FIELD OF THE INVENTION

The invention relates to equipment for and a method of hoisting or lifting particulate solids that are gathered in an underwater environment. The equipment will preferably deliver the solids to a vessel or platform on the water’s surface from a deep underwater environment.

BACKGROUND TO THE INVENTION

Solids of the kind referred to are mined or collected on the ocean seabed or at the bottom of a lake, for example. The invention is concerned with the hydro-transport of such solids to an elevated position above the water’s surface. There are a number of systems proposed to achieve this result in the underwater environment. Pumps are involved and are commonly required to be underwater. There are inefficiencies in the lifting of the solids using the known arrangements. One of the main difficulties relates to the fluidisation or introduction of the solids into a flow of water that serves to convey the solids.

The term “solids” or “particulate solids” as used in this specification should be understood to include material of a particulate nature which may be ore-containing nodules or aggregates that exist on the ocean or lake floors or rock that is mined underwater and which solids may be crushed, processed and/or sorted to a desirable size.

OBJECT OF THE INVENTION

It is an object of the current invention to provide apparatus and/or a method that involves an improved arrangement of components and/or new principles of operation for the lifting of solids from an underwater environment. SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided underwater hoisting apparatus for solids comprising: at least one chamber having a top end and a bottom end; a booster pump connected to a supply water inlet of the chamber; the supply water inlet provided adjacent the top end of the chamber and controlled by a first valve; a solids inlet to the chamber controlled by a second valve; a batching apparatus arranged to feed a batch of solids through the solids inlet; a transfer conduit that extends from the solids inlet and opens at a position inside the chamber spaced apart from the top end; a water vent adjacent the top end of the chamber controlled by a third valve for displaced water to exit the chamber when the solids inlet is opened; the water vent open to an ambient water environment; a solids outlet at the bottom end of the chamber controlled by a fourth valve and connected to an ascending solids/water delivery line; and the first valve and the fourth valve placing the water inlet in communication with the delivery line through the chamber for hoisting of the solids.

The invention further provides: for the booster pump to be located above water and connected through a descending water supply line to the supply water inlet; or, alternatively, for the booster pump to be located at an underwater level near the at least one chamber and connected directly to the supply water inlet; for the batching apparatus to be a batching flask provided above the solids inlet to gravity feed the chamber with a batch of solids for each cycle and the transfer conduit is provided as a chute for gravity transfer of the solids; and for the batching flask to be open to the ambient water environment. The components of the vent and/or batching flask that are open to the ambient water environment are accordingly exposed to ambient water pressure.

Alternatively, the invention provides for the batching apparatus to include a feed pump which feeds a water/solids mixture to the solids inlet; and for a change-over valve to be associated with the feed pump for supply of clear-water to flush the second valve of the solids inlet after a batch of solids has passed through the second valve. The invention further provides for hoisting apparatus as defined, in which: two or more chambers are vertically supported in an adjacent configuration, each with a water inlet connected to the supply line and a solids outlet feeding separately into a manifold that is connected to the delivery line; water jets are provided to flush the second valve after the batching flask is emptied [to push solids through and away from second valve] the batching flask has an overflow level weir to determine a maximum batch volume of solids for a chamber; the solids are pumped as a solids/water mixture from a storage bin to the batching flask; a seabed gathering apparatus feeds solids to the storage bin; and a crusher and/or sizing equipment is located between the gathering apparatus and the storage bin.

The invention further provides for hoisting apparatus as defined, in which: the transfer conduit has an outlet located at a position suitably spaced apart from the top end of the chamber to maintain a substantially clear-water region in a top zone of the chamber; the transfer conduit outlet opens into a lower section of the chamber; the solids inlet is provided at the top end of the chamber; the solids inlet is provided in the top zone of the chamber with the transfer conduit provided as a chute extending from the top zone [centrally] within the chamber; and a space between the transfer chute and a chamber bottom is sufficient for a batch of solids to pile with a clearance remaining below the transfer chute.

The invention further provides for hoisting apparatus as defined, in which: a water by-pass duct extends from a first location above the outlet of the transfer chute to a second location adjacent the bottom end of the chamber [to provide a low resistance channel for water to fluidise and dilute solids exiting the chamber]; the by-pass duct is at least one pipe that extends within the chamber; and the by-pass duct is supported from the transfer chute, with an inlet to the by pass duct spaced upwardly from the outlet from the transfer chute.

[The flow at an outlet of the by-pass duct serves to dislodge and mobilise solids inside the pile adjacent the solids outlet.]

The invention further provides for hoisting apparatus as defined, in which: a primary connection is provided into the top zone of the chamber, above which the solids inlet is located and through which the transfer chute extends into the chamber, a secondary connection is provided that extends into a side of the primary connection, with the water inlet and the water outlet connected to the secondary connection for communication with the chamber through the primary connection, around the transfer chute.

In accordance with a second aspect of the invention there is provided a method of hoisting solids in an underwater environment comprising: a. providing a water-filled chamber with a top end and a bottom end; b. introducing solids into the water-filled chamber by opening a solids inlet connected to a transfer chute that opens at a position suitably spaced apart from a top zone of the chamber to maintain a clear-water region in the top zone of the chamber; c. allowing water displaced by the solids to move out of the chamber through a vent adjacent the top zone of the chamber and into the ambient water environment; and d. opening a supply water inlet adjacent the top end of the chamber and a solids outlet from the bottom end of the chamber to: i. establish a flow through the chamber from a booster pump via a descending clear-water supply line; and ii. displace the solids from the chamber; e. directing the solids into an ascending solids/water delivery line; and f. closing the solids outlet at a stage when there is clear-water exiting the chamber.

The invention further provides for a method as defined, in which: the solids inlet is in communication with an ambient water environment; two or more chambers are operated on cycles to provide a substantially continuous flow of water from the supply line sequentially through the chambers; a batch of solids is introduced into each chamber in a first part of a chamber filling cycle time and for a remainder of the chamber filling cycle time to be used for the solids and accompanying fines in the batch to settle and migrate downwardly under gravity; the solids are delivered into a lower section of the chamber from the solids inlet and through a transfer chute; and a bottom by-pass duct is used to provide a low resistance passage for water from above a pile of settled solids to a position within the pile and adjacent the bottom of the chamber.

[The bottom duct proves a low resistance flow passage for the water to by-pass from the above the solids to the bottom of the chamber. The space around the bottom duct provides a resistance to the solids so they fall more slowly. The intended result is to mix a bottom third (approximately) of solids with a middle third (approximately) of fines/water mixture in roughly equal portions so that the solids concentration of solids exiting the chamber is half that of the settled concentration in the bottom of the chamber after filling.]

Further features of the invention provide for the solids to be concentrated at the bottom of the chamber (i.e. not uniformly mixing them throughout the chamber) via the transfer chute and for a clear-water region to be maintained in the top zone or upper section of the chamber; and for the bottom by-pass duct to be used to connect the upper section of the chamber to the lower section of the chamber (which is filled with solids) for the solids to be fluidised and diluted on exiting of the chamber.

The invention provides for a first valve to be opened for inlet of supply water, a second valve to be opened for inlet of solids, a third valve to be opened for outlet of water displaced by the solids, and a fourth valve at a bottom of the chamber to be opened for outlet of solids.

A further feature of the invention provides for the flow through the chamber to be established from a surface located booster pump via a descending clear-water supply line.

The term “clear-water” or similar terms as used in this specification do not refer in a limited manner to the colour or visual clarity of the water but are rather used to refer to water which is substantially or suitably free of solids and fine solids to allow for desirable or acceptable operation and particularly closing of the chamber valves.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the following description of an embodiment of the invention made by way of example with reference to the following drawing: Figure 1 which shows a schematic illustration of a 3 chamber hydro hoist, only one chamber of which is depicted, in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, underwater hoisting apparatus in accordance with the invention will generally be referred to as a 3 chamber hydro hoist or 3C-HH (100). The 3C-HH (100) is provided for underwater mining. The 3C-HH (100) can be used in lakes or oceans to lift solids from the lake bottom or ocean bed.

Figure 1 only shows a single chamber (102). Flowever, operation of the equipment with three chambers will be understood by a person skilled in the art and from the teaching of this document. The equipment employed by the current invention is related to that described in International patent application number PCT/IB2019/057392 and the disclosure of that specification is incorporated herein in its entirety by reference thereto.

The 3C-HH (100) is provided to vertically lift solids in a solids/water mixture form (which may be referred to as slurry) from an underwater location in the vicinity a mined seabed (104) in this embodiment. The three chambers (102) provide a feeder arrangement to favourably introduce the solids into a stream of water coming down a supply column (106) and going back up a delivery column (108). The intention is that velocities in the supply and delivery columns will be substantially constant to avoid pressure surges (i.e. water hammer).

A booster pump (110) is provided on a mining vessel (112), which will usually be a ship. The pump (110) is connected through the descending supply column, which provides a clear-water supply line or column (106) that may extend through a take-off branch or connection (114) to each of the three chambers (102). The clear-water is conveniently available as sea water, in the case of an ocean-going vessel. The surface, booster pump (110) may be of the centrifugal or positive displacement type. In a variation of the invention, the booster pump will be located at the underwater level of and connected directly to the inlet (114) to the chambers (102). This embodiment avoids the need for a descending column as shown in the drawing.

The three chambers (102) are vertically supported in an adjacent configuration, each with a supply water inlet (116) connected to the supply line (114) and a solids outlet (118) feeding separately into a manifold (not shown) that is connected to an ascending solids/water delivery line (108) provided by the outgoing column.

An arrangement of vertical and flexible risers is provided together with suitable buoyancy apparatus and/or tensile cables tethered to the ship to support the net weight of the risers. In one embodiment, the pipes will be made out of a light-weight flexible Kevlar or other similar type, reinforced polymer so the submerged net density (after buoyancy) is almost neutral. This has a several benefits over thick-walled steel pipes: (a) it can be made as a continuous hose stored and installed from a suitably large reel; (b) the need for no joints is minimized; and (c) it is substantially self- supporting if the specific gravity is just above or below that of the water.

Alternatively, steel pipes could be suspended on high-tensile steel wire ropes which have tensile strengths 3 times that of pipes. Floatation will be required to support most of the weight of the steel in the pipe columns.

The invention provides for the supply (106) and delivery (108) column arrangement to be beneficially employed by rotating the duty of the solids/water delivery to share the wear between the two columns.

Each chamber (102) has a top end (120) and a bottom end (122) with four control valves (124; 126; 128; 130):

• The supply water inlet (116) is located adjacent the top end and controlled by a first valve (124); • A solids inlet (132) is controlled by a second valve (126);

• A water vent (134) [which has a flow control orifice] is provided adjacent the top end (120) and controlled by a third valve (128); and

• The solids outlet (118) at the bottom of the chamber (102) is controlled by a fourth valve (130).

The equipment includes batching apparatus (136) above the solids inlet to gravity feed the chamber with a batch of solids for each cycle. In this embodiment, the batching apparatus is a batching flask (136) above each chamber (102) with an outlet in communication with the solids inlet (132) to gravity feed the chamber (102). The batching flasks are open to the ambient water environment.

A seabed gathering apparatus (137), which may be of any suitable kind, feeds solids to a storage bin (138), which includes a crusher and/or sizing equipment (140). The solids are pumped as a solids/water mixture from a storage bin (138) to the batching flask (136) via a suitable line (139). The batching flask (136) has an overflow level weir (142) to determine a maximum batch volume of solids for a chamber (102). Any overflow from the weir (142) is directed back to the storage bin (138) via a return line (144).

The solids inlet (116) is located through the top end (120) of the chamber (102) with a transfer conduit (146) provided as a substantially vertical chute (146) extending from the top end (120) centrally within the chamber (102). The transfer chute (146) extends from the solids inlet (132) and has an outlet (148) provided at a position suitably spaced apart from the top end (120) of the chamber (102). More specifically, the outlet (148) opens into a lower section of the chamber (102). A space between the transfer chute (146) and a chamber bottom at (122) is sufficient for a batch of solids to settle into a pile with a clearance remaining below the transfer chute (146). The vent (134) and the batching flask (136) are open to an ambient water environment. The vent (134) provides an outlet for displaced water to exit the chamber (102) when the solids inlet (132) is opened.

In an alternative embodiment of the invention, the batching apparatus may be provided by a feed pump arrangement that feeds a water/solids mixture to the solids inlet. The connection will not be open to the ambient water environment. Once a batch of solids has passed through the second valve of the solids inlet, a change-over valve associated with the feed pump will be used for supply of clear-water to flush the second valve.

The invention further provides for each chamber (102) to include a water by-pass duct (150) that extends from a first location above the transfer chute outlet (148) to a second location adjacent the bottom end (122) of the chamber (102). The by-pass duct (150) may be provided as at least one pipe connected to or supported from the transfer chute (146), with an inlet to the by-pass duct (150) spaced upwardly from the outlet (148) from the transfer chute (146).

The four control valves (124; 126; 128; 130) will preferably be actuated non-return valves with an internal pressure equalization function provided for the first and third valves (124; 128), but other types are possible.

The operation of the valves (124; 126; 128; 130) will be timed by a PLC program that instructs valves to open or close. Pressure equalization (within a small margin) will be achieved before opening of valves (124; 126; 128; 130) to avoid sudden large transient flows and associated pressure surges. This will be achieved by ensuring that it is mechanically impossible for an actuator to open or close a valve if pressure equalization is not achieved within a small margin. Pressure transmitters will be used to measure pressures in the chambers and the supply and delivery lines. In use, the second valve (126) is opened to charge a chamber (102) with solids from the batching flask (136). The solids are introduced into the water-filled chamber (102) via the transfer chute (146) under the force of gravity. The solids inlet (132) is in communication with the ambient water environment and connected to a transfer chute (146). The third valve (128) is also opened for outlet of water displaced by the solids. The water displaced by the solids is allowed to move out of the chamber (102) through the vent (134) adjacent the top end (120) of the chamber (102) and into the ambient water environment. The outlet (148) from the transfer chute (146) opens at a position suitably spaced apart from the top end (120) of the chamber (102) to maintain a clear-water region in the annular space around the chute at the top end of the chamber.

A batch of solids is introduced into each chamber (102) in a first part of a chamber filling cycle time and a remainder of the chamber filling cycle time is used for the solids and accompanying fines in the batch, which solids are delivered into a lower section of the chamber (102), to settle and migrate downwardly under gravity.

Water jets (not shown) are optionally provided in the bottom of the batching flasks (136). The jets would be suitably arranged to flush the second valve (126) after the batching flask (136) is emptied. This serves to push solids through and away from second valve (126) and the flushing will also take place in the remainder of the chamber filling cycle time (after the solids have emptied from the batching flask and passed through the second valve).

The solids are concentrated at the bottom of the chamber (i.e. not uniformly mixing them throughout the chamber) via the transfer chute (146) with a clear-water region maintained in an upper section of the chamber. The bottom by-pass duct (150) connects the upper section of the chamber to the lower section of the chamber (which is to be filled with solids). The bottom by-pass duct (150) serves to provide a low resistance passage or channel for water from above a pile of settled solids to a position within the pile and adjacent the bottom (122) of the chamber (102) for the solids to be fluidised and diluted on exiting of the chamber (102). The flow at an outlet (152) of the by-pass duct (150) serves to dislodge and mobilise solids inside the pile adjacent the solids outlet (118).

The first valve (124) is opened for inlet of supply water and the fourth valve (130) at a bottom of the chamber (102) is opened for outlet of solids. These two valves are opened under the desired timing and pressure equalization to establish a flow through the chamber (102) from a booster pump (110) via a descending clear-water supply line (106) as shown in the drawing [or directly via inlet (114) from an underwater booster pump in accordance with the alternative embodiment] and to displace the solids from the chamber (102).

The supply water inlet (116) and the solids outlet (118) place the supply line (106) in communication with the delivery line (108) through the chamber (102) and a differential pressure that results, provides the net force that moves the solids. The solids are fluidised and the flow of the water carrying the solids is directed into the ascending solids/water delivery line (108). The solids outlet (118) is then closed at a stage when there is clear-water exiting the chamber (102).

The three chambers (102) are operated sequentially on cycles to provide a substantially continuous flow of water from the supply line (106) through the chambers (102).

The solids are handled by the equipment of the invention in a manner that allows for each of the four valves (124; 126; 128; 130) associated with each chamber (102) to only be closed in the presence clear-water during normal operation of the 3C-HH.

The invention accordingly involves a solids fed, gravity-filled, bottom-discharge, vertically arranged, 3 chamber hydro hoist which achieves valve closure in clear- water by passing solids into and out of the chambers in a fraction of the “solids filling cycle” and “solids/water delivery cycle” periods followed by flushing with clear-water before closing. Instead of the 3 chambers disclosed, the arrangement may involve the use of one, two, or even four or more chambers.

The invention may further include the use of a secondary safety non-return valve (not shown) in each solids outlet line (118) from the three chambers (102).

The secondary safety non-return valves are provided as a safety feature to prevent significant (unintended) reverse flow from the solids/water delivery column into a chamber should the bottom solids-discharge valve (130) get stuck in an open condition, say due an over-size rock or foreign body.

The secondary safety non-return valves thus serve to minimize the risk of backflow of solids into the chambers in the event of a malfunction elsewhere in the system. These valves do not need to establish a complete seal. The valves may crush some rock under the seat and need only close sufficiently to prevent massive reverse flow rates. This will allow the system to reset on the next cycle and clear any blockages.

The reverse flow arrest feature should avoid the consequence of having to clear a chamber full of solids with a head of solids/water generating significant reverse flows, which would require a major maintenance intervention.

The secondary safety non-return valves will be designed to the design pressure and equipped with durable slurry-type ball/poppet-and-seat trim as is used in high- pressure slurry positive-displacement pumps. Although the pressure duty is high, the slurry non-return valves are arranged to close in clear water most of the time and they are not required seal tightly.

The 3C-HH apparatus and method for hoisting solids in underwater mining offers the following features and advantages:

- a very high lift capability; - high efficiency which stems from having a surface booster pump and the hydraulic energy delivery via a supply feed column;

- elimination of primary hoisting pumps that are located underwater (instead, pumps are located on a ship or dry platform);

- high pressure pumping provides for high lifts and eliminates multiple pumping stages;

- the volume of clear-water displaced by the solids can simply be vented into the ambient water at the depth of the three chambers;

- the solids inlet valve is maintained underwater; and

- the high ambient pressure at depth further enhances the lift capabilities of the apparatus.

Unlike the pressure rating requirements in a mine or above ground, in this underwater application of hoisting equipment, the hydrostatic pressure of the surrounding water at a given depth equalizes the hydrostatic pressure on either side of the pipe wall (i.e. it removes the need for the shell strength of the pipe to withstand the pressure resulting from the depth). The installation components need to withstand the boost pressure from above that is used to overcome friction and lift the solids. This is typically about 8 MPa for a 1600 m lift.

By way of example, a class 1500, 25 MPa valve can be used to lift solids more than 1.6km in an underground. In the underwater application of the invention, the higher ambient pressure at depth reduces the shell pressure requirement. For example, at 3000m the ambient pressure will be about 30 MPa. The class 1500 valve could be operated at 30 + 25 = 55 MPa and the full 25 MPa boost pressure from a booster pump used to lift the solids and overcome friction. Hence a single stage lifting apparatus with one 3C-HH could lift solids 3000m with a class 1500 rated valve, 3C- HH and columns. Higher pressure-rated valves, pumps and columns could be used to lift say up to 6000 m. As an additional feature, the invention allows for the inclusion of suitable flow- resistance devices to be provided above a lower section of the chamber to maintain a (substantially) clear-water environment at a top zone or upper section of the chamber.

Various configurations of flow-resistance devices, transfer chutes and by-pass ducts may be employed depending on the application and design parameters. The configuration of the chambers and connections providing the inlets and outlets may also be varied.

In one embodiment of the invention (not shown) a primary connection will be provided into the top end of the chamber leading down from the second valve. The transfer chute extends concentrically through the primary connection into the chamber. A secondary connection is provided that extends laterally from the primary connection. The water inlet and the water outlet are connected to the secondary connection for communication with the chamber through the primary connection, around the transfer chute.

A person skilled in the art will further understand that a number of variations may be made to the features of the embodiments described without departing from the scope of the invention.