JP4378124B2 - Natural gas hydrate storage method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a natural gas hydrate storage method and apparatus for storing solid natural gas hydrate such as pellets in a storage tank.
[0002]
[Prior art]
Conventionally, LNG (liquefied natural gas) has been transported by tank trucks, etc. as a method of transporting natural gas to areas outside the natural gas supply area by gas conduits, that is, inland areas where gas conduits are not installed. However, since LNG itself is extremely low temperature (minus 162 ° C.), expensive equipment with extremely advanced technology and safety measures is required. For this reason, as a gas transport method replacing the gas conduit, LNG transport using a tank truck or the like has been difficult to spread.
[0003]
Apart from LNG import bases, inland LNG regasification bases (usually called satellite bases), when LNG is regasified, sensible heat of air is used as a heat source instead of seawater. It has been done.
[0004]
However, in that case, since LNG itself is at an extremely low temperature (minus 162 ° C.), moisture contained in the air freezes and accumulates, and in the worst case, the malfunction of the equipment due to freezing freezes. There was a difficulty in equipment management during gasification. For this reason, regasification requires duplication of equipment, and the rated capacity is duplicated, which has contributed to an increase in cost.
[0005]
In addition, the natural gas supplied to the gas turbine combustor needs to be compressed by a gas compressor. In the case of a fuel supply system via a satellite base, a gasifier or the like is used for high-pressure gasification at ultra-low temperatures. There was a problem that the equipment cost increased.
[0006]
By the way, natural gas hydrate (NGH), which has been attracting attention recently, is a hydrate of natural gas and water, and there are two production methods, dry and wet.
[0007]
Briefly, in the case of the dry type, natural gas hydrate is produced by spraying water into the natural gas atmosphere introduced into the production tank under a predetermined pressure and temperature. Hydrate is generated. On the other hand, in the case of a wet type, a natural gas hydrate is produced by jetting natural gas into the water stored in the production tank under a predetermined pressure and temperature, so that it becomes a sherbet.
[0008]
Natural gas hydrates have better transport and storage efficiency when processed and pelletized after being processed into pellets than when transported or stored as powder or sherbet, and natural gas hydrate has By utilizing self-preserving property, it can be transported and stored at normal pressure and low temperature (about minus 20 ° C.), and thus has recently attracted attention as a new method for transporting and storing natural gas.
[0009]
For this reason, gas customers such as satellite bases or relatively large convenience stores in the suburbs, as shown in FIG. 9, pelletized natural gas hydrate (hereinafter referred to as NGH pellets) a under normal pressure. It is stored in the storage tank 2, and when the demand for natural gas is reached, the NGH pellet a is transported to the pressure-resistant regasification tank 4, where hot water c is dropped from the nozzle 9 to regasify it to meet the demand. ing.
[0010]
On the other hand, as shown in FIG. 10, when the demand for the natural gas from the high-pressure pipeline 1 is low, the natural gas is cooled under pressure to be converted into a hydrate and stored in the storage container 5, and the demand is increased. In many cases, a natural gas storage and delivery method for decomposing and vaporizing natural gas in the storage container 5 stored as a hydrate by depressurization and / or heating and sending it as natural gas has been proposed ( For example, see Patent Document 1.)
[0011]
[Patent Document 1]
JP-A-9-49600 (pages 4-5, FIG. 1)
[0012]
[Problems to be solved by the invention]
In the former case, it is possible to store the NGH pellet a in the storage tank 2 at normal pressure and minus 20 ° C. In addition to the storage tank 2, a pressure-resistant regasification tank 4 is required separately. Therefore, a lot of installation space is required for the installation of these tanks.
[0013]
In addition, when the NGH pellet a is cut out from the storage tank 2 to the regasification tank 4, not only a handling device such as a conveyor is required, but also there is a problem that it takes time to transport the NGH pellet a, that is, handling.
[0014]
Moreover, since the system which drops the warm water c from the nozzle 9 is employ | adopted when gasifying the NGH pellet a, the NGH pellet a is gradually gasified from the upper layer part which the warm water c directly hits.
[0015]
Therefore, since it is not suitable for rapid gasification, there is a possibility that it cannot respond to a rapid increase in demand. In addition, as described above, since the method of dropping the hot water c from the nozzle 9 is adopted, it is difficult to control the gas pressure.
[0016]
On the other hand, in the latter case, the first heat exchange system 7, the first refrigerant circulation line 11 provided with a compressor, the second heat exchange system 15 and the second refrigerant circulation line 13 provided with an expansion valve are mainly used. When the hydrate is gasified using a heat pump as a constituent element, the heat stored in the heat storage material of the heat storage tank 17 is supplied to the first heat exchange system 7 provided in the storage container 5 Thus, the hydrate in the storage container 5 is gradually gasified from the portion in contact with the first heat exchange system 7. Therefore, since it is not suitable for rapid gasification, there is a possibility that it cannot respond rapidly to the increase in demand.
[0017]
The present invention has been made to solve such problems, and a first object is to integrate a storage tank for storing NGH pellets and a regasification tank for gasifying NGH pellets into a conveyor or the like. It is an object of the present invention to provide a natural gas hydrate storage method and apparatus that eliminates the handling apparatus and can reduce costs and save space.
[0018]
The second object of the present invention is to provide a natural gas hydrate storage method and apparatus capable of accelerating heat transfer and responding to a rapid increase in demand by circulating slurry NGH pellets themselves. .
[0019]
A third object of the present invention is to provide a natural gas hydrate storage method and apparatus that is easy to control the gas pressure and that is excellent in operability and load followability.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is formed as follows.
[0021]
That is, (1) the method for storing natural gas hydrate of the present invention is to store a predetermined amount of water in advance in the pressure vessel when storing solid natural gas hydrate in the pressure vessel , the solid natural gas hydrates, quantified charged into a pressure vessel which is filled with water from the pellet inlet tube equipped with a lock hopper, then as the pressure in the pressure vessel after loading the natural gas hydrate is a predetermined accumulator And controlling the water level in the pressure vessel.
[0022]
(2) The method of storing natural gas hydrate of the present invention, when storing the solid natural gas hydrate in the pressure vessel, the solid natural gas hydrates, in advance, and stored in a pressure vessel, then Then, water is supplied into the pressure vessel to slurry the solid natural gas hydrate, and then the water level in the pressure vessel is adjusted so that the pressure in the pressure vessel after loading the natural gas hydrate becomes a predetermined pressure accumulation. It is characterized by controlling.
[0023]
(3) The natural gas hydrate storage device of the present invention is a natural gas hydrate storage device for storing solid natural gas hydrate, and has a gas delivery control valve provided at the top of the pressure vessel. provided with a pipe, the pellets introduction pipe provided with a lock hopper on the side of the pressure vessel, and a water injection pipe is provided with a first water level adjusting valve and the valve further prior Symbol the first to the bottom of the pressure vessel A conduit that communicates with the intermediate portion of the water injection pipe located between the water level adjustment valve and the valve is provided, and a circulation path is formed by the water injection pipe on the downstream side of the pipe and the intermediate portion. And a heat exchanger having a hot water amount adjusting valve, and a drain pipe provided with a second water level adjusting valve is connected to an intermediate portion of the water injection pipe.
[0024]
(4) The natural gas hydrate storage device according to the present invention is a natural gas hydrate storage device for storing solid natural gas hydrate, and is provided with a gas delivery control valve at the upper part of the pressure vessel. provided with a tube, and the pellet introduction tube provided with a valve on the side of the pressure vessel, and a water injection pipe is provided with a first water level adjusting valve and the valve, further wherein the first water level at the bottom of the front Symbol pressure vessel A conduit that communicates with the intermediate portion of the water injection pipe in the middle of the adjustment valve and the valve is provided, and a circulation path is formed by the water injection pipe downstream from the pipe and the intermediate portion. A heat exchanger having a hot water amount adjusting valve is provided, and a drain pipe having a second water level adjusting valve is connected to an intermediate portion of the water injection pipe.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
The natural gas hydrate storage method according to the present invention includes two methods: a pellet charging method and a water injection method. First, the pellet charging method will be described, and then the water injection method will be described.
[0027]
(1) Pellet charging method First, the pellet charging method will be described.
In FIG. 1, 51 is a vertically long pressure-resistant container, and a gas delivery pipe 53 provided with a gas amount adjusting valve 52 is connected to the upper part thereof. Further, the pressure vessel 51 includes a pellet introduction pipe 55 provided with a lock hopper 54 on one side thereof, and a water injection pipe 57 provided with a first water level adjustment valve 56 and a valve 67 on the other side thereof. Yes. The pellet introduction pipe 55 includes valves 58 and 59 before and after the lock hopper 54. The valve 67 is normally “closed”.
[0028]
The pressure vessel 51 includes a pipe line 60 that communicates with the bottom of the pressure vessel 51 and the intermediate part 68 of the water injection pipe 57. A circulation path 61 is formed by the pipe 60 and the water injection pipe 57 on the downstream side of the intermediate portion 68. The pipe line 60 includes a rotary valve 62, a circulation pump 63, and a heat exchanger 64 counterclockwise. The heat exchanger 64 includes a gas pressure adjusting valve (warm water amount adjusting valve) 66 in the hot water supply pipe 65.
[0029]
Further, a drain pipe 71 having a second water level adjustment valve 70 is connected to the intermediate portion 68 of the water injection pipe 57.
[0030]
Next, a method for storing NGH pellets in a slurry state using this pellet charging method will be described.
[0031]
In the case of this pellet charging method, as shown in FIG. 2, the first water level adjusting valve 56 and the valve 67 are opened, and water w is injected into the pressure vessel 51 from the water injection pipe 57, and the pressure vessel A predetermined amount of water w is stored in advance in 51.
[0032]
Thereafter, as shown in FIG. 3, the NGH pellet a is introduced into the pressure vessel 51 through the pellet introduction pipe 55. A part of the NGH pellet a introduced into the pressure vessel 51 is gasified and the pressure in the pressure vessel 51 is increased. As a result, it becomes difficult to introduce the NGH pellet a under normal pressure. Therefore, the two valves 58 and 59 provided at the front and rear of the lock hopper 54 are alternately opened and closed to prevent the gas from being blown out. a is stored in the pressure vessel 51. At this time, the water level in the pressure vessel 51 is controlled by controlling the first water level adjustment valve 56 so that the gas pressure in the pressure vessel 51 becomes the final predetermined pressure.
[0033]
In this pellet charging method, the pressure change of the gas phase depends on the incompressible fluid (water) to be input and the amount of gas generated with solid NGH pellets. There is a slight difference between the case where the injection is made almost instantaneously and the case where (b) the fixed amount is supplied at a constant time.
[0034]
In the case of (a), since the amount of water corresponding to the storage amount is determined, it may be considered as no control. In the case of (b), both (water and NGH pellets) are variables and are difficult to control. Therefore, the amount of water that is easy to measure is adjusted by detecting the gas phase pressure.
[0035]
When the water level reduction (drainage) is examined, the gas hydrate amount and the water amount to be finally stored are uniquely determined, and the control as in (b) above is performed. If it is difficult to maintain the pressure, it may be necessary to drain water to adjust the water level. However, the control system becomes complicated and there is not much necessity in practice, so consider draining water. It is not considered necessary.
[0036]
On the other hand, for the gas demand, as shown in FIG. 4, the circulation pump 63 is operated to circulate the so-called NGH slurry e in which the water w and the NGH pellet a are mixed, counterclockwise along the circulation path 61. On the other hand, the warm drainage c is supplied from the warm water supply pipe 65 to the heat exchanger 64.
[0037]
As described above, when the warm drainage c is supplied to the heat exchanger 64, the NGH slurry e circulating in the circulation path 61 is warmed by the warm drainage c, and the NGH pellet a in the pressure resistant vessel 51 is gasified and quickly. In addition, high-pressure natural gas g is obtained.
[0038]
The regenerated high-pressure natural gas g is directly supplied to a power generation medium and small gas turbine combustor (not shown) installed in a convenience store or the like via a gas delivery pipe 53. For this reason, the fuel gas compressor for gas turbines may become unnecessary. The water w increased by regasification of the NGH pellet a is discharged out of the system from the drain pipe 71 provided with the second water level adjustment valve 70.
[0039]
Since the particle size of the NGH pellet a gradually decreases with gasification and the decomposition rate gradually changes, the pressure in the pressure vessel 51 is detected and the amount of hot water serving as a heat source is controlled by the control valve 66. Necessary (maintain the amount of cracked gas constant).
[0040]
(2) Water injection method Next, the water injection method will be described.
This water injection method (see FIG. 5) differs from the pellet injection method only in that a pellet introduction tube 74 provided with a valve 73 is provided instead of the pellet introduction tube 55 with a lock hopper in the pellet injection method. Description of other devices will be omitted.
[0041]
Next, an NGH pellet storage method using this water injection method will be described.
[0042]
In the case of this water injection method, as shown in FIG. 6, the NGH pellet a is introduced into the pressure vessel 51 from the pellet introduction pipe 74, and a predetermined amount of NGH pellet a is stored in the pressure vessel 51 in advance.
[0043]
Thereafter, as shown in FIG. 7, when water w is introduced from the water injection pipe 57 into the pressure vessel 51, a part of the NGH pellet a is gasified and the pressure in the pressure vessel 51 rises. Therefore, the first water level adjustment valve 56 is controlled to control the water level in the pressure vessel 51 so that the gas pressure in the pressure vessel 51 becomes the final predetermined pressure.
[0044]
On the other hand, for the gas demand, as shown in FIG. 8, the circulation pump 63 is operated to circulate the so-called NGH slurry e in which the water w and the NGH pellet a are mixed along the circulation path 61 in the counterclockwise direction. On the other hand, the warm drainage c is supplied from the warm water supply pipe 65 to the heat exchanger 64. When the warm drainage c is supplied to the heat exchanger 64, the NGH slurry e circulating in the circulation path 61 is warmed by the warm drainage c, the NGH pellet a in the pressure vessel 51 is gasified, and the high-pressure natural gas g is quickly generated. can get.
[0045]
The regenerated high-pressure natural gas g is directly supplied to a power generation medium and small gas turbine combustor (not shown) installed in a convenience store or the like via a gas delivery pipe 53. For this reason, the fuel gas compressor for gas turbines may become unnecessary. The water w increased by regasification of the NGH pellet a is discharged out of the system from the drain pipe 71 provided with the second water level adjustment valve 70.
[0046]
Since the particle size of the NGH pellet a gradually decreases with gasification and the decomposition rate gradually changes, the pressure in the pressure vessel 51 is detected and the amount of hot water serving as a heat source is controlled by the control valve 66. Necessary (maintain the amount of cracked gas constant).
[0047]
As described above, according to the present invention, an intended object can be achieved.
[0048]
By the way, although it has already been explained that a part of the NGH pellet a is gasified at the beginning when the NGH pellet a is introduced into the water-filled pressure-resistant vessel 51, the NGH pellets are balanced according to an increase in gasified gas when stored. It is necessary to maintain the conditions. Moreover, it is necessary to maintain the equilibrium in the pressure vessel 51 at a temperature at which the NGH slurry e does not freeze.
[0049]
As will be described later, this is determined by the dimension of the pressure vessel and the amount of water filling. In the case described in the embodiment, among the hydrate equilibrium conditions for natural gas, the pressure is higher than about 3.0332ata (0.2975 MPa), and the NGH is placed in the pressure vessel 51 in a state where the equilibrium temperature does not fall below the freezing point. Form slurry e.
[0050]
The inventors have confirmed the utility of the present invention on paper. The result will be described.
[0051]
【Example】
(Example)
Various conditions such as the volume in the tank are set as follows. However, the numerical value given the underline is a predetermined numerical value.
[0052]
Tank volume (V): 28 m ³
Reservoir (G): 8.9 ton
Input NGH amount (n): 11.6 ton
Turned NGH temperature (t): - 20 ℃
Calculated decomposition NGH (g): 71 kg
NGH density: 800 kg / m ³
NGH product water weight ratio: 0.89
NGH gas weight ratio: 0.11
Gas content: 200 Nm ³
NGH heat of dissociation: 115 kcal / kg
NGH specific heat: 0.497 kcal / kgK
Gas specific heat (kcal / kgK): 0.5
Cracked gas volume: 7.8 kg
Accumulation (P ₁ / P ₂ ): 1.0332 ata (initial) / 3.0332 ata (after loading)
Gas temperature; (t ₁ / t ₂ ): 10 ° C (initial) / 2.5 ° C (after loading)
(T ₁ / T ₂ ): 283 K (initial) / 275.5 K (after loading)
Reservoir temperature; same as gas temperature where
P ₁ ; Initial pressure of the container
P ₂ ; Final pressure of the container
t ₁ ; Initial temperature of the container
t ₂ ; Final temperature of the container
T ₁ ; absolute temperature of t ₁
T ₂ ; absolute temperature of t ₂
Gas specific weight: 0.776 kg / Nm ³
Gas constant R: 47.4 kg · m / kg · K
Set as above.
The initial gas storage amount (W ₁ ) in the container is
(V -G) x P ₁ x 10 ⁴ / (R x T ₁ ) = W ₁ (1)
The amount of stored gas after loading NGH (W ₂ ) is
P ₂ × 10 ⁴ × {V − G− (n−g) /0.8−g × 0.89} / (R × T ₂ )
= W ₂ (2)
The amount of cracked gas is
W ₂ −W ₁ = g × 0.11 (3)
It becomes.
[0053]
Now, calculate the heat balance in the case where NGH is charged into the reservoir and the heat balance after charging as follows.
[0054]
That is, the state (temperature, pressure) in the container corresponding to the charged NGH is determined by calculating the mass / heat balance before and after charging the NGH into the initially water-filled container.
[0055]
NGH sensible heat: n × (−20) × 0.497 (4)
Sensible heat of the initial gas phase: W ₁ × 10 × 0.5 (5)
Sensible heat of liquid phase: G × 10 (6)
Endothermic amount of partially decomposed NGH: -g x 115 (7)
Depending on (4) to (7), total (8)
On the other hand, the amount of heat after filling with NGH:
W ₂ × 0.5 × t ₂ + {G + (n−g) × 0.497 + g × 0.89} × t ₂
(9)
Here, (8) = (9) must be satisfied.
[0056]
Insert a predetermined constant and form NGH slurry after filling, but the equilibrium condition is
P ₂ = 3.0332 ata
t ₂ = 2.5 ° C
Therefore, the decomposed NGH amount (g) is
g = 71 kg
Is obtained.
[0057]
Therefore, the decomposed NGH amount (g) was 71 kg, which was 0.6% with respect to the NGH input amount (n = 11,600 kg). Therefore, it was found that 99.4% of the charged NGH pellets did not decompose and were stably maintained as NGH slurry.
[0058]
【The invention's effect】
(1) As described above, in the first natural gas hydrate storage method of the present invention, the amount of water filling determined by the gas phase pressure is applied to the solid natural gas hydrate through a pellet introduction pipe equipped with a lock hopper. Since the amount of water injected into the pressure vessel is controlled so that the pressure inside the pressure vessel becomes the final predetermined pressure, the gas pressure can be easily controlled and the operability and load are reduced. The followability of has come to greatly improve.
[0059]
Further, according to the present invention, the slurry NGH pellets themselves are circulated, so that heat can be exchanged and the rapid increase in demand can be dealt with.
[0060]
Further, in the present invention, since the regeneration gas has a high pressure, it can be directly supplied to the combustor of the small and medium gas turbine for power generation installed in the convenience store or the like via the gas delivery pipe. Therefore, the fuel gas compressor for gas turbines may be unnecessary.
[0061]
(2) Further, in the second natural gas hydrate storage method of the present invention, the solid natural gas hydrate is stored in the pressure vessel in advance, and then water is supplied into the pressure vessel to form a solid state. In order to control the amount of water injected into the pressure vessel so that the pressure in the pressure vessel becomes the final predetermined pressure, in addition to the effects of the first method invention, There are effects such as easy operation.
[0062]
(3) On the other hand, the first natural gas hydrate storage device of the present invention is provided with a gas delivery pipe provided with a gas amount adjusting valve at the upper part of the pressure vessel and provided with a lock hopper at the side of the pressure vessel. A pellet introduction pipe and a water injection pipe provided with a first water level adjustment valve are provided, and further, a pipe line communicating with the bottom of the pressure vessel and the water injection pipe is provided, and the pipe line and a part of the water injection pipe In addition, a heat exchanger having a circulation pump and a hot water amount adjusting valve is provided in the pipe line, and a drain pipe having a second water level adjusting valve is connected to the water injection pipe. Control of gas pressure has become easier, and operability and followability to loads have been greatly improved.
[0063]
In addition, the present invention integrates a storage tank for storing NGH pellets and a regasification tank for gasifying NGH pellets and eliminates a handling device such as a conveyor, thereby enabling cost reduction and space saving. It was.
[0064]
Further, according to the present invention, since solid NGH pellets are stored in a slurry state, the storage and handling of NGH pellets is facilitated.
[0065]
Further, in the present invention, since the regeneration gas has a high pressure, it can be directly supplied to the combustor of the small and medium gas turbine for power generation installed in the convenience store or the like via the gas delivery pipe. Therefore, the fuel gas compressor for gas turbines may be unnecessary.
[0066]
(4) A second natural gas hydrate storage device according to the present invention is provided with a gas delivery pipe provided with a gas amount adjusting valve in an upper part of a pressure resistant container, and a pellet provided with a valve on a side portion of the pressure resistant container. An introduction pipe and a water injection pipe provided with a first water level adjustment valve are provided, and further, a pipe line communicating with the bottom part and the water injection pipe is provided in the pressure vessel, and is circulated by the pipe line and a part of the water injection pipe. A heat exchanger having a circulation pump and a hot water amount adjusting valve is provided in the pipe line, and a drain pipe having a second water level adjusting valve is connected to the water injection pipe. In addition to the effect of the device invention, the structure can be further simplified.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a natural gas hydrate storage device according to the present invention.
FIG. 2 is an explanatory diagram showing a state in which a predetermined amount of water is stored in a storage container.
FIG. 3 is an explanatory diagram in which NGH pellets are introduced into a storage container, and NGH pellets are slurried and stored.
FIG. 4 is an explanatory diagram for regasifying the slurryed NGH pellets.
FIG. 5 is a schematic configuration diagram showing another embodiment of the natural gas hydrate storage device according to the present invention.
FIG. 6 is an explanatory view showing a state in which a predetermined amount of NGH pellets is stored in a storage container.
FIG. 7 is an explanatory diagram in which water is introduced into a storage container and NGH pellets are slurried and stored.
FIG. 8 is an explanatory diagram for regasifying slurry-like NGH pellets.
FIG. 9 is an explanatory view showing a conventional pellet storage system.
FIG. 10 is a schematic configuration diagram showing a conventional natural gas storage and delivery method.
[Explanation of symbols]
a solid natural gas hydrate e slurry g high pressure gas w water 51 pressure vessel 52 gas amount adjustment valve 53 gas delivery pipe 54 lock hopper 55, 74 pellet introduction pipe 56 first water level adjustment valve 57 water injection pipe 60 pipe 61 circulation Path 63 Circulation pump 64 Heat exchanger 66 Hot water amount adjustment valve 70 Second water level adjustment valve 71 Drain pipe

Claims (4)

When storing solid natural gas hydrate in a pressure vessel , a predetermined amount of water is stored in advance in the pressure vessel, and then solid natural gas hydrate is introduced into a pellet equipped with a lock hopper. quantified poured into water filling the pressure vessel than the pipe, then the natural wherein the pressure in the pressure vessel after loading the natural gas hydrate control the water level in the pressure vessel to a predetermined pressure accumulator Gasuhaido Rate storage method. When storing the solid natural gas hydrate in the pressure vessel , the solid natural gas hydrate is stored in the pressure vessel in advance, and then water is supplied into the pressure vessel to form the solid natural gas. A method for storing a natural gas hydrate, wherein the hydrate is slurried and then the water level in the pressure vessel is controlled so that the pressure in the pressure vessel after the natural gas hydrate is loaded becomes a predetermined pressure accumulation . A storage device for a natural gas hydrate for storing solid natural gas hydrate, wherein a gas delivery pipe provided with a gas amount adjusting valve is provided at an upper portion of the pressure vessel, and a lock hopper is provided at a side portion of the pressure vessel. pellets inlet tube equipped, a water injection tube is provided with a first water level adjusting valve and the valve further to the middle portion of the injection tube at the bottom of the front Symbol pressure vessel in the middle of the first water level adjusting valve and the valve Providing a conduit that communicates, and forming a circulation path by the pipe and a water injection pipe downstream from the intermediate portion , and further providing a heat exchanger having a circulation pump and a hot water amount adjusting valve in the pipeline; and A natural gas hydrate storage device, wherein a drain pipe having a second water level adjusting valve is connected to an intermediate portion of the water injection pipe. A storage device for a natural gas hydrate for storing solid natural gas hydrate, wherein a gas delivery pipe having a gas amount adjusting valve is provided at an upper portion of the pressure vessel, and a valve is provided at a side portion of the pressure vessel. and the pellet introduction tube, and a water injection pipe is provided with a first water level adjusting valve and the valve further communicating with the intermediate portion of the water injection tube at the bottom of the front Symbol pressure vessel in the middle of the first water level adjusting valve and the valve with a conduit for providing a circulation path formed by the downstream side of the water injection pipe from said with the conduit intermediate portion, further provided with a heat exchanger having a circulating pump and hot water amount adjusting valve to the conduit, and wherein A storage device for natural gas hydrate, characterized in that a drain pipe provided with a second water level adjusting valve is connected to an intermediate part of the water injection pipe.

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