JP6681815B2 - Methane recovery device - Google Patents

Description

  The present invention relates to a methane recovery device that recovers methane in methane hydrate existing in the ground.

Recently, with respect to methane hydrate, which is considered to be buried in a huge amount in the sea near Japan, studies are being made on the methane hydrate or a technology for recovering methane contained in the methane hydrate.
Methane hydrate is mainly present in the methane hydrate layer, which is formed several hundred meters below the sea floor on the seafloor at a relatively low temperature and high pressure. Therefore, methane hydrate is decomposed to recover methane. As a different method, a decompression method of decompressing the methane hydrate layer to separate and recover methane from methane hydrate, and a heating method of heating the methane hydrate layer to separate and recover methane from methane hydrate. It has been known.
The decompression method is considered to have better energy efficiency than the heating method, but the reaction of decomposing methane hydrate into methane and water is an endothermic reaction, so the methane hydrate layer is decompressed to recover methane. At that time, the ambient temperature may drop and methane may not be recovered. In addition, since the methane hydrate layer is composed of unconsolidated deposits such as sand and sand / mud, when decompressing with a decompression pump via a sampling pipe, sand and sand / mud are sucked together with methane gas, There are problems such as stopping and breaking down the decompression pump.
On the other hand, in the heating method, as disclosed in Patent Document 1, a heating medium that retains heat is supplied to the methane hydrate layer to heat the methane hydrate and to collect gasified methane in a pipe. Collect through. Then, the recovered methane is cooled by a cooling facility having a liquefying compressor or the like, liquefied and stored and transported. In the heating method, since the methane hydrate layer is heated during recovery, the problem that the temperature of the methane hydrate layer decreases and methane cannot be recovered can be avoided, and it is necessary to decompress the methane hydrate layer. Therefore, it is possible to avoid a failure caused by the decompression pump sucking sand or sand and mud, but the energy recovery amount is small with respect to the input energy.
For the purpose of improving the recovery rate of methane in the depressurization method, there is a production recovery enhancement method such as a depressurization / well heating combined use (Huff & Puff) method in which a small amount of hot water is injected for geothermal recovery after depressurization and well heating.

JP-A-2000-61293

  As described above, the heating method disclosed in Patent Document 1 can avoid the problem of the decompression method. However, in the heating method, it is known from various studies that the amount of methane recovered with respect to the input energy is small, and further, the recovered methane is cooled and liquefied from the viewpoint of storage and transportation. However, much energy is required, and improvement in total energy efficiency has been desired.

  The present invention has been made in view of the above problems, and an object thereof is to appropriately gasify methane hydrate in the ground by a heating method and a Huff & Puff method, while having a relatively simple structure, It is an object of the present invention to provide a methane recovery device that can perform a process of liquefying the liquefied methane gas favorably for the purpose of storage and transportation with high energy efficiency.

A methane recovery device for achieving the above object is a methane recovery device for recovering methane in methane hydrate existing in a methane hydrate layer in the ground, and its characteristic configuration is:
An acoustic tube filled with a working medium and in which sound waves propagate, a heater that heats the working medium from the outside, a cooler that cools the working medium from the outside, and acoustic energy of sound waves between the heater and the cooler. At least one or more prime mover including a first regenerator for amplifying the heat is provided, and a heat absorber for absorbing the heat from the working medium from the outside, a radiator for radiating the working medium to the outside, the heat absorber, and the radiator A thermoacoustic engine provided with at least one or more acoustic heat pump sections consisting of a second regenerator that compresses and expands in the form that sound waves consume acoustic energy between them;
A first heat medium passage that guides a first heat medium having a heat generated from a heat source to the heater;
A second heat medium passage that guides the second heat medium that has passed through at least one of the cooler and the radiator to the methane hydrate layer;
A part of the methane separated and gasified from the methane hydrate in the methane hydrate layer is guided to the warm heat source as a fuel, and the remaining part of the gasified methane is guided to the heat absorber to be liquefied. And a flow path.

Hereinafter, first, the function and effect of the configuration in which the second heat medium flow passage guides the second heat medium from both the cooler and the radiator to the methane hydrate layer will be described.
According to the configuration, in the prime mover of the thermoacoustic engine, for example, the second heat medium having a relatively low temperature such as seawater is guided to the cooler, and the first heat medium having the heat generated from the heat source is supplied to the heater. Since it is guided, a sufficient temperature difference can be generated between the heater and the cooler, and a sound wave having large acoustic energy generated from the temperature difference can be generated in the acoustic tube.
On the other hand, in the acoustic heat pump section of the thermoacoustic engine, for example, a relatively low temperature second heat medium such as seawater is supplied to the radiator as a heat sink and separated from methane hydrate in the methane hydrate layer and recovered. The methane gas can be cooled and liquefied by flowing through the heat absorber. That is, in this configuration, the cooling required for liquefying the methane gas can be realized with a simple configuration without a compressor and without supplying electric power.
In addition, the second heat medium flow passage guides the second heat medium, which has recovered the heat in the cooler of the prime mover and the radiator of the acoustic heat pump unit, to the methane hydrate layer, and the methane hydrate layer in the methane hydrate layer. Can be satisfactorily heated and methane can be gasified and recovered.
From the above, a process of gasifying methane while appropriately heating underground methane hydrate by a heating method with a relatively simple structure, and liquefying the gasified methane gas favorably for the purpose of storage and transportation It is possible to realize a methane recovery device that can perform the above with high energy efficiency.

  Incidentally, in the present invention, a combustion device such as a burner or a combined heat and power device such as an engine is assumed as the heat source, and methane gasified from the methane hydrate layer through the methane passage is used as fuel. It uses the configuration supplied. In such a configuration, for example, a configuration in which fuel is supplied from the auxiliary fuel source to the heat source until the methane gasified from the methane hydrate layer is supplied to the heat source.

  In addition, in the operation and effect described so far, regarding the configuration in which the second heat medium is introduced into the methane hydrate layer from both the cooler of the prime mover and the radiator of the acoustic heat pump unit in the second heat medium passage. explained. However, the second heat medium passage may guide the second heat medium to the methane hydrate layer, the second heat medium having passed through at least one of the cooler and the radiator. However, from the viewpoint of guiding the second heat medium having a large amount of heat at a relatively high temperature to the methane hydrate layer to gasify a large amount of methane, the second heat medium passage has a cooler and a radiator. Among these, it is preferable to adopt a configuration in which at least the second heat medium that has passed through the cooler capable of recovering a relatively large amount of heat is guided to the methane hydrate layer.

A further characteristic configuration of the methane recovery device is
The point is that a decompression pump for decompressing the methane hydrate layer in a form of sucking fluid from the methane hydrate layer is provided.

  According to the above characteristic structure, the methane hydrate layer can be heated by introducing the second heat medium and can be decompressed by the suction action of the decompression pump. Methane can be gasified in the hydrate layer and can be recovered even better.

A further characteristic configuration of the methane recovery device is
The second heat medium passage is configured as a second heat medium circulation passage that circulates a second heat medium between at least one of the cooler and the radiator and the methane hydrate layer.
The second heat medium circulation passage cools the second heat medium after flowing through the underground second heat medium passage that guides the second heat medium to the methane hydrate layer to the cooler. A device-side second heat medium passage, and a radiator-side second heat medium passage that guides the second heat medium to the radiator after passing through the underground second heat medium passage In parallel,
A compressor for compressing the methane before flowing through the heat absorber in the methane passage,
The methane flowing between the heat absorber and the compressor in the methane passage, and the second heat medium after passing through the radiator in the radiator-side second heat medium passage The point is that a first heat exchanger for exchanging heat with and is provided.

According to the above characteristic configuration, the second heat medium is guided in parallel to both the cooler-side second heat medium passage and the radiator-side second heat medium passage, so that, for example, Compared with the case of introducing in series, it is possible to supply the second heat medium which has a relatively low temperature by recovering the cold heat from the methane hydrate layer to both the cooler and the radiator. As a result, in the prime mover, the temperature difference between the cooler and the heater can be made sufficiently large to generate a sound wave of large acoustic energy. By introducing the second heat medium of, the temperature of methane introduced to the heat absorber can be cooled to a lower temperature.
Here, in order to liquefy methane, it is necessary to cool to about −162 ° C. in the vicinity of atmospheric pressure, so it is preferable to cool while increasing the pressure. According to the above-mentioned characteristic configuration, methane obtained by gasifying methane hydrate in the methane hydrate layer is compressed by the compressor to a relatively high pressure (for example, 3 MPa or more and 8 MPa or less), and then the first The liquefaction can be satisfactorily performed by cooling the heat exchanger in such a manner that it exchanges heat with the second heat medium so as to take rough heat, and by cooling the heat absorber in the acoustic heat pump section.
On the other hand, the second heat medium flowing through the second heat medium radiator side flow path acts as a heat sink in the radiator to recover heat, and then the first heat exchanger boosts the pressure in the compressor. It is possible to recover the crude heat of the subsequent methane and supply those heats well to the methane hydrate layer.

A further characteristic configuration of the methane recovery device is
The second heat medium passage is configured as a second heat medium circulation passage for circulating the second heat medium between at least one of the cooler and the radiator and the methane hydrate layer, and at least the above. Circulating the second heat medium between a cooler and the methane hydrate layer,
The first heat medium after passing through the heater in the first heat medium passage and the first heat medium after passing through the cooler in the second heat medium circulation passage are guided to the methane hydrate layer. A second heat exchanger for exchanging heat with the previous second heat medium is provided.

In the present invention, a combustion device such as a burner or a combined heat and power supply device such as an engine is assumed as the heat source, and combustion exhaust gas from the combined combustion device or the combined heat and power supply device is used as the first heat medium. I am assuming. In this case, it is assumed that the first heat medium that has passed through the heater has heat that can be recovered at a relatively high temperature.
Therefore, in the above-mentioned characteristic configuration, the second heat exchanger causes the first heat medium after passing through the heater in the first heat medium passage and the cooler in the second heat medium circulation passage to pass therethrough. By exchanging heat with the second heat medium before flowing through the methane hydrate layer after flowing, the waste heat remaining in the first heat medium is appropriately recovered by the second heat medium, and methane hydrate It can serve for heating methane hydrate in layers.

A further characteristic configuration of the methane recovery device is
The heat source is a combustion device that burns the methane to discharge combustion exhaust gas,
The first heat medium flow passage is configured so that the combustion exhaust gas can flow through the heater as the first heat medium.

  According to the above characteristic configuration, although it depends on the oxygen concentration of the combustion air to be supplied, the combustion exhaust gas having a high temperature of 1500 ° C. or more can be supplied to the heater as the first heat medium, and the cooler and the heater of the prime mover can be supplied. It is possible to generate a large temperature energy and generate a large acoustic energy.

A further characteristic configuration of the methane recovery device is
The warm heat source is a combined heat and power device that generates heat and electric power using the methane as a fuel,
The first heat medium passage is configured such that the first heat medium that retains heat generated by the combined heat and power supply device can freely flow through the radiator.

  According to the above characteristic configuration, by providing the combined heat and power supply device as the heat source, it is possible to generate not only heat but also electric power by using methane as a fuel. Therefore, the electric power is used as an auxiliary device of the device (for example, compression for compressing methane). The energy efficiency of the device as a whole can be further increased.

Schematic configuration diagram of a methane recovery apparatus according to an embodiment of the present invention Schematic configuration diagram of a methane recovery apparatus according to another embodiment of the present invention Schematic configuration diagram of a methane recovery apparatus according to another embodiment of the present invention

  The methane recovery apparatus 100 according to the embodiment of the present invention has a relatively simple configuration, but appropriately gasifies underground methane hydrate by a heating method and a Huff & Puff method, and stores and transports the gasified methane gas. The step of favorably liquefying for the purpose of can be executed with high energy efficiency.

As shown in FIG. 1, the methane recovery device 100 according to the embodiment is a device that normally recovers methane from methane hydrate formed at a relatively high pressure and a low temperature. Since methane hydrate is formed at a relatively high pressure and low temperature, it is normally formed below the sea floor LA1 by several hundred meters above the sea floor with a depth of 500 m or more, except for special environments such as Siberia. It exists in the methane hydrate layer LA2.
In the methane recovery apparatus 100 according to the embodiment, a heater 11 that heats the working medium from the outside and a cooler 12 and the heater 11 that cools the working medium from the outside are placed in an acoustic cylinder T in which the working medium is filled and the sound waves propagate. At least one prime mover 10 including a first regenerator 13 that amplifies acoustic energy of sound waves is provided between the cooling medium and the cooler 12, and a heat absorber 21 that absorbs heat from the outside and a working medium that radiates heat to the outside. A thermoacoustic engine having at least one acoustic heat pump unit 20 including a radiator 22, a heat absorber 21, and a second regenerator 23 that compresses and expands between the radiator 22 and the radiator 22 in a manner that acoustic waves consume acoustic energy. 60 is provided.
Further, in the methane recovery device 100 according to the embodiment, the combustion exhaust gas (first example) that retains the heat generated from the burner 30 (an example of the heat source and the combustion device) that mixes and burns the fuel and the combustion air. A first heat medium passage L4 that guides an example of a heat medium to the heater 11, at least one of the cooler 12 and the radiator 22 (both in this embodiment), and the methane hydrate layer LA2. A second heat medium circulation path C (an example of a second heat medium passage) for circulating a second heat medium (for example, seawater) between the gas and the methane hydrate in the methane hydrate layer LA2. A part of the liquefied methane is guided to the burner 30 as a fuel, and the remaining part of the gasified methane is guided to the heat absorber 21 to be liquefied.

Hereinafter, first, a description will be added for the thermoacoustic engine 60.
As shown in FIG. 1, the thermoacoustic engine 60 includes an acoustic tube T configured by connecting a first loop tube T1 and a second loop tube T2, which are filled with a working medium and propagate sound waves, with a connecting tube. In this embodiment, the single prime mover 10 is provided in the first loop pipe T1, and the single acoustic heat pump unit 20 is provided in the second loop pipe T2.

  Hereinafter, it comprises a heater 11 for heating the working medium from the outside, a cooler 12 for cooling the working medium from the outside, and a first regenerator 13 for amplifying acoustic energy of sound waves between the heater 11 and the cooler 12. The description of the prime mover 10 will be added.

  Although not shown in detail, the heater 11 includes a jacket portion (not shown) that allows the combustion exhaust gas as the first heat medium to flow therethrough, and fins (not shown) extending from the jacket portion into the acoustic tube T. ) And. The heater 11 heats the working fluid in a form in which the fins are heated by the combustion exhaust gas flowing through the jacket portion and the heat is conducted from the fins to the working fluid inside the acoustic tube T.

  The cooler 12 includes a jacket portion (not shown) that allows the second heat medium that circulates in the second heat medium circulation path C to flow therethrough, and a fin (not shown) that extends from the jacket portion into the acoustic tube T. Consists of. The cooler 12 cools the working fluid in such a form that the fins are cooled by cooling water flowing through the jacket portion, and the heat is conducted from the fins to the working fluid inside the acoustic tube T.

The first regenerator 13 provided between the heater 11 and the cooler 12 is, for example, in the cylinder axis direction with the plate surface along the direction orthogonal to the cylinder axis direction of the acoustic tube T. It is composed of a plurality of thin plate-like members (not shown) arranged along the line.
The thin plate member has a thickness of, for example, 50 μm or more and 100 μm or less, and is provided about 300 to 600 sheets. The thin plate member is provided with a large number of through holes (not shown) penetrating in the direction along the axis of the cylinder and having a diameter of about 200 μm to 300 μm.

The working fluid exists inside the acoustic cylinder T in a state in which a minute fluctuation is generated in the cylinder axis direction. In other words, the sound wave propagating through the working fluid forms a traveling wave from one side to the other side and a traveling wave from the other side to the one side between both the heater 11 and the cooler 12.
When forming a traveling wave from the cooler 12 to the heater 11 side, the sound wave propagating through the working fluid passes through a plurality of through holes of the thin plate member as the first regenerator 13 near the heater 11. At the same time, the inner wall of the through hole is heated while being heated, and the fins of the heater 11 are directly heated to expand. On the other hand, when the sound wave propagating through the working fluid forms a traveling wave from the heater 11 to the cooler 12, the plurality of through holes in the thin plate member as the first regenerator 13 near the cooler 12 are formed. When it passes through, the inner wall of the through hole is contacted and cooled, and the fins of the cooler 12 are directly cooled to contract.
As a result, the sound wave as the traveling wave causes self-excited vibration, and the heat energy is converted into the sound energy of the sound wave in a form in which the sound energy is amplified.

  The working medium is composed of a gas that propagates sound waves. Here, since it is desirable that the heat exchange in the first regenerator 13 be performed quickly, helium or hydrogen having a high thermal diffusion coefficient is desirable as the working medium. Further, for the purpose of power generation, a gas having a high molecular weight is desirable, so a gas such as argon may be mixed. Since it is thermally stable, helium is used as the working medium in this embodiment.

The acoustic energy of the sound wave amplified by the prime mover 10 propagates from the first loop tube T1 of the acoustic tube T to the acoustic heat pump unit 20 of the second loop tube T2.
The acoustic heat pump unit 20 compresses and compresses sound waves between the heat absorber 21 in which the working medium absorbs heat from the outside, the radiator 22 in which the working medium radiates heat to the outside, and the acoustic wave consuming acoustic energy between the heat absorber 21 and the radiator 22. And an expanding second regenerator 23.

  Although detailed illustration is omitted, the heat absorber 21 includes a jacket portion (not shown) that allows methane to flow through the methane passage L, and fins that extend from the jacket portion to the inside of the acoustic tube T (see FIG. (Not shown). In the heat absorber 21, the fins absorb heat from the methane flowing through the jacket portion, and the working medium inside the acoustic tube T absorbs heat from the fins.

  The radiator 22 includes a jacket portion (not shown) that allows the second heat medium that circulates in the second heat medium circulation path C to flow therethrough, and a fin (not shown) that extends from the jacket portion into the acoustic tube T. Consists of. In the radiator 22, the working medium inside the acoustic tube T radiates heat to the fins, and the radiated heat is radiated to the second heat medium flowing through the jacket portion, so that the second heat medium is heated. .

In the acoustic heat pump unit 20, the acoustic wave propagating through the working fluid is compressed when forming a traveling wave from the heat absorber 21 to the radiator 22 side, and forms a traveling wave from the radiator 22 to the heat absorber 21 side. The heat absorber 21, the second regenerator 23, and the radiator 22 are arranged at appropriate positions in the acoustic tube T so as to expand in some cases.
Thereby, when the sound wave propagating through the working fluid forms a traveling wave from the heat absorber 21 to the radiator 22, the second regenerator 23 absorbs heat and heats up, and the radiator 22 It radiates heat when the temperature rises and becomes high. Thereby, in the radiator 22, the second heat medium flowing through the jacket portion is heated in a form of heat exchange with the working medium having a temperature higher than that of methane flowing through the jacket portion of the heat absorber 21.
On the other hand, when the sound wave propagating through the working fluid forms a traveling wave from the radiator 22 to the heat absorber 21, the second regenerator 23 radiates heat while cooling to lower the temperature of the heat absorber 21. Absorbs heat when the temperature is low. As a result, in the heat absorber 21, the working medium having a sufficiently low temperature satisfactorily absorbs heat from the methane flowing through the jacket portion.
Incidentally, as described above, in the step of absorbing heat while compressing in the second regenerator 23 and the step of radiating heat while expanding, the acoustic energy of the sound wave is consumed and the sound wave is attenuated, but the acoustic energy is transmitted from the prime mover 10. Since they are sequentially replenished, the heat pump function of the acoustic heat pump unit 20 is maintained.

The second regenerator 23 provided between the heat absorber 21 and the radiator 22 is the same in shape and material as the first regenerator 13.
In addition, the cylinder diameter, the cylinder length, the shape, and the like of the acoustic cylinder T are converted from the thermal energy of the prime mover 10 into the acoustic energy based on the hole diameters of the through holes of the first regenerator 13 and the second regenerator 23, in particular. The efficiency and the conversion efficiency from the acoustic energy of the acoustic heat pump unit 20 to the heat energy are appropriately set.

The methane hydrate layer LA2 is formed several hundred meters below the sea floor LA1, and in order to recover methane from the methane hydrate layer LA2, a boring hole that reaches the methane hydrate layer LA2 on the sea bottom is drilled and produced. Well W is formed.
In the methane recovery device 100, the second heat medium circulation path C that circulates the second heat medium having a relatively high temperature is laid in the methane hydrate layer LA2 via the production well W and the second heat medium circulation path C is provided in the methane hydrate layer LA2. The methane hydrate layer LA2 is heated in a form in which warm heat is supplied via a heat medium.

When the description is added, the second heat medium circulation path C includes an underground second heat medium passage C1 that guides the second heat medium to the methane hydrate layer LA2, and an underground second heat medium passage. The cooler side second heat medium passage C3 for guiding the second heat medium after passing through C1 to the cooler 12 and the second heat after passing through the underground second heat medium passing passage C1. It is composed of a radiator side second heat medium passage C2 for guiding the medium to the radiator 22, and the return second heat medium from the underground second heat medium passage C1 is the cooler side second. The heat medium passage C3 and the radiator-side second heat medium passage C2 are configured to be guided in parallel. Specifically, the return path of the underground second heat transfer passage C1 is located on the forward side of the cooler side second heat transfer passage C3 and on the radiator side via the second three-way flow rate adjusting valve V2. It is connected to the forward path of the second heat medium flow passage C2. The forward path of the underground second heat medium passage C1 is connected to the return path of the cooler side second heat medium passage C3 and the return path of the radiator side second heat medium passage C2. ing. Although illustration is omitted, in order to adjust the balance of the amount of heat recovered by the second heat medium in the cooler 12 and the radiator 22, the control device, for example, sets the return path of the cooler-side second heat medium passage C3. A second three-way flow rate control valve based on the temperature and flow rate of the second heat medium flowing through and the temperature and flow rate of the second heat medium flowing through the return path of the radiator-side second heat medium communication channel C2. The opening degree of V2 is controlled.
Incidentally, a second pump P2 for pumping the second heat medium is provided in the underground second heat medium passage C1.

  Further, in the methane recovery apparatus 100, a decompression flow path L5 is laid via the production well W in order to decompress the methane hydrate layer LA2, and the decompression flow path L5 is used to remove seawater from the methane hydrate layer LA2. A decompression pump P4 for decompressing the methane hydrate layer LA2 in a form of sucking (an example of fluid) is provided.

The methane flow passage L is laid in the methane hydrate layer LA2 via the production well W, and the underground methane flow passage L1 that leads from the methane hydrate layer LA2 to the ground and the underground methane flow passage L1. Is connected to the burner 30 through the first three-way flow rate adjusting valve V1 and guides the methane gas from the underground methane passage L1 to the burner 30, and the underground methane passage L1 is connected to the burner side methane passage L1. 1) A three-way flow rate control valve V1 is connected and a heat absorber side methane passage L3 that guides the methane gas from the underground methane passage L1 to the heat absorber 21. A controller (not shown) guides methane calculated based on the amount of heat required by the heater 11 to the burner-side methane passage L2, and the rest to the heat absorber-side methane passage L3 for liquefaction. Therefore, the opening degree of the first three-way flow rate adjusting valve V1 is controlled.
Incidentally, although not shown, the methane passage L is also configured to be able to recover methane contained in seawater that is sucked and recovered from the methane hydrate layer LA2 in the depressurization flow path L5.

  While the methane hydrate layer LA2 collects methane, the auxiliary fuel such as natural gas is supplied to the burner 30 so that the combustion of the burner 30 is maintained and the combustion exhaust gas is guided to the heater 11. Get burned.

  Furthermore, before the heat absorber 21 is passed through the heat absorber side methane flow passage L3, in order to appropriately perform the liquefaction of methane and to further raise the temperature of the second heat medium guided to the methane hydrate layer LA2. Is provided with a compressor P3 that compresses the methane to increase the pressure to 3 MPa or more and 8 MPa or less. Further, the methane flowing between the heat absorber 21 and the compressor P3 in the heat absorber side methane passage L3, and the heat radiation A first heat exchanger EX1 that exchanges heat with the second heat medium that has flowed through the radiator 22 in the device-side second heat medium passage C2 is provided.

Further, in order to further raise the temperature of the second heat medium introduced to the methane hydrate layer LA2, the combustion exhaust gas after flowing through the heater 11 in the first heat medium passage L4 and the second heat medium on the cooler side. After passing through the cooler 12 in the flow passage C3, heat is exchanged with the second heat medium before flowing through the underground second heat medium passage C1 (before being guided to the methane hydrate layer LA2). The second heat exchanger EX2 is provided.
By adopting the above configuration, the second heat medium heated by the cooler 12 and the second heat exchanger EX2, and the second heat medium heated by the radiator 22 and heated by the first heat exchanger EX1 However, the methane is decomposed from the methane hydrate in the form of being guided to the methane hydrate layer LA2 and radiating heat. Further, the decomposed and gasified methane is boosted by the compressor P3, and the crude heat generated by the boosting is radiated by the first heat exchanger EX1 and further radiated by the heat absorber 21, for example, 3 MPa or more. It is cooled to about -162 ° C at 8 MPa or less and liquefied. The liquefied methane is used for various purposes in the form of being transported by a ship or the like.

[Another embodiment]
(1) In the above embodiment, the thermoacoustic engine 60 having the single acoustic tube T is shown. However, the thermoacoustic engine 60 may employ a configuration having a plurality of acoustic tubes T. The prime mover 10 and the acoustic heat pump unit 20 may also be configured to be provided in plurality.

(2) In the above embodiment, the configuration including the first heat exchanger EX1 and the second heat exchanger EX2 has been illustrated, but depending on the required heat amount to be supplied to the methane hydrate layer LA2 and the flow rate of the recovered methane gas, A configuration not including the first heat exchanger EX1 and the second heat exchanger EX2 may be adopted. When the said structure is employ | adopted, the compressor P3 will also be abbreviate | omitted.
In addition, a configuration that does not include either the first heat exchanger EX1 or the second heat exchanger EX2 is also included in the scope of right of the present application.

(3) As shown in FIG. 2, the radiator-side second heat medium passage C <b> 2 may have a configuration in which the second heat medium does not flow into the radiator 22. That is, the radiator-side second heat medium flow passage C2 is configured to guide the second heat medium to the underground second heat medium flow passage C1 after flowing the second heat medium to the first heat exchanger EX1.
In the said structure, the 3rd heat medium circulation path C5 which circulates a 3rd heat medium between the cooling tower 55 and the radiator 22 is provided, and the said 3rd heat medium functions as a heat sink in the radiator 22. Is preferably adopted.

(4) Further, although not shown in the drawings, a configuration in which the second heat medium circulation path C does not allow the second heat medium to flow to the cooler 12 is also included in the scope of right of the present application.
In this configuration, a configuration is adopted in which the heat medium is circulated between a cooling tower (not shown) that cools the heat medium and the cooler 12, and cold heat is supplied to the cooler 12 to cool the cooler 12. It is preferable to sufficiently secure the temperature difference between the heater 11 and the heater 11.

(5) As the heat source, a configuration including a combined heat and power device that generates heat and electric power using methane as a fuel may be adopted.
Specifically, as shown in FIG. 2, an engine 40 and a synchronous generator 42 connected to a rotating shaft 41 of the engine 40 are provided as a combined heat and power generator, and the frequency of the generated power of the synchronous generator 42 is changed. The frequency of the electric power supplied from the commercial power system 44 is adjustable. Further, the synchronous generator 42 is provided with an automatic voltage regulator that adjusts the voltage, and the automatic voltage regulator causes the generated power voltage to be the same voltage as the power voltage supplied from the commercial power grid 44. Adjusted to. A distribution board 43 is provided between the synchronous generator 42 and the commercial power system 44, and power is supplied from the distribution board 43 to an auxiliary machine (for example, a compressor) of the methane recovery device 100. Is configured.
Further, as the combined heat and power supply device, a configuration including a fuel cell can also be suitably adopted.

(6) In the embodiments described so far, the configuration in which the second heat medium is circulated in the second heat medium circulation path C is shown, but a configuration in which the second heat medium is not circulated is adopted separately. I don't mind.
Hereinafter, a methane recovery device 100 according to another embodiment (6) will be described with reference to FIG. The methane recovery device 100 according to the other embodiment (6) is different from the methane recovery device 100 according to the embodiment shown in FIG. 1 in the configuration related to the second heat medium circulation path C. Then, the configuration will be mainly described, and other configurations will be denoted by the same reference numerals as those in the above-described embodiment, and the description thereof may be omitted.
In the methane recovery device 100 according to the another embodiment (6), at least one of the cooler 12 and the radiator 21 is replaced with the second heat medium circulation path C of the methane recovery device 100 according to the embodiment shown in FIG. The second heat medium passage C is provided for guiding the seawater (one example of a fluid, one example of a second heat medium) that has passed through to the methane hydrate layer LA2. Incidentally, in the example shown in FIG. 3, the second heat medium passage C is configured to guide the second heat medium that has passed through both the cooler 12 and the radiator 21 in parallel to the methane hydrate layer LA2. There is.
If the description is added, the second heat medium passage C is provided with a decompression pump P4 for decompressing the methane hydrate layer LA2 in a form of sucking seawater or the like from the methane hydrate layer LA2, and is laid in the production well W. Cooling that guides the depressurization flow path L5, seawater flowing through the depressurization flow path L5 to the radiator 22 and a second radiator-side heat medium communication flow path C2, and seawater flowing through the depressurization flow path L5 to the cooler 12 Underground for guiding the seawater flowing through the device-side second heat medium passage C3, the radiator-side second heat medium passage C2, and the cooler-side second heat medium passage C3 to the methane hydrate layer LA2 Side second heat medium passage C1 and seawater from the decompression passage L5 flows into the cooler side second heat medium passage C3 and the radiator side second heat medium passage C2. , Are configured to be guided in parallel. Specifically, the outlet of the decompression flow path L5 passes through the second three-way flow rate adjusting valve V2 and the forward path of the cooler-side second heat medium communication path C3 and the radiator-side second heat medium communication path C2. It is connected to the way out.
A control device (not shown) controls the opening degree of the second three-way flow rate adjusting valve V2, as in the embodiment shown in FIG.
In the another embodiment (6), seawater guided to the methane hydrate layer LA2 in the underground second heat medium passage C1 is pressed into the methane hydrate layer LA2. The methane hydrate layer LA2 is heated.
Further, also in the other embodiment (6), a configuration is adopted in which methane contained in seawater flowing through the decompression flow path L5 is recovered from the methane communication flow path L1.

(7) In the methane recovery apparatus 100 shown in the above embodiment, the configuration is shown in which the decompression pump P3 that decompresses the methane hydrate layer LA2 in a form of sucking the liquid from the methane hydrate layer LA2 is provided.
However, a configuration that does not include the decompression pump P3 may be adopted.
That is, the scope of the scope of the present application also includes a case where methane is liquefied and recovered from the methane hydrate layer LA2 only by the heating action of the second heat medium.

  The configurations disclosed in the above-described embodiments (including other embodiments, the same applies below) can be applied in combination with the configurations disclosed in other embodiments as long as no contradiction occurs. The embodiments disclosed in the present specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within a range not departing from the object of the present invention.

  INDUSTRIAL APPLICABILITY The methane recovery device of the present invention has a relatively simple structure, but properly gasifies underground methane hydrate by a heating method and a Huff & Puff method, and satisfactorily stores and transports gasified methane gas. The liquefaction process can be effectively used as a methane recovery device that can be executed with high energy efficiency.

10: prime mover 11: heater 12: cooler 13: first regenerator 20: acoustic heat pump section 21: heat absorber 22: radiator 23: second regenerator 30: burner 40: engine 42: synchronous generator 60: heat Acoustic engine 100: Methane recovery device C: Second heat medium passage, second heat medium circulation passage C1: Underground second heat medium passage C2: Radiator side second heat medium passage C3: Cooling Device-side second heat medium passage C5: Third heat medium circulation passage EX1: First heat exchanger EX2: Second heat exchanger L: Methane passage L4: First heat medium passage LA2: Methane hydrate Rate layer P3: Compressor P4: Decompression pump T: Acoustic tube T1: First loop tube T2: Second loop tube

Claims (6)

A methane recovery device for recovering methane in methane hydrate existing in an underground methane hydrate layer,
An acoustic tube filled with a working medium and in which sound waves propagate, a heater that heats the working medium from the outside, a cooler that cools the working medium from the outside, and acoustic energy of sound waves between the heater and the cooler. At least one or more prime mover including a first regenerator for amplifying the heat is provided, and a heat absorber for absorbing the heat from the working medium from the outside, a radiator for radiating the working medium to the outside, the heat absorber, and the radiator. A thermoacoustic engine provided with at least one or more acoustic heat pump sections consisting of a second regenerator that compresses and expands in the form that sound waves consume acoustic energy between them;
A first heat medium passage that guides a first heat medium having a heat generated from a heat source to the heater;
A second heat medium passage that guides the second heat medium that has passed through at least one of the cooler and the radiator to the methane hydrate layer;
A part of the methane separated and gasified from the methane hydrate in the methane hydrate layer is guided to the warm heat source as a fuel, and the remaining part of the gasified methane is guided to the heat absorber to be liquefied. A methane recovery device having a flow path.   The methane recovery apparatus according to claim 1, further comprising a decompression pump that decompresses the methane hydrate layer in a form of sucking fluid from the methane hydrate layer. The second heat medium passage is configured as a second heat medium circulation passage that circulates a second heat medium between at least one of the cooler and the radiator and the methane hydrate layer.
The second heat medium circulation passage cools the second heat medium after flowing through the underground second heat medium passage that guides the second heat medium to the methane hydrate layer to the cooler. A device-side second heat medium passage, and a radiator-side second heat medium passage that guides the second heat medium to the radiator after passing through the underground second heat medium passage In parallel,
A compressor for compressing the methane before flowing through the heat absorber in the methane passage,
The methane flowing between the heat absorber and the compressor in the methane passage, and the second heat medium after passing through the radiator in the radiator-side second heat medium passage The methane recovery device according to claim 1 or 2, further comprising a first heat exchanger for exchanging heat with and. The second heat medium passage is configured as a second heat medium circulation passage for circulating the second heat medium between at least one of the cooler and the radiator and the methane hydrate layer, and at least the above. Circulating the second heat medium between a cooler and the methane hydrate layer,
The first heat medium after passing through the heater in the first heat medium passage and the first heat medium after passing through the cooler in the second heat medium circulation passage are guided to the methane hydrate layer. The methane recovery device according to any one of claims 1 to 3, further comprising a second heat exchanger that exchanges heat with the previous second heat medium. The heat source is a combustion device that burns the methane to discharge combustion exhaust gas,
The methane recovery device according to any one of claims 1 to 4, wherein the first heat medium flow passage is configured so that the combustion exhaust gas can flow through the heater as the first heat medium. The warm heat source is a combined heat and power device that generates heat and electric power using the methane as a fuel,
The said 1st heat medium flow path is comprised so that the said 1st heat medium which hold | maintains the heat | fever which the said heat and power supply device generate | occur | produces can flow freely to the said radiator. Methane recovery device described.

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