NO20220186A1 - Subsea Nodule Collector - Google Patents

Description

The present invention relates to an apparatus for collecting manganese nodules from the sea bed comprising a vehicle having a body and means for propulsion along the seabed, means extending from the body to the seabed having a conveyor for transporting nodules from the seabed to a nodule collecting bin.

Manganese nodules (also called deep‐ocean polymetallic nodules) are composed of iron and manganese oxides and include numerous minor and trace metals originating from seawater and sediment pore water and grow to a size between 1 and 15 cm in diameter on top or within the first 10 cm of deep‐sea sediments in water depths from 4000 to 6000m. The largest and economically most important deposit is located in the so‐called manganese nodule belt of the Clarion‐Clipperton Zone (CCZ) of the equatorial North Pacific between Hawaii and Mexico.

Apart from manganese, nickel, copper and cobalt, the nodules also contain other metals of economic interest in significant quantities such as molybdenum, titanium, lithium, vanadium and rare earth elements.

Exploitation of Mn nodules requires the use of vast seafloor areas, as the nodules form a two‐dimensional deposit on the surface of deep‐sea sediments. One license for Manganese Nodules can be up to 75.000 km2.

In US Patent No.4685 742 there is described a vehicle for collecting mineral‐rich nodules from the seafloor. The vehicle comprises an arm with its end reaching down to the seafloor and preferably extending about 5 – 10 cm below the seafloor to enable nodules to be harvested. The arm is equipped with a conveyor to transport nodules up to a shaker and from there to a hopper where it is pumped to an underwater silo and then through a riser up to a surface vessel.

A problem with this construction is that it will bring a lot of sediments together with the nodules. Most of these sediments will either be dumped behind the vehicle or, in the case of being transported up to the surface, dumped from the ship.

WO 950329 describes a step conveyor comprising a primary stationary beam and a secondary beam being movable upwards and downwards as well as to and fro relative thereto. The secondary beam (2) is supported by restrictedly pivotable bow‐shaped eccentrically journaled segments (3) resting on a stationary guideway (5). In each position the secondary beam (2) is positioned below the level of the primary beam (1). At its top the secondary beam (2) carries dogs (6) which in a non‐operative rest position are positioned below the level of the primary beam (1) and which in an operational position extend beyond the level of the primary beam (1) and can engage the objects (7) to be transported.

The purpose of the invention is to develop a nodule collecting vehicle that is more efficient and productive than current machines. The special feature of the mining vehicle is that the construction results in less disturbances of sediments on the seabed. This is achieved by constructing the conveyor as a step conveyor consisting of a first set of stationary rails or fingers and a second set of rails alternating with the first rails and being movable upwards and downwards as well as back and forth relative to the first beams.

The distance between the rails together with the motion will help any sediments that is picked up to fall back to the seabed with minimal disturbance.

Another advantage with the invention is that there will be less sediments being carried with the nodules. This will reduce the need for pumping.

In an alternative of the invention, a secondary belt is arranged above and in parallel with the primary conveyor. This belt is provides with bristles or brushes that will further clean away sediments from the nodules.

The invention will now be described in more detail with reference to the enclosed drawings.

Fig.1is a drawing of the collecting system,

Fig.2 is a drawing showing the vehicle body,

Fig.3 is a drawing of the sampling apparatus, and

Fig.4 is a drawing of the module transferring means, and

Fig.5 and 6 shows the module transferring means in various positions, and

Fig.7 shows a detail of the module transferring means.

In Fig 1 there is shown a system for harvesting manganese nodules from the seabed. The system comprises a marine vessel 1 floating on the surface of the ocean above the seabed 3. A riser 4 extends from the vessel down to the seabed. The riser may extend all the way to the seabed or as shown in Fig.1, terminated a distance above the seabed. At the end of the riser 4 there is a pumping station 5 that may include storage facilities for nodules. At least one nodule collecting vehicle 10 is arranged to travel along the seabed for harvesting nodules. The vehicle(s) 10 are connected to the pumping station 5 with an umbilical 6 carrying lines for power and signals as well as a jumper for transporting nodules from the vehicle 10 to the pumping station 5.

As shown in Fig.2 the vehicle includes a body 20 covering the internal parts of the vehicle. The body may include various thrusters 11, 12, 13 for manoeuvrability. A buoyancy system (not shown) may be included to keep the weight on the seabed as low as possible and also to raise the vehicle back to the surface.

As shown in Fig.3 the vehicle comprises wheels or belts 21 for propulsion along the seabed for collecting the nodules.

In the preferred embodiment the vehicle comprises a first conveyor 25 in the front of the vehicle and extending from the seabed and upwards onto an elevation belt 26 to transport the nodules mechanically to an elevation where the nodules can drop into two contrarotating screw conveyers 27 to centralize the volume of nodules before being led into a suction box 28. From the suction box the nodules will be sucked or pumped through the umbilical 6 to the pumping station 4 and then to the vessel.

The transportation system may be equipped with a crushing unit (not shown) at the end of the elevation belt 26 arranged such that smaller nodules drops directly into the screw conveyer 27 while larger nodules are directed to the crushing unit before dropping into the screw conveyer.

The suction box 28 is connected to the flexible jumper 6. A single screw conveyer is located at the bottom of the suction box and arranged to feed the inlet of the jumper with a constant volume of nodules thereby avoiding slugging through the jumper and later in the riser.

In Figs.4 – 6 there is shown the first conveyor 25 in more detail. The conveyor 25 is in the form of a fingerboard or a rack of rails that extends at an incline from the body of the vehicle to the seabed. The front 32 extends a small distance, preferably about 5 – 10 cm below the seafloor and the front of the bars are oblique bevel cut so as to facilitate the collection of the nodules. The conveyor consists of a number of fingers 30, 31 in the shape of long bars or rails. The bars are arranged parallel to each other with a small distance in between. The distance between the bars should be small enough so that smaller nodules will be transported but also so that loose sediment can fall down to the seafloor between the fingers.

A first set of fingers 30 are fixed to a backplate 41. A second set of fingers are arranged so that they can move along a parallelogram in relation to the fixed fingers 30. The movable fingers 31 can move in an up and down motion while moving forwards in the “up” position and back in the return the “return” position in relation to the fingers 30.

In Fig.4 there is shown only one movable finger 31 between two fixed fingers 30 but it should be understood that the conveyor will consist of a number of movable fingers arranged between the stationary fingers.

Two axles 34, 35 are arranged transversely to the fingers, one at approximately each end of the conveyor. The axles extend through holes in the fingers and is rotated by hydraulic or electric motors (not shown). As shown in the detail of Fig.7 the axle has segments 36, 37 with an excentre pin 38 that goes through a hole in the movable finger 31. When the axle (ex. 34) is rotated the movable finger 31 will perform the up and down motion as well as a back‐and‐forth motion. This motion will advance the nodules along the fingerboard. The movable fingers can be equipped with teeth 39 that will help to hinder the nodules to slide back down along the conveyor.

In an alternative embodiment (not shown) only the front axle 34 has the excentre pin while the second axle is stationary. The movable finger 31 has an elongated at rear through which the axle 35 extends. Thus only the front part of the movable finger 31 will move up and down while the rear part only moves back and forth.

The fingers will dig out the nodules and the movable fingers will enable the nodules to travel up along the incline of the conveyor. In addition, these dynamic fingers will shake the nodules as they travel along the inclined conveyor and help sediment removal and thus prevent sediment build‐up on the conveyor. This will also result in less sediment being brought up to the surface.

The top 41 of the conveyor 25 is preferably hinged to the main body of the vehicle to enable the conveyor to accommodate uneven terrain on the seabed.

Above the main conveyor and parallel thereto is a moving belt 45 extending the length of the finger board as well as covering the full width. The belt runs between wheels 46, 47 at each end. The belt has bristles or brushes 48 that extends down towards the fingers. In a first embodiment, the bristles terminate a small distance above the fingers 30, 31. Their main purpose is to brush away sediments that is attached to the surface of the nodules. In a second embodiment, the bristles can be equipped with strips of steel wires extend between the fingers. In that case they will also aid in the transportation of nodules along the inclined conveyor.

The brushing belt is driven by separate motors, and the speed of the belt can be adjusted for optimum transportation of nodules.

As an additional feature, the steel wire strips of the brushing belt will act as a brush and remove sediments from the nodules.

Although the present invention has been shown and described with respect to specific exemplary embodiments, it will be obvious to those skilled in the art that the present invention may be variously modified and altered without departing from the spirit and scope of the invention. That includes the type of motors employed, that can be either electric or hydraulic and power requirements and supply. The system should also include various means to monitor the operation, including sensors and cameras. The vehicles may also be equipped with a programmable device to enable autonomous or semi‐ autonomous operation.

Claims (9)

1. Seabed nodule collecting apparatus comprising a vehicle (10) having a body (20) and means for propulsion (21) of the vehicle along the seabed, conveying means (25) extending from the body to the seabed for transporting nodules from the seabed to a nodule collecting bin (28), characterized in that the conveyor comprises a first (30) and a second (31) set of fingers in an alternating arrangement where the first set of fingers (30) are fixed and the second set of fingers (31) are movable in a parallelogram motion relative to the first fingers (30).

2. Apparatus according to claim 1, characterized in that at least one axle (34, 35) extends transversely through the fingers.

3. Apparatus according to claim 1, characterized in that the axle is rotatable and comprises an eccentric pin (38) attached to the second set of fingers.

4. Apparatus according to claim 1, characterized in that the second set of rails (31) comprises teeth (39).

5. Apparatus according to claim 1, characterized in that it comprises a brushing belt (45) arranged above and parallel with the first conveyor, the belt having bristles or brushes (48) that reaches down to between the fingers.

6. Apparatus according to claim 2, characterized in that the belt comprises rotating rollers (46, 47).

7. Apparatus according to claim 1 characterized in that it comprises a secondary conveyor (26) transporting material from the first conveyor to the bin (28).

8. Apparatus according to claim 1, characterized in that the bin (28) comprises two contra-rotating screw conveyers to centralize the volume of nodules.

9. Apparatus according to claim 1, characterized in that the bin further comprises a suction box