JP2007051508A - System for recovering gas from gas hydrate layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a commercially sufficiently viable system for recovering gas from a gas hydrate layer with high energy efficiency without the need for pumping up a large quantity of water. <P>SOLUTION: A thermal energy generating device is arranged inside or in the vicinity of a gas hydrate layer, and a gas hydrate is decomposed by thermal energy generated by the thermal energy generating device to recover gases in the system for recovering gas from the gas hydrate layer. The thermal energy generating device comprises a steam generating device for generating steam by heating water; a superheated steam generating device for further heating the steam generated by the steam generating device into superheated steam; a jet tube for jetting the superheated steam generated by the superheated steam generating device as a high-speed air current to the gas hydrate layer; and a suction tube for circulating the gas hydrate fused by the thermal energy of the superheated steam by the high-speed air current into a circulating current and circulating a part of it back to the steam generating device. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas recovery system from a gas hydrate layer that recovers a flammable gas such as methane gas from a gas hydrate layer that exists in layers in the vicinity of the sea surface, underground, or near the surface of a cold region.

  Natural gas often exists in a gas state in a gas layer existing in the ground, and is usually excavated from the gas layer and used. Since natural gas exists in the gas layer in the ground in a gaseous state, it can be recovered relatively easily and is widely used commercially.

No recovery method has been established for such natural gas. Or productivity is low. There is unconventional natural gas that has not been used commercially for such reasons. Among the unconventional natural gas, gas hydrate is said to have the largest amount of resources. Gas hydrate is a kind of inclusion compound, and methane (CH ₄ ), ethane, which is a component of natural gas, is contained in a three-dimensional cage inclusion lattice formed by a plurality of water molecules (H ₂ O). (C 2 _{H 6)} molecules, such as enter, has become a clathrate crystal structure.

Since this gas hydrate is filled with natural gas (methane gas or ethane gas) at a high density, the gas hydrate is theoretically converted to gas in the standard state in 1 m ^{3 of} gas hydrate. Natural gas of about 170 m ³ is included, and is attracting a great deal of attention as a next-generation energy source.

  In addition, once gas hydrate is formed under conditions of low temperature and high pressure, it can exist stably under the specific conditions. Exist. Such a gas hydrate layer is referred to as a “gas hydrate layer” or simply a “hydrate layer”.

  Since this “gas hydrate layer” exists under conditions of low temperature and high pressure, it actually exists deep in the ground of cold regions such as the seabed and Siberia, or rarely near the ground surface. In Japan, it has been confirmed that it exists widely in the deep sea floor off Shikoku and is expected to be a new energy source.

  As described above, the gas hydrate is formed under the conditions of low temperature and high pressure. Therefore, the gas hydrate is decomposed and separated into gas and water by increasing the temperature or decreasing the pressure. For this reason, as a typical method for recovering gas from gas hydrate, hot water or the like is injected as thermal energy into the gas hydrate layer existing in the seabed or underground ground, and gas hydrate is gasified in the ground. There is known a method of separating the gas into water and recovering the gas to the surface in a gaseous state.

  However, in order to decompose the gas hydrate and recover the gas, a temperature increase of several tens of degrees Celsius is required under the same pressure. Furthermore, when the latent heat for melting ice is taken into consideration, a large amount of heat energy is required as shown in Patent Document 1, for example. Moreover, since this hot water must be supplied to the seabed at a depth of several hundred meters, where the gas hydrate layer usually exists, it is cooled before reaching the gas hydrate layer and loses considerable heat energy. It will end up.

  Moreover, since a large amount of hot water is supplied to the gas hydrate layer existing in the ground, the same amount of water as the supplied hot water must be collected together with gas from the seabed several hundred meters deep. It needed a lot of power to pump up the water.

  In addition, when using electric power as a heat source for heating, the electric power must be supplied to the seabed at a depth of several hundred meters, so that the voltage drop increases and energy efficiency is increased even if electric power is used. Was difficult.

  For this reason, in Patent Document 2, one or a plurality of horizontal wells are excavated in the gas hydrate layer, and hot water or water vapor is circulated between the paired horizontal wells to decompose the gas hydrate. Is disclosed. However, in this method, if the gas hydrate between the paired horizontal wells is decomposed and fluidized, the fluidized part is more likely to pass hot water and water vapor than the hydrate part. However, hot water or water vapor passes exclusively through the fluidized portion, and it is unavoidable to expand the range of fluidization by decomposing the hydrate portion.

Japanese Patent Laid-Open No. 2003-262083 JP 2005-60957 A

  An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to recover a gas from a gas hydrate layer that is highly energy efficient and does not require a large amount of water to be pumped, and is commercially well profitable. Is to provide.

  In order to solve the above problems, a gas recovery system from a gas hydrate layer according to the present invention has a thermal energy generator disposed in or near the gas hydrate layer, and the thermal energy generated by the thermal energy generator. A gas recovery system from a gas hydrate layer for decomposing gas hydrate and recovering generated gas, wherein the thermal energy generator is a steam generator for heating water to generate steam, A superheated steam generator that further heats the steam generated by the steam generator to form superheated steam, and a jet pipe that jets the superheated steam generated by the superheated steam generator as a high-speed air stream toward the gas hydrate layer And a gas hydrate melted by the thermal energy of the superheated steam is circulated by the high-speed airflow to form a circulating flow, a part of which is the steam Characterized by being configured to have a suction pipe for refluxing the raw device.

  Here, the water that becomes steam in the steam generation device is preferably supplied by a water supply pipe provided alongside a gas recovery pipe, and the superheated steam generation apparatus is disposed around the ejection pipe, A high-frequency heating device that heats with electromagnetic waves is preferable. Further, a steam supply port from the steam generator is provided in the gas recovery pipe, and both ends thereof are disposed at substantially the center of the circulation path that is inclined and opened in the gas hydrate layer, It is preferable that the latter half part forms an ejection pipe and the superheated steam heated by the high-frequency heating device arranged along the ejection pipe is ejected.

  Further, the gas recovery system from the gas hydrate layer according to the present invention is provided with the gas recovery pipe in addition to the respective devices, and a combustion gas supply pipe for supplying the combustible gas and air independently, A power generation device that mixes the combustible gas and air, burns them in a combustion chamber, and rotates a turbine with the combustion gas to generate electric power. The steam generator and superheated steam are generated by the electric power generated by the power generation device. It is characterized in that the apparatus is driven.

  Here, it is preferable that the combustible gas and the air are independently supplied through pipes provided in the gas recovery pipe, and the combustion chamber is disposed close to the turbine of the power generator, Furthermore, the steam generator, the superheated steam generator, the jet pipe, the circulation path, and the power generator constitute one processing unit, and a plurality of the processing units can be connected along the gas recovery pipe. preferable. In addition, it is preferable that the combustion gas supply pipe and the water supply pipe in the processing unit are configured in a circumferentially divided shape that can be used independently for each processing unit.

  The gas recovery system from the gas hydrate layer of the present invention is configured as described above, and a thermal energy generator is disposed in or near the gas hydrate layer, and the thermal energy generated by this thermal energy generator. The gas hydrate is heated to decompose the gas hydrate and recover only the gas, so the hot water supplied from outside is cooled before reaching the gas hydrate layer, greatly reducing the loss of thermal energy. Can be reduced.

  In addition, by disposing a thermal energy generator in or near the gas hydrate layer, almost all of the generated thermal energy can be supplied to the gas hydrate layer, so that a gas with high energy use efficiency can be supplied. A gas recovery system from the hydrate layer can be realized.

  Furthermore, what is supplied from the outside is only combustible gas and air supplied as a heat source, and water that is a raw material for superheated steam as a medium for heating the gas hydrate, both of which are highly fluid fluids. Even if it is a long distance, there is no particular difficulty in supplying it. In addition, since the electric power used mainly as a heat source for heating is generated and used in or near the gas hydrate layer, there is no problem such as a voltage drop.

  Hereinafter, a gas recovery system from a gas hydrate layer according to an embodiment of the present invention will be described in detail. FIG. 1 is a schematic configuration diagram of a gas recovery system from a gas hydrate layer according to the present embodiment, and FIG. 2 is a side sectional view showing details of a hydrate decomposition apparatus which is a main part of the system shown in FIG. is there.

  As shown in FIG. 1, the gas recovery system 10 from the gas hydrate layer according to the present embodiment is a multi-tubular structure that reaches a gas hydrate layer that exists in layers in the vicinity of the sea surface, underground or near the surface of a cold region. It has the structure of. Here, the case where the gas hydrate layer is present in a layered manner on the sea floor at a depth of several hundred meters below the sea surface, which is the most common form of the gas hydrate, will be described as an example.

  This gas circulation system 10 has a double structure of an outer cylinder 12 and an inner cylinder 14, and the inside of the inner cylinder 14 collects gas (methane gas or ethane gas) generated by decomposing gas hydrate. Overheating as a medium for heating the combustible gas and the air, and the gas hydrate that are separated and supplied from the outside as a heat source between the outer cylinder 12 and the inner cylinder 14. A supply pipe 18 for supplying water to be water vapor and a conduction path 22 for a signal line 20 for transmitting and receiving signals are provided.

  The upper end of the gas recovery system 10 is connected to a structure 26 constructed on the seawater surface 24 (or on the shore), and a combustible gas supply device 28 and an air supply device arranged inside the structure 26. The combustible gas, air, and water are supplied from the supply device 30 and the water supply device 32 through the supply pipe 18, and a control signal from the control means 34 is sent through the signal line 20 to control excavation and combustion of the combustible gas. ing.

  The upper end of the gas recovery pipe 16 is connected to a gas tank 36, and water, mud, sand and gravel collected together with the gas are separated and cleaned, and the cleaned gas is directly carried out by a pipeline or desired The tank for transportation is filled or hydrated again.

  A drilling device 38 is provided at the lower end (tip) of the gas recovery system 10. The drilling device 38 excavates and penetrates the upper formation 40 and exists between the upper formation 40 and the lower formation 42. A hydrate decomposition device 46, which will be described in detail later, formed at the front end of the gas recovery system 10 is inserted into the gas hydrate layer 44 to be processed.

  Here, the hydrate decomposition apparatus 46 is not limited to an integrated one as shown in FIG. 1, but needs a unit configuration that can be easily connected and divided as will be described later. Accordingly, it is preferable to arrange a predetermined number.

  As shown in FIG. 2, the hydrate decomposition apparatus 46 is provided with a thermal energy generator 48 and a thermal power generator 50 inside the multiple pipe of the gas recovery system 10, and heat generated by the thermal energy generator 48. The energy becomes superheated steam and is ejected from the ejection pipe 54 of the circulation path 52 to the hydrate layer, and the surrounding hydrate (not shown) is heated to decompose the gas hydrate and separate it into gas and water. To do. Of course, the thermal energy generator 48 and the thermal power generator 50 are not necessarily arranged inside the hydrate layer, and are located in the vicinity of the hydrate layer, and a circulation path 52 described later is arranged inside the hydrate layer. There is no problem even if it is done.

  The thermal energy generator 48 includes, for example, a steam generator 58 that generates steam by heating water supplied by a water supply pipe 56 that forms part of the supply pipe 18 provided inside the multiple pipe of the gas recovery system 10; The steam generator 58 includes a superheated steam generator 60 that further heats the steam generated by the steam generator 58 to form superheated steam, and the above-described circulation path 52 and a jet pipe 54 that forms a part thereof. The water supplied by the water supply pipe 56 is heated by the heater 62 to generate steam, and is jetted into the circulation path 52 from the steam supply port 64 disposed at an inclination.

  The circulation path 52 is provided inside the multiple pipe of the gas recovery system 10, and the steam supply port 64 from the steam generator 58 is opened at both ends inclined toward the gas hydrate layer. In the middle of each, an opening is formed inclining in the direction of the ejection pipe 54 (the second half of the circulation path 52). The circulation path 52 has a jet pipe 54 in the latter half thereof, and a superheated steam generator 60 that further heats the steam generated by the steam generator 58 and turns it into superheated steam along the outer periphery of the jet pipe 54. Has been placed. The superheated steam generator 60 is desirably a high-frequency heating device 66 that is disposed around the ejection pipe 54 and further heats the steam with high-frequency electromagnetic waves.

  Since the thermal energy generator 48 is configured as described above, the steam generated by the steam generator 58 and inclined and ejected in the direction of the ejection pipe 54 is further heated by the high-frequency heating device 66 to be heated at a high temperature and high pressure. It becomes superheated steam, and the flow of the ejected steam is further accelerated to become a high-speed air stream, moves inside the circulation path 52 along the ejection pipe 54, and moves from the opening of the ejection pipe 54 toward the inside of the gas hydrate layer. Then, it is ejected as heated superheated steam. The driving force here is preferably an ejector pump that is less likely to contain foreign matter such as earth and sand or gravel.

  The gas hydrate heated by the heat energy of the superheated steam and melted and flowed becomes a circulating flow circulating in the hydrate layer by the high-speed air stream ejected from the opening of the ejection pipe 54, and the gas The gas is recovered from the recovery port 68 and transferred to the gas tank 36 through the gas recovery pipe 16. At this time, it is desirable to provide an appropriate strainer or filter at the opening of the gas recovery port 68 so that foreign matter such as earth and sand or gravel does not enter from the gas recovery port 68.

  Furthermore, in the gas recovery system according to the present invention, at least one for adjusting the recovered gas pressure in the gas recovery path including the gas recovery pipe 16 between the ground or the sea and the gas hydrate layer. It is preferable to have two pressure adjusting means.

  Further, in the gas recovery path including the gas recovery pipe 16, it is preferable to have at least one conversion means for converting the recovered gas between the ground or the sea and the gas hydrate layer. Here, the gas conversion is, for example, a process of removing impurities in methane gas (actually, a mixed gas containing methane as a main component) obtained as a result of thermal decomposition of methane hydrate, or removing moisture. In addition, a process of changing methane gas to methanol by adding oxygen using a catalyst can be suitably used, but the process is not limited thereto.

  In addition, a part of the circulation flow generated by the high-speed air flow ejected from the opening of the ejection pipe 54 becomes a flow that recirculates to the suction pipe (the first half of the circulation path 52), and is heated by the heater 62 of the steam generator 58. Together with the steam jetted from the steam supply port 64 to the circulation path 52 by heating, it is heated again by the high-frequency heating device 66 and becomes a high-speed air stream of superheated steam, and the gas hydrate layer is formed from the opening of the ejection pipe 54. Erupts toward the inside of the.

  The power generation device 50 is provided in the gas recovery system 10 and is supplied from the outside by a combustible gas supply pipe 70 and an air supply pipe 72 that constitute a combustion gas supply pipe that supplies a combustible gas and air independently. The combustible gas and air are mixed and burned by a burner 76 provided in the combustion chamber 74, and the turbine 78 is rotated by the combustion gas to generate electric power. The turbine 82 is arranged on the left side of the combustion chamber 74, and the rotating blades of the turbine 78 and the rotor 80 of the generator are connected by a rotating shaft 84 rotatably supported by a bearing device (not shown).

  The combustion gas combusted in the combustion chamber 74 is exhausted to the outside through the exhaust pipe 86. In this embodiment, the turbine 78 is rotated again as a waste heat turbine in the middle thereof, and efforts are made to increase power generation efficiency. ing. Further, the exhaust pipe 86 heats the surrounding gas hydrate layer by returning the outer periphery of the gas recovery system 10 or refluxes the outside of the water supply pipe 56 to freeze the water in the water supply pipe 56. Prevention is desirable for effective use of heat.

  Then, the electric power generated by the power generation device 50 is used for heating for generating steam by the heater 62 of the steam generating device 58 and for generating high frequency electromagnetic waves for further heating the steam by the high frequency heating device 66 of the superheated steam generating device 60. It is a power source or a power source for various control devices. Furthermore, even if the power generation efficiency of the power generation device 50 is somewhat deteriorated, since the heat is used to heat the surrounding gas hydrate layer, there is no amount of heat discarded as waste heat.

  Here, the combustible gas used in the power generation device 50 needs to be supplied from the outside at the beginning, but after the gas recovery from the gas hydrate gets on the track, a part of the recovered gas is recovered. It can also be changed to use.

  As the high-frequency electromagnetic wave used here, one having a frequency of about several hundred megahertz to several tens of terahertz can be suitably used. In particular, the terahertz class has the effect of accelerating the decomposition of gas hydrate by penetrating deeply into the inside of gas hydrate and electromagnetic waves of the frequency (generally hundreds to thousands of megahertz) used for the decomposition of gas hydrate. It is also effective to use an appropriate combination of electromagnetic waves having different frequencies.

  Incidentally, it is effective to generate cracks in the gas hydrate layer in order to efficiently recover the gas by the decomposition of the gas hydrate using the circulating flow as described above. As a method of generating cracks in such a gas hydrate layer, it is effective to generate a strain by locally heating and expanding the gas hydrate layer, but in addition to that, giving an impact. Therefore, it is also effective to generate cracks mechanically. The method of giving an impact is not particularly limited, but in general, not a method using mechanical vibration, but a non-contact method in which a shock wave is generated and this is applied to a gas hydrate layer to generate a crack is used. It is easy to do and is effective.

There are various known shock wave generators that can be used here, such as a spark discharge method, a piezo effect method, an electromagnetic conversion method, and an electro-hydraulic method. Any method can be used as long as it can be used.
When actually applying a shock wave, it is preferable to further apply a shock wave to the hydrate layer while irradiating the hydrate layer with ultrasonic waves or microwaves.

  In short, in the gas recovery system according to the present embodiment, by causing a shock wave to act, a crack is generated in the hydrate layer, and the crack is made to function as a base for hydrate decomposition, thereby improving the hydrate decomposition efficiency. It is intended to improve, and a shock wave generated by an arbitrary method can be applied by an arbitrary method (continuous or intermittent) within a range in which this object is achieved.

  The hydrate decomposition apparatus 46 configured as described above includes a steam generator 58, a superheated steam generator 60 and a thermal energy generator 48 including a circulation path 52, a combustion chamber 74, a turbine 78, a rotating shaft 84, and a rotor 80. It is desirable that a power generation device 50 including a generator having a stator 82 is a set, and a plurality of sets of the hydrate decomposition devices 46 are arranged at appropriate intervals along the gas recovery system 10. . By providing a plurality of gasses in this way, gas recovery at a plurality of locations is performed by one gas recovery system 10, and a larger amount of gas can be recovered efficiently.

  At this time, the thermal energy generator 48 and the power generator 50 constitute one unit, and the combustion gas supply pipe and the water supply pipe inside the unit can be used independently for each unit. It is preferable to configure a circumferential division shape (see the example shown in FIG. 3) by combining the division configurations.

  3 is an apparatus accommodation area for accommodating the thermal energy generator 48 and the power generation apparatus 50, and the subdivided areas B11 to B14, B21 to B24,... An insertion area that also serves as an insertion hole for a supply pipe, a water supply pipe, and cables for supplying power for control is shown.

  Here, the meanings of the symbols of the various insertion areas B11 to B14, B21 to B24,... Of the unit will be described. In the first two digits B1, B2,... Of the symbols B21 to B24,..., The insertion areas corresponding to various applications are respectively unit 1, unit 2,... (Here, arranged in the circumferential direction). It is shown that it is configured to be separated and independent so as to correspond to.

  In addition, the first to fourth digits of the above-described symbol are used here to represent independent (in this case, longitudinal or radial direction) positions for water, combustible gas, air, and cable insertion, for example. By configuring in this way, it becomes possible to easily connect and separate pipes when connecting and separating units when the gas recovery system according to the present embodiment is configured as a unit.

  Note that each of the above embodiments shows an example of the present invention, and it is needless to say that appropriate modifications and improvements may be made without departing from the spirit of the present invention.

It is a schematic structure figure of a gas recovery system from a gas hydrate layer concerning one embodiment of the present invention. It is a sectional side view which shows the detail of the hydrate decomposition | disassembly apparatus which is the principal part of the system shown in FIG. It is sectional drawing which shows the structural example of the insertion area in the case of making the gas recovery system which concerns on embodiment into a unit structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas recovery system 12 Outer pipe 14 Inner pipe 16 Gas recovery pipe 18 Supply pipe 20 Signal line 22 Conduction path 24 Sea surface 26 Structure 28 Combustible gas supply apparatus 30 Air supply apparatus 32 Water supply apparatus 34 Control means 36 Gas tank 38 Excavation Device 40, 42 Formation 44 Gas hydrate layer 46 Hydrate decomposition device 48 Thermal energy generator 50 Thermal power generation device 52 Circulation path 54 Jet pipe 56 Water supply pipe 58 Steam generator 60 Superheated steam generator 62 Heater 64 Steam supply port 66 High frequency Heating device 68 Gas recovery port 70 Combustible gas supply pipe 72 Air supply pipe 74 Combustion chamber 76 Burner 78 Turbine 80 Rotor 82 Stator 84 Rotating shaft 86 Exhaust pipe A Device accommodation area B11-B14, B21-B24, ... Insertion area

Claims (8)

Gas recovery from the gas hydrate layer that disposes the gas hydrate using the thermal energy generated by the thermal energy generator and disposes the gas hydrate by arranging the thermal energy generator inside or near the gas hydrate layer A system,
The thermal energy generator;
A steam generator for heating water to generate steam;
A superheated steam generator that further heats the steam generated by this steam generator to form superheated steam;
An ejection pipe for ejecting the superheated steam generated by the superheated steam generation apparatus toward the gas hydrate layer as a high-speed air flow;
The gas hydrate melted by the thermal energy of the superheated steam is circulated by the high-speed air flow to form a circulation flow, and a gas having a suction pipe that recirculates a part thereof to the steam generator Gas recovery system from hydrate layer.   The gas recovery system from a gas hydrate layer according to claim 1, wherein water that becomes steam in the steam generator is supplied by a water supply pipe provided in the gas recovery pipe.   2. The gas recovery system from a gas hydrate layer according to claim 1, wherein the superheated steam generation device is a high-frequency heating device that is disposed around the ejection pipe and is heated by high-frequency electromagnetic waves.   A steam supply port from the steam generator is provided in the gas recovery pipe, and both ends thereof are disposed at substantially the center of the circulation path that is inclined and opened in the gas hydrate layer, and the latter half of the circulation path The gas recovery system from the gas hydrate layer according to claim 1, wherein a superheated steam heated by the high-frequency heating device arranged along the jet pipe is jetted out from the gas hydrate layer. . In addition to the above devices,
A combustion gas supply pipe that is attached to the gas recovery pipe and independently supplies combustible gas and air;
A power generation device that mixes the combustible gas and air and burns it in a combustion chamber, and rotates the turbine with the combustion gas to generate electric power;
The gas recovery system from a gas hydrate layer according to claim 1, wherein the steam generator and the superheated steam generator are driven by electric power generated by the power generator.   The combustible gas and air are independently supplied by pipes provided in the gas recovery pipe, and the combustion chamber is disposed close to a turbine of the power generation device. 5. A gas recovery system from the gas hydrate layer according to 5.   The steam generation device, the superheated steam generation device, the ejection pipe, the circulation path, and the power generation apparatus constitute one unit, and a plurality of units are connected along the gas recovery pipe. 5. A gas recovery system from the gas hydrate layer according to 5.   The gas recovery from the gas hydrate layer according to claim 7, wherein the combustion gas supply pipe and the water supply pipe in the unit are configured in a circumferentially divided shape that can be used independently for each unit. system.

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