JP6140238B2 - Gas recovery apparatus and gas recovery method from bottom methane hydrate - Google Patents

Description

  The present invention relates to a gas recovery apparatus for recovering a gas mainly containing methane from methane hydrate present on the bottom of the sea such as a seabed or a lake bottom, and a gas recovery method from the bottom methane hydrate.

Conventionally, when recovering methane hydrate in the bottom of the water, an apparatus and a method for decomposing the methane hydrate in the bottom of the water near the bottom of the water to convert it into methane gas and recovering the methane gas on the sea surface are provided. (Patent Document 1).
Moreover, the apparatus and method which make methane hydrate into a slurry state and extract on the sea surface are provided (patent document 2).

JP 2006-46009 A JP 2014-201875 A

  In the technique of Patent Document 1, since methane hydrate in the bottom of the water is decomposed near the bottom of the water, the thermal energy supplied for the decomposition becomes excessive, and there is a problem of increasing costs.

In the technology of Patent Document 2, the bottom of the water is excavated and the methane hydrate is made into a slurry state and the inside of the long pipe is taken up to the sea surface. In addition to the methane hydrate, the bottom of the earth also contains sediment, mud and gravel. include. The proportion of methane hydrate in the methane hydrate layer at the bottom of the water is about 10% to 30%, and a lot of earth and sand is pulled up to the surface of the sea, so that costs for processing or disposal of the earth and sand are required.
In addition, since the temperature and pressure of the seawater from the depth of 400m become the decomposition side in the phase equilibrium of methane hydrate, the methane hydrate in the slurry state is lifted up to the sea surface while being decomposed, and the yield is stable. It was difficult to control. As a result, there is a problem that it is difficult to improve the recovery efficiency of methane gas (including gas whose main component is methane).

  In view of the above problems, an object of the present invention is to improve gas recovery efficiency or cost efficiency when recovering gas from methane hydrate in the bottom of water.

  In order to solve the above problems, a gas recovery apparatus according to a first aspect of the present invention is a gas recovery apparatus that gasifies and recovers methane hydrate in the bottom of a water, and includes a slurry containing the methane hydrate in a room. A mixed slurry containing a first chamber body capable of containing water, an underwater holding mechanism for positioning the first chamber body in water, and the methane hydrate and bottom sediment in the bottom of the first chamber. A slurry introduction part for sending a slurry, a gas extraction part from the first chamber body, and a slurry outlet part for sending a sediment slurry mainly containing a bottom sediment from the first chamber body to the bottom. .

  Here, the “water bottom” means a bottom portion of a place where water is present. Further, “methane hydrate” mainly includes methane, and includes those that include other hydrocarbon gas (for example, ethane, propane, etc.) that occur in nature.

According to this aspect, the first chamber body containing the slurry containing methane hydrate (mixed slurry) is positioned at a pressure at which the methane hydrate decomposes and at a water depth, thereby decomposing the indoor methane hydrate. The gas can be gasified, and the gas can be taken out from the first chamber and recovered.
At this time, the sediment slurry containing the bottom sediment remaining after gasifying the methane hydrate is returned from the water in which the first chamber body is located to the bottom, so that the “bottom sediment” and “methane” “Bottom water including hydrate decomposition water” cannot be raised. That is, it is not necessary to treat the bottom sediment and the water at the bottom (including the decomposed water) on the water.

Moreover, it is possible to return the sediment slurry pulled up to the water bottom to the water bottom with less energy than when returning it to the water bottom. Therefore, it is possible to reduce the cost of processing the bottom sediment collected accompanying the gas recovery from the bottom methane hydrate.
In addition, when sending the sediment slurry to the bottom of the water, by sending the methane hydrate layer on the bottom of the bottom to a mixed slurry by excavation or the like and sending it to a region away from the recovery region, the working efficiency in the recovery region is improved. can do.

  Further, the mixed slurry is lifted up to the position of the first chamber body in water, and is not lifted up to the water surface. Therefore, it is possible to reduce the cost for the extraction of the mixed slurry and to make the extraction unstable due to decomposition during the extraction (particularly near the water surface where water pressure and temperature are the decomposition conditions of methane hydrate). Can be reduced. Thereby, the collection | recovery efficiency of the methane gas from a bottom methane hydrate can be improved.

  The gas recovery apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, the gas recovery apparatus includes a pressure adjusting unit that adjusts the pressure in the chamber of the first chamber body.

According to this aspect, since the pressure inside the first chamber body can be adjusted by the pressure adjusting unit, for example, a state where a gas-liquid interface exists in the room can be stably maintained. As a result, stable decomposition can be realized, and the gas and water generated by the decomposition of methane hydrate are separated at the gas-liquid interface, so that the gas can be easily separated and collected from the first chamber. be able to.
In addition, by adjusting the interior of the chamber to be lower than the water pressure at the depth at which the first chamber body is located, the slurry introduction unit can reduce the energy required to send the mixed slurry from the water bottom into the chamber.

The gas recovery apparatus according to a third aspect of the present invention is the gas recovery device according to the second aspect, wherein the gas extraction unit includes an extraction line for sending the gas extracted from the room to a recovery destination, and the pressure adjusting unit is connected to the extraction line. It is provided, It is characterized by the above-mentioned.
Here, the “recovery destination” is used to include storage facilities such as a tank that stores gas and gas fuel utilization facilities such as a gas turbine that uses the gas as fuel.

  According to this aspect, since the pressure adjusting unit is provided in the take-out line that sends the gas taken out from the room to the collection destination, the pressure in the first chamber increased by the gas generated by decomposition of methane hydrate. Can be easily sent to the collection destination using a relief valve or the like.

  A gas recovery device according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, a heating unit that heats water in the first chamber is provided.

  According to this aspect, since the heating unit that heats the water in the first chamber is provided, methane hydrate can be decomposed in the first chamber with high efficiency. It is also possible to decompose the methane hydrate by placing the first chamber body at a pressure at which the methane hydrate does not decompose and at a water depth of water temperature. This increases the degree of freedom of installation conditions of the first chamber body in water.

  The gas recovery device according to a fifth aspect of the present invention is the gas recovery device according to any one of the first to fourth aspects, wherein the slurry introduction unit adjusts the amount of the mixed slurry to be sent to the first chamber body. An amount adjustment unit is provided.

  According to this aspect, since the introduction amount of the mixed slurry is adjusted by the introduction amount adjusting unit and sent into the first chamber, decomposition of methane hydrate in the first chamber can be performed stably.

  A gas recovery device according to a sixth aspect of the present invention is the gas recovery apparatus according to any one of the first to fifth aspects, wherein the underwater holding mechanism section includes a position adjustment mechanism that changes a water depth position of the first chamber body. It is characterized by that.

  According to this aspect, the water depth position of the first chamber body can be changed according to outdoor conditions such as the temperature condition of the water area and the state of the water flow, or indoor conditions such as the decomposition rate of methane hydrate. . Thus, efficient gas recovery can be performed by the gas recovery device.

  The method for recovering gas from bottom methane hydrate according to the seventh aspect of the present invention provides a first feed for feeding a mixed slurry containing methane hydrate and bottom sediment in the bottom into a first chamber located in the water. A step, a decomposition step of decomposing methane hydrate in the first chamber, a gas recovery step of taking out and recovering the gas generated in the decomposition step from the first chamber, and a bottom sediment mainly from the first chamber And a second feeding step for feeding the bottom sediment slurry containing the water bottom to the bottom.

  According to this aspect, there exists an effect similar to the effect in the gas recovery apparatus of a 1st aspect.

  The method for recovering gas from bottom methane hydrate according to an eighth aspect of the present invention is the seventh aspect, wherein the bottom for sending the deposit slurry in the second feeding step is the bottom for the first feeding step. It is the bottom of the water outside the methane hydrate recovery area.

When deposit slurry collected after gasifying methane hydrate in the first chamber is sent to the bottom methane hydrate recovery region, the returned bottom sediment is sent again to the first chamber together with methane hydrate. There is a risk of it. Moreover, since the ratio of the bottom sediment in the said collection | recovery area | region increases, the methane hydrate content rate in the mixed slurry sent to the said 1st chamber body becomes low, and gas recovery efficiency falls.
According to this aspect, the sediment slurry that accumulates after gasifying methane hydrate in the first chamber is returned to the outside of the region for recovering the bottom methane hydrate, so that the bottom methane hydrate is efficiently removed from the first chamber. Can be sent into the body. In addition, the risk of a decrease in gas recovery rate can be reduced.

  A gas recovery method from bottom methane hydrate according to a ninth aspect of the present invention is the seventh aspect or the eighth aspect, in a state in which a pressure that creates a gas-liquid interface is applied to the interior of the first chamber body. It decomposes methane hydrate.

  According to this aspect, stable decomposition of methane hydrate in the room can be realized. Further, since the gas and water generated by the decomposition of methane hydrate are separated at the gas-liquid interface, the gas can be easily separated and collected from the first chamber.

  A gas recovery method from bottom methane hydrate according to a tenth aspect of the present invention is the ninth aspect, wherein the pressure in the interior of the first chamber body is lower than the pressure of the water depth at which the first chamber body is located. The pressure is reduced to a low pressure.

  According to this aspect, the energy required for sending the mixed slurry from the bottom of the water into the room is reduced in the first feeding step by making the room lower than the pressure of the water depth at which the first chamber body is located. be able to.

  In the gas recovery method from bottom methane hydrate according to the eleventh aspect of the present invention, in any one of the seventh aspect to the tenth aspect, the decomposition step adds heat to the water in the first chamber. It is characterized by being performed.

  According to this aspect, methane hydrate can be decomposed with high efficiency in the first chamber.

The schematic block diagram which shows an example of the gas recovery apparatus which concerns on this invention. It is a figure explaining the case where a room | chamber interior is pressure-reduced to the pressure lower than the pressure of the water depth in which a 1st chamber body is located, (A) is a figure which shows the state which made the indoor the pressure of the water depth, (B) The figure which shows the state made into pressure reduction rather than the pressure of no.

[Example 1]
<Schematic configuration of gas recovery device>
A schematic configuration of a gas recovery apparatus 10 for gasifying and recovering methane hydrate in the bottom of the water will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an example of a gas recovery apparatus according to the present invention.

In the present embodiment, as shown in FIG. 1, a case where methane gas G (hereinafter may be simply referred to as gas G) is recovered from the surface type methane hydrate layer 22 of the bottom 20 is taken as an example.
The gas recovery apparatus 10 includes a first chamber body 12 provided in water. The first chamber body 12 is configured such that a slurry containing methane hydrate H (mixed slurry 36 described later) can be placed in the chamber. In the first chamber body, methane hydrate is decomposed in the chamber. The first chamber body 12 has a pressure resistance that can withstand the pressure of the gas G obtained by decomposing the methane hydrate H in the room and the pressure of the water depth in which the first chamber body 12 is provided, and is capable of withstanding pressure reduction conditions. It is also preferable to have pressure resistance.

The gas recovery apparatus 10 is provided with an underwater holding mechanism unit 14 that positions the first chamber body 12 in the underwater 24. In the present embodiment, the underwater holding mechanism unit 14 includes a buoyancy body 16 provided in the first chamber body 12, an anchor 18 that is struck on the water bottom, and a chain 19 that connects the first chamber body 12 and the anchor 18. When the first chamber body 12 itself has sufficient buoyancy, the buoyancy body 16 may be omitted.
As another configuration of the “underwater holding mechanism”, for example, instead of the chain 19 that connects the first chamber body 12 and the anchor 18 on the bottom of the water, for example, the supporting member from above the water (including on the ship and on the ship) can be used. It is also possible to have a configuration in which the lifting of the first chamber body 12 from a predetermined water depth position is suppressed.
Alternatively, the first chamber body 12 may be configured not to have buoyancy, and the first chamber body 12 may be suspended from the water by a wire, a chain, or the like.

A gas extraction portion 26 from the inside of the first chamber body 12 is provided on the upper portion of the first chamber body 12. Reference numeral 28 denotes a gas G take-out port. The gas G taken out from the take-out port 28 is sent through a take-out line 30 and is collected, for example, in a gas collection ship 32 as a collection destination. As the extraction line 30, a flexible cable such as a flexible hose can be used. The collection destination of the gas G is not limited to water, but may be a storage facility such as a tank that stores the gas G, or a gas fuel utilization facility such as a gas turbine that uses the gas G as fuel.
The take-out line 30 is provided with a valve 34 as a “pressure adjusting unit” for adjusting the pressure inside the first chamber body 12. The amount of gas sent from the first chamber 12 to the gas recovery ship 32 is adjusted by adjusting the open / closed state of the valve 34 provided in the take-out line 30, and is increased by the gas G generated by decomposition of methane hydrate. The pressure in the 1st chamber body 12 which became can be adjusted easily.

  In the present embodiment, the gas recovery apparatus 10 includes a heating unit 54 that heats the water in the first chamber body 12. The configuration of the heating unit 54 will be described in detail later.

In addition, a slurry introduction unit 38 for sending a mixed slurry 36 containing methane hydrate H present in the bottom 20 and bottom sediment S such as earth and sand and gravel in the first chamber 12 is provided below the first chamber 12. Is provided.
In the present embodiment, the methane hydrate layer 22 is crushed by excavation by an excavator 44 equipped with a drill, a bucket, or the like, and the methane hydrate H and the bottom sediment S constitute the slurry introduction unit 38. Then, the mixed slurry 36 is sent into the first chamber body 12 by the lifting line 46. The first line 46 is provided with a pump 48 as an “introduction amount adjusting unit” for adjusting the amount of the mixed slurry 36 to be sent to the first chamber body 12. A plurality of buoyancy bodies 49 can be provided on the first line 46.

In addition, at the lower part of the first chamber body 12, a slurry outlet 42 including a second line 50 for sending the sediment slurry 40 mainly containing the bottom sediment S from the first chamber body 12 to the bottom of the water is provided. . The second line 50 is provided with a pump 52 as an adjusting unit that adjusts the feed amount of the deposit slurry 40.
As the first line 46 and the second line 50, a riser pipe, a flexible hose, an umbilical cable, or the like can be used.
The above is the outline of the main configuration of the gas recovery apparatus 10. Other detailed configurations will be described separately during or after the gas recovery method described below.

<About the gas recovery method>
Next, a gas recovery method performed using the gas recovery apparatus 10 will be described.
[First feeding step]
As described above, the bottom methane hydrate layer 22 is crushed by the excavator 44, and the mixed slurry 36 (mixed with the bottom water and methane hydrate H and the bottom sediment S) is the first line 46 (slurry introduction). Part 38) to the first chamber body 12.

  The first chamber body 12 can be positioned at an arbitrary depth of the water 24, but is preferably positioned at a depth of pressure and temperature at which the methane hydrate H hardly decomposes. With such a water depth, it is easy to control the decomposition of methane hydrate H by heating by the heating unit 54. The depth of pressure and temperature at which methane hydrate H does not decompose is around 400 m, although it varies depending on the water area. In the present embodiment, as an example, the first chamber body 12 is positioned at a water depth of 300 m.

[Disassembly process]
Methane hydrate H in the mixed slurry 36 is decomposed in the chamber of the first chamber body 12. By heating the water in the first chamber body 12 by the heating unit 54, the decomposition conditions of the methane hydrate H are satisfied, and the methane hydrate H can be decomposed and gasified.

It is possible to decompose the methane hydrate H by positioning the first chamber body 12 at a water depth that is a decomposition condition of the methane hydrate H, but the decomposition of the methane hydrate H is an endothermic reaction. Therefore, it is desirable to heat the water in the first chamber body 12. By performing the decomposition step by heating the water in the first chamber body 12, the decomposition step can be performed with high efficiency.
In the water 24 in which the first chamber body 12 is located, the water temperature is higher than the water bottom and the water pressure is lower. Therefore, the thermal energy required for the decomposition of methane hydrate H is less than that near the bottom 20, so that the gas recovery cost can be suppressed.

[Gas recovery process]
The gas G generated in the decomposition step in the chamber of the first chamber body 12 is extracted from the first chamber body 12 by the gas extraction unit 26 and recovered by the gas recovery ship 32.

[Second feeding step]
Here, the bottom sediment S collected together with the methane hydrate H as the mixed slurry 36 remains in the chamber of the first chamber body 12. The bottom sediment S tends to settle and deposit at the lower part of the first chamber body 12. The bottom sediment S precipitated in the first chamber body 12 is sent to the bottom 20 as a bottom sediment slurry 40 by the second line 50 (slurry outlet 42).
In addition, after the decomposition | disassembly process of methane hydrate H is started, the water of the bottom 20 collected as mixed slurry 36 and the methane hydrate H are decomposed | disassembled and produced | generated in the indoor water of the 1st chamber body 12. The decomposed water (water that formed methane hydrate) is mixed, and the decomposed water is also water in the bottom 20 that originally existed in the bottom 20.

It is desirable that the decomposition step be performed in a state in which a pressure that creates a gas-liquid interface 60 is applied to the interior of the first chamber body 12. Specifically, a pump 48 provided in the first line 46 for adjusting the feed amount of the mixed slurry 36 and a pump 52 provided in the second line 50 for adjusting the feed amount of the deposit slurry 40. By controlling the above, the gas-liquid interface 60 is formed in the room.
As a result, methane hydrate is decomposed in a state where the gas-liquid interface 60 exists in the chamber of the first chamber body 12, and stable decomposition can be realized. Moreover, since the methane gas and water produced | generated by decomposition | disassembly of methane hydrate are isolate | separated into each of the gas side and the liquid side, the separation and recovery of the decomposition | disassembly produced | generated methane gas from the 1st chamber body 12 can be performed easily.

As described above, the methane hydrate H is decomposed and gasified in the first chamber body 12, and the methane gas G is taken out and collected from the first chamber body 12, thereby obtaining the following effects.
That is, the deposit slurry 40 including the bottom sediment S remaining in the first chamber body 12 after gasifying the methane hydrate H is returned to the bottom 20 from the water 24 where the first chamber body 12 is located. The water in the vicinity of the bottom 20 including the bottom sediment S and the decomposition water of the methane hydrate H is not pulled up. In other words, it is not necessary to treat the water in the vicinity of the bottom sediment S and the bottom 20 on the water.

  Further, the deposit slurry 40 can be returned to the bottom 20 with less energy than when the mixed slurry 36 is pulled up to the water to decompose the methane hydrate H. Therefore, it is possible to reduce the cost of processing the bottom sediment S that is collected accompanying the gas recovery from the bottom methane hydrate.

In addition, since the mixed slurry 36 is taken up to the position of the first chamber body 12 in the water 24, the cost of picking up can be suppressed as compared with the case where the methane hydrate H in the bottom 20 is lifted and decomposed. In addition, it is possible to reduce the instability of the lifting due to the decomposition during the lifting (particularly near the water surface 25 where the water pressure and the water temperature are the decomposition conditions of the methane hydrate H). Thereby, the collection | recovery efficiency of the methane gas from the methane hydrate H of the water bottom 20 can be improved.
Since methane hydrate H has a specific gravity smaller than that of water, the methane hydrate H rises in the water by buoyancy without being lifted by the slurry introducing portion 38, but by using the slurry introducing portion 38, Introduction into the first chamber body 12 can be performed with high efficiency.

  When the deposit slurry 40 is sent to the bottom 20 in the second feeding step, outside the recovery region of the bottom methane hydrate H in the first feeding step (the region where the methane hydrate layer 22 is excavated by the excavator 44). It is desirable to send to a remote location.

  By this, the possibility that the bottom sediment S returned to the bottom 20 will be sent again to the first chamber body 12 together with the methane hydrate H is reduced, and the methane hydrate H can be efficiently sent to the first chamber body 12. it can. In addition, it is possible to reduce the risk of a decrease in gas recovery rate due to an increase in the proportion of the bottom sediment S contained in the mixed slurry 36 due to the bottom sediment S returned to the bottom 20, and work in the recovery region of the methane hydrate H Efficiency can be improved.

In addition, by adjusting the introduction amount of the mixed slurry 36 to be sent to the first chamber body 12 by the pump 48, the decomposition process in the first chamber body 12 can be stably performed.
Further, by stopping the pump 48, the introduction of the mixed slurry 36 into the first chamber body 12 can be quickly stopped.

<Other configuration of gas recovery device>
The underwater holding mechanism unit 14 can be provided with a “position adjustment mechanism” that changes the water depth position of the first chamber body 12.
In the present embodiment, as the “position adjusting mechanism” for changing the water depth position of the first chamber body 12, for example, a reel 62 capable of winding and pulling out the chain 19 can be provided. By changing the length of the chain 19 using the reel 62, the water depth position of the first chamber body 12 can be changed.

  Thus, the first chamber body 12 can be used in accordance with conditions outside the first chamber body 12 such as the temperature condition of the water area and the state of water flow, or conditions within the first chamber body 12 such as the decomposition rate of methane hydrate. The water depth position can be changed. Therefore, the gas G can be efficiently recovered by the gas recovery device 10.

Further, as another configuration of the “underwater holding mechanism portion” provided with the “position adjusting mechanism”, for example, the buoyancy body 16 is a ballast tank in which a liquid (usually water) can be put, and the buoyancy body 16 (ballast tank). It is also possible to change the water depth position where the first chamber body 12 is floated by adjusting the amount of ballast water put into the inside of ().
In addition, as ballast water, it is desirable to use the water of the surrounding water area in the water in which the 1st chamber body 12 is provided.

  The heating unit 54 that heats the water in the first chamber body 12 includes a circulation line 56 that circulates the heat medium, and a heat exchange unit 58 that is provided in the circulation line 56 and applies heat to the heat medium. can do. As the heat medium, water in the same water area as the underwater 24 in which the first chamber body 12 is located can be used. Of course, it is possible to use water in other water areas or a heat medium other than water.

In this embodiment, exhaust heat generated in the gas recovery ship 32 (for example, exhaust heat from a diesel engine) is used as the heat to be given to the heat medium.
By configuring the heating unit 54 in this manner, the heating of the water in the first chamber body 12 can be realized with a simple structure. Further, when the collection destination is a gas fuel utilization facility such as a gas turbine that uses methane gas as fuel, exhaust heat at the time of using the gas fuel can be utilized. In addition, when there is equipment or facility that generates exhaust heat in the vicinity other than the collection destination, the exhaust heat may be used.
The heating of the water in the first chamber body 12 is not limited to that by the circulation line 56 through which the heat medium circulates, and the water in the first chamber body 12 is directly heated by a heater or the like. You can also.
Further, since the water in the water 24 near the water surface 25 is hotter than the water near the water bottom 25, it can be configured to exchange heat with the water in the water 24 near the water surface 25.

  Since the gas recovery apparatus 10 includes the heating unit 54 that heats the water in the first chamber body 12, the methane hydrate H can be decomposed in the first chamber body 12 with high efficiency. In addition, the first chamber body 12 is positioned at a pressure at which the methane hydrate does not decompose, a water temperature depth, in other words, a water depth that reliably satisfies the methane hydrate generation conditions (for example, a water depth of 500 m), and decomposes the methane hydrate H. It is also possible to do this. At this time, by adjusting the amount of heat given to the water in the first chamber body 12 by the heating unit 54, the amount of gas decomposed and generated in the first chamber body 12 can be adjusted up or down. As described above, the provision of the heating unit 54 increases the degree of freedom of installation conditions of the first chamber body 12 in water.

[Example 2]
In Example 2, another embodiment of the gas recovery method for the bottom methane hydrate will be described. FIG. 2 is a diagram illustrating a case where the interior of the chamber is depressurized to a pressure lower than the depth of water where the first chamber body is located. FIG. 2A is a diagram illustrating a state in which the interior of the chamber is at a depth of water. 2 (B) is a diagram showing a state in which the interior is depressurized rather than the water depth.
In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the components is omitted. Moreover, the heating part 54 is abbreviate | omitted in FIG. 2 (A) and FIG. 2 (B).

  In the first embodiment, the interior of the chamber is maintained at a pressure at which the gas-liquid interface 60 is formed, and the decomposition step is performed in the first chamber body 12 with almost no change in the liquid level position [see FIG. 2 (A)]. . For example, when the first chamber body 12 is located at a depth of 300 m, the pressure inside the first chamber body 12 is adjusted to about 3 MPa.

  In Example 2, when performing a decomposition | disassembly process, the inside of the 1st chamber body 12 is pressure-reduced to a pressure lower than the pressure of the water depth in which the 1st chamber body 12 is located. In this embodiment, the room is set to 2.3 MPa.

By reducing the pressure in the first chamber body 12, the energy required for driving the pump 48 for feeding the mixed slurry 36 from the water bottom 20 into the first chamber body 12 can be reduced in the first feeding step. it can.
Note that the decompression of the interior of the first chamber body 12 can be easily performed by adjusting a valve 34 that regulates the amount of gas sent from the interior of the first chamber body 12 to the gas recovery ship 32. Is not required.

In addition, the first chamber body 12 is taken out of the first chamber body 12 by controlling the valve 34 in accordance with the liquid level gauge 66 for measuring the liquid level position in the room and the liquid level position measured by the liquid level gauge 66. A control unit 68 that adjusts the amount of gas generated can be provided.
Here, from the state in which the decomposition process is performed with the inside of the first chamber body 12 set to 3 MPa, the pump 48 (FIG. 1) on the slurry introduction unit 38 side and the pump 52 (FIG. 1) on the slurry outlet unit 42 side are performed. If the inside of the first chamber 12 is changed from 3 MPa to 2.3 MPa without adjusting the energy required for driving, the gas-liquid interface in the room may rise.

  In such a case, for example, when the inside of the first chamber body 12 is depressurized from 3 MPa to 2.3 MPa, and the gas-liquid interface reaches the position 64 shown in FIG. The amount of gas taken out from the chamber body 12 is reduced. When the hydrate H is decomposed in the first chamber body 12 with the valve 34 being throttled, the pressure in the first chamber body 12 increases. When the pressure in the room rises to 3 MPa and the gas-liquid interface reaches the position indicated by reference numeral 60 indicated by a dotted line in FIG. 2B, the valve 34 is opened and the pressure is reduced. By repeating this, the mixed slurry 36 from the water bottom 20 can be introduced into the first chamber body 12 with energy saving.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

10 gas recovery device, 12 first chamber body, 14 underwater holding mechanism, 16 buoyancy body,
18 anchors, 19 chains, 20 water bottoms, 22 methane hydrate layers,
24 underwater, 25 water surface, 26 gas outlet,
28 extraction port, 30 extraction line, 32 gas recovery ship,
34 valve (pressure adjusting part), 36 mixed slurry, 38 slurry introducing part,
40 sediment slurry, 42 slurry outlet, 44 excavator, 46 first line,
48 pump, 50 second line, 52 pump, 54 heating section,
56 circulation line, 58 heat exchanger, 60 gas-liquid interface, 62 reels,
64 gas-liquid interface, 66 liquid level gauge, 68 control unit,
H Methane hydrate, S Bottom sediment

Claims (11)

A gas recovery device for gasifying and recovering methane hydrate from the bottom of the water,
A first chamber body capable of containing a slurry containing the methane hydrate in the chamber;
An underwater holding mechanism for positioning the first chamber body in water so that the entire room is located below the water surface ;
A slurry introduction section for sending a mixed slurry containing the methane hydrate and bottom sediment in the bottom of the first chamber;
A gas outlet from the first chamber;
A slurry outlet for sending sediment slurry mainly containing bottom sediment from the inside of the first chamber to the bottom;
A gas recovery apparatus comprising: The gas recovery apparatus according to claim 1,
A gas recovery apparatus comprising: a pressure adjusting unit that adjusts the pressure in the chamber of the first chamber body. In the gas recovery apparatus according to claim 2,
The gas recovery apparatus, wherein the gas extraction unit includes an extraction line for sending the gas extracted from the room to a recovery destination, and the pressure adjusting unit is provided in the extraction line. In the gas recovery device according to any one of claims 1 to 3,
A gas recovery apparatus comprising a heating unit for heating water in the first chamber. In the gas recovery device according to any one of claims 1 to 4,
The gas recovery apparatus, wherein the slurry introduction unit includes an introduction amount adjustment unit that adjusts an amount of the mixed slurry to be sent to the first chamber body. In the gas recovery device according to any one of claims 1 to 5,
The gas recovery apparatus, wherein the underwater holding mechanism unit includes a position adjusting mechanism that changes a water depth position of the first chamber body. A first feeding step of sending a mixed slurry containing methane hydrate and bottom sediment in the bottom of the water into a first chamber located in the water so that the entire chamber is located below the water surface ;
A decomposition step of decomposing methane hydrate in the first chamber;
A gas recovery step of taking out and recovering the gas generated in the decomposition step from the first chamber;
A second feeding step of sending a bottom sediment slurry containing mainly bottom sediment from the first chamber body to the bottom.
A method for recovering gas from bottom methane hydrate, characterized in that A first feeding step of sending a mixed slurry containing methane hydrate and bottom sediment at the bottom of the water into a first chamber located in the water;
A decomposing step of decomposing methane hydrate in the first chamber in a state in which a pressure that creates a gas-liquid interface is applied to the chamber of the first chamber;
A gas recovery step of taking out and recovering the gas generated in the decomposition step from the first chamber;
A second feeding step of sending a bottom sediment slurry containing mainly bottom sediment from the first chamber body to the bottom,
Depressurizing the interior of the first chamber body to a pressure lower than the pressure of the water depth at which the first chamber body is located;
A method for recovering gas from bottom methane hydrate, characterized in that In the gas recovery method from the bottom methane hydrate according to claim 7 ,
A method for recovering gas from underwater methane hydrate, comprising decomposing methane hydrate in a state in which a pressure that creates a gas-liquid interface is applied to the interior of the first chamber body. In the gas recovery method from the bottom methane hydrate according to any one of claims 7 to 9 ,
The method of recovering gas from bottom methane hydrate, wherein the bottom of the deposit slurry in the second feeding step is a bottom of the bottom methane hydrate recovery region in the first feeding step. . In the gas recovery method from the bottom methane hydrate according to any one of claims 7 to 10,
The method for recovering gas from bottom methane hydrate, wherein the decomposition step is performed by applying heat to the water in the first chamber.

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