Visualization device

Abstract

To provide a visualization device making it possible to observe the behavior of generated bubbles under low-temperature and high-pressure water simulating a sea bottom environment in which methane hydrate occurs.SOLUTION: A visualization device 200 includes: a pressure-resistant container 210 filled with water in which temperature and pressure are matched to those of a sea bottom environment in which methane hydrate occurs; a holding section 220 for holding a film material MB disposed in the pressure-resistant container 210; a discharge section 230 that is disposed in the pressure-resistant container 210, is located below the film material MB, and discharges methane bubbles; an underwater illumination section 240 that is disposed in the pressure-resistant container 210 and applies light to the inside of the pressure-resistant container 210; and an underwater photographing section 250 for photographing methane bubbles discharged from the discharge section 230 and a granular material in which a hydrate film is generated on the surface of the methane bubbles.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a visualization device, and more particularly to a visualization device for visualizing the behavior of methane bubbles and granular materials having a methane hydrate film formed on their surfaces.

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 environmental impact, the development of a technology using a membrane structure including a collection membrane · anti-fouling membrane is in progress.

[0004] In order to establish the above technology, it is necessary to understand the behavior when methane bubbles and granular materials having a methane hydrate film on the surface of the methane bubbles come into contact with the collection membrane, the interaction between the granular materials, the change of the hydrate film due to pressure change, etc.

[0005] Note that Patent Document 1 describes a methane hydrate mixed simulated ground for simulating a seabed ground containing methane hydrate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a visualization device capable of observing behaviors such as generated bubbles in low-temperature and high-pressure water simulating a seabed environment where methane hydrate is present.

Means for Solving the Problems

[0008] The visualization device according to one aspect of the present invention includes a pressure-resistant container filled with water adjusted to the temperature and pressure of the seabed environment where methane hydrate is present, a holding part that holds a membrane material disposed inside the pressure-resistant container, a discharging part that is disposed inside the pressure-resistant container, located below the membrane material, and discharges methane bubbles, an underwater lighting part that is disposed inside the pressure-resistant container and illuminates the inside of the pressure-resistant container, and an underwater imaging part that is disposed inside the pressure-resistant container and captures the methane bubbles discharged from the discharging part and the granular bodies having a hydrate film formed on the surface of the methane bubbles.

[0009] Also, in the visualization device, the pressure-resistant container may include a main body, a lid that closes the opening of the main body, and a cooling jacket that cools the main body.

[0010] Also, in the visualization device, the holding part may have a fixing part to which the membrane material is fixed, a plurality of rods connected to the fixing part and penetrating the pressure-resistant container, and a control part that controls the posture of the fixing part by moving the plurality of rods.

[0011] Also, in the visualization device, the underwater imaging part may be communicatively connected to a computer outside the pressure-resistant container and transmit imaging data to the computer.

[0012] Also, in the visualization device, the underwater lighting part may be disposed so as to face the underwater imaging part with the membrane material interposed therebetween.

[0013] Also, in the visualization device, the underwater lighting unit may be arranged on the same side as the underwater imaging unit.

[0014] Also, in the visualization device, it may further include a pressure equalizing container arranged inside the pressure-resistant container and provided with a through hole, and the film material and the discharge unit may be arranged inside the pressure equalizing container.

[0015] Also, in the visualization device, the underwater lighting unit may be fixed to the first side surface of the pressure equalizing container, and the underwater imaging unit may be provided so as to face a second side surface parallel to the first side surface.

[0016] Also, in the visualization device, the underwater imaging unit may include a camera having a telecentric lens.

[0017] Also, in the visualization device, the holding unit may include a fixing part to which the film material is fixed so that the film surface of the film material can face the bottom surface of the pressure-resistant container, a rotating shaft connected to the fixing part and configured to rotate the fixing part so that the angle formed by the film surface and the bottom surface of the pressure-resistant container changes, and an underwater motor mechanically connected to the rotating shaft and configured to control the posture of the fixing part by rotating the rotating shaft.

[0018] Also, in the visualization device, the underwater lighting unit may be fixed to the fixing part so as to illuminate the film material.

[0019] Also, in the visualization device, it may further include a water flow generating unit arranged inside the pressure-resistant container and configured to generate a water flow for blowing off granular substances attached to the film material.

Advantages of the Invention

[0020] According to the present invention, it is possible to provide a visualization device capable of observing the behavior of generated bubbles in low-temperature and high-pressure water simulating the seabed environment where methane hydrate is present.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

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Figure 5

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Figure 7

Figure 8

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Figure 10

Figure 11A

Figure 11B

Figure 12

Figure 13

Figure 14

Figure 15

MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023] <Environmental test apparatus> The environmental test apparatus 100 according to the embodiment will be described with reference to FIGS. 1 and 2. The environmental test apparatus 100 is an apparatus for performing an aging test by exposing a test sample to an environment (environment of methane-dissolved water at low temperature and high pressure) that simulates the seabed environment where methane hydrate is present.

[0024] As described later, the environmental test apparatus 100 is configured to be able to expose a test sample to methane-dissolved water at low temperature and high pressure 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 granular bodies 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 that coats the surface of the film material.

[0025] In this embodiment, the test sample is a membrane material (sample membrane) used for a collection membrane and / or an anti-fouling membrane. Note that the test sample may be other members constituting the membrane structure. For example, it may be a metal piece (such as titanium) of a metal covering the surface of the membrane material, a support member (skeleton member) supporting the collection membrane and / or the anti-fouling membrane, etc.

[0026] As shown in FIG. 1, the environmental test device 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".

[0027] The pressure-resistant container 110 is configured such that the membrane material MB, which is the test sample, is stored therein, and the 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 constituting a collection membrane for collecting methane gas bubbles gushing out from the seabed or floating during excavation, methane gas granular substances having a hydrate film on the surface, methane hydrate solids, and / or an anti-fouling membrane for preventing fouling diffusion during excavation. The pressure-resistant container 110 can function as a so-called constant temperature and constant pressure bath.

[0028] 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 stored in the pressure-resistant container 110 in a state of being wound with a gap using a support jig SJ.

[0029] In this embodiment, the pressure-resistant container 110 is a cylindrical pressure-resistant container 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-resistant container 110, and an outlet 110b is provided at the other end (here, the upper end) of the pressure-resistant container 110. Conversely, an inlet 110a may be provided at the upper end of the cylindrical pressure-resistant container 110, and an outlet 110b may be provided at the lower end. Further, the shape of the pressure-resistant container 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.

[0030] FIG. 2 is a cross-sectional view showing the detailed configuration of the upper part of the pressure-resistant container 110. As shown in FIG. 2, the pressure-resistant container 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 arranged 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.

[0031] The cooling unit 120 is configured to cool and maintain (keep warm) the pressure-resistant container 110 at a temperature suitable for the seabed environment (for example, 0.5°C). Thereby, the methane-dissolved water MW flowing in the pressure-resistant container 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-resistant container 110 (the methane-dissolved water inside) within a certain range (for example, 0°C to 5°C).

[0032] 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.

[0033] The pressurization 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).

[0034] The pressurization 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 circulation unit 130 may be configured by a syringe pump as in the test system 1000 described later.

[0035] 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.

[0036] The methane gas supply unit 140 is connected to the pipe 132 and supplies methane gas into the pipe 132. The 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, with 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.

[0037] 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.

[0038] The environmental test apparatus 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.

[0039] When a plurality of environmental cells are installed as described above, the environmental test apparatus 100 may include a valve panel for installing or removing any one 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 is configured such that 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.

[0040] Next, after explaining the support jig SJ that supports the membrane material MB of the test sample with reference to FIG. 3, the method of storing the membrane material will be explained with reference to FIG. 4.

[0041] In the present 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. Since the support wire mesh has the thickness d, a gap is ensured between the wound membrane materials MB stored in the environmental cell.

[0042] As shown in Fig. 4(a), the film material MB is placed on the 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 housed in the main body 111.

[0043] In the environmental test, the sample film (film material) needs to be constantly in contact with the methane gas dissolved water, and the methane gas dissolved water flowing through the sample film needs to be replaced with new water so that the methane dissolved water flows through 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 the long-term environmental test, while holding the film material in the environmental cell, the interval between the film materials can be ensured so that the methane gas dissolved water can circulate constantly. Also, since the film material MB is housed in the pressure-resistant container 110 in a wound state, the pressure-resistant container 110 can be downsized.

[0044] (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 housed 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 pressurizing 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.

[0045] 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 exists, 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 over a long period of time. For example, regarding the membrane material MB recovered from the environmental cell after the aging test, the degree and tendency of the aging of the membrane material MB can be evaluated by performing a tensile test, precise thickness measurement, microscopic observation, weight measurement, etc. As a result, knowledge useful for the selection of the membrane material and the design of the membrane structure can be obtained.

[0046] Thus, according to the present embodiment, an environmental test apparatus is realized that can maintain an environment in which the surface of the membrane material continuously circulates without the methane-saturated water staying while continuously maintaining the water temperature and pressure equivalent to those in the methane hydrate occurrence area over a long period of time.

[0047] <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 a methane bubble. In the present application, methane bubbles and granular substances are collectively referred to as "generated bubbles". By means of the visualization device 200, for example, the phenomenon in which the generated bubbles are collected by the membrane can be appropriately grasped. Further, the visualization device 200 can also observe the methane hydrate solid that floats up during excavation and hits the membrane material.

[0048] 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, the dynamic changes of the generated bubbles (bubbling from the granular substance to methane bubbles, re-hydrate formation from methane bubbles to granular substances), etc.

[0049] 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 equalization 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.

[0050] 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) whose temperature and pressure are adjusted to 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).

[0051] 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.

[0052] Also, in the embodiment, the inside of the pressure-resistant container 210 is filled with pure water, but it may be salt water, seawater, or the like.

[0053] 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).

[0054] 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.

[0055] 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 moving 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.

[0056] 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.

[0057] 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 the methane gas little by little so that the behavior of each generated bubble can be observed.

[0058] The pressure equalizing container 235 is disposed inside the pressure-resistant container 210. The pressure equalizing container 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 container 235, and it is kept in a pressure equalized state with the pressure-resistant container 210. By providing the through-hole TH in the bottom surface, the water inside the pressure equalizing container 235 is easily discharged to the outside of the pressure equalizing container 235. Note that the through-hole TH may be provided in the side surface of the pressure equalizing container 235.

[0059] In the present embodiment, the pressure equalizing container 235 is fixed to the back surface of the lid 212 of the pressure-resistant container 210. Further, the discharge part 230 is fixed to the bottom surface of the pressure equalizing container 235, and the underwater lighting part 240 is fixed to the side surface of the pressure equalizing container 235.

[0060] The pressure equalizing container 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 lighting part 240 is fixed to the first side surface of the pressure equalizing container 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.

[0061] The underwater lighting part 240 is disposed inside the pressure-resistant container 210 and illuminates the inside of the pressure-resistant container 210. The underwater lighting part 240 has, for example, a surface light source using a light emitting element such as an LED. As shown in FIG. 5, the underwater lighting 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.

[0062] Note that the underwater lighting part 240 may be disposed on the same side as the underwater imaging part 250 (reflected illumination). In this case, the light emitted from the underwater lighting part 240 is reflected by the inner wall of the pressure-resistant container 210 and illuminates the inside of the pressure-resistant container 210, thereby enabling reflected light imaging.

[0063] 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.

[0064] 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 a micro perspective and a macro perspective.

[0065] Also, the underwater camera may be a camera having a telecentric lens (telecentric camera). The telecentric lens has the characteristics that there is no expansion or contraction of the image within the depth of focus, there is little distortion of the image 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.

[0066] 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 (equalization 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.

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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 there is no conflict with various regulations when used in the experimental apparatus.

[0071] 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.

[0072] After that, the valve 279 is closed, the valve 272 is opened, and the syringe pump 274 is operated in the refill operation. 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).

[0073] After that, the valve 272 is closed, and the syringe pump 274 is operated in the run operation. 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 speed) in the run operation, methane bubbles are discharged from the discharge unit 230. For example, when the bubble delivery speed is 3 ml / min, methane bubbles are discharged from the discharge unit 230 at a rate of 1 bubble per second.

[0074] 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.

[0075] <Modification example of the visualization device> Referring to FIGS. 13 to 15, the visualization device 200A according to a modification of the present embodiment will be described. FIG. 13 is a diagram showing a schematic configuration of the visualization device 200A. FIG. 14 is a view of the fixing portion 221A of the visualization device 200A seen from the side, and FIG. 15 is a view of the fixing portion 221A seen from the front. In FIG. 13, the same components as those of the visualization device 200 are denoted by the same reference numerals.

[0076] As shown in FIG. 13, the visualization device 200A includes a pressure-resistant container 210, a holding portion 220A, a discharging portion 230, an underwater lighting portion 240A, an underwater imaging portion 250, a chiller 260, a methane gas supply portion 270, a pressure pump 280, and a water tank 290.

[0077] Hereinafter, this modification will be described focusing on the differences from the embodiment.

[0078] The holding portion 220A has a fixing portion 221A to which the membrane material MB is fixed, a rotating shaft 222A connected to the fixing portion 221A, and an underwater motor 224A mechanically connected to the rotating shaft 222A.

[0079] The membrane material MB is fixed to the fixing portion 221A so that the membrane surface can face the bottom surface of the pressure-resistant container 210. As shown in FIGS. 14 and 15, the fixing portion 221A has a pair of arms 221Aa and a base 221Ab to which one end of each arm 221Aa is connected.

[0080] The rotating shaft 222A rotates the fixing portion 221A so that the angle formed by the membrane surface of the membrane material MB and the bottom surface of the pressure-resistant container 210 changes. Although not shown in FIG. 13, the rotating shaft 222A is supported by a bearing.

[0081] The underwater motor 224A is installed on the bottom surface of the pressure-resistant container 210. The underwater motor 224A may be installed on the bottom surface of the pressure-resistant container 210 via a mounting table.

[0082] The underwater motor 224A is connected to the rotary shaft 222A via a pulley 222B, a pulley 222C, and a rotary belt 222D, and rotates the rotary shaft 222A. The underwater motor 224A controls the posture of the fixed part 221A by rotating the rotary shaft 222A.

[0083] Note that, for example, when sufficient space can be secured inside the pressure-resistant container 210, the underwater motor 224A may be directly connected to the rotary shaft.

[0084] FIG. 14 and FIG. 15 show a state where the membrane surface of the membrane material MB is perpendicular to the bottom surface of the pressure-resistant container 210. When observing the generated bubbles from the discharge part 230, the underwater motor 224A rotates the rotary shaft 222A so that the angle formed by the membrane surface of the membrane material MB and the bottom surface of the pressure-resistant container 210 becomes, for example, 30° to 70°.

[0085] The underwater lighting part 240A is fixed to the fixed part 221A so as to illuminate the membrane material MB. The underwater lighting part 240A is rotated together with the fixed part 221A by the underwater motor 224A. Thereby, transmission light photography becomes possible.

[0086] According to the visualization device 200A, after the observation regarding the adhesion of the generated bubbles to one membrane surface of the membrane material MB is completed, the rotary shaft 222A is rotated 180° by the underwater motor 224A, and the observation regarding the other membrane surface of the membrane material MB can be continuously performed (without opening the lid 212). Therefore, according to this modification example, the experimental efficiency can be improved.

[0087] Also, according to the visualization device 200A, the angle formed by the membrane surface of the membrane material MB and the bottom surface of the pressure-resistant container 210 can be made larger than the case where the posture of the fixed part (membrane material MB) is controlled by a plurality of rods 222. Thereby, for example, the angle at which the granular material does not adhere to the membrane material MB can be searched, or the behavior of the granular material on the membrane material MB at an angle equal to or greater than the angle can be observed.

[0088] In addition, in this modified example, the discharge unit 230 is disposed near the bottom surface of the pressure-resistant container 210. As a result, the distance from the discharge unit 230 to the membrane material MB becomes longer, so that the state change of the methane bubbles discharged from the discharge unit 230 can be observed for a longer time. In this case, the underwater imaging unit 250 includes a camera having a wide-angle lens.

[0089] Note that the visualization devices 200 and 200A may be disposed inside the pressure-resistant container 210 and may further include a water flow generation unit (not shown) that generates a water flow for blowing off the granular material adhering to the membrane material MB. The water flow generation unit may be disposed near the membrane material MB. The water flow generation unit is constituted by, for example, a thruster. In order to effectively remove the granular material from the membrane surface, the angle of the membrane material MB may be controlled so that the water flow hits the membrane surface of the membrane material MB obliquely.

[0090] By blowing off the granular material by the water flow generation unit and removing it from the membrane material MB, it is possible to avoid an operation that requires time and labor, such as once reducing the pressure inside the pressure-resistant container 210 to remove the granular material adhering to the membrane material MB and then returning to the original pressure. In addition, the environmental conditions (temperature, pressure) under which the granular material is generated can be maintained. Therefore, the experimental efficiency can be improved.

[0091] (Function and effect of the visualization device) As described above, the visualization devices 200 and 200A according to the present embodiment are visualization devices for visualizing the behavior of methane bubbles and granular materials, and include a pressure-resistant container 210 filled with water having a temperature and pressure adjusted to the seabed environment where methane hydrate is present, holding units 220 and 220A that hold a membrane material disposed inside the pressure-resistant container 210, a discharge unit 230 that is disposed inside the pressure-resistant container 210, is located below the membrane material MB, and discharges methane bubbles, underwater lighting units 240 and 240A that are disposed inside the pressure-resistant container 210 and illuminate the inside of the pressure-resistant container 210, and an underwater imaging unit 250 that is disposed inside the pressure-resistant container 210 and images the generated bubbles discharged from the discharge unit 230.

[0092] In the visualization devices 200 and 200A, methane bubbles are generated in 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 bodies with a hydrate film formed on their surfaces. The methane bubbles and the granular bodies are photographed by the underwater photographing unit 250.

[0093] According to the present embodiment, it is possible to observe the behavior of generated bubbles in water at low temperature and high pressure that simulates the seabed environment where methane hydrate exists. 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 the granular bodies, etc.

[0094] As a result, it is possible to appropriately grasp the phenomenon in which methane bubbles and granular bodies having a methane hydrate film are collected on the membrane material, and it becomes possible to obtain knowledge useful for the design of the collection membrane and the anti-fouling membrane.

[0095] When trying 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 realize, and it is also difficult to photograph inside the visualization cell. There are also problems with the method of maintaining the cooling temperature. Therefore, the inventors changed their idea and installed the entire visualization cell in pure water, using an optical camera and a lighting device with a water-resistant and pressure-resistant underwater specification, and observing from pure water. As a result, it is possible to make the structure of the visualization cell extremely lightweight and simple, and to realize a visualization device that can observe generated bubbles from multiple viewpoints and illuminate them.

[0096] Hereinafter, with reference to FIGS. 8 to 11B, the images actually photographed by the visualization device 200 will be described.

[0097] FIG. 8 is an image obtained by photographing a plurality of granular materials attached to the membrane material MB by transmitted light photography. FIG. 9 is an image obtained by photographing a plurality of methane bubbles attached to the membrane material MB by transmitted light photography. FIG. 10 is an image obtained by photographing a plurality of granular materials attached to the membrane material MB by reflected light photography. 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, a tangent method, a Θ / 2 method, an ellipse fitting method, a circle fitting method, etc. are used.

[0098] FIGS. 11A and 11B show images taken at 10 ms intervals by a high-speed camera. It can be seen that after the granular material floats 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 hydrate film of the granular material is trapped by the membrane material (140 ms), the retained portion is stretched and vaporized, and only very little sliding occurs (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.

[0099] <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 pressure pump constituted by a syringe pump.

[0100] 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. Note that the drainage tank 60 is provided outside the laboratory in consideration of the situation where methane gas vaporized from the drainage catches fire.

[0101] 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 in order to perform measurement by the visualization device 200.

[0102] The ball valves 9, 10, 11 are respectively connected in parallel with the needle valves 13, 14, 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.

[0103] The pressure monitors 21, 22, 23, and 24 are pressure transmitters having a pressure sensor and a transmitter that transmits 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 equalizing container 235 of the visualization device 200.

[0104] Temperature monitors 31, 32, 33, and 34 are temperature transmitters each having a temperature sensor and a transmitter for sending the measured temperature data to a computer. Temperature monitor 31 measures the temperature of the refrigerant in the cooling section 120 of the environmental test apparatus 100. Temperature monitor 32 measures the temperature of the methane-dissolved water flowing out of the pressure-resistant container 110. Temperature monitor 33 measures the temperature inside the pressure-resistant container 210 of the visualization apparatus 200. Temperature monitor 34 measures the temperature inside the pressure equalizing container 235 of the visualization apparatus 200.

[0105] The pressurizing mechanism 500 includes ball valves 1 to 7, syringe pumps 41 and 42, and a water tank 50. The pressurizing mechanism 500 is configured to pressurize the water (pure water in this embodiment) pumped up from the water tank 50 by alternately operating the two syringe pumps 41 and 42, and send it to the environmental test apparatus 100 or the visualization apparatus 200 via the valve 8 of the three-way valve.

[0106] The operation when shifting from the environmental test to the visualization test will be described.

[0107] 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.

[0108] By repeating the above operation, the dissolved methane water in the pipe up to valve 7 is replaced with pure water. After the replacement with pure water is completed, valve 9 is closed. Then, the three-way valve of valve 8 is switched to the side of the visualization device 200. At this time, the ports 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.

[0109] After the completion of the visualization test, when restarting the circulation operation for the environmental test, the pressure in the piping system of the pressurizing mechanism 500 from valves 5 and 6 to valve 7 is raised until it matches the pressure on the environmental test device 100 side, and then the three-way valve of valve 8 is switched to the environmental test device 100 side.

[0110] The operation when conducting a test (visualization test) with the visualization device 200 will be described.

[0111] In the visualization test, syringe pumps 41 and 42 and valves 1 to 4 are used to pressurize, depressurize, or hold the pressure in the pressure-resistant container 210, which is a high-pressure tank. At the start of the experiment, since it is necessary to send a large amount of pure water into the pressure-resistant container 210, the syringe pumps 41 and 42 are operated so 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 an operation, when the pressure of the visualization device 200 rises or falls, a substantially continuous increase or decrease in pressure is possible.

[0112] The operation when conducting a test (environmental test) with the environmental test device 100 will be described.

[0113] The water supply and pressurization operations of the valve and syringe pump at the start of the test are the same as those in the visualization test, except for the orientation 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. Open valve 1 and valve 6, close valve 2 and valve 5, raise the piston of syringe pump 41, and lower the piston of syringe pump 42. At this time, in order to maintain the pressure of the entire system, when syringe pump 41 pumps water, syringe pump 42 must absorb water at precisely the same flow rate.

[0114] After the pistons of syringe pumps 41 and 42 reach the top dead center and bottom dead center respectively, close all the valves once. Then, this time open valve 2 and valve 5, close valve 1 and valve 6, raise the piston of syringe pump 42, and lower the piston of syringe pump 41.

[0115] By repeating the above operations, the circulation operation of the environmental test device 100 is performed.

[0116] If the pressure of the entire system deviates from the set pressure, close valve 5 and valve 6, and use valves 1 to 4 to perform water supply / pressurization or drainage / decompression. Also, when removing the environmental cell, as described above, use the valves arranged on the valve panel to close the valve connected to the target environmental cell, decompress 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, use the valves arranged on the valve panel to open the valve connected to the target environmental cell and start pressurization. When installing the environmental cell, since the pressure of the system temporarily drops slightly, a pressurization operation may be performed.

[0117] According to the above test system 1000, a test system that suppresses costs can be realized by implementing the pressurization operation with a syringe pump and sharing the syringe pump between the environmental test device 100 and the visualization device 200.

[0118] 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 Signs

[0119] 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 device 110 pressure-resistant container (environmental cell) 110a inlet 110b outlet 111 body 112 lid 113 lid retainer ring 114 O-ring 120 cooling section 121 cooling tank 122 lid 123 chiller 130 pressurization circulation section 131 pressurization pump 132 pipe 140 methane gas supply section (mixing cell) 150 water tank 200, 200A visualization device 210 pressure-resistant container 211 body 212 lid 213 cooling jacket 220, 220A holding section 221, 221A fixing section 221Aa arm 221Ab base 222 rod 222A Rotating shaft 222B, 222C Pulleys 222D Rotating belt 223 Control unit 224 Servo actuator 224A Submersible motor 230 Discharge unit 235 Pressure equalizing vessel 240, 240A Underwater lighting unit 250 Underwater imaging unit 260 Chiller 270 Methane gas supply unit 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 Pressurizing mechanism 1000 System d Thickness e Strand G Generated bubbles MB Membrane material MW Methane dissolved water RF Refrigerant SJ Support jig TH Through-hole (of the pressure equalizing vessel)

Claims

1. a pressure vessel filled with water whose temperature and pressure are adjusted to those of the seabed environment in which methane hydrate exists; A holding part that holds a membrane material disposed inside the pressure-resistant vessel; an outlet portion disposed inside the pressure vessel and below the membrane material, the outlet portion outleting methane bubbles; An underwater lighting unit disposed inside the pressure-resistant vessel and illuminating the inside of the pressure-resistant vessel; an underwater photography unit disposed inside the pressure vessel for photographing the methane bubbles discharged from the discharge unit and the granular material having a hydrate film formed on the surface of the methane bubbles; A visualization device comprising:

2. The visualization device according to claim 1 , wherein the pressure-resistant container comprises a main body, a lid that closes an opening of the main body, and a cooling jacket that cools the main body.

3. The visualization device of claim 1, wherein the holding unit has a fixed portion to which the membrane material is fixed, a plurality of rods connected to the fixed portion and penetrating the pressure-resistant vessel, and a control unit that controls the attitude of the fixed portion by moving the plurality of rods.

4. The visualization device according to claim 1 , wherein the underwater photography unit is communicatively connected to a computer outside the pressure-resistant vessel and transmits photographed data to the computer.

5. The visualization device according to claim 1 , wherein the underwater lighting unit is disposed opposite the underwater photography unit across the membrane material.

6. The visualization device according to claim 1 , wherein the underwater lighting unit is disposed on the same side as the underwater photography unit.

7. The visualization device according to claim 1 , further comprising a pressure equalizing vessel disposed inside the pressure-resistant vessel and having a through hole, the membrane material and the discharge portion being disposed inside the pressure equalizing vessel.

8. The visualization device according to claim 7 , wherein the underwater lighting unit is fixed to a first side surface of the pressure equalizing vessel, and the underwater photography unit is arranged to face a second side surface that is parallel to the first side surface.

9. The visualization device according to claim 8 , wherein the underwater photography unit includes a camera having a telecentric lens.

10. The visualization device described in claim 1, wherein the holding unit includes a fixed unit to which the membrane material is fixed so that the membrane surface of the membrane material faces the bottom surface of the pressure-resistant vessel, a rotating shaft connected to the fixed unit and rotating the fixed unit so as to change the angle between the membrane surface and the bottom surface of the pressure-resistant vessel, and an underwater motor mechanically connected to the rotating shaft and controlling the attitude of the fixed unit by rotating the rotating shaft.

11. The visualization device according to claim 10 , wherein the underwater lighting unit is fixed to the fixing unit so as to illuminate the membrane material.

12. The visualization device according to claim 1 , further comprising a water flow generating unit disposed inside the pressure vessel and configured to generate a water flow for blowing away granular material adhering to the membrane material.

Images