JP4514506B2 - Gas clathrate manufacturing method and apparatus - Google Patents

Description

  The present invention relates to a gas clathrate production method and apparatus for producing a gas clathrate by reacting a raw material gas such as natural gas and a raw material liquid (fresh water, seawater, antifreeze, liquid host material, host material solution, etc.).

The gas clathrate has been focused on the property of being able to contain a large amount of gas per unit volume and being stored and transported at a relatively high temperature under atmospheric pressure, and attempts have been made to produce the gas clathrate industrially.
As such an industrial gas clathrate production method, the raw water and raw material gas are mixed in the middle of the line to dissolve the raw material gas in the raw water, and the mixed / dissolved process is reacted. There has been proposed a method of generating a gas clathrate by cooling while flowing in a pipeline (see Patent Document 1).
JP-A-2002-356686 (Claim 1)

The method disclosed in Patent Document 1 separates the raw water and raw gas mixing step and the mixture cooling step, and is a breakthrough called a reaction pipe instead of a general reaction tank as a gas clathrate production vessel. By using a typical one, it is possible to efficiently perform gas diffusion / dissolution in raw material water and removal of generated reaction heat, and to make the apparatus simple and compact.
In general, the generation rate of the gas clathrate is higher as the clathrate generation equilibrium temperature corresponding to the pressure is lower, that is, as the degree of supercooling (= [generation equilibrium temperature] − [actual generation temperature]) is higher. Therefore, in Patent Document 1, a reaction vessel having a high cooling efficiency called a reaction pipe is used, and sufficient cooling is performed in the reaction pipe so as to obtain a degree of supercooling necessary for obtaining a sufficient production rate. It was.
On the other hand, in the separator installed on the downstream side of the reaction pipe, any temperature that can prevent decomposition of the gas clathrate generated in the reaction pipe may be used, and is it equal to the clathrate production equilibrium temperature at the separator pressure? A slightly lower temperature is sufficient.

However, in Patent Document 1, as described above, a fluid with a degree of supercooling required in the reaction pipe (a fluid in which any two or more of raw material liquid, raw material gas, and clathrate are mixed) flows into the separator. The temperature was excessively lower than that required for the separator.
That is, in the thing of patent document 1, it cannot be said that it was suitable for the quantity of the clathrate in which the electric power used for cooling means, such as a refrigerator, was generated, the refrigerator, pump, etc. for cooling a reaction pipe line A part of the motive power of the system has been wasted, and there remains a problem of how to eliminate such waste.

  The present invention has been made to solve such a problem, and in a gas clathrate manufacturing method and apparatus using a reaction pipe, the energy efficiency required for cooling the reaction pipe is improved, and gas without waste of energy is provided. It is an object of the present invention to provide a clathrate manufacturing method and apparatus.

In order to solve the above problem, if the cooling of the reaction pipe is weakened so that the degree of supercooling of the fluid in the reaction pipe becomes small, a reaction vessel called a reaction pipe with high cooling efficiency is used in the first place. This is contrary to the idea of increasing the degree of supercooling and increasing the reaction rate to efficiently produce the gas clathrate.
Therefore, the present inventor has no idea how to improve the utilization efficiency of the energy used for cooling the reaction pipe without losing the purpose of efficiently producing the gas clathrate using the reaction pipe. As a result of earnest research on whether or not it should be done, it is possible to increase the efficiency of energy use for cooling the reaction pipe by using the low temperature state of the fluid with a high degree of supercooling in the reaction pipe with good cooling efficiency. The present invention has been completed with the idea of being able to do so.

(1) A gas clathrate production method according to the present invention is a gas clathrate production method for producing a gas clathrate in a reaction pipe while flowing a raw material gas mixed and dissolved in the raw water into the reaction pipe. The reaction pipe is cooled on the upstream side of the reaction pipe, the reaction pipe is not cooled on the downstream side of the reaction pipe, and the degree of subcooling of the fluid at the outlet of the reaction pipe is 2 ° C. or less. In addition, the diameter and length of the downstream reaction pipe line or the flow velocity of the fluid flowing in the downstream reaction pipe line are set.
Here, the degree of supercooling means (gas clathrate production equilibrium temperature) − (actual gas clathrate production temperature).

(2) A gas clathrate production apparatus according to the present invention is a gas clathrate production apparatus that generates a gas clathrate in a reaction pipe while flowing a raw material gas mixed and dissolved in the raw water into the reaction pipe. An uncooled reaction line portion that is not cooled is provided downstream of the reaction line, and the uncooled reaction line portion has a fluid supercooling degree of 2 ° C. or less at the outlet of the uncooled reaction line portion. In addition, the diameter and length of the uncooled reaction pipe line portion are set.

  According to the present invention, the degree of supercooling can be increased on the upstream side of the reaction pipeline to increase the clathrate generation speed, and the downstream side of the reaction pipeline can be upstream without actively cooling like the upstream side. Since the clathrate can be generated by using the energy used for cooling on the side, the power of the refrigerator or the like can be effectively utilized for gas clathrate generation.

<Description of device configuration>
FIG. 1 is a system diagram showing main components of an embodiment of the present invention. First, the component apparatus of this Embodiment is demonstrated based on FIG.
The gas clathrate production apparatus according to the present embodiment includes gas boosters 1 and 2 that increase the pressure of a raw material gas such as natural gas, raw water pumps 3 and 4 that supply raw water, and a mixture of raw water and raw gas. The line mixer 5 for dissolving the raw material gas in the raw material water, the reaction pipe 7 for generating the gas clathrate by cooling the material mixed by the line mixer 5, and the chiller for cooling the pipe wall of the reaction pipe 7 8. A separator 10 is provided on the downstream side of the reaction pipe 7 to separate the gas clathrate, unreacted gas, and raw water.
Each component device is connected by a pipe indicated by a solid line with an arrow in the figure, and a pressure detector 11 is installed at an important point, and each valve 12 installed in the pipe line by a signal from the pressure detector 11. Is controlled, and the pressure and flow rate of the piping line are adjusted.
Hereinafter, the main components will be described in more detail.

  The line mixer 5 according to the present embodiment is entirely composed of a cylindrical body, and a wing body that generates a swirling flow in the raw material water that has flowed into the tubular body, and a swirl flow that is provided on the inner wall of the cylinder and is rotated by the wing body And a mushroom-like collision body with which the raw material water collides. In the line mixer 5 having such a configuration, the raw water supplied by the raw water pump 3 is swirled by the wing body and is pushed to the inner wall side by a violent centrifugal force, which is further intensely caused by the mushroom-like collision body. Stirring is performed, and the raw material gas is engulfed therein and crushed into ultrafine bubbles, and the raw water and the raw material gas are mixed. In addition to the above-mentioned form, the line mixer has various forms such as a method in which a mixed fluid of raw material water and raw material gas is caused to flow in a venturi tube, and the raw material gas is finely pulverized by shock waves generated therein to generate fine bubbles. Can be used.

The reaction pipe line 7 is composed of one or a plurality of bent pipes, and the upstream side is composed of a cooling reaction pipe line 7a cooled by a chiller 8, and the downstream side is not cooled to prevent excessive heat input from the surroundings. It is comprised from the uncooled reaction pipe line 7b by which only the cold storage for carrying out was carried out.
The preferred length of the uncooled reaction line 7b is such that the degree of supercooling of the fluid at the outlet of the uncooled reaction line 7b is 2 ° C. or less. A more preferred length is such that the temperature of the fluid at the outlet of the uncooled reaction line 7b is approximately equal to the equilibrium temperature, i.e. the degree of subcooling of the fluid is approximately zero. With such a length, the clathrate generation reaction is performed even in the non-cooled reaction line without aggressive cooling, and the energy used for cooling the cooling reaction line 7a is the non-cooled reaction. It is used for the generation of clathrate in the pipeline.
The uncooled reaction line 7b does not need to have the same form as the reaction line (cooled reaction line 7a) for performing normal cooling. For example, a connection pipe connecting the cooled reaction line 7a and the separator 10 is used. It may be a longer one. In short, it may be an uncooled pipeline having a length necessary for gas clathrate production between a reaction pipeline portion for performing normal cooling and a separator.

  The separator 10 is for separating gas clathrate, unreacted gas, and raw water. Examples of the separator 10 include a decanter, a cyclone, a centrifuge, a belt press, a screw concentrator / dehydrator, A rotary dryer or the like can be considered.

<Description of operation>
Next, a manufacturing process for manufacturing a gas clathrate by the apparatus of the present embodiment configured as described above will be described. The pressure of the raw material gas (cooled to near the gas clathrate production temperature if necessary) is increased to a predetermined pressure by the gas booster 1. The raw water is also boosted to a predetermined pressure by the raw water pump 3. These pressurized source gas and source water are respectively supplied to the line mixer 5. The raw material gas and raw material water supplied to the line mixer 5 are mixed with a violent momentum by the mechanism described above. At this time, the raw material gas becomes fine bubbles and is mixed into the raw material water, and the dissolution of the raw material gas is promoted.

A raw material gas dissolved in raw material water (containing fine bubbles) is sent to the reaction pipe 7 and cooled by a chiller 8 to generate a gas clathrate.
In the cooling reaction pipe line 7a on the upstream side of the reaction pipe line 7, the outer wall of the cooling reaction pipe line 7a is efficiently cooled by the chiller 8, the degree of supercooling is increased, and the generated reaction heat is efficiently removed. The gas clathrate is efficiently generated because it is often performed.
Further, in the non-cooling pipeline 7b that is downstream of the reaction pipeline 7, the degree of supercooling of the fluid flowing through the pipeline is increased as a result of efficient cooling in the cooling reaction pipeline 7a. The gas clathrate production reaction continues without cooling. However, since the generated reaction heat is not removed in the non-cooling pipeline 7b, the fluid temperature gradually increases. Then, at the outlet of the non-cooling pipeline 7b (inlet of the separator 10), the degree of supercooling of the fluid becomes substantially zero.

The mixture of the gas clathrate, unreacted gas, and raw water sent to the separator 10 is separated into the gas clathrate, unreacted gas, and raw water by the separator 10. The separated raw material water is supplied again to the line mixer 5 by the pump 4, and the unreacted raw material gas is pressurized to a predetermined pressure by the gas booster 2 and supplied to the line mixer 5. On the other hand, the generated gas clathrate is taken out from the separator 10 and sent to the post-processing step.
In the separator 10, the water level in the separator 10 is detected by the level meter 13, and the water level in the separator 10 is controlled to be a certain level or higher. This is because the raw water has a sealing effect so that the gas does not flow into the raw water return line. The raw water unnecessary for the sealing water is boosted to a predetermined pressure by the raw water pump 4 and supplied to the line mixer 5.
Note that the source gas boosted by the gas booster 1 is directly supplied to the separator 10 in order to keep the pressure in the separator 10 at a certain level or higher.

  As described above, in the present embodiment, the upstream cooling pipe line 7a increases the degree of supercooling to increase the hydrate generation rate, and the downstream non-cooling pipe line 7b increases the efficiency on the upstream side. Since the gas clathrate can be generated without actively cooling from the outside by using the low-temperature state by simple cooling, the energy used for cooling the cooling pipe 7a on the upstream side can be effectively utilized for the gas clathrate generation. Can do.

  In addition, although the example which immerses the reaction pipe line 7 in the thermostat cooled with the chiller 8 was shown as a cooling method of the cooling pipe line 7a in FIG. 1, the cooling method of the cooling pipe line 7a is limited to this. Instead, it may be the same type as a commonly used heat exchanger, such as a double-pipe heat exchanger or a multi-pipe heat exchanger.

Further, in the example of FIG. 1, an example in which the downstream side in the reaction pipe line 7 is the non-cooling pipe line 7 b so as not to perform active cooling is shown.
However, for example, as shown in FIG. 2, the temperature detection means 15 is provided on the outlet side of the reaction pipe line 7, and the downstream side 7 c of the reaction pipe line 7 is cooled based on the detection signal of the temperature detection means 15. You may make it provide the temperature control means 17 which controls fluid temperature.
Thus, by providing the temperature control means 17, even if the amount of raw material gas is large and the degree of supercooling is zero before the outlet in the non-cooling pipeline 7b in FIG. The cooling of 17 makes it possible to control so that the degree of supercooling at the outlet of the reaction line 7 becomes substantially zero. As a result, the reaction pipe line 7 can be utilized for the generation of a gas clathrate over the entire length, and the decomposition reaction in the reaction pipe line 7 can be prevented from occurring.

The temperature control means 17 may be one that uses a chiller as an auxiliary, or one that uses the coolant of the upstream chiller 8. As a case where the coolant of the upstream chiller 8 is used, it is conceivable to use a coolant whose temperature has risen to some extent by using it for heat exchange on the upstream side for auxiliary cooling on the downstream side. . If it does in this way, the electric energy which operates chiller 8 can be used more effectively.
When a chiller is used as the temperature control means 17, the chiller may be controlled directly or the refrigerant flow rate supplied from the chiller may be controlled.

In order to verify the effect of the above-described embodiment, an analysis experiment was performed on the apparatus shown in FIG. This analysis experiment is a case where methane is used as a raw material gas and water is used as a raw material liquid, that is, a case where methane hydrate is produced.
The analysis experiment is a comparison between a case where only the 100 m cooling reaction line is provided and a case where a 50 m non-cooling reaction line is provided downstream of the same 100 m cooling reaction line.

FIG. 3 illustrates the relationship between the reaction pipe length, the fluid temperature, and the hydrate volume ratio in the above two cases, where the horizontal axis represents the reaction pipe length (m) and the left vertical axis represents the fluid temperature ( ° C), and the vertical axis on the right side shows the volume fraction of hydrate produced.
In this analysis experiment, as described above, the cooling reaction pipeline is from 0 to 100 m, and the non-cooling reaction pipeline is from 100 to 150 m. Therefore, in the case of only the cooling reaction pipe of 100 m, the circle at the position of 100 m in FIG. 3 indicates the state of the outlet of the reaction pipe. Indicates the state of the outlet of the reaction pipe.
In this analysis experiment, the pressure of the separator installed downstream of the reaction pipe is 8 MPa, and the hydrate formation equilibrium temperature corresponding to this separator pressure is 10.9 ° C. In this example, the diameter of the uncooled reaction line was set equal to the diameter of the cooled reaction line.

As can be seen from FIG. 3, the hydrate formation reaction proceeds efficiently with a sufficient degree of supercooling in each case in the cooling reaction line, and the degree of supercooling remains in the case of only the 100 m cooling reaction line. It flows into the separator at temperature.
On the other hand, when a 50-m uncooled reaction line is added, the hydrate formation reaction further proceeds in the uncooled reaction line using the degree of supercooling in the cooled reaction line. At this time, reaction heat accompanying hydrate generation is generated in the uncooled reaction pipe, but the fluid temperature in the non-cooled reaction pipe rises because it is uncooled.
For the case of only a 100 m cooling reaction line and a case where a 50 m non-cooling reaction line is provided on the downstream side, the reaction line outlet temperature, the hydrate volume ratio at the reaction line outlet, and the hydrate production amount are as follows. The comparison is shown in Table 1 below.

As can be seen from Table 1, the outlet temperature is 6.4 ° C when the cooling reaction line is only 100m and the degree of supercooling is 4.5 ° C, whereas the outlet temperature is lower when a 50m uncooled reaction line is provided. The temperature rises to 9.7 ° C and the degree of supercooling decreases to 1.2 ° C.
On the other hand, the amount of hydrate produced increased by 28.5 kg / h when the 50 m uncooled reaction line was installed. In other words, although the power required for cooling is the same, in this example, the amount of hydrate produced increased by about 22% simply by providing a 50 m uncooled reaction line.
From the above, the energy required for cooling in the 100 m cooling reaction line could be used for hydrate generation in the 50 m uncooled reaction line on the downstream side, and a 50 m uncooled reaction line should be provided. This means that the energy efficiency of hydrate generation is improved.

In the above example, the pipe diameter of the non-cooling reaction pipe is the same as the pipe diameter of the cooling reaction pipe, but the fluid flowing through the pipe is increased by increasing the pipe diameter of the non-cooling reaction pipe. If the flow rate is reduced, the residence time in the non-cooled reaction pipe increases even if the length of the non-cooled reaction pipe is 50 m, which is the same as the above example, so the reaction continues until the degree of supercooling reaches zero It is also possible to make it.
However, if the diameter of the uncooled reaction pipe is made sufficiently large, it is possible to make the degree of supercooling at the outlet zero with an uncooled reaction pipe shorter than 50 m.

It is explanatory drawing of the gas clathrate manufacturing apparatus concerning one embodiment of this invention. It is explanatory drawing of the other aspect of one embodiment of this invention. It is explanatory drawing of the Example of this invention.

Explanation of symbols

1, 2 Gas booster 3,4 Raw material pump 5 Line mixer 7 Reaction line 7a Cooling reaction line 7b Uncooled reaction line 17 Temperature control means

Claims (2)

  In the gas clathrate manufacturing method for generating a gas clathrate in the reaction pipe while flowing the raw material gas mixed and dissolved in the raw water into the reaction pipe, the reaction pipe is cooled on the upstream side of the reaction pipe. The diameter and length of the downstream reaction pipe are not cooled on the downstream side of the reaction pipe and the degree of subcooling of the fluid at the outlet of the reaction pipe is 2 ° C. or lower. Or a method for producing a gas clathrate, characterized by setting a flow rate of a fluid flowing in a downstream reaction pipe.   In a gas clathrate production apparatus that generates a gas clathrate in a reaction pipe while flowing a raw material gas mixed / dissolved in raw water into the reaction pipe, non-cooling that is not cooled downstream of the reaction pipe A reaction pipe section is provided, and the uncooled reaction pipe section has a diameter and length of the uncooled reaction pipe section so that the degree of supercooling of the fluid at the outlet of the non-cooled reaction pipe section is 2 ° C. or less. A gas clathrate production apparatus characterized in that is set.

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