Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21C—MINING OR QUARRYING
  • E21C50/00—Obtaining minerals from underwater, not otherwise provided for
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/08—Dredgers; Soil-shifting machines mechanically-driven with digging elements on an endless chain
  • E02F3/10—Dredgers; Soil-shifting machines mechanically-driven with digging elements on an endless chain with tools that only loosen the material, i.e. with cutter-type chains
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/18—Dredgers; Soil-shifting machines mechanically-driven with digging wheels turning round an axis, e.g. bucket-type wheels
  • E02F3/20—Dredgers; Soil-shifting machines mechanically-driven with digging wheels turning round an axis, e.g. bucket-type wheels with tools that only loosen the material, i.e. mill-type wheels
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/88—Dredgers; Soil-shifting machines mechanically-driven with arrangements acting by a sucking or forcing effect, e.g. suction dredgers
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/88—Dredgers; Soil-shifting machines mechanically-driven with arrangements acting by a sucking or forcing effect, e.g. suction dredgers
  • E02F3/8833—Floating installations
  • E02F3/8841—Floating installations wherein at least a part of the soil-shifting equipment is mounted on a ladder or boom
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/88—Dredgers; Soil-shifting machines mechanically-driven with arrangements acting by a sucking or forcing effect, e.g. suction dredgers
  • E02F3/8858—Submerged units
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/88—Dredgers; Soil-shifting machines mechanically-driven with arrangements acting by a sucking or forcing effect, e.g. suction dredgers
  • E02F3/90—Component parts, e.g. arrangement or adaptation of pumps
  • E02F3/92—Digging elements, e.g. suction heads
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F3/00—Dredgers; Soil-shifting machines
  • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
  • E02F3/88—Dredgers; Soil-shifting machines mechanically-driven with arrangements acting by a sucking or forcing effect, e.g. suction dredgers
  • E02F3/90—Component parts, e.g. arrangement or adaptation of pumps
  • E02F3/92—Digging elements, e.g. suction heads
  • E02F3/9212—Mechanical digging means, e.g. suction wheels, i.e. wheel with a suction inlet attached behind the wheel
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F5/00—Dredgers or soil-shifting machines for special purposes
  • E02F5/006—Dredgers or soil-shifting machines for special purposes adapted for working ground under water not otherwise provided for
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F7/00—Equipment for conveying or separating excavated material
  • E02F7/10—Pipelines for conveying excavated materials
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21C—MINING OR QUARRYING
  • E21C45/00—Methods of hydraulic mining; Hydraulic monitors

Definitions

• the present invention relates generally to underwater mining, and in particular relates to an apparatus for seafloor stockpiling.
• the invention relates, but is not limited, to a seafloor stockpiling device which receives seafloor material, typically ore slurry, from at least one seafloor tool, and from which the seafloor material can be gathered for transfer to a surface vessel.
• Seabed excavation is often performed by dredging, for example to retrieve valuable alluvial placer deposits or to keep waterways navigable.
• Suction dredging involves positioning a gathering end of a pipe or tube close to the seabed material to be excavated, and using a surface pump to generate a negative differential pressure to suck water and nearby mobile seafloor sediment up the pipe.
• Cutter suction dredging further provides a cutter head at or near the suction inlet to release compacted soils, gravels or even hard rock, to be sucked up the tube.
• Large cutter suction dredges can apply tens of thousands of kilowatts of cutting power.
• Other seabed dredging techniques include auger suction, jet lift, air lift and bucket dredging.
• Dredging is thus usually limited to relatively shallow water.
• Subsea boreholes such as oil wells can operate in deeper water of up to several thousand metres depth.
• subsea borehole mining technology does not enable seafloor mining.
• the present invention provides a seafloor stockpiling device that is located on the seafloor in use, the device comprising:
• a slurry inlet for attachment of a slurry transfer pipe and for receiving slurry from a seafloor tool
• walls that substantially define a cavity having a stockpiling volume, the walls being configured to capture and contain seafloor material present in the slurry in the device while permitting egress of water present in the slurry from the device.
• the seafloor stockpiling device is a hood.
• the hood has an open bottom.
• the cavity is defined by the walls together with a seafloor surface on which the seafloor stockpiling device is located.
• the hood is relocatable and at least a portion of the walls are movable sections that reduce drag loads during movement of the seafloor stockpiling device. The movement may be deployment, seafloor relocation, or recovery of the seafloor stockpiling device.
• At least a portion of the walls are water permeable.
• at least a portion of the walls comprise a filter material, such as a geotextile, and/or a filter structure, such as an inclined plate or tube settler, which permits egress of water while containing the desired seafloor material.
• the walls of the seafloor stockpiling device comprise both a filter material portion and a filter structure portion, preferably a geotextile portion and an inclined plate or tube settler portion, respectively.
• the filter material is preferably reversibly mounted such that reversing the mounting of the filter material causes an inward facing surface of the filter material to become outward facing. Reversible mounting of the filter material may present a number of advantages, for example the ability for the filter material to be selectively cleaned when fine seafloor material accumulates on the filter material, as further stockpiling operations will tend to flush such accumulations off the outside surface.
• the seafloor stockpiling device preferably further comprises a friction reduction mechanism which may be utilised to reduce static friction (stiction) between the seafloor stockpiling device and a seafloor surface on which the seafloor stockpiling device is located when lifting the device from the seafloor.
• the friction reduction mechanism may comprise one or more fluid outlets adjacent a bottom portion of the device. The fluid outlets are preferably directed generally towards the seafloor. In use, the fluid outlets preferably fluidise sediment and seafloor material adjacent the seafloor stockpiling device.
• the friction reduction mechanism may alternatively, or additionally, comprise movable walls.
• the movable walls are preferably contained inside the walls of the device and enclose seafloor material contained within the device.
• the movable walls preferably pivot relative to the walls of the device during lifting of the device. As the movable walls pivot they preferably swing away from the seafloor material contained within the device.
• the device preferably has at least one lifting attachment for lifting and manoeuvring the device.
• the lifting attachment is preferably engaged with a movement system that can at least lift the device.
• An offset lifting attachment which is offset from a central axis of the device, preferably located on or adjacent an outer edge of the device, may be provided.
• the offset lifting attachment preferably causes the device to be lifted on an angle during relocation of the device.
• the seafloor stockpiling device is formed from at least two modules configured for separate deployment from a surface vessel and for underwater interconnection.
• the maximum deployment capacity of surface vessel deployment systems may present a constraint to the size of the seafloor stockpiling device and, accordingly, in some embodiments the seafloor stockpiling device is formed in two or more modules configured for separate surface deployment, and configured for interconnection once submerged and/or on the seafloor.
• such a modular seafloor stockpiling device may, in some embodiments, be up to 25 m in diameter and up to 100 T submerged weight once formed from the two or more modules.
• the seafloor stockpiling device may comprise a stockpile removal device enabling material stockpiled within the seafloor stockpiling device to be removed in slurry form.
• the stockpile removal device may comprise an opening port, such as a door in the seafloor stockpiling device, which when open permits a boom mounted suction inlet of a seafloor machine to be introduced into the seafloor stockpiling device to gather stockpiled material, preferably in slurry form, and which when closed restrains stockpiled material.
• the stockpile removal device of the seafloor stockpiling device may comprise a suction inlet and slurry transfer pipe mounted on and extending into the seafloor stockpiling device, so that the suction inlet of the seafloor stockpiling device is placed in a suitable position to mobilise and extract stockpiled material.
• slurry flow rates desired for capturing seafloor material can be significantly different to the slurry flow rates desired for lifting slurry to a surface vessel, such as by a riser and lift system, and thus provides for decoupling of these flow rates by use of a seafloor stockpiling device.
• the respective flow rates may thus be separately optimised.
• a slurry flow rate into the seafloor stockpiling device may for example be about 3,000 m 3 /hour, with an ore concentration of about 3%, while a slurry flow rate to the surface vessel may be around 1 ,000 m 3 / hour at an average ore concentration of about 12%.
• the seafloor stockpiling device is preferably configured such that, when positioned on a relatively flat portion of the seafloor, the seafloor stockpiling device forms a hood which completely encloses a stockpiling volume in a manner to minimise the loss of slow-settling fine particles (referred to herein as "fines").
• the hood preferably permits the egress of water from the stockpiling volume so as to filter and capture the seafloor material from the slurry.
• a significant surface area of the walls of the hood are formed of filter material which contains fines while permitting egress of water from the hood.
• a grade of the filter material being a dimension below which solid particles can pass through the filter material, is preferably selected in order to maximise fines containment while permitting the necessary water flow rate out of the hood to accommodate slurry inflows into the hood.
• the filter material may comprise a silt curtain of 50 micron grade.
• the seafloor hood preferably comprises a space frame supporting the filter material, with the walls of the hood being formed by the filter material.
• Capture of fines from a slurry inflow into the hood can be advantageous both environmentally in avoiding escape of plumes of the seafloor material, and operationally as such fines may represent 30% or more of the seafloor material desired to be gathered.
• the stockpile hood may have angled walls forming a substantially frustoconical shape, the walls being at an angle to approximate the expected rill angle of an ore heap so as to avoid a stockpiled ore heap exerting significant outward pressure on the walls.
• the present invention provides a seafloor stockpiling device adaptable in some embodiments to deployment at significant water depths.
• some embodiments may be operable at depths greater than about 400m, more preferably greater than 1000m and more preferably greater than 1500m depth.
• some embodiments of the present invention may also present a useful seafloor mining option in water as shallow as 100m or other relatively shallow submerged applications.
• references to the seafloor or seabed are not intended to exclude application of the present invention to mining or excavation of lake floors, estuary floors, fjord floors, sound floors, bay floors, harbour floors or the like, whether in salt, brackish, or fresh water, and such applications are included within the scope of the present specification.
• FIG. 1 is a simplified overview of a subsea system utilising a stockpiling hood in accordance with one embodiment of the present invention
• FIGS. 2a to 2f illustrate the stockpiling hood in accordance with an embodiment of the present invention
• FIG. 3 illustrates gathering from the stockpile
• FIG. 4 illustrates overlaid stockpiles
• Figure 5 illustrates a cross sectional view of a stockpiling hood with inclined settler panels
• Figure 6 illustrates a cross sectional view of a stockpiling hood with an offset lifting point
• Figure 7 illustrates a cross sectional view of a stockpiling hood with a friction reduction mechanism
• Figure 8a illustrates a cross sectional view of another friction reduction mechanism in a rest position
• Figure 8b illustrates a cross sectional view of a the friction reduction mechanism illustrated in figure 8a in a lifting position.
• FIG. 1 is a diagrammatic overview of a subsea system 100 in accordance with one embodiment of the present invention.
• a derrick 102 and dewatering plant 104 are mounted upon a surface vessel in the form of an oceangoing production support vessel (PSV) 106.
• PSV 106 has ore transfer facilities to load retrieved ore onto barge 108.
• the present embodiment provides a system 100 operable to around 2500m depth, however alternative embodiments may be designed for operation to 3000m depth or greater.
• SMTs seafloor mining tools
• one or more seafloor mining tools (SMTs) 112 are used to excavate seafloor material, preferably ore, from the seabed 1 10.
• seafloor mining tool 112 Ore mined by the seafloor mining tool 112 is gathered upon being cut and pumped, in the form of slurry, from the seafloor mining tool 112 through a stockpile transfer pipe (STP) 128 to a seafloor stockpiling device 124.
• STP stockpile transfer pipe
• the seafloor stockpiling device 124 captures ore from the slurry while permitting egress of water from the slurry.
• a gathering tool 114 inserts a boom-mouhted suction inlet into the seafloor stockpiling device 124 via a door 220 (see figure 2a), to gather ore in slurry form from inside the seafloor stockpiling device 124.
• the slurry is then transfered to the base of a riser 122 where a subsea lift pump 118 lifts the slurry, via a rigid riser 122, (shown interrupted in Figure 1, and may be up to 2500m long in this embodiment) to PSV 106.
• the slurry is dewatered by plant 104.
• the waste water is returned under pressure back to the seafloor to provide charge pressure for subsea lift pump 118.
• the dewatered ore is offloaded onto transport barge 108 to be transported to a stockpile facility before being transported to a processing site.
• FIGS 2a to 2d illustrate the stockpiling device in the form of a stockpiling hood 124 in more detail.
• the stockpiling hood 124 comprises transfer pipe connectors 202 and 204, which are subsea hose connectors, to permit multiple seafloor tools 112 to gather ore into the hood stockpiling 124 simultaneously. Slurry flow is directed into the hood by the transfer pipe connectors 202 and 204 generally vertically downwards.
• Hood 124 further comprises a lifting attachment in the form of lift gear 206 for deployment, relocation and recovery of hood 124.
• the stockpiling hood 124 has walls comprising panels 208 that, together with the seafloor 110, define a cavity for stockpiling seafloor material (as illustrated in figure 3).
• the panels 208 are removable and formed of a frame 212 with a water permeable skin in the form of a geotextile covering 214.
• the geotextile covering 214 Due to the large geometry of the stockpiling hood 124 there is a large in water added mass associated with the device due to the geotextile covering 214. This added mass causes in water lifting drag to increase dramatically over that of conventional lifts. As a result in this embodiment the geotextile covering 214 is able to be rotated to align with a direction of movement before any lifting operations occur. The panels 208 are able to be opened to reduce water resistance during movement of the stockpiling hood 124. The geotextile covering 214 reduces the outflow velocity to allow settlement of larger spoil particles and retain fines larger than 30 - 60 microns. In case of differential pressure across the filter material rising due to filter pore blockages, a relief valve or flap is provided to avoid rupture of the filter material.
• the stockpiling hood 124 is formed of two modules 124a and 124b which can be separately deployed from a surface vessel and then brought together on the seafloor. This arrangement permits the stockpiling hood 124 as a whole to exceed the weight limits of a surface vessel's deployment systems.
• Figure 2c is a plan view of the stockpiling hood 124
• Figure 2d is an elevation view of the stockpiling hood 124.
• FIGS 2e and 2f show opening flaps 210 in the top of the stockpiling hood 124 in the closed and open positions, respectively, the latter reducing drag during hood movement.
• Flaps 220 are provided at several locations to provide gathering from all sides of the stockpile, and do not require any power to function. The flaps 220 are designed to avoid excessive leakage of slurry when not in use by gathering machine 300.
• This embodiment thus filters the flow of ore slurry being pumped from one or more sea floor production tools.
• This slurry is a high volume flow and the slurry velocity needs to be reduced to allow the ore to settle out of the flow onto the sea floor.
• the stockpiling hood 124 reduces the amount of ore lost from such a slurry flow and is designed to minimise the disturbance of the ore pile created when the stockpiling hood 124 is relocated.
• the stockpiling hood 124 is able to be shifted by an overhead crane on a vessel so as to be re-useable.
• An inflow of ore slurry is slowed inside the stockpiling hood 124 due to the large volume of the stockpiling hood 124, and the large surface area covered in the geotextile covering 214. Larger ore particlesin the slurry are fast setline and settle to the stockpile in a slow flow region. A large volume slurry flow moves through the geotextile covering 214 at low velocity with the geotextile covering 214 filtering slow-settling particles from the flow.
• Figure 3 illustrates a gathering machine 300 gathering ore from a stockpile 500 within the stockpiling hood 124.
• the stockpiling hood 124 is illustrated without the geotextile covering for clarity. With the geotexile covering in place, the gathering portion 302 of the gathering machine 300 is inserted through flaps 220 of the stockpiling hood 124.
• Figure 3 also illustrates the size of a full stockpile 502 contained within the stockpiling hood 124.
• Figures 4a and 4b illustrate a method to increase standard stockpile 500 size using a hood 124 with a rigid skirt 310.
• the skirt 310 provides support for ore in the stockpile 500, permitting overfilling of the stockpiling hood 124 which is not possible with non- load bearing hood walls.
• the method comprises over filling the stockpiling hood 124 with an overfilled stockpile 504, lifting the stockpiling hood 124 off the overfilled stockpile 504; allowing the overfilled stockpile 504 to collapse into a collapsed stockpile 506, and then placing the stockpiling hood 124 on top of the collapsed stockpile 506.
• FIG. 5 illustrates an embodiment of the stockpiling hood 124 where some of the geotextile covering 214 has been replaced with a filter structure in the form of inclined settlers 216.
• the inclined settlers 216 which may be either inclined plate or inclined tube settlers, allow water to flow upward out of the stockpiling hood 124 while capturing solids which slide down inclined surfaces of the inclined settlers 216 back into the stockpiling hood 124 to the stockpile 500.
• the inclined settlers 216 provide have an increased settling area per square meter of outflow cross sectional area which increases the settling rate, relative to just using a geotextile covering 214, allowing the settling capacity of the stockpiling hood 124 to be increased and/or the size of the stockpiling hood 124 to be decreased while maintaining the same capacity output. It is envisaged that the walls in their entirety could comprise inclined settlers 216 instead of having geotextile covering 214 portions as illustrated.
• Figure 6 illustrates a stockpiling hood 124 with an offset lifting attachment in the form of an offset lifting point 218.
• the offset lifting point 218 is positioned on a side of the stockpiling hood 124 and allows the stockpiling hood 124 to be lifted at an angle by a lifting apparatus 218'.
• static friction, or stiction By lifting the stockpiling hood 124 at an angle using the offset lifting point 218, static friction, or stiction, preventing the stockpiling hood 124 from being lifted is reduced.
• a small amount of peripheral sediment 501 can build up around the perimeter of the stockpiling hood 124 which, together with the stockpile 500, creates stiction between the hood 124 and the seafloor 110.
• FIG. 7 illustrates a fiction reduction mechanism that also assists in reducing stiction between the stockpiling hood 124 and the seafloor 1 10.
• Pipe transfer connectors 202 and 204 which are connected to STPs 128, have diverter valves which can be actuated to divert some of the flow down conduits 222 to fluid outlets in the form of nozzles 224 at the bottom of the stockpiling hood 124.
• diverter valves When the diverter valves is actuated, water pumped by the slurry pump system is pumped into the conduits 222 and out of the nozzles 224. This water loosens material around the periphery of the stockpiling hood 124 , including peripheral sediment 501, which reduces friction between the stockpiling hood 124 and the seafloor 110. Once the stiction forces are overcome, the stockpiling hood 124 is relatively easily manoeuvred. It is envisaged that instead of water, air or other fluids could be expelled from nozzles 224.
• Figures 8a and 8b illustrate a further friction reduction mechanism which may be used instead of, or even in addition to, the abovementioned friction reduction mechanism illustrated in figure 7.
• the friction reduction mechanism in figures 8a and 8b has movable walls 230 inside the stockpiling hood 124.
• the movable walls 230 are pivotable relative to the sides of the stockpiling hood 124.
• the stockpile 500 is retained within the movable walls 230 of the stockpiling hood 124.
• the movable walls 230 pivot downwards and away from the stockpile 500. This action effectively eliminates stiction forces between the stockpiling hood 124 and the seafloor 110.

Landscapes

• Engineering & Computer Science (AREA)
• Mining & Mineral Resources (AREA)
• Mechanical Engineering (AREA)
• Civil Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structural Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Geology (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Treatment Of Sludge (AREA)
• Drilling And Exploitation, And Mining Machines And Methods (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=47356437

Family Applications (1)

Country Status (7)

Families Citing this family (9)

Family Cites Families (35)

• 2012
  • 2012-06-15 US US14/125,946 patent/US20140137443A1/en not_active Abandoned
  • 2012-06-15 JP JP2014515006A patent/JP2014522923A/ja active Pending
  • 2012-06-15 KR KR1020137031068A patent/KR20140033369A/ko not_active Application Discontinuation
  • 2012-06-15 CN CN201280029916.9A patent/CN103717835B/zh not_active Expired - Fee Related
  • 2012-06-15 EP EP12800771.3A patent/EP2694779A4/de not_active Withdrawn
  • 2012-06-15 AU AU2012269738A patent/AU2012269738A1/en not_active Abandoned
  • 2012-06-15 WO PCT/AU2012/000696 patent/WO2012171075A1/en active Application Filing

Also Published As

Similar Documents

Legal Events