JP2016166487A - Device and method for treating water associated with methane gas collection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To return water associated with collection of methane gas from methane hydrate at a water bottom, the water being pumped up from the water bottom, to the water bottom where the water came from readily at a low cost.SOLUTION: A treatment device 10 is for treating water W associated with methane gas collection, the methane gas having been shifted to an area of a shallower water depth than a water bottom 12 or above water from the water bottom 12 while collecting the methane gas from methane hydrate in the water bottom 12. The treatment device includes: a first chamber 2 capable of holding carbon dioxide and the water W associated with collection and generating carbon dioxide hydrate using the water W associated with collection as source material water; and a discharging part 8 that discharges the carbon dioxide hydrate generated in the first chamber 2 into water 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for treating methane gas recovery associated with water that has been moved from the bottom of the water to a shallower region of the water or to the water as the methane gas is recovered from the methane hydrate in the bottom of the water, and a method for the same. .

  Conventionally, when recovering methane hydrate on the bottom of the sea or lake, methane hydrate on the bottom of the sea is decomposed in the vicinity of the bottom of the sea to convert it into methane gas. A method and apparatus for recovering methane gas by pumping water is provided (Patent Document 1).

JP 2010-37932 A

In the technique of Patent Document 1, when methane gas is recovered from methane hydrate on the seabed, the water at the bottom is also pumped up on the water surface.
In Patent Document 1, water W after separation of methane gas M from seawater (water W ′) in which methane gas pumped from the seabed is dissolved is drained into the sea as it is (see paragraph 0037 and FIG. 1).

Considering the influence on the marine ecosystem, it is preferable that the water collected from the bottom of the water accompanying the recovery of methane gas (hereinafter referred to as recovery-related water) is returned to the original place, that is, the bottom of the water.
However, the depth of the water bottom where the methane hydrate layer is present is at least 400 m or more, and may exist in the vicinity of 1000 m. Returning water to such a deep water depth with a pump or the like requires a lot of energy and increases costs.

  An object of the present invention is to return the methane gas recovery accompanying water pumped from the bottom of the water to the bottom of the water easily and at low cost when recovering the methane gas from the methane hydrate in the bottom of the water.

  The apparatus for treating methane gas recovery-accompanying water according to the first aspect of the present invention for solving the above-mentioned problem is a region where the water depth is shallower than the water bottom from the water bottom along with the recovery of methane gas from the methane hydrate on the water bottom. Alternatively, it is a treatment apparatus for water associated with methane gas recovery that has been moved to the water, can contain carbon dioxide and the water associated with the recovery, and can generate carbon dioxide hydrate using the water associated with the recovery as raw material water. A first chamber and a discharge unit that discharges carbon dioxide hydrate generated in the first chamber into water.

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.
“Methane gas recovery-related water” is water originally present at the bottom of the methane hydrate, and when the methane gas is recovered from the methane hydrate, it is raised to a shallower area than the bottom of the water or to the water. Say water. Moreover, the decomposition water generated when methane hydrate is decomposed is water derived from the bottom where the methane hydrate was present. Therefore, cracked water generated by decomposing methane hydrate to obtain methane gas in a region shallower than the bottom of the water or on the water is also included in the “methane gas recovery associated water”.

According to this aspect, in recovering methane gas from methane hydrate present in the bottom of the water, water that has been pumped from the bottom of the water to a shallower region of the water or above the water accompanying the methane hydrate or methane gas ( Hereinafter, the first chamber is set to a temperature and pressure (for example, 1 to 10 MPa, 1 to 10 ° C.) satisfying the conditions for generating carbon dioxide hydrate using raw water as methane gas recovery-related water or simply referred to as recovery-related water). Thus, carbon dioxide hydrate can be generated, and the generated carbon dioxide hydrate can be discharged from the discharge section into water containing methane hydrate.
In addition, the “water in which methane hydrate is present” refers to water in the water area connected to the bottom of the water in which the methane hydrate is present. Good.

Here, carbon dioxide hydrate is a specific gravity d is the 1.11~1.13g / cm ³ or so, than water (1.0 g / cm ³⁾ and general sea water (about 1.02 g / cm ³⁾ It is heavy and sinks under its own weight in water.
Therefore, the carbon dioxide hydrate discharged from the discharge unit sinks to the bottom of the water. As a result, the water accompanying the methane gas recovery can be easily returned to the original water bottom in the hydrate state.

  In addition, since the generated carbon dioxide hydrate is discharged into the water and sinks to the bottom due to its own weight, the energy associated with returning the methane gas recovery-accompanying water to the vicinity of the bottom of several hundred to 1000 m as in the conventional case is returned. With less energy, the collected water can be returned to the bottom.

  The methane gas recovery-accompanying water treatment apparatus according to the second aspect of the present invention is characterized in that, in the first aspect, the apparatus includes a floating mechanism that floats the first chamber body in water.

  Here, “floating in water” means not a state of being positioned at the bottom of the water but a state of being positioned at the surface of the water, and a state of floating between the bottom of the water and the surface of the water.

According to this aspect, the first chamber body is floated in the water between the water bottom and the water surface that are neither the water bottom nor the water surface. Carbon dioxide hydrate is generated by adding and reacting methane gas recovery accompanying water as raw material water and carbon dioxide in the first chamber suspended in water.
In the sea or lake where methane hydrate is present, the water temperature is lower and the pressure is higher than the water at the position where the first chamber body is floating. Therefore, the energy required for generating high pressure and low temperature under the conditions for generating carbon dioxide hydrate in the first chamber floated in water is sufficient, thereby suppressing the cost for generating carbon dioxide hydrate. it can.

  The apparatus for treating methane gas recovery-accompanying water according to the third aspect of the present invention is characterized in that, in the first aspect or the second aspect, the discharge part is provided at the bottom of the first chamber body. To do.

  According to this aspect, since the discharge portion is provided at the bottom of the first chamber body, carbon dioxide hydrate having a specific gravity greater than that of water can be efficiently discharged from the first chamber body.

  The treatment apparatus for water associated with methane gas recovery according to a fourth aspect of the present invention, in the second aspect, is a mass of methane hydrate in which the first chamber is located in water and rises from the bottom of the water. And a take-out portion for taking out methane gas generated by decomposition of the methane hydrate in the first chamber.

A mass of methane hydrate rising in the water from the bottom of the water can be received in the first chamber located in the water, and the methane hydrate can be decomposed under the conditions for decomposing the methane hydrate. For example, the interior of the chamber can be made to decompose methane hydrate by heating the water in the first chamber to raise the temperature or lowering the pressure in the first chamber. Methane gas generated by the decomposition can be recovered from the take-out part.
Here, the water rising from the bottom with the methane hydrate lump in the first chamber and the water generated by the decomposition of the methane hydrate are methane gas recovery accompanying water. Methane gas recovery-accompanying water can be discharged into water and submerged to its bottom by its own weight by making it into carbon dioxide hydrate in the same first chamber.

Since the phase equilibrium condition of carbon dioxide hydrate is on the high temperature and low pressure side than the phase equilibrium condition of methane hydrate (see Fig. 4), carbon dioxide hydrate is better than methane hydrate under the same temperature and pressure conditions. It can be said that it is easy to generate. That is, carbon dioxide hydrate can be generated under conditions of temperature and pressure at which the methane hydrate is decomposed.
Accordingly, by setting the first chamber to a temperature at which the methane hydrate is decomposed but the carbon dioxide hydrate is generated at the water pressure of the depth at which the first chamber is located, the methane hydrate is formed in the first chamber. The recovery of methane gas from the rate and the treatment of methane gas recovery accompanying water generated at the time of recovery can be performed simultaneously.

  Particularly, in the range below the phase equilibrium curve of methane hydrate indicated by the solid line in FIG. 4 (low pressure and high temperature) and above the phase equilibrium curve of carbon dioxide hydrate indicated by the dotted line (high pressure and low temperature). Although methane hydrate decomposes, carbon dioxide hydrate is produced. By floating the first chamber body at such a water pressure and water depth position (for example, near 200 m to 400 m), the decomposition of methane hydrate and the generation of carbon dioxide hydrate in the first chamber body are further improved. This can be done with less energy.

  The apparatus for treating methane gas recovery-accompanying water according to the fifth aspect of the present invention, in the second aspect, accepts a mass of methane hydrate from the bottom of the water and decomposes the methane hydrate with the chamber floated in water. A second chamber body is provided, and water in the second chamber body is configured to be sent to the first chamber body as the recovery-accompanying water.

According to this aspect, the methane gas recovery accompanying water generated when methane gas is recovered from the bottom methane hydrate by decomposing methane hydrate in the second chamber body is converted into carbon dioxide hydrate in the first chamber body. Can be returned to.
In this aspect, since the generation of carbon dioxide hydrate from the water accompanying methane gas recovery and the decomposition of methane hydrate levitated from the bottom of the water are performed in separate chambers, the generation of carbon dioxide hydrate in the first chamber The conditions can be set independently of the methane hydrate decomposition conditions in the second chamber. Further, carbon dioxide is not mixed with methane gas generated by the decomposition of methane hydrate. Therefore, the production | generation of the carbon dioxide hydrate in a 1st chamber body and the methane collection | recovery performed by decomposing | disassembling methane hydrate in a 2nd chamber body can be performed more efficiently.

  A methane gas recovery-accompanying water treatment apparatus according to a sixth aspect of the present invention is characterized in that, in the fifth aspect, heat exchange is possible between the first chamber and the second chamber. And

The formation reaction of carbon dioxide hydrate is an exothermic reaction (about 65 kJ / mol). On the other hand, the decomposition reaction of methane gas hydrate is an endothermic reaction (52-57 kJ / mol).
By exchanging generated heat (heat generation) in the first chamber and decomposition heat (heat absorption) in the second chamber, energy necessary for heating in the second chamber can be suppressed.

  The methane gas recovery-accompanying water treatment method according to the seventh aspect of the present invention is the methane gas moved from the water bottom to a shallower region of the water bottom or on the water accompanying the methane gas recovery from the methane hydrate in the water bottom. In the first chamber, a generating step of generating carbon dioxide hydrate using the recovered accompanying water as raw water, and the generated carbon dioxide hydrate is submerged by its own weight in the first chamber. Returning to the bottom of the water.

    According to this aspect, there exists an effect similar to the effect in the processing apparatus of the methane gas collection | recovery accompanying water of a 1st aspect.

  In the seventh aspect of the method for treating methane gas recovery-accompanying water according to the eighth aspect of the present invention, the generating step is performed in a state where the first chamber is floated in water.

  According to this aspect, there exists an effect similar to the effect in the processing apparatus of the methane gas collection | recovery accompanying water of a 2nd aspect.

  In the eighth aspect of the method for treating methane gas recovery-accompanying water according to the ninth aspect of the present invention, the methane hydrate present at the bottom of the water is raised in a lump state and received in the first chamber located in the water. A first raising step of methane hydrate, a first cracking step of bringing methane hydrate into contact with heated water in the first chamber and decomposing it, and taking out the methane gas generated in the cracking step from the first chamber And a first methane gas recovery step of recovering.

  According to this aspect, there exists an effect similar to the effect in the processing apparatus of the methane gas collection | recovery accompanying water of a 4th aspect.

  In the eighth aspect of the method for treating methane gas recovery-accompanying water according to the tenth aspect of the present invention, the methane hydrate present at the bottom of the water is raised in a lump and received in the second chamber located in the water. A second raising step of methane hydrate, a second cracking step of bringing methane hydrate into contact with heated water in the second chamber and decomposing it, and taking out the methane gas generated in the cracking step from the first chamber It has the 2nd methane gas collection | recovery process to collect | recover, and the water supply process which sends the water in the said 2nd chamber body to the said 1st chamber body, It is characterized by the above-mentioned.

  According to this aspect, there exists an effect similar to the effect in the processing apparatus of the methane gas collection | recovery accompanying water of a 5th aspect.

  The method for treating methane gas recovery-accompanying water according to the eleventh aspect of the present invention is characterized in that, in the tenth aspect, heat is exchanged between the first chamber and the second chamber.

  According to this aspect, the same operational effects as the operational effects of the methane gas recovery-accompanying water treatment apparatus of the sixth aspect are achieved.

The schematic block diagram which shows an example of the processing apparatus of the methane gas collection | recovery accompanying water which concerns on this invention. The schematic block diagram which shows the other example of the processing apparatus of the methane gas collection | recovery accompanying water which concerns on this invention. The schematic block diagram which shows the further another example of the processing apparatus of the methane gas collection | recovery accompanying water which concerns on this invention. The figure which shows the phase equilibrium curve of methane hydrate and a carbon dioxide hydrate.

[Example 1]
<Schematic configuration of methane gas recovery associated water treatment apparatus and methane gas recovery associated water treatment method>
The method for treating methane gas recovery-accompanying water will be described with reference to the schematic configuration of the apparatus for treating methane gas recovery-accompanying water according to the present invention. FIG. 1 is a schematic configuration diagram showing an example of a methane gas recovery-accompanying water treatment apparatus according to the present invention.
As shown in FIG. 1, the case where the 1st chamber body 2 is provided in water is demonstrated.

  The methane gas recovery-accompanying water treatment apparatus 10 (hereinafter may be simply referred to as the treatment apparatus 10) is adapted to recover the methane gas from the methane hydrate layer 14 on the sea floor 12 as the water bottom, from the sea floor 12 to the sea surface 15. The methane gas recovery accompanying water W collected in the methane gas recovery ship 16 is a device for processing. The methane recovery ship 16 is a methane gas recovery destination. The collection destination may be a storage facility such as a tank that stores methane gas installed on the ground, or a gas fuel utilization facility such as a gas turbine that uses methane gas as fuel, in addition to the methane recovery ship 16.

In the present embodiment, as an example of methane gas recovery from the methane hydrate layer 14, the methane hydrate is decomposed by the methane gas recovery device 13 provided in the vicinity of the methane hydrate layer 14, and the decomposed methane gas (CH ₄ ) is dissolved. The water W1 in the vicinity of the seabed 12 is collected in the methane gas recovery ship 16 and separated into methane gas and water W1 in the gas-liquid separation unit 17. The separated methane gas is stored in the methane gas storage unit 19.
On the other hand, the water W1 in the vicinity of the sea floor 12 that has been collected together with the methane gas and separated from the methane gas in the gas-liquid separation unit 17 is a treatment target of the treatment apparatus 10 of the present invention. It is processed in the treatment apparatus 10 for recovered associated water.

The methane gas recovery-accompanying water treatment apparatus 10 according to the present embodiment includes a first chamber body 2 provided in the sea 18 as underwater, and a floating mechanism unit 4 that floats the first chamber body 2 in the sea 18. The underwater 18 is the water in the water area connected to the water bottom where the methane hydrate layer 14 is located.
The first Shitsutai 2 is put and the collection associated water W carbon dioxide (CO _2), and is configured to generate carbon dioxide hydrate. The recovery-accompanying water W is sent from the gas-liquid separation unit 17 of the methane gas recovery ship 16 to the first chamber body 2 through the water supply line 6. Carbon dioxide (CO ₂ ) is also sent from the methane gas recovery ship 16 through the CO ₂ introduction line 7 and is put into the first chamber 2.
In addition, as the water supply line 6 and the CO ₂ introduction line 7, a flexible cable such as an umbilical cable can be used.

Conditions under which carbon dioxide hydrate (CO ₂ GH) is generated are conditions of higher pressure and lower temperature than the phase equilibrium curve shown in FIG. 4, for example, 1 to 10 MPa and 1 to 10 ° C.
In the present embodiment, the first chamber body 2 is floated at a water depth position in the sea 18 where the water pressure and temperature in the sea 18 are the conditions for generating carbon dioxide hydrate. In the case of a region, surrounding environment, or ocean, the conditions for producing carbon dioxide hydrate can be generally satisfied at a depth of 200 m to 400 mm or more, although it varies depending on the ocean current.
Therefore, the floating mechanism unit 4 may be configured to float the first chamber body 2 within a range of a water depth of 200 m to 400 m and generate carbon dioxide hydrate in the first chamber body 2.

When the first chamber body 2 is floated in a region shallower than this, pressure may be applied to the first chamber body 2 by the pressure adjusting unit 26 provided in the CO ₂ introduction line 7. The pressure adjustment unit 26 will be described in detail later. It is also possible to provide a temperature adjusting unit (not shown) that adjusts the temperature in the first chamber body 2.

In the present embodiment, the floating mechanism unit 4 is configured such that the water depth position where the first chamber body 2 is floated is variable. As such a floating mechanism unit 4, for example, a ballast tank 20 can be used. By adjusting the amount of the ballast water 22 in the ballast tank 20, the water depth position where the first chamber body 2 is floated can be changed. As the ballast water 22, it is desirable to use water in a water area connected to the bottom of the water where the methane hydrate layer 14 exists, that is, water in the same sea as the sea bottom 12 where the methane hydrate layer 14 exists. .
By changing the water depth position of the first chamber body 2 by the floating mechanism unit 4 (ballast tank 20), the water depth is changed to the appropriate water depth (water temperature satisfying the generation condition of carbon dioxide hydrate, water depth that provides water pressure). Carbon dioxide hydrate can be generated by floating the chamber.

  Further, the first chamber body 2 is provided with a discharge unit 8 for discharging carbon dioxide hydrate generated indoors. The discharge part 8 is provided at the bottom (the seabed 12 side) of the first chamber body 2.

By using the methane gas recovery-accompanying water treatment apparatus 10 configured as described above and executing the method of treating methane gas recovery-accompanying water, the following effects can be obtained.
That is, in the first chamber 2, a generation process for generating carbon dioxide hydrate using methane gas recovery accompanying water W as raw water is performed, and the carbon dioxide hydrate generated in the generation process is discharged from the discharge unit 8 into the sea 18. (Return process). The underwater 18 is the water area of the seabed 12 where the methane gas recovery accompanying water W originally exists, that is, the water area where the methane hydrate layer 14 exists.

Carbon dioxide hydrate has a higher specific gravity than water (water in general, including seawater and lake water), and sinks under its own weight in the sea 18. Therefore, since the carbon dioxide hydrate discharged from the discharge unit 8 sinks to the sea floor 12 due to its own weight, the methane gas recovery accompanying water W can be easily returned to the sea floor 12 in a hydrate state.
Further, since the generated carbon dioxide hydrate is discharged into the sea 18 and sinks to the sea floor 12 due to its own weight, the methane gas recovery accompanying water W can be returned to the sea floor 12 with energy saving.

In the present embodiment, carbon dioxide hydrate is generated in the first chamber body 2 floating in the sea 18.
At a position in the water (underwater 18) such as the sea or lake where the first chamber 2 floats, the water temperature is lower and the pressure is higher than on the water. Therefore, less energy is required to bring the inside of the first chamber body 2 floating in the sea 18 into high pressure and low temperature conditions for generating carbon dioxide hydrate, thereby suppressing the cost for generating carbon dioxide hydrate. can do.
In particular, if the first chamber body 2 is floated in the vicinity of 200 m to 400 m, the inside of the first chamber body 2 can be made to generate carbon dioxide hydrate by the water pressure and the water temperature.

  Moreover, since the discharge part 8 is provided in the bottom part of the 1st chamber body 2, the carbon dioxide hydrate whose specific gravity is larger than water (seawater) can be discharged | emitted from the 1st chamber body 2 efficiently.

<Other configurations of the first chamber>
A gas discharge line 25 is provided in the upper part of the first chamber body 2, and carbon dioxide gas that has passed without being hydrated in the water (methane gas recovery associated water W) in the first chamber body 2 is discharged. It is comprised so that. The gas discharge line 25 is joined to the CO ₂ introduction line 7, and the discharged carbon dioxide is configured to recirculate to the first chamber body 2.
The gas discharge line 25 is provided with a valve 26 as a pressure adjusting unit, and is adjusted so as to apply a pressure at which a gas-liquid interface 23 is formed in the chamber of the first chamber body 2. By adjusting the pressure by the valve 26 and applying substantially the same pressure as the water pressure at the depth at which the first chamber body 2 is located in the chamber of the first chamber body 2, a gas-liquid interface 23 is formed in the chamber.
As a result, the carbon dioxide hydrate formation reaction is performed in a state where the gas-liquid interface 23 exists in the chamber of the first chamber body 2, and a stable reaction can be realized.

  The first chamber body 2 includes a thruster 24 or the like that can adjust the horizontal position of the first chamber body 2 in addition to the floating mechanism 4 that adjusts the position of the first chamber body 2 in the depth direction. Is provided. Thereby, the 1st chamber body 2 can be horizontally moved to a desired position. Moreover, when the flow of the water area in which the first chamber body 2 is provided is fast, the thrust of the thruster 24 resists the flow, and the horizontal position of the first chamber body 2 can be maintained.

The first chamber body 2 can be provided not only in water but also on water. In that case, carbon dioxide hydrate can be generated by setting the inside of the first chamber body 2 as a condition for generating carbon dioxide hydrate by the pressure adjusting unit 26 and the temperature adjusting unit (not shown) described above.
The carbon dioxide hydrate generated in the first chamber body 2 on the water sinks to the bottom of the water due to its own weight simply by throwing it into the water near the surface of the water, so that the hydrated recovered associated water can be easily returned to the bottom of the water. In addition, when providing the 1st chamber body 2 on water, the floating mechanism part 4, the thruster 24, etc. are unnecessary.

[Example 2]
Example 2 demonstrates other embodiment of the processing apparatus of the methane gas collection | recovery accompanying water based on FIG. FIG. 2 is a schematic configuration diagram showing another example of the methane gas recovery-accompanying water treatment apparatus according to the present invention.
In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description of the components is omitted.

The methane gas recovery-accompanying water treatment apparatus 30 according to the present embodiment is configured such that the water in the second chamber body 32 provided in the sea 18 is sent as the recovery-accompanying water W to be processed in the first chamber body 2. Has been. The second chamber body 32 plays a role as a recovery device that recovers methane gas from the methane hydrate layer 14 on the seabed 12.
The second chamber body 32 includes a floating mechanism portion 33 that floats the second chamber body 32 in the sea 18. As the floating mechanism portion 33, a ballast tank or the like is used similarly to the floating mechanism portion 4 of the first chamber body 2, and the depth position where the second chamber body 32 is floated is adjusted by adjusting the amount of ballast water in the ballast tank. It is configured so that it can be changed. The second chamber body 32 is also provided with a propulsion device such as a thruster 37 whose horizontal position can be adjusted.

The second chamber body 32 has a receiving portion 36 for receiving a mass of methane hydrate separated from the methane hydrate layer 14 below the second chamber body 32. The receiving part 36 is provided with an introduction part 34 for guiding a mass of methane hydrate rising in the sea into the room.
In the present embodiment, a bell mouth 50 that is a cylindrical body that is continuous with the receiving portion 36 and that has a bellows shape in which the lower side expands in a bell shape is provided as the introduction portion 34.
The methane hydrate can be stably put into the second chamber body 32 by guiding the mass of methane hydrate rising in the water to the receiving portion 36 by the introduction portion 34 such as the bell mouth 50.

  The methane hydrate layer 14 can be crushed, for example, by blasting with an explosive or the like, and the massive methane hydrate can be separated from the bottom of the water. Moreover, the methane hydrate layer 14 can also be crushed into massive methane hydrate by excavation by an excavator equipped with a drill, a bucket, or the like.

Since the specific gravity of methane hydrate (MGH) is smaller than that of water (seawater), the mass of methane hydrate separated from the methane hydrate layer 14 rises in the sea from the vicinity of the seabed 12. The rising mass of methane hydrate is received in the second chamber body 32 from the receiving portion 36 and is thermally decomposed in the chamber, whereby methane gas is recovered from the methane hydrate on the bottom of the water.
Specifically, the second chamber body 32 includes a heating unit 40 that heats the water in the second chamber body 32 and a methane gas extraction unit 38 that is generated by decomposition of methane hydrate. For example, the heating unit 40 may include a heat exchange unit 56 that applies heat to the heat medium in a circulation line 54 through which the heat medium circulates. Exhaust heat from the methane gas recovery ship 16 can also be used as a heat source for applying heat to the heat medium.

  By contact with the water heated by the heating unit 40, the mass of methane hydrate received in the second chamber body 32 is decomposed to generate methane gas. The decomposition of methane hydrate in the second chamber body 32 will be described in detail later.

  The take-out unit 38 is provided above the second chamber body 32, and the methane gas taken out from the take-out unit 28 is sent through the take-out line 35 and is collected by, for example, the methane gas recovery ship 16 as a collection destination. As the take-out line 35, a flexible cable such as an umbilical cable can be used.

Further, the take-out line 35 is provided with a valve 53 as a pressure adjusting unit that applies a pressure at which a gas-liquid interface 52 is formed in the chamber of the second chamber body 32. A gas-liquid interface 52 is formed in the chamber of the second chamber body 32 by adjusting the valve 53 so that the pressure is substantially the same as the water pressure at the depth at which the second chamber body 32 is located.
Thereby, the thermal decomposition of methane hydrate is performed in the state where the gas-liquid interface 52 exists in the chamber of the second chamber body 32, 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 on the gas side and the liquid side, the separation / recovery from the inside of the 2nd chamber body 32 of decomposition | disassembly production | generation methane gas can be performed easily.

Here, the water generated by the decomposition of the methane hydrate in the second chamber body 32 is the water W1 near the seabed 12, that is, the water W accompanying methane gas recovery. When the methane hydrate is continuously decomposed in the second chamber body 32, methane gas recovery accompanying water W (water generated by the decomposition of methane hydrate) is accumulated in the second chamber body 32.
In particular, if the interior of the chamber is maintained at a pressure at which a gas-liquid interface 52 is formed, the water near the lower end of the bell mouth 50 is transferred to the outside sea 18 by the amount of water generated by the decomposition (water W associated with methane gas recovery). Extruded and the position of the gas-liquid interface 52 is maintained. In other words, under the condition that the gas-liquid interface 52 exists in the second chamber body 32, the methane hydrate lump rises in the introduction portion 34 by buoyancy in the second chamber body 32, Therefore, it can be said that methane hydrate and water are generated by methane hydrate being decomposed by heat with almost no water entering. Therefore, the ratio of the methane gas recovery accompanying water W in the second chamber body 32 is increased.

In the present embodiment, in order to return the recovery associated water W accumulated in the second chamber body 32 to the seabed, the water in the second chamber body 32 is sent into the first chamber body 2 as the recovery associated water W. It is configured.
Specifically, a water supply line 48 for sending water in the second chamber body 32 (collected water W) into the first chamber body 2 is provided. A pump 44 can be provided in the water supply line 48.

  With this configuration, the recovery-accompanying water W generated when methane hydrate is decomposed and methane gas is recovered in the second chamber body 32 can be sent to the first chamber body 2. In the chamber 2, the recovery-accompanying water W can be returned to the seabed 12 as carbon dioxide hydrate.

Further, the carbon dioxide hydrate formation reaction is an exothermic reaction (about 65 kJ / mol). On the other hand, the decomposition reaction of methane gas hydrate is an endothermic reaction (52-57 kJ / mol).
Therefore, the energy required for heating in the second chamber body 32 is suppressed by exchanging heat between the generated heat (heat generation) in the first chamber body 2 and the decomposition heat (heat absorption) in the second chamber body 32. Can do.
Therefore, it is preferable to provide the heat exchange part 42 which performs heat exchange between the first chamber body 2 and the second chamber body 32.

<About the second chamber>
The decomposition (gasification) of methane hydrate performed in the second chamber body 32 will be described.
The second chamber 32 as a gasifier for recovering methane gas from the bottom methane hydrate is composed of the methane hydrate separated from the methane hydrate layer 14 in the second chamber 32 floating in the sea 18. The methane hydrate received can be heated and decomposed by receiving the mass and bringing it into contact with water (seawater) heated in the room.

  At a position in the water where the second chamber body 32 is floating (position between the sea floor 12 and the sea surface 15), the water temperature is higher than the sea floor 12 and the water pressure is lower. Therefore, for example, the thermal energy required for the decomposition of methane hydrate is less than the thermal energy required for decomposing methane hydrate on the seabed 12, for example, so that the cost associated with gasification of methane hydrate can be increased. Can be suppressed.

  Further, for example, there is a case where methane hydrate is collected as a lump to the sea level 15 for the recovery of methane gas. In such a case, due to the decomposition that occurred during the extraction of the methane hydrate lump, the temperature decreased due to heat absorption and the pressure inside the piping increased due to the generated methane gas, resulting in the generation of methane hydrate locally. If the conditions are met, the methane hydrate may harden and the lifting pipe or the like may be blocked. When the second chamber body 32 is used, the range in which the methane hydrate is collected as a lump is up to the position of the second chamber body 32 floating in the sea 18 and is not collected up to the sea level 15. Therefore, it is possible to reduce the risk of problems caused by the solidification of methane hydrate during the tan hydrate lump. Moreover, since it is not picked up to the surface of the sea surface 15, it becomes possible to reduce the instability of the picking due to the decomposition during the picking. Thereby, the recovery efficiency of methane gas from bottom methane hydrate is improved.

  Further, the second chamber body 32 is floated at a water depth (for example, a water depth of 500 m) that reliably satisfies the methane hydrate generation condition, for example, so that the methane hydrate separated from the seabed 12 is hardly decomposed. Therefore, the amount of methane gas to be decomposed can be increased or decreased by adjusting the amount of heat given by the heating unit 40 to the water in the second chamber body 32.

  The floating mechanism unit 33 is configured to float the second chamber body 32 at a depth of 400 m or more, and decomposes methane hydrate in the second chamber body 32 at a water depth that satisfies the conditions for generating methane hydrate at a depth of 400 m or more. It is good to do.

  The boundary of the water depth that satisfies the methane hydrate production condition is about 400 m (depending on the region, surrounding environment, ocean current, etc.). Further, in the region deeper than about 400 m, the energy required for the decomposition of methane hydrate increases as the water depth increases, and the energy decreases as the depth approaches 400 m.

  Therefore, by floating the second chamber body 32 in the vicinity of the boundary of the water depth that satisfies the methane hydrate generation condition, the energy required for the decomposition of the methane hydrate in the second chamber body 32 can be suppressed. Methane gas can be recovered from bottom methane hydrate for energy saving.

The second chamber body 32 is provided with a cylindrical net 58 that guides the methane hydrate mass rising in the water to the second chamber body 32.
The cylindrical net 58 may be configured to be directly attached to the second chamber body 32, or may be configured to be attached via another member (for example, the bell mouth 50).

As described above, the phase equilibrium condition of carbon dioxide hydrate is on the high temperature and low pressure side than the phase equilibrium condition of methane hydrate (FIG. 4). Therefore, for example, when the second chamber body 32 is floated at a water depth (for example, a water depth of 500 m) that reliably satisfies the methane hydrate generation condition, the first chamber body 2 that generates carbon dioxide hydrate is more than the second chamber body 32. Can float in shallow water depths.
In such a case, water (methane gas recovery accompanying water W) in the second chamber body 32 is sent through the water supply line 48 due to a pressure difference between the first chamber body 2 (low pressure) and the second chamber body 32 (high pressure). Therefore, the pump 44 can be omitted.

[Example 3]
In Example 3, another embodiment of the treatment apparatus for water accompanying methane gas recovery will be described with reference to FIG. FIG. 3 is a schematic configuration diagram showing still another example of the methane gas recovery-accompanying water treatment apparatus according to the present invention.
In the present embodiment, the same components as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and the description of the configuration is omitted.

  The methane gas recovery-accompanying water treatment apparatus 60 according to the present embodiment recovers methane gas (decomposition of methane hydrate) from the methane hydrate layer 14 on the seabed 12 performed in the second chamber body 32 in Example 2. ) In the same chamber of the first chamber body 2 that generates carbon dioxide hydrate.

Similar to the first embodiment, the first chamber body 2 is in a state of floating in the sea 18 by the ballast tank 20 (the floating mechanism unit 4).
In the present embodiment, the discharge portion 8 of the first chamber body 2 also serves as a receiving portion 36 that receives a mass of methane hydrate separated from the methane hydrate layer 14, and a bell mouth as an introduction portion 34 on the lower side thereof. 50 is provided. In addition, a cylindrical net 58 is provided for guiding the methane hydrate mass rising in the water to the bell mouth 50.

The first chamber body 2 further includes a heating unit 62 that heats indoor water, and the water heated by the heating unit 62 and the methane hydrate received in the first chamber body 2 from the receiving unit 36 come into contact with each other. It is decomposed by heating to generate methane gas. The generated methane gas is taken out from the take-out section 64 and sent to the methane gas storage section 19 of the methane gas collection ship 16 as a collection destination through the take-out line 66.
Further, the take-out line 66 is provided with a valve 70 as a pressure adjusting unit that applies a pressure at which a gas-liquid interface 68 is formed in the chamber of the first chamber body 2. A gas-liquid interface 68 is created in the interior of the first chamber body 2 by adjusting the valve 70 so that the pressure is substantially the same as the water pressure at the depth at which the first chamber body 2 is located.

Here, the water generated by the decomposition of methane hydrate in the first chamber body 2 is the water W1 in the vicinity of the seabed 12 as described in the second embodiment, and is the water W accompanying methane gas recovery. When the methane hydrate is continuously decomposed in the first chamber body 2, the methane gas recovery accompanying water W accumulates in the first chamber body 2.
In the present embodiment, the recovered associated water W accumulated in the first chamber body 2 is reacted with carbon dioxide in the same first chamber body 2 to form carbon dioxide hydrate (CO ₂ GH).

As described above, carbon dioxide hydrate is easier to produce at lower pressure and higher temperature than methane hydrate. In other words, carbon dioxide hydrate is more easily generated than methane hydrate under the same temperature and pressure conditions. That is, carbon dioxide hydrate can be generated even under temperature and pressure conditions where methane hydrate is decomposed.
For example, in the first chamber body 2, the methane hydrate is decomposed but the carbon dioxide hydrate is generated at the water pressure at the water depth where the first chamber body 2 is located. Decomposition of methane hydrate and treatment of water W accompanying methane gas recovery generated at the time of decomposition (carbon dioxide hydrate conversion) can be performed simultaneously.

  Moreover, since the production | generation (exothermic reaction) of a carbon dioxide hydrate and decomposition | disassembly (endothermic reaction) of methane hydrate are performed within the same 1st chamber body 2, both reaction heat is heat-exchanged through indoor water. Therefore, the energy required for heating in the first chamber body 2 can be suppressed.

The first chamber body 2 is preferably configured to be floated within a range of a water depth of 300 m to 500 m by the floating mechanism 4.
As a result, the first chamber body 2 can be floated near the boundary of the water depth (about 400 m) that satisfies the methane hydrate generation condition, and the amount of heat required for the decomposition of the methane hydrate in the first chamber body 2 is reduced. Can be suppressed. Carbon dioxide hydrate is also generated at water depth that satisfies the methane hydrate generation conditions. Therefore, carbon dioxide hydrate can be generated at the pressure and temperature of the depth of water where the first chamber body 2 is located.

<Other configurations of the first chamber>
It is desirable that the gas taken out from the take-out section 38 is configured to be able to join the CO ₂ introduction line 7 through a line 72 branched from the take-out line 66. The line 72 is provided with a valve 74 that opens and closes the line 72.
When there is carbon dioxide gas that passes without being hydrated in the water in the first chamber body 2 (water W associated with methane gas recovery), the methane gas and the carbon dioxide gas are mixed and sent by the extraction line 66. In such a case, the valve 74 is opened and the valve 70 provided in the take-out line 66 is closed, and a mixed gas in which carbon dioxide gas and methane gas are mixed is circulated to the first chamber body 2. Thereby, mixing of carbon dioxide into the methane gas to be recovered can be suppressed or avoided.

  Also in the present embodiment, the carbon dioxide hydrate generated from the methane gas recovery-accompanying water W in the first chamber body 2 is discharged into the water from the discharge portion 8 of the first chamber body 2, so that the carbon dioxide hydrate is caused by its own weight. Since it sinks, the methane gas recovery accompanying water W can be returned to the water bottom as a hydrate.

  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.

2 first chamber body, 4 floating mechanism, 6 water supply line,
7 CO ₂ introduction line, 8 discharge section,
10 Water treatment equipment associated with methane gas recovery, 12 Sea bottom (water bottom),
13 Methane gas recovery device, 14 Methane hydrate layer,
15 sea surface (water surface), 16 methane gas recovery vessel, 17 gas-liquid separation part,
18 Underwater (underwater), 19 Methane gas reservoir, 20 Ballast tank,
22 ballast water, 23 gas-liquid interface, 24 thrusters, 25 gas discharge line,
26 Valve (pressure adjusting part), 30 Methane gas recovery associated water treatment device 32 Second chamber body, 33 Floating mechanism part, 34 Introducing part,
35 take-out line, 36 receiving section, 37 thruster,
38 extraction section, 40 heating section, 42 heat exchange section, 44 pump, 48 water supply line,
50 bell mouth, 52 gas-liquid interface, 53 valve (pressure adjusting part),
54 circulation line 56 heat exchanger, 58 cylindrical net,
60 Water treatment equipment associated with methane gas recovery, 62 heating section, 64 extraction section,
66 take-out line, 68 gas-liquid interface, 70 valve (pressure adjusting part),
72 lines, 74 valves

Claims (11)

With the methane gas recovery from the methane hydrate in the bottom of the water, a methane gas recovery associated water treatment apparatus moved from the bottom of the water to a shallow area or above the bottom of the water,
A first chamber body capable of containing carbon dioxide and the recovered water, and capable of generating carbon dioxide hydrate using the recovered water as raw water;
A discharge section for discharging carbon dioxide hydrate generated in the first chamber into water;
An apparatus for treating methane gas recovery-accompanying water, comprising: In the methane gas recovery-accompanying water treatment apparatus according to claim 1,
A methane gas recovery-accompanying water treatment apparatus, comprising: a floating mechanism unit that floats the first chamber body in water. In the methane gas recovery associated water treatment apparatus according to claim 1 or 2,
The apparatus for treating methane gas recovery-accompanying water, wherein the discharge part is provided at the bottom of the first chamber body. In the processing apparatus for water accompanying methane gas recovery described in claim 2,
The inside of the first chamber is
A take-out section that is configured to receive a mass of methane hydrate that is located in water and that rises from the bottom of the water, and that extracts methane gas generated by decomposition of the methane hydrate in the first chamber. A methane gas recovery-accompanying water treatment apparatus, comprising: In the apparatus for treating water accompanying methane gas recovery in claim 2,
It has a second chamber body that accepts a mass of methane hydrate at the bottom of the water and decomposes the methane hydrate with the chamber body floating in water.
The apparatus for treating methane gas recovery-accompanying water is configured to send water in the second chamber as the recovery-accompanying water to the first chamber. In the processing apparatus for water accompanying methane gas recovery according to claim 5,
An apparatus for treating methane gas recovery-accompanying water, wherein heat exchange is possible between the first chamber and the second chamber. A process for treating methane gas recovery associated water that has been moved from the water bottom to a shallower area of the water bottom or on the water, along with methane gas recovery from methane hydrate at the bottom of the water,
In the first chamber, a generation step of generating carbon dioxide hydrate using the collected water as raw water,
A step of returning the generated carbon dioxide hydrate to the water bottom by sinking in water by its own weight;
A method for treating water accompanying methane gas recovery, characterized by comprising: The method for treating water accompanying recovery of bottom methane hydrate according to claim 7,
The method for generating water associated with methane gas recovery, wherein the generating step is performed in a state where the first chamber is floated in water. The method for treating water associated with recovery of bottom methane hydrate according to claim 8,
A first raising step of methane hydrate which raises methane hydrate present in the bottom of the water in a lump and is received in the first chamber located in water;
A first decomposition step of decomposing the methane hydrate in contact with heated water in the first chamber;
A first methane gas recovery step of taking out and recovering the methane gas generated in the decomposition step from the first chamber;
A method for treating water accompanying the recovery of bottom methane hydrate, comprising: The method for treating water associated with recovery of bottom methane hydrate according to claim 8,
A second step of raising the methane hydrate present in the bottom of the water in the form of a lump to be received in the second chamber located in the water;
A second decomposing step of decomposing methane hydrate in contact with heated water in the second chamber;
A second methane gas recovery step of taking out and recovering the methane gas generated in the decomposition step from the first chamber;
A water feeding step of sending water in the second chamber to the first chamber;
A method for treating water accompanying the recovery of bottom methane hydrate, comprising: The method for treating water associated with recovery of bottom methane hydrate according to claim 10,
A method for treating water associated with recovery of bottom methane hydrate, wherein heat exchange is performed between the first chamber and the second chamber.

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