JP2001010986A - Device for producing methane hydrate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methane hydrate production device which can efficiently produce methane hydrate and stably the produced methane hydrate. SOLUTION: This methane hydrate production device for bringing natural gas into contact with water under a prescribed high pressure to produce the methane hydrate comprises a pressure-resistant container 1 capable of resisting to a prescribed high pressure, raw material water distribution ducts 5 disposed in the pressure-resistant container 1, coil evaporators 4 disposed in the raw material water distribution ducts 5, respectively, a freezer 6 for supplying a cooling medium to the coil evaporators 4, raw material water-circulating means 11, 13 for extracting the raw material water from the bottom portion of the pressure-resistant container 1 and supplying the extracted raw material water to the bottom portions of raw material water distribution ducts 5, and raw material gas supply means 10, 7 for jetting the natural gas from the bottom portion of the pressure-resistant container 1 into the raw material water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for producing methane hydrate, and more particularly to an apparatus and method for producing methane hydrate, which can produce and store hydrate in the same container. .

[0002]

2. Description of the Related Art Gas hydrate is a hydrate inclusion compound of gas and water such as natural gas and carbon dioxide. Natural gas hydrate is methane hydrate because natural gas is mainly composed of methane. is called. Methane hydrate (hereinafter referred to as NGH. In general, M
Also called H. ) Is similar in appearance to sherbet ice,
When the fire is brought near, it burns gently and produces water. Such NGH has a high density, has a methane-encapsulating property, and generates a small amount of cold heat due to dissociation, which is equal to or larger than ice. Therefore, natural gas storage, transport, supply technology and latent heat storage Application to thermal technology is considered. That is, natural gas (NG), which is clean energy,
Global demand is expected to grow further in the future, but since LNG production requires a large amount of energy to compress and liquefy methane gas, NGH is attracting attention as an energy-saving light hydrocarbon utilization technology that replaces LNG. . However, although it has been confirmed that NGH naturally exists as a sedimentary layer on the continental margins of the sea floor surrounding Japan, its production equipment and production method have not been technically established and its development is expected. Was rare.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an apparatus and a method for producing methane hydrate which can efficiently produce methane hydrate and stably store it in view of the above prior art. Is to do.

[0004]

Means for Solving the Problems To solve the above problems, the invention claimed in the present application is as follows. (1) A methane hydrate production apparatus for producing hydrate by bringing natural gas and water into contact with each other under a predetermined high pressure, comprising: a pressure-resistant container capable of withstanding the predetermined high pressure; and provided in the pressure-resistant container. A raw water distribution duct, a coil evaporator arranged in the raw water distribution duct, a refrigerator for supplying a refrigerant to the coil evaporator, and a raw water distribution duct for extracting raw water from the bottom of the pressure vessel. A methane hydrate producing apparatus, comprising: means for circulating raw water supplied to the bottom of the pressure vessel; and means for supplying raw gas for injecting natural gas into the raw water from the bottom of the pressure vessel.

(2) The apparatus for producing methane hydrate according to the above (1), wherein an unreacted gas circulation pipe connecting the upper space of the pressure vessel and the raw material gas supply means is provided. (3) A heat-dissipating load pipe is provided for extracting the liquid phase from the bottom of the pressure vessel and returning it to the upper space or the liquid phase of the pressure vessel via the load heat exchanger, and extracting the regeneration gas to the upper space of the pressure vessel. The apparatus for producing methane hydrate according to the above (1) or (2), wherein a pipe is connected.

(4) A method for producing methane by contacting natural gas and water under a predetermined high pressure to produce a hydrate, wherein the raw water is disposed in a pressure-resistant vessel capable of withstanding the predetermined high pressure. Forming a circulating flow of raw water that rises in the flow duct and descends along the inner wall surface of the pressure-resistant container, into which natural gas is injected from the bottom of the pressure-resistant container into 0 to 6.5 ° C. A method for producing methane hydrate by bringing the raw material water into contact with the raw water in an atmosphere of 26 to 60 kg / cm ² , and storing the methane hydrate in an upper part of a liquid phase of a pressure-resistant container.

(5) The method for producing methane hydrate according to (4), wherein the temperature of the raw water circulation stream is adjusted by a coil evaporator arranged in the raw water flow duct. (6) The methane hydrate according to (4) or (5), wherein the unreacted natural gas in the upper space of the pressure vessel is circulated to the bottom of the pressure vessel and reused as a raw material gas. Manufacturing method. (7) The temperature of the liquid phase withdrawn from the bottom of the pressure vessel is raised by a load heat exchanger, and then returned to the upper space or the liquid phase of the pressure vessel, and the regeneration gas generated by the melting of methane hydrate is converted into product gas. The method for producing methane hydrate according to any one of the above (4) to (6), wherein the methane hydrate is supplied to a customer.

[0008] The present invention relates to an NGH manufacturing technology, a heat storage technology,
This is a combination of storage technology and / or transportation technology. NGH is produced by blowing natural gas as a raw material into a pressure vessel and chemically reacting with raw water, and the produced hydrate is stored in the same pressure vessel. Is what you do. In the present invention, water is a raw material for producing a hydrate, and also functions as a heat medium that absorbs the heat of reaction when the hydrate is generated and discharges it to the outside of the system.

[0009]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a system of an apparatus for producing methane gas hydrate according to one embodiment of the present invention. In the figure, the apparatus comprises a spherical storage tank 1 as a pressure-resistant container, a plurality of raw water flow ducts 5 provided in the spherical storage tank 1, and a coil evaporator disposed in the raw water flow duct 5. , A refrigerator 6 for supplying a refrigerant to the coil evaporator 4, and a raw material as a means for circulating raw water for extracting raw water from the bottom of the pressure vessel 1 and supplying the raw water to the bottom of the raw water distribution duct 5. It mainly comprises a water pipe 11 and a circulation pump 13, and a raw gas pipe 10 and a raw gas injection nozzle 7 as raw gas supply means for injecting natural gas into the raw water from the bottom of the spherical storage tank 1, This apparatus comprises an upper space portion of a spherical storage tank 1 and a source gas pipe 10 as a source gas supply means.
The liquid phase is extracted from the unreacted gas circulation pipe 9 and the bottom of the spherical storage tank 1 and radiated from the melting spray device 14 via the load heat exchanger 15 and returned to the upper space or the liquid phase of the spherical storage tank 1. Load pipe 18 and product gas pipe 17 connected to the upper space of spherical storage tank 1
It has. 2 is a heat insulating material, 3 is a hydrate-containing slurry in which raw water, natural gas and generated hydrate are mixed, 8 is a blower provided in an unreacted gas circulation pipe 9, 12 is an additive tank, Reference numeral 16 denotes a heater provided in the product gas pipe 17.

In such a configuration, the raw material water filled in the spherical storage tank 1 is extracted from the bottom of the spherical storage tank 1 in a state where the raw material gas is not entrained, and is added by a concentration controller (not shown). After a predetermined amount of additive is added from the tank 12, the pressure is increased, for example, to about 26 to about 26 through the raw water pipe 11 and the raw water circulation pump 13.
It flows into the bottom of the raw water flow duct 5 in the spherical tank 1 adjusted to 60 kg / cm ² , rises while being cooled by the coil evaporator 4, and descends along the inner wall surface of the spherical storage tank 1, for example. A circulating stream of about 0-6.5 ° C is formed.
On the other hand, natural gas, which is a raw material gas, is injected from the bottom of the spherical storage tank 1 into the circulating flow of the raw water through the raw gas pipe 10 and the raw gas injection nozzle 7, and contacts and mixes with the raw water to form methane hydride. Rate generated. The generated methane hydrate rises in the liquid phase by gravity separation, floats at the upper part of the liquid phase, is stored, and is concentrated. The unreacted natural gas rises in the liquid phase and stays in the upper space of the spherical storage tank 1. However, since the pressure of the spherical storage tank 1 is controlled to be constant, the raw gas pipe is passed through the gas circulation pipe 9. It is returned to 10 and reused as a source gas. In the spherical storage tank 1, gravity separation is performed into three layers of unreacted NG in the upper space, NGH in the upper part of the liquid phase, and raw water in the lower part of the liquid phase.

According to this embodiment, the hydrate can be produced in the spherical storage tank 1 for storing the hydrate, so that a compact device capable of easily recovering and reusing the unreacted gas is provided. Become. Further, a transportation pipe for the slurry containing the generated hydrate is not required. According to the present embodiment, by adopting the bubble column system in which natural gas bubbles are blown into the raw water, the calorific value generated in the chemical reaction process of NGH can be efficiently discharged out of the system through the raw water. Therefore, NGH can be manufactured efficiently and continuously. Further, the melting and cooling heat of the produced NGH can be effectively used for cooling a building, cooling a factory, and the like. According to the present embodiment, since the raw water is supplied to the bottom of the raw water flow duct 5 provided in the spherical storage tank 1, the circulation flow velocity of the raw water is increased, and the heat transfer effect due to forced convection is provided. Is improved.

According to this embodiment, since the raw material gas is not blown into the raw water flow duct, methane hydrate does not adhere to the outer wall of the coil evaporator 4 and good heat transfer performance is maintained. can do. Even if methane hydrate adheres to the outer wall of the duct, the cooling capacity of the raw water is not affected. In the present embodiment, when the natural gas supply source cannot follow the gas demand and wants to melt the NGH and regenerate the NG, the raw water in the spherical storage tank 1 is extracted, and a cooling air conditioning system, a factory cooling / heating process device, etc. The hot water produced by passing through the load heat exchanger 15 is sprayed from the melting spray device 14 into the gas phase or the liquid phase of the storage tank 1 through the heat radiation load pipe 18, and NG generated at this time is used as a regeneration gas extraction pipe. Can be supplied to the user via the product gas pipe 17. Therefore, the device of the present invention can be installed near a gas user to serve as a relay base for gas supply. N
Physicochemical conditions for regenerating NG from GH can be easily set by recalling an NGH generation curve (pressure vs. temperature). Although the composition of the regeneration gas is expected to be slightly different from the composition of the natural gas as the raw material, there is no practical problem. Ancillary equipment for reproducing a mixed gas having the same composition as the natural gas used as the raw material can also be provided.

In this embodiment, the pressure in the spherical storage tank 1 which is highly economical is 26 to 60 kg / cm ² , preferably 26 to 50 kg / cm ² , more preferably 30 to ⁴ kg / cm ² .
It is 0 kg / cm ² . If the pressure is too low, the hydrate generation efficiency decreases, and if it is too high, the equipment cost rises or the risk increases. The temperature in the tank 1 is 0 to 6.5.
° C, preferably 1 to 4 ° C. If the temperature is too high or too low, the hydrate phase changes easily,
Hydrate generation efficiency decreases. In addition, according to the pressure-temperature generation curve of the hydrate, NGH can be manufactured even if the pressure and temperature are deviated and the generation conditions are satisfied.
In the present embodiment, it is preferable to provide a plurality of raw water flow ducts 5, and it is preferable to supply the refrigerant to the coil evaporator 4 disposed inside thereof in parallel. This makes it possible to create a uniform temperature field by minimizing the effect of the static pressure on the evaporation temperature of the refrigerant, thereby facilitating the control of the NGH generation temperature.

In the present embodiment, as an additive to be added to the raw water, for example, a hydration inclusion accelerator such as ketones (eg, acetone) and aliphatic amines is used. Can be obtained from As an effect of these additives, it is possible to reduce the pressure of the NGH generation temperature-pressure curve and increase the temperature. In addition, bactericides, preservatives, rust preventives, etc. of harmful microorganisms having different effects from the hydration inclusion promoter can also be used as additives at the same time. In this embodiment, during the NGH production operation, it is preferable to keep the radiation load system and the molten regeneration gas delivery system in a stopped state as much as possible. In addition, low-temperature seawater or river water can be effectively used in the refrigerator unit of this embodiment as an energy-saving measure. Furthermore, running costs can be reduced by using nighttime power. In the present embodiment, it is preferable to devise the internal structure so that the raw water flowing out of the raw water distribution duct 5 and descending along the inner wall surface of the spherical storage tank 1 does not show-pass into the raw water pipe 11. For example, the short path can be prevented by providing a drift plate outside the raw water flow duct 5 or forming the outlet into a trumpet shape.

FIG. 2 is a diagram showing a pressure-temperature equilibrium curve when hydrating a natural gas component. In the figure,
The equilibrium curves of methane, ethane, propane and butane, which are the main components of natural gas, are shown, and the upper left of each curve is the temperature and pressure region where each gas can exist as a hydrate. Natural city gas (13A) is ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), butane (C
₄ H ₁₀ ) and light hydrocarbons such as methane (CH ₄ ). The composition volume ratio is approximately CH ₄ : C ₂ H
₆ : C ₃ H ₈ : C ₄ H ₁₀ = 88: 6: 4: 2. As apparent from the pressure-temperature equilibrium curve in FIG. 2, in the process of producing NGH, butane and propane have a property of being more easily hydrated than methane. Therefore, for example, methane hydrate minimum production conditions of about 0 ° C. and 26 k
Assuming that the production apparatus is operated at g / cm ² or more, heavy hydrocarbons other than methane are already in gas hydrate. Although an unreacted gas is actually generated due to a reaction rate at which hydrate is generated, the unreacted gas can be circulated to the source gas and reused.

According to the present invention, since the NGH generation container and the storage container are the same container, the transportation of the generated NGH slurry by piping is not required, and once the NGH starts to be generated, the NGH is once introduced into the raw water. Since a part of the NGH slurry is always present, the supercooling phenomenon at the time of NGH generation can be avoided by the seed crystal effect of the NGH slurry. The technology of the present invention has utility value as a combined plant of a cold energy supply business and a natural gas storage and supply business. Further, the device of the present invention is obtained by skillfully combining existing elemental technologies, and it is possible to easily design and manufacture devices from small to large according to needs.

[0017]

According to the invention described in claim 1 of the present application,
By providing a duct through which raw water circulates and circulates in the pressure vessel, and by providing a natural gas supply means for injecting natural gas at the bottom of the pressure vessel, the raw water and natural gas are efficiently brought into contact with each other to reduce hydrate. The hydrate can be produced, and the produced hydrate can be stably stored in the upper part of the liquid phase in the pressure vessel. According to the invention described in claim 2 of the present application, by providing the unreacted gas circulation pipe, the natural gas as the raw material can be effectively used in addition to the effects of the above invention. According to the invention described in claim 3 of the present application, by providing the heat radiation load pipe and the regeneration gas extraction pipe, in addition to the effects of the above invention, the produced and stored NGH is melted as necessary, and the regeneration gas is discharged. It can be supplied to users as product gas.

According to the fourth aspect of the present invention, after forming a circulating flow of the raw water in the pressure vessel, natural gas is injected from the bottom of the pressure vessel to come into contact with the raw water at a predetermined temperature and pressure. By doing so, the contact between the raw water and the natural gas is promoted, the hydrate can be efficiently produced, and the produced hydrate can be stably stored in the same container. According to the invention as set forth in claim 5 of the present application, by controlling the temperature of the raw water by the coil evaporator arranged in the raw water flow duct, in addition to the effect of the above-described invention, the surface of the coil evaporator can be cooled. Hydrate can be efficiently produced by preventing the rate from adhering. According to the invention described in claim 6 of the present application, the unreacted natural gas can be reused as the raw material gas, so that the utilization rate of the natural gas is increased in addition to the effect of the above invention. According to the invention described in claim 7 of the present application, in addition to the effects of the above invention, NG
The gas regenerated by melting H can be supplied to the user as a product gas.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a pressure-temperature equilibrium curve at the time of hydrate generation of a natural gas component.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Spherical storage tank, 2 ... Heat insulation material, 3 ... Hydrate containing slurry, 4 ... Coil evaporator, 5 ... Raw material water distribution duct,
6 ... Refrigerator, 7 ... Source gas injection nozzle, 8 ... Blower, 9
... unreacted gas circulation pipe, 10 ... raw gas pipe, 11 ... raw water pipe, 12 ... additive tank, 13 ... circulation pump, 1
4 ... melting spray device, 15 ... load heat exchanger, 16 ... heater, 17 ... product gas piping, 18 ... radiation load piping.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C10L 3/06 F17C 9/02 F17C 9/02 11/00 B 11/00 C10L 3/00 A

Claims (7)

[Claims] 1. A methane hydrate producing apparatus for producing hydrate by bringing natural gas and water into contact with each other under a predetermined high pressure, comprising: a pressure vessel capable of withstanding the predetermined high pressure; A raw water distribution duct, a coil evaporator disposed in the raw water distribution duct, a refrigerator for supplying a refrigerant to the coil evaporator, and a raw water drawn out from the bottom of the pressure-resistant container. An apparatus for producing methane hydrate, comprising: means for circulating raw water supplied to the bottom of a flow duct; and raw gas supply means for injecting natural gas into the raw water from the bottom of the pressure vessel. 2. The apparatus for producing methane hydrate according to claim 1, wherein an unreacted gas circulation pipe connecting the upper space portion of the pressure vessel and the source gas supply means is provided. 3. A heat-dissipating load pipe for extracting a liquid phase from the bottom of the pressure-resistant container and returning the liquid phase to the upper space or the liquid phase of the pressure-resistant container via a load heat exchanger is provided. The methane hydrate production apparatus according to claim 1 or 2, wherein the extraction pipe is connected. 4. A method for producing methane by producing hydrate by bringing natural gas and water into contact with each other under a predetermined high pressure, wherein the raw water is disposed in a pressure vessel capable of withstanding the predetermined high pressure. Forming a circulating flow of raw water that rises in the duct and descends along the inner wall surface of the pressure vessel, and in which natural gas is injected from the bottom of the pressure vessel into the circulating flow, from 0
Methane hydrate by producing methane hydrate by bringing it into contact with the raw water at 6.5 ° C. in an atmosphere of 26 to 60 kg / cm ² , and storing the methane hydrate in the upper part of the liquid phase of the pressure vessel. Manufacturing method. 5. The method for producing methane hydrate according to claim 4, wherein the temperature of the raw water circulation stream is adjusted by a coil evaporator disposed in the raw water flow duct. 6. The methane hydrate according to claim 4, wherein unreacted natural gas in the upper space of the pressure vessel is circulated to the bottom of the pressure vessel and reused as a raw material gas. Production method. 7. The temperature of the liquid phase extracted from the bottom of the pressure vessel is increased by a load heat exchanger, and then the liquid phase is returned to the upper space of the pressure vessel or into the liquid phase, and the regeneration gas generated by the melting of methane hydrate is removed. The method for producing methane hydrate according to any one of claims 4 to 6, wherein the methane hydrate is supplied to a customer as a product gas.