JP2007107663A - Transfer method of natural gas hydrate and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for transferring NGH under a high pressure to under a normal pressure. <P>SOLUTION: In the method for transferring natural gas hydrate (hereinafter referred to as NGH) manufactured by reacting water and natural gas under the high pressure to under the normal pressure by a screw type transfer device, the screw type transfer device 1 comprises a barrel 10 including a supply port 12 of the NGH arranged on one end, and a screw shaft 11 supported in the barrel 10, and is provided with a closed wall body 30 with a discharge port 13 opened on an end or a part continuing to the end of the barrel 10, and further is provided with a pressurizing chamber 2 of a predetermined capacity formed between a tip end part of the screw shaft 11 and the closed wall body 30. The method for transferring the NGH emits the NGH to a low pressure band side while maintaining a high pressure on a supply side during transferring via the screw type transfer device 1 by temporarily accumulating the NGH in the pressurizing chamber 2 by opening and closing a valve device 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the transfer of natural gas hydrates to systems having different pressure levels. For example, natural gas hydrates maintained at a high pressure of 54 ata and a temperature near room temperature of about 5 ° C. The present invention relates to a method and apparatus for continuously and directly transferring to a storage tank or granulator maintained in an atmosphere of −20 ° C.

  In general, the natural gas is transported in the form of liquefied natural gas (hereinafter referred to as LNG). However, in this method, it is necessary to maintain the cryogenic temperature (−162 ° C.). There is a problem in the means for holding and the means for transferring. In recent years, natural gas hydrate (gas hydrate, hereinafter referred to as NGH) has been attracting attention in order to solve the essential problems of this LNG. From the surface, it has been proposed that NGH is molded into a pellet shape such as a spherical shape (diameter of about 10 to 50 mm), stored and transported.

  LNG has a large volume reduction rate per unit volume (1/600 of the original volume of natural gas), but has a remarkably low boiling point. Therefore, it is necessary to transport LNG at an extremely low temperature of −162 ° C. Therefore, there is a danger of rapid vaporization and explosion if the temperature control is wrong.

  On the other hand, NGH has a smaller volume reduction rate per unit volume than 1/13 (1/170 of the original volume of natural gas), but much cooling energy to keep it as a liquid at −162 ° C. like LNG. There is no need to put in, and it can be transported while maintaining a cooling temperature of about -20 to -10 ° C. Furthermore, NGH has a self-preserving effect, that is, the decomposition is suppressed by wrapping the surface of the NGH with ice by thawing latent heat simultaneously with the decomposition of NGH. Although it hardly decomposes at a temperature of 10 ° C., it has the property of being gently decomposed at room temperature, and there is an advantage that it can be stably stored using this property.

  In the production process of NGH, water is contained in a production vessel, and for example, an NGH slurry is produced by maintaining the pressure at 54 at and the temperature at 5 ° C., and bringing the water into contact with natural gas, followed by dehydration, Powdered NGH is obtained. However, if this NGH powder is used as it is, the packing density is small and a high-pressure atmosphere is required as described above, so that it is difficult to store. Therefore, in order to obtain a state and shape suitable for storage, it is stored in a storage tank maintained at normal pressure and low temperature (for example, atmospheric pressure, −20 ° C.) or formed into a pellet.

In the NGH production process, the high-pressure raw material gas is supplied to the production vessel together with the raw water, and a hydration reaction is performed at a temperature of about 0 ° C. under high pressure (for example, 54 ata). A method of bubbling a source gas and a method of spraying source water in a source gas atmosphere have been proposed (for example, Patent Documents 1 and 2).
JP 2000-302701 A JP 2000-256226 A

  According to the method for producing NGH described in Patent Documents 1 and 2, since NGH has a specific gravity smaller than that of water, it floats near the water surface in the production vessel to form an NGH layer containing water. is doing.

  Here, the recovered NGH is powdered in appearance, but depending on its water content, dehydration treatment with a centrifuge, screw press, etc. may be required, and in consideration of handling of NGH, it is in a pellet form rather than a powder form. Is preferred. That is, both require post-treatment of the NGH slurry, and no consideration is given to such a method or a method of depressurizing NGH in a high-pressure state during post-treatment.

  According to Patent Document 1, the NGH recovered from the high-pressure production container is cooled in the cooling container before being sent to the normal-pressure storage container, and then depressurized. The high-pressure natural gas accumulated in the gas phase must be released. Therefore, there is usually a problem that incidental equipment (gas holder, compressor, high-pressure pipe, valve, etc.) for recovering the released gas and recycling it as NGH production raw material gas is required, and extra power is required for that purpose.

  The present invention has been devised to solve the above-mentioned problems, and particularly stores high-concentration NGH produced by an NGH production apparatus operated at high pressure and NGH powder already dehydrated under high pressure under normal pressure. Alternatively, it is an object of the present invention to provide a method and an apparatus for continuously transferring the pellet without forming the released gas when pellet forming is performed.

In order to achieve the above object, the present invention is configured as follows.
1) In a method of transferring gas hydrate produced by reacting water and natural gas under high pressure to a low-pressure zone using a screw type transfer device, the gas hydrate transferred to the transfer terminal of the screw type transfer device It is characterized by temporarily compacting by blocking the discharge of gas or providing resistance to the gas hydrate, and maintaining the pressure in the barrel under a high pressure by the compacted gas hydrate.

  2) In an apparatus for transferring a gas hydrate held under high pressure to a low-pressure zone, the transfer apparatus is supported within a barrel having a gas hydrate supply port disposed at one end thereof. A screw type transfer device comprising a screw shaft, provided with a closing wall body having an outlet opening at the end of the barrel or a part following the end, the outlet being configured to be opened and closed by a valve device, A pressurizing chamber having a predetermined capacity is formed between the distal end portion of the screw shaft and the closing wall body, and the gas hydrate in the pressurizing chamber is temporarily changed by opening and closing the valve device. The gas hydrate is discharged to the low pressure zone side while maintaining the high pressure on the supply side during the transfer via the screw type transfer device. It is characterized in that.

  The present invention uses a screw type transfer device 1 having a special pressure holding function, and forms a pressurizing chamber between the tip end of the screw shaft and the end of the barrel in the screw type transfer device. The NGH powder, which is the object to be transferred, is once confined in the pressure chamber and the portion is made high pressure by the pressing force. As a result, the NGH powder itself has a sealing property, and the inside of the barrel can be maintained at a high pressure. Further, by intermittently operating the valve device, the amount of NGH discharged from the pressurizing chamber to a normal pressure storage tank or the like can be increased or decreased while the NGH powder in the barrel remains at a high pressure. Therefore, the emission gas is not generated, and an incidental facility for recycling the emission gas and its power are not required.

  Further, in the present invention, since the cooling jacket is disposed on the outer periphery of the barrel of the screw type transfer device, the heat generated when the NGH powder is transferred can be removed, and at the same time, the NGH powder exhibits a self-preserving effect. Can be arbitrarily cooled.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows that the NGH powder n held in a high-pressure atmosphere using the screw-type transfer device 1 according to the present invention is applied to the next step in which the NGH powder n is held in a low-pressure atmosphere, such as a storage tank or a pellet molding step. Fig. 2 shows a schematic view of a transfer device for continuous transfer while maintaining the state.
(Transfer device)
In FIG. 1, reference numeral 1 denotes a screw type transfer device according to the present invention, which is composed of a barrel 10 and a screw shaft 11, and features of the present invention between a tip portion of the screw shaft 11 and a closing wall 30 of the barrel 10. A pressurizing chamber 2 is formed, and a decompression chamber 3 is formed adjacent to the pressurizing chamber 2 via a valve 9.

  Then, the NGH powder n having a high pressure (initial pressure P1) transferred from the NGH manufacturing process (not shown) is supplied to the screw type transfer device 1 via the NGH supply pipe 4, and has a special structure to be described later. While being pressurized by the shaft 11, it is transferred while being pushed into the pressurizing chamber 2.

  When the NGH powder n is transferred into the pressurizing chamber 2, the pressure in the pressurizing chamber 2 is higher than the initial pressure P1 as shown in FIG. On the other hand, the decompression chamber 3 is a valve chamber provided with a valve device 16 that opens and closes the discharge port 13 opened in the closing wall 30 of the pressurization chamber 2. The discharge amount of the discharged NGH powder n is limited by the pressing force (reverse pressure) of the valve 9 to adjust and hold the pressure in the pressurizing chamber 2.

The NGH powder n supplied at the initial pressure P1 from the supply port of the transfer device 1 is subjected to a secondary pressure P2 by a series of actions of the screw shaft 11, the pressurizing chamber 2, and the decompression chamber 3 constituting the transfer device 1. The pressure is reduced to 3 and then sent to the NGH storage tank 6. In the present invention, the secondary pressure P2 means a normal pressure that is a pressure that exhibits the self-preserving effect of NGH.
(Screw type transfer device)
As shown in FIG. 2 (A) and FIG. 3, a screw type transfer device 1 for transferring NGH powder n includes a barrel 10, a screw shaft 11 rotatably fitted in the barrel 10, and a barrel 10. It has the decompression chamber 3 arrange | positioned adjacently. The screw type transfer device 1 is provided with a closing wall body 30 having a discharge port 13 opened at the end of the barrel or a portion following the end, and between the front end portion of the screw shaft 11 and the closing wall body. A pressurizing chamber 2 is formed in the pressurizing chamber 2, and NGH is temporarily retained in the pressurizing chamber 2 by opening and closing a valve device provided at the discharge port 13.

  As shown in FIG. 2 (A), the screw shaft 11 is composed of a small diameter portion S1, a medium diameter portion S2, and a large diameter portion S3. The small diameter portion S1 is made of NGH powder n disposed at the position of the supply port 12. In the introduction part, the height of the flight F is higher than the others, and a large transfer volume part V1 with a large unit transfer amount of the NGH powder n is formed.

  The medium diameter portion S2 is disposed between the small diameter portion S1 and the large diameter portion S3 of the screw shaft 11, and is formed so that the shaft diameter gradually increases from the small diameter portion S1 to the large diameter portion S3. A medium transfer volume V2 in which the unit transfer amount of the NGH powder n is gradually reduced is formed.

  The large-diameter portion S3 is formed from the tip of the screw shaft 11 to the front of the medium-diameter portion S2, and the gap between the flight F and the screw shaft 11 is the narrowest compared to the others, and the unit of NGH powder n A small transfer volume V3 having the smallest transfer amount is formed.

  The screw type transfer device 1 has a cooling jacket 15 as a means for cooling while transferring the NGH powder n, and circulates through a brine tank (not shown) and a brine pump (not shown). Thus, the NGH powder n is cooled and held at about -20 ° C. As this temperature control means, in addition to the cooling jacket 15, for example, the inside of the screw shaft 11 may have a double or multiple structure, and brine may be circulated in one of the gaps, or used in combination with the cooling jacket 15. May be.

  In FIG. 3, the NGH powder n supplied to the supply port 12 of the screw type transfer device 1 is supplied to the flight F, its screw shaft 11, and the barrel 10 provided in the small diameter portion S <b> 1 arranged at the position of the supply port 12. The partitioned NGH powder n is accommodated in the transfer volume V1 for transferring, and is transferred to the medium diameter portion S2 region with the rotation of the screw shaft. Since the small-diameter portion S1 is mainly transferred, the powder pressure P of the NGH powder n that is the conveyed object does not increase so much.

  Next, the NGH powder n transferred from the small-diameter portion S1 to the medium-diameter portion S2 is transferred as the diameter of the screw shaft 11 of the medium-diameter portion S2 is gradually increased and the gap with the barrel 10 is further narrowed. Although the volume V2 is compressed and the pressure P of the NGH powder n itself increases, the pressure P of the NGH powder n itself at this time is lower than the initial pressure P1, and the high-pressure gas communication at the initial pressure P1 is communicated. It is not necessary to shut off.

  The NGH powder n that is compressed and pressurized at the medium diameter portion S2 and is transferred is held in the gap between the large diameter portion S3 and the barrel of the screw shaft 11, and the unit transfer amount is greatly reduced. Pushed into volume V3. The pressure P of the NGH powder n itself continues to increase due to the NGH powder n pushed from the medium diameter portion S2 and the compaction caused by being held by the large diameter portion S3. The initial pressure P1 is exceeded over the part.

  Then, the NGH powder n whose pressure has been increased to be higher than the initial pressure P1 in the large diameter portion S3 is pushed into the pressurizing chamber 2, but the discharge amount of NGH is reduced by the pressing force (reverse pressure) of the valve 9 of the valve device 16. The pressure in the pressurizing chamber 2 is adjusted and maintained so as to be higher than the initial pressure P1. In the pressurizing chamber 2, the NGH powder n that is the object to be transported stays and forms a consolidated body having a pressure (P3 to P4) higher than the initial pressure P1.

  This prevents the compacted body from becoming higher than the initial pressure P1 (P3 to P4), so that the initial pressure P1 of NGH supplied to the supply port 12 does not escape to the low pressure side (normal pressure: secondary pressure P2). Thus, a “material seal” that exhibits such an effect is stably formed and held.

  Since the material seal is insufficient in the initial operation of the screw type transfer device 1, the discharge port 13 is closed by the valve 9, and the pressure sensor B1 in the pressurization chamber and the secondary pressure sensor B2 in the decompression chamber The pressure of the valve device 16 is adjusted so that the pressure of the NGH compact is constant. The pressure sensors B1 and B2 close the discharge port 13 when the pressure on the discharge port 13 side rises above the normal pressure to prevent the high pressure gas having the initial pressure P1 from flowing out into the decompression chamber 3. be able to.

Further, in the pressurizing chamber 2, the NGH powder n supplied to the screw-type transfer device 1 forms a compact that is higher than the initial pressure P1 and is discharged from the discharge port 13 of the pressurizing chamber 2. Since it is solidified in the same manner as the NGH pellets molded by a pellet molding process such as a pelletizer, the pellet molding process can be omitted.
(Other embodiment of screw type transfer device)
The screw type transfer device 1 shown in FIG. 4 is provided with a pressing means that further pressurizes the compacted body of NGH powder n formed in the pressurizing chamber 2 at the tip of the screw shaft 11. The pressing means forms a piston 17 into which the pressing member can enter at the tip of the screw shaft 11.

  The piston 17 projects from the tip of the screw shaft 11 to change the volume in the pressurizing chamber 2 and promotes the formation of a compacted body of NGH powder n. Therefore, by adjusting the projecting amount of the compacted body, Changes the pressure of NGH. A compact body with a pressure higher than the initial pressure P1 can be quickly formed by integrally controlling the rotation of the screw shaft 11, the protruding amount of the piston 17, and the operating amount of the valve 9.

  The screw-type transfer device 1 shown in FIG. 5 has a part of the pressurizing chamber 2 formed by a bellows pipe 18, and a high-pressure fluid is fed into the bellows pipe 18 to expand the bellows pipe. The volume of the chamber 2 is changed, and the pressure P of the consolidated body formed in the pressurizing chamber 2 is increased.

  The screw-type transfer device 1 shown in FIG. 6 uses two screw-type transfer devices 1 facing each other, and is arranged so that the discharge ports 13 of the screw-type transfer devices face each other. The discharge port 14 is configured in a state in which the valve device 16 is disposed in the center. Further, the motors M1 and M2 provided in each screw type transfer device 1 can each adjust the speed.

Since the two screw-type transfer devices 1 transfer NGH powder n in parallel from the high pressure (initial pressure P1) to the low pressure (normal pressure: secondary pressure P2), the post-process under normal pressure is transferred. The supply amount for supplying NGH can be increased.

In the embodiment shown in FIG. 7, the supply port 12 of the second screw type transfer device is arranged in series via the connecting pipe 20 to the discharge port 13 of the first screw type transfer device. . Since the double seal structure consisting of the material seal in the first screw type transfer device and the material seal in the second screw type transfer device blocks the pressure difference, the operation of the screw type transfer device becomes easy and NGH transfer The amount can be increased.
(About deformation of pressurizing chamber)
The present invention is characterized in that the screw shaft of the screw type transfer device is shortened from the length of the barrel, and the pressurizing chamber 2 is formed between the tip of the screw shaft and the end of the barrel. In a sense, it acts as an area that provides resistance when NGH passes. Therefore, resistance can be given to the NGH passing through the pressurizing chamber filled with a plurality of spheres.

Further, instead of this sphere, one or a plurality of resistance plates having a large number of slits are arranged in such a state as to give resistance to NGH, so that the pressure shown in FIG. It can also be configured to stably generate the high pressure portion of the change graph.
(Gas leak prevention container)
FIG. 8 is a schematic view in which the NGH screw type transfer device 1 according to the present invention is provided in a pressure vessel.

  In FIG. 8, the screw type transfer device 1 is disposed in the pressure-resistant sealed container 25 together with its piping. The pressure-resistant airtight container 55 is configured to release the leaked gas through a gas exhaust pipe (not shown).

  By arranging the screw type transfer device 1 in the pressure-resistant sealed container 25, safety can be improved.

It is a schematic block diagram of the NGH transfer apparatus which concerns on embodiment of this invention. (A) It is a partially cut sectional view of a screw type transfer device. (B) It is a pressure diagram of a screw type transfer device. It is a partially cut cross-sectional enlarged view of a screw type transfer device. It is a partially cut cross-sectional enlarged view of another example of the screw type transfer device. It is a partially cut cross-sectional enlarged view of another example of the screw type transfer device. It is a partially cut cross-sectional enlarged view of another example of the screw type transfer device. It is a partially cut cross-sectional enlarged view of another example of the screw type transfer device. It is a schematic block diagram which shows other embodiment of a screw type transfer apparatus.

Explanation of symbols

n NGH powder P Pressure of NGH powder F Flight M Motors B1, B2, B3, B4, B5, B6, B7 Pressure sensor P1 Initial pressure P2 Secondary pressure S1 Small diameter part S2 Medium diameter part S3 Large diameter part V1 Large transfer volume V2 Medium transfer volume V3 Small transfer volume 1 Screw type transfer device 2 Pressurization chamber 3 Decompression chamber 4 NGH supply line 5 Discharge line 6 Storage tank 7 Low pressure header 8 Pipe line 9 Valve 10 Barrel 11 Screw shaft 12 Supply port 13 Discharge port 14 Discharge port 15 Cooling jacket 16 Valve device 17 Piston 18 Bellows pipe 19 Cylinder device 20 Connecting pipe 21 Discharge bunker 25 Gas leakage prevention container 26 Receiving container 30 Closing wall

Claims (7)

In a method of transferring a gas hydrate produced by reacting water and natural gas under high pressure to a low pressure zone by a screw type transfer device,
The discharge of the gas hydrate transferred to the transfer terminal end of the screw type transfer device is temporarily consolidated by blocking or giving resistance to the gas hydrate, and the pressure in the barrel is reduced by the consolidated gas hydrate. A method for transferring gas hydrate, characterized by being held under high pressure. In an apparatus for transferring a gas hydrate held under high pressure to a low pressure zone,
The transfer device is a screw type transfer device comprising a barrel having a gas hydrate supply port disposed at one end thereof, and a screw shaft supported in the barrel,
A closing wall body that opens a discharge port at the end of the barrel or a portion following the end is provided, and the discharge port is configured to be opened and closed by a valve device,
Furthermore, a pressurizing chamber having a predetermined capacity is formed between the tip of the screw shaft and the closing wall body,
The gas hydrate in the pressurizing chamber is temporarily retained by opening and closing the valve device, thereby maintaining a high pressure on the supply side while being transferred via the screw type transfer device. A device for transferring gas hydrate, characterized in that gas hydrate is discharged to the side.   The pressurizing chamber formed at the end of the barrel constituting the screw type transfer device is necessary for maintaining a high pressure in the barrel while discharging a predetermined amount of gas hydrate from the discharge port by operating the valve device. 3. The gas hydrate transfer device according to claim 2, wherein the gas hydrate transfer device has a volume for generating an appropriate pressure.   A bellows pipe is arranged on an inner surface of a portion of the barrel of the screw type transfer device forming a pressurizing chamber, and a high-pressure fluid is supplied into the bellows pipe so that the volume of the pressurizing chamber can be changed. The gas hydrate transfer device according to claim 2.   A volume change member that protrudes and retracts into the pressure chamber is provided at the tip of the screw shaft facing the pressure chamber of the screw-type transfer device. 3. The gas hydrate transfer device according to claim 2, wherein the gas hydrate transfer device is configured to change.   A jacket is formed on the outer peripheral surface of the barrel forming the screw type transfer device, the refrigerant is circulated and cooled in the jacket, and the pressure near the normal pressure is discharged until the supplied gas hydrate is discharged. The apparatus for transferring gas hydrate is characterized in that it is cooled to a low temperature such that it can be held stably. The screw shaft forming the screw type transfer device has a shaft shape, a flight shape, and a flight pitch so that the gas hydrate is consolidated from the gas hydrate supply unit side toward the pressurizing chamber side. The gas hydrate transfer device according to claim 2.

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