Energy storage system

Abstract

To provide an energy storage system that efficiently enhances power generation efficiency by using energy in a system and facilitates recovery of carbon dioxide from exhaust gas in a system for liquefying and storing air as energy that can be converted into electric power.SOLUTION: An energy storage system 1 includes: a power generator 130 that generates electric power by using evaporation gas of LNG as fuel; an air liquefier 50 that liquefies air; liquefied air heating heat exchangers 90, 100; an oxygen enrichment air expansion turbine 111; an oxygen enrichment device 120 that extracts oxygen enrichment air with a condensed oxygen concentration by permeating air of an oxygen enrichment air expansion turbine outlet; an exhaust gas circulation line 185 for dividing part of exhaust gas flowing in an exhaust gas discharge line 188 for discharging exhaust gas of the power generator 130 and recirculating the exhaust gas to an inlet of the power generator; and an oxygen enrichment air supply line 184 for supplying the oxygen enrichment air generated by the oxygen enrichment device 120 to the exhaust gas circulation line 185.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an energy storage system that stores energy using liquefied air as a medium, and more particularly to an energy storage system that can generate and utilize oxygen-enriched air.

Background Art

[0002] With the popularization of renewable energy, the need for energy storage systems has been increasing, and energy storage using liquefied air has been proposed as one of the methods. However, there has been a drawback that the charging and discharging efficiency is low because the compression power for liquefying air is extremely large.

[0003] In this regard, Patent Document 1 discloses a technique in which air is liquefied at a low pressure by gradually cooling it with LNG and liquid hydrogen (LH2), the LNG and LH2 using cold heat are used as fuel for power generation equipment, and liquefied air is supplied to the power generation equipment as an oxidant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the technique of Patent Document 1 is premised on LH2, which is difficult to obtain, so the feasibility of the equipment is poor. Even if it can be obtained, the high cost of LH2 is reflected in the equipment operation cost, so there is a high possibility of impairing the profitability. In addition, although there is a description that liquefied air is vaporized with water or air before being expanded by an expansion turbine for power generation, water and air can only reach a temperature of about normal temperature, resulting in low power generation efficiency by the expansion turbine.

[0006] Furthermore, even if LH2 is co-fired with LNG, carbon dioxide in the exhaust gas will be dissipated into the atmosphere. Even when separation and recovery are carried out, recovering low-concentration carbon dioxide in the exhaust gas requires a huge amount of energy, so there is still a high possibility of impairing business viability.

[0007] The present invention has been made to solve such problems, and in a system for liquefying air and storing it as energy convertible into electric power, it is an object of the present invention to efficiently increase the power generation efficiency with the energy within the system and to provide an energy storage system that facilitates the recovery of carbon dioxide from exhaust gas.

Means for Solving the Problems

[0008] (1) The energy storage system according to the present invention includes an LNG storage tank for storing LNG, an LNG pump for boosting the pressure of the LNG stored in the LNG storage tank and discharging it, an LNG discharge line through which the LNG discharged by the LNG pump flows, a power generation device that generates electricity using the evaporation gas of the LNG generated in the LNG storage tank as fuel and / or a power generation device that generates electricity using the vaporization gas of the LNG discharged by the LNG pump as fuel, an air liquefaction device that liquefies air using the cold heat of the LNG discharged by the LNG pump, a liquefied air storage tank for storing the air liquefied by the air liquefaction device, a liquefied air pump for boosting the pressure of the liquefied air stored in the liquefied air storage tank and discharging it, a liquefied air pump discharge line through which the liquefied air discharged by the liquefied air pump flows, a heat exchanger for heating the liquefied air flowing through the liquefied air pump discharge line, an oxygen-enriched air expansion turbine that is disposed downstream of the heat exchanger for heating the liquefied air in the liquefied air pump discharge line and expands the gaseous air flowing through the liquefied air pump discharge line to generate electricity by the rotational force of the turbine, An oxygen enrichment device disposed at the outlet of the air expansion turbine for oxygen enrichment, which allows the air at the outlet of the air expansion turbine for oxygen enrichment to pass through and extracts oxygen-enriched air with a concentrated oxygen concentration. An exhaust gas discharge line for discharging the exhaust gas of the power generation device. An exhaust gas circulation line that diverts a part of the exhaust gas flowing through the exhaust gas discharge line and returns it to the inlet of the power generation device. An oxygen-enriched air supply line that supplies the oxygen-enriched air generated by the oxygen enrichment device to the exhaust gas circulation line, and is characterized by having the above.

[0009] (2) Also, in the one described in the above (1), it is disposed downstream of the heat exchanger for heating liquefied air in the liquefied air pump discharge line, and expands the gaseous air flowing through the liquefied air pump discharge line to generate electricity by the rotational force of the turbine, and is further provided with a power generation expansion turbine that reduces the pressure of the outlet air to atmospheric pressure, and is characterized by having the above.

[0010] (3) Also, in the one described in the above (1) or (2), the heat exchanger for heating liquefied air A heat exchanger for evaporating liquefied air that evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with normal temperature water and / or seawater. A heat exchanger for heating air that heats the air evaporated by the heat exchanger for evaporating liquefied air by heat exchange with the exhaust gas flowing through the exhaust gas circulation line and returning to the inlet of the power generation device, and is characterized by having the above.

Effects of the Invention

[0011] According to the present invention, in a system for liquefying air and storing it as energy convertible into electric power, the power generation efficiency can be efficiently increased with the energy within the system, and the recovery of carbon dioxide from the exhaust gas can be facilitated.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0013] [Embodiment 1] First, with reference to FIG. 1, the configuration and function of Embodiment 1 of the present invention will be described. An 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 apparatus 50, an air liquefaction heat exchanger 60, a liquefied air tank 70, a liquefied air pump 80, a liquefied air evaporation heat exchanger 90, an air heating heat exchanger 100, an oxygen-enriched air expansion turbine 111, a power generation air expansion turbine 112, an oxygen enrichment apparatus 120, and a gas engine power generation apparatus 130.

[0014] The LNG storage tank 10 is a ground-mounted PC (Pre-stressed Concrete) storage tank, which has a steel inner tank and an outer tank, and is circumferentially surrounded by a PC wall. The space between the inner tank and the outer tank is filled with particles called perlite to form a nitrogen atmosphere, which exhibits a high heat insulation effect. As a result, the LNG storage tank 10 stores a large amount of LNG at an extremely low temperature (about -160°C) while suppressing heat input from the outside.

[0015] The LNG pump 20 is, for example, a vertical centrifugal submerged pump disposed on the downstream side of the LNG storage tank 10, and the pump body is immersed inside the pot. The LNG pump 20 boosts the pressure of the LNG supplied from the LNG storage tank 10 through the LNG pump inlet line 171 and discharges it.

[0016] The LNG vaporizer 30 is an ORV (Open Rack Vaporizer) type vaporizer. LNG flows from bottom to top inside a vertically arranged group of heat transfer tubes, and seawater flows from top to bottom outside. By doing so, the LNG supplied from the LNG pump outlet line 172 is completely vaporized and supplied as vapor gas to the gas supply line 173.

[0017] The air liquefaction device 50 is a refrigerator that uses a general nitrogen refrigerant, and cools the atmospheric air taken in from the air inlet line 174 to produce liquefied air.

[0018] The heat exchanger 60 for air liquefaction is a general shell & tube type heat exchanger. As will be described later, it supplies the cold heat of LNG to the nitrogen for the refrigerant in the air liquefaction device 50.

[0019] Figure 2 is a schematic diagram showing the details of the air liquefaction device 50 and the relationship between the air liquefaction device 50 and the heat exchanger 60 for air liquefaction. As shown in Figure 2, the air liquefaction device 50 includes a raw material air compressor 51, an adsorber 53, a compressed air cooler 54, and a nitrogen compressor 55. The raw material air compressor 51 is a centrifugal compressor. It compresses the air introduced from the air inlet line 174 and supplies it to the compressed air line 52.

[0020] 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. Using the cold heat of the liquid nitrogen described later, it cools and liquefies the compressed air flowing through the compressed air line 52.

[0021] The nitrogen compressor 55 is a centrifugal compressor, and compresses the nitrogen gas flowing through the nitrogen circulation line 56. The nitrogen expansion valve 57 is a remotely operated globe valve. It rapidly decompresses the nitrogen gas cooled by LNG in the heat exchanger 60 for air liquefaction to generate liquid nitrogen. The generated liquid nitrogen cools the compressed air in the compressed air cooler 54 and evaporates itself.

[0022] Returning to FIG. 1, the liquefied air tank 70 is a vertical cylindrical steel tank that temporarily stores the liquefied air supplied from the liquefied air supply line 175. The liquefied air pump 80 is a centrifugal pump that pressurizes the liquefied air supplied from the liquefied air pump suction line 176 and supplies it to the liquefied air pump discharge line 177.

[0023] The heat exchanger 90 for liquefied air evaporation is an open rack type heat exchanger that uses normal temperature water such as seawater or warm water as a heating medium to heat and evaporate the liquefied air supplied from the liquefied air pump discharge line 177.

[0024] The heat exchanger 100 for air heating is a shell & tube type heat exchanger that uses the exhaust gas of the gas engine power generation device 130 as a heating medium to heat the air after passing through the heat exchanger 90 for liquefied air evaporation.

[0025] The air expansion turbine 111 for oxygen enrichment is a centrifugal expansion turbine that converts the pressure energy into rotational motion of the turbine by reducing the pressure of the high-pressure air to the pressure required for the operation of the oxygen enrichment device 120 and generates electricity by a generator.

[0026] The air expansion turbine 112 for power generation is a centrifugal expansion turbine that converts the pressure energy into rotational motion of the turbine by reducing the pressure of the high-pressure air to the equivalent of atmospheric pressure and generates electricity by a generator.

[0027] The oxygen enrichment device 120 has a polymer oxygen permeable membrane, preferentially permeates oxygen from the oxygen permeable membrane, and discharges the oxygen-enriched air to the oxygen-enriched air line 184 on the permeation side and the nitrogen-enriched air to the nitrogen-enriched air line 183 on the non-permeation side, respectively.

[0028] The gas engine power generation device 130 is a power generation device using a reciprocating gas engine that generates electricity using the BOG supplied from the LNG storage tank 10 via the BOG supply line 187 as fuel and supplies the generated exhaust gas to the exhaust gas discharge line 188.

[0029] The oxygen enrichment air pressure regulating valve 179 is a remotely operated butterfly valve that regulates the pressure of the air supplied to the oxygen enrichment device 120 via the oxygen enrichment air expansion turbine outlet line 178.

[0030] The power generation air flow regulating valve 182 is a remotely operated butterfly valve that regulates the flow rate of the air discharged to the outside of the system via the power generation air expansion turbine outlet line 181.

[0031] The exhaust gas circulation flow regulating valve 186 is a remotely operated butterfly valve that regulates the flow rate of the exhaust gas that circulates to the intake side via the exhaust gas circulation line 185 among the exhaust gases of the gas engine power generation device 130.

[0032] The exhaust gas discharge flow regulating valve 189 is a remotely operated butterfly valve that regulates the flow rate of the exhaust gas discharged to the outside of the system among the exhaust gases of the gas engine power generation device 130.

[0033] Next, the operation of the energy storage system 1 according to the present embodiment will be described. The energy storage system 1 operates the air liquefaction device 50, liquefies air by utilizing the cold heat of LNG, and stores it in the liquefied air tank 70. Thereby, the energy storage system 1 accumulates energy convertible into electric power in the form of liquefied air.

[0034] The energy storage system 1 operates the liquefied air pump 80 to boost the liquefied air at an extremely low temperature (for example, -190°C) stored in the liquefied air tank 70 and discharges it as high-pressure liquefied air (for example, 10 MPaG) to the liquefied air pump discharge line 177.

[0035] The high-pressure liquefied air discharged to the liquefied air pump discharge line 177 is heated and evaporated in the heat exchanger 90 for liquefied air evaporation, and becomes high-pressure air (supercritical state) at normal temperature (for example, 20°C).

[0036] High-pressure air is heated by the high-temperature (e.g., 350°C) exhaust gas of the gas engine power generation device 130 in the air heating heat exchanger 100 and becomes high-pressure air at a high temperature (e.g., 200°C).

[0037] A part of the high-temperature high-pressure air generated in the air heating heat exchanger 100 is introduced into the air expansion turbine 111 for oxygen enrichment, driving the air expansion turbine 111 for oxygen enrichment with pressure reduction and temperature drop, and generating electric power.

[0038] The air at the outlet of the air expansion turbine 111 for oxygen enrichment is at a low pressure (e.g., 110 kPaG) and is directly introduced into the oxygen enrichment device 120.

[0039] In the oxygen enrichment device 120, a differential pressure of 100 kPa serves as the permeation force of the oxygen enrichment membrane, preferentially permeating oxygen, and discharging the permeated oxygen-enriched air to the oxygen-enriched air line 184. On the other hand, the nitrogen-enriched air that did not permeate is discharged to the nitrogen-enriched air line 183 and dissipated into the atmosphere.

[0040] Among the high-temperature high-pressure air generated in the air heating heat exchanger 100, those not introduced into the air expansion turbine 111 for oxygen enrichment are introduced into the air expansion turbine 112 for power generation, driving the air expansion turbine 112 for power generation with pressure reduction and temperature drop, and generating electric power. The low-pressure air after operating the air expansion turbine 112 for power generation is dissipated into the atmosphere.

[0041] BOG (methane gas) generated in the LNG storage tank 10 flows in the BOG line 187 and is supplied to the gas engine power generation device 130, used as fuel for the gas engine power generation device 130, and converted into electric power.

[0042] In the gas engine power generation device 130, methane gas is supplied from the BOG line 187, and a mixed gas of the recycled portion of its own exhaust gas and the oxygen-enriched air supplied from the permeate side of the oxygen enrichment device 120 through the oxygen-enriched air line 184 is supplied from the exhaust gas circulation line 185. For this reason, exhaust gas containing high-concentration carbon dioxide is discharged from the gas engine power generation device 130 to the exhaust gas discharge line 188. In addition, the gas engine power generation device 130 sucks in and uses air from the intake line 190 as necessary.

[0043] The exhaust gas discharged to the exhaust gas discharge line 188 is cooled to room temperature (for example, 50 °C) by high-pressure air in the air heating heat exchanger 100.

[0044] A part of the exhaust gas cooled to room temperature is diverted to the exhaust gas circulation line 185 and circulates to the intake side of the gas engine power generation device 130 together with the oxygen-enriched air from the oxygen-enriched air line 184. The part of the exhaust gas that has not been diverted to the exhaust gas circulation line 185 is dissipated into the atmosphere through the exhaust gas discharge flow rate control valve 189.

[0045] According to the energy storage system 1 according to the present embodiment, since the cold heat of LNG is effectively utilized in the air liquefaction heat exchanger 60, the air liquefaction device 50 can be operated in an energy-saving manner.

[0046] Further, according to the energy storage system 1 according to the present embodiment, since the cold heat of LNG can be effectively utilized for air liquefaction, the cold heat of LNG that has been discarded into the environment can be reduced. For example, an LNG vaporizer using seawater as a heating medium discarded the cold heat of LNG into the ocean, but the amount can be reduced, so the impact on the ocean can be reduced.

[0047] Further, according to the energy storage system 1 according to the present embodiment, the oxygen enrichment device 120 generates oxygen-enriched air from the air after being used for power generation and mixes it with the circulating exhaust gas of the gas engine power generation device 130. For this reason, by using oxygen-enriched air as an oxidant instead of the atmosphere, the nitrogen content decreases, so that the carbon dioxide concentration in the exhaust gas of the gas engine power generation device 130 can be increased, facilitating the recovery of carbon dioxide from the exhaust gas.

[0048] In the energy storage system 1 according to the present embodiment, by dividing the expansion turbine into an oxygen enrichment air expansion turbine 111 and a power generation air expansion turbine 112, it is possible to limit the expansion turbine in which the pressure after expansion is set high to secure the differential pressure of the oxygen enrichment device 120 and the power generation amount is suppressed. Thereby, it is possible to maximize the power generation output in the entire expansion turbine while ensuring oxygen-enriched air.

[0049] In the present embodiment, the type of heat exchanger including the air liquefaction heat exchanger 60 has been described as a shell & tube type or an open rack type, but it is not limited thereto, and the type is appropriately selected within the scope of design. The same applies to pumps and valves.

[0050] In the present embodiment, although the gas engine power generation device 130 has been described as sucking in and using the atmosphere from the intake line 190 as necessary, it may suck in the outlet air of the power generation air expansion turbine 112. Since the temperature of the outlet air of the power generation air expansion turbine 112 has decreased due to expansion and thus the density has increased, as a result, more oxygen can be supplied to the gas engine power generation device 130 regardless of the season, so that the power generation efficiency of the gas engine power generation device 130 can be improved.

[0051] In addition, in this embodiment, the expansion turbine is divided into an oxygen-enriched air expansion turbine 111 and a power generation air expansion turbine 112. However, the present invention includes those having only the oxygen-enriched air expansion turbine 111. In this case, the initial cost can be reduced. However, regarding the outlet pressure of the oxygen-enriched air expansion turbine 111, it is necessary to set it higher than the atmospheric pressure in consideration of the differential pressure of the oxygen enrichment device 120. Therefore, the power generation output of the oxygen-enriched air expansion turbine 111 decreases.

[0052] In addition, in this embodiment, it has been described that the oxygen-enriched air generated by the oxygen enrichment device 120 is supplied to the gas engine power generation device 130. However, oxygen-enriched air with an even higher oxygen concentration obtained by PSA, TSA, etc. may be supplied. In this case, although it is necessary to consider the initial cost and running cost of PSA, TSA, etc., since the nitrogen supplied to the gas engine power generation device 130 is reduced, the recovery of carbon dioxide from the exhaust gas becomes even easier.

[0053] In addition, in this embodiment, the air heating heat exchanger 100 is disposed in the exhaust gas discharge line 188, but it may be installed in the exhaust gas circulation line 185. In that case, since the exhaust gas that does not flow in the exhaust gas circulation line 185 and is discharged to the outside remains at a high temperature, high-temperature exhaust heat can be supplied to other equipment.

[0054] In addition, in this embodiment, the oxygen-enriched air line 184 is merged into the exhaust gas circulation line 185. However, it is not always necessary for these lines to merge, and any mode in which the oxygen-enriched air is supplied to the intake air of the gas engine power generation device 130 is acceptable.

[0055] [Embodiment 2] Embodiment 1 had a gas engine power generation device 130 that generated power using the evaporation gas generated in the LNG storage tank 10 as fuel. However, as shown in FIG. 3, the energy storage system 200 of this embodiment has a gas turbine power generation device 240 that generates power using the vaporized gas vaporized by the LNG vaporizer 30 as fuel instead of the gas engine power generation device 130. Hereinafter, with reference to FIG. 3, the configuration and function of the energy storage system 200 according to the present embodiment will be described. Note that components having the same configuration and function as those in FIG. 1 are denoted by the same reference numerals.

[0056] The gas turbine power generation device 240 includes a boiler 244 that generates steam to be supplied to the steam turbine 246 using the exhaust heat of the gas turbine 242, a condenser 247 that condenses the exhaust steam of the steam turbine 246, and a condensate pump 248 that feeds the condensate condensed by the condenser 247 to the boiler 244.

[0057] The exhaust gas of the gas turbine 242 is supplied to the boiler 244 via the exhaust gas line 243, the steam generated by the boiler 244 is supplied to the steam turbine 246 via the steam line 245, and the condensate condensed by the condenser 247 is supplied to the boiler 244 via the condensate pump 248.

[0058] The exhaust gas circulation line 249 branches from the exhaust gas line 243 and is connected to the intake line 241 of the gas turbine 242. An air compressor (not shown) is provided in the intake line 241 to supply compressed air to the gas turbine 242.

[0059] A large amount of seawater is supplied to the condenser 247 via the seawater supply line 272. This seawater is cooled by the liquefied air evaporation heat exchanger 90 before being supplied to the condenser 247. Then, the steam is condensed in the condenser 247 by the cooled seawater, and thereafter, the seawater is discharged into the ocean. That is, the low-temperature exhaust heat of the gas turbine power generation device 240 is transferred to the seawater and discarded into the ocean.

[0060] Next, the operation of the energy storage system 200 according to the present embodiment will be described. The high-pressure liquefied air discharged into the liquefied air pump discharge line 177 is heated and evaporated in the liquefied air evaporation heat exchanger 90 to become high-pressure air (supercritical state) at room temperature (for example, 20°C).

[0061] High-pressure air is heated by the high-temperature circulating exhaust gas flowing through the exhaust gas circulation line 249 in the air heating heat exchanger 100 and becomes high-temperature high-pressure air.

[0062] A part of the high-temperature high-pressure air generated in the air heating heat exchanger 100 is introduced into the air expansion turbine 111 for oxygen enrichment, drives the air expansion turbine 111 for oxygen enrichment with decompression and temperature reduction, and generates electricity.

[0063] The air at the outlet of the air expansion turbine 111 for oxygen enrichment is at a low pressure (for example, 110 kPaG) and is directly introduced into the oxygen enrichment device 120.

[0064] In the oxygen enrichment device 120, for example, a differential pressure of 100 kPa becomes the permeation force of the oxygen enrichment membrane, preferentially permeates oxygen, and supplies the permeated oxygen-enriched air to the oxygen-enriched air line 184. On the other hand, the nitrogen-enriched air that has not permeated is discharged to the nitrogen-enriched air line 183 and dissipated into the atmosphere.

[0065] The oxygen-enriched air supplied to the oxygen-enriched air line 184 merges with the circulating exhaust gas flowing through the exhaust gas circulation line 249 and increases its oxygen concentration. Further, the circulating exhaust gas is cooled in the air heating heat exchanger 100 and supplied to the intake line 241.

[0066] According to the energy storage system 200, since the seawater at the inlet of the condenser 247 of the gas turbine power generation device 240 is cooled by low-temperature air, the temperature of the seawater introduced into the condenser 247 becomes lower. As a result, the degree of vacuum of the condenser 247 increases, so the efficiency of the steam turbine 246 increases, and the power generation amount by the gas turbine power generation device 240 increases. Also, generally, it is known that the corrosion of metals by seawater progresses faster as the seawater temperature is higher. However, by reducing the temperature of the seawater introduced into the condenser 247, the corrosion of the heat transfer tubes of the condenser 247 can be suppressed.

[0067] Further, according to the energy storage system 200, since the large flow rate of seawater supplied to the condenser 247 is used as the heat source of the heat exchanger 90 for evaporating the liquefied air, the latent heat of vaporization of the liquefied air several times larger than the sensible heat can be supplied. Therefore, the flow rate of the liquefied air supplied to the heat exchanger 90 for evaporating the liquefied air can be increased, and the outputs of the air expansion turbine 111 for oxygen enrichment and the air expansion turbine 112 for power generation can be increased.

[0068] Further, according to the energy storage system 200 according to the present embodiment, since the circulating exhaust gas with a high temperature (for example, 100°C) flowing through the exhaust gas circulation line 249 is used as the heat source of the heat exchanger 100 for heating air, the temperature of the high-pressure air evaporated in the heat exchanger 90 for evaporating the liquefied air and reaching the normal temperature (for example, 20°C) can be further increased. As a result, the outputs of the air expansion turbine 111 for oxygen enrichment and the air expansion turbine 112 for power generation can be further increased.

[0069] Further, according to the energy storage system 200, since the oxygen-enriched air generated in the oxygen enrichment device 120 is mixed with the circulating exhaust gas and supplied to the gas turbine 242, the amount of nitrogen entering from outside the system can be reduced, and the amount of nitrogen discharged outside the system as exhaust gas can be reduced. By reducing the amount of nitrogen discharged outside the system as exhaust gas, the concentration of carbon dioxide in the exhaust gas can be increased, facilitating the separation and recovery of carbon dioxide, and at the same time, the amount of heat discharged outside the system can be reduced, increasing the thermal utilization efficiency of the entire system.

[0070] In the energy storage system 200, a gas turbine power generation device 240 is installed instead of the gas engine power generation device 130. However, the gas engine power generation device 130 and the gas turbine power generation device 240 may be installed together. In that case, the exhaust gas of the gas engine power generation device 130 may be used to heat the air at the inlets of the air expansion turbine 111 for oxygen enrichment and the air expansion turbine 112 for power generation.

Industrial Applicability

[0071] The present invention can be used as an energy storage system that efficiently increases the power generation efficiency with the energy within the system and facilitates the recovery of carbon dioxide from exhaust gas in a system for storing liquefied air as convertible energy into electricity.

Explanation of Signs

[0072] 1,200 Energy storage system 10 LNG storage tank 20 LNG pump 30 LNG vaporizer 50 Air liquefaction device 51 Raw air compressor 52 Compressed air line 53 Adsorber 54 Compressed air cooler 55 Nitrogen compressor 56 Nitrogen circulation line 57 Nitrogen expansion valve 60 Heat exchanger for air liquefaction 70 Liquid air tank 80 Liquid air pump 90 Heat exchanger for liquid air evaporation 100 Heat exchanger for air heating 111 Air expansion turbine for oxygen enrichment 112 Air expansion turbine for power generation 120 Oxygen enrichment device 130 Gas engine power generation device 171 LNG pump inlet line 172 LNG pump outlet line 173 Gas supply line 174 Air inlet line 175 Liquid air supply line 176 Liquid air pump suction line 177 Liquid air pump discharge line 178 Air expansion turbine outlet line for oxygen enrichment 179 Air pressure regulating valve for oxygen enrichment 181 Air expansion turbine outlet line for power generation 182 Air flow regulating valve for power generation 183 Nitrogen-enriched air line 184 Oxygen-enriched air line 185 Exhaust gas circulation line 186 Exhaust gas circulation flow control valve 187 BOG supply line 188 Exhaust gas discharge line 189 Exhaust gas discharge flow control valve 190 Intake air line 210 Seawater pumping pump 240 Gas turbine power generation device 241 Air supply line 242 Gas turbine 243 Exhaust gas line 244 Boiler 245 Steam line 246 Steam turbine 247 Condenser 248 Condensate pump 249 Exhaust gas circulation line 271 Seawater pumping line 272 Seawater supply line 273 Seawater discharge line

Claims

1. An LNG storage tank for storing LNG, an LNG pump for boosting and discharging the LNG stored in the LNG storage tank, an LNG discharge line through which the LNG discharged by the LNG pump flows, a power generation device that generates electricity using the evaporation gas of the LNG generated in the LNG storage tank as fuel and / or a power generation device that generates electricity using the vaporization gas of the LNG discharged by the LNG pump as fuel, an air liquefaction device that liquefies air using the cold heat of the LNG discharged by the LNG pump, a liquefied air storage tank for storing the air liquefied by the air liquefaction device, a liquefied air pump for boosting and discharging the liquefied air stored in the liquefied air storage tank, a liquefied air pump discharge line through which the liquefied air discharged by the liquefied air pump flows, a heat exchanger for heating the liquefied air flowing through the liquefied air pump discharge line, an air expansion turbine for oxygen enrichment that is disposed downstream of the heat exchanger for heating liquefied air in the liquefied air pump discharge line and expands the gaseous air flowing through the liquefied air pump discharge line to generate electricity by the rotational force of the turbine, an oxygen enrichment device that is disposed at the outlet of the air expansion turbine for oxygen enrichment and extracts oxygen-enriched air with a concentrated oxygen concentration by permeating the air at the outlet of the air expansion turbine for oxygen enrichment, an exhaust gas discharge line for discharging the exhaust gas of the power generation device, an exhaust gas circulation line that diverts a part of the exhaust gas flowing through the exhaust gas discharge line and returns it to the inlet of the power generation device, and an oxygen-enriched air supply line that supplies the oxygen-enriched air generated by the oxygen enrichment device to the exhaust gas circulation line. An energy storage system characterized by having these components.

2. The energy storage system according to claim 1, further comprising an expansion turbine for power generation that is disposed downstream of the heat exchanger for heating liquefied air in the liquefied air pump discharge line, expands the gaseous air flowing through the liquefied air pump discharge line to generate electricity by the rotational force of the turbine, and reduces the pressure of the outlet air to atmospheric pressure.

3. The heat exchanger for heating liquefied air is a heat exchanger for evaporating liquefied air that evaporates the liquefied air flowing through the liquefied air pump discharge line by heat exchange with normal-temperature water and / or seawater. An air heating heat exchanger that heats the air evaporated by the liquefied air evaporator heat exchanger by heat exchange with the exhaust gas flowing through the exhaust gas circulation line and returning to the inlet of the power generation device, characterized in that it has the energy storage system according to claim 1 or 2.

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