also includes a phase-change cold and heat storage tank 8, which is arranged between the third heat exchanger 33 and the fourth heat exchanger 34, and is used to store the heat generated by the liquefaction of the medium in the third heat exchanger 33 in the phase-change cold and heat storage tank 8 and provide heat for the vaporization of the medium in the fourth heat exchanger 34, or store the cold energy generated by the vaporization of the medium in the fourth heat exchanger 34 in the phase-change cold and heat storage tank 8 and provide cold energy for the liquefaction of the medium in the third heat exchanger 33.

[0012] Furthermore, a liquefaction buffer tank 6 is connected in series between the third heat exchanger 33 and the high-pressure liquid storage tank 7. A loop pipe 61 is provided on the liquefaction buffer tank 6. The loop pipe 61 is connected to the input end of the third heat exchanger 33 to form a loop, and can allow the medium that is not completely liquefied to return to the third heat exchanger 33 and be cooled and liquefied again.

[0013] Furthermore, the compressor 5 and the second heat exchanger 32 may be one or more groups, and the fifth heat exchanger 35 and the expansion generator 9 may be one or more groups.

[0014] Furthermore, a sixth heat exchanger 36 is provided at the rear end of the expansion generator 9, and the LNG station is connected to the sixth heat exchanger 36 to provide cold energy for heat exchange of the sixth heat exchanger 36 when the LNG is gasified during the day.

[0015] Furthermore, the medium in the low-pressure liquid storage tank 1 is 0.8Mpa-1.3Mpa of liquid carbon dioxide at -45°C to -35°C, and the medium in the high-pressure liquid storage tank 7 is 6.5Mpa-7.5Mpa of liquid carbon dioxide at 25°C to 35°C.

[0016] At the same time, the present invention also provides a working method of a carbon dioxide energy storage system combined with LNG and freeze drying, which comprises the following steps:

[0017] S1. Energy storage:

[0018] S11, the liquid carbon dioxide of 0.8Mpa-1.3Mpa at -45℃ to -35℃ in the low-pressure liquid storage tank 1 is expanded through the first expansion valve 21 to form isobaric gaseous carbon dioxide, and a large amount of gasification cold energy generated by the expansion is supplied to the freeze-drying equipment production through the first heat exchanger 31;

[0019] S12, the gaseous carbon dioxide of 0.8Mpa-1.3Mpa is compressed by the compressor to form a high-temperature gaseous carbon dioxide of 6.5Mpa-7.5Mpa, the cold medium in the cold storage tank 12 enters the heat storage tank 11 after heat exchange by the second heat exchanger 32, and the high-temperature gaseous carbon dioxide of 6.5Mpa-7.5Mpa is cooled by the second heat exchanger 32 to form an isobaric medium-temperature gaseous carbon dioxide;

[0020] S13, the medium-temperature gaseous carbon dioxide of 6.5Mpa-7.5Mpa is cooled by heat exchange in the third heat exchanger 33 to form isobaric liquid carbon dioxide, and then enters the high-pressure liquid storage tank 7 for storage after passing through the liquefaction buffer tank 6. The heat generated by the liquefaction in the third heat exchanger 33 is stored in the phase change cold and heat storage tank 8;

[0021] S14, the carbon dioxide that is not completely liquefied after cooling is returned to the third heat exchanger 33 through the loop pipe 61 to continue to be cooled until it is completely liquefied;

[0022] S2. Energy release:

[0023] S21, the medium-temperature liquid carbon dioxide of 6.5Mpa-7.5Mpa in the high-pressure liquid storage tank 7 is expanded through the second expansion valve 22 to form isobaric gaseous carbon dioxide, and a large amount of gasification cold energy generated by the expansion is stored in the phase-change cold and heat storage tank 8 through the fourth heat exchanger 34, or when in extreme weather and the ambient temperature is lower than the temperature required for the expansion and gasification of the medium, the heat energy stored in the phase-change cold and heat storage tank 8 provides heat for the gasification of the medium in the fourth heat exchanger 34;

[0024] S22, the heat medium in the heat storage tank 11 enters the cold storage tank 12 after passing through the fifth heat exchanger 35, and the 6.5Mpa-7.5Mpa gaseous carbon dioxide enters the expansion generator 9 after heat exchange and temperature increase through the fifth heat exchanger 35 to expand and generate electricity, and forms 0.8Mpa-1.3Mpa gaseous carbon dioxide;

[0025] S23, the cold energy of the LNG station cools and liquefies the 0.8Mpa-1.3Mpa gaseous carbon dioxide in the second pipeline through the sixth heat exchanger 36, and forms 0.8Mpa-1.3Mpa liquid carbon dioxide at -45℃ to -35℃ and stores it in the low-pressure liquid storage tank 1.

[0026] Furthermore, energy storage is performed at night when electricity prices are low, and energy release is performed during daytime when electricity prices are high, and cold energy for the freeze-drying equipment 4 during the daytime is provided by gasification from the LNG station. Beneficial Effects

[0027] The carbon dioxide energy storage system combined with LNG and freeze-drying of the present invention abandons the single energy storage form of traditional carbon dioxide energy storage for the purpose of power generation, combines carbon dioxide energy storage with production, introduces carbon dioxide energy storage into the freeze-drying industry which requires a large amount of cold, and combines it with the LNG industry which has serious cold waste. The three industries are combined to form a set of LNG-combined energy storage system dominated by the freeze-drying industry; energy utilization is rationalized, equipment investment costs are lowered, and market competitiveness is improved. At the same time, it also has the following advantages: 1. In view of the production characteristics that freeze-drying equipment needs cooling 24 hours a day and LNG only generates a large amount of cold energy during the day, when LNG has no cold energy at night, a large amount of cold energy generated by the gasification of carbon dioxide liquid is used for freeze-drying production. When LNG has cold energy during the day, the cold energy of LNG is used for freeze-drying equipment and carbon dioxide liquefaction, which greatly utilizes the characteristic that LNG cold energy cannot be used; 2. In the liquefaction and gasification stages of carbon dioxide, a large amount of heat generated by liquefaction is stored in the phase-change cold-heat storage tank through the phase-change cold-heat storage tank, and a large amount of cold generated by gasification is stored in the phase-change cold-heat storage tank for heat exchange, so that the temperature is more stable; the carbon dioxide energy storage system combined with LNG and freeze-drying of the present invention has low manufacturing cost and use cost, high energy utilization rate, energy saving and environmental protection, and reliable system operation, stable temperature and good use effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a connection schematic diagram of the carbon dioxide energy storage system combined with LNG and freeze drying of the present invention;

[0029] In the figure: 1. low-pressure liquid storage tank, 11. heat storage tank, 12. cold storage tank, 21. first expansion valve, 22. second expansion valve, 31. first heat exchanger, 32. second heat exchanger, 33. third heat exchanger, 34. fourth heat exchanger, 35. fifth heat exchanger, 36. sixth heat exchanger, 4. freeze-drying equipment, 5. compressor, 6. liquefaction buffer tank, 61. loop pipe, 7. high-pressure liquid storage tank, 8. phase change cold and heat storage tank, 9. expansion generator. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] See also Figure 1The present invention provides a carbon dioxide energy storage system combined with LNG and freeze drying, which includes a low-pressure liquid storage tank 1, a high-pressure liquid storage tank 7, a freeze drying device 4 and an LNG station. The low-pressure liquid storage tank 1 is used to store a low-pressure liquid medium, and the high-pressure liquid storage tank 7 is used to store a high-pressure liquid medium, wherein the medium is carbon dioxide. The low-pressure liquid storage tank 1 is connected to the high-pressure liquid storage tank 7 through an energy storage pipeline, and the medium in the energy storage pipeline is output by the low-pressure liquid storage tank 1 and flows toward the high-pressure liquid storage tank 7. The high-pressure liquid storage tank 7 is connected to the low-pressure liquid storage tank 1 through an energy release pipeline, and the medium in the energy release pipeline is output by the high-pressure liquid storage tank 7 and flows toward the low-pressure liquid storage tank 1, thereby forming a circulation pipeline. A first heat exchanger 31 is provided on the energy storage pipeline, and the first heat exchanger 31 and the LNG station are respectively connected to the freeze drying device 4, wherein the first heat exchanger 31 is used to provide cold energy for the freeze drying device 4 when storing energy at night, and the LNG station is used to provide cold energy for the freeze drying device 4 when LNG is gasified during the day.

[0032] In this embodiment, the medium in the low-pressure liquid storage tank 1 is 0.8Mpa-1.3Mpa liquid carbon dioxide at -45°C to -35°C, and the medium in the high-pressure liquid storage tank 7 is 6.5Mpa-7.5Mpa liquid carbon dioxide at 25°C to 35°C.

[0033] Specifically, the output end of the low-pressure liquid storage tank 1 is connected to the high-pressure liquid storage tank 7 through a first pipeline, and a first expansion valve 21, a first heat exchanger 31, a compressor 5, a second heat exchanger 32 and a third heat exchanger 33 are sequentially arranged along the medium conveying direction on the first pipeline, which forms an energy storage pipeline, and the second heat exchanger 32 and the third heat exchanger 33 sequentially cool the medium in the pipe to liquefy the medium, that is, convert it from gas to liquid; the output end of the high-pressure liquid storage tank 7 is connected to the low-pressure liquid storage tank 1 through a second pipeline, and a second expansion valve 21, a first heat exchanger 31, a compressor 5, a second heat exchanger 32 and a third heat exchanger 33 are sequentially arranged along the medium conveying direction on the second pipeline. 22. The fourth heat exchanger 34, the fifth heat exchanger 35 and the expansion generator 9 form an energy release pipeline. The fourth heat exchanger 34 and the fifth heat exchanger 35 heat up the medium in the pipe in turn. At the same time, internal heat exchange can be achieved between the second heat exchanger 32, the third heat exchanger 33, the fourth heat exchanger 34 and the fifth heat exchanger 35, that is, the second heat exchanger and the third heat exchanger generate heat after heat exchange, and the heat can provide heat energy for heat exchange for the fourth heat exchanger and the fifth heat exchanger, so that the medium in the fourth heat exchanger is vaporized and forms a gas, the medium in the fifth heat exchanger is heated, and the power generation is increased.

[0034] The present application also includes a heat storage tank 11 and a cold storage tank 12. The output end of the heat storage tank 11 is connected to the cold storage tank 12 after passing through the first circulation pump and the fifth heat exchanger 35 in sequence. The heat medium in the heat storage tank 11 heats the fifth heat exchanger 35, and the cold medium after heat exchange is transported to the cold storage tank 12. Through the heat exchange, the medium (carbon dioxide) in the fifth heat exchanger 35 can be heated to increase the power generation. The first circulation pump provides power for the medium in the pipe; the output end of the cold storage tank 12 is connected to the heat storage tank 11 after passing through the second circulation pump and the second heat exchanger 32 in sequence. The cold medium in the cold storage tank 12 cools the second heat exchanger 32, and the hot medium after heat exchange is transported to the heat storage tank 11. Through the heat exchange, the medium in the second heat exchanger 32 can be pre-cooled so that the rear end can achieve rapid liquefaction. The second heat exchanger 32 and the fifth heat exchanger 35 form an internal energy cold and heat balance, and the generated cold and heat are mutually compensated and offset by heat exchange, with high energy utilization and low power consumption.

[0035] At the same time, in the present application, a phase-change cold and heat storage tank 8 is included, in which a phase-change material is arranged. The phase-change material absorbs or releases a large amount of latent heat during the phase change process, thereby generating a cold storage or heat storage function, and its energy density is high. The heat storage density of the phase-change heat storage is 5 to 10 times or even higher than that of the sensible heat storage; the phase-change cold and heat storage tank 8 is arranged between the third heat exchanger 33 and the fourth heat exchanger 34, and is used to store the heat generated by the liquefaction of the medium in the third heat exchanger 33 in the phase-change cold and heat storage tank 8, and provide heat for the gasification of the medium in the fourth heat exchanger 34. The amount of heat generated by the gasification of the medium in the fourth heat exchanger 34 is stored in the phase-change cold and heat storage tank 8 to provide cold energy for the liquefaction of the medium in the third heat exchanger 33. The system can utilize its own heat energy (liquefaction) and cold energy (gasification) to achieve internal heat exchange, thus simplifying the system. At the same time, in extreme weather and when the ambient temperature is lower than the temperature required for the expansion and gasification of the medium, the heat energy stored in the phase-change cold and heat storage tank provides heat for the gasification of the medium in the fourth heat exchanger to ensure that the medium in the pipe is fully gasified, thereby greatly improving the reliability and stability of the overall operation and making the temperature more stable.

[0036] A liquefaction buffer tank 6 is connected in series between the third heat exchanger 33 and the high-pressure liquid storage tank 7. A loop pipe 61 is provided on the liquefaction buffer tank 6. The loop pipe 61 is connected to the input end of the third heat exchanger 33 to form a loop, which can make the medium (carbon dioxide) that is not completely liquefied return to the third heat exchanger 33 and cool and liquefy again, thereby ensuring that the medium is fully liquefied and improving the overall operating reliability and stability of the system.

[0037] In the present application, the compressor 5 and the second heat exchanger 32 constitute a compressor group, which can be one group or multiple groups. When there are multiple groups, they are connected in series in sequence; the fifth heat exchanger 35 and the expansion generator 9 constitute an expansion generator group, which can be one group or multiple groups. When there are multiple groups, they are connected in series in sequence, and it can be adjusted according to different usage requirements.

[0038] At the same time, a sixth heat exchanger 36 is provided at the rear end of the expansion generator 9, and the LNG station is connected to the sixth heat exchanger 36 to provide cold energy for heat exchange of the sixth heat exchanger 36 when LNG is gasified during the day, thereby cooling the medium in the energy release pipeline to form liquid carbon dioxide, which is stored in the low-pressure liquid storage tank 1.

[0039] The carbon dioxide energy storage system combined with LNG and freeze drying of the present invention is mainly divided into two parts, the nighttime energy storage stage and the daytime energy release stage. The freeze drying equipment 4 operates 24 hours a day and requires uninterrupted cooling. The characteristic of LNG is that it only generates a large amount of cooling energy during the day and almost no cooling energy at night. In view of the characteristics of the above three equipments, the operation mode of this energy storage system is as follows:

[0040] Nighttime energy storage stage: When the electricity price is low at night, the 1Mpa -51°C carbon dioxide liquid in the low-pressure liquid storage tank 1 expands through the first expansion valve 21 to form 1Mpa gas, and the large amount of gasification cold generated by the expansion is supplied to the freeze-drying equipment 4 for production through the first heat exchanger 31; the 1Mpa carbon dioxide gas passes through the compressor unit to form high-temperature 7Mpa carbon dioxide gas, and the heat is stored in the heat storage tank 11 through the second heat exchanger 32, and the 7Mpa medium-temperature gaseous carbon dioxide gas passes through the third heat exchanger 33 and the cold in the phase change cold and heat storage tank 8 to form 7Mpa 31°C carbon dioxide liquid and store it in the high-pressure liquid storage tank 7.

[0041] Energy release stage during the day: When electricity prices are high during the day, the 7Mpa 31°C carbon dioxide liquid in the high-pressure liquid storage tank 7 expands through the second expansion valve 22 to form 7Mpa gas. The large amount of vaporized cold energy generated by the expansion is stored in the phase change cold and heat storage tank 8 through the fourth heat exchanger 34, and is vaporized to form carbon dioxide gas. The 7Mpa carbon dioxide gas is heated through the fifth heat exchanger 35 and enters the expansion generator 9 to generate electricity. The expansion generator 9 is a turbine expansion generator, and finally forms 1Mpa carbon dioxide gas. The 1Mpa gaseous carbon dioxide is liquefied through the sixth heat exchanger and LNG cold energy to form carbon dioxide liquid, which is stored in the low-pressure liquid storage tank.

[0042] During the entire operation process, LNG cold energy is used to supply the liquefaction and freeze-drying production of carbon dioxide at 1Mpa during the day; LNG does not supply cold energy at night, and the cold energy required for freeze-drying is all provided by the cold energy generated during the gasification process of carbon dioxide at 1Mpa.

[0043] The present invention combines the freeze-drying industry, the LNG industry and the carbon dioxide energy storage industry, and utilizes their respective advantages to complement each other, thereby improving the energy conversion efficiency of carbon dioxide energy storage, effectively utilizing the waste cold energy of LNG, and reducing the operating cost of freeze-drying equipment. It is mainly divided into a nighttime energy storage stage and a daytime energy release stage. The equipment in the nighttime energy storage stage is mainly composed of a low-pressure liquid storage tank 1, a first expansion valve 21, a first heat exchanger 31, a compressor 5, a second heat exchanger 32, a third heat exchanger 33, a liquefaction buffer tank 6 and a high-pressure liquid storage tank 7. The equipment in the daytime energy release stage is mainly composed of a high-pressure liquid storage tank 7, a fourth heat exchanger 34, a fifth heat exchanger 35, an expansion generator 9, a sixth heat exchanger 36 and a low-pressure liquid storage tank 1. During the operation of the system, a heat storage tank 11 and a cold storage tank 45 are added to complement the cold energy and heat energy generated by the operation of the equipment. The entire set of carbon dioxide energy storage system will be connected to LNG and freeze-drying equipment to form their functional complementarity.

[0044] At the same time, the present invention also provides a working method of a carbon dioxide energy storage system combined with LNG and freeze drying, which comprises the following steps:

[0045] S1. Energy storage:

[0046] S11, the liquid carbon dioxide of 0.8Mpa-1.3Mpa at -45°C to -35°C in the low-pressure liquid storage tank 1 is expanded through the first expansion valve 21 to form isobaric gaseous carbon dioxide, and a large amount of gasification cold energy generated by the expansion is supplied to the freeze-drying equipment 4 for production through the first heat exchanger 31. Preferably, the liquid carbon dioxide of 1Mpa at -41°C in the low-pressure liquid storage tank 1;

[0047] S12, 0.8Mpa-1.3Mpa gaseous carbon dioxide is compressed by the compressor 5 to form 6.5Mpa-7.5Mpa high-temperature gaseous carbon dioxide. Preferably, 1Mpa gaseous carbon dioxide is compressed to form 7Mpa high-temperature gaseous carbon dioxide. The cold medium in the cold storage tank 12 enters the heat storage tank 11 after heat exchange by the second heat exchanger 32. The 6.5Mpa-7.5Mpa high-temperature gaseous carbon dioxide is cooled by the second heat exchanger 32 to form isobaric (same pressure) medium-temperature gaseous carbon dioxide; preferably, 7Mpa liquid carbon dioxide at 31°C is formed after liquefaction;

[0048] S13, the medium-temperature gaseous carbon dioxide of 6.5Mpa-7.5Mpa is cooled by heat exchange in the third heat exchanger 33 to form isobaric (same pressure) liquid carbon dioxide, and then enters the high-pressure liquid storage tank 7 for storage after passing through the liquefaction buffer tank 6. The heat generated by the liquefaction in the third heat exchanger 33 is stored in the phase change cold and heat storage tank 8;

[0049] S14, the carbon dioxide that is not completely liquefied after cooling is returned to the third heat exchanger 33 through the loop pipe 61 to continue to be cooled until it is completely liquefied;

[0050] S2. Energy release:

[0051] S21, the medium-temperature liquid carbon dioxide of 6.5Mpa-7.5Mpa in the high-pressure liquid storage tank 7 is expanded through the second expansion valve 22 to form isobaric gaseous carbon dioxide. Preferably, the 7Mpa liquid carbon dioxide of 31°C in the high-pressure liquid storage tank 7 is expanded to form isobaric gaseous carbon dioxide. A large amount of gasification cold energy generated by the expansion is stored in the phase-change cold and heat storage tank 8 through the fourth heat exchanger 34. Or, when in extreme weather and the ambient temperature is lower than the temperature required for the expansion and gasification of the medium, the heat energy stored in the phase-change cold and heat storage tank 8 provides heat for the gasification of the medium in the fourth heat exchanger 34.

[0052] S22, the heat medium in the heat storage tank 11 enters the cold storage tank 12 after passing through the fifth heat exchanger 35, and the 6.5Mpa-7.5Mpa gaseous carbon dioxide enters the expansion generator 9 after heat exchange and temperature increase through the fifth heat exchanger 35 to expand and generate electricity, and forms 0.8Mpa-1.3Mpa gaseous carbon dioxide. Preferably, the 7Mpa gaseous carbon dioxide is expanded and generated electricity to form 1Mpa gaseous carbon dioxide;

[0053] S23, the cold energy of the LNG station is used to cool and liquefy the 0.8Mpa-1.3Mpa gaseous carbon dioxide in the second pipeline through the sixth heat exchanger 36, and form 0.8Mpa-1.3Mpa liquid carbon dioxide at -45℃ to -35℃ and store it in the low-pressure liquid storage tank 1. Preferably, the 1Mpa gaseous carbon dioxide in the pipe is cooled and liquefied to form 1Mpa liquid carbon dioxide at -41℃.

[0054] Meanwhile, in the above process, energy storage is carried out at night when electricity prices are low, and energy release is carried out during daytime when electricity prices are high, and cold energy for the freeze drying equipment 4 and the sixth heat exchanger 36 is provided by gasification of the LNG station during the daytime.

[0055] The above-mentioned high temperature, medium temperature and low temperature are relative temperatures, and the high pressure, medium pressure and low pressure are relative pressures.

[0056] Through the above temperature and pressure settings, energy utilization can be maximized, and maximum cooling energy and maximum power generation can be generated.

[0057] The carbon dioxide energy storage system combined with LNG and freeze drying of the present invention abandons the single energy storage form of traditional carbon dioxide energy storage for the purpose of power generation, combines carbon dioxide energy storage with production, introduces carbon dioxide energy storage into the freeze drying industry that requires a large amount of cold, and combines it with the LNG industry that wastes a lot of cold. The three industries are combined to form a set of carbon dioxide LNG combined energy storage system dominated by the freeze drying industry; it rationalizes energy utilization, reduces equipment investment costs, and improves market competitiveness; at the same time, it also has the following advantages: 1. In view of the production characteristics of freeze drying equipment that requires cold 24 hours a day and LNG that only generates a large amount of cold energy during the day, when there is no cold energy from LNG at night, A large amount of cold energy generated by the gasification of carbon dioxide liquid is used for freeze-drying production. When LNG has cold energy during the day, the cold energy of LNG is used for freeze-drying equipment and carbon dioxide liquefaction, which makes great use of the fact that LNG cold energy cannot be used. 2. In the liquefaction and gasification stages of carbon dioxide, a large amount of heat generated by liquefaction is stored in the phase-change cold-heat storage tank through the phase-change cold-heat storage tank, and a large amount of cold energy generated by gasification is stored in the phase-change cold-heat storage tank for heat exchange, making the temperature more stable. The carbon dioxide energy storage system combined with LNG and freeze-drying of the present invention has low manufacturing cost and use cost, high energy utilization rate, energy saving and environmental protection, and the system is reliable in operation, the temperature is stable, and the use effect is good.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A carbon dioxide energy storage system combined with LNG and freeze drying, characterized in that: It includes a low-pressure liquid storage tank, a high-pressure liquid storage tank, a freeze-drying device and an LNG station. The low-pressure liquid storage tank and the high-pressure liquid storage tank are respectively connected through an energy storage pipeline and an energy release pipeline to form a circulation pipeline. A first heat exchanger is provided on the energy storage pipeline. The first heat exchanger and the LNG station are respectively connected to the freeze-drying device and are respectively used to provide cold energy for the freeze-drying device during energy storage at night and LNG gasification during the day. The output end of the low-pressure liquid storage tank is connected to the high-pressure liquid storage tank through a first pipeline, and the first expansion valve, the first heat exchanger, the compressor, the second heat exchanger and the third heat exchanger are sequentially arranged on the first pipeline to form the energy storage pipeline, and the second heat exchanger and the third heat exchanger sequentially cool down the medium in the pipe and liquefy it; the output end of the high-pressure liquid storage tank is connected to the low-pressure liquid storage tank through a second pipeline, and the second expansion valve, the fourth heat exchanger, the fifth heat exchanger and the expansion generator are sequentially arranged on the second pipeline to form an energy release pipeline, and the fourth heat exchanger and the fifth heat exchanger sequentially heat up the medium in the pipe, and internal heat exchange can be achieved among the second heat exchanger, the third heat exchanger, the fourth heat exchanger and the fifth heat exchanger; It also includes a heat storage tank and a cold storage tank, wherein the output end of the heat storage tank is connected to the cold storage tank after passing through the first circulation pump and the fifth heat exchanger in sequence, so as to heat the fifth heat exchanger and transport the cold medium after heat exchange to the cold storage tank; the output end of the cold storage tank is connected to the heat storage tank after passing through the second circulation pump and the second heat exchanger in sequence, so as to cool down the second heat exchanger and transport the hot medium after heat exchange to the heat storage tank; A liquefaction buffer tank is connected in series between the third heat exchanger and the high-pressure liquid storage tank. The liquefaction buffer tank is provided with a loop pipe, which is connected to the input end of the third heat exchanger to form a loop, and can make the medium that is not completely liquefied return to the third heat exchanger and be cooled and liquefied again; The heat exchanger further comprises a phase-change cold and heat storage tank, which is arranged between the third heat exchanger and the fourth heat exchanger, and is used to store the heat generated by the liquefaction of the medium in the third heat exchanger in the phase-change cold and heat storage tank and provide heat for the vaporization of the medium in the fourth heat exchanger, or to store the cold energy generated by the vaporization of the medium in the fourth heat exchanger in the phase-change cold and heat storage tank and provide cold energy for the liquefaction of the medium in the third heat exchanger.

2. The carbon dioxide energy storage system combined with LNG and freeze-drying as claimed in claim 1, characterized in that: The compressor and the second heat exchanger form one or more groups, and the fifth heat exchanger and the expansion generator form one or more groups.

3. The carbon dioxide energy storage system combined with LNG and freeze-drying as claimed in claim 1, characterized in that: A sixth heat exchanger is provided at the rear end of the expansion generator, and the LNG station is connected to the sixth heat exchanger for providing cold energy for heat exchange of the sixth heat exchanger when LNG is gasified during the day, so as to liquefy the medium in the energy release pipeline and store it in the low-pressure liquid storage tank.

4. The carbon dioxide energy storage system combined with LNG and freeze drying as claimed in claim 1, characterized in that: The medium in the low-pressure liquid storage tank is 0.8Mpa-1.3Mpa liquid carbon dioxide at -45°C to -35°C, and the medium in the high-pressure liquid storage tank is 6.5Mpa-7.5Mpa liquid carbon dioxide at 25°C to 35°C.

5. A method for operating a carbon dioxide energy storage system combined with LNG and freeze drying as claimed in claim 3, characterized in that: The following steps are involved: S1. Energy storage: S11, the liquid carbon dioxide of 0.8Mpa-1.3Mpa at -45℃ to -35℃ in the low-pressure liquid storage tank is expanded through the first expansion valve to form isobaric gaseous carbon dioxide, and a large amount of gasification cold energy generated by the expansion is supplied to the freeze-drying equipment production through the first heat exchanger; S12, 0.8Mpa-1.3Mpa gaseous carbon dioxide is compressed by a compressor to form 6.5Mpa-7.5Mpa high-temperature gaseous carbon dioxide, the cold medium in the cold storage tank enters the heat storage tank after heat exchange by the second heat exchanger, and the 6.5Mpa-7.5Mpa high-temperature gaseous carbon dioxide is cooled by the second heat exchanger to form isobaric medium-temperature gaseous carbon dioxide; S13, the medium-temperature gaseous carbon dioxide of 6.5Mpa-7.5Mpa is cooled by heat exchange in the third heat exchanger to form isobaric liquid carbon dioxide, and then enters the high-pressure liquid storage tank for storage after passing through the liquefaction buffer tank. The heat generated by the liquefaction in the third heat exchanger is stored in the phase change cold and heat storage tank; S14, the carbon dioxide that is not completely liquefied after cooling is returned to the third heat exchanger through the loop pipe to continue to be cooled until it is completely liquefied; S2. Energy release: S21, the medium-temperature liquid carbon dioxide of 6.5Mpa-7.5Mpa in the high-pressure liquid storage tank is expanded through the second expansion valve to form isobaric gaseous carbon dioxide, and a large amount of gasification cold energy generated by the expansion is stored in the phase-change cold and heat storage tank through the fourth heat exchanger, or when in extreme weather and the ambient temperature is lower than the temperature required for the expansion and gasification of the medium, the heat energy stored in the phase-change cold and heat storage tank provides heat for the gasification of the medium in the fourth heat exchanger; S22, the heat medium in the heat storage tank enters the cold storage tank after passing through the fifth heat exchanger, and the 6.5Mpa-7.5Mpa gaseous carbon dioxide enters the expansion generator for expansion and power generation after being heated by the fifth heat exchanger, and forms 0.8Mpa-1.3Mpa gaseous carbon dioxide; S23. The cold energy of the LNG station cools and liquefies the 0.8Mpa-1.3Mpa gaseous carbon dioxide in the second pipeline through the sixth heat exchanger, and forms 0.8Mpa-1.3Mpa liquid carbon dioxide at -45℃ to -35℃ and stores it in a low-pressure liquid storage tank.

6. The working method of the carbon dioxide energy storage system combined with LNG and freeze drying as claimed in claim 5, characterized in that: Energy storage is carried out at night when electricity prices are low, and energy release is carried out during the day when electricity prices are high. The freeze-drying equipment is provided with cold energy by gasification from the LNG station during the day.

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