Submarine ground drilling equipment

Abstract

To provide an underwater ground excavation device capable of hoisting up sand and mud containing rare metals at the bottom of water and efficiently pushing it up to the surface of the water by attaching fine bubbles around the sand and mud containing rare metals.SOLUTION: An underwater ground excavation device 1 includes a cylindrical mud pumping pipe 3 and a first water pipe 15 that sends compressed air into the mud pumping pipe 3 in the form of fine bubbles along with a water flow. A discharge port of the first water pipe 15 is connected to a lower end 3a of the mud pumping pipe 3. Fine bubbles ejected from the lower end 3a of the mud pumping pipe 3 stir up sand and mud containing rare metals at the bottom of the water. The sand and mud containing air is pushed up to the water via the mud pumping pipe 3. The upper ends of the first water pipe 15 and a second water pipe 16 are connected to a fine bubble generating device 6 provided with a bubble generating medium 11 made of a carbon-based porous material. The bubble generating medium 11 has a bubble generating medium internal passage 11a through which air passes, and releases the air in the bubble generating medium internal passage 11a as fine bubbles into the liquid flowing into the mud pumping pipe 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the technology of underwater ground excavation devices.

Background Art

[0002] Areas where rare earths and rare metals are distributed have been confirmed on the seabed around 200 m deep. The areas where rare metals and the like are distributed are extensive, and it is expected that the mud with a high content of rare metals and the like exists thinly in layers, covered with topsoil containing almost no rare metals and the like. In order to utilize the mineral resources such as rare metals contained in the mud, it has been considered to remove or recover the topsoil with an underwater ground excavation device and recover the sand and mud containing rare metals and the like (see, for example, Patent Document 1).

[0003] As methods for mining such mineral resources of rare metals and the like and pumping the mud to the water surface, mud pumping by a pump lift and mud pumping by an air lift are known. In mud pumping by a pump lift, a pressure hose having one end connected to an excavation mechanism, a pressure pump connected to the other end of the pressure hose, and a mud pumping line for transporting the conveyed material to the water surface by the pressure of the pressure pump are provided, and the non-conveyed material is pressure-pumped to the water surface by the pressure from the pressure pump. Further, in mud pumping by an air lift, a cylindrical mud pumping pipe is provided from the water surface to the excavation location, an air pipe for sending compressed air into the inside of the mud pumping pipe is connected to the tip of the mud pumping pipe, and the compressed air ejected from the lower end of the mud pumping pipe rolls up the sand and mud containing rare metals on the seabed and pushes up the sand and mud containing air through the mud pumping pipe to the water surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In conventional airlift-based sediment lifting, compressed air is delivered as bubbles, with a diameter of several hundred micrometers to several millimeters. These bubbles adhere to sand and sediment particles containing rare metals at the bottom of the sea, causing them to float. However, if the bubbles are too large, they cannot adhere to the fine sand and sediment particles containing rare metals, which reduces the efficiency of the compressed air lift.

[0006] Furthermore, ordinary bubbles have a potential of zero and are not charged. Therefore, the adhesion of fine rare metals to the sand and mud is solely due to surface tension, and they are lifted at the same rate as sand and mud that do not contain rare metal components.

[0007] Therefore, in view of these problems, the present invention provides a seabed excavation device that can efficiently lift sand and mud containing rare metals from the seabed and push them to the surface by attaching fine bubbles to the sand and mud containing rare metals. [Means for solving the problem]

[0008] The problems that this invention aims to solve are as described above, and the means for solving these problems will now be explained.

[0009] In other words, in the present invention, compressed air is introduced into the inside of the sludge lifting pipe as fine bubbles along with the water flow. First water pipe and, Second water pipe that supplies water for ground excavation. And, The aforementioned First water pipe The discharge port is connected to the lower end of the sludge lifting pipe. The water flow ejected from the second water pipe excavates the seabed to expose or agitate sand and mud containing rare metals. By fine bubbles supplied from the first water pipe to the lower end of the sludge pump pipe A seabed excavation device that lifts up the sand and mud containing the rare metals and pushes the air-containing sand and mud to the surface of the water via the mud lifting pipe, The first water pipe and the second water pipe A microbubble generating device, equipped with a bubble generating medium made of a carbon-based porous material, is connected to the upper end. The bubble generating medium has an internal passage through which air passes, The air in the passage within the bubble-generating medium is released as fine bubbles into the water flowing into the sludge pipe.

[0010] Furthermore, in the present invention, First water pipe The discharge outlet may be located at a depth of 200m or more from the water surface. [Effects of the Invention]

[0011] The present invention provides the following effects:

[0012] In this invention, by converting the air contained in the sludge lifting tube into microbubbles, these microbubbles adhere to the surroundings of small-particle sand and sludge, thereby improving the efficiency of sludge lifting. Furthermore, while conventional bubbles adhere to the sand and sludge due to surface tension, the air discharged as microbubbles is negatively charged, making it more likely to adhere to the surroundings of rare metals, which have a positive potential. This enables efficient sludge lifting of rare metals. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic front view showing a seabed excavation device according to the first embodiment. [Figure 2] A partial front cross-sectional view showing the lower end of a sludge lifting pipe according to the first embodiment. [Figure 3] A partial front cross-sectional view showing the lower end of a sludge lifting pipe according to the second embodiment. [Figure 4] A partial front cross-sectional view showing the lower end of a sludge lifting pipe according to the third embodiment. [Figure 5] A partial front cross-sectional view showing the lower end of a sludge lifting pipe according to the fourth embodiment. [Modes for carrying out the invention]

[0014] [First Embodiment] The underwater ground excavation device 1 according to an embodiment of the present invention will be described with reference to FIG. 1. As shown in FIG. 1, the underwater ground excavation device 1 according to the embodiment of the present invention is installed on water such as on the ocean or on a lake, and mines minerals etc. buried in the underwater ground such as the seabed or the lake bottom, pumps the mud up to the ocean surface, and transports it to a storage facility 100 provided on land. In particular, the underwater ground excavation device 1 is a device that performs mud pumping by air lift, which is effective for pumping resources such as rare metals from deep water such as the seabed or the lake bottom.

[0015] In the mud pumping method by air lift, the open lower end 3a of the mud pumping pipe 3 is arranged close to the ground to be excavated. Also, in the mud pumping pipe 3, a water flow for mud pumping is generated from the first water pipe 15 to push up the resources in the mud pumping pipe 3 to the sea.

[0016] The underwater ground excavation device 1 includes a float 2 for mounting each device on water, a mud pumping pipe 3 extending downward from the float 2, a first water pipe 15 for supplying fine bubbles inside the mud pumping pipe 3, a collection device 5 arranged on the water contact surface of the float 2 for collecting sand and mud such as rare metals that have been mud pumped, a first water pipe 15 connected to the tip of the mud pumping pipe 3 for sending the water flow used for mud pumping into the mud pumping pipe 3, a second water pipe 16 for sending the water flow used for ground excavation, a pressure pump 17 for pressure pumping the water flow to the first water pipe 15 and the second water pipe 16, and a fine bubble generator 6 provided on the upstream side of the pressure pump 17 for supplying a water flow containing fine bubbles to the first water pipe 15 and the second water pipe 16.

[0017] The float 2 is a structure that can float on the ocean or on a lake, and is floating at a predetermined position on the water by an anchor etc. not shown in the figure. On the upper surface of the float 2, a fine bubble generator 6, a temporary storage tank 8 for temporarily storing the rare metals collected by the collection device 5, and a pressure pump 17 are mounted.

[0018] The sludge extraction pipe 3 is a cylindrical pipe that connects a float 2 on the ocean or lake to the bottom of the sea where the mining takes place. The sludge extraction pipe 3 is made of a metal pipe such as a steel pipe or a carbon-based resin pipe such as CFRP. The lower end 3a of the sludge extraction pipe 3 is extended to a depth greater than approximately 200m where the rare metal deposit is located. The lower end 3a is an open end, allowing water to enter and exit from near the lake or seabed. Since the sludge extraction pipe 3 is more than 200m long, it is preferable to make it out of a lightweight and durable resin or carbon-based resin pipe rather than a heavy metal pipe. Inside the sludge extraction pipe 3, there is a water flow passage 3b for passing seawater or lake water.

[0019] The lower end 3a of the sludge lifting pipe 3 is located near the mining site. A large amount of microbubbles released from the second water pipe 16 stir up the sand and mud containing rare metals from the bottom of the water. The stirred-up sand and mud containing rare metals is pushed to the surface of the water via the sludge lifting pipe 3 by the buoyancy of the microbubbles.

[0020] The collection device 5 is formed, for example, by a back pressure tank, and uses back pressure to draw in sand and mud that would otherwise sink back into the water due to the bursting of microbubbles near the water surface. The sand and mud collected by the collection device 5 is transported by a conveyor or the like to a temporary storage tank 8 for temporary storage.

[0021] A first water pipe 15 is connected to the sludge lifting pipe 3 to supply water to assist in sludge lifting. The first water pipe 15 is connected to the side of the sludge lifting pipe 3 and supplies water into the water flow passage 3b of the sludge lifting pipe 3. An ejector 15a is provided in the first water pipe 15. The ejector 15a is a device that creates a water flow by creating a vacuum through a narrow section in its internal passage. In addition, a narrow passage 3d, which acts as an aspirator, is provided in the water flow passage 3b of the sludge lifting pipe 3. This creates a reduced-pressure section inside the sludge lifting pipe 3, making it possible to create an upward water flow. Alternatively, a small pump may be installed in the place of the ejector 15a. Furthermore, a second water pipe 16 for excavating the ground is positioned towards the seabed. The second water pipe 16 is an example of a device that excavates the ground using water flow. It excavates the topsoil covering a layer of mud with a high content of rare metals, exposing the mud layer with a high content of rare metals, and then further agitates it with water flow. A jet water nozzle 16a is attached to the tip of the second water pipe 16, and by generating a jet of water from a narrow-diameter injection hole, the surface layer can be excavated. Furthermore, as a method for excavating the ground, for example, a robot equipped with a wirelessly controlled excavator may be used.

[0022] The first water pipe 15 is a pipe that delivers compressed air as fine bubbles to the vicinity of the lower end 3a of the sludge pipe 3, and the outlet of the first water pipe 15 is connected to the lower end 3a of the sludge pipe 3. A pressure pump 17 is connected to the upstream end of the first water pipe 15. The pressure pump 17 is also connected to the second water pipe 16. A microbubble generator 6 is connected to the upstream side of the pressure pump. The microbubble generator 6 comprises a compression pump 6a that pumps ambient air, a water tank 6b that stores water containing microbubbles, and a bubble generating medium 11 that generates microbubbles in the water from the air sent from the compression pump 6a within the water tank 6b.

[0023] As shown in Figures 1 and 2, the bubble-generating medium 11 has numerous fine pores 11b with diameters ranging from several micrometers to tens of micrometers. The bubble-generating medium 11 is composed of a carbon-based porous material. A carbon-based porous material is a composite material containing only carbon or carbon and ceramic. Furthermore, the bubble-generating medium 11 is a conductor whose solid structure is a molecular structure formed by ionic bonds, and the bubbles generated from the bubble-generating medium 11 are negatively charged. In other words, the microbubbles become negatively charged when they pass through the conductive bubble-generating medium 11, as free electrons are added to them. This negative charge prevents the bubbles from repelling each other and merging to form larger bubbles.

[0024] The bubble generating medium 11 has an internal passage 11a through which air passes. The bubble generating medium 11 is configured to be cylindrical, with the internal passage 11a located inside. The bubble generating medium 11 is also formed of a porous composite having countless fine pores 11b. These countless fine pores 11b are distributed throughout the bubble generating medium 11, and their diameters range from several micrometers to tens of micrometers. The internal passage 11a and the surface portion 11c of the bubble generating medium 11 are connected by the pores 11b. Fine bubbles are generated from the surface portions 11c on the sides and bottom of the bubble generating medium 11.

[0025] Next, we will explain a method for excavating sand and mud containing rare metals that have been unearthed by ground excavation.

[0026] First, the rare metal-containing ground at the bottom of the sea is excavated by releasing a water flow containing microbubbles from the second water pipe 16. At greater depths of the seabed, the ground containing rare metals is located relatively close to the surface. Therefore, by excavating with a water flow containing microbubbles from the second water pipe 16, the layer of sandy mud containing rare metals can be easily exposed on the surface of the seabed.

[0027] Secondly, a stream of water containing microbubbles is pumped under pressure to the first water pipe 15. The stream of water containing microbubbles sent to the first water pipe 15 is then sent from the outlet of the first water pipe 15 to the lower end 3a of the sludge lifting pipe 3. The microbubbles that are sent in are then released into the water near the lower end 3a of the sludge lifting pipe 3.

[0028] The large amount of fine bubbles discharged from the bubble-generating medium 11 are mixed with the surrounding water and mud that were stirred up by the water flow from the second water pipe 16 in the first step. The jet stream ejected from the jet water nozzle 16a of the second water pipe 16 excavates the surface layer, exposing the mud layer that will become the deposit of rare metals. Further ejection of the jet stream causes the sand and mud containing rare metals to float to the bottom. At the time of generation, the surface of the fine bubbles has a negative potential due to free electrons, and an attractive force acts between them and the properties of rare metals, which have a positive potential. In addition, the adhesive force due to the surface tension of the fine bubbles also acts, making it easier for the surrounding sand and mud to adhere to the surface of the fine bubbles.

[0029] Furthermore, by ejecting microbubbles into the water surrounding the sand and mud, if the sand and mud contain rare metals with a positive electrical potential, the electrical bonding force will exceed the adhesive force due to the surface tension of the microbubbles, causing the rare metals to preferentially adhere to the microbubbles, thus improving the recovery rate of the rare metals.

[0030] Microbubbles to which sand and mud containing rare metals are attached rise upward due to buoyancy. Furthermore, the water flow supplied from the first water pipe 15 creates an upward water flow, promoting mud lifting. The ejector 15a provided in the first water pipe 15 creates a water flow when water flows into the first water pipe 15, where the pressure is reduced by the Venturi effect. In addition, the narrow passage 3d, which acts as an aspirator and is provided in the water flow passage 3b of the mud lifting pipe 3, creates a reduced pressure area inside the mud lifting pipe 3, creating an upward water flow. When mud water containing microbubbles enters the water flow passage 3b where this upward water flow has been created, the buoyancy of the microbubbles also acts, causing the mud water to rise. With this configuration, mud lifting is performed, and sand and mud containing rare metals are collected in the collection device 5.

[0031] Because microbubbles are permeable, if rare metals with a positive electrical potential are present in sand or mud, they can adhere to the microbubbles while separating them from other components. This property of microbubbles allows for the efficient separation and recovery of rare metals.

[0032] At the bottom of deep lakes or the seabed, the diameter of microbubbles is several hundred nanometers to several micrometers due to water pressure. However, as they rise to the surface, the water pressure decreases, causing the bubble diameters to increase. As the bubbles rise, their diameters increase, and they merge to become even larger, causing only the gas to escape and the force that lifts the muddy water to the surface to be lost. However, since the diameter of the microbubbles released from the bubble-generating medium 11 is several hundred nanometers to several micrometers, a sufficient airlift effect can be obtained even if the bubble diameter increases near the water surface. Furthermore, because the microbubbles are electrically charged, a sufficient airlift effect can be obtained by preventing them from merging to become larger.

[0033] As the fine bubbles rise to the surface, the sand and mud that have floated to the surface through the water flow passage 3b inside the mud lifting pipe 3 are pumped up by a collection device 5 located near the water surface. The sand and mud pumped up by the collection device 5 are stored in a temporary storage tank 8 on the float 2 by a conveyor (not shown), and when a predetermined amount of sand and mud has been stored in the temporary storage tank 8, it is transported by ship or the like to an onshore storage facility 100.

[0034] As described above, the submarine ground excavation device 1 according to the present invention is provided with a cylindrical sludge lifting pipe 3 that communicates from the surface to the excavation site, and a first water pipe 15 and a second water pipe 16 that send compressed air as fine bubbles along with the water flow into the sludge lifting pipe 3, the discharge port of the first water pipe 15 is connected to the lower end 3a of the sludge lifting pipe 3, and the fine bubbles ejected from the lower end 3a of the sludge lifting pipe 3 stir up sand and mud containing rare metals from the seabed, pushing the air-containing sand and mud to the surface via the sludge lifting pipe 3. A fine bubble generating device 6, which is provided with a bubble generating medium 11 made of a carbon-based porous material, is connected to the upper ends of the first water pipe 15 and the second water pipe 16, and the bubble generating medium 11 has an internal passage 11a through which air passes, and the air in the internal passage 11a of the bubble generating medium is released as fine bubbles into the liquid flowing into the sludge lifting pipe 3.

[0035] This configuration eliminates the need for large pumps compared to pump-lift systems, thus reducing costs. Furthermore, even in high-pressure environments, the use of a corrosion-resistant and highly durable bubble-generating medium 11 reduces the frequency of maintenance. Additionally, mud containing many fine bubbles has lower viscosity and frictional resistance, improving the efficiency of mud lifting. Moreover, as mud containing many fine bubbles passes through the water flow passage 3b, the fine bubbles make it easier to remove dirt from the surface of the water flow passage 3b, preventing pipe clogging.

[0036] Furthermore, since the air pumping by the microbubble generator 6 does not require a large pump pressure proportional to the depth compared to lifting by pump lift, rare metals can be extracted even at deep mining sites.

[0037] Furthermore, the outlet of the first water pipe 15 is positioned at a depth of 200m or more from the water surface.

[0038] This configuration allows for the generation of microbubbles in deep water. Therefore, it enables efficient work in locations where rare metal deposits exist, such as at depths of 200 meters or more.

[0039] In this embodiment, the water pipe that sends compressed air as fine bubbles along with the water flow into the sludge pipe 3 is composed of a single first water pipe 15, but it is not limited to this. For example, in deep excavation and sludge lifting processes, the water flow created by a single water pipe may not be sufficient for sludge lifting, so multiple water pipes may be arranged to supply sludge at predetermined depths. Also, in deep excavation and sludge lifting processes, a pressure pump may be installed in the middle of the first water pipe 15 to increase the pressure of the water flow created by the first water pipe 15. Furthermore, in deep excavation and sludge lifting processes, a water pump may be provided at the upper end of the sludge lifting pipe 3 as an auxiliary pump to obtain sufficient lifting power.

[0040] [Second Embodiment] As a second embodiment, as shown in Figure 3, an ultrasonic crushing device 31 may be provided as an excavation device at the lower end of the sludge lifting pipe 3.

[0041] The ultrasonic fracturing device 31 is a device that generates ultrasonic waves to vibrate and break up the inside of the rock mass. A large amount of microbubbles discharged from the bubble generating medium 11 are also released into the water surrounding the sand and mud that is hit by the ultrasonic waves generated by the ultrasonic fracturing device 31. Because the microbubbles are small in size, they easily penetrate the rock mass before the ultrasonic waves are applied. By generating ultrasonic waves in the ground that has been penetrated by the microbubbles, the microbubbles vibrate, making the rock mass around the microbubbles more prone to collapse, thus facilitating excavation.

[0042] Furthermore, when microbubbles are formed, their surface has a negative potential due to free electrons, and this creates an attractive force between them and the properties of rare metals, which have a positive potential. In addition, the adhesive force due to the surface tension of the microbubbles makes it easier for surrounding sand and mud to adhere to the surface of the microbubbles.

[0043] Furthermore, by ejecting microbubbles into the water surrounding the sand and mud, if the sand and mud contain rare metals with a positive electrical potential, the electrical bonding force will outweigh the adhesive force due to the surface tension of the microbubbles, causing the rare metals to preferentially adhere to the microbubbles, thus improving the recovery rate of the rare metals.

[0044] The fine bubbles, to which surrounding sand and mud have attached, float upward due to buoyancy. When mud containing these fine bubbles enters the water in the water passage 3b of the mud lifting pipe 3, the buoyancy of the fine bubbles causes the mud to float upward. This is how mud lifting is performed.

[0045] This configuration eliminates the need for large pumps compared to pump-lift systems, thus reducing costs. Furthermore, even in high-pressure environments, the use of a corrosion-resistant and highly durable bubble-generating medium 11 reduces the frequency of maintenance. Additionally, mud containing many fine bubbles has lower viscosity and frictional resistance, improving the efficiency of mud lifting. Moreover, as mud containing many fine bubbles passes through the water flow passage 3b, the fine bubbles make it easier to remove dirt from the surface of the water flow passage 3b, preventing pipe clogging.

[0046] Furthermore, since the air pumping by the microbubble generator 6 does not require a large pump pressure proportional to the depth compared to lifting by pump lift, rare metals can be extracted even at deep mining sites.

[0047] [Third Embodiment] As a third embodiment, as shown in Figure 4, a drill 41 may be provided as an excavation device at the lower end of the sludge lifting pipe 3. Note that the drill 41 is just one example of an excavation device and may also be a blade or a fan.

[0048] The bubble generating medium 11 is located at the lower end 3a of the sludge lifting pipe 3 and is positioned to eject fine bubbles onto the cutting edge of the drill 41.

[0049] A lubricating fluid ejection device 42 is provided around the drill 41. The lubricating fluid ejection device 42 is a device that ejects a lubricant that can improve the lubrication between the drill 41 and the cut soil during cutting. The lubricating fluid ejection device 42 is equipped with an ejection nozzle 43 and is located near the drill 41. A lubricating fluid tank 44 that supplies lubricating fluid to the lubricating fluid ejection device 42 is located on a float 2 on the water.

[0050] Furthermore, the lubricating fluid bubble generating medium 45 releases oxygen under high pressure into the lubricating fluid as fine bubbles in the lubricating fluid tank 44. The lubricating fluid bubble generating medium 45 has numerous fine pores with diameters ranging from several micrometers to tens of micrometers. The lubricating fluid bubble generating medium 45 is composed of a carbon-based porous material. A carbon-based porous material is a composite material containing only carbon or carbon and ceramic. In addition, the lubricating fluid bubble generating medium 45 is a conductor whose solid structure is a molecular structure formed by ionic bonds, and the bubbles generated from the lubricating fluid bubble generating medium 45 are negatively charged. In other words, the fine bubbles become negatively charged when they pass through the conductive lubricating fluid bubble generating medium 45, as free electrons are added to them. This negative charge prevents the bubbles from repelling each other and merging to form larger bubbles.

[0051] When the drill 41 is driven to rotate, lubricant is ejected from the lubricant ejector 42. The lubricant ejected from the lubricant ejector contains fine bubbles. In this case, the presence of fine bubbles between the drill 41 and the ground being drilled reduces the opportunity for contact between the ground being drilled and the drill 41, thereby improving lubrication.

[0052] Furthermore, depending on the ground conditions, drilling may cause highly corrosive substances, such as hydrogen sulfide, to erupt into the ground. Hydrogen sulfide causes the drill bit 41 to deteriorate due to sulfidation. However, because oxygen is included in the lubricating fluid as fine bubbles, the hydrogen sulfide can be decomposed into sulfur and water, thus suppressing the sulfidation of the drill bit 41. This extends the lifespan of the drill bit 41 and reduces maintenance time.

[0053] The fine bubbles in the ejected lubricating fluid, along with the fine bubbles supplied from the first water pipe 15 and the second water pipe 16 used during sludge lifting, carry the stirred-up sand and sludge into the sludge lifting pipe 3, causing it to float to the surface. As bubbles rise to the surface, the sand and mud that have floated to the surface through the water flow passage 3b inside the mud lifting pipe 3 are pumped up by a collection device 5 located near the water surface. The sand and mud pumped up by the collection device 5 are stored in a temporary storage tank 8 on the float 2 by a conveyor (not shown), and when a predetermined amount of sand and mud has been stored in the temporary storage tank 8, it is transported by ship or the like to an onshore storage facility 100.

[0054] This configuration eliminates the need for a large pump compared to a pump-lift system, resulting in cost savings. Furthermore, even in high-pressure environments, the use of a corrosion-resistant and highly durable bubble-generating medium reduces the frequency of maintenance. In addition, the lifespan of components such as the drill 41 in the drilling device is extended, further reducing maintenance time.

[0055] [Fourth Embodiment] As a fourth embodiment, as shown in Figure 5, a jet water jet ejection device 51 that ejects a water flow containing fine bubbles as a jet stream may be provided at the lower end of the sludge pipe 3 as an excavation device.

[0056] The jet water ejection device 51 is equipped with an ejection nozzle 52. The ejection nozzle 52 is a nozzle that ejects a jet of water onto the ground, and is equipped with a jet water bubble generating medium 53 inside the ejection nozzle 52. The jet water bubble generating medium 53 has many fine pores with diameters ranging from several micrometers to tens of micrometers. The jet water bubble generating medium 53 is made of a carbon-based porous material. A carbon-based porous material is a composite material containing only carbon or carbon and ceramic. Furthermore, the jet water bubble generating medium 53 is a conductor whose solid structure is a molecular structure formed by ionic bonds, and the bubbles generated from the jet water bubble generating medium 53 are negatively charged. In other words, when the fine bubbles pass through the conductive jet water bubble generating medium 53, free electrons are added to them, causing them to become negatively charged. This negative charge prevents the bubbles from repelling each other and merging to form larger bubbles.

[0057] The jet water ejection device 51 ejects a jet of water from the ejection nozzle 52. When the jet water is ejected from the ejection nozzle 52, fine bubbles are generated in the water from the jet water bubble generating medium 53, and the jet water is infused with these fine bubbles. At this time, the fine bubbles, along with the fine bubbles supplied from the air pipe used during sludge lifting, carry the turbulent sand and sludge into the sludge lifting pipe 3 and cause it to float to the surface of the water. As the fine bubbles rise to the surface, the sand and mud that have floated to the surface through the water flow passage 3b inside the mud lifting pipe 3 are pumped up by a collection device 5 located near the water surface. The sand and mud pumped up by the collection device 5 are stored in a temporary storage tank 8 on the float 2 by a conveyor (not shown), and when a predetermined amount of sand and mud has been stored in the temporary storage tank 8, it is transported by ship or the like to an onshore storage facility 100.

[0058] This configuration eliminates the need for a large pump compared to a pump-lift system, resulting in cost savings. Furthermore, even in high-pressure environments, the use of a corrosion-resistant and highly durable bubble-generating medium reduces the frequency of maintenance. [Explanation of Symbols]

[0059] 1. Submarine ground drilling device 2 floats 3 Sludge pumping pipe 3a Bottom end 3b Water flow passage 3d narrow passage 5 Collection device 6. Microbubble Generator 8. Temporary storage tanks 11 Bubble-generating medium 11a Passage within the bubble generating medium 11b hole 11c Surface part 15 First water pipe 15a Ejector 16 Second water pipe 16a Jet water nozzle 31. Ultrasonic fracturing device 41 Drill 42 Lubricating fluid squirting device 43 Spray nozzles 44 Lubricant tank 45. Bubble generating medium for lubricating fluids 51. Water jet ejection device 52 spray nozzles 53 Bubble generating medium for water jets

Claims

1. A cylindrical sludge lifting pipe that connects from the water surface to the mining site, A water pipe is provided inside the aforementioned sludge lifting pipe to send compressed air as fine bubbles along with the water flow, Established, The outlet of the water pipe is connected to the lower end of the sludge lifting pipe, and fine gas is ejected from the lower end of the sludge lifting pipe. The bubbles stir up the sand and mud containing rare metals from the bottom of the water, and the air-filled sand and mud are then lifted into the aforementioned sludge pipe. A seabed excavation device that pushes up to the surface via, At the upper end of the water tube, a microbubble generating medium made of a carbon-based porous material is provided. A bubble generator is connected, The bubble generating medium has an internal passage through which air passes, The air in the passage within the bubble-generating medium is released as fine bubbles into the water flowing into the sludge pipe. ru, A seabed excavation device characterized by the following features. A cylindrical sludge lifting pipe that connects from the water surface to the mining site, A first water pipe that sends compressed air as fine bubbles along with the water flow into the inside of the sludge lifting pipe, A second water pipe is installed to supply the water flow used for ground excavation. The discharge port of the first water pipe is connected to the lower end of the sludge lifting pipe. The water flow ejected from the second water pipe excavates the seabed to expose or agitate sand and mud containing rare metals. A seabed excavation device that uses fine bubbles supplied from the first water pipe to the lower end of the sludge lifting pipe to stir up the sand and mud containing the rare metals, and pushes the air-containing sand and mud to the surface of the water via the sludge lifting pipe, A microbubble generating device, equipped with a bubble generating medium made of a carbon-based porous material, is connected to the upper ends of the first water pipe and the second water pipe. The bubble generating medium has an internal passage through which air passes, The air in the passage within the bubble-generating medium is released as fine bubbles into the water flowing into the sludge pipe. A seabed excavation device characterized by the following features.

2. The outlet of the first water pipe is located at a depth of 200 m or more from the water surface. The underwater ground drilling apparatus according to claim 1.

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