BACKGROUND

The invention relates to a mining system for mining minerals in a deep sea, a method for mining minerals in a deep sea and a mining assembly for use in the sea mining system.

Known deep sea mining systems use a vessel that deploys a self-propelled miner onto the seabed. Such a miner moves along the seabed and collects minerals therefrom. The minerals are stored in a container at the miner and when the container is full the container is or the miner and the container are returned to the vessel to be emptied.

SUMMARY OF THE INVENTION

A disadvantage of the known mining systems is that the miners are affected by the properties of the subsoil when moving along the seabed. The miners can topple over or get stuck.

It is an object of the present invention to provide a deep sea mining system, a method for mining minerals in a deep sea and a mining assembly for use in the sea mining system wherein the mining system is affected less by the subsoil properties of the seabed.

According to a first aspect, the invention provides a mining system for mining minerals from a seabed of a deep sea, wherein the mining system comprises a vessel floating at the water surface and a submerged mining assembly that is suspended from the vessel, wherein the mining assembly comprises a station, at least one first cable that suspends the station from the vessel and that keeps the station above and spaced apart from the seabed, at least one container for shuttling between the station and the vessel, a mining head for mining minerals from the seabed, an intermediate frame that extends between the mining head and the station, wherein the intermediate frame comprises one end that is connected to, preferably hingeably connected to, the station and an opposite end that is connected to, preferably hingeably connected to, the mining head, and a transport arrangement between the mining head and the station for transporting the mined minerals from the mining head into the at least one container, wherein the station, the intermediate frame and the mining head are arranged in series along a longitudinal axis, wherein the mining head comprises a first propulsion arrangement that is configured to move the mining head along the seabed in a direction that is transverse to the longitudinal axis, wherein the mining head comprises a first intake aperture for taking in minerals from the seabed when the mining head is moved in a first intake direction transverse to the longitudinal axis, and a second intake aperture that is opposite to the first intake aperture for taking in minerals from the seabed when the mining head is moved in a second intake direction transverse to the longitudinal axis opposite to the first intake direction, and wherein the mining assembly is configured to switch between a first mode in which the mining head is moved in the first direction by the first propulsion arrangement for taking in minerals through the first intake aperture, and a second mode in which the mining head is moved in the second direction by the first propulsion arrangement for taking in minerals through the second intake aperture.

The mining system according to the invention comprises a mining head that collects minerals in the form of polymetallic nodules from the seabed. The minerals are transported by the transport arrangement from the mining head into a container that is located at the station. The station with the container containing the minerals is suspended from the vessel and is free from the seabed. When the container is full with minerals the container is shuttled to the vessel where it will be unloaded. In the mining system the majority of the weight of the mining assembly and the varying weight of the collected minerals is concentrated in the suspended station. The weight of the mining head that is supported by the seabed is limited to its submerged weight which is relatively low. Due to this low weight the mining head is less prone to topple over or to get stuck as a result of a soft seabed or undulations in the seabed and the mining system therefore is less affected by the seabed properties. The configuration of the intermediate frame allows the mining head to move and tilt with respect to the station while the station hovers at a substantially constant depth. Therefore the mining head can move along the uneven seabed without being hindered by the station. The intermediate frame may also provide support for the transport arrangement.

The mining assembly is moved in a forward mining direction along a notional central mining axis that is substantially parallel to the sailing direction of the vessel. The longitudinal axis is substantially parallel to the central mining axis when viewed from above. The forward movement of the mining assembly is in this example provided by the first propulsion arrangement at the mining head but may also be provided by a propulsion arrangement at the station or at the vessel. As the mining assembly progresses in the mining direction the first propulsion arrangement reciprocatingly moves the mining head in the first intake direction and the second intake direction. Thereby the mining assembly swings around a notional vertical pivot axis and the mining head travels along the seabed along curved mining trajectories that are substantially transverse to the mining direction. The adjacent mining trajectories together form a wide mining track along the central mining axis in the mining direction. By the reciprocating movement of the mining head, the mining track in the mining direction can be wider as compared to a mining assembly that only moves in the mining direction. As a result more minerals can be collected per meter travelled in the mining direction. Alternatively the mining speed in the mining direction can be reduced to collect the same amount of minerals per time unit. Reducing the mining speed results in reduced drag of the mining assembly in the water which may lead to reduced power consumption of the mining system.

In an embodiment the transport arrangement comprises a discharge pipe between the mining head and the station, a return pipe between the mining head and the station, and a pump unit for circulating a fluid through the discharge pipe, via the at least one container, through the return pipe and via the mining head. This arrangement results in a substantially closed hydraulic recirculation loop that transports the minerals from the mining head into the at least one container. As the recirculation loop is substantially closed little sea water from outside the mining head is sucked in during mining so that the flow and swirling of the sea water near the mining head can be kept to a minimum. In this way the transport of the minerals may cause little turbidity near the mining head and thereby may cause little environmental impact. Additionally by keeping the amount of taken in sea water low the power consumption of the mining assembly may be reduced.

In an embodiment the transport arrangement comprises a first discharge valve for controlling the transportation of the mined minerals from the first intake aperture into the at least one container, and a second discharge valve for controlling the transportation of the mined minerals from the second intake aperture into the at least one container, wherein the mining assembly is configured to operate the first discharge valve and the second discharge valve to switch the transport arrangement between the first mode in which the first discharge valve is in an open position to transport the mined minerals from the first intake aperture of the mining head into the at least one container, and the second mode in which the second discharge valve is in an open position to transport the mined minerals from the second intake aperture of the mining head into the at least one container. When the mining head is moved in the first direction, nodules are taken in through the first intake aperture and when the mining head is moved in the opposite second direction nodules are taken in through the second intake aperture. By only using the transportation arrangement at the intake aperture that actually takes in minerals the amount of water that needs to be pumped around may be kept low so that the flow and swirling of the sea water near the mining head can be further reduced. In this way the transport of the minerals may cause even less turbidity near the mining head and thereby may cause even less environmental impact. Furthermore the power consumption of the mining assembly can be further reduced.

In an embodiment the mining assembly is configured to discharge sediment that is associated with the mining of the minerals through the mining head. In this way the sediment may be returned to or close to the seabed in a smooth manner, causing little turbidity and thereby causing little environmental impact.

In an embodiment the transport arrangement comprises a first disposal valve or flush valve for controlling the transportation of sediment that is associated with the mining of the minerals from the at least one container to the first intake aperture, and a second disposal valve or flush valve for controlling the transportation of sediment that is associated with the mining of the minerals from the at least one container to the second intake aperture, wherein in the first mode the second disposal valve is in an open position to discharge sediment that is associated with the mining of the minerals through the second intake aperture of the mining head, and in the second mode the first disposal valve is in an open position to discharge sediment that is associated with the mining of the minerals through the first intake aperture of the mining head. When the mining head is moved in the first direction nodules are taken in through the first intake aperture and sediment may be discharged through the second intake aperture, when the mining head is moved in the opposite second direction nodules are taken in through the second intake aperture and sediment may be discharged through the first intake aperture. In this way the sediment may be discharged during mining of the minerals using the transport arrangement that is also used for the mining of the minerals, whereby a separate transport arrangement for the sediment may not be necessary.

In an embodiment the mining assembly is configured to discharge sediment that is associated with the mining of the minerals in dependency of the concentration of the accumulated sediment in the transport arrangement. In this way the amount of sediment in the process flow may be kept at the optimal value for the mining process.

In an embodiment the mining head comprises at least one dislodging arrangement for mechanically dislodging the minerals from the seabed. By firstly mechanically dislodge the minerals from the seabed, and secondly transport the minerals when the minerals are inside the mining head, as little as possible sediment is taken in during mining of the minerals.

In an embodiment the mining head comprises at least one mining box that is moveably suspended from the mining head. In an embodiment the mining box is rotatable with respect to the mining head around a first mining box rotation axis that is orientated transverse to the longitudinal axis. In an embodiment the mining head comprises at least one pair of mining boxes. In an embodiment the mining boxes of the pair of mining boxes are rotatably connected to each other. In an embodiment the mining boxes of the pair of mining boxes are rotatable with respect to each other around a second mining box rotation axis that is orientated transverse to the first mining box rotation axis. In an embodiment the mining head comprises multiple pairs of mining boxes, and each pair of mining boxes is moveably suspended from the mining head independently of the other pairs of mining boxes. The mining boxes slide separately over the mud of the seabed and will therefore allow for expected seabed undulations.

In an embodiment the intermediate frame is hingeable with respect to the station around a first hinge axis and the mining head is hingeable with respect to the intermediate frame around a second hinge axis, wherein the first hinge axis and the second hinge axis are orientated perpendicular to the longitudinal axis. This configuration allows the mining head to move and rotate with respect to the station in limited directions which makes the relative motions of the mining head with respect to the station better controllable.

In an embodiment the first hinge axis and the second hinge axis are orientated parallel to each other. In an embodiment the first hinge axis is orientated horizontally. This configuration allows the mining head to move upwards and downwards and to rotate forwards and backwards with respect to the station while it prevents the mining head to move and rotate sideways with respect to the station. Therefor the station provides additional stability to the mining head.

In an embodiment the first propulsion arrangement is configured to move the mining head along the seabed in a direction that is parallel to the longitudinal axis. The first propulsion arrangement moves the mining assembly in the forward mining direction along the notional central mining axis. By using the same propulsion arrangement for the movement of the mining head in the mining direction and in the the first and second intake directions the mining assembly can be kept simple and robust.

In an embodiment the first propulsion arrangement comprises an archimedes screw. Archimedes screw propulsion systems have proven to be robust and can be configured to move the mining head along the seabed in multiple directions.

In an embodiment the station comprises a second propulsion arrangement that is configured to move the station in a direction that is transverse to the longitudinal axis. The second propulsion arrangement can keep the mining assembly, more specifically the station, substantially right below the vessel by propelling the station back towards the central mining axis when the station deviates therefrom.

In an embodiment the mining assembly comprises at least one container cable that suspends the at least one container from the vessel, and a cable cursor frame that is arranged along the at least one first cable and the at least one container cable, wherein the cable cursor frame comprises cable guides for the at least one first cable and the at least one container cable, and wherein the cable cursor frame is arranged to shuttle with the at least one container between the station and the vessel. In an embodiment the mining assembly comprises a first container and a second container for alternately shuttling between the station and the vessel, wherein the cable cursor frame comprises container clamps for alternately engaging the cable cursor frame with the first container and with the second container. While being shuttled the cable cursor frame guides the first cables, the container cables and the umbilical cable, and therewith reduces the chance of entanglement thereof. According to a second aspect, the invention provides a method for mining minerals from a seabed of a deep sea by means of a mining system, wherein the mining system comprises a vessel floating at the water surface and a submerged mining assembly that is suspended from the vessel, wherein the mining assembly comprises a station, at least one first cable that suspends the station from the vessel and that keeps the station above and spaced apart from the seabed, at least one container for shuttling between the station and the vessel, a mining head for mining minerals from the seabed, an intermediate frame that extends between the mining head and the station, wherein the intermediate frame comprises one end that is connected to, preferably hingeably connected to, the station and an opposite end that is connected to, preferably hingeably connected to, the mining head, and a transport arrangement between the mining head and the station for transporting the mined minerals from the mining head into the at least one container, wherein the station, the intermediate frame and the mining head are arranged in series along a longitudinal axis, wherein the mining head comprises a first propulsion arrangement that is configured to move the mining head along the seabed in a direction that is transverse to the longitudinal axis, wherein the mining head comprises a first intake aperture for taking in minerals from the seabed when the mining head is moved in a first intake direction transverse to the longitudinal axis, and a second intake aperture that is opposite to the first intake aperture for taking in minerals from the seabed when the mining head is moved in a second intake direction transverse to the longitudinal axis opposite to the first intake direction, and wherein the mining assembly is configured to switch between a first mode in which the mining head is moved in the first direction by the first propulsion arrangement for taking in minerals through the first intake aperture, and a second mode in which the mining head is moved in the second direction by the first propulsion arrangement for taking in minerals through the second intake aperture, wherein the method comprises positioning the vessel at a deep sea location that comprises minable minerals at the seabed, lowering the mining assembly into the sea, wherein the station remains suspended from the vessel and spaced apart from the seabed while the mining head is placed on the seabed, by the first propulsion arrangement moving the mining head along the seabed in a direction that is transverse to the longitudinal axis, by the first intake aperture taking in minerals from the seabed when the mining head is moved in the first intake direction, by the second intake aperture taking in minerals from the seabed when the mining head is moved in the second intake direction, by the transport arrangement transporting the mined minerals from the mining head into the at least one container, and shuttling the at least one container between the station and the vessel.

The method and its embodiments relate to the practical implementation of the mining system according to any one of the aforementioned embodiments and thus have the same technical advantages. In particular, the configuration of the intermediate frame allows the mining head to move and tilt with respect to the station while the station hovers at a substantially constant depth. Therefore the mining head can, during the mining of the minerals, move along the uneven seabed without being hindered by the station. The intermediate frame may also provide support for the transport arrangement.

According to a third aspect, the invention provides a mining assembly for use in a mining system or for use in a method as described above.

The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:

Figure 1A is an isometric side view of a mining system comprising a mining assembly according to an embodiment of the invention;

Figure IB is a top view of a vessel of the mining system;

Figure 1C is a schematic side view of the mining system with the mining assembly shown in its operative lowered position;

Figure 2A is an isometric side view of the operational mining assembly as shown in figure 1C;

Figure 2B is an isometric close up of a mining head of the mining assembly as shown in figure 2A; Figure 3A is a schematic top view of the mining head of figure 2B;

Figures 3B and 3C are a schematic side view of the mining head of figure 3A;

Figures 3D and 3E are a schematic sectional view of the mining head of figures 3B-C;

Figure 4 is a schematic top view of a cable cursor frame of the mining assembly; and

Figures 5A, 5B and 5C are a schematic top view of the mining assembly and show respective steps of the mining process.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1A, IB and 1C show a mining system 10 according to an embodiment of the invention. The mining system 10 comprises a mining vessel 11 that floats in a deep sea 1, having a depth D between the water surface 2 and the seabed 3. In this application by deep sea 1 a sea having a depth D that is greater than the depth D where conventional dredgers, such as trailing suction hopper dredgers, operate in. Conventional dredgers operate in depths D up to approximately 150 meter whereas the mining system 10 typically operates in depths D of 1000 meter, 2000 meter, 3000 meter, 4000 meter, 5000 meter or more. Minerals in the form of polymetallic nodules 5 lie on the seabed 3 or are partially or completely buried in the seabed 3 by sediment. The nodules 5 comprise a high amount of specific metals, such as manganese, nickel, copper or cobalt. Such nodules 5 are typically located in the Central Pacific and are minable.

The mining vessel 11 comprises a hull 12 floating at the level of the water surface 2, a deck 13, a main cabin or accommodation 14 and multiple cargo holds 15. The mining vessel 11 supports on its deck 13 a main suspension 20 and an auxiliary suspension 30 that are embodied as A- frames or derricks. The mining system 10 comprises a mining assembly 100 that is suspended from the main suspension 20 and the auxiliary suspension 30. The mining assembly 100 comprises a station 110, first cables 101 that suspend the station 110 from the main suspension 20, a mining head 130, a second cable 131 that suspends the mining head 130 from the auxiliary suspension 30, an elongate intermediate frame 150 that extends between and is hingeably attached to the station 110 and to the mining head 130, a first skip or container 111a and a second skip or container 111b that alternately shuttle between the station 110 and the vessel 11, and container cables 102 that suspend the containers 111a,b from the main suspension 20. The containers 111a,b are guided by the first cables 101. The cables 101, 102, 131 may be steel cables or synthetic cables. Synthetic cables are applied when working in greater depths D as the aggregated weight of steel cables can become very high in these conditions. Figure IB is a top view of the vessel 11. The first cables 101, the second cables 131 and the container cables 102 are guided through one or more pairs of sheaves 17 to winches 16 that are located at the vessel 11. The winches 16 are operable to lower and raise the mining assembly 100 with respect to the suspensions 20, 30 by paying out and hoisting up the long cables 101, 102, 131.

Not shown motion compensation systems compensate for the influence of the ship motions on the cables 101, 102, 131 in order to keep the station 110 at a substantially constant height with respect to the seabed 3. The motion compensation systems in combination with the winches 16 also compensate for the varying loaded weight of the nodules 5 in the containers 111a,b and the resulting fluctuation of the length of the long cables 101, 102, 131.

The motion compensation system may be a heave compensation system or a constant tension system and may be a stand alone system or a system that is incorporated into the winches 16. The winches 16, the mining system 10 and the motion compensation system are powered and controlled by a not shown power supply unit and a control unit that are located at the vessel 11.

The entire mining assembly 100 is movable with respect to the vessel 11 between an inoperative raised position in which the mining assembly 100 is raised above the water surface 2, preferably with the bottom part of the containers 111a,b raised above the deck 13, and an operative lowered position in which the station 110 is positioned near and spaced apart from the seabed 3 over a distance E of 1-50 meters, and the mining head 130 rests on the seabed 3. The vessel 11 comprises a not shown propulsion arrangement that moves the vessel 11 in a sailing direction. The mining head comprises 130 a first propulsion arrangement 144 that, in the lowered position, moves the mining assembly 100 step-by-step along the seabed 3 in a forward mining direction M along a notional central mining axis P that is substantially parallel to the sailing direction of the vessel 11 and that is substantially right below the vessel 11. Between each forward step the first propulsion arrangement 144 reciprocatingly moves the mining head 130 along the seabed 3 in a direction that is orientated substantially transverse to the mining direction M. The mining assembly 100 thereby swings around a notional vertical pivot axis C that in this example passes through the station 110, more specifically through the end of the station 110 that is opposite to the mining head 130. The mining head 130 travels along the seabed 3 along a curved mining trajectory. The first propulsion arrangement 144 is described in more detail hereafter.

As best shown in figure 2A the station 110 comprises a container frame 112 that determines circular container holes 120 that correspond to and that fit securely around the containers 111a,b. The station 110 comprises two container frame members 108 that protrude horizontally from the container frame 112 at the end thereof at the intermediate frame 150, and a second propulsion arrangement 109 that is attached to the container frame 112 at the end opposite to the intermediate frame 150. The second propulsion arrangement 109 comprises a thruster 103 that is arranged so that the propulsion direction of the thruster 103 is parallel to the seabed 3 and transverse to the mining direction M. Therefore the thruster 103 can keep the station 110 above and aligned with the central mining axis P by propelling the station 110 back towards the central mining axis P when the station 110 deviates therefrom. Additionally the second propulsion arrangement 109 can adjust the heading of the mining assembly 100 by using the thruster 103 to rotate the station 110 in a swivel or rotation direction F around the mining head 130.

As best shown in figures 2A and 4 the containers 111a,b are in this embodiment cylindrically shaped and are tapered towards the bottom. Each container 111a,b defines a top opening 113 at its top, and a smaller bottom opening 114 at its tapered bottom. The top opening 113 is covered and closed off by a lid 115 that has a filling hole 105 and a return hole 106, and the bottom opening 114 is provided with a dump valve 117 to open and close the bottom opening 114. A container flange 118 extends perpendicularly from the circumference of the container 111a,b at the top thereof. The top of the container frame 112 supports the container flange 118, and the container 111a,b sits inside the container holes 120.

The container cables 102 are attached to the top of the container flange 118 at opposite sides of the top opening 113. The container flange 118 is provided with two cable holes 119 at opposite sides of the top opening 113. The first cables 101 pass through the cable holes 119. The containers 111a,b are movable with respect to the station 110 by paying out and hoisting up the container cables 102 while the containers 111a,b are guided by and move along the first cables 101. The containers 111a,b may be additionally or alternatively guided by, for instance, a thruster that is provided on each container 111a,b, wherein the thruster is arranged to move the container 111a,b with respect to the seabed 3 or station 110 while suspended by the container cables 102.

As best shown in figure 2A the station 110, the intermediate frame 150 and the mining head 130 are arranged in series along a longitudinal axis Q of the intermediate frame 150. The intermediate frame 150 comprises an elongate first frame section 151 that is hingeably connected to the station 110 and a second frame section 170 that is at one end rotatably connected to the first frame section 151 and that at the opposite end is hingeably connected to the mining head 130. The first frame section 151 and the second frame section 170 extend along the common longitudinal axis Q. As the station 110 and the mining head 130 are hingeable with respect to the intermediate frame 150, the station 110 and the mining head 130 may have an angled orientation with respect to the longitudinal axis Q of the intermediate frame 150. It is to be understood that, also with the angled orientation, the station 110, the intermediate frame 150 and the mining head 130 are meant to be arranged in series.

The first frame section 151 comprises two substantially parallel top members 152, a bottom member 153 that is parallel to the top members 152, multiple connecting members 154 that connect the top members 152 and the bottom members 153, and at the end near the mining head 130 a tube shaped first collar 164 that is attached to the top members 152 and the bottom member 153 in the extension thereof.

The second frame section 170 comprises a tube shaped second collar 171, two arms 172 that extend obliquely from the second collar 171 at opposite sides thereof and that bend to an orientation parallel to the second collar 171, and tubular beams 173 that space apart the arms 172 from the second collar 171.

The intermediate frame 150 comprises a turning gland 165 between the first collar 164 of the first frame section 151 and the second collar 171 of the second frame section 170. The turning gland 165 allows the first frame section 151 and the second frame section 170 to rotate around the common longitudinal axis Q with respect to each other over a limited rotation stroke.

As best shown in figure 2B the mining head 130 comprises a mining head frame 132 having a U-shaped main support beam 133 that is orientated substantially parallel to the seabed 3, and struts 134 that are attached to the main support beam 133 and that bridge the space between the legs of the U-shaped main support beam 133. The struts 134 form a framework that is partially raised with respect to the main support beam 133 and the seabed 3. The struts 134 provide rigidity to the mining head frame 132 and provide protection for the mining head 130. A three leg sling 135 connects the second cable 131 to the mining head frame 132.

As best shown in figure 2A the intermediate frame 150 comprises a first hinged connection 156 between the top members 152 of the first frame section 151 and the container frame members 108 of the station 110. The first hinged connection 156 allows the first frame section 151 to hinge with respect to the station 110 around a first hinge axis A that is orientated transverse to the longitudinal axis Q of the first frame section 151, and that is orientated substantially parallel to the seabed 3 or substantially horizontal.

The intermediate frame 150 comprises a second hinged connection 175 between the arms 172 of the second frame section 170 and the legs of the U-shaped main support beam 133 of the mining head 130. The second hinged connection 175 allows the mining head 130 to hinge with respect to the second frame section 170 around a second hinge axis B that is orientated transverse to the longitudinal axis Q of the second frame section 170 and substantially parallel to the seabed 3.

The configuration of the station 110, the intermediate frame 150 and the mining head 130, as described above, ensures that the intermediate frame 150 spaces apart the mining head 130 from the station 110. The first hinged connection 156 and the second hinged connection 175 allow the mining head 130 to move upwards and downwards and to rotate forwards and backwards with respect to the station 110. The turning gland 165 allows limited sideways rotation or heel of the mining head 130 with respect to the station 110. The angle over which the turning gland 165 allows the second frame section 170 to rotate with respect to the first frame section 151 over the limited stroke is maximal plus or minus 30 degrees from the center position, in which the first hinge axis A and the second hinge axis B are parallel. This makes the limited total stroke 60 degrees. Preferably the angle over which the turning gland 165 allows the second frame section 170 to rotate with respect to the first frame section 151 is maximal plus or minus 20 degrees from the center position, which makes the total limited stroke 40 degrees.

The mining assembly 100 comprises a discharge pipe 50 and a return pipe 51 that extend through the intermediate frame 150 between the station 110 and the mining head 130, and a pump unit 52 that is, in this example, integrated in the discharge pipe 50. The pump unit 52 may also be integrated in the return pipe 51 or in the mining head 130. The discharge pipe 50, the return pipe 51 and the pump unit 52 are part of a transport arrangement that transports the mined minerals from the mining head 130 into the containers 111a,b. The functioning of the transport arrangement at the mining head 130 and at the station 110 is described in more detail hereafter.

As best shown in figures 2B and 3A-E, in this example, the first propulsion arrangement 144 comprises a pair of parallel archimedes screws 140 that are powered to rotate about their longitudinal center axis. The archimedes screws 140 are attached to the underside of the mining head frame 132 and are orientated parallel to each other transverse to the mining direction M of the mining assembly 100. The two archimedes screws 140 comprise cylinders 141, helical flanges 142 that are provided around the outer surface of the cylinders 141, endcaps 143 at each longitudinal end of the cylinders 141, and not shown drive units for rotationally driving the cylinders 141 around the longitudinal axis thereof with respect to the endcaps 143. The archimedes screws 140 are attached to the mining head frame 132 by spacers 136 that are positioned between the endcaps 143 and the main support beam 133 of the mining head frame 132. The archimedes screws 140 are positioned below and are orientated transverse to the legs of the U- shaped main support beam 133.

The archimedes screws 140 provide traction to move the mining head 130 along the seabed 3. When the archimedes screws 140 are co-rotated in corresponding first rotation directions the mining head 130 is moved forwards in the mining direction M substantially parallel to the longitudinal axis Q when looked at from above, when the archimedes screws 140 are co-rotated in corresponding reversed rotation directions the mining head 130 is moved backwards in the mining direction M, when the archimedes screws 140 are counter-rotated in opposite rotation directions the mining head 130 is moved in a first intake direction R substantially transverse to the longitudinal axis Q when looked at from above, and when the archimedes screws 140 are counter-rotated in reversed opposite rotation directions the mining head 130 is moved in a second intake direction S opposite to the first intake direction R.

It is to be understood that the first propulsion arrangement 144 may comprise other or additional propulsion systems such as continuous tracks, wheels, thrusters, propellers or combinations thereof. The station 110 may also comprise a propulsion arrangement to move the mining assembly 100 along the mining direction M and to therewith move the mining head 130 along the seabed 3 substantially parallel to the longitudinal axis Q. This propulsion arrangement may comprise thrusters or propellers.

The mining head 130 comprises multiple pairs of mining boxes 200a,b that are located between the archimedes screws 140 and that are are arranged side by side along the mining direction M. In the figures the mining boxes 200a,b are shown in a simplified schematic manner. The arrangement and the functioning of the mining boxes 200a,b is explained in more detail hereafter.

As schematically shown in figures 3A-E, in this example, the mining head 130 comprises four pairs of mining boxes 200a,b. Each mining box 200a,b is moveably connected to the mining head frame 132 by, in this example, a pair of steel suspension cables 201. Each pair of suspension cables 201 has a V-configuration as the suspension cables 201 thereof are connected to the leg of the main support beam 133 spaced apart from each other over a distance that is approximately equal to the width of the mining box 200a,b, and are connected to the mining box 200a,b at a joint suspension point 202. The V-configuration prevents the mining box 200a,b from swinging with respect to the mining head frame 132 in the mining direction M.

The two pairs of suspension cables 201 of each pair of mining boxes 200a,b are orientated obliquely downwards and towards each other. This configuration prevents the pair of mining boxes 200a,b from swinging with respect to the mining head frame 132 transverse to the mining direction M. The two point suspension of each pair of mining boxes 200a,b allows the mining boxes 200a,b to rotate with respect to the mining head frame 132 around a first mining box rotation axis L. The first mining box rotation axis L passes through the suspension points 202 of the pair of mining boxes 200a,b and is orientated substantially transverse to the longitudinal axis Q of the mining assembly 100.

Each pair of mining boxes 200a,b comprises a starboard first mining box 200a, a port side second mining box 200b and a hinged mining box connection 203 that hingeably connects the first mining box 200a and the second mining box 200b. The hinged mining box connection 203 allows the mining boxes 200a,b to rotate with respect to each other around a central second mining box rotation axis K that is orientated substantially transverse to the first mining box rotation axis L.

Figures 3D and 3E are a schematic sectional view of the mining head 130 along section line A-A' as indicated in figures 3B and 3C. The mining boxes 200a,b comprise a bottom wall 211, a top wall 212, a back wall 213, a front wall 214 and two sidewalls 215 that together form a prismatic hollow box. The mining boxes 200a,b comprise an intake aperture 216a,b between the bottom wall 211, the front wall 214 and the side walls 215. The first intake aperture 216a of the first mining box 200a and the second intake aperture 216b of the second mining box 200b each face away from the longitudinal axis Q at opposite sides thereof. The first intake aperture 216a and the second intake aperture 216b therefore face away from each other. The mining boxes 200a,b comprise a dislodging arrangement at the intake apertures 216a,b, in this example in the form of dislodging teeth 217 that are arranged along the bottom wall 211 at the intake apertures 216a,b.

In this example the mining boxes 200a,b comprise a guide wall that extends from the top wall 212 parallel to the back wall 213, a discharge opening 218a,b in the top wall 212 between the back wall 213 and the guide wall 224, a flush opening 219a,b in the front wall 214 near the intake aperture 216a,b, a discharge valve 222a,b at the discharge openings 218a,b, and a disposal valve or flush valve 223a,b at the flush opening 219a,b. The mining head 130 comprises a flexible first discharge tube 220a between the first discharge opening 218a of the first mining box 200a and the discharge pipe 50, a flexible first flush tube 221a between the first flush opening 219a of the first mining box 200a and the return pipe 51, a flexible second discharge tube 220b between the second discharge opening 218b of the second mining box 200b and the discharge pipe 50, and a flexible second flush tube 221b between the second flush opening 219b of the second mining box 200b and the return pipe 51. It is to understood that the mining boxes 200a,b are represented schematically and that the mining boxes 200a,b may be embodied in a different manner. For instance, the mining boxes 200a,b may comprise an additional pump near the flush opening 219a,b, the discharge valves 222a,b and the flush valves 223a,b may be arranged at another location, or the discharge openings 218a,b and the flush openings 219a,b extend along the width of the mining boxes 200a,b.

As best shown in figure 2A, the station 110 comprises a first brace 107a and a second brace 107b that are attached to one side of the container frame 112. The braces 107a,b support a filling arrangement 121 that comprises a flexible first filling tube 122a, a flexible second filling tube 122b, a flexible first return tube 123a, and a flexible second return tube 123b. The first filling tube 122a extends between the discharge pipe 50 and the first filling hole 105a of the first container 111a, the second filling tube 122b extends between the discharge pipe 50 and the second filling hole 105b of the second container 111b, the first return tube 123a extends between the return pipe 51 and the first return hole 106a of the first container 111a, and the second return tube 123b extends between the return pipe 51 and the second return hole 106b of the second container 111b. The first brace 107a is operable to move the distal ends of the first filling tube 122a and the first return tube 123a between a filling position wherein these are positioned above the first container 111a at the holes 105a, 106a of the lid 115 to fill the first container 111a, and a shuttling position wherein these are positioned outside the profile of the first container 111a as seen in top view. The second brace 107b is operable to move the distal ends of the second filling tube 122b and the second return tube 123b with respect to the second container 111b in the same manner. The filling arrangement 121 comprises not shown filling valves and return valves which are arranged to switch a process flow between the first container 111a and the second container 111b.

An umbilical cable 104 is connected between the mining assembly 100 and the power supply unit and the control unit on the vessel 11 to provide power and control to, amongst others, the drive units of the archimedes screws 140, the pump unit 52, the discharge valves 222a,b, the flush valves 223a,b, the filling valves, the return valves, and the thruster 103.

As best shown in figures 1A and IB the vessel 11 is provided with a distribution arrangement 40 to distribute the mined nodules 5 to the cargo holds 15. In this example the distribution arrangement 40 comprises collectors 41 that collect the mined nodules 5 from the containers 111. The collectors 41 are supported by longitudinal collector support frames 42 that are orientated parallel to the deck 13 and substantially perpendicular to the longitudinal direction of the vessel 11. The collector support frames 42 are individually movable between an inboard position in which the collectors 41 are located on the deck 13 of the vessel 11 and an outboard position in which the collectors 41 are located below the containers 111 outboard the vessel 11 to receive the nodules 5. The collector support frames 42 hold first conveyors 43 that, in the outboard position, receive the nodules 5 from the collectors 41 and transport them to a second conveyor 44. The second conveyor 44 is positioned on deck 13 level substantially along the longitudinal center line of the vessel 11 and transports the nodules 5 from the first conveyors 43 to third conveyors 45 at the cargo holds 15. The third conveyors 45 transport the nodules 5 from the second conveyor 44 and deposit them in the cargo holds 15.

Figure 4 shows a cable cursor frame 230 of the mining assembly 100. The cable cursor frame 230 is in this example M-shaped, and comprises a main beam 231 and three leg beams 232 that protrude transversely from the main beam 231. When both containers 111a,b sit inside the container holes 120 of the station 110, the cable cursor frame 230 rests on the container flanges 118 of the containers 111a,b. The main beam 231 is arranged at the side opposite to the braces 107a,b of the station 110, the leg beams 232 extends towards the opposite side of the containers 110a,b outside the top openings 113 of the containers 111a,b when looked at from above.

The cable cursor frame 230 comprises cable guides 234 for the first cables 101 of the station 110, for the container cables 102 and for the umbilical cable 104. Furthermore the cable cursor frame 230 comprises two sets of three container clamps 235 that are arranged to engage with the container 111a,b, more specifically to engage with the container flange 118. The three container clamps 235 of each set are uniformly distributed around the perimeter of a respective container 111a,b.

The minerals in the form of polymetallic nodules 5 are mined after sailing the vessel 11 to a deep sea 1 location that comprises minable nodules 5 at the seabed 3. When the vessel 11 is at its position the mining assembly 100 is lowered from its raised position to its lowered position in which the station 110 is positioned to remain near and spaced apart from the seabed 3. Subsequently the mining head 130 is lowered with respect to the station 110 onto the seabed 3 by the second cable 131 and the pump unit 52 of the transport arrangement is switched on.

As shown in figure 5A, subsequently the archimedes screws 140 of the first propulsion arrangement 144 move the mining head 130 in the first intake direction R along the seabed 3 along a curved first mining trajectory. The mining assembly 100 swings around the notional vertical pivot axis C substantially parallel to the seabed 3. As shown in figure 5B, when the mining head 130 has reached the end of an intake stroke the mining assembly 100 is moved a step forward in the mining direction M by the archimedes screws 140. As shown in figure 5C, subsequently the archimedes screws 140 move the mining head 130 in the second intake direction S along the seabed 3 along a curved second mining trajectory that is adjacent to the first mining trajectory. At the end of the second intake stroke the mining assembly 100 is moved a step forward in the mining direction M by the archimedes screws 140 and the archimedes screws 140 of the first propulsion arrangement 144 move the mining head 130 in the first intake direction R again and the swinging sequence of the mining assembly 100 starts over again. The Archimedes screws thus move the mining assembly 100 step-by-step along the seabed 3 in the forward mining direction M along the notional central mining axis P. The adjacent mining trajectories together form a wide mining track in the mining direction M. When the mining head 130 moves along the seabed the thruster 103 of the second propulsion arrangement 109 keeps the station 110 above and aligned with the notional central mining axis P by propelling the station 110 back towards the central mining axis P when the station 110 deviates therefrom. The station 110 hovers while the mining head 130 follows the undulations of the seabed 3 and the vessel 11 follows the mining assembly 100. The length of the cables 101, 102, 131 between the vessel 11 and the mining assembly 100 allows for leeway therebetween in the horizontal direction.

The mining boxes 200a,b slide with their bottom walls 211a,b on the seabed 3. The hinged mining box connections 203 allow the mining boxes 200a,b to rotate with respect to each other around the central second mining box rotation axis K so that the mining boxes 200a,b can follow undulations of the seabed 3 transverse to the mining direction M. The two point suspensions of each pair of mining boxes 200a,b allow the mining boxes 200a,b to rotate around the second mining box rotation axes L so that the mining boxes 200a,b can follow undulations of the seabed 3 parallel to the mining direction M. The first hinged connection 156 and the second hinged connection 175 allow the mining head 130 to move upwards and downwards and to rotate forwards and backwards with respect to the station 110 so that the mining head 130 can follow bigger undulations of the seabed 3. When the mining head 130 encounters an obstruction on the seabed 3 it may be lifted over the obstruction by the second cable 131 while the station 110 remains at the same depth.

As the mining assembly 100 is submerged, the mining boxes 200a,b, the containers 111a,b, the discharge pipe 50, the return pipe 51 and the associated tubes 122a,b, 123a,b, 220a,b, 221a,b, are filled with sea water. The pump unit 52 sucks the sea water through the discharge pipe 50 and therewith establishes a process flow within a substantially closed hydraulic recirculation loop that runs through the discharge pipe 50, the filling tubes 122a,b, the containers 111a,b, the return tubes 123a,b, the return pipe 51, the flush tubes 221a,b, the flush openings 219a,b, the mining boxes 200a,b, the discharge openings 218a,b, and the discharge tubes 220a,b, back into the discharge pipe 50.

When the mining head 130 is moved in the first intake direction R the transport arrangement is switched into a first intake mode in which the first discharge valve 222a and the first flush valve 223a of the first mining box 200a are switched in an open position and the second discharge valve 222b and the second flush valve 223b of the second mining box 200b are switched in a closed position. The process flow passes through the first mining box 200a. By the motion of the first mining box 200a with respect to the seabed 3 the dislodging teeth 217 mechanically dislodge the encountered nodules 5. The dislodging teeth 217 are spaced apart such that the majority of the nodules 5 cannot pass between two adjacent teeth 217 and therefore the nodules 5 are raked from the seabed 3 while entraining as little sediment as possible. Subsequently the loose nodules 5 enter the first mining box 200a through the first intake aperture 216a.

Inside the first mining box 200a the nodules 5 are flushed further towards the back wall 213 by the process flow. The first flush opening 219a is arranged close to the first mining aperture 216a to optimize the initial flushing of the mined nodules 5. As mentioned above the mining boxes 200a,b may comprise an additional pump near the flush opening 219a,b to boost the process flow. The boosted process flow may further aid in the initial flushing of the mined nodules 5, especially when heavy nodules 5 are mined or when nodules 5 are mined in high quantities. The nodules 5 are subsequently sucked from the back of the first mining box 200a through the discharge pipe 50. The guide wall 224 inside the mining boxes 200a,b is so arranged that the process flow that passes between the back wall 213 and the guide wall 224 towards the first discharge opening 218a has sufficient energy and/or velocity to carry the nodules 5 from the first mining box 200a into the first discharge tube 220a. In this example the process flow, comprising the mined nodules 5, sea water and sediment, is hydraulically transported or elevated to the level of the station 110 through the discharge pipe 50 using sea water as the transport medium.

When the mining head 130 is at the end of an intake stroke in the first intake direction R, the archimedes screws 140 are moved in the opposite rotation direction so that the mining head 130 is moved in the opposite second intake direction S. The transport arrangement is switched into a second intake mode in which the first discharge valve 222a and the first flush valve 223a of the first mining box 200a are switched in a closed position and the second discharge valve 222b and the second flush valve 223b of the second mining box 200b are switched in an open position. The process flow now passes through the second mining box 200b. The dislodging and the transportation of the nodules 5 and the recirculation of the process flow is performed analogous to the method described above when the mining head 130 is moved in the first intake direction R, this is not repeated hereafter.

In the mining process of the nodules 5 as described above the mining head 130 progresses step-by-step along the seabed 3 in the mining direction M while after each step the mining head 130 is alternately moved in the first intake direction R or in the second intake direction S. Alternatively the mining assembly 100 is gradually and continuously moved in the mining direction M while the mining head 130 is alternately moved in the first intake direction R and the second intake direction S.

In an additional or alternative embodiment of the mining system 10, when the mining head 130 is moved in the first intake direction R and when the concentration of the accumulated sediment in the process flow exceeds a threshold value, for instance when the process flow exiting the station 110 contains more than ten weight percent of sediment, the transport arrangement is switched into the first intake mode in which the first discharge valve 222a and the first flush valve 223a of the first mining box 200a are switched in an open position, the second discharge valve 222b of the second mining box 200b is switched to a closed position and the second flush valve 223b of the second mining box 200b is switched to an at least partly open position. As a result most of the process flow goes towards the first mining box 200a and a small part, maximum twenty percent, preferably about ten percent, of the process flow goes towards the second mining box 200b. The process flow, with the high concentration of sediment, is discharged from the second mining box 200b through the second intake aperture 216b at the leeside of the mining head 130. At the same time seawater with no or a low concentration of sediment is taken in through the first intake aperture 200a of the first mining box 200a so that the concentration of sediment in the recirculation loop reduces or stabilizes. The process flow with the sediment is returned to or close to the seabed 3 in a smooth manner, causing little turbidity and thereby causing little environmental impact. This process is also called blanketing of the sediment. Blanketing of the sediment may be performed continuously during mining of the nodules 5 or periodically, for instance with each loading cycle of a container 111a,b. The above applies analogously when the mining head 130 is moved in the opposite second intake direction S and the transport arrangement is switched into the second intake mode.

At the station 110 the process flow is directed to the first container 111a. The process flow enters the first container 111a and the heavy nodules 5 sink to the bottom thereof, thereby filling the first container 111a. The bulk of the sediment remains suspended in the sea water. As the first container 111a is closed off by the lid 115 the process flow entering the first container 111a causes an overpressure therein. As a result the sea water with the sediment discharges from the first container 111a through the return pipe 51 which returns the sea water with the sediment to the first mining box 200a where it flushes nodules 5 further towards the back wall 213 and at least a part of the sea water and the sediment is sucked into the discharge pipe again to transport the mined nodules 5 to the station 110.

When the first container 111a is full with nodules 5 the process flow is switched from the first container 111a to the second container 111b by switching the filling valves and return valves of the filling arrangement in order to fill the second container 111b with nodules 5. Subsequently the first filling tube 122a and the first return tube 123a are moved by the first brace 107a from the filling position to the shuttling position. The full first container 111a is then shuttled by the container cables 102 from the station 110 to the main suspension 20 while being guided by the first cables 101. The full first container 111a is then emptied as will be explained below. The empty first container 111a is shuttled back to the station 110 and the first filling tube 122a and the first return tube 123a are moved back to the filling position by the first brace 107a. When the second container 111b is full the shuttling process as described above is repeated for the second container 111b.

During mining of the nodules 5 at least one container 111a,b is located at the station 110 to assure a continuous process flow and therewith a continuous mining of the nodules 5. The filling time of the containers 111a,b is higher than the shuttling time of the containers 111a,b. Factors that influence the filling and shuttling time of the containers 111a,b are, amongst others, the depth of the deep sea 1 and the density of the nodules 5 found on the seabed 3. The filling time is adjustable by tuning, amongst others, the size of the containers 111a,b, the intake speed of the mining head 130 and the volume of the process flow. The shuttling time is adjustable by tuning, amongst others, the size of the containers 111a,b and the shuttling speed of the containers 111a,b.

When both containers 111a,b sit inside the station 110, both sets of container clamps 235 of the cable cursor frame 230 are engaged with the containers 111a,b. When the first container 111a is full the set of container clamps 235 that is associated with the second container 111b will release the second container 111b so that the cable cursor frame 230 shuttles with the first container 111a from the station 110 to the main suspension 20. While being shuttled the cable cursor frame 230 guides the first cables 101, the container cables 102 and the umbilical cable 104 and therewith eliminates any entanglement thereof.

When the full container 111 is raised above the water surface 2 it is emptied by moving the collector support frames 42 to the outboard position wherein the collector 41 is located below the bottom opening 114, then opening the dump valve 117 of the container 111 and thereby releasing the nodules 5 into the collector 41, and then transporting the nodules 5 via the first conveyors 43, second conveyors 44 and third conveyors 45 to the cargo holds 15.

When all the cargo holds 15 are full the mining of the nodules 5 is stopped. The mining assembly 100 is raised from its lowered position to its raised position in which the mining assembly 100 is raised above the water surface 2. The vessel 11 sails to an unloading location and unloads the nodules 5. When the vessel 11 is empty the mining sequence as described above is repeated.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention.