Energy storage system

Abstract

To provide an energy storage system for storing energy by using an oxygen-nitrogen mixed liquid as a medium, which can efficiently utilize cold heat at a cryogenic temperature.SOLUTION: An energy storage system according to the present invention has: an LNG storage tank 70; an LNG pump 20; an LNG delivery line 171; an oxygen-nitrogen liquefaction feed device 50 for generating and feeding a mixed liquid of oxygen and nitrogen by using cold heat of LNG delivered by the LNG pump 20; a carbon dioxide solidification device 90 for solidifying the carbon dioxide contained in the carbon dioxide containing gas by exchanging heat between the oxygen-nitrogen mixed liquid fed by the oxygen-nitrogen liquefaction feed device 50 and the carbon dioxide containing gas; and an air expansion turbine 120 for generating power by expanding a material obtained by heating the oxygen-nitrogen mixed liquid in which the cold heat is utilized and converting it to high pressure gas in the carbon dioxide solidification device 90.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an energy storage system that stores energy using an oxygen-nitrogen mixed liquid as a medium, and relates to an energy storage system that can effectively utilize cryogenic cold. [Background technology]

[0002] With the spread of renewable energy, there is a growing need for energy storage systems, and storing energy using liquefied air has been proposed as one method. However, the extremely large compression power required to liquefy the air has the disadvantage of low charge / discharge efficiency.

[0003] In this regard, Patent Document 1 discloses a technology in which air is gradually cooled with LNG and liquid hydrogen (LH2) to liquefy it at low pressure, and the LNG and LH2 that have used the cold energy are supplied as fuel for a power generation facility, and the liquefied air is supplied to the power generation facility as an oxidant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-8132 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since the facility is based on LH2, which is difficult to obtain, it is unlikely to be feasible, and even if it were possible to obtain it, the high cost of LH2 would be reflected in the facility's operating costs, making it highly likely to undermine its business viability.

[0006] Furthermore, although extremely low temperature liquefied air is produced, the energy efficiency is low in that the cold energy of the extremely low temperature cannot be effectively utilized.

[0007] The present invention has been made to solve such problems, and aims to provide an energy storage system that stores energy using an oxygen-nitrogen mixed liquid as a medium, and that can efficiently utilize cryogenic cold energy. [Means for solving the problem]

[0008] (1) The energy storage system according to the present invention comprises: an LNG storage tank for storing LNG; an LNG pump that pressurizes and discharges the LNG stored in the LNG storage tank; an LNG delivery line through which the LNG delivered by the LNG pump flows; an oxygen-nitrogen liquefaction supply device that generates and supplies a mixed liquid of oxygen and nitrogen by utilizing the cold heat of the LNG discharged by the LNG pump; a carbon dioxide solidification device that solidifies the carbon dioxide contained in the carbon dioxide-containing gas by heat exchange between the oxygen-nitrogen mixed liquid supplied by the oxygen-nitrogen liquefaction supply device and the carbon dioxide-containing gas; and an air expansion turbine that heats the oxygen-nitrogen mixed liquid that has been subjected to cold energy in the carbon dioxide solidification device, turns it into a high-pressure gas, and expands the gas to generate electricity.

[0009] (2) Furthermore, in the above (1), the oxygen-nitrogen liquefaction supply system is characterized by including an air liquefaction system that takes in air and liquefies the air by utilizing the cold energy of the LNG discharged by the LNG pump.

[0010] (3) The device described in (1) above is characterized by comprising an oxygen-nitrogen mixture ratio adjusting device for adjusting the ratio of oxygen and nitrogen in the oxygen-nitrogen mixed liquid.

[0011] (4) In addition, in the above (3), the oxygen-nitrogen liquefaction supply device is provided with a cryogenic separation device that takes in air and separates the taken-in air using the cold heat of the LNG pumped out by the LNG pump to produce liquid oxygen and liquid nitrogen. The oxygen-nitrogen mixture ratio adjusting device is characterized by mixing the liquid oxygen and liquid nitrogen produced in the cryogenic separation device at a predetermined ratio.

[0012] (5) In addition, in the above (3), the oxygen-nitrogen liquefaction supply device includes an air liquefaction device that takes in air and liquefies the taken-in air by utilizing the cold heat of the LNG discharged by the LNG pump, The air liquefaction device has an oxygen enrichment device that generates oxygen-enriched air from the air taken in, The oxygen-nitrogen mixture ratio adjusting device is characterized by adjusting the amount of air passing through the oxygen enrichment device.

[0013] (6) Furthermore, in the above (5), the oxygen enrichment device is an oxygen enrichment membrane unit disposed at the outlet of an air compressor that compresses the air that has been taken in. [Effects of the Invention]

[0014] The present invention provides an energy storage system that stores energy using an oxygen-nitrogen mixed liquid as a medium, and includes a carbon dioxide solidification device that solidifies carbon dioxide contained in combustion exhaust gas generated by combustion of hydrocarbon fuel through heat exchange between the oxygen-nitrogen mixed liquid supplied by an oxygen-nitrogen liquefaction supply device and the combustion exhaust gas, thereby enabling efficient use of cryogenic cold energy. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing an energy storage system according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing the configuration of an air liquefaction device according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a schematic diagram showing an energy storage system according to a second embodiment of the present invention. [Figure 4] FIG. 6 is a schematic diagram showing the configuration of a cryogenic separation device according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram showing an energy storage system according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of an air liquefaction device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Embodiment 1] First, the configuration and functions of the first embodiment of the present invention will be described with reference to FIG. The energy storage system 1 according to the first embodiment of the present invention includes an LNG storage tank 10, an LNG pump 20, an LNG vaporizer 30, an air liquefaction device 50, an air liquefaction heat exchanger 60, a liquefied air tank 70, a liquefied air pump 80, a CO2 solidification device 90, a liquefied air evaporation heat exchanger 100, an air heating heat exchanger 110, an air expansion turbine 120, and a gas engine power generation device 130.

[0017] The LNG storage tank 10 is an aboveground PC (Pre-stressed Concrete) storage tank, and has inner and outer steel tanks surrounded by a circular PC wall. The space between the inner and outer tanks is filled with particles called perlite, creating a nitrogen atmosphere that provides excellent thermal insulation. This allows the LNG storage tank 10 to store large quantities of LNG at extremely low temperatures (approximately -160°C) while suppressing heat input from the outside.

[0018] The LNG pump 20 is, for example, a vertical centrifugal submerged pump disposed downstream of the LNG storage tank 10, and the pump body is submerged inside a pot. The LNG pump 20 pressurizes and discharges LNG supplied from the LNG storage tank 10 via an LNG pump inlet line 171.

[0019] The LNG vaporizer 30 is an ORV (open rack vaporizer) type vaporizer, in which LNG flows from bottom to top inside a group of vertically arranged heat transfer tubes, and seawater flows from top to bottom outside, thereby completely vaporizing the LNG supplied from the LNG pump outlet line 172 and supplying it as vaporized gas to the gas delivery line 173.

[0020] The air liquefaction device 50 is a refrigerator that uses a general nitrogen refrigerant and produces liquefied air by cooling the ambient air taken in through the air inlet line 174. Since liquefied air is a mixed liquid of oxygen and nitrogen, the air liquefaction device 50 constitutes the oxygen-nitrogen liquefied supply system of the present invention.

[0021] The air liquefaction heat exchanger 60 is a typical shell-and-tube type heat exchanger, and supplies the cold energy of LNG to the nitrogen refrigerant in the air liquefaction device 50, as will be described later.

[0022] FIG. 2 is a schematic diagram showing details of the air liquefaction device 50 and the relationship between the air liquefaction device 50 and the air liquefaction heat exchanger 60. As shown in FIG. As shown in FIG. 2, the air liquefaction system 50 includes a feed air compressor 51, an adsorber 53, a compressed air cooler 54, and a nitrogen compressor 55. The feed air compressor 51 is a centrifugal compressor, which compresses the air introduced from the air inlet line 174 and supplies it to the compressed air line 52 .

[0023] The adsorber 53 is an adsorption tower filled with a zeolite-based adsorbent, and adsorbs moisture and carbon dioxide from the compressed air flowing through the compressed air line 52. The compressed air cooler 54 is a plate-type heat exchanger, and uses the cold energy of liquid nitrogen, which will be described later, to cool and liquefy the compressed air flowing through the compressed air line 52.

[0024] The nitrogen compressor 55 is a centrifugal compressor that compresses the nitrogen gas flowing through the nitrogen circulation line 56. The nitrogen expansion valve 57 is a remote-controlled globe valve that rapidly depressurizes the nitrogen gas cooled by LNG in the air liquefaction heat exchanger 60 to generate liquid nitrogen. The generated liquid nitrogen cools the air in the compressed air cooler 54 and then evaporates.

[0025] Returning to Figure 1, liquefied air tank 70 is a vertical cylindrical steel tank that temporarily stores liquefied air supplied from liquefied air supply line 175. Liquefied air pump 80 is a centrifugal pump that pressurizes liquefied air supplied from liquefied air pump suction line 176 and supplies it to liquefied air pump discharge line 177.

[0026] The CO2 solidification device 90 is a scraping-type heat exchanger that solidifies carbon dioxide-containing gas, such as carbon dioxide in exhaust gas generated by the combustion of hydrocarbon fuel, through heat exchange with liquefied air as a refrigerant, and scrapes dry ice off the surface of the heat transfer tubes using a mechanical mechanism, causing it to fall. The fallen dry ice is discharged from the dry ice outlet line 187, while unsolidified nitrogen and oxygen are discharged from the exhaust gas discharge line 186.

[0027] The liquefied air evaporation heat exchanger 100 is an open rack type heat exchanger that uses room temperature water such as seawater or warm water as a heating medium to heat and evaporate liquid or gaseous air supplied from the liquefied air pump discharge line 177. The water at room temperature is water at a temperature of about 0°C to 40°C. Examples other than seawater include water obtained by heating LNG in the vaporizer 30, but are not limited to this.

[0028] The air heating heat exchanger 110 is a shell-and-tube type heat exchanger that uses the exhaust gas from the gas engine power generation unit 130 as a heat source to further heat the air that has passed through the liquefied air evaporation heat exchanger 100, thereby increasing its temperature.

[0029] The air expansion turbine 120 is a centrifugal expansion turbine that reduces the pressure of high-pressure air to atmospheric pressure, converting the pressure energy into rotational motion of the turbine and generating electricity using a generator.

[0030] The gas engine power generation system 130 is a power generation system that uses a reciprocating gas engine, and generates electricity using BOG supplied from the LNG storage tank 10 via a BOG supply line 188 as fuel, and supplies the generated exhaust gas to an exhaust gas discharge line 189.

[0031] Next, the operation of the energy storage system 1 according to this embodiment will be described. The energy storage system 1 operates the air liquefaction device 50, liquefies air by utilizing the cold energy of LNG, and stores the air in the liquefied air tank 70. In this way, the energy storage system 1 stores energy that can be converted into electricity in the form of liquefied air.

[0032] By operating the liquefied air pump 80, the energy storage system 1 pressurizes the extremely low temperature (e.g., -190°C) liquefied air stored in the liquefied air tank 70 and discharges it as high-pressure liquefied air (e.g., 10 MPaG) to the liquefied air pump discharge line 177.

[0033] A portion of the high-pressure liquefied air discharged to the liquefied air pump discharge line 177 is supplied to the CO2 solidification device 90 via a liquefied air branch line 181 and a flow rate control valve 182 for the CO2 solidification device.

[0034] In the CO2 solidification device 90, CO2 contained in the exhaust gas supplied from the exhaust gas inlet line 185 is solidified by heat exchange with the high-pressure liquefied air and is discharged from the dry ice outlet line 187. The low-temperature N2 gas and O2 gas that have not solidified are discharged from the exhaust gas discharge line 186.

[0035] The gaseous or liquid air that has passed through the CO2 solidification device 90 merges with the liquefied air pump discharge line 177 via the CO2 solidification device outlet line 183, and this gaseous or liquid air, along with the liquefied air that has passed through the CO2 solidification device bypass valve 178, is heated and evaporated by heat exchange with water at room temperature in the liquefied air evaporation heat exchanger 100, becoming high-pressure air (supercritical state) at room temperature (for example, 20°C).

[0036] The high-pressure air generated in the liquefied air evaporation heat exchanger 100 is heated in the air heating heat exchanger 110 by the high-temperature (e.g., 350°C) exhaust gas from the gas engine power generation system 130, becoming high-temperature (e.g., 200°C) high-pressure air.

[0037] The high-temperature, high-pressure air generated in the air heating heat exchanger 110 is introduced into the air expansion turbine 120, where it is reduced in pressure and temperature to drive the air expansion turbine 120 and generate electricity. The low-pressure air at the outlet of the air expansion turbine 120 is released into the atmosphere via an air release line 184.

[0038] The BOG generated in the LNG storage tank 10 flows through a BOG supply line 188 and is supplied to the gas engine power generator 130, where it is used as fuel for the gas engine power generator 130 and converted into electricity.

[0039] In the gas engine power generation system 130, methane gas is supplied from the BOG supply line 188, and is burned with air as an oxidizer. The piston movement in the combustion chamber is converted into the rotational movement of a camshaft, which then rotates a generator to generate electricity.

[0040] The exhaust gas from the gas engine power generator 130 discharged into the exhaust gas discharge line 189 is cooled to room temperature (for example, 50°C) by high-pressure air in the air heating heat exchanger 110. The exhaust gas cooled to room temperature is released into the atmosphere.

[0041] According to the energy storage system 1 of this embodiment, the cold energy of LNG is effectively utilized in the air liquefaction heat exchanger 60, so that the air liquefaction device 50 can be operated in an energy-saving manner.

[0042] Furthermore, with the energy storage system 1 according to this embodiment, the cold energy of LNG can be effectively utilized for air liquefaction, thereby reducing the amount of cold energy of LNG that has been discarded into the environment up until now. For example, an LNG vaporizer that uses seawater as a heating medium discards the cold energy of LNG into the ocean, but this amount can be reduced, thereby reducing the impact on the ocean.

[0043] Furthermore, according to the energy storage system 1 of this embodiment, the CO2 solidification device 90 can utilize the cold energy of the liquefied air in the extremely low temperature range to solidify and separate the CO2 in the exhaust gas, thereby making it possible to effectively utilize the cold energy of the liquefied air.

[0044] Furthermore, according to the energy storage system 1 of this embodiment, the high-temperature exhaust gas (for example, 350°C) flowing through the exhaust gas discharge line 189 is used as the heat source for the air heating heat exchanger 110, so that sensible heat can be imparted to the high-pressure air that has evaporated in the liquefied air evaporation heat exchanger 100 and reached room temperature (for example, 50°C), thereby further increasing the temperature. As a result, the output of the expansion turbine can be further increased.

[0045] In this embodiment, the types of heat exchangers, including the air liquefaction heat exchanger 60, have been described as shell-and-tube and open rack types, but the types are not limited to these and may be selected appropriately within the scope of the design. The same applies to pumps and valves.

[0046] Furthermore, in the present embodiment, the exhaust gas generated by the combustion of hydrocarbon fuel has been described as an example of a carbon dioxide-containing gas. However, the carbon dioxide-containing gas also includes biogas generated from methane fermentation facilities, blast furnace exhaust gas from steel mills, and exhaust gas from other chemical plants, and further includes gas obtained by increasing the carbon dioxide concentration from the atmosphere using a carbon dioxide separation membrane or the like.

[0047] Furthermore, in this embodiment, the gas engine power generator 130 uses air as an oxidant, but it is also possible to take in outlet air from the air expansion turbine 120. The outlet air from the air expansion turbine 120 has a higher density because its temperature is lowered by expansion, and as a result, a larger amount of oxygen can be stably supplied to the gas engine power generator 130 regardless of the season, thereby improving the power generation efficiency of the gas engine power generator 130.

[0048] Furthermore, although a heat exchanger is not installed between the liquefied air pump 80 and the CO2 solidification device 90 in this embodiment, a heat exchanger utilizing the cryogenic cold energy of the liquefied air may be installed. For example, by installing a heat exchanger that cools the refrigerated circulating LNG that is returned to the LNG storage tank 10 by insulating the LNG line at the LNG terminal, the cryogenic temperature of the liquefied air, approximately −190°C, can be used to supercool the refrigerated circulating LNG and provide it as a cold source for the LNG storage tank 10. As a result, it is possible to cancel some or all of the various heat inputs to the LNG storage tank 10, such as heat input from the atmosphere and heat input from the work of the LNG pump, thereby reducing the amount of BOG generated from the LNG storage tank 10. The cold energy of the liquefied air in the range of approximately −190°C to −140°C is used to cool the refrigerated circulating LNG, and the CO2 in the exhaust gas is solidified in the CO2 solidification device 90 using a temperature range higher than −140°C, thereby achieving optimal cold energy utilization according to the temperature range of the liquefied air.

[0049] [Embodiment 2] Next, the configuration and functions of the second embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. The energy storage system 200 according to the second embodiment has a cryogenic separation device 210, a liquid oxygen tank 221, a liquid nitrogen tank 222, a liquid oxygen pump 231, a liquid nitrogen pump 232, an exhaust gas analyzer 241, an exhaust gas pressure gauge 242, an oxygen-nitrogen mixture ratio adjustment device 243, an oxygen evaporation heat exchanger 251, a nitrogen evaporation heat exchanger 252, an oxygen heating heat exchanger 261, a nitrogen heating heat exchanger 262, an air heating heat exchanger 263, an oxygen expansion turbine 271, a nitrogen expansion turbine 272, and an air expansion turbine 273.

[0050] 4, cryogenic separation unit 210 has a rectification column 211 in addition to the configuration of air liquefaction unit 50 in FIG. 2, and air cooled with liquid nitrogen in compressed air cooler 54 is separated into liquid oxygen and liquid nitrogen in rectification column 211. Liquid oxygen is supplied from rectification column 211 to liquid oxygen supply line 301, and liquid nitrogen is supplied from rectification column 58 to liquid nitrogen supply line 302. The liquid oxygen and liquid nitrogen produced in the cryogenic separation device 210 are supplied to the CO2 solidification air line 315 via the liquid oxygen branch line 311 and the liquid nitrogen branch line 313, respectively, and mixed there, so the cryogenic separation device 210 constitutes the oxygen-nitrogen liquefaction supply device of the present invention.

[0051] The liquid oxygen tank 221 is a vertical cylindrical tank that temporarily stores the liquid oxygen produced in the cryogenic separation device 210. The liquid nitrogen tank 221 is a vertical cylindrical tank that temporarily stores the liquid nitrogen produced in the cryogenic separation device 210.

[0052] Liquid oxygen pump 231 is a centrifugal submerged pump that pressurizes liquid oxygen stored in liquid oxygen tank 221 and supplied from liquid oxygen pump suction line 303 and dispenses it to liquid oxygen pump discharge line 305. Liquid nitrogen pump 232 is a centrifugal submerged pump that pressurizes liquid nitrogen stored in liquid nitrogen tank 222 and supplied from liquid nitrogen pump suction line 303 and dispenses it to liquid nitrogen pump discharge line 307.

[0053] The exhaust gas analyzer 241 is an analyzer that uses a gas chromatograph, and measures the concentrations of O2 and CO2 in the exhaust gas flowing through the exhaust gas inlet line 185, and transmits the measurement results to the oxygen-nitrogen mixing ratio adjuster 243. The exhaust gas pressure meter 242 is a general-purpose pressure transmitter that measures the pressure of the exhaust gas flowing through the exhaust gas inlet line 185, and transmits the measurement results to the oxygen-nitrogen mixing ratio adjuster 243.

[0054] The oxygen-nitrogen mixture ratio adjuster 243 calculates the solidification temperature characteristics of CO2 from the partial pressure of CO2 in the exhaust gas flowing through the exhaust gas inlet line 185, based on signals from the exhaust gas analyzer 241 and the exhaust gas pressure gauge 242. The oxygen-nitrogen mixture ratio adjuster 243 also adjusts the mixture ratio of liquid oxygen and liquid nitrogen in the liquefied air flowing through the CO2 solidification air line 315 by operating the CO2 solidification oxygen flow rate adjuster valve 312 and the CO2 solidification nitrogen flow rate adjuster valve 314 so that the liquefied air flowing through the CO2 solidification air line 315 releases the latent heat of vaporization at a temperature corresponding to the calculated solidification temperature characteristics of CO2.

[0055] The oxygen evaporation heat exchanger 251 is an open rack type heat exchanger that evaporates liquid oxygen flowing inside vertical heat transfer tubes by heat exchange with room temperature water such as seawater or warm water flowing outside the heat transfer tubes. The nitrogen evaporation heat exchanger 252 is an open rack type heat exchanger that evaporates liquid nitrogen flowing inside vertical heat transfer tubes by heat exchange with room temperature water such as seawater or warm water flowing outside the heat transfer tubes.

[0056] The oxygen heating heat exchanger 261 is a shell-and-tube type heat exchanger, and uses the exhaust gas from the gas engine power generator 130 as a heat source to further heat the oxygen gas supplied from the upstream side of the liquid oxygen pump discharge line 305 . The nitrogen heating heat exchanger 262 is a shell-and-tube type heat exchanger, and uses the exhaust gas from the gas engine power generator 130 as a heat source to further heat the nitrogen gas supplied from the upstream side of the liquid nitrogen pump discharge line 307 .

[0057] The air heating heat exchanger 263 is a shell-and-tube type heat exchanger, and uses the exhaust gas from the gas engine power generator 130 as a heat source to further heat the air evaporated in the CO 2 solidification device 90 .

[0058] The oxygen expansion turbine 271 is a centrifugal expansion turbine, which generates electricity by expanding the high-pressure oxygen gas supplied from the liquid oxygen pump discharge line 305 to rotate the turbine. The nitrogen expansion turbine 272 is a centrifugal expansion turbine, and generates electricity by expanding high-pressure nitrogen gas supplied from the liquid nitrogen pump discharge line 307 to rotate the turbine.

[0059] The air expansion turbine 273 is a centrifugal expansion turbine, and generates electricity by expanding the high-pressure air supplied from the CO2 solidification air line 315 to rotate the turbine.

[0060] The oxygen flow rate control valve 312 for CO2 solidification is a remote-controlled globe valve that controls the flow rate of liquid oxygen that branches off from the liquid oxygen pump discharge line 305 and is supplied to the CO2 solidification device 90. The nitrogen flow rate control valve 314 for CO2 solidification is a remote-controlled globe valve that controls the flow rate of liquid nitrogen that branches off from the liquid nitrogen pump discharge line 307 and is supplied to the CO2 solidification device 90.

[0061] The gas engine oxygen flow rate control valve 323 is a remotely-operated butterfly valve, and adjusts the flow rate of oxygen gas diverted from the oxygen expansion turbine outlet line 318 to the exhaust gas circulation line 326 .

[0062] Next, the operation of the energy storage system 200 according to this embodiment will be described. The explanation of the same functions as those in the first embodiment will be omitted. During times when there is a surplus of electricity and it is necessary to store it, air is taken into the cryogenic separator 210 through the air inlet line 174. Liquid nitrogen and liquid oxygen are produced in the cryogenic separator 210 using the taken-in air as a raw material. Argon can also be produced, but this will not be explained here.

[0063] The liquid oxygen produced in the cryogenic separator 210 is stored in a liquid oxygen tank 221 , and the liquid nitrogen is stored in a liquid nitrogen tank 222 .

[0064] During times when there is a shortage of electricity and it is necessary to generate electricity, the liquid oxygen stored in the liquid oxygen tank 221 is pressurized to a high pressure (for example, 10 MPaG) by the liquid oxygen pump 231 and discharged to the liquid oxygen pump discharge line 305. In addition, the liquid nitrogen stored in the liquid nitrogen tank 222 is pressurized to a high pressure (for example, 10 MPaG) by the liquid nitrogen pump 232 and discharged to the liquid nitrogen pump discharge line 307.

[0065] Of the liquid oxygen discharged to the liquid oxygen pump discharge line 305, the portion that is not used to solidify the CO2 is supplied to the oxygen evaporation heat exchanger 251 via the liquid oxygen discharge flow rate control valve 306, where it evaporates into high-pressure oxygen gas, and is then heated to, for example, 200°C in the oxygen heating heat exchanger 261 by the high-temperature (for example, 350°C) exhaust gas from the gas engine power generator 130. The high-temperature, high-pressure oxygen gas then drives the oxygen expansion turbine 271 to generate electricity.

[0066] A portion of the oxygen gas that drives the oxygen expansion turbine 271 is supplied to an oxygen user (not shown) via an oxygen gas discharge flow rate control valve 321. The remaining oxygen gas is supplied to an exhaust gas circulation line 326 via an oxygen gas junction line 322 and a gas engine oxygen flow rate control valve 323, and is then supplied to the gas engine power generator 130. As a result, the CO2 concentration in the exhaust gas from the gas engine power generator 130 increases.

[0067] Of the liquid nitrogen discharged into the liquid nitrogen pump discharge line 307, the portion that is not used to solidify the CO2 is supplied to the nitrogen evaporation heat exchanger 251 via the liquid nitrogen discharge flow rate control valve 308, where it evaporates and becomes high-pressure nitrogen gas, and is then heated to, for example, 200°C in the nitrogen heating heat exchanger 262 by the high-temperature (for example, 350°C) exhaust gas from the gas engine power generator 130. The high-temperature, high-pressure nitrogen gas then drives the nitrogen expansion turbine 272 to generate electricity.

[0068] Of the liquid oxygen delivered to the liquid oxygen pump discharge line 305, the portion to be used for solidifying CO2 is mixed with liquid nitrogen in the air line 315 for CO2 solidification via the liquid oxygen branch line 311 and the oxygen flow control valve 312 for CO2 solidification.

[0069] Of the liquid nitrogen discharged to the liquid nitrogen pump discharge line 307, the portion used for solidifying CO2 is mixed with liquid oxygen in the air line 315 for CO2 solidification via the liquid nitrogen branch line 313 and the nitrogen flow control valve 314 for CO2 solidification.

[0070] In the CO2 solidification air line 315, the mixed liquid oxygen and liquid nitrogen are supplied to the CO2 solidification device 90.

[0071] Dehumidified exhaust gas is supplied to the CO2 solidification device 90 through an exhaust gas inlet line 185. The components and pressure of the exhaust gas are measured by an exhaust gas analyzer 241 and an exhaust gas pressure gauge 242, and the solidification temperature characteristics of the CO2 contained in the exhaust gas are calculated based on these measurement results by an oxygen-nitrogen mixture ratio adjuster 243. For example, in a 100% CO2 atmosphere at atmospheric pressure, the solid-gas equilibrium temperature of CO2 is approximately -79°C, and further cooling shifts the CO2 solid-gas equilibrium toward the solid side. Therefore, when the CO2 fraction in the exhaust gas is small and the CO2 partial pressure is low, the CO2 solid-gas equilibrium temperature drops below -79°C, decreasing to -100°C, -110°C, -120°C, and so on.

[0072] The oxygen-nitrogen mixture ratio adjuster 243 adjusts the mixture ratio of liquid oxygen and liquid nitrogen depending on how much the partial pressure of CO2 from the exhaust gas is reduced to. Assuming that the pressure of liquid oxygen is 10 MPaG, this exceeds the critical pressure of approximately 5 MPaG, so if the liquid is 100% oxygen, it will release the latent heat of vaporization near the critical temperature of approximately -119°C. Assuming that the pressure of liquid nitrogen is 10 MPaG, this exceeds the critical pressure of approximately 3.4 MPaG, so if the liquid is 100% nitrogen, it will release the latent heat of vaporization near the critical temperature of approximately -147°C.

[0073] In the case of a liquid mixture of liquid oxygen and liquid nitrogen, if the proportion of liquid oxygen is high, the boiling point approaches approximately -119°C, and if the proportion of liquid nitrogen is high, the boiling point approaches approximately -147°C. Taking advantage of this property, the oxygen-nitrogen mixture ratio adjuster 243 operates the oxygen flow rate adjuster valve 312 for CO2 solidification and the nitrogen flow rate adjuster valve 314 for CO2 solidification to adjust the mixture ratio of oxygen and nitrogen in the liquefied air flowing through the air line 315 for CO2 solidification so that the liquefied air releases the latent heat of vaporization at a temperature that requires a large amount of latent heat for solidification of the CO2 in the exhaust gas.

[0074] In the CO2 solidification device 90, solidified CO2 in the exhaust gas is discharged from the dry ice outlet line 187, and unsolidified nitrogen and oxygen are discharged from the exhaust gas discharge line 186. In addition, the high-pressure air evaporated in the CO2 solidification device 90 flows downstream through the CO2 solidification air line 315 and is heated to, for example, 200°C by the air heating heat exchanger 263 using the high-temperature (for example, 350°C) exhaust gas from the gas engine power generator 130. The high-temperature, high-pressure air then drives the air expansion turbine 273 to generate electricity.

[0075] According to the energy storage system 200 of this embodiment, the oxygen-nitrogen mixture ratio adjusting device 243 adjusts the ratio of liquid oxygen and liquid nitrogen supplied to the CO2 solidification device 90, thereby optimizing the exchange of latent heat between the solidification of CO2 in the exhaust gas in the CO2 solidification device 90 and the evaporation of liquid oxygen and liquid nitrogen, thereby maximizing the efficiency of solidification and separation of CO2 from the exhaust gas.

[0076] In this embodiment, it has been described that liquid oxygen and liquid nitrogen are stored when there is a surplus of electricity and consumed when there is a shortage of electricity, but since solidifying CO2 from exhaust gas and cooling the refrigerated circulating LNG mentioned in embodiment 1 are constant needs, the storage and consumption of liquid oxygen and liquid nitrogen to meet these needs may be constant. In this case, the remaining facility capacity is used to store liquid oxygen and liquid nitrogen using surplus electricity.

[0077] In addition, in this embodiment, it has been explained that the liquid oxygen and liquid nitrogen are all evaporated and ultimately supplied to the oxygen expansion turbine and nitrogen expansion turbine for use in power generation, but they may be shipped in the form of liquid oxygen and liquid nitrogen depending on needs.

[0078] [Embodiment 3] Next, the configuration and functions of the third embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. The energy storage system 400 according to the third embodiment includes an air liquefaction device 410 instead of the air liquefaction device 50 in the energy storage system 1 according to the first embodiment.

[0079] The configuration and function of the air liquefaction device 410 will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. The air liquefaction device 410 has an oxygen enrichment membrane unit 411, an oxygen enrichment membrane unit bypass line 412, an oxygen enrichment membrane unit flow control valve 413, an oxygen enrichment membrane unit bypass flow control valve 414, and a non-permeate gas discharge line 415.

[0080] The oxygen enrichment membrane unit 411 is an oxygen-permeable membrane made of a polymer membrane, and by utilizing the fact that oxygen has a higher permeability than nitrogen, it increases the oxygen concentration of the compressed air supplied from the upstream stream and discharges it into the downstream stream. The oxygen enrichment membrane unit 411 also discharges gases that have not permeated, mainly nitrogen, into the non-permeate gas discharge line 414.

[0081] The oxygen enrichment membrane unit flow rate control valve 413 is a remotely controlled globe valve, and adjusts the flow rate of air supplied to the oxygen enrichment membrane unit 411 based on a signal sent from the oxygen-nitrogen mixture ratio control device 243 .

[0082] The oxygen enrichment unit bypass flow rate control valve 414 is a remotely controlled globe valve that adjusts the flow rate of air diverted to the oxygen enrichment membrane unit bypass line 412 based on a signal sent from the oxygen-nitrogen mixture ratio adjustment device 243.

[0083] Next, the operation of the energy storage system 400 according to this embodiment will be described. The explanation of the same functions as those in the first embodiment will be omitted. The oxygen-nitrogen mixing ratio adjuster 243 adjusts the flow rates of the air flowing through the oxygen enrichment membrane unit 411 and the oxygen enrichment membrane unit bypass line 412 by operating the oxygen enrichment membrane unit flow control valve 413 and the oxygen enrichment membrane unit bypass line 412, respectively, so that the liquefied air releases latent heat of vaporization at a temperature that requires a large amount of latent heat of solidification to solidify the CO2 in the exhaust gas.

[0084] As a result, the oxygen-nitrogen mixture ratio adjuster 243 adjusts the temperature at which the liquefied air releases the latent heat of vaporization in the CO2 solidification device 90 between the critical temperature of air and the critical temperature of oxygen (approximately -119°C) in order to appropriately increase the proportion of O2 in the liquefied air.

[0085] According to the energy storage system 400 of this embodiment, the oxygen-nitrogen mixture ratio adjusting device 243 adjusts the flow rate of air flowing through the oxygen enrichment membrane unit 411 and the oxygen enrichment membrane unit bypass line 412, respectively, so that the boiling point can be adjusted arbitrarily between the critical temperature of air and the critical temperature of oxygen (approximately -119°C). This allows for optimal exchange of latent heat between the solidification of CO2 in the exhaust gas in the CO2 solidification device 90 and the evaporation of the liquefied air, thereby maximizing the efficiency of solidification and separation of CO2 from the exhaust gas.

[0086] In this embodiment, the means for enriching oxygen in the air liquefaction device 410 has been described as an oxygen enrichment membrane, but means other than membranes, such as PSA (pressure swing adsorption) or TSA (temperature swing adsorption), may also be used, or these may be combined with the oxygen enrichment membrane. [Industrial Applicability]

[0087] INDUSTRIAL APPLICABILITY The present invention can be used as an energy storage system that stores energy using an oxygen-nitrogen mixed liquid as a medium, and that can efficiently utilize cryogenic cold energy. [Explanation of symbols]

[0088] 1, 200, 400 Energy Storage System 10 LNG storage tank 20 LNG pumps 30 LNG vaporizer 50, 410 Air liquefaction equipment 51 Raw air compressor 52 Compressed air line 53 Adsorption device 54 Compressed Air Cooler 55 Nitrogen Compressor 56 Nitrogen circulation line 57 Nitrogen expansion valve 60 Air liquefaction heat exchanger 70 Liquefied Air Tank 80 Liquefied Air Pump 90 CO2 solidification equipment 100 Liquefied air evaporator heat exchanger 110 Air heating heat exchanger 120 Air expansion turbine 130 Gas engine generator 171 LNG pump inlet line 172 LNG pump outlet line 173 Gas Transmission Line 174 Air Inlet Line 175 Liquefied Air Supply Line 176 Liquefied air pump suction line 177 Liquefied air pump discharge line 178 CO2 solidification device bypass valve 181 Liquefied Air Branch Line 182 Flow control valve for CO2 solidification device 183 CO2 solidification device outlet line 184, 325 Air Dissipation Line 185 Exhaust gas inlet line 186 Exhaust gas discharge line 187 Dry Ice Exit Line 188 BOG supply line 189 Exhaust gas discharge line 210 Cryogenic separation equipment 211 Rectification tower 221 Liquid Oxygen Tank 222 Liquid Nitrogen Tank 231 Liquid oxygen pump 232 Liquid Nitrogen Pump 241 Exhaust Gas Analyzer 242 Exhaust gas pressure gauge 243 Oxygen-nitrogen mixture ratio control device 251 Oxygen evaporation heat exchanger 252 Nitrogen evaporation heat exchanger 261 Oxygen heating heat exchanger 262 Nitrogen heating heat exchanger 263 Air heating heat exchanger 271 Oxygen expansion turbine 272 Nitrogen expansion turbine 273 Air expansion turbine 301 Liquid oxygen supply line 302 Liquid nitrogen supply line 303 Liquid oxygen pump suction line 304 Liquid nitrogen pump suction line 305 Liquid oxygen pump discharge line 306 Liquid oxygen delivery flow control valve 307 Liquid nitrogen pump discharge line 308 Liquid nitrogen dispensing flow control valve 311 Liquid oxygen branch line 312 Oxygen flow control valve for CO2 solidification 313 Liquid nitrogen branch line 314 Nitrogen flow control valve for CO2 solidification 315 CO2 solidification air line 318 Oxygen expansion turbine outlet line 321 Oxygen gas discharge flow control valve 322 Oxygen gas junction line 323 Oxygen flow control valve for gas engines 324 Nitrogen gas diffusion line 326 Exhaust gas circulation line 411 Oxygen Enrichment Membrane Unit 412 Oxygen enrichment membrane unit bypass line 413 Oxygen enrichment membrane unit flow control valve 414 Oxygen enrichment membrane unit bypass flow control valve 415 Non-permeable gas discharge line

Claims

1. an LNG storage tank for storing LNG; an LNG pump that pressurizes and discharges the LNG stored in the LNG storage tank; an LNG delivery line through which the LNG delivered by the LNG pump flows; an oxygen-nitrogen liquefaction supply device that generates and supplies a mixed liquid of oxygen and nitrogen by utilizing the cold heat of the LNG discharged by the LNG pump; a carbon dioxide solidification device that solidifies the carbon dioxide contained in the carbon dioxide-containing gas by heat exchange between the oxygen-nitrogen mixed liquid supplied by the oxygen-nitrogen liquefaction supply device and the carbon dioxide-containing gas; an air expansion turbine that heats the oxygen-nitrogen mixed liquid that has been subjected to cold energy in the carbon dioxide solidification device, turns it into high-pressure gas, and expands the gas to generate electricity.

2. The energy storage system according to claim 1, wherein the oxygen-nitrogen liquefaction supply device includes an air liquefaction device that takes in air and liquefies the taken-in air by using the cold energy of the LNG discharged by the LNG pump.

3. 2. The energy storage system according to claim 1, further comprising an oxygen-nitrogen mixture ratio adjusting device for adjusting the ratio of oxygen and nitrogen in the oxygen-nitrogen mixture liquid.

4. the oxygen-nitrogen liquefaction supply device includes a cryogenic separation device that takes in air and separates the taken-in air using the cold heat of the LNG discharged by the LNG pump to produce liquid oxygen and liquid nitrogen; 4. The energy storage system of claim 3, wherein the oxygen-nitrogen mixture ratio adjusting device mixes the liquid oxygen and liquid nitrogen produced in the cryogenic separation device at a predetermined ratio.

5. The oxygen-nitrogen liquefaction supply device includes an air liquefaction device that takes in air and liquefies the taken-in air by utilizing the cold heat of the LNG discharged by the LNG pump, The air liquefaction device has an oxygen enrichment device that generates oxygen-enriched air from the air taken in, The energy storage system according to claim 3, wherein the oxygen-nitrogen mixture ratio adjusting device adjusts the amount of air passing through the oxygen enrichment device.

6. The energy storage system according to claim 5, wherein the oxygen enrichment device is an oxygen enrichment membrane unit disposed at the outlet of an air compressor that compresses the taken-in atmospheric air.

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