JP2006160828A - Apparatus for forming gas hydrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for forming a gas hydrate, capable of efficiently forming the gas hydrate with a compact structure of the apparatus. <P>SOLUTION: This apparatus has a mixing device which changes a raw material gas into a foamy state and mixes the gas with raw material water and a pipeline where a fluid mixture composed of the raw material gas and the raw material water flows inside the pipeline and the pipeline cools the fluid mixture as a result of heat exchange with the fluid mixture which flows inside the pipeline itself, wherein a temperature of the pipeline is controlled along a direction of flowing of the fluid mixture in proportion to a gas hydrate formation and decomposition equilibrium characteristic specific to a combination of the raw material water and the raw material gas. Further, an inner diameter of the pipeline is controlled so as to be decreased according to traveling of the fluid mixture from an inflow side to an outflow side, for the purpose of keeping a flow rate of the fluid mixture which flows inside the pipeline constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas hydrate generating apparatus, and more particularly to an apparatus for generating gas hydrate from, for example, natural gas, methane gas, carbon dioxide gas or the like.

  A gas hydrate is an ice-like solid substance composed of water molecules and gas molecules, and is a hydrate having a structure in which gas molecules are taken into a cage-like structure formed by water molecules. This gas hydrate has properties such as high gas storage properties, large heat of generation / dissociation, generation of high pressure due to small temperature changes, selectivity of hydrated gas, etc. The use in various applications such as heat storage systems, actuators, and gas separation and recovery is attracting attention and research is being conducted.

  Such a gas hydrate maintains the temperature and pressure of a raw material gas such as natural gas and water within the hydrate generation range indicated by an equilibrium curve (an equilibrium curve in a phase diagram representing gas hydrate generation and decomposition equilibrium characteristics). It is produced by contacting and mixing the two to react. The most important factors governing the production rate of gas hydrate are the size of the gas-liquid interface area between gas and water and the heat removal efficiency that takes away the heat of reaction when the gas and water react.

Conventionally, gas hydrate that efficiently generates gas hydrate by filling the reaction vessel with water and source gas and forcibly bubbling the source gas into water with stirring to increase the gas-liquid interface area Production methods have been proposed and attempts have been made to produce gas hydrates. In this method, generated heat is removed by forced convection by stirring and bubbling.
In addition, a gas hydrate production method has been attempted in which gas is filled in a reaction vessel and water is sprayed into the reaction vessel to increase the gas-liquid interface area to efficiently produce gas hydrate. In this method, the generated heat is removed by the heat capacity of the droplets and the forced convection of the gas.
As described above, in the method of generating gas hydrate in the reaction vessel, it is necessary to secure a certain amount of gas-liquid contact space for contacting the gas and liquid in the reaction vessel, so the volume of the reaction vessel is increased. There is a problem that it is necessary and equipment becomes large.
Also, the removal of reaction heat during gas hydrate production is an important factor in gas hydrate production. In order to sufficiently remove reaction heat, it is necessary to sufficiently cool the raw material gas and water in the reaction vessel. However, each of the above-described methods requires a large reaction vessel volume, and therefore, even when the reaction vessel is directly cooled or a cooling means other than cooling the reaction vessel is provided, There is also a problem that the means become larger and more complicated.

A gas hydrate manufacturing method and a manufacturing apparatus that solve such problems are proposed, for example, in Patent Document 1 below. FIG. 6 is a schematic configuration diagram illustrating a conventional gas hydrate manufacturing system 100 described in Patent Document 1 below.
A gas hydrate production system 100 described in Patent Document 1 below includes gas boosters 101 and 102 that increase the pressure of a raw material gas such as natural gas, raw material water pumps 103 and 119 that supply raw water, and raw water and raw material gas. A line mixer 105 for mixing and dissolving the raw material gas in the raw material water, a reaction pipe 107 for generating a gas hydrate by cooling what is mixed in the line mixer 105, a gas hydrate produced in the reaction pipe 107, And a separator 109 for separating 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 110 is arranged at a key point, and each valve 112 installed in the pipe line by a signal of the pressure detector 110. Is controlled to adjust the pressure and flow rate of the pipe line. Further, the separator 109 is provided with a level meter 121 for detecting the water level in the separator 109, and can be controlled so that the water level in the separator 9 becomes constant.
JP 2002-356665 A

  In such a gas hydrate manufacturing system 100 described in Patent Document 1, a portion where gas hydrate is generated is a reaction pipe 107. In the gas hydrate manufacturing system 100, a mixed fluid in which raw water and raw material gas are mixed by a line mixer 105 flows into the reaction pipe 107. The reaction pipe 107 is composed of one or a plurality of bent pipes, and the peripheral surface of the pipe is cooled by a chiller 117. In the gas hydrate manufacturing system 100 described in Patent Document 1, a mixed fluid obtained by previously mixing raw water and raw material gas is caused to flow through the reaction pipe 107, and the mixed fluid is exchanged by heat exchange between the pipe 107 and the mixed fluid. Cool down. By this cooling, the temperature (and pressure) of the source gas and the source water is adjusted to the hydrate generation range, and the gas hydrate is generated. The gas hydrate is produced in the reaction vessel by using the gas hydrate production system 100 of Patent Document 1 in which the mixed fluid is caused to flow inside the pipe line 107 and the mixed fluid is cooled to produce the gas hydrate. Compared to the case, cooling from the surroundings can be performed efficiently, and the configuration of the apparatus can be made simple and compact.

  In such a gas hydrate production system 100 described in Patent Document 1, in order to efficiently produce gas hydrate, it is necessary to sufficiently cool the mixed fluid by flowing inside the reaction pipe 107. Moreover, sufficient time is required for the raw material gas and the raw water in the mixed fluid to sufficiently react. In order to ensure a sufficient reaction time, the reaction pipe 107 through which the mixed fluid flows needs to have a sufficient length. As described above, in the sufficiently long reaction pipe 107, a distribution occurs in the flow velocity and temperature of the mixed fluid flowing inside.

  In the gas hydrate manufacturing system 100 described in Patent Document 1, as shown in FIG. 6, each component device is connected by a pipe, and a pressure detector 110 is disposed at a main point of the pipe. Each valve 112 is controlled by a signal from the pressure detector 110 to adjust the pressure and flow rate of the piping line. However, there is no means for controlling the flow velocity change of the mixed fluid flowing inside the reaction pipe 107 or the temperature distribution of the reaction pipe 107. For this reason, in the conventional gas hydrate manufacturing system 100, the flow rate change of the mixed fluid inside the reaction pipe line and the distribution of the gas hydrate generation speed due to the temperature distribution inside the reaction pipe line have occurred.

  In the conventional gas hydrate manufacturing system 100, the generated granular gas hydrate mixed in the mixed fluid is partially formed on the inner wall of the reaction pipe 107 due to the change in the flow velocity and the distribution of the gas hydrate generation speed. There was a problem that it would stay. Once partial stagnation of gas hydrate starts on the inner wall of the reaction pipe 107, the flow rate of the mixed fluid further decreases and the stagnation proceeds further. When such staying advances and increases, the inner wall of the reaction pipe 107 becomes uneven, and the pressure loss of the mixed fluid in the reaction pipe 107 increases. When the pressure loss increases as described above, there is a problem that waste of power such as a pump increases. In addition, when the stay has proceeded extremely, the reaction pipe 107 is blocked, the mixed fluid does not flow, the gas hydrate cannot be generated, and the apparatus itself is damaged.

  The present invention has been made paying attention to the above-mentioned conventional problems, and provides a gas hydrate generating apparatus capable of efficiently generating gas hydrate with a compact apparatus configuration.

  In order to solve the above problems, the present invention is an apparatus for generating gas hydrate by reacting raw water and raw material gas under conditions of a predetermined pressure range and a predetermined temperature range, wherein the raw material gas is bubbled A mixer for mixing with raw material water in the form of a gas, and a mixed fluid composed of the raw material gas and the raw water flows inside, and a pipe line for cooling the mixed fluid by heat exchange with the mixed fluid, The gas is characterized in that the pipe has a temperature adjusted along a flowing direction of the mixed fluid according to a gas hydrate formation decomposition equilibrium characteristic determined according to a combination of the raw water and the raw material gas. A hydrate generator is provided.

  It is preferable that the gas hydrate generator of the present invention includes a cooling unit that cools the pipe, and the cooling unit is controlled according to the gas hydrate generation and decomposition equilibrium characteristics. Further, it is preferable that a plurality of cooling means are provided in the pipe line along the direction in which the mixed fluid flows.

  A pressure data acquisition unit that is provided for each partial region of the pipeline corresponding to each of the plurality of cooling units, and that acquires current pressure data of the mixed fluid flowing inside each partial region of the pipeline; Based on the current pressure data and the gas hydrate generation / decomposition equilibrium characteristics, temperature condition setting means for setting and outputting a temperature condition for each partial region so as to satisfy the temperature of the mixed fluid flowing through the pipe A temperature data acquisition means provided for each partial area of the pipe, and for acquiring current temperature data of the mixed fluid flowing inside each partial area of the pipe; and the current data for each partial area The temperature data and the temperature condition for each partial area are received, and the mixture flowing inside each partial area based on the current temperature data and the temperature condition respectively corresponding to each partial area Current temperature is the temperature condition is satisfied in the body, it is preferable that a control means for controlling the cooling intensity of the cooling means for each partial region.

  The temperature condition of each partial region is set to a set temperature that is lower by a preset supercooling temperature than the gas hydrate production decomposition equilibrium temperature at the current pressure determined based on the gas hydrate production decomposition equilibrium characteristics. It is preferable that the condition is to adjust the temperature of the mixed fluid flowing inside each partial region.

  Further, the present invention is an apparatus for generating gas hydrate by reacting raw water and raw material gas under conditions of a predetermined pressure range and a predetermined temperature range, wherein the raw material gas is made into bubbles and the raw water A mixer for mixing, and a pipe for cooling the mixed fluid by heat exchange with the mixed fluid flowing through the inside of the mixed fluid composed of the raw material gas and the raw water, and the pipe The gas hydrate generating device is characterized in that the inner diameter of the pipe is adjusted to be smaller as it goes from the inflow side to the outflow side of the mixed fluid so that the flow velocity of the mixed fluid flowing inside the pipe is constant. Also provided.

  The temperature of the pipe of the gas hydrate generating device is adjusted along the path of the mixed fluid according to the generation and decomposition equilibrium characteristics of gas hydrate determined according to the combination of the raw water and the raw gas. Preferably it is.

  Hereinafter, the gas hydrate production | generation apparatus of this invention is demonstrated in detail based on the preferred Example shown by attached drawing.

FIG. 1 is a schematic configuration diagram illustrating a gas hydrate production system 10 (hereinafter, referred to as system 10) configured to include a hydrate generation unit 20 which is an example of a gas hydrate generation apparatus of the present invention. is there.
A system 10 including a gas hydrate generation unit 20 which is a gas hydrate generation apparatus of the present invention generates a gas hydrate by the gas hydrate generation unit 20 and separates only the generated gas hydrate. Extract.
The system 10 includes gas boosters 11 and 12 that increase the pressure of a raw material gas such as natural gas, raw material water pumps 13 and 14 that supply raw water, and a raw material gas mixed with the raw water. A hydrate generation unit 20 that cools a mixed fluid composed of gas to generate gas hydrate, and a separator 19 that separates the gas hydrate, unreacted gas, and raw water generated by the hydrate generation unit 20 I have.
Each component device is connected by a pipe indicated by a solid line with an arrow in the figure, and a pressure detector 16 is installed at a key point, and each valve installed in the pipe line by a signal from the pressure detector 16 18 is controlled to adjust the pressure and flow rate of the pipe line. The separator 19 is provided with a level meter 21 that detects the water level in the separator 19, and is configured to be controllable so that the water level in the separator 19 is constant.

FIG. 2 is a schematic configuration diagram illustrating the hydrate generation unit 20 that is the gas hydrate generation apparatus of the present invention among the components of the system 10 in more detail.
The hydrate generation unit 20 includes a line mixer 25 for mixing the raw material gas with the raw material water, a reaction line 27 for generating a gas hydrate by cooling the mixed fluid composed of the raw material water mixed with the line mixer 25 and the raw material gas, And a temperature control unit 30 for controlling the temperature of the reaction pipe 27.

  The line mixer 25 is a known line mixer, and crushes the raw material gas into fine bubbles 62 and mixes them with the raw material water 64. The mixed fluid 66 obtained by mixing the raw material water 64 and the fine bubbles 62 of the raw material gas by the line mixer 25 is discharged to the reaction pipe line 27.

  The reaction pipe 27 is composed of one or a plurality of bent pipes (in FIG. 2 and FIG. 5, it is shown in a straight line for simplification). One end of the reaction line 27 is connected to the line mixer 25, and the other end is connected to the separator 19. The mixed fluid 66 discharged from the line mixer 25 flows into the reaction pipe 27, flows through the reaction pipe 27, and flows out to the separator 19. As shown also in FIG. 2, the inner diameter of the reaction pipe 27 gradually decreases as the mixed fluid 66 approaches the outflow side B from the inflow side A along the reaction pipe 27. The length of the reaction conduit 27 is, for example, 100 (m).

  As shown in FIG. 2, the inner diameter of the reaction pipe line 27 gradually decreases in steps as the mixed fluid inflow side A approaches the outflow side B. In the example shown in FIG. 2, a slope 28 that smoothes the change in the inner diameter is provided in a portion where the inner diameter changes. By this inclination 28, the mixed fluid 66 flowing through the reaction pipe 27 can flow through the reaction pipe 27 at a stable flow rate without causing separation or the like at a portion where the inner diameter changes. Thus, the effect of gradually reducing the inner diameter of the reaction pipe line 27 as it approaches from the inflow side A to the outflow side B will be described in detail later.

  The temperature control unit 30 is provided in each of the plurality of cooling means 36 provided along the flow direction of the mixed fluid 66 and each of the partial areas of the reaction pipe line 27 corresponding to the plurality of cooling means 36. Furthermore, the temperature sensor 32 that measures the temperature of the mixed fluid 66 flowing inside the reaction pipe line 27 and outputs the current temperature data, and the pressure of the mixed fluid 66 flowing inside the reaction pipe line 27 for each partial region. And a pressure sensor 34 that outputs current pressure data. The temperature control unit 30 further receives the data (current temperature data and current pressure data) output from the temperature sensor 32 and the pressure sensor 34 for each partial area, and this information and the previously stored gas hydride. A temperature control device 50 is provided for outputting a control signal for controlling the cooling intensity of each cooling means 36 to each cooling means 36 based on the rate generation decomposition equilibrium characteristics.

  The mixed fluid 66 flowing through the reaction pipe 27 is cooled by exchanging heat with the inner wall of the reaction pipe 27. The cooling means 36 cools the reaction pipe 27 in order to control the temperature of the inner wall of the reaction pipe 27. The cooling means 36 is a known cooling means such as a refrigerant circulation type cooler that circulates a refrigerant such as ethylene glycol and cools the peripheral surface of the reaction pipe 27. Each of the plurality of cooling means 36, for example, by changing the temperature of the refrigerant or changing the circulation speed of the refrigerant according to the control signal output from the temperature control device 50, The cooling intensity can be adjusted.

The temperature sensor 32 and the pressure sensor 34 are provided in the reaction pipe line 27 for each partial region corresponding to each of the plurality of cooling means 36. The temperature sensor 32 is a known temperature sensor that measures the temperature of the mixed fluid flowing inside the reaction pipe line 27 and outputs the current temperature data for each partial region. The pressure sensor 34 is the reaction pipe line 27. It is a publicly known pressure sensor that measures the pressure (static pressure) of the mixed fluid flowing inside and outputs the current pressure data for each partial region.
The plurality of temperature sensors 32, the pressure sensor 34, and the cooling means 36 are each connected to the temperature control device 50.

The temperature control device 50 receives the current temperature data and the current pressure data for each partial region of the mixed fluid 66 flowing through the reaction pipe 27 and outputted from the plurality of temperature sensors 32 and pressure sensors 34, and Based on the information, the cooling intensity of the cooling means 36 is adjusted for each partial region, and the temperature of the mixed fluid 66 flowing in each partial region is controlled.
The temperature control device 50 includes a set temperature determination unit 52, a control signal output unit 54, and a memory 56. The temperature control device 50 may have a CPU (not shown), and may be a computer in which each part functions by a program, or each part may be configured by a dedicated device. Further, the temperature control device 50 is connected to an input device (not shown).

The memory 56 can store a gas hydrate generation decomposition equilibrium curve (hereinafter referred to as an equilibrium curve) determined according to the combination of the source gas and the source water. In addition, a desired degree of supercooling in gas hydrate generation can be stored in accordance with an input from an input device (not shown).
FIG. 3 is a diagram for explaining the equilibrium curve stored in the memory 56, which is a phase equilibrium diagram when methane gas and water are mixed, and the solid line shown in FIG. 3 is the equilibrium curve. The equilibrium curve refers to a curve indicating the relationship between temperature and pressure in a phase equilibrium state. In FIG. 3, the region on the left side of the equilibrium curve (the region of lower temperature and higher pressure than the equilibrium state) is a region where gas hydrate is generated, and the region on the right side of the equilibrium curve (higher than the equilibrium state). The temperature and low pressure region) is the region where the gas hydrate is decomposed.
The degree of supercooling is the magnitude of temperature (temperature range) that serves as a reference for determining the set temperature when determining the set temperature of the mixed fluid 66 at the time of gas hydrate generation. The determination of the degree of supercooling and the set temperature will be described in detail later.

  The set temperature determining means 52 is connected to each of the pressure sensors 34 provided for each of the partial areas corresponding to the plurality of cooling means 36, and the current pressure data of the mixed fluid 66 output from the pressure sensor 34 is set for each of the pressure sensors 34. Acquired for each partial area. When the current pressure data is acquired from each of the pressure sensors 34, the set temperature determining means 52 reads the above-described equilibrium curve stored in the memory 56, and calculates the gas hydrate equilibrium temperature at the current pressure for each partial region. Ask. Then, a temperature lower than the equilibrium temperature by a preset supercooling degree ΔT (for example, 3 to 4 (° C.)) is determined as a set temperature for each partial region.

For example, in the example of FIG. 3, when the current pressure data output from the pressure sensor 34 provided in one partial region is P ₁ , the set temperature determination unit 52 determines the current temperature based on the equilibrium curve. The gas hydrate equilibrium temperature T ₁ at the pressure P ₁ is determined. Then, a temperature T _c1 that is lower than the equilibrium temperature T ₁ by a preset degree of supercooling ΔT is determined as the set temperature of this partial region.
That is, the set temperature is a set curve (curved indicated by a broken line in FIG. 3) obtained by translating the equilibrium curve to the lower temperature side by the degree of supercooling ΔT in the phase equilibrium diagram in the combination of the raw water and the raw material gas. , The temperature corresponding to the current pressure data.
The set temperature determining means 52 determines and determines the above set temperature so that the degree of supercooling ΔT is the same for each of the current pressure data transmitted from the plurality of pressure sensors 34 provided in the reaction pipe line 27. Each of the plurality of set temperatures is transmitted to the control signal output means 54. In the example of FIG. 3, for example, when the current pressure is _Pn , the set temperature is _Tcn . The determined set temperature is sent to the control signal output means 54.

Here, the degree of supercooling ΔT indicates the degree of non-equilibrium in hydrate generation, and acts as a driving force for hydrate generation. Fig. 4 is a graph showing the relationship between the degree of supercooling and the hydrate production rate by the hydrate production method using the stirring and bubbling method (Yuichi Kato, Takashi Arai, Shigeru Nagamori, Junji Ono et al., ""Experimental study on production characteristics of natural gas hydrate", Mitsui Engineering & Shipbuilding Technical Report No. 175, February 2002, p6 citation).
In the gas hydrate production method that acquired each data shown in the graph of FIG. 4, the production container is filled with a predetermined amount of water and cooled to the production temperature, and further methane is introduced into the production container to increase the production pressure, After equalizing the temperature of the gas phase and the liquid phase, the stirring blade in the liquid phase is rotated at a predetermined rotation speed, and gas is bubbled into the liquid phase to generate a gas hydrate. At this time, the gas is continuously supplied even during the gas hydrate generation, and the gas hydrate is generated with the pressure in the production container kept constant. The gas flow rate during hydrate generation corresponds to the volume of gas reduced per unit time. That is, the gas flow rate Q _g in hydrate formation corresponds to hydrate the amount M _H That hydrate formation rate per unit time.

FIG. 4 shows the relationship between the degree of supercooling and the gas flow rate for each different stirring condition expressed by different Reynolds numbers when hydrate is generated by varying the generation temperature and the stirring conditions. ing.
From the graph shown in FIG. 4, it can be seen that the gas flow rate greatly increases in proportion to the degree of supercooling. That is, the degree of supercooling ΔT is a driving force for hydrate generation, and the reaction generation rate of hydrate greatly varies with the degree of supercooling. As described above, by determining the set temperature of each part of the reaction pipe line 27 so that the degree of supercooling is constant, the gas hydrate 68 is generated at a uniform production rate in each part of the reaction pipe line 27. Is done.

  Each of the plurality of set temperatures determined according to the current pressure data acquired by the pressure sensor 34 is sent to the control signal output means 54. The control signal output means 54 is connected to a plurality of temperature sensors 32 provided in each partial region. The control signal output means 54 acquires the current temperature data (temperature data acquired at the same timing as the current pressure data) of the mixed fluid 66 output from the temperature sensor 32 provided in each partial region. The control signal output means 54 is also connected to each of the plurality of cooling means 36.

The control signal output means 54 calculates the temperature difference between the current temperature data and the set temperature determined and output by the set temperature determination means 52 for each partial region. Then, a control signal corresponding to the temperature difference is output to the cooling means 36 so that the temperature difference becomes as small as possible. In the cooling means 36, the cooling intensity is adjusted by this control signal, and the temperature of the mixed fluid 66 flowing in the reaction pipe 27 is adjusted to the set temperature for each partial region. In the hydrate generation unit 20, the temperature of the mixed fluid 66 flowing inside the reaction pipe 27 can be controlled in units of ± 1.0 ° C., preferably ± 0.1 ° C. with respect to the set temperature.
In the hydrate generation unit 20, the cooling intensity of the cooling means 36 that cools the reaction pipe line 27 is adjusted along the flow direction of the mixed fluid 66 in this way, and the interior of each partial region corresponding to the cooling means 36 is adjusted. Is adjusted to a set temperature corresponding to the current pressure data of each partial region.

Thus, in the gas hydrate generator of the present invention, the mixed fluid that flows through the inside of each partial region corresponding to each cooling means 36 is provided for each of the plurality of cooling means 36 provided along the flow direction of the mixed fluid 66. The temperature and pressure of 66 are adjusted to the state represented by the setting curve shown in FIG. That is, for each partial region corresponding to each cooling means 36, the temperature of the mixed fluid 66 flowing through the reaction conduit 27 is adjusted according to the pressure of the mixed fluid 66 in the reaction conduit 27. By doing in this way, the temperature of the mixed fluid 66 flowing through each partial region is adjusted so that the degree of supercooling of the mixed fluid 66 flowing through the reaction pipe line 27 is constant in all the partial regions. By adjusting the temperature of the mixed fluid 66 to the same degree of supercooling in any part of the reaction line 27, gas hydrate is generated at the same generation rate in any part of the reaction line 27. Is done.
The hydrate manufacturing system 10 includes such a hydrate generation unit 20.

Hereinafter, a gas hydrate production method (generation / extraction method) by the hydrate production system 10 will be described. First, for example, the pressure of a raw material gas such as natural gas mainly containing methane gas is increased to a predetermined pressure (for example, 60 Mpa) by the gas booster 11. The raw water is also boosted to a predetermined pressure by the raw water pump 13. Then, the pressurized raw water and raw material gas are supplied to the line mixer 25, respectively. In this case, raw water is about 1.0 ^(m 3 / h) feed gas to about 0.1~1.0 ^(m 3 / h), preferably, raw water is about 1.0 ^{(m 3} / H), the raw material gas is supplied to the line mixer 25 at a flow rate of about 0.3 to 0.6 (m ³ / h).

  FIG. 5 is a diagram for explaining hydrate generation in the line mixer 25 and the reaction pipe line 27. The raw material gas and raw material water supplied to the line mixer 25 are mixed with violent momentum by the line mixer 25. At this time, the raw material gas becomes fine bubbles 62 and is mixed into the raw material water 64, and becomes a mixed fluid 66 composed of the raw material water 64 and the fine bubbles (raw material gas) 62. Then, the mixed fluid 66 composed of the fine bubbles 62 and the raw water 64 is discharged to the reaction pipe 27 and cooled to the above-described set temperature in the reaction pipe 27, thereby generating a gas hydrate 68.

The mixed fluid 66 that has flowed into the reaction pipe 27 flows through the reaction pipe 27 from the inflow side A toward the outflow side B. As described above, the temperature of the mixed fluid 66 flowing inside the reaction pipe line 27 is adjusted by the temperature control unit 30 so as to become a set temperature corresponding to the pressure of the mixed fluid 66 flowing through each part of the reaction pipe line 27. Is done. This set temperature is a temperature set so that the degree of supercooling becomes constant according to the pressure of the mixed fluid 66, and the gas hydrate 68 is formed at a uniform generation rate in a plurality of partial regions of the reaction pipe line 27. Is generated.
In the hydrate generation unit 20, the gas hydrate 68 is generated at a uniform generation speed along the length direction of the reaction pipe line 27 (flow direction of the mixed fluid 66).

For example, if a large amount of gas hydrate 68 is locally produced, the gas hydrate 68 stays in the reaction pipe 27.
In the gas hydrate generator of the present invention, gas hydrate 68 is generated in the reaction pipe 27 at any portion of the reaction pipe 27 because the gas hydrate is generated at the same generation rate. There is no fear. Therefore, the pressure loss of the mixed fluid 66 due to partial stagnation of the gas hydrate 68 does not occur inside the reaction pipe line 27. For this reason, the raw material water pump 13 (and the raw material water pump 14) does not require an extra output, and the gas hydrate 68 can be generated efficiently.

In addition, the inner diameter of the reaction pipe 27 described above gradually decreases as it approaches the outflow side from the inflow side of the mixed fluid 66 along the flow direction of the mixed fluid 66.
Immediately after the mixed fluid 66 is discharged from the line mixer 25 and flows into the reaction pipe 27, almost no gas hydrate 68 is generated, and the raw material gas mixed with the raw material water 64 is almost in the state of fine bubbles 62. Exists. In the state of the fine bubbles 62, the raw material gas is a gas, and the volume of the mixed fluid 66 is a volume obtained by adding the volume of the fine bubbles 62 to the volume of the raw material water 64.

When the mixed fluid 66 is cooled to the set temperature by flowing inside the reaction pipe 27, the raw water 64 reacts with the raw gas molecules of the fine bubbles 62, and the gas hydrate 68 is generated at a substantially constant generation rate. Generated. That is, the source gas molecules that existed as a gas in the state of the fine bubbles 62 are in a stable state of being included in the cavity of the three-dimensional cage formed by the water molecules of the source water. Is generated. When the source gas molecules are enclosed in the cavities in this way and gas hydrate is generated, the volume of the enclosed gas molecules becomes almost zero.
That is, the volume of the raw material gas (total volume of the fine bubbles 62) decreases and the volume of the mixed fluid 66 gradually decreases as the mixed fluid 66 flows through the reaction pipe 27 and the generation of gas hydrate proceeds. To do.

If the volume of the mixed fluid 66 is gradually reduced in this way, the flow velocity on the outflow side becomes slower than the inflow side when the inner diameter of the reaction pipe line 27 is constant. This is clear from the so-called continuous equation. In the gas hydrate generator of the present invention, the inner diameter of the reaction pipe 27 is gradually reduced as the mixed fluid approaches the outflow side from the inflow side along the flow direction of the mixed fluid. Thereby, the change in the flow rate of the mixed fluid 66 on the inflow side and the outflow side in the reaction pipe line 27 is eliminated, and the change in the flow rate of the mixed fluid 66 in the reaction pipe line 27 is eliminated.
The inner diameter of the reaction pipe 27 is adjusted according to the gas hydrate generation rate (that is, the reduction rate of the raw material gas volume) so as to eliminate the change in the flow rate of the mixed fluid 66 from the inflow side A to the outflow side B. ing.

  For example, if the flow velocity change of the mixed fluid 66 occurs in the reaction pipe 27, the gas hydrate 68 stays in the reaction pipe 27. In the gas hydrate generator of the present invention, the mixed fluid 66 flows through the reaction pipe 27 at the same flow rate in any part of the reaction pipe 27. For this reason, there is no possibility that the gas hydrate 68 stays in the reaction pipe line 27. Therefore, the partial stagnation of the gas hydrate 68 in the reaction pipe 27 does not cause an excessive pressure loss of the mixed fluid 66. For this reason, the raw material water pump 13 (and the raw material water pump 14) does not require an extra output, and the gas hydrate 68 can be generated efficiently.

In the gas hydrate production system 10, the flow rate (for example, 2.0 (m / s)) of the mixed fluid 66 including the gas hydrate 68 relatively stably flows inside the reaction pipe line 27. The inner diameter of the reaction pipe 27, the output of the pump, and the like are adjusted.
According to the gas hydrate generator of the present invention, the gas hydrate 68 does not stay in the reaction pipe 27 as described above. Therefore, the mixed fluid 66 flows at a stable flow rate from the inflow side to the entire outflow side of the reaction pipe line 27. Therefore, the gas hydrate 68 can be generated efficiently and stably without causing excessive pressure loss in the mixed fluid 66 flowing in the reaction pipe line 27.
In the example shown in FIGS. 2 and 3, the inner diameter of the reaction pipe line 27 is gradually reduced corresponding to each cooling means 36. Thus, in the gas hydrate production | generation apparatus of this invention, it is not limited to reducing an internal diameter corresponding to the cooling means 36. FIG. In the example shown in FIGS. 2 and 3, the inner diameter decreases stepwise with a step, but the inner diameter decreases continuously from the inflow side A to the outflow side B without having a step. Also good.

  The gas hydrate 68 generated by the gas hydrate generation unit 20 flows along the reaction pipe 27 together with unreacted gas (fine bubbles 62) and unreacted raw water (raw water 64) and is sent to the separator 19. The mixture of the gas hydrate 68, unreacted gas, and unreacted raw water sent to the separator 19 is separated into the gas hydrate 68, unreacted gas, and unreacted raw water by the separator 19, respectively. Examples of the separator 19 include a separation tank, a decanter, a cyclone, a centrifuge, a belt press, a screw concentrator / dehydrator, and a rotary dryer.

The separated raw material water is supplied again to the line mixer 25 by the raw material water pump 14, and the unreacted raw material gas is pressurized to a predetermined pressure by the gas booster 12 and supplied to the line mixer 25. On the other hand, the produced gas hydrate 68 is taken out from the separator 19 and sent to various post-processing steps such as cooling, depressurization, and pelletization.
In the separator 19, the water level in the separator 19 is detected by the level meter 21, and the water level in the separator 19 is controlled to be above a certain level. 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 14 and supplied to the line mixer 25. In addition, the source gas boosted by the gas booster 11 is directly supplied to the separator 19 in order to keep the pressure in the separator 19 at a certain level or higher.

  In the gas hydrate production system 10 including the gas hydrate production unit 20 which is the gas hydrate production apparatus of the present invention, the gas hydrate is produced in this way, and only the produced gas hydrate is separated. To extract.

  In the above description, natural gas mainly composed of methane gas is taken as an example of the raw material gas, but other examples include ethane, propane, butane, krypton, xenon, carbon dioxide, and the like.

  In the above embodiment, the inner diameter of the reaction line 27 is gradually reduced so that the change in the flow rate of the mixed fluid 66 in the reaction line 27 is eliminated and the mixed fluid 66 flows at a constant flow rate throughout the reaction line 27. It has been adjusted. In the gas hydrate production | generation apparatus of this invention, it is not limited to the internal diameter of a pipe line being adjusted so that a mixed fluid may always flow with a fixed flow velocity over the whole pipe line in this way. The flow rate of the mixed fluid flowing in the pipe may be changed in the pipe so that the pipe does not block due to generation of an extremely large amount of gas hydrate locally. The inner diameter of the pipe in the present invention only needs to be adjusted to such an extent that a change in the flow velocity sufficient to close the pipe does not occur. In the above embodiment, the same degree of supercooling is set in all partial regions of the reaction pipe line 27. In the present invention, a different degree of supercooling may be set for each partial region to such an extent that an extremely large amount of gas hydrate is locally generated so that the pipeline is not blocked.

  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 thinning the middle of the cylindrical body to generate a negative pressure may be used. Alternatively, a device that performs gas-liquid mixing using a swirling flow in a conical or truncated conical container, such as a swirling fine bubble generating device disclosed in Japanese Patent Application Laid-Open No. 2000-447 may be used. The mixer in this specification includes widely what can mix gas-liquid continuously. In the above-described embodiment, one or a plurality of bent pipes are shown as an example of the reaction pipe 27, but a plurality of branched straight pipes may be used.

  The gas hydrate generator of the present invention has been described above. However, the gas hydrate generator of the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the scope of the present invention. Of course, you may also do.

It is a schematic block diagram explaining the gas hydrate manufacturing system comprised including the hydrate production | generation unit which is an example of the gas hydrate production | generation apparatus of this invention. It is a schematic block diagram explaining in detail about the hydrate production | generation unit which is an example of the gas hydrate manufacturing apparatus of this invention. It is a figure explaining the equilibrium curve memorize | stored in the memory of a hydrate production | generation unit, and is a phase equilibrium diagram at the time of mixing methane gas and water. It is a graph which shows the relationship between the magnitude | size of a supercooling degree and the hydrate production | generation speed | rate by the hydrate production | generation method using a stirring and bubbling method. It is a figure explaining the hydrate production | generation in the hydrate production | generation unit which is an example of the gas hydrate manufacturing apparatus of this invention. It is a schematic block diagram explaining the conventional gas hydrate manufacturing system.

Explanation of symbols

10, 100 Gas hydrate production system 11, 12, 101, 102 Gas booster 13, 14, 103, 119 Raw water pump 16, 110 Pressure detector 20 Gas hydrate generation unit 25, 105 Line mixer 27, 107 Reaction tube Path 28 Inclination 30 Temperature control unit 32 Temperature sensor 34 Pressure sensor 36 Cooling means 50 Temperature control device 52 Set temperature determining means 54 Control signal output means 56 Memory 62 Fine bubbles 63 Gas hydrate 64 Raw water 66 Mixed fluid 109 Separator 112 Valve 121 level meter

Claims (5)

An apparatus for generating gas hydrate by reacting raw water and raw material gas under conditions of a predetermined pressure range and a predetermined temperature range,
A mixer for making the raw material gas into bubbles and mixing with the raw material water;
A mixed fluid composed of the raw material gas and the raw material water flows inside, and a conduit for cooling the mixed fluid by heat exchange with the mixed fluid;
Cooling means for cooling the pipe line,
The cooling means is controlled according to a gas hydrate production decomposition equilibrium characteristic determined according to a combination of the raw water and the raw material gas, and adjusts the temperature of the pipe along the flowing direction of the mixed fluid. A gas hydrate generator characterized by the above.   2. The gas hydrate generation device according to claim 1, wherein a plurality of the cooling units are provided in the pipe line along a direction in which the mixed fluid flows. A pressure data acquisition unit that is provided for each partial region of the pipeline corresponding to each of the plurality of cooling units, and that acquires current pressure data of the mixed fluid flowing inside each partial region of the pipeline;
Based on the current pressure data and the gas hydrate generation decomposition equilibrium characteristics, temperature condition setting means for setting and outputting the temperature condition of the mixed fluid flowing through the pipe line for each partial region;
Temperature data acquisition means provided for each partial region of the pipe, and for acquiring current temperature data of the mixed fluid flowing inside each partial region of the pipe;
The current temperature data for each partial area and the temperature condition for each partial area are received, and the interior of each partial area is determined based on the current temperature data and the temperature condition corresponding to each partial area. 3. The gas hydrate generation according to claim 2, further comprising a control unit that controls a cooling intensity of the cooling unit for each partial region so that a current temperature of the flowing mixed fluid satisfies the temperature condition. apparatus.   The temperature condition of each partial region is determined based on the gas hydrate production / decomposition equilibrium characteristics, and is lower than the gas hydrate production / decomposition equilibrium temperature in the current pressure data by a preset subcooling temperature. The gas hydrate generation device according to claim 3, wherein the temperature of the mixed fluid flowing inside each partial region is adjusted. An apparatus for generating gas hydrate by reacting raw water and raw material gas under conditions of a predetermined pressure range and a predetermined temperature range,
A mixer for making the raw material gas into bubbles and mixing with the raw material water;
A mixed fluid composed of the raw material gas and the raw material water flows inside, and a pipe line for cooling the mixed fluid by heat exchange with the mixed fluid flowing inside,
A gas characterized in that the inner diameter of the pipe is adjusted to be smaller as it goes from the inflow side to the outflow side of the mixed fluid so that the flow velocity of the mixed fluid flowing through the inside of the pipe is substantially constant. Hydrate generator.

Images