KR20110046618A - Hydrogen storage system of ultra low temperature and press type using lng cold energy - Google Patents

Abstract

PURPOSE: An ultralow temperature pressurized type hydrogen storage system using LNG cold energy is provided to ensure economic efficiency by obtaining cold energy for storing hydrogen from LNG. CONSTITUTION: An ultralow temperature pressurized type hydrogen storage system using LNG cold energy comprises an LNG storage tank(10), a hydrogen cooling heat exchanger(20), a hydrogen storage tank(30), and a seawater type heat exchanger(40). The hydrogen cooling heat exchanger receives LNG(Liquefied Natural Gas) from the LNG tank and cooling hydrogen provided from outside through heat exchange between the LNG and the hydrogen. The hydrogen storage tank stores the cooled hydrogen provided from the hydrogen cooling heat exchanger. The seawater type heat exchanger receives LNG passing through the hydrogen cooling heat exchanger and vaporizes LNG through heat exchange between the LNG and the sea water.

Description

Ultra low temperature pressurized hydrogen storage system using LNK cooling heat {HYDROGEN STORAGE SYSTEM OF ULTRA LOW TEMPERATURE AND PRESS TYPE USING LNG COLD ENERGY}

The present invention relates to a cryogenic pressurized hydrogen storage system using LNG cold heat, which can save a lot of energy required when storing hydrogen by receiving cold heat required for storing hydrogen from liquefied natural gas.

Korea has secured an introduction of 17 million tons / year of Liquified Natural Gas (LNG) under a long-term contract with a natural gas producing country, and is the second LNG importing country after Japan in the world.

Natural gas is lowered to -162 ℃ and imported into the tank in the form of Liquified Natural Gas (LNG). The LNG is mainly vaporized through heat exchange with seawater to supply fuel. At this time, LNG not only discharges and disposes the cold heat energy of 202kcal / kg to the outside, but also consumes 0.7% of the cold heat of LNG to drive the pump for transporting seawater, which is a valuable energy resource. This is not utilized and there is a problem that the cold heat is discharged and discarded to the outside. Efforts are currently being made to apply this energy to various industries, but due to economic problems, its application is inadequate, and research on application fields for the use of waste energy will be needed. Hydrogen storage technology is a key element to be developed in order to achieve a hydrogen economy. Currently, commercially available hydrogen storage technologies include a high pressure hydrogen tank and a method of liquefying hydrogen at cryogenic temperatures. Hydrogen storage technology by high pressure hydrogen has the advantage of being easy to design and use, but has a high risk of explosion due to low hydrogen storage density and high pressure. Hydrogen liquefaction technology is a technology for storing hydrogen in a liquid state rather than a gas by lowering the temperature to -250 ℃, has the advantage of showing a high hydrogen storage density, but has a problem that the cost is very high. The metal hydride method has a very high hydrogen storage density per volume, but usually requires a high temperature of 150 to 300 ° C. to release hydrogen in the metal hydride, a slow desorption rate of hydrogen, and there are obstacles such as deterioration due to repeated use. . Carbon Nanotubes (CNT) and Metal Organic Frameworks (MOF), which have been studied in recent years, have better storage characteristics and better adsorption capacity at low temperatures than LaNi ₅ and other metal storage media. High cost to maintain reduces economic efficiency.

So far, Korea has a weak infrastructure in the cold-heating industry of LNG. Although the LNG cold heat industry is already being implemented, it is a problem that the cold heat use industry is not easy due to the inconsistent seasonality due to the climatic characteristics. However, compared to what has been used for energy since the 1980s in Japan, vast amounts of energy are being thrown into seawater.

Accordingly, the present inventors continued to develop a hydrogen storage system by using vaporization heat (cold heat) generated during vaporization of LNG which is not currently used. As a result, a hydrogen cooling heat exchanger capable of attaching and detaching a hydrogen storage tank is liquefied natural gas. The present invention was completed by developing a cryogenic pressurized hydrogen storage system mounted between a storage tank and a seawater heat exchanger.

The problem to be solved by the present invention is to provide a cryogenic pressurized hydrogen storage system using LNG cold heat that can save a lot of energy required for storing hydrogen by receiving the cold heat required for the storage of hydrogen from the liquefied natural gas.

Another object of the present invention is to provide a cryogenic pressurized hydrogen storage system using LNG cold heat that can prevent the risk of explosion generated during the hydrogen storage by the high pressure by cooling the liquefied natural gas and hydrogen by heat exchange.

Ultra-low temperature pressurized hydrogen storage system using the LNG cold heat according to the present invention, the liquefied natural gas storage tank liquefied natural gas is stored; A hydrogen cooling heat exchanger configured to receive liquefied natural gas discharged from the liquefied natural gas storage tank and heat exchange with hydrogen supplied from the outside to cool the hydrogen; A hydrogen storage tank configured to receive and store hydrogen cooled by the hydrogen cooling heat exchanger; It is characterized in that it comprises a seawater heat exchanger for receiving the liquefied natural gas passed through the hydrogen cooling heat exchanger to heat-exchange with seawater to vaporize the liquefied natural gas.

Preferably, the hydrogen-cooling heat exchanger is characterized in that the insertion portion is formed in which the hydrogen storage tank is inserted into the inner surface.

Preferably, the hydrogen-cooling heat exchanger is characterized in that the connection pipe and the hydrogen discharge valve for controlling the discharge of hydrogen connected to the hydrogen storage tank.

Preferably, the hydrogen storage tank is characterized in that the hydrogen storage material for storing the introduced hydrogen.

Preferably, the hydrogen storage material is characterized in that the carbon nanotubes (Carbon Nanotube, CNT) or MOF (Metal Organic Frameworks), or a metal that is an impurity (dopant).

Preferably, the hydrogen storage tank is formed of a double wall having an outer wall and an inner wall, characterized in that the cooling fin is formed on the surface.

Preferably, the method receives a natural gas vaporized through the seawater heat exchanger to generate hydrogen gas, and further includes a hydrogen generation device for providing the hydrogen gas to the heat storage for hydrogen storage.

Preferably, the raw hydrogen growth value is a natural gas reformer that receives the vaporized natural gas and water vapor from the seawater heat exchanger to produce hot hydrogen gas and carbonized gas, and hot hydrogen gas and carbonized gas from the natural gas reformer A water vapor generation heat exchanger for converting water into water vapor and providing water vapor to a natural gas reformer, a hydrogen purifier for removing gaseous by-products other than hydrogen gas from the gas provided from the steam generation heat exchanger, and the hydrogen And a hydrogen compressor for compressing the hydrogen gas provided from the purifier, and a hydrogen supply pressurizing tank for storing the hydrogen gas provided from the hydrogen compressor and supplying the hydrogen gas to a hydrogen cooling heat exchanger.

The hydrogen storage system of the present invention is very economical because it can obtain the cold heat that requires a lot of energy for hydrogen storage from LNG, and can be used without major renovation in the existing system, as well as equivalent carbon dioxide by the application of natural gas reformer. This is a significant advantage in that it contributes to the cleansing of fossil fuels by partial removal.

In addition, it is expected to be very useful in the art as a highly efficient energy system that can obtain additional energy such as power generation and district heating.

Due to the current climatic characteristics, LNG consumption decreases in the summer, and the gas evaporation rate (Boil Off Gas, BOG) increases due to the relatively high temperature. According to the method of integrating the natural gas reformer with the hydrogen storage system of the present invention, by using LNG for hydrogen production, it is possible to reduce the cost for suppressing BOG generation in the summer. In addition to the summer season, it is possible to produce hydrogen through natural gas reformer in addition to LNG supply in consideration of LNG demand and hydrogen demand.

Hereinafter, with reference to the accompanying drawings looks at in detail with respect to the cryogenic pressurized hydrogen storage system using the cold heat of the present invention.

In the cryogenic pressurized hydrogen storage system using the cold heat of the LNG of the present invention, the hydrogen cooling heat exchanger 20 into which the hydrogen storage tank 30 can be attached and detached is a liquefied natural gas storage tank 10 and a seawater heat exchanger 40. ) Is mounted between.

Figure 1 shows an example of the cryogenic pressurized hydrogen storage system of the present invention.

As shown in FIG. 1, the cryogenic pressurized hydrogen storage system using LNG cold heat of the present invention includes a liquefied natural gas storage tank 10 in which liquefied natural gas is stored; A hydrogen cooling heat exchanger 20 which receives the liquefied natural gas discharged from the liquefied natural gas storage tank and heats it with hydrogen supplied from the outside to cool the hydrogen; A hydrogen storage tank 30 for receiving and storing hydrogen cooled by the hydrogen cooling heat exchanger 20; The seawater heat exchanger 40 receives the liquefied natural gas passing through the hydrogen cooling heat exchanger 20 and heat-exchanges with seawater to vaporize the liquefied natural gas.

The hydrogen cooling heat exchanger 20 is located between the liquefied natural gas storage tank 10 and the seawater heat exchanger 40, and supplies hydrogen from the liquefied natural gas discharged from the liquefied natural gas storage tank 10 and the outside. It receives and heat-exchanges each other, and cools hydrogen by cold heat of liquefied natural gas. That is, while the LNG moves from the liquefied natural gas storage tank 10 to the seawater heat exchanger 40, the ultra-cold cooling heat is transmitted to the hydrogen in the hydrogen cooling heat exchanger 20. The hydrogen-cooling heat exchanger 20 has an insertion portion 21 into which a hydrogen storage tank 30 is inserted in one side, and an external connection pipe 22 connected to the hydrogen storage tank and hydrogen for controlling the discharge of hydrogen. A discharge valve 23 is formed. When the sorghum storage tank is positioned in the inserting portion 21, the cold heat of the liquefied natural gas flowing in the cooling heat exchanger 20 is transferred to the surface of the hydrogen storage tank 30 to lower the temperature of the hydrogen storage tank 30 to a low temperature. Can be lowered to increase storage efficiency.

As shown in FIG. 3, the hydrogen cooling heat exchanger 20 branches the supply pipes of the liquefied natural gas, and can be appropriately adjusted according to the demand amount when installed in each supply pipe. can do. Each supply pipe is provided with an LNG supply valve 24 for regulating the supply of liquefied natural gas. At this time, when the hydrogen-cooled heat exchanger 20 is installed in series, the moving distance of the LNG is long, the energy efficiency decreases, and most of the existing pipes must be modified, and the entire supply line must be stopped when repairing the line due to a failure. In order to solve this problem, since a bypass must be installed in each unit, the device cost increases. In the case of parallel type, each unit supply process can be controlled by adjusting each LNG supply valve 24 so that the energy efficiency is excellent and the equipment cost by additional bypass installation is not required. Therefore, the hydrogen cooling heat exchanger 20 is preferably installed in parallel.

The hydrogen storage tank 30 is connected to the connecting pipe 22 of the hydrogen cooling heat exchanger 20 through the coupling part 31, and when the hydrogen inlet valve 32 formed at one side of the coupling part 31 is opened. The hydrogen is cooled and supplied from the heat exchanger 20 for cooling. In addition, when hydrogen storage is completed, the hydrogen inlet valve 32 may be closed and the coupling part 31 may be separated from the connecting pipe 22. On the other hand, the hydrogen storage tank 30 is preferably inserted into and fixed to the insertion portion 21 inside the hydrogen cooling heat exchanger 20, the hydrogen storage in order to receive a low temperature of the liquefied natural gas in the heat exchanger (20) Cooling fins 33 are formed on the surface of the tank 30.

The material of the hydrogen storage tank 30 is made of aluminum or a corresponding material having high thermal conductivity and excellent heat at high pressure and low temperature. In addition, the hydrogen storage tank is preferably formed of a double wall having an outer wall and an inner wall, and is formed in a vacuum between the outer wall and the inner wall.

Inside the hydrogen storage tank 30 is a carbon-based hydrogen storage material 34 is stored so that the introduced hydrogen is stored. Hydrogen storage materials include carbon nanotubes (CNT) or metal organic frameworks (MOF), or metals that are impurities (dopants). The carbon storage material (CNT or MOF) has a property that is well stored at cryogenic temperatures, and has a characteristic that the volume energy density is greatly increased by physical adsorption on the solid surface. Physical adsorption occurs by Van der waals force under pressure and low temperature conditions, and because of the physical bonding, the bonding energy is small, and thus the hydrogen desorption is easy due to slight decompression or elevated temperature.

Hydrogen is cooled to ultra low temperature through a hydrogen cooling heat exchanger 20 through a supply line, and is introduced into and stored in a hydrogen storage tank 30. The hydrogen supply line uses high pressure copper pipe or aluminum pipe with excellent thermal conductivity. Hydrogen supplied to the hydrogen cooling heat exchanger 20 uses hydrogen generated by electrolysis, thermochemical methods, biochemical methods, etc. of hydrogen or water additionally generated in petrochemical processes.

On the other hand, as shown in Figure 4, the natural gas vaporized through the sea water type heat exchanger is a natural gas reformer 50, steam generating heat exchanger 60, hydrogen purifier 70, hydrogen compressor 80 and hydrogen storage Hydrogen may be produced and stored via the pressurizing tank 90.

The natural gas reformer 50 receives a natural gas and water vapor so that a reaction such as Chemical Formulas 1 and 2 is performed to produce a gas made of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and the like.

[Formula 1]

CH4 (g) + H2O (g) → CO (g) + 3H2

[Formula 2]

CO (g) + H2O (g) → CO2 (g) + H2 (g)

The steam generator heat exchanger 60 generates steam by heat-exchanging hot generated gas discharged from the natural gas reformer 50 with water provided from the outside. The steam generated through the heat exchanger 60 for steam generation is introduced and used in the natural gas reformer 50. A part of the steam generated by the steam generating heat exchanger 60 may be supplied to the generator 61 generating a power source of a pump for supplying the seawater to the seawater heat exchanger 40 or may also be used for heating.

The hydrogen purifier 70 separates hydrogen and gas by-products from the generated gas passing through the heat exchanger 60 for steam generation. Hydrogen purifier 70 requires a process such as desulfurization and carbon dioxide in order to produce high purity hydrogen, which may be applied to the removal method or pressure swing adsorption (PSA) using an adsorbent that has been developed and used in the past. have.

The hydrogen compressor 80 compresses and compresses hydrogen separated from the hydrogen purifier, and the compressed hydrogen is stored in the hydrogen storage pressure tank 90. At this time, the hydrogen stored in the hydrogen storage hydrogen tank 90 is introduced into the hydrogen cooling heat exchanger 20 and cooled again.

Figure 1 shows an example of the cryogenic pressurized hydrogen storage system of the present invention.

Figure 2 shows the structure of the side and the top of the hydrogen storage tank to which the fin for the heat exchanger is applied.

3 illustrates one embodiment of a parallel multiple hydrogen cooling heat exchanger structure.

Figure 4 shows the hydrogen storage system of the present invention equipped with a natural gas reformer.

<Brief description of symbols for the main parts of the drawings>

10: LNG gas storage tank 20: heat exchanger for hydrogen cooling

21: insertion portion 22: connector

23: hydrogen discharge valve 30: hydrogen storage tank

31: coupling portion 32: hydrogen inlet valve

33: cooling fin 34: hydrogen storage material

40: seawater type heat exchanger 50: natural gas reformer

60: heat exchanger for steam generation 70: hydrogen purifier

80: hydrogen compressor 90: pressurized tank for hydrogen storage

Claims (9)

A liquefied natural gas storage tank in which liquefied natural gas is stored; A hydrogen cooling heat exchanger for cooling hydrogen by receiving liquefied natural gas discharged from the liquefied natural gas storage tank and heat-exchanging with hydrogen supplied from the outside; A hydrogen storage tank configured to receive and store hydrogen cooled by the hydrogen cooling heat exchanger; The cryogenic pressurized hydrogen storage system using LNG cold heat, characterized in that it comprises a seawater heat exchanger for receiving the liquefied natural gas passed through the hydrogen cooling heat exchanger to heat-exchange with seawater. The cryogenic hydrogen storage system according to claim 1, wherein the hydrogen cooling heat exchanger has an insertion part in which a hydrogen storage tank is inserted into an inner surface thereof. The cryogenic pressurized hydrogen storage system according to claim 2, wherein the hydrogen cooling heat exchanger (20) is connected to a hydrogen storage tank and a hydrogen discharge valve for controlling the discharge of hydrogen. 3. The cryogenic pressurized hydrogen storage system according to claim 2, wherein the hydrogen storage tank (30) includes a hydrogen storage material (34) for storing the introduced hydrogen. The ultra low temperature pressurized hydrogen storage system of claim 4, wherein the hydrogen storage material is carbon nanotube (CNT), metal organic frameworks (MOF), or metals of impurities (dopant). . 3. The cryogenic pressurized hydrogen storage system according to claim 2, wherein the hydrogen storage tank is formed of a double wall having an outer wall and an inner wall, and cooling fins 33 are formed on a surface thereof. The gas generator according to any one of claims 1 to 6, further comprising a hydrogen generation device receiving hydrogenated natural gas through the seawater heat exchanger to generate hydrogen gas, and providing the hydrogen gas to a hydrogen storage heat exchanger. Ultra-low temperature pressurized hydrogen storage system using LNG cold heat, characterized in that. The method of claim 7, wherein the hydrogen growth growth value A natural gas reformer that receives the vaporized natural gas and water vapor from the seawater heat exchanger and generates hot hydrogen gas and carbonized gas; A heat exchanger for generating steam that receives high temperature hydrogen gas and carbonized gas from the natural gas reformer, converts water into steam, and provides steam to natural gas reformer; A hydrogen purifier for removing gas by-products other than hydrogen gas from the gas provided from the steam generating heat exchanger; A hydrogen compressor for compressing the hydrogen gas provided from the hydrogen purifier, and Ultra low temperature pressurized hydrogen storage system using the LNG cold heat, characterized in that for storing the hydrogen gas provided from the hydrogen compressor, and supplying the hydrogen gas to the hydrogen cooling heat exchanger (20). 9. The waste cold heat of LNG according to claim 8, wherein the hydrogen growth value further includes a steam generator which receives water vapor from the steam generating heat exchanger and generates electric power and supplies the steam to the pump of the seawater heat exchanger. Hydrogen storage system

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