MINERAL LIFTING SYSTEM AND MINERAL LIFTING METHOD

Abstract

A mineral lifting system, S includes a seabed working machine 13, having an excavator 131, excavating minerals at a seabed, and a slurry pump 132, sucking in and pumping a solid-liquid mixture of the minerals and seawater, a generator, supplying electric power to the seabed working machine 13 by an electric power cable 12, a main float 20, a mineral lifting pipe 21, conveying the solid-liquid mixture to the main float 20 side, auxiliary floats 22, mounted Co the mineral lifting pipe 21 at predetermined intervals and imparting a buoyancy, and a sorting unit 3, sorting and collecting the minerals from the solid-liquid mixture conveyed to the main float 20 side.

Claims

1. A mineral lifting system comprising: a seabed working machine, capable of being operated to move and having an excavating portion, excavating minerals on a seabed surface or below a seabed, and a pump, sucking in and pumping a solid-liquid mixture containing the minerals obtained by excavating and seawater; an electric power supplying portion, having an electric power cable that supplies electric power to power the seabed working machine; a main float, having a predetermined buoyancy and floated on a sea surface or undersea; a mineral lifting pipe, having a predetermined length, suspended by the main float, connecting the same main float and the pump of the seabed working machine, and at the same time conveying the solid-liquid mixture, sucked in by the pump and containing the minerals and seawater, to the same main float side; auxiliary floats, disposed in large numbers on the suspended mineral lifting pipe at predetermined intervals in a length direction and imparting, at the undersea side, a buoyancy to the same mineral lifting pipe such that the same mineral lifting pipe will not fall off or break due to its own weight; and a mineral sorting portion, sorting and collecting the minerals from the solid-liquid mixture conveyed to the main float side by the mineral lifting pipe.

2. The mineral lifting system according to claim 1, wherein the pump that the seabed working machine has is a slurry pump.

3. The mineral lifting system according to claim 1, comprising: an auxiliary pump that injects a liquid flow of predetermined pressure to a predetermined location of the mineral lifting pipe to assist the conveying of the solid-liquid mixture.

4. The mineral lifting system according to claim 1, comprising: a GPS receiver and a position correcting apparatus, which compares position information, received by the GPS receiver, with a predetermined set position of the mineral lifting system to perform correction of position so as to maintain the set position.

5. The mineral lifting system according to claim 1, comprising: a water feeding/draining apparatus that adjusts the buoyancy of the same main float by feeding water into an interior and draining water to an exterior of the main float.

6. The mineral lifting system according to claim 1, comprising: a working ship; and wherein the working ship has the electric power supplying portion and the mineral sorting portion, and the electric power cable, constituting the electric power supplying portion, and a feed pipe, constituting the mineral sorting portion and receiving the solid-liquid mixture from the mineral lifting pipe, can be disconnected in a state enabling recovery of system operation.

7. The mineral lifting system according to claim 1, comprising: a suspension apparatus, supporting the same mineral lifting pipe, at a portion of the main float to which the mineral lifting pipe is connected, and wherein, at a vicinity of the suspension apparatus, the same mineral lifting pipe is made capable of vibrating within a predetermined range of deflection inside a gap through which the same mineral lifting pipe is passed.

8. The mineral lifting system according to claim 1, wherein the mineral sorting portion includes a wastewater processing apparatus.

9. The mineral lifting system according to claim 1, wherein the wastewater processing apparatus includes a magnetizing apparatus that magnetizes and sorts the minerals.

10. The mineral lifting system according to claim 1, wherein the mineral lifting pipe has a double pipe structure made of steel and a light alloy, a structure, with which a steel pipe is reinforced with carbon fibers, or a structure, with which a peripheral wall is made hollow.

11. (canceled)

12. (canceled)

13. A mineral lifting method wherein a mineral lifting pipe, being suspended by a main float, floated on a sea surface or undersea, and conveying a solid-liquid mixture, containing minerals, excavated at a seabed surface or below the seabed and pulverized, and seawater, to above a sea surface, is imparted at the undersea side, with a buoyancy, such that the mineral lifting pipe will not fall off or break due to its own weight, by auxiliary floats that are disposed in large numbers at predetermined intervals in a length direction.

14. The mineral lifting system according to claim 1, wherein the auxiliary floats are capable of sliding relative to pipe bodies of the mineral lifting pipe and the sliding relative to each other stops upon contact with a flange of a pipe body from below.

15. A mineral lifting system comprising: a seabed working machine, capable of being operated to move and having an excavating portion, excavating minerals on a seabed surface or below a seabed, and a pump, sucking in and pumping a solid-liquid mixture containing the minerals obtained by excavating and seawater; a mineral lifting pipe, having a predetermined length and conveying the solid-liquid mixture, sucked in by the pump of the seabed working machine and containing the minerals and seawater, to above a sea surface; and auxiliary floats, disposed in large numbers on the mineral lifting pipe at predetermined intervals in a length direction and imparting, at the undersea side, a buoyancy to the same mineral lifting pipe such that the same mineral lifting pipe will not fall off or break due to its own weight.

16. A mineral lifting method for preventing a mineral lifting pipe from being broken or dropped off due to the mineral lifting pipe's own load, the mineral lifting pipe conveying a solid-liquid mixture to sea surface, the solid-liquid mixture including minerals and sea water, and the minerals being excavated from seabed surface or below the seabed and pulverized, wherein buoyancy is provided by undersea side to the mineral lifting pipe so that the mineral lifting pipe is not broken or dropped off due to the mineral lifting pipe's own load.

17. A mineral lifting method for preventing a mineral lifting pipe from being broken or dropped off due to the mineral lifting pipe's own load by providing buoyancy to the mineral lifting pipe, the mineral lifting pipe conveying a solid-liquid mixture to sea surface, the solid-liquid mixture including minerals and sea water, wherein the buoyancy is provided by plurality of floats disposed along longitudinal direction of the mineral lifting pipe at a predetermined interval.

18. A mineral lifting pipe conveying a solid-liquid mixture to sea surface, the solid-liquid mixture including minerals and sea water, wherein buoyancy is provided by plurality of floats disposed along longitudinal direction of the mineral lifting pipes at a predetermined interval to prevent the mineral lifting pipe from being broken or dropped off due to the mineral lifting pipe's own load.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0072] FIG. 1 is an explanatory diagram of an embodiment of a mineral lifting system according to the present invention.

[0073] FIG. 2 is a partially-omitted sectional explanatory diagram of a structure that suspends a mineral lifting pipe by means of a main float and auxiliary floats.

[0074] FIG. 3 is a sectional explanatory diagram of a structure of the main float and its vicinity.

[0075] FIG. 4 is an explanatory diagram of a structure of a wastewater processing apparatus included in a working ship used in the mineral lifting system.

[0076] FIG. 5 is a sectional explanatory diagram of a structure of a pipe body that constitutes the mineral lifting pipe used in the mineral lifting system.

[0077] 8 FIG. 6 is a sectional explanatory diagram of another structure of a pipe body that constitutes the mineral lifting pipe used in the mineral lifting system.

[0078] FIG. 7 shows another structure of an auxiliary float, with FIG. 7 (a) being a vertical sectional explanatory diagram and FIG. 7(b) being a sectional explanatory diagram corresponding to A-A.

DESCRIPTION OF EMBODIMENTS

[0079] An embodiment of the present invention shall now be described in further detail with reference to FIG. 1 to FIG. 6.

[0080] A mineral lifting system S includes a mining unit 1, which performs mining of minerals at a seabed, a mineral lifting unit 2, which lifts the mined minerals and seawater to above a sea surface, and a sorting unit 3, which is a mineral sorting portion that sorts valuable minerals from a solid-liquid mixture lifted by the mineral lifting unit 2.

[0081] (Mining Unit 1)

[0082] The mining unit 1 has a seabed working machine 13 that can be externally operated to move. The seabed working machine 13 includes a crawler traveling machine 130, an excavator 131, installed on an upper portion thereof, and a slurry pump 132, which sucks in and pumps the solid-liquid mixture containing the mineral, obtained by excavation, and seawater. The seabed working machine 13 is arranged with a structure capable of working under high pressure at a deep seabed by making respective portions highly watertight, etc. The slurry pump 132, together with respective pressure injection pumps 24 to be described later, constitutes a pump system.

[0083] The excavator 131 is arranged to be capable of pulverizing and excavating minerals of a mineral deposit by rotation or vibration of a drill at a tip. Another structure may be adopted instead for the excavator. The slurry pump 132 is capable of pumping the mixture (solid-liquid mixture) of the excavated and pulverized minerals and seawater and, for example, a diagonal flow type or a mixed flow type may be adopted.

[0084] The slurry pump 132 is not restricted in particular in pumping capability and suffices to have a capability of being able to lift the so lid-liquid mixture of seawater and the pulverized minerals to above the sea surface, at least in cooperation with the pressure injection pumps 24 that are auxiliary pumps to be described later. In this case, for example, a conveying energy from the slurry pump 132 to a lower portion of a mineral lifting pipe 21, to be described later, may be supplied by the slurry pump 132, and a conveying energy inside the mineral lifting pipe 21 further upward may he supplied by the pressure injection pumps 24, which are a plurality of auxiliary pumps to be described later that are provided at intermediate portions of the mineral lifting pipe 21.

[0085] In the seabed working machine 13, an electric power cable 12 arranged to supply electric power to power the crawler traveling machine 130, the excavator 131, and the slurry pump 132, is connected to an electric power receiving portion (symbol omitted). An end portion at a side of the electric power cable 12 above the sea surface is connected once to a float 11 floating on the sea surface and a weight of the electric power cable 12 is thus supported by the float 11. To lighten the weight of the electric power cable 12 applied to the float 11, an auxiliary float that imparts buoyancy may be mounted in the same manner as with the mineral lifting pipe 21 to be described later.

[0086] Electric power from a generator (not shown), which is an electric power supplying portion installed on a working ship 10, which is a mother ship, is arranged to be supplied via an electric power cable 120 to the electric power cable 12 connected to the float 11. Also, a signal cable (not shown), which exchanges signals for performing control of the excavator 131, control of the crawler traveling machine 130, or control of the slurry pump 132 of the seabed working machine 13, etc., with a control portion included in the working ship 10, is installed on the power cables 12 and 120 in a form of being attached thereto.

[0087] (Mineral Lifting Unit 2)

[0088] The mineral lifting unit 2 has the mineral lifting pipe 21. The mineral lifting pipe 21 is formed by connecting a large number of pipe bodies 210 of predetermined length to a length, for example, of 5000 m in correspondence to a depth of a sea area to be subject to mineral lifting work. The structure of each pipe body 210 shall be described in detail later. The long mineral lifting pipe 21 is practically connected to a main float 20 so as to be hung thereon with an upper end side floating on the sea surface. Also, at an undersea side, the mineral lifting pipe 21 is practically connected to auxiliary floats 22 so as to be hung thereon at every predetermined interval in a length direction (at every pipe body 210 in the present embodiment) .

[0089] First, a structure of the main float 20 and a structure connecting the mineral lifting pips 21 to the main float 20 shall be described with reference to FIG. 3.

[0090] The main float 20 has a sealed case 200 with a structure that is watertight and hollow. An outer shape of the sealed case 200 is a so-called donut shape and a space portion 201 is formed in an interior so as to draw a circle in plan view. Also, a through hole 202 of circular hole shape, which is separated by a wall portion from the space portion 201, is provided so as to penetrate through a central portion of the sealed case 200.

[0091] The space portion 201 inside the sealed case 200 is divided into upper and lower portions in a liquid-tight state by a separating member 203 that is fixed across an entire circumference at a substantially middle position in an up/down direction. A water feeding/draining pump 204, which is fixed to the separating member 203 and constitutes a water feeding/draining apparatus, is disposed in an upper space portion 201a. Also, similarly, a battery 205 is disposed that is fixed to the separating member 203, and as the battery 205 in the present embodiment, a waterproof lithium storage battery is adopted and supplies electric power to the water feeding/draining pump 204.

[0092] The battery 205 is connected to a control board 206, and an electric power cable 26 is connected from the exterior to the control board 206. The electric power cable 26 is connected to a generator (not shown), which is an electric power supplying portion installed on a mineral processing ship 30 to be described later, and electric power supplied from the generator is stored in the battery 205.

[0093] A lower space portion 201b, which is divided by the separating member 203 inside the sealed case 200, is a water storage tank, and an arrangement is made so that a water amount (and if necessary an air amount) in an interior of the lower space portion 201b can be adjusted by the water feeding/draining pump 204. By adjustment of the water amount, the main float 20 can be made to float on the sea surface by increasing its buoyancy or can be made to submerge by decreasing the buoyancy as necessary. The submerging may be performed so that just the main float 20 becomes submerged or so that an entirety, including the mineral lifting pipe 21, becomes submerged and a selection can be made as suited.

[0094] A GPS receiver 207, which receives signals from a GPS satellite 27, is installed on an upper surface of the sealed case 200. Electric power is arranged to foe supplied via the electric power cable 26 to the GPS receiver 207 as well. Also, a plurality of propulsion machines 208, which constitute a position correcting apparatus, are mounted to a lower surface of the sealed case 200. Each propulsion machine 208 has a structure by which a propulsive force is obtained by rotating a screw by a motor.

[0095] The arrangement of the position correcting apparatus includes the control board 206, which is a control portion capable of comparing position information, obtained by the GPS receiver, and basis position information, determined in advance, and actuating the respective propulsion machines 208 based on the difference to correct a position. The respective propulsion machines 208 are arranged to be supplied with the electric power from the battery 205, and by suitably combining and driving the respective propulsion machines 208 by automatic control based on GPS, the main float 20 can be moved in a predetermined direction on the sea. surface.

[0096] A pipe body 210 at an upper end portion of the mineral lifting pipe 21 is passed through the through hole 202 of the sealed case 200. Each of the large number of pipe bodies 210 that constitute the mineral lifting pipe 21 has the structure shown in FIG. 5. Each pipe body 210 has connection flanges 211 and 212 at respective ends in a length direction and the pipe portion has a double pipe structure constituted of an inner pipe 213 and an outer pipe 214. A space portion 215 of so-to-speak circular pipe shape, which gives rise to buoyancy to achieve lightweightness, is formed between the inner pipe 213 and the outer pipe 214.

[0097] An outer diameter of the outer pipe 214 of the pipe body 210 is formed to a diameter smaller than an inner diameter of the through hole 202 of the sealed case 200, and a gap 209 is provided between the pipe body 210 and the through hole 202. Also, with the uppermost pipe body 210, the flange 211 (attached after inserting the pipe body 210 through the through hole 202) is at an upper side of the sealed case 200 and a compression coil spring 28, which is made gradually smaller in diameter at an upper portion side, is disposed between the upper surface of the sealed case 200 and the flange 211.

[0098] By the present structure, the pipe body 210 and the large number of other pipe bodies 210 connected therebelow are cushioned by an energizing force of the compression coil spring 28 even upon moving up and down, and impacts and large loads applied to the main float 20 can foe lightened. Also, by an action of the gap 209, the pipe body 210 is made capable of moving freely or swinging within a certain fixed range in an interior of the through hole 202. A flexible supply pipe 25 is connected to an upper end of the pipe body 210 at the upper end portion, and a tip side of the supply pipe 25 is introduced into the sorting unit 3 to be described later.

[0099] As described above, the mineral lifting pipe 21 is arranged by connecting the large number of pipe bodies 210 in watertight manner, and one end portion of a flexible relay pipe 23 of predetermined length is connected to a lower end portion of a lowermost pipe body 210. Another end portion of the relay pipe 23 is connected to a discharge port (symbol omitted) of the slurry pump 132. An intake port (symbol omitted) of the slurry pump 132 is disposed at a vicinity of a drill of the excavator 131 and is made capable of sucking in excavated and pulverized minerals together with seawater.

[0100] As mentioned above, at the undersea side, the long mineral lifting pipe 21 is practically connected at every pipe body 210 to the auxiliary floats 22 in a length direction in a manner such that the upper portion side flanges 211 are hung thereon. Each auxiliary float 22 has a sealed case 220 with a structure that is watertight and hollow. An outer shape of the sealed case 220 is a so-called donut shape and a space portion 221 is formed in an interior so as to draw a circle in plan view. Also, a through hole 222 of circular hole shape, which is separated by a wall portion from the space portion 221, is provided so as to penetrate through a central portion of the sealed case 220.

[0101] An outer diameter of the outer pipe 214 of each pipe body 210 is formed to a diameter smaller than an inner diameter of the through hole 222 of the sealed case 220, and a gap 229 is provided between the pipe body 210 and the through hole 222. Although a specific structure of the auxiliary float 22 is not shown, it is a structure (known structure) that enables installment in a fitting manner onto and detachment from a pipe portion of the pipe body 210 in a lateral direction.

[0102] With the present structure, the large number of auxiliary floats 22 are capable of sliding relative to the respective pipe bodies 210 even when the respective pipe bodies 210 move up and down, and the sliding relative to each other stops when an auxiliary float 22 contacts the flange 211 of a pipe body 210 or contacts an injection pipe 241 of a pressure injection pump 24 to be described below. There is effective mutual clearance between the auxiliary floats 22 and the respective pipe bodies 210 and therefore impacts and large loads are unlikely to act. Also, by an action of the gap 229, each pipe body 210 is made capable of moving freely or swinging within a certain fixed range in an interior of the through hole 202.

[0103] Also, the respective auxiliary floats 22 are capable of imparting a predetermined buoyancy to the mineral lifting pipe 21. This buoyancy may be set, for example, to be the same as a weight of the mineral lifting pipe 21 so that the weight of the mineral lifting pipe 21 is hardly applied to the main float 20. Or, the buoyancy may be set to be slightly less than the weight of the mineral lifting pipe 21 so that the weight of the mineral lifting pipe 21 is applied suitably to the main float 20 and the mineral lifting pipe 21 is more stabilized undersea. An auxiliary float 22 that is positioned in a deep sea may include a rib structure for reinforcement in its interior as in an auxiliary float 22a to be described later so as to withstand high water pressure.

[0104] Injection pipes 241, each connected to a discharge port (symbol omitted) of a pressure injection pump 24, are connected to pipe portions of pipe bodies 210, which, among the pipe bodies 210 constituting the mineral lifting pipe 21, are positioned at predetermined intervals. Each pressure injection pump 24 sucks in seawater in its surroundings and injects it into an interior of the mineral lifting pipe 21 and assists upward conveying (pumping) of the lifted water (solid-liquid mixture) passing through the mineral lifting pipe 21.

[0105] Each pressure injection pump 24 is arranged to be maintained at a predetermined depth by being imparted with a buoyancy of a float 242 connected by a suspending wire 243. Also, electric power is suppled to each pressure injection pump 24 via an electric power cable 240 connected to the generator on the mineral processing ship 30 that is the working ship. A float for imparting buoyancy may also be attached to the electric power cable 240.

[0106] The electric power cable 120, connecting the working

[0107] ship 10 to the float 11, is of a structure enabling disconnection from the float 11. Also, the mineral processing ship 30 is of a structure capable of disconnecting the supply pipe 25 and the electric power cable 26 from the main float 20. By these arrangements, when the working ship 10 and the mineral processing ship 30 are to call at a port, etc., the ships can be made to leave a work site in a state enabling recovery subsequently.

[0108] (Sorting Unit 3)

[0109] The sorting unit 3 is installed on the mineral processing ship 30. The generator (not shown) is installed on the mineral processing ship 30 and this generator supplies electric power to the main float 20 and the respective pressure injection pumps 24. The sorting unit 3 sorts valuable minerals from the solid-liquid mixture of seawater and pulverized minerals lifted by the mineral lifting unit 2.

[0110] FIG. 4 shall now be referenced. A method for processing the solid-liquid mixture, which contains pulverized minerals 50 and has risen inside the mineral lifting pipe 21 and has reached the mineral ore processing ship 30 on the sea surface through the supply pipe 25, shall now be described.

[0111] The sorting unit 3 includes, in the order of processing, a sorting tank 31, a sedimentation tank 32, a water storage tank 33, and a collection tank 34. The sedimentation tank 32, the water storage tank 33, and the collection tank 34 constitute a wastewater processing apparatus.

[0112] The solid-liquid mixture that contains the pulverized minerals 50 is conveyed to the sorting tank 31 from the supply pipe 25. Pulverized minerals 50 that are magnetic materials are magnetized and collected by an electromagnet (symbol omitted) mounted to a tip of an arm of a rotating body 311. Minerals that are not magnetic materials and other valuable minerals are collected by any of various known means, for example, by using a sieve, etc.

[0113] Also, seawater containing sludge, which has passed through the sorting tank 31, is conveyed to the sedimentation tank 32 upon passing through a screen 320 and the sludge sediments to a tank bottom and is thereby separated. The seawater removed of the sludge is conveyed to the water storage tank 33 upon passing through a screen 331 and is conveyed to the subsequent collection tank 34 by a pump 330. Inside the collection tank 34, finer sludge is made to sediment by chemical processing, etc., and is thereby removed, and the clarified seawater after processing is made to pass through a drain pipe 35 and be discharged to the exterior (sea) by a waterwheel 340.

[0114] (Actions)

[0115] Actions of the mineral lifting system s according to the present invention shall now be described by way of a case of performing a process of lifting valuable minerals in the deep sea to above the sea surface as an example.

[0116] As shown in FIG. 1, with the mineral lifting system S, the seabed working machine 13 is disposed at a prescribed deep seabed 4 with a mineral deposit 5 and the main float 20 floats on the sea surface.

[0117] The seabed working machine 13 is operated by signals from a control portion on the working ship 10 and using the electric power supplied via the electric power cable 120 to perform excavation by means of the excavator 131 while moving by means of the traveling machine 130. In parallel to the excavation, the mixture (solid-liquid mixture) of the pulverized minerals 50 (shown in FIG. 4) and seawater is sucked in and pumped upward, from the relay pipe 23 and through the mineral lifting pipe 21, by the slurry pump 132. In this process, energy due to water flows is injected by the large number of pressure injection pumps 24 into a vertical direction path of the mineral lifting pipe 21, the solid-liquid mixture is lifted to the sorting unit 3 on the mineral processing ship 30 at the upper side, and just, the clarified processed water is dumped to the sea.

[0118] Also, the large number of auxiliary floats 22 are connected to the mineral lifting pipe 21 and impart the prescribed buoyancy to the mineral lifting pipe 21. With the mineral lifting system S, a buoyancy that is approximately such that the long mineral lifting pipe 21 of several thousand meters will not drop to the seabed 4 is imparted to the mineral lifting pipe 21 by the main float 20 and the respective auxiliary floats 22. A predetermined number (a large number) of the auxiliary floats 22 are disposed in the length direction of the mineral lifting pipe 21, and therefore the weight of the mineral lifting pipe 21 is sharingly supported according to the pipe bodies 210 by the auxiliary floats 22.

[0119] That is, if when the large number of auxiliary floats 22 are mounted at predetermined intervals in the length direction of the mineral lifting pipe 21, each auxiliary float 22 is made to impart a buoyancy corresponding to just the weight of a length of the mineral lifting pipe 21 between each auxiliary float 22, the load of the long mineral lifting pipe 21 can, in theory, be prevented from acting on an upper portion of the mineral lifting pipe 21.

[0120] By thus making an appropriate buoyancy be imparted by the auxiliary floats 22, a large load in the gravity direction will not act biasedly on a certain portion. The above arrangement is thus also effective in terms of making the load be applied evenly at predetermined intervals in the length direction of the mineral lifting pipe 21. Also by the above, the mineral lifting pipe 21 can be prevented from breaking in the middle due to its own large, load and destruction of a connection portion of a pipe body 210, etc., can be prevented so that a problem of the mineral lifting pipe 21 dropping to the seabed will not occur.

[0121] Although the total buoyancy of the main float 20 and the respective auxiliary floats 22 that float the mineral lifting pipe 21 is set as suited, a buoyancy sufficient to make the uppermost main float 20 float on the seat surface is not necessarily required, and it is preferable for the buoyancy to be such that at least the lower end portion of the mineral lifting pipe 21 can be made buoyant so as to be maintained in a state of not dropping to the seabed, that is, in a state of being adrift undersea without sinking. Also, it is preferable for the buoyancy to be such that can maintain a state where, even if the lower end portion side of the mineral lifting pipe 21 contacts the seabed, at least, a further upper portion side is vertically buoyant undersea.

[0122] The mineral lifting pipe, which is a heavy object, is imparted with buoyancy by the main float and the respective auxiliary floats so that the working ship 10 or the mineral ore processing ship 30 that performs control of the mineral lifting system is not necessarily required to support the mineral lifting pipe, and therefore there is no need to make the ships large.

[0123] Also, while the system is in operation, the practical weight of the mineral lifting pipe 21 will be heavier because the weight of the solid-liquid mixture conveyed through its interior is added thereto. Therefore, the buoyancy provided by the respective floats 2 and 22 must be set in consideration of this point and must not be set on the basis of the weight of the empty mineral lifting pipe 21.

[0124] Also, the main float 20 can be adjusted in buoyancy by adjusting the amount of water in its interior by means of the water feeding/draining pump 204. A portion of the main float 20 can thereby be exposed from the sea surface or the entirety can be sunken below the sea surface, for example, like a submarine. Also, when made to sink, the main float 20 can be adjusted in height (depth) below the sea surface.

[0125] When the main float 20 is sunken below the sea surface, the main float 20 is made less likely to be influenced by waves. For example, if, when the weather is rough, as in a typhoon or when a typhoon approaches, the main float 20 is kept floating on the sea surface, it will receive the influence of violent waves and undergo up/down motion and rolling repeatedly, thereby increasing a possibility of deformation or damage of a mounting portion of the mineral lifting pipe 21 connected to the main float 20 or a peripheral portion thereof.

[0126] Waves at the sea surface occur from several meters to approximately 10 m below the sea. surface in many cases, and therefore if the main float 20 can be maintained, by remote operation, to be buoyant at a deeper position together with an upper portion, of the mineral lifting pipe 21 and floating up of the main float 20 thereafter is made possible, the influence of waves can mostly be avoided even in a typhoon.

[0127] Also the main float 20 includes the GPS receiver 207 and the propulsion machines 208 and a GPS can thus be used to maintain the position of the mineral lifting system S that has been set in advance. That is, the position information, indicating the position of the mineral lifting system, is acquired by the GPS receiver 207 installed on the main float 20, and the position information, which is set in advance and serves as the basis, and the position information acquired by the GPS receiver 207 are compared by means of the position correcting apparatus.

[0128] Then, based on the difference, the position correcting apparatus performs correction of position by actuating the respective propulsion machines 208 so that the position of the main float 20 is maintained at the position (set position) serving as the basis or made to approach (move toward) the position serving as the basis. The correction of position may be performed constantly during the operation of the mineral lifting system S or may be performed at every fixed time interval (intermittently).

[0129] The seabed working machine 13 may he used upon being placed on the seabed in a region that not only has valuable minerals, such as noble metals, rare metals, etc., present on the seabed surface 4 or below the seabed at a water depth, for example, of several thousand meters, but also has large amounts of useful resources, such as methane hydrate (for example, near-surface methane hydrate), which is a fossil fuel, etc. The mineral lifting system S is also usable as a system that lifts such useful resources other than minerals from a deep seabed to above a sea surface.

[0130] FIG. 6 shall now be referenced. FIG. 6 shows another structure of a pipe body that constitutes the mineral lifting pipe used in the mineral lifting system.

[0131] A pipe body 210a has a double pipe structure, with which an outer pipe 214a of an inner pipe 213a, made of steel, is formed integrally front acrylic resin reinforced with carbon fibers. The pipe body 210a is thereby made light in weight and increased in tensile strength. Also, flanges 211a and 212a are provided at respective end portions of the pipe body 210a. By combining the inner pipe 213a, which is made of steel and has sufficient strength, and the lightweight and tough outer pipe 214a, the weight can be suppressed to be equivalent to the pipe body 210 described above while maintaining a prescribed strength.

[0132] FIG. 7 shall now be referenced. An auxiliary float 22a shown in FIG. 7 has a sealed case 220a, formed to be watertight and having an outer shape that is a circular columnar shape. In a space portion 221a in an interior of the sealed case 220a, reinforcing ribs 225, arranged by combining ribs horizontally and vertically, are provided so as to be fixed to an inner surface of the sealed case 220a. The auxiliary float 22a is mounted to the mineral lifting pipe 21 via a coupling member 226. A prescribed buoyancy is thereby imparted to the mineral lifting pipe 21.

[0133] Also, by being provided with the reinforcing ribs 225 in its interior, the auxiliary float 22a can secure the space portion and maintain the prescribed buoyancy without collapsing under deep sea high pressure.

[0134] The terms and expressions used in the present description and the claims are only descriptive, are by no means restrictive, and are not intended to exclude terms and expressions equivalent to features and portions thereof described in the present description and the claims. Also, obviously, various modified modes are possible within a scope of the technical concept of the present invention.

Reference Signs List

[0135] S Mineral Lifting System

[0136] 1 Excavating unit, 10 Working ship, 11 Float,

[0137] 12 Electric power cable, 120 Electric power cable,

[0138] 13 Seabed working machine, 130 Crawler traveling machine,

[0139] 131 Excavator, 132 Slurry pump,

[0140] 2 Mineral lifting unit, 20 Main float, 200 Sealed case,

[0141] 201 Space portion, 201a Upper space portion, 201b Lower space portion,

[0142] 202 Through hole, 203 Separating member, 204 Water feeding/draining pump,

[0143] 205 Battery, 206 Control board,

[0144] 207 GPS receiver, 208 Propulsion machine, 209 Gap,

[0145] 21 Mineral lifting pipe, 210 Pipe body, 211, 212 Flange,

[0146] 213 Inner pipe, 214 Outer pipe, 215 Space portion,

[0147] 210a Pipe body, 211a, 212a Flange, 213a Inner pipe, 214a Outer pipe,

[0148] 22 Auxiliary float, 220 Sealed case, 221 Space portion, 222 Through hole,

[0149] 22a Auxiliary float, 220 a Sealed case, 221a Space, portion,

[0150] 225 Reinforcing rib, 226 Coupling member, 229 Gap,

[0151] 23 Relay pipe, 24 Pressure injection pump, 240 Electric power cable,

[0152] 241 Injection pipe, 242 Float, 243 Suspending wire,

[0153] 25 Supply pipe, 26 Electric power cable, 27 GPS satellite,

[0154] 28 Compression coil spring,

[0155] 3 Sorting unit, 30 Mineral, processing ship, 31 Sorting tank,

[0156] 311 Rotating body,

[0157] 32 Sedimentation tank, 320 Screen, 33 Water storage tank,

[0158] 330 Pump, 331 Screen, 34 Collection tank, 340 Waterwheel,

[0159] 35 Drain pipe

[0160] 5 Mineral deposit, 50 Pulverized minerals