JP2005075950A - Process for producing clathrate hydrate of natural gas and apparatus for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing a clathrate hydrate that enables taking out the clathrate hydrate with reduced energy loss and good efficiency in the case when the resulting clathrate hydrate is under a reduced pressure environment. <P>SOLUTION: A system 20 for taking out the clathrate hydrate as the apparatus for producing the clathrate hydrate is provided with a lower hopper 22 filled with a given liquid LQ and set at the first pressure, a flow path 27 and the third valve 43 through which at least a part of the liquid LQ of the lower hopper 22 into which the clathrate hydrate has been introduced is discharged out of the lower hopper 22 to thereby bring the internal pressure of the lower hopper 22 into a reduced pressure lower than the first pressure, and a flow path 25 through which the clathrate hydrate is taken out of the lower hopper 22 held under the reduced pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for producing natural gas clathrate hydrate.

  Various methods have been proposed for storing and transporting natural gas mainly composed of hydrocarbons such as methane. Recently, natural gas has been converted to clathrate hydrate (Clathrate Hydrate). A method of storing and transporting has been proposed. Natural gas clathrate hydrate is a three-dimensional cage formed by reacting natural gas and water in a high pressure and low temperature environment (for example, 1 to 10 MPa, 0 to 10 ° C.), and a molecule such as methane is formed by a plurality of water molecules. It is generated by entering the inclusion grid. The clathrate hydrate produced is depressurized under an atmospheric pressure and low temperature environment (about 0.1 MPa, about −15 ° C. to −30 ° C.), and then stored and transported. The volume of clathrate hydrate containing a certain mass of natural gas under the atmospheric pressure and low temperature environment is about 100 to 180 times smaller than that of the natural gas in the gaseous state with the same mass, and the volume of the compound is small. Since a cryogenic temperature is not required stably, clathrate hydrate is effective as a form for storage and transportation.

As described above, the natural gas clathrate hydrate is produced in a high-pressure environment, and the produced clathrate hydrate is depressurized to an atmospheric pressure environment when stored and transported. Here, since rapid decompression treatment may cause the clathrate hydrate to decompose, it is necessary to decompress while controlling the atmospheric pressure of the clathrate hydrate produced. In the following document, a tank is filled with gas (natural gas) at a high pressure, and after the clathrate hydrate is charged into the tank, the gas in the tank is discharged to remove the clathrate hydrate under a reduced pressure environment. The technology to do is described.
Proceeding of 2nd International Conferencence of Natural Gas Hydrates June 2-6,1996, Toulouse, P415-422

By the way, the following problems occur in the above-described conventional technology.
If an attempt is made to set the tank to a high pressure using a gas when the clathrate hydrate is introduced into the tank, the gas is a compressible fluid and requires a large amount of gas. For example, the gas required to increase the pressure of the tank is several tens of times the volume of the tank, requires a large amount of gas compression power, and equipment for filling the tank with a large amount of gas to increase the pressure (large pump Etc.) is required. When decompressing the high-pressure tank, a large amount of gas is discharged from the tank, resulting in a large energy loss. The gas used is usually the same natural gas as the clathrate hydrate production process, which reduces the efficiency of the entire system.

  The present invention has been made in view of such circumstances, and when the produced clathrate hydrate is put under a reduced pressure environment, the natural clathrate hydrate can be efficiently taken out while suppressing energy loss. It is an object of the present invention to provide a method and an apparatus for producing a clathrate hydrate of gas.

In order to solve the above-described problems, a method for producing a clathrate hydrate of natural gas according to the present invention includes a generation step of reacting natural gas with water to generate a clathrate hydrate of natural gas, and the generation step. A charging step of charging the clathrate hydrate produced in step 1 into a container filled with a predetermined liquid and set to a first pressure; and the first pressure at which the clathrate hydrate is charged. A part of the liquid in the container and the gas dissolved in the liquid generated by decompression are discharged outside the container in a state where the flow path leading to the outside of the container among the held containers is blocked. A pressure reducing step for setting the inside of the container to a second pressure lower than the first pressure, and a step for taking out the clathrate hydrate from the container set to the second pressure. To do.
An apparatus for producing a clathrate hydrate of natural gas according to the present invention includes a clathrate hydrate generator for reacting natural gas and water to produce a clathrate hydrate of natural gas, and a predetermined liquid. Partitioning the flow path between the storage device set at the first pressure and the storage device and the clathrate hydrate generating device set at the first pressure with a blocking valve; In a state where the storage device into which the Japanese product has been put is made into an independent pressure system, at least a part of the liquid in the storage device or a gas dissolved in the liquid in addition to the liquid is discharged out of the storage device and stored. A pressure reducing device for setting the inside of the device to a second pressure lower than the first pressure, and a take-out device for taking out the clathrate hydrate from the storage device set to the second pressure. And

  According to the present invention, the fluid that fills the container (accommodating device) is a liquid that is an incompressible fluid, so that the amount of liquid that fills the container is slightly smaller than the volume of the container (relative to the volume of the container). It can be increased to a high pressure with only a small amount of power energy. Then, after the clathrate hydrate is introduced into the high-pressure container, the pressure can be reduced only by discharging a small amount of liquid from the container. Therefore, the clathrate hydrate can be taken out efficiently while suppressing energy loss.

  Here, the liquid to be used is preferably a liquid that does not affect the decomposition properties of the clathrate hydrate of natural gas, that is, a liquid that does not have a property of decomposing the clathrate hydrate. A substance having a low freezing point (for example, −30 ° C. or lower) is preferable because it is handled at a low temperature. Further, a substance in which the dissolved amount of natural gas is small (natural gas is difficult to dissolve), that is, a high molecular weight substance is preferable. A substance having a high boiling point is preferred so that it does not evaporate and accompany natural gas. From such a viewpoint, as the liquid to be used, for example, kerosene is preferable.

  In the method for producing a clathrate hydrate of natural gas according to the present invention, the removing step is characterized in that the container is taken out while supplying a liquid. According to this, since the inside of the container is washed with the supplied liquid, it is possible to suppress the clathrate hydrate remaining in the container.

  In the method for producing a clathrate hydrate of natural gas according to the present invention, the take-out step takes out the liquid together with the clathrate hydrate, and a volume corresponding to the take-out volume so as not to hinder the take-out. The liquid and the gas in the gas phase portion of the slurry tank as the take-out destination are returned to the upper part of the container. According to this, the clathrate hydrate can be smoothly taken out by supplying substantially the same amount of liquid or gas as the taken-out matter taken out from the container. In other words, if no gas is supplied to the upper part of the container, the upper part of the container is in a reduced pressure and vacuum state due to gravity applied to the liquid column in the container, and a high flow rate necessary for discharging clathrate hydrate (slurry) is obtained. Although it will not be possible, a gas flow in the gas phase part of the slurry tank to which the contents of the container are discharged is guided to the upper part of the container, so that a vigorous flow utilizing the gravitational force can be realized.

  The apparatus for producing clathrate hydrate of natural gas according to the present invention is characterized by comprising a pressurizing device for supplying the liquid to the housing device and adjusting the pressure of the housing device. According to this, even after the liquid is discharged from the storage device, the inside of the storage device can be set to a predetermined pressure.

  The natural gas clathrate hydrate manufacturing apparatus of the present invention includes a second storage device connected to an upper portion of the storage device via a flow path, and the liquid is one of the flow path and the second storage device. It is characterized by being filled with a part. According to this, the storage device arranged at the lower part of the second storage device via the flow path is completely filled with the liquid, and the gas phase is substantially absent. In addition, by providing two storage devices, the upper second storage device is always set to the same first pressure as in the clathrate hydrate generation step, so that the second storage device can generate the generation device. You can receive clathrate hydrate from all the time. Then, by adjusting the pressure of the storage device provided in the lower portion between the first pressure and the second pressure, the storage device can receive clathrate hydrate by the second storage device. Can perform an independent discharge operation efficiently.

  In the natural gas clathrate hydrate manufacturing apparatus according to the present invention, when the pressure is lowered by discharging a liquid or dissolved gas from the storage device to the outside of the storage device, the exhaust gas is discharged in two or three stages. It is divided into stages, accumulated in a pressure accumulating tank prepared for each stage, and the gas accumulated in the pressure accumulating tank is used when pressurizing the storage device later. According to this, it is possible to save the supply power of the gas from the outside by using the accumulated gas as the pressurized dissolved gas of the storage device.

  The first pressure is the pressure in the clathrate hydrate generation step, and the second pressure is atmospheric pressure. The setting of the second pressure includes an operation of opening to the atmosphere.

  By using a liquid that is an incompressible fluid as the fluid filled in the pressure vessel (accommodating device), the inside of the vessel can be set to a high pressure only by slightly increasing the amount of the liquid filling the vessel with respect to the volume of the vessel. Then, after the clathrate hydrate has been put into the container set to a high pressure, the depressurization treatment can be performed by simply discharging a small amount of liquid from the container. Therefore, the clathrate hydrate can be taken out efficiently while suppressing energy loss.

The natural gas clathrate hydrate production apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a clathrate hydrate production system (clathrate hydrate production apparatus), and FIG. 2 is a schematic view showing a take-out system for taking out the produced clathrate hydrate under reduced pressure.
In FIG. 1, a production system 1 includes a reactor 2 for reacting natural gas and water, a cooling jacket 3 for cooling the reactor 2, and a product produced in the reactor 2 in a gas phase, a liquid phase and a solid phase. And a reaction product separation tank 5 for further separating the liquid phase / solid phase separation separated in the gas / liquid separation tank 4 into a liquid phase and a solid phase. . The reactor 2 has a cylindrical shape, and the cooling jacket 3 has a ring shape surrounding the reactor 2. Inside the reactor 2, a stirring device for stirring natural gas and water and a scraping device for scraping off the product adhering to the inner wall of the reactor 2 are provided.

  The reactor 2 includes a natural gas supply pipe 11 that supplies natural gas into the reactor 2, a water supply pipe 12 that supplies water into the reactor 2, and a clathrate hydrate of natural gas from the reactor 2. And a discharge pipe 13 for discharging a mixture of unreacted natural gas and unreacted water. The discharge pipe 13 is connected to the gas-liquid separation tank 4. The gas-liquid separation tank 4 is provided with a natural gas return pipe 14 that supplies the gas separated therefrom, that is, natural gas, to the reactor 2, and a pipe 15 that supplies a gas other than the separated gas to the reaction product separation tank 5. It has been. An unreacted natural gas circulation compressor 16 for feeding unreacted natural gas is provided in the middle of the natural gas return pipe 14.

  In the reaction product separation tank 5, a water return pipe 17 that supplies the separated liquid, that is, water to the reactor 2, and a reaction product discharge that discharges the clathrate hydrate of natural gas that is the separated reaction product. A tube 18 is provided. The water return pipe 17 is connected to the reactor 2, and an unreacted water circulation pump 19 is provided in the middle of the water return pipe 17. The natural gas return pipe 14 is connected to the natural gas supply pipe 11, and the water return pipe 17 is connected to the water supply pipe 12.

Next, the operation of the generation system 1 having the above configuration will be described.
First, the inside of the reactor 2 is maintained at a constant temperature (for example, 5 ° C.) by the cooling jacket 3, and in this state, natural gas is supplied from the natural gas supply pipe 11 to the reactor 2, and water is supplied to the water. Feed from the tube 12 to the reactor 2. At this time, the supply amount of natural gas is adjusted so that the inside of the reactor 2 has a constant pressure (for example, 2 MPa). By introducing natural gas and water into the reactor 2 maintained at a predetermined temperature and pressure, the natural gas and water come into contact with each other and react to produce clathrate hydrate.

  The produced clathrate hydrate is discharged out of the reactor 2 as a mixture of unreacted natural gas and water. The discharged mixture is supplied to the gas-liquid separation tank 4 via the discharge pipe 13, and the gas-liquid separation tank 4 is separated into unreacted natural gas, unreacted water and natural gas clathrate hydrate. The separated unreacted water and natural gas clathrate hydrate are supplied to the reaction product separation tank 5 through the pipe 15. Here, the substance conveyed through the pipe 15 is a slurry body that is a mixture of clathrate hydrate and unreacted water. Hereinafter, the separated material conveyed through the pipe 15 is referred to as a “first slurry body”. The reaction product separation tank 5 separates the supplied first slurry body into a liquid phase and a solid phase. The liquid phase separated in the reaction product separation tank 5 is supplied as unreacted water to the reactor 2 via the unreacted water circulation pump 19 through the water return pipe 17. Further, the unreacted natural gas separated in the gas-liquid separation tank 4 is supplied to the reactor 2 through the unreacted natural gas circulation compressor 16 by the natural gas return pipe 14.

  On the other hand, the solid phase separated in the reaction product separation tank 5 is a clathrate hydrate slurry suspended in unreacted water, and is sent to the reaction product discharge pipe 18. That is, clathrate hydrate accompanied by unreacted water is sent to the reaction product discharge pipe 18. Hereinafter, the separated material conveyed through the reaction product discharge pipe 18 is referred to as a “second slurry body”. The second slurry body contains about 50% of unreacted water, for example. A filtration device 19 is provided in the middle of the reaction product discharge pipe 18. Unreacted water contained in the second slurry body is separated by the filtering device 19. Unreacted water contained in the second slurry body is reduced to, for example, about 10% by the filtering device 19. A centrifuge may be provided instead of the filtration device. Hereinafter, the slurry body in which the unreacted water is reduced by the filtering device 19 is referred to as a “third slurry body”. The third slurry body is reacted in a reactor (not shown) under the same conditions as the hydration reaction in the reactor 2. That is, the third slurry body is placed under a natural gas atmosphere in a reactor (not shown). The produced hydrate is cooled while being kneaded, and is sent as an inclusion hydrate having a high amount of natural gas to the upper hopper 21 of the take-out system 20 shown in FIG.

  FIG. 2 is a schematic diagram showing a take-out system for taking out the clathrate hydrate produced by the production system 1. As shown in FIG. 2, the take-out system 20 includes an upper hopper (second storage device) 21 and a lower hopper (container, storage device) 22 provided below the upper hopper 21. The clathrate hydrate generated by the generation system 1 is supplied to the upper hopper 21 via the first flow path 23 connected to the upper hopper 21. Further, the upper hopper 21 and the lower hopper 22 are connected via a second flow path 24. The clathrate hydrate supplied from the generation system 1 can be input to the lower hopper 22 via the first flow path 23, the upper hopper 21, and the second flow path 24. A third flow path 25 is provided below the lower hopper 22, and a slurry tank 26 is disposed below the third flow path 25. The clathrate hydrate in the lower hopper 22 can be supplied to the slurry tank 26 via the third flow path 25.

  The second flow path 24 provided at the upper part of the lower hopper 22 is provided with a first valve 41 as a blocking valve, and the third flow path 25 provided at the lower part of the lower hopper 22 is provided with a blocking valve. A second valve 42 is provided. The opening and closing operation of the first valve 41 controls the flow of clathrate hydrate in the second flow path 24, and the opening and closing operation of the second valve 42 controls the flow of clathrate hydrate in the third flow path 25. . That is, the clathrate hydrate supplied from the production system 1 is stored in the upper hopper 21 by closing the first valve 41. On the other hand, by opening the first valve 41 and closing the second valve 42, the clathrate hydrate supplied from the generation system 1 is stored in the lower hopper 22 via the upper hopper 21 and the second flow path 24. By opening the second valve 42, the clathrate hydrate of the lower hopper 22 is supplied to the slurry tank 26.

  The lower hopper 22 is filled with a predetermined liquid LQ in advance. The liquid LQ is disposed in all of the lower hopper 22, the second flow path 24, and a part of the upper hopper 21. That is, the spatially continuous upper hopper 21, second flow path 24, and lower hopper 22 are filled with the liquid LQ in advance. For example, kerosene or a similar medium is used as the liquid LQ, and a liquid medium having a high molecular weight and a high boiling point, a low vapor pressure, and a low pour point is used. For the liquid LQ, a substance that has no or little influence on the degradation properties of the clathrate hydrate charged from the generation system 1 is selected. In addition, the liquid LQ is preferably a low-freezing point, high-molecular-weight, high-boiling substance, and less natural gas dissolves. As long as it is handled at a low temperature, it is desirable that the amount of the vapor that accompanies the natural gas is an amount that does not hinder the operation. Furthermore, the liquid LQ has a density lower than that of the clathrate hydrate (specific gravity is lower than that of the clathrate hydrate). Therefore, the clathrate hydrate is kept in the liquid LQ in a settled state. For this reason, the clathrate hydrate is not accompanied when the liquid and the gas are discharged from the upper part of the hopper to depressurize the hopper.

  A pressure relief flow path (pressure reduction device) 27 is provided on the upper part (top) of the lower hopper 22, and a pressure relief flow path 27 is provided with a third valve 43 as a pressure release valve (pressure reduction device). The other end of the pressure release flow path 27 having one end connected to the lower hopper 22 is connected to a gas-liquid separator (flash drum) 28.

  In a state where the liquid LQ and clathrate hydrate are provided in the lower hopper 22, the liquid LQ and clathrate hydrate in the lower hopper 22 are removed by opening the second valve 42 of the third flow path 25. The slurry is supplied to the slurry tank 26 through the three flow paths 25. Here, a screen (filter) 29 is provided in the slurry tank 26, and the clathrate hydrate and the liquid LQ are separated by filtering the clathrate hydrate. The separated clathrate hydrate is disposed in a space 26A above the screen of the slurry tank 26, and the separated liquid LQ is disposed in a space 26B below the screen of the slurry tank 26.

  One end of the flow path 30 is connected to the space 26 </ b> B of the slurry tank 26, and the other end of the flow path 30 is connected to the lower hopper 22. In the middle of the flow path 30, a pressurizing pump (pressurizing device) 31 for supplying the liquid LQ in the space 26 </ b> B to the lower hopper 22 to pressurize the lower hopper 22 is provided. A fourth valve 44 that controls the flow of the liquid LQ in the flow path 30 is provided in the middle of the flow path 30. Note that the pressurizing pump 31 can supply and pressurize the liquid LQ from a liquid supply unit (not shown) to the lower hopper 22.

  One end of the flow path 32 is connected to the space 26 </ b> B of the slurry tank 26, and the other end of the flow path 32 is connected to the lower hopper 22. The other end of the flow path 32 is connected to the upper part of the lower hopper 22. In the middle of the flow path 32, a liquid replenishment pump 33 that supplies the liquid LQ to the lower hopper 22 from the space 26B and a liquid supply unit (not shown) is provided. Even if the amount of liquid in the hopper is reduced due to processing by the liquid supply operation of the liquid replenishment pump 33, the amount of liquid in the hopper (including the upper hopper, the lower hopper, and the second flow path) is maintained at a predetermined amount. . A fifth valve 45 that controls the flow of the liquid LQ in the flow path 32 is provided in the middle of the flow path 32.

  A flow path 34 is connected to the space 26 </ b> A of the slurry tank 26, and a slurry pump 35 is provided in the middle of the flow path 34. The clathrate hydrate (slurry) separated in the slurry tank 26 and disposed in the space 26A is taken out as a product by the slurry pump 35 via the flow path 34. The third flow path 25, the second valve 42, the slurry tank 26, and the slurry pump 35 provided in the flow path 34 constitute a take-out device that takes out the clathrate hydrate from the lower hopper 22.

Next, a method of taking out the clathrate hydrate produced by the production system 1 by using the take-out system 20 having the above-described configuration and taking it out as a product will be described.
First, with the first valve 41 opened and the second valve 42 closed, the liquid LQ is filled up to the middle of the lower hopper 22, the flow path 24, and the upper hopper 21 as shown in FIG. . That is, the liquid level of the liquid LQ is formed in the upper hopper 21. And the clathrate hydrate produced | generated in 1-10 Mpa and 0-10 degreeC environment (2MPa, 5 degreeC environment in this embodiment) in the production | generation system 1, for example via the 1st flow path 23, the upper hopper 21 Are continuously or intermittently charged. When the clathrate hydrate is introduced, the upper hopper 21 and the lower hopper 22 are subjected to the same pressure (first pressure) as that of the generation process of the generation system 1, that is, about 1 to 10 MPa (in this embodiment, about 2 MPa). ) In the pressure environment. The clathrate hydrate introduced from the first flow path 23 settles in the liquid LQ, moves to the lower part of the lower hopper 22 after moving through the upper hopper 21 and the second flow path 24. Thus, the clathrate hydrate is charged into the lower hopper 22 which is filled with the liquid LQ and set to the first pressure (charging process).

  Next, when a predetermined amount (for example, about 60 to 70% of the volume of the lower hopper 22) of clathrate hydrate is deposited on the lower hopper 22, the liquid replenishment pump 33 that has been stopped is driven. The driving of the liquid replenishing pump 33 is preparation for a cleaning process of the lower hopper 22 described later. At this time, the fifth valve 45 is closed. Further, the pressurizing pump 31 is stopped. Whether or not the time point has been reached since the clathrate hydrate has been added is determined based on the amount of clathrate hydrate produced per unit time (generation rate). When it is determined that a predetermined amount of clathrate hydrate has been deposited in the lower hopper 22, the first valve 41 is closed. At this time, the upper hopper 21 is maintained at the first pressure. Here, the clathrate hydrate is continuously supplied from the generation system 1 (first flow path 23), and the supplied clathrate hydrate is stored in the upper hopper 21.

  When the first valve 41 is closed, the third valve 43 is opened. Here, it is preferable that the time from the closing of the first valve 41 to the opening of the third valve 43 is almost simultaneous or as short as possible. This is because when the first valve 41 is closed and the lower hopper 22 is sealed, the clathrate hydrate in the lower hopper 22 rises in temperature due to the cold heat loss of the lower hopper 22 and decomposes. This is because it occurs and the pressure rises above the desired pressure value. By opening the third valve 43 as the decompression device, at least a part of the liquid LQ in the lower hopper 22 and the dissolved gas separated by the decompression are discharged to the outside through the flow path 27. By discharging the liquid LQ and its dissolved gas to the outside of the lower hopper 22, the inside of the lower hopper 22 is depressurized to a predetermined pressure (second pressure) (decompression step).

  Here, the second pressure is almost atmospheric pressure (about 0.1 MPa). At this time, the discharge amount (discharge speed) of the liquid LQ or its dissolved gas per unit time can be controlled based on the open state of the third valve 43. Therefore, since the pressure reduction speed (pressure decrease value per unit time) in the lower hopper 22 can be controlled, the lower hopper 22 (clathrate hydrate) is not rapidly decompressed.

  The flow path 27 is provided in the upper part (top part) of the lower hopper 22, and the clathrate hydrate in the lower hopper 22 is deposited in the lower part of the lower hopper 22. Therefore, only the liquid LQ and dissolved gas are discharged from the flow path 27, and the clathrate hydrate is discharged from the flow path 27 little or no. In the lower hopper 22, there may be a gas generated by the decomposition of the clathrate hydrate or a gas previously dissolved in the liquid LQ. This gas is also discharged from the flow path 27.

  The liquid LQ and gas components discharged from the lower hopper 22 and flowing through the flow path 27 are sent to the gas-liquid separator 28. The gas-liquid separator 28 separates the liquid LQ and the gas component. The separated liquid LQ is sent to the slurry tank 26 (space 26B) via the flow path 36. On the other hand, the separated gas component is sent to, for example, the generator 2 of the generation system 1 through a flow path (not shown) having a sealing mechanism against the atmosphere.

  When the lower hopper 22 is depressurized to atmospheric pressure, the fifth valve 45 of the flow path 32 is opened. At this time, since the liquid replenishment pump 33 is driven as described above, the liquid LQ is supplied into the lower hopper 22 via the flow path 32. Thereby, the preparation for the cleaning process of the lower hopper 22 described later is completed. By driving the liquid replenishing pump 33 with the third valve 43 and the fifth valve 45 opened, the gas components (bubbles) in the lower hopper 22 are discharged from the flow path 27.

  When the lower hopper 22 is depressurized to atmospheric pressure, the second valve 42 of the third flow path 25 is opened. Thereby, the clathrate hydrate is discharged from the lower hopper 22 to the slurry tank 26 together with the liquid LQ via the third flow path 25. The clathrate hydrate and the liquid LQ discharged to the slurry tank 26 are separated by the screen 29, the separated liquid LQ flows into the space 26B, and the clathrate hydrate remains in the space 26A and is part of the liquid LQ. The product is taken out as a product through the flow path 34 while being mixed (a removal step).

  While the second valve 42 is opened and the clathrate hydrate and the liquid LQ are discharged, the liquid LQ is supplied from the upper part of the lower hopper 22 through the flow path 32 by driving the liquid replenishment pump 33. Yes. That is, the clathrate hydrate is taken out from the lower hopper 22 while supplying the liquid LQ to the lower hopper 22. As a result, the inside of the lower hopper 22 is cleaned by the supplied liquid LQ, so that the clathrate hydrate is prevented from remaining in the lower hopper 22.

  In addition, the gas component in the slurry tank 26 is supplied to the upper part of the lower hopper 22 through the gas-liquid separator 28 after passing through the pipe 36 and further passing through the flow path 27. The supplied gas is in an amount corresponding to the volume of clathrate hydrate (slurry) taken out from the lower hopper 22. Thereby, substantially the same amount of liquid or gas as the slurry taken out from the lower hopper 22 is supplied to the lower hopper 22, and the slurry is taken out smoothly. That is, if no gas is supplied to the upper part of the lower hopper 22, the upper part of the lower hopper 22 is in a reduced pressure / vacuum state due to gravity applied to the liquid column in the lower hopper 22 and is necessary for discharging clathrate hydrate (slurry). Although a vigorous flow cannot be obtained, the gas in the gas phase portion of the slurry tank 26, which is the discharge destination of the contents of the lower hopper 22, is guided to the upper portion of the lower hopper 22, so A good flow can be realized.

  When the clathrate hydrate is discharged from the lower hopper 22, the second valve 42 is closed. At this time, the opening of the fifth valve 45 and the driving of the liquid replenishing pump 33 are maintained, and the liquid LQ is supplied to the lower hopper 22 via the flow path 32. Eventually, the lower hopper 22 is filled with the liquid LQ. Here, the amount of the liquid LQ supplied from the liquid replenishment pump 33 to the lower hopper 22 is substantially the same as the total amount of the clathrate hydrate and the liquid LQ (withdrawal) taken out from the third flow path 25. is there. Thereby, the lower hopper 22 is completely filled with the liquid LQ. The lower hopper 22 is filled again with the liquid LQ.

  When the lower hopper 22 is filled with the liquid LQ, the third valve 43 is closed. Further, the fifth valve 45 is closed and the driving of the liquid replenishing pump 33 is also stopped. Thereby, the lower hopper 22 is sealed in a state filled with the liquid LQ. At this time, there is substantially no gas phase in the lower hopper 22. Subsequently, the pressurization pump 31 is driven and the fourth valve 44 is opened. As a result, a predetermined amount of liquid LQ is added to the lower hopper 22, whereby the inside of the lower hopper 22 is pressurized to the first pressure (pressurizing step).

  When the pressure difference between the upper hopper 21 and the lower hopper 22 falls within the allowable range (when the pressure difference is almost eliminated), the first valve 41 is opened. At this time, the liquid LQ may be supplied from the pressurizing pump 31 to the upper hopper 21 through a flow path (not shown), and the liquid level in the upper hopper 21 may be adjusted. When the first valve 41 is opened, the clathrate hydrate stored in the upper hopper 21 settles in the lower hopper 22 via the second flow path 24. Thereafter, the same processing is repeated.

  By the way, when discharging the liquid LQ from the lower hopper 22 in the pressure reducing step, for example, there are three pressure accumulating tanks 38 connected through the flow path 37 (for example, three accumulating tanks 38 are provided in the figure). In addition, the gas generated from the lower hopper 22 may be stored, and the stored gas may be used in the pressurizing step. Specifically, when the liquid LQ in the lower hopper 22 is discharged, the gas containing the gas component dissolved in the liquid LQ is changed into a plurality of pressure stages (for example, two or three stages) according to the pressure decrease. The gas discharged in each pressure stage is sequentially injected and accumulated in a plurality of pressure accumulating tanks 38, and when the lower hopper 22 is pressurized later, the gas accumulated in the pressure accumulating tanks 38 is used. can do. By using the stored gas as the pressurizing gas for the lower hopper 22, it is possible to save the supply power of the gas from the outside.

  As described above, the clathrate hydrate produced by the production system 1 is applied to the hopper 22 that is substantially free of a gas phase filled with the liquid LQ that does not substantially affect the decomposition properties of the clathrate hydrate. After charging and filling, a part of the liquid LQ (and gas dissolved in the liquid LQ released by decompression) is released from the hopper. Can be under reduced pressure.

  When the clathrate hydrate and the liquid LQ are taken out from the third flow path 25 after the depressurization step, a fluid having a volume corresponding to the total volume flow rate per unit time of the liquid LQ and clathrate hydrate discharged is supplied to the lower hopper. 22 is supplied by the liquid replenishment pump 33 for cleaning the lower hopper 22 through the flow path 32 to supply the liquid LQ, and the remainder is supplied from the gas phase portion of the slurry tank 26. By covering it by introducing, the clathrate hydrate and the liquid LQ can be smoothly discharged from the third flow path 25. Furthermore, when the liquid LQ is supplied to the lower hopper 22 via the flow path 32, the gas component in the lower hopper 22 can be naturally discharged from the flow path 27, so that the interior of the lower hopper 22 is substantially filled only with the liquid LQ. be able to. Therefore, after that, when the pressurizing liquid is injected by the operation of the pressurizing pump 31, the inside of the lower hopper 22 can be pressurized only by injecting a small amount of liquid.

  The upper hopper 21 and the lower hopper 22 are connected via the second flow path 24, the lower hopper 22 is filled with the liquid LQ, and the liquid is formed up to a halfway height so that a liquid level is formed in the upper hopper 21. Since the LQ is provided, the clathrate hydrate generated by the generation system 1 can be continuously input to the upper hopper 21 and the lower hopper is independent of the input operation to the upper hopper 21. Since the pressure reducing operation can be performed at 22, the treatment for clathrate hydrate can be performed efficiently.

  The upper hopper 21 has a liquid level, and a large amount of gas component may be dissolved in the liquid LQ through the liquid level. When the liquid LQ in which the gas component is dissolved is injected into the lower hopper 22 and depressurized. The gas corresponding to the pressure drop is released. Therefore, the discharge gas is discharged in a plurality of stages (for example, two stages or three stages) of pressure stages, and the discharge gas for each pressure stage is stored in each of the plurality of pressure accumulating tanks 38. By using the gas component stored in the pressure accumulating tank 38 in the pressurizing step, the supply of pressurized gas from the outside can be reduced, and the power consumption energy can be reduced.

It is a schematic block diagram which shows one Embodiment of the manufacturing apparatus of the clathrate hydrate of the natural gas of this invention. It is a schematic block diagram which shows one Embodiment of the manufacturing apparatus of the clathrate hydrate of the natural gas of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Production system (clathrate hydrate production | generation apparatus), 20 ... Extraction system (production apparatus)
21 ... Upper hopper (second storage device), 22 ... Lower hopper (container, storage device),
24 ... 2nd flow path, 25 ... 3rd flow path (extraction apparatus),
26 ... Slurry tank (take-out device), 27 ... Flow path (pressure reduction device), 41 ... First valve,
42 ... 2nd valve (extraction device), 43 ... 3rd valve (pressure reduction device),
31 ... Pressurizing pump (pressurizing device), 34 ... Channel (extraction device),
35 ... Slurry pump (extraction device), LQ ... Liquid

Claims (7)

A production process for reacting natural gas with water to produce a clathrate hydrate of natural gas;
A charging step of charging the clathrate hydrate generated in the generating step into a container filled with a predetermined liquid and set to a first pressure;
Generated by part of the liquid in the container and reduced pressure in a state in which the flow path leading to the outside of the container held at the first pressure into which the clathrate hydrate has been charged is blocked. A pressure reducing step of discharging the gas dissolved in the liquid to the outside of the container and setting the inside of the container to a second pressure lower than the first pressure;
A method for producing a clathrate hydrate of natural gas, comprising a step of taking out the clathrate hydrate from the container set at the second pressure.   The method for producing a clathrate hydrate of natural gas according to claim 1, wherein the removing step is performed while supplying a liquid to the container.   In the extraction step, the liquid is taken out together with the clathrate hydrate, and the liquid in a volume corresponding to the removal volume and the gas in the gas phase portion of the slurry tank as the extraction destination are provided so as not to disturb the removal. 2. The method for producing a clathrate hydrate of natural gas according to claim 1, wherein the clathrate is returned to the upper part of the container. A clathrate hydrate generator for reacting natural gas with water to produce a clathrate hydrate of natural gas;
A storage device filled with a predetermined liquid and set at a first pressure;
A flow path between the containing device and the clathrate hydrate generating device set to the first pressure is partitioned by a blocking valve, and the containing device into which the clathrate hydrate has been charged is an independent pressure. In a systematic state, at least a part of the liquid in the storage device or a gas dissolved in the liquid in addition to the liquid is discharged out of the storage device, and the second inside the storage device is lower than the first pressure. A decompressor to set the pressure;
An apparatus for producing a clathrate hydrate of natural gas, comprising: a take-out device for taking out the clathrate hydrate from the storage device set at the second pressure.   The apparatus for producing clathrate hydrate of natural gas according to claim 4, further comprising a pressurizing device for supplying the liquid to the housing device and adjusting the pressure of the housing device. A second storage device connected to the upper portion of the storage device via a flow path;
The said liquid is filled in the said flow path and a part of said 2nd storage apparatus, The manufacturing apparatus of the clathrate hydrate of the natural gas of Claim 4 or 5 characterized by the above-mentioned. When liquid or dissolved gas is discharged from the storage device to the outside of the storage device to reduce the pressure, the exhaust gas is divided into two or three pressure stages and stored in a pressure accumulating tank prepared for each stage. The apparatus for producing clathrate hydrate of natural gas according to any one of claims 4 to 6, wherein the gas accumulated in the pressure accumulating tank is used when pressurizing the storage device later.

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