Method and system for recovering rare earth sludge

Abstract

The rare earth sludge recovery method of the present invention includes the following steps: (A) inserting a sludge collecting pipe into a layer under the sea floor containing rare earth sludge; (B) preparing a slurry containing rare earth by desludging the rare earth sludge in the sludge collecting pipe; and (C) transferring the slurry using a sludge lifting pipe. The recovery method preferably further includes a step of transferring the slurry in the sludge collecting pipe to the sludge lifting pipe between the (B) step and the (C) step.

Description

TECHNICAL FIELD

[0001] The present application relates to a rare earth mud recovery method and a recovery system. BACKGROUND

[0002] On the ocean floor all over the world, there are many natural resources of liquid and gas represented by oil and natural gas. In addition, the existence of solid mineral resources such as manganese nodules has been confirmed. Patent Documents 1 to 4 disclose a method for collecting natural resources of liquid and gas or a method for mining mineral resources in a relatively shallow sea floor.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-172418

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-120063

[0007] Patent Document 3: Japanese Patent Application Publication No. 2019-011568

[0008] Patent Document 4: Japanese Patent No. 3284070 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] It has been confirmed that a layer containing rare earth mud exists under the sea floor of a deep sea with a water depth exceeding 5000 m. The mud is called rare earth mud and is attracting attention as a new resource. However, a technique for efficiently collecting rare earth mud from such a deep sea floor has not yet been established. The present application provides a rare earth mud recovery method and a recovery system that can be applied even to a layer under the sea floor of a deep sea with a water depth exceeding 5000 m.

[0011] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0012] The rare earth mud recovery method according to the present application includes the following steps: (A) causing a mud collecting pipe to penetrate into a layer under the sea floor containing rare earth mud; (B) preparing a slurry containing rare earth by de-muddifying the rare earth mud in the mud collecting pipe; and (C) transferring the above slurry using a mud lifting pipe.

[0013] According to the above-described recovery method, since the sludge is disintegrated and the slurry is prepared in the silt collecting pipe which is isolated from the environment near the sea floor, the slurry having a concentration suitable for the dredging can be stably prepared. Further, since the disturbance in the sea caused by the disintegration of the slurry (for example, the rare earth slurry is stirred in the sea) in the (B) process is generated in the closed space in the silt collecting pipe, the environmental load can be reduced. Furthermore, the "slurry containing a rare earth" in the present application means a mixed fluid of the rare earth slurry having fluidity or at least the rare earth slurry and the sea water.

[0014] The dredging pipe has, for example, a double pipe structure. In this case, the slurry containing a rare earth can be transferred by the circulating flow.

[0015] The above-described recovery method preferably further includes a process (silt collecting pipe slurry transfer process) of transferring the above-described slurry in the silt collecting pipe to the dredging pipe between the (B) process and the (C) process. This process can be performed using, for example, a pump. The above-described recovery method preferably further includes a process of switching the dredging pipe to a state of not communicating with the silt collecting pipe before the (C) process after the above-described slurry in the silt collecting pipe is transferred to the dredging pipe. By performing this process, the pressure required for the transfer of the slurry in the dredging pipe in the (C) process can be prevented from affecting the pressure in the silt collecting pipe. Specifically, the phenomenon (hereinafter, referred to as "boiling") in which the closed state between the silt collecting pipe and the layer of the sea floor is released by the pressure required for the transfer of the slurry and the fluid leaks from between the silt collecting pipe and the layer of the sea floor can be prevented.

[0016] In the (A) process, in order to easily settle the silt collecting pipe in the layer under the sea floor, the following matters can be performed. For example, the silt collecting pipe can be settled while fluid is sprayed downward from a nozzle provided at the front end portion of the silt collecting pipe or the silt collecting pipe can be settled by making the inside of the silt collecting pipe negative pressure.

[0017] The rare earth recovery system according to the present application includes a silt collecting pipe which is inserted into a layer under a sea floor containing a rare earth slurry, a stirring device which disintegrates the rare earth slurry in the silt collecting pipe, and a dredging pipe which is connected to the silt collecting pipe. According to the recovery system, since the disintegration and the slurry preparation can be performed in the silt collecting pipe which is isolated from the environment near the sea floor, the slurry having a concentration suitable for the dredging can be stably prepared. Further, since the disturbance in the sea caused by the disintegration of the rare earth slurry (for example, the rare earth slurry is stirred in the sea) in the silt collecting pipe can be generated in the closed space in the silt collecting pipe, the environmental load caused by this can be reduced.

[0018] The above-described recovery system can further include a pump which transfers the above-described slurry in the silt collecting pipe to the dredging pipe. In the above-described (A) process, in order to form negative pressure for drawing out the sea water in the silt collecting pipe, the pump can be used. The above-described recovery system can further include a nozzle provided at the front end portion of the silt collecting pipe. The nozzle can be used to settle the silt collecting pipe while spraying fluid downward in the above-described (A) process.

[0019] The above-described recovery system preferably further has a flow path switching mechanism configured to be capable of switching between a state in which the sludge collecting pipe is in communication with the sludge raising pipe and a state in which the sludge collecting pipe is not in communication with the sludge raising pipe. With this configuration, it is possible to prevent the pressure required for the transfer of the slurry in the sludge raising pipe from affecting the pressure in the sludge collecting pipe, and specifically, it is possible to prevent boiling from occurring.

[0020] Effects of Invention

[0021] According to the present application, a rare earth sludge recovery method and a recovery system are provided that are applicable even to layers under the seabed of a deep sea having a water depth exceeding 5,000 m. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a cross-sectional view schematically showing one embodiment of a rare earth sludge recovery system according to the present application.

[0023] Figure 2 is a cross-sectional view schematically showing a state in which the sludge collecting pipe is embedded in a layer under the seabed.

[0024] Figure 3 is a cross-sectional view schematically showing a state in which the slurry in the sludge collecting pipe is transferred to the sludge raising pipe.

[0025] Figure 4 is a cross-sectional view schematically showing a state in which the slurry in the sludge raising pipe is transferred upward by a circulating flow. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. The present application is not limited to the following embodiments.

[0027] < Rare Earth Sludge Recovery System >

[0028] Figure 1 is a cross-sectional view schematically showing a rare earth sludge recovery system according to the present embodiment. The recovery system 10 is used to make a rare earth sludge that is present in a layer L under a seabed F of a deep sea having a water depth exceeding 5,000 m into a slurry and recover it. Figure 1 shows a state in which the sludge is disintegrated by the stirring device 3. The recovery system 10 has a sludge collecting pipe 1 that is embedded in the layer L under the seabed F, a stirring device 3, a sludge raising pipe 5 that is connected to the sludge collecting pipe 1, a flow path switching mechanism 7, and a seabed pump 9.

[0029] The mud collecting pipe 1 is used to form a space isolated from the environment near the sea floor. A slurry S containing rare earth mud is prepared in a closed space inside the mud collecting pipe 1. The mud collecting pipe 1 is composed of a cylindrical portion la, an upper plate lb closing the upper end of the cylindrical portion la, an opening lc penetrating the upper plate lb, and a plurality of nozzles Id provided at the front end portion. The inner diameter of the cylindrical portion la is, for example, 3 to 5 m. The length of the cylindrical portion la in the vertical direction is, for example, 12 to 20 m. Figure 1 The mud collecting pipe 1 in FIG. 1 is in a state where the front end thereof is penetrated into the layer L from the sea floor F to a depth of 11 to 19 m. The plurality of nozzles Id are configured to be able to respectively jet fluid (for example, seawater) toward the lower side, and can be used when the mud collecting pipe 1 is lowered to the layer L.

[0030] The stirring device 3 is composed of a drill pipe 3a extending from a ship (not shown) on the sea and a blade 3b provided at the lower end side of the drill pipe 3a and outside. The blade 3b is configured to rotate with the rotation of the drill pipe 3a and to move in the vertical direction with the vertical movement of the drill pipe 3a. Inside the mud collecting pipe 1, the blade 3b moves downward while rotating, thereby forming a depression C in the layer L, and the rare earth mud is mixed with seawater to obtain a slurry S having fluidity.

[0031] The mud lifting pipe 5 is connected to the opening lc of the mud collecting pipe 1 via a flow path switching mechanism 7. By the operation of the flow path switching mechanism 7, the mud lifting pipe 5 can be switched between a state of communicating with the mud collecting pipe 1 and a state of not communicating with the mud collecting pipe 1. In the state of not communicating with the mud collecting pipe 1, the mud lifting pipe 5 can circulate with the drill pipe 3a. Specifically, the mud lifting pipe 5 and the drill pipe 3a constitute a double pipe, and the drill pipe 3a (inner pipe) and the annular portion 5a (a region divided by the outer surface of the drill pipe 3a and the inner surface of the mud lifting pipe 5) can be communicated at a position higher than the upper plate lb (see FIG. 2). Figure 4 ).

[0032] The flow path switching mechanism 7 is composed of a plurality of and various valves, pipes, and the like. The flow path switching mechanism 7 is operated from the ship or by a ROV (remote-operated underwater vehicle). The flow path switching mechanism 7 has, for example, an annular closing mechanism 7a that closes the annular portion 5a as needed, a drill pipe closing valve 7b that closes the drill pipe 3a as needed, a gate mechanism 7c that communicates the inside of the drill pipe 3a and the annular portion 5a as needed, a sea floor control device (not shown) that controls these components, and a sea floor accumulator (not shown) that is a power source for these components. The drill pipe closing valve 7b is provided at a position on the drill pipe 3a corresponding to the lower end of the mud lifting pipe 5, and by operating it, a state in which the mud lifting pipe 5 does not communicate with the mud collecting pipe 1 can be formed. The gate mechanism 7c is provided at a position on the drill pipe 3a higher than the drill pipe closing valve 7b, and by operating it and the annular closing mechanism 7a, the inside of the drill pipe 3a and the annular portion 5a can be communicated at that position.

[0033] Method for recovering rare earth sludge

[0034] Reference Figures 1 to 4 A method for recovering rare earth sludge using the recovery system 10 will be described. The method for recovering rare earth sludge according to the present embodiment includes the following processes.

[0035] (a) A process of making the sludge collecting pipe 1 penetrate into the layer L under the sea floor F containing rare earth sludge (refer to Figure 2 ).

[0036] (b) A process of preparing a slurry S containing rare earth in the sludge collecting pipe 1 by desludging the rare earth sludge (refer to Figure 1 ).

[0037] (c) A process of transferring the slurry S in the sludge collecting pipe 1 into the sludge lifting pipe 5 (refer to Figure 3 ).

[0038] (d) A process of moving the slurry S to a ship on the sea using the sludge lifting pipe 5 (refer to Figure 4 ).

[0039] As shown in Figure 2 , the (a) process is a process of making the sludge collecting pipe 1 penetrate into the layer L under the sea floor F. The sludge lifting pipe 5 is lowered from the ship in a state where the flow path switching mechanism 7 and the sludge collecting pipe 1 are installed at the front end of the sludge lifting pipe 5, and the front end side of the sludge collecting pipe 1 is made to pierce into the sea floor F. The sludge collecting pipe 1 sinks into the layer L due to its own weight. In order to promote the sinking of the sludge collecting pipe 1, the sea floor pump 9 can be driven to suck sea water in the sludge collecting pipe 1 after the sludge collecting pipe 1 comes into contact with the sea floor F, thereby generating a negative pressure in the sludge collecting pipe 1. Alternatively, the sludge collecting pipe 1 can be made to sink while fluid is sprayed from a plurality of nozzles 1d provided at the front end of the sludge collecting pipe 1 toward the layer L.

[0040] The (b) process is a process of preparing the slurry S in the sludge collecting pipe 1 by desludging the rare earth sludge using the blade 3b (refer to Figure 1 ). The blade 3b is lowered in the sludge lifting pipe 5 in a state of being installed at the front end of the drill pipe 3a, and reaches inside the sludge collecting pipe 1. Sea water is supplied from the ship through the drill pipe 3a, and the blade 3b is rotated and gradually lowered while sea water is sprayed from the opening portion (not shown) of the blade 3b. Thus, the rare earth sludge is desludged in the sludge collecting pipe 1 to become fine particles. The slurry S is prepared in the sludge collecting pipe 1 by desludging the rare earth sludge. The concentration of the slurry S can be adjusted by adjusting the amount of sea water supplied from the ship. Furthermore, the physical properties such as the density of the slurry S are measured by a sensor disposed or dropped into the sludge collecting pipe 1.

[0041] The (c) process is a process of transferring the slurry S in the sludge collecting pipe 1 into the sludge lifting pipe 5 (refer to Figure 3). First, the annular closing mechanism 7a is operated to close the annular portion 5a of the dredge pipe 5 and open the pipeline Ll. In this state, sea water is supplied to the inside of the suction pipe 1 through the drill pipe 3a, and the subsea pump 9 is driven. Thus, the slurry S in the suction pipe 1 is transferred to the dredge pipe 5 through the pipeline Ll. This process is called dredging. In order to raise the slurry S in the suction pipe 1 to the dredge pipe 5, unlike the case where the slurry is raised to a ship on the sea, it is not necessary to increase the pressure in the suction pipe 1, thereby preventing boiling from occurring.

[0042] (d) is a process of transferring the slurry S transferred to the dredge pipe 5 in the process (c) to a ship on the sea (see arrow in FIG. 2). Figure 4 ). The annular portion 5a is maintained in the closed state, and on the other hand, the pipeline Ll is made to be closed. The drill pipe closing valve 7b is operated to form a state where the drill pipe 3a is not communicated with the suction pipe 1. In addition, the gate mechanism 7c is operated to communicate the inside of the drill pipe 3a with the annular portion 5a. In this state, by supplying sea water from the drill pipe 3a, a circulating flow can be generated in the dredge pipe 5, and the slurry S is transferred to the ship through the annular portion 5a (see arrow in FIG. 2). This process is called dredging. Furthermore, the transfer destination of the slurry S is not limited to a ship on the sea, and for example, it can be a treatment facility in the sea or on the sea and on land. Figure 4

[0043] According to the above-described embodiment, since the sludge is separated and the slurry is prepared in the suction pipe 1, the slurry of a concentration suitable for dredging can be stably prepared. In addition, since the sludge is separated in the closed space in the suction pipe 1 in the process (b), disturbance in the sea can be prevented, and environmental load can be reduced. In addition, since the dredging in the process (d) is performed in a state where the dredge pipe 5 is not communicated with the suction pipe 1, the pressure required for the dredging of the slurry S does not affect the pressure in the suction pipe 1, and specifically, boiling can be prevented from occurring.

[0044] The above-described embodiment of the present application has been described in detail, but the present application is not limited to the above-described embodiment. For example, in the above-described embodiment, a case where the slurry S is transferred from the suction pipe 1 to the dredge pipe 5 by the subsea pump 9 is exemplified, but the slurry S in the suction pipe 1 can be raised to the dredge pipe 5 by supplying a displacement material having a density (specific gravity) greater than that of the slurry S to the suction pipe 1.

[0045] In addition, in the above-described embodiment, a case where rare earth sludge is recovered from the seafloor of a deep sea having a water depth of more than 5000 m is exemplified, but the present application can be applied to a shallower sea area (for example, a water depth of 1000 to 3000 m or 3000 to 5000 m).

[0046] Explanation of Reference Numerals

[0047] ​1…mud collecting pipe 1a…cylindrical portion 1b…upper plate 1c…opening 1d…nozzle 3…stirring device 3a…drill pipe 3b…blade 5…mud lifting pipe 5a…annular portion 7…flow path switching mechanism 7a…annular closing mechanism 7b…drill pipe closing valve 7c…gate mechanism 9…subsea pump (pump) 10…recovery system C…depression F…subsea L…layer L1…pipeline

Claims

1. A method for recycling rare earth mud, comprising the following steps: (A) To allow the mud collection pipe to penetrate into the layer beneath the seabed containing rare earth mud; (B) A slurry containing rare earth elements is prepared by dissolving the rare earth mud within the mud collection pipe by rotating a stirring device; and (C) The slurry is transferred using a mud-lifting pipe. The stirring device includes a drill rod, the lower end of which extends into the mud collecting pipe, and the upper end of which extends outside the mud collecting pipe. The mud-lifting pipe extends around the upper end of the drill rod and has a double-pipe structure. It transports the slurry via a circulating flow, which flows through an annular portion of the double-pipe structure formed between the outer surface of the drill rod and the inner surface of the mud-lifting pipe. The method for recycling rare earth mud further includes the following steps: introducing fluid from the inside of the drill rod into the annular portion through an opening in the drill rod facing the inner surface of the mud-lifting pipe, thereby generating the circulating flow.

2. The method for recovering rare earth mud according to claim 1, wherein, Between steps (B) and (C), there is also a step of transferring the slurry in the mud collection pipe to the mud lifting pipe.

3. The method for recovering rare earth mud according to claim 2, wherein, The slurry is transferred by a pump.

4. The method for recycling rare earth mud according to claim 1 or 2, wherein, After the slurry in the mud collecting pipe is transferred to the mud lifting pipe, before step (C), there is a step of switching the mud lifting pipe to a state where it is not connected to the mud collecting pipe.

5. The method for recycling rare earth mud according to claim 1 or 2, wherein, In step (A), fluid is sprayed downward from a nozzle located at the front end of the mud collection pipe while the mud collection pipe is allowed to settle.

6. The method for recovering rare earth mud according to claim 1 or 2, wherein, In process (A), the mud collection pipe is made to be under negative pressure, causing the mud collection pipe to settle.

7. A rare earth mud recycling system, comprising: The mud collection pipe is inserted into the layer beneath the seabed containing rare earth mud. A stirring device extends into the mud collecting pipe and is rotatably connected to it. Within the mud collecting pipe, the rare earth mud is disintegrated by rotation to prepare a slurry containing rare earth mud. A mud-lifting pipe, connected to the mud-collecting pipe, is used to transfer the slurry. The stirring device includes a drill rod, the lower end of which extends into the mud collecting pipe, and the upper end of which extends outside the mud collecting pipe. The mud-lifting pipe extends around the upper end of the drill rod and has a double-pipe structure. It transports the slurry via a circulating flow, which flows through an annular portion of the double-pipe structure formed between the outer surface of the drill rod and the inner surface of the mud-lifting pipe. The drill pipe has an opening facing the inner surface of the mud lifting pipe.

8. The rare earth sludge recycling system according to claim 7, wherein, The rare earth mud recycling system also includes a pump that transfers the slurry in the mud collection pipe to the mud lifting pipe.

9. The rare earth sludge recycling system according to claim 7 or 8, wherein, The rare earth mud recycling system also has a flow path switching mechanism, which is configured to switch between a state in which the mud collecting pipe is connected to the mud lifting pipe and a state in which the mud collecting pipe is not connected to the mud lifting pipe.

10. The rare earth sludge recycling system according to claim 7 or 8, wherein, The rare earth mud recycling system also includes a nozzle located at the front end of the mud collection pipe.

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