Liquid compressed carbon dioxide energy storage system and method

Abstract

The present application relates to compressed carbon dioxide energy storage technology field, disclose a kind of liquid compressed carbon dioxide energy storage system and method.The system contains carbon dioxide circulation system, the circulation system includes: first liquid storage tank (1), first evaporation unit (100), energy storage unit (200), second liquid storage tank (6), second evaporation unit (300), energy release unit (400) and condensing unit (500) are sequentially communicated.The system provided by the present application deeply couples liquid compressed carbon dioxide circulation system with waste heat and waste cold in ethylene process, solves the problem of gasification heat source of high-pressure side liquid carbon dioxide and liquefaction cold source of low-pressure side gaseous carbon dioxide in pressure storage system, breaks through the thermal energy utilization bottleneck constraint of previous adiabatic compressed carbon dioxide energy storage system;Compressed heat can be flexibly distributed between industrial steam production and carbon dioxide superheat.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compressed carbon dioxide energy storage, in particular to a liquid compressed carbon dioxide energy storage system and method. BACKGROUND

[0002] As a representative direction of new long-time energy storage, compressed carbon dioxide energy storage is an effective means to smooth the high fluctuation of renewable power, and is currently in the early stage of commercialization. The cycle efficiency of this technology depends heavily on the utilization of heat energy during the energy storage and release stages. In particular, for the mainstream adiabatic compressed carbon dioxide energy storage system, the limited heat recovery during the energy storage stage is only used as the sole heat source for the carbon dioxide heat absorption during the energy release stage, which not only limits the use range of high-grade recovered heat, but also restricts the power generation capacity of the turbine during the energy release stage. In addition, the traditional compressed carbon dioxide energy storage system uses gaseous storage at normal temperature and pressure, which not only occupies a large area, but also increases the construction cost of the system.

[0003] For example, CN114320504A discloses a liquid transcritical carbon dioxide energy storage system, which includes a liquid storage tank, an evaporation assembly, an energy storage assembly, a high-pressure gas storage tank, an energy release assembly, and a condensation assembly. The liquid storage tank stores liquid carbon dioxide. The outlet of the liquid storage tank is connected to the inlet of the high-pressure gas storage tank through a first valve, an evaporation assembly, and an energy storage assembly in sequence. The outlet of the high-pressure gas storage tank is connected to the inlet of the gas storage tank through a second valve, an energy release assembly, and a condensation assembly in sequence. The method includes two stages of energy storage and energy release. This system fully utilizes heat and cold energy, reduces the size of the storage system, increases the flexibility of the system, and can also utilize various types of heat sources such as geothermal, solar, and industrial waste heat to enhance the power generation performance of the system. However, in D1, a separate liquid storage tank and high-pressure gas storage tank are required, which has a high equipment cost, and the compression heat is not recycled.

[0004] Therefore, expanding the heat utilization range and source of the compressed carbon dioxide energy storage system, reducing the construction area of the system, and reducing the construction cost of the system have become important directions for improving the technical and economic efficiency of the system. SUMMARY

[0005] The purpose of the present application is to solve the problems of high construction cost and low cycle efficiency of traditional compressed carbon dioxide energy storage systems.

[0006] In view of the above problems, the inventors, in the research process, combined with the low-grade waste heat and low-temperature waste cold in the ethylene process that is not utilized, fully matched the heat source demand of the liquid compressed carbon dioxide energy storage system, used the low-grade waste heat of the ethylene process or the ethylene low-temperature waste cold with a higher temperature as the gasification heat source of the liquid carbon dioxide, and used the ethylene low-temperature waste cold as the liquefaction (condensation) cold source of the gaseous carbon dioxide at the low-pressure side, thereby improving the cycle efficiency of the system and reducing the construction space and cost of the system.

[0007] To achieve the above object, the first aspect of the present application provides a liquid compressed carbon dioxide energy storage system, which contains a carbon dioxide circulation system, the circulation system comprising: a first liquid storage tank, a first evaporation unit, an energy storage unit, a second liquid storage tank, a second evaporation unit, an energy release unit and a condensation unit connected in sequence;

[0008] The first evaporation unit and the second evaporation unit each contain an evaporator; the evaporator is used to gasify the liquid carbon dioxide material from the upstream, and the heat required in the first gasification process of the first evaporation unit is provided by the ethylene low-temperature waste heat device, and the heat required in the second gasification process of the second evaporation unit is provided by the ethylene low-grade waste heat device;

[0009] The energy storage unit stores energy by compressing and condensing the gaseous carbon dioxide I from the first evaporation unit into liquid carbon dioxide II, and the energy release unit releases energy by heating and expanding to convert the gaseous carbon dioxide II from the second evaporation unit into gaseous carbon dioxide III;

[0010] The condensation unit contains a condenser; the condenser is used to condense the gaseous carbon dioxide III from the upstream, and the cold energy required in the condensation process is provided by the ethylene low-temperature waste heat device;

[0011] The heat generated by compression can be used in the energy release unit and as the heat required for steam in the ethylene production process.

[0012] The second aspect of the present application provides a liquid compressed carbon dioxide energy storage method, which comprises a cyclic energy storage step and an energy release step:

[0013] The energy storage step comprises:

[0014] S1: introducing the liquid carbon dioxide I in the first liquid storage tank into the first evaporation unit for first gasification treatment to obtain gaseous carbon dioxide I; the heat of the first evaporation unit is provided by the waste heat in the ethylene low-temperature waste heat device;

[0015] S2: introducing the gaseous carbon dioxide I into the energy storage unit for compression and first condensation to obtain liquid carbon dioxide II, which is transported to the second liquid storage tank for storage;

[0016] The energy release step comprises:

[0017] S3: introducing the liquid carbon dioxide II in the second liquid storage tank into the second evaporation unit for second gasification treatment to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by the low-grade waste heat in the ethylene low-grade waste heat device;

[0018] S4: introducing the gaseous carbon dioxide II into an energy releasing unit to heat, expand and work, to obtain gaseous carbon dioxide III;

[0019] S5: introducing the gaseous carbon dioxide III into a condensing unit to perform condensing treatment, and then circulating to the first liquid storage tank for storage; the cold energy of the condensing unit is provided by the waste heat in the ethylene low-temperature waste heat device;

[0020] The heat generated by the compression can be used as the heat of the steam required by the ethylene production process and as the heat required for the heating in step S4.

[0021] The gaseous carbon dioxide I, the gaseous carbon dioxide II and the gaseous carbon dioxide III are different; the liquid carbon dioxide I and the liquid carbon dioxide II are different.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] (1) The system provided by the present application deeply couples the liquid compressed carbon dioxide circulation system with the waste heat and waste cold in the ethylene process, solves the problems of the gasification heat source of the liquid carbon dioxide in the storage system and the liquefaction cold source of the gaseous carbon dioxide at the low-pressure side, breaks through the bottleneck constraint of the heat energy utilization of the previous adiabatic compressed carbon dioxide energy storage system, and can realize the elastic distribution of the compression heat between the industrial steam production and the carbon dioxide overheating.

[0024] (2) In terms of technology, the low-grade waste heat generated by the ethylene low-grade waste heat device (quenching water tower or quenching oil tower) in the ethylene process matches the gasification temperature of the liquid carbon dioxide II (high-pressure liquid carbon dioxide), and the low-temperature waste cold generated in the separation process matches the condensation temperature of the gaseous carbon dioxide III (low-pressure gaseous CO2), so that the cycle efficiency of the scheme is improved by more than 10% compared with the adiabatic compressed carbon dioxide energy storage system.

[0025] (3) In terms of economy, the preliminary accounting results for the industrial and commercial electricity price in Guangdong region show that the present application effectively reduces the construction area and the initial investment, while improving the operating income, so that the internal rate of return is increased to 9.73%, the flat-standardized electricity cost in the whole life cycle is less than 0.3 yuan / kWh, and is significantly better than the adiabatic compressed carbon dioxide energy storage system. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flow process schematic diagram of a liquid compressed carbon dioxide energy storage system provided by an embodiment of the present application.

[0027] Figure 2 is a flow process schematic diagram of a liquid compressed carbon dioxide energy storage system provided by another embodiment of the present application.

[0028] Figure 3 is a flow schematic diagram of the adiabatic compressed carbon dioxide energy storage system in Comparative Example 1.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] 100, first evaporation unit; 200, energy storage unit; 300, second evaporation unit; 400, energy release unit; 500, condensation unit;

[0031] 1, first liquid storage tank; 2, first evaporator; 3, compressor; 4, heat exchange device; 5, condenser; 6, second liquid storage tank; 7, second evaporator; 8, turbine; 9, low-temperature storage tank; 10, high-temperature storage tank; 11, steam generator; 12, ethylene low-grade waste heat device; 13, second ethylene low-temperature waste heat device; 14, heater; 15, first condensation assembly; 16, first ethylene low-temperature waste heat device; 17, gas storage tank. DETAILED DESCRIPTION

[0032] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Various

[0033] In the present application, unless otherwise specified, the "first", "second", and the like in the names of each material and each operation, as well as the "I", "II", and the like in the serial numbers, do not represent the order of sequence, nor do they function to limit each material or operation, but are merely used to distinguish each material or operation. For example, "first" and "second" in "first evaporation unit" and "second evaporation unit" are merely used to distinguish, indicating that they are not the same evaporation unit; "liquid carbon dioxide I" and "liquid carbon dioxide II" are merely used to distinguish, indicating that they are not the same liquid carbon dioxide; "first gasification treatment" and "second gasification treatment" are merely used to distinguish, indicating that they are not the same gasification treatment operation. The definitions of the serial numbers in the rest of the material names and operation names are similar, and are not repeated here.

[0034] In the present application, unless otherwise specified, the pressures are all absolute pressures.

[0035] As described above, the first aspect of the present application provides a liquid compressed carbon dioxide energy storage system, which contains a carbon dioxide cycle system, the cycle system comprising: a first liquid storage tank 1, a first evaporation unit 100, an energy storage unit 200, a second liquid storage tank 6, a second evaporation unit 300, an energy release unit 400, and a condensation unit 500 connected in sequence;

[0036] Both the first evaporation unit 100 and the second evaporation unit 300 contain evaporators; the evaporators are used to vaporize liquid carbon dioxide material from upstream, and the heat required for the first vaporization process of the first evaporation unit 100 is provided by the ethylene low-temperature waste cooling device, and the heat required for the second vaporization process of the second evaporation unit 300 is provided by the ethylene low-grade waste heat device.

[0037] The energy storage unit 200 stores energy by compressing and condensing gaseous carbon dioxide I from the first evaporation unit 100 into liquid carbon dioxide II; and the energy release unit 400 releases energy by heating and expanding gaseous carbon dioxide II from the second evaporation unit 300 into gaseous carbon dioxide III.

[0038] The condensation unit 500 includes a condenser; the condenser is used to condense gaseous carbon dioxide III from upstream, and the cold energy required for the condensation process is provided by the ethylene low-temperature waste cooling device.

[0039] The heat generated by the compression can be used in the energy release unit 400 and as heat for steam required in the ethylene production process.

[0040] In some embodiments, the first storage tank 1 is used to store liquid carbon dioxide I (low-pressure liquid carbon dioxide); the second storage tank 6 is used to store liquid carbon dioxide II (high-pressure liquid carbon dioxide).

[0041] In this invention, gaseous carbon dioxide I, gaseous carbon dioxide II, and gaseous carbon dioxide III are different; liquid carbon dioxide I and liquid carbon dioxide II are different.

[0042] The present invention does not particularly limit the source of the carbon dioxide, which can be obtained by those skilled in the art using known technical means. Preferably, it is obtained through carbon capture processes during ethylene production.

[0043] In some embodiments, the first evaporation unit 100 further includes a first ethylene low-temperature waste cooling device 16, which provides the heat required for the first gasification process, and is connected in series with the first evaporator 2 via a pipeline. This preferred embodiment facilitates the release of cold energy from the liquid carbon dioxide I to the high-temperature section of the ethylene process waste cooling system, thereby improving the efficiency of cold energy recycling.

[0044] In this invention, the first evaporator 2 is used to perform a first vaporization treatment on liquid carbon dioxide I from the first storage tank; the inlet of the first evaporator 2 is connected to the outlet of the first storage tank 1.

[0045] According to a preferred embodiment, the second evaporation unit 300 further comprises an ethylene low-grade waste heat device 12, which is used to provide heat required for the second gasification process, and the ethylene low-grade waste heat device 12 is connected in series with the second evaporator 7 through a pipeline. With this preferred embodiment, the low-grade waste heat that is not utilized in the ethylene recovery process is used as the heat required for the second evaporator, which is beneficial to improve energy utilization efficiency.

[0046] In the present application, the second evaporator 7 is used to perform the second gasification process on the liquid carbon dioxide II from the second storage tank 6; the inlet of the second evaporator 7 is connected with the outlet of the second storage tank 6.

[0047] According to another preferred embodiment, the condensation unit 500 further comprises a second ethylene low-temperature waste cooling device 13, which is used to provide cold energy required for the condensation process, and the second ethylene low-temperature waste cooling device 13 is connected in series with the condenser 5 through a pipeline. With this preferred embodiment, it is beneficial to reduce the refrigeration cost of the low-pressure side carbon dioxide liquefaction and improve system economy.

[0048] In the present application, the outlet of the condenser 5 is connected with the inlet of the first storage tank 1.

[0049] According to a preferred embodiment, the system further comprises a low-temperature storage tank 9 for storing cold energy medium and a high-temperature storage tank 10 for storing heat energy medium; the outlet of the low-temperature storage tank 9 is connected in communication with the energy storage unit 200, the inlet of the low-temperature storage tank 9 is connected in communication with the energy release unit 400, and the outlet of the high-temperature storage tank 10 is connected in communication with the energy release unit 400. With this preferred embodiment, it is beneficial to improve the energy circulation efficiency of the internal heat production and utilization of the carbon dioxide energy storage system.

[0050] According to another preferred embodiment, the energy storage unit 200 comprises a first condensation assembly 15 and at least two compression heat exchange assemblies connected in series; each of the compression heat exchange assemblies comprises a compressor 3 and a heat exchange device 4 connected in series, so that the gaseous carbon dioxide I is compressed and heat exchanged in each compression heat exchange assembly in sequence; the first condensation assembly 15 is used to condense the gaseous carbon dioxide after heat exchange in the most downstream compression heat exchange assembly into the liquid carbon dioxide II. The inventors have found that, in this preferred embodiment, the compression efficiency can be further improved, the energy consumption can be reduced, the service life of the equipment can be prolonged, and higher energy can be stored for subsequent expansion work.

[0051] In the present application, when the pressure of the compressed gaseous carbon dioxide I reaches the highest storage pressure designed by the system, the compression is stopped, and then the heat-exchanged gaseous carbon dioxide in the most downstream heat-exchange assembly is introduced into the first condensing assembly 15 for condensation.

[0052] In the present application, the two compressors 3 in the energy storage unit 200 are connected through the heat exchange device 4.

[0053] In the present application, the energy consumed by the compressor is the surplus electricity during the low electricity period or the electricity generated by the renewable energy source.

[0054] In some embodiments, the energy storage unit 200 comprises a first condensing assembly 15, two serially connected compression heat-exchange assemblies.

[0055] In some embodiments, along the carbon dioxide flow direction, the inlet of the compressor 3 in the most upstream compression heat-exchange assembly is connected to the outlet of the first evaporator 2 in the first evaporating unit 100.

[0056] In some embodiments, the system further comprises a throttle valve, the compressor 3 in the most upstream compression heat-exchange assembly is connected to the first evaporator 2 in the first evaporating unit 100 through the throttle valve; the throttle valve is used to adjust the pressure of the gaseous carbon dioxide at the inlet of the compressor 3 in the most upstream compression heat-exchange assembly.

[0057] In some embodiments, along the carbon dioxide flow direction, the inlet of the first condensing assembly 15 is connected to the outlet of the heat exchange device 4 in the most downstream compression heat-exchange assembly, and the outlet of the first condensing assembly 15 is connected to the inlet of the second liquid storage tank 6.

[0058] In some embodiments, the outlet of the low-temperature storage tank 9 is connected to the heat exchange device 4 in each of the compression heat-exchange assemblies. In this way, the outlet of the low-temperature storage tank 9 is connected to the energy storage unit 200.

[0059] According to a preferred embodiment, the working medium at the outlet of each of the compressors 3 is heat-exchanged and recovered through the heat exchange device 4 in the compression heat-exchange assembly by the cold energy medium provided by the low-temperature storage tank 9, a part of which is used in the steam generator 11 as the steam heat required by the ethylene production process, and the remaining part is stored in the high-temperature storage tank 10. The inventors consider the steam demand of the ethylene production process, and adopt this preferred embodiment to use part of the recovered heat (heat generated in the compression process) of the energy storage unit for steam production, which can realize efficient complementation of both and is beneficial to improve the energy utilization efficiency.

[0060] In some embodiments, the energy releasing unit 400 comprises at least two turbine assemblies connected in series, each of the turbine assemblies comprising a heater 14 and a turbine 8 connected in series.

[0061] In some embodiments, the gaseous carbon dioxide II from the second evaporation unit 300 is heated by the heat medium provided by the high temperature storage tank 10 via the heater 14; the gaseous carbon dioxide II heated by the heater 14 enters the turbine 8 to expand and do work, outputting electricity to the outside, and converting the gaseous carbon dioxide II into gaseous carbon dioxide III.

[0062] In the present application, when the turbine inlet pressure drops to the designed minimum value, the expansion and work are stopped, and then the gaseous carbon dioxide III at the outlet of the turbine 8 is introduced into the condensing unit 500 for the condensing treatment.

[0063] In some embodiments, along the flow direction of carbon dioxide, the most upstream heater 14 is in communication with the second evaporator 7 in the second evaporation unit 300, and the outlet of the most downstream turbine 8 is in communication with the inlet of the condenser 5 in the condensing unit 500.

[0064] In some embodiments, the condensing unit further comprises a cryogenic pump for flow regulation of the gaseous carbon dioxide III from the most downstream turbine 8 and pressure maintenance in the condenser 5.

[0065] In some embodiments, the outlet of the high temperature storage tank 10 is in communication with the heater 14 in each of the turbine assemblies. Thus, the outlet of the high temperature storage tank 10 is in communication with the energy releasing unit 400.

[0066] In some embodiments, the heat medium provided by the high temperature storage tank 10 is circulated to the low temperature storage tank 9 after passing through the heater 14.

[0067] In the present application, the outlet of the heater 14 is in communication with the inlet of the low temperature storage tank 9. Thus, the inlet of the low temperature storage tank 9 is in communication with the energy releasing unit 400.

[0068] In some embodiments, the ethylene low-grade waste heat device is selected from at least one of a quench water tower and a quench oil tower.

[0069] In some embodiments, the first ethylene low temperature waste cooling device 16 and the second ethylene low temperature waste cooling device 13 are each independently selected from at least one of a cold box in an ethylene separation process, an ethylene compression refrigeration cycle device, and a propylene compression refrigeration cycle device.

[0070] In some embodiments, the first ethylene low-temperature waste cooling device 16 and the second ethylene low-temperature waste cooling device 13 provide different waste cooling temperatures, and the temperature of the first ethylene low-temperature waste cooling device 16 is higher than that of the second ethylene low-temperature waste cooling device 13. The inventors have found that the preferred embodiment can better reduce energy consumption.

[0071] In some embodiments, the temperature of the low-grade waste heat in the ethylene low-grade waste heat device is greater than 30℃; preferably 45-70℃.

[0072] In some embodiments, the temperature of the waste cooling in the ethylene low-temperature waste cooling device is -160℃ to 40℃. For example, it can be -150℃, -140℃, -130℃, -120℃, -110℃, -100℃, -90℃, -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃, 40℃.

[0073] In some embodiments, the temperature of the waste cooling in the first ethylene low-temperature waste cooling device is -35℃ to 40℃, preferably 20-40℃; the temperature of the waste cooling in the second ethylene low-temperature waste cooling device is -160℃ to -40℃; preferably -60 to -40℃.

[0074] In the present application, the heat exchange mode of carbon dioxide with the cold energy medium in the heat exchanger or the heat energy medium in the heater includes but is not limited to countercurrent heat exchange, cocurrent heat exchange, and multiphase heat exchange.

[0075] In the present application, the heat exchange device and the heater include but are not limited to a shell-and-tube heat exchanger and a plate heat exchanger.

[0076] In the present application, the carrier of the waste cooling is selected from one or more of methane, propylene, and ethylene.

[0077] In some embodiments, the cold energy medium and the heat energy medium are each independently selected from at least one of water and heat-conducting oil.

[0078] The system provided by the present application can improve the energy utilization efficiency of the ethylene process, significantly improve the technical and economic performance of the compressed carbon dioxide energy storage system, provide a new steam source for upstream and downstream production of ethylene, achieve a win-win situation for ethylene production and compressed carbon dioxide energy storage, and provide long-time energy storage resources at the power supply end and the load end for new power systems with high fluctuation of renewable power and high proportion of grid connection.

[0079] As described above, the second aspect of the present application provides a liquid compressed carbon dioxide energy storage method, which comprises a cyclic energy storage step and an energy release step:

[0080] The energy storage step comprises:

[0081] S1: Liquid carbon dioxide I in the first storage tank is introduced into the first evaporation unit for first vaporization treatment to obtain gaseous carbon dioxide I; the heat of the first evaporation unit is provided by the residual cooling in the ethylene low-temperature residual cooling device.

[0082] S2: The gaseous carbon dioxide I is introduced into the energy storage unit for compression and first condensation to obtain liquid carbon dioxide II, which is then transported to the second storage tank for storage.

[0083] The energy release step includes:

[0084] S3: The liquid carbon dioxide II in the second storage tank is introduced into the second evaporation unit for the second vaporization process to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by the low-grade waste heat in the ethylene low-grade waste heat device;

[0085] S4: The gaseous carbon dioxide II is introduced into the energy release unit for heating and expansion to do work, thereby obtaining gaseous carbon dioxide III;

[0086] S5: The gaseous carbon dioxide III is introduced into the condensation unit for condensation treatment and then circulated to the first storage tank for storage; the cold energy of the condensation unit is provided by the residual cooling in the ethylene low-temperature residual cooling device;

[0087] The heat generated by the compression can be used as heat for the steam required for the ethylene production process and as heat required for the heating in step S4.

[0088] The gaseous carbon dioxide I, gaseous carbon dioxide II, and gaseous carbon dioxide III are different; the liquid carbon dioxide I and liquid carbon dioxide II are different.

[0089] According to a preferred embodiment, the energy storage unit includes a first condensation component and at least two compression heat exchange components connected in series; each compression heat exchange component includes a compressor and a heat exchange device connected in series, so that gaseous carbon dioxide I can be compressed and heat exchanged sequentially in each compression heat exchange component. The inventors have found that under this preferred condition, compression efficiency can be further improved, energy consumption reduced, and the service life of the equipment extended.

[0090] According to another preferred embodiment, the energy release unit contains at least two turbine components connected in series, each turbine component containing a heater and a turbine connected in series, so that gaseous carbon dioxide II can be heated and expanded to perform work in each turbine component sequentially. The inventors have found that under this preferred condition, by staged depressurization and interstage reheating, energy recovery efficiency can be better improved and energy loss reduced.

[0091] According to a preferred embodiment, the heat generated by each of the compressors is recovered by heat exchange between the heat exchange device in the compression heat exchange assembly and the cold energy medium provided by the low-temperature storage tank, a part of which is stored in the steam generator to be used as the steam heat required by the ethylene production process, and the remaining part is stored in the high-temperature storage tank to be used as the heat required for heating in step S4. The inventors have found that, under this preferred condition, the energy utilization efficiency can be further improved.

[0092] In some embodiments, the heat required by the heater is provided by the heat energy medium stored in the high-temperature storage tank.

[0093] In some embodiments, the temperature of the cold energy medium is 10-70℃, preferably 10-30℃; and the temperature of the heat energy medium is 100-250℃, preferably 180-220℃.

[0094] In some embodiments, the cold energy medium and the heat energy medium are each independently selected from at least one of water and heat-conducting oil.

[0095] In some embodiments, the temperature of the liquid carbon dioxide I in the first storage tank is -56℃ to -40℃, and the pressure is 0.5-1MPa.

[0096] In some embodiments, the temperature of the liquid carbon dioxide II in the second storage tank is 25-28℃, and the pressure is 6.5-7MPa.

[0097] In some embodiments, the temperature of the low-grade waste heat is greater than 30℃, and the temperature of the waste cold is -160℃ to 40℃.

[0098] In some embodiments, the temperature of the low-grade waste heat is 45-70℃, and the temperature of the waste cold is -160℃ to 40℃. For example, the temperature of the low-grade waste heat can be 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃; and the temperature of the waste cold can be -150℃, -140℃, -130℃, -120℃, -110℃, -100℃, -90℃, -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, or 30℃.

[0099] According to an embodiment, the first evaporation unit contains a first ethylene low-temperature waste cold device and a first evaporator; and the temperature of the waste cold in the first ethylene low-temperature waste cold device is -35℃ to 40℃.

[0100] According to an embodiment, the second evaporation unit contains a second ethylene low-temperature waste cold device and a second evaporator; and the temperature of the waste cold in the second ethylene low-temperature waste cold device is -160℃ to -40℃.

[0101] In some embodiments, in step S1, the conditions of the first gasification process include: temperature of -35 to 40℃, pressure of 0.5-1 MPa. Exemplarily, the temperature can be -30℃, -25℃, -20℃, -15℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃; the pressure can be 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.85 MPa, 0.9 MPa, 0.95 MPa.

[0102] Further preferably, the conditions of the first gasification process include: temperature of 20 to 40℃, pressure of 0.5-0.7 MPa.

[0103] In some embodiments, in step S2, the conditions of the first condensation process include: temperature of 20-30℃, pressure of 6.5-7 MPa.

[0104] In some embodiments, in step S2, the temperature of the cold energy medium in the low-temperature storage tank 9 is controlled so that the temperature of the carbon dioxide working medium after heat exchange at the inlet of the compressor is 15-30℃.

[0105] In some embodiments, in step S2, the conditions of the compression include: the inlet pressure of the working medium of the most upstream compressor is 0.1-1 MPa; the inlet temperature of the working medium is 15-30℃, and the compression ratio of each compressor is independently 2-10:1.

[0106] In some embodiments, in step S2, the efficiency of each compressor is 0.85-0.95, and the energy efficiency of each heat exchange device is 0.85-0.95.

[0107] In some embodiments, the flow rate of the working medium at the inlet of the compressor is 35-45 kg / s relative to a power generation of 10 MW.

[0108] In some embodiments, in step S3, the conditions of the second gasification process include: 30-50℃, pressure of 5-7 MPa. Exemplarily, the temperature of the second gasification is 35℃, 40℃, 45℃, 50℃; the pressure of the second gasification is 5.5 MPa, 6.0 MPa, 6.5 MPa, 7.0 MPa.

[0109] In some embodiments, in step S4, the temperature of the hot energy medium in the high-temperature storage tank 10 is controlled so that the inlet temperature of each turbine working medium after heating is 100-250℃.

[0110] In some embodiments, in step S4, the conditions of the expansion work include: the most upstream turbine working medium inlet pressure is 6.5-7 MPa; the working medium inlet temperature is 100-250℃, and the expansion ratio of each turbine is 2-10:1.

[0111] In some embodiments, in step S4, the efficiency of each turbine is 0.85-0.95.

[0112] In some embodiments, the flow rate of the turbine working medium inlet is 35-45 kg / s relative to a power generation of 10 MW.

[0113] In some embodiments, in step S5, the conditions of the condensation treatment include: the temperature is-160℃ to-40℃, and the pressure is 0.5-1 MPa. Illustratively, the condensation temperature is-150℃, -140℃, -130℃, -120℃, -110℃, -100℃, -90℃, -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 30℃. The pressure is 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.85 MPa, 0.9 MPa, 0.95 MPa.

[0114] Further preferably, the conditions of the condensation treatment include: the temperature is-60℃ to-40℃, and the pressure is 0.5-1 MPa.

[0115] The present application significantly improves the cycle efficiency of the energy storage system by using low-grade waste heat and low-temperature waste cold generated in the ethylene production process as the gasification heat source of liquid carbon dioxide and the liquefaction cold source of gaseous carbon dioxide, respectively, reduces the system construction space and cost, and effectively promotes the energy saving and emission reduction of the ethylene process. At the same time, the temperature of the compression heat can be flexibly adjusted by adjusting the compression ratio and other parameters to meet the demand of different grades of steam; secondly, the proportion of the compression heat used for superheating carbon dioxide in the energy release section and generating steam required for ethylene can be flexibly adjusted, so as to obtain different electricity and steam benefits according to the electricity price and steam policy in different places.

[0116] The system and method provided by the present application are described in detail below with reference to the accompanying drawings.

[0117] Figure 1 is a flow diagram of a liquid compressed carbon dioxide energy storage system of a specific embodiment of the present application, which contains a carbon dioxide cycle system, which includes: a first liquid storage tank 1, a first evaporation unit 100, a throttling valve, an energy storage unit 200, a second liquid storage tank 6, a second evaporation unit 300, an energy release unit 400 and a condensation unit 500 connected in sequence;

[0118] The first evaporation unit 100 and the second evaporation unit 300 each contain an evaporator; the evaporator is used to gasify liquid carbon dioxide material from upstream, and the heat required in the first gasification process of the first evaporation unit 100 is provided by the ethylene low-temperature waste heat device, and the heat required in the second gasification process of the second evaporation unit 300 is provided by the ethylene low-grade waste heat device;

[0119] The energy storage unit 200 stores energy by compressing and condensing gaseous carbon dioxide I from the first evaporation unit 100 into liquid carbon dioxide II; and the energy release unit 400 releases energy by heating and expanding to convert gaseous carbon dioxide II from the second evaporation unit 300 into gaseous carbon dioxide III;

[0120] The condensing unit 500 contains a condenser; the condenser is used to condense gaseous carbon dioxide III from upstream, and the cold energy required in the condensation process is provided by the ethylene low-temperature waste heat device;

[0121] The heat generated by compression can be used in the energy release unit 400 and as heat required for producing ethylene.

[0122] Figure 2 is a flow diagram of a liquid compressed carbon dioxide energy storage system according to a preferred embodiment of the present application, Figure 2 The solid arrows in the figure represent the flow direction of carbon dioxide in the liquid compressed carbon dioxide energy storage system, and the dashed arrows represent the flow direction of heat exchange media such as cold energy media and heat energy media in the liquid compressed carbon dioxide energy storage system;

[0123] From Figure 2 It can be known from the figure that the system contains a carbon dioxide circulation system, which includes a first liquid storage tank 1, a first evaporation unit 100, a throttling valve, an energy storage unit 200, a second liquid storage tank 6, a second evaporation unit 300, an energy release unit 400, and a condensing unit 500 connected in sequence;

[0124] The first evaporation unit 100 includes a first ethylene low-temperature waste heat device 16 and a first evaporator 2 connected in series through a pipeline; the first evaporator 2 is used to perform a first gasification process on liquid carbon dioxide I from the first liquid storage tank 1, and the heat required in the first gasification process is provided by the first ethylene low-temperature waste heat device 16;

[0125] The energy storage unit 200 comprises a first condensing assembly 15, at least two compression heat exchange assemblies connected in series, each of the compression heat exchange assemblies comprising a compressor 3 and a heat exchange device 4 connected in series, so that the gaseous carbon dioxide I is compressed and heat exchanged in each compression heat exchange assembly in turn; the first condensing assembly 15 is used for condensing the heat-exchanged gaseous carbon dioxide at the outlet of the most downstream heat exchange device 4 into liquid carbon dioxide II.

[0126] The second evaporation unit 300 comprises an ethylene low-grade waste heat device 12 and a second evaporator 7 connected in series by pipelines; the second evaporator 7 is used for performing a second gasification process on the liquid carbon dioxide II from the second liquid storage tank 6, and the heat required in the second gasification process is provided by the ethylene low-grade waste heat device 12.

[0127] The energy release unit 400 comprises at least two turbine assemblies connected in series, each of the turbine assemblies comprising a heater 14 and a turbine 8 connected in series; the gaseous carbon dioxide II from the second evaporation unit 300 is heated by the heat energy medium provided by the high-temperature storage tank 10 through the heater 14; the gaseous carbon dioxide II heated by the heater 14 is expanded to do work in the turbine 8, and outputs electric power to the outside, and the gaseous carbon dioxide II is converted into gaseous carbon dioxide III.

[0128] The condensing unit 500 comprises a second ethylene low-temperature waste cooling device 13 and the condenser 5 connected in series by pipelines; the condenser 5 is used for performing a condensing process on the gaseous carbon dioxide III from the upstream, and the cold energy required in the condensing process is provided by the second ethylene low-temperature waste cooling device 13.

[0129] The system further comprises a low-temperature storage tank 9 for storing cold energy medium, a high-temperature storage tank 10 for storing heat energy medium, and a steam generator 11.

[0130] The outlet of the low-temperature storage tank 9 is connected to the heat exchange device 4 in each of the compression heat exchange assemblies; the working medium at the outlet of each of the compressors 3 is heat-exchanged and recovered by the heat exchange device 4 in the compression heat exchange assembly through the cold energy medium provided by the low-temperature storage tank 9, a part of which is stored in the steam generator 11 for use as steam heat required for producing ethylene, and the remaining part is stored in the high-temperature storage tank 10.

[0131] According to a particularly preferred embodiment, the system comprises a carbon dioxide circulation system, which comprises: connecting the outlet of the first liquid storage tank 1 to the inlet of the first evaporator 2; in the direction of carbon dioxide flow, the inlet of the compressor 3 in the most upstream compression heat exchange assembly is connected to the outlet of the first evaporator 2 in the first evaporation unit 100 through a throttle valve; the outlet of the compressor 3 in the most upstream compression heat exchange assembly is connected to the inlet of the heat exchange device 4, the outlet of the heat exchange device 4 in the most upstream compression heat exchange assembly is connected to the inlet of the compressor 3 in the adjacent downstream compression heat exchange assembly, and the outlet of the compressor 3 in the adjacent downstream compression heat exchange assembly is connected to the inlet of the heat exchange device 4; repeating the above connection until the pressure of the compressed gaseous carbon dioxide reaches the highest storage pressure designed by the system, then stopping the compression, and connecting the outlet of the heat exchange device 4 in the most downstream compression heat exchange assembly to the inlet of the first condensation assembly 15, and connecting the outlet of the first condensation assembly 15 to the inlet of the second liquid storage tank 6; connecting the outlet of the second liquid storage tank 6 to the inlet of the second evaporator 7; in the direction of carbon dioxide flow, connecting the outlet of the second evaporator 7 to the inlet of the heater 14 in the most upstream turbine assembly, connecting the outlet of the heater 14 in the most upstream turbine assembly to the inlet of the turbine 8, connecting the outlet of the turbine 8 in the most upstream turbine assembly to the inlet of the heater 14 in the adjacent downstream turbine assembly, and connecting the outlet of the heater 14 in the adjacent turbine assembly to the inlet of the turbine 8; repeating the above connection until the inlet pressure of the turbine decreases to the lowest value designed, then stopping the expansion work, and connecting the outlet of the most downstream turbine 8 to the low-temperature pump in the condensation unit 500, and connecting the low-temperature pump to the inlet of the condenser 5; connecting the outlet of the condenser 5 to the inlet of the first liquid storage tank 1;

[0132] The outlet of the low-temperature storage tank 9 is connected to each heat exchange device 4 in the energy storage unit 200, and the inlet of the low-temperature storage tank 9 is connected to the outlet of the heater 14 in the energy release unit 400; the outlet of the high-temperature storage tank 10 is connected to the inlet of each heater 14 in the energy release unit 400; the inlet of the steam generator 11 is connected to the outlet of each heat exchange device 4 in the energy storage unit 200;

[0133] The first ethylene low-temperature waste heat device 16 is connected to the first evaporator 2 in series through a pipeline, the second ethylene low-temperature waste heat device 13 is connected to the condenser 5 in series through a pipeline, and the ethylene low-grade waste heat device 12 is connected to the second evaporator 7 in series through a pipeline.

[0134] The application provides a preferred liquid compressed carbon dioxide energy storage method, which is carried out by using the system shown in the figure, and the method comprises: a circulating energy storage step and an energy release step: Figure 2 The energy storage step comprises:

[0135] The energy storage step comprises:

[0136] S1: introducing the liquid carbon dioxide I in the first liquid storage tank 1 into the first evaporator 2 of the first evaporation unit 100 to perform a first gasification process, to obtain gaseous carbon dioxide I; the heat of the first evaporation unit is provided by the waste cold in the first ethylene low-temperature waste cold device 16;

[0137] S2: introducing the gaseous carbon dioxide I into the energy storage unit 200 after pressure reduction by a throttle valve to perform compression and first condensation, to obtain liquid carbon dioxide II, which is transported to the second liquid storage tank 6 for storage; the energy storage unit 200 contains a first condensation assembly 15 and at least two compression heat exchange assemblies connected in series; each compression heat exchange assembly contains a compressor 3 and a heat exchange device 4 connected in series, so that the gaseous carbon dioxide I can be compressed and heat exchanged in each compression heat exchange assembly in turn;

[0138] The energy releasing step includes:

[0139] S3: introducing the liquid carbon dioxide II in the second liquid storage tank 6 into the second evaporator 7 of the second evaporation unit to perform a second gasification process, to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by the low-grade waste heat in the ethylene low-grade waste heat device 12;

[0140] S4: introducing the gaseous carbon dioxide II into the energy releasing unit 400 to perform heating and expansion work, to obtain gaseous carbon dioxide III; the energy releasing unit contains at least two turbine assemblies connected in series, and each turbine assembly contains a heater 14 and a turbine 8 connected in series, so that the gaseous carbon dioxide II can be heated and expanded to work in each turbine assembly in turn;

[0141] S5: introducing the gaseous carbon dioxide III into the condenser 5 after pressure increase by a low-temperature pump in the condensation unit to perform condensation processing, to obtain liquid carbon dioxide I, which is recycled to the first liquid storage tank 1 for storage; the cold energy of the condensation unit is provided by the waste cold in the second ethylene low-temperature waste cold device 13;

[0142] Wherein, the heat generated by each compressor is heat-exchanged and recovered by the heat exchange device 4 in the compression heat exchange assembly through the cold energy medium provided by the low-temperature storage tank 9, a part of which is stored in the steam generator 11 to be used as the steam heat required for the production of ethylene, and the remaining part is stored in the high-temperature storage tank 10 to be used as the heat required for the heating in step S4;

[0143] The gaseous carbon dioxide I, the gaseous carbon dioxide II, and the gaseous carbon dioxide III are different; the liquid carbon dioxide I and the liquid carbon dioxide II are different.

[0144] The application will be described in detail below by examples. The experimental methods in the following examples are all conventional methods in the art, unless otherwise specified. The experimental materials used in the following examples are all commercially available, unless otherwise specified.

[0145] The following examples are used to illustrate the system and method for storing energy by liquid compressed carbon dioxide provided by the application. The time of the energy storage stage and the energy release stage in the following examples is 8h.

[0146] Example 1

[0147] This example is implemented by using the liquid compressed carbon dioxide energy storage system described in the application, and the structure of the liquid compressed carbon dioxide energy storage system is as shown in Figure 2

[0148] The method comprises: cyclically performing an energy storage step and an energy release step.

[0149] The energy storage step comprises:

[0150] S1: introducing the liquid carbon dioxide I (temperature: -56℃, pressure: 0.55MPa) in the first liquid storage tank 1 into the first evaporator 2 of the first evaporation unit 100 to perform a first gasification treatment, to obtain gaseous carbon dioxide I; the heat of the first evaporation unit is provided by the residual cold (carrier: propylene, temperature: 30℃) in the first ethylene low-temperature residual cold device 16 (using a propylene compression refrigeration cycle device);

[0151] The conditions of the first gasification treatment are: temperature: 30℃, pressure: 0.55MPa;

[0152] S2: after the gaseous carbon dioxide I is depressurized to 0.1MPa by a throttle valve, it is introduced into the energy storage unit 200 to perform compression and first condensation, to obtain liquid carbon dioxide II (temperature: 27℃, pressure: 6.75MPa), which is transported to the second liquid storage tank 6 for storage; the energy storage unit 200 contains a first condensation assembly 15 and two compression heat exchange assemblies connected in series; each compression heat exchange assembly contains a compressor 3 and a heat exchange device 4 connected in series, so that the gaseous carbon dioxide I can be compressed and heat exchanged in each compression heat exchange assembly in turn;

[0153] The compression conditions are: the most upstream compressor working medium inlet pressure is set to 0.1MPa; the working medium inlet temperature of each compressor is 20℃, the working medium inlet flow rate is 40 kg / s, the compression ratio of each stage is 8.22, the total compression ratio is 67.5, and the efficiency of each compressor is 0.9; the energy efficiency of each heat exchange device is 0.95;

[0154] The temperature of the cold energy medium (L80 heat conducting oil) in the low-temperature storage tank 9 is controlled, so that the temperature of the heat-exchanged carbon dioxide working medium at the compressor inlet is 20℃.​

[0155] The first condensing condition: temperature is 27℃, pressure is 6.75MPa;

[0156] The energy releasing step comprises:

[0157] S3: introducing the liquid carbon dioxide II in the second liquid storage tank 6 into the second evaporator 7 of the second evaporation unit to perform a second gasification treatment, so as to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by the low-grade waste heat (temperature is 50℃) in the ethylene low-grade waste heat device 12 (using a quenching water tower);

[0158] The second gasification treatment condition: temperature is 50℃, pressure is 6.75MPa;

[0159] S4: introducing the gaseous carbon dioxide II into the energy releasing unit 400 to perform heating and expansion work, so as to obtain gaseous carbon dioxide III; the energy releasing unit contains two turbine assemblies connected in series, and each turbine assembly contains a heater 14 and a turbine 8 connected in series, so that the gaseous carbon dioxide II can perform heating and expansion work in each turbine assembly in turn;

[0160] The temperature of the heat energy medium (L80 heat conducting oil) in the high-temperature storage tank 10 is controlled, so that the inlet temperature of each turbine working medium after heating is 200℃;

[0161] The expansion work condition: the inlet pressure of the most upstream turbine working medium is set to 6.75MPa; the inlet temperature of each turbine working medium is 200℃, the inlet flow rate of the working medium is 40kg / s, the expansion ratio of each turbine is 8.22; the total expansion ratio is 67.5, and the efficiency of each turbine is 0.9;

[0162] S5: introducing the gaseous carbon dioxide III into the condenser 5 after being pressurized to 0.55MPa by the low-temperature pump in the condensing unit to perform condensing treatment, so as to obtain liquid carbon dioxide which is recycled back to the first liquid storage tank for storage; the cold energy of the condensing unit is provided by the waste cold (carrier is a cracking gas containing ethylene and methane, temperature is -60℃) in the second ethylene low-temperature waste cold device (using a low-temperature cold box device) 13;

[0163] The condensing treatment condition: temperature is -60℃, pressure is 0.55MPa;

[0164] The heat generated by each of the compressors is recovered by heat exchange between the heat exchange device 4 in the compression heat exchange assembly and the cold energy medium provided by the low-temperature storage tank 9. A part of the heat (accounting for 94% of the total recovered heat) is stored in the high-temperature storage tank 10 and used as the heat required for the heating in step S4, and the remaining heat (accounting for 6% of the total recovered heat) is sent to the steam generator 11 and used as the steam heat required by the ethylene production process.

[0165] The gaseous carbon dioxide I, the gaseous carbon dioxide II and the gaseous carbon dioxide III are different; the liquid carbon dioxide I and the liquid carbon dioxide II are different.

[0166] Example 2

[0167] This example is implemented by using a method similar to that of Example 1, except that:

[0168] In step S2, the heat generated by each of the compressors is recovered by heat exchange between the heat exchange device 4 in the compression heat exchange assembly and the cold energy medium provided by the low-temperature storage tank 9. A part of the heat (accounting for 50% of the total recovered heat) is sent to the steam generator 11 and used as the steam heat required by the ethylene production process, and the remaining heat (accounting for 50% of the total recovered heat) is stored in the high-temperature storage tank 10 and used as the heat required for the heating in step S4.

[0169] In step S4, the temperature of the heat energy medium (L80 heat-conducting oil) in the high-temperature storage tank 10 is controlled so that the inlet temperature of each turbine working medium after heating is 110°C.

[0170] The conditions for expansion work are as follows: the inlet pressure of the most upstream turbine working medium is set to 6.75 MPa; the inlet temperature of each turbine working medium is 110°C, the inlet flow rate of the working medium is 40 kg / s, the expansion ratio of each turbine is 8.22; the total expansion ratio is 67.5, and the efficiency of each turbine is 0.9.

[0171] The remaining steps are the same as those in Example 1.

[0172] Comparative Example 1

[0173] This comparative example is implemented by using a conventional adiabatic compressed carbon dioxide energy storage system that does not contain external heat sources (ethylene process waste heat and waste cold). The structure of the compressed carbon dioxide energy storage system is as shown in Figure 3 ;

[0174] The method includes: a cyclic energy storage step and an energy release step:

[0175] The energy storage step includes:

[0176] S1: introduce gaseous carbon dioxide (temperature 20℃, pressure 0.1MPa) in the gas tank 17 into the energy storage unit 200 for compression and first condensation, to obtain liquid carbon dioxide II (temperature 27℃, pressure 6.75MPa), and deliver to the second liquid storage tank 6 for storage; the energy storage unit 200 contains a first condensation assembly 15 and two compression heat exchange assemblies connected in series; each compression heat exchange assembly contains a compressor 3 and a heat exchange device 4 connected in series, so that gaseous carbon dioxide I can be compressed and heat exchanged in each compression heat exchange assembly in turn;

[0177] The compression conditions are: the most upstream compressor working medium inlet pressure is 0.1MPa; the working medium inlet temperature of each compressor is 20℃, the working medium inlet flow rate is 40 kg / s, the compression ratio of each compressor is 8.22, the total compression ratio is 67.5, and the efficiency of each compressor is 0.9; the energy efficiency of each heat exchange device is 0.95;

[0178] The temperature of the cold energy medium (L80 heat conducting oil) in the low-temperature storage tank 9 is controlled, so that the temperature of the heat-exchanged carbon dioxide working medium at the compressor inlet is 20℃;

[0179] The first condensation conditions are: the temperature is 27℃, and the pressure is 6.75MPa,

[0180] The energy releasing step includes:

[0181] S2: introduce liquid carbon dioxide II in the second liquid storage tank 6 into the second evaporator 7 of the second evaporation unit for second gasification treatment, to obtain gaseous carbon dioxide II;

[0182] The second gasification treatment conditions are: the temperature is 50℃, and the pressure is 6.75MPa;

[0183] S3: introduce the gaseous carbon dioxide II into the energy releasing unit 400 for heating and expansion work, to obtain gaseous carbon dioxide III; the energy releasing unit contains two turbine assemblies connected in series, and each turbine assembly contains a heater 14 and a turbine 8 connected in series, so that gaseous carbon dioxide II can be heated and expanded in each turbine assembly in turn;

[0184] The temperature of the hot energy medium (L80 heat conducting oil) in the high-temperature storage tank 10 is controlled, so that the working medium inlet temperature of each turbine after heating is 140℃;

[0185] The expansion work conditions are: the most upstream turbine working medium inlet pressure is set to 6.75MPa; the working medium inlet temperature of each turbine is 140℃, the working medium inlet flow rate is 40 kg / s, the expansion ratio of each turbine is 8.22; the total expansion ratio is 67.5, and the efficiency of each turbine is 0.9;

[0186] S4: recycling the gaseous carbon dioxide III back to the gas storage tank 17 for storage;

[0187] Wherein, the heat generated by each compressor is recovered by heat exchange with the cold energy medium provided by the low-temperature storage tank 9 through the heat exchange device 4 in the compression heat exchange assembly, and all the heat is stored in the high-temperature storage tank 10 for use as the heat required for heating in steps S3 and S4.

[0188] The project economy of each embodiment and the comparative example was calculated, wherein the main parameters for calculating the project economy are shown in Table 1, the results of the project economic cost are shown in Table 2, and the comparison of the results of the project economy calculation is shown in Table 3.

[0189] Table 1

[0190]

[0191] Table 2

[0192]

[0193] Note: The electricity-electricity cycle efficiency refers to the ratio of the power generation amount to the power consumption amount; the heat-heat cycle efficiency refers to the proportion of the heat recovered by the system in the heat required for heating the carbon dioxide in the release stage; the cycle income is the sum of the power generation income and the steam generation income in the 1 h charging and discharging cycle of the system; the elasticity coefficient = the relative change of the cycle income / the relative change of the peak-valley electricity price difference.

[0194] Table 3

[0195]

[0196] In Example 1, the recovered heat is preferentially used to increase the turbine inlet carbon dioxide temperature (i.e., the recovered heat is preferentially used as the heat required for heating in step S4), and the low-grade waste heat of ethylene stably supplies the heat required for the second gasification treatment of the liquid carbon dioxide from the second liquid storage tank, effectively reducing the consumption of high-grade recovered heat for low-grade gasification heat sources in the conventional adiabatic carbon dioxide compression energy storage system, thereby increasing the turbine inlet carbon dioxide temperature to 200°C, increasing the power generation amount, and improving the electricity-electricity cycle efficiency of the system compared with the adiabatic carbon dioxide compression energy storage system, while additionally providing 1 t of steam.

[0197] In Example 2, the recovered heat is preferentially used to produce steam required for ethylene (i.e., the recovered heat is preferentially used as the heat required for producing steam for ethylene), which reduces the turbine inlet carbon dioxide temperature to 110°C at the cost of providing 8 t of steam, and accordingly, the electricity-electricity cycle efficiency of the system is reduced compared with the adiabatic carbon dioxide compression energy storage system. However, even if the power generation amount is reduced, the cycle income of completing one charging and discharging cycle is still higher than that of the adiabatic system due to the steam income (90 yuan / t).

[0198] In addition, the gaseous carbon dioxide storage on the low pressure side is converted into liquid storage, which can reduce the construction area of the system by half, effectively support the construction of the system in a limited space scenario, and further reduce the system investment and requirements for the construction site.

[0199] The project economic indicators of different carbon dioxide energy storage (CCES) system scenarios in the low-price difference Xinjiang region and the high-price difference Guangdong region are compared in Table 3. Due to the close valley electricity prices in the two regions, the full life cycle of the CCES system in the two regions is close to the flat electricity cost. At the same time, due to the influence of steam production on power generation, in order to show the influence of steam on the system power cost, the steam income is considered in the calculation of the flat electricity cost, so that the degree of electricity cost of embodiment 2 (steam production scene) is slightly lower than that of comparative example 1 (adiabatic scene), and the degree of electricity cost of embodiment 1 (power generation scene) is the lowest, which can be less than 0.3 yuan / kWh. On the other hand, due to the fact that the peak electricity price in Guangdong region is 2.16 times that in Xinjiang region, the internal rate of return of the projects in the two regions is significantly different.

[0200] Overall, the internal rate of return of the CCES project in Guangdong region is better, the internal rate of return (IRR) of embodiment 1 is as high as 9.73%, and the IRR of embodiment 2 is higher than the base rate of 6.68%, both of which are better than that of comparative example 1 (the IRR is 4.81%). The above results show that in the economically developed region with high peak-valley electricity price difference, the present application has good economic feasibility.

[0201] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A liquid compressed carbon dioxide energy storage system, characterized by, The system contains a carbon dioxide circulation system, which comprises: a first liquid storage tank (1), a first evaporation unit (100), an energy storage unit (200), a second liquid storage tank (6), a second evaporation unit (300), an energy release unit (400) and a condensation unit (500) connected in sequence; The first evaporation unit (100) and the second evaporation unit (300) each contain an evaporator; the evaporator is used for gasification treatment of liquid carbon dioxide material from the upstream, and the heat required in the first gasification treatment of the first evaporation unit (100) is provided by an ethylene low-temperature waste heat device, and the heat required in the second gasification treatment of the second evaporation unit (300) is provided by an ethylene low-grade waste heat device; The energy storage unit (200) stores energy by compressing and condensing gaseous carbon dioxide I from the first evaporation unit (100) into liquid carbon dioxide II; and the energy release unit (400) releases energy by heating and expanding to convert gaseous carbon dioxide II from the second evaporation unit (300) into gaseous carbon dioxide III; The condensation unit (500) contains a condenser; the condenser is used for condensation treatment of gaseous carbon dioxide III from the upstream, and the cold energy required in the condensation treatment is provided by an ethylene low-temperature waste heat device; The heat generated by compression can be used in the energy release unit (400) and as the heat required for steam in the ethylene production process; The first evaporation unit (100) further contains a first ethylene low-temperature waste heat device (16), which is used to provide the heat required for the first gasification treatment, and the first ethylene low-temperature waste heat device (16) is connected in series with the first evaporator (2) through a pipeline; The second evaporation unit (300) further contains an ethylene low-grade waste heat device (12), which is used to provide the heat required for the second gasification treatment, and the ethylene low-grade waste heat device (12) is connected in series with the second evaporator (7) through a pipeline; The condensation unit (500) further contains a second ethylene low-temperature waste heat device (13); the second ethylene low-temperature waste heat device (13) is used to provide the cold energy required for the condensation treatment, and the second ethylene low-temperature waste heat device (13) is connected in series with the condenser (5) through a pipeline; The first liquid storage tank (1) is used for storing liquid carbon dioxide I; the second liquid storage tank (6) is used for storing liquid carbon dioxide II; The ethylene low-grade waste heat device is selected from at least one of a quenching water tower and a quenching oil tower.

2. The system of claim 1, wherein, The system further contains a low-temperature storage tank (9) for storing cold energy medium and a high-temperature storage tank (10) for storing heat energy medium; The outlet of the low-temperature storage tank (9) is connected in communication with the energy storage unit (200), and the inlet of the low-temperature storage tank (9) is connected in communication with the energy release unit (400); the outlet of the high-temperature storage tank (10) is connected in communication with the energy release unit (400).

3. The system of claim 2, wherein, The energy storage unit (200) comprises a first condensation assembly (15) and at least two compression heat exchange assemblies connected in series; Each of the compression heat exchange assemblies contains a compressor (3) and a heat exchange device (4) connected in series, so that the gaseous carbon dioxide I is compressed and heat exchanged in each compression heat exchange assembly in turn; The first condensing assembly (15) is used for condensing the gaseous carbon dioxide after heat exchange in the most downstream compression heat exchange assembly into liquid carbon dioxide II.

4. The system of claim 3, wherein, In the direction of carbon dioxide flow, the inlet of the compressor (3) in the most upstream compression heat exchange assembly is in communication with the outlet of the first evaporator (2) in the first evaporating unit (100); In the direction of carbon dioxide flow, the inlet of the first condensing assembly (15) is in communication with the outlet of the heat exchange device (4) in the most downstream compression heat exchange assembly, and the outlet of the first condensing assembly (15) is in communication with the inlet of the second liquid storage tank (6).

5. The system of claim 3, wherein, The outlet of the low-temperature storage tank (9) is in communication with the heat exchange device (4) in each of the compression heat exchange assemblies; The working medium at the outlet of each of the compressors (3) is heat exchanged and recovered by the cold energy medium provided by the low-temperature storage tank (9) through the heat exchange device (4) in the compression heat exchange assembly, a part of which is used as steam heat required by the ethylene production process in the steam generator (11), and the remaining part is stored in the high-temperature storage tank (10).

6. The system of claim 2, wherein, The energy releasing unit (400) comprises at least two turbine assemblies connected in series, each of which contains a heater (14) and a turbine (8) connected in series; The gaseous carbon dioxide II from the second evaporating unit (300) is heated by the heat energy medium provided by the high-temperature storage tank (10) through the heater (14); the gaseous carbon dioxide II heated by the heater (14) enters the turbine (8) to expand and do work, outputs electric power to the outside, and converts the gaseous carbon dioxide II into gaseous carbon dioxide III.

7. The system of claim 6, wherein, In the direction of carbon dioxide flow, the most upstream heater (14) is in communication with the second evaporator (7) in the second evaporating unit (300), and the outlet of the most downstream turbine (8) is in communication with the inlet of the condenser (5) in the condensing unit (500); The outlet of the high-temperature storage tank (10) is in communication with the heater (14) in each of the turbine assemblies; The heat energy medium provided by the high-temperature storage tank (10) is circulated to the low-temperature storage tank (9) after passing through the heater (14).

8. The system of claim 1, wherein, The first ethylene low-temperature waste cold device (16) and the second ethylene low-temperature waste cold device (13) are each independently selected from at least one of a cold box in an ethylene separation process, an ethylene compression refrigeration cycle device, and a propylene compression refrigeration cycle device; The first ethylene low-temperature waste cold device (16) and the second ethylene low-temperature waste cold device (13) provide different waste cold temperatures, and the temperature of the first ethylene low-temperature waste cold device (16) is higher than that of the second ethylene low-temperature waste cold device (13).

9. A liquid compressed carbon dioxide energy storage method, characterized by, The method is carried out in the liquid compressed carbon dioxide energy storage system of any one of claims 1-8, comprising a cyclic energy storage step and an energy releasing step: The energy storage step comprises: S1: introducing liquid carbon dioxide I in a first liquid tank into a first evaporation unit for first gasification treatment to obtain gaseous carbon dioxide I; heat of the first evaporation unit is provided by waste cold in an ethylene low-temperature waste cold device; S2: introducing the gaseous carbon dioxide I into an energy storage unit for compression and first condensation to obtain liquid carbon dioxide II, which is transported into a second liquid tank for storage; the energy releasing step comprises: S3: introducing liquid carbon dioxide II in the second liquid tank into a second evaporation unit for second gasification treatment to obtain gaseous carbon dioxide II; heat of the second evaporation unit is provided by low-grade waste heat in an ethylene low-grade waste heat device; S4: introducing the gaseous carbon dioxide II into an energy releasing unit for heating and expansion work to obtain gaseous carbon dioxide III; S5: after condensation treatment of the gaseous carbon dioxide III in a condensation unit, the gaseous carbon dioxide III is recycled into the first liquid tank for storage; cold energy of the condensation unit is provided by waste cold in the ethylene low-temperature waste cold device; wherein heat generated by the compression can be used as heat of steam required by an ethylene production process and as heat required for the heating in step S4; the gaseous carbon dioxide I, the gaseous carbon dioxide II and the gaseous carbon dioxide III are different; the liquid carbon dioxide I and the liquid carbon dioxide II are different.

10. The method of claim 9, wherein, the energy storage unit contains a first condensation assembly and at least two compression heat exchange assemblies connected in series; each compression heat exchange assembly contains a compressor and a heat exchange device connected in series, so that the gaseous carbon dioxide I can be compressed and heat exchanged in each compression heat exchange assembly in turn; the energy releasing unit contains at least two turbine assemblies connected in series; each turbine assembly contains a heater and a turbine connected in series, so that the gaseous carbon dioxide II can be heated and expanded for work in each turbine assembly in turn.

11. The method according to claim 9 or 10, characterized in that, temperature of the liquid carbon dioxide I in the first liquid tank is -56℃ to -40℃, and pressure is 0.5-1MPa; and / or temperature of the liquid carbon dioxide II in the second liquid tank is 25-28℃, and pressure is 6.5-7MPa.

12. The method of claim 9 or 10, wherein, temperature of the low-grade waste heat is greater than 30℃, and temperature of the waste cold is -160℃ to 40℃.

13. The method of claim 9 or 10, wherein, in step S1, the first gasification treatment has a temperature of -35℃ to 40℃ and a pressure of 0.5-1MPa; and / or in step S2, the first condensation has a temperature of 20-30℃ and a pressure of 6.5-7MPa; and / or in step S2, the compression has a compressor working medium inlet pressure of 0.1-1MPa at the most upstream, a working medium inlet temperature of 15-30℃, and a compression ratio of each compressor independently of 2-10:

1.

14. The method of claim 9 or 10, wherein, in step S3, the second gasification treatment has a temperature of 30-50℃ and a pressure of 5-7MPa; and / or In step S4, the conditions of the expansion work include: the inlet pressure of the working medium of the most upstream turbine is 6.5-7 MPa; the inlet temperature of the working medium is 100-250℃, the expansion ratio of each turbine is 2-10:1; and / or In step S5, the conditions of the condensation treatment include: the temperature is -160℃ to -40℃, and the pressure is 0.5-1 MPa.

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