JP2003262083A - Gas-hydrate recovering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methane-hydrate recovering system which is implemented in a highly economical manner. <P>SOLUTION: The gas-hydrate recovering system 1 is comprised of a transportation pipe 2 and a blowing means 3. The transportation pipe 2 is penetratingly set in the sea from near the sea level to the sea bottom 14. The blowing means 3 blows compressed gas 11 generated by vaporization of a gas-hydrate transported to above the sea by the transportation pipe, to a predetermined location of the transportation pipe. According to the gas-hydrate recovering system 1, the gas hydrate is transported above the sea via the transportation pipe 2 by virtue of an air lift effect, and an ascending current is formed by gas blown by the blowing means 3, whereby the air lift effect can be maintained or accelerated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for recovering natural gas hydrate existing on the seabed as a resource.

[0002]

2. Description of the Related Art Natural gas is a gas layer formed in the ground.
It often exists in a gas state inside (called “free gas layer”), and it is common to excavate and use from such a free gas layer. Alternatively, however, it may exist as a solid-state hydrate produced by hydration of natural gas. This natural gas hydrate (hereinafter,
“Gas hydrate”) is a kind of clathrate compound, and is composed of a plurality of water molecules (H ₂ O).
In the three-dimensional cage-type clathrate (clathrate) formed by methane (CH ₄ ), which is a component of natural gas,
It has a crystal structure in which molecules such as ethane (C ₂ H ₆ ) enter and are included.

Such a gas hydrate is in a state in which natural gas is highly densely packed inside. Theoretically, 1 m ^{3 of} gas hydrate contains about 170 m ³ of natural gas in terms of gas in the standard state, which is attracting much attention as a next-generation energy source.

Since the gas hydrate is produced under the conditions of low temperature and high pressure and can exist stably, it forms a layer in the ground that meets these conditions ("gas hydrate layer", or simply It is called "hydrate layer". Specifically, it has been found that it is widely distributed in the lower part of the permafrost layer in the Arctic Circle, the Antarctic Circle, etc., or in the seabed ground with a depth of about 300 m or less. In addition, it is considered that a large amount will exist in the seabed ground near Japan, such as the Nankai Trough, and investigations or excavation and recovery thereof are about to be carried out sequentially.

[0005] Such a technique for excavating and recovering gas hydrate requires a technology which is significantly different from the technique for excavating and recovering oil. In other words, as already known in the case of oil,
It generally exists as a liquid in a specific area covered by hard rock. Therefore, in order to excavate and recover oil, a sampling hole may be drilled in one place on the rock using a boring device and the like, and suction up to the offshore structure from this sampling hole.

On the other hand, the gas hydrate is a solid and does not always exist in the bedrock, but it often exists laterally in the soft seabed. In addition, like petroleum, it is not always concentrated in a specific place, and it is often scattered in a plurality of layers.
For this reason, it is almost impossible to directly apply the oil drilling and recovery technology such as drilling and sucking up a sampling hole at one place on the seabed to the drilling and recovery of gas hydrate.

As a method for excavating and recovering the gas hydrate that has been proposed so far, hot water or the like is injected into the hydrate layer in the seabed to decompose the gas hydrate in the seabed to form a gas. Some are transported to the sea in the state. However, in such a method, a large amount of heat required for decomposing gas hydrate must be continuously sent over a long distance to the cold seabed. It is very difficult to accurately transfer such heat, and it is difficult to decompose the gas hydrate at a position far away from the injection hole for hot water or the like, and it can be said that the recovery efficiency is good. Absent.

Further, there is a problem that when the gas hydrate is decomposed into a gas state, the handling property is inferior to that in the solid state. In addition, as described above, when gasified, 17% of solid state gas hydrate is obtained.
The volume of natural gas (gas) was 0 times that of the sea, and there was a risk that it would explode on the seabed. In the unlikely event of a sudden blow, not only the gas cannot be effectively recovered, but also various equipment installed on the seabed side may be damaged or damaged.Therefore, it is also necessary to take measures against the blowout, which is expensive and time-consuming to construct. It was For these reasons, the method of gasifying at the seabed is not preferable, and other recovery methods have been desired.

[0009]

In the recovery of gas hydrate from the seabed, in the combustion energy of the fuel obtained from the recovered methane hydrate, the equipment required to recover the methane hydrate and the energy required for maintenance. If the energy balance, which is obtained by subtracting, does not become a positive value, no economic effect can be obtained. Therefore, a system that requires a small amount of energy for recovery and can recover methane hydrate at low cost is desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a methane hydrate recovery system which is highly safe and economical.

[0011]

A gas hydrate recovery system according to the present invention comprises a transportation pipe installed so as to penetrate from near the sea surface to the sea floor, and a gas hydrate transported by the transportation pipe to the sea. And a blowing means for blowing compressed gas generated as a result of blowing into a predetermined position of the transportation pipe, transporting the gas hydrate to the sea through the transportation pipe by an air lift effect, and rising by the gas blown by the blowing means. It is possible to form a flow and maintain or promote the airlift effect.

Further, another gas hydrate recovery system according to the present invention further comprises a flow meter installed in the transportation pipe and adjusting means for adjusting the amount of gas blown by the blowing means. The adjusting means is controlled according to the measured value obtained by.

Further, in the gas hydrate recovery system according to the present invention, if the measured value of the flow meter is less than or equal to a predetermined reference value, the amount of gas blown by the adjusting means is increased to measure the measured value of the flow meter. Is equal to or greater than a predetermined reference value, the amount of gas blown by the adjusting means is reduced or the blowing is stopped.

In these gas hydrate recovery systems, the gas hydrate is preferably methane hydrate.

Further, in these gas hydrate recovery systems, it is preferable that the diameter of the transportation pipe is 1 to 10 m.

According to the gas hydrate recovery system of the present invention, methane hydrate can be recovered from the seabed in a solid state by the airlift effect with simple equipment. Further, in the transportation process in the transportation pipe, the pressure applied to the gas hydrate decreases as it approaches the sea surface, so that the gas hydrate can be recovered as gas near the sea surface. With the gas hydrate recovery system utilizing the air lift effect, it is possible to recover the gas hydrate constantly without requiring a large amount of power.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Here, what is recovered by the gas hydrate recovery system of the present invention is solid-state gas hydrate, particularly methane hydrate, in the seabed. In the following description, methane hydrate will be described, but ethane hydrate and other gas hydrates can be similarly recovered using the system of the present invention, and are not limited to specific gas hydrates. Absent.

In the seabed, methane hydrate exists as a solid-state hydrate. Such a hydrate is a clathrate compound in which methane that is a component of natural gas is clathrated in a three-dimensional cage clathrate lattice formed of a plurality of water molecules (H ₂ O). Exists as. Its composition is represented by CH _4. (H ₂ O) _5.75 and its density is about 0.90 g / cm ³ .

Methane hydrate is in the form of a solid hydrate at about 3 to 8 MPa on the seabed at 2 ° C. to 10 ° C., but is a solid of methane hydrate at around normal pressure, that is, at about 0.1 MPa. Most of the hydrate decomposes into vaporized methane gas and water. Also, methane hydrate usually exists in a state of being confused with earth and sand and other impurities, and the density at that time is about 2.0 to 2.5 g / cm ³ , but pure methane hydrate itself is Is about 1.03g
Since it has a density lower than that of / cm ³ ), it can be floated in the sea by itself when it is excavated into small lumps and separated from relatively dense sediments.

The present invention is not a method of vaporizing methane hydrate existing in a solid state under high pressure in the deep seafloor by applying heat, pressure or chemical action on the seafloor, as described above. Collect as it is through transportation pipes. At that time, the pressure applied to the methane hydrate decreased as it approached the sea level, so that the methane hydrate was partially decomposed into methane gas, which was the focus of attention.

As described above, the gas hydrate is vaporized as it rises toward the sea surface through the transportation pipe or the like, and an ascending current is generated. Due to the air lift effect by this, the solid matter on the sea floor can be pulled up to the sea by the same principle as the air lift pump.

Here, the air lift pump is a pump that blows compressed air from a blower into a standing pipe in water to make a difference in specific gravity between liquid inside and outside the pipe, and pumps up dirty water / dirt along with bubbles rising at that time. It is often used in the field of wastewater treatment. It is essential for such an air lift pump to blow gas into the vertical pipe, but in the present invention, the transported methane hydrate is vaporized as it rises in the sea, and becomes a gas that produces an air lift effect by its action. Therefore, in an ideal state where methane hydrate is abundant and evenly distributed, once a steady upward flow is generated, it is possible to raise the solid matter further without the need to inject gas from the outside. You can However, in reality, the distribution of methane hydrate, other rocks, sediment, etc. is often non-uniform, and it is necessary to devise to make the upward flow steady.

The present invention will be described in detail below with reference to the embodiments with reference to the drawings. The following description does not limit the invention.

A methane hydrate recovery system according to the first embodiment of the present invention is shown in FIG. 1 and described. The illustrated methane hydrate recovery system 1 has a seabed 14
To the sea surface, and a blowing means 3 for injecting the compressed methane gas 11 transported to the sea surface to a predetermined position of the transportation pipe 2.

What is recovered by the gas hydrate recovery system of the present invention is methane hydrate 13 in the solid state, which is mainly in the ground of the seabed 14. Its composition is represented by CH ₄ · (H ₂ O) _5.75 , and it is often buried in a layer about several tens to 100 m from the sea floor.

Since such a methane hydrate 13 has a deposited layer having a thickness of about 50 to several 100 m,
It is necessary to excavate and separate into sediment and methane hydrate, and to make it an appropriate size. Such excavation work can be performed by, for example, scraping by rotating the cut face of the tunnel excavation machine. Details of the excavation work will be described later.

According to the gas hydrate recovery system of the present invention, the solid material excavated from the seabed 14 is transported to the sea due to the airlift effect, so that not only the methane hydrate 13 but also the seabed are transported. It also includes sediments and seawater. Hereinafter, these are referred to as methane hydrate recovered products 10. Further, the methane hydrate recovered product 10 may include other gas hydrate components such as ethane hydrate.

In the present embodiment, the transport pipe 2 is for transporting the methane hydrate recovered matter 10 to the sea by penetrating from near the sea surface to the sea bottom 14. As the transport pipe 2, for example, a pipe having a length of about 1000 m to 4500 m and a diameter of about 1 m to 10 m can be used. The methane hydrate 13 is normally buried in the seabed around 1000 m, and the methane hydrate recovery product 10 is temporarily stored above the sea surface or used by a pipeline provided near the sea surface. Although an appropriate length of the transport pipe 2 is illustrated because it is transported to the destination, the length of the transport pipe 2 can be appropriately determined depending on the depth at which methane hydrate is buried.

The lower end of the transport pipe 2 is located in the soil below the sea floor, and the excavated methane hydrate recovery product 1
Located in a place where you can inhale 0. For example, the lower end of the transportation pipe 2 is preferably located near the methane hydrate deposition layer, but not limited to this. The structure of the lower end of the transport pipe may be, for example, a structure in which the drill hole is covered with the outer cylinder 15 and seawater is introduced from between the outer cylinder 15 and the transport pipe 2 to recover methane hydrate. It is not limited to

On the other hand, the upper end of the transport pipe 2 is connected to a storage means for the methane hydrate recovered product 10 which may be provided near the sea surface, or the methane hydrate recovered product 1
0 is connected to the pipeline for transfer to another place. Alternatively, it may be connected to an apparatus for separating and recovering methane gas and methane hydrate 12 from the methane hydrate recovered product 10 at sea.

The transportation pipe 2 must be fixed by a certain means. For this purpose, means such as fixing of the pipe tip vicinity portion by cementing can be used, but it is not limited to this.

The transport pipe 2 as described above is preferably made of a material which is not damaged or deteriorated by solid methane hydrate 13 and soil and seawater mixed with the solid methane hydrate 13. Further, since the pressure applied to the pipe wall of the transportation pipe 2 increases as the methane hydrate rises in the transportation pipe 2 and vaporizes, it must be manufactured from a pressure resistant material. Specifically, it can be manufactured by a pipe or the like that is made of low-cost carbon steel and is corrosion-resistant coated, but is not limited thereto.

In the present embodiment, the blowing means 3 is means for blowing the compressed methane gas 11 that has been once pulled up to the sea surface and vaporized from the hydrate to a predetermined position of the transportation pipe 2. As a result, an ascending flow is generated in the transportation pipe 2, and the air lift effect is maintained or promoted. As described above, the distribution of methane hydrate is not always uniform, and rocks on the seabed are mixed with mud, so the flow of methane hydrate 13 into the transport pipe 2 may stop or decrease. . The air lift effect may be interrupted due to such fluctuations in the inflow of the methane hydrate 13 into the transportation pipe 2. When this happens, the methane hydrate 13 cannot be stably recovered, so the methane gas 11 compressed by the blowing means 3 is blown into a predetermined position of the transportation pipe 2 to maintain the airlift effect.

The blowing means 3 comprises a nozzle 31 and a pipe 32. By this blowing means 3, the compressed methane gas 11 transported from the sea is blown into the transportation pipe 2.
The compressed methane gas 11 is used without being decompressed as it is once recovered at sea. Methane gas collected at sea usually has a higher atmospheric pressure than normal pressure due to vaporization even after being collected up to the sea. The blowing means 3 may further include a means for further pressurizing the compressed methane gas 11 or a means for depressurizing the compressed methane gas 11. At this time, blow compressed methane gas 1
The pressure of 1 is preferably equal to or higher than the hydrostatic pressure at the position of the nozzle 31, and the blowing amount is, for example, about 1 when the nozzle 31 is installed at a depth of about 2000 m from the sea surface.
It is preferably about 50 Nm ³ / s, and 10 to 2
It is more preferably about 0 Nm ³ / s, but not limited to this. The blowing means 3 does not always have to be operated, and the blowing may be stopped.

The final position of the installation position of the nozzle 31 of the blowing means 3 is determined by the depth of water in which methane hydrate exists, the recovery amount of methane hydrate, the diameter of the transportation pipe, and the like. In order to generate an upward flow over the entire transportation pipe 2, it is preferable to blow the gas from a position near the seabed to some extent, but if the blowing means 3 is installed at a too deep position, the blowing means 3 will be affected. This is because the pressure becomes large and it becomes difficult to install and maintain the blowing means 3.

An example of the hydrate excavation work from the hydrate layer according to the present invention will be described below with reference to FIG. In this example, an excavation recovery device 20 such as a tunnel excavation machine is used. The excavation recovery device 20 includes an excavation base portion 21 installed near the sea bottom and an excavation device portion 22 for excavating the seabed and the methane hydrate 13 layer.
And a shaft 23 that transmits a driving force from the excavation base portion 21 to the excavation device portion 22. The excavation unit 22 is connected to the excavation base 21 by a shaft 23. The excavation base 21 operates the excavation speed and the excavation direction of the excavation device 22 by remote control. The shaft 23 and the double pipe part 24 are extended along with the excavation, and the double pipe part 24 covers the excavation hole formed between the excavation base part 21 and the excavation device part 22.

The lower end of the transport pipe 2 has a digging and recovering device 20.
Although it may be directly connected to the etc., a sediment separating device 40 is provided between the excavating and recovering device 20 and the lower end of the transport pipe 2 to separate the mixed sediment and other impurities from the recovered methane hydrate. After that, it is preferable to send it to the transportation pipe 2. When the sediment separating device 40 is provided, sediment and other impurities can be separated in advance and sent to the transportation pipe 2, and the reduction of the airlift effect due to the mixture of sediment or rock can be prevented.

An enlarged view of the excavation device section 22 is shown in FIG.
Is. The excavation unit 22 has a drill bit 22a at the tip.
The rotary driving force from the excavation base portion 21 is transmitted via the shaft 23, and the excavation bit 22a rotates to excavate the seabed ground and the 13-layer hydrate. A sensor (for example, a neutron sensor) or the like may be attached to the tip of the excavation device unit 22 to excavate the seabed and the hydrate layer 13 while logging them.

The double pipe portion 24 is composed of an outer pipe 24a and an inner pipe 24b which are arranged with a certain gap therebetween. The outer pipe 24a is configured to cover a drill hole between the surface of the seabed and the drill bit 22a, and forms a seawater inlet on the ground surface so that seawater can flow in through a gap between the outer pipe 24a and the inner pipe. The inner pipe 24b is configured with a certain gap from the shaft 23 so as to wrap the shaft 23 in the center thereof, and since it is not connected to the excavation device portion 22, the seawater that has flowed in from the seawater inlet has the outer pipe 24a.
Flows into the gap between the inner pipe 24b and the inner pipe 24b, and further flows into the inner pipe 24b together with the excavated hydrate layer.
Here, the tip end portion of the inner pipe on the side of the excavation bit 22a is provided with a sediment hydrate separation screen 24c which is a screen having a size that allows passage of sediment but does not allow passage of excavated hydrate masses. The earth and sand hydrate separation screen 24c separates the excavated earth and sand hydrate into hydrate and earth and sand,
Sediment is removed to the outer pipe 24a through the eyes of the screen 24c, and only the hydrate can move inside the inner pipe 24b from the drill bit 22a toward the drill base 21. Figure 3
In the above, the screen 24c is provided only on a part of the lower end of the inner tube 24b, but the entire tip of the inner tube 24b may be the screen 24c. Also,
Of the tip portion of the inner pipe 24b, the region where the screen 24c is provided is not particularly limited, and can be appropriately changed depending on the depth at which methane hydrate is buried, the mixing ratio of earth and sand, and the like.

In this figure, the seawater inlet is provided near the seabed ground as a gap between the outer pipe 24a and the inner pipe 24b, but the lower part of the recovery base 21 or the sediment separating device 40.
It may be attached to the lower part or both. further,
You may provide both the seawater inlet provided in the lower part of the collection | recovery base part 21 or the lower part of the earth-and-sand separation apparatus 40, and the seawater inlet of the clearance gap between the outer pipe 24a and the inner pipe 24b. The excavated hydrate is mixed with seawater and rises due to the airlift effect. However, when a seawater inlet is provided at the lower part of the recovery base unit 21 or the lower part of the sediment separating device 40, for example, a suitable belt conveyor or the like. The excavated hydrate may be transported from the excavation device section to the lower portion of the recovery base section 21 or the sediment separating apparatus 40 by using a different transport device.

Next, a mechanism for recovering methane hydrate on the sea floor using the system shown in FIG. 1 will be described.
Solid methane hydrate that has been excavated on the seabed and formed into a lump of an appropriate size is transferred to the lower end portion of the transport pipe 2 of the gas hydrate recovery system 1 according to the present invention by means such as a tunnel drilling machine. It At the start of the recovery system, the inside of the transport pipe 2 is filled with seawater and there is no flow. A pressurized gas such as compressed air or compressed methane gas 11 is blown into the blowing means 3 to generate an upward flow. This upward flow is the transportation pipe 2
By being generated inside, the methane hydrate recovered matter 10 on the seabed 14 is transported toward the sea surface. Once an upflow occurs and the methane hydrate recovered product 10 is transported, as the methane hydrate contained in the methane hydrate recovered product 10 rises in the transport pipe 2, it deprives the surrounding seawater of heat of vaporization. Evaporate to form an upflow. Therefore, the blowing of the pressurized gas can be stopped at this stage.

Once the blowing of the pressurized gas is stopped,
Even if it continues as it is, it becomes possible to blow the recovered methane gas 11. By blowing in the compressed methane gas 11, an upward flow of the blown compressed gas 11 can be generated in the transportation pipe 2 in addition to the upward flow of vaporization of methane hydrate. This is methane hydrate 1 drilled on the seabed 14.
The properties and distribution of 3 are often not uniform, or
This is to form a steady upflow in order to prevent the upflow due to vaporization of the hydrate from being interrupted or weakened depending on the conditions of the seabed 14.

In this way, the gas blown after the start-up is not particularly limited, and may be air, but the gas obtained by vaporizing methane hydrate is compressed to about 1 to 10 MPa even at the time of recovery at sea level. Has been
Stable recovery of methane hydrate or its vaporized gas at sea without using power for transporting the methane hydrate recovered material 10 from the seabed by blowing it as it is or by pressurizing or depressurizing it. You can

A considerable portion of the methane hydrate in the recovered methane hydrate product 10 transported to the vicinity of the sea surface is vaporized into methane gas. Therefore, on the sea, methane gas can be separated and stored from the methane hydrate recovery product 10 obtained by being transported by the transportation pipe 2, or a power plant where methane gas is used by using a pipeline or the like. And so on.

In the recovered substance 10 of methane hydrate, methane hydrate which remains in a solid state without being vaporized also remains. This solid-state methane hydrate can be used in place of cooling cold water to cool combustion air in a power plant or the like by heat exchange. Further, it is possible to cool the methane in a gas state from the methane hydrate together with water to return it to the methane hydrate, and use it for cooling in the same manner as above. According to this method, the cold heat generated when methane hydrate is decomposed into methane and water can be used for cooling the combustion air, and at the same time, the generated methane can be used as a fuel. Such a mode can be used for a power generation plant, particularly a liquefied natural gas combined cycle power generation plant. According to this aspect, it is possible to increase the output of the power plant and stabilize the output at low cost.

According to the first embodiment of the present invention,
There is an advantage that methane hydrate in the sea can be recovered with a relatively simple facility, requiring almost no power.

FIG. 4 shows a gas hydrate recovery system 1a according to a second embodiment of the present invention. The methane hydrate recovery system 1a shown in the figure is different from the gas hydrate recovery system 1 shown in FIG. 1 in that a flow meter 4 for measuring the flow rate of a substance passing through the inside of the transportation pipe 2 and a flow rate of methane gas blown by the blowing means 3 are provided. It further comprises adjusting means 5 for adjusting.

Here, the flowmeter 4 is a device for measuring the amount of substances rising in the transportation pipe 2, in particular, the flow velocity of seawater containing the methane hydrate recovered matter 10. In the transport pipe 2, as described above, not only seawater, methane hydrate, and methane gas, but also sediment and other substances flow from the seabed. Therefore, the specific gravity of the ascending flow also fluctuates greatly, and the flow velocity also fluctuates accordingly. In order to recover the methane hydrate 13 more stably, the blowing amount of the compressed methane gas 11 is controlled according to the flow velocity.

The flow meter 4 is preferably installed near the seabed 14 and closer to the seabed 14 than the blowing means 3. This is because it is necessary to know the true seawater flow rate in the area where gas and liquid are not mixed in order to grasp the amount of methane hydrate recovered. This is because it can be detected.

On the other hand, the adjusting means 5 adjusts the amount of the compressed methane gas 11 blown into the transportation pipe 2 by the blowing means 3 according to the value measured by the flow meter 4. As the adjusting means, for example, a adjusting valve or a damper can be used. Compressed methane gas 11 blown into the transport pipe 2
Increasing the amount can generate a further upward flow in the transport pipe 2 and increase the flow rate.

Further, by using the flow meter 4 and the adjusting means 5 as described above, it is possible to steadily recover methane gas and methane hydrate. This is because if the value of the flow meter 4 is less than or equal to a predetermined reference value, the amount of compressed methane gas 11 blown by the blowing means 3 is increased, and if the value of the flow meter 4 is at least a predetermined reference value, compression is blown by the blowing means 3. This can be done by controlling the adjusting means 5 so as to reduce the amount of methane gas 11 or to stop the blowing.

Specifically, a transport pipe 2 having a length of about 4000 m and a diameter of 2 m is used, a flowmeter 4 is installed at a water depth of 4000 m, and the flow rate in the transport pipe 2 is 14.4 m ^3.
The case of / s can be defined as the reference value. Here, when the measured value of the flow meter 4 becomes less than the reference value, the water depth is 2000 m.
The compressed methane gas 11 by 16
Blow into the transport pipe 2 at Nm ³ / s. This allows
When the measured value of the flow meter 4 reaches the reference value, the blowing can be stopped or the blowing amount can be controlled to be reduced. At this time, the recovered amount of methane hydrate is about 2 × 10 ⁵ kg / h, and it is possible to produce fuel in a power plant scale with an output of 8 MW. Further, the required power when using the gas hydrate recovery system of the air lift system of the present invention is about 1.54 × 10 ⁴ kW.
This is about 1/4 of the power of the conventional pump system and about 1/100 of the power of the heating upflow system. Therefore, it can be seen that the present invention can recover the gas hydrate much more economically than the conventional method.

As described above, according to the second embodiment of the present invention, it is possible to constantly recover methane hydrate in an amount sufficient for use as a fuel. Further, there is an advantage that the power required to recover such methane hydrate is smaller than that of the conventional one.

[0054]

The gas hydrate recovery system according to the present invention requires almost no power,
Due to the airlift effect, methane hydrate can be transported as a solid. Further, in the transportation process, the pressure applied to the gas hydrate decreases as it approaches the sea surface, so that the gas hydrate can be recovered as gas near the sea surface. Further, the flowmeter and the adjusting means can control the recovery amount of methane hydrate, and can constantly recover a constant amount of methane hydrate. With such a gas hydrate recovery system, it is possible to recover the gas hydrate economically, and the gas recovered by such a system can be widely and effectively used as fuel for power generation.

[Brief description of drawings]

FIG. 1 is a diagram showing a methane hydrate recovery system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a hydrate excavation operation from a hydrate layer according to the present invention.

FIG. 3 is an enlarged view of the excavation work shown in FIG. 2.

FIG. 4 is a diagram showing a methane hydrate recovery system capable of adjusting a recovery amount according to a second embodiment of the present invention.

[Explanation of symbols]

1 Methane hydrate recovery system 1a Methane hydrate recovery system 2 transportation pipes 3 blowing means 31 nozzles 32 pipes 4 flow meter 5 Adjustment means 10 Methane hydrate recovered 11 Compressed methane gas 12 Methane gas / Methane hydrate 13 Methane hydrate 14 seabed 15 Outer cylinder 20 Excavation and recovery equipment 21 Excavation base 22 Excavation equipment section 22a drilling bit 23 Shaft 24 Double pipe section 24a outer tube 24b inner tube 24c Sediment hydrate separation screen 40 Sediment Separation Equipment

Claims (5)

[Claims] 1. A transportation pipe installed so as to penetrate from near the sea surface to the bottom of the sea, and a compressed gas produced by vaporization of a gas hydrate transported to the sea by the transportation pipe at a predetermined position of the transportation pipe. And a blowing means for blowing the gas hydrate to the sea through the transportation pipe by the air lift effect, while forming an upward flow by the gas blown by the blowing means, to maintain or promote the air lift effect. Gas hydrate recovery system that enables. 2. A flow meter installed in the transportation pipe, and an adjusting means for adjusting the amount of gas blown by the blowing means, and the adjusting means according to a measurement value obtained by the flow meter. The gas hydrate recovery system according to claim 1, wherein the gas hydrate recovery system is controlled. 3. If the measured value of the flow meter is below a predetermined reference value, the amount of gas blown in by the adjusting means is increased, and if the measured value of the flow meter is above a predetermined reference value,
The gas hydrate recovery system according to claim 2, wherein the amount of gas blown in is reduced or stopped by the adjusting means. 4. The gas hydrate recovery system according to claim 1, wherein the gas hydrate is methane hydrate. 5. The gas hydrate recovery system according to claim 1, wherein the diameter of the transportation pipe is 1 to 10 m.