JP2004107468A - Method and equipment for producing gas clathrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a gas clathrate through efficiently diffusing/dissolving a feedstock gas into/in a feedstock liquid and efficiently removing the generated heat of reaction, and to provide simple and compact equipment for the method. <P>SOLUTION: The method for producing the gas clathrate by reaction between the feedstock liquid and the feedstock gas comprises the 1st step of mixing the feedstock liquid and the feedstock gas together in the midway of the line to dissolve the feedstock gas in the feedstock liquid, forming the gas clathrate by cooling the mixture while allowing it to flow through a reaction tube channel, and separating the gas clathrate thus formed by a separator connected to the reaction tube channel, and also, following the 1st step, one or more steps of the 2nd mixing/dissolving step of dissolving the feedstock gas in the feedstock liquid prior to or in the midway of the step of forming the gas clathrate. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for producing a gas clathrate for producing a gas clathrate by reacting a raw material gas such as natural gas with a raw material liquid (fresh water, seawater, antifreeze, liquid host substance, host substance solution, etc.). .
[0002]
[Prior art]
The gas clathrate (may be simply referred to as “clathrate”. When the host substance is water, it is referred to as gas hydrate, but when referred to as gas clathrate in this specification, it includes gas hydrate). It is an ice-like solid substance containing a high concentration of gas molecules such as natural gas and carbon dioxide inside a basket-like structure composed of molecules of a host substance. Gas clathrates, mainly gas hydrates, can store a large amount of gas per unit volume, and can be stored and transported at a relatively high temperature under atmospheric pressure compared to liquefied natural gas. Its application to storage has attracted attention.
For this reason, studies on the utilization of naturally occurring gas hydrates have been mainly conducted, but in recent years, attempts have been made to industrially produce gas hydrates by focusing on this property.
[0003]
By the way, in the gas hydrate production process, the important factors governing the gas hydrate generation efficiency are the diffusion and dissolution of the raw material gas into the raw material liquid and the heat removal efficiency that takes away the heat of reaction when the gas and water react. is there.
[0004]
Conventionally, gas-liquid contact with a gas space in a tank-shaped pressure-resistant container has been considered as a method for efficiently producing a gas hydrate by increasing the efficiency of dissolving the raw material gas in the raw material liquid and increasing the heat removal efficiency during gas hydrate generation. A porous plate partitioned into spaces is provided, a raw material gas is supplied from below the porous plate, fine bubbles are generated in the gas-liquid contact space through the porous plate, and the raw material liquid is cooled in the gas-liquid contact space. There is a device provided with a coil evaporator (see Patent Document 1).
[0005]
[Patent Document 1]
JP 2001-10985 A
[Problems to be solved by the invention]
However, the above prior art has the following problems.
In the method of introducing air bubbles through the porous plate, the diameter of the air bubbles that can be generated is not so small, and the effect of promoting gas dissolution by enlarging the gas-liquid interface area cannot be expected much.
In addition, a space for installing a porous plate having a certain area or more is required, and a gas-liquid contact space for contacting gas and liquid in the pressure-resistant container needs to be secured for a certain amount or more. Therefore, it is necessary to increase the volume of the pressure vessel, and there is a problem that the equipment becomes large.
Further, the hydrate may adhere to and grow on the porous plate, and in the worst case, the holes may be closed.
[0007]
In addition, since the pressure vessel, which is a reaction vessel, has a large volume, cooling the wall of the pressure vessel alone is not sufficient, and a refrigerant circulation coil is installed inside the pressure vessel to directly cool water and gas. Although the means is adopted, there is a problem that the apparatus becomes large and complicated.
[0008]
As another problem, when gas hydrate is generated in a pressure vessel, the generated gas hydrate floats on the water surface in the pressure vessel, and a means for extracting the gas hydrate (for example, gas hydrate and water And the like, and a device for controlling the water surface at that position, etc.) are required, and the device also has the problem of complexity.
As described above, the conventional technology has a problem that the equipment is complicated and large-scale.
[0009]
The present invention has been made in order to solve such problems, and a gas class capable of efficiently diffusing and dissolving a raw material gas in a raw material liquid and removing heat of formation reaction, and having a simple and compact apparatus. It is intended to obtain a method and an apparatus for producing a rate.
[0010]
[Means for Solving the Problems]
The method for producing a gas clathrate according to the present invention includes a first mixing / dissolving step of mixing a raw material liquid and a raw material gas in the middle of a line and dissolving the raw material gas in the raw material liquid; A gas clathrate generation step of generating a gas clathrate by cooling while flowing, and a separation step of separating the generated gas clathrate by a separator connected to the reaction pipe line, After the dissolving step, one or more second mixing / dissolving steps for dissolving the raw material gas in the raw material liquid before the gas clathrate generating step or in the middle of the gas clathrate generating step are provided.
[0011]
Further, the gas clathrate manufacturing apparatus according to the present invention is a line mixer for mixing the raw material liquid and the raw material gas in the middle of the line to dissolve the raw material gas in the raw material liquid, and while flowing the raw material liquid in which the raw material gas is mixed and dissolved. A reaction pipe for cooling, and a separator connected to the reaction pipe for separating gas clathrate generated, and at least one line mixer is provided upstream of the reaction pipe, A single or a plurality of line mixers are provided in the middle of the reaction pipe.
[0012]
Further, the line mixer is characterized by generating fine bubbles of the raw material gas.
[0013]
Further, a pressure adjusting means for adjusting the line pressure is provided downstream of the line mixer.
[0014]
Further, a flow rate adjusting means for adjusting the flow rate of the fluid flowing through the line is provided downstream of the line mixer.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 5 is an explanatory diagram of an outline of a gas hydrate production process according to an embodiment of the present invention, and shows a case where natural gas is used as a source gas. First, the outline of the gas hydrate production process will be described with reference to FIG.
The natural gas is cooled to 1 to 10 ° C., and heavy components are separated as condensate (S1). On the other hand, water is also cooled to 1 to 10 ° C. (S2), and the cooling water reacts with natural gas at 1 to 10 ° C. and 50 atm to produce gas hydrate (S3). The generated gas hydrate in the form of slurry is separated and dehydrated to be a high-concentration slurry or solid (S4), and the water and unreacted gas separated here are returned to the reaction step (S3) again.
[0015]
The separated and dehydrated gas hydrate is frozen at a temperature of about −15 ° C. (S5). This freezing treatment is to stabilize the gas hydrate by freezing the water attached to the surface of the gas hydrate separated and dehydrated in S4 to form an ice shell.
After the freezing process, a decompression process for reducing the pressure from 50 atm to the atmospheric pressure is performed (S6). Thereafter, the frozen gas hydrate is formed into a pellet (S7), stored in a storage facility such as a silo (S8), and unloaded by a loading facility such as a belt conveyor as required (S9). It is provided for long-distance transport by a transport device such as a transport ship (S10).
The above is the outline of the gas hydrate production process. In the present embodiment, the step (S3) of generating a slurry-like gas hydrate from water and natural gas is devised in the above-mentioned steps, so that it is efficient. Hydrate generation and equipment simplification. Hereinafter, this point will be described in detail.
[0016]
FIG. 1 is a system diagram showing main components of an embodiment of the present invention. First, the components of the present embodiment will be described with reference to FIG. In the following description, a gas clathrate targeted by the present invention will be described as an example.
The gas clathrate manufacturing apparatus according to the present embodiment includes a gas booster 1 for increasing the pressure of a raw material gas such as natural gas, and a raw water (a “raw water” in the present specification means a raw water only). The raw water pumps 3 and 19 for supplying the raw water are mixed with the raw gas and the raw gas is dissolved in the raw water. A first line mixer 5a, a reaction pipe 7 for producing a gas clathrate by cooling and flowing the mixture mixed by the line mixer 5a, and a raw material water provided in the reaction pipe 7 and flowing through the reaction pipe 7 A second line mixer 5b for mixing and dissolving the raw material gas in the raw material gas, and mixing and dissolving the raw material gas in the raw water flowing through the reaction conduit 7 provided on the downstream side of the second line mixer 5b in the middle of the reaction conduit 7; A third line mixer 5c that, produced in the reaction pipe 7 the gas clathrate, and a separator 9 where the unreacted gas, and a raw water to separate.
[0017]
The components are connected by pipes shown by solid lines with arrows in the figure. Gas flow control valves 12a, 12b, and 12c for adjusting gas flow rates are provided in piping lines for supplying raw material gases to the line mixers 5a, 5b, and 5c, respectively.
In addition, a flow rate control valve 14 for adjusting the flow rate of the raw water is provided in a piping line leading from the raw material pumps 3, 19 to the line mixer 5a.
Further, a gas flow control valve 12d for adjusting the supply gas amount is provided on a line for supplying the raw material gas pressurized by the gas pressure booster 1 to the separator 9, and the excess raw material gas in the separator 9 is supplied to the gas separator. A gas flow regulating valve 12e and a gas booster 2 are provided in a line returning to the clathrate generation line. Then, the gas flow control valves 12d and 12e are controlled based on the signal of the pressure detector 10 for detecting the pressure in the separator 9 provided in the separator 9, and the pressure in the separator 9 is adjusted.
[0018]
The configuration of the main components among the above components will be described in more detail.
As shown in FIG. 2 (quoted from Seika Sangyo Co., Ltd., "OHR Line Mixer", page 7 catalog), the line mixers 5a, 5b, 5c of the present embodiment have a large diameter at the entrance side and a small diameter at the exit side. It is composed of a two-stage cylindrical body 11 and has a wing body 13 called a guide vane in a large-diameter part 11a of the cylindrical body 11, and a small-diameter part 11b ahead of the wing body 13 from the inner peripheral surface of the cylinder to the center. It has a plurality of mushroom-shaped collision bodies 15 extending.
In such a line mixer 5, the raw water supplied to the line mixer 5 by the raw water pump 3 becomes a swirling flow by the wing 13, and is pushed outward by violent centrifugal force. The raw material gas is further intensely stirred, and the raw material gas is entrained in the raw material gas, broken into ultrafine bubbles, and the raw water and raw gas are mixed. As a result, the contact area between the raw material gas and the raw water increases, and the raw gas is efficiently dissolved in the raw water.
[0019]
The reaction pipe 7 is formed of a bent pipe, and the peripheral surface of the pipe is cooled by the chiller 17. As described above, since the use of the reaction pipe 7 enables efficient cooling from the surroundings, the gas / raw water is directly cooled by a cooling coil or the like as conventionally performed in general. This eliminates the necessity, and the configuration of the device can be simplified and made compact.
[0020]
It is to be noted that such a reaction pipe 7 can be used because mixing and dissolving of the raw material gas and the raw water are performed by the line mixers 5a, 5b, and 5c, and the reaction pipe 7 is designed mainly for cooling. Because you can do it. That is, in the conventional example shown in Patent Document 1, the mixing / dissolving and the reaction cooling of the raw material gas and the raw water are performed in the clathrate generation vessel in the form of a tank. However, in the present embodiment, the mixing and dissolving of the raw material gas and the raw water and the cooling of the reaction were separated from each other. And cooling with a simple configuration as in the above example becomes possible.
[0021]
The separator 9 separates gas clathrate, unreacted gas, and raw water. Examples of the separator 9 include a decanter, a cyclone, a centrifugal separator, a belt press, a screw concentrator / dehydrator, and a rotary. A dryer or the like is conceivable.
[0022]
Next, a gas clathrate manufacturing method using the apparatus of the present embodiment configured as described above will be described.
The source gas pressurized to a predetermined pressure by the gas booster 1 is supplied to the line mixer 5a via the gas flow control valve 12a. The raw water pumped to a predetermined pressure by the raw water pump 3 is supplied to the line mixer 5 a via the flow rate control valve 14.
The raw material gas and raw water supplied to the line mixer 5a are mixed with a violent force by the mechanism described above. At this time, the raw material gas becomes fine bubbles and is mixed into the raw water, so that the dissolution of the raw material gas is promoted.
[0023]
The raw material water in which the raw material gas is dissolved (the state including undissolved fine bubbles) is sent to the reaction pipe 7 cooled by the chiller 17. In the middle of the reaction pipe 7, the raw material gases are further mixed and dissolved by the line mixers 5 b and 5 c and sent to the separator 9.
At the start of the operation, the pressure of the separator is maintained at the hydrate generation conditions at 12d and 12e, and the pressure of the reaction tube communicating with the separator is also higher. Be started.
[0024]
Here, the mechanism of clathrate generation in the reaction pipe 7 will be described.
The raw material gas and the raw material water are mixed by the line mixer 5a, and the raw material gas becomes fine bubbles, is dissolved in the raw material water, and the whole raw water reaches the equilibrium concentration.
When the raw water reaches the equilibrium concentration, the pressure P in the reaction pipe 7 is higher than the minimum pressure P _{0 for} clathrate generation, and the temperature T of each part of the reaction pipe 7 is lower than the maximum temperature T _{0 for} clathrate generation. Then, generation of the gas clathrate is started. Although will be exothermic to generate the gas clathrate, the amount of heat corresponding to the calorific value by depriving the cooling chiller 17, the temperature of the reaction pipe 7 coercive to a temperature below the clathrate produce the maximum temperature T ₀ Dripping. However, if the material water is excessively cooled, the raw material water solidifies and the flow in the reaction pipe 7 is hindered. Therefore, the cooling capacity of the chiller 17 is set so that the raw water does not fall below the freezing point.
[0025]
When the gas clathrate is generated, the dissolved gas concentration decreases, and the raw material gas is further dissolved until the gas concentration reaches the equilibrium concentration. When the gas concentration exceeds the equilibrium concentration, the gas clathrate is further generated. In order to efficiently generate a large amount of gas clathrate, it is necessary to increase the amount of the raw water that forms clathrate while flowing through the reaction pipe 7. For that purpose, it is necessary to make the amount of the raw material gas dissolved in the raw water close to the theoretical hydration number as much as possible, and for that, the raw material gas can be efficiently dissolved in the raw water when the raw water falls below the equilibrium concentration. It is necessary to create an environment.
[0026]
Therefore, in the present embodiment, the second and third line mixers 5b and 5c are provided in the middle of the reaction pipe 7, and the raw material gas is supplied as fine bubbles in the middle of the reaction pipe 7, so that the raw material gas is supplied. It achieves efficient dissolution. That is, even if the raw material gas, which has become fine bubbles in the first line mixer 5a, is completely dissolved or clathrated in the middle of the reaction pipe 7, or even if it exists as bubbles, the bubbles are generated as the gas flows through the pipe. Are combined to form large bubbles, the contact area with the raw water is reduced, and the dissolving efficiency may be degraded. Therefore, the dissolving efficiency of the source gas is enhanced by supplying the source gas as fine bubbles again in the middle of the reaction pipe 7.
[0027]
The gas clathrate generated as described above flows through the reaction pipe 7 and is sent to the separator 9 together with the raw water and the unreacted gas (when the total amount is converted into clathrate, there is no unreacted gas). Can be
[0028]
When the unreacted gas is sent to the separator 9, the pressure in the separator 9 increases. When the pressure detecting means 10 detects that the pressure exceeds a preset value, the gas flow control valve 12e is shown. The surplus gas is returned to the clathrate generation line under the control of the non-controlling means, whereby the pressure of the separator 9 and the pressure of the reaction line 7 are adjusted.
In the separator 9, the gas clathrate, unreacted gas, and raw water are separated, and the separated raw water is supplied to the line mixer 5 a again by the pump 19.
On the other hand, the generated gas clathrate is taken out of the separator 9 and sent to a post-processing step (steps after S5 in FIG. 5).
[0029]
In the separator 9, the water level in the separator 9 is detected by the level meter 21, and the water level in the separator 9 is controlled to be equal to or higher than a certain level. This is because the raw water has a water sealing effect so that the gas does not flow into the raw water return line. The raw water unnecessary for sealing is raised to a predetermined pressure by the raw water pump 19 and supplied to the line mixer 5a.
[0030]
As described above, according to the present embodiment, by disposing a plurality of line mixers, dissolution of the raw material gas in the raw water is promoted, and efficient generation of the clathrate is realized.
Further, in the present embodiment, the reaction between the raw water and the raw material gas is performed while moving the same in the pipeline. Therefore, in this gas clathrate generation step, all the components (the generated gas clathrate, the unreacted gas, , Raw water) is once sent to the separator 9, and there is no need for a mechanism for extracting only the gas clathrate, which also has the effect of simplifying the configuration of the apparatus.
[0031]
Further, since the raw material gas is continuously dissolved in the raw water by the line mixers 5a, 5b, and 5c each having a cylindrical body, the space can be efficiently saved.
In addition, as a result of dissolving the raw material gas in the raw water using the line mixers 5a, 5b, and 5c separate from the clathrate generation vessel, a pipe-shaped reaction pipe 7 is used instead of the large diameter clathrate generation vessel. Can be used, and a simple and compact cooling means for cooling the peripheral surface of the pipeline can be realized.
In addition, since both the dissolution of the raw material gas by the line mixers 5a, 5b, and 5c and the generation of the gas clathrate in the reaction pipe 7 are continuously performed, the production efficiency of the gas clathrate is drastically improved. Can be.
[0032]
In the above-described embodiment, an example is shown in which two line mixers 5b and 5c are installed downstream of the line mixer 5a, but the number of line mixers installed downstream of the line mixer 5a is one or Three or more units may be used. Further, a plurality of line mixers may be installed on the upstream side of the reaction pipe 7. This is effective when the amount of gas that can be mixed with the amount of raw water is restricted depending on the line mixer.
[0033]
In the above-described embodiment, no means for adjusting the pressure is provided between the line mixer 5a and the reaction pipe 7.
However, as shown in FIG. 3, a pressure adjusting means 27 including a pressure detector 23 and an adjusting valve 25 may be provided between the line mixer 5a and the reaction pipe line 7.
By providing the pressure adjusting means 27, the pressure on the line mixer 5a side can be increased, and the dissolution of the raw material gas into the raw water by the line mixer 5a can be further promoted.
[0034]
In order to further promote the dissolution of the raw material gas in the raw water, as shown in FIG. 4, a stagnation portion 29 as a flow rate adjusting means for reducing the flow rate of the fluid flowing through the line downstream of the line mixer 5a is provided. It may be provided. By providing the stagnation section 29, it is possible to increase the time required for the raw material gas, which has been converted into fine bubbles in the line mixer 5, to be dissolved in the raw water, thereby promoting the dissolution.
In addition, as a specific example of the stagnant portion 29, a tank having a certain volume can be considered.
[0035]
Further, in the description of the above embodiment, the temperature and pressure in each step are not particularly specified, but an example shown in FIG. 5 can be given. However, the optimum values of temperature and pressure in each step are selected depending on various conditions.
[0036]
Further, as another example of the line mixer, a so-called Venturi tube type in which the raw material gas is sucked and mixed by narrowing the middle of the cylindrical body to generate a negative pressure, or Alternatively, a gas-liquid mixing device utilizing a swirling flow in a conical or frustoconical container, such as a swirling type microbubble generator disclosed in Japanese Patent Application Laid-Open No. 2000-4747, may be used. In short, the line mixer in this specification broadly includes a line mixer that can continuously mix gas and liquid.
[0037]
Further, in the above-described embodiment, the case where the number of the reaction pipes is one is shown. However, a plurality of reaction pipes may be provided, and the same number of line mixers may be installed in each of the reaction pipes. Further, the number of line mixers installed in each of the plurality of reaction pipes may be different. Further, the reaction pipe may be branched on the way, and a plurality of line mixers may be installed in the reaction pipe before the branch, and no line mixer may be installed in each of the reaction pipes after the branch. The same number or different number of line mixers may be installed on the road.
[0038]
Further, in the above-described embodiment, the description has been made with natural gas containing methane gas as a main component as a raw material gas, but other examples include ethane, propane, butane, krypton, xenon, and carbon dioxide.
Further, in the above-described embodiment, the type of the raw water is not specified, but for example, freshwater, seawater, antifreeze, and the like can be considered. It is also conceivable to use a raw material liquid such as a liquid host substance or a host substance solution instead of the raw water.
[0039]
【The invention's effect】
As described above, in the present invention, the first mixing / dissolving step of mixing the raw material gas and the raw material gas in the middle of the line to dissolve the raw material gas in the raw material liquid, A gas clathrate generation step of generating a gas clathrate by cooling while flowing, and a separation step of separating the generated gas clathrate by a separator connected to the reaction pipe line, After the dissolution step, before or before the gas clathrate generation step, or in the middle of the gas clathrate generation step, one or more second mixing and dissolution steps for dissolving the source gas in the raw material liquid are provided. The source gas diffusion / dissolution and the heat of formation reaction can be efficiently removed, and efficient gas clathrate generation can be realized.
[Brief description of the drawings]
FIG. 1 is a system diagram showing main components of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a line mixer according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram of another mode of the embodiment of the present invention.
FIG. 4 is an explanatory diagram of another aspect of the embodiment of the present invention.
FIG. 5 is an explanatory diagram of a gas hydrate production process according to an embodiment of the present invention.
[Explanation of symbols]
1, 2 Gas pressure booster 3, 19 Raw water pump 5a, 5b, 5c Line mixer 7 Reaction line 9 Separator

Claims (5)

In a method of producing a gas clathrate by reacting a raw material liquid and a raw material gas,
A first mixing and dissolving step in which the raw material liquid and the raw material gas are mixed in the middle of the line to dissolve the raw material gas in the raw material liquid, and a gas clathrate is produced by cooling while mixing and dissolving the raw material gas in the reaction pipe Gas clathrate generation step, comprising a separation step of separating the generated gas clathrate in a separator connected to the reaction pipe,
After the first mixing / dissolving step, before the gas clathrate generating step or in the middle of the gas clathrate generating step, one or more second mixing / dissolving steps for dissolving the raw material gas in the raw material liquid are provided. A gas clathrate production method characterized by the above-mentioned. In an apparatus for producing a gas clathrate by reacting a raw material liquid and a raw material gas,
A line mixer for mixing the raw material liquid and the raw material gas in the middle of the line to dissolve the raw material gas in the raw material liquid, a reaction pipe for cooling while flowing the raw material liquid in which the raw material gas is mixed and dissolved, and a connection to the reaction pipe; And a separator for separating the gas clathrate that has been generated,
A gas clathrate manufacturing apparatus, wherein at least one line mixer is provided upstream of the reaction pipe, and one or more line mixers are provided in the middle of the reaction pipe. 3. The gas clathrate manufacturing apparatus according to claim 2, wherein the line mixer generates fine bubbles of the raw material gas. 4. The gas clathrate manufacturing apparatus according to claim 2, further comprising a pressure adjusting unit that adjusts a line pressure downstream of the line mixer. The gas clathrate manufacturing apparatus according to any one of claims 2 to 4, wherein a flow rate adjusting means for adjusting a flow rate of a fluid flowing through the line is provided downstream of the line mixer.

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