JP2009256664A - Method for producing gas hydrate, and device for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for producing a gas hydrate, without accumulating water squeezed from NGH (natural gas hydrate) on rolls and also capable of discharging water content while performing compression molding. <P>SOLUTION: In the device for producing the gas hydrate, a molding device 1 for compression-molding the gas hydrate is provided by having a receiving chamber 6 of a funnel form for receiving the dehydrated gas hydrate h2, and a pair of rolls 7 arranged at the lower part of the receiving chamber 6, wherein, at the pair of the rolls 7, a plurality of molding recessed parts 7a for compression-molding the dehydrated gas hydrate h2 are arranged on the circumference of the rolls 7, and further the molding recessed parts 7a are connected with a water-discharging gutter 17 installed along the circumference of the surface of the rolls 7 through a reduced trench 16 installed at the side surface of the molding recessed parts 7a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for compressing and molding a gas hydrate by bringing a gas hydrate into contact with raw water using natural gas such as methane gas or propane gas or a mixed gas thereof.

  Among fuel gases, in particular, natural gas (mixed gas mainly composed of methane gas, propane gas, etc.) is reduced in volume to 1/600 when it is a liquefied natural gas. It is transported from the production area to the consumption area as a form of liquefied natural gas (hereinafter, LNG). An LNG ship equipped with a tank whose periphery is covered with a heat insulating material is used for transportation.

  However, the LNG has an extremely low boiling point of −162 ° C., and the cooling power of the refrigerator for cooling to an extremely low temperature of −162 ° C. during production is large. In addition, since it has the property of being rapidly vaporized (BOG (boil-off gas)) with heat input from outside during storage and transportation, a certain amount of BOG corresponding to the heat input from outside is generated during storage and transportation, and LNG Decrease. In order to reduce BOG, the operation power of the refrigerator for enlarging a heat insulating material or re-liquefying vaporized gas was applied.

  In recent years, attention has been paid to a gas hydrate that can be stably transported at a cooling temperature milder than that of the above-mentioned LNG as a form of fuel gas. This gas hydrate is produced by subjecting a raw material gas such as natural gas and raw material water to gas-liquid contact under a temperature of about 0 to 5 ° C. and a high pressure of about 3 to 5 MPa to cause a hydration reaction. This gas hydrate is in a state where molecules such as natural gas are confined in a lattice formed by aggregating a plurality of water molecules.

  This gas hydrate is a so-called “self-preserving effect” in which the water constituting the lattice freezes due to the latent heat of thawing at the time of decomposition, and this wraps the surface of the gas hydrate with an ice film, thereby suppressing decomposition. This self-preserving effect makes it possible to store and transport over a long period of time in an atmosphere that is considerably milder than LNG at minus 20 ° C. to minus 10 ° C. under atmospheric pressure. is there.

  Furthermore, for example, natural gas hydrate (hereinafter referred to as NGH) has a volume of NGH that is about 1/170 of the volume of gas, and the volume decrease is smaller than that of LNG. It is not necessary to supply refrigeration energy for maintaining LNG at an extremely low temperature of −162 ° C., and since it can be stably stored and transported for a long time under atmospheric pressure, natural gas is stored and transported as NGH. It has been studied.

  By the way, the form of the NGH is powdery snow-like particles, and since the NGH mass (bulk density) per unit volume is small, there is a problem that the filling amount when NGH is filled in a storage container / transport container or the like is reduced. was there. Further, since the particles are powdery snow-like particles, there is a problem that the specific surface area of the particles per unit weight increases, and the decomposition resistance stability slightly decreases.

  In addition, powdered snow-like NGH has a problem that handling properties such as transportation, storage, and removal are not so good because the particles are fine.

In order to solve such a problem, it has been proposed that powdery NGH particles are compression-molded by a roll type pelletizer to form a pellet (see, for example, Patent Document 1).

JP 2003-105362 A

  However, the powdery snow-like NGH particles are in a wet and moist state, and when compressed by a roll type pelletizer, the NGH particles are compressed and the water is squeezed out. This squeezed water collects on the roll. Therefore, NGH with a specific gravity smaller than that of water floats and a sufficient amount of NGH is not supplied to the roll, or the water accumulated on the roll and NGH are mixed, resulting in a state of high moisture. There was a problem that the molding was insufficient and the molding was poor.

  In view of the above-described problems of the prior art, the present invention provides a gas hydrate having a molding apparatus that can drain water while compressing and forming water that has not been squeezed out of NGH. An object is to provide an apparatus.

  The apparatus for producing gas hydrate according to the present invention is configured as follows.

  1) A generator 1 that generates a gas hydrate h by hydrating a raw material gas g1 and raw water w1, and a dehydrator that discharges water w2 contained in the gas hydrate h1 generated by the generator 1 2 and a molding apparatus 3 for compressing and molding the gas hydrate h2 from which the water w2 has been drained by the dehydrating apparatus 2, the molding apparatus 3 includes the dehydrated gas hydrate h2 Has a funnel-shaped receiving chamber 6 and a pair of rolls 7 disposed below the receiving chamber 6, and the pair of rolls 7 compresses the dehydrated gas hydrate h 2. A plurality of molding recesses 7 a are arranged on the circumference of the roll 7, and the pair of rolls 7 discharges water w <b> 2 generated when the gas hydrate h <b> 2 is compressed by the rolls 7. The drainage means includes a drainage groove 17 formed along the circumference of the surface of the roll 7, and a molding recess 7 a provided with a communication portion 16 communicating with the drainage groove 17. It is characterized by that.

  2) A mesh body 21 that separates gas hydrate and moisture is provided in the communicating portion 16 that communicates with the molding recess 7 a and the drainage groove 17.

  3) A receiving tank 10a for moisture w2 discharged from the gas hydrate is provided at the lower part of the pair of rolls 7 of the molding apparatus 3, and the gas hydrate is compression-molded by the roll 7 on the bottom surface of the receiving tank 10a. A guide tube 12 is provided to guide the pellet body h3 to the outside of the tank 10a without getting wet with the water w2.

  4) The surface of the pair of rolls 7 is provided with a water permeable layer 22 through which moisture w3 separated from the gas hydrate passes, and the water permeable layer 22 is a porous body.

  5) The porous body is composed of any one of sintered metal, silica, alumina, ceramic, glass, and resin.

1) In a gas hydrate manufacturing apparatus, a molding recess for compressing and molding gas hydrate is arranged on the circumference of the roll on a roll surface of a molding apparatus that compresses and molds gas hydrate. A drainage means for discharging moisture generated when the gas hydrate is compressed is provided, and the drainage means is formed with a drainage groove formed along the circumference of the surface of the roll and a communication portion communicating with the drainage groove. With the configuration of the recess, the water is drained to the lower side of the roll, and the gas hydrate is prevented from floating above the water accumulated on the roll as in the prior art. That is, conventionally, the moisture squeezed out by compressing the gas hydrate accumulates on the roll, the gas hydrate having a specific gravity smaller than this moisture floats upward, and the gas hydrate flows into the forming recess of the roll. The roll was idled due to insufficient supply, or pellets with weak strength due to insufficient pressing force were produced, but according to the present invention, water was drained without accumulating on the roll, and the gas was discharged onto the roll. Since the hydrate is reliably supplied, it is possible to prevent the idle rotation of the roll and the production of pellets with insufficient strength. Therefore, high-quality pellets can be continuously and stably produced without lowering the production efficiency.

  2) Further, since the incompressible water (unreacted water) is sufficiently squeezed out to form a pellet body, the gas hydrate content of the pellet body is remarkably improved.

  3) Since the mesh body that separates the gas hydrate and moisture is provided in the communication portion that communicates with the molding recess and the drainage groove, the compressed gas hydrate filled in the molding recess and drained through the communication portion. Outflow into the groove is prevented.

  4) Since a water permeable layer that allows moisture separated from the gas hydrate to pass through is provided on the surface of the roll, moisture is discharged from the entire roll surface, so that drainage can be efficiently performed and the production volume Can be increased.

  5) Moreover, the water | moisture content isolate | separated from the gas hydrate can be drained without forming a drainage groove or providing a mesh body.

It is a schematic block diagram of the manufacturing apparatus of the gas hydrate which concerns on this invention. It is the schematic of the shaping | molding apparatus in the manufacturing apparatus of the gas hydrate which concerns on this invention. It is a figure which shows the surface of the roll of a shaping | molding apparatus. It is XX arrow sectional drawing of FIG. It is a YY arrow sectional drawing of FIG. It is a figure which shows the surface of the roll of the other Example of a shaping | molding apparatus. FIG. 7 is a cross-sectional view (enlarged view of main parts) taken along the line XX in FIG. 6. FIG. 7 is a cross-sectional view (enlarged view of main parts) taken along the line YY in FIG. 6. It is a principal part expansion perspective view of FIG. It is a figure which shows the surface of the roll of other Example of a shaping | molding apparatus. It is a principal part expanded sectional view of the roll of the further another Example of a shaping | molding apparatus. It is a figure which shows the surface of the roll of other Example of a shaping | molding apparatus.

Hereinafter, a gas hydrate production apparatus according to the present invention will be illustrated and described.
[Example 1]
As shown in FIG. 1, a gas hydrate production apparatus according to the present invention includes a generator 1 that generates a gas hydrate crystal h by hydrating a raw material gas g1 and raw water w1, and the generator 1 The dehydration device 2 that discharges the moisture of the hydrate slurry h1 containing the gas hydrate crystal h generated in step 1 and the gas hydrate h2 from which the moisture has been discharged by the dehydration device 2 are compression-molded to form a pellet body h3. And a molding device 3.

  The generating apparatus 1 includes a pressure vessel 1A having a supply pipe L1 for a raw material gas g1, a supply pipe L2 for a raw material water w1, and a stirring blade 1B for stirring the aqueous solution in the vessel. A spatter 1C for ejecting the raw material gas g1 into the aqueous solution and a blower B for supplying the raw material gas g1 to the spatterer 1C are provided at the bottom of the sprayer.

  The dehydrator 2 includes a bowl-shaped cylindrical main body 2A into which the gas hydrate generated by the generator 1 is introduced, a dehydration chamber 2B in the middle of the main body 2A, and a screw feeder type transfer machine 2C in the upper part. Is provided. In the dewatering chamber 2B, a number of drain holes communicating with the inside of the dewatering chamber 2B and the inside of the main body 2A are opened on the wall surface of the cylindrical main body 2A. In addition, a reflux pipe L5 for returning the waste water w2 discharged from the gas hydrate to the generator 1 is provided at the lower part of the dehydration chamber 2B.

  The molding device 3 includes a hopper-type (funnel-shaped) receiving chamber 6 that receives the gas hydrate h2 dehydrated by the dehydrating device 2, and a pair of compression rolls 7 disposed below the receiving chamber 6. . Further, a storage chamber 10 for storing the compression roll 7 is provided, and in the lower portion of the storage chamber 10, moisture w3 compressed by the roll 7 and squeezed out from the gas hydrate h2 and the pellet body h3 are provided. A separating guide tube 12 is provided. Furthermore, a drain pipe L8 for returning the water w3 to the generating device 1 is provided in the lower part of the storage chamber 10.

  Further, as shown in FIG. 2, the forming apparatus 3 is provided with a pushing device 9 in the receiving chamber 6 for pushing the gas hydrate h2 supplied to the receiving chamber 6 toward the roll 7 provided below. The pushing device 9 can be, for example, a screw feeder type.

  As shown in FIG. 2, the pair of rolls 7 has a plurality of molding recesses 7a formed in the circumferential direction of the surface of the roll 7, and the molding recesses 7a are, for example, circular as shown in FIG. Is formed. Furthermore, the roll 7 is provided with a drainage means for discharging water squeezed out when the gas hydrate is compressed. The drainage means includes a drainage groove 17 provided along the circumference of the surface of the roll 7, and a molding recess 7 a having a communication portion 16 communicating with the drainage groove 17. For example, the molding recess 7a has a relatively shallow depression (dimple) as shown in FIGS. 4 and 5 so that the compressed and consolidated gas hydrate pellet body h3 can be easily released from the molding recess 7a. As an example, the diameter is 25 mm and the depth is 10 mm. In addition, the shaping | molding recessed part 7a is not restricted circularly, The ellipse shape and the square shape which rounded the corner may be sufficient. Since the size of the dent is an example, the shape is not limited to the above example as long as the shape is excellent in releasability and filling properties.

The drain port 17 is formed with a width of 3 mm and a depth of 3 mm, and the communication portion 16 (reduction groove 16) is formed with a width of 1 mm and a depth of 1 mm. The shape is not limited to the above-described size as long as it is formed in a shape or size that does not cause blockage of the flow path.
(Manufacture of gas hydrate)
Next, production of gas hydrate by the gas hydrate production apparatus according to the present invention configured as described above will be described.

  As shown in FIG. 1, a raw material gas g1 and raw material water w1 are supplied into a reaction vessel 1A of the production apparatus 1, and a temperature is maintained at 0 ° C. to 10 ° C. and a pressure is maintained at 3 to 5 MPa. In the present embodiment, natural gas mainly composed of methane gas is used as the raw material gas g1, and this natural gas is obtained by removing impurities such as carbon dioxide and hydrogen sulfide. As the raw material water w1, general tap water or industrial water is used.

  The raw material gas g1 (natural gas) supplied to the reaction vessel 1A is jetted into the water from the bottom of the vessel 1A via the air diffuser 1C, and is stirred by the stirring device provided with the stirring blade 1B. The raw material gas g1 and the raw material water w1 are hydrated and promoted to generate a gas hydrate h. The source gas g1 is circulated until the content rate of the gas hydrate h is about 5% to 20%, and a new gas is supplied from the source gas supply pipe L1.

  In this way, a gas hydrate slurry h1 in which the gas hydrate h is dispersed in the raw water is formed in the reaction vessel 1A. The gas hydrate slurry h1 is pumped to the dehydrator 2 by the slurry pump P1 through the supply pipe L4.

  The pumped slurry h1 is introduced into the lower part of the cylindrical main body 2A of the dehydrating apparatus 2, and ascends in the main body 2A. Due to the pumping force of the slurry pump P1, the slurry h1 reaches the dehydration chamber 2B provided in the intermediate portion of the main body 2A, and the water w2 (unreacted water) is drained into the dehydration chamber 2B and dehydrated. Further, since the slurry h1 is compressed due to the action of gravity as it rises, the moisture is squeezed out and further dehydrated, and the content of the gas hydrate reaching the upper portion of the main body 2A is 40 to 60%. And is transferred to the molding apparatus 3 by the screw feeder 2C.

  The gas hydrate h2 transferred to the receiving chamber 6 of the molding device 3 is pushed into the pair of rolls 7 by a screw type pushing device 9 provided in the receiving chamber 6 and formed on the surface of the roll 7. 7a (dimple) is filled. The molding recesses 7a formed on the surfaces of the pair of rolls 7 are arranged to face each other, and the gas hydrate h2 is compressed and consolidated in the recesses 7a to form a pellet body h3.

  When the pellet body h3 is formed, the water contained in the gas hydrate h2 is squeezed out, and this water w3 flows out into the drain groove 17 through the communication portion 16 as shown in FIGS. As shown in FIG. 2, the water w <b> 3 is drained to the lower part of the roll 7.

  The formed pellet h3 is guided into a guide tube 12 protruding from the bottom of the storage chamber 10 in which the roll 7 is stored, and is discharged to a downstream device (for example, a cooling / decompression device). The guide tube 12 is configured such that the pellet h3 does not touch the water w3 discharged into the storage chamber 10. The drainage water w3 discharged into the storage chamber 10 is returned to the raw material water supply pipe w1 of the generating device 1 through a drain pipe L8 provided at the bottom of the storage chamber 10.

  With the gas hydrate manufacturing apparatus according to the present invention, the water squeezed from the gas hydrate by the roll is drained to the lower side of the roll, and the water in which the gas hydrate is accumulated on the roll as in the prior art. The water that has floated on the top of the water and NGH mixed on the roll and NGH are not mixed, and there is no more moisture.

According to the present invention, the water is drained without accumulating on the roll, and the gas hydrate is reliably supplied onto the roll, so that the roll is not idle and a pellet body with insufficient strength is not produced. Therefore, a high-quality pellet body can be manufactured continuously and stably without lowering the production efficiency.
[Example 2]
In this embodiment, as shown in FIGS. 6 to 9, a mesh body 21 that separates gas hydrate and moisture is provided between the forming recess 7 a of the roll 7 and the drain groove 17 in the forming apparatus 3. Yes.

As shown in FIG. 6, a large number of molding recesses 7 a are formed on the surface of the roll 7, and drainage grooves 17 formed along the circumference of the surface of the roll 7 are formed while communicating with the molding recesses 7 a. . Further, the drainage groove 17 and the molding recess 7 a are communicated with each other via the communication part 16.

  Further, a mesh body 21 is provided between the molding recess 7a and the drainage groove 17, and as shown in FIGS. 7 to 9, a gas hydrate h2 filled in the molding recess 7a and the hydrate The water w3 discharged from the rate h2 is separated.

  In the present embodiment, the mesh body 21 may be a punching metal having an opening of about φ0.2 mm to 0.7 mm, such as a stainless steel mesh having a roughness of about 30 to 80 mesh. .

According to the present embodiment, the mesh body 21 separates gas hydrate and moisture, so that gas hydrate particles do not flow out during compression molding. Therefore, as shown in FIG. 10, a plurality of communicating portions 16 between the drain grooves 17 and the molding recesses 7a can be formed, and drainage efficiency can be improved.
[Example 3]
In this embodiment, as shown in FIG. 11, a water permeable layer 22 is formed on the surface of the roll 7 of the molding apparatus 3. A porous body such as sintered metal, silica, alumina, ceramic, glass, and resin can be used for the water permeable layer 22. As the sintered metal, powder of stainless steel or copper alloy (10 μm to 1 mm) is press-molded. After that, the one sintered at high temperature is used. As the ceramic, alumina, silica, glass or the like is used. As the resin, polyethylene, polypropylene, polytetrafluoroethylene and the like can be used.

  According to the present embodiment, since moisture is discharged from the entire roll surface, drainage can be efficiently performed, and the production amount can be increased.

Moreover, the water | moisture content isolate | separated from the gas hydrate can be drained, without forming a drain groove or providing a mesh body.
[Example 4]
As shown in FIG. 12, the roll 7 of the molding apparatus 3 in this embodiment is formed so that the molding recesses 7a are arranged in two rows in the width direction.

  In the present embodiment, the communication part 16 between the molding concave part 7 a and the drainage groove 17 communicates with each other on the side where the molding concave part 7 a and the drainage groove 17 are close to each other via the communication part 16. With the roll 7 configured in this way, a larger number of pellets 11 can be produced than in the above-described embodiment.

B blower P1 slurry pump P2 pump h hydrate crystal h1 hydrate slurry h2 dehydrated hydrate h3 hydrate pellet body g1 raw gas w1 raw water w2 drainage w3 compressed water L1 raw gas supply pipe L2 raw water supply pipe L3 gas circulation pipe L4 Slurry transport pipe L5 Drain recirculation pipe L6 Hydrate transport pipe L8 Drain pipe 1 Generator 1A Pressure vessel 1B Stirring blade 1C Spatterer 2 Dehydrator 2A Main body 2B Dehydrator chamber 2C Screw feeder 3 Molding device 3A Electric motor 6 Receiving chamber 7 Roll 7a Molding recess DESCRIPTION OF SYMBOLS 9 Pushing device 10 Accommodating chamber 10a Receiving tank 12 Guide pipe 16 Reduction part 17 Drainage groove 21 Mesh body 22 Water-permeable layer

Claims (5)

A generator that hydrates a raw material gas and raw water to generate gas hydrate, a dehydrator that discharges water contained in the gas hydrate generated by the generator, and a water drainage by the dehydrator A gas hydrate manufacturing apparatus comprising a molding apparatus for compressing and molding the gas hydrate,
The molding apparatus has a funnel-shaped receiving chamber for receiving dehydrated gas hydrate, and a pair of rolls disposed in a lower portion of the receiving chamber, and the pair of rolls includes the dehydrated gas. A plurality of molding recesses for compressing the hydrate are arranged on the circumference of the roll,
Further, the pair of rolls has drainage means for discharging moisture generated when the gas hydrate is compressed by the rolls, and the drainage means is a drainage groove formed along the circumference of the surface of the roll. And an apparatus for producing a gas hydrate, comprising: a molding recess provided with a communication portion communicating with the drainage groove.   The apparatus for producing a gas hydrate according to claim 1, wherein a mesh body that separates gas hydrate and moisture is provided in a communicating portion that communicates with the molding recess and the drainage groove.   A receiving tank for moisture discharged from the gas hydrate is provided at the lower part of the pair of rolls of the molding apparatus, and the pellet body in which the gas hydrate is compression-molded by the roll is wetted with water on the bottom surface of the receiving tank. 2. A gas hydrate manufacturing apparatus according to claim 1, wherein a guide pipe is installed upright to guide the outside of the tank.   The gas hydrate manufacturing apparatus according to claim 1, wherein a water permeable layer that allows moisture separated from the gas hydrate to pass therethrough is provided on the surfaces of the pair of rolls, and the water permeable layer is a porous body.   The gas hydrate manufacturing apparatus according to claim 4, wherein the porous body is made of sintered metal, silica, alumina, ceramic, glass, or resin.

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