Pumping system and method for filling a pressure exchange chamber fluid container

Abstract

A pumping system for pumping a medium such as polymetallic nodules in seawater comprises at least one pressure exchange chamber having a valve arrangement at each end, a medium inlet at one end of the chamber operable to receive the medium, and a filling pump disposed on a side of the chamber opposite the medium inlet and operable to draw medium from the medium inlet through the chamber towards the filling pump to fill the chamber without the medium in the chamber contacting the filling pump.

Description

[Technical Field]

[0001] The present invention relates to pumping systems, particularly for use in the mining and mineral processing industries, and particularly, but not exclusively, for use in hydraulic ore hoisting systems (HOHS). [Background technology]

[0002] In the mineral processing industry, one problem concerns the transportation of ore from underground or subsea locations to surface level. A novel system for such transportation is described in PCT application number PCT / IB2019 / 055957 in the name of Weir Minerals Netherlands BV and is called a HOHS. Other types of HOHS are also available.

[0003] One type of HOHS includes a positive displacement (PD) pump, which is used to move a mixture of ore and water, called ore slurry, through a pressure exchange chamber (PEC) into a riser using a driving fluid. The slurry is a two-phase mixture (a liquid in which solid particles are suspended or otherwise present). A particular advantage of the HOHS as described in PCT / IB2019 / 055957 is the use of PD pumps, which deliver pressure-independent flow rates and allow the use of driving fluids containing fine particles (typically smaller than 500 μm).

[0004] A typical high-level schematic of a HOHS system for use in subsea applications is shown in FIG. 1A, showing both the equipment used and, to some extent, the process flow. After the ore slurry is pumped to the surface through riser 4, it is dewatered (at location 5) and the carrier fluid is reused once more by PD pump 6 as the drive fluid in high-pressure line 7. In FIG. 1A, Cv is the volumetric concentration of solids and Q_up is the total volumetric flow rate of the fluid and solids mixture delivered to the surface. To maintain a balanced volume, an additional volume of fluid equal to the ore removed (i.e., Cv × Q_up) is added to the surface drive fluid reservoir.

[0005] One challenge in designing a HOHS system, particularly for marine (subsea) applications, is that the ore input to the ore slurry conditioning stage 3 is in the form of soft polymetallic nodules that are typically between 10 mm and 200 mm in length. These soft nodules break easily and, once broken, the resulting fines are much more expensive to dewater and process than if the whole nodules were conveyed intact. Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of embodiments of the present invention to obviate or mitigate the above-mentioned or other disadvantages of the prior art, or to provide a useful alternative to or improved operation of the prior art. [Means for solving the problem]

[0007] The various aspects detailed below are independent of one another unless otherwise stated, and any claim corresponding to one aspect should not be construed as incorporating any element or feature of another aspect unless expressly recited in that claim.

[0008] Reference herein to any prior publication (or information derived from a prior publication) or any known matter is not, and should not be taken as, an agreement or admission, or any form of suggestion, that the prior publication (or information derived from a prior publication) or known matter forms part of the common general knowledge in the field of endeavor to which this specification pertains, or is even cited as prior art to the present application.

[0009] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0010] According to a first aspect, there is provided a pumping system for pumping a media including ore suspended in a carrier fluid from a subsurface or subsurface location to a surface at an elevated level, the system comprising: (i) at least one pressure exchange chamber having a fluid container with a valve arrangement at each end and located at an elevation below the elevated level; (ii) a media inlet at one end of the chamber operable to receive media for conveyance into the chamber; and (iii) a fill pump located on a side of the chamber opposite the media inlet and operable to draw media from the media inlet through the chamber toward the fill pump to fill the chamber without the media in the chamber contacting the fill pump.

[0011] The medium may include a fluid that has different properties than another fluid moved by the medium, which may be temperature, salinity, or solids content. The fluid container may have any convenient shape and may have an inlet at one end and an outlet at another end. The fluid container may include a tube. The tube may have any convenient cross-sectional shape (in some embodiments, the tube has a generally circular cross-section) and any convenient aspect ratio (length to width). In some embodiments, the tube may be elongated.

[0012] The fill pump may include a centrifugal pump, or may include a positive displacement pump or another type of pump. The fill pump is preferably in direct pressure communication (or in a direct pressure relationship) with the pressure exchange chamber drive fluid outlet, such that a pressure drop in the fill pump results in a pressure drop in the pressure exchange chamber drive fluid outlet. In other words, the chamber and fill pump form a closed pressure system. In such a system, there are no openings to the environment, which would allow fluid at ambient pressure to be drawn in instead of the medium.

[0013] The pumping system may further include a harvester coupled to the media inlet to supply media to the media inlet. The harvester may produce media including ore suspended in a carrier fluid.

[0014] A drive fluid pump (such as a positive displacement pump or one or more centrifugal pumps) may be provided to move the media from the pressure exchange chamber up a discharge riser to surface level. The discharge riser may be located at an end of the pressure exchange chamber opposite the drive fluid pump. The drive fluid pump may be coupled to the pressure exchange chamber via the drive fluid riser.

[0015] The harvester may include a hydraulic suction device operable to raise ore in the form of nodules from the seabed and to mix the nodules with seawater to create a medium. The nodules may contain particles that are typically between 10 mm and 200 mm in length. The medium may contain the settling particles in a carrier fluid, the mixture being called a settling slurry.

[0016] The pumping system may include multiple pressure exchange chambers, each of which is sequentially filled with a medium. Each pressure exchange chamber includes a fluid container, such as a tube, which may be elongated or extending in any convenient configuration, such as a spiral, or in an orientation, such as horizontal, vertical, or at any desired angle. In some embodiments, the length of the tube may be selected from the range of 20 m to 400 m.

[0017] The (or each) pressure exchange chamber may include a separator between the drive fluid and the medium being pumped, or the drive fluid may be in direct contact with the medium being pumped. A first valve arrangement is preferably located at one end of the pressure exchange chamber and comprises a drive fluid inlet valve, a drive fluid outlet valve, a pressurization valve, and a pressure reduction valve. These valves are preferably suitable for use with high dynamic pressures (e.g., greater than 40 Bar (4 MPa)) since significantly higher pressures may exist above the valve (above the sealing point on the valve seat) than below the valve (below the sealing point on the valve seat).

[0018] These valves may include actuated valves. Preferably, a second valve device is located at the end of the pressure exchange chamber near the pressurized discharge and comprises a pressure-fed fluid (or medium) outlet valve (also called a discharge valve) and a pressure-fed fluid (or medium) inlet valve (also called a suction valve). The pressure-fed fluid inlet valve and the pressure-fed fluid outlet valve open in a pressure equilibrium state when the pressure exchange chamber is appropriately depressurized or pressurized, respectively. These valves may include actuated or self-actuated valves.

[0019] The pressured fluid outlet valve and pressured fluid inlet valve are preferably suitable for use with high pressures (eg, greater than approximately 40 bar (4 MPa)). The drive fluid inlet valve may be opened simultaneously (or approximately simultaneously) with the pressured fluid outlet valve, while the drive fluid outlet valve and the pressured fluid inlet valve remain closed.

[0020] Similarly, the pressured fluid inlet valve may be opened simultaneously (or approximately simultaneously) with the drive fluid outlet valve, while the pressured fluid outlet valve and the drive fluid inlet valve remain closed.

[0021] The underwater location may be the ocean floor, or the bottom of a lake or estuary. By locating the fill pump at the end of the pressure exchange chamber opposite the media inlet (or harvester), the media (and especially the nodules) do not come into contact with any moving or stationary parts in the fill pump. In embodiments where a centrifugal pump is used, the impeller has a particularly adverse effect on the ore particles in the media. In effect, the fill pump draws media from the media inlet (and harvester, if connected) into the pressure exchange chamber. The second valve device can be closed before the media contacts the fill pump. If the nodules are allowed to come into contact with the impeller (or any other part of the pump), there is a significant risk that the nodules will break down into fine particles that are more difficult and expensive to dewater at the surface.

[0022] Another advantage of placing the fill pump at the end of the fluid container opposite the media inlet (or harvester) is that it is easier to control the media flow rate because relatively clean water (rather than slurry) is being pumped.

[0023] Another advantage of locating the fill pump at the end of the fluid container opposite the media inlet is that wear on the fill pump due to the media being conveyed therethrough is prevented or minimized.

[0024] Another advantage of not having the media come into contact with the fill pump is that a pump can be used that is not tolerant of ore particles that may be suspended in the media. Another advantage of not having the media in contact with the fill pump is that when the media contains ore particles suspended in water, the pump is essentially pumping water so that pump performance more closely matches the theoretical pump curve performance than when pumping slurry (ore suspended in water). This makes it easier to control the pump flow rate.

[0025] Placing a feed pump downstream of a PEC is usually not possible in land-based systems because hydraulic losses in the suction system (between the pump inlet and the medium source) cause a pressure drop throughout the suction system, including at the pump inlet. Cavitation occurs when the pressure at the pump inlet drops to or near the vapor pressure of the medium. Vapor pressure at room temperature is close to absolute vacuum, meaning that reduced pressure in the suction system is limited to roughly 1 bar (100 kPa). If suction losses are excessively high, vapor pressure is reached locally in the suction system. Vapor bubbles then form that are carried in the flow. These bubbles collapse violently when the pressure locally exceeds the vapor pressure. This typically occurs within the pump. This process, called cavitation, limits pump operation because flow and pressure generation are restricted under cavitation conditions, and cavitation can be very detrimental to the pump itself.

[0026] Therefore, in the design of shore-based pumping systems, the pump is located as close as possible to the medium source, and the suction system is designed for minimal hydraulic losses. The objective is to have a higher NPSHA (Available Suction Head) of the suction system than the NPSHR (Required Suction Head) of the pump. Because the atmospheric pressure in the ocean is much higher than on land (1 bar per 10 m depth), the risk of cavitation is minimized or virtually non-existent. Understanding this physical difference allows the feed pump to be located anywhere along the pipe, from the slurry preparation to the water outlet of the pressure exchange chamber.

[0027] Another advantage of placing the fill pump at the end of the chamber opposite the harvester is that it is easier to control the flow rate of the medium 32. The flow rate of a centrifugal pump depends on both the pressure load acting on the pump and the density of the mixture and the presence of particles in the mixture. To control the flow rate of the feed pump, the flow rate of the feed pump needs to be measured with a flow meter, and this value can be used as the actual value in the control loop of the centrifugal pump speed. An increase in the centrifugal pump speed will result in an increase in pressure generation by the pump, which will result in an increase in the flow rate.

[0028] Difficulties in prior art systems include the location of the flow sensor and the disturbance of mixture composition to control behavior. Ideally, the flow meter should be positioned as close to the centrifugal pump as possible, typically downstream of the pump. In prior art systems, the flow meter needs to be able to measure the flow rate of a mixture of water and solid particles. While such flow meters exist, accuracy is affected by the presence of solids, and such flow meters also need to be wear-resistant. Alternatively, the flow meter can be positioned downstream of the pressure exchange chamber, in which case it measures a relatively clean water flow. Disadvantages of this approach include the long distance between the pump and the flow meter and the possibility of an intermediate flow restriction device. This makes the downstream flow measurement indirect, limits the bandwidth of the flow measurement, and restricts the speed of the flow control loop. When the feed pump is positioned downstream of the pressure exchange chamber, the flow meter can measure in a relatively clean environment just upstream or downstream of the feed pump. The flow of the feed pump depends only on the pressure load on the pump, not on the mixture being delivered, and the pump receives only relatively clean fluid with a relatively constant density, free of large solid particles. In control terminology, this means fewer disturbances, allowing for more accurate control response.

[0029] According to a second aspect, there is provided a method for filling a pressure exchange chamber fluid container located at a low altitude and having a media inlet coupled to one end of the fluid container and a drive fluid outlet coupled to the other end of the fluid container, the method comprising: (i) opening a media inlet valve at the media inlet to fill the fluid container; (ii) using an energy addition mechanism to create a lower pressure at the drive fluid inlet of the fluid container than at the media inlet of the fluid container to draw media through the media inlet without the media in the fluid container contacting the energy addition mechanism; and (iii) closing the valve to stop the suction of media into the fluid container.

[0030] Optionally, using the energy-addition mechanism includes using a fill pump located at an end of the pressure exchange chamber opposite the media inlet (e.g., at the drive fluid outlet). Alternatively, using the energy-addition mechanism includes providing media (e.g., stored in a tank or reservoir) at a higher altitude than the pressure exchange chamber fluid container such that a hydrostatic head creates a higher pressure at the media inlet of the fluid container than at the drive fluid outlet of the fluid container; such a system may include a control valve located at the end of the pressure exchange chamber opposite the media inlet to control the flow of the media without the media contacting the control valve. When media is provided at a higher altitude, the energy-addition mechanism may further include a fill pump that assists in filling the fluid container with media in addition to the energy added by the tank or reservoir. The combination of the tank (or reservoir), control valve, and additional fill pump provides a net increase in energy to the system, which can be controlled to optimize the flow rate and filling of the fluid container with media.

[0031] The method may include opening a drive fluid outlet valve (on the opposite side of the pressure exchange chamber from the media inlet valve) after (or simultaneously with) opening the media inlet valve at the media inlet.

[0032] The step of closing the valves to stop the intake of medium into the pressure exchange chamber may include closing one or both of the drive fluid outlet valve or the medium inlet valve at the medium inlet. The drive fluid outlet valve may be closed first, or both valves may be closed simultaneously. Closing the drive fluid outlet valve first allows the medium inlet valve to close with less risk of medium being seated on the valve seat.

[0033] According to a third aspect, there is provided a method of filling a pressure exchange chamber fluid container located at a low altitude and having a media inlet coupled to the fluid container, the method comprising the steps of: (i) opening a media inlet valve at the media inlet to fill the pressure exchange chamber fluid container; (ii) using a pressure reducing mechanism to create a pressure within the pressure exchange chamber fluid container that is lower than ambient pressure to draw media through the media inlet without the media in the fluid container contacting the pressure reducing mechanism; and (iii) closing a valve to stop the drawing of media into the pressure exchange chamber fluid container.

[0034] As used herein, "ambient pressure" means the pressure surrounding the pressure exchange chamber at the media inlet. In this manner, the method reduces the pressure within the pressure exchange chamber relative to ambient, as opposed to prior art techniques that increase the pressure at the media inlet so that media flows from the media inlet through the pressure exchange chamber fluid container.

[0035] Creating a sub-ambient pressure within the pressure exchange chamber fluid container can be accomplished by using a fill pump located at the end of the pressure exchange chamber opposite the media inlet.

[0036] The step of closing the valve device may be performed prior to the medium reaching the fill pump to prevent the fill pump from destroying the medium. Low altitudes may include the ocean floor, or underground levels in a mine.

[0037] If the lower elevation includes a subsurface level in a mine, the method may further include conditioning the media at an elevation higher than the pressure exchange chamber such that an elevated pressure exists at the media inlet compared to the media conditioning location. This ensures that a sufficient pressure differential exists between the media conditioning location and the media inlet to the pressure exchange chamber to prevent cavitation and thereby allow a fill pump to be installed downstream of the pressure exchange chamber. For example, the media conditioning location may be located at least 30 m (in some embodiments, at least 50 m; in other embodiments, at least 100 m) above the media inlet. The height selected may depend on the desired cavitation reduction.

[0038] A method of operating a pressure exchange chamber fluid container may include the steps of the second or third aspect and may further include the step of moving the media from the media outlet port of the pressure exchange chamber up a discharge riser to surface level.

[0039] The pressure difference between the ambient pressure and the pressure in the pressure exchange chamber may be selected so that the medium can flow into the pressure exchange chamber fluid container without adverse cavitation effects.

[0040] According to a fourth aspect, there is provided a hydraulic ore lifting system including the pumping system of the first aspect. It will now be appreciated that a hydraulic ore lifting system can be provided which minimizes disruption of the nodules by ensuring that the filling pump does not come into contact with the nodules being conveyed to surface level. If the pumping system were on land, the filling pump would be subject to excessive cavitation, but by locating the filling pump at the same (or similar) elevation as the pressure exchange chamber above the seabed, the hydrostatic head of the water above the pressure exchange chamber ensures that the cavitation effects are reduced.

[0041] According to a fifth aspect, there is provided a pumping system for pumping media, the system comprising: (i) at least one pressure exchange chamber comprising a fluid container having a valve arrangement at each end, the fluid container having a media inlet for receiving media including ore suspended in a carrier fluid for transport into the fluid container; and (ii) a fill pump positioned at an end of the fluid container opposite the media inlet, the fill pump operable to draw media from the inlet towards the fill pump to fill the fluid container.

[0042] According to a sixth aspect, there is provided a method for pumping a medium from a lower region to an upper region, the method comprising the steps of: (i) drawing the medium into a pressure exchange chamber located in the lower region using a filling pump on a drive fluid side of the pressure exchange chamber; and (ii) closing the pressure exchange chamber prior to the medium reaching the filling pump.

[0043] These and other aspects will become apparent from the following detailed description, given by way of example only in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0044] [Figure 1A] FIG. 1 is a simplified diagram of a prior art HOHS for marine applications. [Figure 1B] 1 is a simplified diagram of an HOHS according to a first embodiment of the present invention; [Figure 2] FIG. 1C is a more detailed simplified schematic of the pumping system of FIG. 1B, where the first embodiment uses only a single pressure exchange chamber, the pressure exchange chamber being located on the seabed below the surface from which the medium is to be pumped. [Figure 3] 3 is a simplified diagram of a portion of the pumping system of FIG. 2, namely, a harvester. [Figure 4] 1 is a simplified diagram illustrating an alternative pressure exchange system having three pressure exchange chambers. [Figure 5]1 is a simplified diagram of another embodiment of a pumping system in which the pumping system is land-based and the pressure exchange chamber is located below the area from which the media is pumped. DETAILED DESCRIPTION OF THE INVENTION

[0045] 1B and 2, which are simplified diagrams of a hydraulic ore lifting system (HOHS) 10 according to a first embodiment of the present invention, including a pressure exchange chamber (PEC) 1. The HOHS 10 is used for underwater (subsea, in this embodiment) mining operations. In FIGS. 1B and 2, similar parts use the same reference numbers as in FIG. 1A to indicate that the primary difference is the location of the centrifugal pump 30 at the downstream end of the PEC 1.

[0046] In a typical embodiment, all of the PECs 1 are located at a lower elevation than the final delivery point to which the media is to be delivered by the HOHS 10. In this embodiment, the media comprises ore particles (also called nodules) ranging in size from 10 mm to 200 mm in a carrier fluid (liquid carrier) to create a slurry of entrained and suspended ore particles.

[0047] In this embodiment, the HOHS 10 is a subsea system, the PEC 1 is located at or near the seabed, the ore comprises polymetallic nodules, and the liquid carrier comprises seawater. Other embodiments may be land-based (as described below with reference to FIG. 5) or on the bottom of a freshwater lake or estuary.

[0048] The PEC 1 comprises a single fluid container (tube) 12 having valve assemblies 14, 16 at each end thereof, referred to as a drive fluid valve assembly 14 and a pumped medium valve assembly 16. A pressurized discharge 20 is provided at a delivery end 22 of the PEC 1. In this embodiment, the pressurized discharge 20 is an inlet to a pressurized media riser 24 that extends generally vertically from the delivery end 22 to a collection vessel 26 at a surface 28. A media outlet line 29 connects the pressurized media valve device 16 to the pressurized discharge 20.

[0049] The pumped media riser 24 may be coupled to (and extend downwardly from) a vessel floating on a surface 28. The vessel may include a ship, a barge, or the like. A filling mechanism 30 in the form of a centrifugal pump is provided and is operable to fill the tube 12 with a medium 32 to be pumped to the surface 28. The centrifugal pump 30 fills the tube 12 with the medium 32 via a medium inlet line 31, which connects to the tube 12 at a medium inlet 35. Importantly, the centrifugal pump 30 is located on the opposite side of the PEC1 from the harvester 33 (in other words, the centrifugal pump 30 is downstream of the PEC1). The harvester 33 collects ore particles (or nodules) from the seabed and also collects water from a second fluid source (in this embodiment, the local seawater around the nodules). The mixture of nodules and seawater constitutes the medium 32.

[0050] HOHS 10 also includes a positive displacement pump 34, in this embodiment disposed at surface 28, operable to pump drive fluid 36 through PEC 1 and in direct contact with media 32 such that media 32 is moved from PEC 1 to pressurized discharge 20 and from there via pressured media riser 24 to surface 28. However, in other embodiments, different types of pumps or pump arrangements may be used, or pump-less lifting techniques may be used.

[0051] The positive displacement pump 34 is coupled to the drive fluid valve arrangement 14 via a drive fluid riser 38 and a drive fluid inlet line 40 . A drive fluid outlet line 42 connects PEC 1 (and in particular tube 12 ) to a drive fluid discharge point 44 .

[0052] The combination of pipe 12, drive fluid valve device 14, pumped medium valve device 16, drive fluid inlet and outlet lines 40, 42, and medium inlet and outlet lines 31, 29 is referred to herein as an open PEC1. "Open" refers to direct contact between drive fluid 36 and medium 32. "Pressure exchange" refers to an exchange of pressure between the two different fluids being pumped (drive fluid 36 and medium 32). However, in other embodiments, a spacer may be provided between drive fluid 36 and medium 32 such that it is an indirect pressure exchange system.

[0053] The drive fluid valve arrangement 14 is disposed at the positive displacement pump end 48 and includes a drive fluid inlet valve 50, a drive fluid outlet valve 52, a pressurizing valve 54, a reducing valve 56, a choke valve 57 (which may be in the form of a restriction in the tubing, i.e., a section of tubing with a reduced diameter), and a parent valve actuator 58. The parent valve actuator 58 is provided to operate the various valves 50 to 56 with the correct timing for efficient operation of the HOHS 10, as described in PCT / IB2019 / 055957.

[0054] Although not shown in the drawings, the drive fluid inlet valve 50 is opened and closed by a hydraulic actuator. Similarly, a hydraulic actuator is paired with each of the drive fluid outlet valve 52, the pressurizing valve 54, and the depressurizing valve 56. Each of these hydraulic actuators is controlled by a parent valve actuator 58.

[0055] In this embodiment, the master valve actuator 58 comprises a hydraulic power unit and controls the individual hydraulic actuators in each valve 50 , 52 , 54 , 56 in response to the master valve actuator 58 receiving commands from a system controller 70 .

[0056] In this embodiment, the valves are all high pressure (e.g., above 40 bar) operated non-return poppet seat valves, however, in other embodiments different types of valves may be used.

[0057] To allow the inlet and outlet valves 50, 52 to open in a substantially pressure balanced environment, a pressure balancing line 60 having a restriction (orifice) that functions as a choke valve 57 is provided. The pressure balancing line 60 provides a bypass arrangement by connecting the pressurizing valve 54 to the line 12 (bypassing the drive fluid inlet valve 50) and the depressurizing valve 56 to the line 12 (bypassing the drive fluid outlet valve 52).

[0058] A pressurization valve 54 is provided to bypass the drive fluid inlet valve 50 so that the pressure in the line 12 can be increased prior to opening the drive fluid inlet valve 50, thereby reducing the force required to open the valve 50 and reducing the fluid flow rate through the drive fluid inlet valve 50 when open. This has the advantage of extending the life of the drive fluid inlet valve 50.

[0059] Similarly, a pressure reducing valve 56 is provided to bypass the drive fluid outlet valve 52 so that the pressure in the pipe 12 can be reduced prior to opening the drive fluid outlet valve 52, thereby preventing a high flow rate of drive fluid 36 from passing through the drive fluid outlet valve 52 when the drive fluid outlet valve 52 is open.

[0060] This reduces wear on the pressurization valve 54 and pressure reduction valve 56 by limiting and controlling the flow rate during pressurization and depressurization of the pipe 12 . The pressure-fed medium valve device 16 is disposed at the delivery end 22 and includes a pressure-fed fluid outlet valve 62 (also called a discharge valve), a pressure-fed fluid inlet valve 64 (also called a suction valve or a fill valve), and a master valve actuator 66 for timely actuation of the valves 62, 64. The pressure-fed fluid inlet valve 64 and the pressure-fed fluid outlet valve 62 open in a pressure-balanced condition when the PEC1 is appropriately depressurized or pressurized, respectively.

[0061] In some embodiments, the parent valve actuators 58 and 66 may be combined into a single parent valve actuator that controls all valve actuators of all valves 50, 52, 54, 56, 62, 64 that are actuated.

[0062] In some embodiments, two choke valves (or restrictors) 57 may be provided, one in series with the pressurizing valve 54 and one in series with the depressurizing valve 56. Other arrangements are possible. The HOHS 10 also includes a system controller 70 for controlling the operation of the entire system, including the pumps 30, 34, the valves 50-56 and 62-64, and the parent valve actuators 58, 66.

[0063] The PD pump 34 needs to be provided with a fluid. In this embodiment, a first (surface) fluid source 74 is provided at the surface 28 to provide water for the drive fluid 36. This provides water from the surface 28, which in this embodiment may be seawater. This provides the hydrostatic benefits of using surface water. The fluid source 74 may include a filter to remove large particles from the fluid before providing it to the positive displacement pump 34.

[0064] Reference is now made to Figure 3, which is a simplified diagram of harvester 33. Harvester 33 comprises a chassis 76 within which is mounted a locomotion system 78 (in the form of hydraulic thrusters) operable to move harvester 33 along the seabed 79. Chassis 76 defines an opening 80 located thereunder and aligned with a collection head 82, which is directed through opening 80 toward the seabed 79. Collection head 82 lifts nodules (indicated (not to scale) by numeral 83) from the seabed 79 and deposits them into a nodule hopper 84, which effectively performs the slurry conditioning function 3 of Figure 1B. A flexible suction hose 85 connects nodule hopper 84 to media inlet line 31.

[0065] The nodule harvester 33 also includes a guidance system 86 that provides navigation information to the hydraulic thrusters 78 to guide the nodule harvester 33 to the nodule pile. The guidance system 86 may be connected to a transceiver on the surface vessel by a wired or wireless connection (indicated by the numeral 90 in FIG. 3).

[0066] When the pressure-fed fluid inlet (suction) valve 64 is open and the fill pump 30 is operating, the fill pump 30 reduces the pressure in the tube 12, causing pressure to drop in the media inlet line 31 and the flexible suction hose 85, thereby creating hydraulic suction. The mixture of nodules 83 and seawater (i.e., media 32) from the nodule hopper 84 is then drawn through the flexible suction hose 85, the media inlet line 31, and into the tube 12. The tube 12 is thereby filled without the media 32 coming into contact with the fill pump 30. This reduces damage to the polymetallic nodules 83 entrained in the seawater. This also has the advantage of avoiding the need for a pump on the harvester 33 to fill the tube 12 with media 32.

[0067] The operation of the HOHS10 is generally the same as that of the prior art HOHS1, which is described in detail in PCT / IB2019 / 055957. First, there is a depressurization step for tube 12 to the pressure in drive fluid outlet line 42, which allows drive fluid outlet valve 52 and pressurized fluid inlet valve 64 to be opened. Once depressurized, chamber 12 is filled with medium 32, which automatically flows into tube 12 by the operation of centrifugal (fill) pump 30 (drive fluid outlet valve 52 is in an open position), which reduces the pressure in tube 12. Fill pump 30 draws (or sucks) drive fluid 36 from tube 12 through drive fluid outlet valve 52 so that medium 32 begins to fill tube 12 via suction valve 64. Medium 32 enters tube 12 at a relatively high flow rate, so tube 12 fills relatively quickly.

[0068] Once the tube 12 is filled, the drive fluid outlet valve 52 is closed, thereby stopping the flow of relatively low pressure drive fluid 36 out of the tube 12 and stopping the flow of media 12 into the tube 12 . Nodules in the media 32 are forced to settle to the bottom of the PEC 1 and are also moved away from the seat of the suction valve 64, thereby allowing for better closure of the suction valve 64.

[0069] The chamber 12 is then pressurized to the pressure in the drive fluid inlet line 40 by allowing high pressure drive fluid 36 delivered by the positive displacement pump 34 to enter the tube 12 via the pressurization valve 54 and the pressure balance line 60.

[0070] The drive fluid inlet valve 50 and the pressurized fluid outlet valve 62 are then opened, causing high pressure drive fluid 36 to enter pipe 12, forcing pressurized medium 32 through the pressurized fluid outlet valve 62, medium outlet line 29, pressurized discharge 20 and partially (depending on the height of riser 24) raising the pressurized medium riser 24.

[0071] The drive fluid inlet valve 50 is then closed to stop the flow of drive fluid 36 into the tube 12 and to stop the flow of media 32 out of the tube 12 . Although only a single tube 12 is shown in HOHS 10 of Figure 2, in other embodiments, multiple pressure exchange chambers may be used. For example, in Figure 4, three PECs 201a, 201b, and 201c are provided in pressure exchange system 211, with system controller 270 managing the sequential filling and draining of the three PECs 201a, b, c to provide a continuous flow of media 32 to surface 28.

[0072] Each of the three PECs 201a, b, c includes valves identical to those described with respect to PEC1 of Figure 2 (choke valve 57 is not shown in Figure 4 for clarity, but is included in each PEC 201). Each of the three pressure exchange chambers 201a, b, c is identical to (or at least very similar to, for all practical purposes) PEC1.

[0073] By having multiple PECs 201 arranged in parallel, at least one PEC tube 212a, b, c is always filled with media 32 and ready to drain, thereby allowing for a continuous supply of drive fluid 36 to the PECs 201 and a continuous supply of media 32 to the PECs 201.

[0074] 5, which is a simplified diagram of another embodiment of HOHS 310, in this embodiment, PEC1 (or pressure exchange system 211, which may be used in place of PEC1 if three pipes are desired) is land-based, and pipe 12 (or pipes 212a, b, c) is located below the area from which the media is pumped. In other words, the media conditioning area is at a higher elevation than PEC1.

[0075] The PEC1 in FIG. 5 is identical to that in FIG. 2 and is located at a lower elevation (underground level) within the mine. However, the media is conditioned by an ore mixer 337 (which mixes the ore and water) on a raised shelf 339 located at a higher elevation (e.g., at least 30 m higher) than the pipe 12 so that an elevated pressure exists at the media inlet 35 compared to the static pressure at the ore mixer 337. This ensures that there is a sufficient pressure differential to prevent cavitation and thereby allow a charging pump to be installed at the opposite end of the pressure exchange chamber. In other embodiments, the ore mixer 337 may be located at least 40 m (in some embodiments, at least 50 m; in other embodiments, at least 100 m) above the media inlet 35. The height selected may depend on the desired cavitation reduction.

[0076] Although the above embodiments have described only direct pressure exchange chambers, the above teachings may be equally applied to indirect pressure exchange chambers (i.e., those having a separator between the driving fluid and the medium being pumped to the surface).

[0077] Similarly, although the above embodiments have described only generally horizontal pressure exchange chambers, the above teachings may be equally applied to vertical, angled pressure exchange chambers. Similarly, although the above embodiments have only described positive displacement pumps being used to raise the media to the surface, other pumps (such as centrifugal pumps) may be used.

[0078] In other embodiments, the fill pump may be any type of pump (not just a centrifugal pump) since it only needs to handle relatively clean drive fluid when positioned downstream of the pressure exchange chamber.

[0079] The steps of the methods described herein may be performed in any suitable order, or simultaneously where appropriate. As used herein, the terms "comprising," "including," "incorporating," and "having" are used to list an open-ended, rather than closed, list of one or more elements or steps. When such terms are used, the listed elements or steps do not exclude other elements or steps that may be added to the list.

[0080] Unless otherwise indicated by context, the terms "a" and "an" are used herein to refer to at least one of the subsequently stated elements, whole entities, steps, features, operations or components, but do not exclude additional elements, whole entities, steps, features, operations or components.

[0081] The presence of broadening words and phrases such as "one or more," "at least," "but not limited to," or other similar words and phrases does not imply, and should not be construed to imply, that a narrower case is intended or required, as the case may be, in instances where such broadening word or phrases are not used. (Item 1) 1. A pumping system for pumping a medium containing ore suspended in a carrier fluid from a subsurface or subsurface location to the surface at an elevated level, comprising: (i) at least one pressure exchange chamber comprising a fluid container having a valve device at each end and located at an elevation below the elevated level; (ii) a media inlet at one end of the chamber operable to receive a media for transport into the chamber; (iii) a fill pump, positioned on a side of the chamber opposite the medium inlet and operable to draw the medium from the medium inlet through the chamber toward the fill pump to fill the chamber without the medium in the chamber contacting the fill pump; A pumping system comprising: (Item 2) Item 10. The pumping system of item 1, wherein the fluid container comprises an elongated tube. (Item 3) 3. The pumping system of claim 1, wherein the filling pump comprises a centrifugal pump. (Item 4) 4. The pumping system according to any one of items 1 to 3, comprising a plurality of pressure exchange chambers, each of which is filled sequentially with the medium. (Item 5) 5. The pumping system of claim 1, wherein a first valve device is disposed at one end of the pressure exchange chamber and includes a drive fluid inlet valve, a drive fluid outlet valve, a pressurization valve, and a pressure reduction valve, and a second valve device is disposed at an end of the pressure exchange chamber closer to the pressurization discharge section and includes a medium discharge valve and a medium filling valve. (Item 6) 6. The pumping system of any one of items 1 to 5, wherein the pressure exchange chamber includes a separator between the driving fluid and the medium to be pumped. (Item 7) 7. The pumping system of any one of items 1 to 6, wherein the pressure exchange chamber is located at or near the seabed. (Item 8) 8. The pumping system of any one of items 1 to 7, wherein the pressure exchange chamber is located in an underground mine. (Item 9) 9. The pumping system of claim 8, wherein the pressure exchange chamber is fed from a media supply located at a higher elevation than the pressure exchange chamber. (Item 10) 1. A method of filling a pressure exchange chamber fluid container, the pressure exchange chamber fluid container being located at a low altitude and having a media inlet coupled to one end of the fluid container and a drive fluid outlet coupled to another end of the fluid container, the method comprising: (i) opening a media inlet valve at the media inlet to fill the fluid container; (ii) using an energy-addition mechanism to create a lower pressure at the drive fluid inlet of the fluid container than at the media inlet of the fluid container to draw the media in the fluid container through the media inlet without the media contacting the energy-addition mechanism; (iii) closing a valve to stop the drawing of medium into the fluid container; A method comprising: (Item 11) Item 12. The method of item 11, wherein the step of using the energy addition mechanism includes using a fill pump located at an end of the pressure exchange chamber opposite the media inlet. (Item 12) 13. The method of claim 12, wherein the step of closing the valve is performed before the medium reaches the fill pump to prevent the fill pump from destroying the medium. (Item 13) 11. A hydraulic ore lifting system comprising the pumping system according to any one of items 1 to 10. [Explanation of symbols]

[0082] 1 Pressure Exchange Chamber (PEC) 2 Low-pressure lines 3. Ore slurry preparation 4 Liza 5 Dehydration position 6 PD pump 7 High-voltage lines 9 Low pressure fluid return line 10 Hydraulic Ore Lifting System (HOHS) 12 tubes 14. Drive fluid valve device 16 Pressure-transported medium valve device 20 Pressure discharge section 22 Delivery end 24 Pressurized medium riser 26 Collection Container 28 Surface 29 Medium outlet (outlet) line 30 Filling mechanism 31 Medium inlet line 32 Medium (slurry to be pumped) 33 Baby Boomer Harvester 34 Positive displacement pump 35 Media inlet 36 Driving Fluid 38 Driving Fluid Riser 40 Driving fluid inlet line 42 Driving fluid outlet (outlet) line 44 Driving fluid discharge point 48 Positive Displacement Pump End 50 Driving fluid inlet valve 52 Driving fluid outlet (outlet) valve 54 Pressure valve 56 Pressure reducing valve 57 Choke valve 58 (for valves 50 to 56) parent valve actuator 60 Pressure Equalization Line 62 Pressure-fed fluid outlet valve 64 Pressure-fed fluid inlet valve 66 (for valves 60, 62) parent valve actuator 70 System Controller 74 Surface Fluid Source 76 Harvester chassis 78 Movement System (Hydraulic Thruster) 79 Undersea 80 Chassis opening 82 Collection Head 83 Baby Boomers 84 Baby Boomer Hopper 85 Flexible suction hose 86 Guidance System 90 Guidance system to transmitter / receiver connection 201a Pressure Exchange Chamber (PEC) 201b Pressure Exchange Chamber (PEC) 201c Pressure Exchange Chamber (PEC) 211 Pressure Exchange System 212a tube 212b tube 212c tube 270 System Controller 310 Hydraulic Ore Lifting System (HOHS) 337 Ore Mixer 339 Raised shelf

Claims

1. 1. A pumping system for pumping a medium including ore suspended in a carrier fluid from a subsurface or subsurface location to a surface at an elevated level, the pumping system employing a positive displacement pump to deliver a high pressure drive fluid into a fluid container to move the pressurized medium, (i) at least one pressure exchange chamber comprising a fluid container having a valve arrangement at each end and located at an elevation below said elevated level; (ii) a medium inlet at one end of the chamber operable to receive a low pressure medium for delivery into the chamber; (iii) a fill pump, located on a side of the chamber opposite the medium inlet and operable to draw the medium from the medium inlet at low pressure through the chamber towards the fill pump to fill the chamber without the medium in the chamber contacting the fill pump; A pumping system comprising:

2. The pumping system of claim 1 , wherein the fluid container comprises an elongated tube.

3. The pumping system of claim 1 or 2, wherein the fill pump comprises a centrifugal pump.

4. 4. The pumping system of claim 1, wherein a first valve device is disposed at one end of the pressure exchange chamber and includes a drive fluid inlet valve, a drive fluid outlet valve, a pressurization valve, and a pressure reduction valve, and a second valve device is disposed at an end of the pressure exchange chamber closer to the pressurization discharge section and includes a medium discharge valve and a medium filling valve.

5. 5. The pumping system of claim 1, wherein the pressure exchange chamber includes a separator between the drive fluid and the medium to be pumped.

6. 6. A pumping system according to any one of claims 1 to 5, wherein the pressure exchange chamber is located at or near the seabed.

7. 6. The pumping system of claim 1, wherein the pressure exchange chamber is located in an underground mine.

8. The pumping system of claim 6 , wherein the pressure exchange chamber is fed from a media supply located at a higher elevation than the pressure exchange chamber.

9. 1. A method of filling a pressure exchange chamber fluid container, the pressure exchange chamber fluid container being located at a low altitude and having a media inlet coupled to one end of the fluid container and a drive fluid outlet coupled to another end of the fluid container, the method comprising: (i) opening a media inlet valve at the media inlet to fill the fluid container; (ii) using a fill pump located at an end of the fluid container opposite the media inlet to create a lower pressure at the drive fluid inlet of the fluid container than at the media inlet of the fluid container to draw the media in the fluid container through the media inlet without the media in the fluid container coming into contact with the fill pump; (iii) closing a valve to stop the drawing of medium into the fluid container; A method comprising:

10. 10. The method of claim 9, wherein the step of closing the valve is performed prior to the medium reaching the fill pump to prevent the fill pump from destroying the medium.

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