CN111852409B - A kind of natural gas hydrate extraction device and method - Google Patents

Abstract

The invention relates to the technical field of natural gas hydrate exploitation, and discloses a natural gas hydrate exploitation device and a natural gas hydrate exploitation method, wherein the device comprises: the device comprises a collecting pipeline, a first tank body, a second tank body, a third tank body and a fourth tank body, wherein a collecting and conveying device is arranged in the collecting pipeline; the first conveying pipe is provided with a second transmission valve; the second jar of body is equipped with the second baroceptor on the second jar of body, the buffer tank, be equipped with the third baroceptor on the buffer tank, the buffer tank passes through the sealed intercommunication of first pipeline with the first jar of body, pass through the sealed intercommunication of second pipeline with the second jar of body, the holding vessel, be equipped with the fourth baroceptor on the holding vessel, the holding vessel passes through the sealed intercommunication of third pipeline with the buffer tank, this kind of natural gas hydrate exploitation device and method, can fully separate and decompose natural gas hydrate, avoid natural gas to leak, and can carry out safe storage to the natural gas, be convenient for transport.

Description

A kind of natural gas hydrate extraction device and method

technical field

The invention relates to the technical field of natural gas hydrate exploitation, in particular to a natural gas hydrate exploitation device and method.

Background technique

The conventional oil and natural gas resources in the world are hugely consumed and will soon be exhausted. Scientists' evaluation results show that in the seabed area alone, the distribution area of combustible ice reaches 40 million square kilometers, accounting for 1/4 of the total area of the earth's oceans. The thickness and scale of its deposits are unmatched by conventional natural gas fields. Scientists estimate that the reserves of combustible ice on the sea floor will be enough for humans to use for at least 1,000 years.

Natural gas hydrate, also known as "flammable ice", is an ice-like crystalline substance formed by natural gas and water under high pressure and low temperature, distributed in deep-sea sediments or permafrost in land areas. It is also called "flammable ice" because it looks like ice and can burn when exposed to fire. Its resource density is high, the global distribution is wide, and it has extremely high resource value, so it has become a long-term research hotspot in the oil and gas industry.

Natural gas hydrate produces almost no residue after combustion, and its pollution is much smaller than that of coal, oil and natural gas. 1 cubic meter of combustible ice can be converted into 164 cubic meters of natural gas and 0.8 cubic meters of water. A large amount of methane gas can be released by heating and decompressing the solid "natural gas hydrate" during mining.

Combustible ice is formed at 0-10 °C, and will decompose when it exceeds 20 °C. The temperature of the seabed is generally maintained at about 2-4 °C; when the combustible ice is at 0 °C, only 30 atmospheres of pressure can be generated, and with the depth of the ocean, 30 atmospheres can be easily guaranteed, and the higher the pressure, the less likely the hydrate is. Easily decomposed; sedimentation of organic matter on the seafloor, where abundant carbon undergoes biotransformation, producing sufficient gas sources. The stratum on the seabed is a porous medium. Under the conditions of temperature, pressure and gas source, combustible ice crystals will be formed in the gaps of the medium.

The exploitation of natural gas hydrates will change the temperature and pressure conditions on which natural gas hydrates exist, causing the decomposition of natural gas hydrates. If the temperature and pressure conditions cannot be effectively controlled in the process of gas hydrate exploitation, a series of environmental problems may occur, such as the intensification of the greenhouse effect, changes in marine ecology, and seafloor slumps.

At present, there are few devices capable of exploiting natural gas hydrate, which greatly limits the exploitation process of natural gas hydrate.

SUMMARY OF THE INVENTION

The invention provides a natural gas hydrate exploitation device and method, which can fully separate and decompose the natural gas hydrate, avoid natural gas leakage, and store the natural gas safely and facilitate transportation.

The invention provides a natural gas hydrate extraction device, comprising: a collection pipeline with a collection and conveying device inside, which is used for extracting a mixture of natural gas hydrate and silt from the seabed, and transporting the extracted mixture to a first tank in vivo;

The first tank is communicated with the upper end of the collection pipeline and is used for receiving the mixture; the natural gas hydrate and the sludge are separated in the first tank, and the inner surface of the first tank is provided with a device that can seal the collection pipeline. a first electric blocking cover, and a first air pressure sensor is arranged on the first tank body;

The high-pressure water pipe extends into the first tank and is used to dilute the sludge in the mixture in the first tank to separate the natural gas hydrate, and the high-pressure water pipe is provided with a control valve;

The muddy water conveying pipe is arranged between the first tank body and the collection pipe inclined downward, and the two ends of the muddy water conveying pipe are respectively connected with the first tank body and the lower part of the collection pipe, and are used to dilute the sludge in the first tank to form The muddy water is sent back to the area where the mixture is extracted through the collection pipe, and the mud water conveying pipe is provided with a first transmission valve;

The first conveying pipe is arranged between the first tank body and the second tank body, and the two ends are respectively communicated with the first tank body and the second tank body, and is used to transport the natural gas hydrate or the porous medium fixed with the natural gas hydrate It is conveyed into the second tank, and the first conveying pipe is provided with a second transmission valve;

The second tank is located below the first tank, the second tank is provided with a second air pressure sensor, and the second tank is provided with a heating device for heating and decomposing the natural gas hydrate to decompose the natural gas;

The buffer tank is used to collect natural gas. The buffer tank is provided with a third air pressure sensor. The buffer tank is in sealing communication with the first tank body through the first pipeline. The buffer tank is in sealing communication with the second tank body through the second pipeline. A first gas control valve is provided, and a second gas control valve is provided on the second pipeline;

The storage tank is used to store natural gas, the storage tank is provided with a fourth air pressure sensor, and the storage tank is in sealing communication with the buffer tank through the third pipeline;

Collection and conveying device, control valve, first transmission valve, second transmission valve, first gas control valve, second gas control valve, first electric cover, first air pressure sensor, second air pressure sensor, third air pressure sensor, The fourth air pressure sensor and the heating device are respectively connected with the control system and the power supply, and the control system is connected with the power supply.

The collection pipeline includes multiple sections of pipelines that are detachably connected in sequence. Each section of the pipeline is provided with a collection and conveying device. The collection and conveying device includes a fixing plate. The shaft is connected to the screw conveying blade, the fixing plate is provided with a first conveying port for the mixture to pass through, the first driving motor is connected to the power supply through a wire, and the first driving motor is connected to the control system.

The first tank body is provided with a stirring motor, the output shaft of the stirring motor is fixedly connected to a rotating shaft, the rotating shaft extends into the first tank body, and a stirring blade is arranged on the rotating shaft.

The collection pipeline is communicated with the side of the first tank body through the second delivery port, and the inner side of the second delivery port is provided with a first electric blocking cover for sealing the second delivery port when natural gas hydrate is separated;

The first tank body is also provided with a plurality of high-pressure spray heads, and the plurality of high-pressure spray heads are respectively communicated with the high-pressure water pipes.

The first pipeline and the second pipeline are connected to one end of the intake manifold through a tee joint, and the other end of the intake manifold is communicated with the buffer tank. The intake manifold is provided with a gas suction pump, and the gas suction pump is respectively connected to the power supply. connected to the control system.

A second conveying pipe is arranged between the second tank body and the collection pipe, the two ends of the second conveying pipe are respectively connected with the lower part of the second tank body and the collection pipe, and a third transmission valve is arranged on the second conveying pipe , the third transmission valve is respectively connected with the power supply and the control system.

A method for exploiting natural gas hydrate, comprising the following steps:

S1. Extract the mixture of natural gas hydrate and silt at the bottom of the ocean through the collection and conveying device in the collection pipeline, and transport it into the first tank;

S2. The mixture is injected into the first tank with high-pressure water through a high-pressure water pipe to dilute the sludge, and the natural gas hydrate or the porous medium fixed with the natural gas hydrate is separated;

S3. The diluted mud water is sent back to the area where the mixture is extracted through the mud water conveying pipe and the collecting pipe;

S4, the separated natural gas hydrate and the porous medium fixed with the natural gas hydrate are sent into the second tank through the first conveying pipe and the second transmission valve;

S5, the natural gas hydrate is heated and decomposed by the heating device in the second tank to decompose the natural gas;

S6, the natural gas enters the buffer tank through the second pipeline and the second gas control valve;

S7. When the gas pressure in the buffer tank reaches the set gas pressure, enter the storage tank through the third pipeline;

S8. When the gas pressure in the storage tank reaches the set gas pressure, replace the storage tank with a new one to realize the exploitation of natural gas hydrate.

In the first tank, the mixture is driven by the stirring motor to drive the rotating shaft, and the rotating shaft drives the stirring blade to stir the mixture, fully mixing and diluting the water and the sludge to form mud or mud water, and separate the natural gas hydrate.

The natural gas hydrate is decomposed after being heated in the second tank, and the decomposed natural gas is sucked into the buffer tank by the gas suction pump. During the suction process of the gas suction pump, the pressure of the natural gas hydrate is reduced, and the pressure decreases At the same time, the temperature rises, which can rapidly decompose natural gas hydrate.

Compared with the prior art, the beneficial effects of the present invention are:

In the invention, the mixture of natural gas hydrate and silt is extracted from the seabed by setting the collection pipeline of the collection and conveying device, and the silt is decomposed by high-pressure water in the first tank to separate the natural gas hydrate. During the process of decomposing the silt, part of the natural gas After the pressure of the hydrate is reduced, it is decomposed into natural gas. The decomposed natural gas enters the buffer tank through the first pipeline. The sludge is decomposed into muddy water through high-pressure water flow. The muddy water is sent back to the area where the mixture is extracted through the muddy water transportation pipeline and the collection pipeline. The remaining undecomposed natural gas hydrate is sent to the second tank through the first delivery pipe for heating and decomposing, and the natural gas decomposed by heating and heating enters the buffer tank through the second pipeline. When the natural gas pressure in the buffer tank reaches the set pressure After the pressure reaches the set value, the natural gas in the buffer tank enters the storage tank through the third pipeline, and when the natural gas pressure in the storage tank reaches the set value, the storage tank is replaced.

The device can fully separate the natural gas hydrate and the silt, can decompose the natural gas hydrate, avoid natural gas leakage, and at the same time fill the silt into the mining area after precipitation of the mud water, so as to avoid the collapse of the mining area, which will cause the natural gas hydrate pressure to decrease and then decompose. , The natural gas can be safely stored through the buffer tank and the storage tank, and the storage tank is convenient for the transportation of the natural gas.

Description of drawings

FIG. 1 is a schematic structural diagram of a section of a natural gas hydrate exploitation device provided by the present invention.

2 is a schematic structural diagram of a transmission valve in a natural gas hydrate exploitation device provided by the present invention.

FIG. 3 is a block diagram of the control principle of a natural gas hydrate exploitation device provided by the present invention.

Detailed ways

A specific embodiment of the present invention will be described in detail below with reference to the accompanying drawings 1-3, but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " Rear, Left, Right, Vertical, Horizontal, Top, Bottom, Inner, Outer, Axial, Radial, Circumferential The orientation or positional relationship indicated by etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the technical solutions of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, It is constructed and operated in a particular orientation and is therefore not to be construed as a limitation of the present invention.

As shown in FIG. 1 , a natural gas hydrate extraction device provided in an embodiment of the present invention includes: a collection pipeline 1, which is provided with a collection and transportation device for extracting a mixture of natural gas hydrate and silt from the seabed, and The extracted mixture is transported to the first tank 10;

The first tank 10 communicates with the upper end of the collection pipeline 1 and is used to receive the mixture; the natural gas hydrate and the sludge are separated in the first tank 10, and the first tank 10 is provided with a first air pressure sensor;

The high-pressure water pipe 9 extends into the first tank body 10 and is used to dilute the sludge in the mixture in the first tank body 10 to separate the natural gas hydrate. The high-pressure water pipe 9 is provided with a control valve;

The muddy water conveying pipe 16 is disposed between the first tank body 10 and the collection pipe 1 obliquely downward. The muddy water formed by the dilution of the mud in the body 10 is sent back to the area where the mixture is extracted through the collection pipeline 1, and the muddy water conveying pipe 16 is provided with a first transmission valve 34;

The first conveying pipe 11 is arranged between the first tank 10 and the second tank 19, and the two ends are respectively communicated with the first tank 10 and the second tank 19, and is used for natural gas hydrate or fixed natural gas. The porous medium of hydrate is transported into the second tank 19, and the first transport pipe 11 is provided with a second transmission valve 13;

The second tank 19 is located below the first tank 10, a second air pressure sensor is provided on the second tank 19, and a heating device 32 is provided in the second tank 19 for heating and decomposing the natural gas hydrate, decompose natural gas;

The buffer tank 24 is used to collect natural gas. The buffer tank 24 is provided with a third air pressure sensor. The buffer tank 24 is in sealing communication with the first tank body 10 through the first pipeline 38 , and the buffer tank 24 is connected to the second tank body through the second pipeline 21 . 19 is sealed and connected, the first pipeline 38 is provided with a first gas control valve 39, and the second pipeline 21 is provided with a second gas control valve 23;

The storage tank 25 is used to store natural gas, a fourth air pressure sensor is provided on the storage tank 25, and the storage tank 25 is in sealing communication with the buffer tank 24 through the third pipeline 30;

Collection and delivery device, control valve, first transmission valve 34, second transmission valve 13, first gas control valve 39, second gas control valve 23, first air pressure sensor, second air pressure sensor, third air pressure sensor, fourth air pressure sensor The air pressure sensor and the heating device 32 are respectively connected with the control system and the power supply, and the control system is connected with the power supply.

The collection pipeline 1 includes multiple sections of pipelines that are detachably connected in sequence. Each section of the pipeline is fixedly provided with a collection and conveying device. The collection and conveying device includes a fixing plate 5. The fixing plate 5 is provided with a first driving motor 3. The first driving motor The output shaft of 3 is connected to the screw conveying blade 2 through a coupling. The fixed plate 5 is provided with a first conveying port 4 that allows the mixture to pass through.

The detachable connection is a tongue-and-groove threaded socket.

The first tank body 10 is provided with a stirring motor 35, the output shaft of the stirring motor 35 is fixedly connected to the rotating shaft 36 through a coupling, the lower end of the rotating shaft 36 extends into the first tank body 10, and the rotating shaft 36 is provided with a plurality of stirring Blade 37.

The heating device 32 is a heater, a temperature controller is provided on the heater, and the temperature controller is signally connected to the control system.

The collection pipeline 1 is communicated with the side of the first tank 10 through the second delivery port, and the inner side of the second delivery port is provided with a first electric blocking cover 7, which is used for the second delivery port when separating natural gas hydrate. closed;

The first tank body 10 is further provided with a plurality of high-pressure spray heads 8 , and the plurality of high-pressure spray heads 8 are respectively communicated with the high-pressure water pipes 9 .

The plurality of high-pressure spray heads 8 are evenly arranged on the inner measuring surface of the top of the first tank body 10 , and are located outside the rotation shaft 36 in the circumferential direction.

The first pipe 38 and the second pipe 21 are connected to one end of the intake manifold 40 through a tee joint, and the other end of the intake manifold 40 is communicated with the buffer tank 24 . The intake manifold 40 is provided with a gas suction pump 22 .

A second conveying pipe 33 is arranged between the second tank body 19 and the collection pipe 1, and both ends of the second conveying pipe 33 are respectively connected with the second tank body 19 and the lower part of the collection pipe 1. The second conveying pipe 33 There is a third transmission valve 6 on it.

When there are many impurities in the second tank 19, the impurities are transported into the area where the mixture is mined through the second conveying pipe 33 and the third transmission valve 6, so as to avoid the collapse of the mined area.

The first transmission valve 34, the second transmission valve 13 and the third transmission valve 6 all include: the second driving motor 12, the rotating shaft 17 and the first baffle plate 14 symmetrically arranged on the rotating shaft 17, the output shaft of the second driving motor and the The rotating shaft 17 is fixedly connected by a coupling, the edge of the baffle 14 is provided with a sealing ring, and the size and shape of the first baffle 14 are respectively the same as the shape and size of the first conveying pipe 11, the muddy water conveying pipe 16 and the second conveying pipe 33. Matching, the first transmission valve 34, the second transmission valve 13 and the third transmission valve 6 are in a sealed closed state when the first baffle 14 is perpendicular to the first conveying pipe 11, the muddy water conveying pipe 16 and the second conveying pipe 33 respectively. , otherwise, it is in the open state, and the size of the opening can be adjusted according to the angle between the first baffle 14 and the first conveying pipe 11, the muddy water conveying pipe 16 and the second conveying pipe 33, so as to facilitate the adjustment of the muddy water flow or Regulates the decomposition progress of gas hydrates.

The first transmission valve 34, the second transmission valve 13 and the third transmission valve 6 are respectively connected with the control system signal, and the first transmission valve 34, the second transmission valve 13 and the third transmission valve 6 can be adjusted manually at the same time.

The first electric blocking cover 7, the second electric blocking cover 18 and the third electric blocking cover 20 all include: an electric telescopic rod, a second baffle and a sealing strip, and the free end of the electric telescopic rod is fixed to the inner side of the second baffle The outer side of the second baffle is provided with a sealing strip in the circumferential direction, and the sealing strip matches the position of the opening. After the cover is closed, the second baffle is sealed with the first tank body 10 or the second tank body 19 respectively.

The electric telescopic rod is connected with the signal of the control system, and the electric telescopic rod is waterproof.

The present invention relates to the electric components that are in contact with water, which are all waterproof electric components.

The buffer tank 24 is provided with an exhaust pipe 26, the exhaust pipe 26 is provided with an exhaust valve 27, the storage tank 25 is provided with an intake pipe 28, the intake pipe 28 is provided with an intake valve 29, and the exhaust pipe 26 passes through the No. The three pipes 30 are detachably and sealedly connected to the air intake pipe 28 .

Both the buffer tank 24 and the storage tank 25 are provided with air pressure sensors, and the air pressure sensors are respectively connected with the control system, and the control system is connected with the alarm.

Working principle and process: The whole device can be set on the sea surface or in a submarine. The submarine dives into the seabed under the sea surface. The lower end of the collection pipeline 1 is provided with a cutting port 31, which is convenient for inserting into the seabed of the seabed. The collection pipeline 1 It is composed of multiple pipelines that are detachably connected in sequence. The first drive motor 3 drives the screw conveyor blade 2 to rotate, and the mixture of natural gas hydrate and silt is transported from the bottom to the top from the seabed, and enters the previous pipeline through the first delivery port 4. Inside, the mixture is sequentially transported into the first tank body 10 through a plurality of collecting and transporting devices.

After the mixture enters the first tank 10, the high-pressure water pipe 9 is opened, and high-pressure water is injected into the first tank 10 to separate impurities such as natural gas hydrate and sludge, and the sludge becomes mud under the action of high-pressure water and then becomes At the same time, the stirring motor 35 is started to drive the rotating shaft 36 to rotate, and the mixture and water are stirred by the stirring blade 37 to speed up the separation process of natural gas hydrate and sludge. The first transmission valve 34 is opened, and the muddy water enters the collection pipeline through the muddy water delivery pipe 16 In the lower part of 1, the soil sinks under the action of gravity and gradually fills the area where the mixture was originally extracted, and the collection pipeline 1 is raised, and the muddy water enters the area where the mixture is extracted. 15. The natural gas hydrate can be filtered and collected, and part of the natural gas hydrate will be decomposed into natural gas after the pressure is reduced, and the natural gas enters the buffer tank 24 through the first pipeline 38 and the first gas control valve 39 .

Although the collection pipe 1 is used for the transportation of muddy water while conveying the mixture, the muddy water flows down along the edge of the collection pipe 1 , and the mixture is conveyed upwards along the middle of the collection pipe 1 under the action of the screw conveying blades 2 .

The rest of the natural gas hydrate that is not decomposed falls into the bottom of the first tank 10 under the action of gravity, activates the second transmission valve 13 and enters the second tank 19 through the first conveying pipe 11 .

The first tank body 10 is provided with a liquid level sensor, and the liquid level sensor is connected with the control system.

The natural gas hydrate is heated and decomposed into natural gas in the second tank 19 by the heating device 32. Before heating, the second tank 19 is sealed by the second electric blocking cover 18 and the third electric blocking cover 20 to prevent natural leakage from entering. in the body of water.

The natural gas in the second tank 19 is sucked by the gas suction pump 22, so that the second tank 19 is kept in a near-vacuum state, and then the next decomposition of natural gas hydrate is performed.

When there are many impurities in the second tank 19 , the impurities are transported into the area where the mixture is extracted through the second delivery pipe 33 and the third transmission valve 6 .

A method for exploiting natural gas hydrate, comprising the following steps:

S1. Extract the mixture of natural gas hydrate and silt at the bottom of the ocean through the collection and conveying device in the collection pipeline 1, and transport it into the first tank 10;

S2. The mixture is injected into the first tank 10 through the high-pressure water pipe 9 and high-pressure water is injected to dilute the sludge to separate the natural gas hydrate or the porous medium fixed with the natural gas hydrate;

S3. The diluted mud water is sent back to the area where the mixture is extracted through the mud water conveying pipe 16 and the collecting pipe 1;

S4, the separated natural gas hydrate and the porous medium fixed with the natural gas hydrate are sent into the second tank 19 through the first conveying pipe 11 and the second transmission valve 13;

S5, the natural gas hydrate is heated and decomposed by the heating device in the second tank 19 to decompose the natural gas;

S6, the natural gas enters the buffer tank 24 through the second pipeline 21 and the second gas control valve 23;

S7, when the gas pressure in the buffer tank 24 reaches the set gas pressure, enter the storage tank 25 through the third pipeline 30;

S8. When the gas pressure in the storage tank 25 reaches the set gas pressure, replace the storage tank 25 with a new one to realize the exploitation of natural gas hydrate.

In the first tank 10, the mixture is driven by the stirring motor 35 to drive the rotating shaft 36, and the rotating shaft 36 drives the stirring blade 37 to stir the mixture, fully mixing and diluting the water and the sludge to form mud or muddy water, and separate the natural gas hydrate.

The natural gas hydrate is decomposed after being heated in the second tank 19, and the decomposed natural gas is sucked into the buffer tank 24 by the gas suction pump 22, and the natural gas hydrate is reduced during the suction process of the gas suction pump 22. The pressure, the pressure decrease simultaneously and the temperature increase, can rapidly decompose the gas hydrate.

The invention extracts the mixture of natural gas hydrate and silt from the seabed by setting a collection and conveying device in the collection pipeline, separates the silt and natural gas hydrate through high-pressure water flow in the first tank, separates the natural gas hydrate, and decomposes the natural gas hydrate. During the sludge process, the pressure of part of the natural gas hydrate is reduced and decomposed into natural gas, the decomposed natural gas enters the buffer tank through the first pipeline, the sludge is decomposed into mud water after being decomposed by high-pressure water, and the mud water is sent into the mixture through the mud water pipeline and extracted. The remaining undecomposed natural gas hydrate enters the second tank through the first delivery pipe for heating and decomposition, and the heated and decomposed natural gas enters the buffer tank through the second pipeline. When the natural gas pressure in the buffer tank reaches the set value , the natural gas in the buffer tank enters the storage tank through the third pipeline.

The device can fully separate and decompose natural gas hydrate, avoid natural gas leakage, and can safely store natural gas for easy transportation.

The above disclosures are only a few specific embodiments of the present invention, however, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims (10)

1. a natural gas hydrate exploitation device, is characterized in that, comprises: The collection pipeline (1) is provided with a collection and conveying device for extracting the mixture of natural gas hydrate and silt from the seabed, and transporting the extracted mixture into the first tank (10); The first tank (10) communicates with the upper end of the collection pipeline (1) and is used for receiving the mixture; the natural gas hydrate and the sludge are separated in the first tank (10), and the A first electric blocking cover (7) capable of sealing the collection pipeline (1) is provided on the inner side, and a first air pressure sensor is provided on the first tank body (10); The high-pressure water pipe (9) extends into the first tank (10), and is used for diluting the sludge in the mixture in the first tank (10) to separate the natural gas hydrate. The high-pressure water pipe (9) is provided with a control valve; The muddy water conveying pipe (16) is disposed obliquely downward between the first tank body (10) and the collection pipe (1), and the two ends of the muddy water conveyance pipe (16) are respectively connected to the first tank body (10) and the collection pipe (1). ) is communicated with the lower part of the first tank body (10), and the muddy water formed by the dilution of the mud in the first tank (10) is sent back to the area where the mixture is extracted through the collection pipe (1). The muddy water conveying pipe (16) is provided with a first transmission. valve (34); The first conveying pipe (11) is arranged between the first tank body (10) and the second tank body (19), and the two ends are respectively communicated with the first tank body (10) and the second tank body (19), For conveying the natural gas hydrate or the porous medium fixed with the natural gas hydrate into the second tank (19), the first conveying pipe (11) is provided with a second transmission valve (13); The second tank (19) is located below the first tank (10), the second tank (19) is provided with a second air pressure sensor, and the second tank (19) is provided with a heating device (32), It is used for heating and decomposing natural gas hydrate to decompose natural gas; The buffer tank (24) is used for collecting natural gas, the buffer tank (24) is provided with a third air pressure sensor, the buffer tank (24) is in sealing communication with the first tank body (10) through the first pipeline (38), and the buffer tank ( 24) The second pipe (21) is in sealing communication with the second tank (19), the first pipe (38) is provided with a first gas control valve (39), and the second pipe (21) is provided with a second gas control valve (23); a storage tank (25) for storing natural gas, a fourth air pressure sensor is arranged on the storage tank (25), and the storage tank (25) is in sealing communication with the buffer tank (24) through a third pipeline (30); Collection and conveying device, control valve, first transmission valve (34), second transmission valve (13), first gas control valve (39), second gas control valve (23), first electric blocking cover (7), The first air pressure sensor, the second air pressure sensor, the third air pressure sensor, the fourth air pressure sensor, and the heating device (32) are respectively connected with the control system and the power supply, and the control system is connected with the power supply. 2. The natural gas hydrate extraction device according to claim 1, wherein the collection pipeline (1) comprises multiple sections of pipelines that are detachably connected in sequence, each section of the pipeline is provided with a collection and conveying device, and the collection and conveying device comprises A fixing plate (5), a first driving motor (3) is arranged on the fixing plate (5), and the output shaft of the first driving motor (3) is connected to the screw conveying blade (2) through a coupling, and the fixing plate (5) is provided with a first driving motor (3). A first delivery port (4) for passing the mixture is provided, the first driving motor (3) is connected to the power supply through a wire, and the first driving motor (3) is connected to the power supply and the control system. 3. The natural gas hydrate exploitation device according to claim 1, wherein a stirring motor (35) is provided on the first tank body (10), and the output shaft of the stirring motor (35) is fixedly connected to the rotating shaft (36). ), the rotating shaft (36) extends into the first tank (10), the rotating shaft (36) is provided with a stirring blade (37), and the stirring motor (35) is connected to the power supply and the control system. 4. The natural gas hydrate exploitation device according to claim 1, characterized in that, the collection pipeline (1) is communicated with the side of the first tank (10) through a second delivery port, and the inner side of the second delivery port A first electric blocking cover (7) is provided for sealing the second delivery port when separating natural gas hydrate; The first tank body (10) is further provided with a plurality of high-pressure spray heads (8), and the plurality of high-pressure spray heads (8) are respectively communicated with the high-pressure water pipes (9). 5 . The natural gas hydrate exploitation device according to claim 1 , wherein the third pipeline ( 30 ) is provided with a flow valve and a gas pump, and the flow valve and the gas pump are respectively connected to a power supply and a control system. 6 . 6. The natural gas hydrate exploitation device according to claim 1, wherein the first pipeline (38) and the second pipeline (21) are connected to one end of the intake manifold (40) through a tee joint, and the intake The other end of the main pipe (40) is communicated with the buffer tank (24), and a gas suction pump (22) is arranged on the inlet main pipe (40), and the gas suction pump (22) is respectively connected with the power supply and the control system. 7. The natural gas hydrate extraction device according to claim 1, characterized in that, a second conveying pipe (33) is provided between the second tank (19) and the collection pipeline (1), and the second conveying pipe The two ends of (33) are respectively communicated with the second tank (19) and the lower part of the collection pipe (1). The second conveying pipe (33) is provided with a third transmission valve (6), which is respectively connected with Power and control system connections. 8. A method for exploiting natural gas hydrate, characterized in that, using the device for exploiting natural gas hydrate described in any of claims 1-7, comprising the following steps: S1. The mixture of natural gas hydrate and silt at the bottom of the ocean is extracted through the collection and conveying device in the collection pipeline (1), and transported into the first tank (10); S2. The mixture is injected into the first tank (10) through the high-pressure water pipe (9) to dilute the sludge by injecting high-pressure water, so as to separate the natural gas hydrate or the porous medium in which the natural gas hydrate is fixed; S3. The diluted mud water is sent back to the area where the mixture is extracted through the mud water conveying pipe (16) and the collecting pipe (1); S4, the separated natural gas hydrate and the porous medium fixed with the natural gas hydrate are sent into the second tank (19) through the first conveying pipe (11) and the second transmission valve (13); S5, the natural gas hydrate is heated and decomposed by the heating device in the second tank (19) to decompose the natural gas; S6, the natural gas enters the buffer tank (24) through the second pipeline (21) and the second gas control valve (23); S7, when the gas pressure in the buffer tank (24) reaches the set gas pressure, enter the storage tank (25) through the third pipeline (30); S8. When the gas pressure in the storage tank (25) reaches the set gas pressure, replace the storage tank (25) with a new one to realize the exploitation of natural gas hydrate. 9 . The mining method according to claim 8 , wherein the mixture drives a rotating shaft ( 36 ) through a stirring motor ( 35 ) in the first tank ( 10 ), and the rotating shaft ( 36 ) drives a stirring blade ( 37 ) to the mixture. 10 . Stirring is carried out to fully mix and dilute water and sludge to form mud or mud water, and separate natural gas hydrate. 10. The exploitation method according to claim 8, wherein the natural gas hydrate is decomposed after being heated in the second tank, and the decomposed natural gas is sucked into the buffer tank (22) by the gas suction pump (22). 24), during the suction process of the gas suction pump (22), the pressure of the natural gas hydrate is reduced, the pressure is reduced and the temperature is raised simultaneously, so that the natural gas hydrate can be rapidly decomposed.

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