Liquid compressed carbon dioxide energy storage system and method

Abstract

The invention relates to the technical field of compressed carbon dioxide energy storage, and discloses a liquid compressed carbon dioxide energy storage system and method. The system comprises a carbon dioxide circulation system, and the circulation system 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) which are communicated in sequence. According to the system provided by the invention, a liquid compressed carbon dioxide circulating system is deeply coupled with waste heat and waste cold in an ethylene process, so that the problems of a gasification heat source of liquid carbon dioxide on a high-pressure side and a liquefaction cold source of gaseous carbon dioxide on a low-pressure side of a pressure storage system are solved; the bottleneck constraint of heat energy utilization of the conventional adiabatic compression carbon dioxide energy storage system is broken through; elastic distribution of compression heat between industrial steam production and carbon dioxide overheating can be achieved.

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 storage and release stages. In particular, for the mainstream adiabatic compressed carbon dioxide energy storage system, the limited heat recovery during the storage stage is only used as the sole heat source for the carbon dioxide heat absorption during the 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 release stage per unit of working medium. 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, a storage assembly, a high-pressure gas storage tank, a 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 a 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, a release assembly, and a condensation assembly in sequence. The method includes two stages of storage and 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, D1 requires independent setting of a liquid storage tank and a high-pressure gas storage tank, 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; The first evaporation unit and the second evaporation unit 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 is provided by an ethylene low-temperature waste heat device, and the heat required in the second gasification treatment of the second evaporation unit is provided by an ethylene low-grade waste heat device; The energy storage unit stores energy by compressing and condensing 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 gaseous carbon dioxide II from the second evaporation unit into gaseous carbon dioxide III; The condensation unit 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 for the energy release unit and as heat for the steam required in the ethylene production process.

[0008] 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: The energy storage step comprises: S1: introducing 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; 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; The energy release step comprises: S3: introducing 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; S4: introducing the gaseous carbon dioxide II into the energy release unit for heating, expansion and work to obtain gaseous carbon dioxide III; S5: introducing the gaseous carbon dioxide III into the condensation unit for condensation treatment, and then recycling to the first liquid storage tank for storage; the cold energy of the condensation unit is provided by the waste heat in the ethylene low-temperature waste heat device; The heat generated by the compression can be used as heat of steam required in an ethylene production process and as heat required in 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.

[0009] Compared with the prior art, the present application has the following advantages: (1) The system provided by the present application deeply couples a liquid compressed carbon dioxide circulation system with waste heat and waste cold in an ethylene process, solves the problems of gasification heat source of liquid carbon dioxide in a pressure storage system and liquefaction cold source of gaseous carbon dioxide at a low pressure side, breaks through the bottleneck constraint of heat energy utilization of a previous adiabatic compressed carbon dioxide energy storage system, and can realize elastic distribution of compression heat between industrial steam production and carbon dioxide superheating.

[0010] (2) In the technical aspect, low-grade waste heat generated by an ethylene low-grade waste heat device (a quenching water tower or a quenching oil tower) in the ethylene process matches the gasification temperature of the liquid carbon dioxide II (high-pressure liquid carbon dioxide), and low-temperature waste cold generated in a 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.

[0011] (3) In the economic aspect, preliminary accounting results for industrial and commercial electricity prices in Guangdong show that the present application effectively reduces construction area and initial investment, and at the same time improves operating income, so that the internal rate of return is improved to 9.73%, the flat-standardized cost of electricity 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

[0012] 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.

[0013] 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.

[0014] Figure 3 is a flow process schematic diagram of an adiabatic compressed carbon dioxide energy storage system in Comparative Example 1.

[0015] REFERENCE SIGNS 100, first evaporation unit; 200, energy storage unit; 300, second evaporation unit; 400, energy release unit; 500, condensation unit; 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 condensing assembly; 16, first ethylene low-temperature waste heat device; 17, gas storage tank. DETAILED DESCRIPTION

[0016] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numerical value, however, can include any values up to the stated value, or down to the stated value, in increments of one unit. For ranges, the endpoints are included in the ranges. For numerical values of a range, any intervening value or values between the stated values are also contemplated. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. For values which are fractions of a whole, 0.0001 of the whole is considered to be the smallest unit of precision.

[0017] In the present invention, unless otherwise specified, the "first", "second" and the like in the names of each material and each operation, as well as the serial numbers "I", "II" and the like, do not represent the order of precedence, nor do they limit each material or operation, but are only used to distinguish each material or operation. For example, "first" and "second" in "first evaporation unit" and "second evaporation unit" are only used to distinguish them, indicating that they are not the same evaporation unit. "Liquid carbon dioxide I" and "liquid carbon dioxide II" are only used to distinguish them, indicating that they are not the same liquid carbon dioxide. "First gasification treatment" and "second gasification treatment" are only used to distinguish them, indicating that they are not the same gasification treatment operation. The definitions of the serial numbers in the names of the remaining materials and operations are similar and will not be repeated here.

[0018] In the present invention, unless otherwise specified, the pressures are all absolute pressures.

[0019] As described above, the first aspect of the present invention 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; The first evaporation unit 100 and the second evaporation unit 300 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 treatment of the first evaporation unit 100 is provided by the ethylene low-temperature waste heat device, and the heat required in the second gasification treatment of the second evaporation unit 300 is provided by the 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, expanding and working gaseous carbon dioxide II from the second evaporation unit 300 into gaseous carbon dioxide III. 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 condensing process is provided by the ethylene low-temperature waste heat device. The heat generated by the compression can be used in the energy release unit 400 and as heat for the steam required in the ethylene production process.

[0020] In some embodiments, the first liquid storage tank 1 is used to store liquid carbon dioxide I (low-pressure liquid carbon dioxide); the second liquid storage tank 6 is used to store liquid carbon dioxide II (high-pressure liquid carbon dioxide).

[0021] In the present application, 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] The source of the carbon dioxide in the present application is not particularly limited and can be obtained by known technical means by those skilled in the art. Preferably, it is obtained by a carbon capture process in the ethylene production process.

[0023] In some embodiments, 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 process, and the first ethylene low-temperature waste heat device 16 is connected in series with the first evaporator 2 through a pipeline. With this preferred embodiment, the cold energy in the liquid carbon dioxide I is released to the high-temperature part of the ethylene process waste heat, thereby improving the recycling efficiency of the cold energy.

[0024] In the present application, the first evaporator 2 is used to perform a first gasification process on the liquid carbon dioxide I from the first liquid storage tank; the inlet of the first evaporator 2 is connected to the outlet of the first liquid storage tank 1.

[0025] According to a preferred specific embodiment, 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 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 process is recovered and used as the heat required for the second evaporator, which is beneficial to improve the energy utilization efficiency.

[0026] In the present application, the second evaporator 7 is used to carry out the second gasification treatment on the liquid carbon dioxide II from the second liquid tank 6; the inlet of the second evaporator 7 is connected with the outlet of the second liquid tank 6.

[0027] According to another preferred embodiment, the condensing unit 500 further comprises a second ethylene low-temperature waste cold device 13; the second ethylene low-temperature waste cold device 13 is used to provide the cold energy required for the condensing treatment, and the second ethylene low-temperature waste cold device 13 is connected with the condenser 5 in series through a pipeline. By using this preferred embodiment, the refrigeration cost of the low-pressure side carbon dioxide liquefaction can be reduced, and the system economy can be improved.

[0028] In the present application, the outlet of the condenser 5 is connected with the inlet of the first liquid tank 1.

[0029] 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 with the energy storage unit 200, the inlet of the low-temperature storage tank 9 is connected with the energy release unit 400, and the outlet of the high-temperature storage tank 10 is connected with the energy release unit 400. By using this preferred embodiment, the energy circulation efficiency of the internal heat production and utilization of the carbon dioxide energy storage system can be improved.

[0030] According to another preferred embodiment, the energy storage unit 200 comprises a first condensing 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 turn; the first condensing assembly 15 is used to condense the gaseous carbon dioxide after heat exchange in the most downstream compression heat exchange assembly into 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 more energy can be stored for subsequent expansion work.

[0031] 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 gaseous carbon dioxide after heat exchange in the most downstream heat exchange assembly is introduced into the first condensing assembly 15 for condensation.

[0032] In the present application, the two compressors 3 in the energy storage unit 200 are connected through the heat exchange device 4.

[0033] In the present application, the energy consumed by the compressor is the surplus power grid energy during the low-power period or the electric energy generated by renewable energy sources.

[0034] In some embodiments, the energy storage unit 200 comprises a first condensing assembly 15 and two compression heat exchange assemblies connected in series.

[0035] In some embodiments, 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 along the flow direction of carbon dioxide.

[0036] In some embodiments, the system further comprises a throttle valve, the compressor 3 in the most upstream compression heat exchange assembly is in communication with 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.

[0037] In some embodiments, 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 along the flow direction of carbon dioxide, and the outlet of the first condensing assembly 15 is in communication with the inlet of the second liquid storage tank 6.

[0038] In some embodiments, 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. Thus, the outlet of the low-temperature storage tank 9 is in communication with the energy storage unit 200.

[0039] According to a preferred specific embodiment, the working medium at the outlet of each of the compressors 3 is 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 the 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. 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 the two and is beneficial to improve the energy utilization efficiency.

[0040] In some embodiments, the energy release 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.

[0041] In some embodiments, 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.

[0042] In the present application, when the turbine inlet pressure drops to the designed minimum value, the expansion work is 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.

[0043] In some embodiments, along the carbon dioxide flow direction, 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.

[0044] 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 for maintaining the pressure in the condenser 5.

[0045] In some embodiments, the outlet of the high-temperature storage tank 10 is in communication with the heater 14 in each turbine assembly. Thus, the outlet of the high-temperature storage tank 10 is in communication with the energy releasing unit 400.

[0046] In some embodiments, the heat energy medium provided by the high-temperature storage tank 10 is circulated to the low-temperature storage tank 9 through the heater 14.

[0047] 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.

[0048] 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.

[0049] In some embodiments, the first ethylene low-temperature waste heat device 16 and the second ethylene low-temperature waste heat 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.

[0050] In some embodiments, the first ethylene low-temperature waste heat device 16 and the second ethylene low-temperature waste heat device 13 provide different waste heat temperatures, and the temperature of the first ethylene low-temperature waste heat device 16 is higher than that of the second ethylene low-temperature waste heat device 13. The inventors have found that the preferred embodiment can better reduce energy consumption.

[0051] In some embodiments, the temperature of the low-grade waste heat in the ethylene low-grade waste heat device is greater than 30°C; preferably 45-70°C.

[0052] In some embodiments, the temperature of the waste cold in the ethylene low-temperature waste cold 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℃.

[0053] In some embodiments, the temperature of the waste cold in the first ethylene low-temperature waste cold device is -35℃ to 40℃, preferably 20-40℃; and the temperature of the waste cold in the second ethylene low-temperature waste cold device is -160℃ to -40℃, preferably -60 to -40℃.

[0054] In the present application, the heat exchange mode of carbon dioxide with the cold energy medium in the heat exchanger or the hot energy medium in the heater includes but is not limited to countercurrent heat exchange, cocurrent heat exchange, and multiphase heat exchange.

[0055] 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.

[0056] In the present application, the carrier of the waste cold is selected from one or more of methane, propylene, and ethylene.

[0057] In some embodiments, the cold energy medium and the hot energy medium are each independently selected from at least one of water and heat-conducting oil.

[0058] The system provided by the present application can improve the energy utilization efficiency of 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 of 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.

[0059] As described above, the second aspect of the present application provides a liquid compressed carbon dioxide energy storage method, which comprises a storage step and a release step performed cyclically: The storage step comprises: S1: introducing liquid carbon dioxide I in a first storage tank into a first evaporation unit for first gasification treatment to obtain gaseous carbon dioxide I; the 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 to a second storage tank for storage; The release step comprises: S3: introducing the liquid carbon dioxide II in the second liquid storage tank into a second evaporation unit for a second gasification treatment to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by low-grade waste heat in the low-grade waste heat device of the ethylene production process; S4: introducing the gaseous carbon dioxide II into a energy releasing unit for heating, expansion and work to obtain gaseous carbon dioxide III; S5: introducing the gaseous carbon dioxide III into a condensation unit for condensation treatment and then recycling to the first liquid storage tank for storage; the cold energy of the condensation unit is provided by waste cold in the low-temperature waste cold device of the ethylene production process; The heat generated by the compression can be used as the heat of steam required by the ethylene production process and as the 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.

[0060] According to a preferred embodiment, 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. The inventors have found that under this preferred condition, the compression efficiency can be further improved, the energy consumption can be reduced, and the service life of the equipment can be prolonged.

[0061] According to another preferred embodiment, the energy releasing unit contains at least two turbine assemblies connected in series, and 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. The inventors have found that under this preferred condition, by means of staged pressure reduction and inter-stage reheating, the energy recovery efficiency can be better improved and the energy loss can be reduced.

[0062] According to a preferred embodiment, the heat generated by each compressor is heat exchanged and recovered by a cold energy medium provided by a low-temperature storage tank through a heat exchange device in the compression heat exchange assembly, a part of which is stored in a steam generator for use as the steam heat required by the ethylene production process, and the remaining part is stored in a high-temperature storage tank for use as the heat required for the heating in step S4. The inventors have found that under this preferred condition, the energy utilization efficiency can be further improved.

[0063] In some embodiments, the heat required by the heater is provided by a heat energy medium stored in a high-temperature storage tank.

[0064] In some embodiments, the temperature of the cold energy medium is 10-70°C, preferably 10-30°C; the temperature of the heat energy medium is 100-250°C, preferably 180-220°C.

[0065] In some embodiments, the cold energy medium, the heat energy medium are each independently selected from at least one of water, heat-conducting oil.

[0066] In some embodiments, the temperature of the liquid carbon dioxide I in the first storage tank is -56°C to -40°C, and the pressure is 0.5-1 MPa.

[0067] In some embodiments, the temperature of the liquid carbon dioxide II in the second storage tank is 25-28°C, and the pressure is 6.5-7 MPa.

[0068] In some embodiments, the temperature of the low-grade waste heat is greater than 30°C, and the temperature of the waste cold is -160°C to 40°C.

[0069] In some embodiments, the temperature of the low-grade waste heat is 45-70°C, and the temperature of the waste cold is -160°C to 40°C. For example, the temperature of the low-grade waste heat can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C; the temperature of the waste cold can be -150°C, -140°C, -130°C, -120°C, -110°C, -100°C, -90°C, -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 30°C.

[0070] According to a specific embodiment, the first evaporation unit contains a first ethylene low-temperature waste cold device and a first evaporator; the temperature of the waste cold in the first ethylene low-temperature waste cold device is -35°C to 40°C.

[0071] According to a specific embodiment, the second evaporation unit contains a second ethylene low-temperature waste cold device and a second evaporator; the temperature of the waste cold in the second ethylene low-temperature waste cold device is -160°C to -40°C.

[0072] In some embodiments, in step S1, the conditions of the first gasification treatment include: the temperature is -35°C to 40°C, and the pressure is 0.5-1 MPa. Exemplarily, the temperature can be -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C; 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.

[0073] Further preferably, the conditions of the first gasification process include: a temperature of 20-40°C, and a pressure of 0.5-0.7 MPa.

[0074] In some embodiments, in step S2, the conditions of the first condensation include: a temperature of 20-30°C, and a pressure of 6.5-7 MPa.

[0075] 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°C.

[0076] In some embodiments, in step S2, the conditions of the compression include: the most upstream compressor working medium inlet pressure is 0.1-1 MPa; the working medium inlet temperature is 15-30°C, and the compression ratio of each compressor is independently 2-10:1.

[0077] 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.

[0078] In some embodiments, the flow rate of the compressor working medium inlet is 35-45 kg / s relative to a power generation of 10 MW.

[0079] In some embodiments, in step S3, the conditions of the second gasification process include: a temperature of 30-50°C, and a pressure of 5-7 MPa. Illustratively, the temperature of the second gasification is 35, 40, 45, 50°C; and the pressure of the second gasification is 5.5 MPa, 6.0 MPa, 6.5 MPa, 7.0 MPa.

[0080] 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 working medium inlet temperature of each turbine after heating is 100-250°C.

[0081] 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°C, and the expansion ratio of each turbine is 2-10:1.

[0082] In some embodiments, in step S4, the efficiency of each turbine is 0.85-0.95.

[0083] 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.

[0084] In some embodiments, in step S5, the conditions of the condensing treatment include: a temperature of -160 to -40℃ and a pressure of 0.5-1 MPa. Exemplarily, the condensing 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.

[0085] Further preferably, the conditions of the condensing treatment include: a temperature of -60 to -40℃ and a pressure of 0.5-1 MPa.

[0086] The present application significantly improves the cycle efficiency of the energy storage system, reduces the system construction space and cost, and effectively promotes the energy saving and emission reduction of the ethylene process by using the 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. 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 releasing section and generating steam required for ethylene can be flexibly adjusted, so as to obtain different electricity prices and steam benefits according to the electricity prices and steam policies in different places.

[0087] The system and method provided by the present application are described in detail below with reference to the accompanying drawings.

[0088] Figure 1 is a flow schematic diagram of a liquid compressed carbon dioxide energy storage system of a specific embodiment of the present application, which 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 releasing unit 400 and a condensing 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 cold 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 the gaseous carbon dioxide I from the first evaporation unit 100 into liquid carbon dioxide II; and the energy release unit 400 releases energy by converting the gaseous carbon dioxide II from the second evaporation unit 300 into gaseous carbon dioxide III through heating and expansion. The condensing unit 500 includes a condenser; the condenser is used to condense the gaseous carbon dioxide III from the upstream, and the cold energy required for the condensation process is provided by the ethylene low-temperature waste cooling device; The heat generated by the compression can be used in the energy discharging unit 400 and used as heat for the steam required for the production of ethylene.

[0089] Figure 2 This is a flow chart of a liquid compressed carbon dioxide energy storage system according to a preferred embodiment of the present invention. Figure 2 The solid arrows in the middle 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 medium and hot energy medium in the liquid compressed carbon dioxide energy storage system; from Figure 2 As can be seen, the system contains a carbon dioxide circulation system, which includes: a first liquid storage tank 1, a first evaporation unit 100, a throttle 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; The first evaporation unit 100 includes a first ethylene low-temperature residual cooling device 16 and a first evaporator 2 connected in series via a pipeline; the first evaporator 2 is used to perform a first gasification process on the liquid carbon dioxide I from the first liquid storage tank 1, and the heat required for the first gasification process is provided by the first ethylene low-temperature residual cooling device 16; The energy storage unit 200 includes a first condensing assembly 15 and at least two compression and heat exchange assemblies connected in series. Each compression and heat exchange assembly includes a compressor 3 and a heat exchange device 4 connected in series, so that gaseous carbon dioxide I is compressed and heat exchanged in each compression and heat exchange assembly. The first condensing assembly 15 is used to condense the heat-exchanged gaseous carbon dioxide at the outlet of the downstream heat exchange device 4 into liquid carbon dioxide II. The second evaporation unit 300 includes a low-grade ethylene waste heat device 12 and a second evaporator 7 connected in series via a pipeline; the second evaporator 7 is used to perform a second gasification process on the liquid carbon dioxide II from the second liquid storage tank 6, and the heat required for the second gasification process is provided by the low-grade ethylene waste heat device 12; 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; 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 the electric power is outputted to the outside, and the gaseous carbon dioxide II is converted into gaseous carbon dioxide III; The condensing unit 500 comprises a second ethylene low-temperature waste cold device 13 and the condenser 5 connected in series through pipelines; the condenser 5 is used for condensing 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 cold device 13; 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. The outlet of the low-temperature storage tank 9 is communicated 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 stored in the steam generator 11 and used as the steam heat required for producing ethylene, and the remaining part is stored in the high-temperature storage tank 10.

[0090] According to a particularly preferred embodiment, the system contains a carbon dioxide circulation system, which includes: connecting the outlet of the first liquid storage tank 1 to the inlet of the first evaporator 2; along the flow direction of carbon dioxide, the inlet of the compressor 3 in the most upstream compression and heat exchange component 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 and heat exchange component is connected to the inlet of the heat exchange device 4, the outlet of the heat exchange device 4 in the most upstream compression and heat exchange component is connected to the inlet of the compressor 3 in the adjacent downstream compression and heat exchange component, and the outlet of the compressor 3 in the adjacent downstream compression and heat exchange component is connected to the inlet of the heat exchange device 4; repeating this until the pressure of the compressed gaseous carbon dioxide reaches the maximum storage pressure designed for the system, stopping compression, and then connecting the outlet of the heat exchange device 4 in the most downstream compression and heat exchange component to the first condensation component The inlet of the first condensing assembly 15 is connected, the outlet of the first condensing assembly 15 is connected to the inlet of the second liquid storage tank 6; the outlet of the second liquid storage tank 6 is connected to the inlet of the second evaporator 7; along the flow direction of carbon dioxide, the outlet of the second evaporator 7 is connected to the inlet of the heater 14 in the most upstream turbine assembly, the outlet of the heater 14 in the most upstream turbine assembly is connected to the inlet of the turbine 8, the outlet of the turbine 8 in the most upstream turbine assembly is connected to the inlet of the heater 14 in the adjacent downstream turbine assembly, and the outlet of the heater 14 in the adjacent turbine assembly is connected to the inlet of the turbine 8, and this process is repeated until the turbine inlet pressure drops to the designed minimum value, and the expansion work is stopped. Then, the outlet of the most downstream turbine 8 is connected to the cryogenic pump in the condensing unit 500, and the cryogenic pump is connected to the inlet of the condenser 5; the outlet of the condenser 5 is connected to the inlet of the first liquid storage tank 1; 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; The first ethylene low-temperature waste cooling device 16 is connected to the first evaporator 2 in series through a pipeline, the second ethylene low-temperature waste cooling 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.

[0091] The present invention provides a preferred liquid compressed carbon dioxide energy storage method, which adopts Figure 2 The system shown in FIG. 1 is used for performing the method, and the method comprises: a cyclic energy storage step and an energy release step: The energy storage step comprises: 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; 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; The energy releasing step comprises: 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; 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; 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 process, 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; 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; 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.

[0092] The application will be described in detail below by way of 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 products unless otherwise specified.

[0093] The following examples are used to illustrate the system and method for liquid compressed carbon dioxide energy storage provided by the present application. The time for the energy storage stage and the energy release stage in the following examples is 8h.

[0094] Example 1 This example is implemented by using the liquid compressed carbon dioxide energy storage system described in the present application, and the structure of the liquid compressed carbon dioxide energy storage is as shown in Figure 2 ; The method comprises: an energy storage step and an energy release step which are cyclically performed. The energy storage step comprises: 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 process, so as 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); The condition of the first gasification process is: temperature: 30℃, pressure: 0.55MPa; S2: after the gaseous carbon dioxide I is depressurized to 0.1MPa by a throttle valve, introducing it into the energy storage unit 200 to perform compression and first condensation, so as 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 which are connected in series; each compression heat exchange assembly contains a compressor 3 and a heat exchange device 4 which are 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 condition of the compression is: the inlet pressure of the working medium of the most upstream compressor is set to 0.1MPa; the inlet temperature of the working medium of each compressor is 20℃, the inlet flow rate of the working medium 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; 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 inlet of the compressor is 20℃; The condition of the first condensation is: temperature: 27℃, pressure: 6.75MPa; The energy release step comprises: 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, so as to obtain gaseous carbon dioxide II; the heat of the second evaporation unit is provided by the low-grade residual heat (temperature: 50℃) in the ethylene low-grade residual heat device 12 (using a quenching water tower); The second gasification treatment is carried out at a temperature of 50℃ and a pressure of 6.75MPa. S4: introducing the gaseous carbon dioxide II into the energy releasing unit 400 to be heated and expanded to 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 the gaseous carbon dioxide II can be heated and expanded to work in each turbine assembly; The temperature of the heat energy medium (L80 heat conducting oil) in the high temperature storage tank 10 is controlled so that the temperature of each turbine working medium inlet after heating is 200℃; The expansion working conditions are as follows: the pressure of the most upstream turbine working medium inlet is set to 6.75MPa; the temperature of each turbine working medium inlet is 200℃, the working medium inlet flow rate 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; S5: the gaseous carbon dioxide III is pressurized to 0.55MPa by a low temperature pump in the condensing unit and then enters the condenser 5 to be condensed, to obtain liquid carbon dioxide which is recycled to the first liquid storage tank for storage; the cold energy of the condensing unit is provided by the residual cold (carrier is a cracking gas containing ethylene and methane, temperature is -60℃) in the second ethylene low temperature residual cold device (using a low temperature cold box device) 13; The condensing treatment is carried out at a temperature of -60℃ and a pressure of 0.55MPa; The heat generated by each compressor is recovered by heat exchange between the cold energy medium provided by the low temperature storage tank 9 and the heat exchange device 4 in the compression heat exchange assembly, a part of the heat (accounting for 94% of the total recovered heat) is stored in the high temperature storage tank 10 to be used as the heat required for the heating in step S4, and the remaining part of the heat (accounting for 6% of the total recovered heat) is sent to the steam generator 11 to be used as the steam heat required for the ethylene production process. 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.

[0095] Example 2 This example is carried out by using a method similar to that of Example 1, except that: In step S2, the heat generated by each compressor is recovered by heat exchange between the cold energy medium provided by the low temperature storage tank 9 and the heat exchange device 4 in the compression heat exchange assembly, a part of the heat (accounting for 50% of the total recovered heat) is sent to the steam generator 11 to be used as the steam heat required for the ethylene production process, and the remaining part of the heat (accounting for 50% of the total recovered heat) is stored in the high temperature storage tank 10 to be used as the heat required for the heating in step S4; In step S4, the temperature of the thermal energy medium (L80 heat transfer 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; The conditions for expansion work: the inlet pressure of the turbine working medium at the most upstream position 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; The remaining steps are the same as in Example 1.

[0096] Comparative Example 1 This comparative example is implemented using a conventional adiabatic compressed carbon dioxide energy storage system that does not contain an external heat source (ethylene process waste heat and waste cold), which has a structure as shown in Figure 3 ; The method includes: a cyclic energy storage step and an energy release step: The energy storage step includes: S1: The gaseous carbon dioxide (temperature 20°C, pressure 0.1 MPa) in the gas storage tank 17 is introduced into the energy storage unit 200 for compression and first condensation to obtain liquid carbon dioxide II (temperature 27°C, pressure 6.75 MPa), 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; The compression conditions: the inlet pressure of the working medium of the most upstream compressor is 0.1 MPa; the inlet temperature of the working medium of each compressor is 20°C, the inlet flow rate of the working medium 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; The temperature of the cold energy medium (L80 heat transfer oil) in the low-temperature storage tank 9 is controlled so that the temperature of the carbon dioxide working medium at the inlet of the compressor after heat exchange is 20°C; The first condensation conditions: the temperature is 27°C, and the pressure is 6.75 MPa, The energy release step includes: S2: The liquid carbon dioxide II in the second liquid storage tank 6 is introduced into the second evaporator 7 of the second evaporation unit for second gasification treatment to obtain gaseous carbon dioxide II; The second gasification treatment conditions: the temperature is 50°C, and the pressure is 6.75 MPa; S3: introducing the gaseous carbon dioxide II into the energy releasing unit 400 to heat, expand and work, to obtain gaseous carbon dioxide III; the energy releasing unit contains two turbine assemblies connected in series, each of the turbine assemblies 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; The temperature of the thermal 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 140℃; The working conditions of expansion and work: 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 140℃, 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; S4: circulating the gaseous carbon dioxide III back to the gas storage tank 17 for storage; Wherein, the heat generated by each compressor is exchanged and recovered by the cold energy medium provided by the low temperature storage tank 9 through the 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 in steps S3 and S4.

[0097] The project economy of each embodiment and the comparative example is calculated, wherein the main parameters of the project economy calculation 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.

[0098] Table 1

[0099] Table 2

[0100] Note: The electricity-electricity cycle efficiency refers to the ratio of the system power generation to the power consumption; the heat-heat cycle efficiency refers to the proportion of the system recovered heat in the heat of the carbon dioxide heated in the energy releasing section; the cycle income is the sum of the power generation and steam generation income in the 1h 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.

[0101] Table 3

[0102] In the embodiment 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 is used to stably supply the heat required for the second gasification of the liquid carbon dioxide from the second storage tank, which effectively reduces the consumption of the high-grade recovered heat for the low-grade gasification heat source in the conventional adiabatic compression carbon dioxide energy storage system, thereby increasing the turbine inlet carbon dioxide temperature to 200°C, increasing the power generation, and improving the electric-to-electric cycle efficiency of the system compared with the adiabatic compression carbon dioxide energy storage system, while additionally providing 1 t of steam.

[0103] In the embodiment 2, the recovered heat is preferentially used to produce the steam required for ethylene (i.e. the recovered heat is preferentially used as the heat required for producing the steam for ethylene), which provides 8 t of steam at the cost of reducing the turbine inlet carbon dioxide temperature to 110°C, and correspondingly reduces the electric-to-electric cycle efficiency of the system compared with the adiabatic compression carbon dioxide energy storage system. However, even if the power generation is reduced, the cycle benefit of completing one charge and discharge is still higher than that of the adiabatic system due to the steam benefit (90 yuan / t).

[0104] In addition, the conversion of the gaseous carbon dioxide storage on the low-pressure side into liquid storage can reduce the construction area of the system by half, effectively supporting the construction of the system in a limited space scenario, and further reducing the system investment and requirements for the construction site.

[0105] 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 proximity of the off-peak electricity prices in the two regions, the full life cycle levelized power generation costs of the CCES systems in the two regions are close. At the same time, since the steam production affects the power generation, in order to show the influence of steam on the system power cost, the steam benefit is considered in the calculation of the levelized power generation cost, so that the levelized power generation cost of the embodiment 2 (steam production scenario) is slightly lower than that of the comparative example 1 (adiabatic scenario), and the levelized power generation cost of the embodiment 1 (power production scenario) is the lowest, which can be less than 0.3 yuan / kWh, benefiting from the significant increase in power generation. On the other hand, due to the fact that the peak electricity price in the Guangdong region is 2.16 times that in the Xinjiang region, the internal rate of return of the projects in the two regions is significantly different.

[0106] Overall, the internal rate of return of the CCES project in the Guangdong region is better, the internal rate of return (IRR) of the embodiment 1 is as high as 9.73%, and the IRR of the embodiment 2 is higher than the base rate of 6.68%, both of which are better than that of the comparative example 1 (the IRR is 4.81%). The above results show that in the economically developed regions with high peak-to-valley electricity price difference, the present application has good economic feasibility.

[0107] 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 that each technical feature is combined 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.

2. The system of claim 1, wherein, The first evaporation unit (100) also 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) also 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.

3. The system of claim 2, wherein, The condensation unit (500) also 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.

4. The system of any of claims 1-3, wherein, The system also 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).

5. The system of claim 4, wherein, The energy storage unit (200) comprises 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 gaseous carbon dioxide I is compressed and heat exchanged in each compression heat exchange assembly in sequence; The first condensing assembly (15) is used for condensing gaseous carbon dioxide after heat exchange in the most downstream compression heat exchange assembly into liquid carbon dioxide II.

6. The system of claim 5, 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 evaporation 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).

7. The system of claim 5, 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).

8. The system of claim 4, wherein, The energy releasing unit (400) comprises at least two turbine assemblies connected in series, each of which comprises 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) 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.

9. The system of claim 8, wherein, In the direction of carbon dioxide flow, 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); 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).

10. The system of any of claims 1-3, wherein, The first liquid storage tank (1) is used for storing liquid carbon dioxide I, and 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.

11. The system of claim 3, 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).

12. A liquid compressed carbon dioxide energy storage method, characterized by, The method comprises 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.

13. The method of claim 12, 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.

14. The method according to claim 12 or 13, 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.

15. The method according to claim 12 or 13, characterized in that, temperature of the low-grade waste heat is greater than 30℃, and temperature of the waste cold is -160℃ to 40℃.

16. The method of claim 12 or 13, 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.

17. The method of claim 12 or 13, 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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