JP4676151B2 - Gas hydrate manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for manufacturing a gas hydrate such as natural gas or methane gas.

  Gas hydrate is a hydrate that is stable as a solid formed by incorporating gas into the water molecules, and when the incorporated gas is methane, methane hydrate and natural gas (usually methane as the main component) Is called natural gas hydrate. Natural gas hydrate is stable under low-temperature and high-pressure conditions, and unstable at room temperature and normal pressure. It is attracting attention as a resource.

  On the other hand, in view of the fact that a large amount of gas can be stored in the structure of gas hydrate, natural gas hydrate (NGH) is industrially produced, and new transportation of natural gas to replace liquefied natural gas (LNG) Research is ongoing as a means of storage. For example, natural gas hydrate can be produced under conditions of a temperature of several degrees Celsius and several tens of atmospheres. The produced natural gas hydrate powder or pellets can be transported and stored under the conditions of −10 ° C. and atmospheric pressure.

  As a method for producing such a gas hydrate, a method in which the raw water charged in the production tank is cooled to several degrees C. and brought into contact with the raw material gas under a high pressure condition is performed. However, when the gas hydrate is generated, heat is generated (for example, about 105 kcal / kg), and the water temperature of the generation tank rises. Therefore, considering the generation efficiency of the gas hydrate, the water temperature of the generation tank is set within a predetermined temperature range ( For example, management at 1 to 5 ° C. is performed.

  On the other hand, as a method of bringing the raw material water and the raw material gas into contact with each other in the production tank, a high-pressure raw material gas supplied from a compressor that compresses the raw material gas is jetted into water from a gas outlet at the bottom of the production tank. Gas hydrate is generated by reacting with water in the process of rising in water as bubbles. Since this gas hydrate has a lower specific gravity than water, it floats on the water surface to form a gas hydrate layer, and unreacted source gas is taken into the upper gas phase from the water surface. The unreacted raw material gas accumulated in the gas phase is extracted from the production tank and returned to the water in the production tank via the compressor.

JP 2003-55677 A (FIG. 1)

  However, since the unreacted source gas extracted from the production tank is pressurized after being returned to the low pressure side of the compressor, for example, a large compression power is required to increase the pressure to a high pressure state of several tens of atmospheres. There is a problem of becoming.

  An object of the present invention is to reduce the compression power of a compressor.

  In order to solve the above problems, the present invention provides a gas hydrate production method in which a raw material gas is jetted into raw material water at the bottom of a production tank to produce a gas hydrate. The circulating gas extracted from the gas phase at the top of the generation tank is jetted into the raw material water at the bottom of the generation tank.

  That is, since the source gas circulation system is a circulation line independent from the source gas supply system, the source gas extracted from the generation tank can be ejected to the bottom of the generation tank with a slight increase in pressure. The compression power for can be greatly reduced.

  The circulating gas in this case is formed by the unreacted gas that is part of the raw material gas that has risen in the raw material water and the raw material gas that is replenished to the gas phase. This equipment is pre-equipped and, in actual operation, replenishes the amount of raw material gas produced as gas hydrate in the production tank, thus reducing the production cost of gas hydrate. Can do it.

In this case, for ejecting the circulating gas to the raw water in the bottom of the production tank, with circulating the extracted raw water from the product tank is cooled to generate a suction force at least a portion of the raw water to the circulation, With this suction force, the circulating gas is sucked from the gas layer and led to the bottom of the production tank. In this gas hydrate production method, preferably, the circulating gas spouted into the raw material water at the bottom of the production tank is stirred here by the stirring means to improve the reaction efficiency between this circulating gas and the raw water.

Further, the present invention provides, as an apparatus for carrying out the method for producing the gas hydrate, a generation tank for generating gas hydrate by bringing raw water and raw material gas into contact with each other under a set pressure, and an upper part of the generation tank. A source gas supply pipe for supplying source gas, a source water supply pipe for supplying source water to the generation tank, and a gas circulation for sucking a circulating gas from the gas phase at the top of the generation tank and ejecting it into the water at the bottom of the generation tank And a raw material water circulation means for extracting the raw water from the bottom of the production tank and ejecting the raw water into the raw material water of the production tank from the top of the production tank, and the gas circulation means is an ejector provided in the circulation channel of the raw water circulation means And a gas hydrate manufacturing apparatus formed by communicating the suction port of the ejector with the gas phase in the generation tank .

  The ejector has a function of sucking the raw material gas from the surroundings by the action of the fluid flowing inside and ejecting it from the discharge port in a state where gas and liquid are mixed. Therefore, an ejector is provided in a generally provided water circulation line. By arranging the suction port in the gas phase in the production tank and connecting the discharge port to the water, a circulation system is formed that ejects the circulating gas mixed in the ejector and the raw material water into the water. Thereby, after circulating gas and raw material water are contact-mixed in an ejector, and are ejected in raw material water, the reaction efficiency of a gas-liquid improves and it can raise the production rate of gas hydrate.

  Moreover, the raw material water circulation means may be provided with another circulation channel that branches from the upstream side of the ejector and ejects water into the water in the production tank via the ejector.

  In other words, the eductor has a function of sucking water from the surroundings by the action of the fluid flowing through the inside and ejecting the doubled liquid amount from the nozzle. By ejecting in water, the water stirring action can be exerted. According to this, in the raw material water, the reaction efficiency between the raw material water and the raw material gas is improved, and the production rate of gas hydrate can be increased.

  In this case, since the raw material water circulation means is provided with a cooling means for cooling the raw water, the water temperature rise in the production tank is suppressed and can be controlled within a predetermined temperature range, so that the gas hydrate production reaction can be stabilized. .

  Further, it is preferable that the gas circulation means has at least a descending pipe line disposed in the production tank. If comprised in this way, while being able to inject the circulating gas of a gas phase easily in raw material water, it can be set as a thin-walled structure compared with the case where this downward pipe line is arrange | positioned out of a production | generation tank.

  According to the present invention, the compression power of the compressor can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of an apparatus for carrying out a gas hydrate production method according to the present invention.

  The source gas used in the present embodiment is not particularly limited as long as it generates gas hydrates under predetermined pressure and temperature conditions. For example, methane, natural gas, or the like can be used. In the present embodiment, a case where natural gas is used to generate natural gas hydrate (hereinafter referred to as NGH as appropriate) will be described. Moreover, distilled water is used as the raw water.

  As shown in the figure, the natural gas hydrate production apparatus is produced by a vertical cylindrical production tank 1, a water supply pipe 3 for supplying raw water, and a raw gas supply pipe 5 for supplying raw gas G1. The exhaust pipe 7 for discharging the NGH, the water circulation line 9 for circulating the raw water W, and the stirrer 11 are provided. The generation tank 1 includes a pressure vessel, and the internal pressure and temperature are maintained at the reaction pressure and temperature at which NGH is generated. As these temperature and pressure, the range of 1-5 degreeC and 30-100 atmospheres is preferable, for example. In addition, the generation tank 1 is provided with, for example, a water level sensor and a temperature sensor, and the raw water W in the tank is maintained at a set amount and a set temperature.

  The water supply pipe 3 is connected to the upper end of a supply pipe 17 that is inserted vertically downward from the top of the generation tank 1, and the source gas supply pipe 5 is connected to the top of the generation tank 1. Then, the raw material gas G1 supplied from the raw material gas supply pipe 5 to the gas phase A in the upper part of the generation tank 1 is mixed with the unreacted gas here to form a circulating gas G2 as the raw material gas. One end of the water circulation line 9 constituting the water circulation means is connected to the bottom of the production tank 1, and a water circulation pump 19 and a cooler 21 are sequentially attached to the supply pipe 23 inserted vertically downward from the top of the production tank 1. Connected to the upper end. The water circulation line 9 may be provided with, for example, a flow rate adjustment valve in order to adjust the water circulation flow rate.

  The lower end of the supply pipe 23 is connected to the liquid inlet of the ejector 25. The ejector 25 has a suction pipe 27 connected to the suction port, and a discharge pipe 29 connected to the discharge port. The suction pipe 27 is provided with the opening of the hollow pipe facing upward, and sucks the circulating gas in the generation tank 1 from this opening. The descending pipe 29 is provided by extending a hollow pipe vertically downward, and circulates the circulating gas G2 and the raw water W from the vicinity of the bottom of the production tank 1 or the like. In addition, according to the present embodiment, the descending pipeline 29 is provided vertically downward. However, the present invention is not limited to this. For example, an appropriate angle such as a substantially horizontal direction may be provided.

  As is well known, the ejector 25 is configured such that a nozzle that is tapered from the liquid inlet toward the tip is opened in the suction chamber, and is communicated with a diffuser that is tapered toward the discharge port. A vacuum is generated in the suction chamber by a high-speed liquid jet ejected from the nozzle, gas is sucked from a suction port provided in the suction chamber, mixed with water, and then ejected through a diffuser.

  In the stirrer 11, the rotating shaft 10 is connected to a motor 15, and a stirring blade 13 is attached to the lower end of the rotating shaft 10 inserted vertically downward from the top of the generation tank 1. The gap in which the supply pipes 17 and 23 are inserted into the production tank 1 is welded, and the high pressure mechanical seal or the like is provided in the gap between the rotating shaft 10 of the stirrer 11 and the bearing portion of the production tank 1. It is provided so that the circulating gas G2 and the like are not leaked from the high-pressure production tank 1 to the outside.

  Next, the operation of this embodiment will be described. First, the production tank 1 is filled with a set amount of raw water pressurized to a set pressure from a water supply pipe 3, and then a raw material gas G 1 pressurized to a set pressure is supplied from a source gas supply pipe 5. As a result, the gas phase A and the water phase are formed vertically in the production tank 1.

  The raw material water W extracted from the bottom of the production tank 1 by the water circulation pump 19 is guided to the cooler 21, cooled by exchanging heat with the cooling medium, and then flows into the ejector 25 through the supply pipe 23. The raw material water W that has flowed into the ejector 25 is ejected from the nozzle at a high speed to generate a negative pressure (vacuum), and a gas phase circulation gas G2 composed of the raw material gas and the unreacted gas is sucked from the suction pipe 27. To do. The circulating gas G2 sucked into the ejector 25 comes into contact with the raw material water W in the suction portion and is mixed, and then sequentially passes through the diffuser and the descending conduit 29 and is jetted into the water from the jet outlet 30 at the lower end.

  The circulating gas G2 ejected into the water from the ejection port 30 becomes fine bubbles in the raw material water W, and is engulfed and stirred in the water flow formed by the rotation of the stirring blades 13, so that the circulating gas G2 and the raw water W react. Thus, NGH is generated. Since the generated NGH crystal has a specific gravity smaller than that of water, the NGH crystal floats on the surface of the water and floats to form the NGH layer 32. The NGH layer 32 is scraped by, for example, a scraper (not shown) and discharged from the discharge pipe 7.

  On the other hand, when the unreacted unreacted gas that has floated on the surface of the water without reacting with the raw material water W is taken into the gas phase through the NGH layer 32 and mixed, it is sucked into the ejector 25 and sprayed into the water again. Is done.

  Thus, in this embodiment, negative pressure is generated in the ejector 25 using the flow energy of the raw material water flowing in the water circulation line 9, and the circulating gas G <b> 2 is sucked into the ejector 25 from the gas phase of the production tank 1. Thus, the circulating gas G2 and the raw material water W are jetted into the water in a state of being mixed in the ejector 25 in advance. For this reason, the circulating gas G2 containing the unreacted component is sufficiently contact-mixed with the raw water W, and the production efficiency of the gas hydrate can be improved. In addition, since the water circulation line 9 is provided with the cooler 21 and the raw water W is cooled to a predetermined temperature, the circulating gas G2 sucked into the ejector 25 can be cooled, so that the gas hydrate production efficiency can be further stabilized.

  According to this embodiment, since the ejector 25 is provided, the apparatus configuration is simplified, and the ejector 25 does not require a pressure-resistant structure, so that the equipment cost is reduced.

  Next, a second embodiment of the present invention will be described. FIG. 2 is a block diagram showing a second embodiment of an apparatus for carrying out the gas hydrate production method according to the present invention. In the following description, the same parts as those shown in FIG.

  The feature of this embodiment is that an eductor 33 is used as a means for stirring the raw water in the generation tank 1. Specifically, the circulating water cooled through the cooler 21 in the water circulation line 9 is bifurcated, and through a flow rate adjusting valve, one is connected to the ejector 25 via the supply pipe 23 and the other is the supply pipe. It connects to the eductor 33 through 31. Here, the eductor 33 is disposed in the raw material water W, and the flow energy of the raw material water W in the water circulation line 9 is used as in the case of the ejector 25 described above. That is, negative pressure (vacuum) is generated in the eductor 33, the raw material water W is sucked from the water, and the amount of water increased several times is ejected into the water.

  FIG. 3 is a schematic diagram illustrating a state where water is ejected from the eductor 33. As shown in the figure, since the high-speed liquid jet passing through the eductor 33 creates a vacuum by the Bernoulli effect, the raw water W guided through the supply pipe 31 is ejected from the nozzle 41 and flows into the diffuser 45. The raw material water W1 of several times the amount is sucked from the surroundings. Then, the raw water W and W1 are mixed in the process of passing through the diffuser 45, and jetted into the raw water in the generation tank 1 as the raw water W2. In addition, the water ejected into the water forms a water flow in the entire aqueous phase and exhibits a stirring action.

  According to this embodiment, since it is not necessary to use the stirrer 11 or the like, a high-pressure mechanical seal or the like is not necessary, and the equipment cost and running cost are reduced. In the present embodiment, the raw water W supplied to the ejector 25 and the eductor 33 is covered by the common water circulation line 9. However, separate water circulation lines may be provided.

Next, reference examples of the present invention will be described. Figure 4 is a configuration diagram of a device for carrying out the present embodiment. As shown in the figure, the natural gas hydrate production apparatus of this reference example includes a production tank 1, a water supply pipe 3, a raw material gas supply pipe 5, a discharge pipe 7, a water circulation line 9, and a raw material gas circulation line. 51.

  The production apparatus is provided with a bypass pipe 53 by eliminating the ejector 25 connected to the end of the water circulation line 9 serving as a water circulation means in the production apparatus of FIG. The circulating gas G2 extracted from 1 is again supplied into the raw material water W. The raw water W supplied from the water circulation line 9 is bifurcated through a cooler 21, one of which is a bypass pipe 53 that passes vertically through the top of the supply pipe 31 and the other top of the production tank 1. It is connected to the upper end via flow rate adjusting valves 55 and 57, respectively. The supply pipe 31 may have the same shape as the bypass pipe 53, but is different from the bypass pipe 53 in that an eductor 33 is provided at the lower end.

On the other hand, the raw material gas circulation line 51 serving as a gas circulation means is connected at one end to the top of the production tank 1, and is sequentially provided with a compressor 59 and a cooler 61, and the other end is vertically downward from the top of the production tank 1. It is connected to the upper end of the supply pipe 63 that has been inserted. A hollow pipe nozzle 65 extending in a substantially horizontal direction is connected to the lower end of the supply pipe 63 to form a plurality of small holes. In addition, although the nozzle 65 has shown the ring-shaped nozzle, it is not limited to this, For example, rod shape, U shape, etc. may be sufficient.

Next, the operation of this reference example will be described. First, the raw water W and the raw material gas G1 pressurized to the set pressure are supplied into the production tank 1 from the water supply pipe 3 and the raw material gas supply pipe 5, respectively, so that the gas phase and the water phase move up and down. Formed. A predetermined amount according to the opening degree of the flow rate adjusting valves 55, 57 is extracted from the bottom of the water phase raw water W through the water circulation line 9, cooled in the cooler 21, and then eductor 33 through the supply pipe 31. To the generation tank 1. The eductor 33 can efficiently stir the aqueous phase by sucking the raw water W of the aqueous phase and ejecting the raw water W together with the circulating water.

  Moreover, since the stirring intensity of the raw material water W correlates with the reaction rate and reaction efficiency of NGH, when adjusting these, the opening degree of the flow rate adjusting valves 55 and 57 is adjusted. That is, the stirring intensity can be controlled by distributing a part of the circulating water to the bypass pipe 53 and adjusting the amount of water ejected from the eductor 33. Instead of the bypass pipe 53, an ejector may be provided.

  On the other hand, the circulating gas G2 extracted from the gas phase A is sequentially guided to the compressor 59 and the cooler 61 through the raw material gas circulation line 51, cooled to the set temperature, and then generated from the nozzle 65 through the descending pipe 63. It is ejected into the raw material water W in the tank 1. Bubbles ejected into the raw water W are gradually diffused in the raw water W while forming a water flow, and an NGH generation reaction is started. The generated NGH crystal floats on the water surface to form an NGH layer 32, and is scraped by a scraper or the like and discharged from the discharge pipe 7.

  As described above, even if the circulating gas G2 extracted from the production tank 1 is ejected from the nozzle 65 into the water in the production tank 1, the increased pressure of the circulating gas G2 is the water pressure of the head and the pressure loss when passing through the nozzle 65. Since a small amount corresponding to the amount is sufficient, the compression power for gas circulation can be greatly reduced.

According to the present reference example , the ejection of circulating water by the eductor 33 and the ejection of the circulating gas G2 from the nozzle 65 exhibit the stirring action of the aqueous phase and can improve the gas-liquid contact efficiency. Like the apparatus, it is not necessary to use the stirrer 11.

It is a lineblock diagram concerning a 1st embodiment of a device for carrying out a gas hydrate manufacturing method by the present invention. It is a block diagram which concerns on 2nd Embodiment of the apparatus for enforcing the gas hydrate manufacturing method by this invention. It is a schematic diagram which shows the state which water spouts from the eductor of FIG. It is a configuration diagram according to a reference example of a device for carrying out the gas hydrate production method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generation tank 3 Water supply pipe 5 Raw material gas supply pipe 7 Discharge pipe 9 Water circulation line 19 Water circulation pump 21, 61 Cooler 25 Ejector 27 Suction pipe 33 Eductor 51 Raw material gas circulation line 65 Nozzle

Claims (6)

In the gas hydrate manufacturing method in which the raw material gas is jetted into the raw material water at the bottom of the generation tank to generate gas hydrate,
The raw material gas is supplied to the upper part of the production tank, and the raw water extracted from the production tank is cooled and circulated, and at least a part of the circulated raw material water generates a suction force. A method for producing a gas hydrate comprising sucking a circulating gas from a gas phase at an upper part of the generation tank and ejecting the circulating gas into raw material water at a bottom of the generation tank. The method for producing a gas hydrate according to claim 1, wherein the circulating gas in the gas phase is jetted into the raw material water of the generation tank, and the circulating gas and the raw material water are stirred and mixed by a stirring means. A production tank for bringing a raw material water and a raw material gas into contact with each other under a set pressure to generate a gas hydrate, a raw material gas supply pipe for supplying the raw material gas to the upper part of the production tank, and a raw material water to the production tank Raw material water supply pipe, gas circulation means for sucking circulating gas from the gas phase at the top of the production tank and ejecting it into the raw material water at the bottom of the production tank, and extracting the raw water from the bottom of the production tank A raw material water circulation means for spraying into the raw material water of the generation tank from the upper part of the generation tank,
The gas circulation means has an ejector provided in a circulation flow path of the raw material water circulation means, and is formed by communicating a suction port of the ejector with a gas phase in the generation tank. Hydrate manufacturing equipment. The raw water circulating means, according to claim 3, characterized in that a further circulation passage for ejecting water through the eductor to raw water of the refinery tank branched from the upstream side of the ejector Gas hydrate production equipment. The gas hydrate production apparatus according to claim 3 or 4 , wherein the raw water circulation means includes a cooling means for cooling the raw water. The gas hydrate manufacturing apparatus according to any one of claims 3 to 5 , wherein the gas circulation means has a descending pipeline arranged in the generation tank.

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