Environmental test apparatus

Abstract

To provide an environmental test apparatus capable of performing a long-term deterioration test in which a test sample is exposed for a long period to methane-dissolved water under a low-temperature, high-pressure environment simulating a seafloor environment.SOLUTION: An environmental test apparatus 100 according to an embodiment is an environmental test apparatus for performing a long-term deterioration test in which a test sample is exposed to methane-dissolved water under an environment simulating a seafloor environment where methane hydrate is present and includes: a pressure-resistant vessel 110 which houses the test sample and in which the methane-dissolved water at a temperature and pressure corresponding to the seafloor environment flows through the test sample; a cooling unit 120 that cools and maintains the pressure-resistant vessel 110 at the temperature; and a pressurizing circulation unit 130 that pressurizes the methane-dissolved water flowing out from an outlet 110b of the pressure-resistant vessel 110 and sends it toward an inlet 110a of the pressure-resistant vessel 110.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an environmental test apparatus, and more particularly, to a test sample that constitutes a collection membrane used for collecting methane gas and / or a pollution prevention membrane for preventing pollution diffusion during excavation, etc. in an environment simulating a seabed environment where methane hydrate is present. The present invention relates to an environmental test apparatus for performing an aging test in which a sample is exposed to methane-saturated water.

Background Art

[0002] Methane hydrates existing in the sea area are roughly classified into sand-layer type methane hydrates existing in sandy sediment layers below the seabed surface and surface layer type methane hydrates existing in the seabed surface and shallow mud layers.

[0003] There is a demand for a recovery technology for surface layer type methane hydrates with low environmental impact. For example, in order to recover methane hydrates and methane gas while reducing the environmental impact, the development of technologies using membrane structures including collection membranes and pollution prevention membranes is underway.

[0004] In order to establish the above technology, it is necessary to simulate and verify in advance the durability of membrane materials and the like that constitute the collection membrane and / or the pollution prevention membrane. Specifically, it is necessary to evaluate the aging deterioration of the collection membrane and the pollution prevention membrane when the collection membrane and the pollution prevention membrane are exposed for a long period of time in a low temperature and high pressure environment where methane hydrate is present. In the onshore atmospheric environment, the main cause of aging deterioration is due to ultraviolet rays, whereas in the deep sea environment, the influence of ultraviolet rays is almost negligible. In addition, regarding the influence of seawater on the membrane material, it is possible to use the knowledge of the membrane material used in the shallow sea area.

[0005] Note that Patent Document 1 describes a pressure test apparatus for performing physical property tests of gas hydrates and the like, and Patent Document 2 describes a methane hydrate mixed simulation ground for simulating a seabed ground containing methane hydrate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the seabed area where methane hydrate exists, methane-dissolved water exists, but there is little knowledge about the influence of this methane-dissolved water on the membrane material.

[0008] Therefore, it is required to verify by tests the aging deterioration of the membrane material when the membrane material is exposed to methane-dissolved water for a long period of time.

[0009] The present invention has been made based on the above recognition, and an object thereof is to provide an environmental test apparatus capable of performing an aging deterioration test in which a test sample is exposed to methane-dissolved water for a long period of time in a low-temperature and high-pressure environment simulating the seabed environment.

Means for Solving the Problems

[0010] An environmental test apparatus according to an aspect of the present invention is an environmental test apparatus for performing an aging deterioration test in which a test sample is exposed to methane-dissolved water in an environment simulating the seabed environment where methane hydrate exists, a pressure-resistant container in which a test sample is housed and methane-dissolved water at a temperature and pressure suitable for the seabed environment flows through the test sample, a cooling unit that cools and maintains the pressure-resistant container at the temperature, and a pressurization circulation unit that pressurizes the methane-dissolved water flowing out from the outlet of the pressure-resistant container and sends it toward the inlet of the pressure-resistant container.

[0011] Also, in the environmental test apparatus, The pressure-resistant container may be a cylindrical pressure-resistant container, with the inlet provided at one end of the cylindrical pressure-resistant container and the outlet provided at the other end of the cylindrical pressure-resistant container.

[0012] Also, in the environmental test apparatus, The test sample may be a membrane material used for a collection membrane and / or an anti-fouling membrane, and the membrane material may be housed in the pressure-resistant container in a state of being wound with a gap using a support jig.

[0013] Also, in the environmental test apparatus, The cooling unit may include a cooling tank in which a refrigerant is stored and the pressure-resistant container is disposed in the refrigerant, a lid for closing the opening of the cooling tank, and a chiller connected to the cooling tank for controlling and circulating the refrigerant to the temperature.

[0014] Also, in the environmental test apparatus, The pressurization and circulation unit may include a pressurization pump that pumps water from a water tank, pressurizes it to a predetermined pressure, and sends it to the pressure-resistant container, and a pipe connecting the pressurization pump and the pressure-resistant container.

[0015] Also, in the environmental test apparatus, The environmental test apparatus may further include a methane gas supply unit connected to the pipe of the pressurization and circulation unit for supplying methane gas into the pipe.

[0016] Also, in the environmental test apparatus, The methane gas supply unit may include a cartridge filled with methane gas and a pressure-resistant container that stores water and methane gas in a mixed state and dissolves methane gas in pure water.

[0017] Also, in the environmental test apparatus, A plurality of pressure-resistant containers may be provided.

[0018] Also, in the environmental test apparatus, The test sample may be a metal piece of a film material used for a collection film and / or an antifouling film, or a metal that coats the surface of the film material or constitutes the skeleton of a film structure.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide an environmental test device capable of performing an aging test in which a test sample is exposed to methane-saturated water for a long period of time in a low-temperature and high-pressure environment simulating a seabed environment.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

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Figure 6

Figure 7

Figure 8

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Figure 10

Figure 11A

Figure 11B

Figure 12

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

[0022] <Environmental Test Device> The environmental test device 100 according to the embodiment will be described with reference to FIGS. 1 and 2. The environmental test device 100 is a device for performing an aging test by exposing a test sample to an environment (an environment of low temperature and high pressure methane-dissolved water) that simulates the seabed environment where methane hydrate is present.

[0023] As will be described later, the environmental test device 100 is configured to be able to expose the test sample to low temperature and high pressure methane-dissolved water for a long period (for example, about half a year to one year). Here, the test sample is a material used to collect methane gas bubbles that gush out from the seabed or float during excavation, methane gas granules with a hydrate film on the surface, and solids of methane hydrate, and to prevent the spread of contamination during excavation. Specifically, the test sample is a film material used for the collection film and / or the contamination prevention film, or a metal piece of the metal that constitutes the skeleton of the metal or film structure covering the surface of the film material.

[0024] In this embodiment, the test sample is a membrane material (sample membrane) used for a collection membrane and / or an antifouling membrane. Note that the test sample may be other members constituting the membrane structure. For example, it may be a metal piece of a metal (such as titanium) that coats the surface of the membrane material, a support member (skeletal member) that supports the collection membrane and / or the antifouling membrane, or the like.

[0025] As shown in FIG. 1, the environmental test apparatus 100 includes a pressure-resistant container 110, a cooling unit 120, a pressurization circulation unit 130, a methane gas supply unit 140, and a water tank 150. In the present application, the pressure-resistant container 110 is also referred to as an "environmental cell".

[0026] The pressure-resistant container 110 is configured such that a membrane material MB, which is a test sample, is housed therein, and methane-dissolved water MW at a temperature and pressure (for example, 0.5°C, 6 MPa) adapted to the seabed environment flows through the membrane material MB of the test sample. The membrane material MB is a membrane material that constitutes a collection membrane for collecting methane gas bubbles that gush out from the seabed or float during excavation, methane gas granular bodies with a hydrate film on the surface, methane hydrate solids, and / or an antifouling membrane for preventing fouling diffusion during excavation. The pressure-resistant container 110 can function as a so-called constant temperature and constant pressure bath.

[0027] The pressure-resistant container 110 is provided with an inlet 110a and an outlet 110b, and the low-temperature and high-pressure methane-dissolved water MW flows from the inlet 110a toward the outlet 110b. Although details will be described later, the membrane material MB is housed in the pressure-resistant container 110 in a state of being wound with a gap using a support jig SJ.

[0028] In this embodiment, the pressure vessel 110 is a cylindrical pressure vessel and has a structure capable of withstanding low temperature and high pressure (for example, 0°C, 20 MPa). An inlet 110a is provided at one end (here, the lower end) of the pressure vessel 110, and an outlet 110b is provided at the other end (here, the upper end) of the pressure vessel 110. Conversely, an inlet 110a may be provided at the upper end of the cylindrical pressure vessel 110 and an outlet 110b may be provided at the lower end. Further, the shape of the pressure vessel 110 is not limited to a cylindrical shape, and may be, for example, a rectangular parallelepiped shape, a prismatic shape, a spherical shape, or the like.

[0029] FIG. 2 is a cross-sectional view showing the detailed configuration of the upper part of the pressure vessel 110. As shown in FIG. 2, the pressure vessel 110 of this embodiment includes a cylindrical main body 111 with an open upper part, a lid 112 provided with an outlet 110b to which a pipe 132 is connected, and a lid pressing ring 113 for fixing the lid 112 to the main body 111. An inlet 110a is provided at the lower end of the main body 111, and threads are formed on the outer peripheral surface of the upper part of the main body 111. The lid 112 fits into the opening of the main body 111 and closes the opening. An O-ring 114 is disposed in a groove provided on the peripheral surface of the lid 112, and the O-ring 114 ensures airtightness and liquid tightness. The lid pressing ring 113 is a ring-shaped member, and threads are formed on the inner peripheral surface of the lower part. By screwing the lid pressing ring 113 with the main body 111, the lid 112 is pressed against and fixed to the main body 111 side.

[0030] The cooling unit 120 is configured to cool and maintain (keep warm) the pressure vessel 110 at a temperature suitable for the seabed environment (for example, 0.5°C). Thereby, the methane-dissolved water MW flowing in the pressure vessel 110 is cooled to a temperature suitable for the seabed environment where methane hydrate occurs. Note that the cooling unit 120 may be configured to be able to change the temperature of the pressure vessel 110 (methane-dissolved water inside) within a certain range (for example, 0°C to 5°C).

[0031] In this embodiment, the cooling unit 120 includes a cooling tank 121, a lid 122, and a chiller 123. The refrigerant RF is stored in the cooling tank 121, and the pressure-resistant container 110 is disposed in the refrigerant RF. The lid 122 closes the opening of the cooling tank 121. The chiller 123 is connected to the cooling tank 121 via a pipe through which the refrigerant RF circulates inside, and controls and circulates the refrigerant RF to the above temperature.

[0032] The pressurization and circulation unit 130 is configured to pressurize the methane-dissolved water MW flowing out from the outlet 110b of the pressure-resistant container 110 and send it toward the inlet 110a of the pressure-resistant container 110. The pressure during the test is set to, for example, 10 MPa (equivalent to a water depth of about 1000 m).

[0033] The pressurization and circulation unit 130 includes a pressure pump 131 and a pipe 132. The pressure pump 131 pumps water from the water tank 150, pressurizes it to a predetermined pressure, and sends it to the pressure-resistant container 110. The pipe 132 is a pipe connecting the pressure-resistant container 110 and the pressure pump 131, and the methane-dissolved water MW flows through it. Note that the pressurization and circulation unit 130 may be configured by a syringe pump as in the test system 1000 described later.

[0034] The pipe 132 is composed of, for example, a high-pressure flexible pipe. In addition, a temperature transmitter and a pressure transmitter may be provided in the pipe 132 to monitor the temperature and pressure of the methane-dissolved water.

[0035] The methane gas supply unit 140 is connected to the pipe 132 and supplies methane gas into the pipe 132. This methane gas supply unit 140 includes a cartridge filled with methane gas and a mixing cell that stores water and methane gas in a mixed state. In this embodiment, by using a small cartridge (for example, a capacity of 50 mL) instead of a large cylinder as the cartridge, it is ensured not to conflict with various regulations (handling regulations for high-pressure gases and fire protection regulations) when handling methane gas in experiments. The mixing cell is a pressure-resistant container that stores water and methane gas in a mixed state and dissolves methane gas in pure water.

[0036] The water tank 150 is a tank in which water (pure water in this embodiment) is stored and is connected to the pipe 132. The water in the water tank 150 is pumped up by the pressure pump 131.

[0037] The environmental test device 100 may include a plurality of environmental cells (pressure-resistant containers 110). In this case, the plurality of environmental cells are provided in parallel with respect to the pressure pump 131, and each environmental cell is configured to be detachable from the pressure circulation unit 130 independently. Thereby, a plurality of test samples can be tested simultaneously. Also, any test sample can be installed and removed at any time.

[0038] When a plurality of environmental cells are installed as described above, the environmental test device 100 may include a valve panel for installing or removing any of the plurality of environmental cells while maintaining the pressure and temperature of the entire system. This valve panel is provided with a plurality of valves, and when removing, the valve connected to the environmental cell to be removed is closed to depressurize the inside of the environmental cell, and when installing, the valve connected to the environmental cell to be installed is opened to pressurize the inside of the environmental cell.

[0039] Next, after explaining the support jig SJ that supports the membrane material MB of the test sample with reference to FIG. 3, the storage method of the membrane material will be explained with reference to FIG. 4.

[0040] In this embodiment, as shown in FIGS. 3(a) and 3(b), the support jig SJ is a support wire mesh formed by connecting a plurality of wire elements e obtained by forming thin wires into a net shape and has a thickness d. The thickness d is the height of the convex portion of the wire element e. By the support wire mesh having the thickness d, a space between the membrane materials MB stored in the environmental cell in a wound state is ensured.

[0041] As shown in FIG. 4(a), a film material MB is placed on a support jig SJ. Then, as shown in FIG. 4(b), the film material MB is wound together with the support jig SJ. Since the support jig SJ has a thickness d, the wound film material MB is supported by the support jig SJ in a separated state. Then, as shown in FIG. 4(c), the support jig SJ and the film material MB are stored in the main body 111.

[0042] In the environmental test, it is necessary for the sample film (film material) to be constantly in contact with methane gas dissolved water, and it is necessary for the methane gas dissolved water flowing through the sample film to be newly replaced so that the methane dissolved water touches the sample film. According to the above storage form and storage method, the sample film can be held in a smooth state and the sample films can be prevented from adhering to each other. Thereby, during a long-term environmental test, while holding the film material in the environmental cell, it is possible to secure an interval between the film materials so that the methane gas dissolved water can constantly circulate. Further, since the film material MB is stored in the pressure-resistant container 110 in a wound state, it is also possible to reduce the size of the pressure-resistant container 110.

[0043] (Function and effect of the environmental test device) As described above, the environmental test device 100 according to the present embodiment includes a pressure-resistant container 110 in which a test sample is stored and methane dissolved water at a temperature and pressure adapted to the seabed environment flows through the test sample, a cooling unit 120 that cools and maintains the pressure-resistant container 110 at the temperature of the seabed environment, and a pressurization circulation unit 130 that pressurizes the methane dissolved water MW flowing out from the outlet 110b of the pressure-resistant container 110 and sends it toward the inlet 110a of the pressure-resistant container 110.

[0044] Accordingly, according to the environmental test apparatus of the present embodiment, in an environment (low temperature and high pressure environment) simulating the seabed environment where methane hydrate is present, an aging test can be performed in which a test sample (membrane material MB in the present embodiment) used for collecting methane gas and / or preventing contamination is exposed to methane-saturated water for a long period of time. For example, regarding the membrane material MB recovered from the environmental cell after the aging test, by performing a tensile test, precise thickness measurement, microscopic observation, weight measurement, etc., the degree and tendency of the aging deterioration of the membrane material MB can be evaluated. As a result, knowledge useful for the selection of the membrane material and the design of the membrane structure can be obtained.

[0045] Thus, according to the present embodiment, an environmental test apparatus is realized that can maintain for a long period of time an environment in which the surface of the membrane material continuously circulates without the methane-saturated water staying while maintaining the water temperature and pressure equivalent to those in the methane hydrate occurrence area.

[0046] <Visualization device> With reference to FIGS. 5 to 7, the visualization device 200 according to the present embodiment will be described. The visualization device 200 is a device for visualizing the behavior of methane bubbles and granular substances. Here, the "granular substance" refers to a substance in which a methane hydrate film is formed on the surface of methane bubbles. In the present application, methane bubbles and granular substances are collectively referred to as "generated bubbles". By the visualization device 200, for example, the phenomenon in which the generated bubbles are collected on the membrane can be appropriately grasped. In addition, the visualization device 200 can also observe the methane hydrate solid that floats up during excavation and hits the membrane material.

[0047] The "behavior" of the generated bubbles refers to, for example, the collision of the generated bubbles with the membrane material MB, the movement (such as sliding) of the generated bubbles on the surface of the membrane material MB, the interaction between the generated bubbles, and the dynamic changes of the generated bubbles (bubbling from the granular substance to methane bubbles, re-hydrate formation from methane bubbles to granular substances).

[0048] As shown in Fig. 5, the visualization device 200 includes a pressure-resistant container 210, a holding unit 220, a discharge unit (nozzle) 230, a pressure equalizing container 235, an underwater lighting unit 240, an underwater imaging unit 250, a chiller 260, a methane gas supply unit 270, a pressure pump 280, and a water tank 290.

[0049] The pressure-resistant container 210 is a pressure-resistant container having a structure capable of withstanding low temperature and high pressure (for example, 0°C, 20 MPa). The inside of the pressure-resistant container 210 is filled with water (low-temperature and high-pressure water) adjusted to the temperature and pressure of the seabed environment where methane hydrate exists. Before starting the imaging by the underwater imaging unit 250, the pressure pump 280 pumps water (pure water in this embodiment) from the water tank 290, pressurizes it to a predetermined pressure, and sends it to the pressure-resistant container 210. As a result, the inside of the pressure-resistant container 210 reaches a predetermined pressure (for example, 15 MPa).

[0050] Note that by controlling the pressure pump 280, it is possible to adjust the water pressure inside the pressure-resistant container 210 to a predetermined value (for example, 2 MPa, 3.3 MPa, 6 MPa) for each experiment. It is possible to observe the change in the generated bubbles when the water pressure is changed in this way.

[0051] Also, in the embodiment, the inside of the pressure-resistant container 210 is filled with pure water, but it may be brine, seawater, or the like.

[0052] The pressure-resistant container 210 includes a main body (tank) 211, a lid 212 that closes the opening of the main body 211, and a cooling jacket 213 that cools the main body 211. The cooling jacket 213 is provided so as to cover the main body 211 and is connected to the chiller 260. By circulating the refrigerant sent out from the chiller 260 inside the cooling jacket 213, the cooling jacket 213 cools the water inside the pressure-resistant container 210 to a predetermined temperature (for example, 0.5°C). Note that by controlling the chiller 260, the temperature of the water inside the pressure-resistant container 210 can be changed within a certain range (for example, 0°C to 5°C).

[0053] The holding part 220 holds (suspends in this embodiment) the film material MB disposed inside the pressure-resistant container 210. Specifically, the holding part 220 includes a fixing part 221 to which the film material MB is fixed, a plurality of rods (lifting shafts) 222 connected to the fixing part 221 and penetrating the pressure-resistant container 210, and a control part 223 that controls the posture of the fixing part 221 by moving the plurality of rods 222. The rod 222 penetrates the lid 212 of the pressure-resistant container 210. Specifically, a bearing and a packing are provided on the inner peripheral surface of the through-hole of the lid 212, and the rod 222 can move up and down through the through-hole in an airtight and smooth manner. The control part 223 includes a plurality of servo actuators 224.

[0054] As shown in FIG. 6, in this embodiment, the rods 222 are connected to three locations of the fixing part 221, and each rod 222 is controlled to move up and down (lift) by the corresponding servo actuator 224. Each servo actuator 224 is communicably connected to the computer 300. By controlling the movement amounts of the three rods 222, the three-dimensional inclination, angle, vertical position, etc. of the fixing part 221 (i.e., the film material MB) can be changed.

[0055] Note that the configuration of the holding part 220 is not limited to the above. For example, the holding part 220 may be configured such that the posture control range is expanded by controlling the posture of the fixing part 221 with four or more rods 222. Alternatively, the holding part 220 may be configured without using the rod 222 penetrating the lid 212. In this case, the holding part 220 is configured to control the posture of the fixing part 221 by, for example, an underwater actuator disposed inside the pressure-resistant container 210.

[0056] The discharging part 230 is disposed inside the pressure-resistant container 210 and is located below the film material MB. The discharging part 230 is connected to the methane gas supply part 270 and discharges methane bubbles. The discharging part 230 is configured to be able to discharge methane gas little by little so that the behavior of each generated bubble can be observed.

[0057] The pressure equalizing vessel 235 is disposed inside the pressure-resistant vessel 210. The pressure equalizing vessel 235 is also referred to as a visualization cell or an observation cell. A through-hole TH is provided in the bottom surface of the pressure equalizing vessel 235, and it is maintained in a pressure-equalized state with the pressure-resistant vessel 210. By providing the through-hole TH in the bottom surface, the water inside the pressure equalizing vessel 235 is easily discharged to the outside of the pressure equalizing vessel 235. Note that the through-hole TH may be provided in the side surface of the pressure equalizing vessel 235.

[0058] In the present embodiment, the pressure equalizing vessel 235 is fixed to the back surface of the lid 212 of the pressure-resistant vessel 210. Further, the discharge part 230 is fixed to the bottom surface of the pressure equalizing vessel 235, and the underwater illumination part 240 is fixed to the side surface of the pressure equalizing vessel 235.

[0059] The pressure equalizing vessel 235 is configured, for example, in a polygonal column shape (such as a quadrangular column or a hexagonal column) having a plurality of side surfaces (observation windows) made of a transparent material. In this case, the underwater illumination part 240 is fixed to the first side surface of the pressure equalizing vessel 235, and the underwater imaging part 250 is provided so as to face the second side surface located at a position parallel to the first side surface.

[0060] The underwater illumination part 240 is disposed inside the pressure-resistant vessel 210 and illuminates the inside of the pressure-resistant vessel 210. The underwater illumination part 240 has, for example, a surface-emitting light source using a light-emitting element such as an LED. As shown in FIG. 5, the underwater illumination part 240 is disposed so as to face the underwater imaging part 250 with the film material MB interposed therebetween (transmitted illumination). Thereby, transmitted light imaging becomes possible.

[0061] Note that the underwater illumination part 240 may be disposed on the same side as the underwater imaging part 250 (reflection illumination). In this case, the light emitted from the underwater illumination part 240 is reflected by the inner wall of the pressure-resistant vessel 210 and illuminates the inside of the pressure-resistant vessel 210, so that reflection light imaging becomes possible.

[0062] The underwater imaging unit 250 is disposed inside the pressure-resistant container 210 and images the generated bubbles. Specifically, the underwater imaging unit 250 images the methane bubbles discharged from the discharge unit 230 and the granular bodies with a hydrate film formed on the surface of the methane bubbles. For example, the underwater imaging unit 250 images the behavior on the surface of the film material MB of the generated bubbles. The underwater imaging unit 250 includes an underwater camera, and this underwater camera may be a micro-imaging camera, a macro-imaging camera, or a high-speed camera capable of shooting videos. Also, the underwater camera may be a recording camera capable of recording imaging data.

[0063] Note that the underwater imaging unit 250 may include a plurality of underwater cameras. For example, the underwater imaging unit 250 includes a micro-imaging camera and a macro-imaging camera. Thereby, the generated bubbles can be observed from both micro and macro viewpoints.

[0064] Also, the underwater camera may be a camera having a telecentric lens (telecentric camera). The telecentric lens has the characteristics that there is no image expansion or contraction within the depth of focus, there is little image distortion due to parallax, and there is little unevenness in the brightness of the object when used in combination with coaxial illumination. Therefore, it is suitable for observing the generated bubbles inside the pressure-resistant container 210.

[0065] However, even when using a telecentric camera, if the light does not hit the underwater camera parallelly, shadows will be generated on the generated bubbles. Therefore, the observation cell (isobaric container 235) has a planar structure as an observation window (a polygonal prism structure with parallel opposing faces is preferred). In this case, the surface on which the telecentric camera is provided and the surface on which the underwater camera is provided are opposed to each other. Thereby, the illumination of the underwater illumination unit 240 is such that light hits the underwater illumination unit 240 parallelly from the front, and the shadow of the generated bubbles photographed by the underwater imaging unit 250 can be reduced.

[0066] The underwater imaging unit 250 is communicatively connected to a computer 300 outside the pressure-resistant container 210 and transmits imaging data to the computer 300. Thereby, the behavior of the generated bubbles can be observed in real time. In the case of a high-speed camera, a large-capacity and high-speed interface and recording system are required to transfer the imaging data. In order to reduce the cost of the visualization device 200, after the observation is completed, the imaging data may be transmitted to the computer 300 at the transfer speed of a standard interface (over time).

[0067] Further, in order to suppress an increase in the diameter of the pressure-resistant container 210 due to the installation of the underwater imaging unit 250, the underwater imaging unit 250 may have a vertically long shape in which the optical path is bent by 90 degrees by a reflection prism.

[0068] The methane gas supply unit 270 supplies a small amount of methane gas to the discharge unit so that the discharge unit 230 can discharge methane bubbles. As shown in FIG. 7, in the present embodiment, the methane gas supply unit 270 includes a methane gas cartridge 271, a valve 272, a gas header 273, a syringe pump 274, a water tank 275, and valves 276, 277, 278, 279.

[0069] The methane gas cartridge 271 is a small cartridge filled with methane gas (for example, having a capacity of 50 mL). Since the visualization device 200 handles flammable methane gas at high pressure, it is subject to the regulations of the high-pressure gas handling rules and the fire protection rules. In the present embodiment, by supplying methane gas with a small cartridge, it is ensured that it does not conflict with various regulations when used in the experimental apparatus.

[0070] The operation of the methane gas supply unit 270 will be briefly described. After opening the valve 276 and closing the valve 277, a refill operation (REFILL operation) is performed to lower the piston of the syringe pump 274. As a result, water (pure water in this embodiment) is sucked from the water tank 275 into the syringe pump 274. Then, after closing the valve 276 and opening the valves 277 and 279, a run operation (RUN operation) is performed to raise the piston of the syringe pump 274. Thereby, the water in the syringe pump 274 is sent into the gas header 273. The air in the gas header 273 is expelled to the outside through the valve 279, and the gas header 273 is filled with water.

[0071] After that, the valve 279 is closed, the valve 272 is opened, and the syringe pump 274 is operated in the refill mode. As a result, the water in the gas header 273 is sucked into the syringe pump 274, and methane gas is sucked into the gas header 273. As a result, the methane gas in the gas header 273 reaches the required pressure (for example, the pressure near the pressure in the pressure-resistant container 210).

[0072] After that, the valve 272 is closed, and the syringe pump 274 is operated in the run mode. Thereby, the water in the syringe pump 274 is sent into the gas header 273 and pressurized to a predetermined pressure (the bubble generation pressure, a pressure slightly higher than the pressure in the pressure-resistant container 210). Then, by opening the valve 278 and operating the syringe pump 274 slowly (at the bubble delivery rate), methane bubbles are discharged from the discharge unit 230. For example, when the bubble delivery rate is 3 ml / min, methane bubbles are discharged from the discharge unit 230 at a rate of 1 bubble per second.

[0073] The visualization device 200 according to the present embodiment has been described above. The pressure equalization container 235 can be omitted in the visualization device 200. In this case, the discharge unit 230 and the underwater illumination unit 240 may be fixed to the main body 211 or the lid 212. Alternatively, the discharge unit 230 may be fixed to the main body 211, and the underwater illumination unit 240 may be fixed to the lid 212.

[0074] (Function and effect of the visualization device) As described above, the visualization device 200 according to the present embodiment is a visualization device for visualizing the behavior of methane bubbles and granular substances, and includes a pressure-resistant container 210 filled with water adjusted to the temperature and pressure of the seabed environment where methane hydrate is present, a holding unit 220 that holds a membrane material disposed inside the pressure-resistant container 210, a discharging unit 230 that is disposed inside the pressure-resistant container 210, is located below the membrane material MB, and discharges methane bubbles, an underwater lighting unit 240 that is disposed inside the pressure-resistant container 210 and illuminates the inside of the pressure-resistant container 210, and an underwater imaging unit 250 that is disposed inside the pressure-resistant container 210 and captures the generated bubbles discharged from the discharging unit 230.

[0075] In the visualization device 200, methane bubbles are generated in the water at low temperature and high pressure inside the pressure-resistant container 210. The methane bubbles rise by their own buoyancy in still water and collide with the membrane material MB. Depending on the environmental conditions (temperature, pressure), the methane bubbles change into granular substances with a hydrate film formed on their surface. The methane bubbles and granular substances are photographed by the underwater imaging unit 250.

[0076] According to the present embodiment, it is possible to observe the behavior of the generated bubbles in the water at low temperature and high pressure simulating the seabed environment where methane hydrate is present. For example, it is possible to grasp the behavior when the generated bubbles collide with the surface of the membrane material or other structures, the static and dynamic contact angles, the interaction of granular substances, and the like.

[0077] As a result, it is possible to appropriately grasp the phenomenon in which methane bubbles and granular substances having a methane hydrate film are collected on the membrane material, and it is possible to obtain knowledge useful for the design of the collection membrane and the anti-fouling membrane.

[0078] In addition, when attempting to install the visualization cell under atmospheric pressure, if the entire circumference is made of a material with high optical transparency, it is necessary to configure the visualization cell with a thick transparent material such as acrylic, which is not easy to achieve and makes it difficult to photograph inside the visualization cell. There are also issues with the method of maintaining the cooling temperature. Therefore, the inventors changed their concept and installed the entire visualization cell in pure water, using an optical camera and a lighting device with a water- and pressure-resistant underwater specification, and configured it to be observed from pure water. As a result, the structure of the visualization cell can be made extremely lightweight and simple, and a visualization device capable of observing generated bubbles from multiple viewpoints and applying lighting has been realized.

[0079] Hereinafter, with reference to FIGS. 8 to 11B, the images actually taken by the visualization device 200 will be described.

[0080] FIG. 8 is an image taken by transmitted light photography of a plurality of granular bodies attached to the membrane material MB. FIG. 9 is an image taken by transmitted light photography of a plurality of methane bubbles attached to the membrane material MB. FIG. 10 is an image taken by reflected light photography of a plurality of granular bodies attached to the membrane material MB. In FIGS. 8 and 10, since a ground glass-like region is observed on the surface of the bubbles, it can be seen that a hydrate film is formed. By analyzing these images, the contact angle between the generated bubbles and the membrane material MB can be calculated. For calculating the contact angle, the tangent method, the Θ / 2 method, the ellipse fitting method, the circle fitting method, etc. are used.

[0081] Figures 11A and 11B show images taken at 10 ms intervals by a high-speed camera. After the granular material floats up in water, it collides with and deforms the membrane material (0 ms to 40 ms), and then bounces and moves while rolling on the surface of the membrane material (50 ms to 130 ms). Thereafter, the trailing edge of the hydrated membrane of the granular material is trapped by the membrane material (140 ms), and the trapped portion is stretched and vaporized, and hardly slides any more (150 ms to 160 ms). More than half of the granular material is once vaporized (170 ms) and vibrates for a while (180 ms). Thereafter, the surface of the granular material is hydrated again (190 ms). Thus, according to the visualization device 200, the collision, interaction, and dynamic changes between the membrane material and the granular material can be observed in detail.

[0082] <Test system> Next, a test system 1000 including the above-described environmental test device 100 and visualization device 200 will be described with reference to FIG. 12. In the test system 1000, the environmental test device 100 and the visualization device 200 share a pressurizing pump constituted by a syringe pump.

[0083] The test system 1000 includes ball valves 1 to 11, needle valves 13, 14, 15, pressure monitors 21, 22, 23, 24, temperature monitors 31, 32, 33, 34, a drainage tank 60, an environmental test device 100, a visualization device 200, and a pressurizing mechanism 500. The drainage tank 60 is provided outside the laboratory in consideration of the situation where methane gas vaporized from the drainage catches fire.

[0084] The ball valves 1 to 11 are ball valves that can be remotely controlled by air drive. Among them, valve 8 is a three-way valve. The needle valves 13, 14, 15 are needle valves for fine adjustment or relief. In the normal state, since pressurized water circulates in the environmental test device 100, the ball valve 8 is open to the environmental test device 100 side. The ball valve 8 is opened to the visualization device 200 side only when filling the inside of the pressure-resistant container 210 with high-pressure water to perform measurement by the visualization device 200.

[0085] The ball valves 9, 10, and 11 are each connected in parallel with the needle valves 13, 14, and 15. The combination of these ball valves and needle valves connected in parallel is provided in the drainage path from the high-pressure system to the atmospheric pressure, and is opened when discharging water to the drainage tank 60.

[0086] The pressure monitors 21, 22, 23, and 24 are pressure transmitters having a pressure sensor and a transmitter for transmitting the measured pressure data to a computer (not shown). The pressure monitor 21 measures the pressure of the methane-dissolved water flowing into the pressure-resistant container 110 of the environmental test device 100. The pressure monitor 22 measures the pressure of the methane-dissolved water flowing out of the pressure-resistant container 110. The pressure monitor 23 measures the water pressure inside the pressure-resistant container 210 of the visualization device 200. The pressure monitor 24 measures the water pressure inside the pressure equalization container 235 of the visualization device 200.

[0087] The temperature monitors 31, 32, 33, and 34 are temperature transmitters having a temperature sensor and a transmitter for transmitting the measured temperature data to a computer. The temperature monitor 31 measures the temperature of the refrigerant in the cooling unit 120 of the environmental test device 100. The temperature monitor 32 measures the temperature of the methane-dissolved water flowing out of the pressure-resistant container 110. The temperature monitor 33 measures the temperature inside the pressure-resistant container 210 of the visualization device 200. The temperature monitor 34 measures the temperature inside the pressure equalization container 235 of the visualization device 200.

[0088] The pressurizing mechanism 500 includes the ball valves 1 to 7, the syringe pumps 41 and 42, and the water tank 50. The pressurizing mechanism 500 is configured to pressurize the water pumped from the water tank 50 (pure water in this embodiment) by operating the two syringe pumps 41 and 42 alternately, and send it to the environmental test device 100 or the visualization device 200 through the valve 8 of the three-way valve.

[0089] The operation when shifting from the environmental test to the visualization test will be described.

[0090] First, stop the syringe pumps 41 and 42 that are performing the circulation operation, and close valves 1 to 6. Next, close valve 7 and open the discharge valve 9. Since the syringe pumps and the pipes around them are filled with methane-dissolved water, all of this is discharged and replaced with pure water. Specifically, open valves 1 and 2, and raise the pistons of syringe pumps 41 and 42. When the pistons reach the top dead center, close valves 1 and 2, open valves 3 and 4, and lower the pistons. As a result, pure water is supplied from the water tank 50 to the syringe pumps 41 and 42. When the pistons reach the bottom dead center, close valves 3 and 4, open valves 1 and 2 again, and raise the pistons of syringe pumps 41 and 42.

[0091] By repeating the above operation, the methane-dissolved water in the pipe up to valve 7 is replaced with pure water. After the replacement with pure water is completed, close valve 9. Then, switch the three-way valve of valve 8 to the side of the visualization device 200. At this time, the port on the environmental test device 100 side of valve 8 and the environmental test device 100 sides of valves 5 and 6 are kept at high pressure.

[0092] When restarting the circulation operation for the environmental test after the visualization test, raise the pressure in the pipe system of the pressurizing mechanism 500 from valves 5 and 6 to valve 7 until it matches the pressure on the environmental test device 100 side, and then switch the three-way valve of valve 8 to the environmental test device 100 side.

[0093] The operation when performing a test (visualization test) by the visualization device 200 will be described.

[0094] In the visualization test, syringe pumps 41 and 42 and valves 1 to 4 are used to pressurize, depressurize, or maintain the pressure inside the pressure-resistant container 210, which is a high-pressure tank. At the start of the experiment, since a large amount of pure water needs to be fed into the pressure-resistant container 210, the syringe pumps 41 and 42 are operated such that if one side is for water supply, the other side will be for water absorption. At this time, if valve 1 is open, valves 2 and 3 are closed, valve 4 is open, the piston of syringe pump 41 is raised, and the piston of syringe pump 42 is lowered. When the pistons of syringe pumps 41 and 42 reach the top dead center and bottom dead center respectively, all the valves are once closed. Then, this time valves 2 and 3 are opened, valves 1 and 4 are closed, the piston of syringe pump 41 is lowered, and the piston of syringe pump 42 is raised. By repeating such operations, when the pressure in the visualization device 200 rises or falls, a substantially continuous increase or decrease in pressure is possible.

[0095] The operation when conducting the test (environmental test) by the environmental test device 100 will be described.

[0096] The water supply and pressurization operations of the valves and syringe pumps at the start of the test are the same as those in the case of the visualization test except for the direction of valve 8. After the pressure rises to the set value of the test, it shifts to the circulation operation while maintaining that pressure. In the circulation operation, valves 1, 2, 5, and 6 and syringe pumps 41 and 42 are used. Valve 1 and valve 6 are opened, valves 2 and 5 are closed, the piston of syringe pump 41 is raised, and the piston of syringe pump 42 is lowered. At this time, in order to maintain the pressure of the entire system, when syringe pump 41 supplies water, syringe pump 42 must absorb water at exactly the same flow rate.

[0097] After the pistons of syringe pumps 41 and 42 reach the top dead center and bottom dead center respectively, all the valves are once closed. Then, this time valves 2 and 5 are opened, valves 1 and 6 are closed, the piston of syringe pump 42 is raised, and the piston of syringe pump 41 is lowered.

[0098] By repeating the above operations, the circulation operation of the environmental test apparatus 100 is performed.

[0099] When the pressure of the entire system deviates from the set pressure, valves 5 and 6 are closed, and valves 1 to 4 are used to supply water and pressurize or drain water and depressurize. When removing the environmental cell, as described above, using the valves arranged on the valve panel, close the valve connected to the target environmental cell, depressurize it, and then remove it. On the other hand, when installing the environmental cell, after installing the target environmental cell in the cooling unit 120, using the valves arranged on the valve panel, open the valve connected to the target environmental cell to start pressurization. When installing the environmental cell, since the pressure of the system temporarily drops slightly, a pressurization operation may be performed.

[0100] According to the above test system 1000, a test system with reduced costs can be realized by implementing the pressurization operation with a syringe pump and sharing the syringe pump between the environmental test apparatus 100 and the visualization apparatus 200.

[0101] Based on the above description, those skilled in the art may be able to conceive of additional effects and various modifications of the present invention. However, the aspects of the present invention are not limited to the above-described embodiments. Various additions, changes, and partial deletions are possible without departing from the conceptual ideas and spirit of the present invention derived from the content defined in the claims and their equivalents.

Explanation of Reference Numerals

[0102] 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ball valves 13, 14, 15 needle valves 21, 22, 23, 24 pressure monitors 31, 32, 33, 34 temperature monitors 41, 42 syringe pumps 50 water tank 60 drainage tank 100 environmental test apparatus 110 pressure-resistant container (environmental cell) 110a Inlet 110b Outlet 111 Body 112 Cover 113 Cover retaining ring 114 O-ring 120 Cooling section 121 Cooling tank 122 Cover 123 Chiller 130 Pressurization and circulation section 131 Pressure pump 132 Pipe 140 Methane gas supply section (mixing cell) 150 Water tank 200 Visualization device 210 Pressure-resistant container 211 Body 212 Cover 213 Cooling jacket 220 Holding section 221 Fixing section 222 Rod 223 Control section 224 Servo actuator 230 Discharge section 235 Pressure equalization container 240 Underwater lighting section 250 Underwater photography section 260 Chiller 270 Methane gas supply section 271 Methane gas cartridge 272 Valve 273 Gas header 274 Syringe pump 275 Water tank 276, 277, 278, 279 Valves 280 Pressure pump 290 Water tank 300 Computer 500 Pressurization mechanism 1000 System d Thickness e Strand G Generated bubble MB Membrane material MW Dissolved methane in water RF refrigerant SJ support jig TH (through-hole of pressure equalizing vessel)

Claims

1. An environmental test apparatus for conducting an aging test in which a test sample is exposed to methane-saturated water in an environment simulating a seabed environment where methane hydrate is present, comprising: a pressure-resistant container in which the test sample is housed and through which methane-saturated water at a temperature and pressure corresponding to the seabed environment flows; a cooling unit for cooling and maintaining the pressure-resistant container at the temperature; a pressurization circulation unit for pressurizing the methane-saturated water flowing out from the outlet of the pressure-resistant container and sending it toward the inlet of the pressure-resistant container; The environmental test apparatus comprising the above.

2. The environmental test apparatus according to claim 1, wherein the pressure-resistant container is a cylindrical pressure-resistant container, an inlet is provided at one end of the cylindrical pressure-resistant container, and an outlet is provided at the other end of the cylindrical pressure-resistant container.

3. The environmental test apparatus according to claim 2, wherein the test sample is a membrane material used for a collection membrane and / or an anti-fouling membrane, and the membrane material is housed in the pressure-resistant container in a state of being wound with a gap using a support jig.

4. The environmental test apparatus according to claim 1, wherein the cooling unit comprises a cooling tank in which a refrigerant is stored and the pressure-resistant container is disposed in the refrigerant, a lid for closing an opening of the cooling tank, and a chiller connected to the cooling tank for controlling and circulating the refrigerant to the temperature.

5. The environmental test apparatus according to claim 1, wherein the pressurization circulation unit comprises a pressurization pump for pumping water from a water tank, pressurizing it to a predetermined pressure, and sending it to the pressure-resistant container, and a pipe connecting the pressurization pump and the pressure-resistant container.

6. The environmental test apparatus according to claim 1, further comprising a methane gas supply unit connected to a pipe of the pressurization circulation unit for supplying methane gas into the pipe.

7. The environmental test apparatus according to claim 6, wherein the methane gas supply unit includes a cartridge filled with methane gas and a pressure-resistant container for storing water and methane gas in a mixed state and dissolving methane gas in pure water.

8. The environmental test apparatus according to claim 1, wherein a plurality of pressure-resistant containers are provided.

9. The environmental test apparatus according to claim 1, wherein the test sample is a membrane material used for a collection membrane and / or an anti-fouling membrane, or a metal piece of a metal that coats the surface of the membrane material or constitutes a skeleton of a membrane structure.

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