JP4564324B2 - Gas hydrate production equipment - Google Patents

Description

  The present invention reacts a raw material gas with raw material water to produce a solid gas hydrate, which is drained by a vertical moving bed type dehydrator to produce a low moisture content gas hydrate. The present invention relates to a gas hydrate manufacturing apparatus.

  At present, as a method of storing and transporting natural gas mainly composed of hydrocarbons such as methane, after collecting natural gas from a gas field, it is cooled to a liquefaction temperature and stored in a liquefied natural gas (LNG) state. The method of transport is common.

  However, for example, in the case of methane, which is the main component of LNG, extremely low temperature conditions such as −162 ° C. are necessary for liquefaction, and in order to store and transport while maintaining these conditions, a dedicated storage device or LNG A dedicated means of transportation such as a transport ship is required.

  Manufacturing, maintenance, and management of such devices and the like require very high costs, and therefore, low-cost storage and transportation methods that replace the above methods have been intensively studied.

  As a result of these studies, a method has been found in which natural gas is hydrated with water to form a solid state hydrate, that is, natural gas hydrate, and stored or transported in this solid state. , Has been promising.

  This method does not require cryogenic conditions as in the case of handling LNG. Moreover, since it is a solid, its handling is relatively easy.

  For this reason, a slightly improved version of the existing refrigeration apparatus or existing container ship can be used as a storage apparatus or a transportation means.

  Therefore, it is expected that the cost can be significantly reduced as compared with the case of handling LNG.

This natural gas hydrate is a kind of inclusion compound, and is a molecule constituting each component of natural gas, that is, methane (CH ₄ CH ₄₎ in a cubic cage inclusion lattice formed by a plurality of water molecules. ), Ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and the like are included and included in the crystal structure.

The intermolecular distance between the natural gas constituent molecules included in the cubic cage inclusion lattice is shorter than the intermolecular distance in the gas cylinder when the natural gas is filled with high pressure. This means that a natural gas is produced in a tightly packed solid, for example, under conditions where hydrates of methane are stable, ie at -80 ° C. and atmospheric pressure (1 kg / cm ² ). it can be about 1/170 of the volume compared to the gaseous state.

  Thus, natural gas hydrate can be produced and stably stored under conditions of temperature and pressure that can be obtained relatively easily.

In the above method, the natural gas collected from the gas field is removed from the acidic gas such as carbon dioxide (CO ₂ ) and hydrogen sulfide (H ₂ S) in the acidic gas removal step, and once stored in the gas storage unit, Thereafter, it is hydrated in the production process.

  This natural gas hydrate is in the form of a slurry in which water is mixed, and in the subsequent dehydration process, the mixed unreacted water is removed, and a container such as a container is passed through a regeneration process, a cooling process, and a decompression process. And stored in a storage device adjusted to a predetermined temperature and pressure.

  By the way, the conventional natural gas hydrate generation method described above has the following problems.

  That is, in the natural gas hydrate production plant, the natural gas hydrate immediately after production is in the form of a slurry containing a large amount of water, so if this natural gas hydrate is stored or transported as it is or frozen, The cost of storage and transportation will be enormous as much as water (ice).

Therefore, in order to produce natural gas hydrate with a low moisture content and reduce the cost of storage and transportation, a horizontal screw press type dehydrator is used for slurry natural gas hydrate. A method for producing a natural gas hydrate that is forcibly dehydrated by use has been proposed (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2003-105362 (page 7-10, FIG. 2)

  This screw press type dewatering device has a double structure of a meshed inner wall and a cylindrical body that forms an outer shell outside the inner wall, and is slurried by a screw shaft installed in the inner wall. Since the natural gas hydrate is forced to advance to remove water from the processed mesh of the inner wall, most of the natural gas hydrate is mixed with water during the dehydration (concentration). There is a problem that the recovery rate of natural gas hydrate is reduced.

  In addition, there is a problem in that a power cost for rotating the screw shaft with high torque is required. Furthermore, since high torque is generated in a state where the inside is at a high pressure, the entire equipment is overloaded, and it is necessary to seal the screw shaft from high pressure to atmospheric pressure.

  In order to eliminate such a problem, the present inventors have proposed a dehydration method that is gentle to natural gas hydrate using gravity instead of the conventional forced dehydration, but as shown in FIG. When the resistance of the upper dewatering zone a from the draining part 3 made of wire mesh of the dehydrator 1 is increased, the discharge pressure of the slurry pump 5 that conveys the natural gas hydrate slurry s to the dehydrator 1 is made constant. Or the dehydrator 1 is blocked by natural gas hydrate, or the liquid level (water level) rises to cause dehydration failure, which is stable while maintaining a constant dehydration rate. I couldn't drive. In the figure, symbol b indicates a concentration zone and c indicates a slurry zone.

  The present invention has been made to solve such a problem, and its object is to reduce the movement resistance of the dehydration layer of the gravity dehydrator, to realize stable operation of the dehydrator, An object of the present invention is to provide a gas hydrate production apparatus that enables operation at a constant dehydration rate.

  In order to solve the above problems, the present invention is configured as follows.

In the gas hydrate production apparatus according to claim 1, a raw material gas and raw material water are reacted to generate gas hydrate, and the gas hydrate is drained by a vertical moving bed type dehydrator to reduce the water content. In a gas hydrate production apparatus for producing gas hydrate, the dehydrator is provided in a cylindrical first tower body, and a tubular cylinder provided on the upper portion of the first tower body and having innumerable fine holes. A drainer, a dewatering assembly provided outside the drainer, and a cylindrical second tower provided above the drainer, and a crossing of the drainer and / or the second tower The surface is enlarged continuously or intermittently from below to above.

In the gas hydrate production apparatus according to claim 2, the transverse section of the draining part and / or the second tower body is continuously increased from the lower side to the upper side, and the opening angle θ is set to 1 to 30 °. It is characterized by this.

In the gas hydrate production apparatus according to claim 3, the cross section of the draining portion and / or the second tower body is intermittently increased from the lower side to the upper side, the width of the step portion is a, When the height is b and the bottom tower diameter is d,
a = (1/5 to 1/50) × d
b / a = 2-30
It is characterized by satisfying .

  As described above, according to the first aspect of the present invention, the raw material gas and raw material water are reacted to generate gas hydrate, and the gas hydrate is drained by a vertical moving bed type dehydrator to reduce water content. In the gas hydrate production apparatus for producing a high rate gas hydrate, the dehydrator is provided with a cylindrical first tower body and a cylinder having an infinite number of fine holes provided at the upper portion of the first tower body. And a dewatering gathering portion provided outside the draining portion, and a cylindrical second tower provided at the top of the draining portion. Therefore, the movement resistance of the gas hydrate after dehydration is greatly reduced as compared with the conventional case where the inner diameter of the second tower is constant.

  For this reason, the discharge pressure of the slurry pump that conveys the gas hydrate slurry to the dehydrator is increased, the dehydrator is blocked by the particle layer of the gas hydrate, or the liquid level rises to cause dehydration failure. It was possible to suppress the problem.

  The invention according to claim 2 is the dehydrator according to claim 1, wherein the cross-sectional area of the draining portion and the second tower body is continuously or intermittently extended from below the draining portion to above the second tower body. Therefore, the movement resistance of the gas hydrate in the draining part and the second tower body can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In this embodiment, the case where the cross-sectional area of the second tower body is increased continuously or intermittently from below to above will be described. However, the cross-sectional area of the draining section and the second tower body is increased from below to above. Even if it is continuously or intermittently increased, the same effect is obtained. Furthermore, the same effect can be obtained even if the cross-sectional area of the draining portion is increased continuously or intermittently from below to above.

  In FIG. 1, reference numeral 11 denotes a natural gas hydrate generator (hereinafter referred to as a gas hydrate generator), and 12 denotes a slurry-like natural gas hydrate (hereinafter referred to as a gas hydrate generator 11) generated by the gas hydrate generator 11. A vertical moving bed type dehydrator for dehydrating 13) is a gas hydrate transfer device for horizontally transferring the gas hydrate substantially dehydrated by the dehydrator 12 to the next step (not shown). It is.

  The gas hydrate generator 11 includes a pressure vessel 14, a gas jet nozzle 15 for jetting natural gas into fine bubbles, an object to be processed in the pressure vessel 14, that is, natural gas g and water w, A stirrer 16 for stirring gas hydrate and the like, and a heat transfer unit 17 for removing reaction heat are provided.

  The dehydrator 12 includes a cylindrical first tower body 21, a cylindrical draining section 22 provided on the top of the first tower body 21 and having innumerable fine holes, and an outer side of the draining section 22. Are formed by a jacket-like dewatering assembly portion 23 provided in the upper portion of the water drainage portion 22 and a cylindrical second tower body 24 provided at the upper portion of the draining portion 22.

  The bottom portion 23 a of the dewatering assembly portion 23 is lowered below the lower end portion 22 a of the draining portion 22 by a height H, and stores water dehydrated by the draining portion 22 (unreacted water).

  The draining part 22 is not particularly limited as long as it can separate the gas hydrate and water (unreacted water), but a wire mesh or a perforated cylinder is preferably used. The hole diameter of the wire mesh or the holed cylinder is preferably in the range of 0.1 to 5 mm.

  When the mesh of the metal mesh is less than 0.1 mm, clogging is likely to occur. On the other hand, if the mesh diameter of the wire mesh or the hole diameter of the perforated cylinder exceeds 5 mm, the gas hydrate tends to flow out from the mesh of the wire mesh, and the yield decreases.

  In this invention, the 2nd tower body 24 provided in the upper part of the draining part 22 is made into the reverse cone shape. In other words, the cross-sectional area of the second tower body 24 is continuously increased from the bottom to the top to reduce the movement resistance of the dehydrated gas hydrate.

  Here, the opening angle θ of the inverted conical second tower body 24 is preferably in the range of 1 to 30 °, particularly 2 to 20 ° (see FIG. 2). When the opening angle θ is less than 1 °, there is a gas hydrate movement resistance, the discharge pressure of the slurry pump 5 that conveys the gas hydrate slurry to the dehydrator 12 increases, or the gas hydrate particle layer As a result, the dehydrator 12 may be blocked, or the liquid level may rise to cause dehydration failure. On the other hand, if the opening angle θ exceeds 30 °, the pushing force of the gas hydrate particle layer decreases, and it becomes difficult to transfer the gas hydrate particle layer.

The second tower body 24 may have a step shape (step shape) as shown in FIG. 3 instead of the inverted conical shape. That is, the cross-sectional area of the second tower body 24 is intermittently increased from the bottom to the top, the width of the stepped portion is a, the height of the stepped portion is b, and the diameter of the lowermost tower is d. Time,
a = (1/5 to 1/50) × d
b / a = 2-30
To be satisfied.

  More specifically, a first ring 26 having the same diameter as the first tower body 21, a first ring part 27 fixed to the upper end thereof, and a second ring 28 erected on the outer peripheral surface of the ring part 27. And a second ring portion 29 fixed to the upper end thereof, and a third ring 30 erected on the outer peripheral surface of the ring portion 29.

  The gas hydrate transfer device 13 is formed by a cylindrical horizontal cylindrical body 31 and a screw-like transfer body 34 having a spiral protrusion 33 on the side surface of the shaft body 32, and the shaft body 32 is driven by a motor 35. Is designed to rotate.

  In the figure, reference numeral 37 is a raw material water supply pump, 38 is a raw material gas (natural gas) supply pump, 39 is a circulating gas blower, 40 is a circulating water pump, and 41 is a circulating water cooler.

  Next, the operation of the gas hydrate production apparatus will be described.

  The raw water (water) w supplied into the pressure vessel 14 by the raw water supply pump 37 is cooled to a predetermined temperature (for example, 1 to 3 ° C.) by the refrigerant r supplied to the reaction heat removal heat transfer section 17. Is done.

  Subsequently, when the raw material gas (natural gas) g of a predetermined pressure (for example, 5 MPa) is supplied by the raw material gas supply pump 38 while the stirrer 16 is driven and the raw material water w in the pressure vessel 14 is stirred, the natural gas g Rises as fine bubbles from the gas ejection nozzle 15 and reacts with the water w while reaching the water surface to become gas hydrate.

  Since the gas hydrate in the pressure vessel 14 is in the form of a slurry under the surface of the water (the concentration of the gas hydrate is about 20% at this time), the slurry pump 5 causes the vertical moving bed type. The dehydrator 12 is supplied. The gas hydrate slurry s supplied to the bottom 21 a of the first tower body 21 of the dehydrator 12 rises in the first tower body 21, and water w flows out from the wire mesh forming the draining section 22.

  When the water w flows out from the draining part 22, the gas hydrate h remains in the upper part of the tower. The gas hydrate h is also accumulated in the draining portion 22 to form a hydrate layer bed d. Then, when water (water accompanied by gas hydrate) passes through the hydrate layer bed d, the hydrate layer bed d is pushed upward, so that the dehydrated hydrate layer bed d is placed at the top of the tower (second It can be taken out continuously from the two tower sections 24). At this time, the concentration of the gas hydrate is about 50%.

  The gas hydrate h reaching the second tower section 24 is continuously transferred to the next step (not shown) by the screw-like transfer body 34 of the gas hydrate transfer device 13.

  Unreacted water w separated by the jacket-like dewatering assembly 23 is returned to the pressure vessel 14 by the circulating water pump 40. At that time, the return water w is cooled to a predetermined temperature by the circulating water cooler 41.

It is a schematic block diagram of the gas hydrate manufacturing apparatus which concerns on this invention. It is sectional drawing of an inverted conical 2nd tower body. It is sectional drawing of a step-shaped 2nd tower body. It is sectional drawing of the conventional dehydration tower.

Explanation of symbols

g Raw material gas w Raw material water h Gas hydrate 12 Dehydrator 21 First tower body 22 Draining section 23 Dehydration assembly section 24 Second tower body

Claims (3)

In a gas hydrate production apparatus for producing a gas hydrate by reacting a raw material gas and raw material water, and draining the gas hydrate with a vertical moving bed type dehydrator to produce a low moisture content gas hydrate The dehydrator is provided in a cylindrical first tower body, a cylindrical draining section provided at the upper part of the first tower body and having innumerable fine holes, and outside the draining section. It is formed by a dewatering assembly part and a cylindrical second tower provided at the upper part of the draining part, and the transverse section of the draining part and / or the second tower is continuously or downwardly from below A gas hydrate production apparatus characterized by being intermittently enlarged. The gas hide according to claim 1, wherein the cross section of the draining portion and / or the second tower body is continuously increased from the bottom to the top, and the opening angle θ is set to 1 to 30 °. Rate production equipment. The cross section of the draining portion and / or the second tower body is intermittently increased from the bottom to the top, the stepped portion width is a, the stepped portion height is b, and the bottommost tower diameter is d. When
a = (1/5 to 1/50) × d
b / a = 2-30
Gas hydrate production apparatus according to claim 1, characterized by satisfying the.

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