JP5294110B2 - Methane gas production method from methane hydrate and apparatus for producing methane gas from methane hydrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing methane gas from methane hydrate, as well as a device for producing methane gas, capable of producing methane gas by decomposing methane hydrate without changing a phase equilibrium state of temperature and pressure. <P>SOLUTION: When methane gas M is generated from methane hydrate existing in the sea bottom or the lake bottom, a dissociation chamber 3 including an opening 3a is arranged in such a way that methane hydrate 2 goes into the dissociation chamber 3 through the opening 3a. Then, water W having low methane consistency is supplied into the dissociation chamber 3, so as to dissociate methane from methane hydrate 2, and water W, in which methane is dissolved, in the dissociation chamber 3 is pumped up. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a methane gas production method and methane gas production apparatus from methane hydrate present on the seabed or lake bottom.

  Methane hydrate is attracting attention as a new resource to replace petroleum resources, and the seas around Japan are said to boast the world's largest methane hydrate reserves. This methane hydrate is an ice-like solid crystal in which methane has entered a cage structure of water molecules by hydrogen bonding, and exists stably at low temperature and high pressure. And, because this low temperature and high pressure condition is satisfied in the sediments of several hundred to 1,000 m below the permafrost, the seabed, and the bottom of the lake, the methane hydrate exists in the permafrost, the seabed, and the ground of the lake bottom. .

  In addition, methane hydrate on the sea floor (lake bottom) is exposed to the deep layer methane hydrate that exists in the deep layer of several hundred meters below the sea floor (lake bottom) ground at a depth of several hundreds of meters and the bottom of the sea (lake bottom). For example, there is a surface type methane hydrate existing in the shallow layer. In contrast to deep-layer methane hydrates such as the Nankai Trough, which are currently being studied in Japan, there are still limited examples of surface-type methane hydrates in the world. In Japan, the Okhotsk Sea and Japan Research on surface methane hydrate off the sea Naoetsu has just started. However, from the viewpoint of resource development, surface methane hydrate can be produced more economically, so it is urgently necessary to elucidate various physical properties along with evaluation of the amount of resources.

  In addition, methane hydrate can be decomposed (dissociated) by breaking the phase equilibrium state only by slightly changing the temperature and pressure conditions. For this reason, in deep-layer methane hydrate, methane hydrate is produced by changing the phase equilibrium state by changing the temperature and pressure conditions such as thermal stimulation, decompression, and inhibitor injection as a method for producing methane gas. A method for recovering methane gas by decomposing it into water and water has been studied (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  Here, FIG. 8 shows the temperature and pressure phase equilibrium conditions of methane hydrate. In this figure, the solid line indicates the boundary where methane hydrate is generated, and the upper left side (low temperature, high pressure side) in the figure is the stable region of methane hydrate. And in the water area (sea, lake), this temperature and pressure conditions are reached at a depth of about 400m or deeper. However, since the ground temperature of the seabed (lake bottom) increases with the depth of the ground, the lower limit that satisfies the methane hydrate generation conditions is reached. There is a ground depth, and this ground depth is about 100m to 300m underground. Deep-type methane hydrate exists directly above this lower ground depth, in other words, it exists in a state that is very close to the temperature and pressure phase equilibrium conditions.

In addition, Fig. 8 shows the typical methane hydrate of the Nankai Trough as a deep-type methane hydrate, and the typical methane hydrate temperature and pressure conditions of Lake Baikal and the Sea of Okhotsk as surface-type methane hydrate. Yes. From this figure, it can be seen that the surface layer type methane hydrate is in a region with a high degree of supercooling away from the phase equilibrium condition of temperature and pressure as compared with the deep layer type methane hydrate.
Japanese Patent Laid-Open No. 2004-321852 JP 2004-204562 A Japanese Patent Laid-Open No. 9-158662

  In this way, surface methane hydrate is stable in a region with a high degree of supercooling away from the temperature and pressure phase equilibrium conditions, so the temperature and pressure of the thermal stimulation method, decompression method, inhibitor injection method, etc. When using the method of producing methane gas by changing the above conditions, a large amount of energy is required to change the phase equilibrium state of temperature and pressure.

  In addition, unlike the deep layer methane hydrate, the surface layer type methane hydrate has no ground to serve as a buffer, so unexpected methane gas leakage may occur during the production of methane gas by the thermal stimulation method, decompression method, inhibitor injection method, etc. If generated, methane gas may be released directly into water. For this reason, when producing methane gas by changing the temperature and pressure conditions such as the thermal stimulation method, the decompression method, and the inhibitor injection method, there is a concern about the influence on the ecosystem of the seabed and lake bottom and the global environment.

  In view of the above circumstances, the present invention provides a method for producing methane gas from methane hydrate and a methane gas production apparatus capable of producing methane gas by decomposing methane hydrate without changing the phase equilibrium state of temperature and pressure. The purpose is to do.

  In order to achieve the above object, the present invention provides the following means.

The method for producing methane gas from methane hydrate according to the present invention is a method for producing methane gas from methane hydrate present on the bottom of a sea or a lake, wherein a dissociation chamber formed with an opening is formed through the opening. The water inside the dissociation chamber in which the methane hydrate is exposed, water having a low methane concentration is supplied into the dissociation chamber to dissociate methane from the methane hydrate, and methane is dissolved. The dissociation chamber is provided with a water jet mechanism, and the water jet mechanism allows the water having a low methane concentration sent to the dissociation chamber to flow from the front end side forming the opening of the dissociation chamber. By spraying toward the outside in the substantially axial direction through the opening While cutting the entire ground around the tip of the dissociation chamber and spraying from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis, the ground disposed inside the dissociation chamber is cut while It is characterized by stirring inside to increase the methane concentration .

  In this invention, by supplying water having a low methane concentration into the dissociation chamber and bringing it into contact with methane hydrate, methane can be efficiently removed from the methane hydrate without changing the phase equilibrium state of temperature and pressure. It becomes possible to dissociate. In other words, the seawater or lake water around the surface methane hydrate has a very high methane concentration, and the surface methane hydrate exists stably due to the high methane concentration in the surrounding seawater or lake water. ing. For this reason, it is possible to dissociate methane from methane hydrate by bringing water having a low methane concentration into contact with methane hydrate.

At this time, since methane dissociates from methane hydrate under a high-pressure environment on the seabed or lake bottom, it dissociates from methane hydrate and dissolves in water inside the dissociation chamber. Then, the water inside the dissociation chamber is pumped up and rises to a certain depth, and the dissolved methane is gasified and is automatically ejected from the water. Water and methane gas are easily separated and methane gas is separated. Production (recovery) becomes possible.
Further, in the present invention, water having a low methane concentration sent to the dissociation chamber is jetted substantially outward in the axial direction through the opening from the tip side forming the opening of the dissociation chamber by the water jet mechanism. Accordingly, for example, the ground on the methane hydrate can be cut and removed by the sprayed water, and the dissociation chamber can be suitably installed by penetrating the tip portion into the methane hydrate.
Also, for example, methane hydrate disposed inside the dissociation chamber by injecting water with low methane concentration sent to the dissociation chamber from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis by the water jet mechanism. It is possible to agitate the inside of the dissociation chamber while cutting and removing the upper ground. Then, by raising the muddy water inside the dissociation chamber, it becomes possible to expose the methane hydrate to face the inside of the dissociation chamber. Furthermore, methane hydrate can be dissociated more efficiently by spraying water inward with the methane hydrate exposed and stirring the inside of the dissociation chamber.

  In the method for producing methane gas from methane hydrate of the present invention, it is desirable to supply shallow seawater or lake water into the dissociation chamber.

  In the present invention, by supplying seawater or lake water in shallow water into the dissociation chamber, water having a low methane concentration can be supplied into the dissociation chamber using seawater or lake water. This makes it possible to efficiently dissociate methane from methane hydrate and efficiently produce methane gas.

The apparatus for producing methane gas from methane hydrate according to the present invention is an apparatus for producing methane gas from methane hydrate present on the seabed or lake bottom, and is formed with an opening, and the methane hydrate is formed through the opening. Is connected to one end of the dissociation chamber, the water injection pipe for supplying water having a low methane concentration to the inside of the dissociation chamber, and one end to the dissociation chamber. And a pumping pipe for pumping water inside the dissociation chamber, the water having a low methane concentration sent from the water injection pipe is injected into the dissociation chamber, and the methane concentration inside the dissociation chamber A water jet mechanism for raising the water jet, the water jet mechanism A first injection pipe that cuts the entire ground around the distal end of the dissociation chamber by injecting water having a low methane concentration from the distal end side forming the opening toward the outside in the substantially axial direction through the opening. And agitation in the dissociation chamber while cutting the ground disposed in the dissociation chamber by injecting water having a low methane concentration from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis. And an injection pipe .

In this invention, it becomes possible to supply water with a low methane concentration to the inside of the dissociation chamber through the water injection pipe to make contact with the methane hydrate. This makes it possible to efficiently dissociate methane from this methane hydrate without changing the phase equilibrium state of temperature and pressure. Also, since dissociated methane dissolves in the water inside the dissociation chamber, when this water is pumped through the pumping pipe, it rises to a certain depth and the dissolved methane gasifies and automatically dissociates from the water. It will self-eject. For this reason, water and methane gas can be easily separated to produce (recover) methane gas.
Further, in the present invention, water having a low methane concentration sent to the dissociation chamber is jetted substantially outward in the axial direction through the opening from the tip side forming the opening of the dissociation chamber by the water jet mechanism. Accordingly, for example, the ground on the methane hydrate can be cut and removed by the sprayed water, and the dissociation chamber can be suitably installed by penetrating the tip portion into the methane hydrate.
Also, for example, methane hydrate disposed inside the dissociation chamber by injecting water with low methane concentration sent to the dissociation chamber from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis by the water jet mechanism. It is possible to agitate the inside of the dissociation chamber while cutting and removing the upper ground. Then, by raising the muddy water inside the dissociation chamber, it becomes possible to expose the methane hydrate to face the inside of the dissociation chamber. Furthermore, methane hydrate can be dissociated more efficiently by spraying water inward with the methane hydrate exposed and stirring the inside of the dissociation chamber.

  In the apparatus for producing methane gas from methane hydrate of the present invention, in the state where the dissociation chamber is installed so that the methane hydrate faces the inside through the opening, seawater in shallow water from the other end of the water injection pipe Alternatively, it is desirable that the lake water is sucked and seawater or lake water having a low methane concentration in the shallow water area is supplied into the dissociation chamber.

  In the present invention, shallow water or lake water is sucked from the other end of the water injection pipe, and the sucked sea water or lake water is supplied into the dissociation chamber through the water injection pipe. Thereby, it becomes possible to supply water with low methane concentration into the dissociation chamber using seawater or lake water. In addition, the seawater or lake water inside the dissociation chamber is pumped through the pumping pipe to produce methane gas, and the seawater or lake water in the shallow water area is automatically sucked from the other end of the water injection pipe, and the methane concentration inside the dissociation chamber It is possible to supply seawater or lake water in a shallow shallow water area. Thereby, it becomes possible to efficiently produce (recover) methane gas by pumping seawater or lake water inside the dissociation chamber through the pumping pipe.

  Furthermore, in the methane gas production apparatus from methane hydrate of the present invention, the water injection pipe is an outer pipe, the water pumping pipe is an inner pipe, and the water injection pipe and the water pumping pipe are configured in a double pipe structure, A strainer for sucking seawater or lake water in the shallow water area and supplying it to the inside of the dissociation chamber may be provided on the other end side of the water injection pipe.

  In this invention, the seawater or lake water inside the dissociation chamber is pumped through the pumping pipe, and the seawater or lake water in the shallow water area with low methane concentration is automatically sucked into the water feeding pipe from the strainer provided at the other end of the water pouring pipe. Can be supplied to the inside of the dissociation chamber. Thereby, it becomes possible to efficiently produce (recover) methane gas by pumping seawater or lake water inside the dissociation chamber through the pumping pipe.

  Furthermore, in the apparatus for producing methane gas from methane hydrate according to the present invention, the water jet mechanism includes a plurality of the first injection pipes and the second injection pipes, respectively, and the first injection is provided in a circumferential direction of the dissociation chamber. It is further desirable that the tube and the second injection tube are alternately arranged.

  In this invention, since the plurality of first injection pipes and the second injection pipes are alternately arranged in the circumferential direction of the dissociation chamber, for example, around the tip of the dissociation chamber by water sprayed from the plurality of first injection pipes By cutting and removing the entire ground, it is possible to evenly penetrate the entire tip of the dissociation chamber into the methane hydrate. In addition, the water sprayed from the plurality of second spray pipes can reliably remove, for example, the ground disposed inside the dissociation chamber and can be stirred inside the dissociation chamber, thereby ensuring methane hydrate. It is possible to expose the inside of the dissociation chamber. Thereby, it becomes possible to dissociate methane hydrate more efficiently.

  According to the method for producing methane gas from methane hydrate and the apparatus for producing methane gas according to the present invention, by supplying water having a low methane concentration into the dissociation chamber and bringing it into contact with methane hydrate, the phase equilibrium state of temperature and pressure can be changed. Without changing, methane can be efficiently dissociated from methane hydrate. In addition, by pumping the water inside the dissociation chamber, methane dissolved in this water is gasified and automatically dissociates and self-injects, so water and methane gas are easily separated and produced (recovered). It becomes possible.

  In this way, methane can be dissociated from methane hydrate and methane gas can be produced (recovered) simply by bringing water having a low methane concentration into contact with methane hydrate only in the dissociation chamber and pumping water. For this reason, it becomes possible to reduce the influence which it has on the ecosystem and global environment of a seabed and a lake bottom compared with the method of producing methane gas from methane hydrate by heating conventionally.

  In addition, since methane dissociation from methane hydrate occurs only within the dissociation chamber, the amount of dissociation can be controlled easily, and methane gas can be produced while preventing unexpected methane gas leakage. It becomes possible to do.

  Hereinafter, a method for producing methane gas from methane hydrate and a methane gas production apparatus according to a first embodiment of the present invention will be described with reference to FIG. The present embodiment relates to a method for producing methane gas from methane hydrate present on the seabed (or lake bottom) and a methane gas production apparatus used therefor, and in particular, a methane gas production method and methane gas capable of suitably producing methane gas from surface methane hydrate. It relates to production equipment.

  The methane gas production apparatus A from methane hydrate of this embodiment can attach and detach the methane gas recovery ship 1, the dissociation chamber 3 for dissociating methane from the methane hydrate 2, and the dissociation chamber 3 as shown in FIG. A float 4 for towing in a floating state supported by the methane gas recovery vessel 1, a water injection pipe 5 for supplying water having a low methane concentration (shallow seawater W) into the dissociation chamber 3, and a dissociation chamber 3 is provided with a pumping pipe 6 for pumping water W ′ inside 3, a gas separator 7, and a pumping pump (not shown).

  The dissociation chamber 3 is formed in a substantially cylindrical shape, closed at the upper end, and provided with an opening 3a at the lower end. Further, on the upper end side, a water injection port 3b to which one end of the water injection tube 5 is connected and a water supply port 3c to which one end of the water supply tube 6 is connected are provided. Further, in the dissociation chamber 3, one end of a wire 8 wound around a wire drum of the methane gas recovery ship 1 is connected to the upper end. When towing by the methane gas recovery ship 1, the upper end side is detachably connected to the float 4 and is towed in a floating state. Further, when producing methane gas (at the time of methane gas recovery), the methane gas is separated from the float 4, and the wire 8 is fed out from the wire drum of the methane gas recovery ship 1 and is lowered to the seabed 9. At this time, the dissociation chamber 3 is installed so that the lower end side penetrates into the ground G of the seabed 9 and the surface type methane hydrate 2 faces the inside through the opening 3a.

  A rigid polyethylene pipe is used for each of the water injection pipe 5 and the pumping pipe 6, and the water injection pipe 5 has a length in which the other end is located in a shallow water area in a state where the dissociation chamber 3 is installed at a predetermined position on the seabed 9. It is formed with. The water injection pipe 5 is provided with an on-off valve. On the other hand, the pumping pipe 6 is formed with such a length that the other end is located above the seawater surface 10, and the other end is connected to the gas separator 7. The pumping pipe 6 is provided by being connected to a pumping pump via a gas separator 7 and is provided with an on-off valve. Then, by opening the open / close valve of the pumping pipe 6 and driving the pump, the seawater (water W ′) inside the dissociation chamber 3 flows through the pumping pipe 6 toward the gas separator 7 and is pumped. The

  The gas separator 7 separates the seawater W (W ′) and the methane gas M inside the dissociation chamber 3 pumped from the pumping pipe 6, drains the seawater W into the sea, and a tank (not shown) for the recovered methane gas M It is configured to send to etc.

  Next, a method for producing (recovering) methane gas M from the surface methane hydrate 2 on the seabed 9 using the methane gas production apparatus A having the above-described configuration will be described, and a method for producing methane gas from methane hydrate according to the present embodiment and The operation and effect of the methane gas production apparatus A will be described.

  First, the dissociation chamber 3 attached to the float 4 and floated is towed by the methane gas recovery ship 1 and placed at a predetermined position. Next, one end of the water injection pipe 5 is connected to the water injection port 3b of the dissociation chamber 3, and one end of the water pumping pipe 6 is connected to the water pumping port 3c, and the other end of the water pumping pipe 6 is connected to the gas separator 7, and the dissociation chamber 3 is floated. Remove from 4.

  Then, the wire 8 is fed from the wire drum of the methane gas recovery ship 1 and the dissociation chamber 3 is lowered, and the dissociation chamber 3 is installed with the lower end side penetrating into the ground G of the seabed 9. Thereby, the dissociation chamber 3 is installed so that the surface type methane hydrate 2 may face the inside through the opening 3a. In addition, at the stage where the dissociation chamber 3 is installed at a predetermined position, the other end of the water injection pipe 5 is arranged in a shallow water area, and the other end connected to the gas separator 7 of the pumping pipe 6 is arranged above the seawater surface 10. .

  At the stage where the dissociation chamber 3 is thus installed, the open / close valves of the water injection pipe 5 and the pumping pipe 6 are opened. Then, the pump is driven to pump the seawater W ′ inside the dissociation chamber 3 through the pumping pipe 6. When pumping is performed in this manner, seawater W in the shallow water area is sucked into the water injection pipe 5 from the other end of the water injection pipe 5, and this seawater W is automatically supplied into the dissociation chamber 3.

  Here, it is known that the surface layer type methane hydrate 2 starts to be produced when methane is first dissolved in seawater and the methane concentration of the seawater becomes saturated. For this reason, the seawater around the surface methane hydrate 2 (seawater near the seabed 9) has a very high methane concentration, and thus the methane concentration in the surrounding seawater is extremely high. Hydrate 2 exists in a stable state.

  In the present embodiment, the shallow seawater W having a low methane concentration is supplied into the dissociation chamber 3 to dissociate methane from the surface methane hydrate 2. That is, the seawater W having a low methane concentration is brought into contact with the surface methane hydrate 2 instead of changing the phase equilibrium state of temperature and pressure by applying heat or reducing pressure as in the conventional methane gas production method. Thus, methane is dissociated from the surface type methane hydrate 2. At this time, the seawater W in the shallow water area is supplied into the dissociation chamber 3, and the dissociation of methane from the surface methane hydrate is promoted by mixing and stirring the surface methane hydrate 2 and the seawater W. Is done. The dissociated methane is dissolved in the seawater W inside the dissociation chamber 3 having a low methane concentration because the pressure near the bottom of the sea is high.

  Thus, the seawater W ′ in which methane is dissolved is pumped from the dissociation chamber 3 through the pumping pipe 6. At this time, when the seawater W ′ rises to a certain depth, methane dissolved in the seawater W ′ is gasified and self-injected, and is automatically dissociated from the seawater W ′ and guided to the gas separator 7 on the seawater surface 10. Thereby, the seawater W and the methane gas M are easily separated by the gas separator 7, the seawater W is discharged into the sea, and the methane gas M is collected in a tank or the like.

  Then, as described above, the seawater W having a low methane concentration in the shallow water area is sequentially supplied to the dissociation chamber 3 along with the driving of the pump, and the seawater W ′ from the dissociation chamber 3 is sequentially pumped, whereby the surface methane hydrate 2 Methane gas M will be produced sequentially.

  Therefore, in the method for producing methane gas from methane hydrate and the methane gas production apparatus A according to the present embodiment, the seawater W in the shallow water area having a low methane concentration is supplied into the dissociation chamber 3 and brought into contact with the surface methane hydrate 2. This makes it possible to efficiently dissociate methane from the surface methane hydrate 2 without changing the phase equilibrium state of temperature and pressure.

  At this time, since methane dissociates from the surface type methane hydrate 2 under a high-pressure environment at the seabed 9, it dissociates from the surface type methane hydrate 2 and dissolves in the sea water W inside the dissociation chamber 3. Then, the seawater W ′ inside the dissociation chamber 3 is pumped up and rises to a certain depth, and the dissolved methane is gasified and self-injected. Therefore, the methane gas M can be automatically separated from the seawater W ′. The seawater W and the methane gas M can be easily separated and the methane gas M can be produced (recovered).

  In this way, the seawater W having a low methane concentration is brought into contact with the surface type methane hydrate 2 only in the dissociation chamber 3 and pumped up to dissociate the methane from the surface type methane hydrate 2 to produce methane gas M. it can. For this reason, compared with the method of heating and producing methane gas M from methane hydrate 2 like the past, it becomes possible to reduce the influence which it has on the ecosystem and global environment of the seabed 9.

  Moreover, since dissociation of methane from the surface type methane hydrate 2 occurs only within the dissociation chamber 3, it is easy to control the amount of dissociation and prevent unexpected methane gas M leakage. However, it becomes possible to produce methane gas M.

  Furthermore, in this embodiment, by supplying the seawater W in the shallow water area to the inside of the dissociation chamber 3, it becomes possible to supply the water having a low methane concentration to the inside of the dissociation chamber 3 using the seawater W. . This makes it possible to efficiently dissociate methane from the surface layer type methane hydrate 2 and to efficiently produce methane gas M.

  As mentioned above, although 1st Embodiment of the methane gas production method and methane gas production apparatus from the methane hydrate which concerns on this invention was described, this invention is not limited to said 1st Embodiment, It does not deviate from the meaning. The range can be changed as appropriate. For example, in the first embodiment, the water injection pipe 5 and the pumping pipe 6 are individually connected to the dissociation chamber 3, and the seawater W having a low methane concentration in the shallow water region from the other end of the water injection pipe 5 is introduced into the dissociation chamber 3. The seawater W ′ in which the methane in the dissociation chamber 3 was dissolved was pumped up by the pumping pipe 6. On the other hand, for example, as shown in FIG. 2, the water injection pipe 5 and the water pumping pipe 6 are constituted by a double pipe structure, and the water injection pipe 5 of the outer pipe and the water pumping pipe 6 of the inner pipe communicate with the inside of the dissociation chamber 3. You may make it connect as it does. Further, the other end of the pumping pipe 6 is connected to the gas separator 7, and a strainer 11 is provided at the other end of the water injection pipe 5 disposed in the shallow water area with the dissociation chamber 3 installed at a predetermined position on the seabed 9, and further opened and closed. A valve 12 is provided. And when comprised in this way, while opening the on-off valve 12, while driving the pumping pump 13 connected with the other end of the pumping pipe 6 via the gas separator 7, the inside of the dissociation chamber 3 through the pumping pipe 6 is driven. Seawater W ′ is pumped and seawater W having a low methane concentration in the shallow water region is circulated between the outer water injection pipe 5 and the inner water pumping pipe 6 through the strainer 12 and supplied into the dissociation chamber 3. Thereby, seawater W having a low methane concentration is supplied into the dissociation chamber 3 and methane is dissociated from the surface methane hydrate 2. Therefore, the dissociated methane is dissolved in the seawater W in the dissociation chamber 3 and the seawater W ′ is sequentially pumped up by the pumping pipe 6 so that the methane gas M can be produced (recovered) as in the present embodiment. become.

  In the first embodiment, the methane gas M is produced from the surface layer methane hydrate 2 on the seabed 9. However, even when the methane gas M is produced from the surface layer methane hydrate 2 on the lake bottom, The methane gas M can be efficiently produced in the same manner as in the embodiment. Further, if the deep layer methane hydrate can be exposed to seawater and lake water by appropriate means, and the seawater and lake water in the dissociation chamber 3 can be brought into contact with the deep layer methane hydrate, the deep layer methane hydrate is used. In order to produce methane gas M from the present invention, the present invention may be applied.

  Next, a method for producing methane gas from methane hydrate and a methane gas production apparatus according to a second embodiment of the present invention will be described with reference to FIGS.

  The methane gas production apparatus B from methane hydrate of this embodiment can attach and detach the methane gas recovery ship 1, the dissociation chamber 20 for dissociating methane from the methane hydrate 2, and the dissociation chamber 20 as shown in FIG. A float 4 for towing in a floating state supported by the methane gas recovery vessel 1, a water injection pipe 5 for supplying water with a low methane concentration (shallow seawater W) into the dissociation chamber 20, and a dissociation chamber The water pump 6 for pumping water W ′ inside 20, a gas separator 7, a water pump 21, and a water pump 22 are provided.

  4 to 6, the dissociation chamber 20 of the present embodiment has a substantially cylindrical shape with the upper end (rear end 23a) closed and the lower end (front end 23b) provided with an opening 23c. A water jet mechanism 24 is integrally provided inside the main body 23. The chamber body 23 is formed with an annular first chamber 23d and a second chamber 23e that are partitioned from each other on the upper end side. The chamber main body 23 has one end of the water injection pipe 5 formed by bifurcating one end of the pipe 5a connected to the first chamber 23d and the other end of the branch pipe 5b connected to the second chamber 23e. The water injection pipe 5 is connected.

  On the other hand, the water jet mechanism 24 includes a plurality of first injection tubes 24a and second injection tubes 24b. The first injection tubes 24a and the second injection tubes 24b are arranged in the circumferential direction of the chamber body 23 (dissociation chamber 20). They are arranged alternately with a predetermined interval.

  Each of the first injection pipe 24a and the second injection pipe 24b is supported by an adapter 25 fixed to the inner surface of the chamber main body 23 (dissociation chamber 20), and the tip forms an opening 23c of the chamber main body 23. It is arranged near the lower end (front end portion 23b), and extends toward the upper end (rear end portion 23a) side along the axis O1 direction of the dissociation chamber 20. The first injection pipe 24a is provided with its rear end connected to the first chamber 23d of the chamber body 23, and the second injection pipe 24b is provided with its rear end connected to the second chamber 23e.

  Moreover, as shown in FIG.4 and FIG.7, the 1st injection pipe 24a and the 2nd injection pipe 24b are each provided with the injection nozzle 26 at the front-end | tip. The first injection pipe 24a is supplied with shallow seawater W from the water injection pipe 5 to the first chamber 23d, and the shallow water seawater W in the first chamber 23d circulates from the injection nozzle 26 at the tip thereof. Inject seawater W in shallow water. Further, the second injection pipe 24b is supplied with shallow seawater W from the water injection pipe 5 to the second chamber 23e, and the shallow water seawater W in the second chamber 23e circulates from the injection nozzle 26 at the tip thereof. Inject seawater W in shallow water.

  At this time, as shown in FIG. 3, FIG. 4 and FIG. 7, the first injection tube 24a is substantially axially lined from the tip 23b side forming the opening 23c of the chamber body 23 (dissociation chamber 20) through the opening 23c. An injection nozzle 26 is formed so as to inject seawater W in a shallow water area toward the outer side in the O1 direction. On the other hand, in the second injection pipe 24a, the injection nozzle 26 is formed so as to inject the seawater W in the shallow water area from the inner surface side of the chamber body 23 (dissociation chamber 20) toward the inner side in the direction substantially orthogonal to the axis O1. ing.

  Next, a method for producing (recovering) methane gas from the surface layer methane hydrate on the sea floor using the methane gas production apparatus B having the above configuration will be described, and a methane gas production method and methane gas production apparatus from methane hydrate according to the present embodiment. The operation and effect of B will be described.

  When the methane gas M is produced from the surface layer type methane hydrate using the methane gas production apparatus B of the present embodiment, the dissociation chamber 20 attached to the float 4 and floated as shown in FIG. Towed by ship 1 and placed in place. Then, the water injection pipe 5 and the pumping pipe 6 are respectively connected to the dissociation chamber 20, the wire 8 is fed from the wire drum of the methane gas recovery ship 1 and the dissociation chamber 20 is lowered, and the dissociation chamber 20 is placed on the ground G of the seabed 9. Install. At this time, the dissociation chamber 20 is installed at a predetermined position on the seabed 9 by using the GPS 34 provided on the methane gas recovery ship 1, the azimuth meter 35, the transducer 36, and the transponder 37 provided on the injection pipe 5.

  Next, the one-way opening / closing valve 29 and the bidirectional opening / closing valve 30 are appropriately opened / closed and the water pump 21 is driven. When the drive of the water pump 21 is started in this way, the shallow water seawater W is taken, and the shallow water seawater W is supplied to the first chamber 23d and the second chamber 23e of the dissociation chamber 20 through the water injection pipe 5. Further, the shallow sea water W sent to the first chamber 23d and the second chamber 23e flows through the first injection pipe 24a and the second injection pipe 24b of the water jet mechanism 24, and the first injection pipe 24a and the first injection pipe 24a Each of the two injection pipes 24b is injected from the injection nozzle 26. At this time, for example, the seawater W in the shallow water area is jetted from the jet nozzles 26 of the first jet pipe 24a and the second jet pipe 24b so that the flow velocity becomes 10 m / s or more.

  In addition, the water pump 21 is driven in this manner to inject the seawater W in the shallow water area from the first injection pipe 24a and the second injection pipe 24b, and the one-way opening / closing valve 31 and the bidirectional opening / closing valve 32 are appropriately opened / closed. After that, the drive of the pumping pump 22 is started. Thereby, the pumping of the seawater W ′ inside the dissociation chamber 20 (chamber body 23) is started.

  Then, since the seawater W in the shallow water area is jetted from the distal end portion 23b side of the chamber body 23 toward the outside in the axis O1 direction by the first jet pipe 24a, the ground on the methane hydrate 2 by the jetted seawater W. G1 (G) is removed by cutting. Thereby, the dissociation chamber 20 is installed in a suitable state in which the tip 23b is gradually penetrated into the methane hydrate 2 and the tip 23d is penetrated into the methane hydrate 2.

  At the same time, the seawater W in the shallow water area is jetted from the inner surface side of the dissociation chamber 20 (chamber body portion 23) toward the inner side in the direction substantially perpendicular to the axis O1 by the second jet pipe 24b. The ground G1 on the methane hydrate 2 disposed in the dissociation chamber 20 is removed by cutting. Further, the ground G1 is cut and removed by the seawater W ejected from the second ejection pipe 24b, and the seawater W 'inside the dissociation chamber 20 is agitated. As a result, the muddy water W ″ is pumped up by the pumping pump 22 to surely remove the ground G1, and the methane hydrate 2 is exposed so as to face the inside of the dissociation chamber 20.

  Further, in the state where the ground G1 is cut and removed so that the methane hydrate 2 is exposed, the seawater W is further injected from the second injection pipe 24b to cut the methane hydrate 2 and to remove the inside of the dissociation chamber 20. By stirring the seawater W ′, the methane hydrate 2 is efficiently dissociated, and methane is dissolved in the seawater W ′ in the dissociation chamber 20.

  And when seawater W 'which melt | dissolved methane in this way is pumped up from the dissociation chamber 3 through the pumping pipe 6, like seawater W' will rise to a certain depth like 1st Embodiment, it will be in this seawater W ' The dissolved methane is gasified and self-injected, and is automatically dissociated from the seawater W ′ and guided to the gas separator 7 on the seawater surface 10. Thereby, the seawater W and the methane gas M are easily separated in the separator tank 7a of the gas separator 7, and the methane gas M is recovered.

  Moreover, in this embodiment, since the 1st injection pipe 24a and the 2nd injection pipe 24b are alternately arrange | positioned in the circumferential direction of the chamber main-body part 23, by the seawater W injected from the some 1st injection pipe 24a, The entire ground G1 around the distal end portion 23b of the dissociation chamber 20 is surely cut and removed, and the entire distal end portion 23b of the dissociation chamber 20 is reliably penetrated into the methane hydrate 2. Further, the ground G1 disposed inside the dissociation chamber 20 is surely cut and removed by the seawater W ejected from the plurality of second injection pipes 24b, and is stirred inside the dissociation chamber 20, so that the methane hydrate 2 is surely obtained. Exposed to the inside of the dissociation chamber. Thereby, since the methane hydrate 2 dissociates more efficiently, the methane gas M is efficiently recovered.

  Here, mud water W ″ is introduced into the separator tank 7a of the gas separator 7 by first cutting and removing the ground G1 with the second injection pipe 24b. And if the density | concentration of the methane gas contained in this muddy water W '' is measured sequentially, a methane gas density | concentration will rise gradually. Further, when the ground G1 on the methane hydrate 2 is cut off and the methane hydrate 2 is exposed, the concentration of methane gas is stabilized at a high concentration. For this reason, by sequentially measuring the concentration of the methane gas separated in the separator tank 7a, it is possible to grasp the state of cutting and removing the ground G1, and thus the exposed state of the methane hydrate 2.

  The muddy water W ″ after separation of the methane gas in the separator tank 7a is returned to the vicinity of the seabed 9 by the drainage pump 33 in consideration of the natural environment. Further, when producing the methane gas M as described above, it is desirable to use a polyethylene pipe having high ring rigidity and flexibility in the axial direction as the water injection pipe 5 and the pumping pipe 6. By using the pumping pipe 6 with a margin in length, it is possible to suitably produce the methane gas M while reliably removing the ground G1 as described above.

  Therefore, according to the methane gas production method from methane hydrate and the methane gas production apparatus B from methane hydrate according to the present embodiment, it is possible to obtain the same effects as those of the first embodiment, and the water jet mechanism 24. By injecting shallow seawater W (water with low methane concentration) sent to the dissociation chamber 20 from the front end portion 23b side of the dissociation chamber 20 toward the outside in the direction of the axis O1 by the first injection pipe 24a, methane The ground sea G1 on the hydrate 2 can be cut and removed by the seawater W sprayed, and the dissociation chamber 2 can be suitably installed by penetrating the tip 23b into the methane hydrate 2.

  In addition, the seawater W in the shallow water area sent to the dissociation chamber 20 is ejected from the inner surface side of the dissociation chamber 20 toward the inner side in the direction substantially perpendicular to the axis O1 by the second ejection pipe 24b of the water jet mechanism 24, thereby dissociating the chamber. The ground G <b> 1 on the methane hydrate 2 disposed inside 20 can be removed by cutting and can be stirred inside the dissociation chamber 20. Then, by raising the muddy water W ″ inside the dissociation chamber 20, the methane hydrate 2 can be exposed so as to face the inside of the dissociation chamber 20. Furthermore, with the methane hydrate 2 exposed, the seawater W is jetted inward and the inside of the dissociation chamber 20 is stirred, so that the methane hydrate 2 can be dissociated more efficiently. .

  Furthermore, since the plurality of first injection tubes 24a and the second injection tubes 24b are alternately arranged in the circumferential direction of the dissociation chamber 20, the tip of the dissociation chamber 20 is caused by seawater W injected from the plurality of first injection tubes 24a. The ground G1 around the portion 23b can be removed by cutting, and the entire tip 23b of the dissociation chamber 20 can be evenly penetrated into the methane hydrate 2. In addition, the seawater W injected from the plurality of second injection pipes 24b can surely cut and remove the ground G1 disposed inside the dissociation chamber 20, and can also be stirred inside the dissociation chamber 20. It becomes possible to reliably expose the hydrate 2 to the inside of the dissociation chamber 20. Thereby, it becomes possible to dissociate methane hydrate 2 more efficiently.

As mentioned above, although 2nd Embodiment of the methane gas production method and methane gas production apparatus from the methane hydrate concerning this invention was described, this invention is not limited to said 2nd Embodiment, 1st Embodiment is used. Modifications can be made as appropriate without departing from the spirit of the present invention.

It is a figure which shows the methane gas production apparatus and methane gas production method from the methane hydrate which concern on 1st Embodiment of this invention. It is a figure which shows the modification of the methane gas production apparatus from the methane hydrate and methane gas production method which concern on 1st Embodiment of this invention. It is a figure which shows the methane gas production apparatus and methane gas production method from the methane hydrate which concern on 2nd Embodiment of this invention. It is a figure which shows the dissociation chamber (water jet mechanism) of the methane gas production apparatus from the methane hydrate which concerns on 2nd Embodiment of this invention. It is a X1-X1 line arrow directional view of FIG. FIG. 5 is a view taken along line X2-X2 in FIG. 4. It is a figure which shows the injection nozzle of the water jet mechanism of the methane gas production apparatus from the methane hydrate which concerns on 2nd Embodiment of this invention. It is a figure which shows the phase equilibrium conditions of the temperature and pressure of methane hydrate.

Explanation of symbols

1 Methane gas recovery vessel 2 Methane hydrate (surface type methane hydrate)
3 Dissociation chamber 3a Opening 3b Water inlet 3c Water inlet 4 Float 5 Water inlet 6 Water pump 7 Gas separator 7a Separator tank 8 Wire 9 Sea bottom (lake bottom)
10 Seawater surface (Lake surface)
DESCRIPTION OF SYMBOLS 11 Strainer 12 On-off valve 13 Water pump 20 Dissociation chamber 21 Water pump 22 Water pump 23 Chamber body part 23a Upper end (rear end part)
23b Lower end (tip)
23c Opening 23d First chamber 23e Second chamber 24 Water jet mechanism 24a First injection tube 24b Second injection tube 25 Adapter 26 Injection nozzle 29 One-way on-off valve 30 Bidirectional on-off valve 31 One-way on-off valve 32 Bidirectional on-off valve 33 Drainage pump 34 GPS
35 Azimuth meter 36 Transducer 37 Transponder A Methane gas production device B Methane gas production device G Ground G1 Ground O1 Axis W Shallow water (water with low methane concentration)
W 'Seawater with dissolved methane (Water with dissolved methane)
W '' muddy water

Claims (6)

A method for producing methane gas from methane hydrate present on the seabed or lake bottom,
A dissociation chamber formed with an opening is installed so that the methane hydrate faces the dissociation chamber through the opening,
Supplying water having a low methane concentration into the dissociation chamber to dissociate methane from the methane hydrate,
Pumping the water inside the dissociation chamber in which methane is dissolved ,
A water jet mechanism is provided in the dissociation chamber;
By the water jet mechanism, the water having a low methane concentration sent to the dissociation chamber is jetted from the tip side forming the opening of the dissociation chamber toward the outside in the substantially axial direction through the opening. Cutting the entire ground around the tip of the dissociation chamber, and spraying from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis line, while cutting the ground disposed inside the dissociation chamber A method for producing methane gas from methane hydrate , which is stirred inside to increase the methane concentration . The method for producing methane gas from methane hydrate according to claim 1,
A method for producing methane gas from methane hydrate, wherein seawater or lake water in shallow water is supplied into the dissociation chamber. An apparatus for producing methane gas from methane hydrate present on the seabed or lake bottom,
A dissociation chamber that is formed with an opening, and is disposed so that the methane hydrate faces the inside through the opening, and one end of the dissociation chamber is connected to the dissociation chamber, and water having a low methane concentration is placed inside the dissociation chamber. A water injection pipe for supplying and one end connected to the dissociation chamber, and a pumping pipe for pumping water inside the dissociation chamber,
The dissociation chamber is provided with a water jet mechanism for injecting water having a low methane concentration sent from the water injection pipe and increasing the methane concentration inside the dissociation chamber,
The water jet mechanism is configured to inject water having a low methane concentration from the tip side forming the opening of the dissociation chamber toward the outside in the substantially axial direction through the opening, thereby surrounding the tip of the dissociation chamber. A first injection pipe for cutting the entire ground of
A second injection pipe that stirs the ground while cutting the ground disposed inside the dissociation chamber by injecting water having a low methane concentration from the inner surface side of the dissociation chamber toward the inner side in the direction substantially perpendicular to the axis. An apparatus for producing methane gas from methane hydrate, comprising: In the methane gas production apparatus from the methane hydrate according to claim 3,
In a state where the dissociation chamber is installed so that the methane hydrate faces the inside through the opening, seawater or lake water is drawn from the other end of the water injection pipe, and seawater or methane concentration in the shallow water area is low. An apparatus for producing methane gas from methane hydrate, wherein the apparatus is configured to supply lake water into the dissociation chamber . The apparatus for producing methane gas from methane hydrate according to claim 4,
The water injection pipe is an outer pipe, the water pumping pipe is an inner pipe, the water injection pipe and the water pumping pipe are configured in a double pipe structure, and the other end side of the water injection pipe is seawater or lake water in the shallow water area. methane gas production equipment from methane hydrate, wherein the strainer to be supplied to the interior of the dissociation chamber by inhaling has been found provided. In the methane gas production apparatus from the methane hydrate according to any one of claims 3 to 5 ,
The water jet mechanism includes a plurality of the first injection pipes and the second injection pipes,
An apparatus for producing methane gas from methane hydrate , wherein the first injection pipe and the second injection pipe are alternately arranged in a circumferential direction of the dissociation chamber .

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